The problems with animal testing.

And then there's the monoclonal antibody TGN1412, an artificial antibody designed to bind to certain T-cell receptors, thereby cutting off autoimmune attacks. Instead of dousing the immune response, TGN1412 seems to have bound to cells in a way that unleashed a chemical chain reaction. Animal tests are particularly tricky for monoclonal antibodies—a hot area of development for cancer and autoimmune disease—because these drugs target very complex, specific human proteins. According to a recent FDA-authored review article, only chimpanzees and humans provide realistic models for testing many monoclonal antibodies. And even our fellow primates have divergent immune systems. They can be infected with HIV-like viruses, for example, without getting sick. Plus, the endangered chimps are not the ideal test animals. Different as they are, they seem too much like us to be guinea pigs.