In a Major Breakthrough for Cell and Gene Therapy, Immusoft Has Re-dosed a Patient with ISP-001 in Its Lead Program for MPS I

The re-dose of ISP-001 has been well-tolerated, to date, and Immusoft continues to observe positive results

SAN FRANCISCO, Oct. 7, 2025 /PRNewswire/ -- Immusoft of CA, a clinical stage, engineered B cell company, today announced a historic achievement: the safe and well-tolerated re-dosing of a patient with a gene modified therapeutic product candidate. The patient in Immusoft's first-in-human clinical study has now received two doses – separated by 18 months¹ – of ISP-001 to treat mucopolysaccharidosis type I (MPS I), with an excellent safety and tolerability profile, to date. Moreover, Immusoft continues to observe positive results in this ongoing clinical trial.

This is a momentous event for Immusoft and for the broader gene therapy community, which has long sought the ability to re-dose systemically to express therapeutic proteins at high levels. "The vast majority of gene therapies are not re-dosable with current technologies, for a variety of reasons, which is what initially drew my attention to Immusoft's engineered B cell approach." stated Sean Ainsworth, CEO of Immusoft. "There have long been questions about lifelong durability of one-and-done gene therapies and the ability to safely re-dose has been a much sought after feature in advanced therapeutics. In more recent times, we are seeing that it's difficult for many of these approaches to be safely dosed a first time, let alone a second time."

Based on generally accepted knowledge about B cell biology, as well as the clinical data Immusoft has generated to date, engineered B cells do not elicit the dangerous immune response associated with systemically delivered viral gene therapeutics. They therefore not only avoid the burdensome immunosuppression regimens associated with viral approaches, but also offer the ability to re-dose without triggering an immune response to the drug product. B cells also naturally migrate to and engraft in the bone marrow without the need for a toxic chemotherapy regimen, unlike gene-modified stem cell approaches. This chemotherapy regimen typically requires a several-week hospital stay, is associated with substantial morbidity, and sometimes mortality – all of which make re-treatment impractical and unsafe. By avoiding chemotherapy, engineered B cells provide a safer, better tolerated delivery that accommodates re-dosing.

When engineered B cells engraft in bone marrow, they act as living biofactories, continuously secreting therapeutic proteins into the circulation. The ability to safely re-dose provides the opportunity to extend potential treatment effects, enabling around-the-clock therapeutic protein delivery possibly for the life of the patient. 

The first patient treated with ISP-001 initially received the lowest dose specified for this trial and saw durable benefits beyond a year. They were subsequently re-dosed with double the initial dose with the objective of titrating to effect. This first patient has continued to show positive outcomes since their initial treatment, including pharmacodynamic, functional, and quality-of-life improvements.

Dr. Paul Orchard, 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, commented: "The ability to re-dose is something that the gene therapy field has been striving toward for decades. The results we've seen so far in the Immusoft clinical trial are very encouraging, particularly given the absence of myeloablation or immunosuppression. The engineered B cell approach, if successful, could dramatically change how we treat many genetic diseases like MPS I."

Immusoft also recently dosed the second patient in this clinical trial, who has also exhibited a very clean 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 are encouraging. 

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 a 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
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SOURCE Immusoft