Population Pharmacokinetics and Pharmacodynamics of Itraconazole for Disseminated Infection Caused by Talaromyces marneffei

First-line treatment of talaromycosis with amphotericin B deoxycholate (DAmB) is labour intensive and toxic. Itraconazole is an appealing alternative antifungal agent. Pharmacokinetic data were obtained from 76 patients who were randomized to itraconazole in the Itraconazole versus Amphotericin B for Talaromycosis (IVAP) trial. Plasma levels of itraconazole and its active metabolite, hydroxyitraconazole, were analysed alongside longitudinal fungal colony forming unit counts in a population model. Itraconazole and hydroxyitraconazole pharmacokinetic variability was considerable, with area under the concentration-time curve over 24 hours (AUC 24 ) mean ± standard deviation 3.34 ± 4.31 mg*h/litre and 3.57 ± 4.46 mg*h/litre, respectively. Levels of both analytes were low; itraconazole minimum concentration (Cmin) 0.11 ± 0.16 mg/liter; hydroxyitraconazole Cmin 0.13 ± 0.17 mg/litre. The mean maximal rates of drug-induced killing were 0.206 and 0.208 log 10 CFU/mL/h, respectively. There were no associations between itraconazole Cmin:MIC and time to sterilisation of the bloodstream (HR 1.01, 95% CI 0.99 to 1.03, p=0.43), time to death (HR 0.99, 95% CI 0.96 to 1.02, p=0.77) or early fungicidal activity EFA (coefficient -0.004, 95% CI -0.010 to 0.002, p=0.18). Similarly, there was no relationship between AUC:MIC and time to sterilisation of the bloodstream (HR 1.00, 95% CI 0.99 to 1.00, p=0.50), time to death (HR 1.00, 95% CI 0.99 to 1.00, p=0.91) or EFA (coefficient -0.0001, 95% CI -0.0003 to 0.0001, p = 0.19). This study raises the possibility that the failure of itraconazole to satisfy non-inferiority criteria against DAmB for talaromycosis in the IVAP trial was a pharmacokinetic and pharmacodynamic failure.

Cerebrospinal Fluid Early Fungicidal Activity as a Surrogate Endpoint for Cryptococcal Meningitis Survival in Clinical Trials

Background In cryptococcal meningitis phase 2 clinical trials, early fungicidal activity (EFA) of Cryptococcus clearance from cerebrospinal fluid (CSF) is used as a surrogate endpoint for all-cause mortality. The Food and Drug Administration allows for using surrogate endpoints for accelerated regulatory approval, but EFA as a surrogate endpoint requires further validation. We examined the relationship between rate of CSF Cryptococcus clearance (EFA) and mortality through 18 weeks. Methods We pooled individual-level CSF data from 3 sequential cryptococcal meningitis clinical trials conducted during 2010–2017. All 738 subjects received amphotericin + fluconazole induction therapy and had serial quantitative CSF cultures. The log10-transformed colony-forming units (CFUs) per mL CSF were analyzed by general linear regression versus day of culture over the first 10 days. Results Mortality through 18 weeks was 37% for EFA > = 0.60 (n = 170), 36% for 0.40–0.59 (n = 182), 39% for 0.30–0.39 (n = 112), 35% for 0.20–0.29 (n = 87), and 50% for those with EFA < 0.20 CFU/mL/day (n = 187). The hazard ratio for 18-week mortality, comparing those with EFA < 0.20 to those with EFA > = 0.20, was 1.60 (95% confidence interval, 1.25, 2.04; P = .002). The lowest EFA group had lower median CD4 T-cell counts (P < .01) and lower proportion of patients with CSF pleocytosis (P < .001). Conclusions EFA is associated with all-cause mortality in cryptococcal meningitis. An EFA threshold of > = 0.20 log10 CFU/mL/day was associated with similar 18-week mortality (37%) compared to 50% mortality with EFA < 0.20. This EFA threshold may be considered a target for a surrogate endpoint. This builds upon existing studies to validate EFA as a surrogate endpoint.

A randomized open label trial of tamoxifen combined with amphotericin B and fluconazole for cryptococcal meningitis.

Background: Cryptococcal meningitis is a leading cause of death in HIV-infected patients. International treatment guidelines recommend induction therapy with amphotericin B and flucytosine. This antifungal combination is most effective, but unfortunately flucytosine is expensive and unavailable where the burden of disease is greatest. Where unavailable, guidelines recommend treatment with amphotericin and fluconazole, but this is less effective, with mortality rates of 40-50%. Faster rates of clearance of yeast from cerebrospinal fluid (CSF) are associated with better outcomes - improving the potency of antifungal therapy is likely to be an effective strategy to improve survival. Tamoxifen, a selective estrogen receptor modulator used to treat breast cancer, has anti-cryptococcal activity, appearing synergistic when combined in vitro with amphotericin, and fungicidal when combined with fluconazole. It is concentrated in the brain and macrophages, off-patent, cheap and widely available. We designed a randomized trial to deliver initial efficacy and safety data for tamoxifen combined with amphotericin and fluconazole. Method: A phase II, open-label, randomized (1:1) controlled trial of tamoxifen (300mg/day) combined with amphotericin (1mg/kg/day) and fluconazole (800mg/day) for the first 2 weeks therapy for HIV infected or uninfected adults with cryptococcal meningitis. The study recruits at Cho Ray Hospital and the Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam. The primary end point is Early Fungicidal Activity (EFA-the rate of yeast clearance from CSF), over the first two weeks of treatment. 50 patients will be recruited providing ≈80% and 90% power to detect a difference in the EFA of -0.11 or -0.13 log10CFU/ml/day, respectively. Discussion: The results of the study will inform the decision to proceed to a larger trial powered to mortality. The size of effect detectable has previously been associated with reduced mortality from this devastating disease. Particular side effects of interest include QT prolongation. Trial registration: Clinicaltrials.gov NCT03112031 (11/04/2017)

Transcriptional Profiling of Patient Isolates Identifies a Novel TOR/Starvation Regulatory Pathway in Cryptococcal Virulence

ABSTRACTHuman infection withCryptococcuscauses up to a quarter of a million AIDS-related deaths annually and is the most common cause of nonviral meningitis in the United States. As an opportunistic fungal pathogen,Cryptococcus neoformansis distinguished by its ability to adapt to diverse host environments, including plants, amoebae, and mammals. In the present study, comparative transcriptomics of the fungus within human cerebrospinal fluid identified expression profiles representative of low-nutrient adaptive responses. Transcriptomics of fungal isolates from a cohort of HIV/AIDS patients identified high expression levels of an alternative carbon nutrient transporter gene,STL1, to be associated with poor early fungicidal activity, an important clinical prognostic marker. Mouse modeling and pathway analysis demonstrated a role forSTL1in mammalian pathogenesis and revealed thatSTL1expression is regulated by a novel multigene regulatory mechanism involving theCAC2subunit of the chromatin assembly complex 1, CAF-1. In this pathway, the global regulator of virulence geneVAD1was found to transcriptionally regulate a cryptococcal homolog of a cytosolic protein, Ecm15, in turn required for nuclear transport of the Cac2 protein. Derepression ofSTL1by theCAC2-containing CAF-1 complex was mediated by Cac2 and modulated binding and suppression of theSTL1enhancer element. Derepression ofSTL1resulted in enhanced survival and growth of the fungus in the presence of low-nutrient, alternative carbon sources, facilitating virulence in mice. This study underscores the utility ofex vivoexpression profiling of fungal clinical isolates and provides fundamental genetic understanding of saprophyte adaption to the human host.IMPORTANCECryptococcusis a fungal pathogen that kills an estimated quarter of a million individuals yearly and is the most common cause of nonviral meningitis in the United States. The fungus is carried in about 10% of the adult population and, after reactivation, causes disease in a wide variety of immunosuppressed individuals, including the HIV infected and patients receiving transplant conditioning, cancer therapy, or corticosteroid therapy for autoimmune diseases. The fungus is widely carried in the soil but can also cause infections in plants and mammals. However, the mechanisms for this widespread ability to infect a variety of hosts are poorly understood. The present study identified adaptation to low nutrients as a key property that allows the fungus to inhabit these diverse environments. Further studies identified a nutrient transporter gene,STL1, to be upregulated under low nutrients and to be associated with early fungicidal activity, a marker of poor clinical outcome in a cohort of HIV/AIDS patients. Understanding molecular mechanisms involved in adaptation to the human host may help to design better methods of control and treatment of widely dispersed fungal pathogens such asCryptococcus.

Oral versus Intravenous Flucytosine in Patients with Human Immunodeficiency Virus-Associated Cryptococcal Meningitis

ABSTRACT In a randomized controlled trial of amphotericin B-based therapy for human immunodeficiency virus (HIV)-associated cryptococcal meningitis in Thailand, we also compared the mycological efficacy, toxicity, and pharmacokinetics of oral versus intravenous flucytosine at 100 mg/kg of body weight/day for the initial 2 weeks. Half of 32 patients assigned to the two arms containing flucytosine were randomized to oral and half to intravenous flucytosine. Early fungicidal activity was determined from serial quantitative cultures of cerebrospinal fluid (CSF), and toxicity was assessed by clinical and laboratory monitoring. Flucytosine and fluorouracil concentrations in plasma and CSF were measured by high-performance liquid chromatography. No significant bone marrow or hepatotoxicity was seen, there was no detectable difference in bone marrow toxicity between patients on intravenous and those on oral formulation, and no patients discontinued treatment. In patients receiving intravenous flucytosine, the median 24-h area under the concentration-time curve was significantly higher than in the oral group. Despite this difference, there was no difference in early fungicidal activity between patients on intravenous compared with patients on oral flucytosine. The results suggest that either formulation can be used safely at this dosage in a developing country setting, without drug concentration monitoring. The bioavailability of the oral formulation may be reduced in late-stage HIV-infected patients in Thailand. Concentrations of flucytosine with intravenous formulation at 100 mg/kg/day may be in excess of those required for maximal fungicidal activity.