The U.S. Food and Drug Administration (FDA) has approved the use of the biosimilar ustekinumab-auub (Wezlana) to treat inflammatory diseases, including plaque psoriasis, psoriatric arthritis, Crohn’s disease, and ulcerative colitis. The new biosimilar is interchangeable with ustekinumab (Stelara). Ustekinumab-auub has been indicated for all patients who are 6 years and older with moderate to severe plaque psoriasis—who are candidates for phototherapy or systemic therapy—and active psoriatic arthritis; however, for moderately to severely active Crohn’s disease and moderately to severely active ulcerative colitis, only adult patients may be treated with the novel biosimilar. The FDA’s approval came after researchers conducted a comprehensive review of scientific evidence, including chemical and biological tests, biological assays, comparative human pharmacokinetic data, clinical immunogenicity data, and safety and effectiveness data. They determined that there were no clinically meaningful differences in safety, efficacy, and structural and functional features between ustekinumab-auub and ustekinumab. Patients taking the biosimilar may experience adverse effects such as headaches, fevers, abdominal pain, diarrhea, nausea, vomiting, fatigue, nasopharyngitis, upper respiratory tract infections, injection site erythema, and urinary tract infections. The FDA advised health-care professionals to review the prescribing information on the drug’s label to learn more about its approved uses. “[The new] approval exemplifies the FDA’s longstanding commitment to support a competitive marketplace for biological products … and can empower patients by helping to increase access to safe, effective, and high-quality medications at potentially lower costs,” concluded Sarah Yim, MD, Director of the Office of Therapeutic Biologics and Biosimilars at the Center for Drug Evaluation and Research at the FDA.