Model-Informed Drug Development (MIDD) for Analgesics: Review of Applications, Regulatory Integration, and Emerging Directions.

Analgesic drug development poses distinctive challenges, including high placebo response rates, variability in subjective pain assessment, opioid safety and abuse-liability concerns, and difficulty in optimizing dose across heterogeneous pain conditions. Model-Informed Drug Development (MIDD) - a suite of quantitative modeling and simulation methodologies encompassing population pharmacokinetics (PopPK), physiologically based pharmacokinetic (PBPK) modeling, pharmacokinetic-pharmacodynamic (PK/PD) analysis, exposure-response (E-R) modeling, clinical trial simulation (CTS), and quantitative systems pharmacology (QSP) - offers tools directly relevant to these challenges and is increasingly integrated across all phases of drug development. This narrative review summarizes MIDD methodologies and their applications across clinical trial phases, the regulatory frameworks governing their use, landmark cross-therapeutic-area and analgesic-specific case studies, and emerging directions, with the aim of clarifying both the progress achieved and the gaps that remain in the application of MIDD to analgesic development. This is a non-systematic, narrative review; relevant literature was identified through PubMed and EMBASE searches (through early 2026) and regulatory agency databases (FDA Drugs@FDA, EMA EPAR repository), supplemented by hand-searching of reference lists, without a prespecified protocol or PRISMA methodology. Modeling and simulation analyses collectively contributed to regulatory decisions in more than 60% of novel drug approvals reviewed by the FDA between 2010 and 2020, spanning PopPK, PBPK, and E-R applications; clinical trial simulation has been associated with higher Phase II-to-Phase III transition rates and greater statistical power for a given sample size; and PBPK modeling has increasingly supported pediatric dose selection, with benchmark evaluations demonstrating clearance predictions within twofold of observed values for most studied drugs. Regulatory institutionalization of MIDD - through the FDA's MIDD (Paired) Meeting Program (established under PDUFA VI in 2018 and continued under PDUFA VII), EMA qualification opinions, ICH guidances, and the FDA's Project Optimus initiative for oncology dose optimization (launched 2021; draft guidance 2023; final guidance 2024) - has reduced regulatory uncertainty and created incentives for MIDD investment. Within analgesic development specifically, MIDD tools have been applied to opioid pharmacokinetic-pharmacodynamic and respiratory-safety modeling, population pharmacokinetics informing tapentadol and buprenorphine extended-release development, PBPK-supported bioequivalence of topical and generic analgesics, abuse-deterrent formulation assessment, and simulation-based trial designs addressing placebo response in chronic pain; however, no single analgesic has yet achieved the MIDD-centric development characteristic of oncology or rare disease. MIDD represents a substantial and still-maturing shift toward evidence-driven, model-guided drug development, with meaningful but incompletely realized potential to address the specific scientific and regulatory challenges of analgesic drug development.