Efficacy and safety of SHR-1701 combined with chemoradiotherapy as neoadjuvant treatment for locally advanced rectal cancer.

Locally advanced rectal cancer (LARC) remains challenging to treat due to high recurrence rates and limited therapeutic options, particularly for patients with high-risk features. This prospective, multicenter, single-arm, open-label phase 2 trial (ClinicalTrials.gov identifier: NCT05300269) evaluated the efficacy and safety of SHR-1701, a novel bifunctional fusion protein targeting both PD-L1 and TGF-β, in combination with neoadjuvant chemoradiotherapy (CRT) followed by total mesorectal excision (TME) for high-risk LARC. Eligible patients had at least one high-risk factor, including cT3c-d or cT4 tumors, positive mesorectal fascia, extramural vascular invasion, or involvement of ≥4 lymph nodes. Patients received concurrent SHR-1701 and CRT, followed by two cycles of SHR-1701 plus XELOX and subsequent TME surgery. Postoperatively, patients underwent six additional cycles of SHR-1701 plus XELOX. The primary endpoints were pathological complete response (pCR) rate and safety. Among the 37 enrolled patients, 36 (97.3 %) completed the planned full-dose radiotherapy (50.4 Gy in 28 fractions) and subsequently underwent surgery. The pCR rate was 36.1 % (13/36). The median intervals from neoadjuvant therapy initiation to surgery and from surgery to adjuvant therapy were 112 days (range, 95-139) and 29 days (range, 22-59), respectively. The median follow-up was 9.9 months (range, 2-18) from the first dose of capecitabine. Grade ≥3 treatment-related adverse events during neoadjuvant therapy occurred in 40.5 % (15/37) of patients, most commonly lymphopenia (37.8 %, 14/37) and anemia (5.4 %, 2/37). One patient experienced fatal immune-mediated myocarditis prior to surgery. Overall, the addition of SHR-1701 to CRT demonstrated encouraging efficacy and manageable safety in high-risk LARC, supporting further investigation in larger randomized trials.