Prostaglandin D2

Prostaglandin D₂ (or PGD₂) is a prostaglandin that binds to the receptor PTGDR (DP₁), as well as CRTH2 (DP₂). It is a major prostaglandin produced by mast cells – recruits Th2 cells, eosinophils, and basophils. In mammalian organs, large amounts of PGD₂ are found only in the brain and in mast cells. It is critical to development of allergic diseases such as asthma. Research carried out in 1989 found PGD₂ is the primary mediator of vasodilation (the "niacin flush") after ingestion of niacin (nicotinic acid).

A 2012 research paper indicates a causal link between elevated levels of localized PGD₂ and hair growth inhibition. Applied topically, the researchers found PGD₂ prevents hair growth, and mice that were genetically inclined to produce higher levels of PGD₂ had inhibited hair growth. The researchers also found PGD₂ levels were much higher in balding scalp tissue than nonbalding scalp tissue, through increased levels of prostaglandin D2 synthase. The paper suggested that inhibition of hair growth involved binding of PGD₂ to a DP₂ receptor, and that DP₂ therefore would be a therapeutic target for androgenic alopecia in both men and women with hair loss and thinning. Because PGD₂'s relation to asthma has been known for several years, several drugs that seek to reduce the effect of PGD₂ through blocking the DP₂ are already in clinical trials.

In silico simulations have predicted the following as potential inhibitors of PGD₂ synthase: