RE: Dox and other chemotherapies9 Feb 2023 13:33
An interesting topic JT. I'll have a go at answering parts at least, plus raising some considerations.
1.
AVA6000 has a different TAM from standard doxorubicin in two important respects: Firstly AVA6000, like all pre|CISION substrates only works in FAPa-rich cancers; that is not a consideration for using standard doxorubicin. Secondly, AVA6000 will have certain contraindications where there is a high level of FAPa in other, 'healthy' tissues such as fibrosis, inflammation and soon after major surgery or injury.
2.
Doxorubicin is in the anthracycline class of drugs - drugs that all have the same basic mechanism of action. Is there any reason why AVA6000 shouldn't replace all anthracyclines, subject to (1) above being satisfied? I don't think so. Add this to older people and people in poor health being treatable by an anticancer 'without' side effects and the AVA6000 TAM is enormous.
3.
AVA3996 was first worked on by Arisaph Pharmaceuticals in Boston, where it was given the research code ARI-3996 and exemplified in patents (e.g. US9597410B2).
Another chemical entity worked on by that company was ARI-3099DOX, also called just 3099DOX when exemplified in patents (e.g. WO2015192123A1) and ARI-6000. Now commonly known as AVA6000.
https://fundedresearch.cancer.gov/nciportfolio/search/details;jsessionid=A74DE699A48D0D1B0E898E2563A05FB1?action=abstract&grantNum=2R42CA156930-02&grantID=8714288&grtSCDC=FY%202014&absID=8714288&absSCDC=PUB2014
I'm not aware of Arisaph exemplifying any others. Hopefully they have been exemplified in Bachovchin's patents!
4.
To become a pre|CISION substrate, an anticancer drug needs to be able to form a peptide bond with 5140 (the leaving group), which can subsequently be cleaved by FAPa. From a conformational point of view - a 3D structure that can get in close to the FAP enzyme so that cleavage can take place - the drug would ideally have an exposed free amine (-NH2) group, as doxorubicin has. Velcade has a -NH- group in a ring but no -NH2 group and, as AVA3996 is described an a Velcade analogue, I assume that the peptide bond can't be formed with that -NH- in the ring, so a -NH2 group has been added somewhere in order to form the peptide bond with 5140. A peptide bond could be formed using the -NH- but, as an analogue has been made, I assume the resultant peptide bond couldn't be cleaved by FAP because of conformational (3D structure) issues. As an analogue it is a new chemical entity and so would require full testing for toxicity and efficacy.
These conditions will apply to all the pre|CISION pipeline: a free -NH2 group for the prodrug, otherwise an -NH2 group added and so an analogue; and the drug needs to have a 3D structure that allows the peptide bond to get close to FAP's cleaving site (so, as a general rule of thumb, small structures favoured over bulky ones). As an analogy, a key with a long handle works a lock but a key with a barrel wider than the keyhole won't.