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