Shares of biotech Athenex, Inc. rose 3.8% in premarket trade Monday after the company announced that two Phase 3 studies of KX2-391, an ointment for the treatment of actinic keratosis, had met their primary endpoints. Actinic keratosis is a skin condition caused by exposure to the sun's ultraviolet rays, resulting in patches of thick, scaly skin. Left untreated, the lesions can progress to skin cancer. In one study of 351 patients, 44% of patients receiving KX2-391 cleared their actinic keratosis lesions after 57 days, compared with 5% of those in the control group. In the second study, also of 351 patients, 54% of patients getting the treatment cleared their lesions, compared with 13% of patients in the control group. Side effects were mild to moderate, the company said, and were usually local skin reactions causing itchiness or pain. Shares of Athenex have fallen 16.3% in the year to date, while the S&P 500 has gained 4.2%.