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Medicine

A New Mode of Cancer Treatment 36

Posted by BeauHD from the there's-a-pill-for-everything dept.
As detailed in a paper published in Cell Chemical Biology, researchers have developed a "cancer-killing pill" capable of destroying solid tumors while leaving healthy cells unaffected. The new drug has been in development for 20 years and is now undergoing pre-clinical research in the U.S.. Derek Lowe, a medicinal chemist and freelance writer on science and pharmaceutical topics, writes about the new paper via Science Magazine: It's about a molecule designated AOH1996, which seems to have a unique mode of action in tumor cells, one that might make it more more selective for those as compared to normal ones. The key target here is a protein called PCNA (from its old name of "proliferating cell nuclear antigen"). [...] The current molecule is a traditional direct small molecule binder that is selective for caPCNA over the regular type, which is a very attractive advantage to explore. The team behind it has been working on it for several years now to validate that mechanism, and the new paper linked first above is their report of going all the way into animal models. AOH1996 is a very unremarkable-looking molecule - to be honest, it looks like the sort of stuff that you used to see in old combinatorial chemistry libraries in the late 90s and early 2000s, a couple of aryl-rich groups strung together with amide bonds. It's certainly not going to be the most soluble stuff in the world, but they seem to have been able to formulate it. But I'm definitely not going to make fun of any chemical structure that works! [...]

The new paper shows preclinical toxicity testing in two species (mice and dogs), which is what you need to get to human trials. It seems to pass those very well, with no signs of trouble at 6x the effective dose in either species. And if you were throwing DSBs all over the place in normal tissues, believe me, you'd see tox. It is clean in an Ames test, for example. As for efficacy, in cell assays the concentration needed for 50% growth inhibition across 70 different cancer cell lines averaged around 300nM, while it showed no toxic effects on various non-cancer lines up to 10 micromolar (at least a 30x window). The affected cells show cell-cycle arrest, replication stress, apoptosis, and so on. And application of AOH1996 along with other known chemotherapy agents made the cells much more sensitive to those, presumably because they couldn't deal with those on top of the problems that AOH1996 was already causing.

It also shows growth arrest in xenograft tumors in mouse models, with a no-effect dose at least six times its effective dose, and combination therapy with a topoisomerase inhibitor showed even more significant effects. The compound has entered a Phase I trial in humans on the basis of the above data, and I very much look forward to seeing it advance to Phase II, where it will doubtless be used in combination with several existing therapies. I hope that human cancers will prove vulnerable to this new mode of attack in the clinic, and that they are not able to mutate around it with new forms of caPCNA too quickly, either. The comparison with the peptide agent mentioned above will be especially interesting, too. There's only one way to find out - good luck to everyone involved!
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A New Mode of Cancer Treatment

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