Inhibition of Human Neutrophil Elastase with Peptidyl Electrophilic Ketones. 2. Orally Active PG-Val-Pro-Val Pentafluoroethyl Ketones

Abstract

Valylprolyvalyl pentafluoroethyl ketones with different N-protecting groups were evaluated in vitro and in vivo as inhibitors of human neutrophil elastase (HNE). Several of these compounds were found to be orally active in HNE-induced rat and hamster lung hemorrhage models. The compound with 4-(4-morpholinylcarbonyl)benzoyl as the protecting group, 71 (MDL 101,146), was studied in greater detail. Hydration and epimerization studies were performed on 71 and related compounds in various media, including human blood serum. High-performance liquid chromatography studies on a reversed-phase system as a measure of the lipophilicity of 71 and related compounds revealed a small range of relative retention times wherein the orally active compounds fell. The Ki value determined for 71 vs HNE was 25 nM.

Inhibition of cartilage degradation in rat collagen-induced arthritis but not adjuvant arthritis by the neutrophil elastase inhibitor MDL 101,146

“…2) neutrophil elastase and did not significantly inhibit the serine proteinases cathepsin G and thrombin, the metalloproteinase encephalinase, or the cysteine proteinase cathepsin B at concentrations of 500 M [24]. In addition, MDL 101,146 (50 M) had no inhibitory effect on MMP activity in rat neutrophil lysate and did not inhibit human interstitial collagenase (MMP-1) (data not shown).…”

“…MDL 101,146 was assumed to be a competitive inhibitor of rat neutrophil elastase since it was previously shown to be a competitive reversible inhibitor of human neutrophil elastase [24,25]. Therefore, MDL 101,146 was assayed at 5 different concentrations at a fixed substrate concentration of 0.2 mM, which was approximately equivalent to the K m value.…”

“…1) was synthesized as described previously [24] and was incorporated into rodent chow (Ralston-Purina, Richmond, IN, USA) using a bottle agitator/mixer (Dayton Electric Mfg. Co., Chicago, IL, USA) at a concentration of 0.3%.…”

“…We have shown previously that MDL 101,146 is a reversible competitive inhibitor of human neutrophil elastase with a K i of 25 nM [24,25]. The ability of MDL 101,146 to inhibit rat neutrophil elastase was determined using a rat neutrophil granule lysate and the specific elastase methoxysuccinyl-alaala-pro-val-p-nitroanilide.…”

Strategies for the inhibition of serine proteases

“…Pentafluoroethyl ketones such as 34 have also been shown to be excellent inhibitors of serine proteases. Indeed, there is evidence that the PFEKs have improved pharmacological activity against HNE [97,98] and thrombin [91].…”