Isavuconazole: A new broad-spectrum azole. Part 1: In vitro activity.

Triazoles compounds are first-line agents for the treatment of invasive fungal diseases. Isavuconazole is the most recent triazole compound, approved in 2015 by the FDA and the EMA to treat invasive aspergillosis and mucormycosis. We reviewed here the in vitro activity of isavuconazole against a vast spectrum of species. Isavuconazole MICs were evaluated using CLSI, EUCAST or Etest methods, with no significant differences between the technics. Low MIC50 and MIC90 (<1µg/mL) were described for isavuconazole against the majority of Candida spp., except for C. glabrata and C. krusei. In vitro activity against Aspergillus spp. varied according to the species with an overall MIC90 of 1µg/mL ranging from 0.125µg/mL (A. fumigatus) to 16µg/mL (A. niger, A. tubingiensis). As for Aspergillus, the activity of isavuconazole against agents of mucormycosis varies upon genus and species, with an overall MIC90 from 4 (Rhizopus spp.) to 16µg/mL (Rhizomucor spp. and Mucor spp.). Recently, to help detecting non-wild-type isolates, EUCAST committee has proposed ECOFFs values for C. albicans, C. parapsilosis and C. tropicalis (0.03µg/mL), for Aspergillus fumigatus (2µg/mL), A. nidulans (0.25µg/mL), A. terreus (1µg/mL), A. flavus (2µg/mL) and A. niger (4µg/mL). Moreover, clinical breakpoints (susceptible/resistant) were defined for Aspergillus fumigatus (1µg/mL), A. nidulans (0.25µg/mL) and A. terreus (1µg/mL). Using these breakpoints, isavuconazole showed activity against the vast majority of fungi.

Isavuconazole: A new broad-spectrum azole. Part 2: pharmacokinetics and clinical activity.

Isavuconazole, the active moiety of its prodrug isavuconazonium, is a new extended-spectrum triazole whose activity against yeasts, molds, including Aspergillus and mucorales, and dimorphic fungi has been shown in vitro and in preclinical models. The most relevant pharmacokinetics features are water-solubility of the prodrug, rapid cleavage of the prodrug into active moiety and cleavage product by plasmatic esterases, high oral bioavailability of isavuconazole with an extensive penetration into most tissues and a good safety profile even in case of renal impairment. The results of two main clinical studies have led to an approval by FDA and EMA in the treatment of invasive aspergillosis and invasive mucormycosis. Isavuconazole is non-inferior to voriconazole in terms of response and survival in invasive aspergillosis and has shown improved safety and tolerability. Importantly, less hepatobiliary, skin and eye disorders have been reported in isavuconazole-treated patients. Isavuconazole has therefore been granted a grade A-I recommendation by the European Conference on Infections in Leukemia (ECIL) for the treatment of invasive aspergillosis. Efficacy has also been demonstrated in mucormycosis in an open-label study. Survival was similar to the survival of matched patients from the international Fungiscope registry and treated with an amphotericin B formulation. Isavuconazole failed to show non-inferiority to caspofungin in a large double-blind candidemia trial. The aim of this review is to give the reader an overview of the data available so far to support inclusion of isavuconazole in the anti-mold therapeutic arsenal.