A phase Ib adaptive study of dasatinib for the prevention of oxaliplatin-induced neuropathy in patients with gastrointestinal (GI) cancers receiving FOLFOX chemotherapy with or without bevacizumab

e15613 Background: Neurotoxicity is one of the most significant and disabling side effects of oxaliplatin (OX) and frequently limits the amount of OX that can be used. OX uptake by organic cation transporter 2 (OCT2) into mouse and rat dorsal root ganglia is a prerequisite for OX-induced peripheral neuropathy (OIPN). Preclinical data in rat and mouse models from our group showed that by inhibiting YES1, pre-treatment with dasatinib (D) inactivated OCT2 and prevented acute and chronic OIPN. A phase I trial is ongoing investigating addition of D prior to OX to prevent OIPN. Methods: This is a Bayesian Phase 1b dose-finding study with adaptive dose selection using efficacy-toxicity trade-offs in patients (pts) with GI cancers who are candidates for mFOLFOX6 ± bevacizumab [NCT04164069]. Pts received chemotherapy on day 1 and 15 schedule, every 28 days. D was administered at one of 2 dose levels – 100mg or 140mg PO, given 24 hours and 30 mins prior to OX on C1D14, C1D15 respectively and repeated on C1D28 and C2D1. During cycle 1, pharmacokinetic and pharmacodynamic data was obtained at baseline, during, and up to 24 hours after D or OX administration. Recommended Phase 2 dose (RP2D) was defined as the lowest intermittent dose of D that increases serum biomarkers of OCT2, including methylnicotinamide (NMN) and creatinine, by ≥2-fold without influencing the clearance of oxaliplatin by ≥20%, toxicity profile was evaluated based on CTCAE v. 5.0. Results: 11 pts were screened. 5 pts enrolled in cohort 1 (D 100 mg) and 2 in cohort 2 (D 140 mg). In this preliminary analysis, 5 patients were evaluated for efficacy biomarkers and 4 pts were evaluated for both efficacy biomarkers and toxicity. There were no DLTs observed in either cohort. 3/5 pts had ≥2-fold increase in AUC of NMN, and 4/5 pts had ≥2-fold increase in AUC of creatinine. 4/5 pts had ≤20% change in the clearance of OX. Conclusions: Addition of D 140 mg to traditional FOLFOX regimen was safe and resulted in increasing levels of biomarkers as indication of inhibition of OCT2 in comparison to baseline for the majority of pts enrolled. Enrollment and analysis are ongoing at D 140mg dose to confirm the RP2D to prevent OPIN in a future randomized phase II study. Clinical trial information: NCT04164069 . [Table: see text]