Fenclozic acid (proposed brand name Myalex) is a nonsteroidal anti-inflammatory drug (NSAID) with analgesic, antipyretic, and anti-inflammatory properties developed in the 1960s by ICI Pharmaceuticals. It failed to pass the Phase III clinical trial, and was withdrawn from clinical development in 1971 due to severe dose-related hepatotoxicity and jaundice in humans, despite showing an excellent preclinical safety profile and promising clinical efficacy in animal testing. It is considered a classic example of human-specific drug induced liver injury linked to unique metabolic activation in humans.
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