Tuning sterol extraction kinetics yields a renal-sparing polyene antifungal.

Decades of previous efforts to develop renal-sparing polyene antifungals were misguided by the classic membrane permeabilization model1. Recently, the clinically vital but also highly renal-toxic small-molecule natural product amphotericin B was instead found to kill fungi primarily by forming extramembraneous sponge-like aggregates that extract ergosterol from lipid bilayers2-6. Here we show that rapid and selective extraction of fungal ergosterol can yield potent and renal-sparing polyene antifungals. Cholesterol extraction was found to drive the toxicity of amphotericin B to human renal cells. Our examination of high-resolution structures of amphotericin B sponges in sterol-free and sterol-bound states guided us to a promising structural derivative that does not bind cholesterol and is thus renal sparing. This derivative was also less potent because it extracts ergosterol more slowly. Selective acceleration of ergosterol extraction with a second structural modification yielded a new polyene, AM-2-19, that is renal sparing in mice and primary human renal cells, potent against hundreds of pathogenic fungal strains, resistance evasive following serial passage in vitro and highly efficacious in animal models of invasive fungal infections. Thus, rational tuning of the dynamics of interactions between small molecules may lead to better treatments for fungal infections that still kill millions of people annually7,8 and potentially other resistance-evasive antimicrobials, including those that have recently been shown to operate through supramolecular structures that target specific lipids9.

Efficacy of an oral lipid nanocrystal formulation of amphotericin B (MAT2203) in the neutropenic mouse model of pulmonary mucormycosis.

Invasive mucormycosis (IM) is associated with high mortality and morbidity. MAT2203 is an orally administered lipid nanocrystal formulation of amphotericin B, which has been shown to be safe and effective against other fungal infections. We sought to compare the efficacy of MAT2203 to liposomal amphotericin B (LAMB) treatment in a neutropenic mouse model of IM due to Rhizopus arrhizus var. delemar or Mucor circinelloides f. jenssenii DI15-131. In R. arrhizus var. delemar-infected mice, 15 mg/kg of MAT2203 qd was as effective as 10 mg/kg of LAMB in prolonging median survival time vs placebo (13.5 and 16.5 days for MAT2203 and LAMB, respectively, vs 9 days for placebo) and enhancing overall survival vs placebo-treated mice (40% and 45% for MAT2203 and LAMB, respectively, vs 0% for placebo). A higher dose of 45 mg/kg of MAT2203 was not well tolerated by mice and showed no benefit over placebo. Similar results were obtained with mice infected with M. circinelloides. Furthermore, while both MAT2203 and LAMB treatment resulted in a significant reduction of ~1.0-2.0log and ~2.0-2.5log in Rhizopus delemar or M. circinelloides lung and brain burden vs placebo mice, respectively, LAMB significantly reduced tissue fungal burden in mice infected with R. delemar vs tissues of mice treated with MAT2203. These results support continued investigation and development of MAT2203 as a novel and oral formulation of amphotericin for the treatment of mucormycosis.

Ibrexafungerp is efficacious in a neutropenic murine model of pulmonary mucormycosis as monotherapy and combined with liposomal amphotericin B.

Ibrexafungerp (formerly SCY-078) is the first member of the triterpenoid class that prevents the synthesis of the fungal cell wall polymer ß-(1,3)-D-glucan by inhibiting the enzyme glucan synthase. We evaluated the in vivo efficacy of ibrexafungerp against pulmonary mucormycosis using an established murine model. Neutropenic mice were intratracheally infected with either Rhizopus delemar or Mucor circinelloides. Treatment with placebo (diluent control), ibrexafungerp (30 mg/kg, PO BID), liposomal amphotericin B (LAMB 10 mg/kg IV QD), posaconazole (PSC 30 mg/kg PO QD), or a combination of ibrexafungerp plus LAMB or ibrexafungerp plus PSC began 16 h post-infection and continued for 7 days for ibrexafungerp or PSC and through day 4 for LAMB. Ibrexafungerp was as effective as LAMB or PSC in prolonging median survival (range: 15 days to >21 days) and enhancing overall survival (30%-65%) vs placebo (9 days and 0%; P < 0.001) in mice infected with R. delemar. Furthermore, median survival and overall percent survival resulting from the combination of ibrexafungerp plus LAMB were significantly greater compared to all monotherapies (P ≤ 0.03). Similar survival results were observed in mice infected with M. circinelloides. Monotherapies also reduce the lung and brain fungal burden by ~0.5-1.0log10 conidial equivalents (CE)/g of tissue vs placebo in mice infected with R. delemar (P < 0.05), while a combination of ibrexafungerp plus LAMB lowered the fungal burden by ~0.5-1.5log10 CE/g compared to placebo or any of the monotherapy groups (P < 0.03). These results are promising and warrant continued investigation of ibrexafungerp as a novel treatment option against mucormycosis.

The Combination Treatment of Fosmanogepix and Liposomal Amphotericin B Is Superior to Monotherapy in Treating Experimental Invasive Mold Infections.

Invasive pulmonary aspergillosis (IPA), invasive mucormycosis (IM), and invasive fusariosis (IF) are associated with high mortality and morbidity. Fosmanogepix (FMGX) is a first-in-class antifungal in clinical development with demonstrated broad-spectrum activity in animal models of infections. We sought to evaluate the benefit of combination therapy of FMGX plus liposomal amphotericin B (L-AMB) in severe delayed-treatment models of murine IPA, IM, and IF. While FMGX was equally as effective as L-AMB in prolonging the survival of mice infected with IPA, IM, or IF, combination therapy was superior to monotherapy in all three models. These findings were validated by greater reductions in the tissue fungal burdens (determined by quantitative PCR) of target organs in all three models versus the burdens in infected vehicle-treated (placebo) or monotherapy-treated mice. In general, histopathological examination of target organs corroborated the findings for fungal tissue burdens among all treatment arms. Our results show that treatment with the combination of FMGX plus L-AMB demonstrated high survival rates and fungal burden reductions in severe animal models of invasive mold infections, at drug exposures in mice similar to those achieved clinically. These encouraging results warrant further investigation of the FMGX-plus-L-AMB combination treatment for severely ill patients with IPA, IM, and IF.

Combination treatment of liposomal amphotericin B and isavuconazole is synergistic in treating experimental mucormycosis.

OBJECTIVES: Liposomal amphotericin B (L-AMB) and isavuconazonium sulphate are commonly used antifungal drugs to treat mucormycosis. However, the efficacy of combination therapy of L-AMB/isavuconazonium sulphate versus monotherapy is unknown. We used an immunosuppressed mouse model of pulmonary mucormycosis to compare the efficacy of L-AMB/isavuconazonium sulphate versus either drug alone. METHODS: Neutropenic mice were intratracheally infected with either Rhizopus delemar or Mucor circinelloides. Treatment with L-AMB, isavuconazonium sulphate, or a combination of both started 8 h post-infection and continued through to Day +4. Placebo mice received vehicle control. Survival to Day +21 and tissue fungal burden (by conidial equivalent using quantitative PCR) on Day +4, served as primary and secondary endpoints, respectively. RESULTS: For mice infected with R. delemar, L-AMB and isavuconazonium sulphate equally prolonged median survival time and enhanced survival versus placebo (an overall survival of 50% for either drug alone, versus 5% for placebo). Importantly, combination treatment resulted in an overall survival of 80%. Both antifungal drugs reduced tissue fungal burden of lungs and brain by ∼1.0-2.0 log versus placebo-treated mice. Treatment with combination therapy resulted in 2.0-3.5 log reduction in fungal burden of either organ versus placebo and 1.0 log reduction versus either drug alone. Similar treatment outcomes were obtained using mice infected with M. circinelloides. CONCLUSIONS: The L-AMB/isavuconazonium sulphate combination demonstrated greater activity versus monotherapy in immunosuppressed mice infected with either of the two most common causes of mucormycosis. These studies warrant further investigation of L-AMB/isavuconazonium sulphate combination therapy as an optimal therapy of human mucormycosis.

Selective inhibition of Rhizopus eumelanin biosynthesis by novel natural product scaffold-based designs caused significant inhibition of fungal pathogenesis.

Melanin is a dark color pigment biosynthesized naturally in most living organisms. Fungal melanin is a major putative virulence factor of Mucorales fungi that allows intracellular persistence by inducing phagosome maturation arrest. Recently, it has been shown that the black pigments of Rhizopus delemar is of eumelanin type, that requires the involvement of tyrosinase (a copper-dependent enzyme) in its biosynthesis. Herein, we have developed a series of compounds (UOSC-1-14) to selectively target Rhizopus melanin and explored this mechanism therapeutically. The compounds were designed based on the scaffold of the natural product, cuminaldehyde, identified from plant sources and has been shown to develop non-selective inhibition of melanin production. While all synthesized compounds showed significant inhibition of Rhizopus melanin production and limited toxicity to mammalian cells, only four compounds (UOSC-1, 2, 13, and 14) were selected as promising candidates based on their selective inhibition to fungal melanin. The activity of compound UOSC-2 was comparable to the positive control kojic acid. The selected candidates showed significant inhibition of Rhizopus melanin but not human melanin by targeting the fungal tyrosinase, and with an IC50 that are 9 times lower than the reference standard, kojic acid. Furthermore, the produced white spores were phagocytized easily and cleared faster from the lungs of infected immunocompetent mice and from the human macrophages when compared with wild-type spores. Collectively, the results suggested that the newly designed derivatives, particularly UOSC-2 can serve as promising candidate to overcome persistence mechanisms of fungal melanin production and hence make them accessible to host defenses.

Fosmanogepix (APX001) Is Effective in the Treatment of Pulmonary Murine Mucormycosis Due to Rhizopus arrhizus.

Mucormycosis is a life-threatening infection with high mortality that occurs predominantly in immunocompromised patients. Manogepix (MGX) is a novel antifungal that targets Gwt1, a protein involved in an early step in the conserved glycosylphosphotidyl inositol (GPI) posttranslational modification pathway of surface proteins in eukaryotic cells. Inhibition of fungal inositol acylation by MGX results in pleiotropic effects, including inhibition of maturation of GPI-anchored proteins necessary for growth and virulence. MGX has been previously shown to have in vitro activity against some strains of Mucorales. Here, we assessed the in vivo activity of the prodrug fosmanogepix, currently in clinical development for the treatment of invasive fungal infections, against two Rhizopus arrhizus strains with high (4.0 µg/ml) and low (0.25 µg/ml) minimum effective concentration (MEC) values. In both invasive pulmonary infection models, treatment of mice with 78 mg/kg or 104 mg/kg fosmanogepix, along with 1-aminobenzotriazole to enhance the serum half-life of MGX in mice, significantly increased median survival time and prolonged overall survival by day 21 postinfection compared to placebo. In addition, administration of fosmanogepix resulted in a 1 to 2 log reduction in both lung and brain fungal burden. For the 104 mg/kg fosmanogepix dose, tissue clearance and survival were comparable to clinically relevant doses of isavuconazole (ISA), which is FDA approved for the treatment of mucormycosis. These results support continued development of fosmanogepix as a first-in-class treatment for invasive mucormycosis.

Fosmanogepix (APX001) Is Effective in the Treatment of Immunocompromised Mice Infected with Invasive Pulmonary Scedosporiosis or Disseminated Fusariosis.

There are limited treatment options for immunosuppressed patients with lethal invasive fungal infections due to Fusarium and Scedosporium Manogepix (MGX; APX001A) is a novel antifungal that targets the conserved Gwt1 enzyme required for localization of glycosylphosphatidylinositol-anchored mannoproteins in fungi. We evaluated the in vitro activity of MGX and the efficacy of the prodrug fosmanogepix (APX001) in immunosuppressed murine models of hematogenously disseminated fusariosis and pulmonary scedosporiosis. The MGX minimum effective concentration (MEC) for Scedosporium isolates was 0.03 µg/ml and ranged from 0.015 to 0.03 µg/ml for Fusarium isolates. In the scedosporiosis model, treatment of mice with 78 mg/kg and 104 mg/kg of body weight fosmanogepix, along with 1-aminobenzotriazole (ABT) to enhance the serum half-life of MGX, significantly increased median survival time versus placebo from 7 days to 13 and 11 days, respectively. Furthermore, administration of 104 mg/kg fosmanogepix resulted in an ∼2-log10 reduction in lung, kidney, or brain conidial equivalents/gram tissue (CE). Similarly, in the fusariosis model, 78 mg/kg and 104 mg/kg fosmanogepix plus ABT enhanced median survival time from 7 days to 12 and 10 days, respectively. A 2- to 3-log10 reduction in kidney and brain CE was observed. In both models, reduction in tissue fungal burden was corroborated with histopathological data, with target organs showing reduced or no abscesses in fosmanogepix-treated mice. Survival and tissue clearance were comparable to a clinically relevant high dose of liposomal amphotericin B (10 to 15 mg/kg). Our data support the continued development of fosmanogepix as a first-in-class treatment for infections caused by these rare molds.

Preserving Vascular Integrity Protects Mice against Multidrug-Resistant Gram-Negative Bacterial Infection.

The rise in multidrug-resistant (MDR) organisms portends a serious global threat to the health care system with nearly untreatable infectious diseases, including pneumonia and its often fatal sequelae, acute respiratory distress syndrome (ARDS) and sepsis. Gram-negative bacteria (GNB), including Acinetobacter baumannii, Pseudomonas aeruginosa, and carbapenemase-producing Klebsiella pneumoniae (CPKP), are among the World Health Organization's and National Institutes of Health's high-priority MDR pathogens for targeted development of new therapies. Here, we show that stabilizing the host's vasculature by genetic deletion or pharmacological inhibition of the small GTPase ADP-ribosylation factor 6 (ARF6) increases survival rates of mice infected with A. baumannii, P. aeruginosa, and CPKP. We show that the pharmacological inhibition of ARF6-GTP phenocopies endothelium-specific Arf6 disruption in enhancing the survival of mice with A. baumannii pneumonia, suggesting that inhibition is on target. Finally, we show that the mechanism of protection elicited by these small-molecule inhibitors acts by the restoration of vascular integrity disrupted by GNB lipopolysaccharide (LPS) activation of the TLR4/MyD88/ARNO/ARF6 pathway. By targeting the host's vasculature with small-molecule inhibitors of ARF6 activation, we circumvent microbial drug resistance and provide a potential alternative/adjunctive treatment for emerging and reemerging pathogens.

Galactomannan Is a Biomarker of Fosmanogepix (APX001) Efficacy in Treating Experimental Invasive Pulmonary Aspergillosis.

Galactomannan (GM) detection in biological samples has been shown to predict therapeutic response by azoles and polyenes. In a murine invasive pulmonary aspergillosis model, fosmanogepix or posaconazole treatment resulted in an ∼6- to 7-log reduction in conidial equivalents (CE)/g lung tissue after 96 h versus placebo. Changes in GM levels in BAL fluid and serum mirrored reductions in lung CE, with significant decreases seen after 96 h or 72 h for fosmanogepix or posaconazole, respectively (P < 0.02).

APX001 Is Effective in the Treatment of Murine Invasive Pulmonary Aspergillosis.

Invasive pulmonary aspergillosis (IPA) due to Aspergillus fumigatus is a serious fungal infection in the immunosuppressed patient population. Despite the introduction of new antifungal agents, mortality rates remain high, and new treatments are needed. The novel antifungal APX001A targets the conserved Gwt1 enzyme required for the localization of glycosylphosphatidylinositol-anchored mannoproteins in fungi. We evaluated the in vitro activity of APX001A against A. fumigatus and the in vivo activity of its prodrug APX001 in an immunosuppressed mouse model of IPA. APX001A inhibited the growth of A. fumigatus with a minimum effective concentration of 0.03 µg/ml. The use of 50 mg/kg 1-aminobenzotriazole (ABT), a suicide inhibitor of cytochrome P450 enzymes, enhanced APX001A exposures (area under the time-concentration curve [AUC]) 16- to 18-fold and enhanced serum half-life from ∼1 to 9 h, more closely mimicking human pharmacokinetics. We evaluated the efficacy of APX001 (with ABT) in treating murine IPA compared to posaconazole treatment. Treatment of mice with 78 mg/kg once daily (QD), 78 mg/kg twice daily, or 104 mg/kg QD APX001 significantly enhanced the median survival time and prolonged day 21 postinfection overall survival compared to the placebo. Furthermore, administration of APX001 resulted in a significant reduction in lung fungal burden (4.2 to 7.6 log10 conidial equivalents/g of tissue) versus the untreated control and resolved the infection, as judged by histopathological examination. The observed survival and tissue clearance were comparable to a clinically relevant posaconazole dose. These results warrant the continued development of APX001 as a broad-spectrum, first-in-class treatment of invasive fungal infections.

PCR-Based Approach Targeting Mucorales-Specific Gene Family for Diagnosis of Mucormycosis.

Mucormycosis is an aggressive, life-threatening infection caused by fungi in the order Mucorales. The current diagnosis of mucormycosis relies on mycological cultures, radiology and histopathology. These methods lack sensitivity and are most definitive later in the course of infection, resulting in the prevention of timely intervention. PCR-based approaches have shown promising potential in rapidly diagnosing mucormycosis. The spore coating protein homolog encoding CotH genes are uniquely and universally present among Mucorales. Thus, CotH genes are potential targets for the rapid diagnosis of mucormycosis. We infected mice with different Mucorales known to cause human mucormycosis and investigated whether CotH could be PCR amplified from biological fluids. Uninfected mice and those with aspergillosis were used to determine the specificity of the assay. CotH was detected as early as 24 h postinfection in plasma, urine, and bronchoalveolar lavage (BAL) samples from mice infected intratracheally with Rhizopus delemar, Rhizopus oryzae, Mucor circinelloides, Lichtheimia corymbifera, or Cunninghamella bertholletiae but not from samples taken from uninfected mice or mice infected with Aspergillus fumigatus Detection of CotH from urine samples was more reliable than from plasma or BAL fluid. Using the receiver operating characteristic method, the sensitivity and the specificity of the assay were found to be 90 and 100%, respectively. Finally, CotH was PCR amplified from urine samples of patients with proven mucormycosis. Thus, PCR amplification of CotH is a promising target for the development of a reliable, sensitive, and simple method of early diagnosis of mucormycosis.

Prophylaxis with Isavuconazole or Posaconazole Protects Immunosuppressed Mice from Pulmonary Mucormycosis.

We assessed prophylactic or continuous therapy of isavuconazole, posaconazole, or voriconazole in treating pulmonary murine mucormycosis. In the prophylaxis studies, only isavuconazole treatment resulted in significantly improved survival and lowered tissue fungal burden of immunosuppressed mice infected with Rhizopus delemar. In the continuous treatment studies, isavuconazole and posaconazole, but not voriconazole, equally prolonged survival time and lowered tissue fungal burden compared to placebo-treated mice. These results support the use of isavuconazole and posaconazole in prophylaxis treatment.

Prophylactic Treatment with VT-1161 Protects Immunosuppressed Mice from Rhizopus arrhizus var. arrhizus Infection.

We compared prophylactic or continuous therapy with the investigational drug VT-1161 to that with posaconazole in treating murine mucormycosis due to Rhizopus arrhizus var. arrhizus In the prophylaxis studies, only VT-1161 resulted in improved survival and lowered tissue fungal burden of immunosuppressed infected mice. In the continuous therapy, VT-1161 outperformed posaconazole in prolonging mouse survival time despite its comparable effect in lowering tissue fungal burden. These results support the further development of VT-1161 against mucormycosis.

Monotherapy or combination therapy of isavuconazole and micafungin for treating murine mucormycosis.

OBJECTIVES: Previously we demonstrated the benefit of isavuconazole in treating murine mucormycosis due to Rhizopus. We wanted to determine the efficacy of isavuconazole in treating murine mucormycosis caused by Mucor, the second most common cause of the disease. Furthermore, because we previously determined that Rhizopus possesses the target enzyme for echinocandins and micafungin has activity against murine mucormycosis, we compared the activity of combination therapy (isavuconazole + micafungin) with placebo, either drug alone or standard therapy of liposomal amphotericin B (LAmB) in treating pulmonary murine mucormycosis caused by Rhizopus delemar. METHODS: In vitro susceptibility to isavuconazole of Mucorales was evaluated using the CLSI M38-A2 method. Immunosuppressed mice were intratracheally infected with either Mucor circinelloides or R. delemar. Treatment with isavuconazole (orally), micafungin (intraperitoneally), a combination of both or LAmB (intravenously) was compared, with survival and tissue fungal burden serving as primary and secondary endpoints, respectively. RESULTS: Isavuconazole was as effective as LAmB in prolonging survival of mice infected with M. circinelloides. Against R. delemar-induced mucormycosis, all monotherapy treatments significantly improved survival of mice versus placebo without showing superiority over one another. However, LAmB was superior in lowering fungal burden in target organs. Although combination therapy of isavuconazole + micafungin did not enhance survival of mice over monotherapy, antagonism was not detected between the two drugs. CONCLUSION: Isavuconazole is effective in treating pulmonary murine mucormycosis due to Mucor. In addition, combination therapy of isavuconazole + micafungin does not demonstrate synergy and it is not antagonistic against Rhizopus-induced mucormycosis.

Fob1 and Fob2 Proteins Are Virulence Determinants of Rhizopus oryzae via Facilitating Iron Uptake from Ferrioxamine.

Dialysis patients with chronic renal failure receiving deferoxamine for treating iron overload are uniquely predisposed for mucormycosis, which is most often caused by Rhizopus oryzae. Although the deferoxamine siderophore is not secreted by Mucorales, previous studies established that Rhizopus species utilize iron from ferrioxamine (iron-rich form of deferoxamine). Here we determined that the CBS domain proteins of Fob1 and Fob2 act as receptors on the cell surface of R. oryzae during iron uptake from ferrioxamine. Fob1 and Fob2 cell surface expression was induced in the presence of ferrioxamine and bound radiolabeled ferrioxamine. A R. oryzae strain with targeted reduced Fob1/Fob2 expression was impaired for iron uptake, germinating, and growing on medium with ferrioxamine as the sole source of iron. This strain also exhibited reduced virulence in a deferoxamine-treated, but not the diabetic ketoacidotic (DKA), mouse model of mucormycosis. The mechanism by which R. oryzae obtains iron from ferrioxamine involves the reductase/permease uptake system since the growth on ferrioxamine supplemented medium is associated with elevated reductase activity and the use of the ferrous chelator bathophenanthroline disulfonate abrogates iron uptake and growth on medium supplemented with ferrioxamine as a sole source of iron. Finally, R. oryzae mutants with reduced copies of the high affinity iron permease (FTR1) or with decreased FTR1 expression had an impaired iron uptake from ferrioxamine in vitro and reduced virulence in the deferoxamine-treated mouse model of mucormycosis. These two receptors appear to be conserved in Mucorales, and can be the subject of future novel therapy to maintain the use of deferoxamine for treating iron-overload.

Statin Concentrations Below the Minimum Inhibitory Concentration Attenuate the Virulence of Rhizopus oryzae.

BACKGROUND: Mucormycosis is a destructive invasive mold infection afflicting patients with diabetes and hematologic malignancies. Patients with diabetes are often treated with statins, which have been shown to have antifungal properties. We sought to examine the effects of statins on Rhizopus oryzae, a common cause of mucormycosis. METHODS: Clinical strains of R. oryzae were exposed to lovastatin, atorvastatin, and simvastatin and the minimum inhibitory concentrations (MICs) were determined. R. oryzae germination, DNA fragmentation, susceptibility to oxidative stress, and ability to damage endothelial cells were assessed. We further investigated the impact of exposure to lovastatin on the virulence of R. oryzae RESULTS: All statins had MICs of >64 µg/mL against R. oryzae Exposure of R. oryzae to statins decreased germling formation, induced DNA fragmentation, and attenuated damage to endothelial cells independently of the expression of GRP78 and CotH. Additionally, R. oryzae exposed to lovastatin showed macroscopic loss of melanin, yielded increased susceptibility to the oxidative agent peroxide, and had attenuated virulence in both fly and mouse models of mucormycosis. CONCLUSIONS: Exposure of R. oryzae to statins at concentrations below their MICs decreased virulence both in vitro and in vivo. Further investigation is warranted into the use of statins as adjunctive therapy in mucormycosis.

VT-1161 Protects Immunosuppressed Mice from Rhizopus arrhizus var. arrhizus Infection.

We studied the efficacy of the investigational drug VT-1161 against mucormycosis. VT-1161 had more potent in vitro activity against Rhizopus arrhizus var. arrhizus than against R. arrhizus var. delemar. VT-1161 treatment demonstrated dose-dependent plasma drug levels with prolonged survival time and lowered tissue fungal burden in immunosuppressed mice infected with R. arrhizus var. arrhizus and was as effective as high-dose liposomal amphotericin B treatment. These results support further development of VT-1161 against mucormycosis.

Isavuconazole therapy protects immunosuppressed mice from mucormycosis.

We studied the in vitro and in vivo efficacies of the investigational drug isavuconazole against mucormycosis due to Rhizopus delemar. Isavuconazole was effective, with MIC and minimal fungicidal concentration (MFC) values ranging between 0.125 and 1.00 µg/ml. A high dose of isavuconazole prolonged the survival time and lowered the tissue fungal burden of cyclophosphamide/cortisone acetate-treated mice infected with R. delemar and was as effective as a high-dose liposomal amphotericin B treatment. These results support the further development of this azole against mucormycosis.

Efficacy of liposomal amphotericin B and posaconazole in intratracheal models of murine mucormycosis.

Mucormycosis is a life-threatening fungal infection almost uniformly affecting diabetics in ketoacidosis or other forms of acidosis and/or immunocompromised patients. Inhalation of Mucorales spores provides the most common natural route of entry into the host. In this study, we developed an intratracheal instillation model of pulmonary mucormycosis that hematogenously disseminates into other organs using diabetic ketoacidotic (DKA) or cyclophosphamide-cortisone acetate-treated mice. Various degrees of lethality were achieved for the DKA or cyclophosphamide-cortisone acetate-treated mice when infected with different clinical isolates of Mucorales. In both DKA and cyclophosphamide-cortisone acetate models, liposomal amphotericin B (LAmB) or posaconazole (POS) treatments were effective in improving survival, reducing lungs and brain fungal burdens, and histologically resolving the infection compared with placebo. These models can be used to study mechanisms of infection, develop immunotherapeutic strategies, and evaluate drug efficacies against life-threatening Mucorales infections.