ALBERT

Description: Backgroud: Despite advances in therapy and improved survival, relapsed and refractory B-cell precursor acute lymphoblastic leukemia (r/r BCP-ALL) in pediatric and adult patients still remains a problem. Chimeric antigen receptor T cells against CD19 (CD19 CAR T) show promising results in patients with r/r BCP-ALL. However, relapse of the disease still occurs with appreciable frequency even with this novel therapy. As a significant number of relapses post-CAR T lack surface CD19 expression, further CD19-directed therapy is not an option for these cases. Hypothesis: Sometimes despite CAR T engraftment and establishment of B-cell aplasia, relapse still occurs. We hypothesized that, similarly to cell adhesion mediated chemotherapeutic drug resistance (CAM-DR), cell adhesion mediated CAR T-cell resistance (CAM-CART-R) can contribute to relapse of ALL. Results: To test our hypothesis, primary ALL cells were treated with CD19 CAR T cells either with murine calvaria-derived bone marrow stromal cells, OP9, or cultured only with media in short term cultures. We observed B-ALL cells treated with CD19 CAR T on OP9 has 10-20% higher viability compared to B-ALL and CD19 CAR T co-culture in medium alone, supporting the notion of CAM-CART-R. We also determined that soluble factors in OP9 primed medium may contribute to CAM-CART-R. However, the direct stromal contact mediated significant protection again CAR T induced apoptosis of B-ALL cells. To determine the molecular mechanisms underlying the survival promoting effects of stromal cells on CD19-, these cells were starved in serum-free media for 4hours and then treated with PI3Kδ inhibitor CAL-101 or DMSO and co-cultured with OP9 cells for 1 hour. We found that p-Akt is upregulated by stromal contact in CD19-negative B-ALL cells post-CAR T therapy and that PI3Kδ inhibition using can downregulate p-Akt in CD19-negative B-ALL patients. Critically, we investigated whether CD19 CAR T cells were functional under these conditions. For this purpose, we determined if stromal contact of ALL cells or stromal contact of CAR T cells changes the intracellular cytokine milieu of CD19 CAR T cells and found that intracellular IL-6, TNF- α and IFN-γ were reduced upon stromal contact supporting our hypothesis of a role of stromal cells in CAM-CART-R. We also determined that immune checkpoints molecules on T cells are unaffected by OP9 cells. Despite the reduction of cytokine level in T cells upon co-culture with B-ALL cells on OP9, PD-1, TIM-3 and LAG3 expression on CD19 CAR T cells after 2 days of co-culture was not altered as determined by flow cytometry. Resistance of ALL cells to CD19 CART cells was not mediated through checkpoint inhibition, since the PD-1/PD-L1 inhibitor Nivolumab failed to enhance ALL killing. Phenotypic profiling of thirteen cases of primary ALL relapse post-CD19 CAR T cell therapy showed high expression of adhesion molecules including integrin α4. Phenotypic analysis also revealed high expression of integrins is retained in primary ALL cells after CD19 knockout in one case. To explore possible solutions to overcome CAM-CART-R, we examined a strategy of blocking specifically integrin α4. We have previously shown that blocking integrin α4 can de-adhere CD19-negative B-ALL relapse post-CAR T cell therapy from their respective counter-ligands in vitro and that these cells can benefit from integrin blocking therapy in vivo. We have now confirmed this in NSG mice injected with CD19-negative B-ALL cells from a patient with post-CAR T cell relapse. Mice were treated intraperitoneally (n=6/group) with total immunoglobulin (Ig) control or humanized anti-human integrin α4 antibody Natalizumab (NZM). As a result, Natalizumab monotherapy significantly prolonged survival of leukemic mice compared to control Ig group (66 days (Ig) vs 85 days (NZM) p

Description: Several examples suggest a relationship between in vitro migratory capacity and bone marrow (BM) homing. Pertussis toxin (PTX) is a potent inhibitor of Gi protein coupled receptor signaling and as such, it blocks hemopoietic progenitor cell (HPC) migration in vitro. However, contrary to expectation, no effects on BM homing were observed in previous studies. We therefore re-examined the effect of PTX on BM homing of HPC. We found that prolonged incubation of BM cells or fetal liver cells with PTX inhibited their BM homing in irradiated or non-irradiated recipients by 〉75%. A concomitant increase in circulating CFU-C in blood provided added assurance that the data were not due to non-specific toxicity. This inhibition of BM homing was of functional consequence, since PTX-treated cells provided impaired radioprotection and markedly decreased short-term engraftment. Detailed studies showed that inhibition of in vitro migration and ribosylation of Gi proteins were complete only after extended incubation with PTX, whereas short-term incubation for 1–2 h, as used in previous studies, was insufficient. In addition, the incubation of BM cells with SCF may have exaggerated the negative effect of PTX on the inhibition on BM homing. We next sought to test the basis of the residual 25% homing of PTX treated cells. As PTX did not directly inhibit hemopoietic cell adhesion, we tested homing of PTX-incubated and control BM cells in genetic models deficient in certain adhesion molecules on either the hemopoietic cells or the hemopoietic microenvironment. BM homing of PTX-treated α4integrin-/- BM cells transplanted into wild-type (WT) mice, or PTX-treated WT cells transplanted into EPselectin-/- recipients inhibited BM homing significantly stronger than either modality alone, to 〉90% and 〉95%, respectively. Of note, untreated WT cells have normal homing in EPselectin-/- mice. These data demonstrate cooperativity between Gi blockade and α4integrin or endothelial selectin blockade in inhibiting BM homing of progenitor cells. Absence of β2integrin or L-selectin in the presence or absence of PTX did not inhibit BM homing. In summary, these studies show that Gi protein signals are required for BM homing of progenitor cells. PTX is a very strong inhibitor of BM homing, suggesting that it may inhibit convergent signals from more than one mediator. We further show that the residual BM homing of migration-impaired BM cells is due to participation of α4 integrin on the transplanted cells, or to endothelial selectins on the host side.

Description: Interleukin-15 (IL-15) is a potent T-cell stimulating factor, which has recently been used for pre-clinical in vivo immunotherapy. Here, the IL-15 effect on CD3-stimulated peripheral human T cells was investigated. IL-15 induced a significant T-cell proliferation and upregulated CD25 expression. IL-15 significantly enhanced T-cell production of interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), and IL-10. Between 10- and 100-fold greater concentrations of IL-15 were necessary to reach a biological effect equivalent to that of IL-2. Blockade of IL-2 binding to the high-affinity IL-2 receptor did not affect the IL-15 effects, suggesting that IL-15 did not act by inducing endogenous IL-2. Exogenously administered IL-10 significantly reduced the IL-15 and IL-2–mediated IFN-γ and TNF-α production, whereas T-cell proliferation and CD25 expression were not affected. The inhibitory effects of exogenously administered IL-10 on T-cell cytokine production appeared indirect, and are likely secondary to decreased IL-12 production by accessory cells. Inhibition of endogenous IL-10 binding to the IL-10 receptor significantly increased IFN-γ and TNF-α release from T cells. These data suggest that endogenous IL-10 can regulate activated T-cell production of IFN-γ and TNF-α via a paracrine negative feedback loop. The observations of this study could be of relevance for the therapeutic use of IL-15 in vivo.

Description: Key Points RUNX1 inhibits erythroid differentiation by downregulation of the erythroid gene expression program. RUNX1 can act as an activator and repressor during megakaryocytic differentiation and counteracts the activity of TAL1.

Description: During the past two decades peripheral blood stem cells have become the favored graft source for HSCT with 80 % of allogeneic and almost 100 % of autologous HSCT performed with mobilized blood. The critical role of the interaction between the chemokine receptor CXCR4 and its chief ligand CXCL12 for retention and migration of hematopoietic stem and progenitor cells (HSPC) has been well established. Interference with CXCR4/CXCL12 signalling iscurrentlybeing exploited as a strategy to mobilize HSPC indirectly with the most clinically relevant mobilizing agent to date, G-CSF as well as directly with the bicyclam CXCR4 antagonist Plerixafor (AMD3100).In this study, qualitative and quantitative effects of long-term pharmacologic inhibition of CXCR4/CXCL12 axis within the HSPC compartment were investigated in healthy C57BL/6 mice using the non-peptidic small molecule CXCR4 antagonists Plerixafor and ALT1188 along with the Protein-EpitopeMimeticsInhibitor POL5551. Up to 12-14 fold higher mobilization efficiency was achieved by applying the antagonists via two weeks of continuous infusion (up to 8-10x104 CFU-C and LSK/ml) as compared to bolus treatment (4-6x103 CFU-C and LSK/ml) or 5-day course of G-CSF (3-6x103 CFU-C/ml).Despite dramatic increase in numbers of circulating HSPC, the BM HSPC pool dis not decrease; in fact it expanded up to 2-4-fold compared to steady state reservoir (sham-operated control mice) as measured by immunophenotypical (LSK SLAM) and functional (e.g. serial competitive transplantation) properties of the cells. Thus, in contrast to genetically CXCR4 ablatedHSPC, the reversible long-term blockade of the receptor did not diminish the long-term repopulating capacity of HSPC. Cell cycle analysis showed a 2-3-fold increase in cycling activity of BM HSPC: only 10-20% of LSK and 30-40 % of LSK SLAM cells were found to be quiescent (in G0 phase of the cell cycle) after two weeks of CXCR4 antagonist infusion versus 50-60 % of LSK and 70 % of LSK SLAM found in G0 under homeostatic conditions. This increased proliferation was very similar to the one induced transiently at day 3 G-CSF treatmentand would conceivably explain the sustained mobilization without concomitant depletion of the BM HSPC pool. Profiling of differentially treated BM HSC (LSK SLAM) via microarray analysis did not reveal substantial effects of CXCR4 inhibitor infusion on the expression signature. Ofnote, major cytological changes typically associated with G-CSF induced mobilization, e.g. depletion of bone lining osteoblast lineage cells and macrophages, were not detected in continuous infusion of POL5551 exposed BM suggesting limitedeffects within the BM niche compartment. Moreover analysis of the BM HSPC after different washout periods at the end of continuous infusion treatment revealed a rapid (within 1-3 days after discontinuation of infusion) reestablishment of steady state HSPC numbers in the BM.Our data suggest that prolonged pharmacologic blockade of the CXCR4/CXCL12 axis using multiple small molecule inhibitorsrepresents an approach thatreleasesHSPCwith efficiency superiorto any other knownmobilization strategybut also may serve as an effective method induce cell cycling and thus expand BM HSPCs. Figure Competitive transplantation of POL5551 treated andcontrol BM (n=5 recipients per group, mean±SEM) Figure. Competitive transplantation of POL5551 treated andcontrol BM (n=5 recipients per group, mean±SEM) Disclosures Levesque: GlycoMimetics: Equity Ownership.

Description: The CXCR4 antagonist AMD3100 mobilizes hematopoietic stem/progenitor cells (HSPC), but most available data are on combination with G-CSF, rather than its use as a single modality for HSPC mobilization and transplantation. Because of low efficacy of the standard single-dose regimen, we additionally tested in mice the effect of pulsed or continuous AMD3100-infusion: Repeat injections as little as 4 hours apart for up to 6 days did not result in CFU-C accumulation or curtail the size of AMD3100-responsive HSPC pools. In contrast to the 3-fold increase in circulating CFU-C after bolus or repeat injections, after 5 days of continuous AMD3100-infusion circulating CFU-C were increased 30-fold over baseline, from 301±41/mL to 10,687±757/mL compared to 1,088±75/mL after a bolus. These numbers were sustained at least until day 8 and, of interest, were not further augmented by injection of an AMD3100-bolus, suggesting satiating doses of AMD3100-infusion. Furthermore, at least equally efficient mobilization by AMD3100-bolus or -infusion was documented in splenectomized hosts, indicating that the contribution of spleen to mobilization by AMD3100 is negligible. Long-term repopulating cells in AMD3100-infusion-mobilized blood, assessed by limiting dilution transplantation, were also increased, to 273(205–362) CRU/mL, vs. 77(56–106) CRU/mL after bolus. Of interest, the number of HSPC mobilized by AMD3100-infusion was much higher than by standard twice-daily dosing of G-CSF, and AMD3100 effectively mobilized two G-CSF resistant/refractory mouse models (G-CSFR−/−, Plasminogen−/−), while not surprisingly, mice treated with the Gi protein inhibitor Pertussis toxin were resistant to AMD3100-induced mobilization. Subsequent studies addressed the phenotype and the in vitro and in vivo functional behavior of AMD3100-mobilized HSPC. The immunophenotype of AMD3100-mobilized c-kit+ cells differed significantly from that of steady-state bone marrow (BM) c-kit+ cells. Thus expression of several integrins was lower, while CD26 expression was significantly higher than on BM c-kit+ cells. AMD3100-infusion-mobilized blood and BM CFU-C migrated equally efficiently towards SDF-1 in vitro. In vivo marrow homing of AMD3100-infusion-mobilized blood CFU-C was 〉50% increased over BM CFU-C, similarly to what we recently showed for G-CSF-infusion-mobilized blood. These properties differ from those of in vitro AMD3100-incubated BM-HSPC, in which migration was blocked, and homing was normal or reduced. Kinetics of hematopoietic recovery after transplantation of 100 μl AMD3100- or G-CSF-infusion-mobilized blood to lethally irradiated hosts were similar except for delayed platelet recovery in AMD3100-mobilized blood recipients. Partial BrdU labeling experiments for up to 3 days before mobilization (resulting in 20–40% BrdU labeling of c-kit+ cells in BM) documented that labeled cells were consistently underrepresented (80% of AMD3100-mobilized c-kit+ cells are in G0), but extend it to conclude that such a status precedes their exit from BM, rather than being a consequence of modification in the blood environment. In summary, we are presenting a novel efficacious mobilization scheme which fully supports transplantation demands in normal and G CSF-refractory donors. Furthermore, our data expand previous knowledge about size and turn-over of AMD3100-mobilizable HSPC pools.

Description: Abstract 2565 Chemotherapy drug resistance in acute lymphoblastic leukemia (ALL) remains a major problem, resulting in reduced treatment efficacy and relapse. The bone marrow environment (BME) has been shown to promote resistance of leukemia cells towards chemotherapy, which has been attributed to several proteins, including integrins. Our analysis of 207 children with high-risk (BCR/ABL1−) pre-B ALL revealed that high expression of the laminin-binding integrin VLA6 (alpha6beta1) portends poor clinical outcomes in patients with minimal residual disease (MRD+) on day 29 of induction. In addition, our comparative analysis of pre-B leukemia and normal B-cells revealed that VLA6 is preferentially upregulated on BCR/ABL1+ pre-B ALL blasts. Alterations in adhesion properties have been described for BCR/ABL1+ (p210) chronic myeloid leukemia. The role of integrins and integrin VLA6 in particular for cell adhesion-mediated drug resistance (CAM-DR) in BCR/ABL1+ (p210) ALL has not been addressed. With respect to its role for normal immature hematopoietic cells, contradictory observations have been reported. Therefore, we hypothesized that VLA6-mediated adhesion of ALL cells to the bone marrow stromal niche contributes to drug resistance. We evaluated the role of VLA6 in BCR-ABL1+ leukemia using two of our established models of leukemia, a conditional knockout model of VLA6 in murine BCR-ABL1+ leukemia and a xenograft model of human BCR-ABL1+ leukemia. VLA6fl/fl cells were oncogenically transformed using BCR-ABL1 (p210) and cultured under lymphoid-skewing conditions. Induction of pre- B (B220+ CD19+) ALL was confirmed by flow cytometry. Subsequent transduction with CreERT2 or EmptyERT2 generated leukemia cells in which VLA6 ablation could be induced (CreERT2) or not (EmptyERT2) by addition of Tamoxifen. Conditional ablation of VLA6 in vitro decreased adhesion significantly compared to undeleted controls (19.7%±8.1% vs. 87.7%±6.0%; p=0.00041) and increased apoptosis of murine BCR-ABL1+ leukemia cells as determined by analysis of Annexin V−/7-AAD− viable cells by flow cytometry (VLA6 deleted vs. undeleted: 35.3%±1.1% vs. 75.1%±1.2%; p=0.0001). Moreover, VLA6 deletion sensitized murine ALL to a tyrosine kinase inhibitor (TKI), Nilotinib (p=0.022, 45.6%±2.4% vs. 73.3%±13.0%). To test the effect of VLA6 deletion on leukemic progression in vivo, VLA6 BCR/ABL1+ pre-B (B220+ CD19+) CreERT2+ or control transduced ALL cells were transferred into NOD/SCID mice. 3 days thereafter, VLA6 deletion was induced by Tamoxifen administration to all animals in 2 cycles for 5 days. In vivo deletion of VLA6 in delayed leukemia progression compared to VLA6 competent controls from a median survival time (MST) of 30 days post-leukemia injection to a MST of 43 days post-leukemia injection (p=0.008 Log-rank test). In vivo deletion of VLA6 in combination with Nilotinib treatment delayed leukemia progression compared to VLA6 competent, as Nilotinib-treated control animals have uniformly died of leukemia with a MST of 39.5 days, however the Nilotinib treated VLA6 deleted group is completely alive and is still being monitored (p=0.0025). When VLA6 was ablated before transfer and recipients were observed for leukemia progression, the recipients of VLA6–deficient murine leukemia cells also showed attenuated leukemia progression compared to recipients of VLA6 competent cells. Moreover, we show that VLA6 blockade de-adheres primary ALL cells from their cognate counter receptor laminin in vitro, and sensitizes primary ALL cells to TKI Taken together, modulating the function of VLA6 in ALL offers a new approach to overcome drug resistance in ALL. Given that VLA6 is probably largely redundant for normal immature hematopoiesis, this approach may be preferable over targeting of other integrins in BCR/ABL1+ leukemias on which VLA6 is expressed. Disclosures: No relevant conflicts of interest to declare.

Description: Introduction Haploidentical family donors are becoming an effective alternative for patients in need of an hematopoietic stem cell transplantation (HSCT) but lacking an HLA-matched donor. However, to prevent graft-versus-host disease (GVHD), intensive in-vivo or ex-vivo T-cell depletion is often utilised, resulting in slow immune reconstitution, frequent and often lethal infectious complications and/or high relapse rates, thus decreasing overall survival. To overcome these limitations, we have developed a strategy that allows additional donor lymphocytes to be infused post-HSCT without the risk of inducing severe GVHD and maintaining the ability to react against infections and leukemic cells. Patients and Methods In this open-label, multi-centre phase 2 clinical trial (CR-AIR-007; NCT01794299), 23 patients with high-risk AML or ALL were enrolled. Patients underwent myeloablative conditioning and were given a CD34+ selected stem cell graft from a haploidentical family donor. In addition, donor lymphocytes from the same donor were processed using a selective photodepletion technology, creating a donor lymphocyte product depleted of alloreactive T-cells (ATIR101). ATIR101 was to be given to patients at 28-32 days post-HSCT at a fixed dose of 2x106 CD3+ cells/kg. No post-transplant GVHD prophylaxis was administered. The primary endpoint of the study is transplant-related mortality at 6 months post-HSCT. Patients are followed to determine disease-free and overall survival. Patients undergoing a similar T-cell depleted haploidentical HSCT without ATIR infusion (CR-AIR-006; NCT02188290) were used as controls. Most centers providing the historic control data also participate in this phase 2 trial with ATIR101. Results Twenty-three patients, median age of 41 years (range 21 - 64), have been enrolled into this study. Seventeen patients, 7 male and 10 female, had AML, 12 in CR1 and 5 in CR2 at the time of HSCT. Six patients, 5 male and 1 female, had ALL, 4 in CR1 and 2 in CR2 at the time of HSCT. Conditioning regimen consisted of a] TBI (1200 cGy; n=10) or b] melphalan (120 mg/m2; n=12), along with thiotepa (10 mg/kg), fludarabine (30 mg/m2 x 5d) and ATG (2.5mg/kg x 4d). No patient experienced graft rejection, with neutrophil and platelet engraftment achieved at a median of 11 and 12 days, respectively (range 8-18, range 9-35). 21 patients to date received ATIR101, at a fixed dose of 2x106 CD3+ cells/kg at a median of 28 days (range: 28-73 days) post-transplant. Median follow-up is 270 Days post-HSCT. No patient developed grade III-IV acute GVHD. Two cases of grade II acute GVHD were reported thus far. The onset of these two acute GVHD cases was delayed, at day 173 and day 247 post-HSCT, 145 and 219 post ATIR respectively. No patient died within the first 100 days post-HSCT. There are 3 deaths as a result of transplant related mortality within 6 months post-HSCT (primary endpoint). When compared to the matched historic control group (N=35), TRM was significantly lower in patients given ATIR101 after a T-cell depleted haplotransplant with a 6-month TRM for HSCT + ATIR101 of 17% versus 34% for HSCT only (Figure 1a). Figure 1a: Kaplan Meier of Transplant related mortality: HSCT + ATIR101 vs HSCT alone (p=0.0075), data as per 3 August 2015. Thus far, in CR-AIR-007 study, only one patient experienced a relapse, which occurred at 90 days post-HSCT and resulted in death of the patient on day 122. The overall survival of patients given ATIR101 is significantly improved, compared to the control group, with a 1-year survival of 67% in the HSCT + ATIR101 group and 20% in the control group (Figure 1b). Figure 1b: Kaplan Meier of Overall Survival: HSCT + ATIR101 vs HSCT alone (p=0.0032), data as per 3 August 2015. Conclusions Addition of ATIR101 to a T-cell depleted haploidentical HSCT protocol significantly improves transplantation outcome, with reduced TRM and improved OS. Specifically, no patient died during the first 100 days post-HSCT. Administration of ATIR101 at the dose of 2x106 cells/kg does not induce severe GVHD, confirming the efficacy of alloreactive T-cell elimination from the donor lymphocyte infusion. We attribute the reduced TRM (mainly infections in the control group) to the additive immunological protection afforded by ATIR101. Moreover, the low number of relapses observed thus far is most encouraging and supports the preservation within ATIR101 of T-cells able to recognize leukemic antigens. Figure 1. Figure 1. Figure 2. Figure 2. Disclosures Roy: Kiadis Pharma: Consultancy, Research Funding; Novartis: Honoraria. Rudiger:Kiadis Pharma: Employment. Velthuis:Kiadis Pharma: Employment. Reitsma:Kiadis Pharma: Employment. Gerez:Kiadis Pharma: Employment. Rovers:Kiadis Pharma: Employment.

Description: Abstract 1500 Significant progress notwithstanding, drug resistant acute lymphoblastic leukemia (ALL) remains a therapeutic challenge, as well as acute and long-term off-target toxicity of anti-ALL therapies can be dose-limiting or debilitating. Therefore, the development of more targeted therapies is desirable. We recently provided evidence that chemotherapy resistance of ALL cells can be partly overcome by interfering with the function of VLA4, the alpha4beta1 integrin, in vivo. In those studies, we used the anti-functional antibody Natalizumab. We extended our studies to an alternative VLA4 inhibitor, the novel non-peptidic small molecule TBC3486. Previous in vitro assays and molecular modeling studies indicate that TBC3486 behaves as a ligand mimetic, competing with VCAM-1 for the MIDAS site of VLA-4. As such, the compound has been shown to be efficacious in VLA-4 dependent models of inflammatory and autoimmune disease. The potential usefulness of this novel inhibitor in leukemia treatment was tested in our established in vitro and in vivo assays. LAX7R cells, primary pre-B-ALL with a normal karyotype from a patient with an early relapse, were used throughout for the studies reported here. LAX7R cells were treated with 25μM TBC3486 or THI0012 control, the inactive enantiomer of TBC3486, and seeded onto plates coated with human VCAM-1. Adhesion, scored after 2 days, was significantly inhibited by TBC3486 compared to control treated cells (7.9%±4.0 vs 95.4%±8.0; p=0.003). Proliferation rate and cell viability were unaffected by the treatments. In a co-culture system of LAX7R cells with OP9 stroma cells, which we use as an in vitro model of stroma-mediated chemotherapy resistance, we assessed differential effects of VDL (Vincristine, Dexamethasone, L-Asparaginase) on leukemia cell survival in the presence or absence of TBC3486. Stromal adhesion significantly protected LAX7R cells against VDL chemotherapy; this effect was significantly attenuated by TBC3486 compared to the control as determined by Trypan blue exclusion of dead cells (Cell viability of 39.9%±5.1 vs. 57.2±1.8; p=0.02). After these encouraging observations, we next evaluated the benefit of TBC3486 on leukemia progression in a xenotransplant assay. LAX7R cells were lentivirally labelled with luciferase for in vivo tracking and injected into NOD/SCID hosts. Three days after leukemia cell transfer, mice received either TBC3486 or THI0012 (control) (10mg/kg/d) daily for 2 weeks (intraperitoneally), with or without VDL chemotherapy. This experiment is in progress, but already survival of leukemia-bearing mice was significantly prolonged, from a median survival time (MST) for control mice of 33 days post-leukemia injection to a MST of 47 days post-leukemia injection for TBC3486 treated mice (p=0.02). Similarly, bioluminescence imaging revealed a marked delay of leukemia cell dissemination (p