Conversion from Filgrastim to Tbo-filgrastim: Experience of a Large Health Care System

In 2008, tbo-filgrastim was approved as a biosimilar in Europe and then approved in the United States by the FDA in 2012 as a biologic product with 1 similar indication to filgrastim. Because tbo-filgrastim was less expensive than filgrastim, and clinical information and expert opinion supported similarity, the Pharmacy & Therapeutics Committee of a large health care system approved tbo-filgrastim as the preferred granulocyte-colony stimulating factor (G-CSF) product in March 2014.

To (a) assess the use of filgrastim and tbo-filgrastim products by comparing baseline characteristics, setting of care, indication for use, and payer type and (b) understand potential barriers of conversion to tbo-filgrastim.

A retrospective evaluation of filgrastim and tbo-filgrastim use was conducted on all patients (N = 204) who received the drugs between July 2015 and December 2015 at the 2 largest hospitals in the health system. Baseline characteristics, indication requiring use of filgrastim or tbo-filgrastim, setting of care, and payer information were collected from electronic medical records, and descriptive analyses were conducted.

Overall, G-CSFs were administered to 204 patients for 261 episodes of care (filgrastim and tbo-filgrastim were used in 65 and 196 episodes of care, respectively). Baseline characteristics were similar between the 59 patients who received filgrastim and the 174 patients who received tbo-filgrastim. G-CSF was primarily used in the inpatient setting (163 episodes of care, 63%) with 90% of patients using tbo-filgrastim. In the outpatient setting (98 episodes of care, 38%), filgrastim and tbo-filgrastim were each used by 50% of patients. Tbo-filgrastim was the preferred G-CSF by clinical providers for all indications, except for stem cell mobilization, where filgrastim use was higher (55% vs. 45% of 71 episodes of care). In the outpatient setting, analysis by payers showed that the majority of patients on commercial plans were using filgrastim (58%), while half of Medicare patients were using filgrastim (50%, n = 12). Twelve patients were self-paid, and all were using tbo-filgrastim. Subgroup analysis by hospital showed differences in utilization patterns.

Although tbo-filgrastim was the preferred G-CSF in our formulary, 29% of patients continued to receive filgrastim. Conversion to tbo-filgrastim has been largely successful, but extra steps may be needed to achieve full conversion to biosimilars.

No outside funding supported this study. Agboola was employed by Partners Healthcare at the time of the study. The authors have nothing to disclose. Study concept and design were contributed equally by Agboola and Reddy. Agboola collected the data, and data interpretation was performed by both authors. The manuscript was written primarily by Agboola, with assistance from Reddy. Both authors revised the manuscript.