Immusoft Receives FDA Rare Pediatric Disease Designation for ISP-002 to treat Mucopolysaccharidosis Type II

Designation recognizes ISP-002, an engineered B cell therapy designed for sustained enzyme delivery

SAN FRANCISCO, Jan. 26, 2026 /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 Rare Pediatric Disease (RPD) designation to ISP-002, the company's investigational therapy for the treatment of mucopolysaccharidosis type II (MPS II), also known as Hunter syndrome.

The FDA grants RPD designation for serious or life-threatening diseases that primarily affect children 18 years old or younger and affect fewer than 200,000 people nationwide. RPD designation allows recipient companies, upon approval of their designated treatment, to be eligible for a Priority Review Voucher (PRV¹), which may be used for priority review of a future submission of a New Drug Application or Biologics License Application. Priority review can reduce FDA review time by several months. Priority review vouchers may be sold to a third party and recent prices paid for PRVs have been as much as $200 million.

MPS II is a rare, inherited lysosomal storage disorder caused by a deficiency of the enzyme iduronate-2-sulfatase (IDS), which leads to the accumulation of glycosaminoglycans in tissues and organs throughout the body. The disease primarily affects pediatric patients and is associated with progressive, multisystem involvement, including neurocognitive impairment, cardiopulmonary complications, skeletal abnormalities, and reduced life expectancy. The current standard of care is enzyme replacement therapy, which requires frequent lifelong infusions and may not achieve consistent enzyme exposure across all affected tissues.

ISP-002 is designed to deploy a patient's own B cells as long-lived protein biofactories capable of continuously producing and secreting therapeutic levels of IDS. By leveraging the natural biology of B cells and their ability to engraft in the bone marrow, ISP-002 is intended to enable sustained systemic enzyme exposure following a single treatment. This approach aims to address limitations associated with existing therapies, including treatment burden, fluctuating enzyme levels, and challenges associated with durable tissue penetration.

Immusoft's proprietary platform modifies autologous B cells ex vivo to produce gene-encoded medicines prior to reinfusion into the patient. Once administered, the engineered B cells are designed to persist for extended periods of time and provide continuous protein expression. The company believes this strategy represents a differentiated therapeutic modality for rare diseases that require long-term or lifelong protein replacement.

"The FDA's Rare Pediatric Disease designation for ISP-002 recognizes the serious unmet medical need in pediatric patients with MPS II and underscores the potential of Immusoft's platform as a novel therapeutic approach," said Sean Ainsworth, Chief Executive Officer of Immusoft. "This designation supports our continued efforts to advance engineered B cell therapies designed to deliver durable protein expression while maintaining a favorable safety and tolerability profile."

Preclinical development of Immusoft's engineered B cell platform was supported in part by funding from the California Institute for Regenerative Medicine (CIRM), which invests in regenerative medicine research to accelerate the development of transformative therapies for patients with unmet medical needs.

"This designation will enable Immunosoft to move more quickly to develop their engineered B cell platform in both MPS I and II and help those patients who are living with this debilitating disease," said Lisa Kadyk, PhD, CIRM Fellow, Clinical Development at the California Institute for Regenerative Medicine. "Benefiting patients with no other options is the core mission for all of CIRM's funding programs."

ISP-002 builds on Immusoft's growing pipeline of engineered B cell therapies using its Immune System Programming (ISP™) platform. The platform is also being evaluated clinically in ISP-001, the company's lead investigational therapy for mucopolysaccharidosis type I (MPS I), which has also received FDA Rare Pediatric Disease (RPD) designation. ISP-001 has demonstrated a favorable safety and tolerability profile, along with early evidence of pharmacodynamic activity. Successful re-dosing further underscores its progress, marking an important milestone for the cell and gene therapy field.

Together, these programs reflect Immusoft's broader strategy to establish engineered B cells as a next-generation therapeutic modality for rare genetic and metabolic diseases requiring sustained protein delivery.

Immusoft continues to advance its ISP™ platform with the goal of expanding its applicability across multiple indications where durable systemic protein expression may provide meaningful clinical benefit. The company remains focused on generating clinical data to further characterize the safety, tolerability, and potential therapeutic impact of engineered B cell therapies.

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.

About the California Institute for Regenerative Medicine (CIRM)

CIRM was created by the people of California to fund stem cell and gene therapy research with the goal of accelerating treatments for patients with unmet medical needs. With $8.5 billion in funding allocated through both Proposition 71 in 2004 and Proposition 14 in 2020, CIRM supports stem cell and gene therapy discoveries from inception through clinical trials, trains a workforce in California to fill jobs in the state's thriving biotech and biomedical research industry, and creates infrastructure to make clinical trials accessible for people throughout California. All of CIRM's research, workforce development, and infrastructure programs are designed to benefit the people of California, whose vision created the agency. For more information, visit www.cirm.ca.gov.

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¹ The Rare Pediatric Disease (RPD) Priority Review Voucher program is currently under review in Congress. Continuation or modification of the program remains subject to pending legislative action, and future availability cannot be guaranteed.

SOURCE Immusoft