Eisai Co. Ltd. and Shanghai Henlius Biotech Inc. have entered an exclusive commercialization and co-exclusive development and manufacturing license agreement for the anti-PD-1 antibody serplulimab in Japan.

Serplulimab, a novel anti-PD-1 monoclonal antibody developed by Henlius, is reported to possess a unique binding mode that differs from existing anti-PD-1 antibodies. In China, it has been approved for indications such as squamous non-small cell lung cancer (sqNSCLC), extensive-stage small cell lung cancer (ES-SCLC), non-squamous non-small cell lung cancer (nsNSCLC), and esophageal squamous cell carcinoma (ESCC). In the EU, it has been approved for ES-SCLC. It is the world’s first anti-PD-1 antibody to be used as a first-line treatment for extensive-stage small cell lung cancer (ES-SCLC).

In Japan, Henlius is currently conducting a Phase II bridging clinical trial for ES-SCLC, and plans to submit an application for fiscal year 2026 based on the results of this trial as well as the Phase III clinical trial data that supported approvals for this indication in China and Europe. Furthermore, a Phase III multi-national clinical trial for non-high-frequency microsatellite instability (non-MSI-High) metastatic colorectal cancer is underway, with development for new indications also planned.

Under the terms of this agreement, Eisai will obtain exclusive rights to commercialize serplulimab in Japan. In addition to ES-SCLC and non-MSI-High metastatic colorectal cancer, Henlius plans to also conduct a clinical trial for perioperative gastric cancer in Japan, and will assume the responsibilities of the Marketing Authorization Holder.

Eisai will pay Henlius a contractual upfront payment of $75 million, in addition to regulatory milestone payments of up to $80.01 million, and sales milestone payments of up to $233.3 million. Furthermore, Eisai will pay double-digit royalties based on sales of the product. Eisai anticipates no changes to its consolidated financial forecast for the period ending March 31, 2026.

“We are pleased to collaborate with Eisai in Japan to advance the development of serplulimab in this important market,” said Dr. Jason Zhu, CEO of Henlius. “Serplulimab has demonstrated its potential across multiple tumor types through global clinical development and regulatory approvals, and Japan represents a critical step in its international journey.”

“Serplulimab is an anti-PD-1 monoclonal antibody that has been developed with high priority for indications with significant unmet medical needs, including ES-SCLC, and has already obtained approval for multiple indications in China and the EU. We anticipate that it will also become a promising treatment option in Japan for ES-SCLC and non-MSI-high metastatic colorectal cancer, for which development is underway, as well as for other intractable cancers,” added Toshihiko Yusa, Executive Officer and Head of Japan Business at Eisai.