UPDATE 1-Inspire doubles treatment period in key trial

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July 29 (Reuters) - Inspire Pharmaceuticals Inc (ISPH.O) said the treatment period in a late-stage trial of its inhaled cystic fibrosis drug denufosol will be doubled to 48 weeks, with the main goal of the study being improved breathing in this time-frame.

The company also plans to now enroll about 450 patients in the so-called TIGER-2 trial, 100 more than it had planned for expected.

Inspire also set an upper limit for baseline forced expiratory volume (FEV) -- a measure of lung capacity -- for enrolled patients. The criteria is now set for an FEV greater than or equal to 75 percent and less than or equal to 110 percent predicted normal capacity.

The company said it expects most of the 62 patients currently enrolled in the trial to agree to the extended duration.

Early last month, Inspire's stock rose almost 35 percent after the company announced positive results from the first late-stage trial, TIGER-1.

Since then, the shares have shed all their gains, and closed at $3.85 on Nasdaq Monday. (Reporting by Varsha Tickoo in Bangalore; Editing by Anthony Kurian)