Feasibility, Safety, and Efficacy of Myoblast Transfer Therapy on Duchenne Muscular Dystrophy Boys

Abstract

Five billion normal myoblasts were injected into each of 21 Duchenne muscular dystrophy (DMD) boys aged 6-14 yr to assess the feasibility, safety, and efficacy of the Phase II myoblast transfer therapy (MTT). The Phase II study was designed to strengthen muscles of both lower limbs. Forty-eight intramuscular injections transferred the myoblasts into 22 major muscles at 55.6 x 10(6)/mL in 10 min under general anesthesia. Eleven boys had received 8 million myoblasts each 1 yr ago in the Phase I MTT. In the Phase II study, eight of them had their myoblasts subcultured from reserves frozen 1 yr ago. The donor myoblasts for each of the remaining boys were cultured from satellite cells derived from a 1-g muscle biopsy of a normal male who might or might not be histocompatible with the recipient. The immunosuppressant cyclosporine (Cy) is being administered to recipients for 6 mo after MTT to facilitate donor cell survival. There was no evidence of an adverse reaction to MTT or Cy as determined by serial laboratory evaluations including electrolytes, creatinine, and urea. Early objective functional tests using the KinCom Robotic Dynamometer were conducted on 13 subjects aged 6 to 13 before MTT and at 3 mo after MTT. Of the 69 muscle groups (knee extensors, knee flexors, plantar flexors) tested for isometric force generation in these subjects, 43% showed mean increase of 41.3% +/- 5.9 SEM, 38% showed no change, and 19% showed continuous force reduction of 23.4% +/- 3.1 SEM. The remaining subjects await the 3-mo post-MTT evaluation. The results indicate that 1) MTT is safe; 2) MTT increases muscle strength in DMD: 81% of the muscles tested showed either increase in strength or did not show continuous loss of strength; 3) more than 5 billion myoblasts can be cultured from 1 g normal muscle biopsy, providing unprecedented numbers of cells for MTT; 4) myoblasts, frozen over 1 yr, retain the ability to proliferate from 10 million to 5 billion, and to form normal myofibers; 5) injections of 5 billion myoblasts have not provoked any immunological rejection symptoms in the Phase II subjects, 11 of whom received 8 million myoblasts in the Phase I MTT a year ago; 6) it is safe to perform multiple injections of myoblasts into lower limb muscles without formation of emboli; and 7) donor cell rejection by the recipient can be prevented with Cy when properly managed.

Muscle Satellite Cells and Duchenne Muscular Dystrophy

“…In spite of this success, the subsequent myoblast transplantation performed on DMD boys was unsuccessful (Law et al 1992;Mendell et al 1995;Tremblay et al 1993). In this section, we discuss the problems of myoblast-transplantation and other cell sources for cell therapy of DMD.…”

Exon Skipping and Myoblast Transplantation: Single or Combined Potential Options for Treatment of Duchenne Muscular Dystrophy

“…Mendell et al (Mendell et al, 1995) injected myoblast, once a month for six months, in 12 DMD patients, but this treatment failed to improve strength. Law et al (Law et al, 1992) demonstrated the feasibility and safety of myoblast transplantation, but with a poor clinical improvement. At the end of the 90's, a careful overview of the previous initial trials brought several research teams to identify three problems responsible for the limited results observed: (1) 3 days after the graft, at least 75% of the transplanted myoblasts died (Fan et al, 1996;Guerette et al, 1997;Huard et al, 1994); (2) myoblasts were not able to migrate more than 200 μm away from the intramuscular injection trajectory (Skuk et al, 1999); (3) if immunosuppression was not adequate, the myoblasts were rapidly rejected in less than 2 weeks (Guerette et al, 1994) or were induced to activate apoptosis, such as cyclophosphamide usage (Hardiman et al, 1993;Hong et al, 2002).…”

World’s First Myoblast Treatment of Human Cancer Found Safe and Efficacious

“…Lot release testing consisted of sterility, endotoxin, mycoplasma, and testing for myoblast identity, purity, potency, viability, and cell count on a pooled sample prior to transplant meeting quality control standards [17]. A retain sample of myoblasts was frozen in liquid nitrogen from each transplant.…”

“…Random samples of the myoblasts were tested for their ability to divide, fuse, and form myotubes [17]. Lot release testing consisted of sterility, endotoxin, mycoplasma, and testing for myoblast identity, purity, potency, viability, and cell count on a pooled sample prior to transplant meeting quality control standards [17].…”

“…Myoblasts were cultured in growth medium and incubated in 35˚C -37˚C and 7% CO 2 as previously described [17] [18]. Myoblasts were frozen at different stages so the time allotted for culturing could be coordinated with a scheduled transplant.…”