Evaluation of the microbiota-sparing properties of the anti-staphylococcal antibiotic afabicin

BACKGROUND

Antibiotic use is associated with collateral damage to the healthy microbiota. Afabicin is a first-in-class prodrug inhibitor of the FabI enzyme that, when converted to the pharmacologically active agent afabicin desphosphono, demonstrates a staphylococcal-specific spectrum of activity. An expected benefit of highly targeted antibiotics such as afabicin is microbiome preservation.

OBJECTIVES

To compare the effects of oral treatment with afabicin and standard-of-care antibiotics upon the murine gut microbiota, and to assess the effects of oral afabicin treatment on the human gut microbiota.

METHODS

Gut microbiota effects of a 10 day oral course of afabicin treatment were monitored in mice and compared with clindamycin, linezolid and moxifloxacin at human-equivalent dose levels using 16S rDNA sequencing. Further, the gut microbiota of healthy volunteers was longitudinally assessed across 20 days of oral treatment with afabicin 240 mg twice daily.

RESULTS

Afabicin treatment did not significantly alter gut microbiota diversity (Shannon H index) or richness (rarefied Chao1) in mice. Only limited changes to taxonomic abundances were observed in afabicin-treated animals. In contrast, clindamycin, linezolid and moxifloxacin each caused extensive dysbiosis in the murine model. In humans, afabicin treatment was not associated with alterations in Shannon H or rarefied Chao1 indices, nor relative taxonomic abundances, supporting the findings from the animal model.

CONCLUSIONS

Oral treatment with afabicin is associated with preservation of the gut microbiota in mice and healthy subjects.

Abstract 3443: The IAP antagonist xevinapant, in combination with high-dose cisplatin chemoradiotherapy, induces NF-kB and apoptotic pathway biomarkers in patients with high-risk locally advanced squamous cell carcinoma of the head and neck

Introduction: Inhibitor of Apoptosis Proteins (IAPs) regulate apoptosis and modulate NF-kB signaling, which in turn drives the expression of genes involved in immune and inflammatory responses. Xevinapant (XVT) (a.k.a Debio 1143) is an orally available IAP antagonist shown to enhance tumor response to radiation through the proapoptotic cytokine TNFα and caspase activation. Results from a double-blind, multicenter, randomized, phase II trial in patients with high-risk locally advanced squamous cell carcinoma of the head and neck (LA-SCCHN) revealed significant improvement in overall survival (OS), progression free survival (PFS) and duration of response with XVT in combination with high-dose cisplatin chemoradiotherapy (CRT) vs CRT alone (NCT02022098). We analyzed XVT pharmacodynamic (PD) biomarker time-concentration profiles and explored the association of PD changes over time with clinical efficacy and safety parameters.

Methods: Three serum PD biomarkers were measured during cycle 1: caspase-cleaved cytokeratin 18 fragment (CKM30), a biomarker of epithelial apoptosis, MCP1 and TNFα, both NF-kB target genes. Time course changes in PD biomarker exposure, measured by their Area Under the Curve (AUC), were tested for association with clinical efficacy and safety endpoints, by linear, logistic, and Cox Proportional Hazard models. Clinical response parameters included locoregional control (LRC) at 18 months from end of treatment (EOT), PFS, duration of LRC, time to distant relapse (TTDR), OS and complete response (CR) 6 months after EOT.

Results: The biomarker analysis set was composed of all patients with baseline PD assessments and at least one post-baseline measurement and included 35 and 40 patients in the XVT and placebo (PBO) arms, respectively. All three serum PD biomarkers increased upon administration of CRT + XVT during cycle 1. The increase in CKM30 and MCP1 levels was significantly higher in the CRT + XVT arm vs the CRT + PBO arm, as tested by linear mixed effect models (CKM30: p = 0.0167; MCP1: p = 0.0135). Interestingly, CKM30 AUC appeared to be correlated with response in CRT + XVT but not CRT + PBO (based on LRC at month 18 or CR at month 6). No associations between any of the three biomarkers were observed with the safety endpoints explored.

Conclusions: Xevinapant has demonstrated promising activity in combination with CRT in LA-SCCHN. The outcome of the exploratory PD analyses indicates that XVT modulates NF-kB signaling, leading to serum increases in MCP1 and TNFα while further augmenting CRT-induced apoptotic marker CKM30. Our findings further characterize the mechanism of action of XVT and how it may ultimately result in enhanced clinical responses to CRT.

Citation Format: Luke Piggott, Bruno Gavillet, Franck Brichory, Kathrin Gollmer, Florilene Bouisset, Gregoire Vuagniaux. The IAP antagonist xevinapant, in combination with high-dose cisplatin chemoradiotherapy, induces NF-kB and apoptotic pathway biomarkers in patients with high-risk locally advanced squamous cell carcinoma of the head and neck [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3443.

Abstract 2303: The WEE1 inhibitor Debio 0123 enhances the efficacy of standard of care DNA damaging agents in lung cancer models

Introduction: The WEE1 tyrosine kinase is activated upon DNA damage and regulates the G2-M and S phase cell cycle checkpoints. Inhibition of WEE1, in conjunction with genetic alterations and/or addition of a DNA damaging agent, results in mitotic catastrophe and apoptosis of cancer cells, offering an attractive approach to treating cancer. Debio 0123 is a WEE1 specific inhibitor previously shown to sensitize cancer cells to DNA damaging agents which is currently being assessed in combination with carboplatin in patients with advanced solid malignancies. Small cell lung cancer (SCLC) is an aggressive disease with poor clinical outcomes that carries a high mutational burden and genomic instability. Here we investigated the ability of Debio 0123 to enhance SCLC response to standard of care (SOC) DNA damaging agents carboplatin and etoposide in vitro and in vivo.

Methods: SCLC cell lines were treated with Debio 0123 alone or in combination with etoposide or carboplatin in vitro and apoptosis assessed by flow cytometry. In vivo SCLC patient derived- or cell line derived-xenograft (PDX or CDX, respectively) models were treated with Debio 0123 orally in combination with either carboplatin or etoposide alone or as a triple combination. Tumor growth inhibition was assessed over 3 cycles of treatment and tolerability of the combinations evaluated by monitoring body weight changes.

Results: Debio 0123 synergized with carboplatin and etoposide in vitro leading to a significant increase in the induction of apoptosis. Additionally, Debio 0123 significantly improved the tumor growth inhibitory effect of etoposide and carboplatin in both PDX and CDX models of SCLC in vivo. Triple combination of carboplatin, etoposide and Debio 0123 was well tolerated at therapeutically relevant dosing and resulted in significantly improved tumor response when compared to carboplatin and etoposide treatments alone or to the double combination.

Conclusions: Taken together these results highlight that inhibiting WEE1 with Debio 0123 significantly improves tumor response to SOC DNA damaging agents in models of SCLC, providing the foundation for future clinical exploration of Debio 0123 in SCLC.

Citation Format: Luke Piggott, Anne Vaslin-Chessex, Noemie Luong, Benjamin Tschumi, Gregoire Vuagniaux. The WEE1 inhibitor Debio 0123 enhances the efficacy of standard of care DNA damaging agents in lung cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2303.

Phase I Trial of Debio 1143, an Antagonist of Inhibitor of Apoptosis Proteins, Combined with Cisplatin Chemoradiotherapy in Patients with Locally Advanced Squamous Cell Carcinoma of the Head and Neck

PURPOSE

Debio 1143 is an oral antagonist of inhibitor of apoptosis proteins, which enhances tumor response with concomitant chemoradiotherapy. Addition of Debio 1143 to cisplatin-based chemoradiotherapy in locally advanced squamous cell carcinomas of the head and neck (LA-SCCHN) was evaluated in a phase I/II study to determine the MTD and recommended phase II dose (RP2D). Here, phase I results are reported.

PATIENTS AND METHODS

Treatment-naïve patients with LA-SCCHN (stages III/IVA/IVB) received Debio 1143 (100, 200, 300 mg/day), for 14 days every 3 weeks, with cisplatin (100 mg/m², every 3 weeks), for three cycles, and concomitant conventional fractionation radiotherapy (70 Gy/7 weeks). Dose-limiting toxicity (DLT) was evaluated over 9 weeks using continual reassessment.

RESULTS

Fourteen patients were treated/evaluable for DLT. Median age was 64.5 years, and all patients were current/former smokers. Primary tumors were hypopharynx, oropharynx (all human papillomavirus/p16 negative), larynx, and oral cavity. Two of six patients at 200 mg/day had DLT (grade 3 tubular necrosis, grade 3 aspartate aminotransferase/alanine aminotransferase increase, grade 4 febrile neutropenia, and grade 3 lipase increase), which was considered the MTD and RP2D. Common grade 3-4 adverse events were dysphagia (36%) and mucositis (29%). Laboratory abnormalities were frequent and generally mild, including anemia, white blood cell decrease, and increased creatinine. Addition of Debio 1143 did not compromise chemotherapy administration. Overall locoregional control rate at 18 months was 85%. Overall response rate was 85%, including 69% complete responses. Progression-free survival rate at 24 months was 74%.

CONCLUSIONS

The RP2D of Debio 1143 is 200 mg/day for 14 days, every 3 weeks, when combined with concomitant high-dose cisplatin chemoradiotherapy in LA-SCCHN. Debio 1143 addition to chemoradiotherapy was safe and manageable. Preliminary efficacy is encouraging and supports further development.

The inhibitor of apoptosis proteins antagonist Debio 1143 promotes the PD-1 blockade-mediated HIV load reduction in blood and tissues of humanized mice

The immune checkpoint programmed cell death protein 1 (PD-1) plays a major role in T cell exhaustion in cancer and chronic HIV infection. The inhibitor of apoptosis protein antagonist Debio 1143 (D1143) enhances tumor cell death and synergizes with anti-PD-1 agents to promote tumor immunity and displayed HIV latency reversal activity in vitro. We asked in this study whether D1143 would stimulate the potency of an anti-human PD-1 monoclonal antibody (mAb) to reduce HIV loads in humanized mice. Anti-PD-1 mAb treatment decreased PD-1+ CD8+ cell population by 32.3% after interruption of four weeks treatment, and D1143 co-treatment further reduced it from 32.3 to 73%. Anti-PD-1 mAb administration reduced HIV load in blood by 94%, and addition of D1143 further enhanced this reduction from 94 to 97%. D1143 also more profoundly promoted with the anti-PD-1-mediated reduction of HIV loads in all tissues analyzed including spleen (71 to 96.4%), lymph nodes (64.3 to 80%), liver (64.2 to 94.4), lung (64.3 to 80.1%) and thymic organoid (78.2 to 98.2%), achieving a >5 log reduction of HIV loads in CD4+ cells isolated from tissues 2 weeks after drug treatment interruption. Ex vivo anti-CD3/CD28 stimulation increased the ability to activate exhausted CD8+ T cells in infected mice having received in vivo anti-PD-1 treatment by 7.9-fold (5 to 39.6%), and an additional increase by 1.7-fold upon D1143 co-treatment (39.6 to 67.3%). These findings demonstrate for the first time that an inhibitor of apoptosis protein antagonist enhances in a statistically manner the effects of an immune check point inhibitor on antiviral immunity and on HIV load reduction in tissues of humanized mice, suggesting that the combination of two distinct classes of immunomodulatory agents constitutes a promising anti-HIV immunotherapeutic approach.

A dose-finding study of the SMAC mimetic Debio 1143 when given in combination with avelumab to patients with advanced solid malignancies

2599

Background: Second mitochondria-derived activator of caspase (SMAC) mimetics regulate apoptosis and modulate NFκB signaling which drives the expression of genes involved in immune and inflammatory responses. In patient (pt) tumors, Debio 1143 increased PD-1/PD-L1 expression and tumor infiltrating lymphocytes. In pre-clinical models, it synergizes in vitro and in vivo with PD1/PD-L1 checkpoint inhibitors (CPIs). Methods: In a phase I study, using a mCRM model, avelumab (10 mg/kg i.v. on D1&15 q4w) was combined with escalating doses of Debio 1143 (100 mg/d to 250 mg/d orally, D1-10 & D15-24 q4w) to define the RP2D. Consenting adult pts with advanced solid tumors, normal organ function, and PS-ECOG = 0-1 were eligible provided none received prior CPI. Dose-limiting toxicities (DLTs), efficacy, safety, PK, PD and biomarkers were assessed. Results: As of DEC’18, 16 pts were treated; M/F: 8/8; ECOG = 0 in 6 (38%); median age = 58 (28-79); 5 pts had NSCLC, 2 MPM, 2 ovarian and 7 had other tumors (n = 1 each). Common AEs were: nausea (69%); fatigue (62%); vomiting (50%); cough, dyspnea, myalgia (44% each); diarrhea, anorexia (38% each); pruritus and constipation (31% each). These were generally grade 1-2, occasionally grade 3. One pt had a DLT at 250 mg/d dose: a grade 3 AST/ALT increase. No treatment-related AEs grade 4 or higher occurred. No dose-relationships for laboratory abnormalities were observed, except for ALT/AST increases, which at 200 mg/d were all grade 1 and asymptomatic. Maximal tolerated dose was not reached and there were no dose reductions. In 15 evaluable pts, 1 PR (NSCLC) and 5 SD (RECIST v1.1) were observed. Tumor shrinkage > 15% was seen in 2 other NSCLC pts. PK showed high interpatient variability and dose-proportional increase. TNFα and IFNγ peaked in plasma following Debio 1143 dose on D1 after 8 hrs, and on D17/22, in a dose-proportional manner. Four pts developed anti-avelumab antibodies. Conclusions: Debio 1143 at 200 mg/d can be safely combined with avelumab. Toxicity was predictable and mild. Clinical activity was observed in NSCLC pts. PK was linear; no drug interaction was suspected. PD and biomarker analysis is ongoing. Expansion at this RP2D is ongoing in NSCLC. Clinical trial information: NCT03270176.

The inhibitor apoptosis protein antagonist Debio 1143 Is an attractive HIV-1 latency reversal candidate

Antiretroviral therapy (ART) suppresses HIV replication, but does not cure the infection because replication-competent virus persists within latently infected CD4+ T cells throughout years of therapy. These reservoirs contain integrated HIV-1 genomes and can resupply active virus. Thus, the development of strategies to eliminate the reservoir of latently infected cells is a research priority of global significance. In this study, we tested efficacy of a new inhibitor of apoptosis protein antagonist (IAPa) called Debio 1143 at reversing HIV latency and investigated its mechanisms of action. Debio 1143 activates HIV transcription via NF-kB signaling by degrading the ubiquitin ligase baculoviral IAP repeat-containing 2 (BIRC2), a repressor of the non-canonical NF-kB pathway. Debio 1143-induced BIRC2 degradation results in the accumulation of NF-κB-inducing kinase (NIK) and proteolytic cleavage of p100 into p52, leading to nuclear translocation of p52 and RELB. Debio 1143 greatly enhances the binding of RELB to the HIV-1 LTR. These data indicate that Debio 1143 activates the non-canonical NF-kB signaling pathway by promoting the binding of RELB:p52 complexes to the HIV-1 LTR, resulting in the activation of the LTR-dependent HIV-1 transcription. Importantly, Debio 1143 reverses viral latency in HIV-1 latent T cell lines. Using knockdown (siRNA BIRC2), knockout (CRIPSR NIK) and proteasome machinery neutralization (MG132) approaches, we found that Debio 1143-mediated HIV latency reversal is BIRC2 degradation- and NIK stabilization-dependent. Debio 1143 also reverses HIV-1 latency in resting CD4+ T cells derived from ART-treated patients or HIV-1-infected humanized mice under ART. Interestingly, daily oral administration of Debio 1143 in cancer patients at well-tolerated doses elicited BIRC2 target engagement in PBMCs and induced a moderate increase in cytokines and chemokines mechanistically related to NF-kB signaling. In conclusion, we provide strong evidences that the IAPa Debio 1143, by initially activating the non-canonical NF-kB signaling and subsequently reactivating HIV-1 transcription, represents a new attractive viral latency reversal agent (LRA).

Abstract 4703: The inhibitor of apoptosis protein (IAP) antagonist Debio 1143 enhances the immune response to anti-PD1/L1 inhibitors in vitro and in vivo

Background: Debio 1143 is an oral antagonist of IAPs, currently in clinical development, which sensitizes tumor cells to radiation- or chemotherapy-induced apoptosis. IAPs inhibitors modulate NF-κB signaling and drive the expression of genes relevant for inflammation and immunity. Here, we hypothesized that Debio 1143 could improve antitumor immunity by directly enhancing T-lymphocyte activation and by improving the effects of immune checkpoint inhibitors in vitro and in vivo.

Methods: Ex vivo human PBMC anti-CD3/CD28 stimulation and modified mixed-lymphocyte reaction assays were performed to evaluate the immunostimulatory potential of Debio 1143 alone or in combination with the anti-PD-1 antibody nivolumab (N= 5 donors). T cells' proliferation and activation were measured by flow cytometry and cytokine release was measured by ELISA. The antitumor activity of an anti-PD-L1 antibody (5 mg/kg BIW IP) was tested either alone or in combination with Debio 1143 (100 mg/kg QD1-5 PO) in MBT-2 immunocompetent mouse model of bladder cancer over 3 weeks (n=8 /group).

Results: Debio 1143 significantly enhanced CD4+ and CD8+ intracellular IFNγ expression in a concentration-dependent manner following anti-CD3/CD28 stimulation. This result was confirmed using a mixed-lymphocyte reaction assay, where Debio 1143 at concentrations achieved in clinical studies significantly increased IFNγ expression by activated CD4+ cells, and this effect was even further increased in presence of nivolumab. In MBT-2 tumor-bearing mice, the combination of Debio 1143 and anti-PD-L1 antibody significantly decreased tumor growth (P=0.001 using two-sided t-test) and increased survival, whereas monotherapies only displayed moderate activities (median survival time of 42 days vs. 33 or 28 days for Debio 1143 or anti-PD-L1 alone, respectively).

Conclusion: These data show a key mechanistic role for future combination therapy of the IAP antagonist Debio 1143 and immune-checkpoint agents in cancer patients. This synergy will be further explored in a phase-Ib dose-finding clinical study combining Debio 1143 and Avelumab (anti-PD-L1) in patients with advanced solid malignancies and non-small cell lung cancer (CT# 03270176).

Citation Format: Antoine Attinger, Bruno Gavillet, Anne Vaslin Chessex, Norbert Wiedemann, Gregoire Vuagniaux. The inhibitor of apoptosis protein (IAP) antagonist Debio 1143 enhances the immune response to anti-PD1/L1 inhibitors in vitro and in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4703.

SMAC mimetic Debio 1143 synergizes with taxanes, topoisomerase inhibitors and bromodomain inhibitors to impede growth of lung adenocarcinoma cells

Targeting anti-apoptotic proteins can sensitize tumor cells to conventional chemotherapies or other targeted agents. Antagonizing the Inhibitor of Apoptosis Proteins (IAPs) with mimetics of the pro-apoptotic protein SMAC is one such approach. We used sensitization compound screening to uncover possible agents with the potential to further sensitize lung adenocarcinoma cells to the SMAC mimetic Debio 1143. Several compounds in combination with Debio 1143, including taxanes, topoisomerase inhibitors, and bromodomain inhibitors, super-additively inhibited growth and clonogenicity of lung adenocarcinoma cells. Co-treatment with Debio 1143 and the bromodomain inhibitor JQ1 suppresses the expression of c-IAP1, c-IAP2, and XIAP. Non-canonical NF-κB signaling is also activated following Debio 1143 treatment, and Debio 1143 induces the formation of the ripoptosome in Debio 1143-sensitive cell lines. Sensitivity to Debio 1143 and JQ1 co-treatment was associated with baseline caspase-8 expression. In vivo treatment of lung adenocarcinoma xenografts with Debio 1143 in combination with JQ1 or docetaxel reduced tumor volume more than either single agent alone. As Debio 1143-containing combinations effectively inhibited both in vitro and in vivo growth of lung adenocarcinoma cells, these data provide a rationale for Debio 1143 combinations currently being evaluated in ongoing clinical trials and suggest potential utility of other combinations identified here.

Abstract 283: Smac mimetic and radiotherapy synergize to enhance antitumor immunity in lung cancer by targeting immunosuppressive cells

Purpose

Hypofractionated radiotherapy (RT) directly kills lung cancer cells and stimulates tumor antigen release, the immune response to which can be augmented further by systemic immune-modulating agents. However, local relapses often occur after RT alone, indicating that inhibitory mechanisms may limit the anti-tumor immune responses elicited by apopotic tumor cells. We hypothesized that delivery of Smac mimetic, which sensitizes cells to apoptosis by counteracting the activity of inhibitor of apoptosis (IAP) proteins, following RT might lead to prolonged antitumor immunity by promoting the destruction of immunosuppressive myeloid cells.

Experimental Design

Using a murine model of lung cancer, we tested whether combination treatment with radiotherapy and the Smac mimetic Debio1143 would target immunosuppresive myeloid-derived suppressor cells (MDSCs) in the tumor microenvironment and enhance the efficacy of cytotoxic T cells.

Results

We demonstrate that administration of Debio1143 enhances the efficacy of RT by inducing LLC and LLC-OVA cells apoptosis in vitro. In addition, we show that combining radiotherapy and Debio1143 in vivo synergistically reduces the local accumulation of tumor-infiltrating MDSCs through a cytotoxic T cell-dependent mechanism. Activation of cytotoxic T cells by combination therapy proved to be mediated through the enhanced release of tumor necrosis factor alpha (TNF-α) in the tumor microenvironment.

Conclusions

These data offer a new paradigm to limit immunosuppresion by targeting MDSC and serve as the foundation for future clinical translation of combination therapy with Smac mimetics and radiotherapy.

Citation Format: Zhen Tao, Carey Myers, Norbert Wiedemann, Gregoire Vuagniaux, Larry Harshyne, Adam Dicker, D. Craig Hooper, Bo Lu. Smac mimetic and radiotherapy synergize to enhance antitumor immunity in lung cancer by targeting immunosuppressive cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 283. doi:10.1158/1538-7445.AM2015-283

Oral Debio1143 (AT406), an antagonist of inhibitor of apoptosis proteins, combined with daunorubicin and cytarabine in patients with poor-risk acute myeloid leukemia--results of a phase I dose-escalation study

BACKGROUND

Treatment of acute myeloid leukemia (AML) remains difficult owing to the development of treatment resistance, which might be overcome through antagonists of inhibitors of apoptosis proteins (IAPs).

PATIENTS AND METHODS

The present multicenter, open-label, dose-escalation study aimed to evaluate the tolerability, pharmacokinetics (PK), pharmacodynamics (PD), and efficacy of Debio1143 (formerly AT-406), a new IAP antagonist, when given along with a standard "7 plus 3 regimen" of daunorubicin and cytarabine to poor-risk patients with AML during the induction cycle. Consecutive patient cohorts received once-daily 100, 200, 300, or 400 mg of oral Debio1143 on treatment days 1 to 5. Blood samples were collected regularly until hematologic recovery or response was documented. Bone marrow samples were collected on days 0, 14, and 29 and PK and PD samples on days 1, 3, 5, 8, and 10 and 1, 2, and 8, respectively.

RESULTS

Of the 29 enrolled patients, 23 completed the study. The most common adverse events of any grade deemed related to treatment were nausea (31% of patients), diarrhea (14%), and febrile neutropenia (14%). Exposure exceeded dose proportionality, without accumulation over 5 days. Inhibition of cellular IAP1 was detectable in the CD34/CD117(+) cells and blasts. A total of 11 patients (38%) achieved complete remission, most in the 100-mg dose cohort. Of these, 6 (56%) developed a relapse within the study period. The patients with a response more frequently showed plasma increases of tumor necrosis factor-α and interleukin-8 after the first dose of Debio1143.

CONCLUSION

Debio1143 ≤ 400 mg/d showed good tolerability in combination with daunorubicin and cytarabine. Additional studies in subsets of patients with AML are warranted.

Safety, pharmacokinetics, and pharmacodynamic properties of oral DEBIO1143 (AT-406) in patients with advanced cancer: results of a first-in-man study

Purpose

To assess safety/tolerability, pharmacokinetics (PK), pharmacodynamics (PD), and antitumor activity of DEBIO1143, an antagonist of inhibitor apoptosis proteins.

Methods

This first-in-man study in patients with advanced cancer used an accelerated dose titration design. DEBIO1143 was given orally once daily on days 1–5 every 2 or 3 weeks until disease progressed or patients dropped out. The starting dose of 5 mg was escalated by 100 % in single patients until related grade 2 toxicity occurred. This triggered expansion to cohorts of three and subsequently six patients and reduction in dose increments to 50 %. Maximum tolerated dose (MTD) was exceeded when any two patients within the same cohort experienced dose-limiting toxicity (DLT). On days 1 and 5, PK and PD samples were taken.

Results

Thirty-one patients received doses from 5 to 900 mg. Only one DLT was reported at 180 mg. No MTD was found. Most common adverse drug reactions were fatigue (26 %), nausea (23 %), and vomiting (13 %). Average t_max and T_1/2 was about 1 and 6 h, respectively. Exposure increased proportionally with doses from 80 to 900 mg, without accumulation over 5 days. Plasma CCL2 increased at 3–6 h postdose and epithelial apoptosis marker M30 on day 5; cIAP-1 levels in PBMCs decreased at all doses >80 mg. Five patients (17 %) had stable disease as the best treatment response.

Conclusion

DEBIO1143 was well tolerated at doses up to 900 mg and elicited PD effects at doses greater 80 mg. Limited antitumor activity may suggest development rather as adjunct treatment.

Electronic supplementary material

The online version of this article (doi:10.1007/s00280-015-2709-8) contains supplementary material, which is available to authorized users.

Abstract C20: In vitro effects of Debio 1143, a novel oral IAP inhibitor, in human SCCHN cell lines and tumor specimens

Background: Resistance to radiotherapy and chemotherapy-induced apoptosis is a hallmark of cancer. Inhibitors of apoptosis proteins (IAPs) are negative modulators of apoptosis frequently expressed in various cancers, and, as such, attractive targets to overcome resistance to cancer therapy. The oral SMAC mimetic Debio 1143 (D1143, a.k.a AT-406), an antagonist of multiple IAPs (cIAP1/2 and XIAP), is currently investigated in a Phase I oncology clinical trial. This study aimed at evaluating D1143 activity as a single agent and in combination with TNF-α, TRAIL, cisplatin or carboplatin, in various SCCHN models.

Materials and Methods: The antiproliferative effects of D1143 were evaluated in a panel of 5 human SCCHN cell lines by MTT assay. Baseline and phosphorylated protein levels were detected by Western blot analysis. Tumor samples from SCCHN patients were surgically resected and cut into 300 µm thick slices using a tissue slicer (TIPCAN®). Each slice was exposed to 10 µM D1143 and/or 1 µM of platinum-based drug for 48 hours. Tumor samples were analyzed by immunohistochemistry (IHC) or immunofluorescence to visualize the effects of the treatment on various biomarkers of cell apoptosis, proliferation, and drug target engagement.

Results: A panel of 5 SCCHN cell lines was characterized for the expression of c-IAP1/2, XIAP, Bcl2, LRIG1, and other proteins implicated in resistance to cell death. D1143 alone displayed limited antiproliferative activity in only one cell line (Detroit 562). However, two SCCHN cell lines were sensitive to D1143 and TRAIL combined (SQ20B and SCC15), three were sensitive to D1143 and TNF-α combined (SQ20B, SCC61, and Detroit 562), and one was resistant to both combinations (HEP2). In Detroit 562 sensitive cells, 10 µM D1143 induced sustained cIAP1/2 degradation after 15 minutes of exposure. In contrast, in the HEP2 insensitive cell line, D1143 induced slight and transient inhibition of cIAP1/2. IHC analyses revealed that ex vivo exposure to D1143 of tumor explants freshly resected from SCCHN patients decreased cIAP1 staining. Treatment of tumor samples with D1143 combined with cisplatin or carboplatin augmented the cleavage of caspase 3 compared to controls suggesting induction of apoptosis.

Conclusion: In 4 out of 5 SCCHN cell lines, D1143 induced cIAP1/2 degradation and potentiated TNF-α or TRAIL-induced antiproliferative effects. D1143 combined with carboplatin and cisplatin in SCCHN patient samples induced caspase 3-dependent apoptosis. D1143 in combination with conventional chemotherapies may be considered as a potential treatment for SCCHN patients.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C20.

Citation Format: Marie Serova, Annemilaï Tijeras-Raballand, Sebastien Albert, Sandrine Faivre, Eric Raymond, Anne Vaslin, Claudio Zanna, Gregoire Vuagniaux, Armand de Gramont. In vitro effects of Debio 1143, a novel oral IAP inhibitor, in human SCCHN cell lines and tumor specimens. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C20.

HCV resistance to cyclosporin A does not correlate with a resistance of the NS5A-cyclophilin A interaction to cyclophilin inhibitors

BACKGROUND & AIMS

The cyclophilin (Cyp) inhibitors - cyclosporine A (CsA), NIM811, Debio 025, and SCY 635 - block HCV replication both in vitro and in vivo, and represent a novel class of potent anti-HCV agents. We and others showed that HCV relies on cyclophilin A (CypA) to replicate. We demonstrated that the hydrophobic pocket of CypA, where Cyp inhibitors bind, and which controls the isomerase activity of CypA, is critical for HCV replication. Recent studies showed that under Cyp inhibitor selection, mutations arose in the HCV nonstructural 5A (NS5A) protein. This led us to postulate that CypA assists HCV by acting on NS5A.

METHODS

We tested this hypothesis by developing several interaction assays including GST pull-down assays, ELISA, and mammalian two-hybrid binding assays.

RESULTS

We demonstrated that full-length NS5A and CypA form a stable complex. Remarkably, CsA prevents the CypA-NS5A interaction in a dose-dependent manner. Importantly, the CypA-NS5A interaction is conserved among genotypes and is interrupted by CsA. Surprisingly, the NS5A mutant protein, which arose in CsA-resistant HCV variants, behaves similarly to wild-type NS5A in terms of both CypA binding and CsA-mediated release from CypA. This latter finding suggests that HCV resistance to CsA does not correlate with a resistance of the CypA-NS5A interaction to Cyp inhibitors. Moreover, we found that CypA, devoid of its isomerase activity, fails to bind NS5A.

CONCLUSIONS

Altogether these data suggest that CypA, via its isomerase pocket, binds directly to NS5A, and most importantly, that disrupting this interaction stops HCV replication.

The cyclophilin inhibitor Debio 025 normalizes mitochondrial function, muscle apoptosis and ultrastructural defects in Col6a1-/- myopathic mice

BACKGROUND AND PURPOSE

We have investigated the therapeutic effects of the selective cyclophilin inhibitor D-MeAla(3)-EtVal(4)-cyclosporin (Debio 025) in myopathic Col6a1(-/-) mice, a model of muscular dystrophies due to defects of collagen VI.

EXPERIMENTAL APPROACH

We studied calcineurin activity based on NFAT translocation; T cell activation based on expression of CD69 and CD25; propensity to open the permeability transition pore in mitochondria and skeletal muscle fibres based on the ability to retain Ca(2+) and on membrane potential, respectively; muscle ultrastructure by electronmicroscopy; and apoptotic rates by terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling assays in Col6a1(-/-) mice before after treatment with Debio 025.

KEY RESULTS

Debio 025 did not inhibit calcineurin activity, yet it desensitizes the mitochondrial permeability transition pore in vivo. Treatment with Debio 025 prevented the mitochondrial dysfunction and normalized the apoptotic rates and ultrastructural lesions of myopathic Col6a1(-/-) mice.

CONCLUSIONS AND IMPLICATIONS

Desensitization of the mitochondrial permeability transition pore can be achieved by selective inhibition of matrix cyclophilin D without inhibition of calcineurin, resulting in an effective therapy of Col6a1(-/-) myopathic mice. These findings provide an important proof of principle that collagen VI muscular dystrophies can be treated with Debio 025. They represent an essential step towards an effective therapy for Ullrich Congenital Muscular Dystrophy and Bethlem Myopathy, because Debio 025 does not expose patients to the potentially harmful effects of immunosuppression.

The isomerase active site of cyclophilin A is critical for hepatitis C virus replication

Cyclosporine A and nonimmunosuppressive cyclophilin (Cyp) inhibitors such as Debio 025, NIM811, and SCY-635 block hepatitis C virus (HCV) replication in vitro. This effect was recently confirmed in HCV-infected patients where Debio 025 treatment dramatically decreased HCV viral load, suggesting that Cyps inhibitors represent a novel class of anti-HCV agents. However, it remains unclear how these compounds control HCV replication. Recent studies suggest that Cyps are important for HCV replication. However, a profound disagreement currently exists as to the respective roles of Cyp members in HCV replication. In this study, we analyzed the respective contribution of Cyp members to HCV replication by specifically knocking down their expression by both transient and stable small RNA interference. Only the CypA knockdown drastically decreased HCV replication. The re-expression of an exogenous CypA escape protein, which contains escape mutations at the small RNA interference recognition site, restored HCV replication, demonstrating the specificity for the CypA requirement. We then mutated residues that reside in the hydrophobic pocket of CypA where proline-containing peptide substrates and cyclosporine A bind and that are vital for the enzymatic or the hydrophobic pocket binding activity of CypA. Remarkably, these CypA mutants fail to restore HCV replication, suggesting for the first time that HCV exploits either the isomerase or the chaperone activity of CypA to replicate in hepatocytes and that CypA is the principal mediator of the Cyp inhibitor anti-HCV activity. Moreover, we demonstrated that the HCV NS5B polymerase associates with CypA via its enzymatic pocket. The study of the roles of Cyps in HCV replication should lead to the identification of new targets for the development of alternate anti-HCV therapies.