Drugs of the Future

The A3 receptor has been established as a distinct receptor subtype through cloning and the synthesis of selective agonists. The distribution of this subtype in the body is unique and more limited than for A1 or A2 receptors. Actions associated with this subtype include mast cell degranulation, cerebroprotection, cardioprotection, and possibly alteration of fertility. The effects on the inflammatory system and the high level of A3 receptor expression in the lungs suggests the use of A3 antagonists for asthma. Thus, there is a tremendous potential for development for therapeutic purposes of selective drugs, either agonists or antagonists, acting at this receptor.

Farnesoid X receptor (FXR) is a member of the nuclear receptor superfamily and plays an important role in maintaining bile acid, lipid and glucose homeostasis. Bile acids are endogenous ligands for FXR. However, bile acids may also activate pathways independent of FXR. The development of specific FXR agonists has provided important insights into the role of FXR in metabolism. Recent data have demonstrated that FXR is a therapeutic target for treatment of certain metabolic disorders. This review will focus on recent advances in the role of FXR in metabolic disease.

One of the hallmarks of autoimmune diabetes is the presence of adaptive responses directed to neuroendocrine proteins. One of these proteins is glutamic acid decarboxylase (GAD). While GAD is widely distributed in neuroendocrine tissues, its specific significance in diabetes has paralleled the advances in understanding humoral and cellular immunity in Type 1 diabetes (T1D) and in a subset of Type 2 diabetes (T2D), going from the seminal discoveries of islet autoantibodies to the development and standardization of bioassays as diagnostic tools, to studies on the structure of GAD and its antigenic determinants. GAD65 autoantibodies can accurately predict T1D development in combination with other surrogate humoral biomarkers and they are considered the most sensitive and specific biomarker which identifies a subset of clinically diagnosed T2D termed Latent Autoimmune Diabetes in Adults (LADA). We and others provided evidence indicating that GAD65 autoantibody detection should be part of the diagnostic assessment for clinically diagnosed T2DM mainly because it predicts the rate of progression to insulin requirement in patients affected by LADA. More recently GAD has been used as a "tolerogenic vaccine" to preserve beta cell function in autoimmune diabetes. While the results of Phase III clinical trials did not substantiate the earlier promise of Phase I and II trials, there are still many unanswered questions and approaches that need to be investigated in the applications of GAD in the therapy of T1D and LADA.

Sequence-specific gene silencing with small interfering RNA (siRNA) has transformed basic science research, and the efficacy of siRNA therapeutics toward a variety of diseases is now being evaluated in pre-clinical and clinical trials. Despite its potential value, the highly negatively charged siRNA has the classic delivery problem of requiring transport across cell membranes to the cytosol. Consequently, carrier development for siRNA delivery is one of the most important problems to solve before siRNA can achieve widespread clinical use. An assortment of non-viral carriers including liposomes, peptides, polymers, and aptamers are being evaluated for their ability to shepherd siRNA to the target tissue and cross the plasma membrane barrier into the cell. Several promising carriers with low toxicity and increased specificity for disease targets have emerged for siRNA-based therapeutics. This review will discuss non-viral approaches for siRNA therapeutics, with particular focus on synthetic carriers for in vivo systemic delivery of siRNA.

Novel therapies are urgently needed for the management of cytomegalovirus (CMV) disease in high-risk patients. Currently licensed agents target the viral DNA polymerase, and although they are effective, they are fraught with toxicities to patients. Moreover, emergence of antiviral resistance is an increasing problem, particularly for patients on long-term suppressive therapy. A new agent, letermovir (AIC246), shows great promise for the management of CMV infection. Advantages include its good oral bioavailability, its lack of toxicity, and the apparent absence of drug-drug interactions. Letermovir has a novel mechanism of action, exerting its antiviral effect by interfering with the viral pUL56 gene product and in the process disrupting the viral terminase complex. This agent demonstrates substantial promise as an alternative to more toxic antivirals in patients at high risk for CMV disease, particularly in the transplantation setting.

The prognosis for advanced neuroblastoma remains poor with high risk of recurrence after consolidation. Therapies based on monoclonal antibodies that specifically target disialoganglioside GD2 on tumor cells are improving treatment results for high-risk neuroblastoma. This article reviews the use of anti-GD2 antibodies either as monotherapy or as part of a larger and more complex treatment approach for advanced neuroblastoma. We review how anti-GD2 antibodies can be combined with other treatments or strategies to enhance their clinical effects. Tumor resistance and other problems that decrease the efficacy of anti-GD2 antibodies are discussed. Future developments in the area of anti-GD2 immunotherapies for neuroblastoma are also addressed.

Acquired drug resistance to mycotic infections is rapidly emerging as a major medical problem. Opportunistic fungal infections create therapeutic challenges, particularly in high risk immunocompromised patients with AIDS, cancer, and those undergoing transplantation. Higher mortality and/or morbidity rates due to invasive mycosis have been increasing over the last 20 years, and in light of growing resistance to commonly used antibiotics, novel antifungal drugs and approaches are required. Currently there is considerable interest in antifungal peptides that are ubiquitous in plant and animal kingdoms. These small cationic peptides may have specific targets or may be multifunctional in their mechanism of action. On the basis of recent advances in protein engineering and solid phase syntheses, the utility and potential of selected peptides as efficient antifungal drugs with acceptable toxicity profiles are being realized. This review will discuss recent advances in peptide therapy for opportunistic fungal infections.

The recent pandemic of H1N1 has demonstrated the potential vulnerability of the human population to novel influenza viruses. While there is recent increased interest and effort in developing effective anti-influenza agents, few new products have entered clinical studies. This review will highlight the limited armamentarium of licensed influenza agents, and discuss novel compounds and strategies that have entered clinical studies and may therefore be imminently available to the treating clinician.

Waldenstrom Macroglobulinemia (WM) is a B-cell disorder characterized by the infiltration of the bone marrow (BM) with lymphoplasmacytic cells, as well as detection of an IgM monoclonal gammopathy in the serum. WM is an incurable disease, with an overall medial survival of only 5-6 years. First-line therapy of WM has been based on single-agent or combination therapy with alkylator agents (e.g. chlorambucil or cyclophasphamide), nucleoside analogues (cladribine or fludarabine), and the monoclonal antibody rituximab. Novel therapeutic agents that have demonstrated efficacy in WM include thalidomide, lenalidomide, bortezomib, everolimus, Atacicept, and perifosine. The range of the ORR to these agents is between 25-80%. Ongoing and planned future clinical trials include those using PKC inhibitors such as enzastaurin, new proteasome inhibitors such as carfilzomib, histone deacetylase inhibitors such as panobinostat, humanized CD20 antibodies such as Ofatumumab, and additional alkylating agents such as bendamustine. These agents, when compared to traditional chemotherapeutic agents, may lead in the future to higher responses, longer remissions and better quality of life for patients with WM.

Autophagy is a process in which cellular contents are captured in specialized, membrane-bounded vesicles and delivered to lysosomes for final degradation. Most studies support an inherent connection between autophagy and survival, but increasing evidence also suggests an association between autophagy and cell death. The therapeutic potential of targeting the autophagy pathway in cancer seems clear, but specific strategies for achieving successful eradication of cancer cells are less obvious. Recent developments in the fields of autophagy and programmed cell death, nevertheless, have shed light on therapeutic strategies with significant potential. In this review, we provide an overview of the autophagy process, pathways that modulate autophagy, and promising autophagy-based therapeutic strategies for cancer.

Age-related macular degeneration causes irreversible central blindness in people over the age of 50 and is increasing in prevalence among elderly populations. There are currently limited treatment options available for the exudative form of the disease and no formal treatments for the geographic atrophy form aside from lifestyle change and incorporation of antioxidant supplements in the diet. As such, it is important to be able to assess high-risk AMD patients as early as possible in order to prescribe preventative measures. Carboxyethylpyrrole (CEP) is a promising plasma biomarker suited to this purpose. Both CEP immunoreactivity levels as well as anti-CEP autoantibody titers are significantly elevated in AMD patients and thus provide the potential to assess AMD susceptibility with approximately 80% accuracy when evaluated alongside genomic AMD markers. Moreover, strong evidence implicates CEP as functionally related to AMD pathogenesis, a role which must be explored further. This avenue of research will foster improved understanding of the disease itself and perhaps reveal better therapeutic targets and options. Further research into the role of CEP in AMD pathogenesis and the application of CEP as an AMD biomarker is merited.

Some 15-20% of the population over the age of 65 years suffer from dementia, currently one of the leading causes of death behind cardiovascular diseases, cancer and cerebrovascular diseases. The major forms of dementia share in common overactivation of the CD40-CD40-L complex, leading to high levels of proinflammatory cytokine production by immune cells of the central nervous system (CNS), including microglia and astrocytes. Consequently, both neuronal survival and signaling are negatively affected, leading to the characteristic progressive loss of higher cortical functions. We have reviewed the literature concerning the involvement of this complex in the pathology of three major forms of dementia: Alzheimer's-type, HIV-associated and vascular dementia. This is followed by a discussion of current preclinical and clinical therapies that may influence this interaction, and thus point the way toward a future neuroimmunological approach to inhibiting the effects of CD40-CD40-L in neuropsychiatric disease.

Although cocaine is illegal in most countries of the world, addiction is common and increasing in many populations, and the effectiveness of current treatment options for those afflicted has been very limited. The availability of an anti-cocaine vaccine could offer help to those who wish to quit their addiction. A number of vaccines differing in their chemical nature have been developed, and one has advanced into clinical trials. This review will discuss the successes and limitations of the various vaccines and the results of clinical trials of the vaccine using succinyl norcocaine conjugated to cholera toxin B. This latter vaccine shows considerable promise for those individuals whose antibody response is adequate..

The non-receptor tyrosine kinase Syk has a diverse range of biological functions, including a critical role in the intracellular signalling cascade for the surface immunoglobulin receptor on B lymphocytes, and the Fc receptor expressed on numerous immune effector cells. It is therefore seen as a potential therapeutic target in a variety of conditions, including autoimmune, allergic and malignant diseases. Fostamatinib disodium is the orally bioavailable prodrug of R406, a relatively selective small molecule inhibitor of Syk, that has accordingly shown activity in numerous cell types in vitro, and efficacy in a remarkable range of animal models in vivo, including rodent models of asthma, inflammatory arthritis, lupus, glomerulonephritis, diabetes and lymphoma. Success in these models has translated to phase II clinical trials in autoimmune thrombocytopenia, lymphoma and, most notably, rheumatoid arthritis, in which larger phase III trials are currently in progress. Whilst the diverse biological functions of Syk, coupled to the potential off-target effects of this kinase inhibitor are a source of possible toxicity, the available data thus far augurs well for future clinical use of Fostamatinib in a wide range of human diseases.

Viruses have long been considered potential anticancer treatments. Wild-type viruses have been tested as anticancer agents in clinical trials since the 1960s. The possibility of viral oncolysis as an alternate cancer therapy was transformed by the emergence of modern genetic engineering. The herpes simplex virus (HSV) family offers particular advantages for use as a viral oncolytic. The engineered vectors that make up oncolytic HSVs (oHSVs) have demonstrated remarkable safety in clinical trials, with some evidence of efficacy. The past decade has seen a focus on increasing the efficacy of oncolytic vectors by adding exogenous transgenes to enhance tumor destruction. The current paper describes the various strategies for engineering HSV for increased cancer tissue specificity and efficacy. Presented are the rationale, preclinical data and clinical data where available. This is meant to illustrate a basic framework for the development of a novel therapy meant to exploit the viral life cycle for the killing of cancer.

Eliglustat tartrate (Genz-112638) is a novel, orally administered agent currently in development for the treatment of lysosomal storage disorders, including type 1 Gaucher disease and Fabry disease. This glucosylceramide analogue acts as an inhibitor of glucosylceramide synthase, a Golgi complex enzyme that catalyzes the formation of glucosylceramide from ceramide and UDP-glucose and is the first step in the formation of glucocerebroside-based glycosphingolipids. Pre-clinical pharmacological studies demonstrate that the agent has a high therapeutic index, excellent oral bioavailability and limited toxicity. Phase I studies in healthy volunteers revealed limited toxicity with an excellent pharmacodynamic response, as measured by decreased plasma glucosylceramide concentrations. Phase II studies in patients with type 1 Gaucher disease have demonstrated promising clinical responses, as measured by decreases in spleen size, improvement in hemoglobin concentrations and increased platelet counts. Two randomized phase III trials testing the efficacy and safety of eliglustat tartrate are currently in progress.

Hepatitis C virus (HCV) infects more than 3% of the world's population, leading to an increased risk of cirrhosis and hepatocellular carcinoma. The current standard of care, a combination of pegylated interferon alfa and ribavirin, is poorly tolerated and often ineffective against the most prevalent genotype of the virus, genotype 1. The very recent approval of boceprevir and telaprevir, two HCV protease inhibitors, promises to significantly improve treatment options and outcomes. In addition to the viral protease NS3 and the viral polymerase NS5B, direct-acting antivirals are now in development against NS5A. A multifunctional phosphoprotein, NS5A is essential to HCV genome replication, but has no known enzymatic function. Here we report how the design of small-molecule inhibitors against NS5A has evolved from promising monomers to highly potent dimeric compounds effective against many HCV genotypes. We also highlight recent clinical data and how the inhibitors may bind to NS5A, itself capable of forming dimers.

Genome editing with the use of zinc finger nucleases has been successfully applied to variety of a eukaryotic cells. Furthermore, the proof of concept for this approach has been extended to diverse animal models from Drosophila to mice. Engineered zinc finger nucleases are able to target specifically and manipulate disease-causing genes through site-specific double strand DNA breaks followed by non-homologous end joining or homologous recombination mechanisms. Consequently, this technology has considerable flexibility that can result in either a gain or loss of function of the targeted gene. In addition to this flexibility, gene therapy by zinc finger nucleases may enable persistent long term gene modification without continuous transfection- a potential advantage over RNA interference or direct gene inhibitors. With systemic viral delivery systems, this gene-editing approach corrected the mutant factor IX in models of mouse hemophilia. Moreover, phase I clinical trials have been initiated with zinc finger nucleases in patients with glioblastoma and HIV. Thus, this emerging field has significant promise as a therapeutic strategy for human genetic diseases, infectious diseases and oncology. In this article, we will review recent advances and potential risks in zinc finger nuclease gene therapy.

Given the strong genetic determinants of favorable HDL-C levels, the ability to procure the cardiovascular disease and longevity benefits associated with this mediator of the reverse cholesterol transport pathway through pharmaceutical intervention is challenging. Niacin is still the most robust HDL-C raising pharmaceutical agent on the market at its use leads to elevations up to 35%. Cholesteryl ester transfer protein (CETP) and endothelial lipase (EL) are two targets involved in the reverse cholesterol transport pathway that have become therapeutic targets of various investigations for raising HDL. However, the Investigation of Lipid Level Management to Understand its Impact in Atherosclerotic Events (ILLUMINATE) trial was stopped in December 2006 due to excess mortality in the group of patients treated with torcetrapib, a CETP inhibitor. Other CETP inhibitors being studied include anacetrapib and JTT-705. Other CEPT inhibitors including TA-8995, DRL-17822, JTT-302, and others are under investigation. Additionally a biologic target CETi-1, an investigational vaccine in phase II development designed to elicit antibodies that bind and inhibit the activity of CETP leading to blocking the ability of the protein to transfer cholesterol from HDL to LDL and thus causing HDL cholesterol levels to rise is under clinical investigation for sometime.

The norepinephrine transporter (NET) is located in the plasma membrane of noradrenergic neurons, where it functions to take up synaptically released norepinephrine (NE). The NET thus serves as the primary mechanism for the inactivation of noradrenergic signaling. Some potent and selective or mixed NET inhibitors (e.g., reboxetine and atomoxetine) have been successfully developed to treat a variety of mental disorders such as depression and attention deficit hyperactivity disorder (ADHD). However, to date, only a very limited number of NET-selective inhibitors are available. New potent and selective NET inhibitors may find application in the treatment of mental disorders or in PET imaging, and may enhance our basic understanding of these illnesses. In the present review, both previously reported and newly designed NET inhibitors, as well as their therapeutic and imaging potential, will be discussed. Two types of molecules, the conformationally constrained tropanes and the piperidine-based nocaine/modafinil hybrid ligands, represent new leads and provide good opportunities for discovering novel potent and selective NET inhibitors that are useful as therapies and imaging agents for the NET.

Subjective tinnitus, the phantom ringing or buzzing sensation that occurs in the absence of sound, affects 12-14% of adults; in some cases the tinnitus is so severe or disabling that patients seek medical treatment. However, although the economic and emotional impact of tinnitus is large, there are currently no FDA-approved drugs to treat this condition. Clinical trials are now underway to evaluate the efficacy of N-methyl-d-aspartate (NMDA) and dopamine D(2) antagonists, selective serotonin reuptake inhibitors (SSRIs), γ-aminobutyric acid (GABA) agonists and zinc dietary supplements. Previous off-label clinical studies, while not definitive, suggest that patients with severe depression may experience improvement in their tinnitus after treatment with antidepressants such as nortriptyline or sertraline. A small subpopulation of patients with what has been described as "typewriter tinnitus" have been shown to gain significant relief from the anticonvulsant carbamazepine. Preliminary studies with misoprostol, a synthetic prostaglandin E1 analogue, and sulpiride, a dopamine D(2) antagonist, have shown promise. Animal behavioral studies suggest that GABA transaminase inhibitors and potassium channel modulators can suppress tinnitus. Additionally, improvements in tinnitus have also been noted in patients taking melatonin for significant sleep disturbances. Like other complex neurological disorders, one drug is unlikely to resolve tinnitus in all patients; therapies targeting specific subgroups are likely to yield the greatest success.