Impact of Nonmedical Switches From Reference Infliximab to Biosimilars on Disease Control Within a Rheumatology Practice

<b>Background:</b> Infliximab is an anti-tumor necrosis factor agent used to treat rheumatologic disease. Evidence on the safety of switching to biosimilars and the associated risk factors for flares/loss of disease control within rheumatology is limited. <b>Objective:</b> The primary objective is to evaluate nonmedical switches from reference infliximab to biosimilars in rheumatology on risks and level of disease control. <b>Methods:</b> This retrospective analysis of data was conducted on all adult patients at our institution's rheumatology clinics with a rheumatologic diagnosis who were stable on reference infliximab and switched to the formulary biosimilars infliximab-dyyb or infliximab-abda, during the study period. Patient demographics as well as concomitant rheumatologic medications, markers of disease control, and hospitalization data were collected. <b>Results:</b> Of the 317 patients screened, 48 patients met inclusion criteria. A total of 29 patients (60.4%) were on reference infliximab and 19 patients (39.6%) were switched to biosimilar. Eight patients (42.1%) flared after a switch to biosimilar. Of the biosimilar patients, all patients were on infliximab-dyyb and were mandated to switch by insurance. Two patients who flared after switch to biosimilar (25%) had a delay in treatment due to attempts to receive prior authorization for reference infliximab. <b>Conclusions:</b> In the patients who switched to biosimilar, almost half experienced a flare. Two of these eight patients (25%) had a delay in treatment after the switch, which may be a risk factor for flaring/loss of disease control. Pharmacists should be following patients who switch to biosimilar closely during the transition period, to monitor for signs of flares/loss of disease control.