Outcomes by Candida spp. in the ReSTORE Phase 3 trial of rezafungin versus caspofungin for candidemia and/or invasive candidiasis

Rezafungin is a long-acting, intravenously administered echinocandin for the treatment of candidemia and invasive candidiasis (IC). Non-inferiority of rezafungin vs caspofungin for the treatment of adults with candidemia and/or IC was demonstrated in the Phase 3 ReSTORE study based on the primary endpoints of day 14 global cure and 30-day all-cause mortality. Here, an analysis of ReSTORE data evaluating efficacy outcomes by baseline Candida species is described. Susceptibility testing was performed for Candida species using the Clinical and Laboratory Standards Institute reference broth microdilution method. There were 93 patients in the modified intent-to-treat population who received rezafungin; 94 received caspofungin. Baseline Candida species distribution was similar in the two treatment groups; C. albicans (occurring in 41.9% and 42.6% of patients in the rezafungin and caspofungin groups, respectively), C. glabrata (25.8% and 26.6%), and C. tropicalis (21.5% and 18.1%) were the most common pathogens. Rates of global cure and mycological eradication at day 14 and day 30 all-cause mortality by Candida species were comparable in the rezafungin and caspofungin treatment groups and did not appear to be impacted by minimal inhibitory concentration (MIC) values for either rezafungin or caspofungin. Two patients had baseline isolates with non-susceptible MIC values (both in the rezafungin group: one non-susceptible to rezafungin and one to caspofungin, classified as intermediate); both were candidemia-only patients in whom rezafungin treatment was successful based on the day 30 all-cause mortality endpoint. This analysis of ReSTORE demonstrated the efficacy of rezafungin for candidemia and IC in patients infected with a variety of Candida species.

Critical appraisal beyond clinical guidelines for intraabdominal candidiasis

BACKGROUND

Regardless of the available antifungals, intraabdominal candidiasis (IAC) mortality continues to be high and represents a challenge for clinicians.

MAIN BODY

This opinion paper discusses alternative antifungal options for treating IAC. This clinical entity should be addressed separately from candidemia due to the peculiarity of the required penetration of antifungals into the peritoneal cavity. Intraabdominal concentrations may be further restricted in critically ill patients where pathophysiological facts alter normal drug distribution. Echinocandins are recommended as first-line treatment in guidelines for invasive candidiasis. However, considering published data, our pharmacodynamic analysis suggests the required increase of doses, postulated by some authors, to attain adequate pharmacokinetic (PK) levels in peritoneal fluid. Given the limited evidence in the literature on PK/PD-based treatments of IAC, an algorithm is proposed to guide antifungal treatment. Liposomal amphotericin B is advocated as first-line therapy in patients with sepsis/septic shock presenting candidemia or endophthalmitis, or with prior exposure to echinocandins and/or fluconazole, or with infections by Candida glabrata. Other situations and alternatives, such as new compounds or combination therapy, are also analysed.

CONCLUSION

There is a critical need for more robust clinical trials, studies examining patient heterogeneity and surveillance of antifungal resistance to enhance patient care and optimise treatment outcomes. Such evidence will help refine the existing guidelines and contribute to a more personalised and effective approach to treating this serious medical condition. Meanwhile, it is suggested to broaden the consideration of other options, such as liposomal amphotericin B, as first-line treatment until the results of the fungogram are available and antifungal stewardship could be implemented to prevent the development of resistance.

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.

PK/PD modeling and simulation of the in vitro activity of the combinations of isavuconazole with echinocandins against Candida auris

In vitro combination of echinocandins and isavuconazole against the emerging species Candida auris is mainly synergistic. However, this combination has not been evaluated in clinical settings. A pharmacokinetic/pharmacodynamic modeling and simulation approach based on in vitro data may be helpful to further study the therapeutic potential of these combinations. Therefore, the aims of this study were to characterize the time course of growth and killing of C. auris in response to the combination of the three approved echinocandins and isavuconazole using a semimechanistic model and to perform model-based simulations in order to predict the in vivo response to combination therapy. In vitro static time-kill curve data for isavuconazole and echinocandins combinations against six blood isolates of C. auris were best modeled considering the total killing of the fungal population as dependent on the additive effects of both drugs. Once assessed, the predictive performance of the model using simulations of different dosing and fungal susceptibility scenarios were conducted. Model-based simulations revealed that none of the combinations at standard or higher dosages would be effective against the studied isolates of C. auris and it was predicted that the combinations of isavuconazole with anidulafungin or caspofungin would be effective for minimum inhibitory concentrations up to 0.03 and 0.06 mg/L respectively, whereas the combination with micafungin would lead to treatment failure. The current approach highlights the importance of bridging the in vitro results to the clinic.

Rezafungin versus caspofungin for treatment of candidaemia and invasive candidiasis (ReSTORE): a multicentre, double-blind, double-dummy, randomised phase 3 trial

BACKGROUND

Rezafungin is a next-generation, once-a-week echinocandin in development for the treatment of candidaemia and invasive candidiasis and for the prevention of invasive fungal disease caused by Candida, Aspergillus, and Pneumocystis spp after blood and marrow transplantation. We aimed to compare the efficacy and safety of intravenous rezafungin versus intravenous caspofungin in patients with candidaemia and invasive candidiasis.

METHODS

ReSTORE was a multicentre, double-blind, double-dummy, randomised phase 3 trial done at 66 tertiary care centres in 15 countries. Adults (≥18 years) with systemic signs and mycological confirmation of candidaemia or invasive candidiasis were eligible for inclusion and randomly assigned (1:1) to receive intravenous rezafungin once a week (400 mg in week 1, followed by 200 mg weekly, for a total of two to four doses) or intravenous caspofungin (70 mg loading dose on day 1, followed by 50 mg daily) for no more than 4 weeks. The primary endpoints were global cure (consisting of clinical cure, radiological cure, and mycological eradication) at day 14 for the European Medical Agency (EMA) and 30-day all-cause mortality for the US Food and Drug Administration (FDA), both with a target non-inferiority margin of 20%, assessed in the modified intention-to-treat population (all patients who received one or more doses of study drug and had documented Candida infection based on a culture from blood or another normally sterile site obtained within 96 h before randomisation). Safety was evaluated by the incidence and type of adverse events and deaths in the safety population, defined as all patients who received any amount of study drug. The trial is registered with ClinicalTrials.gov, NCT03667690, and is complete.

FINDINGS

Between Oct 12, 2018, and Aug 29, 2021, 222 patients were screened for inclusion, and 199 patients (118 [59%] men; 81 [41%] women; mean age 61 years [SD 15·2]) were randomly assigned (100 [50%] patients to the rezafungin group and 99 [50%] patients to the caspofungin group). 55 (59%) of 93 patients in the rezafungin group and 57 (61%) of 94 patients in the caspofungin group had a global cure at day 14 (weighted treatment difference -1·1% [95% CI -14·9 to 12·7]; EMA primary endpoint). 22 (24%) of 93 patients in the rezafungin group and 20 (21%) of 94 patients in the caspofungin group died or had an unknown survival status at day 30 (treatment difference 2·4% [95% CI -9·7 to 14·4]; FDA primary endpoint). In the safety analysis, 89 (91%) of 98 patients in the rezafungin group and 83 (85%) of 98 patients in the caspofungin group had at least one treatment-emergent adverse event. The most common treatment-emergent adverse events that occurred in at least 5% of patients in either group were pyrexia, hypokalaemia, pneumonia, septic shock, and anaemia. 55 (56%) patients in the rezafungin group and 52 (53%) patients in the caspofungin group had serious adverse events.

INTERPRETATION

Our data show that rezafungin was non-inferior to caspofungin for the primary endpoints of day-14 global cure (EMA) and 30-day all-cause mortality (FDA). Efficacy in the initial days of treatment warrants evaluation. There were no concerning trends in treatment-emergent or serious adverse events. These phase 3 results show the efficacy and safety of rezafungin and support its ongoing development.

FUNDING

Cidara Therapeutics and Mundipharma.

Comparative efficacy and safety of systemic antifungal agents for candidemia: a systematic review with network meta-analysis and multicriteria acceptability analyses

AIM

Invasive candidiasis is the most common fungal infection in patients attending health services and is associated with high mortality rates and prolonged hospital stay. The aim of this review was to evaluate and compare efficacy and safety of antifungal agents for the treatment of candidemia.

METHODS

A systematic review with network meta-analysis (NMA), surface under the cumulative ranking analysis (SUCRA) and stochastic multicriteria acceptability analyses (SMAA) was performed (PROSPERO-CRD42020149264). Searches were conducted in PubMed and Scopus (Nov-2021). Randomised controlled trials evaluating the effect of oral antifungals (any dose or regimen) on mycological cure, discontinuation rates and adverse events were included.

RESULTS

Overall, 13 trials (n=3632) were analysed. There were no significant differences between therapies for the efficacy outcomes; however, caspofungin (50-150 mg), rezafungin (200-400 mg) and micafungin (100-150 mg) had higher rates of clinical and mycological responses (SUCRA overall response >60%) and were considered the most promising therapies. Fluconazole (400 mg) rated worst for overall response (17%). Rezafungin (200-400 mg) and micafungin (100 mg) were associated with lower discontinuation rates (<40%). Conventional amphotericin B (0.6-0.7 mg/kg) was more likely to be discontinued (odds ratio [OR] 0.08; 95% credibility interval [CrI] 0.00-0.95 vs. caspofungin 150 mg) and may impair liver function (87%).

CONCLUSION

Echinocandins are recommended as first-line treatments for invasive candidiasis following a priority order of caspofungin then micafungin. Rezafungin, an echinocandin under development, represents a potential option that should be further investigated. Azoles and liposomal amphotericin B can be used as second-line treatments in cases of fungal resistance or hypersensitivity.

Postantifungal Effect of Antifungal Drugs against Candida: What Do We Know and How Can We Apply This Knowledge in the Clinical Setting?

The study of the pharmacological properties of an antifungal agent integrates the drug pharmacokinetics, the fungal growth inhibition, the fungicidal effect and the postantifungal activity, laying the basis to guide optimal dosing regimen selection. The current manuscript reviews concepts regarding the postantifungal effect (PAFE) of the main classes of drugs used to treat Candida infections or candidiasis. The existence of PAFE and its magnitude are highly dependent on both the fungal species and the class of the antifungal agent. Therefore, the aim of this article was to compile the information described in the literature concerning the PAFE of polyenes, azoles and echinocandins against the Candida species of medical interest. In addition, the mechanisms involved in these phenomena, methods of study, and finally, the clinical applicability of these studies relating to the design of dosing regimens were reviewed and discussed. Additionally, different factors that could determine the variability in the PAFE were described. Most PAFE studies were conducted in vitro, and a scarcity of PAFE studies in animal models was observed. It can be stated that the echinocandins cause the most prolonged PAFE, followed by polyenes and azoles. In the case of the triazoles, it is worth noting the inconsistency found between in vitro and in vivo studies.

Human plasma protein levels alter the in vitro antifungal activity of caspofungin: An explanation to the effect in critically ill?

BACKGROUND

Recent studies have shown low caspofungin concentrations in critically ill patients. In some patients, the therapeutic target, area under the total plasma concentration curve in relation to the minimal inhibition concentration (AUC_tot /MIC), seems not to be achieved and therapeutic drug monitoring (TDM) has been proposed. Caspofungin is highly protein-bound and the effect of reduced plasma protein levels on pharmacodynamics has not been investigated.

OBJECTIVES

Fungal killing activity of caspofungin in vitro was investigated under varying levels of human plasma protein.

METHODS

Time-kill studies were performed with clinically relevant caspofungin concentrations of 1-9 mg/L on four blood isolates of C. glabrata, three susceptible and one strain with reduced susceptibility, in human plasma and plasma diluted to 50% and 25% using Ringer's acetate.

RESULTS

Enhanced fungal killing of the three susceptible strains was observed in plasma with lower protein content (p < .001). AUC_tot /MIC required for a 1 log₁₀ CFU/ml kill at 24 h in 50% and 25% plasma was reduced with 36 + 12 and 80 + 9%, respectively. The maximum effect was seen at total caspofungin concentrations of 4-9 × MIC. For the strain with reduced susceptibility, growth was significantly decreased at lower protein levels.

CONCLUSIONS

Reduced human plasma protein levels increase the antifungal activity of caspofungin in vitro, most likely by increasing the free concentration. Low plasma protein levels in critically ill patients with candidemia might explain a better response to caspofungin than expected from generally accepted target attainment and should be taken into consideration when assessing TDM based on total plasma concentrations.

Pharmacokinetics/Pharmacodynamics of caspofungin in plasma and peritoneal fluid of liver transplant recipients

Background: The weaker diffusion of echinocandins in the peritoneal fluid (PF) could promote Candida resistant isolates. The aim of this study was to analyse the pharmacokinetics/pharmacodynamics (PK/PD) of caspofungin in plasma and PF of liver transplant recipients.Methods: Liver transplant patients received caspofungin as postoperative prophylaxis. Caspofungin concentrations were quantified in plasma and in PF on Days 1, 3 and 8. Data were analysed using non-linear mixed-effect modelling and Monte Carlo simulations. Area under curve (AUC) in plasma and PF were simulated under three dosing regimens. Probabilities of target attainment (PTA) were calculated using fAUC_0-24/minimal inhibitory concentration (MIC) ratios with MICs ranging from 0.008 to 8 mg/litre. All the patients included were monitored weekly for Candida colonisation and for Candida infections.Results: Twenty patients were included. Median daily dose of caspofungin was 0.81 mg/kg. Plasma (n=395) and peritoneal (n=50) concentrations at steady state were available. A two-compartment model with first-order absorption and elimination was described. Our two-compartment model with first-order absorption and elimination model produced an effective PK/PD relationship in plasma, achieving a PTA ≥90% and MIC ranging from 0.008 to 0.12 mg/L for C. albicans and glabrata. In PF, PTAs at D8 were only optimal for a MIC of 0.008 in patients weighing 60 kg under the three dosing regimens. Among the 16 patients colonized, all MIC values were below the maximal concentration (Cmax) in plasma but not in PF.Conclusion: Peritoneal concentrations of caspofungin were low. Simulations showed that the PTA for Candida spp. in PF were not optimal, that might suggesting a potential risk of resistance.

Population Pharmacokinetics of Rezafungin in Patients with Fungal Infections

Rezafungin is a novel antifungal agent of the echinocandin class with potent activity against species of Candida and Aspergillus, including subsets of resistant strains, and Pneumocystis jirovecii. The objective of this analysis was to develop a population pharmacokinetic (PK) model to characterize the disposition of rezafungin in plasma following intravenous (IV) administration in healthy volunteers and in patients with candidemia and/or invasive candidiasis. The population PK model was based on a previous model from phase 1 data; formal covariate analyses were conducted to identify any relationships between subject characteristics and rezafungin PK variability. A four-compartment model with linear elimination and zero-order drug input provided a robust fit to the pooled data. Several statistically significant relationships between subject descriptors (sex, infection status, serum albumin, and body surface area [BSA]) and rezafungin PK parameters were identified, but none were deemed clinically relevant. Previous dose justification analyses conducted using data from phase 1 subjects alone are expected to remain appropriate. The final model provided a precise and unbiased fit to the observed concentrations and can be used to reliably predict rezafungin PK in infected patients.

[Individualized antifungal therapy in critically ill patients with invasive fungal infection]

Invasive candidiasis (IC) is the most common invasive fungal infection (IFI) affecting critically ill patients, followed by invasive pulmonary aspergillosis (IPA). International guidelines provide different recommendations for a first-line antifungal therapy and, in most of them, echinocandins are considered the first-line treatment for IC, and triazoles are so for the treatment of IPA. However, liposomal amphotericinB (L-AmB) is still considered a second-line therapy for both clinical entities. Although in the last decade the management of IFI has improved, several controversies persist. The antifungal drugs currently available may have a suboptimal activity, or be wrongly used in certain IFI involving critically ill patients. The aim of this review is to analyze when to provide individualized antifungal therapy to critically ill patients suffering from IFI, emphasizing the role of L-AmB. Drug-drug interactions, the clinical status, infectious foci (peritoneal candidiasis is discussed), the fungal species involved, and the need of monitoring the concentration of the antifungal drug in the patient are considered.

Antimycotic Drugs and their Mechanisms of Resistance to Candida Species

Fungal infections have shown an upsurge in recent decades, which is mainly because of the increasing number of immunocompromised patients and the occurrence of invasive candidiasis has been found to be 7-15 fold greater than that of invasive aspergillosis. The genus Candida comprises more than 150 distinct species, however, only a few of them are found to be pathogenic to humans. Mortality rates of Candida species are found to be around 45% and the reasons for this intensified mortality are inefficient diagnostic techniques and unfitting initial treatment strategies. There are only a few antifungal drug classes that are employed for the remedy of invasive fungal infections. which include azoles, polyenes, echinocandins, and pyrimidine analogs. During the last 2-3 decades, the usage of antifungal drugs has increased several folds due to which the reports of escalating antifungal drug resistance have also been recorded. The resistance is mostly to the triazole- based compounds. Due to the occurrence of antifungal drug resistance, the success rates of treatment have been reduced as well as major changes have been observed in the frequency of fungal infections. In this review, we have summarized the major molecular mechanisms for the development of antifungal drug resistance.

Mind the gaps: challenges in the clinical management of invasive candidiasis in critically ill patients

PURPOSE OF REVIEW

Strict adherence to clinical practice guidelines is recognized to improve outcomes but the inconvenient truth is that only a small subset of what is done in medicine has been tested in appropriate, well designed studies. In this article, we aim to review controversial aspects of the clinical management of invasive candidiasis recommended by guidelines.

RECENT FINDINGS

Despite still being recommended by guidelines, we fail to identify a single randomized clinical trial documenting that the use of antifungal drugs in high-risk critically ill patients without microbiologic documentation of Candida infection decreases mortality. Regarding deep-seated Candida infections, most cohort studies of patients with candidemia found less than 5% of patients developed endophthalmitis and endocarditis. In this scenario, it is reasonable to reconsider routine universal screening of both complications in candidemic patients. Finally, a large number of studies have shown that critically ill patients usually have lower echinocandin exposure when compared with other populations. We need more data on the clinical relevance of this finding.

SUMMARY

We need robust studies to validate new strategies for the clinical management of candidemia in ICU, including: the use of fungal biomarkers in the early initiation or interruption of antifungal therapy in high-risk patients to replace the conventional empirical antifungal therapy driven by predictive rules; validation of targeted screening of eye infection and endocarditis with the aid of fungal biomarkers only in high-risk patients; we should clarify if higher doses of candins are necessary to treat invasive candidiasis in critically ill patients, especially in the case of intra-abdominal infections where drug penetration is suboptimal.

Rezafungin versus Caspofungin in a Phase 2, Randomized, Double-Blind Study for the Treatment of Candidemia and Invasive Candidiasis- The STRIVE Trial

Background

Rezafungin (RZF) is a novel echinocandin exhibiting distinctive pharmacokinetics/pharmacodynamics. STRIVE was a phase 2, double-blind, randomized trial designed to compare the safety and efficacy of RZF once weekly (QWk) to caspofungin (CAS) once daily for treatment of candidemia and/or invasive candidiasis (IC).

Methods

Adults with systemic signs and mycological confirmation of candidemia and/or IC were randomized to RZF 400 mg QWk (400 mg), RZF 400 mg on week 1 then 200 mg QWk (400/200 mg), or CAS 70 mg as a loading dose followed by 50 mg daily for ≤4 weeks. Efficacy assessments included overall cure (resolution of signs of candidemia/IC + mycological eradication) at day 14 (primary endpoint), investigator-assessed clinical response at day 14, and 30-day all-cause mortality (ACM) (secondary endpoints), and time to negative blood culture. Safety was evaluated by adverse events and ACM through follow-up.

Results

Of 207 patients enrolled, 183 were in the microbiological intent-to-treat population (~21% IC). Overall cure rates were 60.5% (46/76) for RZF 400 mg, 76.1% (35/46) for RZF 400/200 mg, and 67.2% (41/61) for CAS; investigator-assessed clinical cure rates were 69.7% (53/76), 80.4% (37/46), and 70.5% (43/61), respectively. In total, 30-day ACM was 15.8% for RZF 400 mg, 4.4% for RZF 400/200 mg, and 13.1% for CAS. Candidemia was cleared in 19.5 and 22.8 hours in RZF and CAS patients, respectively. No concerning safety trends were observed; ACM through follow-up was 15.2% (21/138) for RZF and 18.8% (13/69) for CAS.

Conclusions

RZF was safe and efficacious in the treatment of candidemia and/or IC.

Clinical Trials Registration

NCT02734862

Nonstationary Pharmacokinetics of Caspofungin in ICU Patients

Standard dosing of caspofungin in critically ill patients has been reported to result in lower drug exposure, which can lead to subtherapeutic 24-h area under the curve to MIC (AUC_0-24/MIC) ratios. The aim of the study was to investigate the population pharmacokinetics of caspofungin in a cohort of 30 intensive care unit patients with a suspected invasive fungal infection, with a large proportion of patients requiring extracorporeal therapies, including extracorporeal membrane oxygenation (ECMO) and continuous renal replacement therapy (CRRT). Caspofungin was administered as empirical 70 mg antifungal therapy administered intravenously (i.v.) on the first day and at 50 mg i.v. on the consecutive days once daily, and the concentrations were measured after three subsequent doses. Population pharmacokinetic data were analyzed by nonlinear mixed-effects modeling. The pharmacokinetics of caspofungin was described by two-compartment model. A particular drift of the individual clearance (CL) and the volume of distribution of the central compartment (V ₁) with time was discovered and described by including three separate typical values of CL and V ₁ in the final model. The typical CL values at days 1, 2, and 3 were 0.563 liters/h (6.7% relative standard error [6.7%RSE]), 0.737 liters/h (6.1%RSE), and 1.01 liters/h (9.1%RSE), respectively. The change in parameters with time was not explained by any of the recorded covariates. Increasing clearance with subsequent doses was associated with a clinically relevant decrease in caspofungin exposure (>20%). The use of ECMO, CRRT, albumin concentration, and other covariates did not significantly affect caspofungin pharmacokinetics. Additional pharmacokinetic studies are urgently required to assess the possible lack of acquiring steady-state and suboptimal concentrations of the drug in critically ill patients. (This study has been registered at ClinicalTrials.gov under identifier NCT03399032.).

Relative Frequency of Paradoxical Growth and Trailing Effect with Caspofungin, Micafungin, Anidulafungin, and the Novel Echinocandin Rezafungin against Candida Species

Rezafungin is a next-generation echinocandin that has favorable pharmacokinetic properties. We compared the occurrence of paradoxical growth (PG) and trailing effect (TE) characteristics to echinocadins with rezafungin, caspofungin, micafungin and anidulafungin using 365 clinical Candida isolates belonging to 13 species. MICs were determined by BMD method according to CLSI (M27 Ed4). Disconnected growth (PG plus TE) was most frequent with caspofungin (49.6%), followed by anidulafungin (33.7%), micafungin (25.7%), while it was least frequent with rezafungin (16.9%). PG was relatively common in the case of caspofungin (30.1%) but was rare in the case of rezafungin (3.0%). C. tropicalis, C. albicans, C. orthopsilosis and C. inconspicua exhibited PG most frequently with caspofungin, micafungin or anidulafungin. PG never occurred in the case of C. krusei isolates. Against C. tropicalis and C. albicans, echinocandins frequently showed PG after 24 h followed by TE after 48 h. All four echinocandins exhibited TE for the majority of C. auris and C. dubliniensis isolates. Disconnected growth was common among Candida species and was echinocandin- and species-dependent. In contrast to earlier echinocandins, PG was infrequently found with rezafungin.

Influence of Body Weight Category on Outcomes in Candidemia Patients Treated With Anidulafungin

BACKGROUND

Case reports and pharmacokinetic data suggest off-label echinocandin dosing may be needed to reach adequate serum concentrations in obese patients. Few outcome studies exist evaluating this population.

OBJECTIVES

Of this study were to (1) determine the association of body mass index (BMI) with clinical outcomes of candidemia patients on standard doses of anidulafungin and (2) characterize fungal infections by body weight.

METHODS

A retrospective cohort was conducted to evaluate hospitalized patients treated for candidemia with anidulafungin at Food and Drug Administration-labeled dosing for at least 72 hours from January 1, 2014, through January 31, 2018. Candidemia was diagnosed by blood culture or T2 magnetic resonance (T2MR). Patients were compared according to BMI category.

RESULTS

One hundred seventy-three patients were included. Candida albicans and Candida glabrata were identified in 58 (33%) and 57 (33%) patients, respectively. Mortality was comparable according to BMI category: 4 (36.4%) underweight, 8 (25.8%) normal weight, 16 (32.0%) overweight, 20 (33.9%) obese, and 7 (31.8%) morbidly obese, P = .976. Variables associated with mortality included: severe sepsis (adjusted odds ratio [OR] = 5.1, 95% CI: 1.7-14.8) and liver disease (adjusted OR = 3.2, 95% CI: 1.1-9.4). Variables that were protective of mortality included: line removal (adjusted OR = 0.05, 95% CI: 0.02-0.2) and receipt of anidulafungin for at least 5 days (adjusted OR = 0.35, 95% CI: 0.15-0.8).

CONCLUSION

There was no difference detected in mortality among patients with candidemia across BMI category. Larger studies are needed to confirm whether standard doses of anidulafungin are sufficient for candidemia in obese patients.

Antifungal therapeutic drug monitoring: focus on drugs without a clear recommendation

BACKGROUND

The goal of therapeutic drug monitoring (TDM) is to determine the appropriate exposure of difficult-to-manage medications to optimize the clinical outcomes in patients in various clinical situations. Concerning antifungal treatment, and knowing that this procedure is expensive and time-consuming, TDM is particularly recommended for certain systemic antifungals: i.e., agents with a well-defined exposure-response relationship and unpredictable pharmacokinetic profile or narrow therapeutic index. Little evidence supports the routine use of TDM for polyenes (amphotericin B), echinocandins, fluconazole or new azoles such as isavuconazole, despite the fact that a better understanding of antifungal exposure may lead to a better response.

AIMS

The aim of this work is to review published pharmacokinetic/pharmacodynamic data on systemically administered antifungals, focusing on those for which monitoring is not routinely recommended by experts.

SOURCES

A MEDLINE search of the literature in English was performed introducing the following search terms: amphotericin B, fluconazole, itraconazole, voriconazole, posaconazole, triazoles, caspofungin, micafungin, anidulafungin, echinocandins, pharmacokinetics, pharmacodynamics, and therapeutic drug monitoring. Review articles and guidelines were also screened.

CONTENT

This review collects different pharmacokinetic/pharmacodynamic aspects of systemic antifungals and summarizes recent threshold values for clinical outcomes and adverse events. Although for polyenes, echinocandins, fluconazole and isavuconazole extensive clinical validation is still required for a clear threshold and a routine monitoring recommendation, particular points such as liposome structure or complex pathophysiological conditions affecting final exposure are discussed. For the rest, their better-defined exposure-response/toxicity relationships allow access to useful threshold values and to justify routine monitoring. Additionally, clinical data are needed to better define thresholds that can minimize the development of antifungal resistance.

IMPLICATIONS

General TDM for all systemic antifungals is not recommended; however, this approach may help to establish an adequate antifungal exposure for a favourable response, prevention of toxicity or development of resistance in special clinical circumstances.

Caspofungin PK in critically ill patients after the first and fourth doses: suggestions for therapeutic drug monitoring?

We describe caspofungin pharmacokinetics (PK) after the first and fourth doses in 20 critically ill septic patients. Monte Carlo simulation was used to analyze the probability of target attainment (PTA) (AUC/MIC > 865) for Candida spp. Caspofungin concentrations were analyzed by HPLC in plasma and urine. A great variability in PK parameters was observed after both doses. Patients were divided in two groups according to their AUC values (AUC ≤ 75 mg h/L cut-off). In the low-AUC group Cmax, Cmin and AUC were lower, while Vd and Cl were higher than in the high-AUC group (p < 0.05, both at day 1 and 4). The mean 24-h urinary recovery of the drug was 8 ± 6.3% (day1) and 9.8 ± 6.3 (day4). Monte Carlo simulation analysis (0.03-1 mg/L MIC-range) showed that PTA was guaranteed only for MICs ≤ 0.03 mg/L in the low-AUC group, and for MICs ≤ 0.06 mg/L in the high-AUC group. No group had a PTA ≥ 90% for 0.125 mg/L MIC (the epidemiological cut-off). Mortality was higher in low-AUC group (p < 0.01). In our 'real-world' population, no clinical data can predict which patient will have lower, suboptimal caspofungin exposure, therefore we suggest TDM to optimize caspofungin therapy and reduce the risk of selecting resistances (CEAVC, 32366/2015; OSS.15.114, NCT03798600).

Extrapolating Antifungal Animal Data to Humans - Is it reliable?

PURPOSE OF REVIEW

This article aimed to review animal models of antifungals and identifies human literature to assess if the extrapolation of results is reliable.

RECENT FINDINGS

Animal studies have helped identify AUC/MIC targets for new drugs and formulations such as isavuconazole and delayed release posaconazole that have translated to successful outcomes in humans. Models have also been influential in the identification of possible combination therapies for the treatment of aspergillosis, such as voriconazole and echinocandins. However, challenges are endured with animal models when it comes to replicating the pharmacokinetics of humans which has been exemplified with the newest itraconazole formulation. Additionally, animal models have displayed a survival benefit with the use of iron chelators and amphotericin for mucormycosis which was not demonstrated in humans.

SUMMARY

Animal models have been a staple in the development and optimization of antifungal agents. They afford the ability to investigate uncommon diseases, such as invasive fungal infections, that would otherwise take years and many resources to complete. Although there are many benefits of animal models there are also shortcomings. This is why the reliability of extrapolating data from animal models to humans is often scrutinized.

Rezafungin treatment in mouse models of invasive candidiasis and aspergillosis: Insights on the PK/PD pharmacometrics of rezafungin efficacy

Rezafungin acetate is a novel echinocandin in clinical development for prevention and treatment of invasive fungal infections. Rezafungin is differentiated by a pharmacokinetic/pharmacodynamic (PK/PD) profile that includes a long half-life allowing once-weekly administration, front-loaded plasma drug exposures associated with antifungal efficacy, and penetration into deep-seated infections, such as intra-abdominal abscesses. In this series of in vivo studies, rezafungin demonstrated efficacy in the treatment of neutropenic mouse models of disseminated candidiasis, including infection caused by azole-resistant Candida albicans, and aspergillosis. These results contribute to a growing body of evidence demonstrating the antifungal efficacy and potential utility of rezafungin in the treatment of invasive fungal infections.

Antifungal drugs: What brings the future?

The high burden and growing prevalence of invasive fungal infections (IFIs), the toxicity and interactions associated with current antifungal drugs, as well as the increasing resistance, ask for the development of new antifungal drugs, preferably with a novel mode of action. Also, the availability of oral or once-weekly alternatives would enable ambulatory treatment resulting in an improved patient's comfort and therapy adherence. However, only one new azole and two new posaconazole-formulations were marketed over the last decade. This review focuses on the antifungal drugs in the pipeline undergoing clinical evaluation. First, the newest azole, isavuconazole, with its improved safety profile and reduction in DDIs, will be discussed. Moreover, there are two glucan synthase inhibitors (GSIs) in the antifungal pipeline: rezafungin (CD101), a long-acting echinocandin with an improved stability that enables once weekly administration, and SCY-078, an orally available GSI with efficacy against azole- and echinocandin resistant isolates. A new oral formulation of amphotericin B will also be presented. Moreover, the first representative of a new antifungal class, the orotomides, with a broad spectrum and no cross-resistance with current antifungal classes, will be discussed. Finally, an overview of other antifungals that are still in earlier clinical development phases, is provided.

Extended Dosing Regimens for Fungal Prophylaxis

Invasive fungal diseases carry high morbidity and mortality in patients undergoing chemotherapy for hematological malignancies or allogeneic hematopoietic stem cell transplantation. In order to prevent these life-threatening infections, antifungal chemoprophylaxis plays an important role in daily clinical practice. Broad-spectrum antifungal triazoles are widely used but exhibit disadvantages such as relevant drug-drug interactions. Therefore, amphotericin B products or echinocandins can be an alternative in selected patient populations. As these compounds are available as intravenous formulations only, there is growing interest in extended dosing regimens. Although not approved for these agents, this strategy is a rational option, as these compounds have properties suitable for this strategy, including dose-proportional pharmacokinetics, prolonged elimination half-life, and a large therapeutic window. As the use of extended dosing regimens in antifungal prophylaxis is expanding in clinical practice, we reviewed the pharmacokinetic and pharmacodynamic rationale for this strategy, animal model data, dose escalation studies, and clinical trials supporting this concept.

Overview of antifungal dosing in invasive candidiasis

In the past, most antifungal therapy dosing recommendations for invasive candidiasis followed a 'one-size fits all' approach with recommendations for lowering maintenance dosages for some antifungals in the setting of renal or hepatic impairment. A growing body of pharmacokinetic/pharmacodynamic research, however now points to a widespread 'silent epidemic' of antifungal underdosing for invasive candidiasis, especially among critically ill patients or special populations who have altered volume of distribution, protein binding and drug clearance. In this review, we explore how current adult dosing recommendations for antifungal therapy in invasive candidiasis have evolved, and special populations where new approaches to dose optimization or therapeutic drug monitoring may be needed, especially in light of increasing antifungal resistance among Candida spp.

Pre-Existing Liver Disease and Toxicity of Antifungals

Pre-existing liver disease in patients with invasive fungal infections further complicates their management. Altered pharmacokinetics and tolerance issues of antifungal drugs are important concerns. Adjustment of the dosage of antifungal agents in these cases can be challenging given that current evidence to guide decision-making is limited. This comprehensive review aims to evaluate the existing evidence related to antifungal treatment in individuals with liver dysfunction. This article also provides suggestions for dosage adjustment of antifungal drugs in patients with varying degrees of hepatic impairment, after accounting for established or emerging pharmacokinetic–pharmacodynamic relationships with regard to antifungal drug efficacy in vivo.

What has changed in the treatment of invasive candidiasis? A look at the past 10 years and ahead

The treatment of invasive candidiasis has changed greatly in the past decade and must continue to evolve if we are to improve outcomes in this serious infection. A review of recent history may provide insights for the future. The morbidity and mortality of invasive candidiasis remain difficult to measure despite an obvious clinical burden. Current treatment guidelines now recommend echinocandins as first-line empirical treatment, with fluconazole as an acceptable alternative for selected patients, reflecting the efficacy demonstrated by echinocandins and increasing resistance observed with fluconazole. The selection of antifungal therapy now must consider not only resistance but also the shift in predominance from Candida albicans to non-albicans species, notably Candida glabrata. The recent emergence of Candida auris has been met with great interest, although the longer-term implications of this phenomenon remain unclear. The broad goal of treatment continues to be administration of safe, efficacious antifungal therapy as soon as possible. Diagnostic methods beyond traditional blood culture present an opportunity to shorten the time to an accurate diagnosis, and earlier treatment initiation based on prophylactic and empirical or pre-emptive strategies seeks to ensure timely therapeutic intervention. In addition, there are novel agents in the antifungal pipeline. These developments, as well as ongoing studies of dosing, toxicity and resistance development, are important items on the current research agenda and may play a role in future changes to the treatment of invasive candidiasis.