Bristol-Myers Squibb Exercises $2.2 Billion Option on Prothena's Tau-Targeting Alzheimer's Antibody
Key Insights
Bristol-Myers Squibb (search) has exercised its option on Prothena's PRX005, a tau-targeting antibody for Alzheimer's disease (search), in a deal potentially worth $2.2 billion with $55 million upfront.
PRX005 specifically targets the microtubule-binding region (search) of tau protein (search), which correlates more closely with dementia stages than other tau regions according to cerebrospinal fluid analysis.
The antibody completed phase 1 single ascending dose studies showing safety and effective central nervous system penetration, with multiple ascending dose results expected by year-end.
Bristol-Myers Squibb (search) has exercised its option on Prothena's PRX005, a tau protein (search)-targeting antibody for Alzheimer's disease (search), upgrading their long-running alliance in a deal potentially worth $2.2 billion. The pharmaceutical giant will pay $55 million upfront and assume full responsibility for development, manufacturing, and commercialization activities for the early-stage clinical candidate.
The decision represents a significant commitment to Alzheimer's research for BMS, which had previously stepped back from the field. The company initially paid $80 million in 2021 to secure exclusive worldwide opt-in rights to PRX005, inheriting the option through its 2019 acquisition of Celgene, which had originally partnered with Dublin-based Prothena in 2018.
Targeting Tau's Critical Region
PRX005 distinguishes itself by specifically targeting the microtubule-binding region (search) (MTBR) of tau protein (search), which Prothena believes is most closely associated with the pathogenic spread of tau in Alzheimer's patients' brains. According to the Irish biotech, MTBR fragments in cerebrospinal fluid correlate with dementia stages more closely than fragments from other tau protein regions, potentially giving the antibody an advantage over competing therapies.
Richard Hargreaves, who heads BMS's neuroscience research center, stated that PRX005 "has the potential to provide a meaningful disease-modifying treatment option for the millions of people that suffer from Alzheimer's disease (search)."
Clinical Progress and Pipeline Position
The antibody has completed a phase 1 single ascending dose study, with topline data reported in January demonstrating that PRX005 was safe and well-tolerated while effectively crossing into the central nervous system, meeting its primary objectives. An ongoing multiple ascending dose study is expected to report results before the end of the year.
This acquisition makes PRX005 the centerpiece of BMS's neuroscience pipeline, which currently consists of only a handful of early-stage drug candidates. The move marks a notable return to Alzheimer's research for the company, which had largely exited the field nearly a decade ago after abandoning its amyloid-targeting drug avagacestat.
Challenging Tau Landscape
The tau-targeting approach faces significant hurdles, as previous attempts have largely failed in clinical trials. Biogen abandoned its tau antibody gosuranemab in 2021, while Roche and AC Immune's semorinemab failed in the phase 2 TAURIEL trial for early-stage Alzheimer's in 2020. TauRx (search)'s tau aggregation inhibitor HMTM (formerly LMTX) was unable to improve on placebo in a 2016 study, though it remains in development.
Despite these setbacks, there is hope that tau-targeting therapies could enhance the modest clinical effectiveness of amyloid-targeting treatments like Eisai and Biogen's recently-approved Leqembi (lecanemab) if used in combination.
Financial Terms and Future Potential
The latest agreement brings the total amount Prothena has received under the BMS/Celgene alliance to $230 million out of a possible $2.2 billion. The partnership also covers drugs targeting TDP-43 and an undisclosed target, expanding beyond the tau program.
With PRX005 now fully under BMS's control, the pharmaceutical company will be responsible for advancing the antibody through later-stage clinical development, representing a significant bet on the potential of precision tau targeting in Alzheimer's disease (search) treatment.