Thrombosomes: C'est parti

Safety evaluation of a lyophilized platelet-derived hemostatic product.

Barroso J et Al. Transfusion. 2018 Dec;58(12):2969-2977.

BACKGROUND:

Hemorrhage causes significant morbidity and mortality in people aged <65 years. A lyophilized platelet-derived hemostatic agent (Thrombosomes) demonstrated hemostatic efficacy in animal models. We report the results of the first safety trial of autologous Thrombosomes given to normal subjects.

STUDY DESIGN AND METHODS:

Ten subjects received autologous Thrombosomes prepared from their apheresis platelets, and five control subjects received a buffer solution. There were five cohorts, with three subjects per cohort (two in the Thrombosomes group and one in the control group). Doses escalated from 1/1,000 to 1/10 of a proposed efficacious dose. Cohorts 4 and 5 received the highest dose, but in Cohort 5, one-half the dose was infused 2 hours apart. Cohorts 1 through 3 were monitored for 42 days, Cohorts 4 and 5 were monitored for 60 days using hematology, coagulation, and chemistry assays and antibody testing.

RESULTS:

There were no serious adverse events (AEs) and no subject withdrawals. There were eight treatment-related AEs (TRAEs) in 5 of 15 subjects (33%) (four in the Thrombosomes group and one in the control group). Of four subjects receiving the highest doses, three had TRAEs. One had elevated D-dimer, prothrombin fragment 1 + 2, and white blood cell count (subject had concurrent upper respiratory tract infection); one had T-wave inversions in precordial leads V2 and V3 without elevated troponin or symptoms; and one had a platelet autoantibody without change in plateletcount. All subjects' TRAEs resolved by Day 21.

CONCLUSION:

There were no serious AEs in this small study. Thrombosomes were considered safe at the doses assessed. Future, larger trials will be needed to further assess safety and efficacy.