Tipifarnib (ZARNESTRATM in Previously Untreated Poor-Risk AML of the Elderly: Updated Results of a Multicenter Phase 2 Trial.
Authors: Lancet Jeffrey E. , Gotlib Jason , Gojo Ivana , Feldman Eric J. , Morris Lawrence , Thibault Alain , Liesveld Jane L. , Greer Jacqueline , Dugan Kathleen , Raponi Mitch , Wright John J. , Greenberg Peter L. , Karp Judith E. 
Published: October 2019

Farnesyltransferase inhibitors (FTI) make up a novel class of anti-cancer agents that competitively and selectively inhibit farnesyl protein transferase. Early trials of the orally bioavailable non-peptidomimetic FTI tipifarnib (ZARNESTRATM, Johnson & Johnson PRD) demonstrated both clinical responses and excellent tolerability in patients with poor-risk or refractory acute myeloid leukemia (AML). (Karp, et al. Blood97:3361, 2001). We herein report updated results of a multicenter phase 2 trial of tipifarnib in an elderly, previously untreated poor-risk AML population who refused or were deemed unfit for conventional induction chemotherapy. Tipifarnib was administered orally in the outpatient setting at a dose of 600 mg BID for 21 days, followed by a 1–3 week recovery period. Up to 4 cycles of tipifarnib were permitted in patients with complete responses (CR). The primary endpoint was overall response rate (CR + PR). Secondary endpoints included toxicity rates, measurement of markers of farnesylation (HDJ-2) in bone marrow cells, measurement of signaling intermediates ERK and AKT, and RNA microarray expression patterns. Accrual to the trial is complete. 170 patients have been enrolled, 148 of whom are evaluable for response (AML=160; high-risk MDS=4; high-risk CMML=6). The median age was 73 years (range 34–85), and 76 patients (45%) were age = 75. M/F ratio was 2:1. An unfavorable karyotype and/or antecedent MDS was present in 47% and 79% of patients, respectively. The median number of cycles received was 1, and the median number of days of drug received was 36 days. Dose reductions were implemented in 38% of patients, more commonly in cycles subsequent to cycle #1. The overall response rate (CR + PR) was 34%. CR occurred in 18% of patients. Responses were evenly distributed across study centers. In patients ≥ 75 years, the overall response rate was 30% (CR 20 %). Median CR duration was 6.4 months (range 1.5–11+ months). Median overall survival was 5.6 months for all patients. CR patients had a median survival of 14.4 months, with 63% alive at 12 months. In non-responders, median survival was 3.1 months. The incidence of grade = 3 tipifarnib-related non-hematologic adverse events was 43%, comprised mainly of infectious and gastrointestinal complications. The hospitalization rate for tipifarnib-related toxicity was 18% (median duration: 12 days). The death rate from tipifarnib-related toxicity at 6 weeks was 5%. Microarray analysis of pre-and post-treatment bone marrow samples is being performed to identify both predictive and pharmacodynamic gene markers of response to tipifarnib. In summary, tipifarnib is a novel outpatient treatment with activity in previously untreated poor-risk AML. The low hospitalization rate may reflect the low incidence of severe non-hematological toxicity.