Administration of Adult Human Bone Marrow-Derived, Cultured, Pooled, Allogeneic Mesenchymal Stromal Cells in Critical Limb Ischemia Due to Buerger's Disease: Phase II Study Report Suggests Clinical Efficacy

Abstract

Critical limb ischemia (CLI) due to Buerger's disease is a major unmet medical need with a high incidence of morbidity. This phase II, prospective, nonrandomized, open-label, multicentric, dose-ranging study was conducted to assess the efficacy and safety of i.m. injection of adult human bone marrow-derived, cultured, pooled, allogeneic mesenchymal stromal cells (BMMSC) in CLI due to Buerger's disease. Patients were allocated to three groups: 1 and 2 million cells/kg body weight (36 patients each) and standard of care (SOC) (18 patients). BMMSCs were administered as 40-60 injections in the calf muscle and locally, around the ulcer. Most patients were young (age range, 38-42 years) and ex-smokers, and all patients had at least one ulcer. Both the primary endpoints-reduction in rest pain (0.3 units per month [SE, 0.13]) and healing of ulcers (11% decrease in size per month [SE, 0.05])-were significantly better in the group receiving 2 million cells/kg body weight than in the SOC arm. Improvement in secondary endpoints, such as ankle brachial pressure index (0.03 [SE, 0.01] unit increase per month) and total walking distance (1.03 [SE, 0.02] times higher per month), were also significant in the group receiving 2 million cells/kg as compared with the SOC arm. Adverse events reported were remotely related or unrelated to BMMSCs. In conclusion, i.m. administration of BMMSC at a dose of 2 million cells/kg showed clinical benefit and may be the best regimen in patients with CLI due to Buerger's disease. However, further randomized controlled trials are required to confirm the most appropriate dose. Stem Cells Translational Medicine 2017;6:689-699.

Keywords: Bone marrow; Buerger’s disease; Critical limb ischemia; Mesenchymal stromal cells; Stempeucel.

Figure 1

Stempeucel treatment ameliorates ischemia‐induced limb necrosis and limb salvage in mice. (A): Representative photographs of sham control (Aa, Ad), vehicle‐treated limb ischemia (Ab, Ae), and Stempeucel‐treated (Ac, Af) LI on day 7 and day 28 after cell treatment. Stempeucel treatment significantly improved limb salvage in comparison with vehicle. (Ba, Bb, Bc): Hematoxylin and eosin‐stained sections of adductor muscle show severe necrosis (yellow arrows) and infiltration of inflammatory cells (green arrows), which were markedly reduced in the Stempeucel‐treated animals (Bc). Original magnification, ×40; scale bars = 50 µm. Abbreviation: LI, limb ischemia.

Figure 2

Total number of patients screened, allocated in each arm, followed up, and analyzed in the trial. Diagram as per the Consolidated Standards for Reporting Trials (CONSORT) flowchart. MITT population refers to all patients who received Stempeucel and had at least one rest‐pain assessment at visit 4. PP population refers to patients who had both the baseline and visit 6 rest‐pain assessments, with no major protocol deviation. Abbreviations: MITT, modified intention‐to‐treat; PP per protocol; SOC, standard of care.

Figure 3

Assessment of clinical efficacy parameters at various time points. (A): Rest pain assessment: mean change from baseline with SE shown as error bars (modified intention‐to‐treat [MITT] population). Compared with the SOC group, the 1 million cells/kg group had a 0.23 (SE, 0.13)‐unit reduction in rest pain per month (p = .0815; 95% confidence interval [CI], −0.48 to 0.03); the 2 million cells/kg group had a 0.3 (SE, 0.13)‐unit reduction in rest pain per month compared with the SOC group (p = .0193; 95% CI, −0.55 to −0.05). (B): Ulcer area: mean change from baseline, with SE shown as error bars (MITT population). Compared with the SOC group, the group receiving 1 million cells/kg had a 2% (SE, 0.06%) decrease in ulcer size per month (p = .6967; 95% CI, 0.87–1.10); the group receiving 2 million cells/kg had an 11% (SE, 0.05%) decrease in ulcer size per month (p = .0253; 95% CI, 0.80–0.99). (C): ABPI: Mean change from baseline, with SE shown as error bars (MITT population). Compared with the SOC group, the 1 million cells/kg group had a 0.02 (SE, 0.01)‐unit increase in the ABPI per month (p = .1329; 95% CI, −0.01 to 0.05); the 2 million cells/kg group had a 0.03 (SE, 0.01)‐unit increase per month compared with the SOC group (p = .0132; 95% CI, 0.01–0.06). (D): ABPI: Mean change from baseline. The group receiving 1 million cells/kg and the group receiving 2 million cells/kg had a 0.14 and 0.15 increase in ABIP at 6‐month follow‐up compared with a decrease of 0.01 in the SOC arm. (E): Total waking distance: Mean change from baseline, with SE shown as error bars (MITT population). Compared with the SOC group, the 1 million cells/kg group had a 1.03 (SE, 0.01) times greater total walking distance per month (p = .0231; 95% CI, 1–1.06); the 2 million cells/kg group had a 1.03 (SE, 0.02) times greater total walking distance per month (p = .0577; 95% CI, 1–1.07). Abbreviations: ABPI, ankle brachial pressure index; 1M/kg, 1 million cells/kg body weight; 2M/kg, 2 million cells/kg body weight; SOC, standard of care.

Figure 4

Magnetic resonance angiograms (left: baseline; right: 6 month) of one patient (ID number 08016) in the group receiving 2 million cells/kg body weight. Angiograms show overall increase in the vascularity of the affected limb, including development of new posterior collateral at 6‐month follow‐up after Stempeucel administration.