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

ECONOMIST: Thalidomide

The new drug, called a CETP inhibitor, works by blocking the action of a protein which lowers levels of "good" cholesterol in the body.

BBC: Drug raises 'good' cholesterol

It works similarly to many pesticides, by blocking the breakdown of acetylcholine, a major neurotransmitter, leading to a rapid buildup of this chemical in the body.

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It is also present in fat cells, and blocking it seems to help the body more efficiently process sugar and fat from food.

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DPP-4 regulates hundreds of hormones in the body, not just GLP-1, and blocking it can have unintended effects on others.

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