A phase I trial of doxorubicin and flavopiridol in soft tissue sarcoma
9523 Background: Flavopiridol, a potent cyclin dependent kinase inhibitor, has been shown in vitro to enhance doxorubicin induced apoptosis. Using the BWH dediffentiated liposarcoma xenograft model we have shown that sequential therapy with doxorubicin (D) followed 1 hour later by flavopiridol (F) is superior to doxorubicin alone (p=0.006). Single agent flavopiridol was also active in this xenograft model, but less so than the combination. Methods: We have commenced an ongoing phase I study of the combination of D and F on the basis of this preclinical data in soft tissue sarcoma with fixed dose D (60 mg/m2), followed 1 hour later by escalating doses of F (40–70 mg/m2) administered over one hour, every 3 weeks. Standard phase I eligibility criteria apply. No prior anthracycline therapy is allowed. At 300 mg/m2 D, dexrazoxane is added to D F. Patients with responsive or stable disease after cumulative D dose of 600mg/m2 can receive single agent flavopiridol. Results: Median characteristics of 7 evaluable patients: age 52 (31–65), KPS 80% (70–90), 3 males / 4 females, 0 prior regimens (range 0–2). The combination has been well-tolerated, with no dose limiting toxicity (DLT) yet. There has been 1 grade 3 bleed in the setting of progressive disease and 1 grade 4 neutropenia without fever. Grade 1 and 2 diarrhea, related to flavopiridol have been observed. Pharmacokinetic (PK) studies are ongoing. We have observed no partial responses (PR). Prolonged stable disease (SD) has been seen in 3 patients for 6, 6 and 11 months. Two patients with SD have liposarcoma. One patient with liposarcoma continues on single agent flavopiridol with stable disease after having reached the prescribed limit of D of 600 mg/m2. Conclusions: The combination of doxorubicin and flavopiridol is safe, with no unexpected toxicities. Disease stabilization in STS has been observed. This appears to be an encouraging combination in liposarcoma and is consistent with our preclinical model. Flavopiridol dose escalation is continuing. No significant financial relationships to disclose.