HealthDay News — Caplacizumab, an anti-von Willebrand factor humanized single-variable-domain immunoglobulin (Nanobody), shows potential in the treatment of acquired thrombotic thrombocytopenic purpura (TTP), according to research published in the February 11 issue of the New England Journal of Medicine.

Flora Peyvandi, MD, PhD, of the University of Milan in Italy, and colleagues randomly assigned patients with acquired TTP to receive subcutaneous caplacizumab (36 patients) or placebo (39 patients) during plasma exchange and for 30 days afterwards. The primary end point was time to a response, with response being defined as confirmed normalization of the platelet count. Secondary end points included exacerbations and relapses.

The researchers found that patients in the caplacizumab group had a significantly reduced time to a response compared with those in the placebo group (reduction in median time, 39%; P = 0.005). Fewer patients in the caplacizumab group had an exacerbation compared to the placebo group (three versus 11 patients). In the first month after stopping the study drug, eight patients in the caplacizumab group had a relapse; of these, seven had ADAMTS13 activity that remained below 10%, suggesting unresolved autoimmune activity. More patients in the caplacizumab group than in the placebo group experienced bleeding-related adverse events, most of which were mild to moderate in severity (54 versus 38%).

“Caplacizumab, through rapid blocking of von Willebrand factor-mediated platelet aggregation, prevents further platelet aggregation more rapidly than conventional treatment alone, which could potentially prevent short- and long-term end-organ injury due to ischemia,” the authors write.

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Ablynx, the biopharmaceutical company that developed Nanobody, funded the study.

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