Flavopiridol, a cyclin-dependent kinase inhibitor, has promising clinical activity when combined with chemotherapy. Preclinical data indicate that flavopiridol enhances oxaliplatin (OX)- and fluorouracil (5FU)-induced apoptosis in a sequence-dependent manner.
We conducted a phase I trial of flavopiridol + FOLFOX (folinic acid, 5FU, and OX) for advanced solid tumors. Flavopiridol was administered every two weeks with OX before 5FU, based on sequence-dependent growth inhibition. Flavopiridol pharmacokinetics and p53 status were evaluated.
Forty-eight patients were treated on study. With dose escalation of OX (85 mg/m2) and 5FU (2400 mg/m2), dose-limiting toxicities (DLT) included hyponatremia, thrombocytopenia, and neutropenia. 5FU was subsequently reduced to allow for dose escalation of flavopiridol. DLTs with escalation of flavopiridol were nausea, vomiting, and neutropenia. The maximum tolerated dose (MTD) was flavopiridol 70 mg/m2, oxaliplatin 85 mg/m2, and 5FU 1800 mg/m2 continuous infusion over 48 hours. Clinical activity was noted in platinum-refractory germ cell tumors (GCTs): 3 out of 9 (33%) evaluable patients demonstrated a partial response on imaging, and 7 out of 10 (70%) had a decline in serum tumor markers. Responses were also observed in pancreatic, gastric, and sweat gland tumors. Flavopiridol pharmacokinetics had significant interpatient variability. At the MTD, tumor samples were p53 mutant (>30% positive cells) for responders and p53 wild-type for non-responders.
Flavopiridol with FOLFOX is a safe and tolerable regimen. Promising clinical activity was seen across tumor types. Encouraging results in the platinum-refractory GCT population has prompted a phase II trial which is currently open for accrual.