Racial Differences in the Effect of Granulocyte Macrophage Colony‐Stimulating Factor on Improved Walking Distance in Peripheral Artery Disease: The PROPEL Randomized Clinical Trial

BACKGROUND: The effects of race on response to medical therapy in people with peripheral artery disease (PAD) are unknown. METHODS AND RESULTS: In the PROPEL (Progenitor Cell Release Plus Exercise to Improve Functional Performance in PAD) Trial, PAD participants were randomized to 1 of 4 groups for 6 months: supervised treadmill exercise+granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) (Group 1), exercise+placebo (Group 2), attention control+GM‐CSF (Group 3), or attention control+placebo (Group 4). Change in 6‐minute walk distance was measured at 12‐ and 26‐week follow‐up. In these exploratory analyses, groups receiving GM‐CSF (Groups 1 and 3), placebo (Groups 2 and 4), exercise (Groups 1 and 2), and attention control (Groups 2 and 4) were combined, maximizing statistical power for studying the effects of race on response to interventions. Of 210 PAD participants, 141 (67%) were black and 64 (30%) were white. Among whites, GM‐CSF improved 6‐minute walk distance by +22.0 m (95% CI: −4.5, +48.5, P=0.103) at 12 weeks and +44.4 m (95% CI: +6.9, +82.0, P=0.020) at 26 weeks, compared with placebo. Among black participants, there was no effect of GM‐CSF on 6‐minute walk distance at 12‐week (P=0.26) or 26‐week (−5.0 m [−27.5, +17.5, P=0.66]) follow‐up, compared with placebo. There was an interaction of race on the effect of GM‐CSF on 6‐minute walk change at 26‐week follow‐up (P=0.018). Exercise improved 6‐minute walk distance in black (P=0.006) and white (P=0.034) participants without interaction. CONCLUSIONS: GM‐CSF improved 6‐minute walk distance in whites with PAD but had no effect in black participants. Further study is needed to confirm racial differences in GM‐CSF efficacy in PAD. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01408901.