Efficacy and safety of enlonstobart (SG001), a PD-1 inhibitor in patients with PD-L1 positive recurrent/metastatic cervical cancer: A multicenter, single-arm, open-label, phase II study.

5526 Background: Platinum-based chemotherapy with or without bevacizumab is the first-line treatment for patients with recurrent or metastatic cervical cancer, and the treatment options are limited for recurrent or metastatic cervical cancer after first-line treatment. Enlonstobart (SG001) is a fully humanized and high-affinity anti-PD-1 immunoglobulin G4 monoclonal antibody. Previous phase 1b study demonstrated that SG001 had a promising efficacy in patients with PD-L1 positive recurrent/metastatic cervical cancer. Here we present the safety and efficacy results of phase II study (ClinicalTrials. gov identifier: NCT04886700) for SG001. Methods: In this multicenter, single-arm, open-label, phase II study, eligible patients were ≥18 years old with PD-L1-positive (combined positive score ≥ 1) cervical cancer who had progression during or after or intolerance to the first-line platinum-based therapy. Patients received SG001 240 mg every two weeks for up to 24 months or until disease progression, intolerable toxicities, or other study discontinuation criteria were met. The primary endpoints were objective response rate assessed using the Response Evaluation Criteria in Solid Tumors version 1.1 by independent central radiological review. Results: As of May 27, 2023,a total of 107 patients were enrolled, with a median age of 53 years (range 26-72). 64.5% of patients had an ECOG performance status of 1. 39 patients (36.5%) received ≥ 2 prior line of systemic therapy, 34 patients (31.8%) received previous treatment with bevacizumab. After a median follow-up of 13.96 months (range 0.4-21.9), confirmed objective response rate and disease control rate were 29.0% (95% CI 20.6-38.5) and 54.2% (95% CI 44.3-63.9), with two complete responses and twenty-nine partial responses. Median duration of response was 16.6 months (95% CI 10.8-NA), median progression free survival was 3.1 months (95% CI 2.2-6.9). Median overall survival was not reached. 104 patients (97.2%) experienced at least one treatment emergent adverse events, of which 38 patients (35.5%) had grade 3 or higher events. The immune-related adverse events (irAEs) were observed in 44 patients (41.1%). The most common (incidence ≥ 2%) irAEs were hypothyroidism (15.0%), hyperthyroidism (11.2%), elevated thyroid-stimulating hormone level (4.7%), hyperglycemia (4.7%), increased alanine aminotransferase (2.8%), pruritus (2.8%), and rash (2.8%). No treatment-related death occurred. Conclusions: SG001 monotherapy demonstrated durable anti-tumor activity and acceptable safety in patients with PD-L1 positive recurrent/metastatic cervical cancer, whose disease experienced progression after first-line platinum-based therapy. Clinical trial information: NCT04886700 .