Insights into highly engraftable hematopoietic cells from 27-year cryopreserved umbilical cord blood.

Umbilical cord blood transplantation is a life-saving treatment for malignant and non-malignant hematologic disorders. It remains unclear how long cryopreserved units remain functional, and the length of cryopreservation is often used as a criterion to exclude older units. We demonstrate that long-term cryopreserved cord blood retains similar numbers of hematopoietic stem and progenitor cells compared with fresh and recently cryopreserved cord blood units. Long-term cryopreserved units contain highly functional cells, yielding robust engraftment in mouse transplantation models. We also leverage differences between units to examine gene programs associated with better engraftment. Transcriptomic analyses reveal that gene programs associated with lineage determination and oxidative stress are enriched in high engrafting cord blood, revealing potential molecular markers to be used as potency markers for cord blood unit selection regardless of length of cryopreservation. In summary, cord blood units cryopreserved for extended periods retain engrafting potential and can potentially be used for patient treatment.

A Phase Ib Trial of AVID200, a TGFß 1/3 Trap, in Patients with Myelofibrosis.

PURPOSE: Myelofibrosis (MF) is a clonal myeloproliferative neoplasm characterized by systemic symptoms, cytopenias, organomegaly, and bone marrow fibrosis. JAK2 inhibitors afford symptom and spleen burden reduction but do not alter the disease course and frequently lead to thrombocytopenia. TGFß, a pleiotropic cytokine elaborated by the MF clone, negatively regulates normal hematopoiesis, downregulates antitumor immunity, and promotes bone marrow fibrosis. Our group previously showed that AVID200, a potent and selective TGFß 1/3 trap, reduced TGFß1-induced proliferation of human mesenchymal stromal cells, phosphorylation of SMAD2, and collagen expression. Moreover, treatment of MF mononuclear cells with AVID200 led to increased numbers of progenitor cells (PC) with wild-type JAK2 rather than JAK2V617F. PATIENTS AND METHODS: We conducted an investigator-initiated, multicenter, phase Ib trial of AVID200 monotherapy in 21 patients with advanced MF. RESULTS: No dose-limiting toxicity was identified at the three dose levels tested, and grade 3/4 anemia and thrombocytopenia occurred in 28.6% and 19.0% of treated patients, respectively. After six cycles of therapy, two patients attained a clinical benefit by IWG-MRT criteria. Spleen and symptom benefits were observed across treatment cycles. Unlike other MF-directed therapies, increases in platelet counts were noted in 81% of treated patients with three patients achieving normalization. Treatment with AVID200 resulted in potent suppression of plasma TGFß1 levels and pSMAD2 in MF cells. CONCLUSIONS: AVID200 is a well-tolerated, rational, therapeutic agent for the treatment of patients with MF and should be evaluated further in patients with thrombocytopenic MF in combination with agents that target aberrant MF intracellular signaling pathways.

Targeting CHAF1B Enhances IFN Activity against Myeloproliferative Neoplasm Cells.

Interferons (IFNs) are cytokines with potent antineoplastic and antiviral properties. IFNα has significant clinical activity in the treatment of myeloproliferative neoplasms (MPN), but the precise mechanisms by which it acts are not well understood. Here, we demonstrate that chromatin assembly factor 1 subunit B (CHAF1B), an Unc-51-like kinase 1 (ULK1)-interactive protein in the nuclear compartment of malignant cells, is overexpressed in patients with MPN. Remarkably, targeted silencing of CHAF1B enhances transcription of IFNα-stimulated genes and promotes IFNα-dependent antineoplastic responses in primary MPN progenitor cells. Taken together, our findings indicate that CHAF1B is a promising newly identified therapeutic target in MPN and that CHAF1B inhibition in combination with IFNα therapy might offer a novel strategy for treating patients with MPN. Significance: Our findings raise the potential for clinical development of drugs targeting CHAF1B to enhance IFN antitumor responses in the treatment of patients with MPN and should have important clinical translational implications for the treatment of MPN and possibly in other malignancies.

Discovery of a signaling feedback circuit that defines interferon responses in myeloproliferative neoplasms.

Interferons (IFNs) are key initiators and effectors of the immune response against malignant cells and also directly inhibit tumor growth. IFNα is highly effective in the treatment of myeloproliferative neoplasms (MPNs), but the mechanisms of action are unclear and it remains unknown why some patients respond to IFNα and others do not. Here, we identify and characterize a pathway involving PKCδ-dependent phosphorylation of ULK1 on serine residues 341 and 495, required for subsequent activation of p38 MAPK. We show that this pathway is essential for IFN-suppressive effects on primary malignant erythroid precursors from MPN patients, and that increased levels of ULK1 and p38 MAPK correlate with clinical response to IFNα therapy in these patients. We also demonstrate that IFNα treatment induces cleavage/activation of the ULK1-interacting ROCK1/2 proteins in vitro and in vivo, triggering a negative feedback loop that suppresses IFN responses. Overexpression of ROCK1/2 is seen in MPN patients and their genetic or pharmacological inhibition enhances IFN-anti-neoplastic responses in malignant erythroid precursors from MPN patients. These findings suggest the clinical potential of pharmacological inhibition of ROCK1/2 in combination with IFN-therapy for the treatment of MPNs.

Characterization of disease-propagating stem cells responsible for myeloproliferative neoplasm-blast phase.

Chronic myeloproliferative neoplasms (MPN) frequently evolve to a blast phase (BP) that is almost uniformly resistant to induction chemotherapy or hypomethylating agents. We explored the functional properties, genomic architecture, and cell of origin of MPN-BP initiating cells (IC) using a serial NSG mouse xenograft transplantation model. Transplantation of peripheral blood mononuclear cells (MNC) from 7 of 18 patients resulted in a high degree of leukemic cell chimerism and recreated clinical characteristics of human MPN-BP. The function of MPN-BP ICs was not dependent on the presence of JAK2V617F, a driver mutation associated with the initial underlying MPN. By contrast, multiple MPN-BP IC subclones coexisted within MPN-BP MNCs characterized by different myeloid malignancy gene mutations and cytogenetic abnormalities. MPN-BP ICs in 4 patients exhibited extensive proliferative and self-renewal capacity, as demonstrated by their ability to recapitulate human MPN-BP in serial recipients. These MPN-BP IC subclones underwent extensive continuous clonal competition within individual xenografts and across multiple generations, and their subclonal dynamics were consistent with functional evolution of MPN-BP IC. Finally, we show that MPN-BP ICs originate from not only phenotypically identified hematopoietic stem cells, but also lymphoid-myeloid progenitor cells, which were each characterized by differences in MPN-BP initiating activity and self-renewal capacity.

A randomized phase 3 trial of interferon-α vs hydroxyurea in polycythemia vera and essential thrombocythemia.

The goal of therapy for patients with essential thrombocythemia (ET) and polycythemia vera (PV) is to reduce thrombotic events by normalizing blood counts. Hydroxyurea (HU) and interferon-α (IFN-α) are the most frequently used cytoreductive options for patients with ET and PV at high risk for vascular complications. Myeloproliferative Disorders Research Consortium 112 was an investigator-initiated, phase 3 trial comparing HU to pegylated IFN-α (PEG) in treatment-naïve, high-risk patients with ET/PV. The primary endpoint was complete response (CR) rate at 12 months. A total of 168 patients were treated for a median of 81.0 weeks. CR for HU was 37% and 35% for PEG (P = .80) at 12 months. At 24 to 36 months, CR was 20% to 17% for HU and 29% to 33% for PEG. PEG led to a greater reduction in JAK2V617F at 24 months, but histopathologic responses were more frequent with HU. Thrombotic events and disease progression were infrequent in both arms, whereas grade 3/4 adverse events were more frequent with PEG (46% vs 28%). At 12 months of treatment, there was no significant difference in CR rates between HU and PEG. This study indicates that PEG and HU are both effective treatments for PV and ET. With longer treatment, PEG was more effective in normalizing blood counts and reducing driver mutation burden, whereas HU produced more histopathologic responses. Despite these differences, both agents did not differ in limiting thrombotic events and disease progression in high-risk patients with ET/PV. This trial was registered at www.clinicaltrials.gov as #NCT01259856.

Phase 2 study of ruxolitinib and decitabine in patients with myeloproliferative neoplasm in accelerated and blast phase.

Myeloproliferative neoplasms (MPN) that have evolved into accelerated or blast phase disease (MPN-AP/BP) have poor outcomes with limited treatment options and therefore represent an urgent unmet need. We have previously demonstrated in a multicenter, phase 1 trial conducted through the Myeloproliferative Neoplasms Research Consortium that the combination of ruxolitinib and decitabine is safe and tolerable and is associated with a favorable overall survival (OS). In this phase 2 trial, 25 patients with MPN-AP/BP were treated at the recommended phase 2 dose of ruxolitinib 25 mg twice daily for the induction cycle followed by 10 mg twice daily for subsequent cycles in combination with decitabine 20 mg/m2 for 5 consecutive days in a 28-day cycle. Nineteen patients died during the study follow-up. The median OS for all patients on study was 9.5 months (95% confidence interval, 4.3-12.0). Overall response rate (complete remission + incomplete platelet recovery + partial remission) was 11/25 (44%) and response was not associated with improved survival. We conclude that the combination of decitabine and ruxolitinib was well tolerated, demonstrated favorable OS, and represents a therapeutic option for this high-risk patient population. This trial was registered at www.clinicaltrials.gov as #NCT02076191.

Ruxolitinib Therapy Followed by Reduced-Intensity Conditioning for Hematopoietic Cell Transplantation for Myelofibrosis: Myeloproliferative Disorders Research Consortium 114 Study.

We evaluated the feasibility of ruxolitinib therapy followed by a reduced-intensity conditioning (RIC) regimen for patients with myelofibrosis (MF) undergoing transplantation in a 2-stage Simon phase II trial. The aims were to decrease the incidence of graft failure (GF) and nonrelapse mortality (NRM) compared with data from the previous Myeloproliferative Disorders Research Consortium 101 Study. The plan was to enroll 11 patients each in related donor (RD) and unrelated donor (URD) arms, with trial termination if ≥3 failures (GF or death by day +100 post-transplant) occurred in the RD arm or ≥6 failures occurred in the URD. A total of 21 patients were enrolled, including 7 in the RD arm and 14 in the URD arm. The RD arm did not meet the predetermined criteria for proceeding to stage II. Although the URD arm met the criteria for stage II, the study was terminated owing to poor accrual and a significant number of failures. In all 19 transplant recipients, ruxolitinib was tapered successfully without significant side effects, and 9 patients (47%) had a significant decrease in symptom burden. The cumulative incidences of GF, NRM, acute graft-versus-host disease (GVHD), and chronic GVHD at 24 months were 16%, 28%, 64%, and 76%, respectively. On an intention-to-treat basis, the 2-year overall survival was 61% for the RD arm and 70% for the URD arm. Ruxolitinib can be integrated as pretransplantation treatment for patients with MF, and a tapering strategy before transplantation is safe, allowing patients to commence conditioning therapy with a reduced symptom burden. However, GF and NRM remain significant.

Safety and efficacy of combined ruxolitinib and decitabine in accelerated and blast-phase myeloproliferative neoplasms.

Myeloproliferative neoplasms (MPN), including polycythemia vera, essential thrombocythemia, and primary myelofibrosis, have a propensity to evolve into accelerated and blast-phase disease (MPN-AP/BP), carrying a dismal prognosis. Conventional antileukemia therapy has limited efficacy in this setting. Thus, MPN-AP/BP is an urgent unmet clinical need. Modest responses to hypomethylating agents and single-agent ruxolitinib have been reported. More recently, combination of ruxolitinib and decitabine has demonstrated synergistic in vitro activity in human and murine systems. These observations led us to conduct a phase 1 study to explore the safety of combined decitabine and dose-escalated ruxolitinib in patients with MPN-AP/BP. A total of 21 patients were accrued to this multicenter study. Ruxolitinib was administered at doses of 10, 15, 25, or 50 mg twice daily in combination with decitabine (20 mg/m2 per day for 5 days) in 28-day cycles. The maximum tolerated dose was not reached. The most common reasons for study discontinuation were toxicity/adverse events (37%) and disease progression (21%). Fourteen patients died during study treatment period or follow-up. The median overall survival for patients on study was 7.9 months (95% confidence interval, 4.1-not reached). Among evaluable patients, the overall response rate by protocol-defined criteria (complete remission with incomplete count recovery + partial remission) was 9/17 (53%) and by intention-to-treat analysis was 9/21 (42.9%). The combination of decitabine and ruxolitinib was generally well tolerated by patients with MPN-AP/BP and demonstrates potentially promising clinical activity. A phase 2 trial evaluating the efficacy of this combination regimen is ongoing within the Myeloproliferative Disorder Research Consortium.

CHZ868, a Type II JAK2 Inhibitor, Reverses Type I JAK Inhibitor Persistence and Demonstrates Efficacy in Myeloproliferative Neoplasms.

Although clinically tested JAK inhibitors reduce splenomegaly and systemic symptoms, molecular responses are not observed in most myeloproliferative neoplasm (MPN) patients. We previously demonstrated that MPN cells become persistent to type I JAK inhibitors that bind the active conformation of JAK2. We investigated whether CHZ868, a type II JAK inhibitor, would demonstrate activity in JAK inhibitor persistent cells, murine MPN models, and MPN patient samples. JAK2 and MPL mutant cell lines were sensitive to CHZ868, including type I JAK inhibitor persistent cells. CHZ868 showed significant activity in murine MPN models and induced reductions in mutant allele burden not observed with type I JAK inhibitors. These data demonstrate that type II JAK inhibition is a viable therapeutic approach for MPN patients.