A Phase I Study of Tipifarnib Combined with Conventional Induction and Consolidation Therapy for Previously Untreated Patients with Acute Myeloid Leukemia Age 60 and Over.

Standard induction therapy for patients over age 60 with acute myeloid leukemia (AML) has produced complete response (CR) rates of around 55%, but most patients eventually relapse. Tipifarnib (R115777, Zarnestra^R) has shown activity as a single agent in AML, and is well tolerated in older patients at doses up to 600 mg BID. This agent also has additive/synergistic effects on AML cell lines when combined with daunorubicin (DNR). From 2005–2007, patients age 60 and over with previously untreated AML (de novo or secondary) were enrolled in a Phase I study combining tipifarnib with standard induction therapy. The regimen consisted of cytarabine 100 mg/m²/day continuous IV infusion on days 1–7, DNR 60 mg/m²/day IV push x 3 on days 6–8 and tipifarnib orally twice daily on days 6–15. Tipifarnib was escalated over four doses levels in successive patient cohorts (200, 300, 400 and 600 mg). Patients achieving CR were eligible to received one consolidation using the same regimen. Dose-limiting toxicity (DLT) was defined as Grade III–IV non–hematologic toxicity or hematologic recovery times > 40 days unless due to persistent leukemia. Up to 2/6 DLTs were permitted at each dose level. The following DLT’s were identified during induction: Dose level I: 2/6 (grade III hyperbilirubinemia, grade IV transient respiratory arrest), dose level II: 0/3, dose level III: 0/3 and dose level IV: 2/6 (grade III typhlitis, grade III supraventricular tachycardia). Four additional patients were enrolled at dose level IV, with one DLT (grade III diarrhea). There were no DLTs during consolidation. There were no cases of delayed hematologic recovery. Of 22 evaluable patients, there were 9 CR, 3 MLFS, 2 PR and 8 non-responders. Of 7 patients with adverse risk cytogenetics, there were 3 CR, 1 MLFS and 1 PR. In summary, this regimen was well tolerated and the DLT was not reached, although somewhat more GI toxicity was seen at dose level IV. Because of the inherent toxicity of the underlying regimen and the elderly population, it was decided not to escalate further, and tipifarnib 600 mg BID has been chosen as the recommended dose for further study using this regimen.