Impact of tofacitinib on growth in patients with juvenile idiopathic arthritis

Tofacitinib is a Janus kinase inhibitor studied in different categories of juvenile idiopathic arthritis (JIA). This post hoc analysis evaluated the impact of tofacitinib on the growth of patients with JIA and on biomarkers of growth hormone (GH) function and bone metabolism.

The analysis included 225 patients, primarily with polyarticular-course JIA, receiving long-term tofacitinib (median [IQR] follow-up 3.6 [1.9-4.6] years). Height velocities (cm/y) and height Z-scores (based on age- and sex-matched reference data) were calculated. Biomarkers were measured in serum from 137 patients with JIA completing 18 weeks of open-label treatment with tofacitinib.

This population of patients with JIA had a baseline height distribution similar to the general population. During treatment with tofacitinib, patients experienced height velocities that appeared greater (patients ≤12 years) or as expected (patients >12 years) relative to the reference for their ages. Height Z-scores were largely stable during treatment with tofacitinib. In patients in puberty and a height Z-score less than --1.0 at baseline, an increase in height Z-score (P < .05) was detected after 24 months of treatment. Tofacitinib treatment did not impact levels of insulin-like growth factor (IGF)-1, IGF binding protein 3 and osteocalcin in the overall population, but in patients aged 6 to 12 years, IGF-1 levels increased with tofacitinib from baseline to 18 weeks.

This post hoc analysis of patients with JIA indicated normal or higher than expected growth velocity during long-term treatment, with tofacitinib with catch-up growth during puberty and, overall, no concerning changes in biomarkers of GH signalling.