A phase I study of flavopiridol in combination with gemcitabine and irinotecan in patients with metastatic cancer

Background: Flavopiridol (HMR 1275) is a synthetic flavone with antineoplastic properties through inhibition of cyclin-dependent kinase inhibitor. Flavopiridol synergizes in a sequence-dependent fashion with chemotherapy. Major adverse events of flavopiridol in single agent phase I studies are secretory diarrhea, neutropenia, thrombosis, and fatigue. Patients and Methods: Patients with advanced solid tumors were treated with gemcitabine 800 mg/m² and irinotecan 80 mg/m² on day 1, followed by flavopiridol, starting dose of 30 mg/m² on day 2 with increment of 15 mg/m² per dose level, repeated on days 8 and 9 for the first 6 patients (3-week cycle), and then repeated on days 15 and 16 for the remainder patients (4-week cycle). The protocol had to be amended for inability to redose after 1 week. Results: Fourteen women and 7 men with advanced solid tumors were enrolled. The median age was 51 years and the median number of prior chemotherapies was 3 (0-9). Neutropenic sepsis (1 patient), grade 3 diarrhea (1 patient), and neutropenia (2 patients) preventing retreatment on day 8 were observed among the 6 subjects treated on the first schedule. The recommended phase II dose of flavopiridol was 45 mg/m² in combination with irinotecan and gemcitabine every 2 weeks. Dose-limiting toxicities were electrolyte imbalance with fatigue (1 patient), and renal failure and dyspnea with hypoxia (1 patient each), seen at 45 and 60 mg/m² doses, respectively. The most common side effects were fatigue (81%), nausea (71%), diarrhea (67%), transient myelosuppression (43%), and vomiting (24%). Conclusions: The every 2 week dosing is well tolerated with a phase II recommended dose of 45 mg/m² of flavopiridol in combination with irinotecan (80 mg/m²) and gemcitabine (800 mg/m²).