Image from Graham Beards
Platelets (blue) surrounded by red blood cells
The US Food and Drug Administration (FDA) has granted priority review to the new drug application (NDA) for avatrombopag.
Avatrombopag is a second-generation thrombopoietin receptor agonist that is intended to address the limitations of existing treatments for thrombocytopenia.
With this NDA, Dova Pharmaceuticals, Inc., is seeking approval of avatrombopag for the treatment of thrombocytopenia in patients with chronic liver disease who are scheduled to undergo a procedure.
The FDA expects to make a decision on the NDA by May 21, 2018.
The FDA’s goal is to take action on a priority review application within 6 months of receiving it, rather than the standard 10 months.
The FDA grants priority review to applications for products that may provide significant improvements in the treatment, diagnosis, or prevention of serious conditions.
Phase 3 trials
The NDA submission for avatrombopag is supported by 2 identically designed phase 3 trials, ADAPT 1 and ADAPT 2. Results from these trials were presented at the 2017 American Association for the Study of Liver Disease (AASLD) Meeting last month (abstract 217).
The studies randomized 435 patients with thrombocytopenia and chronic liver disease who were scheduled to undergo a procedure.
Patients with low baseline platelet counts (<40x 109/L) were randomized to receive 60 mg of avatrombopag or placebo daily for 5 days.
Patients with higher baseline platelet counts (40 to <50 x 109/L) were randomized to receive 40 mg of avatrombopag or placebo daily for 5 days.
Patients underwent their procedures 5 to 8 days after their last dose of avatrombopag.
In ADAPT-1, 85 patients completed treatment with avatrombopag at 60 mg, 55 completed treatment with avatrombopag at 40 mg, and 78 controls completed the study.
In ADAPT-2, 68 patients completed treatment with avatrombopag at 60 mg, 55 completed treatment with avatrombopag at 40 mg, and 68 controls completed the study.
Efficacy
The primary efficacy endpoint of these trials was the proportion of patients who did not require any bleeding rescue up to 7 days post-procedure. Bleeding rescue included platelet transfusion, fresh frozen plasma, cryoprecipitate, vitamin K (phytonadione), desmopressin, recombinant activated factor VII, aminocaproicacid, tranexamic acid, whole blood transfusion, packed red cell transfusion, surgical intervention, or interventional radiology.
In ADAPT-1, the primary endpoint was achieved by 66% of patients who received avatrombopag at 60 mg and 23% of those who received placebo in the low-platelet-count cohort (P<0.0001). The endpoint was also achieved by 88% of patients who received avatrombopag at 40 mg and 38% of controls in the higher-platelet-count cohort (P<0.0001).
In ADAPT-2, the primary endpoint was achieved by 69% of patients who received avatrombopag at 60 mg and 35% of those who received placebo in the low-platelet-count cohort (P<0.0006). The endpoint was also achieved by 88% of patients who received avatrombopag at 40 mg and 33% of controls in the higher- platelet-count cohort (P<0.0001).
A secondary efficacy endpoint was the proportion of patients achieving the target platelet count (≥50 x 109/L).
In ADAPT-1, this endpoint was met by 69% of patients who received avatrombopag at 60 mg and 4% of controls in the low-platelet-count cohort (P<0.0001). It was also met by 88% of patients who received avatrombopag at 40 mg and 21% of controls in the higher-platelet-count cohort (P<0.0001)
In ADAPT-2, this endpoint was met by 67% of patients who received avatrombopag at 60 mg and 7% of controls in the low-platelet-count cohort (P<0.0001). It was also met by 93% of patients who received avatrombopag at 40 mg and 39% of controls in the higher-platelet-count cohort (P<0.0001).
Safety
The researchers pooled safety data from the 2 trials.
Treatment-emergent adverse events (AEs) occurred in 58.2% of controls and 56% of avatrombopag-treated patients in the low-platelet-count cohort (60 mg). Treatment-emergent AEs also occurred in 50.8% of controls and 51.3% of avatrombopag-treated patients in the higher-platelet-count cohort (40 mg).
The most frequently reported treatment-emergent AEs were pyrexia, abdominal pain, nausea, headache, diarrhea, and fatigue.
One patient experienced partial portal vein thrombosis that was considered non-serious and potentially related to avatrombopag.
Treatment-related AEs occurred in 17.6% of controls and 11.3% of avatrombopag-treated patients in the low-platelet-count cohort. Treatment-related AEs also occurred in 6.2% of controls and 7% of avatrombopag-treated patients in the higher-platelet-count cohort.
Serious AEs occurred in 13.2%, 6.9%, 3.1%, and 7.8%, respectively.
There were 3 deaths—2 in the 40 mg avatrombopag arm in ADAPT-1 and 1 in the control group in ADAPT-2. None of the deaths was considered treatment-related.
Future directions
Dova Pharmaceuticals, Inc., is planning to explore the potential use of avatrombopag in a broader population of patients with thrombocytopenia. This includes patients undergoing surgical procedures associated with a high risk of bleeding and patients who develop thrombocytopenia after receiving chemotherapy.
In addition, the company is exploring a potential regulatory approval pathway for avatrombopag for the treatment of adults with chronic immune thrombocytopenic purpura based on results from a completed phase 3 trial in this patient population.
