A DNA-encoded macrocyclic peptide library was designed and synthesized with 2.4 × 10 members composed of 4-20 natural and non-natural amino acids. Affinity-based selection was performed against two therapeutic targets, VHL and RSV N protein. On the basis of selection data, some peptides were selected for resynthesis without a DNA tag, and their activity was confirmed.

The stereospecific synthesis of a series of alpha-methylpyrrolidine-5,5-trans-lactam inhibitors of human cytomegalovirus (HCMV) protease is described. Examination of the SAR in this series has defined the size and chirality of the alpha-substituent, optimized the acyl substituent on the lactam nitrogen, and defined the steric constraint of this functionality. The SAR of the functionality on the pyrrolidine nitrogen of the trans-lactam has been investigated, and this has led to the discovery of potent serine protease inhibitors that are highly selective for the viral enzyme over the mammalian enzymes elastase, thrombin, and acetylcholine esterase. The mechanism of action of our lead compounds has been established by mass spectrometry, and enzymatic degradation of HCMV deltaAla protease acylated with these inhibitors showed that Ser 132 is the active site nucleophile. The crystal structure of HCMV protease was obtained and used to model the conformationally restricted, chiral (S)-proline-alpha-methyl-5,5-trans-lactams into the active site groove of the enzyme, enabling us to direct and rationalize the SAR in this series. The activity against HCMV deltaAla protease is the greatest with inhibitors based on the dansyl-(S)-proline alpha-methyl-5,5-trans-lactam template, which have low nanomolar activity against the viral enzyme.

No abstract

Mechanism-based inhibitors of human cytomegalovirus (HCMV) protease have been designed based on the pyrrolidine-5,5-trans-lactam ring system. New routes to the beta-methyl-, desmethyl-, and alpha-methyl-pyrrolidine-5,5-trans-lactam templates have been developed from 2,4-diaminobutyric acid. ESI/MS studies have shown that these inhibitors can bind covalently and reversibly to the viral enzyme in a time-dependent manner by a mechanism which is consistent with acylation of HCMV deltaAla protease at the active site nucleophile Ser 132. SAR in this series of pyrrolidine-5, 5-trans-lactams has defined the relative stereochemisty of the methyl substituent adjacent to the lactam carbonyl, the functionality on the lactam nitrogen, and the mechanism of action of this novel series of serine protease inhibitors against the HCMV deltaAla protease. Activity decreases on moving from the alpha-methyl to the desmethyl to the beta-methyl series. This selectivity is the opposite of that observed for these templates against the elastase and thrombin enzymes. The activity against HCMV deltaAla protease is the greatest with inhibitors based on the Cbz-protected alpha-methyl-5,5-trans-lactam template which have low micromolar activity against the viral enzyme.

Activation of MrgX2, an orphan G protein‐coupled receptor expressed on mast cells, leads to degranulation and histamine release. Human MrgX2 binds promiscuously to structurally diverse peptides and small molecules that tend to have basic properties (basic secretagogues), resulting in acute histamine‐like adverse drug reactions of injected therapeutic agents. We set out to identify MrgX2 orthologues from other mammalian species used in nonclinical stages of drug development. Previously, the only known orthologue of human MrgX2 was from mouse, encoded by Mrgprb2. MrgX2 genes of rat, dog (beagle), minipig, pig, and Rhesus and cynomolgus monkey were identified by bioinformatic approaches and verified by their ability to mediate calcium mobilization in transfected cells in response to the classical MrgX2 agonist, compound 48/80. The peptide GSK3212448 is an inhibitor of the PRC2 epigenetic regulator that caused profound anaphylactoid reactions upon intravenous infusion to rat. We showed GSK3212448 to be a potent MrgX2 agonist particularly at rat MrgX2. We screened sets of drug‐like molecules and peptides to confirm the highly promiscuous nature of MrgX2. Approximately 20% of drug‐like molecules activated MrgX2 (pEC50 ranging from 4.5 to 6), with the principle determinant being basicity. All peptides tested of net charge +3 or greater exhibited agonist activity, including the cell penetrating peptides polyarginine (acetyl‐Arg9‐amide) and TAT (49‐60), a fragment of HIV‐1 TAT protein. Finally, we showed that the glycopeptide antibiotic vancomycin, which is associated with clinical pseudo‐allergic reactions known as red man syndrome, is an agonist of MrgX2.