Oyster Therapeutics, formerly Kesmalea, said it closed a $60 million Series A-2 led by 4BIO Capital to move an experimental oral tau-degrading drug toward human trials. Eli Lilly joined the financing, backing a London biotech trying to get protein-degrading medicines across the blood-brain barrier.
Oyster says its lead candidate is designed to remove harmful forms of tau, a protein that accumulates in Alzheimer’s and related neurodegenerative diseases, while preserving healthy tau. The treatment would recruit cells’ own protein-disposal machinery. Many conventional degraders are too large to reach the brain readily, according to the company.
Chief executive Robert Johnson told BioPharma Dive that the drug’s design lets it separate into two smaller molecules, helping them cross cell membranes and enter the brain. Oyster’s SELFTAC platform is designed to let those pieces reassemble into a working degrader where it acts.
The oral approach differs from Arrowhead Pharmaceuticals’ ARO-MAPT, which is injected under the skin and reduces tau production. Arrowhead reported in October that its drug was in Phase 1/2a testing. Oyster has not disclosed when its own candidate will enter the clinic, BioPharma Dive reported.
Oyster also disclosed a sponsored research agreement with Massachusetts General Hospital. The collaboration, supervised by tau researcher Catarina Silva, gives the company access to nerve-cell lines derived from patients and tools for studying oligomeric tau, a clustered form of the protein.