Durable responses to ibrutinib in patients with relapsed CLL after allogeneic stem cell transplantation.

Ibrutinib, a recently approved inhibitor of Bruton's tyrosine kinase (BTK), has shown great efficacy in patients with high-risk CLL. Nevertheless, there are few data regarding its use in patients who relapsed after allogeneic stem cell transplantation (alloSCT). We report clinical data from five CLL patients treated with ibrutinib for relapse after first or even second allogeneic transplantation. Additionally, we performed analyses on cytokine levels and direct measuring of CD4 Th1 and CD4 Th2 cells to evaluate possible clinically relevant immunomodulatory effects of ibrutinib. All patients achieved partial responses including one minimal residual disease (MRD)-negative remission. Within 1 year of follow-up, no relapse was observed. One patient died of severe pneumonia while on ibrutinib treatment. Beside this, no unexpected adverse events were observed. Flow cytometry and analyses of T cell-mediated cytokine levels (IL10 and TNFα) did not reveal substantial changes in T-cell distribution in favor of a CD4 Th1 T-cell shift in our patients. No acute exacerbation of GvHD was reported. In conclusion, these results support further evaluation of ibrutinib in CLL patients relapsing after alloSCT.

Abundant cytomegalovirus (CMV) reactive clonotypes in the CD8(+) T cell receptor alpha repertoire following allogeneic transplantation.

Allogeneic stem cell transplantation is potentially curative, but associated with post-transplantation complications, including cytomegalovirus (CMV) infections. An effective immune response requires T cells recognizing CMV epitopes via their T cell receptors (TCRs). Little is known about the TCR repertoire, in particular the TCR-α repertoire and its clinical relevance in patients following stem cell transplantation. Using next-generation sequencing we examined the TCR-α repertoire of CD8(+) T cells and CMV-specific CD8(+) T cells in four patients. Additionally, we performed single-cell TCR-αß sequencing of CMV-specific CD8(+) T cells. The TCR-α composition of human leucocyte antigen (HLA)-A*0201 CMVpp65- and CMVIE -specific T cells was oligoclonal and defined by few dominant clonotypes. Frequencies of single clonotypes reached up to 11% of all CD8(+) T cells and half of the total CD8(+) T cell repertoire was dominated by few CMV-reactive clonotypes. Some TCR-α clonotypes were shared between patients. Gene expression of the circulating CMV-specific CD8(+) T cells was consistent with chronically activated effector memory T cells. The CD8(+) T cell response to CMV reactivation resulted in an expansion of a few TCR-α clonotypes to dominate the CD8(+) repertoires. These results warrant further larger studies to define the ability of oligoclonally expanded T cell clones to achieve an effective anti-viral T cell response in this setting.