How Could the Loss of Patent Exclusivity Impact Leukemia Drug Costs for Payers?

Generic imatinib could significantly reduce health plan expenditures for TKI therapy and fuel change for the management of the TKI class by payers.

The end of a leukemia drug’s patent exclusivity has the potential to help reduce costs for payers.

Imatinib (Gleevec) is a tyrosine kinase inhibitor (TKI) that targets the BCR-ABL protein in patients with advanced chronic myelogenous leukemia (CML). The inhibitor was approved by the FDA in 2001 to specifically target the signaling pathways in CML cells.

This approval improved the overall survival rate to 84% in 2001 compared with 65% between 1991 and 2000.

The expected end of patent exclusivity for imatinib was January 25, 2016, with the first generic version becoming available February 1.

The generic imatinib has the potential to significantly reduce US health plan expenditures for TKI therapy and help fuel change for the management of the TKI class by payers, according to a study published in American Health & Drug Benefits.

The primary goal of the study was to estimate what the economic impact would be upon the loss of the patent, and to determine the relative economic impact of formulary restrictions required for the use of the generic drug before a branded TKI, once it has been introduced.

The secondary goal was to estimate the economic impact of requiring the use of a preferred branded TKI, as well as the prior authorization (PA) requirement for using generic imatinib before a branded TKI.

Researchers used Truven Health MarketScan Commercial and Medicare Supplemental Data to create a healthcare claims analysis and generate data on key model parameters of market share and the utilization of TKI.

Those eligible for the study had at least 1 claim for TKI between July 1, 2012 and June 20, 2013 and were ≥18-years-old.

The 1-year prevalence of patients who received TKI after a diagnosis, specifically a CML diagnosis, was calculated by dividing the number of enrollees with a least 1 prescription (imatinib, dasatinib, or nilotinib) by the total number of enrollees in the plan during the study period. The result was multiplied by 100,000.

The 1-year prevalence was determined by health plan type, commercial or Medicare and the patients ages (18-64 years or ≥65 years).

The results of the study showed that prevalence rates were high in the Medicare subpopulation (34.7 per 100,000 patients) compared to the commercial subset (10.3 per 100,000 patients).

New TKI therapy patients were applied to the 1 year prevalence. The SEER database was used to access the annual incidence of CML and was stratified by age range (0.90 per 100,000 in people aged 18-64 years, and 6.8 per 100,000 in people aged ≥65 years).

This was in comparison with the prevalence of CML from the claim analysis (6.27 per 100,000 in people aged 18-64 years, and 6.19 per 100,000 in people aged ≥65 years).

The results of the analysis showed that 98.6% of the commercial plan population, as well as 1.7% of the Medicare plan population, ranged from the ages of 18 to 64, while 1.4% of commercial plan members and 98.3% of Medicare plan members were ≥65 years.

The study found that about 15.9% of patients in the commercial plan and 33.7% of patients in the Medicare plan would be new to therapy annually.

The switch from branded imatinib to generic is expected to reduce the costs for commercial and Medicare plans. In commercial plans the use of the generic form could reduce the total TKI spending by 28.8% for each plan.

Additionally there could be a cumulative 2 year savings of $6,840,427 ($0.29 PMPM) for a 1 million member commercial plan and $22,952,646 ($0.96 PMPM) for a Medicare plan.

If newly treated patients are required to use the generic form of imatinib in a 1 million member commercial plan, the spending could be reduced by 1.1% of the total 2 year pharmacy TKI costs before the patent exclusivity ends ($250,491). For the Medicare plan, it could reduce the incremental TKI pharmacy spending by 2.2% ($1,788,877).

It was concluded that the loss of patent exclusivity could potentially reduce total pharmacy spending by nearly 30% for a 2 year period.