** Shares of drug developer Forte Biosciences FBRX.O rise 7% to $22.02 premarket

** Co says its experimental drug, FB102, showed a statistically significant benefit in an early-stage study in vitiligo, an autoimmune condition that causes patches of skin to lose color

** Says patients treated with FB102 showed a 29.6% average improvement in facial vitiligo at Week 24; benefit was seen by Day 64 and continued after treatment ended

** In patients with greater disease involvement, FB102 showed a 43.2% average improvement at Week 24, FBRX says

** Co says FB102 was generally well tolerated, with only mild to moderate side effects

** Data add to earlier positive findings in celiac disease, an autoimmune disorder triggered by gluten; results from an ongoing mid-stage celiac disease study are expected soon - FBRX

** As of last close, FBRX down 24.5% YTD