A phase II study of RC48-ADC in HER2-positive patients with locally advanced or metastatic urothelial carcinoma.

Abstract

4509 Background: Urothelial carcinoma (UC) is the third largest cancer type with HER2 positive cancer. RC48-ADC is a novel humanized anti-HER2 antibody-drug conjugate (ADC). This study was to evaluate the activity of RC48-ADC in HER2-positive patients with locally advanced or metastatic urothelial carcinoma (mUC). Methods: This study is an open-label, multicenter, single-arm, non-randomized phase II study. Eligibility criteria include: histologically confirmed UC, HER2-positive (IHC 2+ or 3+), ECOG PS 0-1, treated with ≥1 prior systemic treatment. The patients received RC48-ADC treatment alone (2 mg/kg IV infusion, q2w) until disease progression, unacceptable toxicity, withdrawal, or study termination. The primary endpoint was objective response rate (ORR). Progress-free survival (PFS), overall survival (OS), and safety was also assessed. Results: Patient enrollment for this study was completed in November 2018. A total of 43 patients were enrolled, with a median age of 64 years old. At baseline, most patients (37/43) had visceral metastasis. Fourteen (32.6%) patients had received ≥ 2 lines treatment and 8 (18.6%) patients had prior immune checkpoint inhibitor (CPI) therapy in second line treatment. The objective response rate was 60.5% (95% CI: 44.4%, 75.0%) and the DCR was 90.7% (39/43). As of Jan 23, 2019, the median PFS for the overall study population was not yet reached, and the median PFS was 7.8 months (95% CI: 4.9, 10.7) for the 9 patients who started RC48-ADC prior to Jun 30, 2018. The ORR was 70.6% (12/17) in patients with HER2 FISH+ or IHC3+. The ORR was 64.9% (24/37) in patients with visceral metastasis and was 70.0% (14/20) in liver metastasis patients especially. The ORR was 64.3% in patients post to ≥ 2 lines treatment and 75.0% in patients post to immunotherapy. Common treatment-related AEs were leukopenia (51.2%), hypoesthesia (41.9%), alopecia (41.9%), neutropenia (37.2%), fatigue (34.9%), ALT increase (32.6%), and AST increase (32.6%); Most were Grade 1 or 2. Conclusions: RC48-ADC has demonstrated a clinically meaningful ORR of 60.5% in pretreated HER-2 positive mUC patients including those who underwent failure to the immunotherapy. Clinical trial information: NCT03507166.