With the use of an NMR-based method, potent (IC50 < 25 nM) nonpeptide inhibitors of the matrix metalloproteinase stromelysin (MMP-3) were discovered. The method, called SAR by NMR (for structure−activity relationships by nuclear magnetic resonance), involves the identification, optimization, and linking of compounds that bind to proximal sites on a protein. Using this technique, two ligands that bind weakly to stromelysin (acetohydroxamic acid, K D = 17 mM; 3-(cyanomethyl)-4‘-hydroxybiphenyl, K D = 0.02 mM) were identified. On the basis of NMR-derived structural information, the two fragments were connected to produce a 15 nM inhibitor of this enzyme. This compound was rapidly discovered (less than 6 months) and required only a minimal amount of chemical synthesis. These studies indicate that the SAR by NMR method can be effectively applied to enzymes to yield potent lead inhibitorsan important part of the drug discovery process.

Cystic fibrosis (CF) patients receive repeated courses of aminoglycoside therapy. These patients would consequently be expected to be more susceptible to cochleotoxicity, a recognized side effect with single courses of aminoglycoside therapy. The primary aim of this retrospective study was to establish the incidence and severity of auditory deficit in CF patients. Standard (0.25-to 8-kHz) and high-frequency (10-to 16-kHz) pure-tone audiometry was carried out in 70 CF patients, and the results were compared with the results from 91 control subjects. These subjects were further divided into pediatric and adult groups. Of 70 CF patients, 12 (1 pediatric) displayed hearing loss considered to be caused by repeated exposure to aminoglycosides. There was a nonlinear relationship between the courses of therapy received and the incidence of hearing loss. The severity of the loss did not appear to be related to the number of courses received. Assuming the risk of loss to be independent for each course, preliminary estimates of per course risk of hearing loss were less than 2%. Upon comparison with previous clinical studies and experimental work, these findings suggest that the incidence of cochleotoxicity in CF patients is considerably lower than would be expected, suggesting that the CF condition may confer protection against aminoglycoside cochleotoxicity.

Objective. In order to investigate potential regulatory mechanisms for the increased production of prostaglandin E2 (PGE2) in interleukin‐1β (IL‐1β)–stimulated rheumatoid synovial fibroblasts (RSF), this study examined the induction of phospholipase A2 (PLA2) and prostaglandin H synthase (PGHS) enzymes and the correlation of these events with PGE2 production in IL‐1β–stimulated RSF. Methods. Protein and messenger RNA (mRNA) levels of cytosolic PLA2 (cPLA2) and PGHS‐2 enzymes in IL‐1β–stimulated RSF were measured by Western and Northern blotting, respectively, using specific antisera and complementary DNA probes. Enzymatic activity of cPLA2 was determined in cell‐free reaction mixtures utilizing mixed micelles of 14C‐phosphatidylcholine and Triton X‐100 as the substrate. PGE2 levels were quantitated using a commercial enzyme immunoassay kit. Results. Incubation of RSF with IL‐1β increased the mRNA and protein levels for the high molecular weight cPLA2 as well as for the mitogen/growth factor–responsive PGHS (PGHS‐2). The IL‐1 receptor antagonist completely abolished the induction of these two enzymes and the stimulation of PGE2 production by IL‐1β in RSF. In contrast, levels of the other known forms of these enzymes, i.e., the 14‐kd secretory group II PLA2 (sPLA2) and the constitutive form of PGHS (PGHS‐1), were unaffected by IL‐1β treatment. Conclusion. These are the first data to demonstrate the coordinate induction by IL‐1 of cPLA2 and PGHS‐2 in RSF. The time‐course for the induction of these enzymes suggests that their increase contributes to the increased production of PGE2 in IL‐1–treated RSF, and may help explain the capacity of RSF to produce large amounts of PGE2.

A novel series of sulfone N-formylhydroxylamines (retrohydroxamates) have been investigated as matrix metalloproteinases (MMP) inhibitors. The substitution of the ether linkage of ABT-770 (5) with a sulfone group 13a led to a substantial increase in activity against MMP-9 but was accompanied by a loss of selectivity for inhibition of MMP-2 and -9 over MMP-1 and diminished oral exposure. Replacement of the biphenyl P1' substituent with a phenoxyphenyl group provided compounds that are highly selective for inhibition of MMP-2 and -9 over MMP-1. Optimization of the substituent adjacent to the retrohydroxamate center in this series led to the clinical candidate ABT-518 (6), a highly potent, selective, orally bioavailable MMP inhibitor that has been shown to significantly inhibit tumor growth in animal cancer models.