Ascletis Pharma (HKG:1672) said its oral small-molecule IL-17A inhibitor ASC50 showed positive results in a 28-day proof-of-concept clinical trial in the U.S. for patients with mild-to-moderate plaque psoriasis, according to a Tuesday filing with the Hong Kong bourse.

The once-daily 200 mg treatment achieved a 48.9% placebo-adjusted reduction in psoriasis area and severity index, or PASI, score after 28 days.

The reduction increased to 60.7% six days after the final dose and 65.9% 15 days after the final dose, the filing said.

The treatment was safe and well tolerated, with all adverse events reported as mild and transient.

Shares of the pharmaceutical firm were down nearly 2% in Tuesday morning trade.