OBJECTIVES: Patients increasingly experience claims denial for prescription drugs due to coverage restrictions and utilization management initiated by insurance plans via formulary design. However, the decision by plans to favor certain products, like choosing one biosimilar over another, is often driven not by clinical considerations but by financial benefits to insurers (i.e. having secured lower prices for one product relative to another through negotiations). We study this phenomenon using Insulin Glargine, which has a branded version (Lantus), that began receiving competition for formulary placement from a biosimilar-like comparator (Basaglar) in 2016.

METHODS: We conducted a retrospective cohort study of the IQVIA Formulary Impact Analyzer, anonymized prescription drug claims sourced from retail U.S. pharmacies, from October 2017 to September 2019. We supplemented the data with information derived from Medi-Span, Red Book, SSR Health, and FDA.gov. We included patients who had a rejected claim (for any reason) for either Lantus or Basaglar. We document the next claim they receive for Insulin Glargine, by product, time, and out-of-pocket costs.

RESULTS: 11,315 patients experienced a rejected claim for Lantus. After this rejected claim the next insulin glargine fill was Lantus (32.1%), Basaglar(29.3%), another rejected claim(14%), None (24.4%) or Cash(1%). The average days to next claim was 57.0(range 1-197). 2,951 patients experienced a rejected claim for Basaglar, their next insulin claim was Lantus(46.5%), Basaglar(20.12%), another rejected claim(15.8%), None(17.6%), and Cash Pay(6.7%), with the average days to next claim 44.5(1-149). Rejected claims for both drugs were more likely in commercial insurance than in Medicare.

CONCLUSIONS: Claims denials driven by non-clinical preference for certain products, likely save insurance plans money due to lower net prices they receive for these products. However, these savings must be considered relative to the disruption in care, and administrative burden put on patients and health systems.