A Phase I Dose-Escalation and Expansion Study of Telaglenastat in Patients with Advanced or Metastatic Solid Tumors

Purpose: Glutamine is a critical fuel for solid tumors. Interference with glutamine metabolism is deleterious to neoplasia in preclinical models. A phase I study of the oral, first-in-class, glutaminase (GLS) inhibitor telaglenastat was conducted in treatment-refractory solid tumor patients to define recommended phase II dose (RP2D) and evaluate safety, pharmacokinetics (PK), pharmacodynamics (PD), and antitumor activity. Patients and Methods: Dose escalation by 3 thorn 3 design was followed by exploratory tumor-/biomarker-specific cohorts. Results: Among 120 patients, fatigue (23%) and nausea (19%) were themost common toxicity. Maximum tolerated dose was not reached. Correlative analysis indicated >90% GLS inhibition in platelets at plasma exposures > 300 nmol/L, > 75% tumoral GLS inhibition, and significant increase in circulating glutamine. RP2D was defined at 800 mg twice-daily. Disease control rate (DCR) was 43% across expansion cohorts (overall response rate 5%, DCR 50% in renal cell carcinoma). Conclusions: Telaglenastat is safe, with a favorable PK/PD profile and signal of antitumor activity, supporting further clinical development.