FDA grants rare pediatric disease designation to VCA-894A for Charcot-Marie-Tooth disease

The FDA has granted rare pediatric disease designation to VCA-894A, an investigational antisense oligonucleotide being developed by Vanda Pharmaceuticals for Charcot-Marie-Tooth disease type 2S (CMT2S), a rare inherited axonal neuropathy with pediatric-onset manifestations, according to a company announcement.¹

“CMT2S is a devastating inherited neuropathy for which patients and families have limited treatment options,” Mihael H. Polymeropoulos, MD, president, chief executive officer, and chairman of Vanda, said in the announcement.¹ The designation does not indicate that the therapy has been shown to be safe or effective, but it may support continued development in a condition with few disease-directed options.

CMT2S is a very rare subtype of Charcot-Marie-Tooth disease associated with progressive sensory and motor impairment. Vanda stated that the FDA determined CMT2S meets the statutory definition of a rare pediatric disease because it is serious or life-threatening, rare, and has manifestations that primarily affect individuals from birth through 18 years of age.¹ Orphanet lists the estimated prevalence of CMT2S as less than 1 in 1,000,000 worldwide.²

VCA-894A is described by the company as a 2'-O-methoxyethyl phosphorothioate oligonucleotide sodium salt. The investigational therapy is designed to target a cryptic splice site variant within IGHMBP2, which Vanda stated is causative for the patient-specific form of CMT2S under development.¹ A 2025 publication described the rationale for a potential antisense oligonucleotide–based personalized approach for CMT2S, but the company announcement did not report clinical efficacy or safety outcomes from a completed trial.³

The rare pediatric disease designation was granted by the FDA’s Office of Orphan Products Development and Office of Pediatric Therapeutics. Under the FDA Rare Pediatric Disease Priority Review Voucher program, a sponsor may be eligible for a priority review voucher if a future marketing application for a qualifying product is approved and statutory requirements are met.¹ Eligibility is determined at the time of review and approval, not at the time of designation.

Clinically, CMT disorders are among the most common inherited peripheral neuropathies, although individual genetic subtypes can be extremely rare. Typical manifestations across CMT include slowly progressive distal weakness, sensory loss, foot deformities, gait impairment, and variable disability. Management is generally supportive and may include physical and occupational therapy, ankle-foot orthoses, pain management, orthopedic evaluation, and genetic counseling.⁴ For ultrarare subtypes such as CMT2S, the evidence base is limited, and treatment decisions are often individualized.

The development approach for VCA-894A reflects a broader movement toward genotype-specific and, in some cases, patient-specific therapeutics for rare neurologic disease. Antisense oligonucleotides can be designed to modulate RNA processing or expression, but translation from molecular rationale to clinical benefit requires careful assessment of dose, biodistribution, durability, and toxicity. In pediatric neuromuscular disease, functional outcomes such as ambulation, motor milestones, respiratory status, and quality of life are likely to be clinically meaningful, but no such outcome data were included in the announcement.

Important limitations remain. Vanda stated that the therapeutic target is a unique variant not yet observed in any other patient, which may constrain generalizability even within CMT2S.¹ The announcement did not identify an active clinical trial, study phase, dosing strategy, route of administration, patient age, follow-up duration, biomarker data, or adverse events. As a result, the designation should be interpreted as a regulatory development milestone rather than evidence of therapeutic efficacy.

Next steps will depend on the FDA development pathway, including whether Vanda advances VCA-894A through an individualized investigational approach or a broader clinical program. For clinicians caring for children with suspected inherited neuropathy, the update underscores the increasing importance of molecular diagnosis, variant interpretation, and referral to centers with expertise in pediatric neuromuscular disease and clinical trial evaluation.

References

1. Vanda Pharmaceuticals announces FDA rare pediatric disease designation for investigational therapy for Charcot-Marie-Tooth disease type 2S. PRNewswire. July 7, 2026. Accessed July 9, 2026. https://www.prnewswire.com/news-releases/vanda-pharmaceuticals-announces-fda-rare-pediatric-disease-designation-for-investigational-therapy-for-charcot-marie-tooth-disease-type-2s-302819555.html

2. Orphanet. Charcot-Marie-Tooth disease type 2S. 2025. Accessed July 9, 2026. https://www.orpha.net/en/disease/detail/443073

3. Smieszek S, et al. Potential ASO-based personalized treatment for Charcot-Marie-Tooth disease type 2S. Mol Ther Nucleic Acids. 2025;36:102479.

4. Pareyson D, Marchesi C. Diagnosis, natural history, and management of Charcot-Marie-Tooth disease. Lancet Neurol. 2009;8(7):654-667.