Safety and Pharmacokinetics of Intravenous and Oral Fosmanogepix, a First-in-Class Antifungal Agent, in Healthy Volunteers

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.

How do I manage refractory invasive pulmonary aspergillosis

BACKGROUND

Invasive aspergillosis is associated with significant morbidity and mortality in patients with haematologic malignancies and haematopoietic cell transplant recipients. The prognosis is worse among patients who have failed primary antifungal treatment.

OBJECTIVES

We aim to provide guidance on the diagnosis and management of refractory invasive pulmonary aspergillosis.

SOURCES

Using PubMed, we performed a review of original articles, meta-analyses, and systematic reviews.

CONTENT

We discuss the diagnostic criteria for invasive pulmonary aspergillosis and the evidence on the treatment of primary infection. We outline our diagnostic approach to refractory disease. We propose a treatment algorithm for refractory disease and discuss the role of experimental antifungal agents.

IMPLICATIONS

For patients with worsening disease while on antifungal therapy, a thorough diagnostic evaluation is required to confirm the diagnosis of aspergillosis and exclude another concomitant infection. Treatment should be individualized. Current options include switching to another triazole, transitioning to a lipid formulation of amphotericin B, or using combination antifungal therapy.

A Mini-Review of In Vitro Data for Candida Species, Including C. auris, Isolated during Clinical Trials of Three New Antifungals: Fosmanogepix, Ibrexafungerp, and Rezafungin

This mini-review summarizes the clinical outcomes and antifungal susceptibility results, where available, for three new antifungals, including fosmanogepix, ibrexafungerp, and rezafungin, against Candida isolates cultured from patients in clinical trials. When reported, most of the data were generated by the Clinical and Laboratory Standards Institute (CLSI) broth microdilution method or by both the CLSI and European Committee on Antimicrobial Susceptibility Testing (EUCAST) methodologies. For fosmanogepix, we summarize the in vitro data for C. auris isolates from 9 patients and for Candida spp. cultured from 20 patients in two clinical trials. Ibrexafungerp has also been evaluated in several clinical trials. From conference proceedings, a total of 176 Candida isolates were evaluated in the FURI and CARES studies, including 18 C. auris isolates (CARES study). However, MIC data are not available for all clinical isolates. Results from the ReSTORE rezafungin phase 3 clinical study also included in vitro results against Candida spp., but no patients with C. auris infections were included. In conclusion, this mini-review summarizes insights regarding clinical outcomes and the in vitro activity of three new antifungals against Candida spp. cultured from patients in clinical trials.

Tn-seq of the Candida glabrata reference strain CBS138 reveals epigenetic plasticity, structural variation, and intrinsic mechanisms of resistance to micafungin

C. glabrata is an opportunistic pathogen that can resist common antifungals and rapidly acquire multidrug resistance. A large amount of genetic variation exists between isolates, which complicates generalizations. Portable Tn-seq methods can efficiently provide genome-wide information on strain differences and genetic mechanisms. Using the Hermes transposon, the CBS138 reference strain and a commonly studied derivative termed 2001 were subjected to Tn-seq in control conditions and after exposure to varying doses of the clinical antifungal micafungin. The approach revealed large differences between these strains, including a 131 kb tandem duplication and a variety of fitness differences. Additionally, both strains exhibited up to 1000-fold increased transposon accessibility in subtelomeric regions relative to the BG2 strain, indicative of open subtelomeric chromatin in these isolates and large epigenetic variation within the species. Unexpectedly, the Pdr1 transcription factor conferred resistance to micafungin through targets other than CDR1 . Other micafungin resistance pathways were also revealed including mannosyltransferase activity and biosynthesis of the lipid precursor sphingosine, the drugging of which by SDZ 90-215 or myriocin enhanced the potency of micafungin in vitro . These findings provide insights into complexity of the C. glabrata species as well as strategies for improving antifungal efficacy.

Summary

Candida glabrata is an emerging pathogen with large genetic diversity and genome plasticity. The type strain CBS138 and a laboratory derivative were mutagenized with the Hermes transposon and profiled using Tn-seq. Numerous genes that regulate innate and acquired resistance to an important clinical antifungal were uncovered, including a pleiotropic drug resistance gene (PDR1) and a duplication of part of one chromosome. Compounds that target PDR1 and other genes may augment the potency of existing antifungals.

Pharmacokinetics, safety, and tolerability of fosmanogepix IV to oral switch and multiple IV doses in healthy participants

Fosmanogepix [FMGX, APX001; active form: manogepix (MGX), APX001A] is a first-in-class, intravenous (IV)/oral antifungal currently being evaluated for invasive fungal disease treatment. Data from two phase 1, placebo-controlled studies [IV-oral switch (study 1) and multiple IV doses (study 2)] evaluating FMGX tolerability, and pharmacokinetics (PK) are presented. Healthy adults (study 1: 18-65 years; study 2: 18-55 years) were eligible (randomized 3:1 to FMGX: placebo). Eleven participants completed study 1. In study 2, 51 participants (48 planned + 3 replacement) were enrolled in six cohorts (8 participants each; 34 completed the study). In study 1, overall MGX systemic exposures were comparable from day 1 to day 42 of dosing; steady-state plasma concentrations were achieved in ≤24 h following two IV loading doses (1,000 mg) and exposures maintained after switching [IV (600 mg) to daily oral doses (800 mg)]. FMGX was safe and well-tolerated. In study 2, FMGX IV doses (loading doses twice daily/maintenance doses once daily; 3-h infusion) of 1,500/900 mg (cohort A), 900/900 mg (cohort B), and 1,000/900 mg (cohort C: with ondansetron) were not well-tolerated; most participants reported nausea and infrequent vomiting. FMGX IV doses of 1,000/750 mg (cohort D), 1,000/850 mg (cohort E), and 1,000/900 mg (cohort F: ondansetron prn) were relatively better tolerated. Steady-state systemic exposures were achieved between days 2 and 4. All cohorts had similar geometric mean (GM) concentrations during maintenance dosing and similar GM PK parameters. Dosing regimen evaluated in study 1 was safe, well-tolerated, and may be used for future clinical evaluations.

Protein lipidation in health and disease: molecular basis, physiological function and pathological implication

Posttranslational modifications increase the complexity and functional diversity of proteins in response to complex external stimuli and internal changes. Among these, protein lipidations which refer to lipid attachment to proteins are prominent, which primarily encompassing five types including S-palmitoylation, N-myristoylation, S-prenylation, glycosylphosphatidylinositol (GPI) anchor and cholesterylation. Lipid attachment to proteins plays an essential role in the regulation of protein trafficking, localisation, stability, conformation, interactions and signal transduction by enhancing hydrophobicity. Accumulating evidence from genetic, structural, and biomedical studies has consistently shown that protein lipidation is pivotal in the regulation of broad physiological functions and is inextricably linked to a variety of diseases. Decades of dedicated research have driven the development of a wide range of drugs targeting protein lipidation, and several agents have been developed and tested in preclinical and clinical studies, some of which, such as asciminib and lonafarnib are FDA-approved for therapeutic use, indicating that targeting protein lipidations represents a promising therapeutic strategy. Here, we comprehensively review the known regulatory enzymes and catalytic mechanisms of various protein lipidation types, outline the impact of protein lipidations on physiology and disease, and highlight potential therapeutic targets and clinical research progress, aiming to provide a comprehensive reference for future protein lipidation research.

Advancements and challenges in antifungal therapeutic development

Over recent decades, the global burden of fungal disease has expanded dramatically. It is estimated that fungal disease kills approximately 1.5 million individuals annually; however, the true worldwide burden of fungal infection is thought to be higher due to existing gaps in diagnostics and clinical understanding of mycotic disease. The development of resistance to antifungals across diverse pathogenic fungal genera is an increasingly common and devastating phenomenon due to the dearth of available antifungal classes. These factors necessitate a coordinated response by researchers, clinicians, public health agencies, and the pharmaceutical industry to develop new antifungal strategies, as the burden of fungal disease continues to grow. This review provides a comprehensive overview of the new antifungal therapeutics currently in clinical trials, highlighting their spectra of activity and progress toward clinical implementation. We also profile up-and-coming intracellular proteins and pathways primed for the development of novel antifungals targeting their activity. Ultimately, we aim to emphasize the importance of increased investment into antifungal therapeutics in the current continually evolving landscape of infectious disease.

Cryptococcosis and Cryptococcal Meningitis: A Narrative Review and the Up-to-Date Management Approach

Cryptococcosis is a fungal infectious disease that enormously impacts human health worldwide. Cryptococcal meningitis is the most severe disease caused by the fungus Cryptococcus, and can lead to death, if left untreated. Many patients develop resistance and progress to death even after treatment. It requires a prolonged treatment course in people with AIDS. This narrative review provides an evidence-based summary of the current treatment modalities and future trial options, including newer ones, namely, 18B7, T-2307, VT-1598, AR12, manogepix, and miltefosine. This review also evaluated the management and empiric treatment of cryptococcus meningitis. The disease can easily evade diagnosis with subacute presentation. Despite the severity of the disease, treatment options for cryptococcosis remain limited, and more research is needed.

Pipeline of Novel Antifungals for Invasive Fungal Disease in Transplant Recipients: A Pediatric Perspective

Invasive fungal disease (IFD) remains a significant cause of morbidity and mortality in children undergoing transplantation. There is a growing armamentarium of novel antifungal agents recently approved for use or in late stages of clinical development. The overarching goal of this review is to discuss the mechanisms of action, spectrum of activity, stage of development, and pediatric-specific data for the following agents: encochleated amphotericin B deoxycholate, fosmanogepix, ibrexafungerp, isavuconazole, olorofim, opelconazole, oteseconazole, and rezafungin. Additionally, key drug attributes of these novel agents and their potential future therapeutic roles in pediatric transplant recipients are discussed.

Calcineurin-dependent contributions to fitness in the opportunistic pathogen Candida glabrata

The protein phosphatase calcineurin is vital for the virulence of the opportunistic fungal pathogen Candida glabrata. The host-induced stresses that activate calcineurin signaling are unknown, as are the targets of calcineurin relevant to virulence. To potentially shed light on these processes, millions of transposon insertion mutants throughout the genome of C. glabrata were profiled en masse for fitness defects in the presence of FK506, a specific inhibitor of calcineurin. Eighty-seven specific gene deficiencies depended on calcineurin signaling for full viability in vitro both in wild-type and pdr1∆ null strains lacking pleiotropic drug resistance. Three genes involved in cell wall biosynthesis (FKS1, DCW1, FLC1) possess co-essential paralogs whose expression depended on calcineurin and Crz1 in response to micafungin, a clinical antifungal that interferes with cell wall biogenesis. Interestingly, 80% of the FK506-sensitive mutants were deficient in different aspects of vesicular trafficking, such as endocytosis, exocytosis, sorting, and biogenesis of secretory proteins in the endoplasmic reticulum (ER). In response to the experimental antifungal manogepix that blocks GPI-anchor biosynthesis in the ER, calcineurin signaling increased and strongly prevented cell death independent of Crz1, one of its major targets. Comparisons between manogepix, micafungin, and the ER-stressing tunicamycin reveal a correlation between the degree of calcineurin signaling and the degree of cell survival. These findings suggest that calcineurin plays major roles in mitigating stresses of vesicular trafficking. Such stresses may arise during host infection and in response to antifungal therapies.IMPORTANCECalcineurin plays critical roles in the virulence of most pathogenic fungi. This study sheds light on those roles in the opportunistic pathogen Candida glabrata using a genome-wide analysis in vitro. The findings could lead to antifungal developments that also avoid immunosuppression.

Molecular basis of the inositol deacylase PGAP1 involved in quality control of GPI-AP biogenesis

The secretion and quality control of glycosylphosphatidylinositol-anchored proteins (GPI-APs) necessitates post-attachment remodeling initiated by the evolutionarily conserved PGAP1, which deacylates the inositol in nascent GPI-APs. Impairment of PGAP1 activity leads to developmental diseases in humans and fatality and infertility in animals. Here, we present three PGAP1 structures (2.66-2.84 Å), revealing its 10-transmembrane architecture and product-enzyme interaction details. PGAP1 holds GPI-AP acyl chains in an optimally organized, guitar-shaped cavity with apparent energetic penalties from hydrophobic-hydrophilic mismatches. However, abundant glycan-mediated interactions in the lumen counterbalance these repulsions, likely conferring substrate fidelity and preventing off-target hydrolysis of bulk membrane lipids. Structural and biochemical analyses uncover a serine hydrolase-type catalysis with atypical features and imply mechanisms for substrate entrance and product release involving a drawing compass movement of GPI-APs. Our findings advance the mechanistic understanding of GPI-AP remodeling.

In vitro manogepix susceptibility testing of South African Emergomyces africanus, Emergomyces pasteurianus, and Blastomyces emzantsi clinical isolates

We performed in vitro antifungal susceptibility testing of manogepix against the yeast phase of 78 Emergomyces africanus, 2 Emergomyces pasteurianus, and 5 Blastomyces emzantsi isolates using a reference broth microdilution method following Clinical and Laboratory Standards Institute recommendations. All three pathogens had low minimum inhibitory concentrations ranging from <0.0005 to 0.008 mg/L. Manogepix should be investigated in animal models and potentially in future human clinical trials for endemic mycoses.

Phase 1b safety and pharmacokinetics of intravenous and oral fosmanogepix in patients with acute myeloid leukaemia and neutropenia

OBJECTIVES

Fosmanogepix (APX001), a first-in-class, intravenous (IV) and oral (PO) antifungal prodrug, is being developed to treat invasive fungal diseases (IFDs). Manogepix (APX001A; active moiety) targets fungal glycosylphosphatidylinositol-anchored cell wall transfer protein 1, inhibiting cell wall synthesis causing loss of viability. This open-label, multicentre, Phase 1b study in patients with AML and neutropenia (absolute neutrophil count <500 cells/μL; >10 days) undergoing chemotherapy aimed to assess tolerability, safety and pharmacokinetics (PK) of IV and PO fosmanogepix.

METHODS

Of 21 adult AML patients undergoing remission induction chemotherapy, 10 received IV fosmanogepix (600 mg; q24h) and 11 received oral fosmanogepix (500 mg; q24h) over 14 days, with a 28 day follow-up. Patients also received remission induction chemotherapy [sequential high-dose cytarabine and mitoxantrone (S-HAM) or 7 + 3 regimen] for AML and IFD prophylaxis (posaconazole). A two-compartmental PK model from previous studies in healthy volunteers was fitted to manogepix plasma data.

RESULTS

Of 26 fosmanogepix-related adverse events (AEs; IV: 14; PO: 12) in 9 (42.9%) patients [IV: 5 (50%); PO: 4 (36.4%)], none were serious or resulted in fosmanogepix discontinuation. Most frequently occurring fosmanogepix-related AEs were Grade 1/2 nausea [four events in three patients (14.3%)]; vomiting, ALT increase, and delirium [two events; two patients (9.5%) each]. One patient experienced fosmanogepix-related Grade 3 hypertension. Dose-corrected geometric mean ratio of AUC (PO-to-IV) was 95%. Elimination half-lives (∼2 days) were consistent with prior studies in healthy volunteers.

CONCLUSIONS

Fosmanogepix was safe and well tolerated in AML patients with neutropenia receiving remission induction chemotherapy. Safety and PK profiles were comparable to healthy volunteers.

New trends in antifungal treatment: What is coming up?

New antifungal agents are needed to overcome limitations of available ones such as poor pharmacokinetic traits, toxicity, drug-drug interactions, limited clinical efficacy, and emerging antifungal resistance. New antifungal drugs belong to well-known families (azoles, polyenes, or beta-d-glucan synthase inhibitors) or to drug families showing completely new mechanisms of action. Some drugs have a head start in terms of potential to reach the clinical setting and are here reviewed.