Eisai and Henlius entered into an exclusive license agreement to commercialize the anti-PD-1 antibody serplulimab (Hetronifly) in Japan.[1][2][4] Eisai will acquire exclusive rights to develop, manufacture and sell the drug for oncology indications in Japan.[1][3] Henlius is conducting a Phase II clinical trial in Japan as a bridge trial for extensive small cell lung cancer (ES-SCLC) and plans to submit a regulatory application in FY 2026.[1][2] A multinational phase III trial for non-MSI-High metastatic colorectal cancer is also ongoing and a clinical trial for perioperative gastric cancer is planned.[1][2] Eisai will pay Henlius a subscription fee of US$75 million, regulatory milestones of up to US$80.01 million and sales milestones of up to US$233.3 million, plus double-digit sales royalties.[1][2] Serplulimab is approved in China for sqNSCLC, ES-SCLC, nsqNSCLC and ESCC, in the EU for ES-SCLC as the first anti-PD-1 drug in the first line for ES-SCLC.[3][4] In Japan, there are an estimated 13,000 patients with ES-SCLC and 28,000 with non-MSI-High metastatic colorectal cancer.[2] The agreement does not affect Eisai's consolidated financial forecast until March 31, 2026.[1][2][6]