Estuary Biotherapeutics, a US-based biotechnology company developing genetic medicines for kidney diseases, announced a $93 million Series A funding round led by RA Capital Management on October 16, 2026. The financing brings the company’s total committed capital to $103 million, including an earlier $10 million seed round.
The Series A included participation from Deep Track Capital, Biogen New Ventures, UPMC Enterprises, Pivotal bioVenture Partners, the National Kidney Foundation Innovation Fund, 4BIO Capital, GV and a family office connected to an individual living with autosomal dominant polycystic kidney disease (ADPKD).
4BIO Capital and GV previously co-led Estuary’s $10 million seed financing and returned as investors in the Series A.
Estuary is led by co-founder and CEO Wayne Sackett. Its scientific co-founders, Dr. Stefan Somlo and Dr. Michael Caplan of Yale School of Medicine, contributed research underpinning the company’s approach to developing gene therapies for inherited kidney disorders.
The company focuses on ADPKD, a progressive genetic condition in which fluid-filled cysts develop and enlarge in the kidneys, potentially causing kidney failure. Estuary is developing locally administered adeno-associated virus (AAV) gene therapies designed to deliver therapeutic genetic material directly to kidney cells and restore polycystin protein expression.
Its two lead development programs address different genetic forms of ADPKD:
- EST-201: A gene-addition therapy designed for patients with PKD2 mutations, delivering a full-length PKD2 gene through an AAV vector.
- EST-101: A gene therapy targeting PKD1-related ADPKD, using an AAV vector to deliver a functional region derived from the polycystin-1 protein.
Estuary anticipates advancing EST-201 into clinical development in 2027, followed by EST-101 in 2028. These timelines remain subject to development progress.
The new financing will support the advancement of both programs toward clinical proof of concept, further development of the company’s kidney-targeted delivery platform and expansion of its therapeutic pipeline.
Estuary’s approach builds on preclinical research demonstrating that restoring polycystin activity can reverse certain structural and functional features of polycystic kidney disease in mouse models. The company aims to investigate whether kidney-directed genetic medicines can produce similar therapeutic benefits in patients.
