Fluconazole plus flucytosine vs fluconazole alone for cryptococcal antigen-positive patients identified through screening: A randomised trial

Background - burden of cryptococcal disease
Despite ART roll-out in Africa, about one-third of HIV-infected individuals still present for care with very low CD4 counts, and the incidence of opportunistic co-infections such as cryptococcal meningitis (CM) in this group is high. Furthermore, each year a number of patients drop out of HIV care, later re-presenting with advanced HIV disease and complications such as CM. Consequently, CM rates are not decreasing in most of Africa. CM is the commonest form of meningitis in sub-Saharan Africa (SSA) and is a key driver of global HIV mortality resulting in ~180,000 deaths/year globally with over 75% in SSA, and accounting for 15-20% of all HIV-related deaths. Targeting cryptococcal disease, prior to the development of life-threatening meningitis, can reduce this persistently high HIV-related mortality: an urgent goal of WHO's 2017 guideline on advanced HIV disease management and in order to achieve the 2030 WHO Sustainable Development Goals.

Cryptococcal antigen (CrAg) screening and pre-emptive treatment
Over half the patients diagnosed with CM die within 10 weeks, a death rate similar to Ebola virus disease. Fortunately, the infection can be detected early, before the development of meningitis, using a simple point-of-care blood test for cryptococcal antigen (CrAg). Studies suggest that 70% of people testing positive for CrAg would progress to develop CM or die without diagnosis and data shows that routine CrAg screening of patients presenting to HIV centres, combined with pre-emptive fluconazole treatment, can cost effectively reduce the risk of developing CM and reduce mortality. CrAg screening has now been incorporated into 28 National Guidelines and screening programs are being rolled out across SSA.

The problem: Need for a more potent antifungal treatment
There is now a considerable body of evidence revealing that CrAg-positive patients treated pre-emptively with fluconazole alone have substantially higher mortality compared to CrAg-negative patients despite this pre-emptive treatment (25-33% mortality vs 9-15% in different studies). In the REMSTART trial, conducted in Tanzania and Zambia, there was 3-fold excess mortality in CrAg-positive asymptomatic patients, compared to CrAg-negative patients with a similar risk of death observed from a recent study in South Africa (SA). This, and other evidence, suggests that more effective antifungal treatment may be needed to reduce these excess deaths and realize the full benefits of screening programmes.

Combined therapy of fluconazole plus flucytosine
The EFFECT trial aims to compare the efficacy of an oral combination of fluconazole plus flucytosine with fluconazole alone (the current recommended treatment) in reducing all-cause mortality in advanced HIV patients in Tanzania and SA. There is now compelling evidence from the recently completed ACTA trial showing that combined treatment of fluconazole plus flucytosine for 2 weeks is well-tolerated and as effective as the standard of 2 weeks intravenous amphotericin B plus flucytosine for in-patients with symptomatic CM. Mortality was almost halved compared to historic cohorts treated with fluconazole alone. Although the ACTA trial results cannot be directly generalised to CrAg-positive patients without symptomatic meningitis, flucytosine plus fluconazole could also be effective in reducing mortality associated with asymptomatic CrAg-positive patients. And importantly, this oral combination could be given to outpatients without any need for hospitalisation.

Impact
The impact of a combined treatment for CrAg-positive patients identified through screening has not yet been tested and robust clinical trial data are urgently needed to inform policy. Demonstrating the effectiveness of the addition of flucytosine to the fluconazole treatment currently in use could have an important global impact on the reduction of late-stage HIV mortality as has been seen for CM inpatients

Cryptococcal meningitis (CM) remains a key driver of AIDS-related mortality resulting in ~180,000 deaths/year globally. Over 75% of deaths occur in Sub-Saharan Africa (SSA), accounting for 15%-20% of all AIDS-related deaths. Targeting cryptococcal disease in its early stages, prior to the development of meningitis, can reduce this persistently high mortality. Screening patients with low CD4 counts using a simple point-of-care test to detect cryptococcal antigen (CrAg) and treatment of CrAg-positive patients in advance of severe disease represents a practical and cost-effective approach to reducing mortality, with such screening programs now recommended in many SSA countries. However, recent data has shown that current pre-emptive treatment with fluconazole alone may be suboptimal with a significant number of patients going on to develop meningitis and die. Testing of more effective antifungal regimens is thus urgently required. A combined treatment of fluconazole and flucytosine was shown to be safe and effective in a recent Phase III trial of those with symptomatic meningitis, with mortality halved compared to historic cohorts treated with fluconazole alone.

The EFFECT trial is a Phase III, multi-centre, pragmatic open-label, 1:1 randomised treatment trial embedded into existing screening programs in South Africa and Tanzania. It will compare 6-month all-cause mortality between those treated with fluconazole alone (1200 mg/day, control arm, current recommended treatment) versus a combined regimen of fluconazole (1200 mg/day) plus flucytosine (25 mg/kg qds, intervention arm) for 2 weeks. In total, 600 participants will be recruited over a 2.5-year period and followed-up to 6 months. The trial will also assess progression to cryptococcal meningitis, tolerability and safety, and cost effectiveness.

A safe and potent oral treatment regimen, which could be administered to outpatients, could have a major impact on survival, driving down AIDS-related mortality.

The ultimate goal of this project is to reduce mortality due to HIV-associated cryptococcal disease by ensuring universal access to affordable, safe, and effective treatment. If combination therapy of fluconazole and flucytosine was shown to be safe and more effective that fluconazole monotherapy, results from this study would lead to evidenced-based changes in regional and international treatment guidelines, and provide an effective and practical treatment, which could be administered to outpatients, with the potential to prevent a significant number of HIV-related deaths.

The study will benefit a range of groups in a number of ways:

1. Patients and health-care providers
CrAg-positive adults at high risk of developing severe cryptococcal meningitis (CM) in low-resource settings, their families and health-care providers will directly benefit from this study. Without appropriate antifungal treatment, over 70% of CrAg-positive patients go on to develop CM requiring hospitalisation, and treatment with expensive and potentially toxic drugs. The proposed study intervention will not require hospitalisation, will allow outpatient treatment and may reduce the need for lumbar punctures in this group. If shown to be safe and effective, the trial could have an important global impact on the reduction of late-stage HIV mortality, as has been seen for inpatients with symptomatic CM.

2. Decision and policy makers, health services
Trial results have a direct relevance to decision makers and practitioners in the field. Data from this pragmatic trial, designed to be integrated into routine CrAg screening programs, will provide robust evidence to inform policy for the treatment of this patient group and critical information on feasibility and cost-effectiveness of the intervention will also be provided. If shown to be effective, Ministries of Health and health care services would benefit from a practical and potentially cost-effective approach to treating out-patients effectively, reducing the burden on hospitals where patients with severe CM are managed and in reducing mortality in late-stage HIV patients. An integrated, pragmatic trial conducted at a time when CrAg screening and pre-emptive treatment with fluconazole alone is being rolled out across Africa would be easily implemented at scale across the continent. It is also worth noting that this intervention is likely to be highly cost-effective given the decreasing price of flucytosine and savings generated by the reduction in meningitis cases requiring hospital care and treatment.

3. Research and clinical staff
The study will be embedded in routine care and specialist training in the management and treatment of these patients will be provided to trial staff and to routine care staff. In addition to the public health impact, substantial capacity development in research methods is envisioned with training and hands-on experience in trial management according to GCP standards provided. The study will also build strong research links between leading UK and African research institutions, help to further develop clinical and research capacity at trial sites, and facilitate the development of local investigators into future research leaders.

4. Wider research community (See 'Academic beneficiaries' section)

5. Industrial partners
Flucytosine is now becoming more widely available and modified-release and low-cost generic formulations are under development. If the proposed study showed that flucytosine is beneficial to optimise pre-emptive therapy, the expanded market for the drug would give rise to substantially increased demand. Importantly, if the benefit of combination treatment was restricted to those with high CrAg titres, semi-quantitative CrAg tests are under development that would enable diagnosis of and selective treatment of high CrAg-titre patients (a priority research gap as identified in recent WHO guidelines).