Treatment for Rare Blood Clotting Disorder Shows Efficacy in Phase 3 Study


The target action date for the FDA’s decision on caplacizumab (Cablivi) is February 6, 2019.

New phase 3 data showed positive results for caplacizumab (Cablivi) in the treatment of acquired thrombotic thrombocytopenic purpura (aTTP) in adults, according to a study published in the New England Journal of Medicine.

Currently, the standard treatment for aTTP includes a daily plasma exchange and immunosuppression. Even with treatment, patients are still at risk of developing acute blood clotting conditions and recurrence of disease.

Caplacizumab, an anti-von Willebrand Factor (vWF) nanobody, inhibits the interaction between ultra large vWF multimeters and platelets, which stops the formation and accumulation of micro-clots that cause thrombocytopenia, tissue ischemia, and organ dysfunction in aTTP.

In the HERCULES phase 3 trial, 145 patients with aTTP received either caplacizumab (10-mg intravenous loading bolus, followed by 10 mg daily subcutaneously) or a placebo during plasma exchange and for 30 days after. According to the data, the median time to normalization of the platelet count was shorter with caplacizumab than with placebo (2.69 days [95% confidence interval {CI}, 1.89 to 2.83] vs. 2.88 days [95% CI, 2.68 to 3.56], P=0.01). Additionally, patients who received caplacizumab were 1.55 times as likely to have normalization of a platelet count as those who received placebo.

The study also showed that treatment with caplacizumab was associated with a 74% reduction in aTTP-related death, recurrence, or at least 1 major thromboembolic event compared with placebo (12% vs. 49%, P<0.001). A significantly lower number of patients treated with caplacizumab had a recurrence of aTTP during the study period than with a placebo (12% vs. 38%, P<0.001).

Based on the data, patients who received caplacizumab also demonstrated a clinically meaningful reduction in use of plasma exchange and had a shorter hospitalization than those who received a placebo. No patients in the caplacizumab group developed refractory disease, whereas 3 patients in the placebo group did.

The most common adverse event was mucocutaneous bleeding, which was reported in 65% of patients in the caplacizumab group and 48% in the placebo group, according to the study.

“aTTP is a life-threatening disease, and the current treatment options do not fully halt the extensive clot formation in small blood vessels throughout the body, leaving patients at risk for significant morbidity and early death,” lead study author Marie Scully, MD, professor of hematology at University College London Hospitals, said in a press release about the findings. “These results demonstrate that Cablivi has the potential to address a major unmet medical need and to help those facing the potentially devastating consequences of this disorder.”

Caplacizumab was developed by Ablynx, a Sanofi company. The target action date for the FDA decision is February 6, 2019.


Scully M, Cataland SR, Peyvandi F, et al. Caplacizumab treatment for acquired thrombotic thrombocytopenic purpura. New England Journal of Medicine. 2019. Doi: 10.1056/NEJMoa1806311

New England Journal of Medicine publishes positive results of the pivotal trial of Cablivi (caplacizumab) for rare blood clotting disorder [news release]. Sanofi’s website. Accessed January 10, 2019.

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