Realizing Effectiveness Across Continents with Hydroxyurea(REACH): A Phase I/II Pilot Study of Hyroxyurea for Children with Sickle Cell Anemia

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ABSTRACT Sickle cell anemia (SCA) is among the world’s most common inherited blood disorders, and causes severe morbidity and early mortality. SCA is highly prevalent in sub-Saharan Africa, affecting over 300,000 births annually, with an estimated 30% increase in the next generation. To address the burden of SCA within Africa, neonatal screening is needed to establish the proper diagnosis, and hydroxyurea treatment is needed to ameliorate morbidity and decrease mortality. Hydroxyurea is listed by the World Health Organization as an Essential Medicine for children with SCA, representing the only realistic and affordable disease-modifying therapy in this setting. Until recently, hydroxyurea had been studied primarily in high-income countries, with virtually no data available regarding its safe and effective use in Africa. To address this critical unmet need, we designed and launched REACH (Realizing Effectiveness Across Continents with Hydroxyurea, NCT01966731), a prospective open-label study of hydroxyurea for young children with SCA in sub-Saharan Africa. In the current funding period, 606 children in four African countries received hydroxyurea escalated to maximum tolerated dose (MTD). Despite COVID, our research teams in Angola, Democratic Republic of Congo, Kenya, and Uganda collected unprecedented data on the safety, feasibility, and benefits of hydroxyurea for SCA in Africa, with >3000 patient-years of treatment. We documented reductions in sickle- related clinical events and found unexpected reductions in malaria, transfusions, and death. We performed whole exome sequencing to investigate inter-patient variability including hydroxyurea pharmacokinetics, pharmacodynamics, and pharmacogenomics. In the renewal, we will make additional contributions by extending hydroxyurea treatment to this unique cohort, whose average age is now 11 years and soon entering puberty, using a continued supply of hydroxyurea donated by Bristol Myers Squibb. Though our initial results are encouraging, REACH does not have a placebo-controlled cohort for comparison. Accordingly, we will enroll a new cohort of age-matched children with SCA at all four sites, to provide pre-treatment data for comparison to our treated cohort. In the first specific aim, we will assess the long-term effects of hydroxyurea at MTD to ameliorate SCA-related clinical complications and preserve organ function (especially brain but also kidneys, spleen, and eyes). We will obtain longitudinal data on the effects of hydroxyurea at MTD on physical growth, sexual development, and overall reproductive health, and collect serial DNA to test for the emergence of clonal hematopoiesis. In the second aim, we will investigate mechanisms by which hydroxyurea reduces malaria infections, combining epidemiological data with in vitro parasite invasion assays and an agnostic search for protective genetic polymorphisms. In the third aim, we will simplify and optimize hydroxyurea treatment using novel and innovative approaches, by testing the feasibility and safety of a pharmacokinetics-based dosing algorithm in the new patient cohort to minimize dose adjustments and lab monitoring, and then by validating our newly identified genetic polymorphisms that predict HbF treatment responses. REACH will expand hydroxyurea treatment in Africa, build local capacity, and establish a robust research infrastructure for future collaborations, including planned NIH curative therapies. REACH is uniquely poised to elucidate benefits and risks of extended hydroxyurea, allowing safe and evidence-based dosing in Africa.