Realized and Projected Cost-Savings from the Introduction of Generic Imatinib Through Formulary Management in Patients with Chronic Myelogenous Leukemia.

Background: Imatinib, a first-generation tyrosine kinase inhibitor (TKI), and the newer second-generation TKIs have dramatically improved outcomes for patients with chronic myelogenous leukemia (CML). A previous model estimated the potential cost-savings over the next 2 years after the loss of patent exclusivity for imatinib in the United States in 2016 and its availability in a generic form. Payers have indeed realized meaningful savings, but it took 2 years for the prices of generic imatinib to decline substantially.

Objective: To quantify the cost-savings for a US health plan from the passive substitution of generic imatinib and the impact of step-edit therapy with the use of generic imatinib before coverage of a second-generation TKI.

Methods: We updated the previously published model utilizing hypothetical 1-million-member commercial and Medicare plans to include current TKI use and pricing combined with recent epidemiologic data. Regression models were used to project utilization to 5 years after the loss of imatinib's patent exclusivity. We compared generic imatinib costs with a scenario in which generic imatinib was not available. The impact of a step-edit therapy restriction was explored for patients with incident CML. The analyses were repeated for the entire US population based on national census data.

Results: The 1-million-member commercial plan saved $0.5 million (3%) from pharmacy spending on TKIs in year 1 and $3.9 million (19%) in year 2 after the loss of patent exclusivity. The projected savings significantly increased to $7.8 million (37%), $8.3 million (39%), and $8.6 million (40%) in years 3, 4, and 5, respectively. Step-edits strategies were projected to result in small incremental savings of $0.3 million (1.5%) annually in years 3 to 5. The 1-million-member Medicare plan saved $1.7 million (3%) in year 1 and $14.1 million (19%) in year 2. The projected savings were $27.8 million (37%), $29.5 million (39%), and $30.8 million (40%), with step-edit estimated to add only $0.9 million (1.2%) annually in years 3 to 5. Generic imatinib saved US payers $2.5 billion (13% of the total spending on TKIs) in years 1 and 2. In years 3 to 5, the cumulative projected savings totaled $12.2 billion, and the savings were expected to grow to 39% as a result of passive generic imatinib substitution, with only 1.7% additional savings from step-edit restriction.

Conclusions: As a result of a lower price for generic imatinib relative to the brand-name version of the drug, substantial cost-savings to US payers over the next 3 years are expected without step-edit formulary management restrictions. Cost-saving strategies, including formulary management restrictions, should adhere to evidence-based guidelines to ensure the appropriate use of generic imatinib and all available TKIs, with the objective to maintain positive outcomes and, in turn, increase the value of patient care.