*Please refer to most recent prescribing information for FDA-approved indications and dosing guidelines.

Clinical Rationale

Rituximab (Rituxan®) is a chimeric monoclonal antibody that targets CD20, which is primarily located on the surface of immune system B cells. Once rituximab binds to CD20, B-cells are destroyed; consequently, rituximab is used to treat diseases that are characterized by excessive amounts of B cells, by overactive B cells, or by dysfunctional B cells. Examples include lymphomas, leukemias, autoimmune disorders and in transplant rejection.

Rituximab was initially approved by the US Food and Drug Administration (FDA) in November 1997 for the treatment of relapsed or refractory B-cell Non-Hodgkin’s Lymphoma (NHL). Additional FDA-labeled indications include Chronic Lymphocytic Leukemia (CLL), rheumatoid arthritis (RA), granulomatosis with polyangiitis (GPA) (Wegener’s granulomatosis)/microscopic polyangiitis (MPA), and moderate to severe pemphigus vulgaris (PV). Standard reference compendia (e.g., Clinical Pharmacology, DrugDex) support rituximab use in a plethora of off-label indications include autoimmune blistering diseases, autoimmune hemolytic anemia, neuromyelitis optica, and many more. Three biosimilar forms of rituximab have been FDA approved: rituximab-abbs (Truxima ® ), rituximab-arrx (Riabni™), and rituximab-pvvr (Ruxience™).

Biosimilar Products⁵

All FDA-approved biological products, including reference products and biosimilar products, undergo a rigorous evaluation so that patients can be assured of the efficacy, safety, and quality of these products. A reference product is the single biological product, already approved by FDA, against which a proposed biosimilar product is compared. A reference product is approved in a “standalone” application that must contain all data and information necessary to demonstrate its safety and effectiveness. Generally, the data and information necessary to demonstrate the safety and effectiveness of a reference product will include clinical trials for the disease indications being sought by the manufacturer. A biosimilar is highly similar to, and has no clinically meaningful differences in safety, purity, and potency (safety and effectiveness) from, an existing FDA-approved reference product.

NCCN guidelines state an FDA approved biosimilar can be substituted for Rituxan. The guidelines do not specify what biosimilars are appropriate for a specific tumor type which allows for use of any of the biosimilars to be used for any indication the innovator product is FDA approved for.