Quantitative structure-activity relationships in a series of endogenous and synthetic steroids exhibiting induction of CYP3A activity and hepatomegaly associated with increased DNA synthesis.

The results of a quantitative structure-activity relationship (QSAR) study on a total of 14 steroids exhibiting induction of a CYP3A-associated activity and increase in liver weight/DNA synthesis is reported. It is found that different, but related, structural descriptors correlate with increase in ethylmorphine N-demethylase activity (r=0.92) and with the increase in liver weight (r=0.78) and DNA synthesis (r=0.78). Although there is a strong correlation between increase in liver weight and DNA content (r=0.999), neither of these correlated with ethylmorphine N-demethylase activity. These findings are discussed in the light of CYP3A induction, substrate specificity and inhibition; a proposed model of human CYP3A4 based on sequence homology with CYP102, a bacterial P450 of known crystal structure, demonstrates the possible mode of interaction between substrates and inhibitors within the putative active site.