“…We and others have written before about the potential utility of understanding the “likeness” of individual molecules to those considered representative of particular classes, such as drug-likeness (e.g., Karakoc et al, 2006; Paolini et al, 2006; Bickerton et al, 2012), natural-product-likeness (Ertl et al, 2008; Jayaseelan et al, 2012), or indeed metabolite-likeness (e.g., Cherkasov, 2006; Gupta and Aires-De-Sousa, 2007; Dobson P. D. et al, 2009; Peironcely et al, 2011; Walters, 2012; O'Hagan and Kell, 2015c; O'Hagan et al, 2015). Clearly this depends on the nature of the encoding used, but, as we see here, it can also depend markedly on the metric of similarity, that can be varied via the Tversky α and β parameters.…”