Rituximab

Rituximab is a genetically engineered monoclonal antibody classified as a CD20-directed immunotherapy. It binds to the CD20 protein present on the surface of many mature B lymphocytes, a type of white blood cell involved in immune responses. By binding to CD20, rituximab promotes B-cell depletion through immune-mediated mechanisms, including antibody-dependent cellular cytotoxicity and complement activation. This activity makes it useful in selected B-cell malignancies and autoimmune diseases in which B cells contribute to disease activity. Rituximab is administered primarily by intravenous infusion under the supervision of trained healthcare professionals in a setting equipped to manage serious infusion reactions. Depending on the indication, it may be used alone or in combination with chemotherapy, methotrexate, or glucocorticoids and other immunosuppressive medicines. Its approved uses include certain forms of non-Hodgkin lymphoma, chronic lymphocytic leukaemia, rheumatoid arthritis, granulomatosis with polyangiitis, microscopic polyangiitis, and pemphigus vulgaris, depending on the product and jurisdiction. Because rituximab affects immune function, treatment can increase susceptibility to infections and reactivate certain latent infections. Screening, vaccination planning, laboratory assessment, and monitoring during and after treatment are important parts of safe clinical use.

Rituximab was developed as a monoclonal antibody targeting CD20 on B lymphocytes, establishing an important approach to treating B-cell malignancies and selected immune-mediated diseases. The United States Food and Drug Administration (FDA) first approved rituximab in November 1997 for relapsed or refractory low-grade or follicular B-cell non-Hodgkin lymphoma. European authorisation for the original rituximab product followed in 1998. Subsequent clinical development expanded its use to additional lymphoma subtypes, chronic lymphocytic leukaemia, rheumatoid arthritis, and selected forms of vasculitis. The pivotal LNH-98.5 study evaluated rituximab combined with CHOP chemotherapy in diffuse large B-cell lymphoma, while the REFLEX clinical trial supported its use in rheumatoid arthritis after inadequate response to tumour necrosis factor inhibitors. The RAVE and RITUXVAS studies contributed evidence for its role in ANCA-associated vasculitis. Regulatory authorities have also authorised rituximab biosimilars following comparative evaluations of quality, safety, and efficacy. In India, the Central Drugs Standard Control Organisation (CDSCO) oversees relevant approvals and regulatory decisions for rituximab products. CDSCO committee recommendations and product-specific marketing authorisations should be distinguished, and the approved indications must be checked against the applicable Indian prescribing information. Approval dates and indications may differ among reference products and biosimilars.

Rituximab is used for selected B-cell cancers and autoimmune conditions. In oncology, approved indications include certain forms of non-Hodgkin lymphoma, including follicular lymphoma and diffuse large B-cell lymphoma, and chronic lymphocytic leukaemia. Depending on the disease subtype and treatment setting, it may be administered as monotherapy or alongside chemotherapy. In autoimmune disease, rituximab is used with methotrexate for selected adults with moderately to severely active rheumatoid arthritis who have not responded adequately to specified previous treatments. It is also used with glucocorticoids for granulomatosis with polyangiitis and microscopic polyangiitis, which are inflammatory diseases affecting blood vessels. Certain rituximab products are approved for moderate to severe pemphigus vulgaris, an autoimmune blistering disorder affecting the skin and mucous membranes. Additional uses may be supported by clinical guidelines in particular settings, but not all uses are formally approved in every country. The exact indication depends on the patient's diagnosis, previous treatment, disease severity, the specific product, and local regulatory authorisation. Rituximab should be prescribed by clinicians experienced in the management of the relevant malignancy or immune-mediated condition.

Rituximab is administered by intravenous infusion and must not be given as an intravenous push or bolus. Dosing depends on the indication, body surface area or body weight where specified, treatment schedule, and whether it is combined with other medicines. For many adult non-Hodgkin lymphoma regimens, a commonly used dose is 375 mg/m² per infusion, given according to the chemotherapy or monotherapy schedule. In chronic lymphocytic leukaemia, it is administered with the relevant chemotherapy regimen using indication-specific dosing. For rheumatoid arthritis, a commonly used regimen is two 1,000 mg intravenous infusions separated by two weeks, with subsequent courses determined by clinical response and prescribing guidance. For granulomatosis with polyangiitis and microscopic polyangiitis, induction regimens may use 375 mg/m² weekly for four doses or another approved regimen, depending on the product and treatment plan. Pemphigus vulgaris has its own induction and maintenance schedule. Premedication, typically including an antipyretic and an antihistamine, is recommended before each infusion; glucocorticoid premedication is used when indicated. Infusion rates are adjusted according to tolerability and product instructions. Treatment duration and retreatment depend on the disease, response, adverse effects, and the applicable prescribing information.

Common side effects of rituximab include infusion-related reactions, fever, chills, fatigue, headache, nausea, itching, rash, and changes in blood pressure during administration. Infusion reactions are particularly common with the first infusion and may become less frequent with subsequent doses. Upper respiratory tract infections and other infections may occur because treatment reduces B-cell activity. Some patients develop low blood counts, including neutropenia, or experience gastrointestinal symptoms and muscle or joint discomfort. In patients receiving rituximab with chemotherapy or other immunosuppressive medicines, adverse effects may also arise from the accompanying treatment. The type and severity of side effects vary according to the indication, dose, treatment combination, and individual medical history. Premedication, careful infusion-rate adjustment, and clinical observation can help manage infusion reactions. Patients should report persistent fever, unusual bruising, worsening fatigue, new respiratory symptoms, or other signs of infection. Regular review allows clinicians to determine whether supportive treatment, additional investigations, or changes to the treatment schedule are needed.

Rituximab carries important warnings for severe or fatal infusion-related reactions, hepatitis B virus reactivation, severe mucocutaneous reactions, and progressive multifocal leukoencephalopathy (PML), a rare but potentially fatal brain infection associated with JC virus. Infusion reactions can involve breathing difficulties, low blood pressure, cardiac complications, or anaphylaxis and require prompt management. Hepatitis B can reactivate during or after treatment, potentially causing severe liver injury; screening and appropriate monitoring are essential. Serious bacterial, viral, fungal, and opportunistic infections can occur, particularly when rituximab is combined with chemotherapy or other immunosuppressants. Rare complications include tumour lysis syndrome in patients with certain malignancies, severe skin or mucosal reactions, and prolonged reductions in immunoglobulin levels or blood cell counts. Rituximab is generally contraindicated in patients with severe hypersensitivity to the medicine or relevant components and should not be administered in the presence of certain severe active infections or profound immunocompromise, according to product-specific guidance. Treatment may need to be delayed, interrupted, or discontinued for serious infusion reactions, severe infection, suspected PML, or other major toxicities. New neurological symptoms, blistering or peeling skin, breathing difficulty, jaundice, or persistent fever require urgent clinical assessment.

Before starting rituximab, assess the patient's diagnosis, previous treatments, infection history, complete blood count, and relevant organ function. Screen for hepatitis B using appropriate serological tests, including hepatitis B surface antigen and core antibody, and arrange specialist assessment and antiviral prophylaxis or monitoring when indicated. Evaluate for active infections and consider immunoglobulin levels in patients with recurrent infections or those receiving repeated courses. Vaccination status should be reviewed before treatment because B-cell depletion can reduce vaccine responses. Where feasible, administer appropriate vaccines before therapy; live vaccines are generally avoided during treatment and until immune recovery is adequate, in accordance with product guidance. Patients should be assessed for cardiovascular and pulmonary risk before infusion, particularly if they have a history of cardiopulmonary disease. Rituximab is a biologic antibody and does not generally have the same pattern of conventional metabolic drug interactions as many small-molecule medicines. However, combining it with chemotherapy, glucocorticoids, or other immunosuppressants can increase infection and blood-count-related risks. Concomitant use with other biologic disease-modifying therapies requires careful consideration because of potential additive immunosuppression. Pregnancy, breastfeeding, and plans for conception require individual assessment because treatment may affect immune-cell populations and fetal or neonatal B-cell counts. Follow product-specific guidance for contraception, treatment timing, and infant vaccination considerations where relevant.

Confirm the indication, exact rituximab product, dosing schedule, and any accompanying chemotherapy or immunosuppressive therapy before treatment. Record the product name and batch number to support biological traceability. Before the first infusion, review hepatitis B screening, infection status, complete blood count, relevant immunoglobulin measurements, vaccination history, and cardiovascular or pulmonary risk. Ensure recommended premedication is administered and that trained staff, emergency medicines, oxygen, and resuscitation facilities are available. Start the infusion at the rate specified by the product information and increase it only as tolerated. Monitor vital signs and symptoms during infusion, with closer observation for patients at increased risk of severe reactions. Counsel patients to report fever, persistent cough, jaundice, unusual bruising, severe skin changes, or new neurological symptoms promptly, including symptoms arising after treatment has ended. Review vaccination timing and infection-prevention measures, particularly when rituximab is combined with chemotherapy or glucocorticoids. Assess response and adverse effects before repeat courses, and consider immunoglobulin monitoring in patients with recurrent infections or prolonged treatment. Coordinate care with oncology, rheumatology, nephrology, dermatology, and pharmacy teams as appropriate to the indication.