Using differential display, we isolated DDC-4, a secreted frizzled-related protein (sFRP), which is induced in the physiological apoptosis of hormonally regulated, reproductive tissues such as mammary gland, prostate, corpus luteum and uterus. The role of this gene in apoptosis was studied in animals overexpressing ectopic DDC-4/sFRP-4. Transgenic mice bearing the DDC-4/sFRP-4 cDNA under the control of the MMTV-LTR promoter showed lactational insufficiency and many apoptotic cells in the alveoli between day 19 of pregnancy and day 4 of lactation as demonstrated by TUNEL reaction and the presence of activated caspase-3. We performed a PKB/Akt kinase assay and studied several of its substrates using phosphorylation-specific antibodies to show reduced phosphorylation in PKB/Akt itself, as well as in glycogen synthetase kinase-3b (GSK-3b), BAD, and Forkhead. Taken together, our results show a role for DDC-4/sFRP-4 in abrogating an epithelial cell survival pathway at the onset of mammary gland involution.

Vaso-occlusion is the major cause of morbidity and mortality in sickle cell disease (SCD). It is a complex multistep process initiated by the adhesion of fragile red cells and leucocytes, primarily neutrophils, to the hypoxic and inflamed endothelium. Attachment of large and rigid neutrophils to the endothelium, particularly in the microcirculation induces vaso-occlusive crisis by activating neutrophils and forming multicellular aggregates with erythrocytes and platelets. Dysregulated nitric oxide (NO) homeostasis contributes to vascular dysfunction in SCD. Hydroxyurea is the standard of care and the only approved therapy for SCD. Hydroxyurea has been shown to exhibit NO donor properties and may act to increase g-globin expression via the second messenger cGMP. PF-04447943 (PDE9i) is a selective inhibitor of the cGMP specific phosphodiesterase-9A (PDE-9A) enzyme (IC50 12nM) being developed for the treatment of SCD. Here, we study the combined effects of this PDE-9A inhibitor and hydroxyurea in a mouse model of acute vaso-occlusion. The effect of PF-04447943 was assessed in the presence and absence of hydroxyurea in vivo using two models, TNF-α treated normal wild-type mice and the Townes model of SCD. C57BL/6J or Townes SCD mice were randomized to treatment with saline or PDE-9 inhibitor alone or in combination with hydroxurea. In wild-type mice, treatment was administered in a prophylactic setting prior to the TNF-α inflammatory challenge or in an acute setting post-TNF-α (0.5 ug/mouse). TNF-α induces a well described acute inflammatory response in the microcirculation associated with neutrophil adhesion to the endothelium and formation of multicellular aggregates. Alexa-488 labeled Ly-6G neutrophil antibody and Dylight-649 labeled CD42c platelet antibody was injected to quantify neutrophils adhered to endothelium and neutrophil-platelet aggregates. Mouse cremaster microvasculature was observed by intravital microscopy. TNF–α treatment of C57BL/6J mice increased the number of adherent neutrophils and neutrophil-platelet aggregates, and decreased the number of rolling neutrophils compared to vehicle treated mice. Treatment with PDE9i or hydroxyurea alone in TNF-α challenged mice had no significant effect on neutrophil adhesion. Co-administration of 100 mg/kg HU in combination with 10 mg/kg PDE9i prior to TNF-α challenge led to a 69% reduction in neutrophils adhered to the endothelium and 89% reduction in neutrophil-platelet aggregates compared to TNF–α treated mice alone. Neutrophil adhesion was also reduced 59% in mice receiving 50 mg/kg hydroxurea and 1 mg/kg PDE9i. There was a significant increase in the neutrophil rolling number and velocity after co-administration of PDE9i and HU in TNF-α challenged mice. However, mice receiving PDE9i and hydroxurea after theTNF-α challenge did not show significant changes in neutrophil adhesion or aggregates. Plasma levels of sP-Selectin, sE-Selectin, sVCAM-1 and sICAM-1 decreased when animals were given a prophylactic combination treatment with PDE9i and hydroxyurea. The Townes sickle cell disease mice exhibit an acute inflammatory response upon surgical exposition of the cremaster muscle and show increased number of adherent neutrophils and large neutrophil-platelet aggregates. Prophylactic treatment of these sickle mice with combination of PDE9i and hydroxyurea also showed a 63% reduction in neutrophil adhesion and a 75% reduction in cell aggregates, leading to reduced vaso-occlusion. In summary, inhibition of PDE9 in mouse models of SCD had beneficial effects in the prophylactic reduction of crisis. Co-administration of PDE9 inhibitor with hydroxyurea, led to a significant reduction in vaso-occlusion associated with sickle cell disease in two distinct animal models of SCD. All experiments were within guidelines and were reviewed and approved by the site institutional animal care and use committee. Disclosures No relevant conflicts of interest to declare.

Hemophilia is a hereditary bleeding disorder caused by intrinsic coagulation pathway deficiencies of Factor VIII (hemophilia A) or Factor IX (hemophilia B). Tissue factor pathway inhibitor (TFPI) is a Kunitz-type serine protease inhibitor that negatively regulates thrombin generation within the extrinsic pathway of coagulation. In hemophilia patients the extrinsic pathway remains intact and thus augmentation of this pathway may circumvent the clotting deficiency in hemophilia. PF-06741086, a monoclonal antibody that binds to and neutralizes the inhibitory activity of TFPI is being developed as a potential treatment for bleeding disorders including hemophilia A and hemophilia B with and without inhibitors. Currently, treatment of inhibitor patients is managed by bypass treatments, such as recombinant Factor VIIa (rFVIIa). The effect of PF-06741086 on thrombin generation in the presence of increasing concentrations of rFVIIa (0.0002 to 20 µg/mL) was studied in severe hemophilia A plasma. A dose-dependent increase in thrombin generation was observed over vehicle control with the addition of rFVIIa to the hemophilia plasma. Addition of a fixed concentration of PF-06741086 (16 µg/mL) in combination with rFVIIa resulted in an increase in thrombin generation including higher peak thrombin and shortening of lag time compared to rFVIIa alone. The TGA profiles with the combination of PF-06741086 and rFVIIa at 0.2, 2, and 20 µg/mL were similar suggesting a saturation of mechanism at these concentrations. The combination of PF-06741086 and rFVIIa restored thrombin generation to normal plasma levels at all rFVIIa concentrations examined. The TFPI inhibitory activity of PF-06741086 on thrombin generation in the presence and absence of rFVIIa was further studied in additional hemophilia A plasmas, including hemophilia A plasmas with inhibitors and hemophilia B plasma. All donors had less than 1% coagulation factor activity. A rFVIIa concentration of 2 µg/mL was selected because it corresponded to plasma levels that could be observed following dosing of FVIIa and because the thrombin generation response in hemophilia plasma was similar with FVIIa added to hemophilia A plasma at 0.2, 2 and 20 µg/mL. The concentration of PF-06741086 was 16 µg/mL in these studies. The effect of PF-06741086 on thrombin generation was also measured in non-hemophilic plasma which would have the full complement of coagulation factors. The addition of PF-06741086 alone or in combination with rFVIIa to hemophilia A and B plasma resulted in an increase in thrombin generation including higher peak thrombin concentration and shortening of lag time compared to addition of rFVIIa alone. In hemophilic plasma samples with inhibitors (3 - 1261 Bethesda Units), PF-06741086 alone also restored thrombin generation. A minimal additive effect in peak thrombin generation was observed with the combination of PF-06741086 (16 µg/mL) and 2 µg/mL rFVIII. The midpoint peak thrombin levels achieved with PF-06741086 alone or in combination with rFVIIa were similar to those observed in non-hemophilic plasma and did not exceed the level observed in non-hemophilic plasma dosed with PF-06741086. To summarize, use of rFVIIa in combination with PF-06741086 results in increased thrombin generation in hemophilia A, hemophilia B and inhibitor plasmas without inducing excessive coagulation. Disclosures Rakhe: Pfizer: Employment. Hett:Pfizer: Employment. Murphy:Pfizer: Employment. Pittman:Pfizer: Employment.

Chronic vaso-occlusion is a major cause of morbidity and mortality in patients with sickle cell disease (SCD). Persistent vaso-occlusion can damage lungs, liver, kidneys or brain and ultimately lead to end-organ dysfunction. Vaso-occlusive pain crisis is a complex multistep process, initiated by adhesion of fragile sickle erythrocytes and rigid neutrophils to hypoxic and inflamed endothelium. Large multicellular aggregates of blood cells, including platelets and sickled erythrocytes, form on these adherent activated neutrophils in the microcirculation, ultimately causing vascular occlusion and tissue ischemia. Inflammatory mediators, such as P-selectin, play a key role in mediating these heterocellular interactions and attract additional leucocytes to the site of occlusion. P- and E-selectin mediate rolling and tethering of blood cells on the endothelium. Here, we explore cellular and animal models of sickle cell disease to assess PSI-697, an orally active small molecule antagonist of P-selectin. PSI-697 inhibits P-selectin binding to P-selectin glycoprotein ligand-1 (PSGL-1) with an IC50 of 50-125 µM (Bedard et al, JPET, 2008). Townes SCD mice were used to assess the efficacy for PSI-697 in preventing vaso-occlusion in SCD. Mice were randomized to treatment with vehicle or PSI-697. Animals were treated in a prophylactic setting prior to the surgical preparation. Surgical preparation induces a well described acute inflammatory response in the microcirculation associated with neutrophil adhesion to the endothelium and formation of multicellular aggregates. Alexa-488 labeled Ly-6G neutrophil antibody and Dylight-649 labeled CD42c platelet antibody were injected to quantify adherent neutrophils and neutrophil-platelet aggregates. Cremaster microvasculature was observed by intravital microscopy. Mice treated with 100 mg/kg of P-selectin inhibitor PSI-697 showed a 55% reduction in adherent neutrophils and a 78% decrease in the number of neutrophil-platelet aggregates compared to vehicle treated animals. Neutrophils showed ~7 fold increase in rolling velocity in mice treated with P-selectin inhibitor. Our results demonstrate that prophylactic administration of PSI-697, a small molecule P-selectin antagonist, improved parameters associated with vaso-occlusion in Townes SCD mice. Disclosures No relevant conflicts of interest to declare.

The pathophysiology of sickle cell disease (SCD) is complex and heterogenous. Tissue hypoxia leads to endothelial activation, and formation of multicellular aggregates of red cells, leucocytes and platelets in the microvasculature. This results in a vaso-occlusion further reducing tissue perfusion. Patients with SCD experience intense pain crisis. Some SCD patients also exhibit elevated cerebral blood flow velocities in transcranial Doppler (TCD) and impaired autoregulation. Higher TCD velocities are associated with imminent risk of ischemic stroke and are an indication for transfusion for SCD patients. Similar to human SCD patients, SCD mice also exhibit an increase in cerebral perfusion (Branch et al, Blood, 2015) and irregularly dilated cerebral microvasculature compared to wild-type (WT) mice (Manci et al, Blood, 2006). Selectins play a critical role in mediating initial tethering and adhesion of hematopoietic cells with endothelial cells, and are attractive targets to treat vaso-occlusion. Rivipansel is a potent small molecule pan-selectin inhibitor with a 100 fold greater inhibitory acitivity for E-selectin over P-selectin. Previous studies have demonstrated the effect of Rivipansel (GMI-1070) in chimeric SCD mice using intravital microscopy (IVM) where bone marrow from Berkeley SCD mice was transplanted in wild type (WT) mice (Chang et al, Blood, 2010). Here, we further investigate the effect of Rivipansel on leukocyte rolling in vitro and in vivo in Townes SCD mice with corresponding changes in inflammatory markers. We also extended these studies to explore the effect of Rivipansel in a cerebral perfusion model in Townes SCD mice. The effect of Rivipansel on cell adhesion in vitro was examined using the microfluidic BioFlux shear flow system. HL-60 cells were continuously flown under physiological conditions over confluent monolayers of Chinese Hamster Ovary cells expressing E-selectin (CHO-E) or P-selectin (CHO-P) treated with Rivipansel, Immunoglobulin G (IgG) control antibody or vehicle. Rivipansel dose-dependently reduced the adhesion of HL-60 to CHO-E monolayers compared to vehicle treated cells, or CHO-P monolayers. In the Townes SCD mice, Rivipansel was evaluated using IVM of the cremaster. Surgical manipulation and the chronic inflammatory conditions in Townes mice, induce an acute vaso-occlusive condition in the post-capillary venules. Rivipansel or vehicle control were dosed at 5, 10 or 20 mgs/kg intravenously prior to surgical preparation and a second dose was administered 70 minutes later. Labeled neutrophil and platelet specific antibodies were injected to quantify neutrophil-platelet aggregates and neutrophils adhered to the vasculature. Neutrophil rolling velocity increased 2.5 fold and there was a dose dependent increase in rolling neutrophils. Rivipansel, dosed at 20 mg/kg resulted in a 69% decrease in neutrophil adhesion to the endothelium and an 85% decrease in neutrophil platelet aggregates (NPA) attached to the vasculature compared to vehicle treated mice. No effect on was observed in mice dosed a 5 mg/kg. Plasma soluble P and E-selectin levels were significantly reduced in mice dosed at 10 and 20 mg/kg compared to vehicle treated mice. Additionally, cultured primary brain endothelial cells stimulated with TNF-α demonstrated a 700 fold increase in E-selectin levels as measured by RNAseq. Based on this observation, we studied the effect of Rivipansel on cerebral perfusion studies in a TNFα induced occlusion model in SCD and WT mice where changes in cerebral microcirculation were measured in real time using laser Doppler tissue perfusion. TNFα treated SCD mice demonstrated a marked reduction in tissue perfusion in contrast to WT mice. This was rapidly reversed by intravenous injection of Rivipansel (20 mg/kg). Brains harvested from TNF treated SCD mice showed increased platelet microthrombi compared to WT mice, and treatment with Rivipansel reduced the platelet aggregates seen in the cerebral microvasculature in SCD mice. In summary, we demonstrated dose dependent decrease in leukocyte adhesion in vitro and in vivo in the Townes mice. In addition administration of Rivipansel is beneficial in improving cerebral perfusion as well improving peripheral microvascular flow in the SCD mice. All experiments were within guidelines and were reviewed and approved by Pfizer institutional animal care and use committee. Disclosures Jasuja: Pfizer: Employment. Suidan:Pfizer: Employment. Hett:Pfizer: Employment. Desai:Pfizer: Employment. Le:Pfizer: Employment. Bell:Pfizer: Employment. Murphy:Pfizer: Employment. Pittman:Pfizer: Employment.