How Risky Is That Risk Sharing Agreement? Mean-Variance Tradeoffs andUnintended Consequences of Six Common Risk Sharing Agreements

摘要

Background. Pharmaceutical risk sharing agreements (RSAs) arecommonly used to manage uncertainties in costs and/or clinical benefits when newdrugs are added to a formulary. However, existing mathematical models of RSAsignore the impact of RSAs on clinical and financial risk. Methods.We develop a model in which the number of patients, total drug consumption perpatient, and incremental health benefits per patient are uncertain at the timeof the introduction of a new drug. We use the model to evaluate the impact ofsix common RSAs on total drug costs and total net monetary benefit (NMB).Results. We show that, relative to not having an RSA in place,each RSA reduces expected total drug costs and increases expected total NMB.Each RSA also improves two measures of risk by reducing the probability thattotal drug costs exceed any threshold and reducing the probability of obtainingnegative NMB. However, the effects on variance in both NMB and total drug costsare mixed. In some cases, relative to not having an RSA in place, implementingan RSA can increase variability in total drug costs or total NMB. We also showthat, for some RSAs, when their parameters are adjusted so that they have thesame impact on expected total drug cost, they can be rank-ordered in terms oftheir impact on variance in drug costs. Conclusions. Although allRSAs reduce expected total drug costs and increase expected total NMB, some RSAsmay actually have the undesirable effect of increasing risk. Payers andformulary managers should be aware of these mean-variance tradeoffs and thepotentially unintended results of RSAs when designing and negotiating RSAs.