Rituxan (rituximab) is immunotherapy, not chemotherapy. It is a monoclonal antibody, a lab-engineered protein designed to lock onto a specific target on the surface of certain cells and flag them for destruction by your immune system. This is fundamentally different from chemotherapy, which uses toxic chemicals to kill rapidly dividing cells throughout the body. The confusion is understandable, though, because Rituxan is very often given alongside chemotherapy drugs as part of the same treatment plan.
How Rituxan Works
Rituxan targets a protein called CD20, which sits on the surface of B cells, a type of white blood cell. Both normal and cancerous B cells carry this protein. When Rituxan binds to CD20, it essentially paints a target on the cell, recruiting your own immune system to find and destroy it. It also disrupts internal survival signals that help cancer cells resist death, making them more vulnerable.
Chemotherapy takes a blunter approach. Traditional chemo drugs poison the process of cell division itself, killing any cell that’s rapidly multiplying. That’s why chemo damages hair follicles, the gut lining, and bone marrow along with cancer cells. Rituxan, by contrast, only attaches to cells displaying the CD20 protein, leaving most other cells alone.
Why It’s Often Given With Chemotherapy
Even though Rituxan isn’t chemotherapy, you’ll rarely hear about it in isolation for cancer treatment. The most well-known example is the R-CHOP regimen, used for non-Hodgkin lymphoma. The “R” stands for rituximab; the remaining letters represent four drugs, most of which are traditional chemotherapy agents. Providers sometimes call this combination “immunochemotherapy” to reflect the fact that it blends both approaches.
Adding Rituxan to the older CHOP regimen in the early 2000s significantly improved cure rates for non-Hodgkin lymphoma and made R-CHOP the new standard of care. The drugs complement each other: chemotherapy directly kills dividing cancer cells, while Rituxan marks cancer cells for immune destruction and weakens their ability to resist the chemo. Research from the American Association for Cancer Research has shown that rituximab can actually sensitize drug-resistant lymphoma cells, making them respond to chemotherapy they had previously survived.
FDA-Approved Uses
Rituxan is approved for both cancer and autoimmune conditions, which further sets it apart from chemotherapy. On the cancer side, its approved uses include several forms of non-Hodgkin lymphoma (both as a standalone treatment and combined with chemo) and chronic lymphocytic leukemia. On the autoimmune side, it’s approved for rheumatoid arthritis that hasn’t responded to other treatments, two forms of blood vessel inflammation (granulomatosis with polyangiitis and microscopic polyangiitis), and pemphigus vulgaris, a serious blistering skin disease.
The autoimmune uses make sense once you understand the mechanism. In these conditions, B cells are misbehaving and attacking your own tissues. Rituxan depletes those B cells the same way it depletes cancerous ones, by targeting CD20.
What Side Effects to Expect
Rituxan’s side effect profile overlaps with chemotherapy in some ways but differs in others. The most distinctive side effect is infusion reactions. Up to 77% of patients experience some type of reaction during their first infusion, ranging from mild fever and chills to more serious symptoms like drops in blood pressure. These reactions tend to be less severe with subsequent infusions.
Some side effects traditionally associated with chemo can still occur with Rituxan, though often less severely. Nausea and vomiting are possible. Hair thinning is listed as a side effect, though it’s generally milder than the dramatic hair loss many people experience with conventional chemotherapy drugs. When Rituxan is given as part of a combination like R-CHOP, the more intense side effects (severe nausea, significant hair loss, immune suppression) are usually driven by the chemotherapy components rather than the Rituxan itself.
How It’s Given
Rituxan is administered either as an intravenous infusion or a subcutaneous injection. The IV version takes roughly 1.5 to 2.5 hours per session. A newer subcutaneous formulation can be injected under the skin in about 5 minutes, though it’s typically only offered after you’ve tolerated at least one full IV infusion without serious reactions.
B-Cell Recovery After Treatment
Because Rituxan depletes B cells, your immune system needs time to rebuild its B-cell population after treatment ends. This isn’t a quick bounce-back. Studies show B-cell depletion commonly lasts 9 to 26 months after the final dose, with some patients still showing depleted levels nearly two years later. During this window, you may be more susceptible to infections, since B cells play a key role in your immune defense. Your care team will typically monitor your blood counts to track recovery.
This prolonged immune effect is another way Rituxan differs from most chemotherapy drugs, which clear the body relatively quickly. With Rituxan, the drug itself is gone within months, but the biological impact of removing B cells lingers much longer.