Washington, DC-based Vanda Pharmaceuticals Inc. (Nasdaq: VNDA) announced that the US FDA has granted Rare Pediatric Disease Designation (RPDD) to VCA-894A, an investigational antisense oligonucleotide (ASO) therapy targeting a cryptic splice site variant within the IGHMBP2 gene, for the treatment of Charcot-Marie-Tooth disease, axonal, type 2S (CMT2S). The designation was granted by the FDA’s Office of Orphan Products Development and Office of Pediatric Therapeutics.
The RPDD matters primarily for its downstream commercial implication: upon approval of a qualifying marketing application, Vanda may become eligible to receive a Priority Review Voucher (PRV) under the Rare Pediatric Disease Priority Review Voucher program. PRVs have recently traded at disclosed values of USD 150–205 million. Eligibility is not guaranteed and will be assessed at the time of any future marketing application review.
VCA-894A is a 2′-O-methoxyethyl (MOE) phosphorothioate oligonucleotide sodium salt. It functions by binding to an aberrant cryptic splice site within IGHMBP2 pre-mRNA, correcting the pathogenic splicing event that underlies CMT2S in the specific patient for whom it was designed. The MOE phosphorothioate backbone confers nuclease resistance and enhanced target binding affinity — chemical properties shared with approved ASO therapies delivered to the central nervous system.
CMT2S is an inherited axonal neuropathy caused by pathogenic variants in IGHMBP2, a gene encoding immunoglobulin mu-binding protein 2. Loss of functional IGHMBP2 leads to alpha-motor neuron degeneration and progressive peripheral nervous system deterioration, manifesting in early childhood as distal muscle weakness, sensory impairment, and loss of motor function. The FDA determined that CMT2S qualifies as a rare pediatric disease because its serious manifestations primarily affect individuals from birth through 18 years of age and the condition meets the statutory definition of a rare disease, with a global prevalence estimated at fewer than 1 in 1,000,000.
VCA-894A is being developed for a single patient first diagnosed at age five with a unique IGHMBP2 variant not documented in any other individual. The program represents an n-of-1 precision medicine approach, designed to correct a patient-specific genetic lesion rather than a shared population-level mutation.