Japanese pharmaceutical firm Eisai Co. has entered into a joint development agreement with China-based startup Bliss Biopharmaceutical (Hangzhou) for BB-1701, an antibody-drug conjugate (ADC) with option rights for a strategic collaboration. If all development, regulatory and sales milestones are achieved, up to a total of $2 billion will be paid in this oncology deal.

BB-1701 is an ADC that is composed of Eisai's in-house developed anti-cancer agent eribulin, and anti-HER2 antibody using a linker, and is expected to have anti-tumour effects on breast, lung and other solid tumours that express HER2. The linker-payload, which uses eribulin as a payload, is a proprietary technology platform developed by Eisai's US research base Exton Site, and Eisai is investigating the possibilities of using this platform to link to various antibodies.

Under a license agreement signed by the two companies in 2018, Eisai has granted BlissBio global exclusive development rights for several ADCs to use eribulin as the payload. Based on the status of the Phase I/II clinical trials of BB-1701 currently being conducted by BlissBio, the both companies have decided to co-develop this drug.

Under the terms of the joint development agreement, Eisai will make upfront and development milestone payments to BlissBio, conduct a Phase II clinical trial in breast cancer, and obtain option rights to develop and commercialise BB-1701 globally, excluding Greater China (China, Hong Kong, Macau, Taiwan).