2026 is shaping up to be a pivotal year for rare disease drugmakers, with key approvals, filings and readouts lined up for this year.
Rare diseases took center stage on the third day of this year’s J.P. Morgan Healthcare conference, with some of the leaders in the space outlining their strategic and clinical roadmaps for 2026.
Rocket To Resume Danon Trial in H1 After FDA Pause
During a company presentation on Wednesday, Rocket Pharmaceuticals CEO Gaurav Shah said 2026 will be a “year of execution, year of excitement” for the New Jersey biotech.
Rocket had a difficult 2025. In October, the company pulled its biologics license application for gene therapy mozafancogene autotemcel, which it was proposing for Fanconi Anemia, citing “business and strategic considerations” rather than safety or efficacy reasons. Months earlier, Rocket had launched a reorganization initiative to cut costs. And in May, the FDA placed a pivotal Phase II trial of Rocket’s gene therapy RP-A501 on hold after a patient death.
Rocket aims to resume dosing patients in its Danon disease program in the first half of this year. At JPM, Shah said RP-A501 has shown “strong durability,” including in two patients who have been followed for more than five years. “All our patients in the Phase I trial, adults as well as pediatric, continue to flourish beyond the age where they would typically demonstrate heart failure,” he added.
Rocket now plans to dose three patients in the first half of 2026, after which it will confer with the FDA to see how it should conduct the rest of the study. “We have no indication that there will be any change, but there may be additional patients that are added,” Shah said.
Beyond Danon, Rocket is looking ahead to an FDA decision on its gene therapy Kresladi by the end of March for severe leukocyte adhesion deficiency-I, an ultrarare disease. The therapy was rejected in June 2024 due to manufacturing concerns. “We hope to move from a late-stage clinical stage company to a commercial-stage gene therapy company,” Shah said on Wednesday.
With Hunter Syndrome Decision Looming, REGENXBIO Anticipates ‘Pivotal’ Year Ahead
Also playing in the rare disease space is REGENXBIO, which on Wednesday affirmed that its Hunter syndrome gene therapy clemidsogene lanparvovec is undergoing regulatory review, with a target action date of February 8.
“This is a really pivotal year for us,” CEO Curran Simpson said during a company presentation at JPM, referring both to the potential Hunter syndrome approval and forthcoming readouts from late-stage, pivotal programs. “No pun intended,” he added.
REGENXBIO’s clemidsogene lanparvovec works by delivering a functional copy of the IDS gene, which is mutated in Hunter syndrome. The FDA accepted clemidsogene lanparvovec’s approval application in May last year, setting a target decision date of Nov. 9. In August, however, the regulator announced a three-month delay to the review process.
Simpson declined to say much about the Hunter program on Wednesday, citing the ongoing review. He noted only that “I don’t think there has been a new treatment in Hunter for 20 years.”
Also during the presentation, Simpson said REGENXBIO is building toward a Phase III readout for its Duchenne muscular dystrophy program RGX-202 in the first half of this year, while data from its wet age-related macular degeneration asset ABBV-RGX-314, in partnership with AbbVie, will come out late this year.
With these pivotal milestones on the horizon, “we’re gearing up . . . for commercial readiness,” Simpson said.
Replimune Rallies Behind RP1, Plots Expansion Plans
In July last year, the FDA delivered a surprise rejection of Replimune’s oncolytic immunotherapy RP1, which the biotech had been proposing for advanced melanoma. Weeks later, researchers and cancer experts, some of whom participated in designing the company’s late-stage IGNYTE trial, penned an open letter to the regulator, responding to issues it cited.
At JPM on Wednesday, Replimune made a similar effort, with CEO Sushil Patel detailing the clinical benefits of the asset in skin cancer and beyond.
“We’ve seen durable responses, systemic responses,” Patel said, noting that the company has so far dosed more than 1,000 patients and consulted “many” healthcare providers who have experience with RP1. “Physicians tell us that this is something that they really want for their patients, given how difficult these patients are to treat,” he added.
In October last year, Replimune refiled its drug application for RP1, with a target action date of April 10. “We’re ready to launch,” Patel said on Wednesday, adding that the company already has a commercial supply of RP1 prepared to roll out.
Replimune is also working to push RP1 beyond skin cancer. The company has looked at the feasibility of injecting RP1 into deeper tissues, such as the liver and the lung, with positive initial results. “What’s encouraging is that we see at least a similar response rate and actually numerically higher for the [deep] lesions,” Patel said.
Kyverna to Cement Leadership in Immune-Directed CAR T Space
“We want to deliver the first autoimmune CAR T in the neuroinflammation space,” Kyverna Therapeutics’ CEO Warner Biddle said during a JPM presentation on Wednesday. To get there, the company is speeding up its stiff-person syndrome (SPS) program.
Affecting fewer than 5,000 patients in the U.S., SPS is a rare neurological and autoimmune disease where antibodies attack cells in the brain and central nervous system. Symptoms include painful spasms and erratic muscle stiffening. Kyverna is advancing mivocabtagene autoleucel for this disease, targeting the CD19 protein on B cells and CD28 on T cells. Through this mechanism, miv-cel, as the asset is also known by, depletes the auto-reactive immune cells.
“We’re the only CAR T company in the autoimmune space with a fully humanized CD19, CD28 co-stimulatory domain with the potential for differentiated safety and differentiated efficacy,” Biddle said. Kyverna is running a pivotal Phase II study of miv-cel in SPS, which currently is 40% enrolled, he added. The biotech plans to file for approval this year.
Last month, Kyverna released data from this pivotal program, touting a 46% median improvement in a key measure of mobility. This effect “exceeded our expectations,” William Blair said at the time.
Beyond SPS, Kyverna is also developing miv-cel for myasthenia gravis and lupus nephritis, for which Phase II and Phase I data are expected this year, Biddle said on Wednesday.
