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Example 37
To improve inhibition potency relative to FAAH, various portions of the t-TUCB molecule were modified to identify potential FAAH pharmacophores. The 4-trifluoromethoxy group on t-TUCB was modified to the unsubstituted ring (A-3), 4-fluorophenyl (A-2) or 4-chlorophenyl (A-26). Potency on both sEH and FAAH increased as the size and hydrophobicity of the para position substituent increased, with 4-trifluoromethoxy being the most potent on both enzymes. Substituting the aromatic ring for a cyclohexane (A-3) or adamantane (A-4) resulted in a complete loss in activity against FAAH. Results are summarized in Table 1 below.
Next, the center portion of the molecule was modified to further investigate the specificity of t-TUCB on FAAH. Switching the cyclohexane linker to a cis conformation (A-5) resulted in a 20-fold loss of potency while removing the ring and replacing it with a butane chain (A-6) resulted in a completely inactive compound. While this suggests the compound must fit a relatively specific conformation in the active site to be active, we found the aromatic linker had essentially the same potency on FAAH (A-7). Although many potent urea-based FAAH inhibitors have a piperidine as the carbamoylating nitrogen, the modification to piperidine here reduced potency 13-fold. Results are summarized in Table 2 below.
Since none of the modifications at this point improved potency towards FAAH, we focused on the benzoic acid portion of the molecule as shown in Table 3. To determine the importance of the terminal acid, the corresponding aldehyde (A-20) and alcohol (A-24) in addition to the amide (A-19) and nitrile (A-11) were tested. While the amide had slightly improved potency, the more reduced forms of the acid (A-20 and A-24) and amide (A-11) had substantially less activity on FAAH. Converting the benzoic acid to a phenol (A-21) increased potency while the anisole (A-22) was completely inactive. Since the amide and acid appeared to be active, the amide bioisostere oxadiazole (A-25) was tested and had 38-fold less potency than the initial compound.
Since the substrates for FAAH tend to be relatively hydrophobic lipids, we speculated that conversion of the acid and primary amide to the corresponding esters or substituted amides would result in improved potency. The methyl ester (A-12) had 4-fold improved potency relative to the acid. Improving the bulk of the ester with an isopropyl group (A-13) results in a 11-fold loss in potency relative to the methyl ester. However, the similar potency of the benzyl ester (A-14) to the methyl ester demonstrates the bulk but not the size affects potency. Reversing the orientation of the ester (A-23) reduces the potency 3.4-fold. Relative to the primary amide, the methyl (A-18), ethanol (A-15) and glycyl (A-16) amides were all slightly less potent; however, the benzyl amide (A-27) was substantially less potent (16-fold). Generating the methyl ester of the glycyl amide (A-17) increased the potency 4-fold compared to the corresponding acid.
Example 20
Coupling of the ligand to the nanoparticle may be achieved uniquely by following an inclusion compound protocol with β-cyclodextrin (β-CD) on the particle spontaneously interacting with adamantane on the peptide or small molecule ligand to form an inclusion complex. Briefly, cyclodextrin-PEG-DSPE derivative will be synthesized via mono-6-deoxy-6-amino-β-cyclodextrin. One of the seven primary hydroxyl groups of β-cyclodextrin will be tosylated using p-toluenesulfonyl chloride. Substitution of the tosyl group by azide and subsequent reduction with triphenylphosphine will yield mono-6-deoxy-6-amino-β-cyclodextrin. Carboxyl-activated PEG-DSPE will be conjugated to mono-6-deoxy-6-amino-β-cyclodextrin to produce cyclodextrin-PEG-DSPE. Adamantane-amine will be directly conjugated through a short spacer in the solid phase peptide synthesis to the carboxyl end of the peptide to produce adamantane-peptide/ligand. The simple room temperature mixing of adamantane-amine and β-cyclodextrin bearing nanoparticle will produce peptide coupled targeted nanoparticle.