Abstract 4660: A randomized phase II study of the telomerase inhibitor imetelstat as maintenance therapy for advanced non-small cell lung cancer.
Authors: Chiappori Alberto , Kolevska Tatjana , Burington Bart , Spigel David , Hager Steven , Rarick Mark , Gadgeel Shirish , Blais Normand , Von Pawel Joachim , Hart Lowell , Reck Martin , Schiller Joan 
Published: August 2014

Tumor regrowth after chemotherapy may be driven by growth of tumor ‘stem cells’. Telomerase, required for indefinite replication, is upregulated in tumor progenitor cells. Imetelstat is a 13-mer oligonucleotide which is a potent and specific telomerase inhibitor. Progression-free survival (PFS) and the duration of responses after 1st-line chemotherapy for non-small-cell lung cancer (NSCLC) are short, which has led to an interest in developing active maintenance therapies.

A randomized phase II study was conducted to assess whether imetelstat, given as maintenance therapy, prolongs PFS in NSCLC. Pts were eligible with advanced NSCLC not progressing after completing 4-6 cycles of platinum-based doublet induction chemotherapy, any NSCLC histology, performance status (PS) ECOG 0 or 1, and not scheduled to receive maintenance with pemetrexed or erlotinib. Pts were randomized 2:1 to imetelstat 9.4 mg/kg (d1 and 8 of a 21d cycle) or observation until progressive disease or unacceptable toxicity (concomitant use of bevacizumab was permitted). The 1o endpoint was PFS; safety/tolerability and objective response rate were 2o endpoints.

116 pts were enrolled between Jul 2010 to Apr 2012, with 114 completing a first visit (i.e. efficacy population). Baseline characteristics of age, gender, PS and number of induction cycles were well balanced. 18.4% had squamous histology; 31.6% received concomitant bevacizumab (bev).

The median number of imetelstat maintenance cycles was 3. In the overall analysis of PFS, a non significant improvement in favor of the imetelstat arm was observed (HR = 0.77, P=0.295, 95% CI 0.48 - 1.25). Median PFS was 2.8m for imetelstat and 2.6m for control. In the subgroup of patients who did not receive bevacizumab, the HR was 0.59 (vs. 1.07 for the bevacizumab subgroup; interaction P=0.15). The objective response rate was 4.3% in the imetelstat arm and 2.8% in the control arm. Six month overall survival was 80% for imetelstat and 72% for control (HR = 0.86, P=0.642, 95% CI 0.44 - 1.66).

Imetelstat was generally well tolerated although hematologic toxicity, predominantly neutropenia and thrombocytopenia, was increased in the imetelstat arm (grade 3/4 neutropenia 18% for imetelstat vs 0% for control, grade 3/4 thrombocytopenia 37% for imetelstat vs 0% for control). The most frequent non-hematologic toxicities were fatigue (imetelstat 42.1% vs control 18.4%), nausea (43.4% vs 7.9%), vomiting (25.0% vs 5.3%) and anaemia (19.7% vs 5.3%).

The overall findings suggest that imetelstat has modest, but not clinically meaningful, activity as a maintenance therapy in pts with NSCLC. A pre-specified exploratory subgroup analysis of PFS by tumor telomere length is reported separately.

Citation Format: Alberto Chiappori, Tatjana Kolevska, Bart Burington, David Spigel, Steven Hager, Mark Rarick, Shirish Gadgeel, Normand Blais, Joachim Von Pawel, Lowell Hart, Martin Reck, Joan Schiller. A randomized phase II study of the telomerase inhibitor imetelstat as maintenance therapy for advanced non-small cell lung cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4660. doi:10.1158/1538-7445.AM2013-4660