In vitro activity of olorofim against clinical isolates of the Fusarium oxysporum and Fusarium solani species complexes

Novel antifungals and treatment approaches to tackle resistance and improve outcomes of invasive fungal disease

SUMMARYFungal infections are on the rise, driven by a growing population at risk and climate change. Currently available antifungals include only five classes, and their utility and efficacy in antifungal treatment are limited by one or more of innate or acquired resistance in some fungi, poor penetration into "sequestered" sites, and agent-specific side effect which require frequent patient reassessment and monitoring. Agents with novel mechanisms, favorable pharmacokinetic (PK) profiles including good oral bioavailability, and fungicidal mechanism(s) are urgently needed. Here, we provide a comprehensive review of novel antifungal agents, with both improved known mechanisms of actions and new antifungal classes, currently in clinical development for treating invasive yeast, mold (filamentous fungi), Pneumocystis jirovecii infections, and dimorphic fungi (endemic mycoses). We further focus on inhaled antifungals and the role of immunotherapy in tackling fungal infections, and the specific PK/pharmacodynamic profiles, tissue distributions as well as drug-drug interactions of novel antifungals. Finally, we review antifungal resistance mechanisms, the role of use of antifungal pesticides in agriculture as drivers of drug resistance, and detail detection methods for antifungal resistance.

Scedosporiosis and lomentosporiosis: modern perspectives on these difficult-to-treat rare mold infections

SUMMARYAlthough Scedosporium species and Lomentospora prolificans are uncommon causes of invasive fungal diseases (IFDs), these infections are associated with high mortality and are costly to treat with a limited armamentarium of antifungal drugs. In light of recent advances, including in the area of new antifungals, the present review provides a timely and updated overview of these IFDs, with a focus on the taxonomy, clinical epidemiology, pathogenesis and host immune response, disease manifestations, diagnosis, antifungal susceptibility, and treatment. An expansion of hosts at risk for these difficult-to-treat infections has emerged over the last two decades given the increased use of, and broader population treated with, immunomodulatory and targeted molecular agents as well as wider adoption of antifungal prophylaxis. Clinical presentations differ not only between genera but also across the different Scedosporium species. L. prolificans is intrinsically resistant to most currently available antifungal agents, and the prognosis of immunocompromised patients with lomentosporiosis is poor. Development of, and improved access to, diagnostic modalities for early detection of these rare mold infections is paramount for timely targeted antifungal therapy and surgery if indicated. New antifungal agents (e.g., olorofim, fosmanogepix) with novel mechanisms of action and less cross-resistance to existing classes, availability of formulations for oral administration, and fewer drug-drug interactions are now in late-stage clinical trials, and soon, could extend options to treat scedosporiosis/lomentosporiosis. Much work remains to increase our understanding of these infections, especially in the pediatric setting. Knowledge gaps for future research are highlighted in the review.

The Role of Olorofim in the Treatment of Filamentous Fungal Infections: A Review of In Vitro and In Vivo Studies

Invasive fungal infections have recently been recognized by the WHO as a major health, epidemiological, and economic issue. Their high mortality rates and the emergence of drug resistance have driven the development of new molecules, including olorofim, an antifungal belonging to a new family of compounds, the orotomides. A review was conducted on the PubMed database and the ClinicalTrials.gov website to summarize the microbiological profile of olorofim and its role in the treatment of filamentous fungal infections. Twenty-four articles were included from the search and divided into two groups: an "in vitro" group focusing on minimum inhibitory concentration (MIC) results for various fungi and an "in vivo" group evaluating the pharmacokinetics (PK), pharmacodynamics (PD), efficacy, and tolerability of olorofim in animal models of fungal infection and in humans. Olorofim demonstrated in vitro and in vivo activity against numerous filamentous fungi, including azole-resistant Aspergillus fumigatus, various dermatophytes, and endemic and dimorphic fungi. in vitro results showed higher MICs for certain Fusarium species and dematiaceous fungi Alternaria alternata and Exophiala dermatitidis; further in vivo studies are needed. Published PK-PD data in humans are limited. The results of the ongoing phase III clinical trial are eagerly awaited to evaluate olorofim's clinical impact.

Update on therapeutic approaches for invasive fungal infections in adults

Invasive fungal infections are increasingly encountered with the expansion of iatrogenic immunosuppression, including not only solid organ and hematopoietic stem cell transplant recipients but also patients with malignancies or autoimmune diseases receiving immunomodulatory therapies, such as Bruton Tyrosine Kinase (BTK) inhibitor. Their attributable mortality remains elevated, part of which is a contribution from globally emerging resistance in both molds and yeasts. Because antifungal susceptibility test results are often unavailable or delayed, empiric and tailored antifungal approaches including choice of agent(s) and use of combination therapy are heterogeneous and often based on clinician experience with knowledge of host's net state of immunosuppression, prior antifungal exposure, antifungal side effects and interaction profile, clinical severity of disease including site(s) of infection and local resistance data. In this review, we aim to summarize previous recommendations and most recent literature on treatment of invasive mold and yeast infections in adults to guide optimal evidence-based therapeutic approaches. We review the recent data that support use of available antifungal agents, including the different triazoles that have now been studied in comparison to previously preferred agents. We discuss management of complex infections with specific emerging fungi such as Scedosporium spp., Fusarium spp., Trichosporon asahii, and Candida auris. We briefly explore newer antifungal agents or formulations that are now being investigated to overcome therapeutic pitfalls, including but not limited to olorofim, rezafungin, fosmanogepix, and encochleated Amphotericin B. We discuss the role of surgical resection or debridement, duration of treatment, follow-up modalities, and need for secondary prophylaxis, all of which remain challenging, especially in patients chronically immunocompromised or awaiting more immunosuppressive therapies.

Invasive fusariosis

Invasive fusariosis is a serious invasive fungal disease, affecting immunocompetent and, more frequently, immunocompromised patients. Localized disease is the typical clinical form in immunocompetent patients. Immunocompromised hosts at elevated risk of developing invasive fusariosis are patients with acute leukemia receiving chemotherapeutic regimens for remission induction, and those undergoing allogeneic hematopoietic cell transplant. In this setting, the infection is usually disseminated with positive blood cultures, multiple painful metastatic skin lesions, and lung involvement. Currently available antifungal agents have poor in vitro activity against Fusarium species, but a clear-cut correlation between in vitro activity and clinical effectiveness does not exist. The outcome of invasive fusariosis is largely dependent on the resolution of immunosuppression, especially neutrophil recovery in neutropenic patients.

An unusual presentation of invasive Fusarium aortitis in a patient who is immunocompromised: A case report

Fusarium (F.) species are ubiquitous filamentous fungi that may cause various opportunistic infections, especially in patients who are immunocompromised. A rare manifestation of disseminated fusariosis affects the aortic valve and results in invasive aortitis, which poses a significant challenge for clinicians in diagnosis and treatment. Here, we report a case of a patient, aged 54 years, who is immunocompromised, presenting initially with Fusarium keratitis and chorioretinitis in both eyes and a new endovascular aortic mass. Positron emission tomography/computed tomography was performed, suggesting aortitis. Transoesophageal echocardiography and electrocardiogram-guided computed tomography-angiography confirmed a large intraluminal mass in the ascending aorta. The aortic mass and a part of the ascending aorta were resected surgically, and a filamentous fungus with the microscopic features of the genus Fusarium was isolated and later identified molecularly as F. petroliphilum. The course of the treatment was complicated by perioperative cerebral embolization and mesenteric ischemia. These complications could be attributed to a preoperatively existing occlusion of the superior and inferior mesenteric artery and a subtotal stenosis of the celiac trunk. This case report describes a rare manifestation of disseminated fusariosis, frequently characterized by protracted clinical courses with poor prognosis. Fusariosis may manifest at different sites at different times or persist as a long-lasting disease with reactivation. This case highlights the importance of the interdisciplinary approach for effectively treating invasive mycoses.

Successful Use of Fosmanogepix for Treatment of Rare Highly Resistant Cutaneous Fusariosis in a Pediatric Patient With STAT3 Hyper-Immunoglobulin E Syndrome and End-Stage Kidney Disease

We describe the successful use of the novel antifungal drug fosmanogepix to treat a chronic case of multidrug-resistant cutaneous Fusarium suttonianum infection in a pediatric patient with STAT3 hyper-IgE syndrome and end-stage kidney disease on peritoneal dialysis.

High Diversity of Fusarium Species in Onychomycosis: Clinical Presentations, Molecular Identification, and Antifungal Susceptibility

Fusarium are uncommon but important pathogenic organisms; they cause non-dermatophyte mould (NDM) onychomycosis. Patients typically respond poorly to treatment owing to Fusarium's native resistance to multiple antifungal drugs. However, epidemiological data for Fusarium onychomycosis are lacking in Taiwan. We retrospectively reviewed the data of 84 patients with positive Fusarium nail sample cultures at Chang Gung Memorial Hospital, Linkou Branch between 2014 and 2020. We aimed to investigate the clinical presentations, microscopic and pathological characteristics, antifungal susceptibility, and species diversity of Fusarium in patients with Fusarium onychomycosis. We enrolled 29 patients using the six-parameter criteria for NDM onychomycosis to determine the clinical significance of Fusarium in these patients. All isolates were subjected to species identification by sequences and molecular phylogeny. A total of 47 Fusarium strains belonging to 13 species in four different Fusarium species complexes (with Fusarium keratoplasticum predominating) were isolated from 29 patients. Six types of histopathology findings were specific to Fusarium onychomycosis, which may be useful for differentiating dermatophytes from NDMs. The results of drug susceptibility testing showed high variation among species complexes, and efinaconazole, lanoconazole, and luliconazole showed excellent in vitro activity for the most part. This study's primary limitation was its single-centre retrospective design. Our study showed a high diversity of Fusarium species in diseased nails. Fusarium onychomycosis has clinical and pathological features distinct from those of dermatophyte onychomycosis. Thus, careful diagnosis and proper pathogen identification are essential in the management of NDM onychomycosis caused by Fusarium sp.

Dihydroorotate dehydrogenase inhibitor olorofim has potent in vitro activity against Microascus/Scopulariopsis, Rasamsonia, Penicillium and Talaromyces species

BACKGROUND

Treatment options against infections caused by rare but emerging moulds may be limited by their reduced susceptibility or resistance to clinically available antifungals. The investigational antifungal olorofim, which targets the biosynthesis of pyrimidines within fungi, has activity against different species of filamentous fungi, including Aspergillus and Scedosporium/Lomentospora prolificans isolates that are resistant to available antifungals.

OBJECTIVE

We evaluated the in vitro activity of olorofim against 160 isolates within the genera Microascus/Scopulariopsis, Penicillium, Talaromyces and the Rasamsonia argillacea species complex.

METHODS

One hundred sixty clinical isolates that had previously been identified to the species level by DNA sequence analysis were included. Antifungal susceptibility testing was performed by CLSI M38 broth microdilution for olorofim, amphotericin B, caspofungin, posaconazole and voriconazole.

RESULTS

Olorofim demonstrated in vitro activity against each of the genera tested. Overall, olorofim MICs ranged from ≤0.008 to 0.5 mg/L against all isolates tested, with MIC₉₀ and modal MIC values ranging from ≤0.008 to 0.25 mg/L and ≤0.008 to 0.03 mg/L, respectively. This activity was also maintained against individual isolates that had reduced susceptibility to or in vitro resistance against amphotericin B, posaconazole and/or voriconazole.

CONCLUSIONS

The investigational agent olorofim demonstrated good in vitro activity against clinical isolates of emerging mould pathogens, including those with reduced susceptibility or resistance to clinically available antifungals. Further studies are warranted to determine how well this in vitro activity translates into in vivo efficacy against infections caused by these fungi.

In vitro antifungal susceptibility profile of Iranian Fusarium isolates: Emphasising on the potent inhibitory effect of efinaconazole compared to other drugs

BACKGROUND

Fusarium species are opportunistic human pathogens that remarkably cause fungal infections ranging from superficial to fatal invasive disseminated infections. Fusarium species are notoriously resistant to the majority of antifungal agents.

OBJECTIVES

Therefore, detailed studies regarding in vitro susceptibility are required and may lead to a better prognosis of severe infections.

METHODS

We evaluated 25 antifungal drugs in vitro against 282 clinical and environmental Fusarium isolates.

RESULTS

Fusarium species demonstrated high MICs/MECs values to the most commonly used antifungal drugs in clinical practice. The geometric mean (GM) MICs for luliconazole (0.004 μg/ml) and lanoconazole (0.012 μg/ml) were the lowest, followed by efinaconazole (0.98 μg/ml) and amphotericin B (1.04 μg/ml).

CONCLUSIONS

Efinaconazole, a novel triazole, may be a promising candidate for the treatment of superficial Fusarium infections. Furthermore, the development of systemic formulations of these drugs as well as further in vitro and in vivo investigations could aid in the treatment of systemic fusariosis.

Biosynthesis of Novel Tellurium Nanorods by Gayadomonas sp. TNPM15 Isolated from Mangrove Sediments and Assessment of Their Impact on Spore Germination and Ultrastructure of Phytopathogenic Fungi

The biosynthesis of nanoparticles using green technology is emerging as a cost-efficient, eco-friendly and risk-free strategy in nanotechnology. Recently, tellurium nanoparticles (TeNPs) have attracted growing attention due to their unique properties in biomedicine, electronics, and other industrial applications. The current investigation addresses the green synthesis of TeNPs using a newly isolated mangrove-associated bacterium, Gayadomonas sp. TNPM15, and their impact on the phytopathogenic fungi Fusarium oxysporum and Alternaria alternata. The biogenic TeNPs were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Raman spectroscopy and Fourier transform infrared (FTIR). The results of TEM revealed the intracellular biosynthesis of rod-shaped nanostructures with a diameter range from 15 to 23 nm and different lengths reaching up to 243 nm. Furthermore, the successful formation of tellurium nanorods was verified by SEM-EDX, and the XRD pattern revealed their crystallinity. In addition, the FTIR spectrum provided evidence for the presence of proteinaceous capping agents. The bioinspired TeNPs exhibited obvious inhibitory effect on the spores of both investigated phytopathogens accomplished with prominent ultrastructure alternations, as evidenced by TEM observations. The biogenic TeNPs impeded spore germination of F. oxysporum and A. alternata completely at 48.1 and 27.6 µg/mL, respectively. Furthermore, an increase in DNA and protein leakage was observed upon exposure of fungal spores to the biogenic TeNPs, indicating the disruption of membrane permeability and integrity. Besides their potent influence on fungal spores, the biogenic TeNPs demonstrated remarkable inhibitory effects on the production of various plant cell wall-degrading enzymes. Moreover, the cytotoxicity investigations revealed the biocompatibility of the as-prepared biogenic TeNPs and their low toxicity against the human skin fibroblast (HSF) cell line. The biogenic TeNPs showed no significant cytotoxic effect towards HSF cells at concentrations up to 80 μg/mL, with a half-maximal inhibitory concentration (IC50) value of 125 μg/mL. The present work spotlights the antifungal potential of the biogenic TeNPs produced by marine bacterium against phytopathogenic fungi as a promising candidate to combat fungal infections.

Non-Aspergillus Hyaline Molds: A Host-Based Perspective of Emerging Pathogenic Fungi Causing Sinopulmonary Diseases

The incidence of invasive sino-pulmonary diseases due to non-Aspergillus hyaline molds is increasing due to an enlarging and evolving population of immunosuppressed hosts as well as improvements in the capabilities of molecular-based diagnostics. Herein, we review the following opportunistic pathogens known to cause sinopulmonary disease, the most common manifestation of hyalohyphomycosis: Fusarium spp., Scedosporium spp., Lomentospora prolificans, Scopulariopsis spp., Trichoderma spp., Acremonium spp., Paecilomyces variotii, Purpureocillium lilacinum, Rasamsonia argillacea species complex, Arthrographis kalrae, and Penicillium species. To facilitate an understanding of the epidemiology and clinical features of sino-pulmonary hyalohyphomycoses in the context of host immune impairment, we utilized a host-based approach encompassing the following underlying conditions: neutropenia, hematologic malignancy, hematopoietic and solid organ transplantation, chronic granulomatous disease, acquired immunodeficiency syndrome, cystic fibrosis, and healthy individuals who sustain burns, trauma, or iatrogenic exposures. We further summarize the pre-clinical and clinical data informing antifungal management for each pathogen and consider the role of adjunctive surgery and/or immunomodulatory treatments to optimize patient outcome.

Novel agents in the treatment of invasive fungal infections in solid organ transplant recipients

PURPOSE OF REVIEW

Recipients of solid organ transplants (SOTs) suffer a significant burden of invasive fungal infections (IFIs). The emergence of drug-resistant fungi and toxicities of currently used antifungal agents as well as drug-drug interactions with immunosuppressants make their treatment challenging. This review discusses selected novel antifungal agents in the development pipeline that can currently be used through clinical trials or may be commercially available in the near future.

RECENT FINDINGS

These agents in development have novel pharmacokinetics and pharmacodynamics, expanded spectra of activity and excellent safety profiles.

SUMMARY

The properties of novel antifungal agents have the potential to expand the therapeutic options for IFIs in recipients of SOTs.

Resistance profiling of Aspergillus fumigatus to olorofim indicates absence of intrinsic resistance and unveils the molecular mechanisms of acquired olorofim resistance

Olorofim (F901318) is a new antifungal currently under clinical development that shows both in vitro and in vivo activity against a number of filamentous fungi including Aspergillus fumigatus. In this study, we screened A. fumigatus isolates for intrinsic olorofim-resistant A. fumigatus and evaluated the ability of A. fumigatus to acquire an olorofim-resistant phenotype. No intrinsic resistance was found in 975 clinical A. fumigatus isolates. However, we found that isolates with increased olorofim MICs (> 8 mg/L) could be selected using a high number of conidia and olorofim exposure under laboratory conditions. Assessment of the frequency of acquired olorofim resistance development of A. fumigatus was shown to be higher than for voriconazole but lower than for itraconazole. Sequencing the PyrE gene of isogenic isolates with olorofim MICs of >8 mg/L identified various amino acid substitutions with a hotspot at locus G119. Olorofim was shown to have reduced affinity to mutated target protein dihydroorotate dehydrogenase (DHODH) and the effect of these mutations was proven by introducing the mutations directly in A. fumigatus. We then investigated whether G119 mutations were associated with a fitness cost in A. fumigatus. These experiments showed a small but significant reduction in growth rate for strains with a G119V substitution, while strains with a G119C substitution did not exhibit a reduction in growth rate. These in vitro findings were confirmed in an in vivo pathogenicity model.

The Antifungal Pipeline: Fosmanogepix, Ibrexafungerp, Olorofim, Opelconazole, and Rezafungin

The epidemiology of invasive fungal infections is changing, with new populations at risk and the emergence of resistance caused by the selective pressure from increased usage of antifungal agents in prophylaxis, empiric therapy, and agriculture. Limited antifungal therapeutic options are further challenged by drug-drug interactions, toxicity, and constraints in administration routes. Despite the need for more antifungal drug options, no new classes of antifungal drugs have become available over the last 2 decades, and only one single new agent from a known antifungal class has been approved in the last decade. Nevertheless, there is hope on the horizon, with a number of new antifungal classes in late-stage clinical development. In this review, we describe the mechanisms of drug resistance employed by fungi and extensively discuss the most promising drugs in development, including fosmanogepix (a novel Gwt1 enzyme inhibitor), ibrexafungerp (a first-in-class triterpenoid), olorofim (a novel dihyroorotate dehydrogenase enzyme inhibitor), opelconazole (a novel triazole optimized for inhalation), and rezafungin (an echinocandin designed to be dosed once weekly). We focus on the mechanism of action and pharmacokinetics, as well as the spectrum of activity and stages of clinical development. We also highlight the potential future role of these drugs and unmet needs.

Invasive Fusariosis in Patients with Hematologic Diseases

Fusarium species are filamentous fungi widely encountered in nature, and may cause invasive disease in patients with hematologic conditions. Patients at higher risk are those with acute leukemia receiving induction remission chemotherapy or allogeneic hematopoietic cell transplant recipients. In these hosts, invasive fusariosis presents typically with disseminated disease, fever, metastatic skin lesions, pneumonia, and positive blood cultures. The prognosis is poor and the outcome is largely dependent on the immune status of the host, with virtually a 100% death rate in persistently neutropenic patients, despite monotherapy or combination antifungal therapy. In this paper, we will review the epidemiology, clinical manifestations, diagnosis, and management of invasive fusariosis affecting patients with hematologic diseases.

Molecular and MALDI-ToF MS differentiation and antifungal susceptibility of prevalent clinical Fusarium species in China

BACKGROUND

Fusarium species are emerging causative agents of superficial and disseminated human infections. Early diagnosis and treatment contribute to better prognosis of severe infection.

OBJECTIVES

To detect the effectiveness of matrix-assisted laser desorption ionisation time of flight mass spectrometry (MALDI-ToF MS) for Fusarium identification, and evaluate the susceptibility profiles to clinical available antifungals.

METHODS

All 203 clinical Fusarium isolates and 25 environmental isolates were identified by using translation elongation factor 1-alpha (TEF1) and RNA polymerase subunit II (RPB2) sequencing and MALDI-ToF MS. Antifungal susceptibility testing was determined by a microdilution method following the CLSI approved standard M38-A3 document.

RESULTS

Correct identification rates at the species and genus levels were 89.04% (203/228) and 95.18% (217/228), respectively, using Bruker Filamentous Fungi Library 1.0 combined with the novel database. Seven species complexes with 19 Fusarium species were identified, including F. solani (59.21%, n = 135), F. verticillioides (17.54%, n = 40), F. proliferatum (6.58%, n = 15) and F. oxysporum (4.39%, n = 10). Four uncommon species complexes (F. incarnatum-equiseti SC, F. dimerum SC, F. redolens SC and F. sporotrichioides SC) were also identified. A high degree of antifungal resistance was observed. Fusarium isolates exhibited lower MICs to luliconazole and terbinafine compared with amphotericin B and voriconazole, which in turn were significantly more active than amorolfine, fluconazole and itraconazole.

CONCLUSIONS

MALDI-ToF MS showed good performance in Fusarium species with an adapted Bruker library and expanded database. Fusarium isolates exhibited lower MICs to luliconazole and terbinafine compared to amphotericin B and voriconazole.