Mean concentrations (mM) of PG1+2, PG3 and PG4+5 in patients with or without MTX-related toxicity at baseline, week 4 and week 24/26 in (A) CONCERTO and (B) MUSICA. N was determined from patients with available MTX PG1+2 data at the time points. AE, adverse event; MTX, methotrexate; PG, polyglutamate; pts, patients. Mean concentrations (mM) of PG1+2, PG3 and PG4+5 in patients with or without MTX-related toxicity at baseline, week 4 and week 24/26 in (A) CONCERTO and (B) MUSICA. N was determined from patients with available MTX PG1+2 data at the time points. AE, adverse event; MTX, methotrexate; PG, polyglutamate; pts, patients. Gerd R Burmester et al. RMD Open 2017;3:e000465 Copyright © BMJ Publishing Group & EULAR. All rights reserved.