Preclinical investigations and a first-in-human phase 1a trial of JS007, a novel anti-CTLA-4 antibody, in patients with advanced solid tumors

Blocking cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) shows substantial antitumor efficacy. Here, we report the preclinical data and outcomes of a first-in-human phase 1a trial of JS007, a novel anti-CTLA-4 antibody, in advanced solid tumors.

JS007 preliminarily demonstrates good tolerance and encouraging antitumor activity in patients with previously treated advanced solid tumors.

In preclinical studies, both in vitro characteristics and in vivo characteristics of JS007 were investigated. The clinical trial included a dose escalation phase and a dose expansion phase. Eligible patients with previously treated advanced solid tumors were enrolled. In the dose escalation phase, JS007 was administered intravenously every 3 weeks at doses of 0.03, 0.3, 1, 3, and 10 mg/kg. Then, 3 and 10 mg/kg were chosen for the dose expansion phase. The primary endpoints included the maximum tolerated dose (MTD) of JS007 based on dose-limiting toxicities (DLTs) and safety.

JS007 could effectively bind to CTLA-4 and induce an immune response in vitro. Potent in vivo antitumor activity of JS007 was observed. Increased T cell infiltration and T regulatory (Treg) cell depletion in tumor microenvironment of cancer cell xenografts were detected after treated with JS007. Pharmacological analysis in experimental animals showed a dose-proportional increase in exposure. In the clinical trial, a total of 28 patients were treated with JS007 across 5 dose levels. No DLTs occurred. The MTD did not reach at the highest dose tested (10 mg/kg). Twenty-three (82.1%) patients experienced at least one treatment-related adverse event (TRAE). The incidence of Grade ≥ 3 TRAEs was 28.6% (8/28) with alanine aminotransferase increase (7.1%, 2/28) being the most frequently reported TRAE. No severe immune-related adverse event (irAE) occurred. Pharmacological profiles of JS007 in patients were similar to those in animal models. Serum concentration of JS007 showed a dose-dependent escalation, and the half-life of JS007 was 9.4 ~ 12.2 days. Treatment-induced anti-drug antibody was detected in 2 patients. The disease control rate was 50% (14/28), and the median overall survival was 14.7 months. Conclusions: JS007 preliminarily demonstrates good tolerance and encouraging antitumor activity in patients with previously treated advanced solid tumors.

ClinicalTrials.gov identifier: NCT05049265 (Sep 20, 2021).