Table 2.

 Comparative mechanisms of action for various anti-tumour necrosis factor (TNF) agents

Agent	Description of biologic construction	Binds soluble TNF	Binds membrane bound TNF	Fixes complement	Mediates &;ADC	Causes T cell apoptosis	Effective in unselected patients	Effective only in patients with elevated CRP
Infliximab	IgG1 chimeric monoclonal antibody	Yes	Yes	Yes	Yes	Yes	Yes	No
Etanercept	Fusion protein comprised of a human IgG1 Fc antibody fragment linked to two human soluble p75 TNF receptors	Yes	Yes	No	No	No	No	?
Adalimumab	Fully human IgG1 monoclonal antibody to TNF	Yes	Yes	Yes	Yes	Yes	?	?
CDP870	Humanised Fab fragment linked to PEG	Yes	Yes	No	No	?	No	Yes
CDP571	Humanised IgG4 monoclonal antibody	Yes	Yes	No	No	?	No	Yes
Onercept	Fully human soluble p55 TNF receptor monomer that binds soluble and membrane bound TNF but does not fix complement	Yes	Yes	No	No	No	No	?

ADC, antibody dependent cytotoxicity; CRP, C reactive protein; PEG, polyethylene glycol.