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 (T) exhibits modest activity in elderly adults with newly diagnosed acute myelogenous leukemia (AML). Based on preclinical synergy, a phase 1 trial of T plus etoposide (E) yielded 25% complete remission (CR). We selected 2 comparable dose levels for a randomized phase 2 trial in 84 adults (age range, 70-90 years; median, 76 years) who were not candidates for conventional chemotherapy. Arm A (T 600 mg twice a day ؋ 14 days, E 100 mg days 1-3 and 8-10) and arm B (T 400 mg twice a day ؋ 14 days, E 200 mg days 1-3 and 8-10) yielded similar CR, but arm B had greater toxicity. Total CR was 25%, day 30 death rate 7%. A 2-gene signature of high RASGRP1 and low aprataxin (APTX) expression previously predicted for T response. Assays using blasts from a subset of 40 patients treated with T plus E on this study showed that AMLs with a RASGRP1/APTX ratio of more than 5.2 had a 78% CR rate and negative predictive value 87%. This ratio did not correlate with outcome in 41 patients treated with conventional chemotherapies. The next T-based clinical trials will test the ability of the 2-gene signature to enrich for T responders prospectively.

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T is a Farnesyltransferase inhibitor with clinical activity in elderly adults with newly diagnosed AML who are not candidates for TCC. For adults ≥ age 65 with poor-risk AML, T 600 mg BID for 21 out of every 28–63 days induces complete remissions (CR) in 15%, median duration 7.3 mos, median survival 18 mos. In vitro, T+E exhibits synergistic anti-AML effects. In an attempt to increase CR rates in elderly AML pts, we are conducting a Phase I trial of oral T+E, with escalating doses of both drugs and 14 vs. 21 days of T every 28–63 days (median time to beginning cycle 2 is Day 31, range 29–43). To date, 60 adults ≥ age 70 (median 77, range 71–91) have been treated at 10 dose levels of T (300, 400 or 600 mg BID, 14 or 21 days) + E (100, 150 or 200 mg daily days 1–3 and 8–10) and have received 145 cycles (median 3, range 1–7). A total of 35 (58%) have had secondary AML and 31 (52%) have had adverse cytogenetics. Marrow blast percent was median 55% (range 20–96%), with 75% >30,000 blasts. Nonhematologic toxicities include oropharyngeal mucositis (15% ≥ grade 2), CNS (overall 30%, with 80% of those ≤ grade 2), renal (6%), hyperbilirubinemia (6%), rash (20%) and fatigue (20%). Toxicities occurred across all T+E dose levels tested to date. Documented infections occurred in 16 (27%) pts during cycle 1 and 22/145 (14%) cycles. Twenty six pts (43%) required hospitalization during cycle 1 for median 7 days (range 2–28). Overall hospitalization rate for all cycles was 28% (41/145). Ten pts (17%) died on study: 6 during cycle 1 (4 infection, 1 emphysema, 1 cerebrovascular) and 4 during cycles 2–4 (3 acute myocardial infarctions, 1 ventricular arrhythmia). For 56 evaluable pts, 12 (21%) have achieved CR and 11(20%) have achieved partial remission/hematologic improvement (PR/HI). All pts achieving CR have done so within 2 cycles (9/12 after cycle 1). Eight of 30 pts (27%) receiving T ≥ 400 mg BID have achieved CR. Median age of CR pts is 79 (range 71–86), 8 (67%) have secondary AML, and 5 (42%) have complex cytogenetics. CR durations to date range from 2+ to 13.5+ mos, with median 7+ months. Three of 12 have relapsed at 3, 10, and 11 mos, 2 have been retreated with T+E, and both have achieved 2nd CRs. In sum, the oral regimen of T+E is tolerable and feasible on an outpatient basis for elderly adults with newly diagnosed AML who are not candidates for TCC, with the suggestion of improvement of CR rates over T alone.

T is a farnesyltransferase inhibitor with clinical activity in elderly adults with newly diagnosed AML who are not candidates for TCC. For adults age ≥ 65 with poor-risk AML, T 600 mg BID for 21 out of 28–63 days induced complete remissions (CR) in 14%, median duration 7.3 mos, median survival 18.3 mos (Lancet JE, et al, Blood109:1387–1394,2007). In vitro, T+E exhibits synergistic anti-AML activity. In an attempt to increase CR rates in elderly AML pts, we conducted a Phase I trial of oral T+E, with escalation of both drugs and 14 vs. 21 days of T every 28–63 days (median 31 days, range 29–50). T+E resulted in a 25% CR rate (21/84 pts), duration 2 – 26+ mos, with best rates achieved with T dose ≥ 400 mg BID for 14 days (Karp JE, et al, Blood108:130a,2006). In the context of this trial, we have conducted longitudinal laboratory studies of changes in DNA damage and apoptosis in AML marrow blasts obtained from 84 patients prior to T+E (Day 0) and on Day 8 of T+E. Blasts were enriched by Ficoll density gradient separation and fixed in 70% ethanol. Persistent, unrepaired DNA damage was quantified by flow cytometry of cells stained with antibody to phosphorylated histone H2AX (γH2AX). Apoptosis was measured by flow cytometry of propidium iodide-stained cells with sub2n DNA content as observed in cell cycle distribution. To date, we have analyzed changes in in vivo γH2AX from 10 pts (4 CR, 6 stable disease or no response, SD/NR). CR pts had a 2-fold increase (range 1.91–2.22) in DNA damage induced by Day 8 of T+E relative to Day 0 values, while patients with SD/NR had no such increase (0–1.06) in DNA damage. Similarly, the apoptotic fraction of the cell cycle distributions of CR patients increase by 2-fold (range 1.2–5.3) for Day 8 marrow blasts. In contrast, changes in apoptosis were widely divergent for SD/NR patients (range 0.2–7.0). Taken together, these preliminary studies on AML marrow blasts obtained prior to and during T+E therapy suggest a possible linkage among induction of DNA damage, apoptotic response, and clinical outcome. Full analysis of all acquired specimens is ongoing.