Dec 8 (Reuters) - Horizon Pharma Plc said its drug, Actimmune, failed the main goal in a late-stage study involving patients with Friedreich's ataxia (FA), a rare, degenerative neuromuscular disorder that has no approved treatments.

The drug failed to demonstrate a statistically significant benefit over a placebo on an FA rating scale after 26 weeks, the Ireland-based company said.

Actimmune is already approved by the U.S. Food and Drug Administration for use in two rare, genetic conditions - chronic granulomatous disease and severe, malignant osteopetrosis.

Trading of the company's shares were halted before the opening bell on Thursday.

(Reporting by Natalie Grover in Bengaluru; Editing by Saumyadeb Chakrabarty)