Controlled Iontophoretic Delivery in Vitro and in Vivo of ARN14140-A Multitarget Compound for Alzheimer's Disease

Recent advances in cutaneous drug delivery by iontophoresis

INTRODUCTION

Iontophoresis has been extensively studied for topical and transdermal drug delivery to stimulate the absorption of molecules that would hardly pass through the outermost layer of the skin passively. Recent research has focused on its combination with nanoparticle-based systems or microneedles to expand its therapeutic applications.

AREAS COVERED

This review explores the fundamental principles of iontophoresis, focusing on key factors influencing its drug transport mechanisms, and provides a discussion of the field's current state. A comprehensive analysis of articles published or available online in 2024 was conducted, categorizing studies by their application areas, drug delivery systems, iontophoretic conditions, and experimental limitations.

EXPERT OPINION

The findings reveal a recent focus on wound healing and skin repair, and advancements in treating inflammation, pain, and skin cancer. Market translation requires standardized experimental protocols, particularly for iontophoretic parameters and preclinical models, along with the development of cost-effective commercial devices. Additionally, while advancements in cutaneous drug delivery have increasingly benefited from machine learning approaches, their application to iontophoresis remains underexplored. With the growing interest in associating iontophoresis with the Internet of Things, such an integration, if combined with AI tools, could offer promising opportunities for personalized, real-time treatments in modern dermatology, and therapeutic systems.

Galantamine-memantine hybrids for Alzheimer's disease: The influence of linker rigidity in biological activity and pharmacokinetic properties

Neurodegenerative processes characterizing Alzheimer's disease (AD) are strictly related to the impairment of cholinergic and glutamatergic neurotransmitter systems which provoke synaptic loss. These experimental evidences still represent the foundation of the actual standard-of-care treatment for AD, albeit palliative, consisting on the coadministration of an acetylcholinesterase inhibitor and the NMDAR antagonist memantine. In looking for more effective treatments, we previously developed a series of galantamine-memantine hybrids where compound 1 (ARN14140) emerged with the best-balanced action toward the targets of interest paired to neuroprotective efficacy in a murine AD model. Unfortunately, it showed a suboptimal pharmacokinetic profile, which required intracerebroventricular administration for in vivo studies. In this work we designed and synthesized new hybrids with fewer rotatable bonds, which is related to higher brain exposure. Particularly, compound 2, bearing a double bond in the tether, ameliorated the biological profile of compound 1 in invitro studies, increasing cholinesterases inhibitory potencies and selective antagonism toward excitotoxic-related GluN1/2B NMDAR over beneficial GluN1/2A NMDAR. Furthermore, it showed increased plasma stability and comparable microsomal stability in vitro, paired with lower half-life and faster clearance in vivo. Remarkably, pharmacokinetic evaluations of compound 2 showed a promising increase in brain uptake in comparison to compound 1, representing the starting point for further chemical optimizations.

Transdermal Delivery of Insulin Using Combination of Iontophoresis and Deep Eutectic Solvents as Chemical Penetration Enhancers: In Vitro and in Vivo Evaluations

A serious challenge in transdermal iontophoresis (IP) delivery of insulin (INS) is the low permeability of the drug across the skin. In this paper, we introduced deep eutectic solvent (DESs) as novel chemical penetration enhancers (CPEs) for transdermal IP of INS across rat skin, both in vitro and in vivo. Three different DESs based on choline chloride (ChCl), namely, ChCl/UR (ChCl and urea), ChCl/GLY (ChCl and glycerol), and ChCl/EG (ChCl and ethylene glycol) in the 1:2 molar ratios have been prepared. To evaluate the capability of studied DESs as CPEs for IP delivery of INS, the rat skin sample was treated with each DES. The effects of different experimental parameters (current density, formulation pH, INS concentration, NaCl concentration, and treatment time) on the in vitro transdermal iontophoretic delivery of INS were investigated. The in vitro permeation studies exhibited that INS was easily delivered employing ChCl/EG, and ChCl/GLY treatments, compared with ChCl/UR: the cumulative amount of permeated INS at the end of the experiment (Q24h) was found to be 131.0, 89.4, and 29.6 µg cm-2 in the presence of ChCl/EG, ChCl/GLY, and ChCl/UR, respectively. The differences in Q24h values of INS are due to the different capabilities of the studied DESs to treat the epidermis layer of skin. In vivo experiments revealed that the blood glucose level in diabetic rats could be decreased using ChCl/EG, and ChCl/GLY as novel CPEs in the IP delivery of INS. The presented work will open new doors towards searching for novel CPEs in the development of transdermal IP of INS.

Iontophoresis for the cutaneous delivery of nanoentraped drugs

INTRODUCTION

The skin is an attractive route for drug delivery. However, the stratum corneum is a critical limiting barrier for drug permeation. Nanoentrapment is a way to enhance cutaneous drug delivery, by diverse mechanisms, with a notable trend of nanoparticles accumulating into the hair follicles when topically applied. Iontophoresis is yet another way of increasing drug transport by applying a mild electrical field that preferentially passes through the hair follicles, for being the pathway of lower resistance. So, iontophoresis application to nanocarriers could further increase actives accumulation into the hair follicles, impacting cutaneous drug delivery.

AREAS COVERED

In this review, the authors aimed to discuss the main factors impacting iontophoretic skin transport when combining nanocarriers with iontophoresis. We further provide an overview of the conditions in which this combination has been studied, the characteristics of nanosystems employed, and hypothesize why the association has succeeded or failed to enhance drug permeation.

EXPERT OPINION

Nanocarriers and iontophoresis association can be promising to enhance cutaneous drug delivery. For better results, the electroosmotic contribution to the iontophoretic transport, mainly of negatively charged nanocarriers, charge density, formulation pH, and skin models should be considered. Moreover, the transfollicular pathway should be considered, especially when designing the nanocarriers.

Iontophoresis application for drug delivery in high resistivity membranes: nails and teeth

Iontophoresis has been vastly explored to improve drug permeation, mainly for transdermal delivery. Despite the skin's electrical resistance and barrier properties, it has a relatively high aqueous content and is permeable to many drugs. In contrast, nails and teeth are accessible structures for target drug delivery but possess low water content compared to the skin and impose significant barriers to drug permeation. Common diseases of these sites, such as nail onychomycosis and endodontic microbial infections that reach inaccessible regions for mechanical removal, often depend on time-consuming and ineffective treatments relying on drug's passive permeation. Iontophoresis application in nail and teeth structures may be a safe and effective way to improve drug transport across the nail and drug distribution through dental structures, making treatments more effective and comfortable for patients. Here, we provide an overview of iontophoresis applications in these "hard tissues," considering specificities such as their high electrical resistivity. Iontophoresis presents a promising option to enhance drug permeation through the nail and dental tissues, and further developments in these areas could lead to widespread clinical use.

Influencing factors and drug application of iontophoresis in transdermal drug delivery: an overview of recent progress

Transdermal drug delivery is limited by the stratum corneum of skin, which blocks most molecules, and thus, only few molecules with specific physicochemical properties (molecular weight < 500 Da, adequate lipophilicity, and low melting point) are able to penetrate the skin. Recently, various technologies have been developed to overcome the strong barrier properties of stratum corneum. Iontophoresis technology, which uses a small current to improve drug permeation through skin, is one of the effective ways to circumvent the stratum corneum. This approach not only provides a more efficient, noninvasive, and patient-friendly method of drug delivery but also widens the scope of drugs for transdermal delivery. In this review, the mechanisms underlying iontophoresis and affecting factors are outlined. The focus will be on the latest advancements in iontophoretic transdermal drug delivery and application of iontophoresis with other enhancing technologies. The challenges of this technology for drug administration have also been highlighted, and some iontophoretic systems approved for clinical use are described.

Current profile controlled transdermal delivery of pramipexole from an iontophoretic patch system in vitro and in vivo

The objective was to evaluate the transdermal iontophoretic delivery of pramipexole using constant and complex multi-phasic current profiles from an iontophoretic patch system in vitro and in vivo. Preliminary in vitro experiments were performed to optimize iontophoretic patch design and configuration. "Single" compartment systems containing only pramipexole dihydrochloride, and designed to maximize delivery efficiency, suffered from an insufficiency of chloride ions with anodal electrochemistry passing from an Ag/AgCl couple to an Ag dissolution electrode. Addition of NaCl to provide more chloride ions decreased pramipexole delivery efficiency due to competition between pramipexole and sodium cations. A "two-compartment" iontophoretic patch where the drug reservoir was separated from the anodal compartment, which now included NaCl, was shown to be a good compromise since it ensured Ag/AgCl electrochemistry at the anode and an acceptable delivery efficiency. In vivo studies using this iontophoretic patch demonstrated that the plasma concentration of pramipexole closely followed the variation of the applied continuous and multi-phasic current profiles and underlined the control provided by iontophoresis and its unique ability to rapidly change drug input rates. The applied current density and duration of current application were also shown to modulate pramipexole delivery to the brain and CSF.

The influence of skin barrier impairment on the iontophoretic transport of low and high molecular weight permeants

The effect of skin barrier impairment on the iontophoretic transport of low (acetaminophen (ACM), lidocaine (LD), ketorolac (KT)) and high molecular weight permeants, (cytochrome c (Cyt c) and ribonuclease T1 (RNase T1)), was evaluated using tape-stripping (TS) and fractional laser ablation for "large-scale" and "localized" barrier disruption. Interestingly, removal of the stratum corneum did not invariably lead to an increase in iontophoretic delivery of the permeants. Decrease of electroosmotic (EO) flow and facilitated transport of Cl^- ions in the cathode-to-anode direction, which reduced cation electromigration (EM), both impacted cation delivery by anodal iontophoresis but the effects were partly offset by enhanced passive diffusion. Decrease in EO increased cathodal iontophoresis of KT but not that of RNase T1. Permeability coefficients confirmed the superiority of EM over EO for small molecules, LD > KT > ACM. A combination of fractional laser ablation and iontophoresis was advantageous for both positively and negatively charged small molecules as passive penetration was significantly enhanced. In conclusion, results demonstrated that (i) skin ablation prior to anodal iontophoresis decreased EO and EM but could be advantageous for delivery if the ablative technique enhanced passive penetration thereby compensating reduction of electrotransport and (ii) reduced EO favored cathodal electrotransport.

Effect of continuous and multi-phasic current profiles on the iontophoretic transport of pramipexole, rasagiline and huperzine A: Depicting temporal variation and biodistribution in the skin

Transdermal iontophoresis is an interesting option for the non-invasive controlled delivery of therapeutic agents to treat neurodegenerative diseases. The current profile controls drug delivery kinetics and enables complex drug input profiles to be obtained. The aim of this study was to investigate the temporal variation in transport of pramipexole (PRA), rasagiline (RAS) and huperzine A (HUP) using continuous and multi-phasic current profiles by measuring cumulative permeation, transdermal flux and drug retention in the skin upon modulation of the applied current profile during a single experiment in vitro. Initial experiments with continuous current were conducted to establish a correlation between total delivery of PRA, RAS and HUP (i.e. sum of the cumulative permeation and skin deposition) and the amount of charge transferred. Subsequent experiments with multi-phasic current profiles, confirmed that the relationship between amounts of charge transferred and total delivery was able to predict the total delivery of each drug. Experimental values were within ± 15% of the predicted values. Current density and duration of current application were also shown to have a significant impact on the skin biodistribution of PRA. These results also provide insight into the rate of formation of iontophoretic drug reservoirs in the skin.

Galantamine-Memantine combination in the treatment of Alzheimer's disease and beyond

Alzheimer's disease (AD) is the most prevalent form of dementia in the elderly population worldwide. Despite the major unmet clinical need, no new medications for the treatment of AD have been approved since 2003. Galantamine is an acetylcholinesterase inhibitor that is also a positive allosteric modulator at the α4β2 and α7nACh receptors. Memantine is an N-methyl-d-aspartate receptor modulator/agonist. Both galantamine and memantine are FDA-approved medications for the treatment of AD. The objective of this review is to highlight the potential of the galantamine-memantine combination to conduct randomized controlled trials (RCTs) in AD. Several studies have shown the combination to be effective. Neurodegenerative diseases involve multiple pathologies; therefore, combination treatment appears to be a rational approach. Although underutilized, the galantamine-memantine combination is the standard of care in the treatment of AD. Positive RCTs with the combination with concurrent improvement in symptoms and biomarkers may lead to FDA approval, which may lead to greater utilization of this combination in clinical practice.

Multi-Target Drug Candidates for Multifactorial Alzheimer's Disease: AChE and NMDAR as Molecular Targets

Alzheimer's disease (AD) is one of the most common forms of dementia among elder people, which is a progressive neurodegenerative disease that results from a chronic loss of cognitive activities. It has been observed that AD is multifactorial, hence diverse pharmacological targets that could be followed for the treatment of AD. The Food and Drug Administration has approved two types of medications for AD treatment such as cholinesterase inhibitors (ChEIs) and N-methyl-D-aspartic acid receptor (NMDAR) antagonists. Rivastigmine, donepezil, and galantamine are the ChEIs that have been approved to treat AD. On the other hand, memantine is the only non-competitive NMDAR antagonist approved in AD treatment. As compared with placebo, it has been revealed through clinical studies that many single-target therapies are unsuccessful to treat multifactorial Alzheimer's symptoms or disease progression. Therefore, due to the complex nature of AD pathophysiology, diverse pharmacological targets can be hunted. In this article, based on the entwined link of acetylcholinesterase (AChE) and NMDAR, we represent several multifunctional compounds in the rational design of new potential AD medications. This review focus on the significance of privileged scaffolds in the generation of the multi-target lead compound for treating AD, investigating the idea and challenges of multi-target drug design. Furthermore, the most auspicious elementary units for designing as well as synthesizing hybrid drugs are demonstrated as pharmacological probes in the rational design of new potential AD therapeutics.

Memantine Derivatives as Multitarget Agents in Alzheimer's Disease

Memantine (3,5-dimethyladamantan-1-amine) is an orally active, noncompetitive N-methyl-D-aspartate receptor (NMDAR) antagonist approved for treatment of moderate-to-severe Alzheimer’s disease (AD), a neurodegenerative condition characterized by a progressive cognitive decline. Unfortunately, memantine as well as the other class of drugs licensed for AD treatment acting as acetylcholinesterase inhibitors (AChEIs), provide only symptomatic relief. Thus, the urgent need in AD drug development is for disease-modifying therapies that may require approaching targets from more than one path at once or multiple targets simultaneously. Indeed, increasing evidence suggests that the modulation of a single neurotransmitter system represents a reductive approach to face the complexity of AD. Memantine is viewed as a privileged NMDAR-directed structure, and therefore, represents the driving motif in the design of a variety of multi-target directed ligands (MTDLs). In this review, we present selected examples of small molecules recently designed as MTDLs to contrast AD, by combining in a single entity the amantadine core of memantine with the pharmacophoric features of known neuroprotectants, such as antioxidant agents, AChEIs and Aβ-aggregation inhibitors.

Tissue Levels of Flurbiprofen in the Rat Plantar Heel after Short-Duration Topical Iontophoresis Are Sufficient to Induce Pharmacodynamic Responses to Local Pain Stimuli

The objective of this study was to investigate the topical iontophoresis of flurbiprofen (FBF) as a means to enhance its local bioavailability and thereby provide an improved and targeted treatment of plantar heel pain. Initial in vitro experiments using porcine ear skin investigated iontophoretic transport of FBF under different conditions. Local FBF biodistribution in the rat paw in vivo was compared after topical or oral administration. Efficacy of pain management was investigated using a plantar incisional model by evaluating pharmacodynamic responses to local pain stimuli. The results demonstrated that iontophoresis of FBF significantly increased cutaneous deposition and transdermal permeation of FBF as compared to passive delivery—it also enabled drug input to be controlled by modulation of current density and drug concentration (r2 > 0.99). Topical iontophoresis of FBF in vivo enabled higher drug levels in skin and muscle in rat plantar aspect and superior pharmacodynamic responses to local pain stimuli, in comparison to oral and passive delivery. In conclusion, short-duration topical iontophoresis of FBF may better help to relieve plantar heel pain than oral or passive administration, which should be of clinical interest.

Percutaneous Delivery of Antihypertensive Agents: Advances and Challenges

Hypertension remains a significant risk factor for several cardiovascular disorders including coronary artery disease and heart failure. Despite the large armamentarium of drugs available for the management of high blood pressure, low oral availability is an ongoing challenge. Researchers are constantly developing alternative drug delivery systems. This review focuses on the transcutaneous delivery of antihypertensive agents. The use of diverse technologies for the delivery of specific antihypertensive agents is emphasized. The advances made and the challenges encountered are highlighted. Several transdermal drug delivery strategies are employed for the transport of this group of therapeutic agents across the skin and the most widely used techniques include microneedles, iontophoresis, sonophoresis, and chemical penetration enhancers. Each of these methods has benefits and limitations, and there are ongoing attempts by scientists to address the shortcomings. For instance, skin irritation continues to be a major challenge with iontophoretic transport while the quantity of a medication that can be incorporated into dissolving microneedles is limited. With skin permeation enhancers, concerns relating to cytotoxicity and irritation are common. Even though the use of ultrasound is exciting, this mode of delivery is also accompanied by challenges such as the design of a battery system that is potent enough to drive a low-frequency sonophoretic cymbal array, while still being portable enough to function as a wearable device. Although most researchers report enhanced drug delivery with the aforementioned methods, it is important to deliver therapeutically useful doses of these medications.