The rare disease drug development sector is experiencing significant momentum, highlighted by discussions at the recent J.P. Morgan Healthcare conference and new regulatory efforts from the U.S. Food and Drug Administration (FDA).
This activity coincides with the 18th anniversary of Rare Disease Day on February 28, an event started by The Europe Organisation for Rare Diseases to advance research, improve diagnosis, and support patients.
Since its launch in 2008, Rare Disease Day has paralleled a shift in investor interest toward rare diseases, which has evolved into a multi-billion dollar market due to factors such as orphan drug incentives and advances in cell and gene therapies.
Industry analysts estimate that the global rare disease treatment market is currently valued between $220 billion and $240 billion. They project that annual growth could raise this figure to as much as $600 billion by the early-to-mid 2030s.
At JPM26, companies including Rocket Pharmaceuticals, REGENXBIO, and Kyverna Therapeutics identified 2026 as a pivotal year for rare disease drug development. Presentations emphasized increased investor focus on rare and chronic diseases.
The FDA has introduced several initiatives aimed at accelerating treatments for rare conditions. In November, it unveiled a plausible mechanism approval pathway intended to speed up access to therapies “for products where a randomized trial is not feasible.” This followed September’s release of the Rare Disease Evidence Principles framework designed to expedite approvals for therapies targeting ultrarare diseases—typically those affecting fewer than 1,000 people in the United States.
Sean Ainsworth, CEO of Immusoft—which is developing a cell and gene therapy (CGT) for mucopolysaccharidosis type II (MPS II)—commented: “I view these programs as a net positive for rare diseases; more specifically, cell and gene therapies for rare diseases in which the mechanism is genetically defined and well characterized.”
MPS II, also known as Hunter syndrome, results from a deficiency of the enzyme iduronate-2-sulfatase (IDS). The condition primarily affects children and leads to progressive symptoms across multiple organ systems along with reduced life expectancy. Current treatment relies on enzyme replacement therapy (ERT), which requires frequent infusions throughout life but may not deliver consistent benefits across all tissues.
REGENXBIO’s clemidsogene lanparvovec seeks to address MPS II by delivering a functional copy of the IDS gene. The FDA will decide on its approval by February 8 under the Prescription Drug User Fee Act timeline.
Immusoft’s investigational therapy ISP-002 uses engineered B cells as an alternative platform to ERT. According to Immusoft’s press release: “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.” The company further stated: “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.”
Ainsworth noted challenges associated with current ERT options: weekly infusions are burdensome for patients; furthermore, because ERTs have short half-lives in plasma—only two or three hours—tissue exposure remains minimal. He described ISP-002 instead as offering “24/7 therapeutic protein.”
He also explained that while many gene therapies use adeno-associated virus vectors that can trigger immune responses limiting future doses, using patients’ own B cells represents a nonviral approach that avoids this issue and allows repeated dosing if needed.
Immusoft recently announced it had received both FDA Rare Pediatric Disease Designation (January 26) and Orphan Drug Designation (December 15) for ISP-002.
