Close to 40% of combat injuries sustained by Service Members in the last 15 years involved severe extremity and craniofacial trauma. Despite the best reconstructive efforts using native tissue, these injuries frequently result in need of amputations. Eighty percent of amputees are then permanently retired while experiencing amputation-related disabilities that include poor professional and social interactions. Vascularized Composite Allotransplantation (VCA) has become a viable approach for functional restoration, and it enables patients to return to a quality of life higher than that afforded by any currently available prosthesis. However, the toxic and debilitating side effects (e.g., infections, nephrotoxicity, cardiovascular disease, diabetes, and cancer) of the multi-drug immunosuppressive therapy necessary to preserve the transplanted limb from rejection counterbalances its benefits and prevents widespread use. In particular, the use of calcineurin inhibitors (e.g., tacrolimus), the current mainstay therapy in VCA, is associated with substantial morbidity and is relatively ineffective in preventing rejection long-term. Minimizing the need for immunosuppression or even altering the recipient’s immune system to tolerate the transplant (by replacing calcineurin inhibitors with tolerance sparing/promoting drugs) will impact the life of a multitude of Service Members by pushing the benefit/risks ratio toward making VCA safer and more broadly applicable.

Biologic agents such as Belatacept (which reduces the activation of lymphocytes) have been developed to overcome this limitation. Despite a significant reduction in side effects, clinical studies have showed that Belatacept is not as effective as an immunosuppressant. Our own studies, however, indicate that the capacity of Belatacept to regulate the immune response against a transplant can be amplified by the co-administration of the JAK-inhibitor Tofacitinib. This combination limits the activation of the destructive arms of the immune system while promoting the function of the regulatory ones. The only limiting factors in the translation of this approach to a clinical application are the difficulties in maintaining the proper concentration of Tofacitininb in the body and the possible toxic effect associated with systemic exposure. To solve this problem, we propose to exploit cutting-edge advances in biomaterial design for drug delivery and improved understanding of graft rejection via a collaboration between three Principal Investigators with complementary expertise.

The goal of our study is to optimize and demonstrate the efficacy of a novel and clinically relevant drug delivery platform designed to suppress the rejection response in a localized and tunable fashion via a regimen that is permissive of immunomodulatory mechanisms. We are developing a novel dual-component therapeutic delivery platform that delivers JAK inhibitors from both microcrystalline drug deposits and from lipid nanoparticles encapsulated within a gel network. Inhibitors are released first from the microcrystalline phase locally to modulate infiltrating immune cells. Nanoparticles are released later in response to local enzymatic activity at the transplant site that occurs during rejection. Released particles traffic to the lymphoid tissues, the site of priming of the rejection response, to deliver their payload. This new material is easily syringe injected into or next to the transplant during surgery. Combining this material with the administration of Belatacept will render a regulated and localized synergism that our experimental data indicate is feasible and very effective in modulating the rejection response.

Thanks to the manufacturing scalability of the biomaterials investigated (capable to meet the demand of clinical use), our proposed studies in a small animal model of VCA will generate the necessary data to initiate a follow-up study in a preclinical large animal model and seek FDA approval. Independently from the outcome, our studies will be vastly informative for the nascent field of bioengineering for the manipulation of transplant rejection. If successful, this strategy will be transformative for VCA patients (service members and civilians), as it will change how immunosuppression is delivered and actuated and will avoid deleterious side effects, while also minimizing the risk of long-term graft loss. The knowledge accrued through this study would improve our understanding of how to optimize drug delivery to maximize the regulation of a transplant rejection response (beyond VCA). It will also impact a broader patient population, where targeted and controlled immunomodulation is needed, such as vaccination or cancer treatment. The proposed strategy addresses Focus Area: Reduce the risks of VCA-associated immunosuppression.

Subtopic: Develop novel approaches for achieving VCA immune tolerance / Identify unique immunotherapy requirements for VCA compared to solid organ transplants.