Allogenic Bone Marrow Mesenchymal Stem Cells Infusion in Patients With Steroid-refractory GVHD

Allogeneic haematopoietic stem cell transplant has become first choice of treatment for many malignant and non malignant haematological disorders. Although great progress has been made to prevent and minimize transplant-associated complications, yet graft versus host disease (GVHD) remains a significant complication affecting these the outcome in these patients. It is a severe inflammatory condition that arises when recipient tissues are attacked by immune mediated donor T cells during transplantation. Acute GVHD predominately affects the skin, upper and lower GI tract, liver and occasionally the eye and oral mucosa, whereas chronic GVHD resembles more with autoimmune disorders in its clinical symptoms. These symptoms can be organ-specific or generalized throughout body.

The pathophysiology of GVHD shows that it has different phases. In first phase i.e., afferent phase, damage to host tissue occurs. In second phase i.e., Induction and expansion phase, donor T cells are triggered and activated by recipient and donor APC as well as the inflammatory cytokines. Activated T cells produce IL-2 and IFN-γ (or Th1 response). Allogeneic immune response is amplified by IL-2, which activates more T cells and natural killer cell responses, triggering macrophages to release TNF-α and further inflammation damages skin and gut. The third phase i.e., effector phase, is characterized by cytotoxic damage against host cells by activated donor T-cell-mediated through Fas-Fas ligand interaction, perforin-granzyme and TNF-α. The latter has a central role in the pathophysiology, stimulating cytokine production (IL-1, IL-6, IL-10, IL-12 and TNF-α). This dysregulation leads to the clinical manifestations of acute GVHD.

The cells involved in GVHD pathophysiology include CD4+ T cells; for maintaining the expansion of CD8+ T cells that mediate GVHD, APCs; these have role in the initiation phase of acute GVHD as described in murine models and Natural killer (NK) cells; contribute to tissue damage in the effector phase by releasing inflammatory cytokines and nitric oxide. However, natural killer cells mediate cell death by two important pathways: Fas-Fas-ligand-mediated apoptosis and perforin-granzyme-B-mediated cytolysis.

HLA differences between donor and recipient are the major predictor of GVHD. Other affecting factors include age, gender mismatch between donor and recipient, minor histocomapatability antigen expression difference(mHA) in otherwise identical HSCT, donor age, source and dose of stem cells (PBSCT greater risk than BM), intensity of conditioning and GVHD prophylaxis.

Steroids are the first line therapy for acute GVHD patients and are standard treatment for grade II-IV acute GVHD. Adverse effects of glucocorticoids include hypertension hyperglycemia and psychosis, immunosuppression, infections, myopathy, osteoporosis and avascular necrosis of bone, cataracts and fat re-distribution etc. If acute GVHD is not improved after 5-7 days treatment with steroids then it is considered as steroid-refractory. Various agents that are being investigated from last two decades as second line therapy include low-dose MTX, MMF, extracorporeal photopheresis, IL-2R targeting, antibody therapy against CD3, CD7, CD25, CD52, CD147, IL-2R, IL-1, and TNF-α (i.e., basiliximab, daclizumab, denileukin, diftitox and alemtuzumab), horse ATG, etanercept, infliximab, and sirolimus and recently infusions of mesenchymal stem cells.

Mesenchymal stem cells (MSCs) are defined as self-renewing, multipotent progenitor cells with potential to differentiate into other cell types of mesodermal origin, such as adipocytes, osteocytes, and chondrocytes. Mesenchymal and Tissue Stem Cell Committee of the International Society for Cellular Therapy developed the minimal criteria for definition of MSCs which is as follows: first, adherence to plastic; Second, positivity for the cell-surface molecules CD105, CD73, and CD90 and negativity for CD45, CD34, CD14 or CD11b, CD79a or CD19, and human leukocyte antigen (HLA)-DR; and third, the ability to differentiate into osteoblasts, adipocytes, and chondroblasts under standard in vitro differentiation conditions. Since Le Blanc and colleagues first reported successful treatment of a patient with severe acute GVHD using third-party haploidentical MSCs in 2004, many clinical trials worldwide have described the benefits of MSC therapy in GVHD.

The proposed project is a phase I/II clinical trial of single group, open label, interventional study design. The objective is to observe the safety and efficacy of intravenous injection of ex-vivo expanded bone marrow mesenchymal cells from a third party donor for treating refractory GVHD. The study will also document the type and frequency of any adverse event or side effects, if discovered.