How does rituximab work?

How does rituximab work? No one knows for sure (much like the IUD)!

This is from Ben Townsend's blog or so I'm guessing:

Rituximab (also known as Rituxan) is emerging as the frontline treatment of Follicular Lymphoma. I have attempted to understand this drug and how it works. It is called a Monoclonal Antibody (thus the “-mab” of Rituximab). Somehow it attaches itself to a cancer cell and causes that cell to be destroyed. The testing at present is attempting to show that the “watchful waiting” until the Lymphoma grows may be a thing of the past. Clinical trials are showing that starting off with Rituximab every two months for a few years keeps the Cancer at bay for approximately 7 to 8 years, much longer than any other treatment has done in the past. This is known as treating the Lymphoma “asymptomatic” (before any symptoms show up). The side effects of Rituximab are much less that Chemotherapy. However, sometimes Rituximab is used in conjunction with Chemotherapy. My Oncologist, the brilliant Dr. Kosinski, told me that adding the Chemotherapy causes the Rituximab to have a 90% effect on the Cancer cells, while the Rituximab alone offers a 60% effect.
Still, it is not known exactly how the Rituximab causes the destruction (a process called “Lysis”) of the Cancer cell. It may cause the cell to be destroyed one of three ways or more.

1. The first way is Apoptosis, which causes the Cancer cell to induce it’s own death (kind of like suicide).
2. The second way is called Antibody-dependent Cell-mediated Cytotoxicity (ADCC), where the NK (Natural Killer) cells send a signal to the target cell, causing it to die.
3. Third, a Complement-dependent Cytoxicity (CDC) which is where holes are punched into the Cancer cell, causing that cell’s death. Also, Rituximab sends a signal to the Cancer cell to stop dividing. All we really do know is that the Rituximab attaches itself to a strand that comes out of the Cancer cell known as the “CD20 Protein.” This long strand loops out of the cell and then back into the cell.

The following pictures shows the portion of the cell that has the CD 20 Protein on it.

http://drbentownsend.wordpress.com/2011/03/02/rituximab-treatment/

What we do know is that this stuff is expensive: Rituxan is costly. It costs about $10,000.00 a treatment, which is simply getting an IV bag of saline with about 750 milligrams of Rituxan in it. 750 mg is equal to about 25 ounces.  The normal Rituxan treatment is one IV every two months for two years, or 12 treatments.