Structure-based design
My current interest is in understanding the non-additivity often seen in structure-activity relationships. The most striking example is seen
in the SAR of HCV protease inhibitors, in which, for example, the replacement of a P3 isopropyl by a cyclohexyl can sometimes yield
a 16-fold boost in potency, while sometimes it has no effect. This was seen at Vertex (see RB Perni et al publications) on scaffolds that differed
very slightly, in the P1' region.
My initial attempt to understand that was to extend the lattice model of Miller and Dill. At some point, that
manuscript-in-preparation "Non-additivity in structure-additivity relationships and molecular recognition",
will be polished and submitted. There I was guessing that binding site side-chain flexibility was the primary source of non-additivity. The lattice
model suggests this is only a modest contributor to the overall non-additivity.
I have a new speculation about what may be the dominant source of non-additivity in SAR's, and am exploring that. I'm scheduled to present that
work at the Boston ACS meeting in August, 2007.
Non-additivity is also interesting in that it may be the answer to something I've long been searching for. As I've commented in print a number of times,
any drug designer has an intuitive sense that some SAR's are "easy", some are "difficult", with all variations in between. I've long wished to have
a way to calibrate that more precisely, much in the way that white-water canoeists rate the difficulty of different rapids. I've developed a single
number which characterizes the degree of non-additivity in a SAR. This metric appears to track with one's intuitive perception of how difficult
an SAR is, and may be one way of accomplishing this rating. When the non-additivity is high, our modelling methods tend to perform poorly, and medicinal
chemists' intuition tends to fall down.
Pharmacophore discovery
These methodologies are also called 'pharmacophore identification', 'pharmacophore perception', or 'receptor mapping'. The first commercial software
for pharmacophore discovery was the Catalyst software, of which
I was one of the co-authors. (DISCO is often cited as the first, but that appeared from Abbott only after they'd seen initial versions
of Catalyst. DISCO did indeed appear in the literature before Catalyst). Catalyst's approach to pharmacophore discovery has
numerous weaknesses, which I've addressed in my latest work on pharmacophore discovery, DANTE, which is described in the following papers.
Those interested in anything related to matters above: send me an e-mail and let's initiate a dialogue.
History
Definition of the term pharmacophore
The material that was here for many years has now been moved to a refereed journal,
in a 2007 article by me
in the IEJMD, an issue dedicated to Monty Kier.
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