(Fixes typo in headlline)
ZURICH, July 10 (Reuters) - Shares in Cassiopea rose as much as 42 percent on Tuesday after the Swiss-listed dermatology company said its investigational medicine for acne had posted "very positive" results in two late-stage clinical trials.
The shares were up 36 percent at 0730 GMT in Zurich, boosting the market capitalisation to about 400 million Swiss francs ($403 million).
In a pair of studies with 1,440 patients, the company's Winlevi, an anti-androgen drug that works against hormones that can lead to the unsightly skin lesions, significantly reduced acne compared to a placebo.
No serious negative side effects were reported in the trials, Italy-based Cassiopea said.
"We are enthusiastic about these top-line results," Chief Executive Diana Harbort said in a statement.
"The U.S. (dermatology) market has not seen a new mechanism for acne since the 1980s."
Shares in Cosmo Pharmaceuticals, which owns 45 percent of Cassiopea, rose 2 percent.
While there are anti-androgen treatments including birth control pills -- such drugs are not suitable for men -- they must be taken orally and may have side effects.
Winlevi, which is being trialed on both men and women, is a small molecule that penetrates the skin to reach the androgen receptors of the sebaceous gland. Cassiopea aims to become the first company to win approval for a topical anti-androgen medicine that acts where needed, not on the whole body.
$1 = 0.9916 Swiss francs Reporting by John Miller; Editing by Michael Shields