In Vitro Activities and Postantifungal Effects of the Potent Dolastatin 10 Derivative Auristatin PHE

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Abstract
The pentapeptide dolavaline-valine-dolaisoleuine-dolaproine-phenylalanine-methyl ester (auristatin PHE) is a derivative of the anticancer drug dolastatin 10 (dolavaline-valine-dolaisoleuine-dolaproine-dolaphenine). Broth microdilution assays with a wide variety of yeast and filamentous fungal species demonstrated the specificity of auristatin PHE for Cryptococcus neoformans and several species of Trichosporon . The duration of the postantifungal effect (PAFE) for C. neoformans was determined for exposure times ranging from 30 min to 2 h. For the derivative, a PAFE was detectable after 45 min of exposure. The effect plateaued after 1 h of exposure, with a PAFE of approximately 6.5 h at four or eight times the auristatin PHE MIC. In contrast, there was no measurable PAFE after 1 h of exposure to dolastatin 10. Human serum greatly prolonged the PAFE of auristatin PHE at eight times the MIC. Auristatin PHE arrested C. neoformans in the budding stage, possibly due to a tubulin-inhibitory action. Auristatin PHE has potential as a narrow-spectrum fungicidal agent and as a probe that can be used to study cryptococcal cell division.