Phospholipase A2 inhibitors in development

Abstract

To date, three isoforms of phospholipase A2 (PLA2) have been identified. Of these, the two Ca2+-dependent isoforms, secretory (sPLA2) and cytosolic phospholipase A2 (cPLA2), are targets for new anti-inflammatory drugs. The catalytic mechanisms and functions of the third isoform, Ca2+-independent cytosolic phospholipase A2 (iPLA2), are unknown at present. sPLA2 and cPLA2 are both implicated in the release of arachidonic acid and prophlogistic lipid mediators. However, recent findings provide evidence that cPLA2 is the dominant isoform in various kinds of inflammation, such as T-cell-mediated experimental arthritis. A triple function of PLA2-derived lipid mediators has been suggested: causing immediate inflammatory signs, involvement in secondary processes, e.g., superoxide free radical (O2) generation, apoptosis, or tumour necrosis factor-alpha (TNF-alpha)-cytotoxicity, and controlling the expression and activation of pivotal proteins implicated in inflammation and cell development, e.g., cytokines, adhesion proteins, proteinases, NF-kappaB, fos/jun/AP-1, c-Myc, or p21ras. In the past, research predominantly focused on the development of sPLA2 inhibitors; however, present techniques enable discrimination of cPLA2, sPLA2, and iPLA2, and specific inhibitors of each of the three isoforms are likely to appear soon. Over the last decade, between 40 and 50 sPLA2 inhibitors have been described; and the list is growing. However, of these, few have the potential for clinical success, and those that do are predominantly active site-directed inhibitors, e.g., BMS-181162, LY311727, ARL-67974, FPL67047, SB-203347, Ro-23-9358, YM-26734, and IS-741. At present, there are no likely clinical candidates emerging from the ranks of cPLA2 and iPLA2 inhibitors in development. Indications for which PLA2 inhibitors are being pursued include, sepsis, acute pancreatitis, inflammatory skin and bowel diseases, asthma, and rheumatoid arthritis. The three main obstacles to the successful development of PLA2 inhibitors include, insufficient oral bioavailability, low affinity for the enzyme corresponding to low in vivo efficacy and insufficient selectivity.

In vitro study of the PLA2 inhibition and antioxidant activities of Aloe vera leaf skin extracts

“…Based on the central role of lipid mediators in the inflammatory processes, the potential value of controlling phospholipid metabolism through PLA2 inhibition has always been acknowledged [30]. Numerous compounds have been proposed as inhibitors of various sPLA2.…”

HPLC assay with UV spectrometric detection for the evaluation of inhibitors of cytosolic phospholipase A2

“…Prostaglandins, leukotrienes, lysophospholipids and the PAF are potent mediators of inflammation [1][2][3]. Thus, inhibition of PLA 2 is considered as an interesting target for the design of new anti-inflammatory drugs [4][5][6][7][8].…”

An Update on Inhibitors of Human 14 kDa Type II s-PLA2 in Development>

“…Inhibitors of phospholipases A 2 have been reviewed in the literature on many occasions [49][50][51][52][53][54][55][56][57]; the most recent comprehensive review being that of Tibes and Friebe in 1997 [58]. It is the intent of this review to provide an update of small molecule inhibitors of human Type II s-PLA 2 since the time of the Tibes and Friebe report, that are in clinical trials or in late-stage development as potential anti-inflammatory agents.…”