Arginine Therapy for Pain in Sickle Cell Disease: A Phase-2 Randomized, Placebo-Controlled Trial

We present a prospective randomized, placebo-controlled trial of intravenous arginine in patients 3-21 years hospitalized with sickle cell disease vaso-occlusive pain episodes (SCD-VOE) at two tertiary-care children's hospitals. Participants were randomized into 1 of 3 arms: Standard-dose (SD; 100 mg/kg/dose) every 8 h, Loading-dose (200 mg/kg followed by SD), or Placebo. The primary outcome was total parenteral opioid use (TPO). Secondary outcomes included time-to-crisis-resolution, pain scores, patient-reported outcomes (PROs), arginine bioavailability, and biomarkers of oxidative stress/mitochondrial function. Of 1548 patients screened, 108 were randomized (36 per study-arm; mean 12.6 ± 3.8 years, 52% female, and 65% hemoglobin-SS). This study did not meet its primary endpoint. TPO, time-to-crisis-resolution, pain scores, and PROs at discharge were similar across arms. Post hoc sensitivity analyses of children 5-16 years old demonstrated nearly double TPO utilization in those receiving placebo versus arginine (n = 87, p = 0.056), achieving significance in patients with plasma arginine < 60 μM. Arginine was low at presentation in 79% of patients (mean 50 ± 28 μM), and increased with arginine therapy (p < 0.001). Arginine bioavailability at VOE presentation inversely correlated with time-to-crisis-resolution (r = -0.39, p = 0.01) after placebo, an association eliminated by arginine supplementation (r = -0.04, p = 0.70). A dose-dependent increase in platelet-mitochondrial activity occurred after arginine versus no change after placebo (p < 0.001); plasma protein-carbonyl levels, a measure of oxidative stress, decreased after arginine therapy (p < 0.001) but increased in the placebo group (p = 0.02). SCD-VOE is associated with an acquired arginine deficiency that correlates with worse clinical outcomes. Arginine improved mitochondrial function and decreased oxidative stress compared to placebo, with clinically relevant opioid-sparing becoming significant in children with the lowest arginine concentration. TRIAL REGISTRATION: Registered with ClinicalTrials.gov (NCT02536170) in August 2015.