LAUSR

Interleukin 6 inhibitors (IL-6i) can increase LDL cholesterol levels, which raises concerns about the risk of myocardial infarction (MI) in patients with rheumatoid arthritis (RA) receiving this therapy. This study aims to compare the risk of MI between people with RA in the UK clinical setting receiving IL-6i or tumour necrosis factor inhibitors (TNFi) overall or by line of therapy (LoT). Patients with RA registered between 01/10/2001 and 27/05/2022 with BSRBR-RA starting IL-6i or TNFi treatments were included. Occurrence of MI was identified from clinical follow-up forms and through cause of death reported by the national UK death register. Only those MIs occurring whilst the patient was actively receiving drug were included. The risk of MI in patients receiving IL6i compared to TNFi was compared using Cox regression, adjusted for baseline co-variates using propensity scores (PS, see Table 1). Follow-up commenced at the start of the drug of interest and patients were censored at occurrence of MI, death, discontinuation of therapy or last follow-up visit, whichever came first. Multiple imputation was used for missing data. To account for known differences in LoT use of TNFi and IL6i (with IL6i more likely as a later line bDMARD), overall analyses adjusted for LoT in PS and secondary analyses by LoT were conducted. Direct switches between originator to biosimilars were considered the same treatment. A total of 29,596 IL6i or TNFi treatments in 20,725 patients were included (3,098 IL-6i; 26,498 TNFi), representing 153,913 person-years of exposure. Compared to patients receiving TNFi, patients starting IL-6i treatment were older, had longer disease duration, less likely to use methotrexate and steroids, and had more comorbidities. During follow-up, 372 MIs occurred, 27 on IL-6i and 345 on TNFi, with an overall lower crude rate of MI in patients receiving IL6i compared to TNFi. After PS adjustment, the risk of MI was not significantly different between the two treatment overall (HR 0.77, 95% CI 0.48-1.24) or when stratified by LoT (Table 1). This study could not identify any difference in risk of MI between IL-6i and TNFi treatment after patient characteristics and LoT were considered. Disclosure Z. Tian: None. L. Kearsley-Fleet: None. K. Lauper: Honoraria; Celltrion, Pfizer, Viatris, Galapagos. S. Haughton: None. K. Watson: None. M. Lunt: None. J. Mclaughlin: None. A. Verma: None. K.L. Hyrich: Honoraria; Abbvie. Grants/research support; Pfizer, BMS.