Phase I study of oral gemcitabine prodrug (LY2334737) alone and in combination with erlotinib in patients (pts) with advanced solid tumors

Abstract

2576 Background: LY2334737 (LY) is an orally available valproic acid prodrug of gemcitabine that was developed to overcome the extensive first-pass metabolism of gemcitabine to 2',2'-difluorodeoxyuridine (dFdU). The objectives of this study were to determine the maximum tolerated dose (MTD), dose limiting toxicity (DLT) and pharmacokinetics (PK) of LY as monotherapy and in combination with erlotinib. Methods: Eligible pts had ECOG PS < 2 and adequate hematologic, renal and hepatic function. In Arm A, LY was given daily for 14 days in a 3-week cycle. Pts assigned to Arm B also received erlotinib daily 100 mg continuously. Dose escalation was based on observed toxicity and the modified continual reassessment method (mCRM). The dose was maximally increased by 100% depending on the toxicity observed in the previous cohort. PK of LY, gemcitabine, dFdU and intracellular metabolites were determined. Results: 33 pts (21 m, 12 f, median age 60 yrs (range 24–81)) were treated at 5 different dose-levels (range 5–50 mg/day). Pts received a median of 3 cycles (range 2–17). Three out of 7 pt treated with 50 mg experienced 5 dose limiting toxicities (DLT). DLTs observed at 40 and 50 mg include fatigue (4 pt), thrombocytopenia (1 pt), GGT elevation (1 pt), AST/ALT elevation (1 pt), fever (1 pt), and pulmonary embolism (1 pt). One death was possibly related to LY intake. This pt, treated with 40 mg LY, developed on day 15 dyspnea, hypovolemic shock, and suddenly died. No grade 3 or 4 toxicities were reported at dose-levels < 40 mg. The most common adverse events were fatigue, vomiting, nausea, pyrexia, anorexia, and diarrhea. Two pts with mesothelioma were stable for > 9 months. One pt with refractory prostate cancer presented a PSA CR as assessed by investigator. The PK show dose-proportional increase in exposure of both LY and gemcitabine. Both LY and gemcitabine are rapidly cleared, thus no accumulation occurs. The metabolite dFdU accumulates due to its long half life. Conclusions: LY displays linear PK. The dose level of 50-mg is non-tolerable and 40-mg is being confirmed as the MTD as single agent and in combination with 100 mg erlotinib. Antitumor activity warrants further development. Pt accrual is ongoing. [Table: see text]