Celltrion's Steqeyma, a biosimilar for autoimmune diseases, captured 16.2% of the U.S. ustekinumab market in July 2026, up from 10.2% in February, according to IQVIA. The product is in its second year since launch and is expanding prescriptions in a U.S. ustekinumab market worth approximately 20 trillion won ($14.7 billion). Celltrion's U.S. direct-sales network has supported growth by securing preferred formulary placement and broader reimbursement through major pharmacy benefit managers and public and private insurers. Yuflyma, the company's adalimumab biosimilar, held 9.4% in July after gaining coverage on the public insurance formularies of two of the three largest U.S. PBMs. Truxima led the rituximab biosimilar market with a 38.6% share and six consecutive months in the No. 1 prescription position, while Inflectra led the infliximab biosimilar market with 30.7%. Truxima's FDA interchangeability designation permits pharmacy-level substitution without prescriber intervention. Celltrion plans to launch Omlyclo for chronic spontaneous urticaria and use its existing portfolio and U.S. sales infrastructure to pursue further revenue growth.