Feldman, Eric J.

Abstract The farnesyltransferase inhibitor tipifarnib exhibits modest activity against acute myelogenous leukemia. To build on these results, we examined the effect of combining tipifarnib with other agents. Tipifarnib inhibited signaling downstream of the farnesylated small G protein Rheb and synergistically enhanced etoposide-induced antiproliferative effects in lymphohematopoietic cell lines and acute myelogenous leukemia isolates. We subsequently conducted a phase 1 trial of tipifarnib plus etoposide in adults over 70 years of age who were not candidates for conventional therapy. A total of 84 patients (median age, 77 years) received 224 cycles of oral tipifarnib (300-600 mg twice daily for 14 or 21 days) plus oral etoposide (100-200 mg daily on days 1-3 and 8-10). Dose-limiting toxicities occurred with 21-day tipifarnib. Complete remissions were achieved in 16 of 54 (30%) receiving 14-day tipifarnib versus 5 of 30 (17%) receiving 21-day tipifarnib. Complete remissions occurred in 50% of two 14-day tipifarnib cohorts: 3A (tipifarnib 600, etoposide 100) and 8A (tipifarnib 400, etoposide 200). In vivo, tipifarnib plus etoposide decreased ribosomal S6 protein phosphorylation and increased histone H2AX phosphorylation and apoptosis. Tipifarnib plus etoposide is a promising orally bioavailable regimen that warrants further evaluation in elderly adults who are not candidates for conventional induction chemotherapy. These clinical studies are registered at www.clinicaltrials.gov as #NCT00112853.

Lenalidomide is approved for red blood cell (RBC) transfusion-dependent anemia due to low or intermediate-1 (int-1) risk myelodysplastic syndromes (MDSs) associated with a chromosome 5q deletion with or without additional cytogenetic abnormalities. We report results of a multicenter, phase 2 trial evaluating lenalidomide therapy for transfusion-dependent patients with low- or int-1–risk MDS without deletion 5q. Eligible patients had 50 000/mm3 or more platelets and required 2 U or more RBCs within the previous 8 weeks; 214 patients received 10 mg oral lenalidomide daily or 10 mg on days 1 to 21 of a 28-day cycle. The most common grade 3/4 adverse events were neutropenia (30%) and thrombocytopenia (25%). Using an intention-to-treat analysis, 56 (26%) patients achieved transfusion independence (TI) after a median of 4.8 weeks of treatment with a median duration of TI of 41.0 weeks. In patients who achieved TI, the median rise in hemoglobin was 32 g/L (3.2 g/dL; range, 10-98 g/L [1.0-9.8 g/dL]) from baseline. A 50% or greater reduction in transfusion requirement occurred in 37 additional patients, yielding a 43% overall rate of hematologic improvement (TI response +‖≥ 50% reduction in transfusion requirement). Lenalidomide has clinically meaningful activity in transfusion-dependent patients with low- or int-1–risk MDS who lack the deletion 5q karyotypic abnormality. This study is registered at www.clinicaltrials.gov as no. NCT00064974.

AbstractOutcomes for older adults with acute myelogenous leukemia (AML) are poor due to both disease and host-related factors. In this phase 2 study, we tested the oral farnesyltransferase inhibitor tipifarnib in 158 older adults with previously untreated, poor-risk AML. The median age was 74 years, and a majority of patients had antecedent myelodysplastic syndrome. Complete remission (CR) was achieved in 22 patients (14%); partial remission or hematologic improvement occurred in 15 patients, for an overall response rate of 23%. The median duration of CR was 7.3 months and the median survival of complete responders was 18 months. Adverse karyotype, age 75 years or older, and poor performance status correlated negatively with survival. Early death in the absence of progressive disease was rare, and drug-related nonhematologic serious adverse events were observed in 74 patients (47%). Inhibition of farnesylation of the surrogate protein HDJ-2 occurred in the large majority of marrow samples tested. Baseline levels of phosphorylated mitogen-activated protein kinase and AKT did not correlate with clinical response. Tipifarnib is active and well tolerated in older adults with poor-risk AML and may impart a survival advantage in those patients who experience a clinical response.