I’m pleased to be able to announce that our latest paper, looking at applying statistical rigour to the expert SAR feature list that Kevin and I (and others, going all the way back to Lijinsky) have been able to assess subjectively, is finally out. We can now say that steric hindrance has a statistically-significant impact decrease on potency, and metabolically-labile features a statistically-significant increase (w.r.t. a hypothetical featureless nitrosamine).
The corollary of this is that we would expect a nitrosamine without activating features to be significantly less potent than NDEA/NDMA, and one with deactivating features to be significantly less potent again.