# Oyster Therapeutics raises $60M in Series A-2 for tau-degrading Alzheimer's drug candidates

- Published: 2026-11-10 14:32 UTC
- Section: Industry & People › Start-ups
- Tags: Oyster Therapeutics, tau protein, tau degrader, Alzheimer's disease, protein degradation, Series A-2 round, 4BIO Capital, Massachusetts General Hospital, Kesmalea Therapeutics
- URL: https://realtech.media/news/rt-57aa63ce0857e18c2233c066_oyster_therapeutics_raises/

**London-based Oyster Therapeutics is developing tau protein degraders for Alzheimer's disease. The lead candidate has not entered the clinic, and the company has not said when it will.**

![Oyster Therapeutics raises $60M in Series A-2 for tau-degrading Alzheimer's drug candidates](https://realtech.media/media/2026/11/fb012ce92c9970b6.jpg)
*U.S. Navy photo by John F. Williams, Wikimedia Commons, Public domain*

London-based biotech startup Oyster Therapeutics said on Tuesday that it raised $60 million in an extension of its Series A round, according to biopharmadive.com [1]. The company develops protein degraders aimed at tau, a protein that, like amyloid, clusters in the brains of Alzheimer's patients [1]. The Series A-2 round was led by the British venture fund 4BIO Capital, and eight other investors, including Lilly, joined it [1].

## How the tau degrader is built

Protein degraders are designed to eliminate their targets rather than block their activity, as many drugs do. Oyster's lead program links a targeting molecule that binds tau with an enzyme that tags the protein for destruction by the cell's internal machinery [1]. The company says the compound targets only disease-causing forms of tau and spares healthy versions [1].

CEO Robert Johnson said the linker includes a fix that splits the drug apart once it enters the body [1]. This leaves two small molecules that, by his account, penetrate cell membranes more easily and can reach the brain [1]. He said the approach could address a problem that has affected earlier protein degraders and tau-targeting biologics. Tau lacks the pockets that traditional drugs use to bind, which makes it a candidate for a different approach [1].

## Stage and context

Amyloid-targeting drugs such as Eli Lilly's Kisunla and Leqembi from Biogen and Eisai have only a modest effect on cognition and do not stop or reverse Alzheimer's [1]. Oyster has not disclosed when its lead candidate will enter the clinic [1]. Several high-profile tau-targeting programs have failed to meaningfully affect the disease, and other medicines that significantly lower tau, including those from Biogen and Arrowhead Pharmaceuticals, are much further along in clinical testing [1].

Johnson said a combination of amyloid- and tau-targeting therapies might be key to treating Alzheimer's and other neuroinflammatory conditions [1]. Oyster, formerly Kesmalea Therapeutics, is also entering a research collaboration with Massachusetts General Hospital to study a form of tau that it calls the most neurotoxic [1]. The company is also examining whether its protein degrading technology could be useful in cancer and immunology [1].

## Sources

1. [biopharmadive.com](https://www.biopharmadive.com/news/oyster-venture-financing-tau-targeted-protein-degraders/874160)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-57aa63ce0857e18c2233c066_oyster_therapeutics_raises/