The antiviral activity of a triazinoindole (SK&F 30097)

Functionalised 1,2,4-Triazino[5,6-b]indoles

3-Ethoxycarbonylmethylthio-5 H-1,2,4-triazino[5,6- b]indole (2) and 5-ethoxycarbonylmethyl-3-ethoxycarbonyl-methylthio-5 H-1,2,4-triazino[5,6- b]indole (4) have been prepared from 2,5-dihydro-3 H-1,2,4-triazino[5,6- b]indole-3-thione (1). The reaction of 2 and 4 with hydrazine hydrate gave the respective mono- and bishydrazide derivatives 3 and 5. Reaction of the monohydrazide 3 with acetylacetone, various carbonyl compounds and monosaccharides afforded the respective hydrazones 6 and 8–14. Dehydrative cyclization of 6 and 9 with boiling acetic anhydride afforded the pyrazole and 1,3,4-oxadiazoline derivatives 7 and 15, and reaction of 3 with CS2/KOH followed by hydrazinolysis afforded 16.

Antifungal properties in a novel series of triazino[5,6-b]indoles

GR99060 and GR99062 are representatives of a series of 1,2,4-triazino[5,6-b]indole compounds. This series possessed broad-spectrum antifungal activity in vitro. The MIC ranges of the two compounds were as follows: 0.25 to 4 micrograms/ml for Candida albicans, 0.25 to 16 micrograms/ml for Candida sp., 1 to 8 micrograms/ml for Aspergillus spp., and 0.25 to 16 micrograms/ml for Cryptococcus neoformans. GR99062 was metabolized in vitro by a mouse liver microsomal preparation, while GR99060 was stable. GR99060 was efficacious in a murine model of systemic candidiasis by oral or parenteral administration, although no clear dose-response was achieved, suggesting that other factors adversely affected the compound's in vivo activity.

Antirhinovirus activity of purine nucleoside analogs

A wide variety of purine nucleoside (mainly tubercidin and adenosine) analogs, which had previously been shown to inhibit the replication of a broad spectrum of RNA viruses, were evaluated for their antirhinovirus activity in human diploid (WI-38) fibroblasts. Tubercidin, 5-(1-hydroxyethyl)tubercidin, 5-(2-buten-1-yl)tubercidin, toyocamycin, and sangivamycin emerged as the most potent inhibitors. These compounds inhibited the replication of rhinovirus types 1A, 1B, and 9 at an MIC well below 1 microgram/ml. However, these compounds proved cytotoxic for the uninfected host cells at concentrations which were only slightly higher (3- to 10-fold, on the average) than those required for inhibition of rhinovirus replication. The most selective inhibitor of rhinovirus replication was 3-deazaguanine, with a selectivity index of 50. None of the carbocyclic and acyclic analogs of adenosine tested exhibited a potent or selective antirhinovirus activity.

Host range mutants of human rhinovirus in which nonstructural proteins are altered

Human rhinovirus type 2 did not replicate in nonpermissive mouse cells; the restriction was not in adsorption but in the early events of virus replication. Mutants which had been adapted to grow in mouse cells had the following characteristics: (i) no change in the structural protein, (ii) a larger nonstructural protein and its precursor protein, and (iii) an altered viral RNA synthesis. The altered nonstructural proteins correlated with a change in host range of the virus and may be involved in viral RNA synthesis.