The FDA has approved eltrombopag as a treatment for pediatric patients with chronic immune thrombocytopenic purpura following a lack of response to other therapies or splenectomy.
Richard Pazdur, MD
The FDA has approved eltrombopag (Promacta) as a treatment for pediatric patients with chronic immune thrombocytopenic purpura (ITP) following a lack of response to other therapies or splenectomy, based on improvements in platelet counts seen across two clinical trials.
In the trials, eltrombopag was compared with placebo for 159 patients aged 1 to 17 with chronic ITP. In the first trial, the phase II PETIT study, 62% of patients treated with eltrombopag experienced an improvement in platelet counts compared with 32% with placebo. In the second study, the phase III PETIT2 trial, platelet counts were improved in 40% of patients receiving eltrombopag versus just 3% with placebo.
Eltrombopag became the first oral platelet growth factor to receive FDA approval in 2008. This initial indication was for adult patients with chronic ITP following an insufficient response to corticosteroids, immunoglobulins, or splenectomy. In June 2015, this indication was extended to children age 6 and older with the same condition, also based on the PETIT and PETIT2 trials.
“Today’s approval of Promacta emphasizes the FDA’s commitment to fully developing treatments in areas of pediatric hematology and oncology,” Richard Pazdur, MD, director of the Office of Hematology and Oncology Products in the FDA’s Center for Drug Evaluation and Research, said in a statement. “This new use in ages one and up builds on a recent approval for ages six years and up, and fills an unmet need for young children whose disease has progressed after use of other available treatments.”
In the phase III PETIT2 trial, 92 patients were randomized to eltrombopag (n = 63) or placebo (n = 29). Patients were stratified by age into 3 groups, 12—17 years, 6–11 years, and 1–5 years. Those who were age 1–5 years received an oral suspension formulation of eltrombopag at a starting dose of 1.2 mg/kg/day or 0.8 mg/kg/day for East Asian patients. The oral suspension formulation used in this study was approved with the new indication.
According to findings published in The Lancet,1 40% of those who received eltrombopag achieved at least a 50 x 109 per liter improvement in platelet counts for 6 of the last 8 weeks of the study. The odds ratio for the difference in response between the eltrombopag arm and placebo was 18.0 (95% CI, 2.3—140.9; P = .0004).
For those aged 12—17, the response was 39% with eltrombopag versus 10% with placebo. In the 6–11 age bracket, platelet counts were improved in 42% of patients treated with eltrombopag versus 0% with placebo. With the oral suspension formulation, the response rate was 36% versus 0% for those aged 5–1.
Following the blinded portion of the study, 87 patients went on to a 24-week open-label treatment period. In this group, 80% of patients achieved platelet counts of 50â€ˆ×â€ˆ109 per liter or more at least once.
In the phase II PETIT trial, 15 patients were initially randomized into an open-label dose-finding stage of the trial. These patients did not continue into the full investigation. In the double-blind portion of the trial, 67 patients were randomized to eltrombopag (n = 45) or placebo (n = 22). In the treatment arm, 16 patients were age 12—17 years, 19 were aged 6–11 years, and ten were aged 1–5 years.
According to data published in the Lancet Haematology,2 at weeks 1 to 6, 62% of patients in the eltrombopag arm achieved a platelet count of 50â€ˆ×â€ˆ109 per liter or more at least once without rescue compared with 32% with placebo (odds ratio, 4.31; 95% CI, 1.39—13.34, P = .011).
In this study, serious adverse events (AEs) were infrequent in both groups and no thrombotic events or malignancies occurred. The most common (AEs with eltrombopag versus placebo, respectively, were headache (30% vs 43%), upper respiratory tract infection (25% vs 10%), and diarrhea (16% vs 5%). Grade 3 or 4 AEs occurred in five (11%) patients receiving eltrombopag and four (19%) patients receiving placebo.
In the phase III study, the most common AEs with eltrombopag versus placebo, respectively, included nasopharyngitis, rhinitis, upper respiratory tract infection, and cough. Serious AEs were more frequently observed with placebo (8% with eltrombopag vs 14% with placebo).
“It’s challenging and often very emotional for parents of a baby or toddler affected by a rare condition to manage their child’s disease with limited treatment options,” Bruno Strigini, president, Novartis Oncology, said in a statement. “Today’s label expansion for Promacta provides a new disease management option for families affected by chronic ITP and highlights our commitment to providing treatments for even the youngest children with rare diseases.”
In addition to ITP, eltrombopag is also approved as a treatment for patients with severe aplastic anemia (SAA) following an insufficient response to immunosuppressive therapy. In addition to its indications for ITP and SAA, eltrombopag is also approved in combination with interferon and ribavirin for patients with chronic hepatitis C—associated thrombocytopenia.
Following a multibillion-dollar product exchange with GlaxoSmithKline that was completed in early March 2015, eltrombopag is now manufactured and developed by Novartis.