Disitamab vedotin, a novel humanized anti-HER2 antibody-drug conjugate (ADC), combined with toripalimab in patients with locally advanced or metastatic urothelial carcinoma: An open-label phase 1b/2 study.
Xinan Sheng, Li Zhou, Kaiwei Yang, Shun Zhang, Huayan Xu, Xieqiao Yan, Siming Li, Juan Li, Chuanliang Cui, Zhihong Chi, Lu Si, Bixia Tang, Lili Mao, Bin Lian, Xuan Wang, Xue Bai, Zhisong He, Hongqian Guo, Jun Guo
Abstract
4566 Background: Disitamab vedotin has shown promising data across a spectrum of HER2 expression in patients with locally advanced or metastatic urothelial carcinoma (la/mUC) who progressed on chemotherapy. This study was conducted to evaluate the safety and efficacy of disitamab vedotin plus anti-PD-1 antibody in advanced urothelial carcinoma. Methods: This is an open-label, multicenter, phase 1b/2 trial to evaluate the safety and activity of RC48-ADC combined with toripalimab, a humanized immunoglobin G 4 monoclonal antibody against PD-1 in mUC. Patients received RC48-ADC at 1.5 or 2 mg/kg, in combination with 3mg/kg toripalimab every two weeks in a dose-escalation and expansion cohort until confirmed disease progression assessed by the investigators, unacceptable toxicity, or voluntary withdrawal. The primary endpoint was safety; secondary endpoints included efficacy and tumor tissue biomarkers. Results: Forty-one la/mUC patients were enrolled (22 males; median age 66 y [42-76]; 61% treatment-naïve). 54% of patients had visceral metastases (mets), including 24% with liver mets. The primary site was in upper tract UC in 54%. HER2 expression IHC 2+ or 3+ was in 59% patients, and PD-L1 positive in 32%. No dose-limiting toxicity was observed and the recommended dose was RC48-ADC 2mg/kg plus toripalimab 3mg/kg every two weeks. By the cutoff date of 18 November 2022, the confirmed ORR was 73.2% (95%CI: 57.1, 85.8), including 9.8% CR. The ORR was 76.0% for treatment-naïve patients. In HER2 IHC 3+/2+, IHC 1+, and IHC 0 subgroups, the ORR was 83.3%, 64.3%, and 33.3%, respectively. The ORR was 61.5% and 78.6% in PD-L1 positive and negative subgroups. DCR was 90.2% (95% CI, 76.9–97.3), with a median progression-free survival (PFS) of 9.2 months (95%CI: 5.7-10.3) and 2-year overall survival (OS) rate of 63.2%. All patients experienced treatment-related adverse events (TRAEs). The most common TRAEs were AST/ALT increase (68.3%), peripheral sensory neuropathy (61.0%), asthenia (61.0%), γ-glutamyl transferase increase (56.1%), hypertriglyceridemia (53.7%), and appetite decrease (51.2%). Grade 3 or greater TRAEs occurred in 43.9% of patients. Twenty-three patients (56.1%) had immune-related AEs (14.6% ≥ G3), including immune-related skin reactions, hyperglycemia, pneumonitis, hepatitis, and myositis. Conclusions: RC48-ADC in combination with toripalimab demonstrated promising efficacy in patients with la/mUC and a manageable safety profile. A phase 3 study is currently ongoing to compare the safety and efficacy of this regimen with standard of care. Clinical trial information: NCT04264936 .