Eisai Co., Ltd, a Tokyo-based pharmaceutical company, and Shanghai Henlius Biotech, Inc. announced an exclusive licensing agreement for serplulimab, a novel anti-PD-1 antibody targeting multiple cancer indications. Under the terms of the deal, Eisai will obtain exclusive commercialization rights for serplulimab in Japan, with Henlius retaining development and marketing authorization responsibilities.

The deal structure includes an upfront payment of USD 75 million from Eisai to Henlius, with potential additional regulatory milestone payments of up to USD 80.01 million and sales milestone payments reaching USD 233.3 million for a total deal value just over USD 388 million. Henlius will also receive double-digit royalties based on product sales.

Deal context

Serplulimab is a fully humanized IgG4 monoclonal antibody that binds to the PD-1 receptor on T cells, blocking its interaction with PD-L1 and PD-L2. The mechanism is similar to other PD-1 inhibitors (e.g., pembrolizumab, nivolumab), but is distinguished by unique epitope recognition and differentiated spatial organization of its heavy and light chains, conferring a higher binding affinity for PD-1 and potentially more robust PD-1 receptor internalization.

Currently approved in China for multiple cancer indications including squamous non-small cell lung cancer, extensive-stage small cell lung cancer (ES-SCLC), and esophageal squamous cell carcinoma. In the EU, serplulimab secured approval as the first anti-PD-1 antibody approved for first-line treatment of ES-SCLC in the market.

Henlius is currently conducting a Phase II bridging study for ES-SCLC in Japan, with plans to submit a regulatory application in fiscal year 2026. Additionally, an ongoing Phase III multinational clinical trial focuses on non-MSI-high metastatic colorectal cancer. The licensing agreement includes provisions for Henlius to conduct a clinical trial for perioperative gastric cancer in Japan.