Invasive Fungal Infections and Approaches to Their Diagnosis

In vitro activity of manogepix and comparators against infrequently encountered yeast and mold isolates from the SENTRY Surveillance Program (2017-2022)

Manogepix is a potent new antifungal agent targeting the fungal Gwt1 enzyme. Manogepix has previously demonstrated potent in vitro activity against clinical isolates of both Candida (except Candida krusei) and Aspergillus species. This study determined the in vitro activity of manogepix and comparators against a large collection of infrequently encountered yeast and molds. Manogepix demonstrated potent in vitro activity against infrequently encountered yeasts exhibiting elevated MIC values to other drug classes, including Candida spp. (MIC50/90, 0.008/0.12 mg/L), Saprochaete clavata (Magnusiomyces clavatus) (MIC50/90, 0.03/0.06 mg/L), Magnusiomyces capitatus (MICrange, 0.016-0.06 mg/L), Rhodotorula minuta (MIC, 0.016 mg/L), and Rhodotorula mucilaginosa (MIC50/90, 0.03/0.12 mg/L). Similarly, manogepix was active against infrequently encountered mold isolates and strains exhibiting elevated MIC/MEC values to echinocandins, azoles, and amphotericin B, including Coprinopsis cinerea (MEC, 0.004 mg/L), Fusarium spp. (MEC50/90, 0.016/0.06 mg/L), Fusarium (Gibberella) fujikuroi species complex (MEC50/90, 0.016/0.03 mg/L), Lomentospora prolificans (MEC50/90, 0.03/0.06 mg/L), Microascus cirrosus (MEC, 0.008 mg/L), Paecilomyces spp. (MEC50/90, ≤0.008/0.016 mg/L), Pleurostomophora richardsiae (MEC, 0.06 mg/L), Sarocladium kiliense (MEC range, 0.016-0.12 mg/L), and Scedosporium spp. (MEC50/90, 0.03/0.06 mg/L). Manogepix demonstrated potent activity against a majority of the infrequently encountered yeast and mold isolates tested including strains with elevated MIC/MEC values to other drug classes. Additional clinical development of manogepix (fosmanogepix) in difficult-to-treat, resistant fungal infections is warranted.

Complete Genome Sequencing and Comparative Analysis of the Clinically-Derived Apiotrichum mycotoxinivorans Strain GMU1709

Over the past decade, Apiotrichum mycotoxinivorans has been recognized globally as a source of opportunistic infections. It is a yeast-like fungus, and its association as an uncommon pulmonary pathogen with cystic fibrosis patients has been previously reported. Immunocompromised patients are at the highest risk of A. mycotoxinivorans infections. Therefore, to investigate the genetic basis for the pathogenicity of A. mycotoxinivorans, we performed whole-genome sequencing and comparative genomic analysis of A. mycotoxinivorans GMU1709 that was isolated from sputum specimens of a pneumonia patient receiving cardiac repair surgery. The assembly of Oxford Nanopore reads from the GMU1709 strain and its subsequent correction using Illumina paired-end reads yielded a high-quality complete genome with a genome size of 30.5 Mb in length, which comprised six chromosomes and one mitochondrion. Subsequently, 8,066 protein-coding genes were predicted based on multiple pieces of evidence, including transcriptomes. Phylogenomic analysis indicated that A. mycotoxinivorans exhibited the closest evolutionary affinity to A. veenhuisii, and both the A. mycotoxinivorans strains and the formerly Trichosporon cutaneum ACCC 20271 strain occupied the same phylogenetic position. Further comparative analysis supported that the ACCC 20271 strain belonged to A. mycotoxinivorans. Comparisons of three A. mycotoxinivorans strains indicated that the differences between clinical and non-clinical strains in pathogenicity and drug resistance may be little or none. Based on the comparisons with strains of other species in the Trichosporonaceae family, we identified potential key genetic factors associated with A. mycotoxinivorans infection or pathogenicity. In addition, we also deduced that A. mycotoxinivorans had great potential to inactivate some antibiotics (e.g., tetracycline), which may affect the efficacy of these drugs in co-infection. In general, our analyses provide a better understanding of the classification and phylogeny of the Trichosporonaceae family, uncover the underlying genetic basis of A. mycotoxinivorans infections and associated drug resistance, and provide clues into potential targets for further research and the therapeutic intervention of infections.

Antimicrobial activity of manogepix, a first-in-class antifungal, and comparator agents tested against contemporary invasive fungal isolates from an international surveillance programme (2018-2019)

OBJECTIVES

Manogepix, the active moiety of the prodrug fosmanogepix, is a novel antifungal with activity against major fungal pathogens including Candida (except Candida krusei), Aspergillus and difficult-to-treat/rare moulds. We tested manogepix and comparators against 2669 contemporary (2018-2019) fungal isolates collected from 82 medical centres in North America (42.3%), Europe (37.9%), Asia-Pacific (12.3%) and Latin America (7.6%). Of these, 70.7% were Candida spp., 3.6% were non-Candida yeasts including 49 Cryptococcus neoformans var. grubii, 21.7% were Aspergillus spp. and 4.1% were other moulds.

METHODS

Isolates were tested for antifungal susceptibility by the CLSI reference broth microdilution method.

RESULTS

Manogepix (MIC_50/90, 0.008/0.06 mg/L) was the most active agent tested against Candida spp. isolates; corresponding anidulafungin, micafungin and fluconazole MIC₉₀ values were 16- to 64-fold higher. Similarly, manogepix (MIC_50/90, 0.5/2 mg/L) was ≥4-fold more active than anidulafungin, micafungin and fluconazole against C. neoformans var. grubii. Against Aspergillus spp., manogepix (MEC_50/90, 0.015/0.03 mg/L) had comparable activity to anidulafungin and micafungin. Low manogepix concentrations inhibited uncommon species of Candida, non-Candida yeasts, and rare moulds including Scedosporium spp. and Lomentospora (Scedosporium) prolificans.

CONCLUSION

Manogepix exhibited potent activity against contemporary fungal isolates, including echinocandin- and azole-resistant strains of Candida and Aspergillus spp., respectively. Although rare, Candida strains that were non-wild type for manogepix demonstrated resistance to fluconazole. However, the clinical relevance of this finding is unknown. The extended spectrum of manogepix is noteworthy for its activity against many less-common yet antifungal-resistant strains. Clinical studies are underway to evaluate the utility of fosmanogepix against difficult-to-treat resistant fungal infections.

Activity of a Long-Acting Echinocandin, Rezafungin, and Comparator Antifungal Agents Tested against Contemporary Invasive Fungal Isolates (SENTRY Program, 2016 to 2018)

We evaluated the activity of rezafungin and comparators, using Clinical and Laboratory Standards Institute (CLSI) broth microdilution methods, against a worldwide collection of 2,205 invasive fungal isolates recovered from 2016 to 2018. Candida (n = 1,904 isolates; 6 species), Cryptococcus neoformans (n = 73), Aspergillus fumigatus (n = 183), and Aspergillus flavus (n = 45) isolates were tested for their susceptibility (S) to rezafungin as well as the comparators caspofungin, anidulafungin, micafungin, and azoles. Interpretive criteria were applied following CLSI published clinical breakpoints (CBPs) and epidemiological cutoff values (ECVs). Isolates displaying non-wild-type (non-WT) echinocandin MIC values were sequenced for hot spot (HS) mutations. Rezafungin inhibited 99.8% of Candida albicans isolates (MIC50/90, 0.03/0.06 μg/ml), 95.7% of Candida glabrata isolates (MIC50/90, 0.06/0.12 μg/ml), 97.4% of Candida tropicalis isolates (MIC50/90, 0.03/0.06 μg/ml), 100.0% of Candida krusei isolates (MIC50/90, 0.03/0.06 μg/ml), and 100.0% of Candida dubliniensis isolates (MIC50/90, 0.06/0.12 μg/ml) at ≤0.12 μg/ml. All (329/329 [100.0%]) Candida parapsilosis isolates (MIC50/90,1/2 μg/ml) were inhibited by rezafungin at ≤4 μg/ml. Fluconazole resistance was detected among 8.6% of C. glabrata isolates, 12.5% of C. parapsilosis isolates, 3.2% of C. dubliniensis isolates, and 2.6% of C. tropicalis isolates. The activity of rezafungin against these 6 Candida spp. was similar to the activity of the other echinocandins. Detection of the HS mutation was performed by sequencing echinocandin-resistant or non-WT Candida isolates. Good activity against C. neoformans was observed for fluconazole and the other azoles, whereas the echinocandins, including rezafungin, displayed limited activity. Rezafungin displayed activity similar to that of the other echinocandins against A. fumigatus and A. flavus These in vitro data contribute to accumulating research demonstrating the potential of rezafungin for preventing and treating invasive fungal infections.

In Vitro Activity of APX001A (Manogepix) and Comparator Agents against 1,706 Fungal Isolates Collected during an International Surveillance Program in 2017

Current antifungal agents cover a majority of opportunistic fungal pathogens; however, breakthrough invasive fungal infections continue to occur and increasingly involve relatively uncommon yeasts and molds, which often exhibit decreased susceptibility. APX001A (manogepix) is a first-in-class small-molecule inhibitor of the conserved fungal Gwt1 protein. This enzyme is required for acylation of inositol during glycosylphosphatidylinositol anchor biosynthesis. APX001A is active against the major fungal pathogens, i.e., Candida (except Candida krusei), Aspergillus, and hard-to-treat molds, including Fusarium and Scedosporium In this study, we tested APX001A and comparators against 1,706 contemporary clinical fungal isolates collected in 2017 from 68 medical centers in North America (37.3%), Europe (43.4%), the Asia-Pacific region (12.7%), or Latin America (6.6%). Among the isolates tested, 78.5% were Candida spp., 3.9% were non-Candida yeasts, including 30 (1.8%) Cryptococcus neoformans var. grubii isolates, 14.7% were Aspergillus spp., and 2.9% were other molds. All isolates were tested by CLSI reference broth microdilution. APX001A (MIC₅₀, 0.008 μg/ml; MIC₉₀, 0.06 μg/ml) was the most active agent tested against Candida sp. isolates; corresponding anidulafungin, micafungin, and fluconazole MIC₉₀ values were 16- to 64-fold higher. Similarly, APX001A (MIC₅₀, 0.25 μg/ml; MIC₉₀, 0.5 μg/ml) was ≥8-fold more active than anidulafungin, micafungin, and fluconazole against C. neoformans var. grubii Against Aspergillus spp., AXP001A (50% minimal effective concentration [MEC₅₀], 0.015 μg/ml; MEC₉₀, 0.03 μg/ml) was comparable in activity to anidulafungin and micafungin. Aspergillus isolates (>98%) exhibited a wild-type phenotype for the mold-active triazoles (itraconazole, posaconazole, and voriconazole). APX001A was highly active against uncommon species of Candida, non-Candida yeasts, and rare molds, including 11 isolates of Scedosporium spp. (MEC values, 0.015 to 0.06 μg/ml). APX001A demonstrated potent in vitro activity against recent fungal isolates, including echinocandin- and fluconazole-resistant strains. The extended spectrum of APX001A was also notable for its potency against many less common but antifungal-resistant strains. Further studies are in progress to evaluate the clinical utility of the methyl phosphate prodrug, APX001, in difficult-to-treat resistant fungal infections.

Chemical and physical strategies in onychomycosis topical treatment: A review

Onychomycosis is a fungal infection of the fingernails or toenails caused by dermatophytes, nondermatophytes, moulds, and yeasts. This condition affects around 10-30% people worldwide, negatively influencing patients' quality of life, with severe outcomes in some cases. Since the nail unit acts as a barrier to exogenous substances, its physiological features hampers drug penetration, turning the onychomycosis treatment a challenge. Currently, there are several oral and topical therapies available; nevertheless, cure rates are still low and relapse rates achieves 10-53%. Also, serious side effects may be developed due to long-term treatment. In light of these facts, researchers have focused on improving topical treatments, either by modifying the vehicle or by using some physical technique to improve drug delivery trough the nail plate, hence increasing therapy effectiveness. Therefore, the aim of this paper is to explain these novel alternative approaches. First, the challenges for drug ungual penetration are presented. Then, the chemical and physical strategies developed for overcoming the barriers for drug penetration are discussed. We hope that the information gathered may be useful for the development of safer and more effective treatments for onychomycosis.

Galactofuranose antigens, a target for diagnosis of fungal infections in humans

The use of biomarkers for the detection of fungal infections is of interest to complement histopathological and culture methods. Since the production of antibodies in immunocompromised patients is scarce, detection of a specific antigen could be effective for early diagnosis. D-Galactofuranose (Galf) is the antigenic epitope in glycoconjugates of several pathogenic fungi. Since Galf is not biosynthesized by mammals, it is an attractive candidate for diagnosis of infection. A monoclonal antibody that recognizes Galf is commercialized for detection of aspergillosis. The linkage of Galf in the natural glycans and the chemical structures of the synthesized Galf-containing oligosaccharides are described in this paper. The oligosaccharides could be used for the synthesis of artificial carbohydrate-based antigens, not enough exploited for diagnosis.

D-Galactofuranose (Galf) is the unit in polysaccharides and glycoconjugates of several pathogenic fungi that is recognized by the immune system. Since Galf is not synthesized by mammals, it is an attractive candidate for diagnosis of infection. Since the production of antibodies in immunocompromised patients is scarce, detection of a specific antigen could be effective for early diagnosis. An antibody that recognizes Galf is commercialized for the detection of aspergillosis. Chemically synthesized Galf-containing oligosaccharides, reviewed in this paper, could therefore be used for the synthesis of artificial carbohydrate-based antigens and in diagnosis.