StrataGraft is an allogeneic cellularized scaffold product indicated for the treatment of adults with thermal burns containing intact dermal elements for which surgical intervention is clinically indicated (deep partial-thickness burns).
StrataGraft has been tested in the task of regenerating skin affected by a thermal burn that has resulted in incomplete necrosis with the growth area intact. Usually in such cases, autografting is performed, when the patient is transplanted with his or her own healthy skin taken from undamaged areas. And while the technique is considered highly effective, it often leads to problems with increasing wound burden and healing of the donor sites, which are painful, itchy, and prone to infection and scarring. Again, if the burn area is large, there are not enough free skin flaps, and so one has to repeatedly transplant tissue from the same area, each time waiting for its integrity to be restored. At such times, the burn surface is protected with, for example, cadaver skin, pigskin, or synthetic material, which play the role of a temporary protective barrier.
Despite the extensive efforts of the industry, no cellular or synthetic product has been proposed so far that independently shows the same efficacy of wound healing of burns as skin autografting does.
StrataGraft, developed by Mallinckrodt Pharmaceuticals, is approved by the U.S. Food and Drug Administration (FDA) in mid-June 2021.
What is StrataGraft
StrataGraft, being the equivalent of healthy human skin tissue, is a bioengineered allogeneic cellularized construct (BACC) designed to treat severe burns.
StrataGraft, which actually replicates the structure of natural skin, is assembled from two layers: an inner dermis-like layer and an outer epidermis-like layer.
The StrataGraft design includes normal human dermal fibroblasts and a fully stratified (multi-layered) biologically active epidermis derived from the NIKS cell line — keratinocyte precursor cells isolated from infant tissue, immortalized, genetically stable, non-tumorigenic, and pathogen-free. Both layers are enclosed in a collagen gel.
Metabolically active cells within StrataGraft produce and release various growth factors and cytokines. These, as well as extracellular matrix proteins, are involved in wound repair and regeneration. StrataGraft provides a viable primary barrier function through the horny layer of the epidermis (stratum corneum), a key component of the fully stratified epithelial layer, and can be bonded and attached to the wound bed with adhesives, staples, or sutures.
StrataGraft, which is devoid of acute immunogenicity, does not cause rejection and does not lead to immune responses against NIKS.
Mallinckrodt took over the StrataGraft project after purchasing its originator, Stratatech, in August 2016. The development was funded by the U.S. Biomedical Advanced Research and Development Authority (BARDA), which had invested $100 million of a planned $261 million in the project as of the fall 2021 date.
StrataGraft: Efficacy and Safety
The STRATA2016 (NCT03005106) phase 3 (randomized, open-label, multicenter) clinical trial validated the efficacy and safety of StrataGraft in adult patients (n=71) in the task of autologous dermal tissue regeneration for complex thermal skin lesions whose burns involved the entire epidermis and over two-thirds of the dermis.
Body, arm, or leg burns still containing intact dermal elements were to be eligible for surgical excision and autologous skin transplantation procedures.
Randomization was performed on each patient when two similar burn areas of the same patient underwent either standard autografting or StrataGraft treatment.
Two primary efficacy endpoints were established, taken at 3 months after treatment. First, the percentage of wound area requiring an additional standard autografting. Second, the proportion of patients showing durable wound closure without the need for autografting — 100% re-epithelialization without drainage or dressing utilization at two consecutive evaluations at intervals of at least 2 weeks but not more than 5 months, including or encompassing the time point of the 3rd month.
A mean of 4.3% (95% CI: 0.0–9.4) of the burn areas treated with StrataGraft required an additional procedure of standard autografting — versus 102.1% (95% CI: 99.0–105.2) of the areas that initially received it. In other words, StrataGraft reduced the need for traditional transplantation of a patient’s own skin by 98% (95% CI: 93.9–101.7; p<0.0001).
83.1% (95% CI: 74.4–91.8) of patients treated with StrataGraft achieved burn wound closure. In the case of standard treatment, 85.9% (95% CI: 77.8–94.0) of patients reached the healing rate.
With regard to cosmetic results, according to the Patient and Observer Scar Assessment Scale (POSAS), they were better with StrataGraft. Thus, the average overall score by observer (evaluating scar characteristics such as vascularization, pigmentation, thickness, relief, pliability, and surface area; less is better) was 6.3 ±1.7 — vs. 16.3 ±7.7 (p<0.0001).
The safety profile of StrataGraft evaluated in its four clinical trials was comparable to that of autograft. The most common adverse event was itching, which was experienced by 11% of patients. All adverse reactions were mild to moderate in severity. No local infection was noted.
StrataGraft: What’s Next
Mallinckrodt is testing StrataGraft in the StrataSOMA (NCT04765202) phase 2 clinical trial, examining it for more severe thermal burns involving all layers of skin up to underlying muscle (full-thickness burns): StrataGraft is applied over an autograft.
A previous clinical trial NCT03005054 phase 2 treatment of adults with the above severe burns with StrataGraft alone did not confirm its therapeutic validity.
Plans are underway to test StrataGraft in the pediatric population.