Pharmacological effects of a specific leukotriene B(4) receptor antagonist (VML 295) on blood leukocytes, cutaneous inflammation and epidermal proliferation.

VML 295 (LY 293111) is a potent and specific leukotriene(4) receptor antagonist. It has previously been shown in human volunteers that VML 295 at a dosage of 48 mg twice daily inhibits the ex vivo leukotriene B(4) (LTB(4))-induced upregulation of CD11b on peripheral blood neutrophils. A clear dose-response relatinship was shown. In addition, VML 295 inhibits various inflammatory aspects resulting from LTB(4) challenge of the skin, again showing a dose-response relationship. In view of the large variation in the elimination half-life of VML 295 (25-88.5 h) in individual human subjects, the present pharmacological study was designed to provide information on the pharmacodynamics of the drug by the assessment of VML 295 plasma concentrations, ex vivo LTB(4)-induced CD11b upregulation of neutrophils, neutrophil accumulation in the skin following epicutaneous application of LTB(4) and epidermal regeneration following standardized surface trauma. A group of 36 healthy volunteers were treated in a double-blind study with VML 295 at 200 mg twice daily, VML 295 at 200 mg once daily or placebo for 7 days. Before treatment, at the end of treatment and following discontinuation of treatment, VML 295 plasma concentrations and CD11b upregulation of blood neutrophils were assessed. In 18 subjects, the effects of the three treatments on LTB(4)-induced inflammatory were assessed before and at the end of treatment, and in the remaining 18 subjects the effects of these treatments on epidermal regeneration were assessed similarly. VML 295 at 200 mg either twice or once daily has a profound inhibitory effect on ex vivo LTB(4)-induced CD11b upregulation of blood neutrophils, LTB(4)-induced neutrophil accumulation in the skin, trauma-induced hyperproliferation of the epidermis and regenerative keratinization. The twice daily dose schedule was significantly more effective than the once daily regimen in reducing ex vivo CD11b stimulation of neutrophils, in blood samples collected 24 h after discontinuation of VML 295 treatment. The twice daily schedule tended to be more efficient in skin biopsies, although this difference was not statistically significant in the number of subjects investigated. A plasma concentration of 100 ng/ml proved to be the threshold for these effects. The profound biological effects, both systemically and cutaneously, as well as the safety profile, make VML 295 a promising drug for skin disorders characterized by epidermal proliferation and neutrophil accumulation.

VML 295 (LY-293111), a novel LTB4 antagonist, is not effective in the prevention of relapse in psoriasis.

Leukotriene B4 (LTB4) receptor antagonists have been the subject of several studies in the treatment of inflammatory diseases, including psoriasis. A novel oral LTB4 antagonist, VML 295 (LY-293111) has recently been developed and has a pronounced effect on epidermal inflammatory parameters. However, oral treatment of psoriasis for 4 weeks did not result in a decrease in disease severity. The present study was performed in order to investigate whether prolonged treatment with VML 295 up to 8 weeks has a beneficial effect on the overall severity of psoriasis. Moreover, we studied to what extent VML 295 is able to prevent relapse in psoriasis. In the present study, 35 patients with stable chronic plaque psoriasis were included. A representative plaque of at least 16 cm2 was initially treated with clobetasol-17-propionate lotion under hydrocolloid occlusion in all patients. Clearance was achieved within 6 weeks in 31 patients. After clearance, the patients were randomized to treatment and received oral VML 295 capsules 200 mg twice daily or placebo for 8 weeks. Twenty-five patients completed the study. The psoriasis area and severity index (PASI) was assessed before treatment, at clearance, and on days 15, 29, 43 and 5 7 of the treatment period. Biopsies were taken from the treated lesion before treatment, after clearance and at relapse, and cells were analysed by flow cytometry with markers for differentiation (keratin 10), inflammation (vimentin), and proliferation (DNA content). After 8 weeks of treatment, 14 of 15 VML 295-treated patients had relapsed and 11 of 16 placebo-treated patients had relapsed. A total of six patients were withdrawn. The time to relapse and the number of relapsed patients was not significantly different comparing the treatment groups. There was no significant difference in PASI scores between VML 295-treated patients and placebo-treated patients after 8 weeks of treatment. Flow cytometric parameters for differentiation, inflammation and proliferation did not show significant differences between VML 295- and placebo-treated patients. We conclude that oral VML 295 (LY-293111) is not effective in preventing relapse in psoriasis, either clinically or at the cellular level, and that in our group of patients VML 295 had no beneficial effect on overall psoriasis severity. Moreover, we conclude that further development of LTB4 modulating drugs for the treatment of psoriasis is not indicated.

Investigation on a novel and specific leukotriene B4 receptor antagonist in the treatment of stable plaque psoriasis.

The aim of the present study was to investigate the efficacy and clinical tolerability of the specific leukotriene B4 receptor antagonist VML295 in the treatment of stable plaque psoriasis. Immunohistochemical and flow cytometrical methods were used to assess the effects on inflammation and epidermal proliferation. VML295 in the treatment of chronic plaque psoriasis was shown to be safe and well tolerated. After treatment, there was a statistically significant difference between patients treated with VML295 and patients treated with placebo with respect to the leukotriene B4-induced CD11b up-regulation on the cell surface of polymorphonuclear leukocytes derived from peripheral blood. Ex vivo CD11b up-regulation in the VML295-treated group was completely inhibited after 7 days of treatment (P = 0.001). This effect persisted until the end of the treatment period (P = 0.004 on day 15 and P < 0.0001 after 4 weeks), whereas CD11b up-regulation in the placebo group remained unaffected. There was no statistically significant difference in the median psoriasis area and severity index between the treatment groups at the end of the treatment period. During treatment, no significant histological changes were observed in the markers for cutaneous inflammation and epidermal proliferation. Although not statistically significant, a tendency for the increased expression of some markers of cutaneous inflammation and epidermal proliferation was observed after 1 week of treatment with VML295, and a decreased expression of these markers was seen after 4 weeks of treatment with VML295. This observation could indicate anti-inflammatory effects of VML295 appearing between 2 and 4 weeks after the start of treatment.

The effect of hypolipidemic agents on the hepatic microsomal drug-metabolizing enzyme system of the rat. Induction of cytochrome(s) P-450 with specificity toward terminal hydroxylation of lauric acid.

The effect of chronic dietary administration of the hypolipidemic agents, clofibrate, methylclofenapate, fenofibrate, and tibric acid, on the hepatic drug-metabolizing enzyme system of the albino rat has been studied. Each compound caused dose-dependent increase in liver size and cytochrome P-450 (methylclofenapate = fenofibrate = tibric acid greater than clofibrate). NADPH-cytochrome c reductase activity was increased only after clofibrate and methylclofenapate treatment. There was no overall increase in the metabolism of a number of commonly used model substrates in parallel with the cytochrome P-450 induction. Aminopyrine and ethoxyresorufin dealkylation, biphenyl 4-hydroxylation, testosterone 16 alpha-hydroxylation, and o-aminophenol and chloramphenicol glucuronidation showed no change or inhibition, whereas ethoxycoumarin and phenacetin dealkylation and testosterone 6 beta-hydroxylation were increased (only up to 2-fold). Using clofibrate as a representative of this class of pharmacological agent, the enzymatic changes were essentially reversed within 6 days after removal of drug from the diet. Clofibrate administration also increased liver size and, to a lesser extent, hepatic cytochrome P-450 content in the albino (CD-1) mouse but had no effect in the marmoset monkey. In the rat, clofibrate administration specifically increased the hepatic microsomal omega-hydroxylation of lauric acid approximately 28-fold, which contrasted with the specific increase in (omega - 1)-hydroxylation caused by phenobarbital administration. The specific increase in microsomal cytochrome P-450-mediated omega-oxidation of a medium length, straight chain, saturated fatty acid is similar to the documented increase in peroxisomal and mitochondrial fatty acid beta-oxidation caused by administration of hypolipidemic agents.