Cell-based assays:Layout 1 14/1/10 19:58 Page 78
Assays
a GPCR specific like that. It’s just too diverse. But seem to work well. So the pharmacology was fine,
kinases are different. The kinase... it’s really just the background was fine, and you could use your
the ATP binding site type libraries. own cryopreserved stocks, or in one case we have
also bought stocks from a frozen cell providers.
Richard Eglen: So there’s no allosteric-rich frag- But we find it doesn’t work for every receptor or
mented library or something like that? every assay, probably because it’s related to that
receptor, sometimes we need to grow the cells a
David Marks: No. few days before we use them, or it doesn’t really
work, or we don’t have the time to optimise it. But
Arthur Christopoulos: Having said that, I’m aware it’s common to use them in our organisation, not
of at least one or two instances where colleagues in just for HTS, but also for head and lead optimisa-
pharma have said to me they’ve gone back and tion. You can use special cells for a very long time
enriched a focused library for allosteric modulators because projects take a long time and you want to
for a given target. have consistent results.
David Marks: Oh, for one target, yes. Not for gen- David Marks: For selectivity, I think that’s really an
eral kinases, no. advantage to use cryopreserved cells.
Arthur Christopoulos: And if you could do that, I Martin Valler: We’ve taken as our default strategy
think there’s something wrong with your concept. for assays, initial analysis can we produce frozen
cells do they provide the same data as cultivated
Martin Valler: For us, after the primary screen we cells and in most cases that is the case. So that is
go back and identify classes which could be default. The quality advantage is the batches are
enriched by external purchasing of compounds, the same, we can control with a fair degree of con-
but I’m sure the compound collection gradually fluence, and the quality control is better from day
assumes and increases the GPCR relevance. to day. We employ them predominantly for pri-
mary screening.
David Marks: Because screening is really not a bot-
tleneck at this point, we really don’t try to restrict Richard Eglen: The only thing that may come up on
our screen to a very small selective class. Just for an the horizon is if the world used screening in primary
example, we have seen a number of leads come out cell lines, what would it mean for primary cell lines
of what we have classified as a traditional kinase to cryopreserve them, some of the more esoteric cell
library. We find very good GPCR antagonists out types are a bit more finicky. DDW
of this. So we wouldn’t restrict ourselves to non-
kinase libraries when we screen for GPCRs, so we
wouldn’t want to miss those.
Martin Valler: Exactly, it’s not a bottleneck any-
more, and we want the full data picture at the
beginning to really pick the best. And the best is
really the core structural types, the phenotypes, the
class of the compound, but of course to go further,
it’s not just only the binding or activity, it’s also the
developability of the compounds, they have to
have a synthetic advantage and can we actually
make the compound and variations.
Robert Jordan: There’s been a lot of hype recently
about assay-ready, cryo-preserved frozen cells,
aliquots... are there any downsides to that
approach, do you think?
Guido Zaman: I don’t think so. What we’ve done
is carefully examine these cells, and look at what
the quality was, and in many cases, they really
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