PALO ALTO, Calif. (TheStreet) -- An experimental topical lotion developed by Anacor Pharmaceuticals (ANAC) cleared eczema skin rash better than a placebo, according to results from two late-stage clinical trials announced Monday.

Anacor intends to seek U.S. approval for the lotion, known as crisaborole, in the first half of next year, based on the data collected from the studies.

Shares of Anacor were up 57% to $133.02 in Monday's premarket session, driven by the crisaborole results and takeover speculation. Anacor's stock had already jumped 162% this year in anticipation of the crisaborole study results, giving the company a market value of $3.7 billion before Monday's announcement.

Anacor conducted two phase III studies, each enrolling 750 patients with mild to moderate atopic dermatitis, better known as eczema. The patients were randomized two-to-one to receive crisaborole applied to the infected skin twice per day or a placebo control lotion.

After one month of treatment, 32.8% and 31.4% of patients responded to crisaborole in the two studies, compared to 25.4% and 18% of patients in the control group. The difference in responses in both studies was statistically significant, favoring crisaborole.

Response was defined by a physician's assessment that the eczema skin rash was clear or almost clear at day 29, with at least a two-grade improvement from baseline.

Atopic dermatitis is a chronic skin rash which causes inflammation and itching. Anacor says 18 million to 25 million people in the U.S. suffer from the disease, which is typically treated with generic steroid lotions. Crisaborole was not compared to steroid lotions directly in the phase III studies. 

Rivals Regeneron Pharmaceuticals (REGN - Get Report) and Celgene (CELG - Get Report) are also developing drugs to treat atopic dermatitis.

Anacor already has one approved drug, Kerydin, which is used to treat toenail fungus. A subsidiary of Novartis ( NVS - Get Report) sells Kerydin in the U.S., where it  competes against Valeant Pharmaceuticals' ( VRX) Jublia.

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