Global health and economic impact of expanding the WHO essential medicines list for psoriasis: a health economic modelling study

Background Psoriasis affects at least 60 million people globally, but access to effective biologic treatments is limited, particularly in low- and middle-income countries. This study models the incremental global health and economic impact of large-scale access expansion for adalimumab and ustekinumab biosimilars following their inclusion on the World Health Organization (WHO) Essential Medicines List (EML) for psoriasis, as recommended by the 25th WHO Expert Committee on Selection and Use of Essential Medicines. Methods An empirical decision-analytic health economic model was developed to estimate the incremental costs and quality-adjusted life-years (QALYs) over a five-year horizon, using a 3% discount rate. The model compared the hypothetical current status quo with an EML expansion scenario for a target population of 8.9 million adults with moderate-to-severe psoriasis refractory to conventional systemic therapies. Findings Expanded biosimilar access under EML implementation was simulated to generate an incremental 0.625 QALYs per patient at an additional cost of $13,973 USD over five years. Extrapolated to the global target population, this policy could deliver a total health gain of 5.56 million QALYs, with an associated incremental budget impact of $124.35 billion USD over five years. One-way and probabilistic sensitivity analyses confirmed the robustness of these findings: probabilistic analysis mean of 5.67 million QALYs (95% Credible Interval [CrI] 0.38–12.84 million). These findings should be interpreted as upper-bound estimates derived from a simplified model that assumes full access in the eligible population, 60% optimal response, sustained five-year treatment benefit with uniform persistence, no switching or waning efficacy, and full biosimilar costs regardless of response. Interpretation The recent expansion of the WHO EML for psoriasis to include biosimilars could yield over 5.5 million QALYs globally. The profound health and access implications of the world-wide implementation of this EML expansion will require regional monitoring. Funding This study was funded by the International League of Dermatological Societies (ILDS). SML is funded by LifeArc and DEBRA.