Oyster Therapeutics raises $60M Series A for an oral tau degrader
Eli Lilly joins a $60 million round led by 4BIO Capital in London's Oyster Therapeutics, which is developing oral tau degraders designed to reach the brain.
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London, United Kingdom
London-based Oyster Therapeutics raises $60 million in what it calls a Series A led by 4BIO Capital, with Eli Lilly among the new investors, to take an oral, brain-penetrant tau degrader toward the clinic.
BioPharma Dive notes that several high-profile tau programs have failed. Eli Lilly, which sells the anti-amyloid drug Kisunla, has just joined a London tau round anyway. Here is the round, the science behind it and the investor list.
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4BIO leads, Lilly joins the cap table
Oyster Therapeutics, the London company formerly known as Kesmalea Therapeutics, announced the $60 million financing on November 10, 2026 in a press release carried by GlobeNewswire and BIA. At the xe.com mid-market rate of 0.90176 on November 11, that converts to about €54.1 million.
The release headline calls it a Series A, the body of the same release calls it a Series A-2, and BioPharma Dive’s Gwendolyn Wu describes it as an extension of the Series A. The company has not disclosed the amounts of earlier rounds.
4BIO Capital, the London-based life science venture firm, led the round. Eli Lilly and Company, CE Ventures, Actium Group and TOHO Ventures, managed by Global Brain, came in as new investors. Existing investors Syncona, Oxford Science Enterprises, Mission BioCapital and MGB Ventures also took part.
The company says the money will move its lead oral, brain-penetrant tau degrader toward clinical development and advance its SELFTAC platform. “This financing accelerates our progress towards the clinic,” said CEO Rob Johnson. Owen Smith, a partner at 4BIO Capital, said “this is where science meets unmet medical need.”
A degrader built to cross the blood-brain barrier
Oyster’s lead program is a small oral protein degrader aimed at tau. The company says it is designed to remove disease-causing tau while sparing healthy tau, with Alzheimer’s disease as the first focus.
The blood-brain barrier blocks most large molecules, and bifunctional degraders are large. According to the company, SELFTAC converts those larger degraders into smaller molecules that can cross the barrier and then reassemble into active degraders. The modular design also supports high-throughput screening.
Part of the lab work runs through a sponsored research agreement with Massachusetts General Hospital, supervised by Dr. Catarina Silva of the Mass General Brigham Neuroscience Institute and Harvard Medical School. It covers patient-derived neuronal cells and the generation and detection of oligomeric tau. BioPharma Dive also reports that the company is exploring oncology and immunology applications. The company has not given a date for a first clinical trial.
Market context and comparable rounds
Visiongain, in a report published on February 6, 2026, sizes the Alzheimer’s therapeutics market at $6.75 billion in 2026 and forecasts a compound annual growth rate of 18.2 percent over 2026-2036. Market sizing varies by publisher, so treat any single estimate as a reference point.
BioPharma Dive notes that the anti-amyloid treatments, Lilly’s Kisunla and Biogen and Eisai’s Leqembi, have only a modest effect on cognition and do not stop or reverse the disease.
Among the biotech rounds in our fundraising data announced between November 5 and November 10, Oyster’s €54.1 million sits between the €31.5 million seed raised by SRTD Biotech on November 9 and the €80.3 million Series A raised by Alethio Therapeutics on November 5, led by Sofinnova Partners and RA Capital. T-Therapeutics raised a $133 million Series B on November 5, co-led by Advent Life Sciences and British Business Bank.
Why Lilly’s participation stands out
“Big pharma investors are very interested in tau,” Johnson told BioPharma Dive. Lilly’s name on the investor list is the clearest evidence of that interest in this round. The company behind an anti-amyloid drug now holds a stake in a tau approach that has not yet reached the clinic.
The competition is ahead. According to BioPharma Dive, tau-lowering drugs from Biogen and Arrowhead Pharmaceuticals are much further along in clinical trials, and Wu writes that Oyster faces a difficult path.
The investor mix is the notable detail: a London lead, an Oxford backer in Oxford Science Enterprises, and Lilly, all at the same table before a first trial.
The next number is a clinical start date
Johnson says the money accelerates the move toward the clinic, and the release stops short of a date. That date is the figure to watch, and we will cover it when it comes.
