On July 13, the US Food and Drug Administration (FDA) approved Tremfya (guselkumab) to treat moderate to severe plaque psoriasis. Tremfya, developed by Johnson & Johnson's subsidiary Janssen, of Beers, Belgium, is the first and only human monoclonal antibody (mAb) that selectively blocks interleukin 23 (IL-23), a pro-inflammatory cytokine involved in the pathogenesis of plaque psoriasis (Nat. Biotechnol. 34, 1218–1219, 2016). The FDA expedited its review because Janssen used a Priority Review Voucher it won in 2012 for the approval of Sirturo (bedaquiline), a treatment for multi-drug-resistant tuberculosis. Tremfya will launch at an annual wholesale acquisition cost of $58,100, says spokesperson Brian Kenney. Tremfya's approval also marks the first antibody produced using MorphoSys' HuCAL (Human Combinatorial Antibody Library) technology platform, for which Planegg, Germany's MorphoSys will receive an undisclosed milestone payment. Tremfya targets and shuts off IL-23, a cytokine at the top of the inflammatory cascade that, in turn, will block disease-causing T-helper-17 cells that produce IL-17, known to play a pivotal role in the disease. But IL-23 is a heterodimer with two subunits, p19 and p40. Tremfya is the first agent to block only the p19 subunit, whereas other approved biologics work by inhibiting both components, including Janssen's Stelara (ustekinumab). Stelara targets the p40 component that is shared between the IL-23 and IL-12 pathways. A selective anti-p19 therapy was deemed a bonus and, indeed, in phase 3 data, Tremfya outscored the placebo on complete and near-complete skin clearance at week 16. With Tremfya, 70% of patients scored a significant improvement in skin clearance (PASI 90), including less itch, pain and stinging, compared with 50% skin clearance with Humira (adalimumab); an anti-TNF inhibitor from North Chicago, Illinois–based AbbVie (Nat. Biotechnol. 34, 1218–1219, 2016). In addition, Stelara non-responder patients showed significant improvements in plaque clearance when treated with Tremfya. The dosing regimen at one injection every 8 weeks is less frequent than with other biologics. Tremfya is in phase 3 development for treating psoriatic arthritis. Janssen is also conducting a phase 3 trial comparing Tremfya with IL-17-blocker Cosentyx (secukinumab) from Novartis of Basel, Switzerland.