REscuing Bone Marrow Function in Patients with AplaStic AnaEmia and Bone Marrow FaiLure Post AllogEneiC Transplantation 2

Allogeneic stem cell transplantation involves the transplanting of donor blood stem cells into a recipient, this is performed mainly for the treatment of blood cancers. The bone marrow is the organ that produces all blood cells and allogeneic stem cell transplantation results in the replacement of abnormal recipient bone marrow with donor blood cells as well as the production of donor immune cells from the donor bone marrow. The production of donor immune cells will hopefully lead to an immune response directed at any persisting cancerous cells leading to their eradication. As such, one of the key measures of success of a transplant is establishment of donor engraftment.

Engraftment is considered successful when the patient has normal blood cell counts on routine laboratory testing as well as confirmation that the blood cells are being produced by donor bone marrow cells. Confirming donor blood cell production is done by a process called chimerism. Poor graft function (PGF) is a complication of allogeneic stem cell transplantation related to engraftment, manifested by low blood counts despite complete donor chimerism. This has significant consequences for the patient leaving them susceptible to infection because of low white blood cells and bleeding because of low platelets (the cell components that are important for blood clotting). There is currently no established treatment for this condition and patients with this condition who do not recover have a poor survival.

Aplastic anaemia (AA) is a rare autoimmune condition that results in a patient's own immune system attacking important components of their bone marrow resulting in low blood counts. The current treatments for AA include suppressing the immune system or a bone marrow transplant, however long term survival for patients who do not respond to these treatments or relapse is poor and more effective treatments are required.

There is emerging evidence that demonstrates that the components of the immune system are dysfunctional and result in excessive immune activation resulting in suppression of the bone marrow characteristic of PGF. Similar features of immune dysfunction has been demonstrated in AA. Ruxolitinib is a drug that may be able to reduce this excessive immune activation. Eltrombopag is a drug that has been shown to stimulate the production of blood cells. The aim of this study is to evaluate whether the combination of ruxolitinib and eltrombopag is safe and effective in the treatment of PGF and AA.