Sanofi’s Cablivi Becomes First FDA-Approved Treatment for Pediatric aTTP

The FDA has approved Cablivi (caplacizumab-yhdp) for injection to treat pediatric patients aged 12 years and older with acquired thrombotic thrombocytopenic purpura (aTTP), in combination with plasma exchange and immunosuppressive therapy.

Cablivi was initially approved for adults in 2019. This is the first FDA approval of a drug specifically indicated for pediatric patients with this rare blood disorder.

Sanofi’s January 2025 pricing disclosure lists Cablivi’s US wholesale acquisition cost (WAC) at $8,571.68 per single-dose 11 mg vial kit.

The approval applies to use in the acute treatment setting alongside plasma exchange and immunosuppressive therapy. Plasma exchange helps remove disease-causing antibodies from the blood and restore ADAMTS13 activity, while immunosuppressive therapy is used to limit further antibody production.

Children with aTTP have generally been treated using approaches extrapolated from adult care, as no FDA-approved therapies were labeled for pediatric patients.

aTTP is a rare and potentially life-threatening autoimmune disorder caused by a severe deficiency of ADAMTS13, an enzyme responsible for regulating blood clot formation.

When ADAMTS13 activity is reduced, von Willebrand factor builds up in the blood and causes platelets to clump together more than they should. This can lead to small clots forming in narrow blood vessels, reducing blood flow to organs such as the brain, heart and kidneys.

The condition is associated with low platelet counts, destruction of red blood cells and acute organ injury. In children, aTTP is especially uncommon, occurring in roughly one in 10 million annually.

Cablivi is a nanobody-based therapy, built on Sanofi’s NANOBODY technology, that targets von Willebrand factor, a protein that plays a central role in platelet adhesion and clot formation in aTTP. It works by binding to the A1 domain of von Willebrand factor, blocking its interaction with platelets and helping to reduce the microvascular clots that define the disease.

Nanobodies are small antibody fragments derived from heavy-chain-only antibodies naturally found in camelids, such as llamas. Their smaller size compared with conventional antibodies allows them to bind tightly to specific disease-related targets.

The FDA’s pediatric approval was supported by data from a retrospective chart review that evaluated the use of caplacizumab-yhdp in 30 patients aged two to 18 years with aTTP. In this analysis, 80% of patients achieved clinical remission, defined as normalization of platelet counts and lactate dehydrogenase levels below 1.5 times the upper limit of normal for at least 30 days. Lactate dehydrogenase is commonly used as a marker of red blood cell breakdown in aTTP.

The study did not include a comparator group, reflecting the challenges of conducting prospective trials in very rare pediatric conditions.

Cablivi is administered by injection and is intended for use in combination with plasma exchange and immunosuppressive therapy. Treatment includes an initial intravenous dose followed by daily subcutaneous injections during plasma exchange and for a defined period afterward, depending on clinical response.

Because caplacizumab-yhdp interferes with platelet-mediated clotting, bleeding is an important safety consideration. Serious and potentially fatal bleeding events have been reported, particularly in patients with underlying clotting disorders or those receiving other blood-thinning medications.

For this pediatric indication, Cablivi has received an Orphan Drug designation.

Based on publicly available listings on clinicaltrials.gov under aTTP, as of this article, registered studies include observational research, including a retrospective analysis in Germany evaluating real-world use of Cablivi.

Amid broader efforts to expand pediatric drug development in rare diseases, the FDA bestowed Rare Pediatric Disease designation for Solid Biosciences’ SGT-212 investigational gene therapy for Friedreich’s ataxia in December 2025. It is being evaluated in an early-stage clinical trial.

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