Rituxan (rituximab), from Biogen and Genentech (part of the Roche group), is a prescription medicine for the treatment of different types of cancer, including follicular lymphoma. In Europe, Rituxan is marketed under the brand name MabThera.
As it is a slow-growing lymphoma, follicular lymphoma does not always require immediate treatment. The U.S. Food and Drug Administration (FDA) approved Rituxan in 2006 as a first-line treatment for follicular lymphoma, combined with or following chemotherapy. In January 2011, its indication was expanded by the FDA to include Rituxan’s use as a maintenance therapy for follicular lymphoma patients following chemotherapy.
How Rituxan works
Follicular lymphoma is caused by the abnormal behavior and growth of B-cells, a type of immune cell.
Rituxan is a monoclonal antibody, meaning it is a protein designed to interact with a specific target. It binds to CD20, a protein found on B-cells that is commonly over-produced in certain types of lymphomas.
When Rituxan binds to CD20, it triggers the death of cancerous B-cells. Researchers think that two mechanisms may be involved in this destruction: complement dependent cytotoxicity (CTC), a mechanism where antibodies target cells and activate the complement cascade, leading to cell death; or antibody dependent cell-mediated cytotoxicity (ADCC), an immune mechanism through which cells are destroyed as a result of the interaction between proteins present on the cell surface and antibodies such as Rituxan.
Rituxan in clinical trials
Rituxan has been investigated extensively in clinical trials for follicular lymphoma, both alone and in combination with other therapies.
One of the key trials that led to the FDA approval was a Phase 3 clinical trial, called M39021, which enrolled 322 patients with advanced CD20-positive follicular lymphoma who had not yet received chemotherapy. These patients were randomly assigned to receive eight cycles of either CVP (chlorambucil, vincristine, prednisone) chemotherapy alone or a combination of Rituxan and CVP (R-CVP) therapy.
The results were published in the scientific journal, Blood. The researchers reported a significant improvement in median progression-free survival at 15 months with CVP therapy alone and at 32 months with the R-CVP combination therapy. The median time to treatment failure was also lesser in patients who received chemotherapy alone (seven months) compared to R-CVP (27 months).
Rituxan was approved as a follicular lymphoma maintenance therapy based on the results of an open-label, randomized, Phase 3 trial (NCT00140582) called the PRIMA study. The trial recruited 1,217 patients with previously untreated advanced follicular lymphoma at 223 sites in 25 non-U.S. countries. Patients were initially treated with a Rituxan and chemotherapy induction regimen, with 1,018 people achieving a partial response. These patients were randomly assigned to receive either Rituxan or no maintenance treatment (observation only) for up to two years.
Results, published in the journal The Lancet, suggested that Rituxan as a single agent maintenance therapy can significantly improve progression-free survival. At a median follow-up time of 36 months, progression-free survival was 74.9 percent in the Rituxan group and 57.6 percent in the observation group. However, overall survival was not significantly affected by Rituxan therapy.
Further clinical studies involving Rituxan are ongoing or recruiting participants. Examples include the Phase 3 FLIRT trial (NCT02303119), comparing the safety and efficacy of a standard intravenous infusion of Rituxan compared to a new formulation in which Rituxan injected under the skin. This trial may still be recruiting up to 202 patients at multiple sites in France. Other trials are assessing Rituxan alone or in combination with other therapies, such as Imbruvica (ibrutinib, NCT02451111) and bendamustine (NCT02423837).
Some serious side effects may occur with Rituxan treatment and should be brought immediately to a doctor’s attention, namely:
- infusion reactions, which may occur during or within 24 hours of treatment. Symptoms include hives, rash, itching, facial or oral swelling, sudden cough, shortness of breath, difficulty breathing, weakness, dizziness, feeling faint, racing heart, or chest pain.
- severe skin and mouth reactions with painful sores, ulcers, or blisters on the skin, lips or mouth, peeling skin, rashes, or pustules.
- reactivation of hepatitis B virus.
- progressive multifocal leukoencephalopathy (PML), a rare brain infection. Symptoms include thinking difficulties, loss of balance, changes in speech or walking, weakness on one side of the body, or blurred or lost vision.
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