Here’s an update on the research in Ethan Perlstein’s lab, in which he raises an interesting question. When you screen against some sort of purified protein, you’re optimizing on potency, but not necessarily on many other properties (except perhaps, at some level, solubility in the buffer system). But a cell-based screen for an intracellular target is a higher bar. Now your compounds not only have to hit the target, enough to affect the readout, but they have to get into cells in the first place. And that’s not always easy. Outside of the “normal” polarity and molecular weight ranges, cell penetration can be pretty haphazard. There are a number of mechanisms to get across the cell membrane, but they each have their own preferences and idiosyncracies, which are not always clear.
Perlstein, though, is testing in nematodes, and those organisms have a famously impermeable cuticle. So you’re not going to diffuse into them; everything they get is an oral dose, if that’s the right word. Then a compound has to face the somewhat alien nemadotinal (nematoid?) digestive system. They don’t have a liver per se, so digestion and metabolic clearance are sort of blended together. And again assuming an intracellular target, any compound that’s active in such an assay will have had to survive the digestive enzymes, get absorbed, and then pass through cell membranes to reach its site of action. So the question is, will these compound then have even more of a leg up than the ones from a traditional cellular assay?
The compound shown in the post certainly performed well after an oral dose in mice, but Perlstein himself isn’t sure how general an effect this might be, and neither am I. I’m going to betray my lack of nematodal (nematodish?) experience, but has anyone generated transgenic ones with humanize protein targets? Does that even work? If so, it might turn out to be a good way to work through a large screening set, cutting right down to the compounds that have some built-in advantages.