Updated with new information, stock price/

SAN RAFAEL, Calif. ( TheStreet) -- BioMarin Pharmaceuticals ( BMRN - Get Report) said Monday that patients with a rare genetic disorder known Morquio A Syndrome were able to walk further following treatment with the company's experimental drug GALNS, satisfying the main goal of a late-stage study.

Based on the positive results from the Morquio A study, BioMarin plans to seek regulatory approval for GALNS in the first quarter of 2013.

BioMarin shares opened for regular trading Monday up 25% to $46.80. GALNS is seen as the most important drug in the BioMarin's pipeline, with the potential to double the company's revenue.

"We view the result as clearly positive for BioMarin and see it as a best-case outcome," writes JP Morgan analyst Cory Kasimov in a note to clients. Kasimov expects BioMarin shares to move higher not only because of GALNS' sales potential but because generalist investors will likely start buying BioMarin given the orphan drug experience with the Genzyme unit of Sanofi ( SNY - Get Report)and Alexion Pharmaceuticals ( ALXN - Get Report).

In patients with Morquio syndrome, also known as MPS IV, a missing enzyme prevents the breakdown of keratan sulftate in cells, leading to progressive skeletal and spinal cord malformation. GALNS is a replacement enzyme that reduces the harmful levels of keratin sulfate.

Morquio syndrome is a rare disease, with an estimated prevalence of between 1,000 and 1,500 patients in the U.S., Europe and Japan and between 1,500 and 2,000 patients in the rest of the world, BioMarin estimates.

In the phase III study, patients treated with a weekly infusion of GALNS were able to walk an average of 22.5 meters further in six minutes compared to patients treated with a placebo. The benefit in walking distance, the study's primary endpoint, was statistically significant.

BioMarin also tested an every other week dose of GALNS but walking distance was not improved compared to placebo.

Treatment with GALNS every week also demonstrated improved trends in three-minute stair climb and a statistically significant 41% reduction in keratan sulfite levels in the urine. Lung function in patients was also improved.

GALNS was shown to be generally well tolerated with adverse events similar to what's observed in other enzyme replacement therapies, BioMarin said.

-- Reported by Adam Feuerstein in Boston.

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