Immusoft Secures FDA Orphan Drug Designation for ISP-002 in MPS II, a Progressive Lysosomal Storage Disease

Orphan Drug Designation for MPS II builds on Immusoft's clinical progress in MPS I and supports expansion of its engineered B cell platform across multiple indications

SAN FRANCISCO, Dec. 15, 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 Orphan Drug Designation to ISP-002, the Company's investigational engineered B cell therapy for the treatment of mucopolysaccharidosis type II (MPS II), also known as Hunter syndrome, a rare and life-threatening lysosomal storage disorder.

MPS II is caused by a deficiency of the enzyme iduronate-2-sulfatase (IDS), which leads to the progressive accumulation of glycosaminoglycans throughout the body. The disease results in multi-system pathology, including skeletal abnormalities, cardiopulmonary complications, and reduced life expectancy. While enzyme replacement therapies are available, they require lifelong, frequent infusions and patients continue to face significant unmet needs related to treatment burden, durability of enzyme exposure, and long-term disease control.

ISP-002 leverages Immusoft's proprietary engineered B cell platform, which programs a patient's own B cells to continuously produce therapeutic enzymes inside the body. By enabling sustained enzyme production, the approach has the potential to be a paradigm shift in the treatment of genetic diseases, while addressing key limitations associated with approved therapeutic approaches and investigational gene therapies.

"Orphan Drug Designation for ISP-002 is an important milestone for our MPS II program and further validates the potential of our engineered B cell platform," said Sean Ainsworth, Chief Executive Officer of Immusoft. "This designation underscores our commitment to developing durable, redosable therapies that address the long-term needs of patients and families living with rare genetic diseases."

Immusoft's clinical progress in mucopolysaccharidosis type I (MPS I) has provided important validation of its engineered B cell platform. ISP-001, the Company's lead investigational therapy, is the first engineered B cell therapy to be tested in humans and is currently being studied in an ongoing Phase 1/2 clinical trial. Early clinical experience has demonstrated a favorable safety and tolerability profile to date, including successful re-dosing without lymphodepletion, immunosuppression, or any pre-conditioning, supporting further development of the platform and its expansion into additional indications.

"The clinical progress achieved in MPS I provides a strong foundation for advancing this approach into MPS II," said Paul Harmatz, MD, a leading MPS clinician and clinical investigator on the ISP-001 trial. "A therapy capable of sustained endogenous enzyme production has the potential to meaningfully impact disease burden and could represent an important advance for patients with Hunter syndrome."

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.

"CIRM is proud to have supported the early development of Immusoft's engineered B cell platform in both MPS I and II," said Lisa Kadyk, PhD, CIRM Fellow, Clinical Development at the California Institute for Regenerative Medicine. "Innovative approaches like this have the potential to change how rare genetic diseases are treated, and we are encouraged by Immusoft's continued progress toward the clinic."

With Orphan Drug Designation secured, Immusoft plans to continue advancing ISP-002 toward clinical development while expanding its engineered B cell platform across additional lysosomal storage disorders and other indications.

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.

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SOURCE Immusoft