Comparing Adoption of Breakthrough and "Me-too" Drugs among Medicare Beneficiaries: A Case Study of Dipeptidyl Peptidase-4 Inhibitors.

PURPOSE: "Me-too" drugs are new pharmaceuticals with the mechanism of action of an existing drug and are considered less innovative than breakthrough drugs. The objective of this study was to evaluate whether the adoption patterns of the breakthrough drug sitagliptin and the "me-too" drug saxagliptin differed; and to assess whether the patterns differed between Medicare stand-alone (PDP) and Medicare-Advantage Part D (MA-PD) plans.
METHODS: Pharmacy claims from a 5% random sample of Medicare Part D beneficiaries were used to identify all prescriptions filled for sitagliptin (breakthrough drug) and saxagliptin ("me-too" drug) between October 1, 2006 and December 31, 2011. The number of new sitagliptin and saxagliptin users by month and type of plan were plotted, and Bass diffusion models were constructed to estimate the rate of diffusion.
RESULTS: Sitagliptin had a longer adoption life than saxagliptin, and its adoption was quicker among MA-PD than PDP beneficiaries: it peaked at 51 and 66.7 months after its approval, respectively. However, the adoption of saxagliptin did not differ by type of plan: it peaked at 20.5 months in PDP and 22.9 months in MA-PD. At the end of our study, the market share of the innovative drug sitagliptin measured as the cumulative number of users since market entry was almost nine times higher than the "me-too" drug, saxagliptin.
CONCLUSIONS: The breakthrough drug sitagliptin had a much longer adoption life compared to the "me-too" drug saxagliptin, and the breakthrough drug sitagliptin was adopted quicker among managed care plans compared to PDP plans.