RU2816847C2 - Methods of treating using anti-cd123 immunoconjugates - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: group of inventions relates to a method of treating a hematologic malignant tumour in humans. Method of treating a hematologic malignant tumour in a human, comprising administering to a subject an anti-CD123 immunoconjugate containing an anti-CD123 antibody or an antigen-binding fragment thereof, linked to an indolinobenzodiazepine (IGN) DNA alkylator, wherein the immunoconjugate is administered in dose of 0.045 mg/kg to less than 0.3 mg/kg, and wherein said anti-CD123 antibody or its antigen-binding fragment contains: a. CDR1 of the variable region of the heavy chain containing the amino acid sequence SEQ ID NO: 5; CDR2 of the variable region of the heavy chain containing the amino acid sequence SEQ ID NO: 6; and a heavy chain variable region CDR3 comprising the amino acid sequence SEQ ID NO: 7; and b. CDR1 of the light chain variable region containing the amino acid sequence SEQ ID NO: 8; CDR2 of the light chain variable region containing the amino acid sequence SEQ ID NO: 9; and a light chain variable region CDR3 comprising the amino acid sequence SEQ ID NO: 10. Method of treating a hematologic malignant tumour in a human, comprising administering to a subject an anti-CD123 immunoconjugate containing an anti-CD123 antibody or an antigen-binding fragment thereof, linked to an indolinobenzodiazepine (IGN) DNA alkylator, wherein from 0.015 mg/kg to 0.09 mg/kg of the immunoconjugate is administered three times in 21-day cycle, and wherein said anti-CD123 antibody or its antigen-binding fragment contains said heavy chain variable regions having said amino acid sequence. Method of treating a hematologic malignant tumour in a human, comprising administering to a subject an anti-CD123 immunoconjugate containing an anti-CD123 antibody or an antigen-binding fragment thereof, associated with an indolinobenzodiazepine (IGN) DNA alkylator, wherein from 0.015 mg/kg to 0.09 mg/kg of the immunoconjugate is administered twice in 21-day cycle, and wherein said anti-CD123 antibody or antigen-binding fragment thereof also comprises said variable heavy chain regions having said amino acid sequence.

EFFECT: use of the group of inventions provides the use of therapeutically effective modes of administration, which minimize undesirable side effects in treating hematologic malignant tumours in humans.

53 cl, 7 dwg, 7 tbl, 4 ex

Description

TECHNICAL FIELD

[0001] This invention relates generally to the use of anti-CD123 immunoconjugates for the treatment of diseases such as cancer. This document proposes therapeutically effective dosing regimens that minimize unwanted side effects.

BACKGROUND ART

[0002] Cancer is one of the leading causes of death in developed countries, with more than one million people diagnosed with cancer and 500,000 deaths annually in the United States alone. It is estimated that more than a third of people will develop some form of cancer during their lifetime.

[0003] CD123 is the alpha subunit of the interleukin-3 receptor (IL-3Rα). CD123 expression on normal hematopoietic stem cells is low (Testa et al., Biomark Res., 10;2(1):4.(2014), Jordan et al., Leukemia, 14(10): 1777-84 (2000) ). However, CD123 is overexpressed in numerous hematological malignancies of both myeloid and lymphoid origin, including acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), B-cell acute lymphoblastic leukemia (B-ALL), chronic myeloid leukemia in blast crisis/ blast phase (BC-CML), and blast plasmacytoid dendritic cell neoplasm (BPDN) (Testa 2014). Interleukin-3 is produced by activated T lymphocytes. IL-3, together with other growth factors, stimulates the development and mediates the survival of a wide range of hematopoietic cells in the bone marrow (Testa 2014). Levels of CD123 on normal hematopoietic stem cells are very low, but early common myeloid progenitor cells express higher levels of CD123 (Testa 2014, Jordan 2000). Moderate to high expression of CD123 on normal tissues is limited to rare populations of white blood cells such as plasmacytoid dendritic cells and basophils (Jordan 2000, Testa 2014).

[0004] Acute myeloid leukemia is the most common form of acute leukemia in adults and accounts for the largest number of leukemia deaths in the United States. An estimated 21,380 people will be diagnosed with AML in 2017 and 10,590 will die from the disease (Siegel et al., CA Cancer J Clin. 2017;67(l):7-30 (2017)). The median age of diagnosis is 66 years. First-line chemotherapy for AML is reported to induce a complete response (CR) in 70% to 80% of patients aged 60 years or less, and in approximately 50% of older patients. "Eligible" patients are considered to be able to tolerate intensive treatment, are often younger (<60 years), and typically receive one to two cycles of "7+3" induction, a combination of cytarabine and an anthracycline, typically daunorubicin. Thereafter, such eligible patients may receive high-dose cytarabine over one or more cycles, and may receive a stem cell transplant. Standard induction and post-induction therapies result in a median duration of remission of approximately one year and potential cure in 25%-35% of patients. "Unsuitable" patients, often older age, typically receive azacitidine, which is a hypomethylating agent. Most patients with AML relapse over time, and salvage therapies for AML have poor results with significant toxicity. Thus, new treatments with limited toxicity in this relapsed population are needed.

[0005] Blast plasmacytoid dendritic cell neoplasm is a rare, aggressive hematologic malignancy arising from myeloid dendritic cell precursors that often presents with skin lesions in addition to lymph node, blood, and bone marrow involvement. Characterized by the expression of CD4, CD56, and CD123, among other markers, PDDN blasts express high levels of CD123. Unfortunately, there is no standard treatment for PDDN, and initial treatment regimens are used for acute lymphoblastic leukemia (ALL) and AML. Despite CR rates of 47-86% when the disease is initially treated, median overall survival is approximately 12-16 months. Most patients with PDDN relapse over time in the absence of standard treatment options.

[0006] Acute lymphoblastic leukemia is a rare, aggressive hematologic malignancy arising from lymphoid progenitor cells that often involves lymph nodes, blood, and bone marrow. B-cell acute lymphoblastic leukemia and some T-cell acute lymphoblastic leukemia blasts express CD123 at levels similar to AML blasts. Although initial remission rates are high, long-term survival rates are 35%-40% in patients under 60 years of age, and less than 10% in older patients (Goldstone 2008). Patients with relapsed ALL have several chemotherapy options, as well as immunotherapy using the US Food and Drug Administration-approved anti-CD19 bispecific antibody blinatumomab. However, long-term survival for these patients remains low.

[0007] Given the inadequacy of currently available therapeutic agents for the treatment of many hematologic malignancies, there is a need for more effective interventions.

SUMMARY OF THE INVENTION

[0008] This invention provides a method of treating a hematologic malignancy in a human, comprising administering to said subject an anti-CD123 immunoconjugate comprising an anti-CD123 antibody or antigen-binding fragment thereof associated with a cytotoxic agent, wherein the immunoconjugate is administered at a dose of from about 0.045 mg/kg to less than 0.3 mg/kg. In some embodiments, the subject is administered from about 0.045 mg/kg to about 0.09 mg/kg of the immunoconjugate. In some embodiments, about 0.045 mg/kg of the immunoconjugate is administered to the subject. In some embodiments, about 0.09 mg/kg of the immunoconjugate is administered to the subject. In some embodiments, about 0.135 mg/kg of the immunoconjugate is administered to the subject. In some embodiments, about 0.18 mg/kg of the immunoconjugate is administered to the subject. In some embodiments, the immunoconjugate is administered to a subject once in a 21-day cycle.

[0009] This invention also provides a method of treating a hematologic malignancy in a human, comprising administering to said subject an anti-CD123 immunoconjugate comprising an anti-CD123 antibody or antigen-binding fragment thereof associated with a cytotoxic agent, wherein from about 0.015 mg/kg to about 0. 09 mg/kg immunoconjugate is administered three times in a 21-day cycle. In some embodiments, the first administration is on day 1 of a 21-day cycle. In some embodiments, the second administration occurs on day 4 of a 21-day cycle. In some embodiments, the third administration is administered on day 8 of a 21-day cycle. In some embodiments, the first, second, and third administrations are administered on day 1, day 4, and day 8, respectively, of a 21-day cycle. In some embodiments, about 0.015 mg/kg of the immunoconjugate is administered three times in a 21-day cycle. In some embodiments, approximately 0.045 mg/kg of the immunoconjugate is administered three times in a 21-day cycle. In some embodiments, approximately 0.06 mg/kg of the immunoconjugate is administered three times in a 21-day cycle. In some embodiments, approximately 0.09 mg/kg of the immunoconjugate is administered three times in a 21-day cycle.

[0010] In some cases, from about 0.015 mg/kg to about 0.06 mg/kg of the immunoconjugate is administered at each of three time points in a 21-day cycle. In some embodiments, the first administration is on day 1 of a 21-day cycle. In some embodiments, the second administration occurs on day 4 of a 21-day cycle. In some embodiments, the third administration is administered on day 8 of a 21-day cycle. In some embodiments, the first, second, and third administrations are administered on day 1, day 4, and day 8, respectively, of a 21-day cycle. In some embodiments, about 0.015 mg/kg of the immunoconjugate is administered three times in a 21-day cycle. In some embodiments, approximately 0.03 mg/kg of the immunoconjugate is administered three times in a 21-day cycle. In some embodiments, approximately 0.06 mg/kg of the immunoconjugate is administered three times in a 21-day cycle.

[0011] The invention also provides a method of treating a hematologic malignancy in a human, comprising administering to said subject an anti-CD123 immunoconjugate comprising an anti-CD123 antibody or antigen binding fragment thereof coupled to a cytotoxic agent, wherein from about 0.015 mg/kg to about 0.135 mg /kg of immunoconjugate is administered three times in a 21-day cycle. In some embodiments, the first administration is on day 1 of a 21-day cycle. In some embodiments, the second administration is administered on day 4 of a 21-day cycle. In some embodiments, the third administration is administered on day 8 of a 21-day cycle. In some embodiments, the first, second, and third administrations are administered on day 1, day 4, and day 8, respectively, of a 21-day cycle. In some embodiments, approximately 0.135 mg/kg of the immunoconjugate is administered three times in a 21-day cycle.

[0012] This invention also provides a method of treating a hematologic malignancy in a human, comprising administering to said subject an anti-CD123 immunoconjugate comprising an anti-CD123 antibody or antigen-binding fragment thereof associated with a cytotoxic agent, wherein from about 0.015 mg/kg to about 0. 09 mg/kg immunoconjugate is administered three times in a 21-day cycle. In some embodiments, the first administration is on day 1 of a 21-day cycle. In some embodiments, the second administration is administered on day 8 of a 21-day cycle. In some embodiments, about 0.015 mg/kg of the immunoconjugate is administered twice in a 21-day cycle. In some embodiments, approximately 0.045 mg/kg of the immunoconjugate is administered twice in a 21-day cycle. In some embodiments, approximately 0.09 mg/kg of immunoconjugate is administered twice in a 21-day cycle.

[0013] The invention also provides a method of treating a hematologic malignancy in a human, comprising administering to said subject an anti-CD123 immunoconjugate comprising an anti-CD123 antibody or antigen-binding fragment thereof coupled to a cytotoxic agent, wherein from about 0.015 mg/kg to about 0.135 mg /kg of immunoconjugate is administered three times in a 21-day cycle. In some embodiments, the first administration is on day 1 of a 21-day cycle. In some embodiments, the second administration is administered on day 8 of a 21-day cycle. In some embodiments, approximately 0.135 mg/kg of the immunoconjugate is administered twice in a 21-day cycle.

[0014] In some embodiments, the immunoconjugate is administered in one cycle.

[0015] In some embodiments, the immunoconjugate is administered over more than one cycle. In some embodiments, the immunoconjugate is administered for at least 2 cycles, at least 3 cycles, at least 4 cycles, at least 5 cycles, at least 6 cycles, at least 7 cycles, at least 8 cycles , at least 9 cycles, or at least 10 cycles. In some embodiments, the immunoconjugate is administered for about 2-4 cycles, about 2-6 cycles, about 2-8 cycles, or about 2-10 cycles.

[0016] In some embodiments, the hematologic malignancy is a recurrent hematologic malignancy. In some embodiments, the relapse is a first relapse. In some embodiments, the hematologic malignancy is a refractory hematologic malignancy. In some embodiments, the hematologic malignancy is a primary refractory hematologic malignancy. In some embodiments, the hematologic malignancy is acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), B-cell acute lymphoblastic leukemia (B-ALL), blast crisis/phase chronic myeloid leukemia (BC-CML), and blast plasmacytoid dendritic cell neoplasm (BPDN). In some embodiments, the hematologic malignancy is AML. In some embodiments, the AML is relapsed AML. In some embodiments, the AML is refractory AML. In some embodiments, the hematologic malignancy is PDDN. In some embodiments, the BPDN is a recurrent BPDN. In some embodiments, the BPDN is a refractory BPDN. In some embodiments, the BPDN is a first-line BPDN. In some embodiments, the hematologic malignancy is ALL. In some embodiments, the ALL is relapsing ALL. In some embodiments, the ALL is refractory ALL. In some embodiments, the hematologic malignancy is chronic myelomonocytic leukemia (CMML). In some embodiments, the CMML is recurrent CMML. In some embodiments, the CMML is refractory CMML. In some embodiments, the hematologic malignancy is myelofibrosis (MF). In some embodiments, the MF is recurrent MF. In some embodiments, the MF is refractory MF. In some embodiments, the hematologic malignancy is MDS. In some embodiments, the MDS is recurrent MDS. In some embodiments, the MDS is refractory MDS.

[0017] In some embodiments, the subject is a pediatric patient, e.g., a pediatric patient with PDND, ALL, or AML).

[0018] In some embodiments, the subject has an Eastern Cooperative Oncology Group (ECOG) performance status score of ≤1. In some embodiments, the subject has an adverse European Leukemia Network (ELN) genetic risk score, such as an ASXL1, RUNX1, and/or FLT3-ITD mutation. In some embodiments, the subject has previously received treatment failure with SL-401 (tagraxofusp). In some embodiments, the hematologic malignancy is refractory to CLAG-M (cladribine + cytarabine + mitoxantrone).

[0019] In some embodiments, the hematologic malignancy is a CD123-expressing hematologic malignancy. In some embodiments, CD123 was detected in a sample obtained from a hematologic malignancy prior to said administration. In some embodiments, CD123 is detected using flow cytometry.

[0020] In some embodiments, the methods disclosed herein further include detecting CD123 in a sample obtained from a hematologic malignancy prior to said administration. In some embodiments, at least 80% of the cells in the hematologic malignancy express CD123. In some embodiments, CD123 was detected in at least 80% of the cells in a sample obtained from a hematologic malignancy prior to administration. In some embodiments, the methods disclosed herein further comprise detecting CD123 in at least 80% of the cells in a sample obtained from a hematologic malignancy prior to said administration. In some embodiments, the subject has an absolute neutrophil count greater than 500/μL.

[0021] In some embodiments, the subject has received at least one prior line of therapy. In some embodiments, the subject has received at least two prior lines of therapy. In some embodiments, the subject has received at least three prior lines of therapy. In some embodiments, the subject has received no more than three prior lines of therapy. In some embodiments, the subject has received four prior lines of therapy. In some embodiments, the subject has received five prior lines of therapy. In some embodiments, the subject has received no more than five prior lines of therapy. In some embodiments, the subject has previously received a stem cell transplant.

[0022] In some embodiments, administration reduces the number of bone marrow blasts in a subject.

[0023] In some embodiments, the subject was pretreated with a corticosteroid prior to administration of the immunoconjugate. In some embodiments, the methods disclosed herein further comprise pre-treating the subject with a corticosteroid prior to administration of the immunoconjugate. In some embodiments, the corticosteroid is diphenhydramine, acetaminophen, paracetamol, dexamethasone, or a combination thereof.

[0024] In some embodiments, the immunoconjugate is administered intravenously.

[0025] In some embodiments, the method further includes administering a reduced dose of the immunoconjugate after the occurrence of dose-limiting toxicity in the subject, reducing to baseline or grade ≤2.

[0026] In some embodiments, the anti-CD123 antibody or antigen binding fragment in the immunoconjugate comprises: (a) a heavy chain variable region CDR1 comprising the amino acid sequence of SEQ ID NO: 5; Heavy chain variable region CDR2 containing the amino acid sequence of SEQ ID NO: 6; and a heavy chain variable region CDR3 comprising the amino acid sequence of SEQ ID NO: 7; and (b) a light chain variable region CDR1 comprising the amino acid sequence of SEQ ID NO: 8; Light chain variable region CDR2 containing the amino acid sequence of SEQ ID NO: 9; and a light chain variable region CDR3 comprising an amino acid sequence selected from the group consisting of: SEQ ID NO: 10.

[0027] In some embodiments, the anti-CD123 antibody or antigen binding fragment in the immunoconjugate comprises a heavy chain variable region (VH) comprising the amino acid sequence set forth in SEQ ID NO: 1 and/or a light chain variable region (VL) comprising the amino acid sequence set forth in SEQ ID NO: 2. In some embodiments, the anti-CD123 antibody or antigen binding fragment in the immunoconjugate comprises a heavy chain constant region and/or a light chain constant region. In some embodiments, the heavy chain constant region comprises a human IgG1 immunoglobulin heavy chain constant region and/or the light chain constant region comprises a human IgGκ immunoglobulin light chain constant region. In some embodiments, the anti-CD123 antibody or antigen binding fragment in the immunoconjugate comprises a heavy chain comprising the amino acid sequence set forth in SEQ ID NO:3 and/or a light chain comprising the amino acid sequence set forth in SEQ ID NO:4. In some embodiments, the anti-CD123 antibody or antigen binding fragment in the immunoconjugate is a full-length antibody. In some embodiments, the anti-CD123 antibody or antigen binding fragment in the immunoconjugate is an antigen binding fragment. In some embodiments, the cytotoxic agent in the immunoconjugate is a DNA alkylating agent. In some embodiments, the DNA alkylating agent is an indoline benzodiazepine (IGN) DNA alkylator. In some embodiments, the IGN DNA alkylator is DGN549-C. In some embodiments, the immunoconjugate contains a peptide linker. In some embodiments, the immunoconjugate is administered in a pharmaceutical composition containing immunoconjugates of the following structure:

,

Where

G4723A contains a heavy chain containing the amino acid sequence presented in SEQ ID NO:3, and a light chain containing the amino acid sequence presented in SEQ ID NO:4.

[0028] In one case (I1), a method of treating a hematologic malignancy in a human comprises administering to said subject an anti-CD123 immunoconjugate comprising an anti-CD123 antibody or antigen-binding fragment thereof coupled to a cytotoxic agent, wherein the immunoconjugate is administered at a dose of about 0.045 mg /kg to less than 0.3 mg/kg.

[0029] In one of the cases (I2) I1, the subject is administered approximately 0.045 mg/kg of the immunoconjugate. In one case (I3) I1, the subject is administered approximately 0.09 mg/kg of the immunoconjugate. In one case (I4) I1, the subject is administered approximately 0.135 mg/kg of the immunoconjugate. In one case (I5) I1, the subject is administered approximately 0.18 mg/kg of the immunoconjugate.

[0030] In one of the cases (I6) of any of I1-I5, the immunoconjugate is administered to the subject once in a 21-day cycle.

[0031] In one case (I7), a method of treating a hematologic malignancy in a human comprises administering to said subject an anti-CD123 immunoconjugate comprising an anti-CD123 antibody or antigen-binding fragment thereof coupled to a cytotoxic agent, wherein from about 0.015 mg/kg to about 0.09 mg/kg immunoconjugate is administered three times in a 21-day cycle.

[0032] In one of the cases (I8) I7, the first administration is carried out on day 1 of a 21-day cycle. In one of the cases (I9) I7 or I8, the second administration is carried out on day 4 of the 21-day cycle. In one of the cases (I10) of any of I7-I9, the third administration is carried out on day 8 of the 21-day cycle.

[0033] In one of the cases (I11) of any of I7-I10, the third administration is carried out on day 1, day 4 and day 8, respectively, of the 21-day cycle.

[0034] In one of the cases (I12) of any of I7-I11, approximately 0.015 mg/kg of the immunoconjugate is administered three times in a 21-day cycle. In one of the cases (I13) of any of I7-I11, approximately 0.045 mg/kg of immunoconjugate is administered three times in a 21-day cycle. In one of the cases (I14) of any of I8-I11, approximately 0.09 mg/kg of immunoconjugate is administered three times in a 21-day cycle.

[0035] In one case (I15), a method of treating a hematologic malignancy in a human comprises administering to said subject an anti-CD123 immunoconjugate comprising an anti-CD123 antibody or antigen-binding fragment thereof coupled to a cytotoxic agent, wherein from about 0.015 mg/kg to about 0.09 mg/kg immunoconjugate is administered three times in a 21-day cycle.

[0036] In one of the cases (I16) I15, the first administration is carried out on day 1 of a 21-day cycle. In one of the cases (I17) I15 or I16, the second administration is carried out on day 8 of the 21-day cycle. In one of the cases (I18) of any of I15-I17, approximately 0.015 mg/kg of immunoconjugate is administered twice in a 21-day cycle. In one of the cases (I19) of any of I15-I17, approximately 0.045 mg/kg of the immunoconjugate was administered twice in a 21-day cycle. In one of the cases (I20) of any of I15-I17, approximately 0.09 mg/kg of immunoconjugate is administered twice in a 21-day cycle.

[0037] In one of the cases (I21) of any of I6-I20, the immunoconjugate is administered in one cycle. In one of the cases (I22) of any of I6-I20, the immunoconjugate is administered over more than one cycle. In one of the cases (I23) of any of I6-I20, the immunoconjugate is administered for at least 2 cycles, at least 3 cycles, at least 4 cycles, at least 5 cycles, at least 6 cycles, at least 7 cycles, at least 8 cycles, at least 9 cycles or at least 10 cycles. In one of the cases (I24) of any of I6-I20, the immunoconjugate is administered for about 2-4 cycles, about 2-6 cycles, about 2-8 cycles, or about 2-10 cycles.

[0038] In one of the cases (I25) of any of I1 to I24, the hematological malignancy is a recurrent hematological malignancy. In one of the cases (I26) of any of I1-I24, the hematological malignancy is acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), B-cell acute lymphoblastic leukemia (B-ALL), chronic myeloid leukemia in blast crisis/ phase (BC-CML), or blast plasmacytoid dendritic cell neoplasm (BPDN).

[0039] In one of the cases (I27) of any of I1-I24, the hematological malignancy is AML. In one of the cases (I28) I27, the AML was recurrent AML. In one of the cases (I29) I27 or I28, the AML is refractory AML.

[0040] In one of the cases (I30) of any of I1-I24, the hematological malignancy is PDDN. In one of the cases (I31) I30, BPDN is a recurrent BPDN. In one of the cases (I32) I31 or I32, BPDN is refractory BPDN.

[0041] In one of the cases (I33) of any of I1-I24, the hematological malignancy is ALL. In one of the cases (I34) I33, the ALL was relapsing ALL. In one of the cases (I35) I33 or I34, the ALL is refractory ALL.

[0042] In one of the cases (I36) of any of I1-I24, the hematological malignancy is chronic myelomonocytic leukemia (CMML). In one of the cases (I37) I36, CMML is relapsing CMML. In one of the cases (I38) I36 or I37, CMML is refractory CMML.

[0043] In one of the cases (I39) of any of I1-I24, the hematological malignancy is myelofibrosis (MF). In one of the cases (I40) I39, the MF was recurrent MF. In one of the cases (I41) I39 or I40, MF is refractory MF.

[0044] In one of the cases (I42) of any of I1-I24, the hematological malignancy is myelodysplastic syndrome (MDS). In one of the cases (I43) I42, the MDS is recurrent MDS. In one of the cases (I44) I42 or I43, the MDS is refractory MDS.

[0045] In one of the cases (I45) of any of I1 to I44, the hematological malignancy is a CD123-expressing hematological malignancy.

[0046] In one of the cases (I46) of any of I1-I45, CD123 was detected in a sample obtained from a hematological malignancy prior to said administration. In one case (I47), I46,CD123 was detected by flow cytometry.

[0047] In one of the cases (I48) of any one of I1-I47, the method further includes detecting CD123 in a sample obtained from a hematological malignancy prior to said administration.

[0048] In one of the cases (I49) of any of I1-I48, at least 80% of the cells in the hematologic malignancy express CD123.

[0049] In one of the cases (I50) of any of I1-I49, CD123 was detected in at least 80% of the cells in the sample obtained from the hematological malignancy before the specified administration.

[0050] In one of the cases (I51) of any one of I1-I50, the method further includes detecting CD123 in at least 80% of the cells in a sample obtained from a hematological malignancy prior to said administration.

[0051] In one of the cases (I52) of any of I1-I51, the subject has an absolute neutrophil count greater than 500/μl.

[0052] In one of the cases (I53) of any of I1-I52, the subject had received at least one prior line of therapy. In one of the cases (I54) of any of I1-I52, the subject had received at least two prior lines of therapy. In one of the cases (I55) of any of I1-I52, the subject had received at least three prior lines of therapy.

[0053] In one of the cases (I56) of any of I1-I55, the subject was pretreated with a corticosteroid prior to administration of the immunoconjugate. In one case (I57) of any of I1-I55, the method further comprises pre-treating the subject with a corticosteroid prior to administration of the immunoconjugate. In one of the cases (I58) I56 or I57, the corticosteroid is diphenhydramine, acetaminophen, paracetamol, dexamethasone, or a combination thereof.

[0054] In one of the cases (I59) of any of I1-I58, the immunoconjugate is administered intravenously.

[0055] In one of the cases (I60) of any of I1-I59, the method further includes administering a reduced dose of the immunoconjugate after the subject experiences dose-limiting toxicity, reducing to baseline or ≤grade 2.

[0056] In one of the cases (I61) of any one of I1-I60, the anti-CD123 antibody or antigen binding fragment in the immunoconjugate comprises: (a) a heavy chain variable region CDR1 containing the amino acid sequence of SEQ ID NO: 5, a heavy chain variable region CDR2 containing the amino acid sequence SEQ ID NO: 6; and a heavy chain variable region CDR3 comprising the amino acid sequence of SEQ ID NO: 7; and (b) a light chain variable region CDR1 comprising the amino acid sequence of SEQ ID NO: 8; Light chain variable region CDR2 containing the amino acid sequence of SEQ ID NO: 9; and a light chain variable region CDR3 comprising an amino acid sequence selected from the group consisting of: SEQ) ID NO. 10. In one case (I62), I61, the anti-CD123 antibody or antigen binding fragment in the immunoconjugate contains a heavy chain variable region (VH) containing the amino acid sequence presented in SEQ ID NO:1 and/or a light chain variable region (VL ), containing the amino acid sequence presented in SEQ ID NO: 2.

[0057] In one of the cases (I63) of any of I1-I62, the anti-CD123 antibody or antigen binding fragment in the immunoconjugate contains a heavy chain constant region and/or a light chain constant region. In one case (I64) of I63, the heavy chain constant region comprises a human IgG1 immunoglobulin heavy chain constant region and/or the light chain constant region comprises a human IgGκ immunoglobulin light chain constant region.

[0058] In one of the cases (I65) of any of I1-I62, the anti-CD123 antibody or antigen binding fragment in the immunoconjugate contains a heavy chain containing the amino acid sequence presented in SEQ ID NO:3, and/or a light chain containing the amino acid sequence , presented in SEQ ID NO:4.

[0059] In one of the cases (I66) of any of I1-I65, the anti-CD123 antibody or antigen binding fragment in the immunoconjugate is a full-length antibody. In one of the cases (I67) of any of I1-I65, the anti-CD123 antibody or antigen binding fragment in the immunoconjugate is an antigen binding fragment.

[0060] In one of the cases (I68) of any of I1-I67, the cytotoxic agent in the immunoconjugate is a DNA alkylating agent. In one case (I69) I68, the DNA alkylating agent is an indolinobenzodiazepine (IGN) DNA alkylator. In one of the cases (I70) I69, the DNA alkylator indicated by IGN is DGN549-C.

[0061] In one of the cases (I71) of any of I1-I70, the immunoconjugate contains a peptide linker.

[0062] In one of the cases (I72) of any of I1-I71, the immunoconjugate is administered in a pharmaceutical composition containing immunoconjugates of the following structure:

wherein G4723A comprises a heavy chain comprising the amino acid sequence set forth in SEQ ID NO:3 and a light chain containing the amino acid sequence set forth in SEQ ID NO:4.

[0063] In one case (I73), a method of treating a hematologic malignancy in a human comprises intravenously administering to a subject a pharmaceutical composition containing immunoconjugates of the following structure:

wherein G4723A comprises a heavy chain comprising the amino acid sequence set forth in SEQ ID NO:3 and a light chain comprising the amino acid sequence set forth in SEQ ID NO:4, wherein the immunoconjugate is administered at a dose of from about 0.045 mg/kg to less than 0 .3 mg/kg once per 21-day cycle.

[0064] In one case (I74) I73, the subject is administered about 0.045 mg/kg, about 0.09 mg/kg, about 0.135 mg/kg, or about 0.18 mg/kg immunoconjugate. In one of the cases (I75) I73 or I74, the hematological malignancy is acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), chronic myeloid leukemia in blast crisis/phase (BC-CML), blast plasmacytoid dendritic cell neoplasm (BPDN) , chronic myelomonocytic leukemia (CMML), myelofibrosis (MF), or acute lymphoblastic leukemia (ALL), wherein the ALL is not necessarily B-cell acute lymphoblastic leukemia (B-ALL).

BRIEF DESCRIPTION OF GRAPHIC MATERIALS

[0065] In FIG. Figure 1 depicts the study design of IMGN632 (an anti-CD123 immunoconjugate) in the dose escalation phase and maximum tolerated dose (MTD) extension cohorts of clinical trials. R/R: relapsed or refractory; AML: acute myeloid leukemia; BPDN: blast plasmacytoid dendritic cell neoplasm; CRC: clinical research center; RP2D: Recommended Phase 2 Dose; ALL: acute lymphoblastic leukemia.

[0066] FIG. Figure 2 shows the best percentage change in bone marrow blasts in patients treated with IMGN632 who achieved progressive disease (PD; boxed bars), stable disease (SD; open bars), complete remission (CR), complete remission with partial recovery (CR/CR; bars with forward diagonal shading), partial remission (PR; bars with reverse diagonal shading), and minimal residual disease (MRD; gray bars). Each bar represents the best percentage change in bone marrow blasts for an individual patient, and the number above or below the bar indicates the cohort number (see Tables 5 and 6) to which the indicated patient belongs.

[0067] FIG. 3 shows the percentage of CD123-positive leukemia cells in patients treated with IMGN632.

[0068] FIG. Figure 4 shows the percentage of CD123 receptor saturation in patients in Cohorts 1-6.

[0069] FIG. 5 demonstrates the concentration of IMGN632 in patients in Cohorts 1-6.

[0070] FIG. 6A shows the chemical structure of IMGN632. IMGN632 is a composition containing immunoconjugates containing the anti-CD123 antibody G4723A coupled to the cytotoxic payload DGN549-C in sodium bisulfite. Most of the immunoconjugate in the composition is in the sulfonated form shown in FIG. 6A.

[0071] FIG. 6B depicts a non-sulfonated form of the immunoconjugate containing the anti-CD123 antibody G4723A coupled to the cytotoxic payload DGN549-C (monoimine structure), which may also be present in the IMGN632 composition.

DETAILED DESCRIPTION OF THE INVENTION

Definitions

[0072] The terms "cancer" and "cancerous" refer to or describe a physiological condition in mammals in which a population of cells is characterized by unregulated cellular growth. Examples of cancer include, but are not limited to, carcinoma, lymphoma, blastoma, sarcoma and leukemia. "Tumor" and "neoplasm" refer to one or more cells that form as a result of excess cellular growth or proliferation, whether benign (noncancerous) or malignant (cancerous), including precancerous lesions. Cancer, as disclosed herein, may be a hematologic malignancy. Examples of hematologic malignancies include, for example, acute myeloid leukemia (AML), chronic myeloid leukemia (CML), myelodysplastic syndrome (MDS), acute lymphoblastic leukemia (ALL), such as B-cell acute lymphoblastic leukemia (B-ALL), T -cell acute lymphoblastic leukemia (T-ALL), undifferentiated leukemia ALL (UNL-ALL), B-cell progenitor cell ALL (BCP-ALL), Ph+ ALL, Ph-like ALL, chronic lymphocytic leukemia (CLL), chronic myeloid leukemia in blast crisis/phase (BC-CML) and blast plasmacytoid dendritic cell neoplasm (BPDN). Additional examples of "cancers" include B-cell lymphomas, including NHL, lymphoblastic leukemia/B-cell progenitor lymphoma, and mature B-cell neoplasms, such as B-cell chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL), B-cell prolymphocytic leukemia, lymphoplasmacytic lymphoma, mantle cell lymphoma (MCL), follicular lymphoma (FL), including low-, intermediate- and high-grade FL, cutaneous follicular center lymphoma, B-cell marginal zone lymphoma (from lymphoid tissue associated with mucosal (MALT), nodular and splenic type), hairy cell leukemia, diffuse large B-cell lymphoma, Burkitt's lymphoma, plasmacytoma, plasma cell myeloma, post-transplant lymphoproliferative disorder, Waldenström's macroglobulinemia and anaplastic large cell lymphoma (ALCL). The cancer may be a cancer that expresses CD123 (“CD123-expressing cancer”).

[0073] The terms “cancer cell,” “tumor cell,” and grammatical equivalents refer to the general population of cells isolated from a tumor or precancerous lesion, including both non-tumor-forming cells, which form the bulk of the tumor cell population, and tumor-forming stem cells (cancer stem cells). cells). As used herein, the term “tumor cell” will be modified by the term “non-tumor cell” when used to refer only to tumor cells that do not have the ability to renew and differentiate, to distinguish such tumor cells from cancer stem cells.

[0074] “Refractory” cancer is cancer that progresses despite the cancer patient receiving anticancer treatment, such as chemotherapy. An example of a refractory cancer is platinum refractory.

[0075] “Recurrent” is a cancer in which the cancer or signs and symptoms of cancer return after a period of improvement.

[0076] "Complete response" or "complete remission" or "CR" indicates the disappearance of all signs of a tumor or cancer in response to treatment. This does not always mean curing cancer. “CV” refers to morphologically complete remissions with incomplete hematological (by blood test) recovery. “PVMOZ-” refers to complete recovery without measurable evidence of residual disease.

[0077] "RCC" or "complete clinical remission" indicates no evidence of disease with some skin changes not indicative of active disease. “CR with partial hematologic recovery” or “PRh” refers to hematologic recovery, which is defined as the patient showing no evidence of leukemia, but one or more blood parameters (eg, platelets and neutrophils) do not return to normal levels (eg, absolute neutrophil count ( ANC) more than 500/µl and platelet count more than 50,000/µl).

[0078] "Partial response" or "PR" refers to a decrease in the size or volume of one or more tumors or lesions, or the spread of cancer in the body, in response to treatment.

[0079] “Progressive disease” refers to the appearance of one [or] more new lesions or tumors and/or definite progression of existing non-target lesions. Progressive disease may also refer to tumor growth of more than 20% since the start of treatment, as a result of an increase in tumor mass or spread.

[0080] The term “antibody” means an immunoglobulin molecule that recognizes and specifically binds to a target, such as a protein, polypeptide, peptide, carbohydrate, polynucleotide, lipid, or combinations thereof, through at least one antigen recognition site in the variable region of the immunoglobulin molecule. As used herein, the term “antibody” includes intact polyclonal antibodies, intact monoclonal antibodies, chimeric antibodies, humanized antibodies, human antibodies, antibody-containing fusion proteins, and any other modified immunoglobulin molecule, provided that the antibodies exhibit the desired biological activity. An antibody can be classified into any of the five major classes of immunoglobulins: IgA, IgD, IgE, IgG and IgM, or their subclasses (isotypes) (for example, IgG1, IgG2, IgG3, IgG4, IgA1 and IgA2), based on the identity of their constant domains heavy chain, designated alpha, delta, epsilon, gamma and mu, respectively. Different classes of immunoglobulins have different and well-known subunit structures and three-dimensional configurations. Antibodies can be “naked” or conjugated to other molecules such as toxins, radioisotopes, etc.

[0081] The term "antibody fragment" refers to a portion of an intact antibody with sufficient positive charge to bind to the cation exchange resin. "Antigen-binding fragment" refers to the portion of an intact antibody that binds to an antigen and has a sufficient positive charge to bind to the cation exchange resin. The antigen-binding fragment may comprise antigen-determining variable regions of an intact antibody. Examples of antibody fragments include, but are not limited to, Fab, Fab', F(ab')2 and Fv fragments, linear antibodies and single chain antibodies.

[0082] The term “cysteine-modified” antibody or antigen-binding fragment thereof includes an antibody or antigen-binding fragment thereof with at least one cysteine (“Cys”) that is not typically present at a given light chain or heavy chain residue of the antibody or antigen-binding fragment thereof. Such Cys, which may also be referred to as “modified Cys,” may be modified using any conventional molecular biology or recombinant technology (eg, by replacing the coding sequence of a non-cysteine residue at the target residue position with a Cys coding sequence). For example, if the original residue is Ser with the coding sequence 5'-UCU-3', then the coding sequence can be mutated (eg, by site-directed mutagenesis) to 5'-UGU-3', which encodes Cys. In certain embodiments, the Cys-modified antibody or antigen-binding fragment thereof has a Cys-modified heavy chain. In certain embodiments, the modified Cys is located in or near the CH3 domain of the heavy chain. In certain embodiments, the modified Cys is located at residue 442 of the heavy chain (EU/OU numbering; EU index, Kabat et al, Sequences of Proteins of Immunological Interest, 5th Ed., NTH publication No. 91-3242, 1991, contents which is incorporated herein by reference in its entirety). In certain embodiments, the Fc region contains a cysteine at one or more of positions 239, 282, 289, 297, 312, 324, 330, 335, 337, 339, 356, 359, 361, 383, 384, 398, 400, 440 , 422 and 442, in accordance with the EU index numbering. In certain embodiments, any one or more of the following residues may be replaced with a cysteine: V205 (Kabat numbering) light chain; A118 (EU numbering) heavy chain; and S400 (EU numbering) heavy chain Fc region. In certain embodiments, the light chain variable domain, for example, scFv, has a cysteine at position 100 of Kabat. In certain embodiments, the heavy chain variable domain, for example, scFv, has a cysteine at Kabat position 44. Cysteine-modified antibodies can be prepared as described, for example, in US Pat. No. 7,521,541, US Pat. No. 7,855,275, US Pub. Application No. 20110033378, and WO 2011/005481.

[0083] A “monoclonal” antibody or antigen-binding fragment thereof refers to a homogeneous population of antibody or antigen-binding fragment involved in highly specific recognition and binding of a single antigenic determinant or epitope. This distinguishes them from polyclonal antibodies, which typically comprise different antibodies directed against different antigenic determinants. The term “monoclonal” antibody or antigen-binding fragment thereof covers both intact and full-length monoclonal antibodies, as well as antibody fragments (such as Fab, Fab', F(ab')2, Fv), single chain (scFv) mutants, fusion proteins, containing an antibody site and any other modified immunoglobulin molecule containing an antigen recognition site. In addition, a “monoclonal” antibody or antigen binding fragment thereof refers to antibodies and antigen binding fragments thereof produced by any means, including, but not limited to, hybridoma, phage selection, recombinant expression and transgenic animals.

[0084] The term “humanized” antibody or antigen-binding fragment thereof refers to forms of non-human (eg, murine) antibodies or antigen-binding fragments that are specific immunoglobulin chains, chimeric immunoglobulins, or fragments thereof containing minimal non-human (eg, murine) sequences. Typically, humanized antibodies or antigen binding fragments thereof are human immunoglobulins in which residues from a complementarity determining region (CDR) are replaced by residues from a CDR from a non-human species (eg, mouse, rat, rabbit, hamster) that have the desired specificity, affinity and potency (“CDR grafting”) (Jones et al., Nature 321:522-525 (1986); Riechmann et al., Nature 332:323-327 (1988); Verhoeyen et al., Science 239:1534–1536 (1988)). In some cases, framework region (FR) residues of a human immunoglobulin Fv are replaced with corresponding residues in an antibody or fragment from a non-human species that have the desired specificity, affinity and potency. The humanized antibody or antigen binding fragment thereof may be further modified by substituting additional residues within the Fv framework region and/or among the substituted non-human residues to improve and optimize the specificity, affinity and/or ability of the antibody or antigen binding fragment thereof. In general, a humanized antibody or antigen binding fragment thereof will comprise substantially all of at least one, and typically two or three, variable domains containing all or substantially all of the CDR regions that correspond to a non-human immunoglobulin, while all or essentially all FR regions refer to the human immunoglobulin consensus sequence. The humanized antibody or antigen binding fragment thereof may also comprise at least a portion of an immunoglobulin constant region or domain (Fc), typically a human immunoglobulin. Examples of methods used to produce humanized antibodies are described in US Pat. No. 5,225,539; Roguska et al., Proc. Natl. Acad. Sci., USA, 91(3):969-973 (1994), and Roguska et al., Protein Eng. 9(10):895-904 (1996). In some embodiments, a “humanized antibody” is a surface-modified antibody.

[0085] An antibody "variable region" refers to an antibody light chain variable region or an antibody heavy chain variable region, alone or in combination. The heavy and light chain variable regions each consist of four framework regions (FRs) connected by three complementarity determining regions (CDRs), also known as hypervariable regions. CDRs on each chain are held a short distance apart by FR and, together with CDRs from the other chain, participate in the formation of the antigen-binding site of antibodies. There are at least two methods for determining CDRs: (1) an approach based on interspecies sequence variation (i.e., Kabat et al., Sequences of Proteins of Immunological Interest (5th ed., 1991, National Institutes of Health, Bethesda Md. .), "Kabat"); and (2) an approach based on crystallographic studies of antigen-antibody complexes (Alazikani et al, J. Molec. Biol. 273:927-948 (1997)). In addition, combinations of these two approaches are sometimes used in the art to determine CDR.

[0086] The Kabat numbering system is commonly used when describing a residue in a variable domain (approximately light chain residues 1-107 and heavy chain residues 1-113) (e.g., Kabat et al., Sequences of Immunological Interest (5th Ed., 1991, National Institutes of Health, Bethesda, Md.) (“Kabat”).

[0087] Kabat amino acid position numbering refers to the numbering system used for heavy chain variable domains or light chain variable domains of antibody arrays in Kabat et al. (Sequences of Immunological Interest. (5th Ed., 1991, National Institutes of Health, Bethesda, Md.), "Kabat"). When using this numbering system, the actual linear amino acid sequence may contain fewer or additional amino acids corresponding to the shortening, or insertion, into the FR or CDR of the variable domain. For example, a heavy chain variable domain may include an insertion of a single amino acid (residue 52a according to Kabat) after residue 52 of H2 and inserted residues (e.g., residues 82a, 82b and 82c, etc. according to Kabat) after residue 82 of FR heavy chains. Kabat residue numbering can be determined for a given antibody by aligning homologous regions of the antibody sequence with the Kabat numbered “standard” sequence. In contrast, Chothia indicates the position of structural loops (Chothia and Lesk, J. Mol. Biol. 196:901-917 (1987)). The end of the Chotia loop CDR-H1, when numbered using the Kabat numbering system, is located in the region between H32 and H34 depending on the length of the loop (this is because the Kabat numbering scheme places insertions at positions H35A and H35B; and if neither 35A , nor 35B is present, then the loop ends at position 32; if only 35A is present, the loop ends at position 33; and if both 35A and 35B are present, then the loop ends at position 34). AbM hypervariable regions represent a compromise between Kabat's CDRs and Chotia's structural loops, and are used in Oxford Molecular's AbM antibody modeling application.

A loop Kabat AbM Chotia L1 L24-L34 L24-L34 L24-L34 L2 L50-L56 L50-L56 L50-L56 L3 L89-L97 L89-L97 L89-L97 H1 H31-H35B H26-H35B H26-H32..34 (numbering according to Kabat) H1 H31-H35 H26-H35 H26-H32 (numbered according to Chotia) H2 H50-H65 H50-H58 H52-H56 H3 H95-H102 H95-H102 H95-H102

[0088] The term “human” antibody or antigen binding fragment thereof means an antibody or antigen binding fragment thereof produced by a human, or an antibody or antigen binding fragment thereof having an amino acid sequence corresponding to an antibody or antigen binding fragment thereof produced by a human, produced using any technique known specialists. This definition of a human antibody or antigen-binding fragment thereof includes intact or full-length antibodies and fragments thereof.

[0089] The term “chimeric” antibodies or antigen-binding fragments thereof refers to antibodies or antigen-binding fragments thereof whose amino acid sequence is derived from two or more species. Typically, the variable region of both the light and heavy chains corresponds to the variable region of antibodies or antigen-binding fragments thereof obtained from a single mammalian species (eg, mouse, rat, rabbit, etc.) with the desired specificity, affinity and ability, while as constant regions are homologous to sequences of antibodies or antigen-binding fragments thereof obtained from another [species] (usually humans), in order to avoid the occurrence of an immune response in that species.

[0090] The terms “epitope” or “antigenic determinant” are used interchangeably herein and refer to the portion of an antigen that is capable of being recognized and specifically bound by a particular antibody. When the antigen is a polypeptide, epitopes can be formed from either a contiguous sequence of amino acids or from non-contiguous amino acids brought together during tertiary folding of the protein. Epitopes formed from a contiguous sequence of amino acids are typically retained upon protein denaturation, whereas epitopes formed by tertiary folding are typically lost upon protein denaturation. An epitope typically includes at least 3, and more often at least 5 or 8-10 amino acids in a unique spatial conformation.

[0091] “Binding affinity” generally refers to the strength of the generalized non-covalent interactions between a particular binding site of a molecule (eg, an antibody) and its binding partner (eg, an antigen). Unless otherwise specified, as used herein, “binding affinity” refers to the characteristic binding affinity that reflects the 1:1 interaction between members of a binding pair (eg, antibody and antigen). The affinity of a molecule X for its partner Y can be generally represented by the dissociation constant (Kd). Affinity can be measured by conventional methods known in the art, including those described herein. Low-affinity antibodies typically bind antigen slowly and dissociate easily, while high-affinity antibodies typically bind antigen more quickly and remain bound longer. Various methods for measuring binding affinity are known in the art, and any of them can be used for the purposes of this invention. Specific illustrative embodiments are described below.

[0092] “Or better,” when used in relation to binding affinity, refers to a stronger bond between a molecule and its binding partner. “Or better,” as used herein, refers to stronger binding, represented by a lower Kd numerical value. For example, [if] an antibody has an affinity for an antigen of “0.6 nM or better,” [then] the affinity of the antibody for an antigen is <0.6 nM, i.e. 0.59 nM, 0.58 nM, 0.57 nM, etc., or any value less than 0.6 nM.

[0093] “Specifically binds” generally means that an antibody binds to an epitope through its antigen binding domain, and that said binding involves some degree of complementarity between the antigen binding domain and the epitope. According to this definition, an antibody is said to “specifically bind” to an epitope when it binds to that epitope through its antigen binding domain more readily than it would bind to a random unrelated epitope. The term "specificity" is used herein to define the relative affinity with which a particular antibody binds to a particular epitope. For example, antibody "A" may be thought to have higher specificity for a given epitope than antibody "B", or antibody "A" may be thought to bind to epitope "C" with higher specificity than to the related epitope "D" "

[0094] “Preferably binds” means that an antibody specifically binds to a certain epitope more readily than it would bind to a related similar, homologous, or similar epitope. Thus, an antibody that "preferentially binds" to a given epitope will be more likely to bind to that epitope than to a related epitope, even though such antibody may cross-react with the related epitope.

[0095] The terms "polypeptide", "peptide" and "protein" are used interchangeably herein to refer to amino acid polymers of any length. Said polymer may be linear or branched, it may contain modified amino acids, and it may contain non-amino acid units. These terms also include an amino acid polymer that has been modified naturally or by intervention; for example, by formation of a disulfide bond, glycosylation, lipidation, acetylation, phosphorylation, or any other manipulation or modification, such as conjugation to a tag moiety. These definitions also include, for example, polypeptides containing one or more amino acid analogues (including, for example, unnatural amino acids, etc.), as well as other modifications known in the art. It is understood that since the polypeptides of this invention are antibody based, in certain embodiments the polypeptides may exist as single chains or associated chains.

[0096] The term "immunoconjugate" or "conjugate", as used herein, refers to a compound or derivative thereof that is associated with a cell binding agent (i.e., an anti-CD123 antibody or fragment thereof) and is defined by the general formula: C-A, where C = cytotoxin (eg, such as an indoline benzodiazepine (IGN) DNA alkylator (eg, DGN549-C)), and A = antibody or antigen binding fragment thereof, eg, anti-CD123 antibody or antibody fragment. An immunoconjugate may optionally contain a linker and be defined by the general formula C-L-A, where C = cytotoxin, L = linker and A = antibody or antigen binding fragment thereof, for example, anti-CD123 antibody or antibody fragment. Immunoconjugates can also be defined by a general formula written in reverse order: C-A or A-L-C. Immunoconjugates may also contain multiple cytotoxins (C) per antibody or antigen binding fragment (A), or multiple cytotoxins (C) and linkers (L) per antibody or antigen binding fragment (A).

[0097] A “linker” is any chemical moiety capable of linking a compound, typically a drug (such as IGN DNA alkylators), to a cell binding agent (such as an anti-CD123 antibody or fragment thereof) in a stable covalent manner. Linkers may be sensitive or substantially resistant to acid cleavage, light-induced cleavage, peptidase-induced cleavage, esterase-induced cleavage, and disulfide bond cleavage, under conditions under which the compound or antibody remains active. Suitable linkers are well known in the art and include, for example, disulfide groups, thioester groups, acid-labile groups, photolabile groups, peptidase-labile groups and esterase-labile groups. Linkers also include charged linkers, and hydrophilic forms thereof, as described herein and known in the art. In some embodiments disclosed herein, the linker is a peptide linker.

[0098] The phrase "pharmaceutically acceptable" indicates that the substance or composition must be compatible chemically and/or toxicologically with the other ingredients constituting the composition and/or the mammal being treated with it.

[0099] The term "pharmaceutical composition" refers to a preparation that is in a form that provides effective biological activity of the active ingredient and which does not contain additional components that are unacceptably toxic to the subject to whom the composition will be administered. The composition may be sterile.

[0100] An "effective amount" of an antibody, immunoconjugate, or other drug disclosed herein is an amount sufficient to achieve a specifically stated purpose. "Effective amount" may be determined empirically and in the normal manner with respect to the stated purpose.

[0101] The term "eligible AML" as used herein refers to a subject with AML suitable for intensive care. Indicators for determining a subject with eligible AML include, for example, physical performance (eg, according to the Eastern Cooperative Oncology Group Performance Status (ECOG PS) definition, Kamofsky Performance Status (KPS), and the Short Physical Performance Test Battery (SPPB), comorbidities (defined by Charlson Comorbidity Index (CCI) or Hematopoietic Stem Cell Transplantation (HSCT) Comorbidity Index), cognitive function, and prognostic models (including, but not limited to, cytogenetic group, age, white blood cell count) cells, LDH, AML type). In some cases, the subject with eligible AML is a subject who is 60 years of age or under 60 years of age.

[0102] The term "unfit AML" as used herein refers to a subject having AML unsuitable for intensive care. Indicators for determining a subject with ineligible AML include, for example, physical performance (eg, according to the Eastern Cooperative Oncology Group performance status (ECOG PS), Kamofsky performance status (KPS), and the Short Physical Performance Battery (SPPB) ), comorbidities (defined by the Charlson Comorbidity Index (CCI) or hematopoietic stem cell transplantation (HSCT) comorbidity index), cognitive function, and prognostic models (including, but not limited to, cytogenetic group, age, white blood cell count, LDH, AML type ). In some cases, the subject with unsuitable AML is a subject over 60 years of age.

[0103] The term “therapeutically effective amount” refers to an amount of an antibody, immunoconjugate, or other drug effective to “treat” a disease or disorder in a subject or mammal. In the case of cancer, a therapeutically effective amount of a drug can reduce the number of cancer cells; reduce tumor size or burden; inhibit (ie, slow to some extent and, in a certain embodiment, stop) the infiltration of cancer cells into peripheral organs; relieve to some extent one or more symptoms associated with cancer; and/or lead to a favorable response such as complete remission (CR), complete remission with partial recovery (CR); PR without minimal residual disease (PRMR-); complete clinical remission (CCR); state without morphological leukemia; partial remission (PR); and reduction of progressive disease (PD). See the definition of “treatment” provided in this document. To the extent that a drug can prevent the growth and/or destroy existing cancer cells, it may be cytostatic and/or cytotoxic. “Prophylactically effective amount” refers to an amount effective at the dosages and for periods of time necessary to achieve the desired prophylactic result. Typically, but not necessarily, since the prophylactic dose is used in subjects before or early in the disease process, the prophylactically effective amount will be less than the therapeutically effective amount.

[0104] The term “respond favorably” generally refers to creating a favorable state in a subject. In relation to the treatment of cancer, the term refers to providing a therapeutic effect to a subject. Beneficial therapeutic effects in cancer can be measured in a number of ways (see, W. A. Weber, J. Nucl. Med. 50:1S-10S (2009)). A favorable response can be assessed, for example, as complete remission (CR), complete remission with partial recovery (CR); PR without minimal residual disease (PRMR-); complete clinical remission (CCR); state without morphological leukemia; partial remission (PR); reduction of progressive disease (PD), or any combination thereof.

[0105] The terms "IL-3Rα", "interleukin-3 receptor alpha" and "CD123", used interchangeably herein, refer to mammalian CD123 polypeptides, including, without limitation, native CD123 polypeptides and isoforms of CD123 polypeptides unless otherwise specified other. The terms include "full-length", unprocessed CD123 polypeptides, as well as any form of CD123 polypeptide resulting from cellular processing. The term also covers naturally occurring variants of CD123, such as those encoded by splice variants and allelic variants. The CD123 polypeptides described herein can be isolated from various sources, such as human tissue types or other sources, or obtained by recombination or synthesis methods. Where specifically indicated, "CD123" may be used to refer to a nucleic acid encoding a CD123 polypeptide. Human CD123 sequences are known and include, for example, those associated with National Center for Biotechnology Information (NCBI) accession numbers NP_002174 and NM_002183 (human CD123 protein and nucleic acid sequences, variant 1), and NP_001254642 and NM_001267713 (human CD123 protein and nucleic acid sequences , option 2). As used herein, the term “human CD123” refers to CD123 containing the sequence SEQ ID NO: 11 or SEQ ID NO: 12.

1 MVLLWLTLLL IALPCLLQTK EDPNPPITNL RMKAKAQQLT WDLNRNVTDI ECVKDADYSM

61 PAVNNSYCQF GAISLCEVTN YTVRVANPPF STWILFPENS GKPWAGAENL TCWIHDVDFL

121 SCSWAVGPGA PADVQYDLYL NVANRRQQYE CLHYKTDAQG TRIGCRFDDI SRLSSGSQSS

181 HILVRGRSAA FGIPCTDKFV VFSQIEILTP PNMTAKCNKT HSFMHWKMRS HFNRKFRYEL

241 QIQKRMQPVI TEQVRDRTSF QLLNPGTYTV QIRARERVYE FLSAWSTPQR FECDQEEGAN

301 TRAWRTSLLI ALGTLLALVC VFVICRRYLV MQRLFPRIPH MKDPIGDSFQ NDKLWWEAG

361 KAGLEECLVT EVQWQKT (SEQ ID NO: 11)

1 MVLLWLTLLL IALPCLLQTK EGGKPWAGAE NLTCWIHDVD FLSCSWAVGP GAPADVQYDL

61 YLNVANRRQQ YECLHYKTDA QGTRIGCRFD DISRLSSGSQ SSHILVRGRS AAFGIPCTDK

121 FVVFSQIEIL TPPNMTAKCN KTHSFMHWKM RSHFNRKFRY ELQIQKRMQP VITEQVRDRT

181 SFQLLNPGTY TVQIRARERV YEFLSAWSTP QRFECDQEEG ANTRAWRTSL LIALGTLLAL

241 VCVFVICRRY LVMQRLFPRI PHMKDPIGDS FQNDKLVVWE AGKAGLEECL VTEVQVVQKT

(SEQ ID NO:12)

[0106] The term "anti-CD123 antibody" or "antibody that binds CD123" refers to an antibody capable of binding CD123 with sufficient affinity such that the antibody is useful as a diagnostic and/or therapeutic agent when targeting CD123 (eg antibody in IMGN632). The extent of binding of an anti-CD123 antibody to an unrelated non-CD123 protein may be less than about 10% of the binding of the antibody to CD123 as measured, for example, by radioimmunoassay (RIA).

[0107] The term "IMGN632" refers to the immunoconjugate composition depicted in FIG. 6A and 6B. The immunoconjugate composition contains immunoconjugates containing an average of 1.5 to 2.1 DGN549-C cytotoxic agents per huCD123-6Gv4.7 (“G4723A”) antibody in the sulfonated form (Figure 6A). The immunoconjugate composition may also contain a non-sulfonated immunoconjugate (monoimine structure depicted in Fig. 6B).

[0108] As used in this specification and claims, the singular forms include the plural forms unless clearly inconsistent with the context.

[0109] It should be understood that where embodiments are described herein using the term “comprising”, it is also intended to include otherwise similar embodiments described using the language “consisting of” and/or “consisting essentially of "

[0110] It is intended that the term “and/or” when used in a phrase such as “A and/or B” herein shall include both “A and B” and “A or B”, “A” and "B". Likewise, the term “and/or” when used in a phrase such as “A, B and/or C” shall cover each of the following embodiments: A, B and C; A, B or C; A or C; A or B; B or C; A and C; A and B; B and C; A (only); B (only); and C (only).

Anti-CD123 immunoconjugates

[0111] The methods described herein provide methods for administering immunoconjugates that specifically bind to CD123. Such agents are referred to herein as “CD123 immunoconjugates” or “anti-CD123 immunoconjugates.” Such immunoconjugates contain an anti-CD123 antibody or an antigen-binding fragment thereof and a drug (eg, a cytotoxic agent). A drug (eg, a cytotoxic agent) can be attached to the anti-CD123 antibody or antigen binding fragment thereof via a linker.

[0112] In some embodiments, the anti-CD123 antibodies or antigen binding fragments thereof are humanized antibodies or antigen binding fragments thereof. In some embodiments, the humanized antibody or fragment is a surface-edited antibody or an antigen-binding fragment thereof. In other embodiments, the antibodies or antigen binding fragments thereof are a fully human antibody or antigen binding fragment thereof.

[0113] In one embodiment, provided herein is an immunoconjugate represented by the following formula:

wherein CBA is an anti-CD123 antibody or antigen binding fragment or polypeptide covalently linked to CyC1 through a cysteine residue; and WC is 1 or 2.

[0114] In the above formula, CyC1 is represented by the following formulas:

or

or a pharmaceutically acceptable salt thereof, wherein the double line between N and C represents a single bond or a double bond, with the proviso that when it is a double bond, X is absent and Y is -H or (C1-C4)-alkyl; and when it is a single bond, X is -H or an amino protecting moiety, Y is -OH or -SO3M, and M is H+ or a cation;

R5 represents -H or (C1-C3)-alkyl;

P represents an amino acid residue or a peptide containing 2-20 amino acid residues;

Ra and Rb, in each case, independently represent -H, (C1-C3)-alkyl, or a charged substituent or ionizable group Q;

W' represents -NRe',

Re' represents -(CH2-CH2-O)n-Rk;

n denotes an integer from 2 to 6;

Rk is -H or -Me;

Rx3 is (C1-C6)-alkyl; And

Lc represents , s1 represents the site covalently linked to CBA, and s2 represents the site covalently linked to the -C(=O) group of CyC1; Where:

R19 and R20 are, in each case, independently -H or (C1-C3)-alkyl;

m” denotes an integer from 1 to 10; And

Rh represents -H or (C1-C3)-alkyl.

[0115] In certain embodiments, Ra and Rb are both H; and R5 is H or Me.

[0116] In certain embodiments, P is a peptide containing 2-5 amino acid residues. For example, P may be selected from Gly-Gly-Gly, Ala-Val, Val-Ala, Val-Cit, Val-Lys, Phe-Lys, Lys-Lys, Ala-Lys, Phe-Cit, Leu-Cit, Ile -Cit, Trp, Cit, Phe-Ala, Phe-N9-tosyl-Arg, Phe-N9-nitro-Arg, Phe-Phe-Lys, D-Phe-Phe-Lys, Gly-Phe-Lys, Leu-Ala -Leu, Ile-Ala-Leu, Val-Ala-Val, Ala-Leu-Ala-Leu, β-Ala-Leu-Ala-Leu, Gly-Phe-Leu-Gly, Val-Arg, Arg-Val, Arg -Arg, Val-D-Cit, Val-D-Lys, Val-D-Arg, D-Val-Cit, D-Val-Lys, D-Val-Arg, D-Val-D-Cit, D-Val -D-Lys, D-Val-D-Arg, D-Arg-D-Arg, Ala-Ala, Ala-D-Ala, D-Ala-Ala, D-Ala-D-Ala, Ala-Met and Met -Ala. In certain embodiments, P is Gly-Gly-Gly, Ala-Val, Ala-Ala, Ala-D-Ala, D-Ala-Ala, or D-Ala-D-Ala. In certain embodiments, Q is -SO3M

[0117] In certain embodiments, R19 and R20 are both H; and m” denotes an integer from 1 to 6.

[0118] In certain embodiments, -LC- is represented by the following formula:

[0119] In certain embodiments, the immunoconjugate is represented by the following formulas:

or

or pharmaceutically acceptable salts thereof, wherein the double line between N and C denotes a single bond or a double bond, provided that when it denotes a double bond, X is absent and Y is -H, and when it denotes a single bond, X is -H and Y is -OH or -SO3M.

[0120] As an example, an anti-CD123 antibody or antigen binding fragment thereof may be present in an immunoconjugate used in the methods of this invention. Anti-CD123 antibodies or antigen binding fragments thereof have been described (see, for example, US Patent No. 10077313 B2, the contents of which are incorporated herein by reference in their entirety). The anti-CD123 antibody or antigen binding fragment thereof may be the huCD123-6Gv4.7 (“G4723A”) antibody (see WO 2017/004025, WO 2017/004026 and PCT/US2018/052212, the contents of each of which are incorporated herein by references in their entirety) or may contain antibody sequences G4723A, for example, as listed below in Tables 1-3. For example, an anti-CD123 antibody or antigen binding fragment thereof for use in the methods provided herein may comprise heavy chain variable region CDR-1, CDR-2 and CDR-3 comprising the sequences SEQ ID NOs: 5, 6 and 7. respectively, and/or CDR-1, CDR-2 and CDR-3 of the light chain variable region comprising the sequences of SEQ ID NO: 8, 9 and 10, respectively. An anti-CD123 antibody or antigen binding fragment thereof for use in the methods provided herein may comprise a heavy chain variable region domain containing the sequence set forth in SEQ ID NO: 1. An anti-CD123 antibody or antigen binding fragment thereof for use in the methods provided herein herein may comprise a light chain variable region domain containing the sequence set forth in SEQ ID NO:2. An anti-CD123 antibody or antigen binding fragment thereof for use in the methods provided herein may comprise a heavy chain variable domain containing the sequence set forth in SEQ ID NO: 1 and a light chain variable domain containing the sequence set forth in SEQ ID NO:2. An anti-CD123 antibody or antigen binding fragment thereof for use in the methods provided herein may comprise a heavy chain comprising the sequence set forth in SEQ ID NO:3. An anti-CD123 antibody or antigen binding fragment thereof for use in the methods provided herein may comprise a light chain comprising the sequence set forth in SEQ ID NO:4. An anti-CD123 antibody or antigen binding fragment thereof for use in the methods provided herein may comprise a heavy chain comprising the sequence set forth in SEQ ID NO:3 and a light chain containing the sequence set forth in SEQ ID NO:4.

Table 1. Variable regions of the heavy and light chains of huCD123-6Gv4.7

Name Subsequence Heavy chain variable region huCD123-6Gv7 Light chain variable region huCD123-6Gv4
(SEQ ID NO:2)

Table 2. Full-length heavy and light chains of huCD123-6Gv4.7-C442

Name Subsequence Full length heavy chain huCD123-6Gv7-C442
Full length light chain huCD123-6Gv4

Table 3. Complementarity determining regions of the variable regions of the heavy and light chains of huCD123-6Gv4.7

Name Subsequence Heavy chain variable region CDR1 huCD123-6Gv7 SSIMH (SEQ ID NO:5) CDR2 heavy chain variable region huCD123-6Gv7 YIKPYNDGTKYNEKFKG (SEQ ID NO:6) CDR3 heavy chain variable region huCD123-6Gv7 EGGNDYYDTMDY (SEQ ID NO: 7) CDR1 light chain variable region huCD123-6Gv4 RASQDINSYLS (SEQ ID NO: 8) CDR2 light chain variable region huCD123-6Gv4 RVNRLVD (SEQ ID NO:9) CDR3 light chain variable region huCD123-6Gv4 LQYDAFPYT (SEQ ID NO: 10)

[0121] An anti-CD123 antibody or antigen binding fragment thereof for use in the methods provided herein can bind to an epitope within amino acids 205-346 of human CD123.

[0122] An anti-CD123 antibody or antigen binding fragment thereof for use in the methods provided herein can be produced by recombinant methods. For example, an anti-CD123 antibody or antigen binding fragment thereof for use in the methods provided herein can be produced in a mammalian cell line, such as Chinese hamster ovary (CHO) cells.

[0123] An anti-CD123 antibody or antigen binding fragment thereof for use in the methods provided herein may be a cysteine-modified antibody or fragment. Cysteine-modified antibodies can be covalently conjugated to cytotoxic agents of interest to form immunoconjugates.

[0124] As used herein, the expression “associated with a cell binding agent” or “associated with an anti-CD123 antibody or fragment” refers to a conjugate molecule containing at least one cytotoxic agent associated with a cell binding agent, for example , anti-CD123 antibody or fragment, by means of a suitable linking group or a precursor thereof. Linkers include, for example, peptide linkers.

[0125] An immunoconjugate may contain multiple cytotoxic agents bound to an antibody or antigen binding fragment thereof. As provided herein, in certain cases, from about 1 to about 3 drug molecules, such as cytotoxic agents, are associated with an anti-CD123 antibody or antigen binding fragment thereof. In one aspect, the immunoconjugate contains 1, 2 or 3 cytotoxic agents per antibody or antigen binding fragment thereof.

[0126] A composition containing immunoconjugates may contain immunoconjugates with varying amounts of bound cytotoxic agents per antibody or antigen binding fragment thereof. Thus, compositions containing immunoconjugates may contain an average number of bound cytotoxic agents per antibody or antigen-binding fragment thereof. In one aspect, a pharmaceutical composition comprising anti-CD123 immunoconjugates contains from about 1 to about 3 cytotoxic agents per anti-CD123 antibody or antigen-binding fragment thereof, from about 1.5 to about 2.5 cytotoxic agents per anti-CD123 antibody, or an antigen binding fragment thereof, from about 1.5 to about 2.1 cytotoxic agents per anti-CD123 antibody or antigen binding fragment thereof, or from about 1.5 to about 2.0 cytotoxic agents per anti-CD123 antibody or antigen binding fragment thereof.

[0127] In some cases, the pharmaceutical composition for use in the methods provided herein contains anti-CD123 immunoconjugates containing from about 1 to about 3 cytotoxic agents per antibody or antigen-binding fragment thereof, for example, in which the average number of cytotoxic agents per the antibody or antigen binding fragment thereof is from about 1 to about 3 (e.g., 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8 , 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0).

[0128] In some cases, the pharmaceutical composition for use in the methods provided herein contains anti-CD123 immunoconjugates containing an average of about 1 ± 0.2, about 1.1 ± 0.2, about 1.2 ± 0 ,2, approximately 1.3 ± 0.2, approximately 1.4 ± 0.2, approximately 1.5 ± 0.2, approximately 1.6 ± 0.2, approximately 1.7 ± 0.2, approximately 1 .8 ± 0.2, approximately 1.9 ± 0.2, approximately 2.0 ± 0.2, approximately 2.1 ± 0.2, 2.2 ± 0.2, 2.3 ± 0.2, 2.4 ± 0.2, 2.5 ± 0.2, or 2.6 ± 0.2 attached drug molecules (eg, cytotoxic agents) per antibody or antigen-binding fragment. In certain aspects, the pharmaceutical composition provided herein comprises anti-CD123 immunoconjugates containing an average of about 1.5 to 2.1 drug molecules (eg, cytotoxic agents) per antibody.

[0129] Antibodies or antigen-binding fragments thereof for use in this invention can be linked to cytotoxic agents, for example, by linkage to a Lys side chain amino group, a Cys side chain thiol group, or an oxidized Ser/Thr N-terminus. Cytotoxic agents include, for example, DNA alkylating agents such as indolinobenzodiazepine (IGN) DNA alkylating agents. In some cases, the anti-CD123 immunoconjugate for use in this invention contains DGN549-C.

Applications and methods

[0130] Anti-CD123 immunoconjugates are useful, for example, in the treatment of hematological malignancies. Accordingly, the present invention relates to a dosing regimen of an anti-CD123 immunoconjugate (eg, IMGN632) to a patient for the treatment of a hematologic malignancy. Treatment may result in a decrease in the number of bone marrow blasts.

[0131] In certain embodiments, the anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, the anti-CD123 immunoconjugate (eg, IMGN632) is administered three times in a three-week cycle, for example, on Day 1, Day 4, and Day 8 of a 21-day cycle.

[0132] In certain embodiments, one cycle of treatment is therapeutically effective. In certain embodiments, two cycles of treatment are therapeutically effective. In certain embodiments, one to four cycles of treatment are therapeutically effective.

[0133] In some embodiments, patients may undergo one three-week (21-day) treatment cycle, for example, in which the immunoconjugate is administered once per three-week cycle or three times per three-week cycle. In some embodiments, patients may undergo at least two three-week (21-day) treatment cycles, for example, in which the immunoconjugate is administered once per three-week cycle or three times per three-week cycle. In some embodiments, patients may undergo at least three three-week (21-day) treatment cycles, for example, in which the immunoconjugate is administered once per three-week cycle or three times per three-week cycle. In some embodiments, patients may undergo at least four three-week (21-day) treatment cycles, for example, in which the immunoconjugate is administered once per three-week cycle or three times per three-week cycle. In some embodiments, patients may undergo at least five three-week (21-day) treatment cycles, for example, in which the immunoconjugate is administered once per three-week cycle or three times per three-week cycle. In some embodiments, patients may undergo at least six three-week (21-day) treatment cycles, for example, in which the immunoconjugate is administered once per three-week cycle or three times per three-week cycle. In some embodiments, patients may undergo at least seven three-week (21-day) treatment cycles, for example, in which the immunoconjugate is administered once per three-week cycle or three times per three-week cycle. In some embodiments, patients may undergo at least eight three-week (21-day) treatment cycles, for example, in which the immunoconjugate is administered once per three-week cycle or three times per three-week cycle. In some embodiments, patients may undergo at least nine three-week (21-day) treatment cycles, for example, in which the immunoconjugate is administered once per three-week cycle or three times per three-week cycle. In some embodiments, patients may undergo at least ten three-week (21-day) treatment cycles, for example, in which the immunoconjugate is administered once per three-week cycle or three times per three-week cycle.

[0134] In some embodiments, patients may undergo one to ten three-week (21-day) treatment cycles, for example, in which the immunoconjugate is administered once per three-week cycle or three times per three-week cycle. In some embodiments, patients may undergo two to ten three-week (21-day) treatment cycles, for example, in which the immunoconjugate is administered once per three-week cycle or three times per three-week cycle. In some embodiments, patients may undergo three to ten three-week (21-day) treatment cycles, for example, in which the immunoconjugate is administered once per three-week cycle or three times per three-week cycle. In some embodiments, patients may undergo four to ten three-week (21-day) treatment cycles, for example, in which the immunoconjugate is administered once per three-week cycle or three times per three-week cycle. In some embodiments, patients may undergo five to ten three-week (21-day) treatment cycles, for example, in which the immunoconjugate is administered once per three-week cycle or three times per three-week cycle.

[0135] In certain embodiments, from about 0.015 mg/kg to about 1.0 mg/kg of the anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle.

[0136] In certain embodiments, from about 0.015 mg/kg to about 0.18 mg/kg of the anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle.

[0137] In certain embodiments, 0.045 mg/kg to 0.18 mg/kg of anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle.

[0138] In certain embodiments, from about 0.045 mg/kg to 0.3 mg/kg of the anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, from about 0.045 mg/kg to less than 0.3 mg/kg of the anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, from at least 0.045 mg/kg to less than 0.3 mg/kg of the anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, 0.045 mg/kg to 0.25 mg/kg of an anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, 0.045 mg/kg to 0.2 mg/kg of anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, 0.045 mg/kg to 0.09 mg/kg of anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle.

[0139] In certain embodiments, from about 0.18 mg/kg to 0.3 mg/kg of the anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, from about 0.18 mg/kg to less than 0.3 mg/kg of the anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, from at least 0.18 mg/kg to less than 0.3 mg/kg of the anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, 0.18 mg/kg to 0.25 mg/kg of anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, 0.18 mg/kg to 0.2 mg/kg of anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle.

[0140] In certain embodiments, about 0.015 mg/kg of anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, about 0.045 mg/kg of the anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, about 0.09 mg/kg of the anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, about 0.135 mg/kg of the anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, about 0.18 mg/kg of the anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, about 0.3 mg/kg of the anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, about 0.45 mg/kg of the anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, approximately 0.67 mg/kg of the anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, about 1.0 mg/kg of anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle.

[0141] In certain embodiments, about 0.19 mg/kg of anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, about 0.2 mg/kg of anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, about 0.21 mg/kg of the anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, about 0.22 mg/kg of the anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, about 0.23 mg/kg of the anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, about 0.24 mg/kg of anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, about 0.25 mg/kg of the anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, approximately 0.26 mg/kg of the anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, approximately 0.27 mg/kg of anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, approximately 0.28 mg/kg of anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle. In certain embodiments, about 0.29 mg/kg of the anti-CD123 immunoconjugate (eg, IMGN632) is administered once per three-week (21-day) cycle.

[0142] In certain embodiments, from about 0.015 mg/kg to about 0.09 mg/kg of anti-CD123 immunoconjugate (e.g., IMGN632) is administered three times in a three-week cycle, for example, on Day 1, Day 4, and Day 8 21 -day cycle. In certain embodiments, from about 0.015 mg/kg to about 0.045 mg/kg of an anti-CD123 immunoconjugate (eg, IMGN632) is administered three times in a three-week cycle, for example, on Day 1, Day 4, and Day 8 of a 21-day cycle. In certain embodiments, from about 0.015 mg/kg to about 0.06 mg/kg of an anti-CD123 immunoconjugate (e.g., IMGN632) is administered three times in a three-week cycle, e.g., on Day 1, Day 4, and Day 8 of a 21-day cycle . In certain embodiments, from about 0.045 mg/kg to about 0.09 mg/kg of an anti-CD123 immunoconjugate (e.g., IMGN632) is administered three times in a three-week cycle, e.g., on Day 1, Day 4, and Day 8 of a 21-day cycle .

[0143] In certain embodiments, about 0.015 mg/kg of anti-CD123 immunoconjugate (eg, IMGN632) is administered three times in a three-week cycle, for example, on Day 1, Day 4, and Day 8 of a 21-day cycle. In certain embodiments, about 0.03 mg/kg of anti-CD123 immunoconjugate (eg, IMGN632) is administered three times in a three-week cycle, for example, on Day 1, Day 4, and Day 8 of a 21-day cycle. In certain embodiments, about 0.045 mg/kg of anti-CD123 immunoconjugate (eg, IMGN632) is administered three times in a three-week cycle, for example, on Day 1, Day 4, and Day 8 of a 21-day cycle. In certain embodiments, about 0.06 mg/kg of anti-CD123 immunoconjugate (eg, IMGN632) is administered three times in a three-week cycle, for example, on Day 1, Day 4, and Day 8 of a 21-day cycle. In certain embodiments, about 0.09 mg/kg of anti-CD123 immunoconjugate (eg, IMGN632) is administered three times in a three-week cycle, for example, on Day 1, Day 4, and Day 8 of a 21-day cycle.

[0144] In certain embodiments, from about 0.015 mg/kg to about 0.135 mg/kg of an anti-CD123 immunoconjugate (e.g., IMGN632) is administered three times in a three-week cycle, for example, on Day 1, Day 4, and Day 8 of a 21-day cycle. In certain embodiments, from about 0.045 mg/kg to about 0.135 mg/kg of the anti-CD123 immunoconjugate (eg, IMGN632) is administered three times in a three-week cycle, for example, on Day 1, Day 4, and Day 8 of a 21-day cycle. In certain embodiments, about 0.135 mg/kg of anti-CD123 immunoconjugate (eg, IMGN632) is administered three times in a three-week cycle, for example, on Day 1, Day 4, and Day 8 of a 21-day cycle.

[0145] In certain embodiments, from about 0.015 mg/kg to about 0.09 mg/kg of an anti-CD123 immunoconjugate (e.g., IMGN632) is administered twice in a three-week cycle, for example, on Day 1 and Day 8 of a 21-day cycle . In certain embodiments, from about 0.015 mg/kg to about 0.045 mg/kg of an anti-CD123 immunoconjugate (eg, IMGN632) is administered twice in a three-week cycle, for example, on Day 1 and Day 8 of a 21-day cycle. In certain embodiments, from about 0.045 mg/kg to about 0.09 mg/kg of anti-CD123 immunoconjugate (eg, IMGN632) is administered twice in a three-week cycle, for example, on Day 1 and Day 8 of a 21-day cycle.

[0146] In certain embodiments, about 0.015 mg/kg of anti-CD123 immunoconjugate (eg, IMGN632) is administered twice in a three-week cycle, for example, on Day 1 and Day 8 of a 21-day cycle. In certain embodiments, about 0.045 mg/kg of anti-CD123 immunoconjugate (eg, IMGN632) is administered twice in a three-week cycle, for example, on Day 1 and Day 8 of a 21-day cycle. In certain embodiments, about 0.09 mg/kg of anti-CD123 immunoconjugate (eg, IMGN632) is administered twice in a three-week cycle, for example, on Day 1 and Day 8 of a 21-day cycle.

[0147] In certain embodiments, from about 0.015 mg/kg to about 0.135 mg/kg of the anti-CD123 immunoconjugate (eg, IMGN632) is administered twice in a three-week cycle, for example, on Day 1 and Day 8 of a 21-day cycle. In certain embodiments, from about 0.045 mg/kg to about 0.135 mg/kg of anti-CD123 immunoconjugate (eg, IMGN632) is administered twice in a three-week cycle, for example, on Day 1 and Day 8 of a 21-day cycle. In certain embodiments, about 0.135 mg/kg of anti-CD123 immunoconjugate (eg, IMGN632) is administered twice in a three-week cycle, for example, on Day 1 and Day 8 of a 21-day cycle.

[0148] The administration regimens provided herein can be used to treat a hematologic malignancy in a human, for example, by a method comprising administering to a subject a therapeutically effective amount of a CD123 binding agent (eg, a subject in need of treatment). In some embodiments, the hematologic malignancy is of myeloid origin. In some embodiments, the hematologic malignancy is lymphoid in origin. In some embodiments, the hematologic malignancy is of both myeloid and lymphoid origin. In certain embodiments, the hematologic malignancy is a B-cell malignancy. In certain embodiments, the hematologic malignancy is a CD123-expressing hematologic malignancy. In certain embodiments, the hematologic malignancy is selected from the group consisting of acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), acute lymphoblastic leukemia (ALL), B-cell acute lymphoblastic leukemia (B-ALL), T-cell acute lymphoblastic leukemia (T ALL), chronic myeloid leukemia in blast crisis/phase (BC-CML) and blast plasmacytoid dendritic cell neoplasm (BPDN).

[0149] In certain embodiments, the hematologic malignancy is a recurrent hematologic malignancy. In certain embodiments, the relapse is a first relapse. In certain embodiments, the hematologic malignancy is a refractory hematologic malignancy. In certain embodiments, the hematologic malignancy is a primary refractory hematologic malignancy.

[0150] In certain embodiments, the hematologic malignancy is AML. In certain embodiments, the AML is relapsed AML. In certain embodiments, the AML is refractory AML. In certain embodiments, the AML is not secondary AML. In certain embodiments, the subject with AML is a pediatric patient.

[0151] In certain embodiments, the hematologic malignancy is PDDN. In certain embodiments, BPDN is recurrent BPDN. In certain embodiments, the BPDN is a refractory BPDN. In certain embodiments, the BPDN is a first-line BPDN. Patients with first-line (1L) PDDN are defined as (i) unsuitable for intensive chemotherapy and/or (ii) unsuitable for other approved CD123-targeted therapies, such as SL-401. In certain embodiments, the subject with PDND is a pediatric patient.

[0152] In certain embodiments, the hematologic malignancy is ALL. In certain embodiments, the ALL is relapsing ALL. In certain embodiments, the ALL is refractory ALL. In certain embodiments, the subject with ALL is a pediatric patient.

[0153] In certain embodiments, the hematologic malignancy is MDS. In certain embodiments, the MDS is a high-risk MDS.

[0154] In certain embodiments, the hematologic malignancy is chronic myelomonocytic leukemia (CMML).

[0155] In certain embodiments, the hematologic malignancy is myelofibrosis (MF).

[0156] In some embodiments, the subject is a pediatric patient. The pediatric patient is less than 18 years of age. In some embodiments, the pediatric patient is at least 2 years of age and less than 18 years of age.

[0157] In some embodiments, the subject has an Eastern Cooperative Oncology Group (ECOG) performance status score of ≤1.

[0158] In some embodiments, the subject has an unfavorable European Leukemia Network (ELN) genetic risk score, such as an ASXL1, RUNX1, and/or FLT3-ITD mutation. In some embodiments, the subject has previously received unsuccessful treatment with SL-401. In some embodiments, the hematologic malignancy is CLAG-M refractory.

[0159] In certain embodiments, the hematologic malignancy is resistant to chemotherapy.

[0160] In certain embodiments, the hematologic malignancy is sensitive to chemotherapy.

[0161] In some embodiments, at least about 80% of the hematologic malignancy cells are CD123+.

[0162] In some embodiments, it is determined prior to administration that at least 80% of the hematologic malignancy cells are CD123+.

[0163] In some cases, the subject has received at least one prior cancer treatment regimen. In some cases, the subject had received one prior cancer treatment regimen. In some cases, the subject had received two prior cancer treatment regimens. In some cases, the subject had received two prior cancer treatment regimens. In some cases, the subject had received no more than six prior cancer treatment regimens. In some cases, the subject had received at least one prior treatment, but no more than six prior cancer treatment regimens. In some cases, the subject had received no more than three prior cancer treatment regimens. In some cases, the subject had received at least one prior treatment, but no more than three prior cancer treatment regimens. In some embodiments, the subject has previously received a stem cell transplant.

[0164] As provided herein, anti-CD123 immunoconjugates can be administered in a pharmaceutical composition. In some cases, the pharmaceutical composition contains anti-CD123 immunoconjugates (eg, IMGN632) and a pharmaceutically acceptable carrier. Accordingly, provided herein are methods of administering pharmaceutical compositions containing anti-CD123 immunoconjugates (eg, IMGN632) having the desired degree of purity in a physiologically acceptable carrier, excipient or stabilizer (Remington's Pharmaceutical Sciences (1990) Mack Publishing Co., Easton, PA ). Acceptable carriers, excipients or stabilizers are nontoxic to recipients at the dosages and concentrations used (see, for example, Gennaro, Remington: The Science and Practice of Pharmacy with Facts and Comparisons: Drugfacts Plus, 20th ed. (2003); Ansel et al. , Pharmaceutical Dosage Forms and Drug Delivery Systems, 7th ed., Lippencott Williams and Wilkins (2004); Kibbe et al., Handbook of Pharmaceutical Excipients, 3rd ed., Pharmaceutical Press (2000)). Said compositions intended for use by in vivo administration may be sterile. This can be easily achieved by filtration through, for example, sterile filtration membranes.

[0165] In some embodiments, patients receiving an anti-CD123 immunoconjugate as disclosed herein are pretreated with a corticosteroid. Accordingly, in some embodiments, the methods provided herein include administering a corticosteroid to a patient prior to administering an anti-CD123 immunoconjugate to the patient. In some cases, the corticosteroid may be selected from the group consisting of prednisone, prednisolone, methylprednisolone, beclamethasone, betamethasone, dexamethasone, fludrocortisone, hydrocortisone and triamcinolone. In some cases, the corticosteroid is given intravenously. In some cases, the steroid is administered orally.

[0166] For example, in some embodiments, patients receiving an anti-CD123 immunoconjugate as disclosed herein are pretreated with diphenhydramine. In some embodiments, patients receiving an anti-CD123 immunoconjugate as disclosed herein are pretreated with 25-50 mg of diphenhydramine. In some embodiments, diphenhydramine is administered intravenously. In some embodiments, diphenhydramine is administered orally. Accordingly, in some embodiments, the methods provided herein include administering diphenhydramine to a patient prior to administering an anti-CD123 immunoconjugate to the patient.

[0167] In some embodiments, patients receiving an anti-CD123 immunoconjugate as disclosed herein are pretreated with acetaminophen. In some embodiments, patients receiving an anti-CD123 immunoconjugate as disclosed herein are pretreated with 325-650 mg of acetaminophen. In some embodiments, acetaminophen is administered intravenously. In some embodiments, acetaminophen is administered orally. Accordingly, in some embodiments, the methods provided herein include administering acetaminophen to a patient prior to administering an anti-CD123 immunoconjugate to the patient.

[0168] In some embodiments, patients receiving an anti-CD123 immunoconjugate as disclosed herein are pretreated with paracetamol. In some embodiments, patients receiving an anti-CD123 immunoconjugate as disclosed herein are pretreated with 325-650 mg of paracetamol. In some embodiments, paracetamol is administered intravenously. In some embodiments, paracetamol is administered orally. Accordingly, in some embodiments, the methods provided herein include administering paracetamol to a patient prior to administering an anti-CD123 immunoconjugate to the patient.

[0169] In some embodiments, patients receiving an anti-CD123 immunoconjugate as disclosed herein are pretreated with dexamethasone. In some embodiments, patients receiving an anti-CD123 immunoconjugate as disclosed herein are pretreated with 8 mg dexamethasone. In some embodiments, dexamethasone is administered intravenously. In some embodiments, dexamethasone is administered orally. Accordingly, in some embodiments, the methods provided herein include administering dexamethasone to a patient prior to administering an anti-CD123 immunoconjugate to the patient.

EXAMPLES

[0170] It is understood that the examples and embodiments described herein are for illustrative purposes only, and that various modifications or variations thereof as may be suggested by those skilled in the art are intended to be included within the spirit and scope of this application. .

Example 1:

Phase 1 clinical trial design

[0171] A multicenter, open-label, phase 1 study of IMGN632 was designed to evaluate the effects of intravenous IMGN632 in adult patients with recurrent or recurrent CD123+ AML and other CD123+ hematologic malignancies. The phase 1 study design is shown in Fig. 1. The study design included a dose escalation phase to determine the maximum tolerated dose (MTD), and then expansion cohorts were treated at MTD. As described in more detail below, the dose escalation phase included two dosing regimens. In Schedule A, IMGN632 was administered intravenously every three weeks (Q3W) on Day 1 of each 21-day cycle. In Schedule B, IMGN632 is administered intravenously two or three times every three weeks, i.e. on Days 1 and 8 of each 21-day cycle or on Days 1, 4 and 7 of each 21-day cycle.

Subjects

[0172] Patients with recurrent or relapsed CD123+ AML or PDDN by cohort are identified based on the following inclusion and exclusion criteria.

Inclusion criteria:

• Patients in dose escalation and all expansion cohorts except first relapse AML could have received up to three prior lines of therapy. Patients with relapsed AML (using the previously established maximum tolerated dose in the expansion population only) had received up to two prior lines of therapy.

• Dose escalation - Relapsed or refractory AML (excluding acute promyelocytic leukemia) or PDDN, based on World Health Organization classification. All patients enrolled in these studies had CD123+ disease.

• Extended Dose Cohort #1 - Patients with relapsed CD123+ PDDN. Patients with prior Cd123-targeting agents are eligible, provided that the blasts retain detectable CD123 expression.

• Extended Dose Cohort #2 - Patients with first relapse CD123+ AML.

• Extended Dose Cohort #3 - Patients with relapsed CD123+ ALL.

• Extended Dose Cohort #4 - Patients with relapsed CD123+ “other” hematologic malignancies not included in the above cohorts (eg, high-risk/very high-risk MDS, myeloproliferative neoplasms (MPN), CMML, CML with blast crisis). Other CD123+ malignancies may be considered.

Exclusion criteria:

• Patients with available standard of care therapies are excluded.

• AML patients with active central nervous system (CNS) disease are excluded.

• Patients with a history of veno-occlusive liver disease are excluded.

• Patients with a history of grade 3-4 capillary leak syndrome or extracardiac edema were not included in the studies, eg those associated with SL-401 or other etiologies were excluded.

• Patients were excluded with myocardial infarction within six months prior to recruitment, or with New York Heart Association class III or IV heart failure, uncontrolled angina, severe uncontrolled ventricular arrhythmias, or electrocardiographically documented acute ischemia or active conduction system abnormalities during the period prior to inclusion in the study.

• Patients who received any anticancer therapy, including chemotherapy, immunotherapy, radiotherapy, hormonal, biological, or any investigational agents within 14 days or five half-lives, whichever is greater, prior to drug administration are excluded. means of this research.

Treatment

[0173] Patients received a premedication regimen before each IMGN632 infusion. Premedication includes (i) 25–50 mg diphenhydramine (intravenously (IV) or orally [PO]); (ii) 325-650 mg acetaminophen or paracetamol (IV or po) and/or (iii) 8 mg dexamethasone (po or IV). If individual patients required more intensive or alternative treatment to prevent infusion reactions (eg, different corticosteroid, different dose of any agent), then the regimen could be modified according to standard established practice.

[0174] The planned treatment consisted of two cycles (i.e., a total of six weeks), with second doses administered to patients at least 21 days after their first doses. Additional cycles, for example up to 10 or more in total, may be administered to patients benefiting from such a regimen.

[0175] For the purposes of this study, the safety observation period extended from the time the patient provided informed consent to participate in the study until the last safety observation visit. Patients who withdrew from studies for reasons other than disease progression (DP) had disease assessment procedures (bone marrow aspirates or blood tests [CBC]) every 12 weeks (± three weeks) until documented PZ, initiation of subsequent anticancer therapy, or for one year from the last evaluation of their tumor, whichever comes first. After documentation of PD or initiation of new cancer therapy, the patient is contacted every 12 weeks (± three weeks) for subsequent cancer therapy and to determine survival up to one year after the first dose of study drug (IMGN632) for the last patient.

Pharmacokinetic assays

[0176] Blood samples were collected at predetermined time points to assess IMGN632 pharmacokinetics (PK), total antibody content, and free payload. Metabolites of IMGN632 were also assessed.

Security ratings

[0177] Safety is assessed by reported/emerged adverse events (AEs), laboratory results including hematology and blood chemistry, vital signs, physical examination, and electrocardiogram/echocardiogram, as indicated. The evaluation of treatment-emergent AEs (TEAEs) included serious AEs (SAEs), AEs leading to discontinuation of the study drug, and AEs related to the study drug. All AEs occurring from the time of informed consent until 30 days after the last study drug administration were recorded, regardless of severity, severity, or relationship to the study drug.

[0178] Patients who developed dose-limiting toxicity (DLT) could continue treatment at a reduced dose level (at a minimum, a reduction of at least one dose) if TEAEs returned to baseline or were reduced to ≤grade 2. Definitions of DLT are given in Table 4 below.

Table 4: Dose-limiting toxicities (DLTs) and adverse events (AEs)

TOXICITY CRITERIA Hematology Failure to recover an absolute neutrophil count (ANC) of ≥0.5 x 109/L and/or a platelet count of ≥25 x 109/L when bone marrow values otherwise indicate remission by day 42 after the first day of IMGN632.
Aplasia (ie, bone marrow cellularity <5%) that does not recover within 42 days after the first day of IMGN632.
Failure to restore quantitative parameters with demonstrated bone marrow activity is not considered EBRT. Gastrointestinal Vomiting or nausea of ≥Common Terminology Criteria for Adverse Events (CTCAE) grade 3 despite use of optimal antiemetics.
Diarrhea CTCAE grade ≥3 despite use of optimal antidiarrheals Renal Serum creatine ≥3.0 × upper limit of normal [ULN] (excluding isolated elevations - see below) Hepatic Bilirubin, alanine aminotransferase (ALT) or aspartate aminotransferase (AST) ≥5 × FN (excluding isolated elevations - see below)
For any dose-limiting liver toxicity, evaluation should be performed to determine the underlying etiology and rule out drug-induced liver injury (High's Law). Adverse events that are NOT DLT Fatigue, asthenia, anorexia, grade 3 fever or constipation
Grade 3 nausea, vomiting, or diarrhea not requiring enteral tube feeding, total parenteral nutrition (TPN), or hospitalization
Grade 3 or 4 infection, bleeding, or other expected direct complications of cytopenias due to active leukemia
Febrile neutropenia grade 3 or 4
Grade 3 infusion reaction, including cytokine release syndrome (CRS), if managed successfully and which resolves within 72 hours
Tumor lysis syndrome (TLS) grade 3 or 4, with successful clinical management, and resolving within 7 days without ischemic organ damage Other adverse events Nonhematologic toxicities of CTCAE grade ≥3 are considered DLT, EXCEPT for isolated grade 3 laboratory chemistry elevations without associated clinical symptoms that resolve to grade ≤1 or baseline values in ≤7 days. These include electrolyte abnormalities that respond to medical intervention.

Antitumor activity

[0179] Conduct response assessments to determine differentials and biomarkers on bone marrow aspirates collected on Day 21 ± 7 days of Cycle 1. Subsequent bone marrow aspirates are collected approximately every 1-2 cycles, as clinically indicated, and at the 30 follow-up visit. days. Data are collected when bone marrow aspirates are taken more frequently. Repeat bone marrow samples are not required if no response (CR without minimal residual disease [PRMD-], CR, CR with partial recovery [CR], clinical CR [RCC only; RPDN], or partial remission/response [PR]) or PD will be definitively diagnosed based on peripheral blood tests or if the investigator finds the bone marrow test to be inconclusive at any point in time.

Example 2:

Schedule A - Administration of IMGN632 once per 21-day cycle

[0180] The starting dose of IMGN632 in Schedule A is 0.015 mg/kg. Doses from 0.015 mg/kg to 1.0 mg/kg were determined as described in Table 5.

Table 5: Planned Dose Escalation Cohorts of Regimen A

Dose escalation cohorts IMGN632 (mg/kg/dose) Dose increase factor compared to the previous dose level 1 0.015 - 2 0.045 3 3 0.09 2 4 0.18 2 5 0.3 1.67 6 0.45 1.5 7 0.67 1.5 8 1.0 1.5

results

Response criteria for AML and other heme malignancies excluding PDDN:

[0181] For patients with AML and other heme malignancies excluding PDDN, subjects were assessed as having (i) complete remission (CR) without minimal residual disease (MRRD-); (ii) complete remission, (iii) complete remission with partial recovery (CR); (iv) condition without morphological leukemia; (v) partial remission (PR); (vi) relapse after complete response; (vii) stable disease (SD); or (viii) progressive disease (PD). Patients were also assessed as having PRG.

[0182] Complete remission (CR) for AML and other heme malignancies, excluding PDDN, requires all of the following: morphological CR <5% blasts; absolute neutrophil count >1000/µl; platelets ≥100,000/µl; the patient is not dependent on transfusions; lack of data on residual active extramedullary disease; and MOH+ or unknown.

[0183] CR without minimal residual disease (PRMD-) for AML and other heme malignancies, excluding PDDN, includes all criteria for CR with genetic marker negativity as determined by RT-qPCR, or CR with negativity by multiparametric flow cytometry ( MPC).

[0184] Complete remission with partial cure (CR) for AML and other heme malignancies, excluding PDDN, meets the requirements for CR, except for ACN <1000/μL or platelets <100,000/μL.

[0185] The morphologic leukemia-free status for AML and other heme malignancies excluding PDDN includes bone marrow with <5% blasts in a spiculated aspirate; absence of blasts with Auer rods or persistence of extramedullary disease; and the bone marrow must be not just “aplastic”; at least 200 cells must be counted or the cellularity must be at least 10%.

[0186] Partial remission (PR) for AML and other heme malignancies, excluding PDDN, includes a reduction of at least 50% in the percentage of blasts to 5-25% in the bone marrow aspirate and normalization of blood cell counts, as described above.

[0187] Relapse after complete response for AML and other heme malignancies, excluding PDDN, is defined as the reappearance of leukemic blasts in the peripheral blood or the detection of more than 5% blasts in the bone marrow not otherwise explained (eg, bone marrow regeneration after consolidation treatment (or extramedullary relapse).

[0188] Stable disease (SD) for AML and other heme malignancies, excluding PDDN, is defined as the absence of PVMOZ-, PR, PR, PR, morphological leukemia-free state (MLFS); and non-compliance with PP criteria.

[0189] Progressive disease (PD) for AML and other heme malignancies, excluding PDDN, includes evidence of an increase in the percentage of blasts in the bone marrow and/or an increase in the total number of blasts in the blood:

• Increased or persistent bone marrow disease without at least 100% improvement (i.e., doubling) in ANC to an absolute level (>0.5 x 109/L [500/µL], and/or platelet count to >50 x 109/L [50000/µL] without transfusion):

(A) >50% increase in marrow blasts over baseline (in cases with baseline blasts <30%, a minimum 15 percentage point increase is required); or

(B) persistent bone marrow blast percentage >70% for at least 3 months

• >50% increase in peripheral blasts (leukocytes × % blasts) to >25×109/l (>25000/μl) (in the absence of differentiation syndrome); or

• New extramedullary disease.

Response criteria for BPDN:

[0190] For patients with PDDN, subjects were assessed as having CR; ChV; complete clinical remission (CCR); CR; NW; and PZ. Patients were also assessed as having PRG.

[0191] Complete remission (CR) includes normalization of peripheral blood and bone marrow; absence of active disease according to imaging using positron emission tomography/computed tomography; normal liver and spleen size without active nodules and lack of skin involvement documented by examination and biopsy of previously affected areas.

[0192] FR meets CR requirements except for ACN <1000/μL or platelets <100,000/μL. RCC satisfies the requirements for PR except for microscopic residual skin disease.

[0193] PR includes a reduction in bone marrow blasts of greater than 50% (if blasts were >10% at study enrollment); a reduction by more than 50% in the sum of products of diameters (SPD) to the six largest nodes dominant by mass (if they are present at the time of enrollment in the study); no increase in the size of other lymph nodes; a decrease of more than 50% in the SPD of splenic or liver nodules (if they are present at the time of enrollment in the study); no increase in the size of the liver or spleen; and a greater than 50% reduction in skin lesions (if present at study enrollment).

[0194] SD includes failure to achieve at least PR in patients without bone marrow involvement and without evidence of disease progression in the skin, lymph nodes, liver or spleen. Finally, PZ includes any new lymph nodes or new skin lesions; OR an increase from nadir of >50% in the SPD of any individual previously involved lymph node or the total estimated lymph node mass; OR an increase from a nadir of >50% in the SPD of liver or spleen nodes or an increase of >50% in the size of the liver or spleen.

Results of Scheme A

[0195] Patients in Cohorts 1-6 were treated with IMGN632 on Schedule A. As a measure of efficacy, the reduction of bone marrow blasts in each patient was measured. As shown in FIG. 2, five of the 25 patients assessed had formalized responses (CR or PR) and two patients had informal responses (>30% reduction). In some patients, responses were observed after only 1 or 2 cycles. In some patients, responses improved (eg, PR to CR) between cycles 2 and 4 of treatment.

[0196] Patient safety was assessed in patients receiving IMGN632 in Schedule A in Cohorts 1-6. Infusion-related reactions have been identified in some patients. Specifically, approximately 50% of patients experienced grade 1-2 infusion-related reactions that were modified by steroid premedication. In some cases, patients developed suspected unexpected serious adverse reactions (SUSARs), including in some cases, for example, tachycardia/hypertension, fever/headache. Grade 3 adverse events were identified in some patients, including febrile neutropenia, lung infection, and elevated ALT/AST levels. Dose-limiting toxicities were observed in Cohorts 5 and 6. In Cohort 5, myelosuppression and infection-related toxicities were also observed in 4 of 5 patients, and 1 prolonged neutropenia (>42 days) was observed. Four deaths that occurred shortly after the DLT period were due to infection-related complications. In Cohort 6, liver toxicity (HT) and neutropenia were observed. Two patients in Cohort 5 who had more than 5% blasts before treatment achieved bone marrow clearance (MRV <0.1% achieved), but both had reduced cell counts (<5%) and died before achieving recovery. These data support the activity of IMGN632, but in the context of excess toxicity.

[0197] Summary results obtained for use of Schedule A in Cohorts 1-6 are presented in Table 6.

Table 6: Summary of Scheme A results.

Cohort 1 Cohort 2 Cohort 3 Cohort 4 Cohort 5 Cohort 6 Dose 0.015 mg/kg
(Q3W) 0.045 mg/kg
(Q3W) 0.09 mg/kg
(Q3W) 0.18 mg/kg
(Q3W) 0.3 mg/kg
(Q3W) 0.45 mg/kg
(Q3W) Number of patients 3 12 8 7 5 2 results ChV PR, CHV, CR ChV ETC DLT: prolonged neutropenia; 4 deaths related to infection DLT: veno-occlusive disease (VOD)

[0198] Additional studies measured CD123 levels. As shown in FIG. 3, most patients had high CD123 homogeneity (ie, at least 80% of leukemia cells in most patients were CD123+). In addition, the average CD123 receptor saturation was measured. As shown in FIG. 4, complete saturation was observed for Cohorts 3 and above, but remained transient in most patients.

[0199] Pharmacokinetic (PK) parameters of IMGN632 were also measured. As shown in FIG. 5, measurements of antibody-drug conjugate (ADC) in plasma after a single intravenous infusion at doses ranging from 0.015 mg/kg to 0.45 mg/kg indicate that (i) sustained exposure was observed over 48 hours after infusion at doses >0 .18 mg/kg; (ii) continuous increase in maximum concentrations and exposure with increasing dose; and (iii) consistent PK parameters within each dose cohort and after multiple dose cycles.

[0200] Based on these results, expansion cohort studies were conducted with patients receiving doses of 0.045 mg/kg IMGN632 every 3 weeks (Q3W), 0.09 mg/kg IMGN632 Q3W, and 0.18 mg/kg IMGN632 Q3W. Patients with ANC <500/µL received 0.09 mg/kg IMGN632 Q3W, and patients with ACN >500/µL received 0.18 mg/kg IMGN632 Q3W.

Example 3:

Regimen B - Repeated administration of IMGN632 in a 21-day cycle

[0201] In Schedule B, IMGN632 is administered in equal doses over three days of a 21-day cycle (i.e., 1/3 of the total dose is administered on days 1, 4, and 8 each). The following doses were administered.

Table 7: Planned Dose Escalation Cohorts of Regimen B

Dose escalation cohorts Dose of IMGN632 per dose Days of introduction Total dose for a 21-day cycle B1 0.015 mg/kg Days 1, 4 and 8 0.045 mg/kg B2 0.045 mg/kg Days 1, 4 and 8 0.135 mg/kg B3 0.09 mg/kg Days 1, 4 and 8 0.27 mg/kg

[0202] The Day 4 dose may be canceled on Day 4 if the PK profile does not require it. Thus, for example, 0.015 mg/kg could be administered on Days 1 and 8, for a total dose of 0.03 mg/kg over a 21-day cycle. Additionally, 0.045 mg/kg may be administered on Days 1 and 8, for a total dose of 0.09 mg/kg over a 21-day cycle. Additionally, 0.09 mg/kg may be administered on Days 1 and 8, for a total dose of 0.18 mg/kg over a 21-day cycle.

Example 4:

Therapeutic efficacy of IMGN632

[0203] 74 patients (67 AML, 7 PDDN) received IMGN632 in nine dose-escalation cohorts in two regimens, with dose escalation of 0.015-0.45 mg/kg in regimen A (n=61) and 0.015-0.06 mg /kg on days 1, 4 and 8 according to regimen B (n=13). The median age of patients was 69 years (range 33-83). Forty-seven percent had secondary AML and 70% of classified AML patients were in the European Organization for Research and Treatment of Leukemia (ELN) adverse risk group (32/46). Twenty-six percent were primarily refractory to first-line therapy. Thirty-two percent were enrolled at first relapse and forty-one percent had other relapsed-refractory disease. Sixty-eight percent of patients had received prior intensive therapy, including stem cell transplantation in 19%.

[0204] In the evaluated AML population (n=66), 37 (55%) demonstrated decreased bone marrow blasts and 13 (20%) achieved an objective response (3 CR, 8 PR, 2 morphologic leukemia free status (MLFS)) broadly dose range (from 0.045 to 0.3 mg/kg). Notably, the majority of respondents (77%) had failed prior intensive therapy (including three with prior transplantation), 62% had an ELN adverse risk classification (including complex karyotype, ASXL1, RUNX1 and FLT3 mutations) -ITD) and 23% were primary refractory.

[0205] Of the seven relapsed/refractory (r/r) patients with BPDN, three (43%) achieved objective responses (CR, PR, PR), two others had stable disease, and two were clinical. The PR patient had previously had a partial response to SL-401, responded to a combination of cyclophosphamide, hydroxydaunomycin, Oncovin, and prednisone (CHOP), received a transplant, and was refractory to decitabine with venetoclax; on IMGN632, this patient experienced clearing of bone marrow (28% to 0%) after one dose and clearing of skin (biopsy negative) and CT lesions after 2 doses. The patient with CV was refractory to SL-401, CLAG-M, and CLAG and achieved clearance of bone marrow (37% to 0%), skin, and CT lesions after a single dose of 0.045 mg/kg IMGN632. The PR patient had a previous partial response to SL-401; on IMGN632, this patient demonstrated complete clearance of bone marrow blasts (87% to 0%) and significant improvement in skin and CT lesions after a single dose of IMGN632.

* * *

[0206] The scope of this description should not be limited to the specific implementations described herein. In fact, various modifications of the present invention in addition to those described will be apparent to those skilled in the art from the foregoing description and accompanying figures. Such modifications are to be considered within the scope of the appended claims.

[0207] All sources (e.g., publications or patents or patent applications) referenced herein are incorporated herein by reference in their entirety and in all respects to the same extent as if for each individual source (e.g., publication or patent or patent application) has been specifically and individually indicated to be incorporated by reference in its entirety in all respects.

[0208] Other embodiments are within the scope of the following claims.

--->

LIST OF SEQUENCES

<110> ImmunoGen, Inc.

<120> TREATMENT METHODS USING ANTI-CD123 IMMUNOCONJUGATES

<130> 2921.104PC04/EKS/CLD

<150>US 62/881,137

<151> 2019-07-31

<150> US 62/860,565

<151> 2019-06-12

<150> US 62/752,832

<151> 2018-10-30

<160> 12

<170> Patent In version 3.5

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Ile Pro Cys Thr Asp Lys Phe Val Val Phe Ser Gln Ile Glu Ile Leu

195 200 205

Thr Pro Pro Asn Met Thr Ala Lys Cys Asn Lys Thr His Ser Phe Met

210 215 220

His Trp Lys Met Arg Ser His Phe Asn Arg Lys Phe Arg Tyr Glu Leu

225 230 235 240

Gln Ile Gln Lys Arg Met Gln Pro Val Ile Thr Glu Gln Val Arg Asp

245 250 255

Arg Thr Ser Phe Gln Leu Leu Asn Pro Gly Thr Tyr Thr Val Gln Ile

260 265 270

Arg Ala Arg Glu Arg Val Tyr Glu Phe Leu Ser Ala Trp Ser Thr Pro

275 280 285

Gln Arg Phe Glu Cys Asp Gln Glu Glu Gly Ala Asn Thr Arg Ala Trp

290 295 300

Arg Thr Ser Leu Leu Ile Ala Leu Gly Thr Leu Leu Ala Leu Val Cys

305 310 315 320

Val Phe Val Ile Cys Arg Arg Tyr Leu Val Met Gln Arg Leu Phe Pro

325 330 335

Arg Ile Pro His Met Lys Asp Pro Ile Gly Asp Ser Phe Gln Asn Asp

340 345 350

Lys Leu Val Val Trp Glu Ala Gly Lys Ala Gly Leu Glu Glu Cys Leu

355 360 365

Val Thr Glu Val Gln Val Val Gln Lys Thr

370 375

<210> 12

<211> 300

<212>PRT

<213> Homo sapiens

<400> 12

Met Val Leu Leu Trp Leu Thr Leu Leu Leu Ile Ala Leu Pro Cys Leu

1 5 10 15

Leu Gln Thr Lys Glu Gly Gly Lys Pro Trp Ala Gly Ala Glu Asn Leu

20 25 30

Thr Cys Trp Ile His Asp Val Asp Phe Leu Ser Cys Ser Trp Ala Val

35 40 45

Gly Pro Gly Ala Pro Ala Asp Val Gln Tyr Asp Leu Tyr Leu Asn Val

50 55 60

Ala Asn Arg Arg Gln Gln Tyr Glu Cys Leu His Tyr Lys Thr Asp Ala

65 70 75 80

Gln Gly Thr Arg Ile Gly Cys Arg Phe Asp Asp Ile Ser Arg Leu Ser

85 90 95

Ser Gly Ser Gln Ser Ser His Ile Leu Val Arg Gly Arg Ser Ala Ala

100 105 110

Phe Gly Ile Pro Cys Thr Asp Lys Phe Val Val Phe Ser Gln Ile Glu

115 120 125

Ile Leu Thr Pro Pro Asn Met Thr Ala Lys Cys Asn Lys Thr His Ser

130 135 140

Phe Met His Trp Lys Met Arg Ser His Phe Asn Arg Lys Phe Arg Tyr

145 150 155 160

Glu Leu Gln Ile Gln Lys Arg Met Gln Pro Val Ile Thr Glu Gln Val

165 170 175

Arg Asp Arg Thr Ser Phe Gln Leu Leu Asn Pro Gly Thr Tyr Thr Val

180 185 190

Gln Ile Arg Ala Arg Glu Arg Val Tyr Glu Phe Leu Ser Ala Trp Ser

195 200 205

Thr Pro Gln Arg Phe Glu Cys Asp Gln Glu Glu Gly Ala Asn Thr Arg

210 215 220

Ala Trp Arg Thr Ser Leu Leu Ile Ala Leu Gly Thr Leu Leu Ala Leu

225 230 235 240

Val Cys Val Phe Val Ile Cys Arg Arg Tyr Leu Val Met Gln Arg Leu

245 250 255

Phe Pro Arg Ile Pro His Met Lys Asp Pro Ile Gly Asp Ser Phe Gln

260 265 270

Asn Asp Lys Leu Val Val Trp Glu Ala Gly Lys Ala Gly Leu Glu Glu

275 280 285

Cys Leu Val Thr Glu Val Gln Val Val Gln Lys Thr

290 295 300

<---

Claims (61)

1. A method of treating a hematologic malignancy in a human, comprising administering to the subject an anti-CD123 immunoconjugate containing an anti-CD123 antibody or an antigen-binding fragment thereof linked to an indolinobenzodiazepine (IGN) DNA alkylator, wherein the immunoconjugate is administered at a dose of 0.045 mg/kg to less than 0.3 mg/kg, and wherein said anti-CD123 antibody or antigen-binding fragment thereof contains: a. Heavy chain variable region CDR1 containing the amino acid sequence of SEQ ID NO: 5; Heavy chain variable region CDR2 containing the amino acid sequence of SEQ ID NO: 6; and a heavy chain variable region CDR3 comprising the amino acid sequence of SEQ ID NO: 7; And b. Light chain variable region CDR1 containing the amino acid sequence of SEQ ID NO: 8; Light chain variable region CDR2 containing the amino acid sequence of SEQ ID NO: 9; and a light chain variable region CDR3 comprising the amino acid sequence of SEQ ID NO: 10. 2. The method according to claim 1, characterized in that the subject is administered from 0.045 mg/kg to 0.09 mg/kg of the immunoconjugate. 3. The method according to claim 1, characterized in that the subject is administered 0.045 mg/kg of the immunoconjugate. 4. The method according to claim 1, characterized in that the subject is administered 0.09 mg/kg of the immunoconjugate. 5. Method according to any one of paragraphs. 1-4, characterized in that the immunoconjugate is administered to a subject once per 21-day cycle. 6. A method of treating a hematological malignancy in a person, comprising administering to the subject an anti-CD123 immunoconjugate containing an anti-CD123 antibody or an antigen-binding fragment thereof, linked to an indolinobenzodiazepine (IGN) DNA alkylator, and from 0.015 mg/kg to 0.09 mg/ kg of immunoconjugate is administered three times in a 21-day cycle, and wherein said anti-CD123 antibody or antigen-binding fragment thereof contains: a. Heavy chain variable region CDR1 containing the amino acid sequence of SEQ ID NO: 5; Heavy chain variable region CDR2 containing the amino acid sequence of SEQ ID NO: 6; and a heavy chain variable region CDR3 comprising the amino acid sequence of SEQ ID NO: 7; And b. Light chain variable region CDR1 containing the amino acid sequence of SEQ ID NO: 8; Light chain variable region CDR2 containing the amino acid sequence of SEQ ID NO: 9; and a light chain variable region CDR3 comprising the amino acid sequence of SEQ ID NO: 10. 7. A method of treating a hematological malignancy in a person, comprising administering to the subject an anti-CD123 immunoconjugate containing an anti-CD123 antibody or an antigen-binding fragment thereof, linked to an indolinobenzodiazepine (IGN) DNA alkylator, and from 0.015 mg/kg to 0.09 mg/ kg of immunoconjugate is administered twice in a 21-day cycle, and wherein said anti-CD123 antibody or antigen-binding fragment thereof contains: a. Heavy chain variable region CDR1 containing the amino acid sequence of SEQ ID NO: 5; Heavy chain variable region CDR2 containing the amino acid sequence of SEQ ID NO: 6; and a heavy chain variable region CDR3 comprising the amino acid sequence of SEQ ID NO: 7; And b. Light chain variable region CDR1 containing the amino acid sequence of SEQ ID NO: 8; Light chain variable region CDR2 containing the amino acid sequence of SEQ ID NO: 9; and a light chain variable region CDR3 comprising the amino acid sequence of SEQ ID NO: 10. 8. Method according to any one of paragraphs. 5-7, characterized in that the immunoconjugate is administered over more than one cycle. 9. Method according to any one of paragraphs. 5-7, characterized in that the immunoconjugate is administered for at least 2 cycles, at least 3 cycles, at least 4 cycles, at least 5 cycles, at least 6 cycles, at least 7 cycles, at least at least 8 cycles, at least 9 cycles or at least 10 cycles. 10. Method according to any one of paragraphs. 5-7, characterized in that the immunoconjugate is administered over 2-4 cycles, 2-6 cycles, 2-8 cycles or 2-10 cycles. 11. Method according to any one of paragraphs. 1-10, characterized in that the hematological malignancy is a recurrent hematological malignancy. 12. Method according to any one of paragraphs. 1-10, characterized in that the hematological malignancy is acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), B-cell acute lymphoblastic leukemia (B-ALL), chronic myeloid leukemia in blast crisis/phase (BC-CML ) or blast plasmacytoid dendritic cell neoplasm (BPDN). 13. Method according to any one of paragraphs. 1-10, characterized in that the hematological malignant tumor is AML. 14. The method according to claim 13, characterized in that the AML is relapsed AML and/or refractory AML or unfit AML. 15. Method according to any one of paragraphs. 1-10, characterized in that the hematological malignant tumor is BPDN. 16. The method according to claim 15, characterized in that the BPDN is recurrent BPDN and/or refractory BPDN. 17. The method according to claim 15, characterized in that the BPDN is a first-line BPDN. 18. The method according to claim 17, characterized in that the subject is unsuitable for intensive chemotherapy. 19. The method according to claim 17 or 18, characterized in that the subject is unsuitable for SL-401 therapy. 20. Method according to any one of paragraphs. 1-10, characterized in that the hematological malignant tumor is ALL. 21. The method according to claim 20, characterized in that the ALL is relapsed ALL and/or refractory ALL. 22. Method according to any one of paragraphs. 1-10, characterized in that the hematological malignancy is chronic myelomonocytic leukemia (CMML). 23. The method according to claim 22, characterized in that the CMML is recurrent CMML and/or refractory CMML. 24. Method according to any one of paragraphs. 1-10, characterized in that the hematological malignancy is myelofibrosis (MF). 25. The method according to claim 24, characterized in that the MF is recurrent MF and/or refractory MF. 26. Method according to any one of paragraphs. 1-10, characterized in that the hematological malignancy is myelodysplastic syndrome (MDS). 27. The method according to claim 26, characterized in that the MDS is recurrent MDS and/or refractory MDS. 28. Method according to any one of paragraphs. 1-27, characterized in that the subject is a pediatric patient. 29. Method according to any one of paragraphs. 1-28, wherein the hematological malignancy is a CD123-expressing hematological malignancy. 30. Method according to any one of paragraphs. 1-29, characterized in that CD123 was detected in a sample obtained from a hematological malignant tumor prior to said administration. 31. The method according to claim 30, characterized in that CD123 is detected using flow cytometry. 32. Method according to any one of paragraphs. 1-31, further comprising detecting CD123 in a sample obtained from a hematological malignancy prior to said administration. 33. Method according to any one of paragraphs. 1-32, characterized in that at least 80% of the cells in the hematologic malignancy express CD123. 34. Method according to any one of paragraphs. 1-33, characterized in that CD123 was detected in at least 80% of the cells in a sample obtained from a hematological malignancy prior to said administration. 35. Method according to any one of paragraphs. 1-34, further comprising detecting CD123 in at least 80% of the cells in a sample obtained from a hematologic malignancy prior to said administration. 36. Method according to any one of paragraphs. 1-35, characterized in that the subject has an absolute neutrophil count greater than 500 neutrophils/μl. 37. Method according to any one of paragraphs. 1-16 and 18-36, characterized in that the subject has received at least one prior line of therapy. 38. Method according to any one of paragraphs. 1-16 and 18-37, characterized in that the subject has received at least two prior lines of therapy. 39. Method according to any one of paragraphs. 1-16 and 18-38, wherein the subject has received at least three prior lines of therapy, at least four prior lines of therapy, or at least five prior lines of therapy. 40. Method according to any one of paragraphs. 1-39, characterized in that the subject was pretreated with a corticosteroid prior to administration of the immunoconjugate. 41. Method according to any one of paragraphs. 1-39, further comprising pre-treating the subject with a corticosteroid prior to administration of the immunoconjugate. 42. The method according to claim 40 or 41, characterized in that the corticosteroid is prednisone, prednisolone, methylprednisolone, beclomethasone, betamethasone, dexamethasone, fludrocortisone, hydrocortisone, triamcinolone, or a combination thereof. 43. Method according to any one of paragraphs. 1-42, characterized in that the immunoconjugate is administered intravenously. 44. Method according to any one of paragraphs. 1-43, further comprising administering a reduced dose of the immunoconjugate after dose-limiting toxicity occurs in the subject and is reduced to baseline or grade ≤2. 45. Method according to any one of paragraphs. 1-44, characterized in that the anti-CD123 antibody or antigen binding fragment in the immunoconjugate contains a heavy chain variable region (VH) containing the amino acid sequence presented in SEQ ID NO:1, and a light chain variable region (VL) containing the amino acid sequence , presented in SEQ ID NO: 2. 46. Method according to any one of paragraphs. 1-45, characterized in that the anti-CD123 antibody or antigen-binding fragment in the immunoconjugate contains a heavy chain constant region and a light chain constant region. 47. The method according to claim 46, characterized in that the heavy chain constant region comprises a human IgG ₁ immunoglobulin heavy chain constant region and/or in that the light chain constant region comprises a human IgGκ immunoglobulin light chain constant region. 48. Method according to any one of paragraphs. 1-45, characterized in that the anti-CD123 antibody or antigen binding fragment in the immunoconjugate contains a heavy chain containing the amino acid sequence presented in SEQ ID NO:3, and a light chain containing the amino acid sequence presented in SEQ ID NO:4. 49. Method according to any one of paragraphs. 1-48, characterized in that the anti-CD123 antibody or antigen-binding fragment in the immunoconjugate is a full-length antibody. 50. Method according to any one of paragraphs. 1-47, characterized in that the anti-CD123 antibody or antigen binding fragment in the immunoconjugate is an antigen binding fragment. 51. Method according to any one of paragraphs. 1-50, characterized in that said IGN DNA alkylator is DGN549-C. 52. Method according to any one of paragraphs. 1-51, characterized in that the immunoconjugate contains a peptide linker. 53. Method according to any one of paragraphs. 1-52, characterized in that the immunoconjugate is administered in a pharmaceutical composition containing immunoconjugates of the following structure: , where G4723A contains a heavy chain containing the amino acid sequence presented in SEQ ID NO:3, and a light chain containing the amino acid sequence presented in SEQ ID NO:4.