Conditions: Chronic Thrombocytopenia Immune Thrombocytopenia
Keywords: Chronic Immune Thrombocytopenia
Allocation: RANDOMIZED | Intervention model: PARALLEL
Enrollment: 49
Healthy volunteers: no

Brief summary:
Core Study:

To demonstrate that the efficacy of avatrombopag (in addition to standard of care) is superior to placebo (in addition to standard of care) for the treatment of adult participants with chronic immune thrombocytopenia (idiopathic thrombocytopenic purpura) (ITP) as measured by cumulative number of weeks of platelet response over 6 months of once daily treatment in adults participants who received at least 1 prior ITP therapy.

Extension Phase:

To evaluate the safety and tolerability of long-term therapy with avatrombopag in participants with chronic ITP (cITP).

Detailed description:
This study consists three phases: Prerandomization, Randomization (Core Study) and Extension study. The overall duration of treatment (Core and Extension) is approximately 104 weeks with the Core study being 26 weeks and the Extension study being 76 weeks. Approximately 45 participants 18 years of age and over who meet all the eligibility requirements will be randomized. No single platelet count should be greater than 35x10\^9/L (liter). Participants will be centrally stratified at randomization by splenectomy status, baseline platelet count, and use of concomitant ITP medication at baseline, and randomized to receive either double-blind avatrombopag or placebo in a 2:1 ratio. Participants will receive blinded therapy at a starting dose of 20 mg avatrombopag or placebo once daily. Participants will be allowed to have their dose titrated up (maximum dose 40 mg avatrombopag or matching placebo) or down (minimum dose 5 mg for avatrombopag or matching placebo) depending on their response to study drug. The goal of dose modification is to maintain the platelet count at levels greater than or equal to 50x10\^9/L and less than or equal to 150x10\^9/L, and to decrease the need for ITP-directed concomitant medications.

Arms:
arm 1: Avatrombopag will be administered orally as 5 mg, 10 mg, 20 mg, 30 mg, or 40 mg in a flexible dose design for 26 weeks. Participants will receive blinded therapy at a starting dose of 20 mg avatrombopag, one daily and allowed to have their dose titrated up (maximum dose of 40 mg avatrombopag) or down (minimum dose of 5 mg avatrombopag) depending on their response to study drug. arm 2: Placebo will be administered as 5 mg, 10 mg, 20 mg, 30 mg or 40 mg in a flexible dose design for 26 weeks. Placebo will be administered orally at a starting dose of 20 mg, once daily. Afterwards the dose can be titrated up (maximum dose of 40 mg avatrombopag) or down (minimum dose of 5 mg avatrombopag) depending on the participant's response to the study drug; placebo titration will be used to maintain the blind. arm 3: Participants who meet all eligibility criteria requirements of extension phase and who discontinue the core study because of lack of treatment effect will continue into the extension phase. Avatrombopag will be administered to participants who enter extension phase, with a starting dose of 20 mg avatrombopag, once daily for 76 weeks and undergo dose titration.

Interventions: intervention 1: Avatrombopag intervention 2: Placebo intervention 3: Standard of care
Intervention descriptions: intervention 1: None intervention 2: None intervention 3: Permitted ITP concomitant background therapies are as follows:

* Corticosteroids and/or azathioprine taken at a stable dose for 4 weeks before randomization;
* Mycophenolate mofetil (MMF) or danazol taken at a stable dose for at least 12 weeks before randomization;
* Cyclosporine A (CsA) (due to the fact that it is a P-glycoprotein-mediated transport \[P-gp\] inhibitor) is to be avoided unless deemed medically necessary; CsA taken at a stable dose for at least 12 weeks before randomization.

At the discretion of the investigator, participants will be allowed to use aspirin, other salicylates, or approved adenosine diphosphate (ADP) receptor antagonists, (eg, clopidogrel, prasugrel) during the study once their platelet count had risen.

Participants treated with proton pump inhibitors (PPIs) and H2 antagonist therapy will receive a stable dose for at least 6 weeks prior to randomization. Treatment with these therapies must have been completed at least 2 weeks prior to randomization.

Protocol document: