birinapant (IGM-9427)

Several Survivin inhibitors, including YM-155, Debio1143, EM1421, LQZ-7I, and TL32711, have emerged as potential anticancer drugs awaiting validation in clinical trials. Furthermore, Wi-AREAL treatment activated apoptosis signaling, as evidenced by reduced PARP-1 and Bcl-2 levels, increased procaspase-3, and elevated Cytochrome C. Additionally, treating cells with a nontoxic low concentration (0.01%) of Wi-AREAL inhibited migration and invasion, as well as EMT (epithelial-mesenchymal transition) signaling. By combining computational and experimental approaches, we demonstrate the potential of Wi-A and Wi-AREAL as natural inhibitors of Survivin, which may be helpful in cancer treatment.

P1, N=272, Active, not recruiting, IGM Biosciences, Inc. | Recruiting --> Active, not recruiting | N=430 --> 272

Co-treatment with bazedoxifene and the SMAC-mimetics, LCL161 or Birinapant, that target the IAP family of proteins, demonstrated increased apoptosis and reduced proliferation in colorectal cancer cells. Our findings provide evidence that bazedoxifene treatment could be combined with SMAC-mimetics and chemotherapy to enhance tumour cell apoptosis in colorectal cancer, where gp130 receptor signalling promotes tumour growth and progression.

To find out actionable targets able to re-enforce leukemic cells vulnerability to CD3 mAbs, including the clinically relevant Teplizumab, we identified the molecular program induced by CD3 mAbs in PDXs-derived from T-ALL cases...We show in vivo that Etanercept, a sink for TNF/LTenhancesCD3 anti-leukemic properties, indicating that TNF/TNFR survival pathways interferes with TCR-induced leukemic cell death. However, suppression of TNF-mediated survival and switch to TNFR-mediated cell death through inhibition of c-IAP1/2 with the SMAC mimetic Birinapant synergized with -CD3 to impair leukemia expansion in a RIPK1-dependent manner and improve mice survival. Thus, our results advocate the use of either TNFa/LTa inhibitors, or Birinapant/other SMAC mimetics to improve anti-CD3 immunotherapy in T-ALL.

Using immunophenotyping and gene expression analysis in patient biospecimens along with in silico modeling and a preclinical model with a pan-IAP antagonist, this study revealed an interplay between increased TAMs, TNF-α signaling, and XIAP activation during (immune) stress in IBC. These data demonstrate the potential of IAP antagonists as immunomodulators for improving IBC therapeutic regimens.

P1, N=13, Terminated, National Cancer Institute (NCI) | N=34 --> 13 | Trial completion date: Jul 2024 --> Dec 2023 | Active, not recruiting --> Terminated | Trial primary completion date: Jul 2024 --> Nov 2023; Drug supply issues

P1, N=34, Active, not recruiting, National Cancer Institute (NCI) | Recruiting --> Active, not recruiting

P1, N=430, Recruiting, IGM Biosciences, Inc. | Trial completion date: Jan 2027 --> Aug 2027 | Trial primary completion date: Nov 2026 --> Jun 2026

Of all tested compounds birinapant, a peptidomimetic of second mitochondrial-derived activator of caspases (SMAC) and inhibitor of apoptosis protein (IAP) family proteins and the hypomethylating agent (HMA) decitabine showed the strongest improvement of CAR T cell cytotoxicity in an additive but also in a synergistic manner. Our data suggest that high throughput drug interaction screens are a reliable approach to investigate the impact of chemical compounds on the functionality of AML-specific CAR T-cell products. HMA and SMAC mimetics are promising candidates that may potentially enhance the cytotoxicity of CAR T-cells. Ongoing studies are evaluating the effect of HMAs and SMAC mimetics on CAR T-cell proliferation and anti-tumor efficacy against AML cell lines and primary AML patient samples upon serial antigen stimulation.

P1, N=430, Recruiting, IGM Biosciences, Inc.

Of interest, two Smac mimetics, birinapant and SM164, exhibited this kind of differential enhancement. In tumor xenograft studies, combinations of immunotoxin and birinapant caused complete regressions in MDA-MB-468tumor-bearing mice but not in mice with A431 tumors. We propose that IAPs constitute a barrier to immunotoxin efficacy which can be overcome with combination treatments that include Smac mimetics.

P1, N=430, Recruiting, IGM Biosciences, Inc. | Phase classification: P1a/1b --> P1

At last, birinapant suppressed the activation of mitogen-activated protein kinase (MAPK) signaling pathway and K48-linked ubiquitinated degradation of TRAF3 in MH-S cells after LPS administration. In conclusion, the results proved that birinapant protected against LPS-induced ALI through inhibiting MAPK activation and K48-linked ubiquitination of TRAF3 in alveolar macrophages.

This was consistent with previous reports that BET inhibitors (e.g., OTX015, mivebresib or ABBV-075 and JQ1) are effective against 3q26.2-r AML cell lines, patient-derived (PD) AML cells and PDX models...In follow-up experiments, XIAP/cIAPs inhibitors birinapant (10-1000 nM) or SM-164 (30-1000 nM), chosen based on the MIPE screen outcomes, induced significantly more dose-dependent apoptosis in 3q26.2-r versus the other AML cell lines...Treatment with the dual mTOR/PIK3CA inhibitor NVP-BGT226 (1-30 nM) or navitoclax or Bcl-xL-specific BH3 mimetic A-1155463 also exerted lethality and synergistically induced apoptosis with mivebresib in AML cells with inv3/t(3; 3)...Co-treatment with birinapant and tegavivint also synergistically induced apoptosis in 3q26.2-r AML cells...Additionally, compared to each drug or vehicle control, co-treatment with birinapant and the BETi OTX015 (30 mg/kg/day, by oral gavage) was more effective in reducing AML burden in the xenograft model. These findings demonstrate promising preclinical activity of IAP protein inhibition against the cellular models of AML with inv3/t(3; 3) with EVI1 overexpression, supporting the rationale to further evaluate in vivo efficacy of birinapant and/or BETi-based combinations against this AML sub-type.

We tested in vivo sensitivity to 5 drugs of disparate mechanisms of action: birinapant and LCL-161 (SMAC mimetics), JQ-1 (BRD-4 inhibitor), venetoclax (BCL-2 antagonist), and quizartinib (FLT-3 inhibitor) in 4-9 different PDX models each. Overall, we demonstrate that acquired resistance to targeted therapy in AML is accompanied by common mechanism of reduction in mitochondrial priming along with drug-specific resistance mechanisms. Further, we find that, even in the context of a multiply-resistant PDX model, DBP can still identify therapeutic vulnerabilities that can be efficaciously exploited in vivo.

Using a patient-derived xenograft model, we demonstrate that treatment with the cIAP1/2 inhibitor, birinapant, during the MRD phase delays the onset of resistance to BRAF inhibitor and MEK inhibitor combination therapy. Together, our data suggest that cIAP2 upregulation in SOX10-deficient subpopulations of melanoma cells induces drug tolerance to MAPK targeting agents and provides a rationale to test a novel therapeutical approach to target MRD.

P1, N=34, Recruiting, National Cancer Institute (NCI) | Trial completion date: Jul 2023 --> Jul 2024 | Trial primary completion date: Jul 2023 --> Jul 2024

IAP antagonists have shown great promise for head and neck cancer, especially in combination with radiation therapy. Here, we review recent preclinical and clinical studies on the use of these novel targeted agents for head and neck cancer.

This proteogenomic study provides a comprehensive resource for investigating NMIBC and MIBC heterogeneity and highlights the potential of TRAIL-induced apoptosis as a treatment option for FGFR3-mutated bladder tumors, warranting a clinical investigation.

Combined treatment using birinapant and chloroquine significantly retarded AML progression in both a subcutaneous xenograft model injected with HEL cells and an orthotopic xenograft model injected intravenously with C1498 cells. Collectively, our data suggested that XIAP inhibition can induce autophagy, apoptosis and differentiation, and combined inhibition of XIAP and autophagy may be a promising therapeutic strategy for AML.

Notably, ex vivo drug screening revealed sensitivity of IKZF1plus blasts for drugs active against Ph-like ALL such as Birinapant and histone deacetylase inhibitors. We provided data in a large setting of a rare condition (DS-ALL) supporting that these patients, not associated with other high-risk features, need tailored therapeutic strategies.

Critically, all the PDXs resistant to Birinapant and ATG alone (n=11) obtained an additive (n=5) or synergic effect (n=6) with asignificant decrease in cell viability (Fig1D). These results provide a strong rationale for the combination of SMAC mimetic with ATG immunotherapy inducing TNFα signaling in T-ALL. T cell acute lymphoblastic leukemia

Treating G164 spheroids with birinapant, an antagonist of cellular inhibitor of apoptosis protein, induced CAR-T cell cytotoxicity...Using these different human 3D in vitro models, we uncovered malignant cell-intrinsic factors and novel mechanisms involving fibroblasts which may influence CAR-T cell activity. Complex human cell models may accelerate preclinical research into CAR-T cell therapies in solid tumors.

Preliminary Western blot experiments revealed that treatment of birinapant-sensitive and resistant PDX tumors in vivo and PDxOs in vitro with birinapant causes degradation of cIAP1 and cIAP2, but only causes apoptosis in birinapant-sensitive lines. Therefore, there may be a disruption of necessary downstream apoptotic signaling in the birinapant-resistant lines. Through follow-up Western blot experiments we determined that at baseline, birinapant-resistant PDxOs do not lack the TNFR extrinsic apoptosis proteins required for apoptosis signaling after IAP degradation, nor is there an abundance of these proteins in the birinapant-sensitive PDxOs.

Additionally, birinapant and AZD1775 combination treatment decreased cell proliferation and survival in combination with radiotherapy, a critical source of TNFα. These results support further investigation of IAP and WEE1 inhibitor combinations in preclinical and clinical studies in HNSCC.

We previously conducted a phase 2 clinical trial of the single-agent SMAC mimetic birinapant and observed minimal drug response in women with recurrent ovarian cancer despite demonstrating on-target activity...We show here that this synergy observed both in vitro and in vivo results from multiple convergent pathways to include increased caspase activation, HDAC inhibitor-mediated TNF-α upregulation, and alternative NF-kB signaling. These findings provide a rationale for the integration of SMAC mimetics and HDAC inhibitors in clinical trials for recurrent ovarian cancer where treatment options are still limited.

The screening process revealed that subset of CCA with GEM/CIS resistance acquired vulnerability to the small-molecule second mitochondrial-derived activator of caspases (SMAC) mimetics LCL161 and Birinapant. Our findings suggest that activation of cIAP2 allows CCA to escape GEM/CIS, and that suppression of cIAP2 reestablishes the apoptotic profile of CCA, thus restoring its vulnerability to GEM/CIS. The results of this study indicate that combining the SMAC mimetic LCL161 with GEM/CIS inhibits and prevents the emergence of multidrug resistance in CCA.

In addition, birinapant could promote the activation of NF-κB signaling pathways in antigen-stimulated CAR T cells, and with a birinapant-resistant tumor model we showed that birinapant had no deleterious effect on CAR T cell functions in vitro and in vivo. Overall, we demonstrated the potential of combining the IAP antagonist birinapant with CAR T cells as a novel and feasible approach to overcoming tumor antigen heterogeneity and enhancing CAR T cell therapy for GBM.

Performing an ex-vivo drug screening with 174 drugs in early to late clinical trials on blasts of 3 IKZF1plus DS-ALL patients and on 14 controls (5 B-cell lymphoblastoid cell lines, 3 PBMCs, 3 T-cells and 3 CD34+ cells, all derived from healthy donors) we observed the efficacy of drugs known to be effective in Ph-like patients such as Birinapant, a SMAC mimetic, and HDAC inhibitors...Ph-like signature and IKZF1 deletions were associated with poor outcome, with the risk of relapse further increased for IKZF1plus patients. These alterations characterize subgroups of DS-ALL patients who need tailored therapeutic strategies.

After 48h monotherapy treatment by CHZ868, we detected decreased cell viability (20-75% at IC50), which increased in the combination with dexamethasone...Importantly, combination of BIBF1120 and CHZ868 showed a synergistic effect (-45%, at IC50)...Indeed, active caspase 3 increased after ruxolitinib and chloroquine (autophagy inhibitor) combination (+20% vs ruxolitinib alone, p<0.01)...Instead, AT9283 (p<0.001 vs LCLs), Fedratinib (p<0.01 vs LCLs) and Gandotinib (p<0.05 vs LCLs) were found to be potent, specific, and non-toxic JAK2 inhibitors. Additionally, this extended screening led us to identify drugs, not belonging to JAK inhibitors, specific and non-toxic for rearranged JAK2 cohort, such as Birinapant (Smac mimetic), JQ1 (BRD4 inhibitor), Fludarabine (Chemotherapy) among the others. CHZ868 is a promising drug for the treatment of JAK2 fusions. Further studies will focus on effective and specific novel drugs found to be highly effective and specific on JAK2 rearrangements in BCP-ALL.

Finally, we show that LATS1-SMAC interaction is regulated by the SMAC mimetic Birinapant, which requires C-IAP1 inhibition and the degradation of XIAP, suggesting that the MST2 pathway is part of the mechanism of action of Birinapant. Overall, the current work shows that SMAC-dependent apoptosis is regulated by the LATS1 tumour suppressor and supports the idea that LATS1 is a signalling hub that regulates the crosstalk between the MST2 pathway, the apoptotic network and the ERK pathway.

P1, N=34, Recruiting, National Cancer Institute (NCI) | Trial completion date: Jul 2022 --> Jul 2023 | Trial primary completion date: Jul 2022 --> Jul 2023

Using organoid culture and xenograft models, we demonstrate the highly selective use of birinapant based combinations for the treatment of RB-deficient tumors. Together, these data illustrate the critical role of RB-pathway in response to many agents used to treat ER+ breast cancer, whilst informing new therapeutic approaches that could be deployed against resistant disease.

Since NFKB signaling can be pharmacologically enhanced by the SMAC mimetics, we studied the effect of the combination of Birinapant with Fulvestrant on IFNg response, cytokine secretion, T cell mediated cytotoxicity and migration. Our studies indicate that the transcriptional activity of NFKB is augmented by silencing of ER signaling, suggesting that the crosstalk between ER and NFKB has a key role in the diminished response to IFNg mediated by ER. These results suggest that the combination of endocrine treatment and a SMAC mimetic is a potential novel therapeutic approach to leverage immune based therapies in ER+ BC.

In addition, Birinapant could inhibit tumor growth via increasing the secretion of and the sensitivity to TNF-α in a TNBC xenotransplantation mouse model. Consequently, liposomes encapsulating Birinapant and siPD-L1 mediated a form of combination therapy based on two drugs to significantly increase the therapeutic effects toward TNBC.

LCL161 and panobinostat interacted synergistically to induce apoptosis in diverse MM cell lines, including those resistant to bortezomib (PS-R). Similar interactions were observed with other histone deacetylase inhibitors (MS-275) or inhibitors of apoptosis protein antagonists (birinapant)...Notably, this regimen overcomes various forms of resistance, is active against primary MM cells, and displays significant in vivo activity. This strategy warrants further consideration in MM.

However, 10–50% of newly diagnosed patients with AML may not respond to venetoclax and HMA or LDAC, and 3–15% patients may not respond to venetoclax with intensive or non-intensive chemotherapy.1–6 In addition, up to 40% of responding patients may relapse with low rates of response of 20% to salvage therapy and poor overall survival of 2 months after relapse.7 Clinical and biological factors associated with primary and acquired resistance to venetoclax include secondary AML, monocytic differentiation, complex cytogenetics, mutations in TP53, BAX, dependence on other anti- apoptotic proteins, altered metabolism of nicotinamide, fatty acids, and oxidative phosphortylation.3,8–14 Several novel inhibitors of BCL-2 are currently being tested in clinic, including BGB 11417, APG-2575, LP-108 and others...There is strong pre-clinical rationale for targeting MCL-1 alone as well as in conjunction with BCL-2 inhibition in AML.15 Recently several selective and highly potent MCL-1 inhibitors have entered pre-clinical and clinical development including S63845, AZD5991, AMG397, and others. Questions remain regarding the therapeutic window of these inhibitors given the important physiologic role of MCL-1 in vital organs and early reports of cardiac adverse events from the AMG176 phase 1 trial.15,16 Multiple pre-clinical studies have expectedly shown synergism between BCL- 2 and MCL-1 inhibition making it a promising path for clinical development of these agents.17,18 Multifactorial challenges in design of specific MCL-1 inhibitors also led to interest in compounds which downregulate MCL-1 expression. Cyclin dependent kinase (CDK) inhibitors including alvocidib, dinaciclib, voruciclib are in various stages of evaluation. Although addition of alvocidib to intensive chemotherapy improved response rates but failed to improve event-free or overall survival.19 Novel CDK inhibitors are currently in early phase trials including AZD4573, CYC065, TG02-101, and others. Inhibition of Nedd8 activating enzyme has complex repercussions for the intrinsic apoptotic pathway with eventual increase in Noxa leading to MCL-1 neutralization.20 Pevonedistat has shown promising early results in AML and myelodysplastic syndrome and is being investigated multiple clinical trials for solid tumors as well. BCL-xL Inhibition Another anti-apoptotic protein BCL-xL had been long recognized as a potential therapeutic target in AML, in particular AML from preceding MPN and AML recurrent post venetoclax failure, but toxicity of earlier inhibitors precluded clinical development.21–23 Recently, AZD0466, a dual BCL-2/xL inhibitor with a favorable therapeutic index and robust activity has been developed and is undergoing pre-clinical development and planned for phase iin hematological malignancies.24 Targeting the Extrinsic Apoptosis Pathway Inhibitor of apoptosis protein (IAP) inhibition: X-linked IAP (XIAP), cellular IAP (cIAP) and survivin have been of long- standing interest in AML. Prior clinical trials with XIAP inhibitor AEG35156, cIAP targeting agent birinapant, and survivin targeting agent LY2181308 have not succeeded in clinc.16,25 ASTX660 is a dual antagonist of XIAP and cIAP which is currently being investigated in phase 1/2 trials in solid tumors and in combination with HMA in relapsed or refractory AML.26,27 TRAIL Agonism Agonists of the TNF-related apoptosis-inducing ligand (TRAIL) receptors have been tested in AML with low response rates.28,29 Previous agents have had limited success in part due to suboptimal clustering of TRAIL receptors.30 Novel antibodies against TRAILR1 and TRAILR2 including an IgM molecule IGM-8444, a tetravalent compound INBRX-109, and HLX56 are currently in phase 1 trials and preclinical data suggests potential synergy with venetoclax.31 FLIP Inhibition FLICE-like inhibitor protein (FLIP or CFLAR) is a key regulator of the death-inducing signaling complex (DISC) involved in the extrinsic apoptotic pathway...This can be augmented by inhibiting p53 degradation via MDM2, which is often upregulated in AML.34 Idasanutlin in combination with venetoclax showed anti- Figure 1 leukemic activity in the dose finding stage in R/R AML.35 Several other inhibitors of MDM2 and dual MDM2/X inhibitors are currently in various stages of pre-clinical and clinical development including HDM-201, KRT-232, BI-9078282, and others.34 Conclusions Opportunities to target the apoptosis machinery in AML has considerably evolved in the last decade. While venetoclax heralded a paradigm shift for patients, we are now faced with challenges in patients who relapse or remain refractory. We have novel clinical stage compounds to methodologically target different facets of the apoptotic pathway and optimize novel combinations with the goal to improve the cure rates in AML patients.