Walden Biosciences to Present Phase 1+ and Phase 2 Data for WAL0921 at American Society of Nephrology Kidney Week

Late-breaking poster presentation to showcase initial activity of WAL0921 in proteinuric kidney disease Additional poster demonstrates WAL0921 is safe, well tolerated, and reduces circulating suPAR levels in healthy participants Cambridge, Massachusetts, October 2, 2026 — Walden Biosciences, Inc. (“Walden” or “the Company”), a private, clinical-stage biotechnology company dedicated to developing disease-modifying medicines to treat rare chronic kidney diseases, today announced that it will present data at two poster sessions at the American Society of Nephrology’s 59 th Annual Kidney Week, being held in Denver, Colorado, from October 22 – 25, 2026, including a late-breaking poster highlighting initial data from the ongoing basket study of the anti-suPAR/uPAR monoclonal antibody, WAL0921, in proteinuric chronic kidney disease. A second presentation will include data from the Phase 1+ single ascending dose study in healthy volunteers. “The data being presented at Kidney Week demonstrate a favorable pharmacokinetic and tolerability profile of WAL0921, with a rapid reduction of circulating suPAR levels. Further, they establish the potential for WAL0921 to introduce a novel mechanism of action to the treatment of proteinuric kidney diseases. These data also informed dosing in our ongoing Phase 2 basket study of WAL0921 in diabetic kidney disease and multiple proteinuric chronic kidney diseases, including FSGS, IgAN, and membranous nephropathy. We look forward to providing initial data from the ongoing study in our late-breaking abstract poster presentation, which will highlight initial data from patients with diabetic kidney disease,” said Blaine McKee, Ph.D., Chief Executive Officer at Walden Biosciences. Presentation Details Abstract Number: 4592035 Title: Activity of the Novel Anti-Soluble Urokinase Plasminogen Activator Receptor (suPAR) Monoclonal Antibody WAL0921 in Diabetic Kidney Disease Date and Time: October 22, 2026, 10:00 a.m. – 12:00 p.m., MDT Session Title: Late-Breaking Research Posters Location: TH-PO1245 Presenter: Laura Kooienga, M.D., Division Director, CKC Research Department, Colorado Kidney Care, Denver, Colorado Abstract Number: 4560499 Title: WAL0921, an Anti-Soluble Urokinase Plasminogen Activator Receptor (suPAR) Monoclonal IgAN Antibody, Is Safe and Well Tolerated in a Phase 1 Single Ascending Dose (SAD) Study and Reduces Circulating suPAR in Healthy Participants Date and Time: October 23, 2026, 10:00 a.m. – 12:00 p.m., MDT Session Title: Glomerular Diseases: Clinical, Outcomes, and Therapeutics Research Location: FR-PO0660 Presenter: Alexander Duncan, Ph.D., Chief Scientific Officer, Walden Biosciences About Walden Biosciences Walden Biosciences is a private, clinical-stage biotechnology company focused on developing disease-modifying medicines to treat rare chronic kidney diseases. Walden is applying unique, multi-disciplinary approaches designed to prevent kidney damage and stop disease progression. Walden’s product candidates are well-differentiated from current therapies as they have novel mechanisms of action and are not hemodynamic modulators and are non-immunosuppressive. Walden’s programs directly target two cell types critical for kidney function: podocytes and proximal tubular cells. Dysfunction of these cells is a critical hallmark of the majority of proteinuric kidney diseases. Walden’s Phase 2 program, WAL0921, is a humanized monoclonal antibody that inhibits urokinase plasminogen activator in both its soluble (suPAR) and membrane bound (uPAR) forms and is being evaluated in a global basket study ( NCT06466135 ). Walden’s second most advanced program is a Phase 1-stage small molecule, WAL0623, that is designed to stabilize and restore the function of dynamin, an enzyme responsible for the maintenance of the cytoskeletal architecture and function of podocytes and proximal tubule cells. Both programs offer the promise to deliver breakthrough therapies that transform the treatment of kidney disease. For more information, please visit www.waldenbiosciences.com or follow us on LinkedIn . For More Information Investor Contact: Precision AQ Anne Marie Fields [email protected] Media Contact: Ten Bridge Communications Michael Galfetti [email protected]

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