An inhaled formulation of levodopa from Acorda Therapeutics (ACOR - Get Report) improved the motor function of Parkinson's disease patients during so-called "off" periods when their symptoms re-emerge, according to results from a late-stage clinical trial announced by the company on Thursday.

Acorda intends to file for U.S. marketing approval for the drug, CVT-301, in the second quarter, pending results from two long-term safety studies. A European regulatory filing will be submitted by the end of the year, the company said.

Acorda shares were up 12% to $23 in Thursday premarket trading. The stock closed Wednesday at $20.40.

CVT-301 is dry powder formulation of levodopa packed into an inhaler and designed to deliver a faster-acting dose of the standard Parkinson's medicine through the lungs rather than conventional levodopa pills, which must first travel through the gastrointestinal tract.

Acorda is pursuing approval of CVT-301 as a treatment for Parkinson's patients experiencing muscle stiffness and tremors -- the classic motor symptoms of the neurodegenerative disease -- during the "off" periods when carbidopa/levodopa pills stop working.

The company acquired CVT-301 through the purchase of Civitas Therapeutics in 2014. Acorda believes the drug could deliver $500 million in U.S. sales if approved.

The phase III study compared 12 weeks of treatment with two doses of CVT-301 or a placebo in 339 Parkinson's patients on a stable dose of oral carbidopa/levodopa. Parkinson's patients treated with the high dose of CVT-301 showed a 9.83-point improvement in their Unified Parkinson's Disease Rating Scale-Part 3 (UPDRS III) score, which measures motor impairment. The placebo patients had an UPDRS III score improvement of 5.91 points. The benefit favoring CVT-301 was statistically significant, achieving the primary endpoint of the study, Acorda said.

The effect size of CVT-301 relative to placebo reported in the phase III study Thursday was smaller than what was seen in the prior phase II study.

Acorda did not provide results from the lower dose of CVT-301, nor did the company say how the drug performed on secondary efficacy endpoints.

Fifteen percent of patients treated with CVT-301 reported cough as the most prevalent side effect in the study. Acorda said the cough was generally mild but caused discontinuation from the study in three patients. Six percent of patients using the high dose of CVT-301 experienced upper respiratory tract infections.

Two safety studies examining use of CVT-301 over 12 months are still ongoing.

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