Evaluation of anti-herpesvirus activity of (1'S,2'R)-9-[[1',2'-bis(hydroxymethyl)cycloprop-1'-yl]methyl]- guanine (A-5021) in mice.

The anti-herpesvirus activity of (1'S,2'R)-9-[[1',2'-bis(hydroxymethyl)cycloprop-1'-yl]methyl]guani ne (A-5021) was evaluated in murine cells and in several murine models of herpes simplex virus (HSV) infection. Against HSV type 1 (HSV-1), A-5021 was 15-30- and 30-60-fold more active, and against HSV type 2 (HSV-2), it was 2- and 8-fold more active than acyclovir and penciclovir in Balb/3T3 cells, respectively. When antiviral compounds were administered orally (once daily) to mice infected intraperitoneally with HSV-1 (Tomioka), A-5021 was more active than acyclovir or famciclovir in spite of its relatively low oral bioavailability. A-5021 was as active as penciclovir when the antiviral compounds were given intravenously (three times daily) to mice infected intraperitoneally with HSV-2 (186). In mice with a cutaneous HSV-1 (KOS) infection, three times daily oral therapy with A-5021 at 25 mg/kg per day produced more significant reduction in severity of skin lesions than equivalent treatment with acyclovir or famciclovir. In mice infected intracerebrally with HSV-1 (Tomioka), complete survival was observed in the group treated intravenously with A-5021 at 25 mg/kg per day (three times daily), while more than 50% of mice died in the groups treated intravenously with acyclovir of up to 100 mg/kg per day (three times daily). Moreover, A-5021 was more effective than acyclovir in clearing infectious virus from the brain. These findings demonstrate that A-5021 has potent anti-HSV activity in several murine models.     

Synthesis and evaluation of stilbene and dihydrostilbene derivatives as potential anticancer agents that inhibit tubulin polymerization

An array of cis-, trans-, and dihydrostilbenes and some N-arylbenzylamines were synthesized and evaluated for their cytotoxicity in the five cancer cell cultures A-549 lung carcinoma, MCF-7 breast carcinoma, HT-29 colon adenocarcinoma, SKMEL-5 melanoma, and MLM melanoma. Several cis-stilbenes, structurally similar to combretastatins, were highly cytotoxic in all five cell lines and these were also found to be active as inhibitors of tubulin polymerization. The most active compounds also inhibited the binding of colchicine to tubulin. The most potent of the new compounds, both as a tubulin polymerization inhibitor and as a cytotoxic agent, was (Z)-1-(4-methoxyphenyl)-2-(3,4,5-trimethoxyphenyl)ethene (5a). This substance was almost as potent as combretastatin A-4 (1a), the most active of the combretastatins, as a tubulin polymerization inhibitor. Compound 5a was found to be approximately 140 times more cytotoxic against HT-29 colon adenocarcinoma cells and about 10 times more cytotoxic against MCF-7 breast carcinoma cells than combretastatin A-4. However, 5a was found to be about 20 times less cytotoxic against A-549 lung carcinoma cells, 30 times less cytotoxic against SKMEL-5 melanoma cells, and 7 times less cytotoxic against MLM melanoma cells than combretastatin A-4. The relative potencies 5a greater than 8a greater than 6a for the cis, dihydro, and trans compounds, respectively, as inhibitors of tubulin polymerization are in agreement with the relative potencies previously observed for combretastatin A-4 (1a), dihydrocombretastatin A-4 (1c), and trans-combretastatin A-4 (1b). The relative potencies 5a greater than 8a greater than 6a were also reflected in the results of the cytotoxicity assays. Structure-activity relationships of this group of compounds are also discussed.     

Anti-herpesvirus activity of (1'S,2'R)-9-[[1',2'-bis(hydroxymethyl)-cycloprop-1'-yl]methyl] x guanine (A-5021) in vitro and in vivo

The novel nucleoside analog (1S',2R')-9-[[1',2'-bis(hydroxymethyl)cycloprop-1-yl]methyl]guanine (A-5021) was previously shown to be a potent inhibitor of the replication of herpes simplex virus type 1 and 2 (HSV-1 and HSV-2) and varicella zoster virus (VZV), both in vitro and in vivo (J. Med. Chem. 41, 1284-1298; Antimicrob. Agents Chemother. 42, 1666-1670). Here we demonstrate that A-5021 is also a potent inhibitor of Epstein-Barr virus (EBV) and human herpes virus 6 (HHV-6A and HHV-6B), but that the compound lacks activity against HHV-8. A-5021, in comparison to acyclovir, was also assessed for protective activity against HSV-1-induced mortality in SCID mice. The compounds were administered at 50 mg/kg per day by subcutaneous injection for four consecutive days and treatment was initiated at either 2 h, 1 or 2 days post infection (p.i.). When administered from day 0 to 4 p.i., A-5021 conferred complete protection against the infection (as assessed at 22 days p.i.), whereas acyclovir delayed virus induced mortality by only 5 days. When treatment was begun on day 1 or 2, A-5021 still afforded marked protection against the infection, whereas acyclovir was virtually devoid of any activity under these conditions. Our data underline that A-5021 may offer great promise for the treatment of herpesvirus infections.     

Antiviral activities of 2′-deoxyribofuranosyl and arabinofuranosyl analogs of sangivamycin against retro- and DNA viruses

Eight sugar-modified pyrrolopyrimidine nucleoside analogs related to the antibiotic sangivamycin were evaluated in cell culture against herpes simplex types 1 (HSV-1) and 2 (HSV-2), cytomegalovirus (CMV), adenovirus, and visna virus. Five of the compounds were highly active against most of the viruses with 50% inhibition (ED₅₀) values of 1–10 μM. The selectivity of the agents was low, with inhibition of uninfected cell proliferation occurring within 5-fold that of the virus ED₅₀ for most of the viruses. The compounds did not possess RNA virus-inhibitory activity when evaluated against certain myxo-, paramyxo-, picorna-, reo-, rhabdo-, and togaviruses. Two of the nucleosides were tested further in a cell line persistently infected with Friend leukemia virus where they were inhibitory to both virus yield and cell proliferation at 4–5 μM. Several of the sangivamycin analogs were tested in animal models using a twice-a-day treatment regimen. They proved to be inactive against HSV-1, murine CMV and/or Friend leukemia virus infections in mice.     

Sterigmatocystins from the deep-sea-derived fungus Aspergillus versicolor

Three new sterigmatocystin derivatives, oxisterigmatocystin A (1), oxisterigmatocystin B (2) and oxisterigmatocystin C (3), together with one known compound, 5-methoxysterigmatocystin (4), were isolated from the deep-sea-derived fungus Aspergillus versicolor. The structures of the new compounds were elucidated by spectroscopic methods. The cytotoxicities of compounds 1-4 were evaluated against the A-549 and HL-60 cell lines. Compound 4 exhibited moderate cytotoxicities against the A-549 and HL-60 cell lines with IC(50) value of 3.86 and 5.32?μM, respectively.     

6-N-Acyltriciribine analogues: structure-activity relationship between acyl carbon chain length and activity against HIV-1

Triciribine (TCN) and triciribine-5'-monophosphate (TCN-P) are active against HIV-1 at submicromolar concentrations. In an effort to improve and better understand this activity, we have conducted a structure-activity relationship study to explore the tolerance of TCN to structural modifications at the 6-position. A number of 6-N-acyltriciribine analogues were synthesized and evaluated for antiviral activity and cytotoxicity. The cytotoxicity of these compounds was minimal in three human cell lines (KB, CEM-SS cells, and human foreskin fibroblasts (HFF)). The compounds were marginally active or inactive against herpes simplex virus type 1 (HSV-1) and human cytomegalovirus (HCMV). In contrast, most of the compounds exhibited moderate to high activity against human immunodeficiency virus type 1 (HIV-1), IC(50)'s = 0.03 to 1 microM. This structure-activity relationship study identified the N-heptanoyl group as having the optimal carbon chain length. This compound was as active against HIV-1 as TCN and TCN-P. Reverse phase HPLC of extracts from uninfected cells treated with 6-N-acyltriciribines detected sufficient TCN-P to account for anti-HIV activity thereby suggesting a prodrug effect. Studies in an adenosine kinase deficient cell line showed that the 6-N-acyl derivative was not phosphorylated directly but first was metabolized to triciribine which then was converted to TCN-P.     

Farnesyltransferase inhibition: a novel method of immunomodulation

Farnesyltransferase inhibitors (FTIs) are anticancer compounds that inhibit Ras GTPases. Since Ras GTPases play key roles in T cell activation and function, we hypothesized that FTIs have immunomodulatory properties and are potential antirejection agents. An investigation was performed on a potent FTI to evaluate this hypothesis in the in vitro setting.The in vitro effects of the FTI A-228839 were evaluated. Lectin- or antigen presenting cell (APC)-induced lymphocyte proliferation in the presence of A-228839 was measured. The effects of A-228839 on 1E5 T cell polarity were assessed by microscopy. Intracellular calcium ([Ca(2+)](i)) kinetics of lectin-activated lymphocytes was monitored by flow cytometry. The effects of A-228839 on peripheral blood mononuclear cell (PBMC) cytokine production was assessed by a cytometric bead array method. Activation-induced apoptosis was measured with an annexin V staining assay.A-228839 inhibited lectin-induced proliferation (IC(50)=0.24+/-0.11 microM). The inhibitory effects of A-228839 on lectin induced lymphocyte proliferation were additive to those of CsA. A-228839 was more effective in inhibiting APC-induced T cell proliferation (IC(50)=0.10+/-0.09 microM). A-228839 significantly disrupted the polarized shape of 1E5 T cells at physiologic concentrations. A-228839 altered PBMC baseline [Ca(2+)](i) but did not affect [Ca(2+)](i) kinetics during lectin-induced lymphocyte activation. A-228839 inhibited lymphocyte Th1 cytokine production at submicromolar levels and promoted apoptosis in lectin-activated lymphocytes.A-228839 potently inhibits lymphocyte activation and function. Our results suggest that FTIs may represent a new class of clinically useful immunomodulatory agents. A-228839 has potent in vitro immunomodulatory properties that warrant in vivo evaluation as an antirejection agent.     

Synthesis of substituted benzylamino- and heterocyclylmethylamino carbodithioate derivatives of 4-(3H)-quinazolinone and their cytotoxic activity

A new series of substituted benzylamino- and heterocyclylmethylamino carbodithioate derivatives of 4-(3H)-quinazolinone were synthesized via four steps starting from 2-amino-5-methylbenzoic acid and initially screened against A-549 (human non-small cell lung cancer), HCT-8 (human colon cancer), and Bel-7402 (human liver cancer) cell lines at the single concentration of 5 microg/mL using the colorimetric MTT assay. The IC50 values were determined for the compounds reaching > or = 70% inhibition in primary screening by serial dilution. Among the newly synthesized compounds, 9n exhibited potent in vitro cytotoxicity against A-549, HCT-8, and Bel-7402 cell lines with the IC50 values of 1.65, 0.93, and 1.43 microM, respectively.     

Synthesis and structure-activity relationship study of potent cytotoxic analogues of the marine alkaloid Lamellarin D

The marine alkaloid, Lamellarin D (Lam-D), has shown potent cytotoxicity in numerous cancer cell lines and was recently identified as a potent topoisomerase I inhibitor. A library of open lactone analogues of Lam-D was prepared from a methyl 5,6-dihydropyrrolo[2,1-a]isoquinoline-3-carboxylate scaffold (1) by introducing various aryl groups through sequential and regioselective bromination, followed by Pd(0)-catalyzed Suzuki cross-coupling chemistry. The compounds were obtained in a 24-44% overall yield, and tested in a panel of three human tumor cell lines, MDA-MB-231 (breast), A-549 (lung), and HT-29 (colon), to evaluate their cytotoxic potential. From these data, the SAR study concluded that more than 75% of the open-chain Lam-D analogues tested showed cytotoxicity in a low micromolar GI50 range.     

New antimitotic agents with activity in multi-drug-resistant cell lines and in vivo efficacy in murine tumor models.

During a screen for compounds that could inhibit cell proliferation, a series of new tubulin-binding compounds was identified with the discovery of oxadiazoline 1 (A-105972). This compound showed good cytotoxic activity against non-multi-drug-resistant and multi-drug-resistant cancer cell lines, but its utility in vivo was limited by a short half-life. Medicinal chemistry efforts led to the discovery of indolyloxazoline 22g (A-259745), which maintained all of the in vitro activity seen with oxadiazoline 1, but also demonstrated a better pharmacokinetic profile, and dose-dependent in vivo activity. Over a 28 day study, indolyloxazoline 22g increased the life span of tumor-implanted mice by up to a factor of 3 upon oral dosing. This compound, and others of its structural class, may prove to be useful in the development of new chemotherapeutic agents to treat human cancers.     

Application of real-time PCR for testing antiviral compounds against Lassa virus, SARS coronavirus and Ebola virus in vitro

This report describes the application of real-time PCR for testing antivirals against highly pathogenic viruses such as Lassa virus, SARS coronavirus and Ebola virus. The test combines classical cell culture with a quantitative real-time PCR read-out. The assay for Lassa virus was validated with ribavirin, which showed an IC(50) of 9 micrograms/ml. Small-scale screening identified a class of imidazole nucleoside/nucleotide analogues with antiviral activity against Lassa virus. The analogues contained either dinitrile or diester groups at the imidazole 4,5-positions, and many of which possessed an acyclic sugar or sugar phosphonate moiety at the imidazole 1-position. The IC(50) values of the most active compounds ranged from 5 to 21 micrograms/ml. The compounds also inhibited replication of SARS coronavirus and Ebola virus in analogous assays, although to a lesser extent than Lassa virus.     

Identification of compounds that inhibit the interaction between core and surface protein of hepatitis B virus

Specific interactions of the human hepatitis B virus (HBV) surface proteins with the core protein of nucleocapsid are critical for the envelopment of virus particles, and inhibition of this process may prevent the production of infectious virus. A modified enzyme-linked immunosorbent assay (ELISA), which measured the interaction between the core protein and PreS region of the surface protein, was used to screen a chemical library for compounds that would block this interaction. Few inhibitory compounds were identified from a chemical library consisting of 5600 compounds. Among them, two compounds inhibited the production of HBV particles from transiently HBV-producing HuH7 cells. The IC50 values of these compounds for inhibition of HBV production in HuH7 cells were in the micromolar concentration range. These results indicate that compounds that prevent the interaction between the core protein and PreS region of the surface protein may possibly be useful as anti-HBV agents.     

Identification of active antiviral compounds against a New York isolate of West Nile virus

The recent West Nile virus (WNV) outbreak in the United States has increased the need to identify effective therapies for this disease. A chemotherapeutic approach may be a reasonable strategy because the virus infection is typically not chronic and antiviral drugs have been identified to be effective in vitro against other flaviviruses. A panel of 34 substances was tested against infection of a recent New York isolate of WNV in Vero cells and active compounds were also evaluated in MA-104 cells. Some of these compounds were also evaluated in Vero cells against the 1937 Uganda isolate of the WNV. Six compounds were identified to be effective against virus-induced CPE with 50% effective concentrations (EC50) less than 10 microg/ml and with a selectivity index (SI) of greater than 10. Known inhibitors of orotidine monophosphate decarboxylase and inosine monophosphate dehydrogenase involved in the synthesis of GTP, UTP, and TTP were most effective. The compounds 6-azauridine, 6-azauridine triacetate, cyclopententylcytosine (CPE-C), mycophenolic acid and pyrazofurin appeared to have the greatest activities against the New York isolate, followed by 2-thio-6-azauridine. Anti-WNV activity of 6-azauridine was confirmed by virus yield reduction assay when the assay was performed 2 days after initial infection in Vero cells. The neutral red assay mean EC50 of ribavirin was only 106 microg/ml with a mean SI of 9.4 against the New York isolate and only slightly more effective against the Uganda isolate. There were some differences in the drug sensitivities of the New York and Uganda isolates, but when comparisons were made by categorizing drugs according to their modes of action, similarities of activities between the two isolates were identified.     

Lipoproteins account for part of the broad non-specific antiviral activity of human serum.

Several antiviral substances have been detected in human serum but few have been shown to possess broad antiviral activity. These broadly active antiviral molecules could be of significance as innate defense mechanisms. We have previously identified and characterized a broadly antiviral glycoprotein, UTI3, which accounts for 50 antiviral units/ml of human and mammalian sera. In addition there are reports of antiviral activity of human serum apolipoprotein A-1 (apo A-1), an important constituent of high density lipoprotein (HDL), against human immunodeficiency virus (HIV) and herpesvirus. Therefore we investigated (1) whether HDL is broadly antiviral, (2) how much of the broad antiviral activity of serum is due to HDL, and (3) the mechanism(s) of HDL's antiviral action. In this paper we report that (1) HDL does have broad antiviral activity, (2) HDL accounts for a modest but significant portion of the antiviral activity of serum, and (3) HDL acts by preventing virus penetration. Overall, HDL may be one of the broadly antiviral defences in the bloodstream.     

Synthesis and structure-activity relationship of 2-aminobenzophenone derivatives as antimitotic agents

A new type of inhibitor of tubulin polymerization was discovered on the basis of the combretastatin molecular skeleton. The lead compounds in this series, compounds 6 and 7, strongly inhibited tubulin polymerization in vitro and significantly arrested cells at the G(2)/M phase. Compounds 6 and 7 yielded 50- to 100-fold lower IC(50) values than did combretastatin A-4 against Colo 205, NUGC3, and HA22T human cancer cell lines as well as similar or greater growth inhibitory activities than did combretastain A-4 against DLD-1, HR, MCF-7, DU145, HONE-1, and MES-SA/DX5 human cancer cell lines. Structure-activity relationship information revealed that introduction of an amino group at the ortho position of the benzophenone ring plays an integral role for increased growth inhibition.     

2-取代胺甲基-5(6)-(E)-取代亚甲基环戊(己)酮盐酸盐类化合物的设计、合成及其抗肿瘤活性

目的设计合成20个2,5(6)-双取代环戊(己)酮类化合物,进行抗肿瘤活性研究。方法以WB852为先导化合物,设计合成了20个2-取代胺甲基-5(6)-(E)-取代亚甲基环戊(己)酮盐酸盐类化合物。利用MTT法对其中17个化合物进行了体外细胞毒活性筛选,所用肿瘤细胞株为人乳腺癌细胞T47D、MCF-7、MCF-7/Adr;通过Habig的酶动力学方法,测试了部分目标化合物细胞外对GSTπ活性的影响。结果与结论合成了20个2-取代胺甲基-5(6)-(E)-取代亚甲基环戊(己)酮盐酸盐类化合物,其中16个为未见文献报道的新化合物,其结构均经1H-NMR、MS和IR确证。体外抗肿瘤活性筛选结果,17个化合物对3种肿瘤细胞均有不同程度的生长抑制活性,A-16、A-17、A-18、A-19等4个化合物活性显著,值得进行深入研究。9个化合物均有不同程度地抑制GSTπ的活性,其中A-4、8、9、11和15等5个化合物对GSTπ的抑制作用强于WB852。取代胺甲基部分、取代亚甲基侧链的改变以及环的大小对抗肿瘤活性和选择性影响不大,但显著影响对GSTπ的抑制作用。A-16、A-17、A-18、A-19对MCF-7/Adr的生长抑制作用与WB852相当,但均低于对MCF-7细胞的活性,对耐药细胞的活性与GSTπ抑制无关。     

Distinct requirements for activation at CCK-A and CCK-B/gastrin receptors: studies with a C-terminal hydrazide analogue of cholecystokinin tetrapeptide (30-33)

We describe here the properties of tert-butyloxycarbonyl-Trp-Leu-Asp-Phe-NHNH2 (A-57696), a C-terminal hydrazide analogue of tert-butyloxycarbonyl-CCK4 (Boc-Trp-Met-Asp-Phe-NH2), at four cholecystokinin (CCK) receptor-bearing tissues, the guinea pig pancreas and gall bladder (Type A), guinea pig cortex (Type B), and NCI-H345 cells, a human small cell lung cancer cell line that expresses CCK-B/gastrin receptors. Using 125I-Bolton-Hunter-cholecystokinin octapeptide (26-33) (125I-Bolton-Hunter-CCK8) as the radioligand, A-57696 was found to be selective for cortical CCK-B receptors (IC50 = 25 nM), compared with pancreatic CCK-A receptors (IC50 = 15 microM). A-57696 behaved as a competitive antagonist in reversing CCK8-stimulated pancreatic amylase secretion and phosphoinositide breakdown. By Schild analysis, its Kd was determined to be 4.7 and 6.8 microM in amylase and phosphoinositide assays, respectively. A-57696 (100 microM) did not elicit gall bladder contraction, and it inhibited contractions induced by CCK8. The Kd of A-57696 at gall bladder CCK-A receptors was 19 microM. In contrast, A-57696 behaved as a partial agonist (80% of maximal CCK8 response) in stimulating calcium mobilization at CCK-B/gastrin receptors on NCI-H345 cells. A-57696 and CCK8 inhibited each other in calcium mobilization experiments utilizing the fluorescent dye Indo-1. Stimulatory actions of CCK8 and A-57696 were reversed by the CCK-B-selective (R)-L-365,260 (100 nM), whereas at the same concentration, the CCK-A-selective (S)-L-365,260 was ineffective. Binding studies using 125I-Bolton-Hunter-CCK8 and 125I-gastrin indicated that binding sites labeled by these two ligands displayed similar affinities for CCK8, desulfated CCK8, gastrin, A-57696, and both enantiomers of L-365,260. A-57696 represents a new class of CCK-A peptide antagonist at guinea pig pancreas a new class of CCK-A peptide antagonist at guinea pig pancreas and gall bladder. Its contrasting functional activities at guinea pig CCK-A and CCK-B/gastrin receptors in a human tumor cell demonstrate that, in addition to the previously described differences in binding specificity for selective agonists and antagonists, CCK-A receptors and CCK-B/gastrin receptors have different requirements for activation.     

Identification of a clinical compound losmapimod that blocks Lassa virus entry

OBJECTIVE To identify small molecule compounds with activity against the entry of Lassa virus(LASV) and study their antiviral mechanism. METHODS An HIV based pseudotyped Lassa virus(LASV-GP/HIVluc) was used to evaluate 102 clinical investigative drugs for anti-LASV entry activity. Twelve HIV based pseudotyped are naviruses were used to evaluate the broadspectrum anti-arenavirus activity of compounds. RNAi was used to evaluate the effect of specific cel ular pathway on the anti-LASV activity of compounds. Time-of-addition assay and cell-cell fusion assay were used to identify the specific step in which compounds exert their antiviral effect. Site-directed mutagenesis was employed to identify the molecular target of the compounds. RESULTS This study identified the clinical investigative P38 MAPK inhibitor losmapimod with activity against LASV entry, with an EC_(50) of 3.68 μmol·L~(-1). Losmapimod inhibited the entry of four lineages of LASV, with EC_(50) of 0.9-2.7 μmol·L~(-1), and it has no effect on the entry of eight other human pathogenic arenaviruses(EC_(50)>30 μmol · L~(-1)). Losmapimod retained its anti-LASV activity on P38 down-regulated cells. Losmapimod has no effect on LASV attachment on cell surface; instead, it inhibited LASV-GP mediated viral fusion. Losmapimod lost its anti-LASV activity on SSP-TM mutated pseudotyped LASV. CONCLUSION Losmapimod specifically inhibits the entry of LASV through targeting the SSP-GP2 interface of LASV glycoprotein, blocking the LASV-GP mediated viral fusion, thereby thwarting LASV entry into host cells.     

胆木茎中一个新的吲哚生物碱苷

目的研究中药胆木水溶性部位的化学成分。方法采用大孔吸附树脂，硅胶柱色谱和Sephadex LH20凝胶柱色谱分离纯化，通过光谱分析鉴定化合物的结构。结果从胆木水溶性部位中分离得到7个化合物，分别鉴定为： naucleamide A-10-O-β-D-glucopyranoside (I)， 5-β-carboxystrictosidin (II)， 獐牙菜苷(III)， 番木鳖苷A(IV)， 3,4-dimethoxyphenyl-β-D-glucopyranoside (V)， 3,4,5-trimethoxyphenyl-β-D-glucopyranoside (VI)， 2-phenethylrutinoside (VII)。结论化合物I为新的吲哚类生物碱苷，化合物I～VII均为首次从该植物中分得。     

Identification and characterization of potent small molecule inhibitor of hemorrhagic fever New World arenaviruses

Category A arenaviruses as defined by the National Institute of Allergy and Infectious Diseases (NIAID) are human pathogens that could be weaponized by bioterrorists. Many of these deadly viruses require biosafety level-4 (BSL-4) containment for all laboratory work, which limits traditional laboratory high-throughput screening (HTS) for identification of small molecule inhibitors. For those reasons, a related BSL-2 New World arenavirus, Tacaribe virus, 67-78% identical to Junín virus at the amino acid level, was used in a HTS campaign where approximately 400,000 small molecule compounds were screened in a Tacaribe virus-induced cytopathic effect (CPE) assay. Compounds identified in this screen showed antiviral activity and specificity against not only Tacaribe virus, but also the Category A New World arenaviruses (Junín, Machupo, and Guanarito). Drug resistant variants were isolated, suggesting that these compounds act through inhibition of a viral protein, the viral glycoprotein (GP2), and not through cellular toxicity mechanisms. A lead compound, ST-294, has been chosen for drug development. This potent and selective compound, with good bioavailability, demonstrated protective anti-viral efficacy in a Tacaribe mouse challenge model. This series of compounds represent a new class of inhibitors that may warrant further development for potential inclusion in a strategic stockpile.