Ritchie, Ellen K.

7061 Background: Glasdegib is a small molecule inhibitor of the Sonic Hedgehog pathway, and data from the single arm, lead-in cohort of a phase 1b/2 trial in myelofibrosis (MF) are shown. Methods: Patients (age ≥18 yrs) with primary/secondary MF previously-treated with ≥1 Janus Kinase inhibitor (JAKi) were enrolled and received glasdegib 100 mg QD orally in 28 day cycles. AEs and laboratory abnormalities were assessed. Key efficacy endpoints were proportion of patients with spleen volume reduction (SVR) ≥35% and ≥50% reduction in total symptom score (TSS) measured by the MPN Symptom Assessment Diary (MPN-SAD) at Week 24. Results: 21 patients were enrolled between Oct '14-Oct '15 in this ongoing study. Mean age was 69.3 yrs (range 58-83). Median duration of treatment was 85 days (22-343). 52% were refractory patients with inadequate response to prior JAKi. Baseline symptoms were mostly mild (1-4), except fatigue (>4). No patients achieved SVR ≥35%, 5 patients had some SVR (maximum 2.3-21.4% reduction from baseline), and no progressive disease prior to Day 71. At week 24, 1 patient had ≥50% reduction in TSS, but 3/21 and 4/21, respectively showed 30% and 20% TSS reduction. Of 14 patients with severe baseline symptoms (1 with ≥5, or ≥2 with ≥3), 1, 1, and 2 achieved 50%, 30%, and 20% TSS reduction, respectively at week 24. TSS, spleen-related, and constitutional symptom scores showed a trend of reduction over 24 weeks with spleen-related symptoms, inactivity, and fatigue showing greatest improvement (52%, 58%, and 36%, respectively). Dysgeusia (N=13), muscle spasms (N=12), alopecia (N=8), decreased appetite (N=7), fatigue (N=7), lipase increase (N=5), and weight decrease (N=5) occurred in ≥20% patients. None, except 1 episode of fatigue, were considered serious AEs. Glasdegib steady state PK was consistent with previous single agent data. Conclusions: Glasdegib has an acceptable toxicity profile in patients with primary/secondary MF previously treated with JAKi. Symptom responder definition for refractory patients may not be the same as for JAKi naïve patients. Patient reported symptom improvement may be a more sensitive indicator of treatment benefit vs SVR. Further study of glasdegib may be warranted. Clinical Trial Information: NCT02226172.

7003 Background: Gilteritinib, a highly selective FLT3/AXL inhibitor, has displayed antileukemic activity in FLT3 mutation-positive (FLT3mut+) relapsed/refractory (R/R) AML in the CHRYSALIS Phase I/II study (NCT02014558), specifically at doses ≥80 mg/d. This exploratory analysis assessed molecular response to gilteritinib in a CHRYSALIS subpopulation. Methods: Molecular response was assessed from bone marrow aspirates obtained at baseline and at ≥1 additional time point from FLT3mut+ patients (≥18 y) treated with 120 or 200 mg/d gilteritinib. These doses were identified due to their ability to induce consistent, potent FLT3 inhibition and high clinical response rates. FLT3-ITD and total FLT3 were quantified by NGS to assess molecular response. A Cox regression model of overall survival (OS) by Kaplan-Meier estimation established a FLT3-ITD:total FLT3 ratio (ITD signal ratio) of 10−2as the threshold for improved survival. Results: Of 147 FLT3-ITDmut+ patients who received gilteritinib 120 or 200 mg/d, 80 were included in this analysis. Composite response rate for these 80 patients was 55%. During response, 20 patients (25%) had an ITD signal ratio of ≤10−2. Of these 20 patients, 18 had a ratio of ≤10−3 (major molecular response [MMR]) and 13 had a ratio of ≤10−4 (minimal residual disease [MRD] negative). Median time to achieve minimum signal ratio was 54 days. Elimination of morphologic leukemia was observed in 80% of patients with ITD signal ratios <10−2. Patients who had a signal ratio ≤10−2, MMR, or were MRD negative had significantly longer median OS than those who did not (Table). Conclusions: Molecular responses to gilteritinib in FLT3-ITDmut+ R/R AML correlated with clinical response and improved OS. This is the first demonstration of molecular response to a FLT3 inhibitor in AML. These data suggest ITD signal ratio may predict durable clinical benefit of gilteritinib. Clinical trial information: NCT02014558. [Table: see text]

Key Points In the largest study of HMAs in RR-AML to date, 16% of patients achieved CR/CRi and experienced a median OS of 21 months. Low proliferative disease (peripheral blood blasts <5%) was associated with improved response and OS.

SummaryMyelofibrosis (MF) is a Philadelphia chromosome–negative stem cell myeloproliferative neoplasm (MPN) associated with cytopenias, splenomegaly, constitutional symptoms, and poor prognosis. MF patients commonly express JAK2 V617F mutation and activation of Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signalling. Agents targeting the JAK/STAT pathway have demonstrated efficacy in patients with MF. This study evaluated panobinostat, a pan‐deacetylase inhibitor that depletes JAK2 V617F levels and JAK/STAT signalling in MPN cells, in patients with primary MF, post–essential thrombocythaemia MF, and post–polycythaemia vera MF. Patients received panobinostat 40 mg administered three times per week. Dose reductions were permitted for toxicities. The primary endpoint was response rate at 6 months using International Working Group for Myelofibrosis Research and Treatment (IWG‐MRT) consensus criteria. Analyses of peripheral blood cells from treated patients revealed that panobinostat inhibited JAK/STAT signalling, decreased inflammatory cytokine levels, and decreased JAK2 V617F allelic burden. However, panobinostat was poorly tolerated at the dose and schedule evaluated, and only 16 of 35 patients completed ≥2 cycles of treatment. One patient (3%) achieved an IWG‐MRT response. Common adverse events were thrombocytopenia (71·4%) and diarrhoea (80·0%). Although molecular correlative analyses suggested that panobinostat inhibits key intracellular targets, limited clinical activity was observed because of poor tolerance.

Abstract 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. This study is registered at www.clinicaltrials.gov as #NCT00602771.

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.