Study Examines Uptake, Costs in Filgrastims After Biosimilar Introduction

The biggest cost difference in filgrastim administrations was seen in the commercially insured population after the launch of a biosimilar, according to a study published Monday in Health Affairs.

The study examined the uptake trends of biosimilar filgrastim and reference filgrastim in Medicare Advantage (MA), as well patient spending and plan costs.

The researchers, from the Mayo Clinic and the University of Minnesota, used data from the OptumLabs Data Warehouse from January 2104 to March 2018. During that period, the originator filgrastim (Neupogen) saw the entry of competition from biosimilar filgrastim (Zarxio) in 2015; a follow-on filgrastim (Granix, or tbo-filgrastim) received FDA approval under a standard biologics license application in 2012 and was launched in 2014.

The authors used procedure billing codes to identify all administrations of the 3 filgrastims and focused on incident use, requiring that patients have 6 months’ prior enrollment in medical and pharmacy benefits with no use of the relevant drug (although they could have used another formulation). They also recorded at least 10 days of follow-up after drug administration.

Using episode-level data, the researchers described trends in quarterly average patient out-of-pocket (OOP) spending and total (OOP spending plus health plan costs) drug costs per administration. Reported costs included drug costs only.

In the commercially insured group, the share of originator filgrastim was 88% at the time of biosimilar filgrastim approval in March 2015; the share of the originator did not begin to fall until the following year.

In the MA population, originator filgrastim was 84% in March 2015 but 39% in March 2018.

By March 2018, biosimilar filgrastim uptake rose to 47% of administrations in commercial insurance and 42% in MA populations. Follow-on filgrastim increased from about 9% in January 2016 to 18% in March 2018.

The study included 17,671 incident episodes, of which 11,598 (65.6%) were originator filgrastim, 3014 (17.1%) were follow-on filgrastim, and 3059 (17.3%) were biosimilar filgrastim.

The cost analysis sample included 11,207 episodes of originator filgrastim, 2778 episodes of biosimilar filgrastim, and 2338 episodes of follow-on filgrastim (569 episodes that included multiple types of filgrastim are not reported).

For the commercially insured group, biosimilar filgrastim entered the market with an average total cost (OOP spending plus health plan costs) of $520 per administration date in the first quarter of 2016, 31% lower than the cost of originator filgrastim, which averaged $759.

The average total cost of follow-on filgrastim was $714 in the first quarter of 2016.

By the first quarter of 2018, biosimilar filgrastim averaged $641, originator filgrastim $835, and follow-on filgrastim $628.

The authors said their results were consistent with an earlier study reporting 32% market share in fee-for-service Medicare by December 2016 compared with 34% in MA.

In the MA population, the initial cost difference between the originator and biosimilar was negligible. The average total cost per administration in the first quarter of 2016 was $358 for originator filgrastim, $350 for biosimilar filgrastim, and $291 for follow-on filgrastim.

Two years later, the average total costs were $347, $258, and $223, respectively. Average total costs dropped for biosimilar filgrastim and follow-on filgrastim, but not for originator filgrastim.

Average OOP spending per administration date for the commercially insured was $21 for originator filgrastim, $14 for biosimilar filgrastim, and $15 for follow-on filgrastim in 2016. Two years later, it was $28, $21, and $11, respectively, in 2018.

For MA enrollees, average OOP spending was higher in 2016: $42 for originator filgrastim, $31 for biosimilar filgrastim, and $30 for follow-on filgrastim. Two years later, average OOP spending fell to $36, $27, and $24, respectively.

The authors noted that although industry reports said that the wholesale acquisition cost of biosimilar filgrastim at launch was 15% percent lower than that of originator filgrastim, their study found a 31% cost differential between the originator and the biosimilar. By contrast, total costs at launch in the MA population showed little cost differential between originator and biosimilar.

The rapid uptake and cost savings seen in the United States with filgrastims are similar to what has been seen in Europe, the authors noted, but they also pointed out that legal battles here can delay entry. In addition, some manufacturers of originator biologics offer rebates to insurers to keep their place on plan formularies.

Additional studies should include an examination of factors at the patient, provider, and geographic levels associated with uptake, as well as the effect of reimbursement policies that encourage or discourage the use of biosimilars, the authors said.

Reference

Karaca-Mandic P, Chang J, Go R, Schondelmeyer S, Weisdorf D, Moore JM. Biosimilar filgrastim uptake and costs among commercially insured, Medicare Advantage. Health Aff (Millwood). 2019;(11)38: 1887—1892. doi: 10.1377/hlthaff.2019.00253.