Prospective identifcation of variables as outcomes for treatment (PIVOT): study protocol for a randomised, placebo-controlled trial of hydroxyurea for Ghanaian children and adults with haemoglobin SC disease

Abstract

Background Haemoglobin SC (HbSC) is a common form of sickle cell disease (SCD), especially among individuals of West African ancestry. Persons with HbSC disease sufer from the same clinical complications and reduced quality of life that afect those with sickle cell anaemia (HbSS/Sβ0 ). Retrospective anecdotal data suggest short-term safety and benefts of hydroxyurea for treating HbSC, yet rigorous prospective data are lacking regarding optimal dosing, clinical and laboratory efects, long-term safety and benefts, and appropriate endpoints to monitor. Prospective Investigation of Variables as Outcomes for Treatment (PIVOT) was designed with three aims: (1) to measure the toxici‑ ties of hydroxyurea treatment on laboratory parameters, (2) to assess the efects of hydroxyurea treatment on sickle related clinical and laboratory parameters, and (3) to identify study endpoints suitable for a future defnitive phase III trial of hydroxyurea treatment of HbSC disease. Methods PIVOT is a randomised, placebo-controlled, double blind clinical trial of hydroxyurea. Approximately 120 children and 120 adults ages 5–50 years with HbSC disease will be enrolled, screened for 2 months, and then ran‑ domised 1:1 to once-daily oral hydroxyurea or placebo. Study treatment will be prescribed initially at 20±5 mg/kg/ day with an opportunity to escalate the dose twice over the frst 6 months. After 12 months of blinded study treat‑ ment, all participants will be ofered open-label hydroxyurea for up to 4 years. Safety outcomes include treatment related cytopenias, whole blood viscosity, and adverse events. Efcacy outcomes include a variety of laboratory and clinical parameters over the frst 12 months of randomised treatment, including changes in haemoglobin and fetal haemoglobin, intracranial arterial velocities measured by transcranial Doppler ultrasound, cerebral oxygena‑ tion using near infrared spectrometry, spleen volume and kidney size by ultrasound, proteinuria, and retinal imaging. Exploratory outcomes include functional erythrocyte analyses with ektacytometry for red blood cell deformability and point-of-sickling, patient-reported outcomes using the PROMIS questionnaire, and 6-min walk test. Discussion For children and adults with HbSC disease, PIVOT will determine the safety of hydroxyurea and identify measurable changes in laboratory and clinical parameters, suitable for future prospective testing in a defnitive multi centre phase III clinical trial.