In this episode of The CheckRare Brief, we discuss two recent FDA approvals for rare diseases, including Zanvastro for Alexander disease and Besremi for essential thrombocythemia (ET). We also examine a new gene therapy application for Huntington’s disease and what it could mean for patients with this devastating inherited disorder.
The FDA has approved Zanvastro, the first drug indicated to treat patients with Alexander disease, an extremely rare and progressive neurological disorder affecting approximately 1 to 3 people per million. The disease is caused by mutations in the GFAP gene that result in abnormal GFA protein accumulation in brain cells. Zanvastro is designed to reduce production of this abnormal protein. The approval was based on data from 49 patients, along with additional data from an open-label extension study. Ionis Pharmaceuticals also received a Rare Pediatric Disease Priority Review Voucher, which can provide priority review for a future FDA application and can have significant financial value.
The FDA also approved Besremi for adults with essential thrombocythemia (ET), a rare blood disorder in which the bone marrow produces too many platelets. This can increase the risk of blood clots and abnormal bleeding. Besremi is an interferon-based therapy that reduces abnormal platelet production and is already approved for polycythemia vera. Expanding an existing therapy into additional rare diseases is an increasingly common strategy in drug development, allowing companies to build on existing clinical and safety data while potentially reaching new patient populations.
Another important development involves Huntington’s disease, a devastating inherited neurological disorder caused by a mutation in the HTT gene. Symptoms typically emerge in adulthood and can include progressive movement problems, as well as cognitive, psychological, and behavioral changes. uniQure has submitted a Biologics License Application ( BLA), to the FDA for its gene therapy candidate. The submission follows extensive discussions between uniQure and the FDA, with the agency ultimately agreeing that existing three-year data could support a BLA under the accelerated-approval pathway. The application now moves into the formal FDA review process, making this an important development to watch for patients and families affected by Huntington’s disease.
Together, these developments highlight several important trends in rare disease drug development—from new approaches for extremely rare genetic disorders, to expanding existing therapies into additional indications, to the growing potential of gene therapy. As researchers continue to better understand the biology of rare diseases, these approaches could open new possibilities for patients who have historically had few treatment options.
References
FDA approved Zanvastro for Alexander disease
https://www.fda.gov/news-events/press-announcements/fda-approves-first-drug-treat-alexander-disease
FDA approved Besrimi for essential thrombocythemia
https://checkrare.com/fda-approves-besremi-for-treatment-of-adults-with-essential-thrombocythemia/
Uniqure submits BLA with the FDA for a gene therapy for Huntington’s disease
https://www.uniqure.com/investors-media/press-releases