STOCKHOLM—Swedish Orphan Biovitrum AB (Sobi) announced today that the company has dosed its first patient with avatrombopag, a thrombopoietin receptor agonist (TPO-RA), for treatment of immune thrombocytopenia (ITP) in pediatric patients. Avatrombopag is an orally administered TPO-RA that stimulates the development and maturation of megakaryocytes, which results in an increased platelet count.

This Phase 3 study, AVA-PED-301, plans to evaluate efficacy, safety, and pharmacokinetics of avatrombopag in the treatment of eligible pediatric subjects with ITP, with platelet counts <30×10⁹/L. Patients will enter a 12-week double-blind phase, followed by an open-label extension phase up to 2 years in duration. 

The study will enroll a total of 72 pediatric subjects, aged ≥1 to <18 years, in nine countries. Subjects will be randomized to blinded therapy of either avatrombopag or placebo, in a 3:1 ratio. Enrollment into the study will be staggered by descending age cohort, and the company plans to conduct a safety and pharmacokinetic review before the next cohort opens for enrollment.

“We are excited to announce the start of this important study,” noted Ravi Rao, head of Research & Development at Sobi. “Our hope is to provide a new treatment option for children with ITP with the potential to decrease the treatment burden that impacts their daily lives.” 

In children with ITP — an autoimmune disorder that occurs when the body attacks its own platelets — the body produces platelets normally, but destroys them too quickly. Platelets survive for only a few hours, instead of the normal seven to 10 days. The result is a low platelet count in the blood, and symptoms like petechiae, easy bruising, and bleeding events. 

Spontaneous remission is common in the pediatric population, but 10-20 percent of children will develop chronic ITP. The disorder is considered chronic when symptoms last more than 12 months. These patients have usually relapsed after various treatments, and generally require treatment to reduce the risk of clinically significant bleeding.

Symptoms in children with ITP can vary, but sporadic and unpredictable bleedings along with low platelet counts can lead to anxiety among both the affected children and their parents. In children with more severe ITP, the disease has been shown to decrease school attendance and participation in athletic activities.

Avatrombopag has approved by both the FDA and the European Medicines Agency (EMA) for the treatment of thrombocytopenia in adult patients with chronic liver disease who are scheduled to undergo a procedure. Avatrombopag has also been approved by the FDA and the EMA for the treatment of primary chronic ITP in adult patients who are refractory to other treatments such as corticosteroids and immunoglobulins.