Preclinical Evaluation of the Stability, Safety, and Efficacy of CD101, a Novel Echinocandin

Azole Combinations and Multi-Targeting Drugs That Synergistically Inhibit Candidozyma auris

Limited antifungal treatment options and drug resistance require innovative approaches to effectively combat fungal infections. Combination therapy is a promising strategy that addresses these pressing issues by concurrently targeting multiple cellular sites. The drug targets usually selected for combination therapy are from different cellular pathways with the goals of increasing treatment options and reducing development of resistance. However, some circumstances can prevent the implementation of combination therapy in clinical practice. These could include the increased risk of adverse effects, drug interactions, and even the promotion of drug resistance. Furthermore, robust clinical evidence supporting the superiority of combination therapy over monotherapy is limited and underscores the need for further research. Despite these challenges, synergies detected with different antifungal classes, such as the azoles and echinocandins, suggest that treatment strategies can be optimized by better understanding the underlying mechanisms. This review provides an overview of multi-targeting combination strategies with a primary focus on Candidozyma auris infections.

Treatment Outcomes Among Patients With a Positive Candida Culture Close to Randomization Receiving Rezafungin or Caspofungin in the ReSTORE Study

BACKGROUND

Rezafungin, a novel, once-weekly echinocandin for the treatment of candidemia and/or invasive candidiasis (IC) was noninferior to caspofungin for day 30 all-cause mortality (ACM) and day 14 global cure in the phase 3 ReSTORE trial (NCT03667690). We conducted preplanned subgroup analyses for patients with a positive culture close to randomization in ReSTORE.

METHODS

ReSTORE was a multicenter, double-blind, double-dummy, randomized trial in patients aged ≥18 years with candidemia and/or IC treated with once-weekly intravenous rezafungin (400 mg/200 mg) or once-daily intravenous caspofungin (70 mg/50 mg). This analysis comprised patients with a positive blood culture drawn between 12 hours before and 72 hours after randomization or a positive culture from another normally sterile site sampled between 48 hours before and 72 hours after randomization. Efficacy endpoints included day 30 ACM, day 14 global cure rate, and day 5 and 14 mycological response. Adverse events were evaluated.

RESULTS

This analysis included 38 patients randomized to rezafungin and 46 to caspofungin. In the rezafungin and caspofungin groups, respectively, day 30 ACM was 26.3% and 21.7% (between-group difference [95% confidence interval], 4.6% [-13.7%, 23.5%]), day 14 global response was 55.3% and 50.0% (between-group difference, 5.3% [-16.1%, 26.0%]), and day 5 mycological eradication was 71.1% and 50.0% (between-group difference, 21.1% [-0.2%, 40.2%]). Safety was comparable between treatments.

CONCLUSIONS

These findings support the efficacy and safety of rezafungin compared with caspofungin for the treatment of candidemia and/or IC in patients with a positive culture close to randomization, with potential early treatment benefits for rezafungin.

Coagulation dysfunction events associated with echinocandins: a real-world study from FDA adverse event reporting system (FAERS) database

BACKGROUND

Echinocandins belong to the fourth generation of antifungals, and there are no systematic studies on their risk in coagulation dysfunction; this study will predict the risk of coagulation dysfunction of echinocandins using the US Food and Drug Administration Adverse Event Reporting System (FAERS) database.

METHOD

Data from January 2004 to March 2024 were obtained from FAERS. We examined the clinical characteristics of the coagulation dysfunction events and conducted disproportionality analysis by using reporting odds ratios (ROR) to compare echinocandins with the full database.

RESULTS

There were 313 reports of coagulation dysfunction related to echinocandins as the primary suspect (PS) drug. The median time to incident for coagulation dysfunction was 3 (interquartile range [IQR] 1-9) days. Compared to triazoles and polyenes, echinocandins have a stronger signal (ROR 3.18, 95%CI 2.81-3.51, p < 0.01) of coagulation dysfunction. Compared to caspofungin and micafungin, anidulafungin has a stronger signal (ROR 6.84, 95%CI 4.83-9.70, p < 0.01). The strongest signal corresponding to disseminated intravascular coagulation (DIC), platelet count decreased, thrombocytopenia, gastrointestinal haemorrhage, cerebral haemorrhage, pulmonary haemorrhage and thrombotic thrombocytopenic purpura (TTP) is micafungin (ROR 27.19, 95%CI 18.49-39.98), micafungin (ROR 3.50, 95%CI 2.36-5.19), anidulafungin (ROR 9.75, 95%CI 5.22-18.19), micafungin (ROR 3.17, 95%CI 2.02-4.97), micafungin (ROR 4.95, 95%CI 2.81-8.72), caspofungin (ROR 20.76, 95%CI 11.77-36.59), micafungin (ROR 20.43, 95%CI 8.49-49.14), respectively.

CONCLUSIONS

For coagulation dysfunction, we found stronger signals for echinocandins than triazoles and polyenes, and stronger signals for anidulafungin than micafungin and caspofungin. Coagulation parameters should be closely monitored while using the respective drugs.

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.

Management of invasive candidiasis: A focus on rezafungin, ibrexafungerp, and fosmanogepix

Management of invasive fungal infections is challenging with growing antifungal resistance. Broad antifungal use has resulted in greater intrinsic and acquired resistance among Candida spp. It is important for clinicians to recognize the relationship between host susceptibility, site of infection, Candida resistance profiles, specific drug pharmacokinetics and pharmacodynamics, and the role of novel antifungal agents. This narrative review covers the role of rezafungin, ibrexafungerp, and fosmanogepix in the management of invasive candidiasis (IC). The PubMed Database, Embase, and ClinicalTrials.gov were searched between January 2006 and January 2024 using the following terms: rezafungin, CD101, ibrexafungerp, SCY-078, fosmanogepix, APX001, candidemia, and invasive candidiasis. Review articles, prospective clinical trials, and observational studies published in the English language were reviewed. Studies evaluating pharmacology, pharmacokinetics, efficacy, and safety in animals and humans were also reviewed. Promising data continues to emerge in support of novel drug therapies for IC and candidemia. Rezafungin possesses a unique pharmacodynamic profile that might be advantageous compared to other echinocandins, with a practical, once-weekly dosing interval. Ibrexafungerp, currently approved for vulvovaginal candidiasis, has been studied off-label for use in IC and candidemia, and initial data is encouraging. Lastly, fosmanogepix, a mechanistically novel, investigational antifungal agent, may be a potential future option in the management of IC and candidemia. Future research is needed to evaluate the potential use of these agents among diverse patient populations.

Phase I study of the pharmacokinetics and safety of rezafungin in subjects with moderate/severe hepatic impairment and matched control subjects

INTRODUCTION

Rezafungin is a second-generation, once-weekly echinocandin antifungal approved for the treatment of invasive candidiasis, including candidemia. In phase II/III studies of rezafungin versus caspofungin, patients with severe hepatic impairment were excluded due to lack of caspofungin data in this population. This open-label, single-dose, phase I study evaluated the pharmacokinetics (primary objective) and safety of rezafungin in subjects with moderate or severe hepatic impairment versus matched, healthy subjects with normal hepatic function.

METHODS

Eight subjects each with moderate (Child-Pugh B) or severe (Child-Pugh C) hepatic impairment were matched 1:1 with healthy subjects for age, sex, and body mass index. Each subject received a single 400-mg, intravenous, 1-h infusion of rezafungin. Plasma pharmacokinetic sampling was performed at various time points through 336 h postdose. Pharmacokinetic parameters were derived by non-compartmental analysis. Safety was assessed throughout.

RESULTS

All 32 subjects received study treatment and were included in all analyses. Despite overlapping distributions of total plasma concentrations, based on geometric least-squares (LS) mean ratios, the area under the plasma concentration-time curve from time zero (prior to the start of infusion) to infinity (AUC0-∞) was 32% lower in subjects with moderate (LS mean ratio, 67.55; 90% confidence interval [CI]: 53.91, 84.65) and severe (LS mean ratio, 67.84; 90% CI: 57.49, 80.05) hepatic impairment versus matched healthy subjects. The maximum plasma concentration (Cmax) was 12% lower in moderate hepatic impairment and 28% lower in severe hepatic impairment groups. Linear regression showed no significant trend in the degree of hepatic impairment (based on Child-Pugh score) on AUC0-∞ or Cmax (p > 0.05). Treatment-emergent adverse events were reported in seven subjects (21.9%; three subjects in each of the hepatic impairment groups, and one healthy subject), none of which were severe, serious, or resulted in withdrawal.

CONCLUSIONS

Rezafungin is well tolerated and can be administered to patients with moderate or severe hepatic impairment without the need for dose adjustment. The modest reduction in exposures in subjects with hepatic impairment is not clinically meaningful and is unlikely to impact efficacy.

In Vitro Activitiy of Rezafungin in Comparison with Anidulafungin and Caspofungin against Invasive Fungal Isolates (2017 to 2022) in China

The efficacy of different echinocandins is assessed by evaluating the in vitro activity of a novel antifungal, rezafungin, against invasive fungal isolates in comparison with anidulafungin and caspofungin. Using the broth microdilution (BMD) method, the susceptibility of 1000 clinical Candida isolates (including 400 C. albicans, 200 C. glabrata, 200 C. parapsilosis, 150 C. tropicalis and 50 C. krusei) and 150 Aspergillus isolates (100 A. fumigatus and 50 A. flavus) from the Eastern China Invasive Fungi Infection Group (ECIFIG) was tested for the antifungals including anidulafungin, rezafungin, caspofungin and fluconazole. The echinocandins showed strong activity against C. albicans that was maintained against fluconazole-resistant isolates. The GM MIC (geometric mean minimum inhibitory concentration) value of rezafungin was found to be comparable to that of anidulafungin or caspofungin against the five tested common Candida species. C. tropicalis exhibited higher resistance rates (about 8.67-40.67% in different antifungals) than the other four Candida species. Through the sequencing of FKS genes, we searched for mutations in echinocandin-resistant C. tropicalis isolates and found that all displayed alterations in FKS1 S654P. The determined MEC (minimal effective concentration) values against A. fumigatus and A. flavus for rezafungin (0.116 μg/mL, 0.110 μg/mL) are comparable to those of caspofungin (0.122 μg/mL, 0.142 μg/mL) but higher than for anidulafungin (0.064 μg/mL, 0.059 μg/mL). Thus, the in vitro activity of rezafungin appears comparable to anidulafungin and caspofungin against most common Candida and Aspergillus species. Rezafungin showed higher susceptibility rates against C. glabrata. Rezafungin indicates its potent activity for potential clinical application.

Efficacy and safety of rezafungin and caspofungin in candidaemia and invasive candidiasis: pooled data from two prospective randomised controlled trials

BACKGROUND

Rezafungin, a new US Food and Drug Administration-approved, long-acting echinocandin to treat candidaemia and invasive candidiasis, was efficacious with a similar safety profile to caspofungin in clinical trials. We conducted pooled analyses of the phase 2 STRIVE and phase 3 ReSTORE rezafungin trials.

METHODS

ReSTORE was a multicentre, double-blind, double-dummy, randomised phase 3 trial conducted at 66 tertiary care centres in 15 countries. STRIVE was a multicentre, double-blind, double-dummy, randomised phase 2 trial conducted at 44 centres in 10 countries. Adults (≥18 years) with candidaemia or invasive candidiasis were treated with once-a-week intravenous rezafungin (400 mg and 200 mg) or once-a-day intravenous caspofungin (70 mg and 50 mg). Efficacy was evaluated in a pooled modified intent-to-treat (mITT) population. Primary efficacy endpoint was day 30 all-cause mortality (tested for non-inferiority with a pre-specified margin of 20%). Secondary efficacy endpoint was mycological response. Safety was also evaluated. The STRIVE and ReSTORE trials are registered with ClinicalTrials.gov, NCT02734862 and NCT03667690, and both studies are complete.

FINDINGS

ReSTORE was conducted from Oct 12, 2018, to Oct 11, 2021, and STRIVE from July 26, 2016, to April 18, 2019. The mITT population, pooling the data from the two trials, comprised 139 patients for rezafungin and 155 patients for caspofungin. Day 30 all-cause mortality rates were comparable between groups (19% [26 of 139] for the rezafungin group and 19% [30 of 155] for the caspofungin group) and the upper bound of the 95% CI for the weighted treatment difference was below 10% (-1·5% [95% CI -10·7 to 7·7]). Mycological eradication occurred by day 5 in 102 (73%) of 139 rezafungin patients and 100 (65%) of 155 caspofungin patients (weighted treatment difference 10·0% [95% CI -0·3 to 20·4]). Safety profiles were similar across groups.

INTERPRETATION

Rezafungin was non-inferior to caspofungin for all-cause mortality, with a potential early treatment benefit, possibly reflecting rezafungin's front-loaded dosing regimen. These findings are of clinical importance in fighting active and aggressive infections and reducing the morbidity and mortality caused by candidaemia and invasive candidiasis.

FUNDING

Melinta Therapeutics and Cidara Therapeutics.

An evaluation of Rezafungin: the latest treatment option for adults with candidemia and invasive candidiasis

INTRODUCTION

Invasive fungal infections, especially candidemia and invasive candidiasis, continue to cause substantial morbidity and mortality. In addition, the emergence of drug-resistant Candida species, notably C. glabrata and C. auris, along with limitations in available treatments, highlights the urgent need for novel, effective antifungal agents.

AREAS COVERED

This review discusses the results of in vitro studies evaluating the spectrum and highlights the pharmacokinetic/pharmacodynamic properties. It also includes discussions on two key clinical studies that assess safety, tolerability, and efficacy.

EXPERT OPINION

Rezafungin has demonstrated comparable efficacy to other echinocandins in two clinical studies and exhibits in vitro activity against a broad range of Candida species and Aspergillus spp. It has a favorable safety profile with minimal side effects, and no drug interactions or effects on QT intervals. In contrast to other echinocandins, it demonstrates dose-dependent killing, a prolonged half-life, and low clearance make it suitable for once-weekly dosing, which is supported by clinical trials confirming its efficacy. Rezafungin offers a promising option for the outpatient management of difficult to treat fungal infections. It has become a valuable addition to the antifungal arsenal, with the potential to reduce hospital length of stay and hospitalization costs and combat drug-resistant Candida species.

Specifically Targeting Metacaspases of Candida: A New Therapeutic Opportunity

The World Health Organization (WHO) recently published a list of fungal priority pathogens, including Candida albicans and C. auris. The increased level of resistance of Candida is raising concern, considering the availability of only four classes of medicine. The WHO is seeking novel agent classes with different targets and mechanisms of action. Targeting Candida metacaspases to control intrinsic cell death could provide new therapeutic opportunities for invasive candidiasis. In this review, we provide the available evidence for Candida cell death, describe Candida metacaspases, and discuss the potential of Candida metacaspases to offer a new specific target. Targeting Candida cell death has good scientific rationale given that the fungicidal activity of many marketed antifungals is mediated, among others, by cell death triggering. But none of the available antifungals are specifically activating Candida metacaspases, making this target a new therapeutic opportunity for non-susceptible isolates. It is expected that antifungals based on the activation of fungi metacaspases will have a broad spectrum of action, as metacaspases have been described in many fungi, including filamentous fungi. Considering this original mechanism of action, it could be of great interest to combine these new antifungal candidates with existing antifungals. This approach would help to avoid the development of antifungal resistance, which is especially increasing in Candida.

Insight into advances for the biosynthetic progress of fermented echinocandins of antifungals

Invasive fungal infections have increased remarkably, which have become unprecedented concern to human health. However, the effectiveness of current antifungal drugs is limited due to drug resistance and toxic side-effects. It is urgently required to establish the effective biosynthetic strategy for developing novel and safe antifungal molecules economically. Echinocandins become a promising option as a mainstay family of antifungals, due to specifically targeting the fungal specific cell wall. To date, three kinds of echinocandins for caspofungin, anidulafungin, and micafungin, which derived from pneumocandin B0 , echinocandin B, and FR901379, are commercially available in clinic and have shown potential in managing invasive fungal infections in a cost-effective manner. However, current echinocandins-derived precursors all are produced by environmental fungal isolates with long fermentation cycle and low yields, which challenge the production efficacy of these precursors in industry. Therefore, understanding their biosynthetic machinery is of great importance for improving antifungal titres and creating new echinocandins-derived products. With the development of genome-wide sequencing and establishment of gene-editing technology, there are a growing number of reports on echinocandins-derived products and their biosynthetic gene clusters. This review briefly summarizes the discovery and development history of echinocandins, compares their structural characteristics and biosynthetic processes, and sums up existed strategies for improving their production. Moreover, the genomic analysis of related biosynthetic gene clusters of echinocandins is discussed, highlighting the similarities and differences among the clusters. Last, the biosynthetic processes of echinocandins are compared, focusing on the activation and attachment of side-chains and the formation of the hexapeptide core. This review aims to provide insights into the development and production of new echinocandin drugs by modifying the structure of echinocandin-derived precursors and/or optimizing the fermentation processes; and achieve a new microbial chassis for efficient production of echinocandins in heterologous hosts.

Lipopeptides development in cosmetics and pharmaceutical applications: A comprehensive review

Lipopeptides are surface active, natural products of bacteria, fungi and green-blue algae origin, having diverse structures and functionalities. In analogy, a number of chemical synthesis techniques generated new designer lipopeptides with desirable features and functions. Lipopetides are self-assembly guided, supramolecular compounds which have the capacity of high-density presentation of the functional epitopes at the surface of the nanostructures. This feature contributes to their successful application in several industry sectors, including food, feed, personal care, and pharmaceutics. In this comprehensive review, the novel class of ribosomally synthesized lipopeptides is introduced alongside the more commonly occuring non-ribosomal lipopeptides. We highlight key representatives of the most researched as well as recently described lipopeptide families, with emphasis on structural features, self-assembly and associated functions. The common biological, chemical and hybrid production routes of lipopeptides, including prominent analogues and derivatives are also discussed. Furthermore, genetic engineering strategies aimed at increasing lipopeptide yields, diversity and biological activity are summarized and exemplified. With respect to application, this work mainly details the potential of lipopeptides in personal care and cosmetics industry as cleansing agents, moisturizer, anti-aging/anti-wrinkling, skin whitening and preservative agents as well as the pharmaceutical industry as anitimicrobial agents, vaccines, immunotherapy, and cancer drugs. Given that this review addresses human applications, we conclude on the topic of safety of lipopeptide formulations and their sustainable production.

Emerging Diagnostics and Therapeutics for Invasive Fungal Infections

Recently, there have been significant advances in the diagnosis and management of invasive fungal infections. Compared with traditional fungal diagnostics, molecular assays promise improved sensitivity and specificity, the ability to test a range of samples (including noninvasive samples, ie, blood), the detection of genetic mutations associated with antifungal resistance, and the potential for a faster turnaround time. Antifungals in late-stage clinical development include agents with novel mechanisms of action (olorofim and fosmanogepix) and new members of existing classes with distinct advantages over existing antifungals in toxicity, drug-drug interactions, and dosing convenience (oteseconazole, opelconazole, rezafungin, ibrexafungerp, encochleated amphotericin B).

Candida parapsilosis sensu stricto Antifungal Resistance Mechanisms and Associated Epidemiology

Fungal diseases cause millions of deaths per year worldwide. Antifungal resistance has become a matter of great concern in public health. In recent years rates of non-albicans species have risen dramatically. Candida parapsilosis is now reported to be the second most frequent species causing candidemia in several countries in Europe, Latin America, South Africa and Asia. Rates of acquired azole resistance are reaching a worrisome threshold from multiple reports as in vitro susceptibility testing is now starting also to explore tolerance and heteroresistance to antifungal compounds. With this review, the authors seek to evaluate known antifungal resistance mechanisms and their worldwide distribution in Candida species infections with a specific focus on C. parapsilosis.

Invasive Candida infection: epidemiology, clinical and therapeutic aspects of an evolving disease and the role of rezafungin

INTRODUCTION

Invasive Candida Infections (ICIs) have undergone a series of significant epidemiological, pathophysiological, and clinical changes during the last decades, with a shift toward non-albicans species, an increase in the rate of exogenous infections and clinical manifestations ranging from candidemia to an array of highly invasive and life-threatening clinical syndromes. The long-acting echinocandin rezafungin exhibits potent in-vitro activity against most wild-type and azole-resistant Candida spp. including C.auris.

AREAS COVERED

The following topics regarding candidemia only and ICIs were reviewed and addressed: i) pathogenesis; ii) epidemiology and temporal evolution of Candida species; iii) clinical approach; iv) potential role of the novel long-acting rezafungin in the treatment of ICIs.

EXPERT OPINION

Authors' expert opinion focused on considering the potential role of rezafungin in the evolving context of ICIs. Rezafungin, which combines a potent in-vitro activity against Candida species, including azole-resistant strains and C.auris, with a low likelihood of drug-drug interactions and a good safety profile, may revolutionize the treatment of candidemia/ICI. Indeed, it may shorten the length of hospital stays when clinical conditions allow and extend outpatient access to treatment of invasive candidiasis, especially when prolonged treatment duration is expected.

A review of prophylactic regimens to prevent invasive fungal infections in hematology patients undergoing chemotherapy or stem cell transplantation

INTRODUCTION

The recent introduction of targeted therapies, including monoclonal antibodies, tyrosine-kinase inhibitors, and immunotherapies has improved the cure rate of hematologic patients. The implication of personalized treatment on primary antifungal prophylaxis will be discussed.

AREAS COVERED

We reviewed the literature for clinical trials reporting the rate of invasive fungal infections during targeted and cellular therapies and stem cell transplant, and the most recent international guidelines for primary antifungal prophylaxis.

EXPERT OPINION

As the use of personalized therapies is growing, the risk of invasive fungal infection has emerged in various clinical settings. Therefore, it is possible that the use of mold-active antifungal prophylaxis would spread in the next years and the risk of breakthrough infections would increase. The introduction of new antifungal agents in the clinical armamentarium is expected to reduce clinical unmet needs concerning the management of primary antifungal prophylaxis and improve outcome of patients.

Absence of Clinically Meaningful Drug-Drug Interactions with Rezafungin: Outcome of Investigations

Rezafungin is a novel once-weekly echinocandin for intravenous injection currently in development for the treatment of Candida infections and the prevention of Candida, Aspergillus, and Pneumocystis infections in allogeneic blood and marrow transplant recipients. While in vitro data indicated that rezafungin exposure was unlikely to be affected by commonly prescribed medicines, interactions resulting in the altered systemic exposure of some drugs coadministered with rezafungin could not be excluded. Two phase 1 open label crossover studies, conducted in healthy subjects, examined drug interactions between rezafungin and multiple drug probe cytochrome P450 (CYP) substrates and/or transporter proteins, immunosuppressants, and cancer therapies. Statistical analysis compared the outcomes for drugs coadministered with rezafungin to those for the drugs administered alone. The geometric mean ratio was reported, and a default 90% confidence interval (CI) no-effect equivalence range of 80 to 125% was used for the maximal plasma concentration (Cmax), the area under the curve from time zero to the final sampling time point (AUC0-t), and the AUC from time zero to infinity (AUC0-∞). Most probes and concomitant drugs were within the equivalence range. For tacrolimus, ibrutinib, mycophenolic acid, and venetoclax, the AUC or Cmax was reduced (10 to 19%), with lower bounds of the 90% CI values falling outside the no-effect range. The rosuvastatin AUC and Cmax and the repaglinide AUC0-∞ were increased (12 to 16%), with the 90% CI being marginally above the upper bound. Overall, the in vitro and in vivo data demonstrated a low drug interaction potential with rezafungin via CYP substrate/transporter pathways and commonly prescribed comedications, suggesting that coadministration was unlikely to result in clinically significant effects. Treatment-emergent adverse events were typically mild, and rezafungin was generally well tolerated. IMPORTANCE Antifungal agents used to treat life-threatening infections are often associated with severe drug-drug interactions (DDIs) that may limit their usefulness. Rezafungin, a newly approved once-weekly echinocandin, has been shown to be free of DDIs based on extensive nonclinical and clinical testing described in this study.

Rezafungin: First Approval

Rezafungin (Rezzayo™), an intravenous once-weekly echinocandin that inhibits 1,3-β-D-glucan synthase, is being developed by Cidara Therapeutics. In March 2023, rezafungin received approval in the USA for the treatment of candidaemia and invasive candidiasis in patients aged ≥ 18 years who have limited or no alternative treatment options. Rezafungin is also being developed for the prevention of invasive fungal diseases in blood and marrow transplant recipients. This article summarizes the milestones in the development of rezafungin leading to the first approval for the treatment of candidaemia and invasive candidiasis.

Multicentre validation of a modified EUCAST MIC testing method and development of associated epidemiologic cut-off (ECOFF) values for rezafungin

OBJECTIVES

Rezafungin EUCAST MIC testing has been associated with notable inter-laboratory variation, which prevented ECOFF setting for C. albicans. We assessed in vitro susceptibility and reproducibility for a modified EUCAST methodology and established associated wild-type upper limits (WT-ULs).

METHODS

MICs against 150 clinical Candida isolates (six species), molecularly characterized fks mutants (n = 13), and QC strains (n = 6) were determined at six laboratories according to E.Def 7.3 but using Tween 20 supplemented medium. WT-ULs were determined using the derivatization method, the ECOFFinder programme and visual inspection. Consensus WT-ULs were determined.

RESULTS

The laboratory- and species-specific MIC distributions were Gaussian with >99.5% MICs within four 2-fold dilutions except for C. parapsilosis (92.8%). The following consensus WT-UL were determined: C. albicans 0.008 mg/L; C. dubliniensis and C. glabrata 0.016 mg/L; C. krusei and C. tropicalis 0.03 mg/L; and C. parapsilosis 4 mg/L. Adopting these WT-UL, six clinical isolates were non-wild-type, five of which harboured Fks alterations. For 11/13 mutants, all 670 MICs were categorized as non-wild-type whereas MICs for C. glabrata Fks2 D666Y and C. tropicalis Fks1 R656R/G overlapped with the corresponding wild-type distributions. Repeat testing of six reference strains yielded 98.3%-100% of MICs within three 2-fold dilutions except for C. albicans CNM-CL-F8555 (96%) and C. parapsilosis ATCC 22019 (93.3%).

CONCLUSIONS

The modified EUCAST method significantly improved inter-laboratory variation, identified wild-type populations and allowed perfect separation of wild-type and fks mutants except for two isolates harbouring weak mutations. These consensus WT-UL have been accepted as ECOFFs and will be used for rezafungin breakpoint setting.

Therapeutic Approaches for Combating Aspergillus Associated Infection

Now-a-days fungal infection emerges as a significant problem to healthcare management systems due to high frequency of associated morbidity, mortality toxicity, drug-drug interactions, and resistance of the antifungal agents. Aspergillus is the most common mold that cause infection in immunocompromised hosts. It's a hyaline mold that is cosmopolitan and ubiquitous in nature. Aspergillus infects around 10 million population each year with a mortality rate of 30-90%. Clinically available antifungal formulations are restricted to four classes (i.e., polyene, triazole, echinocandin, and allylamine), and each of them have their own limitations associated with the activity spectrum, the emergence of resistance, and toxicity. Consequently, novel antifungal agents with modified and altered chemical structures are required to combat these invasive fungal infections. To overcome these limitations, there is an urgent need for new antifungal agents that can act as potent drugs in near future. Currently, some compounds have shown effective antifungal activity. In this review article, we have discussed all potential antifungal therapies that contain old antifungal drugs, combination therapies, and recent novel antifungal formulations, with a focus on the Aspergillus associated infections.

Pharmacodynamics, Mechanisms of Action and Resistance, and Spectrum of Activity of New Antifungal Agents

Several new antifungals are currently in late-stage development, including those with novel pharmacodynamics/mechanisms of action that represent new antifungal classes (manogepix, olorofim, ATI-2307, GR-2397). Others include new agents within established classes or with mechanisms of action similar to clinically available antifungals (ibrexafungerp, rezafungin, oteseconazole, opelconazole, MAT2203) that have been modified in order to improve certain characteristics, including enhanced pharmacokinetics and greater specificity for fungal targets. Many of the antifungals under development also have activity against Candida and Aspergillus strains that have reduced susceptibility or acquired resistance to azoles and echinocandins, whereas others demonstrate activity against species that are intrinsically resistant to most clinically available antifungals. The tolerability and drug–drug interaction profiles of these new agents also appear to be promising, although the number of human subjects that have been exposed to many of these agents remains relatively small. Overall, these agents have the potential for expanding our antifungal armamentarium and improving clinical outcomes in patients with invasive mycoses.

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.

Invasive candidiasis: Investigational drugs in the clinical development pipeline and mechanisms of action

INTRODUCTION

The epidemiology of invasive Candida infections is evolving. Infections caused by non-albicans Candida spp. are increasing; however, the antifungal pipeline is more promising than ever and is enriched with repurposed drugs and agents that have new mechanisms of action. Despite progress, unmet needs in the treatment of invasive candidiasis remain and there are still too few antifungals that can be administered orally or that have CNS penetration.

AREAS COVERED

The authors shed light on those antifungal agents active against Candida that are in late-stage clinical development. Mechanisms of action and key pharmacokinetic and pharmacodynamic properties are discussed. Insights are offered on the potential future roles of the investigational agents MAT-2203, oteseconazole, ATI-2307, VL-2397, NP-339, and the repurposed drug miltefosine.

EXPERT OPINION

Ibrexafungerp and fosmanogepix have novel mechanisms of action and will provide effective options for the treatment of Candida infections (including those caused by multiresistant Candida spp). Rezafungin, an echinocandin with an extended half-life allowing for once weekly administration, will be particularly valuable for outpatient treatment and prophylaxis. Despite this, there is an urgent need to garner clinical data on investigational drugs, especially in the current rise of azole-resistant and multi-drug resistant Candida spp.

A Phase 1 Randomized, Double-Blind, Single Subcutaneous Dose Escalation Study to Determine the Safety, Tolerability, and Pharmacokinetics of Rezafungin in Healthy Adult Subjects

Rezafungin is a novel echinocandin being developed for the treatment and prevention of invasive fungal infections. The objectives of this randomized, double‐blind study in healthy adults were to determine the safety, tolerability, and pharmacokinetics of rezafungin after subcutaneous (s.c.) administration. The study design consisted of six sequential cohorts of eight subjects, except for the first cohort with four subjects. The subjects were randomized in a 3:1 ratio of rezafungin to placebo and were to receive a single dose of 1, 10, 30, 60, 100, or 200 mg. The most common adverse events (AEs) were increased alanine aminotransferase and sinus bradycardia (unsolicited) and erythema at the injection site (solicited). Unsolicited AEs were generally mild to moderate and not rezafungin‐related. Although the study was terminated after the 10 mg dose cohort due to concerns of potential increased severity of injection site reactions, no predetermined dose escalation halting criteria were met. Following the 10 mg single s.c. dose of rezafungin (n = 6), the geometric mean (GM) maximum concentration (C_max) was 105.0 ng/ml and the median time to C_max was 144 h. The GM area under the concentration‐time curve was 32,770 ng*h/ml. The median estimated terminal half‐life was 193 h. The GM apparent oral clearance was 0.255 L/h and the GM apparent volume of distribution was 68.5 L. This study demonstrates that a single s.c. dose of rezafungin in healthy adult subjects: (1) did not result in serious AEs, death, or withdrawal from the study due to an AE; and (2) produced a pharmacokinetic profile with long exposure period postadministration. In an effort to reduce the occurrence of injection site reactions, a re‐evaluation of the rezafungin s.c. formulation could be considered in the future.

Novel antifungal agents in clinical trials

Invasive fungal diseases due to resistant yeasts and molds are an important and increasing public health threat, likely due to a growing population of immunosuppressed hosts, increases in antifungal resistance, and improvements in laboratory diagnostics.  The significant morbidity and mortality associated with these pathogens bespeaks the urgent need for novel safe and effective therapeutics.  This review highlights promising investigational antifungal agents in clinical phases of development: fosmanogepix, ibrexafungerp, rezafungin, encochleated amphotericin B, oteseconazole (VT-1161), VT-1598, PC945, and olorofim.  We discuss three first-in-class members of three novel antifungal classes, as well as new agents within existing antifungal classes with improved safety and tolerability profiles due to enhanced pharmacokinetic and pharmacodynamic properties.

Echinocandins - structure, mechanism of action and use in antifungal therapy

With increasing number of immunocompromised patients as well as drug resistance in fungi, the risk of fatal fungal infections in humans increases as well. The action of echinocandins is based on the inhibition of β-(1,3)-d-glucan synthesis that builds the fungal cell wall. Caspofungin, micafungin, anidulafungin and rezafungin are semi-synthetic cyclic lipopeptides. Their specific chemical structure possess a potential to obtain novel derivatives with better pharmacological properties resulting in more effective treatment, especially in infections caused by Candida and Aspergillus species. In this review we summarise information about echinocandins with closer look on their chemical structure, mechanism of action, drug resistance and usage in clinical practice. We also introduce actual trends in modification of this antifungals as well as new methods of their administration, and additional use in viral and bacterial infections.

Evaluation of Rezafungin Provisional CLSI Clinical Breakpoints and Epidemiological Cutoff Values Tested against a Worldwide Collection of Contemporaneous Invasive Fungal Isolates (2019 to 2020)

Rezafungin is a new echinocandin under development for the treatment of candidemia and invasive candidiasis. CLSI recently approved provisional susceptible-only breakpoints and epidemiological cutoff values for Candida spp. and rezafungin. The activities of rezafungin and comparators against 2019 to 2020 invasive fungal isolates was evaluated by applying the new CLSI breakpoints. Rezafungin demonstrated potent activity against Candida albicans (MIC 50 /MIC 90 , 0.03/0.06 mg/L; 100.0% susceptible), Candida tropicalis (MIC 50 /MIC 90 , 0.03/0.06 mg/L; 100% susceptible), Candida glabrata (MIC 50 /MIC 90 , 0.06/0.06 mg/L; 98.3% susceptible), Candida krusei (MIC 50 /MIC 90 , 0.03/0.03 mg/L; 100% susceptible), and Candida dubliniensis (MIC 50 /MIC 90 , 0.06/0.12 mg/L; 100% susceptible) when tested by the CLSI broth microdilution method. Rezafungin inhibited 99.6% of Candida parapsilosis isolates (MIC 50 /MIC 90 , 1/2 mg/L) at the susceptible breakpoint of ≤2 mg/L. All C. albicans , C. tropicalis , and C. krusei isolates, as well as most C. glabrata (96.2% to 97.9%) and C. parapsilosis (86.2% to 100%) isolates, were susceptible to comparator echinocandins. Fluconazole resistance was detected among 0.5%, 4.5%, 10.5%, and 1.2% of C. albicans , C. glabrata , C. parapsilosis , and C. tropicalis isolates, respectively. All echinocandins displayed limited activity against Cryptococcus neoformans . Rezafungin and other echinocandins were active against Aspergillus fumigatus (minimum effective concentration for 90% of isolates tested [MEC 90 ] range, 0.015 to 0.06 mg/L) and Aspergillus section Flavi (MEC 90 range, 0.015 to 0.03 mg/L). All but 16 (8.6%) A. fumigatus isolates were susceptible to voriconazole, and 100% of Aspergillus section Flavi isolates were WT to mold-active azoles. When applying the CLSI clinical breakpoints, rezafungin displayed high susceptibility rates (>98.0%) against Candida isolates from invasive fungal infections and showed potent activity against Aspergillus isolates.

Drug Resistance and Novel Therapeutic Approaches in Invasive Candidiasis

Candida species are the leading cause of invasive fungal infections worldwide and are associated with acute mortality rates of ~50%. Mortality rates are further augmented in the context of host immunosuppression and infection with drug-resistant Candida species. In this review, we outline antifungal drugs already in clinical use for invasive candidiasis and candidaemia, their targets and mechanisms of resistance in clinically relevant Candida species, encompassing not only classical resistance, but also heteroresistance and tolerance. We describe novel antifungal agents and targets in pre-clinical and clinical development, including their spectrum of activity, antifungal target, clinical trial data and potential in treatment of drug-resistant Candida. Lastly, we discuss the use of combination therapy between conventional and repurposed agents as a potential strategy to combat the threat of emerging resistance in Candida.

OUP accepted manuscript

Candida auris is an emerging, multi drug resistant fungal pathogen that has caused infectious outbreaks in over 45 countries since its first isolation over a decade ago, leading to in-hospital crude mortality rates as high as 72%. The fungus is also acclimated to disinfection procedures and persists for weeks in nosocomial ecosystems. Alarmingly, the outbreaks of C. auris infections in Coronavirus Disease-2019 (COVID-19) patients have also been reported. The pathogenicity, drug resistance and global spread of C. auris have led to an urgent exploration of novel, candidate antifungal agents for C. auris therapeutics. This narrative review codifies the emerging data on the following new/emerging antifungal compounds and strategies: antimicrobial peptides, combinational therapy, immunotherapy, metals and nano particles, natural compounds, and repurposed drugs. Encouragingly, a vast majority of these exhibit excellent anti- C. auris properties, with promising drugs now in the pipeline in various stages of development. Nevertheless, further research on the modes of action, toxicity, and the dosage of the new formulations are warranted. Studies are needed with representation from all five C. auris clades, so as to produce data of grater relevance, and broader significance and validity.

Consensus guidelines for optimising antifungal drug delivery and monitoring to avoid toxicity and improve outcomes in patients with haematological malignancy and haemopoietic stem cell transplant recipients, 2021

Antifungal agents can have complex dosing and the potential for drug interaction, both of which can lead to subtherapeutic antifungal drug concentrations and poorer clinical outcomes for patients with haematological malignancy and haemopoietic stem cell transplant recipients. Antifungal agents can also be associated with significant toxicities when drug concentrations are too high. Suboptimal dosing can be minimised by clinical assessment, laboratory monitoring, avoidance of interacting drugs, and dose modification. Therapeutic drug monitoring (TDM) plays an increasingly important role in antifungal therapy, particularly for antifungal agents that have an established exposure-response relationship with either a narrow therapeutic window, large dose-exposure variability, cytochrome P450 gene polymorphism affecting drug metabolism, the presence of antifungal drug interactions or unexpected toxicity, and/or concerns for non-compliance or inadequate absorption of oral antifungals. These guidelines provide recommendations on antifungal drug monitoring and TDM-guided dosing adjustment for selected antifungal agents, and include suggested resources for identifying and analysing antifungal drug interactions. Recommended competencies for optimal interpretation of antifungal TDM and dose recommendations are also provided.

Our pursuit for effective antifungal agents targeting fungal cell wall components, where are we?

Invasive mycotic infections account for an unacceptably high mortality rates in humans. These infections are initiated by the fungal cell wall which mediates host-fungi interactions. The cell wall is fused to the physiology of fungi, and it is involved in essential functions in the entire cell functionality. Components of the cell wall are synthesised and modified in the cell wall space by the activities of cell wall proteins through a range of signalling pathways that have only been described in many fungi, therefore making them suitable drug targets. The echinocandins class of cell wall-active drugs block cell wall β-1,3-glucan biosynthesis through inhibiting the catalytic subunit of the synthetic protein complex. Resistance to echinocandins can be through the acquisition of single nucleotide polymorphisms and/or through activation of cell wall signalling pathways resulting in altered cell wall proteome and elevated chitin content in the cell wall. Countering the cell wall remodelling process will enhance the effectiveness of β-1,3-glucan-active antifungal agents. Cell surface proteins are also important antifungal targets which can be used to develop rapid and robust diagnostics and more effective therapeutics. The cell wall remains a crucial target in fungi that needs to be harnessed to combat mycotic infections.

Metabolism, Excretion, and Mass Balance of [14C]-Rezafungin in Animals and Humans

Rezafungin is a novel echinocandin being developed for treatment of candidemia and invasive candidiasis and for prevention of invasive fungal disease caused by Candida, Aspergillus, and Pneumocystis spp. in recipients of blood and marrow transplantation. Studies using [¹⁴C]-radiolabeled rezafungin were conducted in rats, monkeys, and humans to characterize the mass balance, excretion, and pharmacokinetics of [¹⁴C]-rezafungin and to evaluate relative amounts of rezafungin metabolites compared with parent drug. Fecal excretion was the main route of elimination in rats, monkeys, and humans. Radioactivity was primarily excreted as unchanged drug, with ≥95% average total recovery in rats (through 336 h) and monkeys (through 720 h). In humans, cumulative recovery of radioactivity through the first 17 days was 52% (38% in feces, 14% in urine) with estimated mean overall recovery through day 60 of 88.3% (73% in feces, 27% in urine). The clinical pharmacokinetics of rezafungin following a single 400-mg intravenous infusion (200 μCi of [¹⁴C]-rezafungin) were similar in plasma, plasma total radioactivity, and whole blood total radioactivity. Unchanged rezafungin represented the majority of total radioactivity in plasma, and the partitioning of total radioactivity into red blood cells was negligible. Across species, rezafungin was primarily metabolized by hydroxylation of the terphenyl, pentyl ether side chain. In these excretion/mass balance, metabolism, and PK studies, clinical observations were consistent with findings in the rat and monkey demonstrating the minimal metabolism and slow elimination of rezafungin after intravenous administration, with fecal excretion as the major route of elimination.

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.

Antifungal Pipeline

In many ways, fungal diseases are forgotten or neglected. Given the significantly lower frequency compared to similar bacterial etiologies across the spectrum of infectious syndromes, it makes sense that anti-bacterial agents have seen the bulk of development in recent decades. The vast majority of new antifungal medications approved for use in the past 10 years have been new versions in the same class as existing agents. Clinical mycology is crying out for new mechanisms of action in the setting of rising resistance and emergence of new organisms. Fortunately, this trend appears to be reversing. There are numerous agents in advanced stages of development offering novel dosing regimens and mechanisms of action to combat these threats. Herein we review seven antifungal agents that we hope to see come to market in the coming years to aid physicians in the treatment of mucocutaneous and invasive fungal infections.

Pharmacological management of antifungal agents in pulmonary aspergillosis: an updated review

INTRODUCTION

Aspergillus may cause different types of lung infections: invasive, chronic pulmonary or allergic bronchopulmonary aspergillosis. Pharmacological management with antifungals poses as a challenge. Patients diagnosed with pulmonary aspergillosis are complex, as well as the problems associated with antifungal agents.

AREAS COVERED

This article reviews the pharmacology of antifungal agents in development and currently used to treat pulmonary aspergillosis, including the mechanisms of action, pharmacokinetics, pharmacodynamics, dosing, therapeutic drug monitoring and safety. Recommendations to manage situations that arise in daily clinical practice are provided. A literature search of PubMed was conducted on November 15^th, 2020 and updated on March 30^th, 2021.

EXPERT OPINION

Recent and relevant developments in the treatment of pulmonary aspergillosis have taken place. Novel antifungals with new mechanisms of action that extend antifungal spectrum and improve pharmacokinetic-related aspects, drug-drug interactions and safety are under current study. For those antifungals already marketed, new data related to pharmacokinetics, pharmacodynamics, dose adjustments in special situations, therapeutic drug monitoring and safety are available. To maximize efficacy and reduce the risk of associated toxicities, it is essential to choose the most appropriate antifungal; optimize its dose, interval, route of administration and length of treatment; and prevent side effects.

Update on Candida krusei, a potential multidrug-resistant pathogen

Although Candida albicans remains the main cause of candidiasis, in recent years a significant number of infections has been attributed to non-albicans Candida (NAC) species, including Candida krusei. This epidemiological change can be partly explained by the increased resistance of NAC species to antifungal drugs. C. krusei is a diploid, dimorphic ascomycetous yeast that inhabits the mucosal membrane of healthy individuals. However, this yeast can cause life-threatening infections in immunocompromised patients, with hematologic malignancy patients and those using prolonged azole prophylaxis being at higher risk. Fungal infections are usually treated with five major classes of antifungal agents which include azoles, echinocandins, polyenes, allylamines, and nucleoside analogues. Fluconazole, an azole, is the most commonly used antifungal drug due to its low host toxicity, high water solubility, and high bioavailability. However, C. krusei possesses intrinsic resistance to this drug while also rapidly developing acquired resistance to other antifungal drugs. The mechanisms of antifungal resistance of this yeast involve the alteration and overexpression of drug target, reduction in intracellular drug concentration and development of a bypass pathway. Antifungal resistance menace coupled with the paucity of the antifungal arsenal as well as challenges involved in antifungal drug development, partly due to the eukaryotic nature of both fungi and humans, have left researchers to exploit alternative therapies. Here we briefly review our current knowledge of the biology, pathophysiology and epidemiology of a potential multidrug-resistant fungal pathogen, C. krusei, while also discussing the mechanisms of drug resistance of Candida species and alternative therapeutic approaches.

Novel antifungal agents in clinical trials

Invasive fungal diseases due to resistant yeasts and molds are an important and increasing public health threat, likely due to a growing population of immunosuppressed hosts, increases in antifungal resistance, and improvements in laboratory diagnostics.  The significant morbidity and mortality associated with these pathogens bespeaks the urgent need for novel safe and effective therapeutics.  This review highlights promising investigational antifungal agents in clinical phases of development: fosmanogepix, ibrexafungerp, rezafungin, encochleated amphotericin B, oteseconazole (VT-1161), VT-1598, PC945, and olorofim.  We discuss three first-in-class members of three novel antifungal classes, as well as new agents within existing antifungal classes with improved safety and tolerability profiles due to enhanced pharmacokinetic and pharmacodynamic properties.

Organic Antifungal Drugs and Targets of Their Action

In recent decades, there has been a significant increase in the number of fungal diseases. This is due to a wide spectrum of action, immunosuppressants and other group drugs. In terms of frequency, rapid spread and globality, fungal infections are approaching acute respiratory infections. Antimycotics are medicinal substances endorsed with fungicidal or fungistatic properties. For the treatment of fungal diseases, several groups of compounds are used that differ in their origin (natural or synthetic), molecular targets and mechanism of action, antifungal effect (fungicidal or fungistatic), indications for use (local or systemic infections), and methods of administration (parenteral, oral, outdoor). Several efforts have been made by various medicinal chemists around the world for the development of antifungal drugs with high efficacy with the least toxicity and maximum selectivity in the area of antifungal chemotherapy. The pharmacokinetic properties of the new antimycotics are also important: the ability to penetrate biological barriers, be absorbed and distributed in tissues and organs, get accumulated in tissues affected by micromycetes, undergo drug metabolism in the intestinal microflora and human organs, and in the kinetics of excretion from the body. There are several ways to search for new effective antimycotics: - Obtaining new derivatives of the already used classes of antimycotics with improved activity properties. - Screening of new chemical classes of synthetic antimycotic compounds. - Screening of natural compounds. - Identification of new unique molecular targets in the fungal cell. - Development of new compositions and dosage forms with effective delivery vehicles. The methods of informatics, bioinformatics, genomics and proteomics were extensively investigated for the development of new antimycotics. These techniques were employed in finding and identification of new molecular proteins in a fungal cell; in the determination of the selectivity of drugprotein interactions, evaluation of drug-drug interactions and synergism of drugs; determination of the structure-activity relationship (SAR) studies; determination of the molecular design of the most active, selective and safer drugs for the humans, animals and plants. In medical applications, the methods of information analysis and pharmacogenomics allow taking into account the individual phenotype of the patient, the level of expression of the targets of antifungal drugs when choosing antifungal agents and their dosage. This review article incorporates some of the most significant studies covering the basic structures and approaches for the synthesis of antifungal drugs and the directions for their further development.

Comparison of In Vitro Killing Activity of Rezafungin, Anidulafungin, Caspofungin, and Micafungin against Four Candida auris Clades in RPMI-1640 in the Absence and Presence of Human Serum

Candida auris is an emerging and frequently multidrug-resistant pathogen against which the echinocandins are the preferred therapeutic option. We compared killing activities of anidulafungin, caspofungin, micafungin, and rezafungin against 13 isolates representing four C. auris clades (South Asian n = 3; East Asian n = 3; South African n = 3; South American n = 4, of which two were of environmental origin). Minimum inhibitory concentration MICs and killing kinetics in RPMI-1640 and RPMI-1640 plus 50% serum (50% serum) were determined. The four echinocandins were never fungicidal and induced large aggregates in RPMI-1640 and, less markedly, in 50% serum. Colony forming unit CFU decreases were found more consistently in 50% serum than in RPMI-1640. Isolates from the East Asian clade were killed at ≥1-≥ 4 mg/L with all echinocandins regardless of media. Anidulafungin and micafungin produced killing at peak drug serum concentration (8 mg/L) against environmental but not clinical isolates from the South American and the South African clades. Micafungin at ≥8 mg/L but not anidulafungin produced CFU decreases against the South Asian clade as well. In 50% serum, rezafungin at ≥1-≥ 8 mg/L produced killing against all four clades. The next generation echinocandin, rezafungin, showed the same or better activity at clinically attainable trough concentration regardless of media, compared with anidulafungin, caspofungin, and micafungin against all four tested C. auris clades.

Modulation of co-stimulatory signal from CD2-CD58 proteins by a grafted peptide

Peptides were designed to inhibit the protein-protein interaction of CD2 and CD58 to modulate the immune response. This work involved the design and synthesis of eight different peptides by replacing each amino acid residue in peptide 6 with alanine as well as grafting the peptide to the sunflower trypsin-inhibitor framework. From the alanine scanning studies, mutation at position 2 of the peptide was shown to result in increased potency to inhibit cell adhesion interactions. The most potent peptide from the alanine scanning was further studied for its detailed three-dimensional structure and binding to CD58 protein using surface plasmon resonance and flow cytometry. This peptide was used to graft to the sunflower trypsin inhibitor to improve the stability of the peptide. The grafted peptide, SFTI-a1, was further studied for its potency as well as its thermal, chemical, and enzymatic stability. The grafted peptide exhibited improved activity compared to our previously grafted peptide and was stable against thermal and enzymatic degradation.

Efficacy of Rezafungin in Prophylactic Mouse Models of Invasive Candidiasis, Aspergillosis, and Pneumocystis Pneumonia

Antifungal prophylaxis is recommended to prevent invasive fungal disease caused by Candida spp., Aspergillus spp., and Pneumocystis jirovecii in patients at risk for opportunistic infections, such as allogeneic blood or marrow transplant recipients, patients with hematological disease undergoing chemotherapy, or patients on immunosuppressive therapies. Current approaches to antifungal prophylaxis require multiple agents to cover these key fungi. Rezafungin, a novel echinocandin designed for next-generation properties (e.g., greater stability and long-acting pharmacokinetics for once-weekly dosing), has demonstrated in vitro activity against Candida and Aspergillus spp. and efficacy against Pneumocystis spp. biofilms. Rezafungin was evaluated in in vivo studies of prophylactic efficacy using immunosuppressed mouse models of invasive candidiasis, aspergillosis, and Pneumocystis pneumonia. Rezafungin reduction of Candida CFU burden was generally greater with increasing drug concentrations (5, 10, or 20 mg/kg) and when rezafungin was administered closer to the time of fungal challenge (day -1, -3, or -5). Similarly, in the aspergillosis model, survival rates increased with drug concentrations and when rezafungin was administered closer to the time of fungal challenge. Against Pneumocystismurina, rezafungin significantly reduced trophic nuclei and asci counts at all doses tested. Rezafungin prevented infection at the two higher doses compared to vehicle and had comparable activity to the active control trimethoprim-sulfamethoxazole at human equivalent doses for prevention. These findings support phase 3 development of rezafungin and the potential for single-agent prophylaxis against invasive fungal disease caused by Candida spp., Aspergillus spp., and Pneumocystis jirovecii.

Rezafungin: a novel antifungal for the treatment of invasive candidiasis

Rezafungin is a novel echinocandin with exceptional stability and solubility and a uniquely long half-life allowing for front-loaded drug exposure with once-weekly dosing. Rezafungin has been shown comparable to other echinocandins, with activity against Candida spp. and Aspergillus spp. including subsets of echinocandin-resistant Candida auris and azole-resistant Aspergillus isolates. Available clinical data show robust safety and promising efficacy. Phase III trials will provide data on efficacy of rezafungin for the treatment of candidemia and invasive candidiasis and for the prevention of invasive fungal disease in blood and bone marrow transplant recipients. Rezafungin is a promising new candidate in the antifungal arsenal that opens up clinical possibilities based on its impressive half-life, such as early hospital discharge for stable patients and use as prophylaxis in immunocompromised patients.

Rezafungin-Mechanisms of Action, Susceptibility and Resistance: Similarities and Differences with the Other Echinocandins

Rezafungin (formerly CD101) is a new β-glucan synthase inhibitor that is chemically related with anidulafungin. It is considered the first molecule of the new generation of long-acting echinocandins. It has several advantages over the already approved by the Food and Drug Administration (FDA) echinocandins as it has better tissue penetration, better pharmacokinetic/phamacodynamic (PK/PD) pharmacometrics, and a good safety profile. It is much more stable in solution than the older echinocandins, making it more flexible in terms of dosing, storage, and manufacturing. These properties would allow rezafungin to be administered once-weekly (intravenous) and to be potentially administered topically and subcutaneously. In addition, higher dose regimens were tested with no evidence of toxic effect. This will eventually prevent (or reduce) the selection of resistant strains. Rezafungin also has several similarities with older echinocandins as they share the same in vitro behavior (very similar Minimum Inhibitory Concentration required to inhibit the growth of 50% of the isolates (MIC50) and half enzyme maximal inhibitory concentration 50% (IC50)) and spectrum, the same target, and the same mechanisms of resistance. The selection of FKS mutants occurred at similar frequency for rezafungin than for anidulafungin and caspofungin. In this review, rezafungin mechanism of action, target, mechanism of resistance, and in vitro data are described in a comparative manner with the already approved echinocandins.

Novel Antifungal Agents and Their Activity against Aspergillus Species

There is a need for new antifungal agents, mainly due to increased incidence of invasive fungal infections (IFI), high frequency of associated morbidity and mortality and limitations of the current antifungal agents (e.g., toxicity, drug-drug interactions, and resistance). The clinically available antifungals for IFI are restricted to four main classes: polyenes, flucytosine, triazoles, and echinocandins. Several antifungals are hampered by multiple resistance mechanisms being present in fungi. Consequently, novel antifungal agents with new targets and modified chemical structures are required to combat fungal infections. This review will describe novel antifungals, with a focus on the Aspergillus species.

Antifungal drugs: An updated review of central nervous system pharmacokinetics

Invasive fungal infections (IFIs) in the central nervous system (CNS) are particularly hard to treat and are associated with high morbidity and mortality rates. Four chemical classes of systemic antifungal agents are used for the treatment of IFIs (eg meningitis), including polyenes, triazoles, pyrimidine analogues and echinocandins. This review will address all of these classes and discuss their penetration and accumulation in the CNS. Treatment of fungal meningitis is based on the antifungal that shows good penetration and accumulation in the CNS. Pharmacokinetic data concerning the entry of antifungal agents into the intracranial compartments are faulty. This review will provide an overview of the ability of systemic antifungals to penetrate the CNS, based on previously published drug physicochemical properties and pharmacokinetic data, for evaluation of the most promising antifungal drugs for the treatment of fungal CNS infections. The studies selected and discussed in this review are from 1990 to 2019.

Review of the Novel Echinocandin Antifungal Rezafungin: Animal Studies and Clinical Data

Rezafungin is a novel echinocandin drug being developed as a first-line option for treatment and prevention of invasive fungal infections. As a result of a structural modification in its parent molecule anidulafungin, rezafungin has acquired unique chemical stability conferring prolonged pharmacokinetics, as well as an administration advantage in the clinical setting compared to other drugs in the same class. Rezafungin displays potent in vitro activity against a wide spectrum of fungal pathogens, which is reflected in robust in vivo efficacy and/or pharmacodynamic studies using various animal models as well as in promising clinical trials data. This review describes in vivo characterization of rezafungin using animal models, current status of clinical development and key findings from these studies.

Review on Current Status of Echinocandins Use

Fungal infections are rising all over the world every year. There are only five medical compound classes for treatment: triazoles, echinocandins, polyenes, flucytosine and allylamine. Currently, echinocandins are the most important compounds, because of their wide activity spectrum and much lower sides effects that may occur during therapy with other drugs. Echinocandins are secondary metabolites of fungi, which can inhibit the biosynthesis of β-(1,3)-D-glucan. These compounds have fungicidal and fungistatic activity depending on different genera of fungi, against which they are used. Echinocandin resistance is rare—the major cause of resistance is mutations in the gene encoding the β-(1,3)-D-glucan synthase enzyme. In this review of the literature we have summarized the characteristics of echinocandins, the mechanism of their antifungal activity with pharmacokinetics and pharmacodynamics, and the resistance issue.

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.