A First-in-human Phase I Study of TAS-117, an Allosteric AKT Inhibitor, in Patients with Advanced Solid Tumors.

Purpose TAS-117 is a highly potent and selective, oral, allosteric pan-AKT inhibitor under development for advanced/metastatic solid tumors. The safety, clinical pharmacology, pharmacogenomics and efficacy were investigated. Methods This phase I, open-label, non-randomized, dose-escalating, first-in-human study enrolled patients with advanced/metastatic solid tumors and comprised three phases (dose escalation phase [DEP], regimen modification phase [RMP], and safety assessment phase [SAP]). The SAP dose and regimen were determined in the DEP and RMP. Once-daily and intermittent dosing (4 days on/3 days off, 21-day cycles) were investigated. The primary endpoints were dose-limiting toxicities (DLTs) in Cycle 1 of the DEP and RMP and incidences of adverse events (AEs) and adverse drug reactions (ADRs) in the SAP. Secondary endpoints included pharmacokinetics, pharmacodynamics, pharmacogenomics, and antitumor activity. Results Of 66 enrolled patients, 65 received TAS-117 (DEP, n = 12; RMP, n = 10; SAP, n = 43). No DLTs were reported with 24-mg/day intermittent dosing, which was selected as a recommended dose in SAP. In the SAP, 98.5% of patients experienced both AEs and ADRs (grade ≥ 3, 67.7% and 60.0%, respectively). In the dose range tested (8 to 32 mg/day), TAS-117 pharmacokinetics were dose proportional, and pharmacodynamic analysis showed a reduction of phosphorylated PRAS40, a direct substrate of AKT. Four patients in the SAP had confirmed partial response. Conclusion Oral doses of TAS-117 once daily up to 16 mg/day and intermittent dosing of 24 mg/day were well tolerated. TAS-117 pharmacokinetics were dose proportional at the doses evaluated. Antitumor activity may occur through AKT inhibition. Trial registration jRCT2080222728 (January 29, 2015).