UPDATE 1-Dusa to stop developing acne treatment; shares fall

(Recasts; adds details, stock movement)

Oct 22 (Reuters) - Dusa Pharmaceuticals DUSA.O will stop developing its Levulan Photodynamic Therapy to treat moderate to severe acne, after the proposed treatment combination failed to show statistically significant results in a mid-stage trial.

Shares of the company fell 27 percent to $1.07 in trading after the bell. They closed at $1.46 Wednesday on Nasdaq.

The trial was comparing the safety and efficacy of Dusa's Levulan solution in combination with its BLU-U lighting-based treatment against a group receiving only the latter.

The results showed no statistically significant difference between the two groups, but demonstrated that both treatments were safe and well tolerated with no serious adverse events.

The treatment combination, called Levulan PDT, is Dusa's main product, and is approved for the treatment of precancerous skin lesions of the face or scalp called actinic keratoses.

It is also used "off-label" in photodynamic therapy to make sun-damaged skin look better. (Reporting by Esha Dey in Bangalore; Editing by Pratish Narayanan)