Eisai Secures Exclusive Japan Commercial Rights to Henlius’ Anti-PD-1 Serplulimab

Eisai and Shanghai Henlius Biotech (Henlius) announced on Feb. 5, 2026 that they have entered an exclusive commercialization and co-exclusive development and manufacturing license agreement for the anti-programmed cell death protein 1 (PD-1) monoclonal antibody (mAb) serplulimab in Japan, expanding the mAb’s global footprint into a major oncology market with significant unmet need (1).

Under the agreement, Eisai will obtain exclusive rights to commercialize serplulimab in Japan, while Henlius will retain responsibility as the marketing authorization holder and continue leading clinical development activities. The collaboration positions serplulimab for regulatory submission in Japan, initially targeting extensive-stage small cell lung cancer (ES-SCLC). Serplulimab is marketed as Hansizhuang in China and Hetronifly in the European Union (EU).

“We are pleased to collaborate with Eisai in Japan to advance the development of serplulimab in this important market,” said Jason Zhu, MD, PhD, CEO of Henlius, in a company press release (1). “By combining Henlius’ innovation capabilities with Eisai’s deep local expertise, we aim to support the efficient development of serplulimab and address unmet medical needs for patients in Japan.”

How could serplulimab address high-unmet-need cancers in Japan?

Serplulimab is a novel anti-PD-1 mAb developed by Henlius that features a unique binding mode distinct from currently marketed PD-1 inhibitors. In China, the mAb has received approvals across multiple tumor types, including squamous and non-squamous non-small cell lung cancer, ES-SCLC, and esophageal squamous cell carcinoma. In the EU, it is approved for ES-SCLC and is the first anti-PD-1 antibody globally authorized as a first-line treatment for this aggressive disease, according to Henlius (1).

In Japan, Henlius is conducting a Phase II bridging study in ES-SCLC and plans to submit a regulatory application in fiscal year 2026, supported by global Phase III data that enabled approvals in China and Europe. A multinational Phase III trial in non-microsatellite-instability-high metastatic colorectal cancer is also ongoing, with additional indications planned, including perioperative gastric cancer.

These development programs target patient populations with limited therapeutic options. Japan is estimated to have approximately 13,000 patients with ES-SCLC and 28,000 patients with non-MSI-high metastatic colorectal cancer, underscoring the potential clinical relevance of expanding access to new immunotherapy options (2).

What are the financial and strategic terms of the agreement?

Under the license, Eisai will pay Henlius an upfront fee of ¥11.6 billion (US$75 million), along with regulatory milestone payments of up to ¥12.4 billion (US$80.01 million) and sales-based milestones of up to ¥36.2 billion (US$233.3 million). Henlius is also eligible to receive double-digit royalties on net sales in Japan (1).

What does this deal signal for global immuno-oncology development?

The agreement reflects a broader trend of region-specific licensing strategies that leverage global clinical data while pairing innovative biologics with established local commercialization capabilities. For Henlius, the partnership supports continued international expansion of serplulimab beyond China and Europe. For Eisai, the deal strengthens its oncology portfolio in Japan with a late-stage immunotherapy asset targeting difficult-to-treat cancers.

“Serplulimab has already obtained approval for multiple indications in China and the EU, including first-line treatment for ES-SCLC,” said Toshihiko Yusa, executive officer and head of Japan Business at Eisai, in the release. “We anticipate that it could become a promising treatment option in Japan for cancers with high unmet need, and Eisai will work closely with Henlius to deliver it to patients as quickly as possible.”

As competition in the PD-1 class intensifies, differentiated clinical positioning and efficient regional execution may increasingly determine which therapies reach patients in high-need markets (3).

References

1. Eisai. Eisai and Henlius Enter into Exclusive Commercial License Agreement for Anti-PD-1 Antibody Serplulimab in Japan. Press Release. Feb. 5, 2026.
2. National Cancer Center Japan. Cancer Information Service, Cancer Statistics (Japanese only). ganjoho.jp. Accessed Feb. 5, 2026.
3. Mordor Intelligence. PD-1 And PD-L1 Inhibitors Market Size & Share Analysis—Growth Trends and Forecast (2026 - 2031). Market Research Report. 2025.