Abstract
PURPOSE: To develop a population pharmacokinetic (PK) model for intravitreal ranibizumab in infants with retinopathy of prematurity (ROP) and assess plasma free vascular endothelial growth factor (VEGF) pharmacodynamics (PD). METHODS: The RAnibizumab compared with laser therapy for the treatment of INfants BOrn prematurely With retinopathy of prematurity (RAINBOW) trial enrolled 225 infants to receive a bilateral intravitreal injection of ranibizumab 0.1 mg, ranibizumab 0.2 mg, or laser in a 1:1:1 ratio and included sparse sampling of blood for population PK and PD analysis. An adult PK model using infant body weight as a fixed allometric covariate was re-estimated using the ranibizumab concentrations in the preterm population. Different variability, assumptions, and covariate relationships were explored. Model-based individual predicted concentrations of ranibizumab were plotted against observed free VEGF concentrations. RESULTS: Elimination of ranibizumab had a median half-life of 5.6 days from the eye and 0.3 days from serum, resulting in an apparent serum half-life of 5.6 days. Time to reach maximum concentration was rapid (median: 1.3 days). Maximum concentration (median 24.3 ng/mL with ranibizumab 0.2 mg) was higher than that reported in adults. No differences in plasma free VEGF concentrations were apparent between the groups or over time. Plotted individual predicted concentrations of ranibizumab against observed free VEGF concentrations showed no relationship. CONCLUSIONS: In preterm infants with ROP, elimination of ranibizumab from the eye was the rate-limiting step and was faster compared with adults. No reduction in plasma free VEGF was observed. The five-year clinical safety follow-up from RAINBOW is ongoing. TRANSLATIONAL RELEVANCE: Our population PK and VEGF PD findings suggest a favorable ocular efficacy: systemic safety profile for ranibizumab in preterm infants.