Estuary Biotherapeutics

About

Estuary Biotherapeutics develops genetic medicines for patients with serious kidney diseases. The company says its lead programs, EST-201 and EST-101, are aimed at the two most common genetic subtypes of autosomal dominant polycystic kidney disease. Wayne Sackett is co-founder and CEO.

The company announced on 2026-10-16 that it launched with $103 million in total committed financing. The $93 million Series A was led by RA Capital Management, with Deep Track Capital, Biogen New Ventures, UPMC Enterprises, Pivotal bioVenture Partners, the National Kidney Foundation Innovation Fund, and a family office connected to an individual living with ADPKD. 4BIO Capital and GV co-led a $10 million seed and also participated in the Series A. This page records the Series A and the $103 million total. The seed is not a separate round page. The family office is not named, so it has no investor page.

4BIO Capital's post writes Pivotal bioVentures and the National Kidney Foundation. The company release and the Raise Track Update say Pivotal bioVenture Partners and the National Kidney Foundation Innovation Fund. This page uses those names. Fierce Biotech and the BioSpace deals article report the $93 million Series A and the $10 million seed. Fierce names Deep Track Capital, Biogen New Ventures and UPMC Enterprises and does not list every participant.

The release is datelined Menlo Park, Calif., and Newton, Mass. The company site says a San Francisco Bay Area headquarters is coming soon and lists a Greater Boston office in Newton, Mass. The Raise Track Update calls the company Newton, MA-based. A Form D filed on 2026-10-16 gives Menlo Park, California as the issuer city and reports $40,654,685 sold of $103,654,385 offered. It does not name a round type. Sandra's issue does not list that filing in Section 3, so it is not a separate round page, and those figures are not stored. No city is stored. The page uses the announced $93 million Series A and the $103 million total committed financing.

This page is not indexed by search engines yet. It is promoted once a second source states a headquarters city the other sources agree with.

Funding history

Total funding reported by the sources: $103M.

Investors

• RA Capital Management lead
• Deep Track Capital participant
• Biogen New Ventures participant
• UPMC Enterprises participant
• Pivotal bioVenture Partners participant
• National Kidney Foundation Innovation Fund participant
• 4BIO Capital participant
• GV participant

Sources

Last verified: 2026-10-19

1. https://estuarybio.com/news/estuary-series-a
   Type: company announcement. Accessed 2026-10-19.
   Company release labeled 16 October 2026, datelined MENLO PARK, Calif., and NEWTON, Mass. Announces a launch with $103 million in total committed financing. The $93 million Series A was led by RA Capital Management, with Deep Track Capital, Biogen New Ventures, UPMC Enterprises, Pivotal bioVenture Partners, the National Kidney Foundation Innovation Fund, and a family office connected to an individual living with ADPKD. 4BIO Capital and GV co-led a $10 million seed and also participated in the Series A. The contact block says headquarters in the San Francisco Bay Area is coming soon and lists a Greater Boston office in Newton, Mass. Street addresses and email addresses are not published.
2. https://www.4biocapital.com/single-post/estuary-biotherapeutics-launches-with-103-million-to-advance-targeted-gene-therapies-for-kidney-dis
   Type: official investor website. Accessed 2026-10-19.
   4BIO Capital post datelined London, 16 October 2026. Says 4BIO participated in the USD 93 million Series A after co-leading the USD 10 million seed with GV, and that the financings provide USD 103 million. Names the Series A lead as RA Capital Management. Writes Pivotal bioVentures and the National Kidney Foundation, without the words Innovation Fund or bioVenture Partners.
3. https://www.fiercebiotech.com/biotech/estuary-emerges-stealth-103m-its-gene-therapies-kidney-disease
   Type: reputable publication. Accessed 2026-10-19.
   Fierce Biotech, labeled Oct 16, 2026, 6:30am. Reports $103 million in funding, a $10 million seed, and a $93 million Series A led by RA Capital Management. Names Deep Track Capital, Biogen New Ventures, UPMC Enterprises, 4BIO Capital and GV. Does not name a headquarters city.
4. https://www.biospace.com/deals/estuary-sails-into-kidney-disease-space-with-103m-for-gene-therapies
   Type: reputable publication. Accessed 2026-10-19.
   BioSpace deals article by Annalee Armstrong, October 16, 2026. Reports a $93 million Series A led by RA Capital Management and an earlier $10 million seed. Names Deep Track Capital, Biogen New Ventures and others, plus 4BIO Capital and GV. Does not name a headquarters city.
5. https://www.sec.gov/Archives/edgar/data/2138862/000213886226000003/0002138862-26-000003-index.htm
   Type: sec filing. Accessed 2026-10-19.
   SEC Form D for Estuary Biotherapeutics, Inc. EDGAR filing date 2026-10-16. Signed 2026-10-14. First sale 2026-07-01. Total amount sold $40,654,685 of an offering amount of $103,654,385. 25 investors already invested. Issuer address city is Menlo Park, California. Jurisdiction of incorporation is Delaware. Year of incorporation on the form: 2022. Industry group is Biotechnology. The form does not name the purchasers or a round type. This filing is not a separate round page. Its sold and offered amounts are not stored. Street addresses are not published.
6. https://buttondown.com/raisetrack/archive/raise-track-update-2026-10-19/
   Type: other verified public source. Accessed 2026-10-19.
   Raise Track Update for 2026-10-19, Section 1. Calls Estuary Biotherapeutics a Newton, MA-based biotechnology company and says it raised $93 million in a Series A led by RA Capital Management. Names the same participants as the company release, including Pivotal bioVenture Partners, the National Kidney Foundation Innovation Fund, 4BIO Capital and GV. Says the raise brought the total to $103 million. The Investors line does not include the family office. Section 3 does not list this company.