1. MM McDermott and coauthors
Effect of Granulocyte-Macrophage Colony-Stimulating Factor With or Without Supervised Exercise on Walking Performance in Patients With Peripheral Artery Disease
The PROPEL Randomized Clinical Trial
Published online November 15, 2017

2. Background
Circulating endothelial progenitor cells differentiate into endothelial cells and promote angiogenesis.
Benefits of granulocyte-macrophage colony-stimulating factor (GM-CSF) peripheral artery disease (PAD) are unclear.
Walking exercise may augment the effects of GM-CSF in PAD, since exercise-induced ischemia enhances progenitor cell release and may promote progenitor cell homing to ischemic calf muscle.

3. Primary Specific Aim
To determine whether GM-CSF + supervised treadmill exercise improves 6-minute walk distance at 12-week follow-up, compared to:
GM-CSF alone
Supervised treadmill exercise alone
To determine whether GM-CSF alone improves the 6-minute walk distance at 12-week follow-up, compared to placebo.
To determine whether exercise improves the 6-minute walk more than a control intervention.

4. PROPEL Study Design Randomized trial with 2 X 2 factorial design
Participants randomized to one of four groups:
GM-CSF + supervised exercise
GM-CSF + attention control
Placebo + supervised exercise
Placebo + attention control

5. PROPEL Trial Outcomes
Primary outcome: Change in 6-minute walk distance at 12-week follow-up.
Secondary outcomes: Change in maximal treadmill walking time and brachial artery flow-mediation dilation (FMD) at 12-week follow-up.
Exploratory outcomes: Change in 6-minute walk, maximal treadmill walking time, and brachial artery FMD at 6-week and 6-month follow-up.

6. Baseline Characteristics of PROPEL Trial Participants
Overall
(N=210)
Trial Assignment
GM-CSF + Exercise
(N=53)
GM-CSF + Attention control
Placebo + Exercise (N=53)
Placebo + attention control
(N=51)
Age (years), mean (SD)
67.0 (8.6)
66.6 (9.5)
67.9 (7.5)
67.5 (8.7)
66.0 (8.6)
Ankle-brachial index, mean (SD)
0.70 (0.19)
0.70 (0.20)
0.71 (0.17)
0.69 (0.19)
Women, n (%)
82 (39)
20 (38)
19 (36)
23 (43.)
20 (39.)
Black, n (%)
141 (67)
35 (66)
33 (62)
38 (75)
Current smoker, n (%)
71 (34)
21 (40)
12 (23)
18 (35)
Diabetes, n (%)
80 (38)
18 (34)
20 (39)
Classic intermittent claudication, n (%)
64 (30)
11 (21)
16 (31)

7. Changes in progenitor cells in response to study interventions

8. 12-week changes in six-minute walk by study group

9. 12-week change in treadmill walking time by study group
Exercise + GM-CSF GM-CSF alone Exercise alone
Attention control + placebo

10. 12-week change in brachial artery flow-mediated dilation
P = 0.40
Exercise + GM-CSF GM-CSF alone
Exercise alone
Attention Control + Placebo

11. PROPEL Trial: Temporal effects of study interventions on the six-minute walk

12. PROPEL Trial: Temporal effects of study interventions on treadmill walking time
Exercise + GM-CSF
Exercise alone
GM-CSF alone
Attention control + placebo

13. Study Limitations
2-week GM-CSF therapy may be too short to observe a benefit in walking performance
It is possible that benefit may have been observed before 6 weeks or after 6 months.

14. Additional Findings
In response to supervised exercise, the six-minute walk improved more gradually than treadmill walking performance.
Circulating progenitor cells did not increase in response to exercise.
Results did not differ according to presence or absence of classical claudication symptoms

15. Conclusions
Supervised exercise significantly improved 6-minute walk distance compared to attention control group at 12-week follow-up.
GM-CSF did not significantly improve walking performance in people with PAD when used alone or when combined with supervised treadmill exercise.