Avatrombopag for chemotherapy-induced thrombocytopenia in patients with non-haematological malignancies: an international, randomised, double-blind, placebo-controlled, phase 3 trial

Background Chemotherapy-induced thrombocytopenia is common and causes chemotherapy dose reductions or treatment delays, bleeding, and suboptimal oncological outcomes. We aimed to evaluate avatrombopag, a thrombopoietin receptor agonist that increases platelet counts, in patients with non-haematological cancer and platelet counts lower than 50x10(9) cells per L. Methods In this randomised, double-blind, placebo-controlled, phase 3 study, patients aged 18 years or older at 71 hospitals or cancer treatment centres in China, Hungary, Poland, Russia, Serbia, Ukraine, and the USA and with ovarian, bladder, or lung cancer receiving chemotherapy who had severe thrombocytopenia were randomly assigned (2:1) to oral avatrombopag 60 mg or oral placebo once daily given 5 days before and after chemotherapy, with randomisation stratified by number of chemotherapy drugs used. Patients, investigators, and data collectors were masked to group allocation. Eligibility required two previous lines of chemotherapy or fewer, an ECOG performance status of 2 or less, and no previous history of chemotherapy-induced thrombocytopenia. The composite primary endpoint was the proportion of responders not requiring platelet transfusion or either a 15% or more chemotherapy dose reduction or a 4-day or more chemotherapy delay due to thrombocytopenia following study treatment until the start of the subsequent cycle. Analyses were done on the intention-to-treat and per protocol populations. Safety was analysed in all patients who received at least one dose of avatrombopag. The trial is registered with ClinicalTrials.gov, NCT03471078, and has been completed. Findings Between Oct 12, 2018, and June 28, 2020, 122 patients were enrolled and randomly assigned to receive avatrombopag (n=82) or placebo (n=40). Median follow-up was 31 days (IQR 22-61). Similar proportions of patients reached the primary endpoint in the avatrombopag and placebo groups (intention-to-treat: 57 [70%, 95% CI 58-79] of 82 vs 29 [73%, 95% CI 56-85] of 40; difference -3.0% (95% CI -21.6 to 15.6); p=0.72; per protocol: 51 [85%, 95% CI 73-93] of 60 vs 27 [84%, 95% CI 67-95] of 32; 0.6% (95% CI -20.8 to 22.1); p=0.96). 15 (18%) of 82 patients had serious adverse events in the avatrombopag group and eight (20%) of 40 in the placebo group, of which thrombocytopenia was most common (4 [5%] of 82 and 4 [10%] of 40 patients). Common grade 3-4 treatment emergent adverse events were neutropenia (22 [27%] of 82 and 16 [40%] of 40 patients), leukopenia (19 [23%] of 82 and 5 [13%] of 40), anaemia (16 [20%] of 82 and 9 [23%] of 40), and thrombocytopenia (16 [20%] of 82 and 14 [35%] of 40). Most adverse events were considered unrelated to study drug. No treatment-related deaths were reported. Interpretation In this population of patients with non-haematological malignancies who are relatively chemotherapy naive, chemotherapy-induced thrombocytopenia treatment outcomes were similar between the avatrombopag and placebo groups. Given its safety and ability to augment platelet counts in patients with chemotherapy-induced thrombocytopenia, evaluation of avatrombopag in populations with more persistent chemotherapy-induced thrombocytopenia is warranted. Copyright (C) 2022 Elsevier Ltd. All rights reserved.