Bifunctional anti-PD-L1/TGF-βRII agent SHR-1701 plus chemotherapy as first-line treatment for advanced esophageal squamous cell carcinoma (ESCC): Survival results of a phase II trial.

411 Background: Recently, several clinical trials have demonstrated synergistic efficacy by combining immune checkpoint inhibitors (ICIs) with chemotherapy. However, only a subset of patients (pts) derived benefits. Combining ICIs with agents blocking immunosuppressive pathway may expand the clinical benefit of ICIs to more pts. Transforming growth factor β (TGF-β) participates in tumor immune escape. SHR-1701, a novel bifunctional fusion protein consisting of a monoclonal antibody targeting PD-L1 fused with the extracellular domain of TGF-β receptor II, was evaluated in a phase II trial (ChiCTR2000039909) to assess its efficacy and safety when combined with chemotherapy for pts with unresectable locally advanced, recurrent or metastatic ESCC in China. Methods: This trial enrolled treatment-naive pts with histologically or cytologically confirmed unresectable locally advanced, recurrent, or metastatic ESCC. Eligible pts received SHR-1701 (30mg/kg, iv, d1, q3w) in combination with up to six cycles of albumin-bound paclitaxel (125mg/m 2 , iv, d1, d8, q3w) and cisplatin (75mg/m 2 , iv, d1, q3w). For those without progressive disease, maintenance treatment was administered with SHR-1701 monotherapy until disease progression or unacceptable toxicity. The primary endpoint was objective response rate (ORR). Secondary endpoints included progression-free survival (PFS), overall survival (OS), disease control rate (DCR) and safety. Results: At the data cut-off, March 1, 2024, 24 pts had received at least one dose of the study treatment and were included in both the intention-to-treat (ITT) analysis and safety analysis sets. 3 and 12 pts achieved confirmed complete and partial responses, respectively. The confirmed ORR was 62.5% and DCR was 87.5%. With a median follow-up of 20.8 months (95% CI, 15.5-NR), the median duration of response was 9.1 months (95% CI, 6.9-NR). The median PFS was 10.8 months (95% CI, 7.8-NR) and the median OS was 26.1 months (95% CI, 8.6-NR). 12-month PFS and OS rates were 41.4% (95% CI, 22.5-76) and 64.8% (95% CI, 47.8-87.9), respectively. Grade 3-4 treatment-related adverse events occurred in 11 (45.8%) pts and no treatment-related death was observed. Conclusions: The results highlighted that SHR-1701 plus chemotherapy as first-line therapy maintained long-term, durable survival benefit in pts with advanced ESCC. Clinical trial information: ChiCTR2000039909.