Tissue Distribution and Penetration of Isavuconazole at the Site of Infection in Experimental Invasive Aspergillosis in Mice with Underlying Chronic Granulomatous Disease

Pharmacokinetics of isavuconazole at different target sites in healthy volunteers after single and multiple intravenous infusions

BACKGROUND

Invasive aspergillosis is a severe fungal infection that affects multiple organ systems including the CNS and the lungs. Isavuconazole, a novel triazole antifungal agent, has demonstrated promising activity against Aspergillus spp. However, data on the penetration of isavuconazole into the CNS and ELF and intracellular accumulation remain limited.

MATERIALS AND METHODS

We conducted a prospective single-centre pharmacokinetic (PK) study in 12 healthy volunteers. Subjects received seven doses of 200 mg isavuconazole to achieve an assumed steady-state. After the first and final infusion, plasma sampling was conducted over 8 and 12 h, respectively. All subjects underwent one lumbar puncture and bronchoalveolar lavage, at either 2, 6 or 12 h post-infusion of the final dose. PBMCs were collected in six subjects from blood to determine intracellular isavuconazole concentrations at 6, 8 or 12 h. The AUC/MIC was calculated for an MIC value of 1 mg/L, which marks the EUCAST susceptibility breakpoint for Aspergillus fumigatus and Aspergillus flavus.

RESULTS

C max and AUC0-24h of isavuconazole in plasma under assumed steady-state conditions were 6.57 ± 1.68 mg/L (mean ± SD) and 106 ± 32.1 h·mg/L, respectively. The average concentrations measured in CSF, ELF and in PBMCs were 0.07 ± 0.03, 0.94 ± 0.46 and 27.1 ± 17.8 mg/L, respectively. The AUC/MIC in plasma, CSF, ELF and in PBMCs under steady-state conditions were 106 ± 32.1, 1.68 ± 0.72, 22.6 ± 11.0 and 650 ± 426 mg·h/L, respectively.

CONCLUSION

Isavuconazole demonstrated moderate penetration into ELF, low penetrability into CSF and high accumulation in PBMCs. Current dosing regimens resulted in sufficient plasma exposure in all subjects to treat isolates with MICs ≤ 1 mg/L.

Bronchopulmonary penetration of isavuconazole in lung transplant recipients

Isavuconazole's (ISA) pharmacokinetics was studied among lung transplant recipients to evaluate its bronchopulmonary penetration. This study included 13 patients and showed mean serum concentrations of 3.30 (standard deviation [SD] 0.45), 5.12 (SD 1.36), and 6.31 (SD 0.95) at 2 h, 4 h, and 24 h respectively. Mean concentrations in the epithelial lining fluid were 0.969 (SD 0.895), 2.141 (SD 1.265), and 2.812 (SD 0.693) at the same time points. ISA is a drug with a tolerable safety profile that achieves adequate concentrations in the lung.

Observed isavuconazole exposure: 5-year experience of azole TDM from a Spanish reference laboratory

We aimed to assess patient exposure to isavuconazole (ISZ) from samples received in our laboratory for therapeutic antifungal monitoring. We used liquid chromatography coupled with ultraviolet (UV) absorbance detection adapted from a multiplex-validated method with photodiode array (PDA) detection to monitor the analytes. The latter device allows the characterization of the azoles UV spectra. The method was validated according to international guidelines for efficient ISZ monitoring. The assay exhibited linearity between 0.25 and 16 mg/l for ISZ. Accuracy and intra- and inter-day precision were within acceptable ranges, and the method was successfully applied to quantify azoles and major metabolites from clinical samples collected from treated patients. We focus on ISZ blood concentrations and compared them to those of voriconazole, posaconazole, and itraconazole for a period of 5 years (2017-2021). Median ISZ concentration was 2.92 mg/l (interquartile range 1.82-5.33 mg/l) with 89% of measurements classified as adequate exposure (> 1 mg/l). Additionally, 71% of samples reach concentration values > 2 mg/l. Different ISZ exposure between adults to children were found. In conclusion, ISZ achieves excellent blood concentrations compared to other azole drugs, they are almost identical to those previously described, they exceed the MICs of most fungi for which its use was recommended and they differ depending on the patient's age. The method we describe for antifungal monitoring is simple, robust, and efficient. It simultaneously analyzes azoles and metabolites, and can be used for tailored interventions, achieve exposures associated with therapeutic success, decrease treatment-related toxicity, and help prevent resistance emergence due to continuous azole sub-optimal concentrations.

Potential Implication of Azole Persistence in the Treatment Failure of Two Haematological Patients Infected with Aspergillus fumigatus

Invasive aspergillosis (IA) is a major cause of morbidity and mortality in patients receiving allogeneic haematopoieticcell transplantation. The deep immunosuppression and a variety of potential additional complications developed in these patients result in IA reaching mortality rates of around 50-60%. This mortality is even higher when the patients are infected with azole-resistant isolates, demonstrating that, despite the complexity of management, adequate azole treatment can have a beneficial effect. It is therefore paramount to understand the reasons why antifungal treatment of IA infections caused by azole-susceptible isolates is often unsuccessful. In this respect, there are already various factors known to be important for treatment efficacy, for instance the drug concentrations achieved in the blood, which are thus often monitored. We hypothesize that antifungal persistence may be another important factor to consider. In this study we present two case reports of haematological patients who developed proven IA and suffered treatment failure, despite having been infected with susceptible isolates, receiving correct antifungal treatment and reaching therapeutic levels of the azole. Microbiological analysis of the recovered infective isolates showed that the patients were infected with multiple strains, several of which were persisters to voriconazole and/or isavuconazole. Therefore, we propose that azole persistence may have contributed to therapeutic failure in these patients and that this phenomenon should be considered in future studies.

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.

Successful Multimodal Therapy with Intracerebral Liposomal Amphotericin B and Systemic High-Dose Isavuconazole in Proven Disseminated Aspergillosis

We report the case of a 32-year-old man receiving chemotherapeutics for an acute B-lymphoblastic leukemia who developed proven cerebral and pulmonary aspergillosis with Aspergillus flavus. Because of progressive fungal disease with neurological deterioration despite adequate systemic antifungal therapy and surgical debridement, intracerebral administration of liposomal amphotericin B was initiated at 5 mg twice weekly. This led to improvement of the cerebral infection. Surgical debridement of a pleural Aspergillus empyema was necessary, and pleural trough level of isavuconazole was found to be subtherapeutic despite adequate blood trough levels, which led us to increase the dose of isavuconazole. We conclude that intralesional amphotericin B might be beneficial at 5 mg twice weekly in cerebral aspergillosis if systemic antifungals and surgical debridement fail. In Aspergillus empyema, measurement of pleural isavuconazole trough levels should be considered.

Gram stain to the rescue: a case report of cerebral phaeohyphomycosis by Cladophialophora bantiana in an immunocompetent 24-year-old

BACKGROUND

Fungal brain abscesses in immunocompetent patients are exceedingly rare. Cladophialophora bantiana is the most common cause of cerebral phaeohyphomycosis, a dematiaceous mold. Radiological presentation can mimic other disease states, with diagnosis through surgical aspiration and growth of melanized fungi in culture. Exposure is often unknown, with delayed presentation and diagnosis.

CASE PRESENTATION

We present a case of cerebral phaeohyphomycosis in a 24-year-old with no underlying conditions or risk factors for disease. He developed upper respiratory symptoms, fevers, and headaches over the course of 2 months. On admission, he underwent brain MRI which demonstrated three parietotemporal rim-enhancing lesions. Stereotactic aspiration revealed a dematiaceous mold on staining and the patient was treated with liposomal amphotericin B, 5-flucytosine, and posaconazole prior to culture confirmation. He ultimately required surgical excision of the brain abscesses and prolonged course of antifungal therapy, with clinical improvement.

CONCLUSIONS

Culture remains the gold standard for diagnosis of infection. Distinct microbiologic findings can aid in identification and guide antimicrobial therapy. While little guidance exists on treatment, patients have had favorable outcomes with surgery and combination antifungal therapy. In improving awareness, clinicians may accurately diagnose disease and initiate appropriate therapy in a more timely manner.

Isavuconazole for treatment of refractory coccidioidal meningitis with concomitant cerebrospinal fluid and plasma therapeutic drug monitoring

Coccidioidal meningitis (CM) is a life-threatening infection with limited treatment options. Small series have reported success with isavuconazole; however, limited data exist on cerebrospinal fluid (CSF) penetration. Paired plasma and CSF isavuconazole concentrations were measured. Eleven CSF levels were tested, (7 ventricular, 4 lumbar) in three CM patients. Ventricular CSF levels were undetectable despite detectable plasma levels. All lumbar CSF levels were detectable (mean 1.00 µg/mL). Three pairs of lumbar CSF/plasma concentrations taken within one hour of each other yielded a mean CSF/plasma ratio of 0.31. Isavuconazole was detectable in lumbar but not ventricular CSF in three patients treated for refractory CM.

Penetration of Isavuconazole in Ascites Fluid of Critically Ill Patients

Fungal peritonitis is a life-threatening condition which is not only difficult to diagnose, but also to treat. Following recent guidelines, echinocandins and azoles are the recommended antimycotics for the management of intra-abdominal Candida spp. infections, with a favor for echinocandins in critically ill patients. However, the new extended spectrum triazole isavuconazole also has a broad spectrum against Candida spp. Data on its target-site penetration are sparse. Therefore, we assessed isavuconazole concentrations and penetration ratios in ascites fluid of critically ill patients. Obtaining of Isavuconazole plasma and ascites fluid levels as well penetration ratios using paracentesis in critically ill patients. Isavuconazole concentrations were quantified in human plasma and ascites by a liquid chromatography/tandem mass spectrometry (LC-MS/MS) method. Isavuconazole concentrations in plasma and ascites fluid were measured in sixteen critically ill patients. Isavuconazol levels in ascites fluid (1.06 µg/mL) were lower than plasma levels (3.08 µg/mL). Penetration ratio was 36%. In two out of sixteen patients, Candida spp., in detail C. glabrata and C. tropicalis, could be isolated. Cmax/MIC Ratio in plasma of 560 for C. glabrata and 2166 for C. tropicalis could be observed. Following our results, isavuconazole penetrates into ascites. Successful treatment in Candida spp. peritonitis depends on pathogen susceptibility.

Clinical manifestations, diagnosis, and treatment outcome of CNS aspergillosis: A systematic review of 235 cases

Aspergillus is a ubiquitous ascomycete that can cause a variety of clinical presentations depending on immune status. Central nervous system aspergillosis is a fatal disease with non-specific clinical features. The aim of this systematic review was to evaluate the epidemiology, clinical features, diagnosis and therapeutic interventions in CNS aspergillosis patients. We also aimed to examine the possible predictors of mortality in neuroaspergillosis. Literature search was performed in Medline, PubMed, and Google scholar and all patients≥18 years with proven CNS aspergillosis were included. A total of 175 articles (235 patients) were included in the final analysis. Their mean age was 51 years and the majority were male (57.4%). Overall case-fatality was 45.1%. Aspergillus fumigatus was the most common species (70.8%) followed by A. flavus (18.6%). Corticosteroids (22.6%), malignancy (19.1%) and diabetes mellitus (14%) were the most common risk factors. Neuroimaging findings included cerebral abscess (70.2%), meningitis (14%), infarction (13.2%) and mycotic aneurysm (8.9%). Disseminated disease (29.2% vs 17.8%, p 0.03), CSF hypoglycorrhachia (48.1% vs 22.2%, P: 0.001) and heightened CSF galactomannan (3.62 vs 2.0ng/ml, p 0.05), were the factors associated with poor outcome in neuroaspergillosis. Persons infected with Aspergillus flavus (13.1% vs 3.1%, P: 0.01), and having been treated with Voriconazole (51.9% vs 29.2%, P: 0.004) were more likely to survive. Our review will provide insight into the different spectrums of CNS aspergillosis. Notwithstanding the promising role of Voriconazole, future work is required to ascertain the role of combination antifungal therapy.

Antifungal drugs: An updated review of central nervous system pharmacokinetics

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

Successful treatment of Aspergillus fumigatus sternal osteomyelitis with isavuconazole in a heart transplant recipient

A 65-year-old man was diagnosed with an invasive Aspergillus fumigatus infection with sternal osteomyelitis 4 months after heart transplantation. Unfortunately, after 8 weeks patient developed severe cutaneous and neurological toxicities induced by voriconazole leading to drug discontinuation. Therefore, isavuconazole was chosen as second-line therapy. The patient presented a favorable outcome and tolerance was excellent after ten months monotherapy. Here, we report for a first time, an successful isavuconazole-based treatment of sternal osteomyelitis aspergillosis in a cardiac recipient.

Isavuconazole Diffusion in Infected Human Brain

We report the cases of a 39-year-old woman with chronic lymphocytic leukemia and a 21-year-old man with chronic granulomatous disease treated for cerebral aspergillosis. The patients required radical surgery for infection progression despite adequate isavuconazole plasma concentration or neurological complication. We thus decided to measure the brain isavuconazole concentration. These results suggest that the concentrations of isavuconazole obtained in the infected brain tissue clearly differ from those obtained in the normal brain tissue and the cerebrospinal fluid.

Central Nervous System Infections Due to Aspergillus and Other Hyaline Molds

Central nervous system infections due to Aspergillus spp and other hyaline molds such as Fusarium and Scedosporium spp are rare but fatal conditions. Invasion of the central nervous system (CNS) tends to occur as a result of hematogenous dissemination among immunocompromised patients, and by local extension or direct inoculation secondary to trauma in immunocompetent hosts. Efforts should be directed to confirm the diagnosis by image-guided stereotactic brain biopsy when feasible. Non-culture methods could be useful to support the diagnosis, but they have not been validated to be performed in cerebral spinal fluid. Treatment of these infections is challenging given the variable susceptibility profile of these pathogens and the penetration of antifungal agents into the brain.