Contributions
Abstract: S1578
Type: Oral Presentation
Presentation during EHA23: On Sunday, June 17, 2018 from 08:45 - 09:00
Location: Room A7
Background
Drugs with novel mechanisms of action are essential to overcome resistance to current standards of care in MM. Recently, the BCL-2 inhibitor, venetoclax, has demonstrated to be effective in this disease, particularly in patients bearing the t(11;14) translocation. However, overexpression of MCL-1 seems to be more important in MM pathogenesis, which raises the possibility of using the new MCL-1 inhibitor, S63845, as a promising therapeutic agent for the treatment MM.
Aims
The aim of the present work was to evaluate the efficacy and mechanism of action of S63845 (MCL1i) alone and in combination with venetoclax (BCL2i) in preclinical in vitro and in vivo models of MM.
Methods
S63845 was provided by Servier. In vitro activity of MCL1i and BCL2i alone and in combination was evaluated on different myeloma cell lines. The combination index (CI) was calculated with Calcusyn software based on results from MTT assay. Four cell lines with different sensitivity to MCL1i (MM.1S, JJN3, KMS12-BM and NCI-H929) were chosen for the mechanistic studies. Effects on apoptosis and cell cycle were evaluated by flow cytometry. BCL-2 family protein levels were analysed by Western blot. The mechanism of action was assessed by immunoprecipitation assays. Finally, a plasmacytoma model in CB17-SCID mice and a disseminated model in BRG mice were used for in vivo studies.
Results
The MCL1i, S63845, showed a strong anti-tumor dose-dependent effect on nine multiple myeloma cell lines, with IC50 values at 48 hours ranging from 2.6 to 465 nM. The sensitivity to S63845 was independent of the genetic alterations and the basal expression of the different BCL-2 family members. Although co-culture with stromal cells induced MCL-1 expression, S63845 remained active in these conditions. While no changes were observed in cell cycle, S63845 treatment induced apoptosis, triggered by mitochondrial outer membrane permeabilization. S63845 did not significantly modify the levels of MCL-1 or other BCL-2 family member in MM.1S or KMS12-BM, although immunoprecipitation assays in MM.1S, JJN3, NCI-H929 and KMS12-BM cell lines showed that S63845 impaired the MCL-1/BIM interaction. Interestingly, a compensatory increase in the BCL-2/BIM interaction in the two less sensitive cell lines tested, MM.1S and JJN3, was observed after treatment with S63845. On the other hand, the BCL-2 inhibitor displayed the opposite effect, with an impairment of the BCL-2/BIM interaction but a compensatory increase of the binding of MCL-1 to BIM. Accordingly, we hypothesized that the simultaneous inhibition of MCL-1/BIM and BCL-2/BIM interactions could result in significant synergistic induction of apoptosis. In this regard, the combination of MCL1i + BCL2i led to pronounced synergy, with CIs ranging from 0.1 to 0.4, in MM1S, JJN3, KMS-12.BM and NCI-H929 (Figure 1). Moreover, the triple combination MCL1i + BCL2i + dexamethasone showed an even stronger synergy than the double treatment of MM.1S and in JJN3 (CI<0.06 and CI<0.2, respectively). The efficacy of the triple combination MCL1i + BCL2i + dexamethasone is currently being evaluated in two murine models of human myeloma, a subcutaneous plasmacytoma and a disseminated one.
Conclusion
Our preclinical data demonstrate the potent activity of the combination of MCL1 and BCL2 inhibitors (+/- dexamethasone) in MM, and provides the rationale for the clinical development of this combination in relapsed or refractory MM patients.
This project was supported by Norvartis Pharmaceuticals and by the Spanish Projects GRS 1604/A/17, ISCIII-FIS PI15/00067 and ISCIII-FIS PI15/02156.
Session topic: 13. Myeloma and other monoclonal gammopathies – Biology & Translational Research
Keyword(s): BCL2, Mcl-1, Multiple Myeloma
Abstract: S1578
Type: Oral Presentation
Presentation during EHA23: On Sunday, June 17, 2018 from 08:45 - 09:00
Location: Room A7
Background
Drugs with novel mechanisms of action are essential to overcome resistance to current standards of care in MM. Recently, the BCL-2 inhibitor, venetoclax, has demonstrated to be effective in this disease, particularly in patients bearing the t(11;14) translocation. However, overexpression of MCL-1 seems to be more important in MM pathogenesis, which raises the possibility of using the new MCL-1 inhibitor, S63845, as a promising therapeutic agent for the treatment MM.
Aims
The aim of the present work was to evaluate the efficacy and mechanism of action of S63845 (MCL1i) alone and in combination with venetoclax (BCL2i) in preclinical in vitro and in vivo models of MM.
Methods
S63845 was provided by Servier. In vitro activity of MCL1i and BCL2i alone and in combination was evaluated on different myeloma cell lines. The combination index (CI) was calculated with Calcusyn software based on results from MTT assay. Four cell lines with different sensitivity to MCL1i (MM.1S, JJN3, KMS12-BM and NCI-H929) were chosen for the mechanistic studies. Effects on apoptosis and cell cycle were evaluated by flow cytometry. BCL-2 family protein levels were analysed by Western blot. The mechanism of action was assessed by immunoprecipitation assays. Finally, a plasmacytoma model in CB17-SCID mice and a disseminated model in BRG mice were used for in vivo studies.
Results
The MCL1i, S63845, showed a strong anti-tumor dose-dependent effect on nine multiple myeloma cell lines, with IC50 values at 48 hours ranging from 2.6 to 465 nM. The sensitivity to S63845 was independent of the genetic alterations and the basal expression of the different BCL-2 family members. Although co-culture with stromal cells induced MCL-1 expression, S63845 remained active in these conditions. While no changes were observed in cell cycle, S63845 treatment induced apoptosis, triggered by mitochondrial outer membrane permeabilization. S63845 did not significantly modify the levels of MCL-1 or other BCL-2 family member in MM.1S or KMS12-BM, although immunoprecipitation assays in MM.1S, JJN3, NCI-H929 and KMS12-BM cell lines showed that S63845 impaired the MCL-1/BIM interaction. Interestingly, a compensatory increase in the BCL-2/BIM interaction in the two less sensitive cell lines tested, MM.1S and JJN3, was observed after treatment with S63845. On the other hand, the BCL-2 inhibitor displayed the opposite effect, with an impairment of the BCL-2/BIM interaction but a compensatory increase of the binding of MCL-1 to BIM. Accordingly, we hypothesized that the simultaneous inhibition of MCL-1/BIM and BCL-2/BIM interactions could result in significant synergistic induction of apoptosis. In this regard, the combination of MCL1i + BCL2i led to pronounced synergy, with CIs ranging from 0.1 to 0.4, in MM1S, JJN3, KMS-12.BM and NCI-H929 (Figure 1). Moreover, the triple combination MCL1i + BCL2i + dexamethasone showed an even stronger synergy than the double treatment of MM.1S and in JJN3 (CI<0.06 and CI<0.2, respectively). The efficacy of the triple combination MCL1i + BCL2i + dexamethasone is currently being evaluated in two murine models of human myeloma, a subcutaneous plasmacytoma and a disseminated one.
Conclusion
Our preclinical data demonstrate the potent activity of the combination of MCL1 and BCL2 inhibitors (+/- dexamethasone) in MM, and provides the rationale for the clinical development of this combination in relapsed or refractory MM patients.
This project was supported by Norvartis Pharmaceuticals and by the Spanish Projects GRS 1604/A/17, ISCIII-FIS PI15/00067 and ISCIII-FIS PI15/02156.
Session topic: 13. Myeloma and other monoclonal gammopathies – Biology & Translational Research
Keyword(s): BCL2, Mcl-1, Multiple Myeloma