Protease inhibitors suppress the in vitro and in vivo replication of rotavirus.

Rotaviruses are major causes of infectious gastroenteritis in humans and other animals. We found that a variety of protease inhibitors suppressed the replication of the SA-11 strain of rotavirus in MA-104 cell cultures. Three of these compounds, leupeptin, pentamidine, and bis (5-amidino-2-benzimidazolyl) methane (BABIM) also restricted the intestinal replication of the murine strain of rotavirus when protease inhibitor and virus were administered simultaneously to suckling mice. Repeated administration of BABIM resulted in significantly reduced levels of intestinal rotaviral antigen even if administration of the compound was begun as late as 48 h after viral inoculation. Additionally, BABIM-treated animals had significantly less intestinal replication of rotavirus than did placebo-treated controls when placed in a heavily rotavirus-contaminated environment. The use of protease inhibitors represents a novel approach to the control of this important gastrointestinal pathogen and is a potential modality for the prevention and treatment of diseases caused by other enteric viruses, for which proteolytic cleavage is necessary for efficient replication.

Aromatic Tris-amidines. A new class of highly active inhibitors of trypsin-like proteases.

A number of novel aromatic Tris-amidines have been synthesized and investigated for their antiproteolytic property. The basic structure of the compounds is that of mesitylene where each of the methyl groups has been substituted with a 3- or 4-amidinophenoxy moiety. The compounds displayed considerable activity against trypsin (EC 3.4.21.4) and thrombin (EC 3.4.21.5), but proved most effective against porcine pancreatic kallikrein (EC 3.4.21.8). With this enzyme a Ki value of 2.43-10(-8) M was recorded for alpha,alpha',alpha''-tris(4-amidino-2-bromophenoxy)mesitylene at pH 8.1 and 37 degrees C. The most potent thrombin inhibitor, alpha,alpha',alpha''-tris(3-amidinophenoxy)mesitylene, had a Ki value of 6.51-10(-7) M and was also a strong overall anticoagulant. The inhibitors were able to interfere with the kinin release by human plasma kallikrein at concentrations as low as 1-10(-10) M. However, despite this remarkable antikallikrein effect and the known importance of plasma kallikrein in the activation of Hageman factor (factor XII), the compounds had only little influence on the early stages of blood coagulation.

New aromatic diamidines with central alpha-oxyalkane or alpha, omega-dioxyalkane chains. Structure-activity relationships for the inhibition of trypsin, pancreatic kallikrein, and thrombin and for the inhibition of the overall coagulation process.

A series of omega-amidinophenylalkyl amidinophenyl ethers was synthesized and examined for inhibitory activity against trypsin, pancreatic kallikrein, and thrombin. Modifications of the compounds included lengthening of the alkane chain, variation in the position of the amidino groups, and substitution of halogen on the benzene rings. The compounds act as competitive reversible inhibitors, and many of them possess considerable potency. An outstanding trypsin inhibitor was found in 4-amidinophenylethyl 4 amidino-2-bromophenyl ether (compound 7) with a Ki value of 7.3 x 10(-8) M (pH 8.1, 37 degrees). A number of aromatic diamidines with a central dioxyalkane chain were similarly studied. Here, 1-(4-amidino-2-iodophenoxy)-5-(3-amidinophenoxy)pentane (compound 32) was a highly effective inhibitor of bovine thrombin (Ki = 1.1 x 10(-6) M), of human thrombin, and of the overall clotting process of human plasma.

Novel bis(benzamidino) compounds with an aromatic central link. Inhibitors of thrombin, pancreatic kallikrein, trypsin, and complement.

A series of novel aromatic diamidines was synthesized and evaluated for antiproteolytic activity. The compounds were distignuished by inclusion of an aromatic ring structure--either benzene or bisbenzene or naphthalene--in the link between two amidinobenzene moieties. A highly potent inhibitor of bovine thrombin was discovered in alph, alph'-bis(4-amidino-2-iodophenoxy)-p-xylene with a Ki value of 1.1 X 10(-7) M (pH 8.1, 37 degrees), while alpha, alpha'-bis(4-amidino-2-iodophenoxy)-m-xylene was found to be an outstanding inhibitor of porcine pancreatic kallikrein (Ki = 3.1 X 10(-8) M). Several of the compounds investigated also demonstrated a considerable blocking effect on typsin and on the complement-dependent immune lysis of red cells.

Aromatic amidines: comparison of their ability to block respiratory syncytial virus induced cell fusion and to inhibit plasmin, urokinase, thrombin, and trypsin.

Two series of amidine derivatives consisting of a total of 24 compounds were examined for a correlation between their blocking effect on respiratory syncytial virus induced cell fusion and their inhibitory activity against selected trypsin-like protease. Although no correlation was evident between the two activities, several potentially important discoveries were made. A highly selective inhibitor of plasmin over thrombin (compound 10) was obtained, and a potent new blocker of virus-induced cell fusion (compound 22) was identified.

Synthesis of isosteres of p-amidinophenylpyruvic acid. Inhibitors of trypsin thrombin, and pancreatic kallikrein.

A series of amino acids, amidino acids, and amidino esters was synthesized and the compounds were evaluated for their inhibitory activity against bovine trypsin, bovine thrombin, and porcine pancreatic kallikrein and as anticoagulants. Among these compounds, ethyl 4-amidino-2-iodophenoxyacetate was found to be the most effective inhibitor of the enzymes in question, with a potency (Ki = 3.16 x 10-6 M vs. trypsin; Ki = 4.8 x 10-5 M vs. thrombin) similar to that of p-amidinophenylpyruvic acid (Ki = 6.0 x 10-6 M vs. trypsin; Ki = 2.0 x 10-5 M vs. thrombin). Ethyl 4-amidino-2-iodophenoxyacetate was also found to be the most effective in blocking the clotting activity of plasma, as indicated by significant prolongation of the partial thromboplastin time. This paper reports the synthetic methods, the enzyme inhibitory activity, and the structure-activity relationships observed.

Diarylamidine derivatives with one or both of the aryl moieties consisting of an indole or indole-like ring. Inhibitors of arginine-specific esteroproteases.

A series of 62 diarylamidine derivatives was evaluated for their antiproteolytic activity. In all but two of the compounds one or both of the amidino-substituted aryl moieties was either an indole or an indole-like ring. The latter included indene, benzimidazole, benzofuran, benzol[beta]thiophene, and several other related nitrogen-containing heterocycles. Several of the compounds exhibited considerable inhibitory potency against thrombin, trypsin, and pancreatic kallikrein. An outstanding inhibitor of trypsin was found in bis(5-amidino-2-benzimidazolyl)methane (compound 42) with a Ki value of 1.7 X 10(-8) M(pH. 8.1, 37 degrees C). Another derivative, 1,2-di(4-amidino-2-benzofuranyl)ethane (compound 21), proved to be a highly effective inhibitor of the overall blood clotting process. From a general structure-activity standpoint these compounds demonstrate that minor structural variations of low-molecular-weight inhibitors can result in significant changes in specificity and potency with regard to antiproteolytic activity.

Structure-activity relationships for the inhibition of acrosin by benzamidine derivatives.

A series, consisting of 52 benzamidine derivatives, was evaluated for inhibitory activity against homogeneous boar sperm acrosin. All of the compounds in the series proved to be more potent than benzamidine (Ki = 4.0 x 10(-6) M), with one of the derivatives, alpha-(4-amidino-2,6-diiodophenoxy)-3-nitrotoluene (compound 16), showing outstanding potency with a Ki value of 4.5 X 10(-8) M. Although all of the derivatives were effective acrosin inhibitors, structural specificity was observed within homologous groups of compounds. The information gained from this preliminary study should prove extremely beneficial in the design and synthesis of future acrosin inhibitors.

Analogues of 1,5-bis(4-amidinophenoxy)pentane (pentamidine) in the treatment of experimental Pneumocystis carinii pneumonia.

A series of 33 analogues of the anti-Pneumocystis carinii drug 1,5-bis(4-amidinophenoxy)pentane (pentamidine) was synthesized for screening against a rat model of P. carinii pneumonia (PCP). Twenty-five of the compounds showed efficacy against PCP when compared to a saline-treated control group. Two compounds, 1,4-bis(4-amidinophenoxy)butane (butamidine, 6) and 1,3-bis(4-amidino-2-methoxyphenoxy)propane (DAMP, 16), were statistically more effective than the parent drug in treating PCP in the rat model of infection. In addition to their activity against PCP, the compounds were also evaluated for antitrypsin activity, ability to inhibit thymidylate synthetase, affinity for DNA, and toxicity. No correlation was observed between the tested molecular interactions of the diamidines and their effectiveness against PCP.

Specific inhibition of platelet agglutination and aggregation by aromatic amidino compounds.

A series of aromatic amidino compounds were investigated for their inhibitory effect on platelet agglutination and platelet aggregation. Agglutination of fresh or fixed platelets was produced by bovine plasma or by human plasma in combination with ristocetin, while aggregation of fresh platelets was induced by ADP, thrombin or collagen. Highly effective inhibitors were found for both types of platelet clumping, but there was no parralelism between the inhibitory activities in the two test system. 5-(5-amidino-2-benzimidazolyl)-2-(4-hydroxybenzene)benzimidazole suppressed agglutination exclusively. Pentamidine, on the other hand, strongly blocked the aggregation reaction, but did not interfere with agglutination, even at high concentrations. Compounds which inhibited aggregation also prevented the liberation of serotonin from the platelets.

Mucoepidermoid carcinoma in a cervical cyst: a case of branchiogenic carcinoma?

A patient with a primary oral epidermoid carcinoma with presumed neck metastasis is presented who at operation was found to have a cervical mucoepidermoid carcinoma arising in the wall of a benign cyst. The case for considering this tumor a primary branchioma of mucoepidermoid type is presented, and the criteria for making the diagnosis of branchiogenic carcinoma are discussed.

Control of glucan-induced systemic granulomatosis by cyclosporine A.

This study has shown that cyclosporine A (CyA), under certain conditions, is a powerful inhibitor of intravascular and extravascular monocyte/macrophage accumulation. Experiments were carried out in Lewis rats in which intravenous injection of particulate glucan calls forth a striking granulomatous response in lung, liver, and spleen and produces a marked stimulation of splenic erythro- and myelopoiesis. In agreement with the results of others, there was also a considerable elevation in monocyte/macrophage chemoattractant levels in the bronchoalveolar lavage fluid, which is held to be a key reaction in the pathogenesis of the histologic lesions. Treatment of the animals with subcutaneous injections of CyA prevented the rise in the chemoattractant activity and suppressed the granulomatous organ infiltration as well as the splenic hemopoiesis. The findings supply new insights into the activities of CyA and would support its clinical use in macrophage-dominated diseases.

The inhibition of urokinase by aromatic diamidines.

1. Structure-activity relationships have been established for the inhibition of urokinase by aromatic diamidines. In an assay system employing purified urokinase and human plasminogen the most potent inhibitor was found in 4',4''-diamidino-2-hydroxy-1,4-diphenoxybutane which proved 5600 times more active on a molar bases than epsilon-aminocaproic acid (E-ACA). 2. 4',4''-diamidino-2-hydroxy-1,4-diphenoxybutane behaved as a competitive inhibitor of the urokinase catalyzed hydrolysis of N-alpha-acetyl-L-lysine methyl ester. At pH 7.85 and 37 degrees C the K-1 value was determined as 3.18 times 10-6 M which compares with a value of 6.79 times 10-5 M for p-aminobenzamidine and 3.57 times 10-2 M for E-ACA. 3. In two fibrinolytic tests including urokinase as activator the superiority of diamidines over E-ACA was less marked than in the pure plasminogen activation system. This was due to the presence of certain plasma proteins in the fibrinolysis assays which augmented the inhibitory strength of E-ACA. The order of effectiveness of diamidines in the lysis tests was also different from the one in the activation test. In a human fibrin clot lysis test the most active inhibitor was 3',3''-diamidino-2-hydroxy-1,4-diphenoxybutane which was 1700 times more effective on a molar basis than E-ACA. In a human plasma clot lysis test the strongest inhibitor, 2-hydroxy-stilbamidine, was 70 times more powerful than E-ACA.

Current concepts on action of synthetic thrombin inhibitors.

The development of synthetic inhibitors of thrombin and of related arginine-specific esteroproteases is reviewed. The superiority of bis- and tris-benzamidines over benzamidine is disccussed and related to the presence on the enzyme of secondary binding sites beyond the specificity pocket. It is demonstrated that inhibitors with marked specificity for a single enzyme can be produced, and with the help of such selective compounds it is shown that inhibition of factor Xa is more significant for overall anticoagulant effect than inhibition of thrombin.