Enher-tu, Eisai? Japanese drugmaker inks Bliss ADC deal to tee up challenge to AstraZeneca-Daiichi Sankyo blockbuster

Eisai is joining the HER2 antibody-drug conjugate (ADC) gold rush. After seeing AstraZeneca and Daiichi Sankyo validate the approach, Eisai has struck a $2 billion biobucks deal with Bliss Biopharmaceutical for a spot alongside BioNTech in the chasing pack. 

AstraZeneca and Daiichi have linked their HER2-directed ADC Enhertu to improved outcomes in multiple settings, including patients with breast cancer that have low levels of the receptor. The data supported an explosive launch, with sales growing (PDF) more than 140% last year to turn the product into a blockbuster, and a clutch of companies see space for me-too drugs. 

Eisai is the latest drugmaker to show an interest in the sector—and has identified BlissBio’s phase 1/2 asset BB-1701 as its way in. In return for an upfront fee of undisclosed size, Eisai has secured the chance to co-develop the HER2-directed ADC with BlissBio through the option period. 

If Eisai exercises its option, the Japanese drugmaker will receive ex-China rights to BB-1701. The option exercise payment and development and commercial milestones are collectively worth up to $2 billion. Neither party has disclosed the size of the upfront or  option fees. Earlier this year, BioNTech paid $170 million upfront and committed up to $1.5 billion in milestones for a HER2 ADC and another candidate.   

BlissBio took BB-1701 into the clinic early in 2020 and has now tested the ADC in more than 100 patients with a range of tumor types in the U.S. and China. The development program will now benefit from the support of Eisai.

If Eisai takes up its option on BB-1701, it will join biotechs including Ambrx, BioNTech, GeneQuantum Healthcare and Jiangsu HengRui Medicine in the pack of companies with potential rivals to Enhertu in development.