Drug disposition in neonatal Göttingen Minipigs: Exploring Effects of Perinatal Asphyxia and Therapeutic Hypothermia .

Asphyxiated neonates often undergo therapeutic hypothermia (TH) to reduce morbidity and mortality. Since both perinatal asphyxia (PA) and TH influence physiology, altered pharmacokinetics (PK) and pharmacodynamics (PD) are expected. Given that TH is the standard of care for PA with moderate to severe hypoxic-ischemic encephalopathy (HIE), disentangling the effect of PA versus TH on PK/PD is not possible in clinical settings. However, animal models can provide insights into this matter. The (neonatal) Göttingen Minipig, the recommended strain for nonclinical drug development, was selected as translational model. Four drugs - midazolam (MDZ), fentanyl (FNT), phenobarbital (PHB), and topiramate (TPM), were intravenously administered under four conditions: control (C), therapeutic hypothermia (TH), hypoxia (H), hypoxia + TH (H+TH). Each group included six healthy male neonatal Göttingen Minipigs anesthetized for 24 hours. Blood samples were drawn at 0 (pre-dose), and 0.5, 2, 2.5, 3, 4, 4.5, 6, 8, 12, 24 hours post-drug administration. Drug plasma concentrations were determined using validated bioanalytical assays. The PK parameters were estimated through compartmental and non-compartmental PK analysis (NCA). The study showed a statistically significant decrease in FNT clearance (CL, 66% decrease) with approximately 3-fold longer half-life (t 1/2 ) in the TH group. The H+TH group showed a 17% reduction in FNT CL with a 62% longer t 1/2 compared to the C group, however non-statistically significant. Trends towards lower CL and longer t 1/2 were observed in the TH and H+TH groups for MDZ and PHB. Additionally, TPM demonstrated a 28% decrease in CL in the H group compared to controls. Significance Statement The overarching goal of this study using the neonatal Göttingen Minipig model was to disentangle the effects of systemic hypoxia and TH on PK, using four model drugs. Such insights can subsequently be used to inform and develop a physiologically-based pharmacokinetic (PBPK) model, which is useful for drug exposure prediction in human neonates.