The public has mostly focused on Erbitux's ability to slow tumor growth by blocking epidermal growth factor receptor, a key growth-promoting protein that is overabundant in many cancer cells.

FORBES: Bristol, ImClone File On Erbitux

The drugs work by blocking an enzyme called factor 10a that helps spur the production of a crucial clot-promoting protein called thrombin.

FORBES: Magazine Article

Thalidomide works, in part, by blocking the production of tumour necrosis factor-alpha, a biochemical which promotes inflammation in the body.

ECONOMIST: Thalidomide

By blocking a protein called the vascular endothelial growth factor (VEGF), it prevents arteries from growing around tumors, literally starving them.

FORBES: Genentech's Rite Of Spring

Enbrel works by blocking a long-mysterious protein in the immune system known as tumor necrosis factor, or TNF.

FORBES: Chemical Chameleon