On the verge of top-line data from its phase IIb trial with oral small-molecule CC chemokine receptor 4 (CCR4) antagonist zelnecirnon in atopic dermatitis (AD), due around the middle of this year, Rapt Therapeutics Inc. said the U.S. FDA has imposed a clinical hold on that study with the otherwise promising drug, also known as RPT-193, in AD as well as the phase IIa trial with the same compound in asthma.

A Japanese study has shown that targeting the chemokine receptor CCR4 using treatment with the monoclonal antibody mogamulizumab (Poteligeo, Kyowa, Amgen) depleted immune regulatory T cells and significantly improved survival in a canine model of advanced prostate cancer.

Rapt Therapeutics Inc. CEO Brian Wong said RPT-193 monotherapy in atopic dermatitis (AD) “looks really promising, but there’s still quite a bit to learn” about the small molecule, designed to inhibit the migration of Th2 cells into inflamed tissues by blocking CCR4. Investors saw enough to push the shares of South San Francisco-based Rapt up 115.5%, or $21.45, to close at $40.02, after trading as high as $41.99 during the day.