Drug Dipyridamole Research Articles

Evaluation of aspartame as a co-former in the preparation of co-amorphous formulations of dipyridamole using spray drying

Co-amorphous systems (CAMs) have shown promise in addressing the challenges associated with poorly water-soluble drugs. However, the limited selection of co-formers and the use of lab-scale techniques for their preparation present challenges in fully utilizing the advantages of CAMs. In this study, we used aspartame (a methyl ester of the aspartic acid/phenylalanine) as a model dipeptide with the BCS class II drug dipyridamole, to prepare co-amorphous systems using spray drying. The feed solutions were prepared by dissolving the drug and co-former into methanol–water mixtures. The spray drying process was evaluated and solid-state properties were compared with those of the individual amino acids, amino acid mixtures and aspartame as co-formers. Co-amorphous systems prepared with aspartame (AspPhe) exhibited better solid-state properties, including a higher glass transition temperature (Tg), compared to the individual amino acids and the mixture of amino acids. Additionally, this formulation showed improved physical stability when stored at 25 °C/60 % RH conditions. Hirshfeld Surface (HS) analysis was employed to visualize and analyse the molecular interaction sites within the crystal structures of dipyridamole and aspartame. The observed interactions were then correlated with the molecular interactions identified through FT-IR spectroscopic analysis within the CAMs. The spectroscopic analysis revealed molecular interactions between the sites found at the shortest distances in the HS analysis. The dominant hydrogen bond interactions identified in the co-amorphous DPM-AspPhe system was found to contribute significantly to its improve stability. X-ray powder diffraction in non-ambient mode reveals that both temperature and humidity play a role in the crystallization of the co-amorphous DPM-AspPhe. Crystallization rates increased notably at high temperature and humidity. To predict stability under accelerated conditions, the crystallization rates from DPM-AspPhe were fitted to a modified Arrhenius equation. However, the predictive accuracy of the resulting model was limited to a specific range of conditions.

PH-responsive intermediary layer cross-linked micelles from zwitterionic triblock copolymers and investigation of their drug-release behaviors.

ABC-type triblock copolymers, namely poly[(ethylene glycol)methyl ether]-block-poly(tert-butyl methacrylate)-block-poly[2-N-(diisopropylamino)ethyl methacrylate] (MPEG-b-PBuMA-b-PDPA), were first synthesized and then the middle blocks were successfully converted into poly(methacrylic acid) to obtain MPEG-b-PMAA-b-PDPA zwitterionic triblock copolymers. These block copolymers were soluble in water and formed micellar aggregates with complex cores via hydrogen bonding interactions between MPEG and PMAA blocks below pH 4.0. When the pH was between 5.0 and 7.0, due to charge compensation between partially protonated PDPA and partially ionized PMAA blocks, micelles with polyion complex cores were observed. If the solution pH was above 8.0, deprotonation of tertiary amine groups provided a hydrophobic character to the PDPA block, which resulted in the formation of PDPA-core micelles while MPEG/anionic PMAA hybrid blocks formed hydrated coronas. Intermediary layer cross-linked (ILCL) micelles from PDPA-core micelles were also prepared by cross-linking the inner PMAA shell. The hydrophobic drug dipyridamole (DIP) was used to investigate the release profile of ILCL micelles. DIP can be loaded to the PDPA cores of the micelles in basic aqueous media. An increase in the degree of cross-linking causes slower release for the model drug. It was concluded that the more complex matrix formation in the intermediary layer of the micelles via cross-linking retards the drug release from the core.

Modification of a hollow fiber membrane with silver/multiwall carbon nanotube/polyaniline nanocomposite as a highly sensitive sensor for voltammetric measurement of antioxidant drug dipyridamole

In this study, a hollow fiber membrane (HFM was subjected to modification with a nanocomposite of silver/multi-walled carbon nanotube/polyaniline (AgNP/MWCNT/PANI). The sensor was utilized as a tool for voltammetric determination of the antioxidant drug Dipyridamole (DIP) in aqueous solution. The surface morphology and electrochemical properties of the proposed electrode were assessed through the use of Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX), and electrochemical impedance spectroscopy (EIS). The electrochemical performance of the electrode was analyzed using differential pulse voltammetry (DPV) and cyclic voltammetry (CV) techniques. All parameters that could potentially impact the application of the new electrode were thoroughly investigated. A linear correlation between oxidation current and DIP concentration was established within the range of 0.01–50.0 μM (R2 = 0.99), with a detection limit of 1.0 × 10−3 μM. The new electrode was successfully employed for the determination of DIP in real samples, including pharmaceutical formulations and biological samples.

Determination of Dipyridamole Using a MIP-Modified Disposable Pencil Graphite Electrode

A new method for the determination of the antiplatelet drug dipyridamole (DIP) in pharmaceuticals using a molecularly imprinted polymer (MIP)-modified pencil graphite electrode (PGE) is proposed. The modified electrode was prepared simply and rapidly by electropolymerization of caffeic acid (CA) in the presence of DIP and subsequent DIP extraction with ethanol, resulting in a cost-effective, eco-friendly disposable modified electrode (MIP_PGE). Several working conditions (monomer and template concentration, number of voltametric cycles, scan rate extraction time, and solvent) for the MIP_PGE preparation were optimized. The differential pulse voltammetric (DPV) oxidation signal of DIP obtained at MIP_PGE was 28% higher than that recorded at bare PGE. Cyclic voltammetry emphasized DIP irreversible, pH-dependent, diffusion-controlled oxidation at MIP_PGE. Differential pulse and adsorptive stripping voltammetry at MIP_PGE in phosphate buffer solution pH = 7.00 were applied for the drug quantitative determination in the range of 1.00 × 10−7–1.00 × 10−5 and 1.00 × 10−8–5.00 × 10−7 mol/L DIP, respectively. The obtained limits of detection were at the tens nanomolar level.

Клініко-анамнестичні характеристики та медикаментозний супровід вагітних жінок із обтяженим акушерським анамнезом і тромбофіліями

The purpose of the study was to determine the clinical and anamnestic features (age characteristics of women and anamnestic features of previous pregnancies) of pregnant women with burdened obstetric history and thrombophilia with the establishment of the main pharmacological mechanisms of therapeutic support. Materials and methods. The study was performed at the Department of Clinical Laboratory Diagnostics of Kharkiv National Medical University and at the Kharkiv Clinical Laboratory Center in the period from 2017 to 2021. We examined 137 pregnant women: the main group (101 women – pregnant women with a burdened obstetric history and thrombophilia aged 29.0 to 37.0 years) and the control group (36 women – pregnant women with a burdened obstetric history without thrombophilia aged 26.0 to 30.0 years). In general, the predominance of one (35.8 %) and two (46.7 %) pregnancies in the history of women with a burdened obstetric history compared to three (17.5 %) was noted. Results and discussion. An increase (U = 706.0; p <0.001) in the chances of developing negative consequences of pregnancy in thrombophilia with increasing age due to negative idiopathic thromboembolic effects due to thrombophilia was noted. A higher mean age of pregnant women with a burdened obstetric history in the presence of thrombophilia (33.0 [29.0; 37.0] years) was determined compared with the control (28.0 [26.0; 30.0] years). The maximum negative manifestations of idiopathic thromboembolic effects due to thrombophilia in the first pregnancy were found. The predominance of cases of fetal death in the first pregnancy of women with two (94.1 %) and three (78.3 %) pregnancies was determined. In general, the need for antiplatelet therapy in thrombophilia was stated. Its use (χ2 = 46,950; p <0.001) was determined in 85.1 % of cases, the majority (65.3 %) of one drug (probably (χ2 = 164.54; p <0.001) more often (52.5 %) acetylsalicylic acid compared with dipyridamole (5.9 %)). It was found that anti aggregate therapy, which included two drugs (combination: acetylsalicylic acid, dipyridamole or klexan) was most often used in the first (40.7%) pregnancy in contrast to the second (11.8%) and third (13.0 %). Conclusion. The study found that antiplatelet therapy with only one drug (acetylsalicylic acid, dipyridamole or klexan) was more commonly used in the second (74.5%) and third (73.9%) pregnancies than in the first one (40.7%). It was naturally determined that the absence of any medication was noted most often by pregnant women in the first (18.5%) pregnancy in contrast to the second (13.7%) and third (13.0%)

A Comparative Study of an Anti-Thrombotic Small-Diameter Vascular Graft with Commercially Available e-PTFE Graft in a Porcine Carotid Model

Background:We have designed a reinforced drug-loaded vascular graft composed of polycaprolactone (PCL) and polydioxanone (PDO) via a combination of electrospinning/3D printing approaches. To evaluate its potential for clinical application, we compared the in vivo blood compatibility and performance of PCL/PDO + 10%DY grafts doped with an antithrombotic drug (dipyridamole) with a commercial expanded polytetrafluoroethylene (e-PTFE) graft in a porcine model.Methods:A total of 10 pigs (weight: 25–35 kg) were used in this study. We made a new 5-mm graft with PCL/PDO composite nanofiber via the electrospinning technique. We simultaneously implanted a commercially available e-PTFE graft (n = 5) and our PCL/PDO + 10%DY graft (n = 5) into the carotid arteries of the pigs. No anticoagulant/antiplatelet agent was administered during the follow-up period, and ultrasonography was performed weekly to confirm the patency of the two grafts in vivo. Four weeks later, we explanted and compared the performance of the two grafts by histological analysis and scanning electron microscopy (SEM).Results:No complications, such as sweating on the graft or significant bleeding from the needle hole site, were seen in the PCL/PDO + 10%DY graft immediately after implantation. Serial ultrasonographic examination and immunohistochemical analysis demonstrated that PCL/PDO + 10%DY grafts showed normal physiological blood flow and minimal lumen reduction, and pulsed synchronously with the native artery at 4 weeks after implantation. However, all e-PTFE grafts occluded within the study period. The luminal surface of the PCL/PDO + 10%DY graft in the transitional zone was fully covered with endothelial cells as observed by SEM.Conclusion:The PCL/PDO + 10%DY graft was well tolerated, and no adverse tissue reaction was observed in porcine carotid models during the short-term follow-up. Colonization of the graft by host endothelial and smooth muscle cells coupled with substantial extracellular matrix production marked the regenerative capability. Thus, this material may be an ideal substitute for vascular reconstruction and bypass surgeries. Long-term observations will be necessary to determine the anti-thrombotic and remodeling potential of this device.

Optimized copolymeric microstructured platforms for smart controlled delivery of an anticoagulant drug: Preparation, in vitro assessment and crossover study in healthy adult human volunteers

In the present study, novel micro-structured copolymeric carriers were developed based on the grafting technology where acrylamide was chemically crosslinked with different types of Eudragits® (NE30D, L100, RL30D, or RS30D) based on a 41*21 factorial design. The designed systems efficiently engulfed the anticoagulant drug dipyridamole (DIP), within their formed entangled mesh of crosslinked polymeric network. An optimized formulation, ECOP4 with a desirability-value of 0.706, (in which DIP is engulfed within a copolymeric network of acrylamide and Eudragit® RS30D) showed high engulfment capacity (97.13 ± 1.34%) and controlled DIP release over 8 h. FTIR studies revealed absence of interactions between DIP and the formed copolymer. ECOP4 was further inserted within an easily-administered safe raft forming system composed of a mixture of LM-pectin and gellan gum. A pharmacokinetic study was performed using human volunteers to determine DIP concentration in their plasma after administering the designed formulation using the high-performance liquid chromatography (HPLC) method. A crossover design was adopted comparing the designed formulation with Persantin® 25 mg tablets as a reference standard. Superior results were obtained for the optimized formulation regarding the measured pharmacokinetic parameters (AUC0-24h, Cmax, and Tmax) with a 2.31 fold increase in relative bioavailability, which reveals the usefulness of the designed grafted dipyridamole formulation in site-specific delivery system.

Automated in vivo drug screen in zebrafish identifies synapse-stabilising drugs with relevance to spinal muscular atrophy.

ABSTRACTSynapses are particularly vulnerable in many neurodegenerative diseases and often the first to degenerate, for example in the motor neuron disease spinal muscular atrophy (SMA). Compounds that can counteract synaptic destabilisation are rare. Here, we describe an automated screening paradigm in zebrafish for small-molecule compounds that stabilize the neuromuscular synapse in vivo. We make use of a mutant for the axonal C-type lectin chondrolectin (chodl), one of the main genes dysregulated in SMA. In chodl−/− mutants, neuromuscular synapses that are formed at the first synaptic site by growing axons are not fully mature, causing axons to stall, thereby impeding further axon growth beyond that synaptic site. This makes axon length a convenient read-out for synapse stability. We screened 982 small-molecule compounds in chodl chodl−/− mutants and found four that strongly rescued motor axon length. Aberrant presynaptic neuromuscular synapse morphology was also corrected. The most-effective compound, the adenosine uptake inhibitor drug dipyridamole, also rescued axon growth defects in the UBA1-dependent zebrafish model of SMA. Hence, we describe an automated screening pipeline that can detect compounds with relevance to SMA. This versatile platform can be used for drug and genetic screens, with wider relevance to synapse formation and stabilisation.

Морфофункціональні зміни сім’яників щурів, народжених від матерів зі змодельованою фетоплацентарною недостатністю і за її корегування

Nowadays, it is almost unknown how fetoplacental insufficiency of mothers affects the formation of the reproductive system in male offspring during puberty. Therefore, the aim of this work was to study the histological structure of the testes of male offspring born to mothers of different ages with fetoplacental insufficiency and to evaluate the effectiveness of a new pharmaceutical composition for the correction of pathological conditions of pregnancy. The experiment involved healthy mature female Wistar rats in young (3–4 months) and mature (8–10 months) reproductive age. Eight groups with 7 pregnant females in each one were formed: groups 1 and 2 — intact animals of young and mature reproductive age, respectively; groups 3 and 4 — females with experimental fetoplacental insufficiency of young and mature reproductive age; groups 5 and 6 — young and mature animals with experimental fetoplacental insufficiency and addition to food depending on the weight of animals from 11 to 19 days of pregnancy pharmaceutical composition. Groups 7 and 8 — young and mature animals with experimental fetoplacental insufficiency with addition a comparison drug Dipyridamole to the food. Modeling of fetoplacental insufficiency was performed by daily subcutaneous injection to females from the 12th to the 18th day of pregnancy 50% oil solution of carbon tetrachloride at a dose of 2 ml/kg body weight. Offspring were decontaminated on the 50th day of life (puberty) by rapid decapitation. Samples of male testicles were fixed in 10% formalin solution, performed on alcohols of increasing strength, poured into paraffin. Sections were made from the blocks, which were stained with hematoxylin and eosin. Qualitative assessment of histostructure was performed on sections of the body in rats. Summing up the results of histological analysis and morphometric parameters characterizing the condition of the testicles of rats, we can draw the following conclusions. In the offspring born to reproductively young females with fetoplacental insufficiency, inhibition of the rate of germ cell differentiation was found, while in the offspring born to reproductively mature females with fetoplacental insufficiency, the negative effects of this effect were leveled and the rate of spermatogenesis increased. When the pharmaceutical composition was administered to both young and mature pregnant females on the background of fetoplacental insufficiency, it activated the processes of proliferation and differentiation of spermatogenic epithelium in their offspring, which was reflected in the appearance of mature sperm in the seminal tubules. The comparison drug Dipyridamole, administered according to the same regimen to both young and mature pregnant females with fetoplacental insufficiency, also helped the 50-day-old offspring of these females to restore the rate of spermatogenesis at the level of the pharmaceutical composition.

Kinetic stability of amorphous dipyridamole: A fast scanning calorimetry investigation.

One of the main tasks of modern pharmaceutics is enhancing the solubility of drugs. The approaches for solving this problem include producing active pharmaceutical ingredients in the amorphous state. However, the use of amorphous drugs requires the determination of their kinetic stability. The latter is often assessed using isothermal techniques, which are time-consuming. Alternatively, non-isothermal methods can be employed, allowing to determine the kinetic triplet more rapidly. Also, such techniques can be used to develop predictive models for storage stability. The production of the amorphous state itself typically requires fast cooling rates, which may not be easily accessible. Fast scanning calorimetry is a promising tool for the investigation of amorphous drug systems. In the present work, the crystallization of the model drug dipyridamole was investigated using the fast scanning calorimetry method. The kinetic stability of the amorphous form of the drug was evaluated using both, isothermal and non-isothermal methods. The Nakamura crystallization model was found to be applicable for the prediction of the temporal stability of the amorphous drug forms. The obtained results may find applications in the investigation of the kinetic stability of amorphous drug systems.

Biophysical insights into the binding characteristics of bovine serum albumin with dipyridamole and the influence of molecular interaction with β cyclodextrin

The binding characteristic of anti-platelet drug dipyridamole has been investigated with a transport protein, serum albumin. A multi-spectroscopic approach has been employed, and the results were well supported by in silico molecular docking and simulation studies. The fluorescence quenching of serum albumin at three different temperatures revealed that the mechanism involved is static and the binding constant of the interaction was found to be of the order of 104 M−1. The reaction was found to be spontaneous and involved hydrophobic interactions. Synchronous, 3D fluorescence and CD spectroscopy indicated a change in conformation of bovine serum albumin (BSA) on interaction with DP. Using site-selective markers, the binding site of DP was found to be in subdomain IB. Molecular docking studies further corroborated these results. Molecular dynamic (MD) simulations showed lower RMSD values on interaction, suggesting the existence of a stable complex between DP and BSA. Furthermore, since β-Cyclodextrin (βCD) is used to improve the solubility of DP in ophthalmic solutions, therefore, the effect of (βCD) on the interaction of BSA and DP was also studied, and it was found that in the presence of βCD, the binding constant for BSA-DP interaction decreased. The present study is an attempt to characterize the transport of DP and to improve its bioavailability, consequently helping in dosage design to achieve optimum therapeutic levels. Communicated by Ramaswamy H. Sarma

Multi-walled carbon nanotube-based systems for improving the controlled release of insoluble drug dipyridamole.

Applicability of multi-walled carbon nanotubes (MWCNTs) in loading dipyridamole (DDM), a poorly soluble drug, was evaluated. Additionally, the effect of drug-loading efficiency on the release behavior of the MWCNT-DDM system was also investigated. DDM as a model drug was incorporated into MWCNTs with different drug-loading rates (10, 25 and 50%) using the solvent deposition method. The MWCNT-DDM system was successfully established and characterized using common solid-state characterization methods. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption analysis and Fourier transform-infrared (FT-IR) spectroscopy were carried out to observe the progress of drug loading. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were used to systematically assess the crystalline state of the DDM after being loaded into the MWCNTs. Improvements in dissolution rate were evaluated by the dissolution test. The results revealed that with the increase of drug loading, the form of DDM in the MWCNTs changed from amorphous to crystalline state. Also, the release rate of DDM decreased upon increasing the drug-loading rate of carriers. In conclusion, MWCNTs are proven to be promising carriers for loading DDM.

An actionable sterol-regulated feedback loop modulates statin sensitivity in prostate cancer

ObjectiveThe statin family of cholesterol-lowering drugs has been shown to induce tumor-specific apoptosis by inhibiting the rate-limiting enzyme of the mevalonate (MVA) pathway, HMG-CoA reductase (HMGCR). Accumulating evidence suggests that statin use may delay prostate cancer (PCa) progression in a subset of patients; however, the determinants of statin drug sensitivity in PCa remain unclear. Our goal was to identify molecular features of statin-sensitive PCa and opportunities to potentiate statin-induced PCa cell death. MethodsDeregulation of HMGCR expression in PCa was evaluated by immunohistochemistry. The response of PCa cell lines to fluvastatin-mediated HMGCR inhibition was assessed using cell viability and apoptosis assays. Activation of the sterol-regulated feedback loop of the MVA pathway, which was hypothesized to modulate statin sensitivity in PCa, was also evaluated. Inhibition of this statin-induced feedback loop was performed using RNA interference or small molecule inhibitors. The achievable levels of fluvastatin in mouse prostate tissue were measured using liquid chromatography–mass spectrometry. ResultsHigh HMGCR expression in PCa was associated with poor prognosis; however, not all PCa cell lines underwent apoptosis in response to treatment with physiologically-achievable concentrations of fluvastatin. Rather, most cell lines initiated a feedback response mediated by sterol regulatory element-binding protein 2 (SREBP2), which led to the further upregulation of HMGCR and other lipid metabolism genes. Overcoming this feedback mechanism by knocking down or inhibiting SREBP2 potentiated fluvastatin-induced PCa cell death. Notably, we demonstrated that this feedback loop is pharmacologically-actionable, as the drug dipyridamole can be used to block fluvastatin-induced SREBP activation and augment apoptosis in statin-insensitive PCa cells. ConclusionOur study implicates statin-induced SREBP2 activation as a PCa vulnerability that can be exploited for therapeutic purposes using clinically-approved agents.

Oxidative stress and inflammation as links in a chain in patients with chronic cerebrovascular diseases

Cerebrovascular diseases (CVD) are the main cause of death and permanent disability. The urgency of the problem of chronic CVD is associated with an increase of the absolute number of elderly and senile age in the population, a trend towards slowly increasing, sluggish pathological processes. It is obvious that any somatic disease in such patients is comorbid to cerebrovascular diseases that suggests a unified mechanism of the pathogenesis for both the main and concomitant diseases. The article notes that microangiopathy is the most common cause of CVD. The main etiopathogenetic factor affecting cerebral vessels of small caliber is endothelial dysfunction, systemic inflammation and oxidative stress. Understanding the molecular components that underlie functional abnormalities and damage of small blood vessels gives the key to the modern strategies in therapy, forming the foundation for an adequate pathogenetically justified therapy. This impact should be gradual, complex and aimed at correcting pathochemical disorders in general and neurotransmitter imbalance in particular. The drug dipyridamole, which has pleiotropic effects, can be considered as one of the pathogenetically justified means in complex drug therapy in patients with CVD.

Rehabilitation therapy as a component of the complex approach to the treatment of chronic forms the pelvic inflammatory disease in women

Issues of treatment and rehabilitation patients with pelvic's inflammatory diseases are still remain highly relevant, so relapses and chronic inflammation processes are worsen the prognosis for generative function in women, which is an important social and economic problem in modern time. Purpose of the study. Monitoring the effectiveness of therapeutic measures of rehabilitation step in chronic forms of this disease. Materials and methods. We examined 110 patients who handled to the clinic for women with complaints about the absence of pregnancy, of which a survey group was formed. The duration of pelvic inflammatory desiase (PID) in patients of the examination group did not exceed 2 years. The age of the patients was 25-35 years old. In patients of the examination group, according to clinical, laboratory and ultrasound ultrasound, laparoscopy, hysteroscopy and morphological findings, PID was verified including the presence of chronic endometritis and other endometrial pathology (for example, endometrial polyp, simple endometrial hyperplasia). Results. The rehabilitation stage of treatment (6 months) in patients with PID was aimed at restoring the morphofunctional potential of the tissue and eliminating the effects of secondary injuries, which include the restoration of hemodynamics and activity of the endometrial receptors. This stage of treatment is extremely important, especially for reproductive disorders. At this stage, the patients of the examination group were given hormone therapy and treatment with vasoactive drug (dipyridamole). The obtained results testified to the significance of the restoration of the vascular blood flow of the uterus and the functional layer of the endometrium. Conclusion. Rehabilitation therapy in patients with PID was primarily aimed at restoring the functional ability of the endometrium. Hormone therapy was a priority role, but at modern time, role of the vasoactive drugs that affect the blood flow in the uterus is emphasized. One of these drugs is dipyridamole, which contributes to the formation of collaterals (bypass paths) in ischemic zones. The results indicate that at the end of the 6-month rehabilitation phase, than of a three-layer endometrium was diagnosed (according to ultrasound on day 8-10 of the cycle) in 85 (77.27±4.00%) patients in the examination group.

PLLA-PHB fiber membranes obtained by solvent-free electrospinning for short-time drug delivery.

Fibers of poly(L-lactic acid) (PLLA)/polyhydroxybutyrate (PHB) with different concentrations of the drug dipyridamole (DPD) were prepared using solvent-free melt electrospinning to obtain a polymeric drug delivery system. The electrospun fibers were morphologically, structurally, thermally, and dynamically characterized. Crazes that resemble lotus root crevices were interestingly observed in the 7:3 PLLA/PHB fibers with 1% DPD. The crystallinity of PLLA slightly decreased as PHB was incorporated, and the addition of DPD significantly reduced the melting temperature of the composite. The interactions between PLLA and PHB mainly occurred at a proportion of 7:3, and drug encapsulation in the fibers was verified. The kinetic profiles of drug release demonstrated the predominant multiple patterns involving a diffusional stage in the short-term mode of release and kinetic process related to the hydrolysis of the biopolymers. Furthermore, the dynamic behavior of the polymer molecules was evaluated based on the segmental mobility using probe electron spin resonance spectroscopy. The segmental mobility in the amorphous fraction of PLLA decreased with increasing PLLA content. The 9:1 PLLA/PHB system was more resistant to polymer hydrolysis than to the 7:3 system and the rate of diffusion transport was approximately two times higher for the 7:3 PLLA/PHB fibers than for the 9:1 PLLA/PHB fibers.

Utilization of Gastrointestinal Simulator, an in Vivo Predictive Dissolution Methodology, Coupled with Computational Approach To Forecast Oral Absorption of Dipyridamole.

Weakly basic drugs exhibit a pH-dependent dissolution profile in the gastrointestinal (GI) tract, which makes it difficult to predict their oral absorption profile. The aim of this study was to investigate the utility of the gastrointestinal simulator (GIS), a novel in vivo predictive dissolution (iPD) methodology, in predicting the in vivo behavior of the weakly basic drug dipyridamole when coupled with in silico analysis. The GIS is a multicompartmental dissolution apparatus, which represents physiological gastric emptying in the fasted state. Kinetic parameters for drug dissolution and precipitation were optimized by fitting a curve to the dissolved drug amount-time profiles in the United States Pharmacopeia apparatus II and GIS. Optimized parameters were incorporated into mathematical equations to describe the mass transport kinetics of dipyridamole in the GI tract. By using this in silico model, intraluminal drug concentration-time profile was simulated. The predicted profile of dipyridamole in the duodenal compartment adequately captured observed data. In addition, the plasma concentration-time profile was also predicted using pharmacokinetic parameters following intravenous administration. On the basis of the comparison with observed data, the in silico approach coupled with the GIS successfully predicted in vivo pharmacokinetic profiles. Although further investigations are still required to generalize, these results indicated that incorporating GIS data into mathematical equations improves the predictability of in vivo behavior of weakly basic drugs like dipyridamole.

Effect of External Factors on the Structure of Ultrathin Fibers of Poly(3-Hydroxybutyrate) and Dipyridamole

Fibrous materials based on poly(3-hydroxybutyrate) containing the drug dipyridamole were investigated. The structural–dynamic characteristics of the materials were studied by scanning electron microscopy, differential scanning calorimetry, and ESR spectroscopy. The effect of a series of aggressive factors (temperature, water, ozone) on the structure of the poly(3-hydroxybutyrate) fibers with dipyridamole was investigated for the first time. It was established that the enthalpy of fusion of the fibers increases when dipyridamole is added. Complex relationships between the specific enthalpy of fusion of the crystallites and the molecular mobility of the radical are observed during the action of aggressive factors on the fibrous materials.

Abstract B132: Discovery of small molecule allosteric modulators of Abl kinase activity and function

Abstract The Abl protein-tyrosine kinase regulates intracellular signaling pathways controlling diverse cellular processes and forms oncogenic fusion proteins that drive several cancer types. The kinase activity of Abl is repressed by intramolecular interactions involving its regulatory SH3 and SH2 domains. The SH3 domain interacts with a polyproline type II helix formed by the SH2-kinase linker, while the SH2 domain interacts with the back of the C-lobe of the kinase domain. In addition, the myristoylated N-terminal cap region (Ncap) binds a hydrophobic pocket in the C-lobe of the kinase domain, clamping the SH3 and SH2 domains against the back of the kinase domain. Small molecules that allosterically regulate Abl kinase activity through its non-catalytic domains may represent selective probes of Abl function. In this study, we developed a high-throughput screening (HTS) assay to identify chemical modulators of Abl kinase activity that target the regulatory SH3:linker interaction. The fluorescence polarization (FP) assay employs a purified recombinant Abl protein comprised of the regulatory N-cap, SH3 and SH2 domains plus the SH2-kinase linker (Abl N32L protein) and a short fluorescein-labeled peptide probe that selectively binds to the Abl SH3 domain. During assay development, we found that the peptide probe binds to the recombinant Abl N32L protein in vitro, producing a robust FP signal that can be competitively displaced by excess unlabeled peptide. The FP signal is not observed in control N32L proteins bearing either an inactivating mutation in the SH3 domain or enhanced SH3:linker interaction. A pilot screen of 1200 FDA-approved compounds in the FP assay identified four compounds that specifically reduced the FP signal by at least three standard deviations from the untreated controls. Secondary assays demonstrated that one of the hits, the antithrombotic drug dipyridamole, enhances Abl kinase activity in vitro to a greater extent than the previously described Abl agonist, DPH. Docking studies predicted that this compound binds to a pocket formed at the interface of the SH3 domain and the linker, suggesting that it activates Abl by disrupting this regulatory interaction. Interestingly, this compound does not significantly affect the kinase activity of Hck, a Src family member that is regulated by similar SH3:linker interactions. Treatment with dipyrimadole in combination with DPH led to strong enhancement of Abl kinase activity in transfected cells. The Abl N32L FP assay has been implemented in a fully automated format and used to screen diversity libraries totaling 60,000 compounds. The Z-factor coefficients from this HTS campaign indicated that the FP assay performed well and several additional scaffolds were identified for future development. These results demonstrate that screening assays that incorporate the non-catalytic domains of Abl can identify allosteric small molecule regulators of kinase function, providing a new approach to selective drug discovery for this important kinase system. Citation Format: Prerna Grover, Haibin Shi, Matthew Baumgartner, David Close, Paul A. Johnston, Carlos J. Camacho, Thomas E. Smithgall. Discovery of small molecule allosteric modulators of Abl kinase activity and function. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B132.

Fluorescence Polarization Screening Assays for Small Molecule Allosteric Modulators of ABL Kinase Function.

The ABL protein-tyrosine kinase regulates intracellular signaling pathways controlling diverse cellular processes and contributes to several forms of cancer. The kinase activity of ABL is repressed by intramolecular interactions involving its regulatory Ncap, SH3 and SH2 domains. Small molecules that allosterically regulate ABL kinase activity through its non-catalytic domains may represent selective probes of ABL function. Here we report a screening assay for chemical modulators of ABL kinase activity that target the regulatory interaction of the SH3 domain with the SH2-kinase linker. This fluorescence polarization (FP) assay is based on a purified recombinant ABL protein consisting of the N-cap, SH3 and SH2 domains plus the SH2-kinase linker (N32L protein) and a short fluorescein-labeled probe peptide that binds to the SH3 domain. In assay development experiments, we found that the probe peptide binds to the recombinant ABL N32L protein in vitro, producing a robust FP signal that can be competed with an excess of unlabeled peptide. The FP signal is not observed with control N32L proteins bearing either an inactivating mutation in the SH3 domain or enhanced SH3:linker interaction. A pilot screen of 1200 FDA-approved drugs identified four compounds that specifically reduced the FP signal by at least three standard deviations from the untreated controls. Secondary assays showed that one of these hit compounds, the antithrombotic drug dipyridamole, enhances ABL kinase activity in vitro to a greater extent than the previously described ABL agonist, DPH. Docking studies predicted that this compound binds to a pocket formed at the interface of the SH3 domain and the linker, suggesting that it activates ABL by disrupting this regulatory interaction. These results show that screening assays based on the non-catalytic domains of ABL can identify allosteric small molecule regulators of kinase function, providing a new approach to selective drug discovery for this important kinase system.