Synthesis and characterization of semisynthetic analogs of the antifungal occidiofungin

Previously Uncharacterized Variants, OCF-E-OCF-J, of the Antifungal Occidiofungin Produced by Burkholderia contaminans MS14

The rise of multidrug resistant fungal infections highlights the need to identify and develop novel antifungal agents. Occidiofungin is a nonribosomally synthesized glycolipopeptide that has a unique mechanism of action, disrupting actin-mediated functions and inducing cellular apoptosis. Antifungal activity has been observed in vitro against various fungal species, including multidrug resistant Candida auris, and in vivo efficacy has been demonstrated in a murine vulvovaginal candidiasis model. Occidiofungin, a cyclic glycolipopeptide, is composed of eight amino acids and in previous studies, an asparagine residue was assigned at position 7 (ASN7). In this study, new structural variants of occidiofungin have been characterized which have aspartic acid (ASP7), glutamine (GLN7), or glutamic acid (GLU7) at position 7. The side chain of the ASP7 variant contains the only terminal carboxylic acid in the peptide and provides a useful site for selective chemical modifications. Analogues were synthesized at the ASP7 position and tested for antifungal activity. These analogues were shown to be more active as compared to the ASP7 variant against a panel of Candida species. The naturally occurring variants of occidiofungin with a side chain containing a carboxylic acid at the seventh amino acid position can be used to develop semisynthetic analogues with enhanced therapeutic properties.

Intravaginal Gel for Sustained Delivery of Occidiofungin and Long-Lasting Antifungal Effects

Fungal infections are caused by opportunistic pathogens that can be life threatening or debilitating. Candida spp. are becoming increasingly resistant to current clinically approved antifungal therapeutics. Candida infections afflict not only immunosuppressed but also immunocompetent individuals. Recurrent vulvovaginal candidiasis (RVVC) is a disease that afflicts 5-9% of women. Occidiofungin is a novel cyclic peptide that has a broad spectrum of antifungal activity with a novel fungicidal mechanism of action. A gel formulation containing occidiofungin (OCF001) is being developed for use to treat vulvovaginal candidiasis. The formulated gel for intravaginal application used hydroxyethyl cellulose as the primary gelling agent and hydroxypropyl β-cyclodextrin as a solubilizing agent for occidiofungin. Franz cells and LC-MS/MS were used to determine the rate of drug substance diffusion in the gel formulation. The formulation was tested in an ex vivo mouse skin efficacy study, and the safety was tested following repeat intravaginal administration in rabbits. In this study, the gel formulation was shown to reduce the drug substance rate of diffusion across a skin memetic membrane. The study showed that the formulation extends exposure time to inhibitory concentrations of occidiofungin over a 24-h period and supports a single daily application for the treatment of RVVC.