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Research Letter Reports Reassuring Safety, Marginal Cost Savings Associated With Biosimilar G-CSF


Researchers found a $2522 mean cost for biosimilar and follow-on filgrastim versus a $2516 mean cost for reference filgrastim.

While the European Union has extensive experience with biosimilar drugs and the cost savings that these agents are able to provide to national healthcare systems, US experience with such agents is more limited, with biosimilar and follow-on granulocyte colony-stimulating factor (G-CSF) therapies having had the longest tenure in the US market, and with few studies available evaluating these products and their associated cost savings in real-world use.

In an effort to provide greater data on biosimilars in the US market, a recent research letter, published in JAMA Oncology, assessed the incidence of febrile neutropenia (FN), adverse events (AEs) related to G-CSF therapy, and drug costs among commercially insured US patients with cancer who were undergoing chemotherapy.

The letter’s authors analyzed deidentified health claims data on adult patients with cancer from a large, commercially insured population. The study included patients who received G-CSF therapy to prevent FN from 2012 to 2017. Patients received reference filgrastim (Neupogen), biosimilar filgrastim (Zarxio), or follow-on filgrastim (tbo-filgrastim, Granix). The follow-on product was approved prior to the establishment of the biosimilar approval pathway in the United States, and is thus not regulated as a biosimilar product, though it references the brand-name filgrastim.

The investigators divided the population of patients (n = 11,202) into a reference group (n = 9671) and a biosimilar/follow-on group (n = 1531), and then observed the patients for 21 days after the first filgrastim use to assess cost, FN, and AEs.

The incidence of FN according to a broad definition—comprising either neutropenia or fever—was similar between groups; FN was observed in 11.3% of the biosimilar/follow-on group versus 9.4% of the reference group. Incidence of FN according to a strict definition—both neutropenia and fever—was 4.5% and 3.9% in the 2 groups, respectively. There was no observed difference in the rate of AEs, with 6.9% of the biosimilar/follow-on group experiencing and AE versus 6.4% of the reference group.

The mean filgrastim drug costs per patient were similar between the biosimilar/follow-on and reference groups, with a $2522 mean cost for biosimilar and follow-on agents and a mean $2516 cost for reference filgrastim. The cost per day of use was 2.3% lower for biosimilar/follow-on agents, and compared with reference filgrastim, the mean total costs per patient and per day of use were 6.1% and 10.8% lower with Zarxio than with the reference product. These costs were marginally higher for Granix, at a 2.7% and 2.3% savings versus the reference.

“The findings suggest biosimilar filgrastim is similar to reference filgrastim in terms of safety and effectiveness in the real-world setting. The results are reassuring regarding the intended clinical outcomes associated with filgrastim,” write the authors. However, they add, “The savings associated with biosimilar filgrastim have been modest because early adoption of biosimilar agents has been slow, and current pricing for biosimilar drugs is closely tracking that of the brand-name product.”


Chen X, Agiro A, Barron J, Debono D, Fisch M. Early adoption of biosimilar growth factors in supportive cancer care. JAMA Oncol. 2018;4(12): 1779-1781. doi: 10.1001/jamaoncol.2018.5090.

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