Matched molecular pair analysis (MMPA) is an SAR analysis technique that has a particular attraction for medicinal chemists. As most medicinal chemists are initially trained as synthetic chemists, the concept of linking two molecules by an ‘alchemical reaction’ is quite intuitive to them. We also borrow from synthetic chemistry and use the term ‘transformation’ to denote the chemical change from one molecule in a matched pair to another. Although MMPA has been part of the ‘folk practice’ of medicinal chemistry for decades it is only in the last 20 years that it has been more formalised.¹  This formalisation has...