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Eltrombopag (Promacta) Gets FDA Nod for Treatment of Rare Blood Disorder in Children

Drug increases platelet counts in phase III trial

The FDA has approved eltrombopag (Promacta, Novartis) for the treatment of children 6 years of age and older with chronic immune thrombocytopenia (ITP) who have had an insufficient response to corticosteroids, immunoglobulins, or splenectomy. The drug was approved in 2008 for use in adults with the same condition.

Eltrombopag is a once-daily oral thrombopoietin receptor agonist that works by inducing the stimulation and differentiation of megakaryocytes from bone-marrow stem cells to increase platelet production.

ITP affects as many as five in 100,000 children each year and is characterized by a low platelet count. Up to 30% of affected children experience persistent disease for more than 6 months and are diagnosed with chronic ITP. Pediatric patients with chronic ITP are at risk of significant bleeding.

The approval of eltrombopag for its new indication was based on data from two double-blind, placebo-controlled trials, including the largest phase III clinical study in patients with ITP. Treatment with eltrombopag significantly increased and sustained platelet counts among some pediatric patients with chronic ITP, and some patients taking concomitant ITP medications were able to reduce or discontinue their use of these treatments, primarily corticosteroids.

The PETIT trial was a phase II, multicenter, three-part study investigating the efficacy, safety, and tolerability of eltrombopag in pediatric patients with previously treated chronic ITP. Part 1 was an open label, dose-finding study; part 2 was double-blind and placebo-controlled; and part 3 was an open-label extension. The study’s primary endpoint –– the percentage of participants who achieved a platelet count of 50 Gi/L or greater without rescue therapy at least once between weeks 1 and 6 –– was met by 63% and 18% of eltrombopag- and placebo-treated patients, respectively (P = 0.0043). Secondary efficacy endpoint analyses demonstrated clinically meaningful benefit in terms of a decreased need for rescue treatment (14% of the eltrombopag group compared with 59% of the placebo group).

The PETIT2 trial was a phase III, multicenter, two-part study investigating the efficacy, safety, and tolerability of eltrombopag in pediatric patients with previously treated chronic ITP. Part 1 was randomized, double-blind, and placebo-controlled, and part 2 was an open-label extension. The trial’s primary endpoint –– the percentage of subjects who achieved a platelet count of 50 Gi/L or greater without rescue therapy for at least 6 out of 8 weeks between weeks 5 and 12 of part 1 of the study –– was met by 43% of the patients treated with eltrombopag compared with 4% of the patients treated with placebo (P = 0.0011). This result was consistent across the age cohorts. Secondary efficacy endpoint analyses demonstrated a decreased need for rescue treatment (18% of the eltrombopag group compared with 22% of the placebo group) and the reduction or discontinuation of baseline ITP medications (50% of patients [5/10] in the open-label phase who were receiving other ITP therapies at baseline) compared with the randomized and eltrombopag-only treatment periods.

In both studies, the most common adverse events in patients 6 years of age and older with chronic ITP included upper respiratory-tract infection, nasopharyngitis, and rhinitis.

Promacta (eltrombopag) was previously approved for the treatment of:

  • thrombocytopenia in adult patients with chronic ITP who have had an insufficient response to corticosteroids, immunoglobulins, or splenectomy.
  • thrombocytopenia in patients with chronic hepatitis C to allow the initiation and maintenance of interferon-based therapy.
  • patients with severe aplastic anemia who have had an insufficient response to immunosuppressive therapy.

Sources: Novartis; June 11, 2015; and Promacta Prescribing Information; April 2015.

 

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