Developmental Programming of Drug Response: Microbiota as a Missing Dimension in Perinatal Drug Discovery.

Drug exposure during pregnancy and early life is typically considered a short-term clinical intervention rather than a determinant of long-term pharmacological outcomes. Consequently, the developmental context is largely absent from drug discovery and drug development paradigms, where efficacy, safety and target engagement are evaluated predominantly in adult, steady-state systems. This disconnect may contribute to unexplained variability in drug response and toxicity later in life. Pregnancy is accompanied by dynamic remodeling of the maternal gut microbiota and its metabolic output, generating bioactive microbial metabolites that regulate immune tone, metabolic homeostasis and the expression of drug-metabolizing enzymes and transporters. These microbial signals intersect with pharmacological interventions across gestation, shaping maternal pharmacokinetics, placental regulation and fetal drug exposure during developmentally sensitive windows. Importantly, microbiota-drug interactions initiated during pregnancy do not terminate at birth. Instead, they extend into infancy through vertical microbial transmission, breast milk-mediated metabolic signaling, and the immaturity of neonatal drug-handling systems, collectively contributing to developmental programming of drug responsiveness beyond early life. In this review, we propose a microbiota-informed framework that reframes perinatal drug exposure as a developmentally embedded signal operating across a maternal-placental-infant continuum. This perspective introduces a missing developmental dimension into drug discovery and highlights new opportunities to improve translational predictability and precision pharmacotherapy across the life course.