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. 2020 Nov 20;12(11):3464.
doi: 10.3390/cancers12113464.

IL3RA-Targeting Antibody-Drug Conjugate BAY-943 with a Kinesin Spindle Protein Inhibitor Payload Shows Efficacy in Preclinical Models of Hematologic Malignancies

Dennis Kirchhoff  1 , Beatrix Stelte-Ludwig  2 , Hans-Georg Lerchen  2 , Antje Margret Wengner  1 , Oliver von Ahsen  1 , Pascale Buchmann  2 , Stephan Märsch  2 , Christoph Mahlert  2 , Simone Greven  2 , Lisa Dietz  2 , Michael Erkelenz  1 , Ruprecht Zierz  1 , Sandra Johanssen  1 , Dominik Mumberg  1 , Anette Sommer  1
Affiliations

IL3RA-Targeting Antibody-Drug Conjugate BAY-943 with a Kinesin Spindle Protein Inhibitor Payload Shows Efficacy in Preclinical Models of Hematologic Malignancies

Dennis Kirchhoff et al. Cancers (Basel). .

Abstract

IL3RA (CD123) is the alpha subunit of the interleukin 3 (IL-3) receptor, which regulates the proliferation, survival, and differentiation of hematopoietic cells. IL3RA is frequently expressed in acute myeloid leukemia (AML) and classical Hodgkin lymphoma (HL), presenting an opportunity to treat AML and HL with an IL3RA-directed antibody-drug conjugate (ADC). Here, we describe BAY-943 (IL3RA-ADC), a novel IL3RA-targeting ADC consisting of a humanized anti-IL3RA antibody conjugated to a potent proprietary kinesin spindle protein inhibitor (KSPi). In vitro, IL3RA-ADC showed potent and selective antiproliferative efficacy in a panel of IL3RA-expressing AML and HL cell lines. In vivo, IL3RA-ADC improved survival and reduced tumor burden in IL3RA-positive human AML cell line-derived (MOLM-13 and MV-4-11) as well as in patient-derived xenograft (PDX) models (AM7577 and AML11655) in mice. Furthermore, IL3RA-ADC induced complete tumor remission in 12 out of 13 mice in an IL3RA-positive HL cell line-derived xenograft model (HDLM-2). IL3RA-ADC was well-tolerated and showed no signs of thrombocytopenia, neutropenia, or liver toxicity in rats, or in cynomolgus monkeys when dosed up to 20 mg/kg. Overall, the preclinical results support the further development of BAY-943 as an innovative approach for the treatment of IL3RA-positive hematologic malignancies.

Keywords: CD123; IL3RA; acute myeloid leukemia; antibody-drug conjugate; kinesin spindle protein inhibitor.

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Conflict of interest statement

All authors are current or former employees of Bayer AG and inventors on Bayer AG patent applications. Anette Sommer, Hans-Georg Lerchen, Stephan Märsch, Michael Erkelenz, and Dominik Mumberg have ownership interest as shares in Bayer AG.

Figures

Figure 1
Figure 1
Characterization of the interleukin 3 receptor subunit alpha (IL3RA) antibody TPP-9476 and schematic representation of the IL3RA antibody–drug conjugate (ADC) BAY-943. (A) The binding of the IL3RA-targeting antibody (IL3RA Ab) TPP-9476 to IL3RA-positive hematologic cell lines as determined by flow cytometry. The obtained EC50 values were 2.73 × 10−9 M for MOLM-13, 6.53 × 10−9 M for MV-4-11, and 4.54 × 10−9 M for KG-1 cells. (B,C) The internalization of the IL3RA Ab TPP-9476 and an isotype control antibody into IL3RA-positive MOLM-13 (B) and MV-4-11 (C) cells as determined by flow cytometry-based imaging. (D) The colocalization of the IL3RA Ab TPP-9476 in lysosomes in the IL3RA-positive MOLM-13 and IL3RA-negative HBL-1 cells. (E) Schematic representation of the IL3RA-ADC BAY-943. TPP-9476 represents the IL3RA-Ab. The “cell trapper” functionality indicates a non-cell-permeable payload metabolite that enables maximal retention in target cells after cleavage. (F) The binding of the IL3RA-ADC BAY-943 to IL3RA-positive MOLM-13 cells as determined by flow cytometry. The obtained EC50 values were 20.4 × 10−9 M for ILRA3A-ADC and 18.7 × 10−9 M for ILRA3A Ab, respectively.
Figure 2
Figure 2
Antitumor efficacy of the IL3RA-ADC BAY-943 in the systemic MOLM-13 and MV-4-11 leukemia xenograft models. A-B. Kaplan–Meier survival plots of mice transplanted with the MOLM-13 human acute myeloid leukemia (AML) cells and treated intravenously (i.v.) with the isotype control ADC (10 mg/kg, Q7D) or IL3RA-ADC at 2.5 mg/kg (A) or 10 mg/kg (B); Q7D, Q14D, or Q21D. C-D. Kaplan–Meier survival plots of mice transplanted with the MV-4-11 human biphenotypic leukemia cells and treated i.v. with the isotype control ADC (10 mg/kg, Q7D) or IL3RA-ADC at 2.5 mg/kg (C) or 10 mg/kg (D); Q7D, Q14D or Q21D. The vertical dashed gray lines delineate the treatment period, and the arrows indicate time of treatment. Data were analyzed using the Cox proportional hazards model and corrected for family-wise error rate using Sidak’s method. Asterisks and hashtags indicate statistical significance in comparison to the vehicle (** p < 0.01, *** p < 0.001) or isotype control ADC (### p < 0.001).
Figure 3
Figure 3
Antitumor efficacy of the IL3RA-ADC BAY-943 in the patient-derived AM7577 and AML11655 AML xenograft models. (A) Tumor burden on day 56 in mice transplanted with AM7577 cells and treated i.p. with the isotype control ADC (10 mg/kg, Q7D) and IL3RA-ADC (2.5 + 10 mg/kg or 10 mg/kg, Q7D). In the 2.5 + 10 mg/kg IL3RA-ADC treatment group, the first dose was 2.5 mg/kg (day 38) and the two subsequent doses (on days 45 and 59) 10 mg/kg. (B) Kaplan–Meier survival plots of mice described in panel A. Treatment days in all groups except for the 2.5 + 10 mg/kg IL3RA-ADC treatment group are indicated with gray arrows. (C) Tumor burden on day 54 in mice transplanted with AML11655 cells. Intraperitoneal treatments with the isotype control ADC (10 mg/kg, Q7D) were initiated on day 34 and with IL3RA-ADC (10 mg/kg, Q7D) on day 5 (preventive setting) or 34 (therapeutic setting). (D) Kaplan–Meier survival plots of mice described in panel C. Treatment days are indicated with red arrows. The data were analyzed using the Cox proportional-hazards model and corrected for family-wise error rate using Sidak’s method. Asterisks and hashtags indicate statistical significance in comparison to vehicle (* p < 0.05, *** p < 0.001) and the isotype control ADC (### p < 0.001).
Figure 4
Figure 4
Antitumor efficacy of the IL3RA-ADC BAY-943 in the subcutaneous HDLM-2 Hodgkin lymphoma xenograft model. Mice were transplanted with HDLM-2 cells and treatments with IL3RA-ADC (5 or 10 mg/kg, Q7D×2, i.p.) or ispinesib (10 mg/kg, Q7D×3, i.v.) were initiated on day 49. (A) Tumor growth curves. ADC treatment days are indicated with red arrows and ispinesib administration is indicated with blue arrows. (B) Tumor volume on day 84. Statistical analyses were performed using a linear mixed-effects model with random intercepts and slopes for each subject (n = 6–7). Mean comparisons between the treatment and control groups were performed using the estimated linear mixed-effects model and corrected for family-wise error rate using Sidak’s method. Asterisks indicate statistical significance in comparison to vehicle (*** p < 0.001).
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