asapiprant (Torii Pharmaceutical)

Asapiprant (TO-203) is a small molecule antagonist of the prostaglandin D2 receptor 1 (DP1), currently under development by Torii Pharmaceutical for the treatment of house dust mite-induced asthma. Prostaglandin D2 (PGD2) is a major pro-inflammatory mediator released by mast cells during allergic reactions, and its interaction with the DP1 receptor is involved in the pathogenesis of allergic diseases, including asthma and allergic rhinitis. By selectively blocking the DP1 receptor, asapiprant aims to inhibit PGD2-mediated allergic inflammation and airway hyperresponsiveness. Originally discovered by Shionogi and licensed to Torii for development in Japan, TO-203 is being evaluated in a sublingual formulation, a delivery method that leverages Torii's established expertise in sublingual immunotherapy. Clinical development is currently in Phase I, focusing on safety and tolerability in patients sensitized to house dust mite allergens.