Hologene 5: A Phase II/III Clinical Trial of Combined Cell and Gene Therapy of Junctional Epidermolysis Bullosa

Abstract

Epidermolysis bullosa (EB) is a group of devastating genetic diseases characterized by skin and mucosal fragility and formation of blisters, which develop either spontaneously or in response to minor mechanical trauma. There is no definitive therapy for any form of EB. Intermediate junctional EB (JEB) caused by mutations in the gene LAMB3 has been the first genetic skin disease successfully tackled by ex vivo gene therapy. Here, we present a multicenter, open-label, uncontrolled phase II/III study that aims at confirming the efficacy of Hologene 5, a graft consisting of cultured transgenic keratinocytes and epidermal stem cells and meant to combine cell and gene therapy for the treatment of LAMB3-related JEB. Autologous clonogenic keratinocytes will be isolated from patients’ skin biopsies, genetically corrected with a gamma-retroviral vector (γRV) carrying the full-length human LAMB3 cDNA and plated onto a fibrin support (144cm2). The transgenic epidermis will be transplanted onto surgically prepared selected skin areas of at least six JEB patients (four pediatric and two adults). Evaluation of clinical efficacy will include, as primary endpoint, a combination of clinical parameters, such as percentage of re-epithelialization, cellular, molecular, and functional parameters, mechanical stress tests, and patient-reported outcome (PRO), up to 12months after transplantation. Safety and further efficacy endpoints will also be assessed during the clinical trial and for additional 15years in an interventional non-pharmacological follow-up study. If successful, this clinical trial would provide a therapeutic option for skin lesions of JEB patients with LAMB3 mutations and pave the way to a combined cell and gene therapy platform tackling other forms of EB and different genodermatoses.Clinical Trial Registration: EudraCT Number: 2018-000261-36.

Epidermolysis Bullosa: A Review of the Tissue-Engineered Skin Substitutes Used to Treat Wounds

“…In each case, subconfluent keratinocyte cultures were monitored for holoclone-forming stem cells [52], providing an indirect estimate of EpiSCtargeting efficiency, and therefore, graft durability [33][34][35]. Data from these trials demonstrated that only a small population of holoclone-forming stem cells corresponding to approximately 5% of the total grafted cells were responsible for the long-term maintenance of a functioning transgenic epidermis [50]. This equated to the transplantation of approximately 1.8 × 10 3 EpiSCs per cm 2 to regenerate and maintain nearly the entire epidermis of the severely affected boy [33].…”

“…It is possible that resident C7-mutant keratinocytes from the wound edges or epidermal stem cell reservoirs colonised the grafted wound bed and outcompeted the grafted revertant cells RDEB [ 42 ] Case report 1 Keratinocytes from genetically revertant skin carrying two COL7A1 gene reversions cultured on a feeder layer of murine fibroblasts into keratinocyte sheets 16 years Mechanical displacement an issue for some grafts; however, the grafted site on the right knee remained closed for 16 years [ 48 ] [ 48 ] Investigator-initiated trial 3 Keratinocytes from genetically revertant skin carrying COL7A1 gene reversions cultured on a feeder layer of murine fibroblasts into keratinocyte sheets 76 weeks Eight refractory ulcers treated on each of three patients. 100% of grafts fully epithelialised for two patients and 52.6% for the third, achieving the trial’s primary endpoint of >50% Gene therapy JEB [ 35 , 49 , 50 ] Phase I/II trial 1 Genetically corrected keratinocyte sheets generated on a feeder layer of murine fibroblasts. For genetic modification, LAMB3 -deficient keratinocytes were grown with an amphotrophic retroviral packaging cell line expressing wild type full-length LAMB3 cDNA controlled under the MLV LTR within an MFG retroviral backbone 15 years Complete epidermal adhesion in the absence of blistering, inflammation or infection.…”

“…Final CEAs were grafted onto nine sites on the patient’s legs, which either had a fragile epidermis or poorly healing and infected ulcers. Epidermal adhesion in the absence of blistering, inflammation, or infection was reported after one year, with the clinical benefits persisting for over 16 years as reported at a later follow-up [ 49 , 50 ]. Another successful case was later reported using the same method, this time to treat a larger (80cm 2 ) refractory ulcer on the leg of another LAMB3 -deficient patient with JEB [ 34 ].…”

“…Another successful case was later reported using the same method, this time to treat a larger (80cm 2 ) refractory ulcer on the leg of another LAMB3 -deficient patient with JEB [ 34 ]. The grafted area remained healed for the duration of the two-year follow-up, with histological analysis confirming a healthy BMZ and epidermis [ 34 , 50 ].…”

“…Despite the success achieved in the two JEB clinical studies, one criticism was the small total area grafted (~0.06m 2 ), which did not have a significant impact on the patients’ quality of life [ 34 , 35 , 50 ]. To assess the suitability of this treatment to treat large skin lesions, a compassionate use study used gene-modified CEAs to cover widespread blistering on a LAMB3 -deficient boy with severe JEB [ 33 ].…”