The human monoclonals can also result in hypersensitivity reactions such as serum sickness. I've had serum sickness from Rituxan twice, so am very leery of the monoclonals. My Rheumatologist kept trying to push me into using Belimumab (Benlysta) which is a human antibody. I kept telling her no because I didn't want to risk it. She kept assuring me that the human antibody was different. About a year after she first brought it up, she told me that a new warning had just been added to include serum sickness to the list of side effects and that I was right to avoid it.
There is no way to know whether or not a person is at risk until they try, and the fact is that they could do just fine with a human vs mouse antibody. Knowing that I am susceptible to hypersensitivity reactions though, I prefer to stay away from the monoclonals. Having serum sickness twice was enough for me.
Infusion-related events occurred with dose 1 (300 mg) in 12 pts and with dose 2 (1000 mg) in 7 pts; all infusion events were grade 1–2 except 2 grade 3 events (rash, serum sickness).
ash.confex.com/ash/2010/webprogram/Paper29639.html
Monoclonal antibodies: Monoclonal antibodies (mAbs) are manufactured in vitro to recognize specific targeted Ags; they are used to treat solid and hematopoietic tumors and inflammatory disorders. The mAbs that are currently in clinical use include
Murine
Chimeric
Humanized
Murine mAbs are produced by injecting a mouse with an Ag, harvesting its spleen to obtain plasma cells that are producing Ab specific to that Ag, fusing those cells with immortal mouse myeloma cells, growing these hybridoma cells (eg, in cell culture), and harvesting the Ab. Although mouse antibodies are similar to human antibodies, clinical use of murine mAbs is limited because they induce human anti-mouse Ab production, can cause immune complex serum sickness (a type III hypersensitivity reaction), and are rapidly cleared. An exception is muromonab-CD3 (OKT3), which effectively prevents acute rejection of solid organ transplants; it is typically given only once or twice to a patient receiving other immunosuppressants (see Transplantation: Monoclonal antibodies (mAbs)).
To minimize the problems due to use of pure mouse Ab, researchers have used recombinant DNA techniques to create monoclonal Abs that are part human and part mouse. Depending on the proportion of the Ab molecule that is human, the resultant product is termed chimeric or humanized. In both cases, the process usually begins as above with production of mouse hybridoma cells that make Ab to the desired Ag. Then the DNA for some or all of the variable portion of the mouse Ab is merged with DNA for human immunoglobulin. The resultant DNA is placed in a mammalian cell culture, which then expresses the resultant gene, producing the desired Ab. If the mouse gene for the whole variable region is spliced next to the human constant region, the product is termed "chimeric"; if only parts of the mouse gene for the binding portion of the variable region are used, the product, termed "humanized," is even more human.
www.merckmanuals.com/professional/immunology_allergic_disorders/biology_of_the_immune_system/immunotherapeutics.html
