Estuary Biotherapeutics Launches with $103 Million for Kidney Gene Therapies

Estuary Biotherapeutics has launched with $103 million in committed financing to develop targeted gene therapies for autosomal dominant polycystic kidney disease (ADPKD), a genetic condition that causes cysts to grow in the kidneys and can lead to kidney failure.

Announced on October 16, 2026, the biotechnology company will use the funding to advance its two lead candidates, EST-201 and EST-101, toward clinical trials. The programs aim to address the genetic causes of ADPKD rather than simply slow the progression of the disease.

The financing includes a $93 million Series A round led by RA Capital Management, with participation from Deep Track Capital, Biogen New Ventures, UPMC Enterprises, Pivotal bioVenture Partners and the National Kidney Foundation Innovation Fund. Existing investors 4BIO Capital and GV, which co-led the company’s $10 million seed round, also participated.

ADPKD is one of the most common inherited kidney diseases, affecting more than eight million people worldwide. It is mainly caused by mutations in either the PKD1 or PKD2 gene. These mutations lead to the growth of fluid-filled cysts in the kidneys, gradually damaging healthy tissue and reducing kidney function. Some patients eventually require dialysis or a kidney transplant.

Current treatments can help slow disease progression, but options that directly address its underlying genetic causes remain limited.

Estuary is developing gene therapies designed to restore the function of proteins affected by these genetic mutations. The company’s approach uses adeno-associated viruses (AAVs) to deliver genetic material directly to kidney cells, with the aim of improving treatment delivery while limiting exposure to other parts of the body.

Its lead candidate, EST-201, is designed for patients with ADPKD caused by mutations in the PKD2 gene. The company expects to advance the program into clinical trials in 2027.

The second candidate, EST-101, targets ADPKD associated with PKD1 mutations. It uses a functional region of the polycystin-1 protein to address the effects of the genetic mutation and is expected to enter clinical development in 2028.

Both programs build on research by Estuary’s scientific co-founders, Stefan Somlo and Michael Caplan of Yale School of Medicine. Their research in mice showed that restoring polycystin protein activity could reverse structural and functional features of established polycystic kidney disease. However, these findings have not yet established whether the approach will be safe or effective in humans.

Wayne Sackett, co-founder and chief executive officer of Estuary Biotherapeutics, said the company aims to overcome one of the major challenges in kidney gene therapy: delivering treatment directly to the affected organ. The company plans to use the new funding to advance its programs toward clinical proof of concept and expand its kidney-targeting technology platform.

With its launch and new financing, Estuary joins the growing group of biotechnology companies developing genetic medicines for kidney disease. Its upcoming clinical studies will help determine whether targeted gene therapy can offer a new treatment approach for people living with ADPKD.

EST-201 and EST-101 are investigational therapies and have not been approved by the U.S. Food and Drug Administration (FDA) or any other regulatory authority. Their safety and effectiveness have not yet been established.