Background Tofacitinib is a novel, oral Janus kinase (JAK) inhibitor for the treatment of rheumatoid arthritis (RA). Tofacitinib inhibits JAK3 and/or JAK1 with functional selectivity over JAK2.

Objectives To characterise changes in haemoglobin (Hb) and incidence of anaemia following tofacitinib treatment and evaluate the relationship between anaemia and fatigue or vitality.

Methods Changes in Hb and incidence of anaemia as defined by the OMERACT criteria were analysed from five randomised controlled Phase (P) 3 (N=3314) and two open-label long-term extension (LTE) (N=3515) studies in patients (pts) with RA. Fatigue and vitality were assessed in pts with and without anaemia using the Functional Assessment of Chronic Illness Therapy (FACIT) and the Short Form Health Survey (SF)-36 Vitality scores, respectively.

Results In the P3 studies, mean increases in Hb were seen in pts on tofacitinib 5 mg twice daily (BID), with little change in pts on tofacitinib 10 mg BID or placebo. Similar rates of decreased Hb, including anaemia, were observed between tofacitinib and placebo pts. Most cases of anaemia were mild to moderate. Clinically significant Hb changes (change ≥3 g/dL from baseline or Hb ≤7 g/dL) were seen in 0.1% of pts in the tofacitinib 10 mg BID and placebo groups and in no pts in the tofacitinib 5 mg BID group during Month 0-3, and in <0.1% of pts in the tofacitinib 10 mg BID and in no pts in the tofacitinib 5 mg BID groups (no placebo after Month 6) over 12 months. Changes from baseline in Hb and incidence of anaemia were stable over 4 years in LTE. FACIT-fatigue scores were improved following tofacitinib treatment with no numerical differences between pts with or without anaemia in P3 or LTE. Correlations between fatigue and anaemia were small and not significant with a correlation coefficient of 0.18 and 0.06 with tofacitinib 5 and 10 mg BID, respectively, at Month 12 in P3 and 0.15 in tofacitinib 5 and 10 mg BID doses combined at Month 24 in LTE. Similar results were seen with the SF-36 Vitality scores including tiredness/worn out.

Conclusions Rates of decreased haemoglobin and incidence of anaemia were low and similar across treatment groups in the tofacitinib RA development programme. Fatigue and vitality improved with tofacitinib treatment and there was no observable association between fatigue or vitality and anaemia in pts treated with tofacitinib.

Disclosure of Interest H. Schulze-Koops Grant/research support from: Abbot, BMS, Novartis, MSD, Consultant for: Abbott, Actelion, AstraZeneca, Biotest, BMS, Celgene, Chugai, GSK, Hoffmann-La Roche, MSD, Medac, Merck, Mundi Pharma, Novartis, Nycomed, Pfizer, Roche, Savient, UCB, 4SC, B. Benda Shareholder of: Pfizer Inc., Employee of: Pfizer Inc., G. Wallenstein Shareholder of: Pfizer Inc., Employee of: Pfizer Inc., R. Riese Shareholder of: Pfizer Inc., Employee of: Pfizer Inc., S. Zwillich Shareholder of: Pfizer Inc., Employee of: Pfizer Inc., K. Kwok Shareholder of: Pfizer Inc., Employee of: Pfizer Inc., L. Wang Shareholder of: Pfizer Inc., Employee of: Pfizer Inc., J. Bradley Shareholder of: Pfizer Inc., Employee of: Pfizer Inc.