Oyster Therapeutics raises $60M in Series A-2 for tau-degrading Alzheimer's drug candidates
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.
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 biopharmadive.com
biopharmadive.combiopharmadive.comOpen source ↗. The company develops protein degraders aimed at tau, a protein that, like amyloid, clusters in the brains of Alzheimer's patients. The Series A-2 round was led by the British venture fund 4BIO Capital, and eight other investors, including Lilly, joined it.
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. The company says the compound targets only disease-causing forms of tau and spares healthy versions.
CEO Robert Johnson said the linker includes a fix that splits the drug apart once it enters the body. This leaves two small molecules that, by his account, penetrate cell membranes more easily and can reach the brain. 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.
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 biopharmadive.com
biopharmadive.combiopharmadive.comOpen source ↗. Oyster has not disclosed when its lead candidate will enter the clinic. 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.
Johnson said a combination of amyloid- and tau-targeting therapies might be key to treating Alzheimer's and other neuroinflammatory conditions. 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. The company is also examining whether its protein degrading technology could be useful in cancer and immunology.
