Eisai Opts Out of BB-1701 Deal, BlissBio to Advance HER2-Directed ADC Independently

In a surprising turn of events, Japanese pharmaceutical giant Eisai has decided not to exercise its option on BB-1701, a promising HER2-directed antibody-drug conjugate (ADC) developed by Bliss Biopharmaceutical (BlissBio). The decision comes as a setback to what was once touted as a potential challenger to AstraZeneca and Daiichi Sankyo's blockbuster drug, Enhertu.

Eisai's Decision and Financial Implications

Eisai's choice not to pursue BB-1701 further was quietly revealed in a recent financial report, where the company disclosed an impairment loss related to the decision. This move effectively ends a partnership that began in 2023 when Eisai agreed to pay BlissBio up to $2 billion for the option on BB-1701, highlighting the drug's perceived potential at the time.

The Japanese drugmaker had initially identified BB-1701 as a possible best-in-class molecule, citing its innovative eribulin-based payload-linker technology as a key differentiator in the competitive HER2 space. Despite early promise and reported responses in solid tumors, including in breast cancer patients previously treated with other anti-HER2 ADCs, Eisai has chosen to step away from the program.

BlissBio's Path Forward

Despite Eisai's withdrawal, BB-1701 is set to continue its development journey. BlissBio, a Chinese biopharmaceutical company, has confirmed its intention to progress the ADC program independently. This decision demonstrates BlissBio's confidence in BB-1701's potential, even without the backing of a major global pharmaceutical partner.

The ongoing phase 2 study of BB-1701 remains active, with full efficacy results yet to be disclosed. Angle, a liquid biopsy company involved in the trial, reported that their circulating tumor cell analysis assay has shown promise in measuring changes in HER2 status over time, potentially offering an advantage over traditional tissue-based assessments.

Competitive Landscape and Future Prospects

BlissBio now faces the challenge of advancing BB-1701 in an increasingly competitive market. In China, the company contends with local players such as Duality Biologics, GeneQuantum Healthcare, and Jiangsu HengRui Medicine, all vying for a share of the HER2-directed ADC market.

The global landscape is equally competitive, with major pharmaceutical companies making significant moves in the space. BioNTech secured ex-China rights to DualityBio's candidate in 2023, while Johnson & Johnson acquired a HER2-directed ADC through its $2 billion takeover of Ambrx last year.

As BlissBio charts its course forward, the company will need to leverage its eribulin payload technology, which Eisai will continue to license, to differentiate BB-1701 in the crowded HER2 market. The success of this endeavor could reshape the competitive dynamics in the ADC field and potentially offer new treatment options for cancer patients worldwide.