Oncothyreon Presents Final Results From First Phase 1 Trial Of ONT-380

(RTTNews) - Oncothyreon Inc. (ONTY) announced the presentation of final results from the first Phase 1 trial of ONT-380 at the American Association for Cancer Research Special Conference on Advances in Breast Cancer Research in San Diego.

ONT-380 (also known as ARRY-380) is an orally active, reversible and selective small-molecule HER2 inhibitor being developed by Oncothyreon in collaboration with Array BioPharma Inc. (ARRY), Boulder, Colorado.

According to the company, the first-in-human Phase 1 trial, with both dose-escalation and expansion components, enrolled a total of 50 patients, 43 of whom had HER2+ metastatic breast cancer. In this study, ONT-380 demonstrated an acceptable safety profile; treatment-related adverse events were primarily Grade 1. Because ONT-380 is selective for HER2 and does not inhibit EGFR, there was a low incidence and severity of treatment-related diarrhea, rash and fatigue, side effects which have been associated with EGFR inhibition.

The company noted that a single patient experienced Grade 2 treatment-related diarrhea and no patient developed treatment-related Grade 3 diarrhea; one patient had a Grade 3 rash. Additionally, there were no treatment-related cardiac events or Grade 4 treatment-related adverse events reported. The maximum tolerated dose of ONT-380 established in this Phase 1 trial was 600 mg twice daily. The dose-limiting toxicity was reversible elevation in liver enzymes.

In this trial, 22 HER2+ breast cancer patients with measurable disease were treated with ONT-380 at doses greater than or equal to 600 mg BID. In this heavily pretreated patient population, there was a clinical benefit rate (partial response [n = 3] plus stable disease for at least 6 months [n = 3]) of 27%. Notably, two of the patients with partial responses during treatment with ONT-380 had confirmed progressions while on prior lapatinib- and trastuzumab-containing regimens, the company said.