Structure-activity relationships of a lead hydroxamic acid inhibitor of recombinant human stromelysin were systematically defined by taking advantage of a concise synthesis that allowed diverse functionality to be explored at each position in a template. An ex vivo rat model and an in vivo rabbit model of stromelysin-induced cartilage degradation were used to further optimize these analogs for oral activity and duration of action. The culmination of these modifications resulted in CGS 27023A, a potent, orally active stromelysin inhibitor that blocks the erosion of cartilage matrix.

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The matrix metalloproteinase enzyme MMP-13 plays a key role in the degradation of type II collagen in cartilage and bone in osteoarthritis (OA). An effective MMP-13 inhibitor would therefore be a novel disease modifying therapy for the treatment of arthritis. Our efforts have resulted in the discovery of a series of carboxylic acid inhibitors of MMP-13 that do not significantly inhibit the related MMP-1 (collagenase-1) or tumor necrosis factor-alpha (TNF-alpha) converting enzyme (TACE). It has previously been suggested (but not proven) that inhibition of the latter two enzymes could lead to side effects. A promising carboxylic acid lead 9 was identified and a convergent synthesis developed. This paper describes the optimization of 9 and the identification of a compound 24f for further development. Compound 24f is a subnanomolar inhibitor of MMP-13 (IC(50) value 0.5 nM and K(i) of 0.19 nM) having no activity against MMP-1 or TACE (IC(50) of >10000 nM). Furthermore, in a rat model of MMP-13-induced cartilage degradation, 24f significantly reduced proteoglycan release following oral dosing at 30 mg/kg (75% inhibition, p < 0.05) and at 10 mg/kg (40% inhibition, p < 0.05).

Cytokines, interleukin-1 (IL-I), tumor necrosis factor a, and the neurotransmitter, substance P, have been implicated in the pathogenesis of arthritis because they stimulate synovial cells to secrete prostaglandin E, and collagenase in vitro. We investigated in vivo changes in intraarticular substance P and the degradation of cartilage proteoglycan in response to intraarticular cytokine injections in rabbits. Twenty-four hours after a single injection of 10 ng, 30 ng, or 100 ng of recombinant human &la (rHuIL-la) per joint, the mean f SEM levels of substance P detected in the cell-free joint lavage fluid were 250 & 67 fmoles, 480 2 60 fmoles, and 530 & 130 fmoles (n = 4-9, respectively. The level of substance P in the contralateral knees injected with diluent was 58 -c 8 fmoles (n = 12). The level of substance P had increased by 2 hours after IL-1 injection and remained elevated in the joint 48 hours after injection. Cytokineinduced proteoglycan depletion was also time-and dosedependent. Proteoglycan concentrations in articular cartilage dissected from the weight-bearing condyles were calculated as the ratio of sulfated glycosaminoglycan measured using 1,9-dimethyImethylene blue:hydroxyproline. After 48 hours, 10 ng, 30 ng, or 100 ng of rHuIL-la per joint decreased proteoglycan levels by 9 f 4%, 14 f 4%, and 21 2 3% (n = a), respectively. Likewise, the injection of recombinant human