Case Report: rapid clinical complete response to Iparomlimab and Tuvonralimab combined with radiotherapy and chemotherapy in a patient with MSS/pMMR locally advanced rectal cancer

Objective To investigate the efficacy and safety of Iparomlimab and Tuvonralimab, a PD-1/CTLA-4 bispecific antibody, in combination with chemoradiotherapy for a patient with microsatellite stable/mismatch repair proficient (MSS/pMMR) locally advanced rectal cancer (LARC), and to analyze the mechanism of achieving short-term clinical complete response (cCR). Methods This case report presents a 61-year-old male with stage cT3N2aM0 IIIB MSS/pMMR rectal cancer. The patient received neoadjuvant therapy with Iparomlimab and Tuvonralimab (300mg per dose) plus XELOX regimen chemotherapy and radiotherapy (45Gy/25F). Responses were regularly assessed via digital rectal examination, imaging, endoscopy, and pathology. Results After treatment, clinical complete response (cCR) was initially evidenced by MRI at week 12 and subsequently confirmed by endoscopic assessment combined with pathologic biopsy at week 20. No grade 3 or higher immune-related adverse events occurred. At the last follow-up in March 2026, no recurrence was observed. Conclusion This case suggests that Iparomlimab and Tuvonralimab combined with chemoradiotherapy may induce rapid cCR in MSS/pMMR LARC, offering a promising organ-preserving strategy through immunotherapy. Further large-sample studies are warranted.