The Rituxan (Rituximab)

The Rituxan (Rituximab) antibody is a genetically engineered chimeric murine/human monoclonal antibody directed against the CD20 antigen found on the surface of normal and malignant B lymphocytes.

Mechanism of action:
The antigen CD20, human B-lymphocyte-restricted differentiation antigen, located on pre-B, mature B-lymphocytes and B-cell non-Hodgkin’s lymphomas (NHL). The CD20 antigen is not expressed on hematopoietic stem cells, pro-B-cells; normal plasma cells or other normal tissues.CD20 activation results in the activation of cell cycle and differentiation and possibly regulates a calcium ion channel.
 

Rituximab binds specifically to the CD20 antigen and activates specific cell lysis by different mechanisms including complement-dependent cytotoxicity (CDC) and antibody-dependent cell mediated cytotoxicity (ADCC).

Uses:
Rituximab is indicated as second and third line treatment for patients with relapsed or refractory, low-grade or follicular, CD20-positive, B-cell, non-Hodgkin’s lymphoma.
 

Rituximab is indicated as a first-line treatment for patients with:
- follicular, CD20-positive, B-cell non-Hodgkin’s lymphoma in combination with CVP chemotherapy.
- diffuse large B-cell, CD20-positive, non-Hodgkin’s lymphoma in combination with CHOP or other anthracycline-based chemotherapy regimens.
 

Rituximab is indicated following first-line treatment with CVP chemotherapy for patients with low-grade, CD20-positive, B-cell non-Hodgkin’s lymphoma achieving a stable disease or a complete response.
 

Dose and administration:
Rituximab is given by intravenous drip (infusion). It is usually given at a dose of:
375 mg/m2 of Rituxan weekly for 4 to 8 weeks.

The dose is given with special precautions to possible infusion reactions.

Duration of therapy:
Relapsed or Refractory, Low-Grade or Follicular, CD20-Positive, B-Cell Non-Hodgkin’s Lymphoma:
Rituxan is administered at a dose of 375 mg/m2 IV infusion once weekly for 4 or 8 doses.
 

Retreatment Therapy:
Rituxan is given at a dose of 375 mg/m2 IV infusion once weekly for 4 doses for patients relapsing after a previous response to Rituxan.
 

Previously Untreated, Follicular, CD20-Positive, B-Cell NHL:
Rituxan is administered at a dose of 375 mg/m2 IV infusion, given on Day 1 of each 21 days cycle of CVP chemotherapy, for up to 8 doses.
 

Previously Untreated, Low-Grade, CD20-Positive, B-Cell NHL:
Rituxan is given for patients who did not progress following 6–8 cycles of CVP chemotherapy at a dose of 375 mg/m2 IV infusion, once weekly for 4 doses every 6 months for up to 16 doses.
 

Diffuse Large B-Cell NHL:
Rituxan is given at a dose of 375 mg/m2 IV per infusion on Day 1 of each 21 days cycle of chemotherapy for up to 8 infusions.

Toxicity:

The side effects of rituximab are generally mild mostly during the first dose and are usually milder with following doses.
 

The most serious reactions to Rituximab are:
1. Fatal Infusion Reactions.
2. Tumor Lysis Syndrome (TLS).
3. Mucocutaneous Reactions.
4. Progressive Multifocal Leukoencephalopathy (PML).

1. Fetal infusion reaction:
   Reports of fatal reactions for Rituximab following an infusion are very concerning. The reaction is in the form of hypoxia, pulmonary infiltrates, acute respiratory distress syndrome, myocardial infarction, ventricular fibrillation, or cardiogenic shock. 80% of these reactions occurred within the first infusion and is an indication for drug discontinuation.

2. Tumor lysis syndrome:
   A fatal acute renal failure requiring dialysis has been reported in patients with non-Hodgkin’s lymphoma (NHL) patients treated with Rituxan. The incidence is higher in patients with high numbers of circulating malignant cells (>25,000/mm3) or high tumor burden (tumor size greater than 10cm).

3. Mucocutaneous Reactions:
   Fatal severe mucocutaneous reactions, some with fatal outcome, have been reported in association with Rituxan treatment. These reports described different skin reactions like Stevens-Johnson syndrome, lichenoid dermatitis, vesiculobullous dermatitis, and toxic epidermal necrolysis. The reaction may occur 1–13 weeks following Rituxan therapy.

4. Progressive Multifocal Leukoencephalopathy (PML): A rare form of brain infection and death has been reported in patients treated with Rituxan.

Refrences:

The information contained in this page is based on Rituximab factsheet which is prodived by relaible sources which you can visit for more information like:

- FDA website.
- National Comprehensive Cancer Network NCCN.