Cost to Medicare of Delayed Adalimumab Biosimilar Availability

Launched in 2002, originator adalimumab (Humira) is the top revenue-generating drug in the United States. Between 2016 and 2019, the US Food and Drug Administration approved 5 adalimumab biosimilars, yet none have been marketed owing to patent dispute settlements. We sought to calculate the cost of this delayed entry to Medicare over this period by estimating the difference between reported spending on originator adalimumab and estimated spending on originator and biosimilar adalimumab products assuming timely biosimilar market entry. Estimates of potential biosimilar spending were calculated based on the following evidence-based projections: (i) market capture of 15% for the first biosimilar and 5.5% for successive biosimilars in their first year on the market, and 5% annually thereafter; (ii) price reductions of 3.5% per year and 2.4% per additional biosimilar entry for originator adalimumab; and (iii) price discounts of 25% at launch, 3.4% per year, and 1.7% per additional biosimilar entry for biosimilar adalimumab. Based on these assumptions, had adalimumab biosimilars launched upon approval, estimated non-rebate spending on them would have been $18.3 million in 2016, $225.7 million in 2017, $436.2 million in 2018, and $727.7 million in 2019, whereas estimated non-rebate spending on originator adalimumab would have been $2.33 billion, $2.04 billion, $1.78 billion, and $1.42 billion. Cumulative spending on adalimumab would have thus been $8.98 billion instead of an observed $12.11 billion. Accounting for estimated rebates, total predicted savings would have been $2.19 billion. Reforms for timely biosimilar availability will be critical in ensuring optimal savings for Medicare after biosimilar approval.