e48 Effects of baricitinib on haematological laboratory parameters in patients with rheumatoid arthritis

Abstract

Aim: Rheumatoid arthritis is associated with an increased neutrophil and platelet count, and decreased lymphocyte count. Methods: To summarise changes in absolute neutrophil counts (ANC), absolute lymphocyte counts (ALC), platelet counts, and haemoglobin (Hgb), and associated adverse events, with baricitinib (BARI [JAK1/2 inhibitor]) treatment. Data were pooled from completed Phase 1/2/3 studies and an extension study. Results: BARI treatment was associated with a decrease in ANC and an increase in ALC and platelets, which stabilized and returned to baseline with prolonged treatment or treatment discontinuation. Neutropaenia (<1000 cells/mm3) was rare (<1%) and was not associated with higher risk of overall or serious infections. Lymphopaenia was associated with slightly higher rate of overall infections. Incidence of overall and serious infections in ALL BARI-RA set was 29.9 and 2.9 per 100 patient-years, respectively. More BARI 4-mg (2.3%) as compared to placebo-treated (1.3%) patients had platelet count ≥600x109/L. In 6-study placebo-controlled set (0-24 weeks), 5 BARI 4-mg-treated patients (vs 0 placebo-treated) had “deep vein thrombosis” (DVT) and/or “pulmonary embolism” (PE). Incidence of overall and serious DVT/PE in ALL BARI-RA set remained low at 0.5 and 0.3 per 100 patient-years, respectively. The proportion of patients with high platelet levels (≥600x109/L) was comparable between patients with DVT/PE vs those without DVT/PE (at baseline: 0 vs 0.5%; post-baseline: 6.5% vs 3.3%). With long-term BARI treatment, Hgb levels decreased transiently before returning to levels slightly higher than baseline at Week-52. Incidence of severe treatment-emergent shifts in Hgb (grade <3 to grade ≥3: <8 and ≥6.5 g/dL) was low across all treatment groups (<0.5%). Conclusions: No associations were observed between ANC decrease and infections or thrombocytosis and DVT/PE. BARI treatment was not associated with an increased incidence of erythropaenia-related events or anaemia as compared to placebo. Few patients interrupted/discontinued BARI due to TE laboratory abnormalities.