Combined application of targeted therapy and immunotherapy in chronic myeloid leukaemia

Combining vaccination against leukaemia-derived antigens and treatment with tyrosine kinase inhibitors (TKI) in chronic phase CML is potentially a promising strategy to eradicate a reservoir of TKI resistant leukaemic cells. Previous studies have documented conflicting effects of TKIs on the immune response. I aimed to determine the in vivo immunomodulatory effects of TKIs on T and B-cell immune responses to antigens in patients with CML on TKIs. I first demonstrated that that the B-cell response to H1N1 influenza vaccine was significantly better in patients with CML compared to patients with other haematological malignancies. I then performed a more comprehensive analysis of T and B cell responses to a viral (seasonal influenza) and bacterial (pneumococcus) vaccine. I did not find a significant quantitative or qualitative difference in T cell responses to influenza vaccine in patients with CML on TKI compared to controls. However, I demonstrated that CML patients on TKIs have impaired IgM responses to pneumococcal vaccine, associated with lower frequencies of IgM memory B cells. Moreover, treatment with imatinib was associated with a significant reduction in IgM memory B cells. In vitro co-incubation of B-cells with plasma from CML patients on TKI or directly with imatinib, dasatinib or nilotinib, induced a dose-dependent inhibition of Bruton's tyrosine kinase, a tyrosine kinase essential for B cell signalling and survival. These data suggest that the loss of memory B-cell subsets and impaired humoral immune responses may be driven by the off-target kinase inhibitory activity of TKIs. I further explored the implications of Philadelphia positive (Ph+) lymphopoiesis on B cell function. I found that nearly 50% of CML patients at diagnosis have evidence of Ph+ B lymphopoiesis. Interestingly, the presence of Ph+ B cells predicted for worse prognosis, suggesting the involvement for a more committed progenitor with biphenotypic self-renewal capacity

Nonmyeloablative Peripheral Blood Haploidentical Stem Cell Transplantation for Refractory Severe Aplastic Anemia

New transplant approaches are urgently needed for patients with refractory severe aplastic anemia (SAA) who lack a matched sibling or unrelated donor (UD) or who have failed UD or cord blood transplant. Patients with refractory SAA are at risk of later clonal evolution to myelodysplastic syndrome and acute leukemia. We report our pilot findings with haploidentical hematopoietic stem cell transplantation (haploHSCT) using uniform reduced-intensity conditioning with postgraft high-dose cyclophosphamide in 8 patients with refractory SAA or patients who rejected a prior UD or cord blood transplant. Six of 8 patients engrafted. Graft failure was associated with donor-directed HLA antibodies, despite intensive pre-HSCT desensitization with plasma exchange and rituximab. There was only 1 case of grade II skin graft-versus-host disease. We show that haploHSCT can successfully rescue refractory SAA patients who lack donor-directed HLA antibodies but not in the presence of donor-directed HLA antibodies. This novel protocol for haploHSCT for SAA has been adopted by the European Group for Blood and Marrow Transplantation Severe Aplastic Anaemia Working Party for a future noninterventional, observational study to further evaluate its efficacy

Omacetaxine may have a role in chronic myeloid leukaemia eradication through downregulation of Mcl-1 and induction of apoptosis in stem/progenitor cells

Chronic myeloid leukaemia (CML) is maintained by a rare population of tyrosine kinase inhibitor (TKI)-insensitive malignant stem cells. Our long-term aim is to find a BcrAbl-independent drug that can be combined with a TKI to improve overall disease response in chronic-phase CML. Omacetaxine mepesuccinate, a first in class cetaxine, has been evaluated by clinical trials in TKI-insensitive/resistant CML. Omacetaxine inhibits synthesis of anti-apoptotic proteins of the Bcl-2 family, including (myeloid cell leukaemia) Mcl-1, leading to cell death. Omacetaxine effectively induced apoptosis in primary CML stem cells (CD34<sup>+</sup>38<sup>lo</sup>) by downregulation of Mcl-1 protein. In contrast to our previous findings with TKIs, omacetaxine did not accumulate undivided cells <i>in vitro</i>. Furthermore, the functionality of surviving stem cells following omacetaxine exposure was significantly reduced in a dose-dependant manner, as determined by colony forming cell and the more stringent long-term culture initiating cell colony assays. This stem cell-directed activity was not limited to CML stem cells as both normal and non-CML CD34<sup>+</sup> cells were sensitive to inhibition. Thus, although omacetaxine is not leukaemia stem cell specific, its ability to induce apoptosis of leukaemic stem cells distinguishes it from TKIs and creates the potential for a curative strategy for persistent disease

De-escalation of tyrosine kinase inhibitor dose in patients with chronic myeloid leukaemia with stable major molecular response (DESTINY): an interim analysis of a non-randomised, phase 2 trial

BACKGROUND: Discontinuation of tyrosine kinase inhibitor (TKI) therapy is feasible for some patients with chronic myeloid leukaemia (CML) with deep molecular responses, defined as stable MR4 (BCR-ABL1/ABL1 ratio 0.1%) on two consecutive samples. The study endpoint is the proportion of patients who lose their MMR on de-escalation and regain MMR on TKI resumption. The trial was registered at https://clinicaltrials.gov/ as NCT 01804985.FINDINGS: During the 12 months of half-dose therapy, 12 patients had molecular recurrence, all of whom regained MMR within 4 months of full dose TKI resumption. Recurrence was lower in the MR4 cohort (3 of 121 evaluable patients; 2.5%, 90% CI: 0.2-4.8%) than in the MMR cohort (9 of 48 evaluable patients; 18.8%, 90% CI: 9.5-28%) (p = 0.0007), but was unrelated to prior TKI or TKI therapy duration. Many adverse events improved during the first 3 months of de-escalation, though not thereafter. Overall, de-escalation saved 46.7% from an expected TKI budget (without de-escalation) of £4,156,969.INTERPRETATION: TKI de-escalation is safe for the vast majority of patients with excellent responses to TKI therapy, and is associated with improvement in symptoms and significant financial savings. The data imply that lower TKI doses may maintain responses in these patients

Autoimmune hemolytic anemia after allogeneic hematopoietic stem cell transplantation: analysis of 533 adult patients who underwent transplantation at King's College Hospital.

Autoimmune hemolytic anemia (AIHA) is a recognized complication of hematopoietic stem cell transplantation (HSCT); it is often refractory to treatment and carries a high mortality. To improve understanding of the incidence, risk factors, and clinical outcome of post-transplantation AIHA, we analyzed 533 patients who received allogeneic HSCT, and we identified 19 cases of AIHA after HSCT (overall incidence, 3.6%). The median time to onset, from HSCT to AIHA, was 202 days. AIHA was associated with HSCT from unrelated donors (hazard ratio [HR], 5.28; 95% confidence interval [CI], 1.22 to 22.9; P = .026). In the majority (14 of 19; 74%) of AIHA patients, multiple agents for treatment were required, with only 9 of 19 (47%) patients achieving complete resolution of AIHA. Patients with post-transplantation AIHA had a higher overall mortality (HR, 2.48; 95% CI, 1.33 to 4.63; P = .004), with 36% (4 of 11 cases) of deaths attributable to AIHA

The occurrence and management of fluid retention associated with TKI therapy in CML, with a focus on dasatinib

Tyrosine kinase inhibitors (TKIs) like dasatinib and nilotinib are indicated as second-line treatment for chronic myeloid leukemia resistant or intolerant to the current first-line TKI imatinib. These are agents are well tolerated, but potent and as such should be monitored for potentially serious side-effects like fluid retention and pleural effusions. Here we present key clinical trial data and safety considerations for all FDA approved TKIs in context for effective management of fluid retention and pleural effusions. Altering the dasatinib regimen from 70 mg twice daily to 100 mg daily reduces the risk of pleural effusion for patients taking dasatinib. Should pleural effusion develop, dasatinib should be interrupted until the condition resolves. Patients with a history of pleural effusion risk factors should be monitored closely while taking dasatinib. Patients receiving imatinib and nilotinib are not without risk of fluid retention. All patients should also be educated to recognize and report key symptoms of fluid retention or pleural effusion. Pleural effusions are generally managed by dose interruption/reduction and other supportive measures in patients with chronic myeloid leukemia receiving dasatinib therapy