This is a novel trivalent nanobody comprised of monovalent camelid-derived (ie, from the Camelidae family of mammals, such as camels, llamas, and alpacas) nanobodies specific to human interleukin IL17A, IL17F, and human serum albumin. Nanobodies are a novel class of proprietary therapeutic proteins based on single-domain, camelid, heavy-chain-only antibodies. Sonelokimab is an investigational ~40kDa humanized nanobody consisting of three VHH domains covalently linked by flexible glycine-serine spacers. With two domains, sonelokimab selectively binds with high affinity to IL17A and IL17F, thereby inhibiting the naturally occurring IL17A/A, IL17A/F, and IL17F/F dimers. A third central domain binds to human albumin, facilitating further enrichment of sonelokimab at sites of inflammatory edema. It demonstrates a rapid and durable clinical response in patients with moderate-to-severe plaque-type psoriasis.