Evaluation of acute toxicity and pharmacokinetics of a natural phaeosphaeride A derivative in laboratory rodents

Introduction. The determination of metabolism and pharmacokinetics is an essential requirement in the development of any drug. Phaeosphaeride A (PPA) is an anticancer agent belonging to the group of natural compounds with antitumor properties, which was first isolated from the endophytic fungus FA39 by Harvard scientists (Claudy et al.) in 2006. In this study, we investigate compound AV6, which is a derivative of natural phaeosphaeride A.

Objective. To study the acute toxicity and pharmacokinetic characteristics of the semi-synthetic substance AV6 obtained based on phaeosphaeride A, a natural phytotoxin with antitumor properties, following a single intragastric administration of AV6 in laboratory rodents.

Materials and methods. The acute toxicity of AV6 was studied using 30 male Balb/c mice, which were divided into five groups of six animals each. The control group received a single intragastric administration of a solvent (oil-alcohol emulsion, 300 μL volume), while four experimental groups received AV6 at doses of 5, 50, 300, and 2000 mg/kg bw. Body weight dynamics were evaluated, and organ mass coefficients were calculated. The pharmacokinetic study was performed following a single intragastric administration of AV6 at a dose of 25 mg/kg bw to outbred male Wistar rats. The AV6 dose for the pharmacokinetic study was determined based on acute toxicity data, accounting for the interspecies conversion factor. Quantitative determination of AV6 in blood plasma and urine was performed using the MS/MS method. Statistical analysis was conducted using GraphPad Prism 5 software.

Results. According to the acute toxicity data following intragastric administration, the AV6 phaeosphaeride A derivative can be classified as hazard class 3 (animal mortality was observed exclusively in the 2000 mg/kg bw group). Visual examination of internal organs revealed no apparent macroscopic signs of pathology. No statistically significant changes in the mass coefficients of internal organs were detected in experimental animals compared to controls. A quantitative determination procedure for AV6 was developed based on HPLC–MS/MS analysis. Metabolites formed in rats in vivo were identified. A comparison of rat blood plasma chromatograms 1 h and 10 h after intragastric AV6 administration showed that, after 1 h, the AV6 peak intensity was 20 times higher than the M2 peak. However, after 10 h, the AV6 peak intensity decreased, while the metabolite M2 peak intensity increased.

Conclusion. Compound AV6 is classified as a moderately hazardous substance. Data on the structure of AV6 metabolites (a derivative of natural phaeosphaeride A) obtained during pharmacokinetic studies in rats indicate a relatively low metabolic rate of the compound. This is primarily due to chemical transformations at the nitrogen atom of the lactam ring, resulting in metabolites that may be excreted in urine. The most probable mechanisms of these transformations are oxidative deacylation followed by hydrolysis. The completed preclinical study evaluating the acute toxicity, metabolism, and pharmacokinetics of AV6 represents a crucial step in translating previous findings on the antitumor potential of this derivative of natural phaeosphaeride A and advancing in vivo research.

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