Discovery and evaluation of a non-Zn chelating, selective matrix metalloproteinase 13 (MMP-13) inhibitor for potential intra-articular treatment of osteoarthritis.

Osteoarthritis (OA) is a nonsystemic disease for which no oral or parenteral disease-modifying osteoarthritic drug (DMOAD) is currently available. Matrix metalloproteinase 13 (MMP-13) has attracted attention as a target with disease-modifying potential because of its major role in tissue destruction associated with OA. Being localized to one or a few joints, OA is amenable to intra-articular (IA) therapy, which has distinct advantages over oral therapies in terms of increasing therapeutic index, by maximizing drug delivery to cartilage and minimizing systemic exposure. Here we report on the synthesis and biological evaluation of a non-zinc binding MMP-13 selective inhibitor, 4-methyl-1-(S)-({5-[(3-oxo-3,4-dihydro-2H-benzo[1,4]oxazin-6-ylmethyl)carbamoyl]pyrazolo[1,5-a]pyrimidine-7-carbonyl}amino)indan-5-carboxylic acid (1), that is uniquely suited as a potential IA-DMOAD: it has long durability in the joint, penetrates cartilage effectively, exhibits nearly no detectable systemic exposure, and has remarkable efficacy.

A new class of potent matrix metalloproteinase 13 inhibitors for potential treatment of osteoarthritis: Evidence of histologic and clinical efficacy without musculoskeletal toxicity in rat models.

OBJECTIVE: Matrix metalloproteinases (MMPs) have long been considered excellent targets for osteoarthritis (OA) treatment. However, clinical utility of broad-spectrum MMP inhibitors developed for this purpose has been restricted by dose-limiting musculoskeletal side effects observed in humans. This study was undertaken to identify a new class of potent and selective MMP-13 inhibitors that would provide histologic and clinical efficacy without musculoskeletal toxicity. METHODS: Selectivity assays were developed using catalytic domains of human MMPs. Freshly isolated bovine articular cartilage or human OA cartilage was used in in vitro cartilage degradation assays. The rat model of monoiodoacetate (MIA)-induced OA was implemented for assessing the effects of MMP-13 inhibitors on cartilage degradation and joint pain. The surgical medial meniscus tear model in rats was used to evaluate the chondroprotective ability of MMP-13 inhibitors in a chronic disease model of OA. The rat model of musculoskeletal side effects (MSS) was used to assess whether selective MMP-13 inhibitors have the joint toxicity associated with broad-spectrum MMP inhibitors. RESULTS: A number of non-hydroxamic acid-containing compounds that showed a high degree of potency for MMP-13 and selectivity against other MMPs were designed and synthesized. Steady-state kinetics experiments and Lineweaver-Burk plot analysis of rate versus substrate concentration with one such compound, ALS 1-0635, indicated linear, noncompetitive inhibition, and Dixon plot analysis from competition studies with a zinc chelator (acetoxyhydroxamic acid) and ALS 1-0635 demonstrated nonexclusive binding. ALS 1-0635 inhibited bovine articular cartilage degradation in a dose-dependent manner (48.7% and 87.1% at 500 nM and 5,000 nM, respectively) and was effective in inhibiting interleukin-1alpha- and oncostatin M-induced C1,C2 release in human OA cartilage cultures. ALS 1-0635 modulated cartilage damage in the rat MIA model (mean +/- SEM damage score 1.3 +/- 0.3, versus 2.2 +/- 0.4 in vehicle-treated animals). Most significantly, when treated twice daily with oral ALS 1-0635, rats with surgically induced medial meniscus tear exhibited histologic evidence of chondroprotection and reduced cartilage degeneration, without observable musculoskeletal toxicity. CONCLUSION: The compounds investigated in this study represent a novel class of MMP-13 inhibitors. They are mechanistically distinct from previously reported broad-spectrum MMP inhibitors and do not exhibit the problems previously associated with these inhibitors, including selectivity, poor pharmacokinetics, and MSS liability. MMP-13 inhibitors exert chondroprotective effects and can potentially modulate joint pain, and are, therefore, uniquely suited as potential disease-modifying osteoarthritis drugs.

In vitro and in vivo anticancer activities of synthetic (-)-laulimalide, a marine natural product microtubule stabilizing agent.

Laulimalide is a cytotoxic natural product isolated from marine sponges. It is structurally distinct from taxanes. However, like paclitaxel, laulimalide binds to tubulin and enhances microtubule assembly and stabilization. It exhibits potent inhibition of cellular proliferation with IC50 values in the low nM range against numerous cancer cell lines. In contrast to paclitaxel, however, laulimalide is also very potent against multidrug-resistant (MDR) cancer cell lines which overexpress P-glycoprotein (PgP). It has unique structural and biological properties, and attempts at synthesis have attracted considerable effort in recent years, resulting in more than ten published total syntheses. Despite this extensive attention, there have been no reported in vivo evaluations of laulimalide to date, probably due to the structural complexity of laulimalide and the scarcity of natural material. In our studies to explore the therapeutic potential of laulimalide, a total synthesis capable of producing gram quantities of laulimalide was designed, which enabled both in vitro and in vivo evaluation. Our in vitro results with synthetic material confirmed the previous reports that laulimalide is a mitotic blocker that can inhibit the growth of a variety of both non-MDR and MDR human cancer cell lines. However, despite demonstrating promise in cell-based and pharmacokinetic studies, laulimalide exhibited only minimal tumor growth inhibition in vivo and was accompanied by severe toxicity and mortality. The unfavorable efficacy to toxicity ratio in vivo suggests that laulimalide may have limited value for development as a new anticancer therapeutic agent.

Microtubule-stabilizing natural products as promising cancer therapeutics.

Paclitaxel and related taxanes exhibit their anticancer activity by promoting tubulin polymerization and stabilizing microtubules, which results in mitotic G2/M arrest and apoptosis. The clinical success of paclitaxel in treating a wide array of tumor types has led to numerous efforts to identify novel natural products with paclitaxel-like mechanisms of action, but which may overcome some of the liabilities of the taxanes. Although the list of natural products that share the paclitaxel-like mechanism is relatively small, it continues to expand and currently includes a number of structurally distinct classes. Despite the mechanistic similarities between these classes, differences exist which may translate into their differential efficacy in the clinic. The past several years have seen a considerable amount of pre-clinical and clinical progress in developing these novel microtubule-stabilizing natural products as cancer therapeutics. This review focuses primarily on recent advances published since 2002.

Synthesis and biological evaluation of (-)-laulimalide analogues.

Analogues of the marine natural product (-)-laulimalide were prepared by total synthesis and evaluated in vitro for anticancer activity.