1779TiP Phase II clinical study evaluating the efficacy and safety of disitamab vedotin in patients (pts) with HER2-expressing urothelial carcinoma (RC48G001)

Abstract

More than 212,000 deaths annually are related to bladder cancer worldwide (Sung 2021), with 5-year survival rates of <5% in metastatic urothelial carcinoma (UC) (Witjes 2021). Nearly half of all pts cannot tolerate standard cisplatin-based first line (1L) chemotherapy and opportunity still exists to improve outcomes in both 1L and later lines of therapy. Human epidermal growth factor receptor 2 (HER2) is overexpressed in multiple malignant tumors and overexpression of HER2 may be associated with poor outcomes in UC (Zhao 2015). No HER2-directed therapies are currently approved for locally advanced unresectable or metastatic UC (LA/mUC). Disitamab vedotin (DV; RC48-ADC) is an investigational antibody–drug conjugate (ADC) comprised of a HER2-directed monoclonal antibody conjugated to monomethyl auristatin E (MMAE) via a protease-cleavable linker. DV elicits antitumor activity through MMAE-directed cytotoxicity and bystander effect (Li 2020). DV is conditionally approved in LA/mUC and gastric cancer in China and was granted Breakthrough Therapy designation by the FDA for second-line treatment of HER2-expressing LA/mUC after platinum-containing chemotherapy. RC48G001 (NCT04879329) is a phase 2, multicohort, open-label, multicenter trial to evaluate DV in pts with HER2-expressing LA/mUC. Pts are enrolled in 2 cohorts defined by HER2 expression (by immunohistochemistry [IHC]) and gene amplification (by in situ hybridization [ISH]) by central laboratory: Cohort A (IHC 3+, or 2+ and ISH+) and Cohort B (IHC 2+ and ISH-, or IHC 1+). Eligible pts must have measurable disease per RECIST v1.1, ECOG Performance Status of 0 or 1, and must have received 1 or 2 lines of prior systemic therapy, including 1 line of platinum-containing chemotherapy. The primary endpoint is confirmed objective response rate (ORR) assessed by blinded independent central review. Secondary endpoints include ORR assessed by investigator, duration of response, progression-free survival, disease control rate, overall survival, safety, and pharmacokinetic parameters. Enrollment for cohorts A and B is ongoing in North America and EU, and planned in LATAM, APAC, and Israel. NCT04879329. Under guidance of the authors, assistance in medical writing was provided by Hanna Thomsen, PhD, of Seagen Inc. and was funded by Seagen Inc. in accordance with Good Publication Practice (GPP3) guidelines. Seagen Inc.