Peek behind the paper: a randomized controlled clinical trial of a hypothermically stored amniotic membrane for use in diabetic foot ulcers
In this feature, we peek behind the paper with lead study author Michael Sabolinski (Sabolinski LLC; MA, USA) to better understand how the use of a novel, hypothermically stored amniotic membrane (HSAM) for the treatment of diabetic foot ulcers (DFUs) was investigated.
Please could you introduce yourself and your affiliate institution(s)?
I currently serve as Managing Member and CMO of Sabolinski LLC (MA, US) – a group of healthcare and legal professionals committed to a multidisciplinary approach towards integrating medicine, science, law and government affairs, to enhance the value of medical products and healthcare businesses.
I have 39 years of experience in immunobiology, medicine and clinical research. I trained in Dermatology at New York University and SUNY Buffalo School of Medicine (both NY, USA) and am a member of the American Academy of Dermatology (IL, USA). I have previously served as CEO of Organogenesis Inc. (MA, USA), CEO of HealOr Ltd. (Rechovot, Israel), CMO of FoxKiser LLP (DC, USA) and CMO of NitroMed Inc. (MA, USA).
I have also acted as medical and regulatory lead in the development of living cell-based therapies; my work resulted in securing the first US FDA approval of a living manufactured human organ – a viable bi-layered skin equivalent – indicated for the treatment of venous leg ulcers and diabetic foot ulcers (DFUs).
What prompted you to conduct this research?
We formulated a working hypothesis for this research based on previous characterization work on a fresh, hypothermically stored amniotic membrane (HSAM). Data showed that the HSAM demonstrated high cell viability with pronounced activity of cytokines and growth factors that positively affected keratinocyte and fibroblast proliferation and migration. Fibroblasts have been associated with the deposition of extracellular matrix proteins, which are important in the granulation process of healing chronic wounds. It was also known that chronic wounds become stalled in the initial inflammatory phase of wound healing and it was hypothesized that active anti-inflammatory cytokines, elaborated by the viable cells of fresh amniotic membrane allografts, would stimulate the wound to move from a chronic state of inflammation to an active phase of proliferation.
Prior to the conduct of this study, clinical trials had evaluated only dehydrated and cryopreserved amniotic membrane allografts; this trial was the first to examine HSAM."
In general terms, HSAM – an active wound therapy – when compared with the standard of care (SOC), a passive wound therapy, was thought to have essential properties that might activate the wound healing cascade and lead to wound closure. The possible correlation of HSAM viable cells and native extracellular matrix with chronic wound healing had not been investigated in systematic clinical trials. Our starting clinical question was therefore whether a fresh HSAM would demonstrate effectiveness in healing DFUs. And, if effectiveness was able to be shown, how would the frequency of, and time to, wound closure of HSAM plus SOC compare with those of SOC alone?
Previous clinical trials had shown the efficacy of some human cell and tissue products for the management of chronic wounds. The proposed mechanism of action was the delivery of growth factors and cytokines, and the reduction of proteases. Novel processing technologies and hypothermic storage conditions that better preserve amnion components had been developed to maintain viable, differentiated cell populations, stem cells, growth factors, cytokines and extracellular matrix proteins. Delivery of these native, constitutive components of the amniotic membrane to the wound site was hypothesized to be associated with positive clinical outcomes for the management of chronic wounds in general, and DFUs in particular. Prior to the conduct of this study, clinical trials had evaluated only dehydrated and cryopreserved amniotic membrane allografts; this trial was the first to examine HSAM.
What criteria did you employ to define your study cohort and what limitations may these impose on your study outcomes?
We defined strict inclusion and exclusion criteria for out study population. Key inclusion criteria required patients to have received a diagnosis of Type 1 or 2 diabetes, to have DFIs located below the medial aspect of the malleolus and for patients to have well controlled blood glucose levels, with HbA1c measurements of less than 12%.
Key exclusion criteria included evidence of underlying comorbid conditions that would adversely affect wound closure, receipt of concomitant medications that would compromise wound closure and patients with ulcers that healed 20% or more during a 2-week run-in screening period.
Limitations of this trial, due to the narrowly defined cohort of patients and disease characteristics studied, are inherent in randomized controlled trials (RCTs). The primary purpose of a RCT is to establish efficacy; efficacy is best demonstrated when confounding factors are minimized.
By effectively holding as many patient, disease and treatment variables as constant as possible, the most accurate conclusions may be drawn on true treatment effects of an investigational intervention compared with a control group. However, by including a well-defined population of patients – with restricted, prespecified characteristics – other clinically significant patient groups may not be included for clinical assessment. More severe, or less severe, disease states may be underrepresented in a RCT. In a real-world comparative effectiveness research (CER) study, a broader patient population is treated and available for analysis. CER studies of large, national and worldwide databases provide valuable evidence to clinicians practicing in diverse types of treatment settings.
Limitations of this trial, due to the narrowly defined cohort of patients and disease characteristics studied, are inherent in randomized controlled trials (RCTs). The primary purpose of a RCT is to establish efficacy; efficacy is best demonstrated when confounding factors are minimized."
This trial had high ‘internal validity’ because of randomization, careful participant selection and standardized treatment protocols; the objective of the study was to maximize the possibility of observing a treatment effect, if it existed. While RCTs are considered ‘level one’ evidence in determining if a product can actually work, there are limitations in the generalizability or ‘external validity’ of the clinical data generated. Because this RCT of HSAM versus SOC required compliance to the defined inclusion and exclusion criteria – only partially listed above – rigorous monitoring and adherence to the treatment protocol, clinical evaluations in ordinary settings and in broader populations are recommended.
How did you determine ‘success’ – greater comparative effectiveness – of the HSAM in your study?
‘Success’ was prospectively defined in the statistical analysis plan by the primary endpoint – wound healing. Secondary endpoints were considered as supportive evidence upon ‘success’ in achieving the primary endpoint. The conclusion of having achieved greater comparative effectiveness required that the primary endpoint achieve statistically significant superiority results (HSAM-treated group compared with SOC-treated group; p<0.05). Showing superiority for all or some of the secondary endpoints was not considered sufficient to demonstrate superiority between treatment groups, in the absence of success in achieving the primary endpoint of wound closure at an α level of 0.05.
Secondary endpoints included reductions in ulcer sizes of more than 60% and reductions in ulcer volumes of more than 75% from baseline. These minimum levels of reduction were established from analyses of over 40,000 patients showing that these percentage reductions act as strong surrogates for predicting long-term ulcer healing beyond 16 weeks.
What is the importance of conducting follow-up, real-world studies comparing the use of HSAMs to other amniotic membrane allografts for the management DFUs? What may these real-world studies demonstrate that randomized controlled trials do not?
CER studies of HSAM compared to other skin substitutes in general, and placental membrane allografts in particular, are vital to support the future, expanded use of skin substitutes. Cost–effectiveness analyses of CER databases may act as important tools to shape health care policy for private and government payors. CER studies of DFUs would serve to provide critical information complimentary to the data generated in RCTs. Retrospective CER analyses of tens of thousands of patients would add more complete information on treatment effectiveness in broader patient populations presenting with a range of wounds under real-world conditions.
Better informed clinical practice decisions rely on both RCTs and CER studies. Each have strengths and weaknesses inherent in their respective study designs."
Whereas RCTs show what a treatment can do, under the conditions of the study protocol, CER studies show what a treatment does do, in the real-world, as the product is actually used. Real-world studies, without restrictions regarding the number of treatment applications, the duration of time between treatments or the use of adjunctive treatments (e.g. negative-pressure wound therapy, hyperbaric oxygen), act to inform clinical practice, influence wound care treatment algorithms and aid wound care professionals in providing optimal patient care.
Better informed clinical practice decisions rely on both RCTs and CER studies. Each have strengths and weaknesses inherent in their respective study designs.
Do you have future studies planned, or know of other studies in the field, for further assessing the benefits of HSAMs for patients with DFUs?
Planned HSAM studies include the collection and analysis of comprehensive data on clinically important DFU subgroups, using both RCT and CER study designs. These studies will include broader patient populations, different wound types and expanded wound and treatment characteristics that have yet to be addressed.
We urge that future HSAM studies commit to real-world CER initiatives that use large, de-identified wound care databases comparing the effectiveness of HSAM with other amniotic membrane allografts marketed in the USA as human cell tissue products. These CER studies will include large numbers of patients and more clinical facilities than have been studied in previous trials and published in recent research articles.
Prospective, multicenter, parallel group RCTs, which include only older patients, would be of particular benefit to the clinical community and healthcare policy decision makers."
RCT trials would lend themselves, by design, to the assessment of combination treatments of two or more classes of skin substitutes. ‘Rescue therapy’ study designs that allow for cross-over assignments for all treatment arms have yet to be systematically conducted. To date, no clinically meaningful conclusions have been able to be drawn for patients who fail on one skin substitute subsequently treated with a different class of skin substitute. Prospective, multicenter, parallel group RCTs, which include only older patients, would be of particular benefit to the clinical community and healthcare policy decision makers. Generating sufficient data that would allow for efficacy analyses of wound care products when used to treat patients with specific, common co-morbidities is encouraged. Long-term, follow-up studies of 1 year and longer, to enable data collection on emergency room visits, hospitalizations, ulcer recurrence, infections, cellulitis, osteomyelitis, amputations, sepsis, and deaths, are needed to evaluate and compare longitudinal effectiveness of wound care products.
The current HSAM trial results show valid information that may help to change current wound treatment algorithms regarding the use of skin substitutes. HSAM is currently in use in the USA (HSAM is marketed in the USA as a human cell tissue product) not only for DFUs, but also for dehisced wounds, pressure ulcers, venous leg ulcers and other wounds with exposed bone and tendon. What remains to be pursued by clinicians and clinical researchers is the systematic collection of clinical data for these and other wounds types, patient populations and clinical practice settings.