Study to Evaluate Safety and Efficacy of ALLO-ASC-SHEET in Subjects With Dystrophic Epidermolysis Bullosa

Key Inclusion Criteria: 1. Subject diagnosed as dystrophic epidermolysis bullosa confirmed by clinical criteria and one of the following: 1. Immunostaining test: patients who have reduced or no type 7 collagen in staining degree of immunofluorescence. Other antigens (laminin-332, type 17 collagen, plectin, integrin α6β4, type 5 and type 14 keratin, etc.) are normal in immune-staining. 2. COL7A1 mutational analysis: confirmation of COL7A1 genetic mutation. 2. Subject with skin ulcer lesions of dystrophic epidermolysis bullosa meet the following criteria, on the screening start day (Visit 1) and treatment start day (enrollment day) (Visit 3): 1. Subject has two skin ulcer lesions judged as comparable to compare the safety and efficacy by investigator during screening period and prior to the IP application (enrollment day). 2. Two skin ulcer lesions meeting criteria stated in 2a) should be sized 5-20 cm2 (inclusive) 3. Subject who has two comparable target skin ulcer lesions, and each lesions with a change of size equal to or less than ±50% at treatment day (Visit 3) compared to that of screening day (Visit 1) 4. Subject who has no clinical evidence of infection related signs/symptoms, or visible necrosis in the target skin ulcer area (area including ulcer lesion and surrounding area where the IP is to be applied). Key Exclusion Criteria: 1. Subject who requires antibiotics due to bacterial infection on skin of the target skin ulcer area (area including ulcer lesion and surrounding area where the IP is to be applied). 2. Female subjects: pregnant woman (indicated by serum hCG test result at screening), breast-feeding patient, all sexually active patient, with child bearing potential in case of female\*, who is not willing to contracept\*\* during the clinical trial.