A controlled trial for preventing priapism in sickle cell anemia: hydroxyurea plus placebo vs hydroxyurea plus tadalafil

Abstract Recurrent ischemic priapism is a common complication of sickle cell anemia (SCA) and is associated with devastating physical and psychosocial consequences. All previous trials for priapism prevention have failed to demonstrate clear efficacy. We conducted a randomized, controlled, double-blind phase 2 feasibility trial comparing fixed moderate-dose hydroxyurea plus placebo (usual-care arm) with fixed moderate-dose hydroxyurea plus tadalafil (experimental arm) in 64 males (aged 18-40 years) with at least 3 episodes of SCA-related priapism in the past 12 months. Priapism data were obtained via daily text messages to the participants. The trial’s primary outcome measures were 100% recruitment, 98.4% retention, and 93.5% adherence rates. Over a median of 10 months (interquartile range, 3-12), 2.5 and 3.02 priapism events per participant-month were recorded in the usual-care and the experimental arms, with an incidence rate ratio of 0.8 (95% confidence interval [CI], 0.3-1.9; P = .654). The rates of serious adverse events (P = .999) and hospitalization (P = .289) were similar in the 2 arms. Sperm concentration, motility, and normal morphology significantly decreased on hydroxyurea therapy but recovered to prehydroxyurea levels 3 months after therapy cessation. Post hoc, single-arm, pre-post analysis showed a 58.3% priapism incidence rate reduction in the usual-care arm (5.9-2.5 events per month; difference, 3.4; 95% CI, 1.1-5.8; P = .005) and a 66.3% priapism reduction in the experimental arm (8.9-3.02 events per month; difference, 5.9; 95% CI, 3.4-8.5; P < .001) compared with the prerandomization rates. A randomized controlled trial for priapism prevention is feasible in men with SCA. This trial was registered at www.clinicaltrials.gov as #NCT05142254.