From Nature:
Researchers are trying to explain how a prototype drug that manipulates the immune system triggered devastating side effects in a British clinical trial. The trial shot into headlines earlier this week when all six patients who took an experimental antibody fell rapidly and severely ill. Such an extreme reaction among so many trial participants is extremely rare. The UK medical products regulatory agency swiftly halted the trial and launched an investigation.
It is not clear whether the problem is due to a manufacturing error, contamination or the wrong dosage. It is also possible that this first trial in humans simply shows we are affected by the drug in a way that animals are not. The drug, an antibody called TGN1412, is being developed by German company TeGenero with the aim of directing the immune system to fight cancer cells, or calm joints inflamed by rheumatoid arthritis. The antibody binds to a receptor molecule called CD28 on the surface of the immune system’s infection-fighting T cells.
More here.