Vanda Pharmaceuticals Inc. (Vanda) (NASDAQ:VNDA) today announced that Japan's Ministry of Health, Labour and Welfare (MHLW) has granted orphan drug designation to imsidolimab, a high‑affinity humanized immunoglobulin G4 (IgG4) monoclonal antibody, for the treatment of generalized pustular psoriasis (GPP).

Imsidolimab inhibits interleukin‑36 (IL‑36) receptor signaling, addressing the deficiency in the endogenous IL‑36 receptor antagonist regulator that is commonly observed in patients with GPP.1

The MHLW grants orphan drug designation to medicines intended to treat rare diseases with significant unmet medical need. In Japan, approximately 2,200 people have been diagnosed with GPP.2  IL36RN genetic variants—which are associated with dysregulation of the IL‑36 pathway—are enriched in the Japanese population, including well‑characterized founder families in Hokkaido.3

In Japan, orphan drug designation provides development incentives, including subsidies for research and development costs, as well as the potential for up to 10 years of market exclusivity following approval.

This designation follows similar regulatory recognition in the United States and underscores the global interest in the potential of imsidolimab to address the significant unmet medical needs of patients with GPP, a rare and severe inflammatory skin disease associated with systemic complications and increased mortality.4