Pertuzumab + trastuzumab for HER2-positive metastatic biliary cancer: Preliminary data from MyPathway.

Abstract

402 Background: Biliary cancers have a high mortality rate, with limited treatment options. While HER2 is overexpressed in 9-20% of biliary cancers, it has not been fully explored as a therapeutic target. MyPathway is a multi-basket study evaluating the efficacy and safety of targeted therapies in non-indicated tumor types harboring relevant genetic alterations. We present preliminary data for patients with HER2-positive metastatic biliary cancer receiving HER2-targeted treatment with pertuzumab + trastuzumab. Methods: MyPathway (NCT02091141) is an open-label, multicenter, phase IIA study. Patients in this subset analysis had refractory metastatic biliary cancer with HER2 amplification/overexpression or putative activating mutations by gene sequencing, FISH, or IHC. Patients received standard doses of pertuzumab + trastuzumab until disease progression or unacceptable toxicity. The primary endpoint is investigator-assessed overall response rate (RECIST v1.1). Results: As of July 31, 2016, 11 patients with HER2-positive biliary cancer (HER2-amplified/overexpressed, n = 8; HER2-mutated, n = 3 [D277Y, S310F, and A775-G776insYVMA]) have been enrolled. At a median follow-up of 4.2 (range 2.0–12.0) months, 4 patients had partial responses (PR) and 3 had stable disease (SD) for > 4 months (Table). Safety was consistent with the package inserts. Conclusions: Preliminary results indicate that pertuzumab + trastuzumab has activity in HER2 amplified/overexpressed/mutated metastatic biliary tumors, suggesting HER2 as a therapeutic target for these rare cancers. Accrual to MyPathway is ongoing. Clinical trial information: NCT02091141. [Table: see text]