Abstract 1276: Identification of S65487/VOB560 as a potent and selective intravenous 2nd-generation BCL-2 inhibitor active in wild-type and clinical mutants resistant to Venetoclax

The B-cell Lymphoma 2 (BCL-2) gene family encodes pro-apoptotic and anti-apoptotic proteins that are key regulators of the apoptotic process. Overexpression of the pro-survival member BCL-2 is a well-established mechanism contributing to oncogenesis and chemoresistance in several cancers, including lymphoma and leukemia. Venetoclax (Venclexta™), a selective BCL-2 inhibitor, is the first member of a new class of anti-cancer drugs, called BH3 mimetics, to be approved for CLL and AML. Here, we describe the identification of a novel potent and selective BCL-2 inhibitor named S65487/VOB560 that has a different binding mode on BCL-2 compared to Venetoclax. This inhibitor binds to the BH3 hydrophobic groove of BCL-2. Its selectivity profile demonstrates lack of significant binding to MCL-1, BFL-1 and poor affinity for BCL-XL. S65487/VOB560 induces apoptosis in a panel of hematological cancer cell lines and inhibits cell proliferation with IC50s in the low nM range. S65487/VOB560 induces complete regression in BCL-2-dependent RS4;11 tumors in vivo after a single IV (intravenous) administration. Strong and persistent tumor regression in xenograft models of lymphoid malignancies in mouse and rat were observed at well tolerated doses following weekly IV administration of S65487 in combination with the MCL-1-specific inhibitor, S64315/MIK665. These positive findings were further confirmed in a panel of AML PDX tumor models. Recently, acquired BCL-2 mutations (such as G101V and D103Y) were identified in patients with Chronic Lymphocytic Leukemia becoming resistant to Venetoclax. Interestingly, S65487/VOB560 is active on such BCL-2 mutants and induces apoptosis in preclinical resistance models. Altogether, these data demonstrate that S65487/VOB560 has significant therapeutic potential against human lymphoid and myeloid malignancies as well as in patients with Venetoclax resistant leukemias. Clinical studies are currently ongoing with S65487/VOB560 (NCT03755154).

Citation Format: Arnaud Le Tiran, Audrey Claperon, James Davidson, Jérôme-Benoit Starck, Thierry Le Diguarher, Maïa Chanrion, Prakash Mistry, Youzhen Wang, Elodie Monceau, Fabienne Bernhardt, Francesca Rocchetti, Gaelle Lysiak-Auvity, Ijen Chen, Zoe Daniels, Chris Pedder, Mandy Fallowfield, Jean-Michel Henlin, Imre Fejes, Janos Tatai, Miklos Nyerges, Didier Durand, Marion Zarka, Sneha Sanghavi, Anne-Marie Girard, Marie Schoumacher, Laurence Kraus-Berthier, Rick Newcombe, Ensar Halilovic, Sébastien Banquet, Alain Rupin, Heiko Maacke, James Murray, Erick Morris, Francesco Hofmann, Frédéric Colland, Olivier Geneste. Identification of S65487/VOB560 as a potent and selective intravenous 2nd-generation BCL-2 inhibitor active in wild-type and clinical mutants resistant to Venetoclax [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1276.

Abstract 4482: S64315 (MIK665) is a potent and selective Mcl1 inhibitor with strong antitumor activity across a diverse range of hematologic tumor models

Mcl-1 is highly expressed in a variety of human cancers (including those of hematopoietic and lymphoid origin) and is exploited by cancer cells to evade cell death and to develop resistance to diverse chemotherapeutic agents. We disclose, for the first time, the structure of S64315 (also named MIK665) a highly potent and selective inhibitor of Mcl-1 with improved potency over its predecessor S63845 (Kotschy et al, Nature, 2016). S64315/MIK665 is currently in phase 1 in AML (Acute Myeloid Leukemia) and MDS (Myelodysplastic Syndrome) (EudraCT 2016-003768-38, NCT 02979366) and in MM (Multiple Myeloma) and lymphoma (NCT02992483). A fragment-based, structure-guided drug discovery effort led to the identification of S64315/MIK665 that binds to human Mcl-1 with a sub-nanomolar affinity (Ki 0.048 nM) and selectively over other anti-apoptotic Bcl-2 family members. It has similar affinity for human, rat, dog and monkey Mcl-1 but about a ten-fold lower affinity for mouse Mcl-1. S64315/MIK665 causes dose-dependent activation of the intrinsic apoptosis pathway in a Bax/Bak-dependent manner, as measured by increased caspase activity and cleaved PARP. S64315/MIK665 shows strong cell killing activity in a diverse panel of human hematological tumor cell lines, including AML, lymphoma and MM. The activity profile of S64315/MIK665 is distinct from that of venetoclax, a selective Bcl2 inhibitor. In vivo, S64315 as single agent demonstrated potent and dose-dependent apoptotic and antitumor response after intravenous administration in several human hematological tumor models grafted in immuno-compromised mice and rats. Complete regression of established tumors, at well tolerated doses, was achieved using different intravenous dosing regimens in rats as well as in mice. Finally, dual BH3-mimetic targeting approach combining S64315/MIK665 with BCL2 inhibitors showed strong and durable antitumor responses in several hematological tumor models both in vitro and in vivo.

Citation Format: Ana Leticia Maragno, Prakash Mistry, András Kotschy, Zoltán Szlavik, James Murray, James Davidson, Gaëtane Le Toumelin-Braizat, Maïa Chanrion, Alain Bruno, Audrey Claperon, Heiko Maacke, Erick Morris, Youzhen Wang, Alix Derreal, Márton Csekei, Attila Paczal, Zoltán Szabo, Szabolcs Sipos, Agnes Proszenyak, Balázs Balint, Allan Surgenor, Pawel Dokurno, Natalia Matassova, Ijen Chen, Gaëlle Lysiak-Auvity, Anne-Marie Girard, Fabienne Grave, Frédéric Colland, Ensar Halilovic, Olivier Geneste. S64315 (MIK665) is a potent and selective Mcl1 inhibitor with strong antitumor activity across a diverse range of hematologic tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4482.

Abstract 257: Targeting AML through apoptosis activation using Bcl-2/Mcl-1 or Bcl-2/Hdm2 inhibitor combination therapies

Acute myeloid leukemia (AML) is an aggressive and heterogeneous hematologic malignancy, characterized by uncontrolled proliferation and impaired differentiation of myeloid cells. With the exception of certain subtypes, the average long-term survival rate remains low, thus underlining the need to further improve the outcome of AML patients. Since AML is one of the least mutated cancer types, the majority of AML patients may not carry targetable genetic alterations. However, the anti-apoptotic proteins of the Bcl-2 family, such as Bcl-2 and Mcl-1, are often overexpressed in AML, allowing deregulated survival; hence pro-apoptosis priming with small molecule inhibitors of Bcl-2 and Mcl-1 may provide a broader therapeutic benefit across the disease. In addition, a majority of AML patients carry wild-type p53, providing therapeutic opportunity for Hdm2 inhibitors to stabilize p53 and lead to expression of pro-apoptotic molecules (e.g., PUMA & BAX). Therefore, targeting the combined apoptosis mechanisms by inhibiting different anti-apoptotic Bcl-2 family of proteins and activating p53 concomitantly may synergistically enhance apoptotic cell death of AML tumor cells.

We tested the combination of Bcl-2 inhibitors (BCL201/S55746 or venetoclax) with either MIK665/S64315, a novel and selective inhibitor of Mcl-1 or HDM201, a selective small molecule inhibitor of p53:Hdm2 interaction, in a series of in vitro and in vivo studies in AML. In vitro, strong combination synergy was observed with a remarkable induction of cell death for both combinations. In vivo, the combination of Bcl-2 inhibitors with MIK665/S64315 or HDM201 lead to complete and durable antitumor responses in a variety of p53wt AML patient-derived xenograft models of heterogeneous genetic profiles. Notably, lowering the dose of HDM201 by 4 fold from its most efficacious dose, resulted in a high degree of tumor regressions while mitigating the toxicity effects on platelets. Taken together, these data demonstrate that a combination of Bcl-2 inhibitor (BCL201/S55746 or venetoclax) with MIK665/S64315 or HDM201 provide therapeutic benefit over the monotherapy, and support a rationale for testing these apoptosis enhancing combination approaches in AML patients.

Citation Format: Youzhen Wang, Shumei Qui, Sneha Sanghavi, Iain Mulford, Gaëlle Lysiak, Maïa Chanrion, Prakash Mistry, Ulrike Pfaar, Marie Schoumacher, Audrey Claperon, Laurence Kraus-Berthier, Sébastien Banquet, Alix Derreal, Claire Fabre, Heiko Maacke, Frédéric Colland, Olivier Geneste, Erick Morris, Ensar Halilovic. Targeting AML through apoptosis activation using Bcl-2/Mcl-1 or Bcl-2/Hdm2 inhibitor combination therapies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 257.

Abstract 4477: MIK665/S64315, a novel Mcl-1 inhibitor, in combination with Bcl-2 inhibitors exhibits strong synergistic antitumor activity in a range of hematologic malignancies

One of the hallmarks of cancer is evasion of apoptosis. The B-cell lymphoma-2 (Bcl-2) family of proteins represents a crucial point of control of apoptosis. The Bcl-2 family comprises both pro- and anti-apoptotic members, the latter of which (Bcl-2, Bcl-xL, Bcl-w, Mcl-1 and Bcl-2A1) are often overexpressed in cancer cells, supporting their aberrant survival. Thus, these anti-apoptotic proteins have become an attractive target for cancer therapy. BH3 mimetics have been shown to bind to the BH3 binding groove of anti-apoptotic Bcl-2 family members and inhibit their function, resulting in apoptotic cell death, and one such BH3 mimetic, ABT-199 (venetoclax), has recently been approved for treatment of relapsed or refractory Chronic Lymphocytic Leukemia. We have developed two novel and potent BH3 mimetics: MIK665/S64315, a highly selective inhibitor of Mcl-1 and BCL201/S55746, a selective Bcl-2 inhibitor. Both compounds, individually induce apoptosis in hematological cancer cell lines, primary patient samples and demonstrate anti-tumor efficacy in xenograft models. MIK665/S64315 is currently in phase 1 clinical development in AML and MDS (NCT 02979366) and in MM and lymphoma (NCT02992483). Here, we describe the activity of the combination of MIK665/S64315 with BCL201/S55746 or venetoclax, both in vitro and in vivo, across a range of hematological indications (AML, MM and DLBCL). In vitro, a strong synergy was observed with these combinations, resulting in a remarkable induction of cell death in majority of cell lines tested. In vivo, MIK665/S64315 and BCL201/S55746 combinations lead to complete and durable antitumor responses in many different xenograft models in mice and rats. Taken together, these data demonstrate that a combination of MIK665/S64315 and BCL201/S55746 provide strong therapeutic benefit over either monotherapy, and support a rationale for testing Mcl-1 and Bcl-2 inhibitor combinations in patients with hematological malignancies.

Citation Format: Ensar Halilovic, Maïa Chanrion, Prakash Mistry, Markus Wartmann, Shumei Qiu, Sneha Sanghavi, Yan Chen, Gaëlle Lysiak, Ana Leticia Maragno, Ulrike Pfaar, Felix Huth, Marie Schoumacher, Audrey Claperon, Laurence Kraus-Berthier, Sébastien Banquet, Alix Derreal, Heiko Maacke, Frédéric Colland, Olivier Geneste, Erick Morris, Youzhen Wang. MIK665/S64315, a novel Mcl-1 inhibitor, in combination with Bcl-2 inhibitors exhibits strong synergistic antitumor activity in a range of hematologic malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4477.

Combining BH3-mimetics to target both BCL-2 and MCL1 has potent activity in pre-clinical models of acute myeloid leukemia

Improving outcomes in acute myeloid leukemia (AML) remains a major clinical challenge. Overexpression of pro-survival BCL-2 family members rendering transformed cells resistant to cytotoxic drugs is a common theme in cancer. Targeting BCL-2 with the BH3-mimetic venetoclax is active in AML when combined with low-dose chemotherapy or hypomethylating agents. We now report the pre-clinical anti-leukemic efficacy of a novel BCL-2 inhibitor S55746, which demonstrates synergistic pro-apoptotic activity in combination with the MCL1 inhibitor S63845. Activity of the combination was caspase and BAX/BAK dependent, superior to combination with standard cytotoxic AML drugs and active against a broad spectrum of poor risk genotypes, including primary samples from patients with chemoresistant AML. Co-targeting BCL-2 and MCL1 was more effective against leukemic, compared to normal hematopoietic progenitors, suggesting a therapeutic window of activity. Finally, S55746 combined with S63845 prolonged survival in xenograft models of AML and suppressed patient-derived leukemia but not normal hematopoietic cells in bone marrow of engrafted mice. In conclusion, a dual BH3-mimetic approach is feasible, highly synergistic, and active in diverse models of human AML. This approach has strong clinical potential to rapidly suppress leukemia, with reduced toxicity to normal hematopoietic precursors compared to chemotherapy.

S55746 is a novel orally active BCL-2 selective and potent inhibitor that impairs hematological tumor growth

Escape from apoptosis is one of the major hallmarks of cancer cells. The B-cell Lymphoma 2 (BCL-2) gene family encodes pro-apoptotic and anti-apoptotic proteins that are key regulators of the apoptotic process. Overexpression of the pro-survival member BCL-2 is a well-established mechanism contributing to oncogenesis and chemoresistance in several cancers, including lymphoma and leukemia. Thus, BCL-2 has become an attractive target for therapeutic strategy in cancer, as demonstrated by the recent approval of ABT-199 (Venclexta™) in relapsed or refractory Chronic Lymphocytic Leukemia with 17p deletion. Here, we describe a novel orally bioavailable BCL-2 selective and potent inhibitor called S55746 (also known as BCL201). S55746 occupies the hydrophobic groove of BCL-2. Its selectivity profile demonstrates no significant binding to MCL-1, BFL-1 (BCL2A1/A1) and poor affinity for BCL-XL. Accordingly, S55746 has no cytotoxic activity on BCL-XL-dependent cells, such as platelets. In a panel of hematological cell lines, S55746 induces hallmarks of apoptosis including externalization of phosphatidylserine, caspase-3 activation and PARP cleavage. Ex vivo, S55746 induces apoptosis in the low nanomolar range in primary Chronic Lymphocytic Leukemia and Mantle Cell Lymphoma patient samples. Finally, S55746 administered by oral route daily in mice demonstrated robust anti-tumor efficacy in two hematological xenograft models with no weight lost and no change in behavior. Taken together, these data demonstrate that S55746 is a novel, well-tolerated BH3-mimetic targeting selectively and potently the BCL-2 protein.

Endothelin-converting enzyme-1 is expressed in human cerebral cortex and protects against Alzheimer's disease

Cerebral accumulation of beta-amyloid peptide (A beta) is a central event in the pathogenesis of Alzheimer's disease (AD). Endothelin-converting enzyme-1 (ECE-1) is a candidate A beta-degrading enzyme in brain, but its involvement in AD pathogenesis was never assessed. We first performed brain immunocytochemistry, using a monoclonal anti-ECE-1 antibody, and observed neuronal ECE-1 expression in various cortical regions of nondemented subjects. In the hippocampus, ECE-1 immunoreactivity showed a stereotypical pattern inversely correlated with susceptibility to A beta deposition, further suggesting a physiological role in A beta clearance. In order to undertake a genetic association study, we identified a functional genetic variant (ECE1B C-338A) located in a regulatory region of the ECE1 gene. We showed that the A allele is associated with increased transcriptional activity in promoter-reporter gene assays and with increased ECE-1 mRNA expression in human neocortex. In a case-control study involving 401 patients with late-onset AD and 461 aged controls, we found that homozygous carriers of the A allele had a reduced risk of AD (OR=0.47, 95% CI 0.25-0.88). This finding was strengthened by the analysis of two other genetic variants of the ECE1 gene, which showed that the genetic association is extended over at least 13 kilobases of the gene sequence. Our results suggest that ECE-1 expression in brain may be critical for cortical A beta clearance and offer new potential targets for therapeutic interventions in AD.