HD affects muscle coordination and leads to deterioration of mental abilities and physical control.
IONIS-HTT Rx, which is currently in phase 1/2a study, is an antisense drug designed to reduce the production of the huntington (HTT) protein, the genetic cause of HD.
The benefits of orphan drug designation include a seven-year period of market exclusivity for the indication after approval and tax credits associated to clinical trial expenses.
It will be exempted from the FDA-user fee, and the regulator will assist in clinical study design.
The European Medicines Agency has also granted orphan drug designation to IONIS-HTT Rx to treat patients with HD.
Ionis Pharmaceuticals senior vice president of research Frank Bennett said: "Although the toxic protein produced from the huntingtin (HTT) gene in HD patients has been a target of interest for many years, IONIS-HTT Rx is the first therapy to enter clinical development that is designed to treat the underlying cause of this fatal disease.
"The granting of Orphan Drug Designation in both the US and Europe highlights the significant need for a drug that could transform the treatment of HD."
Ionis is already collaborating with Roche to develop antisense drugs to treat HD.
Roche has so far made $52m upfront and milestone payments to Ionis. The partnership also includes additional milestone payments as IONIS-HTT Rx progresses in development, as well as royalties on sales upon commercialization.
Roche has the option to license IONIS-HTT Rx from Ionis after completing the phase 1/2a trial.
Image: Ionis said IONIS-HTT Rx id the first therapy designed to directly target the cause of HD. Photo: courtesy of Ionis Pharmaceuticals.