Estuary Biotherapeutics launched with $103 million, backing kidney-targeted AAV gene therapy aimed at autosomal dominant polycystic kidney disease (ADPKD). The round includes a $93 million Series A led by RA Capital Management and an additional $10 million seed co-led by 4BIO Capital and GV. The company’s thesis centers on delivery: two lead AAV programs are designed as locally administered, potentially one-time treatments intended to restore polycystin levels across the nephron. That differentiates Estuary’s approach from current standard therapy exemplified by Otsuka’s tolvaptan, which slows progression without correcting the genetic cause. Estuary said the financing will carry its programs through clinical proof of concept and fund development of its kidney-targeting platform. For the field, the funding also reinforces how delivery, dosing durability, and organ-specific administration are becoming as central as target biology in kidney gene therapy development.