Sobi Pharma North America announced on December 12th (Eastern Time) that the U.S. Food and Drug Administration (FDA) has accepted its supplemental New Drug Application (sNDA) for avatrombopag for the treatment of thrombocytopenia in children aged 1 year and older with persistent or chronic immune thrombocytopenic purpura (ITP) who have not responded adequately to prior treatment. The FDA has set a target action date of July 24, 2025, for the Prescription Drug User Fee Act (PDUFA).
In addition, the company has also accepted the New Drug Application (NDA) for Avatrombopag oral suspension. This is a capsule formulation containing granules that can be sprinkled onto soft foods or liquids before administration.
Immune thrombocytopenic purpura (ITP) is an autoimmune disease characterized by a low platelet count, leading to an increased risk of bleeding. Symptoms can vary widely and include bruising, small spots of skin indicating minor bleeding, bleeding gums or nose, hematuria/melena, and weakness/fatigue. When symptoms persist for more than 12 months, the disease is considered chronic. In the long term, primary chronic ITP is associated with an increased risk of infection, bleeding events requiring hospitalization, hematologic malignancies, and mortality. There is currently no cure, and patients with chronic ITP often relapse after various treatments and still require treatment to reduce the risk of clinically significant bleeding.
Avatrombopag is an orally administered, bioavailable small molecule thrombopoietin receptor agonist (TPO-RA) that stimulates the proliferation and differentiation of bone marrow progenitor cells into megakaryocytes, thereby increasing platelet production. Avatrombopag does not compete with TPO for binding to the TPO receptor. Previously, this drug was approved under the brand name Doptelet for the treatment of thrombocytopenia in adult patients with chronic liver disease scheduled for surgery and in adult patients with chronic ITP who have had an inadequate response to previous treatment.
The sNDA submission included results from the randomized, double-blind, placebo-controlled phase 3b AVA-PED-301 study (ClinicalTrials.gov identifier: NCT04516967), which evaluated the efficacy and safety of avatrombopag in 75 pediatric patients aged 1 to 18 years with ITP for at least 6 months.
Students were randomized in a 3:1 ratio to receive either avatrombopag or placebo orally once daily for 12 weeks.
The primary endpoint was durable platelet response (defined as a platelet count ≥50 × 10⁹/L for at least 6 out of 8 weeks in the absence of rescue medication, between weeks 5 and 12).
Results showed that 28% of patients receiving avatrombopag achieved a durable platelet response compared to those receiving placebo, meeting the primary endpoint (95% CI, 15.8–39.7; P = .0077).
Furthermore, 81.5% of patients treated with avatrombopag achieved a platelet count of at least 50 × 10⁹/L for two consecutive sessions (a key secondary endpoint), compared to 0% in placebo-treated patients (95% CI, 71.1–91.8; P < .0001).
Dr. Jamie Freedman, Chief Medical Officer of Sobi North America, stated, “These applications for avatrombopag bring us one step closer to an additional treatment option urgently needed by adolescents and children with persistent and chronic ITP. We now have the opportunity to address an unmet need in the pediatric population with this additional formulation, an oral suspension that may be more suitable for some patients.”
