S63845

The FLT3 and IRAK4 inhibitor emavusertib (CA4948), the MCL1 inhibitor S63845, the BCL2 inhibitor venetoclax, and the HSP90 inhibitor PU-H71 were assessed as single agents and in combination for their ability to induce apoptosis and cell death in leukemic cells in vitro. The combination of CA4948 and BH3-mimetics may be effective in the treatment in FLT3-mutated AML with differential target specificity for MCL1 and BCL2 inhibitors. Moreover, the combination of CA4948 and PU-H71 may be a candidate combination treatment in FLT3-mutated AML.

Pro-survival proteins: MCL-1, BCL-2 and BCL-XL were inhibited using S63845, ABT-199 and A-1331852 respectively. Furthermore, MCL-1 inhibition led to enhanced binding between BCL-XL and BIM, while blocking BCL-XL increased MCL-1/BIM complex formation, indicating the cooperative role of these proteins. Stromal interactions alter the dependence on BCL-2 family members, providing a rationale for dual inhibition to abrogate the protective effect of stroma and restore sensitivity to CFZ.

Thus, we investigated the effects of ABT-737 and ABT-263, which target Bcl-2, Bcl-xL and Bcl-w as well as the Bcl-2-selective ABT-199 and the Mcl-1-selective S63845, in a panel of four BRAF-mutated and BRAF-WT melanoma cell lines. These findings demonstrate that melanoma cells can be efficiently targeted by BH3 mimetics, but the right combinations have to be selected. The observed pronounced activation of apoptosis pathways demonstrates the decisive role of apoptosis in the loss of cell viability by BH3 mimetics.

BH3 mimetics, including the BCL2/BCLXL/BCLw inhibitor navitoclax and MCL1 inhibitors S64315 and tapotoclax, have undergone clinical testing for a variety of neoplasms...Building on the observation that BH3 mimetic monotherapy induces AMP kinase (AMPK) activation in multiple acute leukemia cell lines, we report that the AMPK inhibitors (AMPKis) dorsomorphin and BAY-3827 sensitize these cells to navitoclax or MCL1 inhibitors...Conversely, dorsomorphin synergizes with navitoclax or the MCL1 inhibitor S63845 to induce cell death in primary acute leukemia samples ex vivo and increases the antitumor effects of navitoclax or S63845 in several xenograft models in vivo with little or no increase in toxicity in normal tissues. These results suggest that AMPK inhibition can sensitize acute leukemia to multiple BH3 mimetics, potentially allowing administration of lower doses while inducing similar antineoplastic effects.

At the functional level, we showed that among the 13 genes, p53-regulated BAX expression correlated to, and directly impacted, the MCL1 BH3 mimetic S63845 sensitivity of myeloma cells by decreasing MCL1-BAX complexes...Nevertheless, scRNAseq analysis showed that myeloma cells surviving to the combination had lower p53 score, showing that myeloma cells with higher p53 score were more sensitive to BH3 mimetics. Taken together, we established a functional p53 score that identifies myeloma cells with biallelic TP53 invalidation, demonstrated that p53-regulated BAX is critical for optimal cell response to BH3 mimetics, and showed that MCL1 and BCL2 BH3 mimetics combination may be of interest for patients with biallelic TP53 invalidation, for whom there is still an unmet medical need.

MethodsA diverse panel of EBV+ T/NK lymphoma cell lines including SNK1, MECO4, SNK6, SNT8, SNK10, SNT15 and SNT16 were evaluated for sensitivity to MMAE alone and with specific BH3 family inhibitors including A1331852, inhibiting BCL-XL, venetoclax inhibiting and BCL-2 and the MCL-1 inhibitor S63845 (Generon). These data show the potential of BV with BCL-XL inhibition to be an effective and tolerable treatment for ENKTL. We are now planning a detailed preclinical study to better understand the efficacy and safety of this combination in vivo and progress towards a future clinical trial.

Our previous studies have shown that pegcrisantaspase (PegC), a long-acting pegylated crisantaspase, synergizes with the BCL2 inhibitor, Venetoclax (Ven), to kill several AML cell lines and patient-derived primary AML cells with complex karyotype in vitro and in vivo in a xenograft mouse model... Using a panel of 4 human AML cell lines (MOLM14, MV411, MonoMac6, HL60) as well as primary AML patient samples, weestablished the anti-leukemic activity of the BCL2 inhibitor S55746 and the MCL1 inhibitor S63845 alone and in combination with the long-acting E. coli asparaginase, calaspargase pegol-mknl (CalPegA)... We report that the E. coli asparaginase, CalPegA, enhances the anti-leukemic effect of the BCL2 inhibitor, S55746, but does not impact the activity of the MCL1 inhibitor, S63845, in AML cell lines, patient derived primary AML samples, and in an AML xenograft mouse model. Ongoing studies are further investigating the anti-leukemic mechanism of S55476/S63845 + CalPegA and examining the efficacy and pharmacodynamic/pharmacokinetic effects of these agents in a patient derived xenograft model of AML.

5µM, KS18 demonstrated efficacy against bortezomib-resistant MM cells, outperforming other Mcl-1 inhibitors in clinical trials such as S63845, VU661013, and AZD5991. According to these results, KS18 may be able to overcome resistance by concentrating on Mcl-1. These encouraging findings have prompted the development of many models of drug-resistant MM and AML for in vivo evaluation of this potential chemical.

These data highlight that the application of BH3-mimetics may differ between first line treatment and relapsed disease. Combination of NK cell-based immunotherapy with BH3-mimetics may further increase killing of chemoresistant neuroblastoma, outlining a new treatment strategy for relapsed neuroblastoma.

Additionally, statins sensitize to apoptosis induced by MCL1 inhibitor, S63845. Statins sensitize MM cells to venetoclax by upregulating two pro-apoptotic proteins: PUMA via a p53-independent mechanism, and NOXA via the integrated stress response. These findings provide rationale for prospective testing of statins with venetoclax regimens in MM.

In an effort to further confirm these results, and examine the extent to which peptide-based BH3 profiling predicts sensitivity to selective BH3 mimetics in MTCL, cell lines were treated with venetoclax, A1155463 (a BCL-xL selective antagonist), navitoclax (a BCL-2/BCL-xL antagonist), or S63845 (MCL-1 antagonist), and cell viability determined. These findings suggest that BCL-xL is a therapeutic vulnerability for MTCL subsets, particularly non-ALCL subtypes that are TCR dependent, and provide a robust pre-clinical rationale for future studies investigating navitoclax in these lymphomas.

However, the clinical utility of navitoclax, a BCL-xL and BCL-2 dual inhibitor, as demonstrated in combination with JAK2 inhibitor ruxolitinib in patients with myelofibrosis (Harrison et al...In this study, we evaluated the pre-clinical efficacy of DT2216 in combination with ruxolitinib, 5-azacytidine (AZA), or MCL-1 inhibitor S63845 in JAK2-mut AML models...CONCLUSIONS These findings highlight the promising efficacy of DT2216 in JAK2-mut AML, as evidenced by reduced cell viability, on-target degradation of BCL-xL, and synergistic anti-leukemia effects when combined with AZA, ruxolitinib or MCL-1 inhibitor. These results provide valuable insights into future therapeutic strategies for the treatment of JAK2-mut AML, particularly in the context of post-MPN AML.

We observed that venetoclax-resistant clones were resistant to most standard-of-care anti-MM agents including alkylating agents (Melphalan, cyclophosphamide, bendamustine), proteasome inhibitors (bortezomib and carfilzomib) or immunomodulatory drugs (lenalidomide and pomalidomide) than parental cells, suggesting a broad resistance to anti-cancer agents possibly due to reduced apoptotic signaling...Simultaneous inhibition of MCL1 (via S63845) or BCL-XL (via A155463) and BCL2 (via venetoclax) increased BIM release and enhanced cell death in the resistant clones compared to single agents, with combination index (CI) values < 0.3 in all doses tested...We observed that both antibody-dependent cellular cytotoxicity (ADCC) induced by Daratumumab and BCMA targeting CAR-T cells induced comparable cell death in venetoclax-resistant clones and parental cells. Moreover, myeloma cells from a patient with t(11; 14) MM progressing on venetoclax, showed significant cytotoxicity to anti-BCMA CAR T cells in vitro and achieved a deep response subsequently when treated with Cilta-cel. In conclusion, we report that resistance to venetoclax confers broad resistance to standard-of-care myeloma drugs and that immunotherapies, especially CAR-T cells and CD38 monoclonal antibody, may remain effective, thus conferring potential benefits in managing acquired resistance to venetoclax.

Recently, the BH3 mimetic-Bcl2 inhibitor venetoclax (VEN), has been approved by FDA in 2018 for the treatment of patients with AML in combination with a hypomethylating agent (HMA) such as azacytidine (AZA)...ADSS2 KO also led to a noteworthy reduction in the IC50 values of both VEN and the Mcl1 inhibitor S63845 in these cell lines...Collectively, our observation revealed that targeting ADSS2 is critical for sensitizing AML cells to BH3 mimetics. We are now conducting preclinical assessments of ADSS2 inhibitors.

This shift was also reflected in an ex vivo drug treatment assay showing decreased sensitivity to the MCL-1 inhibitor S63845 and the BCL-XL inhibitor A-1331852 in ALL cells from VEN- treated mice compared to control- treated mice (S63845 EC50 1.5 vs. 2.2 µM, A-1331852 EC50 9.3 vs. 15.3 µM). Taken together, acquired VEN-resistance was recapitulated in a co-clinical trial model of BCP-ALL with repeated in vivo treatment cycles showing lower drug sensitivities along with increasingly reduced in vivo anti-ALL activity of VEN. Characterization of acquired VEN-resistance revealed decreased functional dependency on anti-apoptotic proteins and downregulation of pro-apoptotic BIM and BAX, thus pointing to an imbalance of pro- and anti-apoptotic molecules, which can be potentially targeted by directed compounds bypassing resistance to specific BCL-2 inhibition.

Our study supports the notion that the efficiency of an agent designed to target a single protein can largely depend on the phenotype of cancer cells. Thus, it is important to define appropriate phenotype determinants to stratify the patients for the novel therapy.

The use of combined MCL1 inhibitors with cisplatin in TNBC effectively initiates TAp73 anti-tumor effects on cell cycle arrest and apoptosis. This observation provides a molecular profile that can be exploited to identify sensitive TNBCs.

Elevated susceptibility to PU-H71 and venetoclax was associated with primary AML with CD117 > 80% and CD11b < 45%. The combination of HSP90 inhibitor PU-H71 and MCL1 inhibitor S63845 may be a candidate treatment for FLT3-mutated AML with moderate CD34 positivity while the combination of HSP90 inhibitor PU-H71 and BCL2 inhibitor venetoclax may be more effective in the treatment of primitive AML with high CD117 and low CD11b positivity.

Previously, we demonstrated that BAPTA enhanced apoptosis induced by venetoclax, a BCL-2 antagonist, in diffuse large B-cell lymphoma (DLBCL)...In this study, we discovered that BAPTA alone induced apoptosis in hematological cancer cell lines that were highly sensitive to S63845, an MCL-1 antagonist...Secondly, cellular effects caused by BAPTA are not necessarily related to Ca signaling. Our data support the need for a reassessment of the role of Ca in cellular processes when findings were based on the use of BAPTA.

The Bellini study demonstrated that combination therapy of BH3-mimetic venetoclax with velcade improves progression-free survival (PFS) and response rates in this subgroup of MM patients...Simultaneous inhibition of MCL1 (via S63845) or BCL-XL (via A155463) and BCL2 (via venetoclax) increased BIM release and enhanced cell death in the resistant clones compared to single agents, with combination index (CI) values < 0.3 in all doses tested. In conclusion, we report that resistance to Venetoclax in in vitro models of MM evolves from the outgrowth of persister clones with a shift in mitochondrial dependency that confers broad resistance to all anti-tumor agents, including standard-of-care myeloma drugs.

We tested the efficacy of BH3 mimetics, including venetoclax and S63845, in primary Aza-resistant AML cells treated with FUS-ERG. The disturbance of chromatin organisation might induce this by co-repressors, including BCOR, NCOR2, and RCOR1. MCL1 inhibition could partially overcome Aza resistance in FUS-ERG-harbouring AML cells.

Ex vivo drug treatments included: BCL2i (inhibitor): venetoclax; MCL-1i: AZD5991, S63845 and BCLXLi: A133. The genomic landscape of BCL2-R CLL is characterized by a high frequency of trisomy 12, subclonal NOTCH and RAS pathway mutations, as well as BCL2 and MLL2 mutations. Protein expression, BH3 profiling and viability assays data are consistent with nearly exclusive dependence on Bcl-2.

Here we describe that the AKT inhibitors MK-2206 and Gsk690693 sensitize multiple leukemia cells to the MCL1 inhibitor S63845. Knockdown of BAD significantly inhibits MK-2206-induced sensitization to S63845. Thus, our results suggest that MK-2206 sensitizes multiple leukemia cells to S63845-induced apoptosis, with the mechanisms involving BAD dephosphorylation and BCLX downregulation.

1, 2 Treatment of CLL cells with entospletinib, but not other BCR-signaling inhibitors, led to a disruption of BAFF-BCR cross-talk and downmodulation of MCL1 mRNA and protein, thus implicating SYK in transduction of multiple pro-survival signals emanating from the tumor microenvironment.1 Entospletinib has shown promising clinical activity in CLL, alone or in combination with obinutuzumab, including in patients with high-risk disease such as TP53 aberrant.3, 4 The drug is very well tolerated, however its development in CLL has been halted. Meanwhile, we have shown that luxeptinib, a dual SYK/BTK kinase inhibitor, has activity in BTK inhibitor-resistant lymphoid models in vitro.5 Luxeptinib is now being investigated in lcinical trials in hematologic malignancies...The early results of MS-553, a selective PKC-β inhibitor, indicates that this agent is tolerable and effective both as single agent and in combination with venetoclax.8 Proteolysis-targeting chimeras (PROTACs) are a new class of small molecules with two covalently-linked ligands recruiting target protein and E3 ubiquitin ligase together to trigger and enable proteasomal degradation of the target protein.9 “BTK degraders”, such as NRX- 2127 (Nurix Therapeutics) and BGB-16673 (Beigene), have entered clinical trials in patients with lymphoid malignancies...Additionally, NX-2127 has shown preclinical activity similar to immunomodulatory drugs (IMiDs) by catalyzing the ubiquitination of Ikaros (IKZF1) and Aiolos (IKZF3), resulting in increased T-cell activation.10 Early results of an ongoing clinical trial of NX-2127 demonstrate an ORR of 33% in heavily pre-treated patients with CLL, and overall good tolerability 11...The preclinical activity of AZD5991 has shown that selective targeting of MCL1 induced metabolic dysfunction and abrogated survival of diffuse large B cell lymphoma and ibrutinib-resistant mantle cell lymphoma cell lines in vivo and in vitro.13 Other BH3-mimetics targeting MCL1 include AMG176 and S63845.14-16 In an experimental design testing the effects of AMG-176 on CLL and normal hematopoietic cell death it was demonstrated that AMG-176 is an active agent in inducing CLL cell death while sparing normal blood cells...Anti-CD20 monoclonal antibodies – rituximab, obinutuzumab and ofatumumab – have significantly improved the survival outcomes. The B cell activating factor receptor (BAFF-R) is one of the main pro-survival receptors in B cells.18 In a preclinical study, ianalumab (VAY-736), a humanized defucosylated engineered antibody directed against BAFF-R, antagonized pro-survival effects of BAFF in CLL cells and showed promising activity both as a single agent and in combination with ibrutinib.19 A phase 1 study of dose escalation and dose expansion investigated the combination of ianalumab with ibrutinib in 32 patients with CLL with median one prior line of therapy (range, 0-4)...This study showed promising results not expected with ibrutinib alone.20 Tafasitamab – a Fc-enhanced, humanized, monoclonal antibody to CD19 – in combination with idelalisib or venetoclax in 24 patients has been associated with an ORR of 77% and 91%, respectively...In a phase 1 study involving 26 patients with R/R CLL, cirmtuzumab administered at four biweekly infusions was shown to have a long plasma half-life and did not have dose-limiting toxicity, potentially providing another treatment opportunity for patients with CLL.22 Immune Cell Enabling Therapies...A recent report of a phase 1/2 study of lisocabtagene maraleucel, an autologous CD19-directed CAR T-cell therapy (TRANSCEND CLL 004), confirmed efficacy in patients with R/R CLL.23 In this study, 23 patients with median 4 prior lines of therapy (range 2-11) were enrolled, 10 of whom were considered double exposed/refractory...In total, 65% of patients required administration of tocilizumab and/or corticosteroids.23 In addition to the ongoing phase 2 portion of this study, efforts now focus on innovative CAR T-cell designs as well as combination strategies...A phase 1b/2 ongoing trial is currently examining the safety and tolerability of the product in patients with R/R CLL. The early results suggest that epcoritamab administered subcutaneously is well tolerated in a heavily pretreated patient population with multiple high-risk features and shows clinical activity.25 Furthermore, an ongoing study is demonstrating preliminary efficacy of epcoritamab in patients with Richters transformation, a notoriously difficult-to-treat complication of CLL.26

The findings of this study suggest that S63845 may reduce cell proliferation by modulating the lipid compositions, especially, by increasing ceramide levels in AML cell lines. Additionally, the study highlights that S63845 has a distinct impact on the lipid profiles of different AML cell lines, indicating the potential of using lipidomic profiles asmarkers. Importantly, our study proposes that the increases in Cer levels in response to S63845 treatment may occur due to SM hydrolysis and may be linked to the anti-inflammatory effects of S63845 in AML cell lines, which deserve further investigation to fully understand the specific mechanisms.

Although oral AZA, CC486, and Oral DAC, ASTX727, are currently available in some countries, OR21 has the advantage that it is a single compound and less myelosuppressive...We found that MCL-1 expression correlates inversely with sensitivity to OR21 plus Ven, but not to OR21 plus S63845, a selective MCL-1 inhibitor... Ven increased ROS with reduction of AMPK and suppression of autophagy. OR21 enhanced ROS accumulation with attenuated mitophagy response, leading to increased anti-leukemia effects. OR21 plus Ven is a promising oral combination therapy for AML.

Background: Venetoclax (ven) in combination with hypomethylating agents or low dose cytarabine leads to rapid and durable remission in patients (pts) with acute myeloid leukemia (AML) unfit for intensive chemotherapy (IC), however, pts with TP53 mutations ( TP53 mut ) exhibit adverse prognosis...Deletion of DELE1 or OMA1 in AML cell lines blocked eIF2α activation and induction of the transcription factor ATF4, a critical ISR effector, in response to the mitochondrial stressor FCCP, ven, and azacitidine, and resulted in ven resistance similar to that of TP53 deficient cells...Further screening of these cell lines for ven sensitizing activity revealed the BH3 mimetic S63845, which targets MCL1, as the top hit, suggesting that combined BH3 mimetics may overcome ven resistance during ISR pathway defects... These data suggest that defective ISR signaling may be a factor in TP53 mut AML treatment outcome and point to DELE1 dysregulation as a driver of ISR inactivation in pts with TP53 mut AML. The ISR induces the expression of NOXA, which displaces MCL1 from BIM and lowers the apoptotic threshold. Our data identify p53, DELE1, and OMA1 as regulators of NOXA expression post ven treatment and indicate that co-targeting MCL1 in pts with TP53 mut AML may be beneficial to overcome ven resistance.

109 AML samples' blast-specific ex vivo responses to venetoclax (BCL-2 inhibitor), navitoclax (BCL-2/BCL-XL inhibitor), A-1331852 (BCL-XL inhibitor) and S-63845 (MCL-1 inhibitor) were profiled by flow cytometry... In the computational comparison analysis of VenEx trial participants' genetic aberrations and BH3 mimetic ex vivo responses, TP53 mutation (p=0.005) and complex karyotype (p=0.003) were the strongest predictors of venetoclax resistance, while IDH2 (p=0.006) and SRSF2 (p=0.007) mutations predicted favorable responses (Figure A)... This study showed that AML patients harboring TP53 mutations have reduced ex vivo sensitivity to venetoclax, which might be associated with decreased BCL-2 protein expression. In contrast, our BH3 mimetic drug screening results demonstrated that the dual inhibition of BCL-2 and BCL-XL by navitoclax is capable of inducing apoptosis in myeloid blast cells regardless of TP53 mutation status. However, larger patient cohorts and more extensive functional analysis of the anti/pro-apoptotic dependencies in this patient group is warranted.

Combined treatment with S63845 and ABT-737 or MAPK pathway inhibitor enhanced apoptosis but also induced differentiation of tested cells, as well as altering the expression of the MCL-1 protein. Taken together, our data provide the rationale for further studies regarding the use of MCL-1 inhibitor in combination with other pro-survival protein inhibitors.

The current study reveals the subtype specificity of BCL-2 expression and sheds light on the mechanism of venetoclax resistance in SCLC. Additionally, we provide preclinical evidence that combined BCL-2 and MCL-1 targeting is an effective approach to overcome venetoclax resistance in high BCL-2-expressing SCLCs with intact BAX.

The maturation of the erythroid lineage in the intramedullary and extramedullary segments was blocked to varying degrees, and both the intramedullary and extramedullary lymphoid lineages were inhibited. This study provides a complete description of the effects of MCL-1 inhibitor on the intramedullary and extramedullary hematopoietic lineages, which is important for the selection of combinations of antitumor drugs and the prevention of adverse hematopoiesis-related effects.

Our data indicated that PCDH7 mediated the resistance of CRC cells to ABT-263 (a small-molecule Bcl-2 inhibitor that induces apoptosis) by inhibiting cell apoptosis, which was supported by the downregulation of caspase-3, caspase-9, and PARP cleavage. Taken together, although PCDH7 inhibited the migration and invasion of CRC cells, it could facilitate the development of drug resistance in colorectal cancer cells by positively modulating Mcl-1 expression. The application of the Mcl-1 inhibitor S63845 could be a potential strategy for CRC chemotherapy, especially in CRC with high levels of PCDH7.

BH3 mimetics such as ABT-737 not only induce cell death, but also activate autophagy. Furthermore, STING KO diminishes navitoclax- or S63845-induced apoptosis, suggesting that STING activation enhances rather than inhibits apoptosis. Thus, our findings provide new insights into the regulations of navitoclax- or S63845-induced autophagy and cell death.

Co-inhibition of BCL2 and BCL-XL (ABT-263) with inhibition of MCL1 (S63845) induces potent synergistic cytotoxicity in multiple HGSOC models. Thus, these results support the exploration of LbL NPs as a strategy to deliver potent drug combinations to recurrent HGSOC. While these findings are described for co-encapsulation of a BCL2/XL and a MCL1 inhibitor, the modular nature of LbL assembly provides flexibility in the range of therapies that can be incorporated, making LbL NPs an adaptable vehicle for delivery of additional combinations of pathway inhibitors and other oncology drugs.

However, in combination with the Mcl-1 inhibitor S63845, the effects of vemurafenib were strongly enhanced in BRAF-mutated cell lines, and the effects of SCH772984 were enhanced in both BRAF-mutated and BRAF-WT cells. The combination finally resulted in downregulation of antiapoptotic Bcl-2 and enhanced expression of the proapoptotic Noxa. In conclusion, combined inhibition of ERK and Mcl-1 revealed an impressive efficacy both in BRAF-mutated and WT melanoma cells, and may thus represent a new strategy for overcoming drug resistance.

The challenge is the observed resistance to venetoclax, for which the MCL-1 protein may be largely responsible. Molecules with the potential to break the associated resistance include S63845, S64315, chidamide and arsenic trioxide (ATO)...Knockdown of the PD-L1 gene in preclinical studies was associated with increased levels of BCL-2 and MCL-1 in lymphocytes T, which could increase their survival and promote tumor apoptosis. A trial (NCT03969446) is currently underway to combine inhibitors from both groups.

Background: Venetoclax (ven) in combination with hypomethylating agents or low dose cytarabine leads to rapid and durable remission in patients (pts) with acute myeloid leukemia (AML) unfit for intensive chemotherapy (IC), however, pts with TP53 mutations (TP53mut) exhibit adverse prognosis...Deletion of DELE1 or OMA1 in AML cell lines blocked eIF2α activation and induction of the transcription factor ATF4, a critical ISR effector, in response to the mitochondrial stressor FCCP, ven, and azacitidine, and resulted in ven resistance similar to that of TP53 deficient cells...Further screening of these cell lines for ven sensitizing activity revealed the BH3 mimetic S63845, which targets MCL1, as the top hit, suggesting that combined BH3 mimetics may overcome ven resistance during ISR pathway defects... These data suggest that defective ISR signaling may be a factor in TP53mut AML treatment outcome and point to DELE1 dysregulation as a driver of ISR inactivation in pts with TP53mut AML. The ISR induces the expression of NOXA, which displaces MCL1 from BIM and lowers the apoptotic threshold. Our data identify p53, DELE1, and OMA1 as regulators of NOXA expression post ven treatment and indicate that co-targeting MCL1 in pts with TP53mut AML may be beneficial to overcome ven resistance.

We assessed how these cell lines resisted cell death triggered by a general apoptotic inducer, staurosporine (STS), and a highly specific inhibitor for MCL1 (S63845, MCL1i). Our results show that overexpression of other BCL2 family members can substantially buffer against the detrimental effects of both STS and MCL1i. Together, our data indicate that the expression levels of the BCL2 family likely explain why the PEL tumor cells are highly addicted to MCL1. More importantly, our results suggest that caution should be taken when considering MCL1i as a single treatment regimen for cancer, as resistance to this class of inhibitor can easily develop.

In this study we evaluated the effects of highly specific inhibitors for Bcl-x L (WEHI-539), Bcl-2 (ABT-199), and Mcl-1 (S63845) as well as dual inhibition of Bcl-x L /Bcl-2 (ABT-263) in commonly occurring solid tumors...Following Epirubicin treatment, breast cancer cell lines showed a downregulation of antiapoptotic Bcl-2 protein expressions. Conclusions Our findings indicate that among antiapoptotic Bcl-2 proteins, targeting Bcl-x L might break resistance to radiation in NSCLC, CCA and breast cancer in vitro. Especially for breast cancer, Mcl-1 could also be a promising target that needs to be further investigated.