A phase I dose-escalation and pharmacokinetic study of enzastaurin combined with capecitabine in patients with advanced cancer

Abstract

2048 Background: Enzastaurin (ENZ), an oral inhibitor of protein kinase C (PKC), affects signal transduction associated with angiogenesis, proliferation, and survival. The combination of ENZ and capecitabine (CAPE) has the potential for additive or synergistic anticancer effects without excessive toxicity. Methods: Patients (pts) with advanced, refractory, solid tumors received lead-in treatment with ENZ for 7–14 days (cycle 1), to achieve steady-state exposures. In subsequent 21-day cycles, ENZ was given once daily, orally, on days 1–21 and CAPE twice daily (bid), orally, on days 1–14 in 3 dose levels (L): L 1 = ENZ 350 mg + CAPE 750 mg/m2; L 2 = ENZ 350 mg + CAPE 1000 mg/m2; L 3 = ENZ 525 mg (some pts received 500 mg tablets) + CAPE 1000 mg/m2. PK for ENZ was assessed on day 1–3 and 7 in cycle 1 and day 8 in cycle 2 and for CAPE on day 1, 8 in cycle 2. Therapy continued until disease progression or unacceptable toxicity occurred. Results: 27 pts (13 males; 14 females, ECOG ≤1) with a median age of 58 yrs (range: 38–74 yrs), received a median number of 3 cycles (range: 2–14 cycles). High interpatient PK variability was noted for total ENZ analytes. Ratio of geometric mean AUC (90% CI) of ENZ with CAPE versus ENZ alone at 500/525 mg was 0.65 (0.38–1.11, n=6) and of Cmax was 0.66 (0.42–1.10, n=4). PK parameters of CAPE in the presence of ENZ were similar to those previously reported for CAPE alone. No grade (Gr) 4 toxicities occurred. Gr 3 toxicities were anemia (1 pt), headache (1 pt), intestinal perforation (1 pt with gastric carcinoma), fatigue (1 pt), hand-foot syndrome (2 pts), and cardiac ischemia (1 pt). PBMCs demonstrated PKC inhibition following exposure to ENZ. Plasma VEGF and bFGF levels did not reflect any significant changes. No objective tumor responses were seen. Five pts had stable disease (lung, breast, pancreas, head/neck, and hemangiopericytoma) for ≥ 6 months (range: 6–9.7 months). Conclusions: The recommended phase II dose is ENZ 500 mg, qd and Cape 1000 mg/m2 bid, days 1–14 every 21 days. This regimen was well tolerated, and exposures of ENZ and CAPE did not appear to be significantly altered when given in combination. [Table: see text]