Rimantadine Research Articles

Preclinical Drug Development of a Novel Antiviral Target in Rotavirus

In 2021, rotavirus is the leading cause of severe gastroenteritis for children under the age of 5. While there is currently no cure for this virus, the use of medication is relied upon to alleviate pain from symptoms. A study conducted by the CDC in 2019 found that while only >1% of rotavirus infections under the age of 5 are fatal in high‐income countries, children from low‐income countries account for roughly 82% of all annual rotavirus‐related deaths. As a result, it is critical to developing new effective and affordable drugs to help improve accessibility in addition to decreasing the rates of infection. As the virally encoded ion channel (viroporin), non‐structural protein 4 (NSP4), is central to the replication and pathogenesis of rotavirus, it is a prime target for drug discovery studies. Similar viroporin proteins from HIV‐1 (Vpu) and Influenza A (M2) have been successfully targeted to treat their corresponding viral infections, but this method has not yet been tested for rotavirus infections. In this experiment, an E. coli‐based assay was developed to test known, antiviral ion channel inhibitors for their ability to bind and inhibit the channel activity of rotavirus NSP4. The subsequent data demonstrates that viroporin activity can be measured in a 96‐well format, rather than previous versions that employed 1‐2L cultures. As well, there is no perturbation of NSP4 protein expression or growth kinetics of the E.coli strains used in the assay. Ongoing experiments seek to test the anti‐viroporin activity of compounds representing a variety of core structures and mechanistic targets (Azelnidipine, Rimantadine hydrochloride, and 5‐(N,N‐Hexamethylene)amiloride). These compounds are being utilized to uncover the most effective molecular mechanism of NSP4 inhibition and to provide some biophysical information about the nature of inhibitor interactions with NSP4. These assays, along with drug binding kinetics being determined by thermofluor assay, will give us the first glimpse into NSP4 as a possible target for the treatment of rotavirus infections.

Repurposing potential of rimantadine hydrochloride and development of a promising platinum(II)-rimantadine metallodrug for the treatment of Chikungunya virus infection

Most of the patients infected with Chikungunya virus (CHIKV) develop chronic manifestations characterized by pain and deformity in joints, impacting their quality of life. The aminoadamantanes, in their turn, have been exploited due to their biological activities, with amantadine and memantine recently described with anti-CHIKV activities. Here we evaluated the antiviral activity of rimantadine hydrochloride (rtdH), a well-known antiviral agent against influenza A, its platinum complex (Pt-rtd), and the precursor cis-[PtCl2(dmso)2], against CHIKV infection in vitro. The rtdH demonstrated significant antiviral activity in all stages of CHIKV replication (29% in pre-treatment; 57% in early stages of infection; 60% in post-entry stages). The Pt-rtd complex protected the cells against infection in 92%, inhibited 100% of viral entry, mainly by a virucidal effect, and impaired 60% of post-entry stages. Alternatively, cis-[PtCl2(dmso)2] impaired viral entry in 100% and post-entry steps in 60%, but had no effect in protecting cells when administered prior to CHIKV infection. Collectively, the obtained data demonstrated that rtdH and Pt-rtd significantly interfered in the early stages of CHIKV life cycle, with the strongest effect observed to Pt-rtd complex, which reduced up to 100% of CHIKV infection. Moreover, molecular docking analysis and infrared spectroscopy data (ATR-FTIR) suggest an interaction of Pt-rtd with CHIKV glycoproteins, potentially related to the mechanism of inhibition of viral entry by Pt-rtd. Through a migration retardation assay, it was also shown that Pt-rtd and cis-[PtCl2(dmso)2] interacted with the dsRNA in 87% and 100%, respectively. The obtained results highlight the repurposing potential of rtdH as an anti-CHIKV drug, as well as the synthesis of promising platinum(II) metallodrugs with potential application for the treatment of CHIKV infections.Importance Chikungunya fever is a disease that can result in persistent symptoms due to the chronic infection process. Infected patients can develop physical disability, resulting and high costs to the health system and significant impacts on the quality of life of affected individuals. Additionally, there are no licensed vaccines or antivirals against the Chikungunya virus (CHIKV) and the virus is easily transmitted due to the abundance of viable vectors in epidemic regions. In this context, our study highlights the repurposing potential of the commercial drug rimantadine hydrochloride (rtdH) as an antiviral agent for the treatment of CHIKV infections. Moreover, our data demonstrated that a platinum(II)-rimantadine metallodrug (Pt-rtd) poses as a potent anti-CHIKV molecule with potential application for the treatment of Chikungunya fever. Altogether, rtdH and Pt-rtd significantly interfered in the early stages of CHIKV life cycle, reducing up to 100% of CHIKV infection in vitro.

Ultrasensitive determination of underivatized adamantane analogs in biological fluids by capillary electrophoresis with contactless conductivity detection

Separation techniques are promising for the detection of adamantane analogs with various functional groups. The derivatization of adamantane analogs with chromophores or fluorophores should be conducted using a separation technique combined with a common ultraviolet–visible or fluorescence detector. However, limited research has been conducted on underivatized adamantane analogs. Therefore, we present a highly rapid and sensitive method for detecting underivatized adamantane analogs by integrating ultrasound-assisted dispersive liquid–liquid microextraction (UADLLME), field-amplified sample stacking (FASS)-related capillary electrophoresis (CE), and capacitively coupled contactless conductivity detection (C4D). In the proposed system, UADLLME is used for sample clean up and analyte enrichment, whereas FASS-related CE provides on-line concentration of underivatized adamantane analogs during CE separation. A mixture of memantine (MT), amantadine (AT), and rimantadine (RT) was separated at baseline within 8 min through the application of optimized UADLLME (mixing extraction solvent, 50 μL of 1,1,2,2-tetrachloroethane (C2H2Cl4) and dispersive solvent, 200 μL of acetonitrile; mixing solution was injected into 1 mL of the sample solution at pH 12.5), FASS (buffer, 1.5 M acetic acid; additive, 0.05 mM β-cyclodextrin; pH 2.5), and C4D (amplitude, 2 Vpp; frequency, 500 kHz). The calibration curve exhibited acceptable linearity, with a coefficient of determination higher than 0.99. The limits of detection (signal-to-noise ratio of 3) were estimated to be 0.9, 1.0, and 1.2 nM for MT, AT, and RT, respectively. The relative standard deviations of peak areas varied from 8.9% to 9.3% (n = 5), whereas the sensitivity improvement of three underivatized adamantane analogs ranged from 1342 to 1766. The feasibility and accuracy of the present method for the determination of MT, AT, and RT in human serum and urine was satisfactorily confirmed by the excellent recovery and relative error. The proposed method exhibited high enrichment factors and offers excellent precision, high accuracy, and a short analysis time.

Increased Dissociation of Adamantanamines in Influenza A M2 S31N with Partial Block by Rimantadine

The ubiquitous mutation from serine (WT) to asparagine at residue 31 (S31N) in the influenza A M2 channel renders it insensitive to amantadine (AMT) and rimantadine (RMT) block, but it is unknown whether the inhibition results from weak binding or incomplete block. Two-electrode voltage clamp (TEVC) of transfected Xenopus oocytes revealed that the M2 S31N channel is essentially fully blocked by AMT at 10 mM, demonstrating that, albeit weak, AMT binding in a channel results in complete block of its proton current. In contrast, RMT achieves only a modest degree of block in the M2 S31N channel at 1 mM, with very little increase in block at 10 mM, indicating that the RMT binding site in the channel saturates with only modest block. From exponential curve fits to families of proton current wash-in and wash-out traces, the association rate constant (k1) is somewhat decreased for both AMT and RMT in the S31N, but the dissociation rate constant (k2) is dramatically increased compared with WT. The potentials of mean force (PMF) from adaptive biasing force (ABF) molecular dynamics simulations predict that rate constants should be exquisitely sensitive to the charge state of the His37 selectivity filter of M2. With one exception out of eight cases, predictions from the simulations with one and three charged side chains bracket the experimental rate constants, as expected for the acidic bath used in the TEVC assay. From simulations, the weak binding can be accounted for by changes in the potentials of mean force, but the partial block by RMT remains unexplained.

PHYSICOCHEMICAL PROPERTIES AND BIOLOGICAL ACTIVITY OF THE NEW ANTIVIRAL SUBSTANCE

Objective: To develop a set of quality control procedures for the promising antiviral pharmaceutical substance L-histidyl-1-adamantylethylamine dihydrochloride monohydrate, a derivative of rimantadine.
 Methods: Substances and solvents: synthesized in laboratory L-histidyl-1-adamantylethylamine dihydrochloride monohydrate (H-His-Rim•2HCl•H2O), rimantadine hydrochloride (Rim•HCl), 99%, ethanol 96%, N, N-dimethylformamide (DMF) anhydrous, 99.8% and n-hexane anhydrous, 95%, deionized high-resistance water (18.2 MΩ•cm at 25 °C, Milli-Q system), silver nitrate. Infrared (IR) Spectroscopy–Cary 630 Fourier Transform IR Spectrometer, elemental analysis–elemental composition analyzer CHNS-O EuroEA3000, ultraviolet (UV) spectrometry–Cary-60 spectrophotometer, polarimetry–POL-1/2 polarimeter with an external Peltier module, granulometric analysis by optical microscopy (Altami BIO 2 microscope) and low-angle laser light scattering (LALLS)–Master Sizer 3600, measurement of potential for hydrogen–potentiometer PB-11, Spirotox method–the study of temperature dependences of Spirostomum ambiguum lifetime to characterize the biological activity of the studied compounds.
 Results: The substance H-His-Rim•2HCl•H2O is an amorphous yellowish powder, slightly soluble in water, soluble in ethanol, freely soluble in N, N-dimethylformamide, and practically insoluble in n-hexane. A study of the elemental composition has confirmed the authenticity of H-His-Rim•2HCl•H2O. Comparison of the spectral characteristics of H-His-Rim•2HCl•H2O and Rim•HCl by IR spectroscopy and UV spectrometry confirmed the authenticity of the substance. The racemic form of the substance Rim•HCl with an insignificant amount of impurity of the levorotatory enantiomer was proved polarimetrically: α =-0.0126±0.0003 (1% aqueous solution, 20±0.5 °С). The specific optical rotation of 1% aqueous solution H-His-Rim•2HCl•H2O . In 1% ethanol solution -10.32±0.12. Using the method of laser light diffraction for a substance H-His-Rim•2HCl•H2O, the dimensional spectra «fraction of particles, %-d, μm» were characterized, the maximum of which in hexane is in the region of 40–50 μm. Arrhenius’s kinetics on the Spirotox model established statistically significant differences in ligand-receptor interactions, which are characterized by values of observed apparent activation energy °bsEa, kJ/mol: 132.36±1.55 for H-His-Rim•2HCl•H2O and 176.15±0.48 for Rim•HCl.
 Conclusion: The developed set of methods for assessment of physical and chemical properties and biological activity of a new antiviral substance H-His-Rim•2HCl•H2O is the basis for establish of regulatory documentation.

Rapid and Simple Spectrophotometric Method for the Determination of Antiviral and Anti-Parkinsonism Drugs

A rapid and sensitive spectrophotometric method has been developed for the quantitative analysis of three antiviral, anti-parkinsonism drugs, namely, amantadine (AMA), memantine (MET), and rimantadine (RIM). The method is based on the usage of 1,3-indandione (IDO) as a chromogenic reagent to form charge transfer complexes with the studied drugs and produce colored reaction products with an absorbance maximum at 522 nm, allowing quantitative analysis of these drugs. In addition, the study was validated according to the official guidelines that permits usage in quality control laboratories. Many factors (reagent volume, diluting solvent, temperature, reaction and stability time) influencing the reactions were studied and optimized. The results showed that this method is able to detect AMA, MET, or RIM over a linear range between 10–140 μg/mL with high selectivity and robustness. Furthermore, the study results were applied to analyze the drugs in their pharmaceutical preparations with acceptable accuracy and precision.

Binding Without Block. An Analysis of Amantadine and Rimantadine Block of the Influenza M2 S31N Channel

The mutation from serine to asparagine at residue 31 (S31N) of the influenza A M2 channel is ubiquitous in the strains circulating in humans. This M2 mutant variant is insensitive to block by amantadine (AMT) and rimantadine (RMT), two previously FDA approved M2 blockers. It is unclear whether the inhibition results from weak binding or incomplete block. We addressed the question of “binding without block” using two-electrode voltage clamp (TEVC) electrophysiology. Data was collected in the wild-type (WT) and S31N M2 channels. Analysis of the electrophysiology data for complete or partial block by AMT and RMT was done using a one-site binding model nonlinear least squares curve fit with the to obtain rate constants. Results show that the S31N M2 channel is completely blocked by AMT at 10 mM, suggesting (proving?) there is no binding without block for AMT. In contrast, RMT achieves a modest maximal level of block in the S31N M2 channel at 1 mM, with very little increase in block at 10 mM. This suggests RMT binding has reached saturation and that there is binding without block. The rate constants obtained from the curve fit show a significant change in AMT or RMT and protein association. In both cases, the on rate constant has decreased whereas the off rate has increased in the S31N M2 variant compared to the rate constants in the WT M2 channel. These rate constants could be used to compare with molecular dynamics binding simulations to better understand the change in M2-AMT/RMT association.

Heat capacity and decomposition of rimantadine hydrochloride

Heat capacities of the antiviral drug rimantadine hydrochloride in the crystalline state were measured by adiabatic calorimetry and differential scanning calorimetry in the temperature range from (7 to 453) K. A broad low-enthalpy solid-state phase anomaly was detected between (170 and 250) K. Thermodynamic functions for crystalline rimantadine hydrochloride were derived. Decomposition of the studied compound was probed by the Knudsen effusion method and thermogravimetry with the support of quantum chemical calculations. The enthalpy of decomposition of rimantadine hydrochloride into the corresponding amine and hydrogen chloride was estimated from those data. The thermodynamic functions of the corresponding amine in the ideal gaseous state, including enthalpy of formation, were obtained using statistical thermodynamics with the necessary molecular parameters computed using quantum chemical methods. The enthalpy of formation of crystalline rimantadine hydrochloride was estimated.

Automated Stopped-Flow Fluorimetric Sensor for Biologically Active Adamantane Derivatives Based on Zone Fluidics.

A zone-fluidics (ZF) based automated fluorimetric sensor for the determination of pharmaceutically active adamantine derivatives, i.e., amantadine (AMA), memantine (MEM) and rimantadine (RIM) is reported. Discrete zones of the analytes and reagents (o-phthalaldehyde and N-acetylcysteine) mix and react under stopped-flow conditions to yield fluorescent iso-indole derivatives (λex/ λem = 340/455 nm). The proposed ZF sensor was developed and validated to prove suitable for quality control tests (assay and content uniformity) of commercially available formulations purchased from the Greek market (EU licensed) and from non-EU web-pharmacies at a sampling rate of 16 h−1. Interestingly, a formulation obtained through the internet and produced in a third—non-EU—country (AMA capsules, 100 mg per cap), was found to be out of specifications (mean assay of 85.3%); a validated HPLC method was also applied for confirmatory purposes.

Optical Resolution of Rimantadine.

This work discloses a new procedure for the resolution of commercially available racemic rimantadine hydrochloride to enantiomerically pure (S)-rimantadine using (R)-phenoxypropionic acid as a recyclable resolving reagent. Good chemical yields, operational ease, and low-cost structure underscore the preparative value of this method for the production of enantiomerically pure rimantadine for medicinal or synthetic studies.

Computational investigation of influenza A virus M2 protein inhibitionmechanism by ion channel blockers

The M2 protein of the influenza A virus, responsible for flu, is a homotetramer transmembrane protein, forming a transmembrane ion channel, where His 37s act as pH sensors and Trp 41s and Asp 44s act as channel gates. Opening of this channel leads to transfer of virus RNA into the human host. Thus, blocking this transfer is an important pharmaceutical strategy to stop infection. As a result of viral drug resistance, commercially available channel inhibitors, rimantadine (RIM) and amantadine (AMA), are not as effective as they used to be. Understanding binding sites and outcomes of binding will lead to new inhibitor design studies. Here, utilizing molecular docking with classical and constant pH molecular dynamics simulations, two novel binding sites for RIM and AMA molecules were revealed. Both structural and chemical effects of inhibitors on M2 protein on the closed, inactive M2 channel structure were investigated. Upon binding of the inhibitor molecules, decrease in ion channel cross-distances was observed. Meanwhile, RIM binding did not alter protonation of His 37s and Asp 44s, whereas AMA binding drastically increased the protonation population of two residues from different monomers, creating a more basic channel at physiological pH.

New insights into the prevention of viral infections in patients with bronchial asthma

One of the main concepts today in the management of asthma is the control of the disease. Worldwide research suggests that viral respiratory infections are the most common cause of dyspnea and asthma exacerbations in children and adults. The purpose of our study was to prove the feasibility of using Rimantadine hydrochloride in patients with asthma, in order to prevent viral infections. Patients in the main group received complex therapy including Rimantadine hydrochloride, namely at a dose of 100 mg twice a day for 15 days. The majority of patients, namely 86.6 % (n=52), reported a deterioration in their health status in cases of acute respiratory infections and flu. Also, our patients in 81.6 % (n=49) cases complained of a prolonged reduction in the function of external respiration after the disease, in addition 48.3 % (n=29) of patients needed help from the doctor to decide on the change in therapy for more low step. Our study continued the flu epidemic of 2017–2018, we came to the conclusion about the incidence of viral infections such as influenza. So we have found that out of 30 patients in the main group, only 4 men were ill and the disease was not serious. Patients in the comparison group had more negative outcomes from 30 patients, 11 were ill, of which 7 patients were referred for emergency care or were hospitalized.

Toward Expanded Diversity of Host–Guest Interactions via Synthesis and Characterization of Cyclodextrin Derivatives

Researchers developing software to predict the binding constants of small molecules for proteins have, in recent years, turned to host–guest systems as simple, computationally tractable model systems to test and improve these computational methods. However, taking full advantage of this strategy requires aqueous host–guest systems that probe a greater diversity of chemical interactions. Here, we advance the development of an experimental platform to generate such systems by building on the cyclodextrin (CD) class of hosts. The secondary face derivative mono-3-carboxypropionamido-β-cyclodextrin (CP-β-CD) was synthesized in a one-pot strategy with 87% yield, and proved to have much greater aqueous solubility than native β-CD. The complexation of anionic CP-β-CD with the cationic drug rimantadine hydrochloride was explored using one- and two-dimensional nuclear magnetic resonance; NOESY analysis showed secondary face binding of the ammonium moiety of the guest, based on cross-correlations between the amic acid functionality and the side-chain of rimantadine. Isothermal titration calorimetry was furthermore used to determine the standard Gibbs energy and enthalpy for this binding reaction, and the results were compared with those of rimantadine with native β-CD.

Synthesis and Antibacterial Activity of Bis-[1-(Adamantan-1-Yl)Ethyl]Amine Hydrochloride

An impurity in rimantadine hydrochloride drug substance that was previously undescribed in regulatory documents and the literature was identified. Its structure was elucidated and confirmed by a convergent synthesis. A method for synthesizing bis-[1-(adamantan-1-yl)ethyl]amine hydrochloride under laboratory conditions was developed. The antibacterial activity of the synthesized compound was assessed.

Differential Binding of Rimantadine Enantiomers to Influenza A M2 Proton Channel.

Rimantadine hydrochloride (α-methyl-1-adamantane-methalamine hydrochloride) is a chiral compound which exerts antiviral activity against the influenza A virus by inhibiting proton conductance of the M2 ion channel. In complex with M2, rimantadine has always been characterized as a racemic mixture. Here, we report the novel enantioselective synthesis of deuterium-labeled (R)- and (S)-rimantadine and the characterization of their protein-ligand interactions using solid-state NMR. Isotropic chemical shift changes strongly support differential binding of the enantiomers to the proton channel. Position restrained simulations satisfying distance restraints from (13)C-(2)H rotational-echo double-resonance NMR show marked differences in the hydrogen-bonding pattern of the two enantiomers at the binding site. Together these results suggest a complex set of interactions between (R)-rimantadine and the M2 proton channel, leading to a higher stability for this enantiomer of the drug in the channel pore.

Синтез и антибактериальная активность бис-(1-(адамантан-1-ил)этил)амина гидрохлорида

Идентифицирована ранее не описанная в нормативной документации и литературных источниках примесь субстанции римантадина гидрохлорида. Установлена и подтверждена встречным синтезом структура обнаруженной примеси. Разработан метод синтеза бис-(1-(адамантан-1-ил)этил)амина гидрохлорида в лабораторных условиях, произведена оценка антибактериальной активности полученного соединения.

In children with clinically or serologically confirmed influenza A, do amantadine and rimantadine improve outcomes?

In children with clinically or serologically confirmed influenza A, do amantadine and rimantadine improve outcomes?

The Effect of Intravenous Sulfobutylether7-β-Cyclodextrin on the Pharmacokinetics of a Series of Adamantane-Containing Compounds

Intravenously administered (i.v.) drug-cyclodextrin (CD) inclusion complexes are generally expected to dissociate rapidly and completely, such that the i.v. pharmacokinetic profile of a drug is unchanged in the presence of CD. The altered pharmacokinetics of a synthetic ozonide in rats has been attributed to an unusually high-binding affinity (2.3 × 10(6) M(-1) ) between the drug and sulfobutylether7 -β-cyclodextrin (SBE7 -β-CD) with further studies suggesting a significant binding contribution from the adamantane ring. This work investigated the binding affinity of three adamantane derivatives [amantadine (AMA), memantine (MEM) and rimantadine (RIM)] to SBE7 -β-CD and the impact of complexation on their i.v. pharmacokinetics. In vitro studies defined the plasma protein binding, as well as the impact of SBE7 -β-CD on erythrocyte partitioning of each compound. SBE7 -β-CD binding constants for the compounds were within the typical range for drug-like molecules (10(2) -10(4) M(-1) ). The pharmacokinetics of AMA and MEM were unchanged; however, significant alteration of RIM plasma and urinary pharmacokinetics was observed when formulated with CD. In vitro studies suggested two factors contributing to the altered pharmacokinetics: (1) low plasma protein binding of RIM, and (2) decreased erythrocyte partitioning in the presence of high SBE7 -β-CD concentrations. This work demonstrated the potential for typical drug-cyclodextrin interactions to alter drug plasma pharmacokinetics.

1,2-Naphthoquinone-4-sulfonic acid sodium salt as a reagent for spectrophotometric determination of rimantadine and memantine

A selective ultraviolet and visible spectrophotometric method (UV-Vis) for the determination of memantine (MM) and rimantadine (RM) hydrochlorides after derivatization with 1,2-naphtoquinone-4-sulfonic acid sodium salt (NQS) and extraction with dichloromethane was developed and optimized. The reaction of the NQS (0.7%, w/v solution) with memantine was carried out for 40 min in a buffer medium of NaOH/KCl (pH 12.0) at 80°C. A mixture of NQS (0.2%) and rimantadine was heated for 20 min at 50°C, in a medium of NaOH/KCl (pH 12.0). The linearity of the determinations of MM (0.05–0.60 mg/mL) and RM (0.05–0.30 mg/mL) was evaluated. LOD (28 mg/mL for MM, 11 mg/mL for RM) and LOQ (84 mg/mL for MM, 32 mg/mL for RM) values and parameters of precision and accuracy were determined. The UV-Vis method for the determination of rimantadine hydrochloride tablets was validated (selectivity, linearity, precision, accuracy).

Crystal Structure Explains Crystal Habit for the Antiviral Drug Rimantadine Hydrochloride

The crystal structure of the antiviral drug rimantadine hydrochloride, C12H22N+ Cl−, has been elucidated by a single-crystal X-ray structure analysis. The structure consists of 1-(1- adamantyl)ethanamine (rimantadinium) cations and chloride anions. The Cl− anions link the rimantadinium cations via N-H...Cl hydrogen bonds into infinite rectangular chord-like structural units with charged groups in the inner channel and aliphatic groups on the surface, and oriented along the unit cell c axis. In contrast to strong electrostatic and hydrogen bonding inner interactions the chords in the crystal are held together by weak van der Waals forces only. A two-fold symmetry axis passes through the center of the chord. By indexing of the crystal faces it has been shown that the maximal dimension of the needle-like crystals coincides with the direction of the unit cell c axis. These structural features explain the crystal habit and the anisotropy of the mechanical properties of rimantadine hydrochloride crystals observed upon slicing and cleavage.