A Study of SYS6010, Enlonstobart, and Chemotherapy for First-Line Treatment of Esophageal Squamous Cell Carcinoma.

Phase II study comprises a safety lead-in stage, a dose expansion stage, and a randomized treatment stage. The Phsae III study is randomized controlled trial.

Phase II (safety lead-in stage): the safety lead-in stage employs a 3+3 design. It aims to evaluate the safety and tolerability of combination therapy-comprising capecitabine/5-FU administered at a descending dose level starting from DL0 alongside fixed doses of SYS6010 and SG001-in previously untreated patients with unresectable locally advanced or metastatic ESCC. The primary objectives are to determine the Maximum Tolerated Dose (MTD) and the Recommended Phase II Dose (RP2D).

Phase II (dose expansion stage): Upon completion of the safety evaluation and confirmation of tolerability for a dose cohort in the safety lead-in phase, expansion of that cohort may be initiated, with plans to expand 1-2 dose cohorts.

Phase II (randomized treatment stage): Upon determination of the RP2D based on prior data, a randomized controlled study will be conducted in a first-line advanced/metastatic esophageal squamous cell carcinoma (ESCC) patient population. Patients will be randomly assigned to three arms: Arm 1: SYS6010+SG001+ capecitabine/5-FU; arm2: investigator's choice of SOC; arm3: SYS6010+SG001.

Phase III is a randomized, controlled, open-label, multicenter study designed to evaluate the efficacy of SYS6010+SG001+capecitabine/5-FU versus investigator's choice of treatment as first-line therapy for advanced/metastatic esophageal squamous cell carcinoma. The Phase III trial design will be finalized based on Phase II results. The preliminary plan is to randomized patients in a 1:1 ratio to either the investigational arm or the control arm. Investigational arm: SYS6010+SG001+capecitabine/5-FU; control arm: investigator's choice of SOC.