Bioavailability of three novel oral, sustained-release pellets, relative to an immediate-release tablet containing 500 mg flucytosine: A randomized, open-label, crossover study in healthy volunteers.

The opportunistic fungal infection cryptococcal meningoencephalitis is a major cause of death among people living with HIV in sub-Saharan Africa. We report pharmacokinetic (PK) and safety data from a randomized, four-period crossover phase I trial of three sustained-release (SR) oral pellet formulations of 5-flucytosine conducted in South Africa. These formulations were developed to require less frequent administration, to provide a convenient alternative to the current immediate release (IR) formulation, A. Formulations B, C, and D were designed to release 5-flucytosine as a percentage of the nominal dose in vitro. We assessed their safety and PK profiles in a single dose (1 × 3000 mg at 0 h), relative to commercial IR tablets (Ancotil 500 mg tablets; 3 × 500 mg at 0 h and 3 × 500 mg at 6 h) in healthy, fasted participants. Forty-two healthy participants were included. All treatments were well-tolerated. The primary PK parameters, maximum observed plasma concentration (Cmax ) and area under the concentration-time profiles, were significantly lower for the SR formulations than for the IR tablets, and the geometric mean ratios fell outside the conventional bioequivalence limits. The median maximum time to Cmax was delayed for the SR pellets. Physiologically-based PK modeling indicated a twice-daily 6400 mg dose of SR formulation D in fasted condition would be optimal for further clinical development. This regimen is predicted to result in a rapid steady-state plasma exposure with effective and safe trough plasma concentration and Cmax values, within the therapeutic boundaries relative to plasma exposure after four times per day administration of IR tablets (PACTR202201760181404).

Time to embrace access programmes for medicines: lessons from the South African flucytosine access programme.

BACKGROUND: Cryptococcal meningitis (CM) is estimated to cause 181 000 deaths annually, with the majority occurring in Sub-Saharan Africa. Flucytosine is recommended by the World Health Organization as part of the treatment for CM. Widespread use of flucytosine could reduce mortality in hospital by as much as 40% compared to the standard of care, yet due to market failure, quality-assured flucytosine remains unregistered and largely inaccessible throughout Africa. METHODS: The recently established South African flucytosine clinical access programme is an attempt to address the market failure that led to a lack of public sector access to flucytosine for CM, by making the medicine freely available to tertiary hospitals in South Africa. RESULTS: Between November 2018 and September 2019, 327 CM patients received flucytosine through this programme, with efforts to support sustainable national scale-up presently ongoing. We describe why this programme was needed, its catalytic potential, what is still required to ensure widespread access to flucytosine, and observations from this experience that may have wider relevance. CONCLUSIONS: The South African flucytosine access programme illustrates how access programmes may be one part of the solution to addressing the vicious cycle of perceived low demand, limiting manufacturer interest in specific product markets.