Despite recent new therapeutic options, allogeneic Stem Cell Transplantation remains the only curative option in patients with Myelofibrosis. Therefore, optimalization of this therapy remains a major challenge. Improvement of the clinical condition of these patients, decreasing spleen size can be accomplished by JAK2 inhibitor treatment and might improve SCT outcome. In addition, selective JAK2 inhibitors might modulate GvHD which can also add to improved SCT outcome. Also, decreasing the burden/activity of the disease before allo-SCT might also improve final disease response. The first, limited, clinical data of ruxolitinib treatment before allo-SCT show controversial effects on the outcome of SCT. Therefore, additional prospective clinical trials have to be done to establish the role of JAK2 inhibition before allogeneic SCT. Since ruxolitinib has considerable myelosuppressive effects which might limit the clinical use in some MF patients, other selective JAK2 inhibitors might be useful in this setting. Pacritinib, as a JAK2/FLT3 inhibitor, has a very potent JAK2 inhibitory activity without myelosuppressive effects and might therefore be more suitable than ruxolitinib. The major possible side effects are gastro-intestinal and can be managed with medication. In several studies, pacritinib has shown to be effective in decreasing spleen size and has shown to improve clinical condition of patients. Therefore, this compound seems promising in improving the outcome of allo-SCT. Although pacritinib causes no inhibition of JAK1 activity and therefore might have limited effects in decreasing inflammatory response, this might also be of benefit since a withdrawal syndrome as has been described after cessation of ruxolitinib is not to be expected.~With this trial, using pacritinib treatment before allo-SCT, the issue of improvement of SCT outcome will be investigated.
The only curative treatment for patients with myelofibrosis (MF) is allogeneic stem cell transplantation (SCT). Treatment with JAK2 inhibitors like pacritinib improves condition of MF patients, decreases spleen size and might diminish graft-versus-host disease (GvHD), thereby improving the outcome of SCT.