The Effects of Daily Prednisone and Tocilizumab on Hemoglobin A1c During the Treatment of Giant Cell Arteritis

Abstract

Objective: To study the longitudinal effects of both glucocorticoids and tocilizumab, an interleukin-6 receptor inhibitor, on hemoglobin A_1c (HbA_1c ) levels during glucocorticoid tapering.

Methods: We analyzed patients with complete data from the Giant Cell Arteritis Clinical Research Study (GiACTA) to investigate the impact of both glycemic and nonglycemic factors on changes in HbA_1c levels over the 52-week trial. Giant cell arteritis (GCA) patients were randomized to receive either tocilizumab or placebo in addition to glucocorticoids. We used a multivariable mixed-effects model to evaluate associations of HbA_1c level with daily glucocorticoid dose, randomization to receive tocilizumab, and red blood cell count in patients with and those without diabetes mellitus at baseline, over 52 weeks.

Results: In 209 patients, the median HbA_1c level decreased by 0.50% (P < 0.01) in the group that received both tocilizumab and glucocorticoids (tocilizumab/glucocorticoid) and by 0.10% (P < 0.01) in the glucocorticoid-only group. Randomization to tocilizumab/glucocorticoid was associated with lower HbA_1c (β = -0.209% in those without diabetes, P < 0.01; β = -0.290% in those with diabetes, P = 0.23). These changes had a sizable impact on glucose tolerance classification: 42.5% of patients in the tocilizumab/glucocorticoid group improved from prediabetes status to normal, compared to only 12.5% of patients treated with glucocorticoids alone. Daily glucocorticoid dose was associated with HbA_1c level in patients with baseline diabetes (β = 0.018%/mg, P < 0.01) and those without baseline diabetes (β = 0.005%/mg, P < 0.01).

Conclusion: Tocilizumab treatment was associated with a substantial reduction in HbA_1c level, independent of glucocorticoid exposure, which may be achieved through a combination of glycemic and nonglycemic effects.