Orlando, Florida—Data being presented at the 2019 ASH Annual Meeting suggest that fostamatinib administered as second-line therapy in patients with immune thrombocytopenic purpura (ITP) and those with persistent ITP may lead to higher response rates than if the drug is used in later lines of therapy or for later-stage ITP.

“Since gaining FDA approval in April 2018, fostamatinib has been prescribed to a wide range of ITP patients, including those with persistent disease and those for whom fostamatinib is second-line therapy,” explained Ralph Boccia, MD, Center for Cancer and Blood Disorders, Bethesda, Maryland, and colleagues.

“We conducted a post hoc analysis of the phase 3 clinical study data in patients for whom fostamatinib was second-line therapy as well as in patients with earlier stage disease,” they continued.

Patients in the studies included in the analysis (N = 145; median age, 50 years) had persistent or chronic ITP, did not respond to ≥1 prior therapies, and had ≥3 platelet counts <30,000/μL at screening. Furthermore, the patients were given an initial dose of fostamatinib 100 mg twice daily before being increased to 150 mg twice daily depending on tolerability and if platelets were <50,000/μL after 4 weeks.

Dr Boccia et al defined an overall platelet response as achieving ≥1 platelet count of ≥50,000/µL (without rescue therapy). They included patients previously given corticosteroids with or without immunoglobulins and no other therapies for ITP in their analysis of fostamatinib as second-line therapy, and categorized patients based on ITP duration (ie, 3 months to <1 year (persistent), 1-2 years, and ≥2 years).

Among the 145 patients included in the study, the median duration of ITP was 2.7 years and median platelet count was 21,000/μL, and 32 (22%) were given fostamatinib as second-line therapy. Approximately 80% of these 32 patients had an overall platelet response, which Dr Boccia and colleagues said compares favorably with the 47% response rate in the 113 patients given third-line or later fostamatinib therapy.

Among the 32 patients receiving fostamatinib as second-line-therapy, hypertension, diarrhea, upper respiratory tract infection, nausea, vomiting, elevated liver enzymes, petechiae, and headache were the most common adverse events (AEs).

“AEs were primarily mild to moderate in severity and resolved or were managed by dose reduction, dose interruption, and/or secondary medication. The type and frequency of AEs in the second-line patients were consistent with that of the overall study population,” Dr Boccia and co-investigators said.

In addition, a subset of 29 patients with early-stage disease—11 of whom were given fostamatinib second-line therapy—was evaluated. Of 10 patients with persistent ITP (<1 year), 9 (90%) achieved overall responses to fostamatinib; the same was observed for 11 (57%) of 19 patients with 1 to 2 years of ITP, and 58 (50%) of 116 patients with 2 to 53 years of ITP.

Across the entire phase 3 population, the overall response rate was 54%.

“A higher percentage of patients had an overall response to fostamatinib as second-line therapy for ITP (78%) compared with later lines of therapy (47%), and a higher percentage with persistent ITP (90%) responded than those with earlier stage (1-2 years) chronic ITP (57%) or later stage chronic ITP (50%),” Dr Boccia and colleagues said.

“These data suggest that higher response rates may be seen with the use of fostamatinib as second-line therapy for ITP and in persistent ITP patients as compared with later lines of therapy and later stage ITP,” they concluded.—Hina Porcelli

Boccia R, Boxer MA, Ghanima W, et al. Enhanced responses to fostamatinib as second-line therapy and in persistent immune thrombocytopenia (ITP) patients. Presented at: the 2019 ASH Annual Meeting & Exposition; December 7-10, 2019; Orlando, FL. Abstract 1069.