Background: Preclinical studies have shown the combination of imetelstat (GRN163L), an inhibitor of telomerase, and T results in synergistic growth inhibition and restoration of T sensitivity in T-resistant cells (Clin Can Res 12(10):3184–92, 2006). Here we translate those findings to the clinic with the first-in-man phase I trial of imetelstat+ T in patients (pts) with T-refractory HER2+ metastatic disease.

Methods: T (6 mg/kg q3 wk) was administered with increasing doses of imetelstat (240/300/375 mg/m2 q3 wk) using a standard 3+3 dose escalation design. Maximum Tolerated Dose (MTD) was based on toxicity observed during cycle 1. Responding or stable pts continued treatment until progression. Tumor biopsy and bone marrow aspirate for biologic correlates were obtained at baseline and prior to cycle 2. Limited pharmacokinetics (PK) for T and imetelstat were included.

Results: Ten pts were enrolled; median age was 54 (28–64). Patients were extensively pre-treated with the number of prior regimens ranging from 3 to >12. Prior cytotoxic therapies included anthracyclines (n = 9), taxanes (n = 9), vinorelbine (n = 8), capecitabine (n = 8), gemcitabine (n = 6), ixabepilone (n = 4), and eribulin (n = 4). Prior anti-HER2 targeted therapies included trastuzumab (n = 10), capecitabine (n = 8), T-DM1 (n = 6), and pertuzumab (n = 1). Therapy was well tolerated; no treatment related grade 4 toxicities were observed. Myelosuppression was limited to one pt with Grade 2 anemia and one each with Grade 2/3 thrombocytopenia. MTD was not reached. There were no objective responses; 2 pts. in cohort 3 had SD. Serial tumor biopsies and bone marrow aspirates have been analyzed for 7 pts (cohort 1: 001–004; cohort 2: 005–007; cohort 3: analysis ongoing). Tumor hTERT (p = ns) and phosphorylated HER2 (p = 0.03) decreased after treatment in nearly all pts. Bone marrow S-phase did not change consistently with treatment.

Conclusion: The combination of trastuzumab + imetelstat is well tolerated and results in decreases in HER2 phosphorylation similar to that seen in preclinical models. Additional biologic correlates and PK analyses are ongoing. Further study of this combination in less heavily pre-treated patients is planned.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-18-13.