The second is a bivalent nanobody, caplacizumab, which is a tandemly repeated VHH for the anti-von Willebrand factor (vWF) linked via a trialanine linker that has been approved for the treatment of acquired thrombotic thrombocytopenic purpura (aTTP) [40, 41]. The gene discussed is VWF; the disease is acquired thrombotic thrombocytopenic purpura.