Immusoft Receives FDA Fast Track Designation for ISP-001, a First-in-Class Engineered B Cell Therapy for MPS I

Prospectively designed for scalability and re-dosability, Immusoft's engineered B cells represent the next generation of advanced therapeutics

SAN FRANCISCO, Oct. 21, 2025 /PRNewswire/ -- Immusoft of CA, a clinical-stage biotechnology company pioneering engineered B cell therapies, today announced that the U.S. Food and Drug Administration (FDA) has granted Fast Track designation to ISP-001, the Company's lead investigational therapy for the treatment of mucopolysaccharidosis type I (MPS I), a rare and life-threatening lysosomal storage disorder.

"Receiving Fast Track designation is an important recognition of both the urgent need for new treatment options for MPS I and the groundbreaking potential of our engineered B cell platform," said Sean Ainsworth, Chief Executive Officer of Immusoft. "In light of our recent successful re-dosing of a patient, receiving Fast Track designation represents a paradigm shift in how genetic diseases can be treated, one that offers the potential for long-term, continuous therapeutic protein delivery that avoids many of the limitations of traditional gene therapy approaches."

Fast Track is a process designed to facilitate the development and expedite the review of new drugs and biologics intended to treat serious conditions with unmet medical needs. The designation underscores the potential of ISP-001 to transform treatment for patients living with MPS I and represents a significant regulatory milestone for Immusoft and the field of gene and cell therapy.

ISP-001 is the first ever clinical-stage engineered B cell investigational therapy that deploys a patient's own B cells to function as "living biofactories", which continuously produce and secrete potentially therapeutic proteins. ISP-001 is designed to secrete therapeutic levels of α-L-iduronidase (IDUA), the enzyme deficient in MPS I patients. By leveraging the natural biology of B cells, ISP-001 aims to overcome key challenges associated with current therapies, including the "sawtooth effect" (spike and trough enzyme levels) associated with frequent enzyme replacement therapy infusions, as well as mortality and safety concerns associated with stem cell transplants.

Early clinical data from Immusoft's ongoing Phase 1/2 trial of ISP-001 have demonstrated a favorable safety and tolerability profile, to date, including the ability to safely re-dose a patient, a milestone achievement for the field of cell and gene therapy. This first re-dosed patient has continued to show positive outcomes since their initial treatment, including pharmacodynamic, functional, and quality-of-life improvements. Beyond improvements in biomarkers of activity, the patient achieved a 239-meter (261-yard) improvement in the 6-minute walk test at one year following the first dose, and also reported meaningful reductions in pain.

Immusoft recently dosed the second patient in this clinical trial, who has also exhibited an excellent safety and tolerability profile to date. This patient received the mid dose specified for this trial, approximately three times the first patient's first dose. Initial pharmacodynamic results and functional improvements are encouraging. 

"The FDA's decision to grant Fast Track designation reflects the promise of our approach and the potential impact it could have on the lives of people with MPS I," said Paul Orchard, M.D., Professor of Pediatrics, Division of Blood and Marrow Transplant & Cellular Therapy at the University of Minnesota Medical School and Principal Investigator of the ISP-001 clinical trial. "If successful, this therapy could dramatically change how we treat this devastating disease and many others like it."

The trial is supported by an $8 million award from the California Institute for Regenerative Medicine (CIRM), which funds cell and gene therapy research and clinical trials in California.

About Immusoft

Immusoft of CA is a wholly owned subsidiary of Immusoft Corporation. Immusoft is a clinical-stage next-generation, advanced therapeutics company focused on developing novel therapies for rare diseases using sustained delivery of protein therapeutics from a patient's own cells. The company has developed a technology platform called Immune System Programming (ISP™), which modifies a patient's B cells and instructs the cells to produce gene-encoded medicines. The B cells that are reprogrammed using ISP become miniature protein therapeutic biofactories that are expected to persist for many years. For more information, visit www.immusoft.com.

Media Contact:
Susan Roberts
Roberts Communications
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SOURCE Roberts Communications