Optimizing Hydroxyurea Therapy in Children With SCA In Malaria Endemic Areas

All children enrolled in NOHARM received hydroxyurea treatment at a fixed daily dose of 20 mg/kg/day. This dose was selected as a likely safe dose, but does not escalate hydroxyurea to MTD as is commonly done in the US. Without this information, we cannot know whether hydroxyurea treatment at the MTD would be feasible (since it requires closer monitoring to avoid hematological toxicities), safe (since adverse events may be greater with MTD, risk of malaria may be altered by MTD, and risk of infections as a result of neutropenia could also be greater with MTD) or beneficial (MTD is associated with higher hemoglobin and fetal hemoglobin concentration).

In this extension MTD study of open-label hydroxyurea for children in NOHARM who complete the initial study, consented children will be randomized to either fixed-dose or MTD hydroxyurea treatment for a minimum of 24 months. If hydroxyurea treatment continues to prove safe and effective in this low-resource malaria endemic area, and an optimal dosing scheme is determined, then the long-term goal is for all study children to transition to hydroxyurea treatment provided through the Ugandan Ministry of Health. To provide for a smooth transition, we will continue all children at either MTD or fixed dose hydroxyurea until a common end date (November 2019), at which time all study participants will have received a minimum of 24 months of additional hydroxyurea (either MTD or fixed dose). Addmedica, the Paris-based pharmaceutical company that provides the current active drug and placebo for the NOHARM trial, has agreed to provide additional hydroxyurea for this MTD study at no cost to the study or the participants.

The Specific Aims of the NOHARM MTD proposal include two initiatives for participants who are currently enrolled in NOHARM:

Aim 1. To determine the safety and efficacy of maximum tolerated dose (MTD) vs. fixed dose (20 mg/kg/day) hydroxyurea treatment in children with SCA in a low-resource, malaria endemic setting. For safety, we will compare adverse events and severe adverse events, including hematologic toxicities. For efficacy, we will assess hemoglobin level, fetal hemoglobin percentage (% HbF), and incidence of vaso-occlusive events such as pain crisis and acute chest syndrome.

Aim 2. To compare the clinical outcomes of MTD vs. fixed dose hydroxyurea treatment in children with SCA in a low-resource, malaria endemic setting. Clinical outcomes assessed will include growth and malaria incidence over a 24-month follow-up period, and differences in renal, splenic, and cerebrovascular function between study entry and 24-month follow-up.

Inclusion criteria

• Children with confirmed SCA who participated in the NOHARM study of hydroxyurea at the Mulago Hospital Sickle Cell Clinic (MHSCC), will be eligible for the MTD study after completing both 12-months of blinded study treatment and then an additional 12-months of open-label hydroxyurea for the second year of the study.
• The age range for enrollment into NOHARM, which began in 2014, was 1-4 years. Therefore, the children who will be enrolled in the follow up MTD study will be 3-6 years of age.

Exclusion criteria

• Not willing to come for all scheduled clinical visits or accept randomization