In vitro activity of ibrexafungerp against clinically relevant echinocandin-resistant Candida strains.

Invasive candidiasis is a major hospital-acquired infection. Usually, echinocandins are considered first-line treatment. However, resistant phenotypes have emerged. Ibrexafungerp (IBX) is a new antifungal substance with potent anti-Candida activity. We challenged IBX with a library of 192 pheno-/genotypically echinocandin-resistant Candida isolates, focusing on the substance susceptibility, its activity on certain FKS hotspot (HS) mutated strains, and applying WTULs (wild-type upper limits). Therefore, a 9-year-old strain and patient data collection provided by the German National Reference Center for Invasive Fungal Infections were analyzed. Species identification was confirmed through ITS-sequencing. Molecular susceptibility testing was performed by sequencing HS of the FKS gene. Anidulafungin (AND) and IBX EUCAST-broth-microdilution was conducted. The four most common echinocandin-resistance mediating mutations were found in Candida glabrata [112/192 isolates; F659-(43×) and S663-(48×)] and Candida albicans [63/192 isolates; F641-(15×) and S645-(39×)]. Mutations at the HS-start sequence were associated with higher IBX MIC-values (F659 and F641 (MIC 50/90 mg/L: >4/>4 and 2/4 mg/L) in comparison to AND (F659 and F641 (MIC 50/90: 1/4 and 0.25/1 mg/L). MIC-values in HS-center mutations were almost equal [MIC50/90 in S663: 2/4 (AND and IBX); in S645: 0.5/1 (AND) and 0.25/1 (IBX) mg/L]. In total, 61 vs 78 of 192 echinocandin-resistant isolates may be classified as IBX wild type by applying WTULs, whereas the most prominent effect was seen in C. albicans [48% (30/63) vs 70% (44/63)]. IBX shows in vitro activity against echinocandin-resistant Candida and thus is an addition to the antifungal armory. However, our data suggest that this effect is more pronounced in C. albicans and strains harboring mutations, affecting the HS-center.

Ibrexafungerp is efficacious in a neutropenic murine model of pulmonary mucormycosis as monotherapy and combined with liposomal amphotericin B.

Ibrexafungerp (formerly SCY-078) is the first member of the triterpenoid class that prevents the synthesis of the fungal cell wall polymer ß-(1,3)-D-glucan by inhibiting the enzyme glucan synthase. We evaluated the in vivo efficacy of ibrexafungerp against pulmonary mucormycosis using an established murine model. Neutropenic mice were intratracheally infected with either Rhizopus delemar or Mucor circinelloides. Treatment with placebo (diluent control), ibrexafungerp (30 mg/kg, PO BID), liposomal amphotericin B (LAMB 10 mg/kg IV QD), posaconazole (PSC 30 mg/kg PO QD), or a combination of ibrexafungerp plus LAMB or ibrexafungerp plus PSC began 16 h post-infection and continued for 7 days for ibrexafungerp or PSC and through day 4 for LAMB. Ibrexafungerp was as effective as LAMB or PSC in prolonging median survival (range: 15 days to >21 days) and enhancing overall survival (30%-65%) vs placebo (9 days and 0%; P < 0.001) in mice infected with R. delemar. Furthermore, median survival and overall percent survival resulting from the combination of ibrexafungerp plus LAMB were significantly greater compared to all monotherapies (P ≤ 0.03). Similar survival results were observed in mice infected with M. circinelloides. Monotherapies also reduce the lung and brain fungal burden by ~0.5-1.0log10 conidial equivalents (CE)/g of tissue vs placebo in mice infected with R. delemar (P < 0.05), while a combination of ibrexafungerp plus LAMB lowered the fungal burden by ~0.5-1.5log10 CE/g compared to placebo or any of the monotherapy groups (P < 0.03). These results are promising and warrant continued investigation of ibrexafungerp as a novel treatment option against mucormycosis.

Efficacy and safety of oral ibrexafungerp in Chinese patients with vulvovaginal candidiasis: a phase III, randomized, double-blind study.

PURPOSE: To evaluate the efficacy and safety of oral ibrexafungerp (HS-10366) versus placebo in Chinese patients with vulvovaginal candidiasis (VVC). METHODS: A double-blind, placebo-controlled, randomized, multicenter phase III study was conducted in symptomatic VVC patients. Patients received (2:1) twice-daily oral ibrexafungerp 300 mg or matching placebo for 1 day. The primary endpoint was clinical cure (vulvovaginal signs and symptoms [VSS] score = 0) at test-of-cure (TOC) on day 11 ± 3. The secondary endpoints included mycological eradication, overall response, and clinical improvement (VSS score ≤ 1) at TOC, and vulvovaginal symptom resolution at follow-up on day 25 ± 4. RESULTS: In total, 360 patients were included in the modified intention-to-treat set (defined as positive Candida cultured and receiving at least one study drug; 239 for ibrexafungerp, 121 for placebo). Compared with placebo, patients receiving ibrexafungerp had a significantly higher proportion of clinical cure (51.0% vs. 25.6%), mycological eradication (55.6% vs. 18.2%), overall response (33.9%, vs. 8.3%) at TOC and complete symptom resolution (74.5% vs. 39.7%, all P < 0.001) at follow-up. Subgroup analysis of clinical cure indicated that patients with C. albicans could benefit from ibrexafungerp over placebo. A similar benefit trend was also observed in those with non-albicans Candida by post-hoc analysis. Further analyses revealed similar efficacy of ibrexafungerp between patients with fluconazole non-susceptible C. albicans and fluconazole susceptible C. albicans regarding clinical cure and mycological eradication. Ibrexafungerp was generally well tolerated. Adverse events were primarily gastrointestinal and were mainly mild in severity. CONCLUSIONS: As a first-in-class antifungal agent, ibrexafungerp demonstrated promising efficacy and favorable safety for VVC treatment in Chinese patients. CHINADRUGTRIALS.ORG. CN REGISTRY NUMBER: CTR20220918.

New Antifungals for Vulvovaginal Candidiasis: What Is Their Role?

New antifungals, ibrexafungerp and oteseconazole, are now available for treatment of vulvovaginal candidiasis. Both have novel antimicrobial and pharmacokinetic properties and advantages over fluconazole, although comparative trials have involved only placebo. In the absence of allergy, intolerance, and resistance, it is unclear whether these antifungals will replace fluconazole.

Safety, tolerability, and pharmacokinetics of ibrexafungerp in healthy Chinese subjects: a randomized, double-blind, placebo-controlled phase 1 trial.

Ibrexafungerp (code name in China: HS-10366) is a first-in-class and orally active triterpenoid antifungal agent with broad antifungal activity against Candida spp., Aspergillus spp., and other fungal pathogens. It was approved by the U.S. Food and Drug Administration for the treatment of vulvovaginal candidiasis. The study aimed to evaluate the safety, tolerability, and pharmacokinetic (PK) characteristics of oral ibrexafungerp in healthy Chinese adults. A single-center, randomized, double-blind, placebo-controlled single ascending dose (SAD, n = 42), and multiple ascending dose (MAD, n = 28) study was conducted in healthy Chinese subjects from March to October 2022. There were three cohorts in the SAD stage (300, 600, and 1,500 mg) and two cohorts in the MAD stage [450 mg once daily (QD) for 7 days; a loading dose of 750 mg twice daily (BID) for the first 2 days followed by a maintenance dose of 750 mg QD for consecutive 5 days]. Eligible participants in each cohort were randomly assigned in a 6:1 ratio to receive either ibrexafungerp or placebo orally. The primary objectives were to evaluate the safety and tolerability. The secondary objective was to evaluate PK parameters, including Cmax, AUC, and t1/2. A total of 70 healthy Chinese subjects were enrolled in the study. The mean (SD) age was 29.0 (6.32), and 55.7% were male. All treatment-emergent adverse events (TEAEs) were mild or moderate. There were no serious adverse events, and no subjects were discontinued from the study due to TEAEs. All TEAEs were recovered or resolved. The most common TEAEs were diarrhea, abdominal pain, and nausea. In the SAD stage, Cmax, and AUC increased in an approximately dose-proportional manner in the dose range of 300-1,500 mg. The mean t1/2 was within 18.29-21.30 hours. In the MAD stage, an accumulation of exposure (Cmax and AUC) was observed following multiple doses. This phase 1 study demonstrates a favorable safety, tolerability, and PK profile of ibrexafungerp in healthy Chinese subjects.

Yeasts from blood cultures in the wake of the COVID-19 pandemic in a tertiary care hospital: Shift in species epidemiology, steady low antifungal resistance and full in vitro ibrexafungerp activity.

Several institutions reported a rise not only in fungemia incidence but also in the number of cases caused by Candida auris or fluconazole-resistant C. parapsilosis during the COVID-19 pandemic. Since the pandemic broke out in early 2020, we studied its impact on fungemia incidence, species epidemiology, potential patient-to-patient transmission, and antifungal resistance in 166 incident yeast isolates collected from January 2020 to December 2022. Isolates were molecularly identified, and their antifungal susceptibilities to amphotericin B, azoles, micafungin, anidulafungin, and ibrexafungerp were studied following the European Committee on Antimicrobial Susceptibility Testing (EUCAST) method, and genotyped. The fungemia incidence (episodes per 1000 admissions) tended to decrease over time (2020 = 1.60, 2021 = 1.36, 2022 = 1.16); P > .05). Species distribution was C. albicans (50.6%, n = 84), C. parapsilosis (18.7%, n = 31), C. glabrata (12.0%, n = 20), C. tropicalis (11.4%, n = 19), C. krusei (3.0%, n = 5), other Candida spp. (1.2%, n = 2), and non-Candida yeasts (3.0%, n = 5). The highest and lowest proportions of C. albicans and C. parapsilosis were detected in 2020. The proportion of isolates between 2020 and 2022 decreased in C. albicans (60.3% vs. 36.7%) and increased in C. parapsilosis (10.3% vs. 28.6%; P < .05) and C. tropicalis (8.8% vs. 16.3%; P > .05). Only three C. albicans intra-ward clusters involving two patients each were detected, and the percentages of patients involved in intra-ward clusters reached 9.8% and 8.0% in 2020 and 2021, respectively, suggesting that clonal spreading was not uncontrolled. Fluconazole resistance (5%) exhibited a decreasing trend (P > .05) over time (2020 = 7.6%; 2021 = 4.2%; and 2022 = 2.1%). Ibrexafungerp showed high in vitro activity.

Fungemia incidence increased during the COVID-19 pandemic in our hospital, however, clonal spreading was not uncontrolled. The proportion of C. parapsilosis and C. tropicalis cases constantly increased. Antifungal resistance remained very low, and fluconazole-resistant C. parapsilosis was undetected.

Ibrexafungerp in the Treatment of Vulvovaginal Candidiasis.

OBJECTIVE: To review the pharmacology, efficacy, and safety of ibrexafungerp in the management of vulvovaginal candidiasis (VVC). DATA SOURCES: Literature was sought using PubMed (1966-February 2022) and EMBASE (1973-February 2022), and clinicaltrials.gov. Search terms included ibrexafungerp, SCY-078, and VVC. STUDY SELECTION AND DATA EXTRACTION: All studies including humans and published in English with data assessing the efficacy and safety of ibrexafungerp for the treatment of VVC were evaluated. DATA SYNTHESIS: A phase 2 dose-finding study found ibrexafungerp had similar efficacy to fluconazole in the clinical cure of VVC (51.9% vs 58.3%, respectively). Two phase 3 clinical trials demonstrated ibrexafungerp had statistical superiority over placebo for clinical cure in moderate to severe VVC (P < 0.001 and P = 0.023, respectively). The most frequently reported adverse reactions in the clinical trials were gastrointestinal-related symptoms. To date, data comparing efficacy of ibrexafungerp and topical imidazoles in the treatment of VVC are nonexistent. RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE: Topical imidazoles and oral fluconazole are effective for the treatment of uncomplicated VVC. Due to increased resistance, limited fluconazole coverage for non-Candida albicans species, and potential for significant drug interactions associated with fluconazole use, alternative treatments for VVC are needed. Ibrexafungerp is a new oral triterpenoid antifungal agent indicated for the treatment of VVC. Additional clinical trials are needed to evaluate long-term safety data as well as efficacy and safety in specialty populations. CONCLUSION: Ibrexafungerp, a recently approved triterpenoid antifungal agent, is an effective and well-tolerated option for the treatment of VVC.

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.

Investigational Antifungal Agents for Invasive Mycoses: A Clinical Perspective.

Treatment of invasive fungal infections (IFIs) remains challenging, because of the limitations of the current antifungal agents (ie, mode of administration, toxicity, and drug-drug interactions) and the emergence of resistant fungal pathogens. Therefore, there is an urgent need to expand our antifungal armamentarium. Several compounds are reaching the stage of phase II or III clinical assessment. These include new drugs within the existing antifungal classes or displaying similar mechanism of activity with improved pharmacologic properties (rezafungin and ibrexafungerp) or first-in-class drugs with novel mechanisms of action (olorofim and fosmanogepix). Although critical information regarding the performance of these agents in heavily immunosuppressed patients is pending, they may provide useful additions to current therapies in some clinical scenarios, including IFIs caused by azole-resistant Aspergillus or multiresistant fungal pathogens (eg, Candida auris, Lomentospora prolificans). However, their limited activity against Mucorales and some other opportunistic molds (eg, some Fusarium spp.) persists as a major unmet need.

Ibrexafungerp Versus Placebo for Vulvovaginal Candidiasis Treatment: A Phase 3, Randomized, Controlled Superiority Trial (VANISH 303).

BACKGROUND: Current treatment of vulvovaginal candidiasis (VVC) is largely limited to azole therapy. Ibrexafungerp is a first-in-class triterpenoid antifungal with broad-spectrum anti-Candida fungicidal activity. The objective of this study was to evaluate the efficacy and safety of ibrexafungerp compared with placebo in patients with acute VVC. METHODS: Patients were randomly assigned 2:1 to receive ibrexafungerp (300 mg twice for 1 day) or placebo. The primary endpoint was the percentage of patients with a clinical cure (complete resolution of vulvovaginal signs and symptoms [VSS] = 0) at test-of-cure (day 11 ± 3). Secondary endpoints included the percentage of patients with mycological eradication, overall success (clinical cure and mycological eradication), clinical improvement (VSS ≤ 1) at test-of-cure, and symptom resolution at follow-up (day 25 ± 4). RESULTS: Patients receiving ibrexafungerp had significantly higher rates of clinical cure (50.5% [95/188] vs 28.6% [28/98]; P = .001), mycological eradication (49.5% [93/188] vs 19.4% [19/98]; P < .001), and overall success (36.0% [64/178] vs 12.6% [12/95]; P < .001) compared with placebo. Symptom resolution was sustained and further increased with ibrexafungerp compared with placebo (59.6% [112/188] vs 44.9% [44/98]; P = .009) at follow-up. Post hoc analysis showed similar rates of clinical cure and clinical improvement at test-of-cure for Black patients (54.8% [40/73] and 63.4% [47/73], respectively) and patients with a body mass index >35 (54.5% [24/44] and 68.2% [30/44], respectively) compared with overall rates. Ibrexafungerp was well tolerated. Adverse events were primarily gastrointestinal and mild in severity. CONCLUSIONS: Ibrexafungerp provides a promising safe and efficacious oral treatment that mechanistically differs from current azole treatment options for acute VVC.

Phase 2 Randomized Study of Oral Ibrexafungerp Versus Fluconazole in Vulvovaginal Candidiasis.

BACKGROUND: Vulvovaginal candidiasis affects approximately 75% of women in their lifetime. Approved treatment options are limited to oral or topical azoles. Ibrexafungerp, a novel, first-in-class oral triterpenoid glucan synthase inhibitor, has demonstrated broad fungicidal Candida activity and a favorable tolerability profile. The primary objective of this dose-finding study was to identify the optimal dose of oral ibrexafungerp in patients with acute vulvovaginal candidiasis. METHODS: Patients with vulvovaginal signs and symptoms score ≥7 were randomized equally to 6 treatments groups: 5 treatment doses of oral ibrexafungerp or oral fluconazole 150 mg. The primary endpoint was the percentage of patients with a clinical cure (complete resolution of vulvovaginal signs and symptoms) at the test-of-cure visit (day 10). RESULTS: Overall, 186 patients were randomized into the 6 treatment groups. Results, using the modified intent-to-treat population (baseline positive culture), are reported for ibrexafungerp 300 mg twice daily (BID) for 1 day (n = 27), which was the dose selected for phase 3 studies, and fluconazole 150 mg for 1 day (n = 24). At day 10, the clinical cure rates for ibrexafungerp and fluconazole were 51.9% and 58.3%, respectively; at day 25, patients with no signs or symptoms were 70.4% and 50.0%, respectively. During the study ibrexafungerp patients required less antifungal rescue medications compared with fluconazole (3.7% vs 29.2%, respectively). Ibrexafungerp was well tolerated, with the most common treatment-related adverse events being mild gastrointestinal events. CONCLUSIONS: Ibrexafungerp is a well-tolerated novel antifungal with comparable efficacy to fluconazole in the treatment of acute vulvovaginal candidiasis. CLINICAL TRIALS REGISTRATION: NCT03253094.

Efficacy and safety of oral ibrexafungerp for the treatment of acute vulvovaginal candidiasis: a global phase 3, randomised, placebo-controlled superiority study (VANISH 306).

OBJECTIVE: To evaluate the efficacy and safety of ibrexafungerp versus placebo for acute vulvovaginal candidiasis (VVC) treatment. DESIGN: Global phase 3, randomised, placebo-controlled superiority study. SETTING: Study sites in the USA (n = 19) and Bulgaria (n = 18). POPULATION: Female patients aged ≥12 years with acute VVC and a vulvovaginal signs and symptoms (VSS) score ≥4 at baseline. METHODS: Patients were randomly assigned 2:1 to ibrexafungerp (300 mg twice for 1 day) or placebo. MAIN OUTCOME MEASURES: The primary endpoint was the percentage of patients with a clinical cure (VSS = 0) at the test-of-cure visit (day 11 ± 3). Secondary endpoints included percentages of patients with mycological eradication, clinical cure and mycological eradication (overall success), clinical improvement (VSS ≤1) at test-of-cure visit, and complete resolution of symptoms at follow-up visit (day 25 ± 4). RESULTS: At the test-of-cure visit, patients receiving ibrexafungerp had significantly higher rates of clinical cure (63.3% [119/188] versus 44.0% [37/84]; P = 0.007), mycological eradication (58.5% [110/188] versus 29.8% [25/84]; P < 0.001), overall success (46.1% [82/188] versus 28.4% [23/84]; P = 0.022) and clinical improvement (72.3% [136/188] versus 54.8% [46/84]; P = 0.01) versus those receiving placebo. Symptom resolution was sustained and further increased with ibrexafungerp (73.9%) versus placebo (52.4%) at follow-up (P = 0.001). Ibrexafungerp was generally well tolerated. Adverse events were primarily gastrointestinal and were mild to moderate in severity. CONCLUSIONS: Ibrexafungerp demonstrated statistical superiority over placebo for the primary and secondary endpoints. Ibrexafungerp is a promising novel, well-tolerated and effective oral 1-day treatment for acute VVC. TWEETABLE ABSTRACT: Ibrexafungerp is statistically superior to placebo for the treatment of vulvovaginal candidiasis.

In Vitro pH Activity of Ibrexafungerp against Fluconazole-Susceptible and -Resistant Candida Isolates from Women with Vulvovaginal Candidiasis.

The vaginal environment with candidiasis has a pH of 3.8 to 4.5 and this has a negative effect on the activity of antifungals. Ibrexafungerp was evaluated against 187 Candida isolates, including fluconazole-sensitive and -resistant Candida albicans, Candida glabrata, Candida krusei, Candida parapsilosis, and Candida tropicalis with the media adjusted to pH 7.0 and pH 4.5. Ibrexafungerp MIC values were not adversely affected when tested at pH 4.5. Ibrexafungerp exhibited significant activity against all isolates at pH 4.5.

A Second-Generation Fungerp Analog, SCY-247, Shows Potent In Vitro Activity against Candida auris and Other Clinically Relevant Fungal Isolates.

Due to the increase of antifungal drug resistance and difficulties associated with drug administration, new antifungal agents for invasive fungal infections are needed. SCY-247 is a second-generation fungerp antifungal compound that interferes with the synthesis of the fungal cell wall polymer ß-(1,3)-d-glucan. We conducted an extensive antifungal screen of SCY-247 against yeast and mold strains compared with the parent compound ibrexafungerp (IBX; formerly SCY-078) to evaluate the in vitro antifungal properties of SCY-247. SCY-247 demonstrated similar activity to IBX against all of the organisms tested. Moreover, SCY-247 showed a higher percentage of fungicidal activity against the panel of yeast and mold isolates than IBX. Notably, SCY-247 showed considerable antifungal properties against numerous strains of Candida auris Additionally, SCY-247 retained its antifungal activity when evaluated in the presence of synthetic urine, indicating that SCY-247 maintains activity and structural stability under environments with decreased pH levels. Finally, a time-kill study showed SCY-247 has potent anti-Candida, -Aspergillus, and -Scedosporium activity. In summary, SCY-247 has potent antifungal activity against various fungal species, indicating that further studies on this fungerp analog are warranted.

A Second-Generation Fungerp Analog, SCY-247, Shows Potent In Vivo Activity in a Murine Model of Hematogenously Disseminated Candida albicans.

Echinocandins are a first-line therapy for Candida infections through their ability to inhibit the synthesis of polymer ß-(1,3)-d-glucan. However, there has been an emergence of multidrug-resistant fungal species necessitating the development of novel antifungal agents to combat invasive fungal infections. SCY-247, a second-generation glucan synthase inhibitor of the triterpenoid class (fungerps), is currently being developed as a potential therapy option. We determined the pharmacokinetics (PKs) of SCY-247 following oral (gavage) administration in mice and evaluated the efficacy of SCY-247 in a murine model of hematogenously disseminated candidiasis caused by Candida albicans Plasma concentrations of SCY-247 were measurable through the last collected time point in all dose groups. Mean concentrations of SCY-247 increased with dose levels, with concentrations of SCY-247 higher after multiple doses than after a single dose. Treatment with SCY-247 resulted in decreased fungal burden and improvement in survival rates against C. albicans disseminated infection. Treatment with 10 mg/kg of body weight of SCY-247 showed a significant reduction in CFU compared with the untreated control (3-log decrease on average) (P = 0.008). Similarly, 40 mg/kg SCY-247 demonstrated a statistically significant reduction in kidney CFU compared with untreated mice (average log CFU ± SD of 2.38 ± 2.58 versus 6.26 ± 0.51; P = 0.001). Mice treated with SCY-247 at 40 mg/kg exhibited a 100% survival rate at the end of the study, contrasted with 62.5% (5 of 8) survival rate in untreated mice. The results of this investigation indicate that SCY-247 is a promising novel anti-fungal agent with activity against Candida infections.

Ibrexafungerp Demonstrates In Vitro Activity against Fluconazole-Resistant Candida auris and In Vivo Efficacy with Delayed Initiation of Therapy in an Experimental Model of Invasive Candidiasis.

Candida auris is an emerging pathogen that has rapidly spread to many countries on multiple continents. Invasive infections caused by this species are associated with significant mortality, and treatment options are limited due to antifungal resistance. Ibrexafungerp is the first-in-class member of the triterpenoids, which inhibit the production of (1,3)-ß-d-glucan and can be administered orally. We evaluated the in vitro activity and in vivo efficacy of ibrexafungerp against C. auris Antifungal susceptibility was tested by broth microdilution against 54 C. auris isolates. Neutropenic mice were intravenously infected with a clinical isolate, and a 7-day treatment course was begun 24 h postinoculation with vehicle control, ibrexafungerp (20, 30, and 40 mg/kg orally twice daily), fluconazole (20 mg/kg orally once daily), or caspofungin (10 mg/kg intraperitoneally once daily). Fungal burden was assessed by colony counts in the kidneys on day 8 and on day 21 or as mice became moribund in the survival arm. Ibrexafungerp demonstrated consistent activity, with MICs ranging between 0.25 and 2 µg/ml against all isolates. Marked improvements in survival were observed in mice treated with the higher doses of ibrexafungerp and caspofungin. Similarly, reductions in kidney fungal burden were also observed in these groups. No improvements in survival or reductions in fungal burden were observed with fluconazole, consistent with the in vitro resistance of the isolate used to establish infection to this azole. These results demonstrate that ibrexafungerp is effective in vivo against C. auris even when the start of therapy is delayed.

Ibrexafungerp: An orally active ß-1,3-glucan synthesis inhibitor.

We previously reported medicinal chemistry efforts that identified MK-5204, an orally efficacious ß-1,3-glucan synthesis inhibitor derived from the natural product enfumafungin. Further extensive optimization of the C2 triazole substituent identified 4-pyridyl as the preferred replacement for the carboxamide of MK-5204, leading to improvements in antifungal activity in the presence of serum, and increased oral exposure. Reoptimizing the aminoether at C3 in the presence of this newly discovered C2 substituent, confirmed that the (R) t-butyl, methyl aminoether of MK-5204 provided the best balance of these two key parameters, culminating in the discovery of ibrexafungerp, which is currently in phase III clinical trials. Ibrexafungerp displayed significantly improved oral efficacy in murine infection models, making it a superior candidate for clinical development as an oral treatment for Candida and Aspergillus infections.

Efficacy of Ibrexafungerp (SCY-078) against Candida auris in an In Vivo Guinea Pig Cutaneous Infection Model.

Candida auris has been shown to have a high risk of skin colonization in hospitalized patients, possibly contributing to nosocomial spread. In a guinea pig skin model, animals were evaluated for clinical appearance, tissue fungal burden, histology, and pharmacokinetics. Oral dosing with 10 mg/kg ibrexafungerp (IBX) reduced the severity of lesions and significantly reduced the C. auris fungal burden in infected animals compared with untreated controls. This indicates promise for use of IBX in controlling skin infection and colonization of hospitalized patients.

Combination Therapy with Ibrexafungerp (Formerly SCY-078), a First-in-Class Triterpenoid Inhibitor of (1→3)-ß-d-Glucan Synthesis, and Isavuconazole for Treatment of Experimental Invasive Pulmonary Aspergillosis.

Ibrexafungerp (formerly SCY-078) is a semisynthetic triterpenoid and potent (1→3)-ß-d-glucan synthase inhibitor. We investigated the in vitro activity, pharmacokinetics, and in vivo efficacy of ibrexafungerp (SCY) alone and in combination with antimold triazole isavuconazole (ISA) against invasive pulmonary aspergillosis (IPA). The combination of ibrexafungerp and isavuconazole in in vitro studies resulted in additive and synergistic interactions against Aspergillus spp. Plasma concentration-time curves of ibrexafungerp were compatible with linear dose proportional profile. In vivo efficacy was studied in a well-established persistently neutropenic New Zealand White (NZW) rabbit model of experimental IPA. Treatment groups included untreated control (UC) rabbits and rabbits receiving ibrexafungerp at 2.5 (SCY2.5) and 7.5 (SCY7.5) mg/kg of body weight/day, isavuconazole at 40 (ISA40) mg/kg/day, or combinations of SCY2.5+ISA40 and SCY7.5+ISA40. The combination of SCY+ISA produced an in vitro synergistic interaction. There were significant in vivo reductions of residual fungal burden, lung weights, and pulmonary infarct scores in SCY2.5+ISA40, SCY7.5+ISA40, and ISA40 treatment groups versus those of the SCY2.5-treated, SCY7.5-treated, and UC (P < 0.01) groups. Rabbits treated with SCY2.5+ISA40 and SCY7.5+ISA40 had prolonged survival in comparison to that of the SCY2.5-, SCY7.5-, ISA40-treated, or UC (P < 0.05) groups. Serum galactomannan index (GMI) and (1→3)-ß-d-glucan levels significantly declined in animals treated with the combination of SCY7.5+ISA40 in comparison to those of animals treated with SCY7.5 or ISA40 (P < 0.05). Ibrexafungerp and isavuconazole combination demonstrated prolonged survival, decreased pulmonary injury, reduced residual fungal burden, and lower GMI and (1→3)-ß-d-glucan levels in comparison to those of single therapy for treatment of IPA. These findings provide an experimental foundation for clinical evaluation of the combination of ibrexafungerp and an antimold triazole for treatment of IPA.

In Vitro Activity of Ibrexafungerp (SCY-078) against Candida auris Isolates as Determined by EUCAST Methodology and Comparison with Activity against C. albicans and C. glabrata and with the Activities of Six Comparator Agents.

Ibrexafungerp (SCY-078) is a novel first-in-class antifungal agent targeting glucan synthase. Candida auris is an emerging multidrug-resistant species that has caused outbreaks on five continents. We investigated the in vitro activity of ibrexafungerp against C. auris by applying EUCAST E.Def 7.3.1 methodology. C. albicans and C. glabrata, as well as anidulafungin, micafungin, amphotericin B, fluconazole, voriconazole, and isavuconazole, were included as comparators. Three C. auris reference strains (CBS12372, CBS12373, and CBS10913) and 122 C. auris, 16 C. albicans, and 16 C. glabrata isolates were evaluated. C. albicans ATCC 64548, C. parapsilosis ATCC 22019, and C. krusei ATCC 6258 served as quality control strains. Echinocandin-resistant isolates were fks sequenced. MIC ranges and modal MIC and MIC50 values were determined. Wild-type upper limits (the upper MIC value where the wild-type distribution ends) were determined according to EUCAST principles for setting ECOFFs. Nine repetitions of three QC strains and MICs for C. albicans and C. glabrata yielded narrow MIC ranges with modal MICs in agreement with established EUCAST modal MICs, confirming a robust test performance. The ibrexafungerp MICs against C. auris isolates displayed a Gaussian distribution with a modal MIC (range) of 0.5 mg/liter (0.06 to 2 mg/liter), suggesting uniform susceptibility. Of 122 isolates, 8 were echinocandin resistant and harbored the S639F Fks1 alteration. All but one were fluconazole resistant, and the MIC distributions for voriconazole and isavuconazole were multimodal confirming variable susceptibility. Ibrexafungerp demonstrated promising activity against C. auris, including isolates resistant to echinocandins and/or other agents. The MICs were similar to those reported for the Clinical and Laboratory Standards Institute method, suggesting that a common clinical breakpoint may be appropriate.