1157. Clinical Safety, Efficacy, and Pharmacokinetics of Fosmanogepix, a Novel First-in-class Antifungal, in Patients with Renal Insufficiency: Subset Analysis from a Phase 2 Candidemia Trial

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.

The Role of Novel Antifungals in the Management of Candidiasis: A Clinical Perspective

Mucosal and invasive candidiasis can be challenging to treat in the setting of drug intolerance, antifungal resistance, drug-drug interactions, or host immune status. Antifungals with novel mechanisms of action and distinct pharmacokinetic/pharmacodynamic properties have been developed in recent years. Rezafungin is an echinocandin with high-tissue penetration and an extended half-life that allows for once-weekly administration, making it a convenient treatment option for invasive candidiasis while obviating the need for central catheter placement. Ibrexafungerp is an oral glucan synthase inhibitor that is active against most echinocandin-resistant Candida species. At present, it is approved for the treatment of acute vulvovaginal candidiasis and is under investigation as an oral step-down therapy following initial treatment with an echinocandin for cases of invasive candidiasis. Oteseconazole is a long-acting tetrazole that exhibits a higher affinity for the fungal enzyme CYP51, resulting in a potentially lower risk of drug-drug interactions and side effects compared to other azoles. It is currently approved for the treatment of recurrent vulvovaginal candidiasis. Fosmanogepix has a novel mechanism of action and potent activity against several Candida strains resistant to other antifungals. Due to its considerable bioavailability and tissue penetration, it holds promise as a potential treatment option in patients with invasive candidiasis, including those with chorioretinitis or meningitis. Results from clinical trials and observational studies will further delineate the role of these agents in the management of candidiasis. As the usage of these novel antifungals becomes widespread, we expect to acquire a greater understanding of their efficacy and potential benefits.

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.

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.