AABB22: Clinical Effectiveness of Mirasol-Treated Platelets Explored with Novel Bleeding Endpoint

The use of pathogen reduction (PR) technology has been shown to effectively inactivate a number of infectious pathogens in platelets, and the technology is in wide use. However, “the question that needs to be answered is whether pathogen-reduced platelets are as clinically effective as conventional apheresis platelets,” said Scott Koepsell, MD, PhD, vice chair of clinical operations and medical director of transfusion and transplantation support services at the University of Nebraska Medical Center in Omaha.

Koepsell presented data from a non-inferiority study comparing Mirasol-reduced platelets (Terumo) with untreated platelets at Sunday’s plenary session. Mirasol uses riboflavin (vitamin B2) and ultraviolet light to inactivate pathogens.

PR platelets did not meet the requirements for non-inferiority. In fact, the trial was stopped early due to futility after review of a planned interim analysis.

This prospective controlled study included patients with hematologic malignancy and hypoproliferative thrombocytopenia, who were expected to have platelet counts of 10,000 or less and at least two platelet transfusions.

Patients received either leukoreduced single-donor apheresis platelets stored in plasma or Mirasol-treated Trima Accel single-donor apheresis platelets in plasma. Platelets in either arm were gamma irradiated at the discretion of the treating physician. “Ultimately, many of the products used in this study were irradiated,” noted Koepsell.

The researchers used a novel primary endpoint — the number of days with at least grade 2 bleeding (as defined by the World Health Organization, or WHO) in the 28 days after the first platelet transfusion or transfusion dependence (10 days without platelet transfusion).

In the intent-to-treat (ITT) group, grade 2 or greater bleeding was an average of 4.38 days with Mirasol (N=145) and 2.1 days for the control group (N=152). The relative rate of days with grade 2 or greater bleeding was 2.79.

Secondary endpoints included the proportion of patients with grade 2 or greater bleeding, 1-hour/24-hour corrected increments, transfusion episodes per patient, days of platelet support, and total RBC transfusions. Safety was measured by the number, type, and relatedness of transfusion-emergent adverse events.

The percentage of patients with grade 2 or greater bleeding was 40% of those receiving mirasol platelets and 30.3% for the control group (p=0.08). Koepsell noted that most of the mirasol primary bleeding locations were genitourinary and pulmonary. The average number of platelet transfusions per patient was 6.23 and 4.76 for Mirasol and control groups respectively. There was no significant difference between the groups in terms of treatment-related adverse events. 

When compared to previously published studies on PR technologies, individuals receiving Mirasol-treated platelets had similar proportions of subjects with grade 2 or greater bleeding between the Mirasol and control groups. The safety profile was similar between subjects receiving Mirasol and conventional platelets.

Several study authors received research support from Terumo BCT; study authors included Terumo employees. The study was supported by the Biomedical Advanced Research and Development Authority.