Improving drug delivery to the brain: the prodrug approach.

INTRODUCTION: The prodrug approach has been thought to be a simple solution to improve brain drug delivery for decades. Nevertheless, it still comes as a surprise that there is relatively little success in the field. The best example anti-parkinsonian drug levodopa has been serendipitously discovered to be a transporter-utilizing brain-delivered prodrug rather than a rationally developed one. AREAS COVERED: The lack of success can mainly be explained by the insufficient understanding of the role of membrane proteins that can facilitate drug delivery at dynamic barriers, such as the blood-brain barrier (BBB), but also by the sparse knowledge of prodrug bioconverting enzymes in the brain. This review summarizes the current status of the prodrug attempts that have been developed in the past to improve brain drug delivery. EXPERT OPINION: With the expandingly improved analytical and computational technologies, it is anticipated that enhanced brain drug delivery will be eventually achieved for most of the central nervous system (CNS) acting drugs. However, this requires that carrier-mediated (pro)drug delivery methods are implemented in the very early phases of the drug development processes and not as a last step to survive a problematic investigational drug candidate.

Transporter Protein Expression of Corneal Epithelium in Rabbit and Porcine: Evaluation of Models for Ocular Drug Transport Study.

The transcorneal route is the main entry route for drugs to the intraocular parts, after topical administration. The outer surface, the corneal epithelium (CE), forms the rate-limiting barrier for drug permeability. Information about the role and protein expression of drug and amino acid transporter proteins in the CE is sparse and lacking. The aim of our study was to characterize transporter protein expression in rabbit and porcine CE to better understand potential drug and nutrient absorption after topical administration. Proteins, mainly Abc and Slc transporters, were characterized with quantitative targeted absolute proteomics and global untargeted proteomics methods. In the rabbit CE, 24 of 48 proteins were detected in the targeted approach, and 21 of these were quantified. In the porcine CE, 26 of 58 proteins were detected in the targeted approach, and 20 of these were quantified. Among these, 15 proteins were quantified in both animals: 4f2hc (Slc3a2), Aqp0, Asct1 (Slc1a4), Asct2 (Slc1a5), Glut1 (Slc2a1), Hmit (Slc2a13), Insr, Lat1 (Slc7a5), Mct1 (Slc16a1), Mct2 (Slc16a7), Mct4 (Slc16a3), Mrp 4 (Abcc4), Na+/K+-ATPase, Oatp3a1 (Slco3a1), and Snat2 (Slc38a2). Overall, the global proteomics results supported the targeted proteomics results. Organic anion transporting polypeptide Oatp3a1 was detected and quantified for the first time in both rabbit (1.4 ± 0.4 fmol/cm2) and porcine (11.1 ± 5.3 fmol/cm2) CE. High expression levels were observed for L-type amino acid transporter, Lat1, which was quantified with newly selected extracellular domain peptides in rabbit (48.9 ± 11.8 fmol/cm2) and porcine (37.6 ± 11.5 fmol/cm2) CE. The knowledge of transporter protein expression in ocular barriers is a key factor in the successful design of new ocular drugs, pharmacokinetic modeling, understanding ocular diseases, and the translation to human.

Amino acid transporters in neurological disorders and neuroprotective effects of cysteine derivatives.

For most diseases and disorders occurring in the brain, the full causes behind them are yet unknown, but many show signs of dysfunction of amino acid transporters or abnormalities in amino acid metabolism. The blood-brain barrier (BBB) plays a key role in supporting the function of the central nervous system (CNS). Because of its unique structure, the BBB can maintain the optimal environment for CNS by controlling the passage of hydrophilic molecules from blood to the brain. Nutrients, such as amino acids, can cross the BBB via specific transporters. Many amino acids are essential for CNS function, and dysfunction of these amino acid transporters can lead to abnormalities in amino acid levels. This has been linked to causes behind certain genetic brain diseases, such as schizophrenia, autism spectrum disorder, and Huntington's disease (HD). One example of crucial amino acids is L-Cys, the rate-limiting factor in the biosynthesis of an important antioxidant, glutathione (GSH). Deficiency of L-Cys and GSH has been linked to oxidative stress and has been shown as a plausible cause behind certain CNS diseases, like schizophrenia and HD. This review presents the current status of potential L-Cys therapies and gives future directions that can be taken to improve amino acid transportation related to distinct CNS diseases.

Specific transport of temozolomide does not override DNA repair-mediated chemoresistance.

Temozolomide (TMZ) a DNA alkylating agent, is the standard-of-care for brain tumors, such as glioblastoma multiforme (GBM). Although the physicochemical and pharmacokinetic properties of TMZ, such as chemical stability and the ability to cross the blood-brain barrier (BBB), have been questioned in the past, the acquired chemoresistance has been the main limiting factor of long-term clinical use of TMZ. In the present study, an L-type amino acid transporter 1 (LAT1)-utilizing prodrug of TMZ (TMZ-AA, 6) was prepared and studied for its cellular accumulation and cytotoxic properties in human squamous cell carcinoma, UT-SCC-28 and UT-SCC-42B cells, and TMZ-sensitive human glioma, U-87MG cells that expressed functional LAT1. TMZ-AA 6 accumulated more effectively than TMZ itself into those cancer cells that expressed LAT1 (UT-SCC-42B). However, this did not correlate with decreased viability of treated cells. Indeed, TMZ-AA 6, similarly to TMZ itself, required adjuvant inhibitor(s) of DNA-repair systems, O6-methylguanine-DNA methyl transferase (MGMT) and base excision repair (BER), as well as active DNA mismatch repair (MMR), for maximal growth inhibition. The present study shows that improving the delivery of this widely-used methylating agent is not the main barrier to improved chemotherapy, although utilizing a specific transporter overexpressed at the BBB or glioma cells can have targeting advantages. To obtain a more effective anticancer prodrug, the compound design focus should shift to altering the major DNA alkylation site or inhibiting DNA repair systems.

Altering distribution profile of palbociclib by its prodrugs.

Palbociclib, a cyclin-dependent kinase (CDK) 4/6 inhibitor, is currently used clinically for treating hormone receptor-positive and human epidermal growth factor receptor 2 negative breast cancer. Additionally, it has the potential to be utilized in the treatment of various tumors, including malignant glioblastoma. Previous research has indicated that palbociclib is a substrate for two efflux transporters, P-glycoprotein (P-gp; MDR1) and breast cancer-resistant protein (BCRP), which restrict the brain exposure of palbociclib. In the present study, our objective was to alter the brain distribution pattern of palbociclib by creating and assessing two novel prodrugs through in vitro, in situ, and in vivo evaluations. To this end, we synthesized two prodrugs of palbociclib by attaching it to the tyrosine promoiety at the para- (PD1) and meta-(PD2) position via a carbamate bond. We hypothesized that the prodrugs could bypass efflux transporter-mediated drug resistance by leveraging the l-type amino acid transporter (LAT1) to facilitate their transport across the blood-brain barrier (BBB) and into cancer cells, such as glioma cells that express LAT1. The compounds PD1 and PD2 did not show selective binding and had limited inhibitory effects on LAT1 in three cell lines (MCF-7, U87-MG, HEK-hLAT1). However, PD1 and PD2 demonstrated the ability to evade efflux mechanisms, and their in vitro uptake profiles were comparable to that of palbociclib, indicating their potential for effective cellular transport. In in situ and in vivo studies, brain uptake was not significantly improved compared to palbociclib, but the pharmacokinetic profiles showed encouraging enhancements. PD1 exhibited a higher AUCbrain/plasma ratio, suggesting safer dosing, while PD2 showed favorable long-acting pharmacokinetics. Although our prodrug design did not significantly improve palbociclib brain delivery due to the potential size limitation of the prodrugs, the study provides valuable insights for future prodrug development and drug delivery strategies targeting specific transporters.

Amino acid derivative of probenecid potentiates apoptosis-inducing effects of vinblastine by increasing oxidative stress in a cancer cell-specific manner.

Many chemotherapeutic drugs suffer from multidrug resistance (MDR). Efflux transporters, namely ATP-binding cassettes (ABCs), that pump the drugs out of the cancer cells comprise one major reason behind MDR. Therefore, ABC inhibitors have been under development for ages, but unfortunately, without clinical success. In the present study, an l-type amino acid transporter 1 (LAT1)-utilizing derivative of probenecid (PRB) was developed as a cancer cell-targeted efflux inhibitor for P-glycoprotein (P-gp), breast cancer resistant protein (BCRP) and/or several multidrug resistant proteins (MRPs), and its ability to increase vinblastine (VBL) cellular accumulation and apoptosis-inducing effects were explored. The novel amino acid derivative of PRB (2) increased the VBL exposure in triple-negative human breast cancer cells (MDA-MB-231) and human glioma cells (U-87MG) by 10-68 -times and 2-5-times, respectively, but not in estrogen receptor-positive human breast cancer cells (MCF-7). However, the combination therapy had greater cytotoxic effects in MCF-7 compared to MDA-MB-231 cells due to the increased oxidative stress recorded in MCF-7 cells. The metabolomic study also revealed that compound 2, together with VBL, decreased the transport of those amino acids essential for the biosynthesis of endogenous anti-oxidant glutathione (GSH). Moreover, the metabolic differences between the outcomes of the studied breast cancer cell lines were explained by the distinct expression profiles of solute carriers (SLCs) that can be concomitantly inhibited. Therefore, attacking several SLCs simultaneously to change the nutrient environment of cancer cells can serve as an adjuvant therapy to other chemotherapeutics, offering an alternative to ABC inhibitors.

Targeting Glial Cells by Organic Anion-Transporting Polypeptide 1C1 (OATP1C1)-Utilizing l-Thyroxine-Derived Prodrugs.

OATP1C1 (organic anion-transporting polypeptide 1C1) transports thyroid hormones, particularly thyroxine (T4), into human astrocytes. In this study, we investigated the potential of utilizing OATP1C1 to improve the delivery of anti-inflammatory drugs into glial cells. We designed and synthesized eight novel prodrugs by incorporating T4 and 3,5-diiodo-l-tyrosine (DIT) as promoieties to selected anti-inflammatory drugs. The prodrug uptake in OATP1C1-expressing human U-87MG glioma cells demonstrated higher accumulation with T4 promoiety compared to those with DIT promoiety or the parent drugs themselves. In silico models of OATP1C1 suggested dynamic binding for the prodrugs, wherein the pose changed from vertical to horizontal. The predicted binding energies correlated with the transport profiles, with T4 derivatives exhibiting higher binding energies when compared to prodrugs with a DIT promoiety. Interestingly, the prodrugs also showed utilization of oatp1a4/1a5/1a6 in mouse primary astrocytes, which was further supported by docking studies and a great potential for improved brain drug delivery.

Metformin derivatives - Researchers' friends or foes?

Metformin has been used for ages to treat diabetes mellitus due to its safety profile and low cost. However, metformin has variable pharmacokinetics in patients, and due to its poor oral absorption, the therapeutic doses are relatively high, causing unpleasant gastrointestinal adverse effects. Therefore, novel derivatives of metformin have been synthesized during the past decades. Particularly, after the mid-2000 s, when organic cation transporters were identified as the main metformin carriers, metformin derivatives have been under intensive investigation. Nevertheless, due to the biguanide structure, derivatives of metformin have been challenging to synthesize. Moreover, the mechanisms of metformin's action are not fully understood to date, and since it has multifunctional properties, the interests have switched to re-purposing for other diseases. Indeed, metformin derivatives have been demonstrated in many cases to be more effective than metformin itself and have the potential to be used in different diseases, including several types of cancers and neurodegenerative diseases. On the other hand, the pleiotropic nature of metformin and its derivatives can also create challenges. Not all properties are fit for all diseases. In this review, the history of the development of metformin-like compounds is summarized, and insights into their potential for future drug discovery are discussed.

Nigrostriatal 6-hydroxydopamine lesions increase alpha-synuclein levels and permeability in rat colon.

Increasing evidence suggests that the gut-brain axis plays a crucial role in Parkinson's disease (PD). The abnormal accumulation of aggregated alpha-synuclein (aSyn) in the brain is a key pathological feature of PD. Intracerebral 6-hydroxydopamine (6-OHDA) is a widely used dopaminergic lesion model of PD. It exerts no aSyn pathology in the brain, but changes in the gut have not been assessed. Here, 6-OHDA was administered unilaterally either to the rat medial forebrain bundle (MFB) or striatum. Increased levels of glial fibrillary acidic protein in the ileum and colon were detected at 5 weeks postlesion. 6-OHDA decreased the Zonula occludens protein 1 barrier integrity score, suggesting increased colonic permeability. The total aSyn and Ser129 phosphorylated aSyn levels were elevated in the colon after the MFB lesion. Both lesions generally increased the total aSyn, pS129 aSyn, and ionized calcium-binding adapter molecule 1 (Iba1) levels in the lesioned striatum. In conclusion, 6-OHDA-induced nigrostriatal dopaminergic damage leads to increased aSyn levels and glial cell activation particularly in the colon, suggesting that the gut-brain axis interactions in PD are bidirectional and the detrimental process may start in the brain.

Substituent effects of sulfonamide derivatives of metformin that can dually improve cellular glucose utilization and anti-coagulation.

Metformin, the most frequently prescribed medicine for the management of type 2 diabetes, has been shown to reduce cardiovascular events in diabetic patients in pre-clinical and clinical studies. The present work reports the design, synthesis, and biological assessment of the impact of six benzenesulfonamide biguanides on various aspects of hemostasis, cell function, red blood cell integrity (RBC), and their ability to uptake glucose in human umbilical endothelial cells (HUVECs). It was found that all synthesized o- and m-benzenesulfonamides, particularly derivatives with nitro (3) and amino groups (4), are characterized by a good safety profile in HUVECs, which was further confirmed in the cellular integrity studies. The biguanide analogues with methoxy group (1, 2) and an amino substituent (5, 6) significantly increased glucose utilization in HUVECs, similarly to the parent drug. Intriguingly, compounds 1, 3, and 6 favourably influenced some of the coagulation parameters. Furthermore, derivative 3 also slowed the process of fibrin polymerization, indicating more beneficial anti-coagulant properties than metformin. None of the novel metformin analogues interact strongly with the erythrocyte lipid-protein bilayer. Our findings indicate that derivative 3 has highly desirable anti-coagulant properties, and compounds 1 and 6 have potential dual-action activity, including anti-hyperglycaemic properties and anti-coagulant activity. As such, these derivatives can be used as lead molecules for further development of anti-diabetic agents with a beneficial effect on hypercoagulability.

Sodium-Dependent Neutral Amino Acid Transporter 2 Can Serve as a Tertiary Carrier for l-Type Amino Acid Transporter 1-Utilizing Prodrugs.

Membrane transporters are the key determinants of the homeostasis of endogenous compounds in the cells and their exposure to drugs. However, the substrate specificities of distinct transporters can overlap. In the present study, the interactions of l-type amino acid transporter 1 (LAT1)-utilizing prodrugs with sodium-coupled neutral amino acid transporter 2 (SNAT2) were explored. The results showed that the cellular uptake of LAT1-utilizing prodrugs into a human breast cancer cell line, MCF-7 cells, was mediated via SNATs as the uptake was increased at higher pH (8.5), decreased in the absence of sodium, and inhibited in the presence of unselective SNAT-inhibitor, (α-(methylamino)isobutyric acid, MeAIB). Moreover, docking the compounds to a SNAT2 homology model (inward-open conformation) and further molecular dynamics simulations and the subsequent trajectory and principal component analyses confirmed the chemical features supporting the interactions of the studied compounds with SNAT2, which was found to be the main SNAT expressed in MCF-7 cells.

Structural Features Affecting the Interactions and Transportability of LAT1-Targeted Phenylalanine Drug Conjugates.

L-type amino acid transporter 1 (LAT1) transfers essential amino acids across cell membranes. Owing to its predominant expression in the blood-brain barrier and tumor cells, LAT1 has been exploited for drug delivery and targeting to the central nervous system (CNS) and various cancers. Although the interactions of amino acids and their mimicking compounds with LAT1 have been extensively investigated, the specific structural features for an optimal drug scaffold have not yet been determined. Here, we evaluated a series of LAT1-targeted drug-phenylalanine conjugates (ligands) by determining their uptake rates by in vitro studies and investigating their interaction with LAT1 via induced-fit docking. Combining the experimental and computational data, we concluded that although LAT1 can accommodate various types of structures, smaller compounds are preferred. As the ligand size increased, its flexibility became more crucial in determining the compound's transportability and interactions. Compounds with linear or planar structures exhibited reduced uptake; those with rigid lipophilic structures lacked interactions and likely utilized other transport mechanisms for cellular entry. Introducing polar groups between aromatic structures enhanced interactions. Interestingly, compounds with a carbamate bond in the aromatic ring's para-position displayed very good transport efficiencies for the larger compounds. Compared to the ester bond, the corresponding amide bond had superior hydrogen bond acceptor properties and increased interactions. A reverse amide bond was less favorable than a direct amide bond for interactions with LAT1. The present information can be applied broadly to design appropriate CNS or antineoplastic drug candidates with a prodrug strategy and to discover novel LAT1 inhibitors used either as direct or adjuvant cancer therapy.

Comparative Modelling of Organic Anion Transporting Polypeptides: Structural Insights and Comparison of Binding Modes.

To better understand the functionality of organic anion transporting polypeptides (OATPs) and to design new ligands, reliable structural data of each OATP is needed. In this work, we used a combination of homology model with molecular dynamics simulations to generate a comprehensive structural dataset, that encompasses a diverse set of OATPs but also their relevant conformations. Our OATP models share a conserved transmembrane helix folding harbouring a druggable binding pocket in the shape of an inner pore. Our simulations suggest that the conserved salt bridges at the extracellular region between residues on TM1 and TM7 might influence the entrance of substrates. Interactions between residues on TM1 and TM4 within OATP1 family shown their importance in transport of substrates. Additionally, in transmembrane (TM) 1/2, a known conserved element, interact with two identified motifs in the TM7 and TM11. Our simulations suggest that TM1/2-TM7 interaction influence the inner pocket accessibility, while TM1/2-TM11 salt bridges control the substrate binding stability.

Current approaches to facilitate improved drug delivery to the central nervous system.

Although many pharmaceuticals have therapeutic potentials for central nervous system (CNS) diseases, few of these agents have been effectively administered. It is due to the fact that the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSF) restrict them from crossing the brain to exert biological activity. This article reviews the current approaches aiming to improve penetration across these barriers for effective drug delivery to the CNS. These issues are summarized into direct systemic delivery and invasive delivery, including the BBB disruption and convection enhanced delivery. Furthermore, novel drug delivery systems used at the nanoscale, including polymeric nanoparticles, liposomes, nanoemulsions, dendrimers, and micelles are discussed. These nanocarriers could contribute to a breakthrough in the treatment of many different CNS diseases. However, further broadened studies are needed to assess the biocompatibility and safety of these medical devices.

Aminopeptidase B can bioconvert L-type amino acid transporter 1 (LAT1)-utilizing amide prodrugs in the brain.

A prodrug approach is a powerful method to temporarily change the physicochemical and thus, pharmacokinetic properties of drugs. However, in site-selective targeted prodrug delivery, tissue or cell-specific bioconverting enzyme is needed to be utilized to release the active parent drug at a particular location. Unfortunately, ubiquitously expressed enzymes, such as phosphatases and carboxylesterases are well used in phosphate and ester prodrug applications, but less is known about enzymes selectively expressed, e.g., in the brain and enzymes that can hydrolyze more stable prodrug bonds, such as amides and carbamates. In the present study, L-type amino acid transporter 1 (LAT1)-utilizing amide prodrugs bioconverting enzyme was identified by gradually exploring the environment and possible determinants, such as pH and metal ions, that affect amide prodrug hydrolysis. Based on inducement by cobalt ions and slightly elevated pH (8.5) as well as localization in plasma, liver, and particularly in the brain, aminopeptidase B was proposed to be responsible for the bioconversion of the majority of the studied amino acid amide prodrugs. However, this enzyme hydrolyzed only those prodrugs that contained an aromatic promoiety (L-Phe), while leaving the aliphatic promoeities (L-Lys) and the smallest prodrug (with L-Phe promoiety) intact. Moreover, the parent drugs' structure (flexibility and the number of aromatic rings) largely affected the bioconversion rate. It was also noticed in this study, that there were species differences in the bioconversion rate by aminopeptidase B (rodents > human), although the in vitro-in vivo correlation of the studied prodrugs was relatively accurate.

Small Molecule Inhibitors of Lymphocyte Perforin as Focused Immunosuppressants for Infection and Autoimmunity.

New drugs that precisely target the immune mechanisms critical for cytotoxic T lymphocyte (CTL) and natural killer (NK) cell driven pathologies are desperately needed. In this perspective, we explore the cytolytic protein perforin as a target for therapeutic intervention. Perforin plays an indispensable role in CTL/NK killing and controls a range of immune pathologies, while being encoded by a single copy gene with no redundancy of function. An immunosuppressant targeting this protein would provide the first-ever therapy focused specifically on one of the principal cell death pathways contributing to allotransplant rejection and underpinning multiple autoimmune and postinfectious diseases. No drugs that selectively block perforin-dependent cell death are currently in clinical use, so this perspective will review published novel small molecule inhibitors, concluding with in vivo proof-of-concept experiments performed in mouse models of perforin-mediated immune pathologies that provide a potential pathway toward a clinically useful therapeutic agent.

Enhanced drug delivery by a prodrug approach effectively relieves neuroinflammation in mice.

AIMS: Neuroinflammation is a prominent hallmark in several neurodegenerative diseases (NDs). Halting neuroinflammation can slow down the progression of NDs. Improving the efficacy of clinically available non-steroidal anti-inflammatory drugs (NSAIDs) is a promising approach that may lead to fast-track and effective disease-modifying therapies for NDs. Here, we aimed to utilize the L-type amino acid transporter 1 (LAT1) to improve the efficacy of salicylic acid as an example of an NSAID prodrug, for which brain uptake and intracellular localization have been reported earlier. MAIN METHODS: Firstly, we confirmed the improved LAT1 utilization of the salicylic acid prodrug (SA-AA) in freshly isolated primary mouse microglial cells. Secondly, we performed behavioural rotarod, open field, and four-limb hanging tests in mice, and a whole-brain proteome analysis. KEY FINDINGS: The SA-AA prodrug alleviated the lipopolysaccharide (LPS)-induced inflammation in the rotarod and hanging tests. The proteome analysis indicated decreased neuroinflammation at the molecular level. We identified 399 proteins linked to neuroinflammation out of 7416 proteins detected in the mouse brain. Among them, Gps2, Vamp8, Slc6a3, Slc18a2, Slc5a7, Rgs9, Lrrc1, Ppp1r1b, Gnal, and Adcy5/6 were associated with the drug's effects. The SA-AA prodrug attenuated the LPS-induced neuroinflammation through the regulation of critical pathways of neuroinflammation such as the cellular response to stress and transmission across chemical synapses. SIGNIFICANCE: The efficacy of NSAIDs can be improved via the utilization of LAT1 and repurposed for the treatment of neuroinflammation. This improved brain delivery and microglia localisation can be applied to other inflammatory modulators to achieve effective and targeted CNS therapies.

L-type Amino Acid Transporter 1 Utilizing Ferulic Acid Derivatives Show Increased Drug Delivery in the Mouse Pancreas Along with Decreased Lipid Peroxidation and Prostaglandin Production.

Oxidative stress and pathological changes of Alzheimer's disease (AD) overlap with metabolic diseases, such as diabetes mellitus (DM). Therefore, tackling oxidative stress with antioxidants is a compelling drug target against multiple chronic diseases simultaneously. Ferulic acid (FA), a natural antioxidant, has previously been studied as a therapeutic agent against both AD and DM. However, FA suffers from poor bioavailability and delivery. As a solution, we have previously reported about L-type amino acid transporter 1 (LAT1)-utilizing derivatives with increased brain delivery and efficacy. In the present study, we evaluated the pharmacokinetics and antioxidative efficacy of the two derivatives in peripheral mouse tissues. Furthermore, we quantified the LAT1 expression in studied tissues with a targeted proteomics method to verify the transporter expression in mouse tissues. Additionally, the safety of the derivatives was assessed by exploring their effects on hemostasis in human plasma, erythrocytes, and endothelial cells. We found that both derivatives accumulated substantially in the pancreas, with over a 100-times higher area under curve compared to the FA. Supporting the pharmacokinetics, the LAT1 was highly expressed in the mouse pancreas. Treating mice with the LAT1-utilizing derivative of FA lowered malondialdehyde and prostaglandin E2 production in the pancreas, highlighting its antioxidative efficacy. Additionally, the LAT1-utilizing derivatives were found to be hemocompatible in human plasma and endothelial cells. Since antioxidative derivative 1 was substantially delivered into the pancreas along the previously studied brain, the derivative can be considered as a safe dual-targeting drug candidate in both the pancreas and the brain.

Increased/Targeted Brain (Pro)Drug Delivery via Utilization of Solute Carriers (SLCs).

Membrane transporters have a crucial role in compounds' brain drug delivery. They allow not only the penetration of a wide variety of different compounds to cross the endothelial cells of the blood-brain barrier (BBB), but also the accumulation of them into the brain parenchymal cells. Solute carriers (SLCs), with nearly 500 family members, are the largest group of membrane transporters. Unfortunately, not all SLCs are fully characterized and used in rational drug design. However, if the structural features for transporter interactions (binding and translocation) are known, a prodrug approach can be utilized to temporarily change the pharmacokinetics and brain delivery properties of almost any compound. In this review, main transporter subtypes that are participating in brain drug disposition or have been used to improve brain drug delivery across the BBB via the prodrug approach, are introduced. Moreover, the ability of selected transporters to be utilized in intrabrain drug delivery is discussed. Thus, this comprehensive review will give insights into the methods, such as computational drug design, that should be utilized more effectively to understand the detailed transport mechanisms. Moreover, factors, such as transporter expression modulation pathways in diseases that should be taken into account in rational (pro)drug development, are considered to achieve successful clinical applications in the future.

Structural Comparison of Sulfonamide-Based Derivatives That Can Improve Anti-Coagulation Properties of Metformin.

Due to its high efficiency, good safety profile, and potential cardio-protective properties, metformin, a dimethyl biguanide, is the first-line medication in antihyperglycemic treatment for type 2 diabetic patients. The aim of our present study was to assess the effects of eight new sulfonamide-based derivatives of metformin on selected plasma parameters and vascular hemostasis, as well as on endothelial and smooth muscle cell function. The compounds with an alkyl chain (1-3), trifluoromethyl substituent (4), or acetyl group (5) significantly elevated glucose utilization in human umbilical endothelial cells (HUVECs), similarly to metformin. Our novel findings showed that metformin analogues 1-3 presented the most beneficial properties because of their greatest safety profile in the WST-1 cell viability assay, which was also proved in the further HUVEC integrity studies using RTCA DP. Compounds 1-3 did not affect either HUVEC or aortal smooth muscle cell (AoSMC) viability up to 3.0 mM. Importantly, these compounds beneficially affected some of the coagulation parameters, including factor X and antithrombin III activity. In contrast to the above-mentioned metformin analogues, derivatives 4 and 5 exerted more profound anticoagulation effects; however, they were also more cytotoxic towards HUVECs, as IC50 values were 1.0-1.5 mM. In conclusion, the chemical modification of a metformin scaffold into sulfonamides possessing alkyl substituents results in the formation of novel derivatives with potential bi-directional activity including anti-hyperglycemic properties and highly desirable anti-coagulant activity.