Ro 21-7634, a new antiallergic agent with potent oral activity

Ro 21-7634 was examined for oral antiallergic activity in two in vivo models commonly used to evaluate anti-allergics. In the rat PCA test, this drug had an oral ID₅₀ of 1.14 mg/kg and was found to be more potent than several other antiallergics including Disodium Cromoglycate (cromoglycate), Oxatomide, Doxanthrazole, Xanoxate, 2,6-bis (ethoxyoxalylamino) pyridine, PRD-92-EA and M+B 22,948. In contrast to cromoglycate, Ro 21-7634 was found to be an orally active inhibitor of antigen-induced bronchoconstriction in passively sensitized rats (ID₅₀=0.2 mg/kg). In addition, Ro 21-7634 inhibited antigen-induced histamine release in an in vivo passive peritoneal anaphylaxis test system, following intraperitoneal administration. Ro 21-7634 demonstrated no end organ antagonism toward histamine, methacholine or serotonin in the guinea pig.     

The effect of Ro 21-7634 on the antigen-induced production of bronchoconstrictive arachidonic acid metabolites in the guinea pig lung

Ro 21-7634 has previously been shown to inhibit histamine and SRS-A release from actively-sensitized guinea pig lung fragments upon antigen challenge. In the studies described herein, it was observed that Ro 21-7634 does not decrease SRS-A release but instead acts to inhibit the synthesis of this mediator. This was confirmed by studying SRS-A synthesisin vitro in rat peritoneal cells after challenge with ionophore A23187. In the peritoneal cell system, Ro 21-7634 exhibited an IC₅₀ of 500 M, in comparison with 5,8,11,14-eicosatetraynoic acid, phenidone and BW755C (IC₅₀'s of 2, 100, and 100 M, respectively). When studied at 10^–4 and 10^–3 M in perfused guinea pig lung, Ro 21-7634 inhibited antigen-induced thromboxane A₂ production by 68 and 96%, respectively. In this system, antigen is believed to induce thromboxane A₂ production through the release of histamine and SRS-A from lung tissue. These mediators then interact at receptor sites in the lung parenchyma to induce thromboxane A₂ synthesis. Ro 21-7634 could thus be inhibiting thromboxane A₂ production by preventing the release of histamine and synthesis of SRS-A in the perfused lung system. Such a mechanism is suggested by the fact that although Ro 21-7634 was effective in inhibiting antigen-induced thromboxane production, it was ineffective in inhibiting thromboxane A₂ production induced in the guinea pig lung system by the direct perfusion of histamine or SRS-A through the lung.     

The pharmacological profile and initial clinical evaluation of tiacrilast (Ro 22-3747): a new antiallergic agent

Tiacrilast (Ro 22-3747) is an allergic mediator release inhibitor which has demonstrated potent oral activity in two IgE-mediated animal models of immediate hypersensitivity: the rat passive cutaneous anaphylaxis test (ID₅₀ of 0.65 mg/kg) and a model in which anaphylactic bronchospasm is induced in passively sensitized rats (ID₅₀ of 0.022 mg/kg). In addition to oral efficacy, in the latter model Ro 22-3747 was 23-fold more potent than cromoglycate by the aerosol (nebulization) route of administration.In vitro studies have confirmed that the mechanism of action of Ro 22-3747 in thein vivo models is through allergic mediator release inhibition since Ro 22-3747 was a potent inhibitor of antigen-induced (IgE-mediated) histamine release from passively sensitized rat peritoneal cellsin vitro (IC₅₀ values of 0.25 and 1.5 M for Ro 22-3747 and cromoglycate, respectively), and Ro 22-3747 did not display end organ antagonism to histamine, serotonin, or the leukotrienes. Clinical evaluations of Ro 22-3747 at a 350 mg oral dose have been conducted in patients with allergic asthma and allergic rhinitis. In a limited study in allergic asthmatics, Ro 22-3747 demonstrated significant inhibitory activity relative to placebo in reducing acute airway responses to inhaled pollen extracts in patients with ragweed sensitivity (measured by changes in log PD₂₀ FEV₁ and log PD₃₅ SGaw). The activity seen, however, was less than that observed with cromoglycate (20 mg) administered by inhalation. In a pilot evaluation in patients with allergic rhinitis, Ro 22-3747 administered at a 350 mg oral dose exhibited activity significantly greater than placebo in terms of improvements in the objective measurement of changes in nasal airflow at 2 and 3 hrs after treatment and the subjective overall global evaluation made by the patients at the end of the treatment period. The preclinical pharmacology and initial clinical efficacy of Ro 22-3747 support the continued clinical evaluation of this drug for prophylactic use in the management of asthma and other allergic disorders.     

In vitro activity of Ro 24-6392, a novel ester-linked co-drug combining ciprofloxacin and desacetylcefotaxime

In preliminary in vitro susceptibility tests Ro 24-6392 (desacetylcefotaxime with a 3-ciprofloxacin substitution) demonstrated activity against a wide spectrum of aerobic bacteria, 98.6 % of strains being inhibited by 8 mg/l. Of the commonly isolated species tested, only enterococcal strains were resistant (MICs32 mg/l). The potency of Ro 24-6392 was generally between that observed for the two hydrolysis components, except in the case ofProvidencia stuartii and penicillin-resistant pneumococci isolates which were more susceptible to Ro 24-6392. This new dual-action compound appears to be slightly more active than the previously studied peer drug Ro 23-9424, principally because of the superior activity of the fluoroquinolone component, ciprofloxacin.     

In vitro activity of Ro 09-1428 compared to other cephalosporins

The in vitro activity of Ro 09-1428, a new catechol-type parenteral cephalosporin, was compared to that of ceftazidime, E-1040, cefpirome and cefepime against gram-positive and gramnegative organisms. Ro 09-1428 inhibited group A streptococci at 0.12 µg/ml, and group B, C and G streptococci andStreptococcus pneumoniae at 0.5 µg/ml, whereas forStaphylococcus aureus Ro 09-1428 had MICs of 8–16 µg/ml similar to ceftazidime and E-1040. AgainstPseudomonas aeruginosa Ro 09-1428 was the most active agent, inhibiting isolates at 0.12–2 µg/ml, and inhibited ceftazidime-resistant isolates. The majority ofEscherichia coli, Klebsiella spp.,Proteus mirabilis, Citrobacter diversus, Providencia, Salmonella andShigella were inhibited by 0.5 µg/ml as with the other cephalosporins. For mostCitrobacter freundii andEnterobacter cloacae Ro 09-1428 had higher MICs of 4–16 µg/ml; most ceftazidime-resistant isolates of these species were resistant. Anaerobes, enterococci andListeria monocytogenes were resistant to Ro 09-1428. Ro 09-1428 was not hydrolyzed by TEM-1, TEM-2,Staphylococcus aureus PC-1,Moraxella catarrhalis Bro-1,Enterobacter P-99,Pseudomonas aeruginosa Sabath-Abraham orKlebsiella beta-lactamases, but was hydrolyzed by TEM-3, TEM-7 and TEM-9. Ro 09-1428 was markedly less active at an acid pH.     

Thein vivo andin vitro activity of AHR-13268D,a new antiallergic/antihistaminic agent

AHR-13268D (4-[3-[4-[Bis(4-flurophenyl)hydroxymethyl]-1-piperidinyl]propoxy]benzoic acid, sodium salt) is a potent, long-acting water soluble, antiallergic and antihistaminic agent. AHR-13268D protects sensitive guinea pigs from collapse induced by aerosolized antigen; 1, 5, and 24 h ED₅₀s in the test were 0.27, 0.25, 0.93 mg/kg, PO, respectively. AHR-13268D was also active when given as an aerosol, the 1 h ED₅₀=0.29%. In the rat passivefoot anaphylaxis test, AHR-13268D was slightly more active (1.55 times) than AHR-5333B when given orally 1 h prior to challenge and equipotent to cromolyn when given intravenously immediately prior to challenge. AHR-13268D displayed potent, long-acting antihistaminic activity in naive guinea pigs; the 1, 5, and 24 h oral ED₅₀s being in the range of 0.3 mg/kg. AHR-13268D (10 to 20 mg/kg, PO) attenuated the skin responses to ascaris antigen in sensitive dogs and did not alter the EEG pattern or sleep/wake patterns of cats at doses in vast excess of its antihistaminic activity.In vitro, AHR-13268D was a potent inhibitor of histamine release from rat peritoneal mast cells (IC₅₀=0.51 nM) and was as potent as the reference 5-LO inhibitor phenidone in inhibiting antigen-induced contractions of guinea pig ileum in the presence of pyrilamine, atropine, and imidazole (IC₅₀300 M). AHR-13268B was bioavailable (88%) from capsules or from oral solutions.     

In vitro,in vivo studies of a new amphiphilic adsorbent for the removal of low-density lipoprotein

A new amphiphilic adsorbent for the removal of low-density lipoprotein (LDL) was prepared according to the literature (Artif. Cells Blood Subs., Immob. Biotechnol. 30 (4) (2002) 285). The effects of sulfonation and grafting time of cholesterol on the swelling property of adsorbent were studied. When sulfonation and grafting time of cholesterol was 3 and 5 h, respectively, the amphiphilic adsorbent had a high adsorption capacity for LDL without significantly adsorbing high-density lipoprotein. The adsorption capacity of the adsorbent for the removal of LDL, total cholesterol (TC) and TG was 1.916, 2.132, 1.349 mg/ml, respectively. Hyperlipidemia rabbits were developed by feeding with fodder containing high content of cholesterol or yolk, which was then perfused with an optimal amount of amphiphilic adsorbent. After 2 h hemoperfusion, the LDL levels decreased from 3.619+/-0.354 to 0.724+/-0.07 mmol/l, which showed that the adsorbent could effectively remove LDL without side effect.     

Comparative in vitro activity of Ro 40-6890, Ro 41-3399, and other antimicrobial agents against anaerobic bacteria

The in vitro activity of the ester Ro 41-3399 and its free active acid Ro 40-6890 was tested against 189 strains of anaerobic bacteria in comparison to other oral cephalosporins and to antimicrobial agents established in the treatment of anaerobic infections.Prevotella, Porphyromonas, Peptostreptococcus, Fusobacterium andClostridium spp. were susceptible to Ro 40-6890, with few exceptions. Due to its lack of activity against the major pathogens of theBacteroides fragilis group, Ro 40-6890 does not promise to be of major use in the treatment of infections caused by anaerobes.     

In vitro studies with fexofenadine,a new nonsedating histamine H1 receptor antagonist,on isolated human basophils

Inflammation Research -     

Reticuloendothelial-depressing substance: studies on the mechanism of action

This study was carried out to evaluate the mechanism of action of a reticuloendothelial (RE)-depressing substance. This RE-depressing substance was obtained from the plasma of dogs subjected to 3 hr of intestinal ischemia. RE-depressing substance was partially purified by dialysis and reverse-phase column chromatography. The assay of RE-depressing activity was based on the depression of the rate of clearance of colloidal carbon from the blood of rats or mice. The effect of RE-depressing substance on three other RE system (RES) test particles (gelatinized lipid emulsion, formalinized sheep erythrocytes, and IgM-coated erythrocytes) was determined. RE-depressing substance did not affect the clearance rate or the organ localization of these three test particles. Therefore, RE-depressing substance affected only the clearance of colloidal carbon. Since platelet aggregation has been shown to contribute to the clearance of colloidal carbon, the effect of RE-depressing substance on platelet aggregation was evaluated. RE-depressing substance depressed in vitro platelet aggregation induced by ADP or collagen. It was concluded that the effect of RE-depressing substance on the clearance of colloidal carbon was due to a depression of platelet aggregation rather than to a depression of hepatic macrophage phagocytic function.     

In vitro studies on the mechanism of herpesvirus plaque growth inhibition by sensitized lymphocytes.

Inhibition of herpesvirus plaque growth was observed when herpes simplex virus (HSV)-sensitized rabbit lymphocytes were placed in contact with an HSV-infected human foreskin monolayer. This inhibition was obtained as early as 3 h when a ratio of 6 viable lymphocytes to target cells was used, and the supernatants of these cultures also demonstrated plaque size reduction when put onto newly infected cell monolayers. Interferon, which is present in this system, had no effect on HSV when tested on human foreskin monolayers, indicating that interferon was not the mechanism for plaque size reduction. Plaque growth inhibition was attributed to the T lymphocyte, because purified T cells reduced plaque growth and anti-rabbit thymocyte serum eliminated the effect of T cells. The specificity of this assay was determined by the facts that nonsensitized lymphocytes did not reduce the size of a plaque and the recognition of an infected cell by the sensitized lymphocyte was necessary for the release of a soluble mediator into the supernatant fluid. This cytotoxic lymphocyte was detected in the peripheral blood of rabbits as early as 4 days after initial corneal infection, with a maximum response at 7 to 10 days.     

In vitro evaluation of E-4695, a new fluoro-naphthyridine

Compound E-4695, a C-7 azetidinyl fluoro-naphthyridine, was compared to six structurally related quinolones and was generally two- to four-fold more active than ciprofloxacin. E-4695 was particularly active againstStaphylococcus aureus (MIC90 0.06 mg/l),Staphylococcus haemolyticus (MIC90 0.5 mg/l),Klebsiella spp. (MIC900.015 mg/l),Serratia marcescens (MIC90 0.06 mg/l),Acinetobacter spp. (MIC900.015 mg/l),Pseudomonas aeruginosa (MIC90 0.5 mg/l),Xanthomonas maltophilia (MIC90 0.5 mg/l), andNeisseria gonorrhoeae (MIC900.001 mg/l). This new quinolone-like drug requires further investigations to confirm these promising in vitro findings.     

In vitro immunotoxicity of +/- 2'-deoxy-3'-thiacytidine, a new anti-HIV agent.

The present study compares the in vitro effect of (+/-)-2'-deoxy-3'-thiacytidine (BCH 189) a new synthetic anti-HIV-1 dideoxynucleoside, with 3'-azido-3'-deoxythymidine (AZT) on the immune function of lymphocytes from 10 normal and 12 HIV-1+ patients (CDC II and III). The effect of different doses of BCH 189 and AZT was analysed in vitro on: (i) T cell proliferation after stimulation with concanavalin A (Con A) or anti-CD3 MoAb; (ii) B cell proliferation and immunoglobulin production after stimulation with pokeweed mitogen (PWM); (iii) cytokine production (IL-2, IL-6, GM-CSF, tumour necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma) from lymphocytes stimulated with anti-CD3 MoAb or phytohaemagglutinin (PHA). BCH 189 inhibited the proliferation of B and T lymphocytes from normal and HIV+ subjects less than AZT; even if lymphocytes from HIV+ (CDC III) subjects produced higher levels of IL-6 and TNF-alpha, neither BCH 189 nor AZT molecule interfered with cytokine release. Immunoglobulin production from B lymphocytes was inhibited only by a high concentration (50 microM) of BCH 189 or AZT. These results show that BCH 189 affects lymphocyte proliferation in vitro less than AZT, and support its use in clinical trials in HIV-infected patients.     

In vitro studies of S-25930 and S-25932, two new 4-quinolones

The in vitro activity of S-25930 and S-25932 was compared with that of ciprofloxacin, norfloxacin and nalidixic acid against 740 clinical isolates. The data indicate that S-25930 was more active against Enterobacteriaceae than S-25932 and the latter was more active against gram-positive species. A study of clinical isolates resistant to chemically non-related classes of antibiotics revealed no cross-resistance. Nalidixic acid resistant Enterobacteriaceae showed an eight-fold decrease in susceptibility to the new agents. The killing kinetics of both compounds were good, S-25932 having an optimal bactericidal effect at a concentration of 0.5 mg/l. The data suggests that both agents are effective broad spectrum antibiotics.     

In vitro studies on the mechanism of increased serum IgM levels in primary biliary cirrhosis.

To evaluate the mechanisms underlying the increase in serum IgM in primary biliary cirrhosis (PBC) studies were designed to examine IgM production in vitro and to assess the relative contribution of intrinsic B cell activity and immunoregulatory T cell balance to IgM synthesis. The number of peripheral blood lymphocytes (PBL) producing IgM (spontaneous and pokeweed mitogen (PWM) stimulated) at the end of a seven day culture period was similar in PBC patients and control subjects while the amount of IgM synthesized (spontaneous and PWM stimulated) during this period was significantly greater in the patient group, implying that the amount of IgM produced per B cell was increased in PBC. Co-culture of autologous and allogeneic T and B lymphocytes and irradiation of T lymphocytes from patients and normal subjects clearly implicated abnormal suppressor T cell function, rather than autonomous B cell hyperactivity, as the cause of the increased IgM synthesis. Direct studies of T cell function indicated that although concanavalin A (Con A) activated suppressor cells inhibited proliferation of IgM producing B cells in the majority of PBC patients, they were unable to inhibit IgM synthesis. The demonstration of a disparity between IgM synthesis and the proliferation of IgM-producing B cells, together with the observation that the abnormality of T cell function is largely confined to the control of IgM secretion, is consistent with the presence of at least two different suppressor subpopulations regulating IgM production. In PBC the main suppressor cell abnormality seems to affect regulation of IgM secretion rather than B cell proliferation.