Current Medicinal Chemistry - Volume 25, Issue 23, 2018

In the last four decades, the several classes of diuretics, currently available for clinical use, have been the first line option for the therapy of widespread cardiovascular and non-cardiovascular diseases. Diuretic drugs generally exhibit an overall favourable risk/benefit balance. However, they are not devoid of side effects. In particular, all the classes of diuretics cause alteration of potassium homeostasis. In recent years, understanding of the physiological role of the renal outer medullary potassium (ROMK) channels, has shown an intriguing pharmacological target for developing an innovative class of diuretic agents: the ROMK inhibitors. This novel class is expected to promote diuretic activity comparable to (or even higher than) that provided by the most effective drugs used in clinics (such as furosemide), with limited effects on potassium homeostasis. In this review, the physio-pharmacological roles of ROMK channels in the renal function are reported, along with the most representative molecules which have been currently developed as ROMK inhibitors.

Background: The Kv7 (KCNQ) subfamily of voltage-gated potassium channels consists of 5 members (Kv7.1-5) each showing characteristic tissue distribution and physiological roles. Given their functional heterogeneity, Kv7 channels represent important pharmacological targets for the development of new drugs for neuronal, cardiovascular and metabolic diseases. Objective: In the present manuscript, we focus on describing the pharmacological relevance and potential therapeutic applications of drugs acting on neuronally-expressed Kv7.2/3 channels, placing particular emphasis on the different chemotypes, and highlighting their pharmacodynamic and, whenever possible, pharmacokinetic peculiarities. Methods: The present work is based on an in-depth search of the currently available scientific literature, and on our own experience and knowledge in the field of neuronal Kv7 channel pharmacology. Space limitations impeded to describe the full pharmacological potential of Kv7 channels; thus, we have chosen to focus on neuronal channels composed of Kv7.2 and Kv7.3 subunits, and to mainly concentrate on their involvement in epilepsy. Results: An astonishing heterogeneity in the molecular scaffolds exploitable to develop Kv7.2/3 modulators is evident, with important structural/functional peculiarities of distinct compound classes. Conclusion: In the present work we have attempted to show the current status and growing potential of the Kv7 pharmacology field. We anticipate a bright future for the field, and express our hopes that the efforts herein reviewed will result in an improved treatment of hyperexcitability (or any other) diseases.

Background: Mitochondria play a central role in ATP-generating processes. Indeed, in mammalian tissues, up to 90% of ATP is generated by mitochondria through the process of oxidative phosphorylation; furthermore, mitochondria are involved in multiple signal transduction pathways. A rapidly expanding body of literature has confirmed that mitochondria play a pivotal role in apoptosis, cardio- and neuro-protection, and various neurodegenerative disorders, ranging from Parkinson's to Alzheimer's disease. Mitochondria are also the targets of multiple drugs, some of these are specifically designed to affect mitochondrial function, while others have primary targets in other cellular locations but may interact with mitochondria because of the presence of numerous targets on this organelle. In this regard, mitochondrial potassium (mitoK) channels play a critical role in mitochondrial function and, consequently, in the metabolism of the whole cell. Objective: To describe mitoK channels from a structural point of view and investigate their pathophysiological roles, focusing on possible specific modulators that might be useful as pharmacological tools in the treatment of various pathologies characterized by mitoK involvement. Results: mitoK channels play a decisive role in several pathologies, including cardiovascular diseases, particularly in myocardial infarction and neurodegenerative diseases, and they are emerging as promising oncological targets. Conclusions: mitoK channels represent novel targets, and mitoK channel modulators represent an exciting tool for pharmacological intervention against such pathological conditions.

The discovery of the high-affinity, high-specificity folate receptor in mamalian kidney cells, coupled with the ability of folate to enter cells by folate receptor-mediated endocytosis and the subsequent elucidation of the folate receptor's overexpression in specific cancer cell types; heralded the arrival of the area of chemotherapeutic folate targeting. The application of purely organic folate-based small-molecule drug conjugates that selectively target the folate receptor, which is over expressed in several diseases such as cancer, is well established. The application of inorganic folate-targeted drugs offers significant potential to expand and enhance this therapeutic approach. From the data made available to date, it is apparent that this aspect of inorganic medicinal chemistry is in its youth but has the capability to contribute greatly to cancer research, both in therapy and diagnosis. The union of folate-receptor targeting and inorganic medicine may also lead to the development of treatments for disorders such as chronic-inflammation, tuberculosis, neurodegenerative disease and leishmaniasis. In this review, we summarize what is known about the coordination chemistry of folic acid and the therapeutic potential of such complexes. We also describe approaches adopted to conjugate platinum drugs to folate- or folate-carrier- systems and their prospective ability to overcome problems associated with unwanted side-effects and resistance by improving their delivery and/or selectivity. The literature pertaining to non-platinum metal complex conjugates with folic acid is also reviewed revealing that this is an area that offers significant potential to develop targeted therapeutic approaches in areas such as chemotherapy and molecular imaging for diagnostics.

Hepatitis B Virus (HBV) is a major global health burden. Interferon alpha and nucleos(t)ide analogues are currently the standard-of-care for chronic HBV infection. However, these antiviral agents have limited efficacy and do not result in a sustained virological response in the majority of infected patients. Virtual Screening (VS) strategies have now a strong impact on drug discovery, the strength of this research field has been corroborated by recent contributions in the development of novel drug candidates which are in clinical trials or which are already available in the clinics. In this context, different VS strategies have been applied to HBV in order to discover novel inhibitors. In this review, we summarize the VS efforts to identify and design novel HBV interventions. We believe that the combination of in silico and in vitro tools can lead to faster validation of novel drug targets which could accelerate the HBV drug discovery and development efforts.

The clustered DNA lesions are a characteristic feature of ionizing radiation and are defined as two or more damage sites formed within 20 bps after the passage of a single radiation track. The clustered DNA lesions are divided into two major groups: double-stranded breaks (DSBs) and non-DSB clusters also known as Oxidatively-induced Clustered DNA Lesions (OCDLs), which could involve either two opposing strands or the same strand. As irradiation is gaining greater interest in cancer treatment as well as in imaging techniques, the detailed knowledge of its genotoxicity and the mechanisms of repair of radiation-induced DNA damage remain issues to explore. In this review we look at the ways the cell copes with clustered DNA lesions, especially with 5′,8-cyclo-2′-deoxypurines. As the base excision repair deals with isolated lesions, complex damage is more difficult to repair. Depending on the number of lesions within a cluster, their types and mutual distribution, long-patch BER or NER are activated. During the repair of opposing lesions, DSBs could be generated, which are repaired either by nonhomologous end joining (NHEJ) or homologous recombination (HR). The repair of individual lesions within a cluster progresses gradually. This slower processing of particular damage might lead to severe biological consequences such as misrepair, mutations and chromosomal rearrengement as it enhances the plausibility of a cluster encountering a replication fork prior to its repair. The consequences of clustered DNA lesions on cell survival and their relevance to the efficacy and safety of radiotherapy and radiodiagnosis will also be discussed.

The β-amyloid (Aβ) plaques presented within the brain parenchyma have been widely proved to be one of the hallmarks of Alzheimer's disease (AD). According to the amyloid cascade hypothesis, the accumulation of Aβ plaques in the brain is intrinsic and fundamental for disease onset, and much research about the early diagnosis of AD is based on this. A recent development in Aβ detection has focused on the mapping of the molecule events in the brain using an exquisite, noninvasive, and inexpensive optical imaging technique, which has stimulated the rapid development of Aβ-specific fluorescent probes. Among them, nearinfrared (NIR) fluorophores have gained adequate attention due to the weak light attenuation in tissues and avoidance from auto-fluorescence of biological matter. In this review, we showcase the current developments of fluorescent probes that are subject to in vitro or in vivo detection of Aβ plaques in the brain, and give an emphasis on the probes used for in vivo twophoton microscopy and NIR imaging by highlighting their biological and photochemical properties.