The dominant current paradigm of drug discovery identifies potentially useful targets through one of a number of mics platform technologies.The target undergoes validation, compounds are screened and hits are developed into drug-like molecules.The identification of CP2117 as a potential anti-fibrotic agent has occurred through a process similar to earlier models of drug discovery based on the recognition of properties in existing compounds (drugs or endogenous substances) that have new, but under-optimised therapeutic potential.2-methoxyestradiol (2MEO) is a metabolite of estradiol with anti-proliferative, anti-angiogenic, cytotoxic and pro-apoptotic activities that confer on it anti-tumour properties.We identified that 2MEO inhibits proliferation of human cultured airway smooth muscle (HASM), albeit at concentrations that have agonist activity at high affinity estrogen receptors (ER) (Hughes et al., 2002).Estrogenic activity (Sutherland et al., 2005) together with the well-established microtubule inactivating actions of 2MEO were considered to limit its theratpeutic potential, by conferring endocrine and cytotoxic adverse effects, respectively.