Current Drug Targets - Volume 20, Issue 16, 2019

Beta-thalassemia is a genetic disorder characterized by the impaired synthesis of the betaglobin chain of adult hemoglobin. The disorder has a complex pathophysiology that affects multiple organ systems. The main complications of beta thalassemia are ineffective erythropoiesis, chronic hemolytic anemia and hemosiderosis-induced organ dysfunction. Regular blood transfusions are the main therapy for beta thalassemia major; however, this treatment can cause cardiac and hepatic hemosiderosis – the most common cause of death in these patients. This review focuses on unique future therapeutic interventions for thalassemia that reverse splenomegaly, reduce transfusion frequency, decrease iron toxicity in organs, and correct chronic anemia. The targeted effective protocols include hemoglobin fetal inducers, ineffective erythropoiesis correctors, antioxidants, vitamins, and natural products. Resveratrol is a new herbal therapeutic approach which serves as fetal Hb inducer in beta thalassemia. Hematopoietic stem cell transplantation (HSCT) is the only curative therapy for beta thalassemia major and is preferred over iron chelation and blood transfusion for ensuring long life in these patients. Meanwhile, several molecular therapies, such as ActRIIB/IgG1 Fc recombinant protein, have emerged to address complications of beta thalassemia or the adverse effects of current drugs. Regarding gene correction strategies, a phase III trial called HGB-207 (Northstar-2; NCT02906202) is evaluating the efficacy and safety of autologous cell transplantation with LentiGlobin. Advanced gene-editing approaches aim to cut DNA at a targeted site and convert HbF to HbA during infancy, such as the suppression of BCL11A (B cell lymphoma 11A), HPFH (hereditary persistence of fetal hemoglobin) and zinc-finger nucleases. Gene therapy is progressing rapidly, with multiple clinical trials being conducted in many countries and the promise of commercial products to be available in the near future.

Implementation of novel and biocompatible polymers in drug design is an emerging and rapidly growing area of research. Even though we have a large number of polymer materials for various applications, the biocompatibility of these materials remains as a herculean task for researchers. Aptamers provide a vital and efficient solution to this problem. They are usually small (ranging from 20 to 60 nucleotides, single-stranded DNA or RNA oligonucleotides which are capable of binding to molecules possessing high affinity and other properties like specificity. This review focuses on different aspects of Aptamers in drug discovery, starting from its preparation methods and covering the recent scenario reported in the literature regarding their use in drug discovery. We address the limitations of Aptamers and provide valuable insights into their future potential in the areas regarding drug discovery research. Finally, we explained the major role of Aptamers like medical imaging techniques, application as synthetic antibodies, and the most recent application, which is in combination with nanomedicines.

Background: Hepatitis B is a very harmful and epidemic disease caused by hepatitis B virus (HBV). Although an effective anti-HBV vaccine is available, chronic infection poses still a huge health burden in the whole world. The present anti-HBV drugs including nucleoside analogues and interferonalpha have their limitations without exception. There is no effective drug and therapeutic method that can really and truly cure hepatitis B so far. The variability of HBV genome results in that a significant number of patients develop drug resistance during the long-term use of anti-HBV drugs. Hence, it is urgently needed to discover novel targets and develop new drugs against hepatitis B. Objective: The review aims to provide the theory support for designing of the anti-HBV innovative drugs by offering a summary of the current situation of antiviral potential targets. Results and Conclusion: Since HBV is obligate intracellular parasite, and as such it depends on host cellular components and functions to replicate itself. The targeting both virus and host might be a novel therapeutic option for hepatitis B. Accordingly, we analyse the advances in the study of the potential drug targets for anti-HBV infection, focusing on targeting virus genome, on targeting host cellular functions and on targeting virus-host proteins interactions, respectively. Meanwhile, the immune targets against chronic hepatitis B are also emphasized. In short, the review provides a summary of antiviral therapeutic strategies to target virus factors, host factors and immune factors for future designing of the innovative drug against HBV infection.

Schizophrenia is a debilitating mental disorder with relatively high prevalence (~1%), during which positive manifestations (such as psychotic states) and negative symptoms (e.g., a withdrawal from social life) occur. Moreover, some researchers consider cognitive impairment as a distinct domain of schizophrenia symptoms. The imbalance in dopamine activity, namely an excessive release of this neurotransmitter in the striatum and insufficient amounts in the prefrontal cortex is believed to be partially responsible for the occurrence of these groups of manifestations. Second-generation antipsychotics are currently the standard treatment of schizophrenia. Nevertheless, the existent treatment is sometimes ineffective and burdened with severe adverse effects, such as extrapyramidal symptoms. Thus, there is an urgent need to search for alternative treatment options of this disease. This review summarizes the results of recent preclinical and clinical studies on phosphodiesterase 10A (PDE10A), which is highly expressed in the mammalian striatum, as a potential drug target for the treatment of schizophrenia. Based on the literature data, not only selective PDE10A inhibitors but also dual PDE2A/10A, and PDE4B/10A inhibitors, as well as multifunctional ligands with a PDE10A inhibitory potency are compounds that may combine antipsychotic, precognitive, and antidepressant functions. Thus, designing such compounds may constitute a new direction of research for new potential medications for schizophrenia. Despite failures of previous clinical trials of selective PDE10A inhibitors for the treatment of schizophrenia, new compounds with this mechanism of action are currently investigated clinically, thus, the search for new inhibitors of PDE10A, both selective and multitarget, is still warranted.

Introduction: The Global Initiative for Chronic Obstructive Lung Disease (GOLD) 2019 recommends the use of absolute blood eosinophil count as a guide for the escalation and de-escalation of inhaled corticosteroids (ICS) in the pharmacological management of patients with chronic obstructive pulmonary disease (COPD). We evaluated the risk of moderate or severe exacerbations among patients escalating and de-escalating ICS therapy by absolute blood eosinophil thresholds in this systematic review. Methods: Through a comprehensive literature search of Pubmed/MEDLINE, EMBASE, and clinical trial sites up to April 2019, we identified relevant studies. We used generic inverse variance method with fixed-effects estimates to compare the risk of moderate or severe exacerbations among COPD patients with elevated blood eosinophil counts exposed to inhaled corticosteroids (ICS) versus non-ICS treatments groups expressed as risk ratios. Results: Ten studies (8 randomised control trials and 2 observational studies) were included, with a total of 85,059 COPD patients. In our pooled analysis, we found an overall reduction in risk of moderate or severe exacerbations in patients with absolute blood eosinophil thresholds ranging from ≥ 100 to ≥ 340 cells/μL among patients escalating ICS (RR, 0.77, 95% CI, 0.73-0.81). For studies evaluating the effects of de-escalation of ICS on moderate to severe exacerbations using blood eosinophil thresholds of ≥ 300 to ≥ 340 cells/μL had an increased risk of moderate or severe exacerbations following the de-escalation of ICS (RR, 1.66, 95% CI, 1.31-2.10). Conclusion: This study confirms the validity of the recommended absolute blood eosinophil count thresholds for the escalation and de-escalation of ICS among COPD patients. However, this recommendation is for COPD patients with prior exacerbations rather than among newly diagnosed COPD patients as observed in this study. COPD patients with current or past history of asthma represent a unique phenotypic group which should be further evaluated.

Amylin is a neuroendocrine peptide hormone secreted by pancreatic β-cells; however, amylin is toxic to β-cells when it is aggregated in type 2 diabetes mellitus (T2DM). It is important to understand amylin’s structures and aggregation mechanism for the discovery and design of effective drugs to inhibit amylin aggregation. In this review, we investigated experimental and computational studies on amylin structures and inhibitors. Our review provides some novel insights into amylin, particularly for the design of its aggregation inhibitors to treat T2DM. We detailed the potential inhibitors that have been studied hitherto and highlighted the neglected need to consider different amylin attributes that depend on the presence/absence of physiologically relevant conditions, such as membranes. These conditions and the experimental methods can greatly influence the results of studies on amylininhibitor complexes. Text-mining over 3,000 amylin-related PubMed abstracts suggests the combined therapeutic potential of amylin with leptin and glucagon-like peptide-1, which are two key hormones in obesity. The results also suggest that targeting amylin aggregation can contribute to therapeutic efforts for Alzheimer’s disease (AD). Therefore, we have also reviewed the role of amylin in other conditions including obesity and AD. Finally, we provided insights for designing inhibitors of different types (small molecules, proteins, peptides/mimetics, metal ions) to inhibit amylin aggregation.

The fibrinolytic system consists of a balance between rates of plasminogen activation and fibrin degradation, both of which are finely regulated by spatio-temporal mechanisms. Three distinct inhibitors of the fibrinolytic system that differently regulate these two steps are plasminogen activator inhibitor type-1 (PAI-1), α2-antiplasmin, and thrombin activatable fibrinolysis inhibitor (TAFI). In this review, we focus on the mechanisms by which PAI-1 governs total fibrinolytic activity to provide its essential role in many hemostatic disorders, including fibrinolytic shutdown after trauma. PAI-1 is a member of the serine protease inhibitor (SERPIN) superfamily and inhibits the protease activities of plasminogen activators (PAs) by forming complexes with PAs, thereby regulating fibrinolysis. The major PA in the vasculature is tissue-type PA (tPA) which is secreted from vascular endothelial cells (VECs) as an active enzyme and is retained on the surface of VECs. PAI-1, existing in molar excess to tPA in plasma, regulates the amount of free active tPA in plasma and on the surface of VECs by forming a tPA-PAI-1 complex. Thus, high plasma levels of PAI-1 are directly related to attenuated fibrinolysis and increased risk for thrombosis. Since plasma PAI-1 levels are highly elevated under a variety of pathological conditions, including infection and inflammation, the fibrinolytic potential in plasma and on VECs is readily suppressed to induce fibrinolytic shutdown. A congenital deficiency of PAI-1 in humans, in turn, leads to life-threatening bleeding. These considerations support the contention that PAI-1 is the primary regulator of the initial step of fibrinolysis and governs total fibrinolytic activity.