Anidulafungin

Echinocandins were incubated with aldehyde-bearing surfaces and reductive amination was carried out using sodium cyanoborohydride. Then surfaces were washed using PBS solution alone, PBS followed by SDS solution, or PBS followed by SDS solution at 70 ℃. XPS revealed the relative amount of nitrogen remaining on the surface after washing (Fig. 3). The presence of nitrogen in the PBS-washed samples showed that all three echinocandins have the ability to adsorb to aldehyde plasma polymer surfaces. Using SDS washing, anidulafungin could be completely desorbed and small amounts of reversibly-adsorbed micafungin and caspofungin could be removed. These reductions are likely explained by the disruption of weak physical forces holding them to the surface. When washed with SDS at 70 ℃, physisorbed micafungin could be completely removed along with an additional loss of 0.4% N for caspofungin. The fact that only caspofungin (which amongst these echinocandins is capable of forming amine bonds with aldehyde-functionalized surfaces) remains after aggressive washing suggests that SDS washing at 70 ℃ is required to remove physisorbed compounds. We therefore infer that amine linkages formed between caspofungin and the plasma polymer surface is responsible for this compound's irreversible chemical binding to the surface. It should be noted that XPS survey spectra did not show any traces of elements fromthe binding and washing steps after final rinses with water (B, Na, Cl, K, P, S) suggesting that the washing procedures remove all traces of buffer salts, reducing agent and surfactant.

Caspofungin is the first approved semisynthetic echinocandin product followed by micafungin, and anidulafungin (Fig. 1). Though the mechanisms of action are similar, the spectrum of antifungal activity varies. For instance anidulafungin is effective against a wide range of azole or polyene resistant Candida sp and Aspergillus sp. Hence, these antifungal agents are truly life saving drugs. The frequency of echinocandin resistance remains low with Candida sp, as it facilitates escape through the formation of characteristic FKS hot-spot mutations. However, enchinocandin resistance has been observed in C. glabrata, thus this poses a serious clinical challenge in immunocompromised patients. Even though b-(1,3)-D-glucan synthase inhibitors are a significant alternative to ergosterol-binding antimycotic agents, poor oral bioavailabilty is their main limitation. Due to their large chemical structure echinocandins are available only as intra- venous formulations. To overcome this particular drawback, the semi-synthetic modification of a natural product, triterpene glycoside enfumafungin and its derivatives, is in progress. One such example is SCY-078, a novel oral glucan synthase inhibitor, developed and investigated for its pharmacodynamic property with a suggestion to promote SCY-078 as a promising oral option to treat Candida infections.