Study: High-risk Population Still in Need of G-CSF Biosimilars

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The arrival of biosimilars for filgrastim and pegfiltrastim coincided with higher use of granulocyte colony-stimulating factor (G-CSF) for prophylaxis against febrile neutropenia, but many high-risk patients still do not receive the treatment.

The approval of biosimilars of granulocyte colony-stimulating factor (G-CSF) and of a new injection device contributed to increased use of G-CSF among patients with cancer with a high risk of febrile neutropenia (FN), but many eligible patients still do not receive the preventive treatment, according to a new study.

G-CSF is a growth factor that helps the bone marrow to regenerate white blood cells following myelosuppressive chemotherapy and to ward off infection.

From 2014 to 2019, use of G-CSF to prevent FN in high-risk patients rose from 75% to 83% for the commercially insured population and from 75% to 86% for the Medicare population, according to the research published by University of Florida investigators in JAMA Network Open in November.

Older age, receiving a high–FN risk regimen, and history of neutropenia were associated with use of G-CSF.

However, as of late 2019, 14% to 17% of patients with high FN risk who were on chemotherapy still did not receive the preventive treatment, despite National Comprehensive Cancer Network (NCCN) guidelines recommending they receive primary prophylaxis using G-CSF.

The study authors note the NCCN has offered short-term guidance expanding recommended uses for G-CSF. The organization stated that in the context of the COVID-19 pandemic, clinicians may consider giving prophylactic therapy to patients receiving intermediate-risk regimens.

Biosimilar Launches

There are 2 G-CSF products for which biosimilars are available: Neupogen (filgrastim) and Neulasta (pegfilgrastim). During the study period, the filgrastim biosimilars Zarxio and Nivestym came on the market. A third competing filgrastim product (Granix) also launched, although this is not officially a biosimilar, as it was approved under a different regulatory pathway.

Two pegfilgrastim biosimilars were approved and launched during the study period: Fulphila and Udenyca. The Onpro, a wearable injector pegfilgrastim device, also was launched, and this has a roughly 50% share of the market for pegfilgrastim. Onpro uses the reference product (Neulasta), not a biosimilar, and there are no wearable injector biosimilar G-CSF devices on the market.

“The availability of biosimilar G-CSF presents an opportunity to reassess the cost-effectiveness of prophylactic G-CSF use in patients receiving myelosuppressive chemotherapy regimens. Evidence shows that using biosimilar G-CSFs for primary prophylaxis among patients with intermediate risk can be a cost-effective strategy even without risk factors,” the authors wrote.

Practice-improvement policy initiatives, along with decision support tools meant to reduce overutilization and inefficient practices, may have driven observed decreases in G-CSF use among patients receiving intermediate– or low–FN risk regimens in the commercially insured population, the study authors say.

Several biosimilars of the G-CSF products filgrastim and longer-acting pegfilgrastim were launched between 2015 and 2019, and the Onpro wearable injector was launched in 2017, expanding treatment options for patients.

The study, which examined 119,129 courses of chemotherapy given to patients with cancer from 2014 to 2019, found use of the filgrastim biosimilar Zarxio surpassed that of the filgrastim originator. The biosimilar accounted for 55.6% of all short-acting G-CSF use in the commercially insured population in the fourth quarter of 2019 and 22.2% of all short-acting G-CSF use in the fourth quarter of 2018 in the Medicare population.

In two nationally representative samples, there was increased G-CSF use among patients with high FN risk from 2014 to 2019 in a commercially insured population and from 2014 to 2018 in the Medicare population, but 14% to 17% of patients with high risk did not receive prophylaxis.

Among all long-acting G-CSF use in the last observable quarter of each data source, Onpro accounted for 44.9% of use in the commercial insurance data and 52.4% in the Medicare data. Pegfilgrastim biosimilars saw rapid initial uptake, accounting for 29.8% of all long-acting G-CSF use in the fourth quarter of 2019 in the commercially insured population.

The investigators note the G-CSF market is dominated by long-acting products, primarily the Onpro delivery service, where biosimilar uptake is lower than with short-acting therapy.

“Preference for the [Onpro] device may limit the adoption of long-acting biosimilar G-CSF products and undermine the potential cost savings implied with biosimilar availability in this therapeutic area. While a simulation study has demonstrated cost savings from biosimilar adoption, a variety of barriers exist,” they wrote.

For example, a biosimilar may not cut costs for patients considering the need for a second visit to a clinic and associated costs.

The authors say biosimilar device development or more aggressive reimbursement or formulary structures may be needed to drive use of G-CSF biosimilars. Future studies that use real-world data to show the cost savings from pegfilgrastim biosimilars could strengthen payer and clinician confidence and facilitate broader adoption, they say.

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