Substance P is an intriguing neurotrans-mitter molecule that has frustrated a generation of pharmacologists. For decades, it has been known to be highly active in both the brain and the gut — but it cannot easily be lured into the medicine cabinet. Researchers at drug giant Merck, in particular, have moved heaven and Earth to study the molecule and associated compounds. But the best they have managed so far is approval for the related drug Emend (aprepitant), which reduces nausea in chemotherapy patients and managed sales last year of only US$80 million or so. Last month, Merck gave up the chase, announcing that it would close down the research unit at Terlings Park, near London, that had been spearheading its investigation of Substance P.
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