(Celltrion) Celltrion said Wednesday that its blood cancer treatment Truxima received interchangeability designation from the US Food and Drug Administration, becoming the first biosimilar version of rituximab to secure the status and its associated exclusivity period.Truxima is approved in the US for all adult indications held by its reference biologic, including non-Hodgkin lymphoma, chronic lymphocytic leukemia, rheumatoid arthritis and microscopic polyangiitis.The FDA's interchangeability designation means a biosimilar can be substituted for its reference biologic at the pharmacy level without clinically meaningful differences in safety or effectiveness.Celltrion said the designation further validates Truxima's clinical profile and is expected to strengthen physician confidence and expand its presence in the US market.According to IQVIA, Truxima accounted for 35.8 percent of US rituximab prescriptions as of February, making it the market leader ahead of both competing biosimilars and the reference biologic. It marked the first time a Korean-developed biosimilar had become the top-selling product in its category in the US market.The product has also emerged as a major earnings contributor for Celltrion. Truxima generated more than 300 billion won ($194 million) in North American sales last year, up more than 40 percent from a year earlier.Celltrion said it plans to use the designation to further strengthen Truxima's position in the US rituximab market while supporting the expansion of its broader oncology biosimilar portfolio."As the US biosimilar market continues to evolve, we will improve patient access to treatment and help reduce healthcare costs by leveraging Truxima's extensive clinical data and real-world prescribing experience," a Celltrion official said.