Non-neutralizing, factor VIII–specific IgG antibodies can contribute significantly to reductions in factor VIII half-life in patients with hemophilia A, according to a study published online in Blood.
Screening for factor VIII–specific IgG may aid in tailoring factor VIII prophylactic regimens for hemophilia A patients, said Christoph J. Hofbauer, Ph.D., of the biopharmaceutical company Baxalta in Vienna, and his associates at the Medical University of Vienna.
Christoph J. Hofbauer, Ph.D.
The researchers examined the effect of factor VIII–specific IgG antibodies on factor VIII half-life in 42 adult patients with hemophilia A without inhibitors. Patients ranged in age from 18-61 years, and 37 of them had severe disease. Of the cohort, 31 received recombinant factor VIII concentrates and 11 received plasma-derived factor VIII concentrates (Blood. 2016 May 23 [Epub ahead of print])
In the initial antibody screen, 15 patients tested positive for factor VIII–binding IgG with titers of at least 1:20. Factor VIII–specific antibodies were found at titers of at least 1:40 in 9 of the 15 subjects. Most had low- to moderate-affinity IgG1 and IgG3 antibodies. One patient with high-affinity IgG4 antibodies went on to develop low titers of factor VIII inhibitors.
Patients with factor VIII–specific antibodies had a shorter factor VIII half-life (median 7.8 hours) than did patients without antibodies (median 10.4 hours).
Dr. Hofbauer is employed by Baxalta, which makes a variety of antihemophilic factors.
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