The Food and Drug Administration has granted Orphan Drug Designation to sovleplenib for primary immune thrombocytopenia, Hutchmed announced on October 29 in a release furnished to the SEC. Sovleplenib is a selective, once daily oral inhibitor of spleen tyrosine kinase, or Syk, a signaling component in the immune pathway that destroys platelets in the disease.
The designation is an incentives package, not an approval. Orphan status covers diseases affecting fewer than 200,000 people in the United States, and if the drug is later approved for the designated indication it brings seven years of United States market exclusivity, tax credits for qualified clinical trials, prescription drug user fee waivers and specialized regulatory guidance during development. Hutchmed retains all worldwide rights to the drug.
The more advanced program is in China. New Drug Applications for sovleplenib in primary immune thrombocytopenia and in warm antibody autoimmune hemolytic anemia are under review by China’s National Medical Products Administration, supported by the pivotal ESLIM-01 and ESLIM-02 trials respectively. Sovleplenib sits on the immunology side of a portfolio better known for its oncology drugs, which makes the United States designation a broadening of the company’s regulatory footprint rather than an extension of an existing approval.
The clinical need is the chronicity of the disease. Primary immune thrombocytopenia causes immune destruction of platelets and reduced platelet production, raising bleeding and bruising risk; the company cites adult incidence of 3.3 per 100,000 per year and prevalence of 9.5 per 100,000, with fatigue reported in up to 39 percent of adults. Existing treatments with different mechanisms exist, but many patients develop resistance and relapse, which is the population a Syk inhibitor is aimed at. What the announcement does not contain is a United States trial plan or timeline, and that, rather than the designation itself, is the next thing to watch.