Allogeneic Stem Cell Transplantation (ALLOSCT) in Recessive Dystrophic Epidermolysis Bullosa (RDEB)

Epidermolysis bullosa (EB), is a diverse group of genodermatoses, which is considered a rare
and orphan disease and affects approximately 1 in 20,000 people in the United States for a
cumulative total of close to 20,000[1-4]. There are three major subtypes of inherited EB,
including EB simplex (EBS), junctional EB (JEB), and dystrophic EB[1-4]. RDEB is among the
most severe and represents approximately 10% of all forms of EB[1-4]. A rough estimate would
then project that there are several thousand patients with RDEB in the U.S. at the current
time. Up to 30 different clinical phenotypes and mutations in at least 10 structural genes
in different sub-types of EB have been reported[4-8]. In addition to heritable subtypes of
EB, there is an acquired autoimmune form in which the patients develop auto-antibodies
directed against similar proteins of the inherited dystrophic forms of EB, including EB
acquisita (EBA).

We have previously reported our experience with RIC with BFA [48] in pediatric AlloSCT
recipients (mean age 9.5 yrs [1.4-21], 11/4 M/F, 10 non-malignant, 5 malignant disease, [6
sibling, 5 UCB, 5 matched unrelated donor]); median time to ANC ≥ 500/mm3 and platelet count
≥20K/mm3 was 22 and 30 days, respectively. Probability of day +180 and 365 donor chimerism
was 90% (Figure 7), and OS was 95% (Figure 8). This conditioning regimen therefore results
in a high degree of donor chimerism and survival with minimal regimen related mortality.