In Vivo Studies with Ambruticin in Murine Histoplasmosis

Abstract

Ambruticin (W7783) was evaluated in vivo in mice subacutely or nonlethally infected with Histoplasma capsulatum. Results were compared with those obtained with amphotericin B, the drug of choice in human histoplasmosis. In one experiment, ambruticin was shown to be capable of curing infected animals as evidenced by totally negative liver and spleen cultures obtained when mice were sacrificed after 4 weeks of oral treatment with 150 mg of drug per kg per day. The 50% cure dose for ambruticin was between 75 and 150 mg/kg per day; the 50% cure dose for oral amphotericin B in this experiment was between 1.56 and 6.25 mg/kg per day. In a second experiment, both oral ambruticin (150 mg/kg per day) and oral amphotericin B (25 mg/kg per day) were again curative, but to a lesser degree than in the first experiment. Biological cures were obtained with both drugs after 3 and 4 weeks of treatment but not after 2 weeks.Ambruticin (W7883) has been shown to be a relatively broad-spectrum antifungal agent active in vitro against a variety of filamentous and dimorphic fungal pathogens (4-6). It already has been shown to be active in vivo in mice experimentally infected with Coccidioides immitis and, moreover, capable both of protecting experimental animals against infection with this organism and of producing biological cures (1, 2). The studies to be reported here compared the in vivo efficacy of orally administered ambruticin with that of orally administered amphotericin B in mice experimentally infected with Histoplasma capsulatium. Cultural studies. In both experiments, cultural studies were performed on target organs of surviving animals at the end of the treatment period. In these studies, spleens and livers were removed from sacrificed survivors, placed in 3-to 4-nil volumes of saline contained in plastic bags, and squashed to produce suspensions which were then plated on Mycosel agar (BBL) with added chloramphenicol. Approximately 1 ml, or 25% of each organ suspension, was plated. The inoculated plates were incubated at 28°C until sufficient growth was present to permit accurate mycological identification. Growth was scored on the basis of + (-10 colonies), ++ (10 to 100 colonies), and +++ to ++++ (greater than 100 colonies, or confluent growth with few or no discrete colonies). Identifications for at least one-third of all positive plates from each group of animals were confirmed by microscopic examination. MATERIALS AND METHODSIn the second experiment, 10 treated, infected mice from each of the two treatment regimen groups as well as the group of placebo-treated mice were sacrificed at the end of each week of treatment. One group of 10 infected but untreated mice was sacrificed on the first day of treatment. Livers and spleens were removed from these animals and processed as above for cultural studies.

In Vitro Studies with Ambruticin, a New Antifungal Antibiotic

“…Similar results have been obtained in mice experimentally infected with H. capsulatum (11). Infections caused by the dermatophytic fungi are among the most common diseases of humans.…”

Fungistatic and Fungicidal Effects of Amphotericin B, Ketoconazole and Fluconazole (UK 49, 858) against Histoplasma capsulatum in vitro and in vivo

“…Williams et al (22) found Amph B to prolong survival in nu/nu mice infected with this fungus. Shadomy et al (20) demostrated both life prolongation and biological cures with Amph B in murine histoplasmosis. In the latter study, at doses of 6.25 mg Amph B/kg/day, all spleen cultures were negative for fungi at the end of the 28 day treatment period.…”

Enantioselective Total Synthesis of the Putative Biosynthetic Intermediate Ambruticin J

“…[11] Several studies using ambruticins and their derivatives, in both in vitro and in vivo plant and murine models of fungal infection, have shown therapeutic properties including low toxicity and promising activity against fungal infections including histoplasmosis and coccidiomycosis both intravenously and orally administered. [2,9,10,[12][13][14] Structurally, the ambruticins consist of a trisubstituted divinylcyclopropane ring core appended with two pyrans (Figure 1). Ambruticin congeners vary in the C5 position, but it is the atypical trisubstituted cyclopropane core and promising biological activity that have made these molecules popular synthetic targets.…”

“…A recent study of the effect of ambruticin VS3 on soil myxobacteria confirms an impact on a group III hybrid histidine kinase (HHK) and provides an environmental advantage by affecting the development of competitive myxobacterial species [11] . Several studies using ambruticins and their derivatives, in both in vitro and in vivo plant and murine models of fungal infection, have shown therapeutic properties including low toxicity and promising activity against fungal infections including histoplasmosis and coccidiomycosis both intravenously and orally administered [2,9,10,12–14] . Structurally, the ambruticins consist of a trisubstituted divinylcyclopropane ring core appended with two pyrans (Figure 1).…”