Camrelizumab plus low-dose apatinib and SOX in the first-line treatment of advanced gastric/gastroesophageal junction (G/GEJ) adenocarcinoma: A single-arm, dose escalation and expansion study (SPACE study).

365 Background: The dose escalation phase was presented early, and confirmed that the recommended phase II dose (RP2D) was camrelizumab (200 mg, d1) plus apatinib (250 mg, qd), S-1(40 mg, bid, d1-14) and oxaliplatin (130 mg/m 2 , d1) every 3 weeks followed by camrelizumab (200 mg, d1) plus apatinib (250 mg, qd) every 3 weeks. Methods: Patients (pts) aged 18-75 years, with unresectable or potentially resectable G/GEJ adenocarcinoma, HER2-negative or unknown HER2 status and no previous systemic therapy, were enrolled to receive combination therapy. Primary endpoint was Objective response rate (ORR) by RECIST 1.1, secondary endpoints included progression free survival (PFS), overall survival (OS), disease control rate (DCR), surgical resection rate and safety. Results: From Jun, 2020 to July 2022, 35 pts were enrolled (9 pts in dose escalation phase, 26 pts in dose expansion phase), with a median follow-up of 8.0 months (95% CL, 6.7-12.2). Median age (range) was 59(19-68), 94.3% (33/35) were male, 20% (7/35) were diagnosed with GEJ adenocarcinoma, 60% (21/35) had liver metastases. At data cutoff, 33 pts were included in the efficacy analysis. The ORR was 90.9%, with 30 (90.9%) PR. SD were 1 (3.0%) with a DCR of 93.9%. In addition, 9 pts showed an unconfirmed PR with a confirmed ORR of 80.8%. Median PFS was 10.2 months (95% CI, 5.5-22.3), with the median OS not reached yet. Conversion to resectable G/GEJ adenocarcinoma was identified in 9 (25.7%) pts. Of them, 2 pts were observed complete pathology response. 94.3% pts experienced treatment related adverse event (TRAE), with 45.7% being grade ≥3. The most frequent grade ≥3 TRAE were GGT increased (31.4%, 11/35), rash (11.4%, 4/35), alkaline phosphatase increased (11.4%, 4/35)、neutrophil count decreased (8.6%, 3/35). No new safety signal was identified. Conclusions: Camrelizumab plus apatinib and SOX followed by camrelizumab plus apatinib demonstrated encouraging antitumor activity and manageable toxicity as first line therapy for patients with G/GEJ adenocarcinoma. Clinical trial information: ChiCTR2000034109 .