Repurposing Treprostinil for Enhancing Hematopoietic Progenitor Cell Transplantation

Drug Repurposing of Generic Drugs: Challenges and the Potential Role for Government

Drug repurposing is the process of identifying a new use for an existing drug or active substance in an indication outside the scope of the original indication. Drug repurposing has important advantages including reduced development time and costs, and potentially large societal healthcare cost savings. However, current generic drug repurposing research faces a number of challenges in obtaining research funds. Furthermore, regardless of the success of a repurposing trial, commercial parties often lack interest in pursuing marketing authorisation for financial reasons, and academic researchers lack the knowledge, time and funding. Therefore, the new indication of a repurposed drug often does not make it 'on label'. We propose a large increase in public funding for generic drug repurposing research, including funds for the marketing authorisation process when a trial is successful, and a reduction in the regulatory burden of the marketing authorisation process for repurposed generic drugs.

Effects of treprostinil on pulmonary arterial hypertension during surgery for congenital heart disease complicated with severe pulmonary arterial hypertension

BACKGROUND

The aim of this study is to evaluate the effects of treprostinil injection on the control of pulmonary blood pressure in children with congenital heart disease (CHD) complicated by severe pulmonary arterial hypertension (PAH).

METHODS

Eighty children with CHD complicated by severe pulmonary arterial hypertension admitted to our hospital from January 2015 to June 2018 were selected and randomly divided into a control group (N.=40) and a treatment group (N.=40). Based on standard treatment, the treatment group was intravenously infused with 8-12 ng/kg·min treprostinil, while the control group received the same dose of normal saline. Hemodynamic parameters such as BP, AP, P and SpO<inf>2</inf>% were monitored before anesthesia induction (T0), before cardiopulmonary bypass (T1), 1 h after cardiopulmonary bypass (T2) and at the end of cardiopulmonary bypass (T3). Pulmonary arterial pressure parameters (PASP, PADP and PAMP) were measured at T1, T2 and T3 by transesophageal echocardiography.

RESULTS

For the treatment group, the HR values at T2 and T3 were lower than that at T0 (P<0.05). For the control group, HR at T3 was lower than that at T0 (P<0.05). HR at T3 of the treatment group was lower than that of the control group (P<0.05). SpO<inf>2</inf> of the treatment group was higher than that of the control group at T3 (P<0.05). At T2 and T3, PASP, PADP and PAMP of both groups were lower than those before surgery (P<0.05), and the values of the treatment group were lower than those of the control group (P<0.05).

CONCLUSIONS

Treprostinil can improve cardiac function and reduce pulmonary circulation resistance in PAH children.

Regimen-dependent synergism and antagonism of treprostinil and vildagliptin in hematopoietic cell transplantation

The cell dose in umbilical cord blood units is a major determinant for the outcome of hematopoietic cell transplantation. Prostaglandin analogs and dipeptidylpeptidase-4 (DPP4/CD26)-inhibitors enhance the ability of hematopoietic stem cells (HSCs) to reconstitute hematopoiesis. Here we explored the synergism between treprostinil, a stable prostaglandin agonist, and the DPP4/CD26-inhibitor vildagliptin. The combination of treprostinil and forskolin caused a modest but statistically significant increase in the surface levels of DPP4/CD26 on hematopoietic stem and progenitor cells (HSPCs) derived from murine bone and human cord blood. Their migration towards stromal cell-derived factor-1 (SDF-1/CXCL12) was enhanced, if they were pretreated with treprostinil and forskolin, and further augmented by vildagliptin. Administration of vildagliptin rescued 25% of lethally irradiated recipient mice injected with a limiting number of untreated HSPCs, but 90 to 100% of recipients injected with HSPCs preincubated with treprostinil and forskolin. The efficacy of vildagliptin surpassed that of treprostinil (60% rescue). Surprisingly, concomitant administration of vildagliptin and treprostinil resulted in poor survival of recipients indicating mutual antagonism, which was recapitulated when homing of and colony formation by HSPCs were assessed. These observations of regimen-dependent synergism and antagonism of treprostinil and vildagliptin are of translational relevance for the design of clinical trials. KEY MESSAGES: Pretreatment with treprostinil increases surface levels of DPP4/CD26 in HSPCs. Vildagliptin enhances in vitro migration of pretreated HSPCs. Vildagliptin enhances in vivo homing and engraftment of pretreated HSPCs. Unexpected mutual antagonism in vivo by concomitant administration of vildagliptin and treprostinil.

The Biological and Clinical Relevance of G Protein-Coupled Receptors to the Outcomes of Hematopoietic Stem Cell Transplantation: A Systematized Review

Hematopoietic stem cell transplantation (HSCT) remains the only curative treatment for several malignant and non-malignant diseases at the cost of serious treatment-related toxicities (TRTs). Recent research on extending the benefits of HSCT to more patients and indications has focused on limiting TRTs and improving immunological effects following proper mobilization and engraftment. Increasing numbers of studies report associations between HSCT outcomes and the expression or the manipulation of G protein-coupled receptors (GPCRs). This large family of cell surface receptors is involved in various human diseases. With ever-better knowledge of their crystal structures and signaling dynamics, GPCRs are already the targets for one third of the current therapeutic arsenal. The present paper assesses the current status of animal and human research on GPCRs in the context of selected HSCT outcomes via a systematized survey and analysis of the literature.

Treprostinil reduces endothelial damage in murine sinusoidal obstruction syndrome

Abstract

Sinusoidal obstruction syndrome (SOS) is a major complication after hematopoietic stem cell transplantation and belongs to a group of diseases increasingly identified as transplant-related systemic endothelial disease. Administration of defibrotide affords some protection against SOS, but the effect is modest. Hence, there is unmet medical need justifying the preclinical search for alternative approaches. Prostaglandins exert protective actions on endothelial cells of various vascular beds. Here, we explored the therapeutic potential of the prostacyclin analog treprostinil to prevent SOS. Treprostinil acts via stimulation of IP, EP₂, and EP₄ receptors, which we detected in murine liver sinusoidal endothelial cells (LSECs). Busulfan-induced cell death was reduced when pretreated with treprostinil in vitro. In a murine in vivo model of SOS, concomitantly administered treprostinil caused lower liver weight-to-body weight ratios indicating liver protection. Histopathological changes were scored to assess damage to liver sinusoidal endothelial cells, to hepatocytes, and to the incipient fibrotic reaction. Treprostinil indeed reduced sinusoidal endothelial cell injury, but this did not translate into reduced liver cell necrosis or fibrosis. In summary, our observations provide evidence for a beneficial effect of treprostinil on damage to LSECs but unexpectedly treprostinil was revealed as a double-edged sword in SOS.

Key messages

Murine liver sinusoidal endothelial cells (LSECs) express prostanoid receptors.

Treprostinil reduces busulfan-induced cell death in vitro.

Treprostinil lowers liver weight-to-body weight ratios in mice.

Treprostinil positively affects LSECs in mice but not hepatic necrosis/fibrosis.

NGR (Asn-Gly-Arg)-targeted delivery of coagulase to tumor vasculature arrests cancer cell growth

Induction of selective thrombosis and infarction in tumor-feeding vessels represents an attractive strategy to combat cancer. Here we took advantage of the unique coagulation properties of staphylocoagulase and genetically engineered it to generate a new fusion protein with novel anti-cancer properties. This novel bi-functional protein consists of truncated coagulase (tCoa) and an NGR (GNGRAHA) motif that recognizes CD13 and α_vβ₃ integrin receptors, targeting it to tumor endothelial cells. Herein, we report that tCoa coupled by its C-terminus to an NGR sequence retained its normal binding activity with prothrombin and a_vβ₃ integrins, as confirmed in silico and in vitro. Moreover, in vivo biodistribution studies demonstrated selective accumulation of FITC-labeled tCoa-NGR fusion proteins at the site of subcutaneously implanted PC3 tumor xenografts in nude mice. Notably, systemic administration of tCoa-NGR to mice bearing 4T1 mouse mammary xenografts or PC3 human prostate tumors resulted in a significant reduction in tumor growth. These anti-tumor effects were accompanied by massive thrombotic occlusion of small and large tumor vessels, tumor infarction and tumor cell death. From these findings, we propose tCoa-NGR mediated tumor infarction as a novel and promising anti-cancer strategy targeting both CD13 and integrin α_vβ₃ positive tumor neovasculature.

The Second-Generation PGI2 Analogue Treprostinil Fails to Chemoprevent Tumors in a Murine Lung Adenocarcinoma Model

Prostacyclin (prostaglandin I₂, PGI₂) overproduction in FVB/N mice prevents the formation of carcinogen and tobacco smoke-induced adenomas, and administration of the oral prostacyclin analogue iloprost to wild-type mice also prevented carcinogen-induced mouse lung adenoma formation. Former smokers taking oral iloprost showed improved bronchial dysplasia histology compared with placebo. Next-generation oral prostacyclin analogues, like treprostinil, were developed for the treatment of pulmonary arterial hypertension (PAH). On the basis of our prior studies with iloprost, we performed preclinical studies examining the ability of treprostinil to chemoprevent urethane-induced murine lung adenocarcinoma. We determined the MTD in chow (prior studies had delivered treprostinil by gavage), and this dose produced serum levels in the experimental animals similar to those found in PAH patients treated with treprostinil. We then examined the chemopreventive efficacy of treprostinil exposure initiated both before (1 week) and after (6 weeks) urethane exposure to better model chemoprevention studies conducted in former smokers. Neither of these dosing strategies prevented murine lung cancer; however, we did detect changes in pulmonary inflammatory cell infiltrate and expression of CXCR4 (a chemokine receptor previously shown to increase in response to treprostinil exposure) in tumor-bearing, treprostinil-treated animals, indicating that the drug was bioavailable. One potential explanation stems from iloprost and treprostinil differentially activating cell surface prostaglandin receptors and intracellular peroxisome proliferator-activated receptors. When murine lung tumor cells were treated with treprostinil, their proliferation rate increased; in contrast, iloprost had no effect on proliferation. Future investigations comparing these two agents will provide insight into iloprost's chemopreventive mechanisms. Cancer Prev Res; 10(11); 671-9. ©2017 AACR.

RGD delivery of truncated coagulase to tumor vasculature affords local thrombotic activity to induce infarction of tumors in mice

Induction of thrombosis in tumor vasculature represents an appealing strategy for combating cancer. Herein, we combined unique intrinsic coagulation properties of staphylocoagulase with new acquired functional potentials introduced by genetic engineering, to generate a novel bi-functional fusion protein consisting of truncated coagulase (tCoa) bearing an RGD motif on its C-terminus for cancer therapy. We demonstrated that free coagulase failed to elicit any significant thrombotic activity. Conversely, RGD delivery of coagulase retained coagulase activity and afforded favorable interaction of fusion proteins with prothrombin and α_vβ₃ endothelial cell receptors, as verified by in silico, in vitro, and in vivo experiments. Although free coagulase elicited robust coagulase activity in vitro, only targeted coagulase (tCoa-RGD) was capable of producing extensive thrombosis, and subsequent infarction and massive necrosis of CT26 mouse colon, 4T1 mouse mammary and SKOV3 human ovarian tumors in mice. Additionally, systemic injections of lower doses of tCoa-RGD produced striking tumor growth inhibition of CT26, 4T1 and SKOV3 solid tumors in animals. Altogether, the nontoxic nature, unique shortcut mechanism, minimal effective dose, wide therapeutic window, efficient induction of thrombosis, local effects and susceptibility of human blood to coagulase suggest tCoa-RGD fusion proteins as a novel and promising anticancer therapy for human trials.