Background Cryptococcal meningitis is a leading cause of HIV-related mortality in sub-Saharan Africa. Based on phase-II data, we performed a phase-III randomized controlled non-inferiority trial to determine the efficacy of a single high-dose liposomal amphotericin B based treatment regimen. Methods HIV-positive adults with cryptococcal meningitis in Botswana, Malawi, South Africa, Uganda and Zimbabwe were randomized 1:1 to induction therapy of either (i) single, high-dose liposomal amphotericin B 10mg/kg given with 14 days of flucytosine 100mg/kg/day and fluconazole 1200mg/day (AmBisome group), or (ii) the current WHO recommended treatment of 7 daily doses of amphotericin B deoxycholate (1mg/kg/day) plus flucytosine (100mg/kg/day), followed by 7 days of fluconazole 1200mg/day (control group). The primary endpoint was all-cause mortality at 10 weeks with the trial powered to show non-inferiority at a 10% margin. Results We randomized 844 participants. None were lost-to-follow-up. In intention-to-treat analysis, 10-week mortality was 24.8% (101 of 407; 95% confidence interval [CI] 20.7-29.3%) in the AmBisome group and 28.7% (117 of 407; 95% CI 24.4-33.4%) in controls. The absolute difference in mortality was -3.9%, with an upper 1-sided 95% confidence interval of 1.2%. Fungal clearance from cerebrospinal fluid was -0.40 log 10 CFU/ml/day in the AmBisome group and -0.42 log 10 CFU/ml/day in the control group. Fewer participants experienced grade 3 or 4 adverse events in the AmBisome group than the control group (50.0% vs. 62.3%). Conclusions Single dose liposomal amphotericin B (10mg/kg) on a backbone of flucytosine and fluconazole was non-inferior to the current WHO recommended standard of care for HIV-associated cryptococcal meningitis and associated with fewer adverse events. (Trial registration number: ISRCTN72509687.)

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Background There are limited data describing clinical flucytosine pharmacokinetics (PK). The variability of flucytosine partitioning into the CNS is not known. We described the interindividual variability in flucytosine PK in patients with HIV-associated cryptococcal meningoencephalitis. In addition, we quantified the extent and variability of CSF partitioning of flucytosine. Methods A PK study was conducted in 64 patients with confirmed HIV-associated cryptococcal meningoencephalitis in Blantyre, Malawi. A four-compartment PK model was developed, and Monte Carlo simulations were performed with flucytosine administered at different doses and in different schedules. Results The estimated mean apparent volume of the central compartment was 17.50 (SD 9.99) L; mean apparent clearance was 5.88 (SD 3.35) L/h; mean apparent volume of the CNS compartment was 41.73 (SD 13.66) L. From the Bayesian posterior estimates, AUC24 values at steady state (144–168 h) with doses of 25 mg/kg q6h were median (IQR) 890.38 (603.81–1213.70) mg.h/L in plasma and 595.66 (425.69–776.64) mg.h/L in CSF. The ratio of CSF:plasma AUC24 was 0.69 (IQR 0.58–0.82). Conclusions This study revealed significant interindividual variability in flucytosine PK in plasma and CSF in patients with HIV-associated cryptococcal meningoencephalitis. The population PK model is a first critical step for revised flucytosine regimens that maximize fungal killing and minimize toxicity and the emergence of resistance.