A first-in-human phase I/Ib dose-escalation clinical trial of the autophagy inducer ABTL0812 in patients with advanced solid tumours

BACKGROUND

ABTL0812 is an autophagy inducer that promotes cancer cell death by activation of cytotoxic autophagy selectively in tumour cells. ABTL0812 induces endoplasmic reticulum stress and blocks the Akt-mTOR axis; both actions converge to activate a robust and sustained autophagy leading to cancer cell death. Preclinical data supported the initiation of clinical trials in patients with cancer.

PATIENTS AND METHODS

This first-in-human trial consisted of an escalation phase (3 + 3 design), followed by an expansion phase, to assess safety and tolerability of ABTL0812. Secondary objectives were determining the recommended phase II dose (RP2D), clinical antitumour activity, pharmacokinetics (PK) and pharmacodynamics (PD).

RESULTS

A total of 29 patients were enrolled and treated; fifteen patients were treated in four escalation dosing cohorts (ranging from 500 mg once a day to 2000 mg twice a day) and fourteen in the expansion phase (dosed with 1300 mg three times a day). No maximum tolerated dose was attained, and RP2D was determined by PK/PD modelling. Most drug-related adverse events were gastrointestinal grade I-II. Correlation between drug levels and pAkt/Akt ratio was found. Two cases of long-term (>1 year) stable disease were observed.

CONCLUSIONS

ABTL0812 is safe and has an acceptable tolerability profile, allowing a long-term oral dosing. RP2D of 1300 mg three times a day was determined according to PK/PD modelling, and preliminary antitumour efficacy was observed.

CLINICAL TRIAL REGISTRATION NUMBER

NCT02201823.

The New Antitumor Drug ABTL0812 Inhibits the Akt/mTORC1 Axis by Upregulating Tribbles-3 Pseudokinase

PURPOSE

ABTL0812 is a novel first-in-class, small molecule which showed antiproliferative effect on tumor cells in phenotypic assays. Here we describe the mechanism of action of this antitumor drug, which is currently in clinical development.

EXPERIMENTAL DESIGN

We investigated the effect of ABTL0812 on cancer cell death, proliferation, and modulation of intracellular signaling pathways, using human lung (A549) and pancreatic (MiaPaCa-2) cancer cells and tumor xenografts. To identify cellular targets, we performed in silico high-throughput screening comparing ABTL0812 chemical structure against ChEMBL15 database.

RESULTS

ABTL0812 inhibited Akt/mTORC1 axis, resulting in impaired cancer cell proliferation and autophagy-mediated cell death. In silico screening led us to identify PPARs, PPARα and PPARγ as the cellular targets of ABTL0812. We showed that ABTL0812 activates both PPAR receptors, resulting in upregulation of Tribbles-3 pseudokinase (TRIB3) gene expression. Upregulated TRIB3 binds cellular Akt, preventing its activation by upstream kinases, resulting in Akt inhibition and suppression of the Akt/mTORC1 axis. Pharmacologic inhibition of PPARα/γ or TRIB3 silencing prevented ABTL0812-induced cell death. ABTL0812 treatment induced Akt inhibition in cancer cells, tumor xenografts, and peripheral blood mononuclear cells from patients enrolled in phase I/Ib first-in-human clinical trial.

CONCLUSIONS

ABTL0812 has a unique and novel mechanism of action, that defines a new and drugable cellular route that links PPARs to Akt/mTORC1 axis, where TRIB3 pseudokinase plays a central role. Activation of this route (PPARα/γ-TRIB3-Akt-mTORC1) leads to autophagy-mediated cancer cell death. Given the low toxicity and high tolerability of ABTL0812, our results support further development of ABTL0812 as a promising anticancer therapy. Clin Cancer Res; 22(10); 2508-19. ©2015 AACR.

Abstract LB-C18: First-in-Human Clinical Trial of ABTL0812, a Compound that Inhibits PI3K/Akt/mTOR Pathway by Upregulating TRIB3, in Patients with Advanced Solid Tumors

Background: ABTL0812 is a first-in-class antitumor drug whose mechanism of action relies on the inhibition of PI3K/Akt/mTOR (PAM) pathway by upregulation of TRIB3 levels, an endogenous inhibitor of Akt activity that prevents Akt phosphorylation. Preclinical studies showed good efficacy of ABTL0812 in xenograft models with high safety margin. Here we describe the First-in-Human (FiH) Phase I/Ib clinical trial of ABTL0812 in patients with advanced solid tumors (NCT02201823).

Methods: ABTL0812 was dosed daily, by the oral route, in 28-day cycles. The study included a 4-cohort dose escalation, in a 3+3 dose escalating design, followed by an expansion cohort. The trial objectives were to determine safety and tolerability, to evaluate signs of efficacy, to determine drug pharmacokinetics (PK) in plasma and to analyze inhibition of Akt phosphorylation in platelets by MSD® as pharmacodynamic (PD) biomarker. Pretreatment tumor biopsies were analyzed by next generation sequencing to identify mutations in a panel of 50 cancer-related genes.

Results: Fifteen patients were recruited in the escalation part and 14 patients in the expansion cohort (February 2014 to May 2015). No dose-limiting-toxicities were detected and the recommended Phase II was 1300 mg tid based on PK/PD modeling. The median number of previous chemotherapy lines was 2 (range 0-11). The profile of ABTL0812 grade 1-2 related adverse events (AEs) included asthenia, nausea/vomiting and throat burning (34%, 31% and 24% of patients, respectively). Only one case of grade 3-4 AE (elevated hepatic enzymes) appeared. ABTL0812 half-life was short (3-5 h), which supported the increase in the administration schedule from once to twice and finally to three times a day. Biomarker analysis showed inhibition of Akt phosphorylation with increasing doses, with average 90% inhibition in the expansion cohort; furthermore it correlated with C-trough plasma levels. Five patients had stable disease (SD) for at least 16 weeks: 1 endometrial cancer (62 weeks), 1 cholangiocarcinoma (35 weeks, ongoing on Sep 15th, 2015), 2 colorectal cancer (28 and 22 weeks) and 1 lung adenocarcinoma (16 weeks). The median time to progression in the expansion cohort was 11 weeks (range 1-≥35 weeks). Interestingly, the tumor biopsy from the patient with endometrial cancer had activating mutations in Akt1 (E17K) and PIK3CA (R88Q). The tumor from the patient with colorectal cancer (28 weeks SD) showed deleterious mutations in TP53 (R248W) and APC (Q1469Ter). None of these samples included major mutations in Ras.

Conclusions: ABTL0812 is a PAM pathway inhibitor acting by a novel mechanism of action that involves upregulation of TRIB3 levels. The FiH Phase I/Ib study in patients with advanced solid tumors showed excellent tolerability and safety profile and demonstrated dose-dependent inhibition of Akt phosphorylation. ABTL0812 treatment induced several long term disease stabilizations (5/29), being the best responder a patient with endometrial cancer (68 weeks) with activating mutations in Akt1 and PIK3CA. Based on these data, a Phase II clinical trial in patients with endometrial cancer is planned.

Citation Format: Laura Vidal, Lydia Gaba, Ivan Victoria, Marta Gil-Martin, Berta Laquente, Marc Cortal, Merce Brunet, Pilar Paredes, Mariana Gomez-Ferreria, Jose Alfon, Carles Domenech, Pedro Gascon. First-in-Human Clinical Trial of ABTL0812, a Compound that Inhibits PI3K/Akt/mTOR Pathway by Upregulating TRIB3, in Patients with Advanced Solid Tumors. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr LB-C18.

Abstract 672: ABTL0812, a new antitumor drug that inhibits the axis Akt/mTOR through a novel mechanism of action

Background: ABTL0812 is a first-in-class orally administered compound currently in Phase I/Ib First in Human Clinical Trial in patients with advanced solid tumors (NCT02201823). ABTL0812 has cytotoxic effect on a wide range of human tumor cell lines, including those which have become resistant to standard therapy. We hereby dissect the anti-tumor activity of ABTL0812, which relies on a novel mechanism of action that promotes inhibition of the Akt/mTOR axis in cancer cells.

Material & methods: ABTL0812 molecular targets were identified by in silico analysis, comparing ABTL0812 chemical structure against a database including more than one million receptor-ligand interaction data. Functional relevance of the targets was confirmed biochemically and pharmacologically. ABTL0812 mechanism of action was established using human lung and pancreatic tumor cells, MEF KO cells, as well as tumor xenografts.

Results: In silico screening showed that ABTL0812 binds four targets which regulate tumor progression through Akt/mTOR axis. Two of them are the transcription factors PPARα and PPARγ (Peroxisome-Proliferator Activating Receptors). In lung and pancreatic tumor cells ABTL0812 activated PPARα/γ-dependent gene transcription, while pharmacological inhibition with PPARα/γ antagonists impaired ABTL0812 cytotoxic effect. Interestingly, ABTL0812 induced transcription of the endogenous Akt inhibitor TRIB3 (tribbles homologue 3) through PPARα/γ activation. TRIB3 is a pseudokinase that inhibits Akt by direct binding and preventing its phosphorylation by mTORC2 complex. According to this, ABTL0812-induced TRIB3 overexpression resulted in inhibition of Akt phosphorylation, impaired phosphorylation of the Akt substrates TSC2 and PRAS40 and mTORC1 inhibition (pS6), which in turn promoted autophagy-mediated tumor cell death. MEF TRIB3-/- cells were resistant to ABTL0812-induced cell death, indicating that TRIB3 mediates ABTL0812 citotoxicity. Finally, Akt inhibition was observed in human lung and pancreatic tumor xenograft models treated with ABTL0812 and in human platelets incubated with ABTL0812. This supported the rational for using Akt phosphorylation as a pharmacodynamic biomarker to monitor activity of ABTL0812 in patients included in the Clinical Trial.

Conclusion: ABTL0812 promotes autophagy-mediated cell death in different cancer paradigms by inhibiting the Akt/mTOR axis through a novel mechanism of action. ABTL0812 induces PPARα/γ-mediated transcription of the TRIB3 gene. Upregulated TRIB3 protein binds and inhibits Akt, leading to mTORC1 inhibition and reduction of tumor growth. These findings provide evidences that ABTL0812 may be an effective therapeutic strategy for targeting cancer.

Citation Format: Tatiana Erazo, Mariana Gomez-Ferreria, Jose Alfon, Mar Lorente, Maria Salazar, Anna Lopez, Marc Cortal, Pau Munoz-Guardiola, Pedro Gascon, Guillermo Velasco, Carles Domenech, Jose M. Lizcano. ABTL0812, a new antitumor drug that inhibits the axis Akt/mTOR through a novel mechanism of action. [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 672. doi:10.1158/1538-7445.AM2015-672