IAP Antagonists Research Articles

Epigenetic Priming by Hypomethylation Enhances the Immunogenic Potential of Tolinapant in T-cell Lymphoma.

The IAP antagonist tolinapant can induce necroptosis, a key immune-activating event, in TCL. Combination with DNA hypomethylation enhances tolinapant sensitivity and primes resistant cells by re-expressing necrosome proteins. In addition, this combination leads to increases in genes involved in IFN signaling and neoantigen expression, providing further molecular rationale for this novel therapeutic option.

251 (PB-067) Poster - XIAP overexpressing Inflammatory Breast Cancer Patients have high Infiltration of immunosuppressive subsets and increased TNFR1 signaling targetable with Birinapant, a pan- IAP antagonist

251 (PB-067) Poster - XIAP overexpressing Inflammatory Breast Cancer Patients have high Infiltration of immunosuppressive subsets and increased TNFR1 signaling targetable with Birinapant, a pan- IAP antagonist

XIAP overexpressing inflammatory breast cancer patients have high infiltration of immunosuppressive subsets and increased TNFR1 signaling targetable with Birinapant

ObjectiveTo assess the expression pattern of X-linked inhibitor of apoptosis protein (XIAP), a cellular stress sensor, and delineate the associated changes in the tumor immune microenvironment (TiME) for prognostic value and new therapeutic targets in inflammatory breast cancer (IBC). MethodsImmunohistochemistry was conducted to assess the spatial localization of immune subsets, XIAP, and PDL1 expression in IBC and non-inflammatory breast cancer (nIBC) pretreatment tumors (n = 142). Validation and further exploration were performed by gene expression analysis of patient tumors along with signaling studies in a co-culture model. ResultsHigh XIAP in 37/81 IBC patients correlated significantly with high PD-L1, increased infiltration of FOXP3+ Tregs, CD163+ tumor-associated macrophages (TAMs), low CD8/CD163 ratio in both tumor stroma (TS) and invasive margins (IM), and higher CD8+ T cells and CD79α+ B cells in the IM. Gene set enrichment analysis identified cellular stress response- and inflammation-related genes along with tumor necrosis factor receptor 1 (TNFR1) expression in high-XIAP IBC tumors. Induction of TNFR1 and XIAP was observed when patient-derived SUM149 IBC cells were co-cultured with human macrophage-conditioned media simulating TAMs, further demonstrating that the TNF-α signaling pathway is a likely candidate governing TAM-induced XIAP overexpression in IBC cells. Finally, addition of Birinapant, a pan IAP antagonist, induced cell death in the pro-survival cytokine-enriched conditions. ConclusionUsing 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.

AVPI analogs and conjugates: Molecular docking studies and in vitro biological evaluation

In recent years, small peptide and non-peptide AVPI-/Smac-mimetics have been developed as IAP antagonists and are in clinical trials to overcome resistance to apoptosis in various cancer types. In this study, we present molecular modeling studies and in vitro biological evaluation of a set of AVPI-mimetics, including parent AVPI, tetrapeptide AVPI-mimetics and AVPI-conjugates.Combined molecular modeling studies and HYDE analyses provided valuable information regarding the protein–ligand interactions within the binding site of cIAP1-BIR3 and XIAP-BIR3 domains, showing that the binding part of both domains (cIAP1- and XIAP-BIR3) are formed from 22 amino acid residues, and their active part of 11 AAs. Moreover, 5 amino acids are defined common for both targets, namely Lys299, Gly306, Leu307, Trp310, and Trp323. Based on the observed docking models, six amino acid residues for cIAP1-BIR3 and five amino acids for XIAP-BIR3 are recognized actively involved in the formation of H-bonds with the respective ligand. The amino acid sequence 308 (Arg308 in cIAP1-BIR3, Thr308 in XIAP-BIR3), simultaneously forming two H-hydrogen bonds, seems to plays a key role in improvement of binding affinity.Apart from docking results the synthesized set of AVPI-mimetics was tested in vitro using cell biology (MTT assay) and parallel artificial membrane permeability assay (PAMPA). The results showed that the double modification of AVPI via substitution of Pro3 with Hyp3, as well as elongation of AVPI’s C-terminus by its conjugation with RGD-analogs, significantly increase the antiproliferative effects of AVPI-conjugates on all tested cancer cell lines (MDA-MB-231, MCF-7, HepG2 and HT-29 cells) compared to the parent AVPI peptide. SARs analysis defined this modification beneficial for the overall biological activity of the AVPI-mimetics and pointed out AVHypI-AgbGD as the most active conjugate with an IC50 of 348 µM for MDA-MB-231, 457 µM for MCF-7, 399 µM for HepG2, and 578 µM for HT-29 cells. Though the calculated IC50 values were still high, we consider AVHypI-AgbGD peptide as a good basis for further modifications. In addition, PAMPA results showed that substitution of Pro with Hyp improved the BBB permeability of AVHypI peptide compared to its parent molecule.

Epigenetic Priming By Hypomethylation Enhances the Immunogenic Potential of Tolinapant in T-Cell Lymphoma

Background:Durable single-agent responses with the IAP antagonist, tolinapant (ASTX660), have been reported in peripheral T-cell lymphoma (PTCL) and cutaneous TCL (CTCL) patients (NCT02503423, Michot et al., EHA 2022). We have found that tolinapant has the potential to drive immunogenic form of cell death (ICD), such as necroptosis, in preclinical models of TCL (Ferrari et al., Blood Adv. 2021). Here, we further explored this by modulating key necrosome components in TCL cell lines and analysing changes in cell death signalling. We hypothesised the epigenetic mechanisms that limit induction of ICD could be reversed by combining tolinapant and hypomethylating agents, such as decitabine. Our biomarker-led approach demonstrated that this novel combination could overcome inherent resistance to a form of cell death that can engage a strong immune response. Materials and Methods: Key necrosome components were modified in human and mouse TCL cell lines by CRISPR knockout and activation, and effects of tolinapant on their viability measured in vitro. Promoter methylation was assessed by pyrosequencing following bisulfite treatment (EpigenDx). Effects of tolinapant and decitabine, as single-agents and in combination, on cytokine/chemokine release were assessed using Meso Scale Discovery (MSD) or Luminex assay. ICD biomarkers in cells and tumor lysates were analysed by ELISAs, MSD assays, qPCR and Western blotting. In vivo activity of tolinapant and decitabine were tested in caspase-8 knockout EL4 cells in a syngeneic setting. PTCL patient plasma samples were analysed by Human ExplorerMAP™ v. 1.0 (Luminex xMAP® technology). Results: Loss of necrosome components or necrosome inactivation led to reduced sensitivity of TCL cells to tolinapant. We confirmed decitabine treatment resulted in re-expression of necrosome proteins (e.g., RIPK3) and cancer testis antigens. Combination of decitabine and tolinapant led to increased lytic cell death over monotherapies, and this was accompanied by increased levels of interferon signalling and ICD biomarkers (e.g., HMGB1). Tolinapant treatment alone, or in combination with decitabine, led to elevated chemokine release from dying TCL cells. These observations indicate activation of necroptosis. In vivo, the combination treatment prolonged survival of mice bearing caspase-8 knockout EL4 tumors while monotherapies had limited effects. We also report that IP-10 (CXCL10) levels were increased in plasma samples of tolinapant-treated PTCL patients, as well as other plasma proteins, implying immune activation. Conclusions: We demonstrate that tolinapant acts as an immune modulator via promoting ICD, and this can be enhanced by epigenetic reprogramming with decitabine. These findings provide a rationale to support the on-going combination study of tolinapant with ASTX727 (oral decitabine and cedazuridine) that recently started in PTCL (ASCERTAIN-P, NCT05403450). It has also identified putative biomarkers of immunomodulatory activity that could be utilized in clinic.

TRAF2/3 deficient B cells resist DNA damage-induced apoptosis via NF-κB2/XIAP/cIAP2 axis and IAP antagonist sensitizes mutant lymphomas to chemotherapeutic drugs

Deletion of TRAF2 or TRAF3 in B cells prolongs their survival. However, it remains unknown whether deletion of such factors affects B cells’ ability to tolerate DNA damage, which can be induced by chemotherapeutics and cause apoptosis. Genetic alterations of TRAF2 or TRAF3 are observed in subsets of human B-cell lymphomas and B cell-specific deletion of TRAF3 led to lymphoma development in aged mice. However, it remains unknown whether double deficiency of TRAF2 and TRAF3 accelerates B-cell lymphomagenesis. Here, we showed that B cell-specific TRAF2/3 double deficient (B-TRAF2/3-DKO) B cells were remarkably more resistant to DNA damage-induced apoptosis via upregulating cIAP2 and XIAP, which in turn attenuates caspase-3 activation. Mechanistically, resistance to DNA damage-induced apoptosis required NF-κB2, which effects by upregulating XIAP and cIAP2 transcription. B-TRAF2/3-DKO mice exhibited a shorter lifespan and succumbed to splenomegaly and lymphadenopathy. Unexpectedly, the incidence of B-cell lymphoma development in B-TRAF2/3-DKO mice was relatively rare (∼10%). Sequencing B cell receptor repertoire of diseased B cells revealed that TRAF2/3 deficiency caused abnormal oligoclonal or clonal expansion of B cells. While a fraction of mutant B cells (25–43%) from aged diseased mice harbored recurrent chromosomal translocations, primary B cells isolated from young B-TRAF2/3-DKO mice had no detectable chromosomal alterations, suggesting that TRAF2/3 deficiency per se does not cause evident genomic instability in B cells. Chemo-resistant TRAF3-deficient B-cell lymphomas were sensitized to chemotherapeutic drugs by blocking IAP activity using IAP antagonist. We conclude that double deficiency of TRAF2 and TRAF3 does not accelerate B-cell lymphomagenesis. Our studies provide insight into mechanisms regulating DNA damage-induced apoptosis and may help develop effective therapies targeting mutant B-cell lymphomas using IAP antagonist.

Natural Flavonoids Quercetin and Kaempferol Targeting G2/M Cell Cycle-Related Genes and Synergize with Smac Mimetic LCL-161 to Induce Necroptosis in Cholangiocarcinoma Cells.

Cholangiocarcinoma (CCA) is an aggressive cancer associated with a very poor prognosis and low survival rates, primarily due to late-stage diagnosis and low response rates to conventional chemotherapy. Therefore, there is an urgent need to identify effective therapeutic strategies that can improve patient outcomes. Flavonoids, such as quercetin and kaempferol, are naturally occurring compounds that have attracted significant attention for their potential in cancer therapy by targeting multiple genes. In this study, we employed network pharmacology and bioinformatic analysis to identify potential targets of quercetin and kaempferol. The results revealed that the target genes of these flavonoids were enriched in G2/M-related genes, and higher expression of G2/M signature genes was significantly associated with shorter survival in CCA patients. Furthermore, in vitro experiments using CCA cells demonstrated that quercetin or kaempferol induced cell-cycle arrest in the G2/M phase. Additionally, when combined with a Smac mimetic LCL-161, an IAP antagonist, quercetin or kaempferol synergistically induced RIPK1/RIPK3/MLKL-mediated necroptosis in CCA cells while sparing non-tumor cholangiocyte cells. These findings shed light on an innovative therapeutic combination of flavonoids, particularly quercetin and kaempferol, with Smac mimetics, suggesting great promise as a necroptosis-based approach for treating CCA and potentially other types of cancer.

Abstract 6158: BGB-24714, a novel oral IAP antagonist, displayed significant anti-tumor activities in preclinical models as a monotherapy and in combination with paclitaxel

Abstract Background: Evasion of apoptosis is identified as one of the essential hallmarks of cancer and upregulation of inhibitor of apoptosis proteins (IAPs) is one of the mechanisms by which tumor cells evade apoptosis. An oral SMAC mimetic and antagonist of cellular IAP1 (cIAP1) and X-linked IAP (XIAP), BGB-24714, is currently investigated in a phase 1a/1b oncology trial in patients with advanced or metastatic solid tumors (NCT05381909). Here, we evaluated the anti-tumor activity of BGB-24714 as a single agent or in combination with paclitaxel in preclinical models. Results: BGB-24714 effectively inhibited cIAP1 by inducing its degradation in MDA-MB-231 cells, with an EC50 of 2.5 nM. BGB-24714 also potently antagonized the inhibitory interaction of XIAP with caspase-9 and induced caspase-9 autoactivation in MDA-MB-231 cells, with an EC50 of 23 nM. In a total of 25 breast cancer cell lines treated with TNFα, BGB-24714 potently inhibited the in vitro proliferation of 5 breast cancer cells with EC50 < 100 nM. In pharmacodynamics studies, single dose administration of BGB-24714 significantly induced degradation of cIAP1 and antagonism of the XIAP: Smac interaction in the MDA-MB-231 xenograft model in a dose dependent manner. Using the same model, BGB-24714 exhibited dose-dependent anti-tumor activities as a single agent. The tumor growth inhibition rates were 30%, 52% and 73% in low to high dosage treatment groups. Furthermore, BGB-24714 at medium dosage level demonstrated synergized anti-tumor activity in HCC1806 xenograft model when used in combination with paclitaxel. In intermittent dosing study, BGB-24714 with the intermittent dosing schedule demonstrated significant but slightly less effective anti-tumor activity than the continuous dosing schedule. In summary, BGB-24714, as a novel oral IAP antagonist, showing significant anti-tumor activities in preclinical models, which is promising and warrants the testing of the compound in human. Citation Format: Jie Li, Nan Hu, Yilu Zhang, Xiaolong Yang, Minjuan Deng, Wenfeng Gong, Longbo Yin, Yong Liu, Yajuan Gao, Wei Wei, Xing Wang, Xinyi Liang, Yanwen Ma, Xuxing Sang, Chang Liu, Jingyuan Wang, Qianqian Lu, Fengtao Song, Xi Yuan, Yibing Wang, Jing Li, Wei Jin, Xuesong Liu, Xiaomin Song. BGB-24714, a novel oral IAP antagonist, displayed significant anti-tumor activities in preclinical models as a monotherapy and in combination with paclitaxel [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6158.

Tumor microenvironment mimicking 3D models unveil the multifaceted effects of SMAC mimetics

Small molecule IAP antagonists - SMAC mimetics (SM) - are being developed as an anticancer therapy. SM therapy was demonstrated not only to sensitize tumor cells to TNFα-mediated cell death but also to exert immunostimulatory properties. Their good safety and tolerability profile, plus promising preclinical data, warrants further investigation into their various effects within the tumor microenvironment. Using invitro models of human tumor cells and fibroblast spheroids co-cultured with primary immune cells, we investigated the effects of SM on immune cell activation. SM treatment induces the maturation of human PBMC- and patient-derived dendritic cells (DC), and modulates cancer-associated fibroblasts towards an immune interacting phenotype. Finally, SM-induced tumor necroptosis further enhances DC activation, leading also to higher T-cell activation and infiltration into the tumor site. These results highlight the relevance of using heterotypic invitro models to investigate the effects of targeted therapies on different components of the tumor microenvironment.

Key Subsets of Immune Cells in Bone Marrow Myeloid Compartment Indicate Degree of Tumor Infiltration and Avenues for Successful Immunotherapy in Multiple Myeloma

With the onset of single-cell omics, the complete gene expression landscape of immune cells can be leveraged to differentiate distinct subsets with inherently diverse functions. By analyzing the sample-specific composition of these distinct cellular groups, we can decipher the hallmarks of healthy and fully tumor-infiltrated bone marrow microenvironments as well as compositional modulations during effective immunotherapy. Unique to our approach, our analyses leverage over 500,000 existing RNA-Seq experiments packaged in the ARCHS4 repository to strengthen the biological signal and quality of our tertiary analyses by informing us in an unbiased way about lesser known immune-typologies. We applied this technique to our well-established immunocompetent mouse model of multiple myeloma (MM) which we rendered sensitive to IMiDs by introducing a human CRBN transgene: Vk*MYChCRBN. In multiple single cell experiments measuring effectiveness of Iberdomide in combination with Dexamethasone and an additional experiment comparing aged and untreated Vk*MYC mice with multiple myeloma (MM), key compositional patterns emerge in the murine bone marrow niche. Two distinct polarities of C1q expressing macrophages are present within murine bone marrow and spleen-one expressing Fcgr4 and present in untreated, tumor-bearing samples and a separate population elevated in Apoe, Vcam1, and MHC-II markers that can be found in healthy and tumor-bearing mice. Among splenocytes, we observed that the proportion of C1q macrophages correlates strongly with tumor burden and that BM and spleen samples in the process of tumor debulking via effective immunotherapy dramatically reduce relative frequencies of C1q macrophages. We hypothesize that the C1q macrophages without MHC-II features represent a tumor-associated macrophage (TAM) phenotype that is MM dependent and promotes tumor progression within the BM niche.1 Additional analyses of murine splenocytes have revealed that effective immunotherapy via an IAP antagonist induces the presence of immature or migratory dendritic cells (high expressers of Ccl5 and likely key immune recruiters) and that tumor-bearing splenocytes typically maintain large segments of immature neutrophils (high expressers of Ngp and Camp) without other neutrophils in more advanced stages of development2-while both immature and mature neutrophils are found in healthy controls. When comparing the BM composition of an aged, tumor-bearing mouse with that of a young, healthy mouse, key differences emerge. While multiple subsets of progenitors in murine BM niche can be identified via single cell, a unique population of cells over-expressing Cxcl12 that resemble Lepr+ mesenchymal stem cells from existing experiments (GSM3676085) are nearly absent in the young mouse, highly represented in the aged mouse, and may be a critical in creating a BM niche that supports tumor expansion.3 Curiously, a sizeable population of basophils is evident in the young, non-tumor bearing mouse but not found in the adult, tumor-bearing mouse. In addition, both types of C1q macrophages have expanded frequencies in the aged mouse. In total, single-cell analyses provide a snapshot of the compositional landscape of immune cell types thus illustrating hallmarks of tumor-infiltrated, healthy, and therapy modulated BM niches, providing potential new therapeutic targets.

P1293: COMBINING THE IAP ANTAGONIST, TOLINAPANT, WITH A DNA HYPOMETHYLATING AGENT ENHANCES ANTI-TUMOUR MECHANISMS IN PRECLINICAL MODELS OF T-CELL LYMPHOMA.

Background: Tolinapant is a potent, non-peptidomimetic antagonist of cIAP1, cIAP2 and XIAP. In a Phase 2 trial (NCT02503423), tolinapant has shown activity against highly pre-treated peripheral and cutaneous T-cell lymphoma (Samaniego et al., Hematological Oncology, 2019). Hypomethylating agents (HMAs) have also shown clinical responses in some subsets of PTCL (Lemonnier et al., Blood, 2019). Both HMAs and IAP antagonists show immunomodulatory anti-cancer potential in preclinical studies. Aims: Here we have undertaken a biomarker-driven approach to understand the potential for induction of immunogenic forms of cell death, such as necroptosis, by rational combination of our clinical compounds in preclinical models of TCL. Methods: On-target effects of decitabine and tolinapant were measured by analysing levels of DNMT1 and cIAP1, respectively, by Western blotting in mouse and human cell lines. Levels of key necroptosis biomarkers (RIPK3, MLKL) were also monitored by Western blotting to provide evidence of lytic cell death contributing to a potential immune response. Karpas-299 cells genetically-manipulated to express RIPK3 were used to demonstrate involvement of necroptosis in drug-induced cell death (Cytotox NIR) in vitro. Cell death was monitored by viability (CellTiterGlo) or real-time microscopy (IncuCyte) assays. Levels of key immunomodulatory mediators or DAMPS were measured in tissue culture supernatants and mouse plasma. Levels of methylation in RIPK3 promoter regions were measured by pyrosequencing after bisulfite conversion. Comparative changes in gene expression were measured by RT-qPCR. Results: TCL cell lines treated with tolinapant, decitabine or both led to depletion of cIAP1 and DNMT1 in TCL cell lines, demonstrating target engagement of both agents. The combination of tolinapant and decitabine synergistically reduced viability of some human T-cell lymphoma cell lines. Some cell lines, including Karpas-299, were resistant to tolinapant treatment and showed low expression of RIPK3, which was found to be due to promoter methylation. Increased expression of RIPK3 in Karpas-299 by genetic manipulation or by decitabine treatment resulted in enhanced lytic cell death upon tolinapant treatment. Decitabine and tolinapant treatments resulted in expression of cytokines, chemokines and DAMPs, suggesting potential for immune activation and the effects were enhanced when combined. Furthermore, normally silenced cancer/testis antigen expression was increased by decitabine, potentially increasing the immunogenicity of the cells. Evaluation of the combination of agents in mouse models suggested that increased necroptosis signal and immune-potentiating biomarker modulation can be achieved in vivo. Summary/Conclusion: These data demonstrate that hypomethylating agents enhance immunogenic cell death induced by tolinapant through the re-expression of genes in the necroptotic pathway. In addition, modulation of cytokine response and cancer/testis antigen expression could enhance anti-tumour response. These findings provide a strong rationale to explore this combination clinically.

P1278: ACTIVATION OF THE NECROPTOSIS PATHWAY PLAYS A ROLE IN SYNERGISM WITH COMBINATION OF THE IAP ANTAGONIST, TOLINAPANT AND HYPOMETHYLATING AGENTS (HMA) IN IN VITRO MODELS OF T-CELL LYMPHOMA (TCL).

Background: Peripheral T-cell lymphoma (PTCL) are a highly aggressive and heterogeneous group of non-Hodgkin lymphomas that often carry a poor prognosis with standard chemotherapy. Tolinapant is a potent, non-peptidomimetic antagonist of cIAP1, cIAP2 and XIAP. In an ongoing Phase 2 trial (NCT02503423), tolinapant has shown activity against highly pre-treated peripheral and cutaneous T-cell lymphoma. HMAs have also shown clinical responses in some subsets of PTCL. Both HMAs and IAP antagonists show immunomodulatory anti-cancer potential in pre-clinical studies. We have also shown that decitabine and tolinapant as single agent induced necroptosis in mouse TCL cell lines with the activation of the RIPK1/RIPK3/MLKL necroptosis pathway. In addition, re-expression of RIPK3 in CT26 cells by CRISPR increased lytic cell death on treatment with tolinapant indicating its essential role in the necroptosis pathway. Aims: We explored the sensitivity of a range of TCL lines to tolinapant, established the synergy coefficient and interrogated the role of necroptosis in the mechanism of synergy between tolinapant and drugs active against PTCL, the HMAs; azacytidine and decitabine Methods: A panel of 10 human TCL lines were tested in proliferation assays (CellTiterGlo) for sensitivity to tolinapant in the presence or absence of 10 ng/ml of TNFa. For combination studies, each drug was tested at the IC10, IC20 and IC40 concentrations, in the presence or absence of TNFa. Synergy coefficient was calculated using the Excess over Bliss model with SynergyFinder. Additionally, the on-target effects of the drugs were measured by analyzing levels of the IAPs, DNMTs and key apoptosis and necroptosis markers, such as PARP and RIPK3 by Western blotting. Results: TCL Lines demonstrate varying sensitivities to tolinapant with the most sensitive cell line, ALK+ ALCL SUP-M2, having an IC50 as low as 20 nM ± 1 nM while a resistant CTCL cell line HH had an IC50 of over 20 µM. In combination experiments using both cell lines, tolinapant plus azacytidine or decitabine displayed a very high degree of synergism; Average synergy score of 50.9 and 49.8 with azacytidine and 22.6 and 31.3 with decitabine for HH and SUP-M2, respectively. Of note, a high degree of synergism was also seen with concentrations 10 fold lower of azacytidine or 100 fold lower of decitabine, added daily (Figure 1). The combination of tolinapant and the HMAs led to a decrease in the levels of cIAP1 and DNMT3a in TCL lines, demonstrating on-target activity of tolinapant and the HMAs, respectively. In addition, both azacytidine and decitabine increased the levels of RIPK3 up to 3-4 fold and 6-8 fold respectively, in a concentration dependent manner at 72Hrs by western blot analysis, indicating activation of the necroptosis pathway. Image:Figure 1: 3D synergy plots showing average synergy scores for decitabine in combination with tolinapant in the CTCL line HH.Summary/Conclusion: Tolinapant has demonstrated varying cytotoxic effects against a range of TCL lines as a single agent. Tolinapant, in combination with the HMAs, azacytidine and decitabine, displays a very high degree of synergism, in vitro, even at very low concentrations of both HMA drugs. The HMAs were able to activate the necroptosis pathway, as shown by the increase in RIPK3. Thus, activation of the necroptosis pathway, is a possible mechanism for the high degree of synergism displayed when HMAs are used in combination with tolinapant in the TCL lines in vitro. These data provide the rationale to initiate clinical trials with the combination of tolinapant and decitabine.

The combination of the IAP antagonist, tolinapant and hypomethylating agents (HMA) is highly synergistic in in vitro models of T-cell lymphoma (TCL).

e15088 Background: Peripheral T-cell lymphoma (PTCL) are a highly aggressive and heterogeneous group of non-Hodgkin lymphomas that often carry a poor prognosis with standard chemotherapy. Tolinapant is a potent antagonist of inhibitors of apoptosis proteins (cIAP1/2 and XIAP). In a phase 2 trial (NCT02503423), tolinapant showed activity against heavily pre-treated patients with TCL. We explored the sensitivity of a range of TCL lines to tolinapant, established the synergy coefficient and interrogated the mechanism of synergy between tolinapant and drugs active against PTCL including romidepsin, pralatrexate, and the HMAs; azacytidine and decitabine. Methods: A panel of 10 human TCL lines were tested in proliferation assays (CellTiterGlo) for sensitivity to tolinapant in the presence or absence of 10 ng/ml of TNFα. For combination studies, each drug was tested, in the presence or absence of TNFα. Synergy coefficient was calculated using Excess over Bliss. Additionally, the on-target effects of the drugs were measured by analyzing levels of the IAPs, acetylated histones, DNMTs and key apoptosis and necroptosis markers by Western blotting. Results: TCL Lines demonstrated varying sensitivities to tolinapant with the most sensitive cell line, ALK+ ALCL SUP-M2, having an IC50 as low as 20 nM ± 1 nM while a resistant CTCL cell line HH had an IC50 of over 20 µM. In combination experiments using both cell lines, tolinapant plus azacytidine or decitabine displayed the highest degree of synergism, compared to romidepsin or pralatrexate. Of note, a high degree of synergism was also seen with concentrations 10 folds lower of azacytidine or 100 folds lower of decitabine, added daily (Table). The combination of tolinapant and the HMAs led to a decrease in the levels of cIAP1 and DNMT3a in TCL lines, demonstrating on-target activity of tolinapant and the HMAs, respectively. In addition, both azacytidine and decitabine increased the levels of RIPK3 and MLKL by western blot analysis, indicating activation of the necroptosis pathway. Conclusions: Tolinapant has demonstrated varying cytotoxic effects against a range of TCL lines as a monotherapy and displays a very high degree of synergism in combination with the HMAs, azacytidine and decitabine, also at low concentration, in vitro. The HMAs were also able to activate the necroptosis pathway, providing a possible mechanism for the high degree of synergism displayed when combined with tolinapant in the TCL lines in vitro. These data provide the rationale to initiate phase I trials with the combination of tolinapant and HMAs. Average synergy scores at 48 hrs for drugs used in combination with tolinapant in a CTCL line HH and ALK+ ALCL line SUP-M2. Above 10 indicates synergy.[Table: see text]

Targeted protein degradation and drug discovery

Targeted protein degradation attracts attention as a novel modality for drug discovery, as well as for basic research. Various types of degrader molecules have been developed so far, which include proteolysis-targeting chimaeras (PROTACs) and specific and nongenetic IAP-dependent protein erasers (SNIPERs), E3 modulators, hydrophobic tagging molecules, IAP antagonists and deubiquitylase inhibitors. PROTACs and SNIPERs are chimeric degrader molecules consisting of a target ligand linked to another ligand that binds to an E3 ubiquitin ligase. In the cells, they recruit an E3 ligase to the target protein, thereby inducing ubiquitylation and proteasomal degradation of the target protein. Because of their modular structure, novel PROTACs and SNIPERs targeting proteins of your interest can be rationally developed by substituting target ligands. In this article, various compounds capable of inducing protein degradation were overviewed, including SNIPER compounds developed in our laboratory.

MMP-responsive transformation nanomaterials with IAP antagonist to boost immune checkpoint therapy

The clinical effect of immune checkpoint therapy is limited by the poor blocking efficiency of immune checkpoints and the insufficient infiltration of tumor-specific T cells. Here, we constructed enzyme-responsive PVA–peptide conjugates (PPCs) to achieve re-assembly with enhanced accumulation in the tumor region, enable enhanced PD-L1 occupancy and improve the blocking efficiency. The self-assembled PPC-1 nanoparticles can enter tumor environment, whereas the enzyme-cleavable peptide was digested under overgenerated matrix metalloproteinases (MMP). The accumulated PPC-1 simultaneously transformed into β-sheet fibrous structures around the solid tumor and remained stable for over 96 h, which led to efficiently interrupting the PD-1/PD-L1 interaction. Upon introduction of the IAP antagonists, the non-classical NF-κB pathway of dendritic cells was activated and increased the infiltration of T cells in tumors. With the synergistic contribution of IAP antagonists from the substantial increase in expression of chemokines (CCL5 and CXCL9) and adequate T-cell infiltration in tumor sites, PPC-1 improved the biodistribution and accumulation of PD-L1 antagonists in tumor regions ultimately realizing higher-performance (P < 0.01) tumor growth inhibition efficiency (~80%) than PPC-2 group (~58%) in B16F10 tumor-bearing mice. The growth of the second tumor at the distal end was obviously inhibited (P < 0.01) after the resection of the primary tumor. The combined efficacy was similar to that observed in a Pan02 pancreatic cancer tumor model. This strategy aims to offer novel perspective for the development of locational assembly platforms in vivo and the optimal design of immune checkpoint combination therapy.

Synthesis of a IAP antagonist analogue and its binding investigation with BSA/HSA

The development of new drugs especially novel anti-cancer drugs has become a hot-spot issue that catches scholars’ attention in every field. Here a IAP antagonist analogue (IAPA) was synthesized and characterized by NMR and HRMS spectra. Its interaction with proteins, including bovine serum albumin (BSA) and human serum albumin (HSA), were investigated by spectral methods and molecular simulation. Fluorescence quenching, together with UV absorption spectrum and time-resolved fluorescence spectrums indicated a static process in BSA/HSA-IAPA system. Thermodynamic parameters including ΔH and ΔS calculated by Vant't Hoff equation were all positive, showing that hydrophobic force was the major force in the interaction of compound IAPA and BSA/HSA. Site marker competitive displacement experiments proved that IAPA bound to site I at BSA/HSA. Synchronous fluorescence spectrum and three-dimensional fluorescence spectrum were also used to investigate the conformational changes of BSA/HSA after binding with compound IAPA. The above results were further verified by molecular docking.

Combining the IAP Antagonist Tolinapant with a DNA Hypomethylating Agent Enhances Immunogenic Cell Death in Preclinical Models of T-Cell Lymphoma

Introduction: Tolinapant is a potent, non-peptidomimetic antagonist of cIAP1, cIAP2 and XIAP. In ongoing Phase 2 trial (NCT02503423), tolinapant has shown activity against highly pre-treated peripheral and cutaneous T-cell lymphoma (Samaniego et al., Hematological Oncology, 2019). Hypomethylating agents (HMAs) have also shown clinical responses in some subsets of PTCL (Lemonnier et al., Blood, 2019). Both HMAs and IAP antagonists show immunomodulatory anti-cancer potential in pre-clinical studies. A Phase 1 clinical study investigating the combination of tolinapant and ASTX727 (oral decitabine) in AML is currently in progress (NCT04155580). Here we have undertaken a biomarker-driven approach to understand the potential for induction of immunogenic forms of cell death (ICD), such as necroptosis, by rational combination of our clinical compounds in pre-clinical models of T-cell lymphoma (TCL).Methods: On-target effects of decitabine and tolinapant were measured by analysing levels of DNMT1 and cIAP1, respectively, by Western blotting in mouse and human cell lines. Levels of key apoptosis, necroptosis or pyroptosis biomarkers were also monitored by Western blotting to provide evidence of lytic cell death contributing to a potential immune response. RIPK3- or MLKL-knockout cell lines were generated by CRISPR to demonstrate involvement of necroptosis in drug-induced cell death in a T-cell lymphoma cell line (BW5147.G.1.4) in vitro. Cell death was monitored by viability (CellTiterGlo) or real-time microscopy (IncuCyte) assays. Levels of key inflammatory mediators or DAMPS were measured in tissue culture supernatants and mouse plasma by Luminex assay (Ampersand).Results: Combined treatment of tolinapant and decitabine led to depletion of cIAP1 and DNMT1 in TCL cell lines, demonstrating on-target activity of tolinapant and decitabine, respectively. The combination of tolinapant and decitabine acted synergistically in mouse and human T-cell lymphoma cell lines to reduce viability in proliferation assays.Necroptosis was induced by decitabine or tolinapant alone in mouse TCL cell lines with robust activation of the RIPK1/RIPK3/MLKL necroptosis pathway when caspase activity was inhibited, and the combination of both agents enhanced loss of viability.Furthermore, we demonstrated decitabine treatment led to re-expression of both RIPK3 and MLKL in mouse cell lines, supporting published evidence that methylation can silence these key biomarkers (Koo et al., Cell Research, 2015; Koch et al., Neoplasia, 2021). Enhanced release of chemokine, cytokine and DAMPs was demonstrated with the combination of agents in vitro and in vivo.By removal of key necroptosis pathway components using CRISPR, we confirmed the importance of this lytic cell death pathway by demonstrating that RIPK3 -/- and MLKL -/- T-cell lymphoma (BW5147.G.1.4) cell lines had reduced necroptosis potential after treatment with tolinapant or decitabine alone or in combination; and demonstrate reduced release of inflammatory mediators in vitro.Finally, our in vivo evaluation of the combination of agents in mouse syngeneic models suggested that increased anti-tumour activity and immune-potentiating systemic biomarker modulation can be achieved with a tolerated dosing regimen of both compounds.Conclusion: These data demonstrate that decitabine enhances immunogenic cell death induced by tolinapant through the re-expression of genes in the necroptotic pathway. This finding provides strong rationale to explore this combination clinically. DisclosuresSims: Astex Pharmaceuticals: Current Employment. Davis: Astex Pharmacueticals: Current Employment. Smyth: Astex Pharmaceuticals: Current Employment.

Tolinapant (ASTX660), a Non-Peptidomimetic Antagonist of cIAP1/2 and XIAP, and the HDAC Inhibitor Romidepsin Are Synergistic in in Vitro Models of T Cell Lymphoma

Background: The PTCL are a heterogeneous group of non-Hodgkin lymphomas originating from mature T-lymphocytes. They are aggressive diseases, often resistant to conventional chemotherapy. Despite the fact that a number of new agents have been approved, treatment paradigms tailored to the biology of the disease have yet to emerge. Tolinapant (ASTX660) is a potent antagonist of both cellular and X-linked inhibitors of apoptosis proteins (cIAP1/2 and XIAP), and is presently in phase I/II trials in patients with advanced solid tumors and lymphomas (NCT02503423). IAP antagonists enhance tumor necrosis factor (TNF) receptor superfamily mediated apoptosis (Ward GA, et al. Mol Cancer Ther. 2018), are potent anti-tumor immune enhancers and induce markers of immunogenic cell death such as damage associated molecular patterns (DAMPs; Ye W, et al, Oncoimmunology, 2020). Objectives: We explored the sensitivity of a range of T-cell lymphoma (TCL) cell lines to tolinapant. We establish the synergy coefficient between tolinapant and the HDAC inhibitor, romidepsin, and interrogated the molecular basis of their synergistic interaction. Methods: A panel of human T-cell lymphoma cell lines were tested in proliferation assays (CellTiterGlo) for sensitivity to tolinapant in the presence or absence of 10ng/ml of TNF alpha. For combination studies, with tolinapant and romidepsin, each drug was tested at the IC10 and IC40 concentrations in the presence or absence of TNF alpha. Synergy scores using the Excess over Bliss (EOB) model were calculated using SynergyFinder (Aleksandr Ianevski et al; Nucleic Acids Research, 2020). Additionally, the effects of tolinapant and romidepsin on the IAPs and caspases were analyzed by western blots. TNFR1 receptor expression and induction of DAMPs were also analyzed by flow cytometry. Results: TCL Lines demonstrated varying sensitivities to tolinapant in the presence or absence of TNF alpha. The most sensitive cell lines, ALK+ ALCL and SUP-M2, had IC50 concentrations ranging from 200nM ± 100nM to 20nM ± 1nM in the absence or presence of TNF alpha, respectively, at 24, 48 and 72hrs, while a resistant CTCL cell line HH had an IC50 concentration of over 20mM, even in the presence of TNF alpha. Interestingly, using western blot analysis, we found that the presence of TNF alpha increased the levels of cIAP1 in the tolinapant sensitive SUP-M2 cell line, but not in the resistant HH cell line. However, there was a concentration dependent decrease in cIAP1 but not in XIAP in both cell lines treated with tolinapant. Flow cytometry analysis demonstrated that tolinapant increases the expression of TNFR1 and DAMPs in a dose dependent manner on the sensitive SUP-M2, but not in the resistant HH cells. In combination experiments, using the EOB model, tolinapant plus romidepsin was found to be synergistic in the absence of TNF alpha, at 36hrs, in both the sensitive cell line SUP-M2 and the resistant cell line HH. In the presence of TNF alpha, synergism was seen only in the sensitive cell line SUP-M2 and antagonistic in the HH cell line (Fig. 3). In the tolinapant plus romidepsin treated samples, cIAP1 levels decreased in the SUP-M2 cell line, in the absence of TNF alpha, however, addition of TNF alpha did not alter the levels of cIAP1 in the SUP-M2 cells. The cIAP1 levels decreased in the HH cells treated with the combination, in both the presence or absence of TNF alpha (Figure). Our findings indicate that the synergy of the tolinapant plus romidepsin is not dependent on the presence of TNF alpha. Conclusion: Tolinapant has demonstrated potent cytotoxic effects against a broad range of TCL lines both as a monotherapy and in combination with the HDAC Inhibitor, romidepsin. In in vitro studies, T cell lymphoma cell lines demonstrated varying sensitivity to tolinapant with certain cell lines being more resistant, even in the presence of TNF alpha. Interestingly, the addition of romidepsin appeared to overcome the intrinsic resistance to tolinapant in the absence of TNF alpha. These data provide the rationale to continue to explore the combination of tolinapant and romidepsin in vivo and to investigate additional combinations with T-cell specific agents (e.g. pralatrexate, belinostat, azacitidine and decitabine). [Display omitted] DisclosuresSmyth: Astex Pharmaceuticals: Current Employment. Sims: Astex Pharmaceuticals: Current Employment. Loughran: Kymera Therapeutics: Membership on an entity's Board of Directors or advisory committees; Bioniz Therapeutics: Membership on an entity's Board of Directors or advisory committees; Keystone Nano: Membership on an entity's Board of Directors or advisory committees; Dren Bio: Membership on an entity's Board of Directors or advisory committees. Marchi: Kyowa Kirin: Honoraria; Myeloid Therapeutics: Honoraria; Astex: Research Funding; BMS: Research Funding; Merck: Research Funding; Kymera Therapeutics: Other: Scientific Advisor.

Antagonism of inhibitors of apoptosis proteins reveals a novel, immune response-based therapeutic approach for T-cell lymphoma

Tolinapant (ASTX660) is a potent, nonpeptidomimetic antagonist of cellular inhibitor of apoptosis proteins 1 and 2 (cIAP1/2) and X-linked IAP, which is currently being evaluated in a phase 2 study in T-cell lymphoma (TCL) patients. Tolinapant has demonstrated evidence of single-agent clinical activity in relapsed/refractory peripheral TCL and cutaneous TCL. To investigate the mechanism of action underlying the single-agent activity observed in the clinic, we have used a comprehensive translational approach integrating in vitro and in vivo models of TCL confirmed by data from human tumor biopsies. Here, we show that tolinapant acts as an efficacious immunomodulatory molecule capable of inducing complete tumor regression in a syngeneic model of TCL exclusively in the presence of an intact immune system. These findings were confirmed in samples from our ongoing clinical study showing that tolinapant treatment can induce changes in gene expression and cytokine profile consistent with immune modulation. Mechanistically, we show that tolinapant can activate both the adaptive and the innate arms of the immune system through the induction of immunogenic forms of cell death. In summary, we describe a novel role for IAP antagonists as immunomodulatory molecules capable of promoting a robust antitumor immune response in TCL.

Clinical Positioning of the IAP Antagonist Tolinapant (ASTX660) in Colorectal Cancer.

Inhibitors of apoptosis proteins (IAPs) are intracellular proteins, with important roles in regulating cell death, inflammation, and immunity. Here, we examined the clinical and therapeutic relevance of IAPs in colorectal cancer. We found that elevated expression of cIAP1 and cIAP2 (but not XIAP) significantly correlated with poor prognosis in patients with microsatellite stable (MSS) stage III colorectal cancer treated with 5-fluorouracil (5FU)-based adjuvant chemotherapy, suggesting their involvement in promoting chemoresistance. A novel IAP antagonist tolinapant (ASTX660) potently and rapidly downregulated cIAP1 in colorectal cancer models, demonstrating its robust on-target efficacy. In cells co-cultured with TNFα to mimic an inflammatory tumor microenvironment, tolinapant induced caspase-8-dependent apoptosis in colorectal cancer cell line models; however, the extent of apoptosis was limited because of inhibition by the caspase-8 paralogs FLIP and, unexpectedly, caspase-10. Importantly, tolinapant-induced apoptosis was augmented by FOLFOX in human colorectal cancer and murine organoid models in vitro and in vivo, due (at least in part) to FOLFOX-induced downregulation of class I histone deacetylases (HDAC), leading to acetylation of the FLIP-binding partner Ku70 and downregulation of FLIP. Moreover, the effects of FOLFOX could be phenocopied using the clinically relevant class I HDAC inhibitor, entinostat, which also induced acetylation of Ku70 and FLIP downregulation. Further analyses revealed that caspase-8 knockout RIPK3-positive colorectal cancer models were sensitive to tolinapant-induced necroptosis, an effect that could be exploited in caspase-8-proficient models using the clinically relevant caspase inhibitor emricasan. Our study provides evidence for immediate clinical exploration of tolinapant in combination with FOLFOX in poor prognosis MSS colorectal cancer with elevated cIAP1/2 expression.