Immusoft Receives CIRM Grant to Advance Engineered B Cell Therapy ISP-001 for MPS I

Mar 30, 2026-

Immusoft, a clinical-stage biotechnology company developing engineered B cell therapies, has received a $15 million grant from the California Institute for Regenerative Medicine (CIRM) to support expanded clinical development of ISP-001, its lead investigational therapy for mucopolysaccharidosis type I (MPS I).

MPS I is a rare and life-threatening lysosomal storage disorder caused by mutations that prevent the body from producing sufficient alpha-L-iduronidase (IDUA), an enzyme required to break down glycosaminoglycans (GAGs). The resulting accumulation of these molecules leads to progressive organ damage, neurological decline, and early death, particularly in severe forms such as Hurler syndrome, where symptoms appear in infancy.

ISP-001 represents a novel approach in cell and gene therapy, using genetically engineered B cells derived from the patient to function as “living biofactories.” These modified cells continuously produce and secrete therapeutic proteins—in this case IDUA enzyme—with the goal of providing sustained enzyme replacement within the body.

Early clinical results from the company’s ongoing Phase 1/2 trial have shown a favorable safety and tolerability profile, along with encouraging pharmacodynamic and functional improvements. Notably, the study achieved a milestone in the field by demonstrating the ability to safely re-dose a patient, an important advance for cell and gene therapy platforms where repeat dosing is often difficult.

The first patient who received a second dose of ISP-001 continues to demonstrate positive pharmacodynamic signals and improvements in quality-of-life measures. A second patient, treated with a dose approximately three times higher than the initial dose used in the first patient, has also shown favorable safety results and encouraging early functional improvements.

Current treatments for MPS I, including enzyme replacement therapy and hematopoietic stem cell transplantation, have significant limitations. Enzyme replacement therapy requires frequent infusions and often results in fluctuating enzyme levels, while stem cell transplantation carries substantial safety risks and limited accessibility. By enabling continuous enzyme production within the body, engineered B cell therapies such as ISP-001 aim to overcome these challenges.

The CIRM CLIN2 funding program, which awarded the grant, supports clinical trials for regenerative medicine therapies addressing serious diseases with significant unmet medical needs. According to CIRM leadership, therapies like ISP-001 represent the type of transformative innovation the program was designed to accelerate.

ISP-001 has already received multiple regulatory designations from the U.S. Food and Drug Administration (FDA), including Orphan Drug, Rare Pediatric Disease, and Fast Track designations, reflecting the urgent need for new treatments in MPS I.

The therapy is currently being evaluated in a Phase 1 clinical trial (NCT05682144). With the support of CIRM funding, Immusoft plans to continue advancing the program and expand clinical development, including future studies in pediatric patients.