A phase I study of oral belinostat (PXD101) in patients with advanced solid tumors
14092 Background: Belinostat (PXD101) is a hydroxamate HDAC inhibitor which demonstrates broad anti-neoplastic activity in vitro and in vivo. In Phase I studies in patients (pts) with advanced cancer, IV belinostat is well-tolerated up to 1000 mg/m2 daily x5. Preliminary results of an oral formulation of belinostat showed that the oral bioavailability was 20 - 50%. This Phase I trial of oral belinostat will determine the maximal tolerated dose (MTD) of once and twice daily dosing, tolerability and pharmacokinetics (PK) in pts with advanced solid tumors. Methods: Sequential cohorts of 3–6 pts with advanced solid tumors refractory to standard therapy or for which no standard therapy exists were administered belinostat 250–500mg once or twice daily in 4 week cycles. Fasting (day 1) and non-fasting (day 7) pharmacokinetic studies were performed on all patients along with serial ECGs to evaluate any potential effects on QTc prolongation. Patients were evaluated with routine blood work weekly and tumor imaging at the end of cycle 1 then every other cycle. Results: Sixteen pts have been treated in 3 dose levels at 250mg QD (6 pts), 500mg QD (6 pts) and 250mg BID (4 pts). The median number of cycles of therapy is 1 (range 1–5), nine pts continue to be treated. The most common reasons for discontinuation were adverse event (3 pts) and PD (3 pts). No DLTs were identified at 250mg QD or 250mg BID. DLTs of grade 3 dehydration and grade 3 fatigue were reported at 500mg QD. In pts from the first 3 dose cohorts, there were no grade 4/5 events reported. Other Grade 3 toxicities were fatigue (2 pts), abdominal pain (1 pt), ataxia (1 pt), prolonged INR (1 pt), prolonged PTT (1 pt) and confusion (1 pt). Symptoms were transient and usually resolved after drug was held. In > 500 ECG’s collected, there were no QTcF > 500 ms, and no QTcF increase > 60 ms above baseline. To date, the best clinical response observed has been SD in 7 patients. Conclusions: Oral belinostat at doses of 250mg QD and 250mg BID given on a continuous schedule appears to be well tolerated. Alternative dosing schedules are being explored to further dose escalate the belinostat. Updated safety, activity and pharmacokinetic data will be presented on these and alternate dose schedules. [Table: see text]