Modification of lead structures for improved Sample Clauses

Modification of lead structures for improved cell permeability and oral bioavailability: Because AGs are highly charged, water soluble compounds, they have poor intestinal absorption and are usually injected. In addition, AGs are short-lived in the circulatory system, rapidly eliminated by glomerular filtration in the kidney. They also exhibit poor permeability into eukaryotic cells, which requires higher dosages that often cause harmful side effects that limit their use in therapy. In order to overcome these limitations we designed different sets of compounds. One of such sets (Fig. 6) considers that all hydroxyls of the AG are replaced by esters. The rationale is to increase the lipophilicity and cell-permeability of the drugs, improve in-vivo half-life and oral bioavailability. These changes should provide important therapeutic benefit over treatment with the initial lead alone. The suggested modifications on NB124 and G418 (Fig. 6) to yield the corresponding per-benzoate esters (OBz, 51 and 52, respectively) are based on the following observations. (i) In our most recent comparative study of our lead compounds using an extended repertoire of CF cell lines, reporters, assays and animal models, comp. NB124 was able to most effectively rescue CFTR function, was superior to gentamicin, exhibited favorable pharmacokinetics, and was less cytotoxic than gentamicin in the explant model of ototoxicity10; (ii) the benzoate esters 51 and 52 are chemically more stable than the corresponding simple alkyl asters (like acetate, isobutirate, isopropionate); (iii) the poly-esters 51 and 52 can easily be prepared in good overall yields from the corresponding AGs in three steps (Boc2O, Et3N, H2O/MeOH; BzCl, Py, 4DMAP; TRA, CH2Cl2); (iv) to test our hypothesis we initially used 52 as a prototype derived from commercial G418. Preliminary tests of 52 against its parent G418 demonstrated that 52 lacks any readthrough activity both in cell free (see the data in the 1st year research report) assays and HEK293 cells stably expressing UGAC/CGAC dual luciferase (Fig. 7A) even when the incubation time was extended up to 72 hrs. Interestingly, when we tested the antibacterial activities of G418 and 52, we found that while the activity of 52 was similar to that of G418 against various G- and G+ WT bacteria, the MIC values of 52 were significantly lower than that of G418 in bacterial strains harboring plasmids of AG resistance determinant enzymes (see the data in the 1st year research report). Encouraged, we argued that HEK293 ...