CD39 in the development and progression of pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is a devastating progressive disease characterised by pulmonary arterial vasoconstriction and vascular remodelling. Endothelial dysfunction has emerged as a contributing factor in the development of PAH. However, despite progress in the understanding of the pathophysiology of this disease, current therapies fail to impact upon long-term outcomes which remain poor in most patients. Recent observations have suggested the disturbances in the balance between ATP and adenosine may be integral to the vascular remodelling seen in PAH. CD39 is an enzyme important in regulating these nucleos(t)ides which may also provide a novel pathway to target for future therapies. This review summarises the role of adenosine signalling in the development and progression of PAH and highlights the therapeutic potential of CD39 for treatment of PAH.

Pulmonary embolus in patients with COVID-19: an Australian perspective.

Pulmonary embolus (PE) is a known complication of coronavirus disease 2019 (COVID-19). The diagnosis of PE in our hospitalised patients with COVID-19 correlated with more severe disease and occurred despite the use of routine thromboprophylaxis. Higher D-dimers were seen on admission in patients who developed PE and rose at PE diagnosis, suggesting a role for D-dimer in risk stratification.

The pharmacokinetics and pharmacodynamics of busulfan when combined with melphalan as conditioning in adult autologous stem cell transplant recipients.

Busulfan (Bu) is an alkylating agent widely used in conditioning regimes prior to stem cell transplantation (SCT), most commonly in combination with cyclophosphamide (Bu-cy) or fludarabine (Bu-flu) as myeloablative conditioning prior to allograft or with high-dose melphalan (Bu-mel) prior to autologous SCT. Despite many decades of Bu use, initially orally but now intravenously (IV), a paucity of pharmacokinetic (PK) and pharmacodynamic (PD) data exists to inform evidence-based guidelines as how best to balance the efficacy and toxicity of this agent. This is a non-randomized retrospective real-world study at three hospitals investigating the role of PK guidance in dosing Bu in the setting of IV Bu-mel autologous SCT. The primary intent was to examine how effectively PK assessment could be used to achieve a desirable drug exposure and to evaluate factors, particularly, age, sex, actual weight, body mass index (BMI), body surface area (BSA), disease, number of prior treatments, renal function, and the use of concomitant medications that may influence Bu exposure. All patients underwent PK analysis on a test dose of Bu (1.6 mg/kg, i.e., 50% of the first dose) on D-7 and subsequently received a second 1.6 mg/kg dose on D-6. Bu dose was calculated using actual body weight (ABW) if patients were less than ideal body weight (IBW), or adjusted ideal body weight (AIBW) if ABW was greater than IBW. Thereafter, at the discretion of the investigator, the group was divided into two; a weight-based cohort at two hospitals and a PK-guided cohort at the third hospital. Thirty-seven patients received PK-adjusted dosing guided by the results of the initial PK results, targeting a specific Bu exposure expressed as the area-under-the-concentration-versus-time curve (AUC) of between 4000 and 5000 µmol min/day (median 4800). The remaining 27 patients received unadjusted weight-based doses with a further three doses of 3.2 mg/kg of Bu infused over 180 min (D-5 to - 3) irrespective of their initial PK results. For the purposes of the analysis, we selected a target AUC of 4800 µmol min/day in this group, equivalent to the median targeted AUC in the PK-adjusted group. All patients subsequently had repeated PK analysis on D-5 after receiving their "therapeutic" Bu dose. Mel (140 mg/m2 or 100 mg/m2) IV was given on D-2. Sixty-four adult patients were enrolled. Patients who received PK-guided Bu dosing received a higher median Bu dose than the unadjusted weight-based cohort (3.5 mg/kg vs 3.2 mg/kg respectively, p = 0.007). Eighty-one percent (30/37) of patients in the PK-guided group achieved their target AUC (± 15%) compared with 56% (15/27) in the weight-based cohort (p = 0.027). The respective median AUCs of 5064 µmol min/day (range 3639-6157 µmol min/day) and 4854 µmol min/day (range 3251-6305 µmol min/day) were not significantly different (p = 0.16). Multivariate analysis identified ABW as the only independent variable that affected the relationship between Bu dosing and exposure (p = 0.02) with heavier patients achieving lower than anticipated AUCs for the dose they received. On D-5, within the weight-based cohort, the mean AUCs were 12% higher than anticipated based on initial D-7 PK. No correlation between AUC and grade 3-4 transplant-related toxicities were observed, although only three patients had AUCs > 6000 µmol min/day. These results suggest that PK-directed Bu dosing may be of benefit in achieving a target level of drug exposure, with larger studies needed to determine the clinical significance of this strategy.

Prevalence and causes of preoperative anaemia in elective major surgery patients.

BACKGROUND: Preoperative anaemia is associated with increased morbidity and mortality in surgical patients. Recent national patient blood management guideline recommended screening surgical patients for anaemia, particularly iron deficiency anaemia, without reference to the prevalence of anaemia or iron deficiency anaemia in this patient population. AIMS: To establish the prevalence and cause of preoperative anaemia in elective major surgery patients. METHODS: Patients attending the anaesthetic pre-admission clinics from 1 July 2013 to 30 June 2014 prior to their major elective surgery in our institution were screened for anaemia and iron deficiency by measuring full blood count, iron studies and C-reactive protein. Patients who were anaemic were either further assessed in the haematology clinic or had their medical records reviewed to ascertain the cause of the anaemia. RESULTS: Of 1494 patients, 208 (13.9%) were anaemic, with a male predominance (70.7%); 57 (27.4%) of them had iron deficiency anaemia. Other common causes of anaemia include underlying malignancy (18.3%), end-stage renal failure (11.5%) and other chronic diseases (7.2%). In 53 patients (25.5%), the cause was unknown. Anaemia was most commonly found in patients scheduled for gastrointestinal surgery. CONCLUSION: Preoperative anaemia affects 13.9% of patients undergoing elective major surgery. The most common causes are iron deficiency and chronic diseases. The cause was unexplained in 25.5% of patients with anaemia. The prevalence of anaemia in different surgical specialties may have implications on the approach to screening, particularly in resource-limited areas.

Development of endothelial-targeted CD39 as a therapy for ischemic stroke.

BACKGROUND: Ischemic stroke is characterized by a necrotic lesion in the brain surrounded by an area of dying cells termed the penumbra. Salvaging the penumbra either with thrombolysis or mechanical retrieval is the cornerstone of stroke management. At-risk neuronal cells release extracellular adenosine triphosphate, triggering microglial activation and causing a thromboinflammatory response, culminating in endothelial activation and vascular disruption. This is further aggravated by ischemia-reperfusion injury that follows all reperfusion therapies. The ecto-enzyme CD39 regulates extracellular adenosine triphosphate by hydrolyzing it to adenosine, which has antithrombotic and anti-inflammatory properties and reverses ischemia-reperfusion injury. OBJECTIVES: The objective off the study was to determine the efficacy of our therapeutic, anti-VCAM-CD39 in ischaemic stroke. METHODS: We developed anti-VCAM-CD39 that targets the antithrombotic and anti-inflammatory properties of recombinant CD39 to the activated endothelium of the penumbra by binding to vascular cell adhesion molecule (VCAM)-1. Mice were subjected to 30 minutes of middle cerebral artery occlusion and analyzed at 24 hours. Anti-VCAM-CD39 or control agents (saline, nontargeted CD39, or anti-VCAM-inactive CD39) were given at 3 hours after middle cerebral artery occlusion. RESULTS: Anti-VCAM-CD39 treatment reduced neurologic deficit; magnetic resonance imaging confirmed significantly smaller infarcts together with an increase in cerebrovascular perfusion. Anti-VCAM-CD39 also restored blood-brain barrier integrity and reduced microglial activation. Coadministration of anti-VCAM-CD39 with thrombolytics (tissue plasminogen activator [tPA]) further reduced infarct volumes and attenuated blood-brain barrier permeability with no associated increase in intracranial hemorrhage. CONCLUSION: Anti-VCAM-CD39, uniquely targeted to endothelial cells, could be a new stroke therapy even when administered 3 hours postischemia and may further synergize with thrombolytic therapy to improve stroke outcomes.

Bcl-xL-inhibitory BH3 mimetics can induce a transient thrombocytopathy that undermines the hemostatic function of platelets.

BH3 mimetics are a new class of proapo-ptotic anticancer agents that have shown considerable promise in preclinical animal models and early-stage human trials. These agents act by inhibiting the pro-survival function of one or more Bcl-2-related proteins. Agents that inhibit Bcl-x(L) induce rapid platelet death that leads to thrombocytopenia; however, their impact on the function of residual circulating platelets remains unclear. In this study, we demonstrate that the BH3 mimetics, ABT-737 or ABT-263, induce a time- and dose-dependent decrease in platelet adhesive function that correlates with ectodomain shedding of the major platelet adhesion receptors, glycoprotein Ibα and glycoprotein VI, and functional down-regulation of integrin α(IIb)ß(3). Analysis of platelets from mice treated with higher doses of BH3 mimetics revealed the presence of a subpopulation of circulating platelets undergoing cell death that have impaired activation responses to soluble agonists. Functional analysis of platelets by intravital microscopy revealed a time-dependent defect in platelet aggregation at sites of vascular injury that correlated with an increase in tail bleeding time. Overall, these studies demonstrate that Bcl-x(L)-inhibitory BH3 mimetics not only induce thrombocytopenia but also a transient thrombocytopathy that can undermine the hemostatic function of platelets.

Two distinct pathways regulate platelet phosphatidylserine exposure and procoagulant function.

Procoagulant platelets exhibit hallmark features of apoptotic cells, including membrane blebbing, microvesiculation, and phosphatidylserine (PS) exposure. Although platelets possess many well-known apoptotic regulators, their role in regulating the procoagulant function of platelets is unclear. To clarify this, we investigated the consequence of removing the essential mediators of apoptosis, Bak and Bax, or directly inducing apoptosis with the BH3 mimetic compound ABT-737. Treatment of platelets with ABT-737 triggered PS exposure and a marked increase in thrombin generation in vitro. This increase in procoagulant function was Bak/Bax- and caspase-dependent, but it was unaffected by inhibitors of platelet activation or by chelating extracellular calcium. In contrast, agonist-induced platelet procoagulant function was unchanged in Bak(-/-)Bax(-/-) or caspase inhibitor-treated platelets, but it was completely eliminated by extracellular calcium chelators or inhibitors of platelet activation. These studies show the existence of 2 distinct pathways regulating the procoagulant function of platelets.

Early Endothelial Activation in a Mouse Model of Graft vs Host Disease Following Chemotherapy.

Allogenic hematopoietic stem cell transplant (allo-HSCT) can lead to sinusoidal obstruction syndrome (SOS) and graft-versus-host disease (GvHD) in some individuals. GvHD is characterised by an immune triggered response that arises due to donor T cells recognizing the recipient tissue as "foreign". SOS results in impaired liver function due to microvascular thrombosis and consequent obstruction of liver sinusoids. Endothelial damage occurs following chemotherapy and allo-HSCT and is strongly associated with GvHD onset as well as hepatic SOS. Animal models of GvHD are rarely clinically relevant, and endothelial dysfunction remains uncharacterised. Here we established and characterised a clinically relevant model of GvHD wherein Balb/C mice were subjected to myeloablative chemotherapy followed by transplantation of bone marrow (BM) cells± splenic T-cells from C57Bl6 mice, resulting in a mismatch of major histocompatibility complexes (MHC). Onset of disease indicated by weight loss and apoptosis in the liver and intestine was discovered at day 6 post-transplant in mice receiving BM+T-cells, with established GvHD detectable by histology of the liver within 3 weeks. Together with significant increases in pro-inflammatory cytokine gene expression in the liver and intestine, histopathological signs of GvHD and a significant increase in CD4+ and CD8+ effector and memory T-cells were seen. Endothelial activation including upregulation of vascular cell adhesion molecule (VCAM)- 1 and downregulation of endothelial nitric oxide synthase (eNOS) as well as thrombosis in the liver indicated concomitant hepatic SOS. Our findings confirm that endothelial activation is an early sign of acute GvHD and SOS in a clinically relevant mouse model of GvHD based on myeloablative chemotherapy. Preventing endothelial activation may be a viable therapeutic strategy to prevent GvHD.

Activated platelets in the tumor microenvironment for targeting of antibody-drug conjugates to tumors and metastases.

Rationale: Platelets are increasingly recognized as mediators of tumor growth and metastasis. Hypothesizing that activated platelets in the tumor microenvironment provide a targeting epitope for tumor-directed chemotherapy, we developed an antibody-drug conjugate (ADC), comprised of a single-chain antibody (scFv) against the platelet integrin GPIIb/IIIa (scFvGPIIb/IIIa) linked to the potent chemotherapeutic microtubule inhibitor, monomethyl auristatin E (MMAE). Methods: We developed an ADC comprised of three components: 1) A scFv which specifically binds to the high affinity, activated integrin GPIIb/IIIa on activated platelets. 2) A highly potent microtubule inhibitor, monomethyl auristatin E. 3) A drug activation/release mechanism using a linker cleavable by cathepsin B, which we demonstrate to be abundant in the tumor microenvironment. The scFvGPIIb/IIIa-MMAE was first conjugated with Cyanine7 for in vivo imaging. The therapeutic efficacy of the scFvGPIIb/IIIa-MMAE was then tested in a mouse metastasis model of triple negative breast cancer. Results: In vitro studies confirmed that this ADC specifically binds to activated GPIIb/IIIa, and cathepsin B-mediated drug release/activation resulted in tumor cytotoxicity. In vivo fluorescence imaging demonstrated that the newly generated ADC localized to primary tumors and metastases in a mouse xenograft model of triple negative breast cancer, a difficult to treat tumor for which a selective tumor-targeting therapy remains to be clinically established. Importantly, we demonstrated that the scFvGPIIb/IIIa-MMAE displays marked efficacy as an anti-cancer agent, reducing tumor growth and preventing metastatic disease, without any discernible toxic effects. Conclusion: Here, we demonstrate the utility of a novel ADC that targets a potent cytotoxic drug to activated platelets and specifically releases the cytotoxic agent within the confines of the tumor. This unique targeting mechanism, specific to the tumor microenvironment, holds promise as a novel therapeutic approach for the treatment of a broad range of primary tumors and metastatic disease, particularly for tumors that lack specific molecular epitopes for drug targeting.

The effect of tyrosine kinase inhibitor interruption and interferon use on pregnancy outcomes and long-term disease control in chronic myeloid leukemia.

The management of CML in pregnancy is challenging with the need to balance disease control against potential teratogenic effects of TKI therapy. In this multi-center case-cohort study of 16 women in chronic phase, CML ceased TKI treatment pre- or post-conception during their first pregnancy. Thirteen patients were on imatinib; 9 ceased their TKI prior to conception and 7 ceased at pregnancy confirmation. Twelve patients had achieved either MMR or better at time of TKI cessation. Eleven women lost MMR during pregnancy and two patients lost CHR. Fourteen women reestablished MMR on TKI recommenced. The depth molecular response prior to conception appeared to correlate well with restoration of disease control on TKI recommencement though duration of MMR did not appear to be as important. While interruption of TKI treatment for pregnancy usually leads to loss of molecular response, loss of hematological response is uncommon and disease control is reestablished with resumption of therapy in the majority of women.