Ab0670 Switching From Intravenous to Subcutaneous Tocilizumab in Rheumatoid Arthritis: Single Centre Experience and Systematic Literature Review

Background: Tocilizumab (TCZ), a monoclonal antibody against Interleukin-6 receptor (IL-6r), is approved for rheumatoid arthritis (RA) management, and for COVID-19 in patients on corticosteroids who need supplemental oxygen treatment or mechanic ventilation. TCZ is available both intravenously (IV) and subcutaneously (SC); the two formulations proved similar efficacy in registration trials, therefore switching from the former route to the latter can be an available strategy for those who prefer self-administration. During COVID-19 pandemics, given the high demand for patients admitted to the ICU, many RA patients were forced to switch, due to unavailability of IV-TCZ. Several real-world studies reported worsening symptoms in RA patients undergoing this switch. Objectives: The aim of this study was to describe the retention rate of SC-TCZ and to find predictors of successful IV-to-SC switch in RA patients, alongside collecting existing literature evidence about this topic. Methods: We conducted a retrospective, single-centre observational study collecting socio-demographic, clinical and laboratory data from 31 RA patients who started IV-TCZ infusions (01/09/2005-30/12/2021) at the Rheumatology Unit of the St. Anna Hospital in Ferrara and subsequently switched to SC-TCZ. Unsuccessful switchers were defined at first follow up visit after switch as the need to revert to IV-TCZ ("back IV" group, BI) while successful switchers as "go on SC" group (GoS); follow-up timing was influenced by COVID-19-related access restrictions, being 3.5 months for BI and 5.5 months for GoS group. Then, patients were followed for a mean 37.09±17.95 months, until 21/12/2023. Concurrently, we conducted a systematic literature review (SLR) in Medline, in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines, to explore the outcome of IV-to-SC TCZ switch in RA patients. We included articles in Italian or English. Fisher's exact test, Pearson's Chi-squared test and Wilcoxon sum rank test were applied. Results: After a mean follow up of 4.57±2.42 months, 17/30 patients were classified as BI and 13/30 as GoS; one patient was lost to follow up after the switch. The SC-TCZ retention rate was 43.33%. Baseline demographic characteristics, disease- (seropositivity for ACPA/FR, presence of bone erosions, failure of previous bDMARDs) and therapy-related items (dose and previous duration of IV-TCZ, concomitant use of glucocorticoids or csDMARDs) did not differ between the groups. However, the BI group had a higher baseline DAS28-ESR (2.3±1.1 versus 1.6±1.4, p=0.034) (Figure 1A), mainly conditioned by patient-reported Global Health score (GH, 0-100) (44.1±19.1 versus 25.4±23.3, p=0.017). 94.1% of BI had tried SC route due to COVID-conditioned public health directives, versus 69.2% of GoS. BI patients returned to IV-TCZ after a mean 4.2±2.7 months, mainly due to subjective arthralgias (23.5%) rather than clinically confirmed flare (70.6%) (Table 1). DAS28-ESR at first follow up visit was significantly higher in this group compared to the GoS (2.8±1.1 versus 1.3±0.9 respectively, p<0.001), as well as mean GH and tender joint count (55.9±13.7 vs 23.8±24.7, p=0.001, and 3.1±3.2 vs 0.3±0.9, p=0.001, respectively). The probability to revert to IV infusions increased for each 1 mm increment of baseline GH scale (odds ratio (OR) 1.05 [95% CI 1.01-1.10], p=0.034) and it decreased as patients made the switch willingly (OR 0.03 [95% CI 0.00-0.21], p=0.003). Ten articles were included in the SLR. The mean retention rate at 3 or 6 months (5 studies) was 75.63% (Figure 1B). Conclusion: Switching from IV-to-SC TCZ was not associated with arthritic flare; however, clinimetric tools highlighted an early increased disease activity during follow up, mainly due to the relative weight of subjective items. Therefore, a non-desired switch may influence patients' perception of their disease. Compared with data from literature, our drug retention rate was overall lower, despite similar to other experiences during COVID pandemics. REFERENCES: NIL. Acknowledgements: NIL. Disclosure of Interests: None declared.