The 2026 European Society for Radiotherapy and Oncology (ESTRO 2026) was held in Stockholm, Sweden, from May 15 to 19 local time. At this conference, Henlius' innovative anti-PD-1 monoclonal antibody(mAb) serplulimab was officially presented in an oral report for its neoadjuvant therapy study results in locally advanced high-risk colon cancer (LACC). The study was jointly initiated by Professor Sanjun Cai and Professor Zhen Zhang of Fudan University Shanghai Cancer Center. The results showed that radiochemotherapy combined with serplulimab demonstrated favorable efficacy, with the pathological complete response (pCR) rate significantly increased to 42.5%, representing more than a four-fold improvement over the control group. This offers a new treatment option for high-risk LACC and further validates the therapeutic value of serplulimab in the field of gastrointestinal cancers.

Colorectal cancer (CRC) is among the most common gastrointestinal malignancies and remains a major health burden in China and worldwide. In 2022, there were approximately 1.926 million new cases worldwide and about 904,000 deaths; among them, China accounted for 517,000 new cases and 240,000 deaths, ranking second in incidence and fourth in mortality among malignancies.¹⁻² Based on the site of occurrence, colorectal cancer is divided into colon cancer and rectal cancer. Approximately 10%-15% of colon cancer patients are already in a locally advanced stage at initial diagnosis, with relatively poor prognosis.³ For advanced colorectal cancer, Henlius is actively promoting a global multicenter Phase 3 clinical study (ASTRUM-015) of serplulimab combined with bevacizumab and chemotherapy as first-line treatment for metastatic colorectal cancer (mCRC). Patient enrollment has been completed globally, aiming to fill the clinical gap in immunotherapy for non-MSI-H mCRC. Meanwhile, in locally advanced colon cancer, multiple investigator-initiated trials (IITs) are underway to further assess the therapeutic value of serplulimab.

At this ESTRO conference, the Phase 2 study of serplulimab combined with chemoradiation as neoadjuvant therapy for MSS/pMMR-type LACC was selected for oral presentation. The results showed significant efficacy, with the pCR rate reaching more than four times that of the chemotherapy control group, offering an innovative neoadjuvant treatment model for locally advanced high-risk colon cancer. This study was previously presented at the 2026 ASCO GI conference, and this conference provided updated data; all enrollment data were also selected for ASCO 2026 and will be presented in poster form, continuously validating its stable clinical benefits.

Serplulimab is the world's first and only anti-PD-1 mAb to achieve success in a Phase 3 registrational study for perioperative gastric cance and the first anti-PD-1 mAb approved for the first-line treatment of SCLC*, marking global breakthroughs in both lung and gastrointestinal cancers. Serplulimab demonstrates unique advantages in treating various solid tumors via its differentiated mechanism. The drug not only induces stronger PD-1 internalization—reducing PD-1 receptor presence on T cells for rapid and potent immune activation⁴—but also minimizes PD-1-mediated recruitment of the co-stimulatory molecule CD28, thereby preserving CD28 signaling,^5-7 enhancing downstream AKT activity,⁸ and promoting sustained T-cell activation. Focused on gastrointestinal cancers and lung cancer, serplulimab has been approved for the treatment of squamous non-small cell lung cancer (sqNSCLC), extensive-stage small cell lung cancer (ES-SCLC), ESCC, and non-squamous non-small cell lung cancer (nsqNSCLC)**. Up to date, it has been approved in over 40 countries and regions including China, the United Kingdom, the European Union, Singapore, India, Switzerland, and Peru, covering nearly half of the global population.

The results of the study released at 2026 ESTRO are as follows:

Title: Neoadjuvant radiotherapy combined with CAPOX and PD-1 inhibitor for MSS/pMMR high-risk locally advanced colon cancer: a randomized phase Ⅱ Trial

Study design: A total of 120 LACC (T4/bulky N+M0，pMMR/MSS) patients will be randomized to either a chemotherapy group or a radiotherapy group. The chemotherapy group receives 4 cycles of CAPOX. The radiotherapy group receives SCRT（25Gy in 5 fraction）and 4 cycles of the PD-1 inhibitor (serplulimab) combined with CAPOX. The radiotherapy target volume includes only the primary colon tumor and enlarged lymph nodes, without elective nodal irradiation. After neoadjuvant therapy, patients will be evaluated for radical colon resection. The primary endpoint is pathological complete response (pCR) rate. The secondary endpoints include tumor downstaging, R0 resection, 3-year disease free survival (DFS), 3-year overall survival (OS), 3-year local recurrence-free survival and treatment-related toxicity.

Results: As of October 31, 2025, 120 patients have been enrolled and randomized. Of these, 12 withdrew from the study, leaving 108 remaining. 100 patients have completed neoadjuvant treatment and 89 have received surgery (49 in the chemotherapy group, 40 in the radiotherapy group). All 89 patients achieved radical resection, with R0 resection rates of 95.9% (47/49) in the chemotherapy group, and 95.3% (38/40) in the radiotherapy group. The pCR rate (ypT0N0) was 10.2% (5/49) in chemotherapy group and 42.5% (17/40) in the radiotherapy group. The most common grade 3-4 adverse event (AE) among patients completing neoadjuvant treatment was thrombocytopenia, that 18.4% (9/49) in the chemotherapy group and 22.5% (9/40) in the radiotherapy group.

Conclusion: The combination of PD-1 inhibitor, SCRT, and chemotherapy shows promising efficacy and may significantly improve pCR rates in patients with MSS/pMMR high risk LACC. This regimen may provide a new therapeutic option to achieve R0 resection and improve long-term survival.

* As of May 19, 2026

** Approved indications may vary by country or region. Please refer to announcements issued by local regulatory authorities for approved indications in each market.