Improvement of pyrazolo[3,4-d]pyrimidines pharmacokinetic properties: nanosystem approaches for drug delivery

An Update on Emergent Nano-Therapeutic Strategies against Pediatric Brain Tumors

Pediatric brain tumors are the major cause of pediatric cancer mortality. They comprise a diverse group of tumors with different developmental origins, genetic profiles, therapeutic options, and outcomes. Despite many technological advancements, the treatment of pediatric brain cancers has remained a challenge. Treatment options for pediatric brain cancers have been ineffective due to non-specificity, inability to cross the blood-brain barrier, and causing off-target side effects. In recent years, nanotechnological advancements in the medical field have proven to be effective in curing challenging cancers like brain tumors. Moreover, nanoparticles have emerged successfully, particularly in carrying larger payloads, as well as their stability, safety, and efficacy monitoring. In the present review, we will emphasize pediatric brain cancers, barriers to treating these cancers, and novel treatment options.

Chemical and biological versatility of pyrazolo[3,4-d]pyrimidines: one scaffold, multiple modes of action

Plain language summary Pyrazolo[3,4-d]pyrimidines are chemical compounds possessing remarkable versatility and significance in both biological and chemical contexts. These compounds are composed of specific arrangements of atoms, forming a unique ring structure, which is able to form bonds in a similar way as purines do. In the realm of chemistry, pyrazolo[3,4-d]pyrimidines showcase impressive flexibility due to their ability to easily react with various molecules, opening avenues for the creation of novel compounds with diverse properties for potential applications in medicinal chemistry. In a biological context, pyrazolo[3,4-d]pyrimidines play a crucial role due to their interaction with proteins such as enzymes. In fact, these compounds can impact various biological processes, including cancer cell proliferation, oxidative stress and inflammation. This has led to investigations into their potential as therapeutic agents: by designing pyrazolo[3,4-d]pyrimidines with specific biological targets in mind, new drugs can be developed for the effective treatment of a range of medical conditions. Finally, novel administration tools (e.g., nanomaterials and functionalized liposomes) are being studied as effective ways to overcome the main unwanted characteristics of pyrazolo[3,4-d]pyrimidines (scarce solubility and off-target side effects), thereby increasing their efficacy and specificity toward cell targets. In conclusion, pyrazolo[3,4-d]pyrimidines are fascinating molecules with a dual role in chemistry and biology. Their adaptability in chemical reactions makes them valuable building blocks for designing new compounds with diverse applications. Additionally, their interaction with biological molecules holds promise for the development of innovative medicines. Ongoing research into the properties and behaviors of these compounds could lead to significant advancements in both scientific fields.

Biological Evaluation and In Vitro Characterization of ADME Profile of In-House Pyrazolo[3,4-d]pyrimidines as Dual Tyrosine Kinase Inhibitors Active against Glioblastoma Multiforme

The therapeutic use of tyrosine kinase inhibitors (TKIs) represents one of the successful strategies for the treatment of glioblastoma (GBM). Pyrazolo[3,4-d]pyrimidines have already been reported as promising small molecules active as c-Src/Abl dual inhibitors. Herein, we present a series of pyrazolo[3,4-d]pyrimidine derivatives, selected from our in-house library, to identify a promising candidate active against GBM. The inhibitory activity against c-Src and Abl was investigated, and the antiproliferative profile against four GBM cell lines was studied. For the most active compounds endowed with antiproliferative efficacy in the low-micromolar range, the effects toward nontumoral, healthy cell lines (fibroblasts FIBRO 2-93 and keratinocytes HaCaT) was investigated. Lastly, the in silico and in vitro ADME properties of all compounds were also assessed. Among the tested compounds, the promising inhibitory activity against c-Src and Abl (K_i 3.14 µM and 0.44 µM, respectively), the irreversible, apoptotic-mediated death toward U-87, LN18, LN229, and DBTRG GBM cell lines (IC₅₀ 6.8 µM, 10.8 µM, 6.9 µM, and 8.5 µM, respectively), the significant reduction in GBM cell migration, the safe profile toward FIBRO 2-93 and HaCaT healthy cell lines (CC₅₀ 91.7 µM and 126.5 µM, respectively), the high metabolic stability, and the excellent passive permeability across gastrointestinal and blood-brain barriers led us to select compound 5 for further in vivo assays.

Novel pyrazolo[3,4-d]pyrimidines as dual Src/Bcr-Abl kinase inhibitors: Synthesis and biological evaluation for chronic myeloid leukemia treatment

The Bcr-Abl tyrosine kinase (TK) is the molecular hallmark of chronic myeloid leukemia (CML). Src is another TK kinase whose involvement in CML was widely demonstrated. Small molecules active as dual Src/Bcr-Abl inhibitors emerged as effective targeted therapies for CML and a few compounds are currently in clinical use. In this study, we applied a target-oriented approach to identify a family of pyrazolo[3,4-d]pyrimidines as dual Src/Bcr-Abl inhibitors as anti-leukemia agents. Considering the high homology between Src and Bcr-Abl, in-house Src inhibitors 8a-l and new analogue compounds 9a-n were screened as dual Src/Bcr-Abl inhibitors. The antiproliferative activity on K562 CML cells and the ADME profile were determined for the most promising compounds. Molecular modeling studies elucidated the binding mode of the inhibitors into the Bcr-Abl (wt) catalytic pocket. Compounds 8j and 8k showed nanomolar activities in enzymatic and cellular assays, together with favorable ADME properties, emerging as promising candidates for CML therapy. Finally, derivatives 9j and 9k, emerging as valuable inhibitors of the most aggressive Bcr-Abl mutation, T315I, constitute a good starting point in the search for compounds able to treat drug-resistant forms of CML. Overall, this study allowed us to identify more potent compounds than those previously reported by the group, marking a step forward in searching for new antileukemic agents.

Benefits and limitations of nanomedicine treatment of brain cancers and age-dependent neurodegenerative disorders

The treatment of central nervous system (CNS) malignancies, including brain cancers, is limited by a number of obstructions, including the blood-brain barrier (BBB), the heterogeneity and high invasiveness of tumors, the inaccessibility of tissues for early diagnosis and effective surgery, and anti-cancer drug resistance. Therapies employing nanomedicine have been shown to facilitate drug penetration across the BBB and maintain biodistribution and accumulation of therapeutic agents at the desired target site. The application of lipid-, polymer-, or metal-based nanocarriers represents an advanced drug delivery system for a growing group of anti-cancer chemicals. The nanocarrier surface is designed to contain an active ligand (cancer cell marker or antibody)-binding structure which can be modified to target specific cancer cells. Glioblastoma, ependymoma, neuroblastoma, medulloblastoma, and primary CNS lymphomas were recently targeted by easily absorbed nanocarriers. The metal- (such as transferrin drug-loaded systems), polymer- (nanocapsules and nanospheres), or lipid- (such as sulfatide-containing nanoliposomes)-based nano-vehicles were loaded with apoptosis- and/or ferroptosis-stimulating agents and demonstrated promising anti-cancer effects. This review aims to discuss effective nanomedicine approaches designed to overcome the current limitations in the therapy of brain cancers and age-dependent neurodegenerative disorders. To accent current obstacles for successful CNS-based cancer therapy, we discuss nanomedicine perspectives and limitations of nanodrug use associated with the specificity of nervous tissue characteristics and the effects nanocarriers have on cognition.

Nanotechnology-Based Diagnostic and Therapeutic Strategies for Neuroblastoma

Neuroblastoma (NB), as the most common extracranial solid tumor in childhood, is one of the critical culprits affecting children's health. Given the heterogeneity and invisibility of NB tumors, the existing diagnostic and therapeutic approaches are inadequate and ineffective in early screening and prognostic improvement. With the rapid innovation and development of nanotechnology, nanomedicines have attracted widespread attention in the field of oncology research for their excellent physiological and chemical properties. In this review, we first explored the current common obstacles in the diagnosis and treatment of NB. Then we comprehensively summarized the advancements in nanotechnology-based multimodal synergistic diagnosis and treatment of NB and elucidate the underlying mechanisms. In addition, a discussion of the pending challenges in biocompatibility and toxicity of nanomedicine was conducted. Finally, we described the development and application status of nanomaterials against some of the recognized targets in the field of NB research, and pointed out prospects for nanomedicine-based precision diagnosis and therapy of NB.

The Pyrazolo[3,4-d]Pyrimidine Derivative Si306 Encapsulated into Anti-GD2-Immunoliposomes as Therapeutic Treatment of Neuroblastoma

Si306, a pyrazolo[3,4-d]pyrimidine derivative recently identified as promising anticancer agent, has shown favorable in vitro and in vivo activity profile against neuroblastoma (NB) models by acting as a competitive inhibitor of c-Src tyrosine kinase. Nevertheless, Si306 antitumor activity is associated with sub-optimal aqueous solubility, which might hinder its further development. Drug delivery systems were here developed with the aim to overcome this limitation, obtaining suitable formulations for more efficacious in vivo use. Si306 was encapsulated in pegylated stealth liposomes, undecorated or decorated with a monoclonal antibody able to specifically recognize and bind to the disialoganglioside GD2 expressed by NB cells (LP[Si306] and GD2-LP[Si306], respectively). Both liposomes possessed excellent morphological and physio-chemical properties, maintained over a period of two weeks. Compared to LP[Si306], GD2-LP[Si306] showed in vitro specific cellular targeting and increased cytotoxic activity against NB cell lines. After intravenous injection in healthy mice, pharmacokinetic profiles showed increased plasma exposure of Si306 when delivered by both liposomal formulations, compared to that obtained when Si306 was administered as free form. In vivo tumor homing and cytotoxic effectiveness of both liposomal formulations were finally tested in an orthotopic animal model of NB. Si306 tumor uptake resulted significantly higher when encapsulated in GD2-LP, compared to Si306, either free or encapsulated into untargeted LP. This, in turn, led to a significant increase in survival of mice treated with GD2-LP[Si306]. These results demonstrate a promising antitumor efficacy of Si306 encapsulated into GD2-targeted liposomes, supporting further therapeutic developments in pre-clinical trials and in the clinic for NB.

Functionalized Liposome and Albumin-Based Systems as Carriers for Poorly Water-Soluble Anticancer Drugs: An Updated Review

Cancer is one of the leading causes of death worldwide. In the available treatments, chemotherapy is one of the most used, but has several associated problems, namely the high toxicity to normal cells and the resistance acquired by cancer cells to the therapeutic agents. The scientific community has been battling against this disease, developing new strategies and new potential chemotherapeutic agents. However, new drugs often exhibit poor solubility in water, which led researchers to develop functionalized nanosystems to carry and, specifically deliver, the drugs to cancer cells, targeting overexpressed receptors, proteins, and organelles. Thus, this review is focused on the recent developments of functionalized nanosystems used to carry poorly water-soluble drugs, with special emphasis on liposomes and albumin-based nanosystems, two major classes of organic nanocarriers with formulations already approved by the U.S. Food and Drug Administration (FDA) for cancer therapeutics.

UV/vis spectrophotometric determination of slow equilibrated N(1)-H missing deprotonation constant of a pyrimidine and thiopyrimidine: The final situation of the four pKa values

The missing acidity constant of recently synthesized 5-benzoyl-1-(methylphenylmethyleneamino)-4-phenyl-1H-pyrimidine-2-one (I) and 5-benzoyl-1-(methylphenylmethyleneamino)-4-phenyl-1H-pyrimidine-2-thione (II) are investigated as a function of time at pH values from 1.0 to 3.20 for I and from 1.0 to 4.06 for II using UV/vis spectroscopic analysis of their aged solutions, at a temperature of 25 ± 0.1 °C. In this study, a novel time-dependent isosbestic point method was developed to confirm the presence of any weak acid - base equilibrium and the detection of related equilibration time. The missing acidity constants for each of I and II were determined in 5.0% v/v aqueous methanol. Plausible acid base equilibrium mechanism for the missing acidity constant was presented for each of the compounds based on the extensive experimental UV/vis data. In this context, all the acid base equilibria for each of the regarding compounds were completely revised through different pH values.

Therapeutic efficacy of nanoparticles and routes of administration

In modern-day medicine, nanotechnology and nanoparticles are some of the indispensable tools in disease monitoring and therapy. The term “nanomaterials” describes materials with nanoscale dimensions (< 100 nm) and are broadly classified into natural and synthetic nanomaterials. However, “engineered” nanomaterials have received significant attention due to their versatility. Although enormous strides have been made in research and development in the field of nanotechnology, it is often confusing for beginners to make an informed choice regarding the nanocarrier system and its potential applications. Hence, in this review, we have endeavored to briefly explain the most commonly used nanomaterials, their core properties and how surface functionalization would facilitate competent delivery of drugs or therapeutic molecules. Similarly, the suitability of carbon-based nanomaterials like CNT and QD has been discussed for targeted drug delivery and siRNA therapy. One of the biggest challenges in the formulation of drug delivery systems is fulfilling targeted/specific drug delivery, controlling drug release and preventing opsonization. Thus, a different mechanism of drug targeting, the role of suitable drug-laden nanocarrier fabrication and methods to augment drug solubility and bioavailability are discussed. Additionally, different routes of nanocarrier administration are discussed to provide greater understanding of the biological and other barriers and their impact on drug transport. The overall aim of this article is to facilitate straightforward perception of nanocarrier design, routes of various nanoparticle administration and the challenges associated with each drug delivery method.

Plasmin-Binding Tripeptide-Decorated Liposomes Loading Pyrazolo[3,4-d]pyrimidines for Targeting Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most fatal cancer types worldwide. HCC cells were proved to overexpress c-Src and Sgk1, a tyrosine and a serine-threonine kinase, respectively, whose role is crucial for the development and progression of the tumor. Pyrazolo[3,4-d]pyrimidine derivatives are a class of tyrosine kinase inhibitors that have shown good activity against HepG2. HCC cells were also proved to overexpress plasmin, which is localized on the cell surface bound to its receptors. In this study, a tripeptide with sequence d-Ala-Phe-Lys, which binds a specific reactive site of plasmin, was synthesized and characterized. This tripeptide was used to decorate liposomes encapsulating three selected pyrazolo[3,4-d]pyrimidines. Liposomes bearing tripeptide have been characterized, not showing remarkable differences with respect to the corresponding tripeptide-free liposomes. In vitro HepG2 cell uptake profiles and cytotoxicities showed that the presence of the tripeptide on the liposomal membrane surface improves the cell-penetrating ability of liposomes and increases the activity of two of the three tested compounds.

Carbamazepine-loaded solid lipid nanoparticles and nanostructured lipid carriers: Physicochemical characterization and in vitro/in vivo evaluation

Solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) represent promising alternatives for drug delivery to the central nervous system. In the present work, four different nanoformulations of the antiepileptic drug Carbamazepine (CBZ) were designed and prepared by the homogenization/ultrasonication method, with encapsulation efficiencies ranging from 82.8 to 93.8%. The formulations remained stable at 4 °C for at least 3 months. Physicochemical and microscopic characterization were performed by photon correlation spectroscopy (PCS), transmission electron microscopy (TEM), atomic force microscopy (AFM); thermal properties by differential scanning calorimetry (DSC), thermogravimetry (TGA) and X-ray diffraction analysis (XRD). The results indicated the presence of spherical shape nanoparticles with a mean particle diameter around 160 nm in a narrow size distribution; the entrapped CBZ displayed an amorphous state. The in vitro release profile of CBZ fitted into a Baker-Lonsdale model for spherical matrices and almost the 100% of the encapsulated drug was released in a controlled manner during the first 24 h. The apparent permeability of CBZ-loaded nanoparticles through a cell monolayer model was similar to that of the free drug. In vivo experiments in a mice model of seizure suggested protection by CBZ-NLC against seizures for at least 2 h after intraperitoneal administration. The developed CBZ-loaded lipid nanocarriers displayed optimal characteristics of size, shape and drug release and possibly represent a promising tool to improve the treatment of refractory epilepsy linked to efflux transporters upregulation.

Water Solubility Enhancement of Pyrazolo[3,4-d]pyrimidine Derivatives via Miniaturized Polymer-Drug Microarrays

A miniaturized assay was optimized to evaluate the enhanced apparent water solubility of pyrazolo[3,4-d]pyrimidine derivatives used extensively as anticancer drug scaffolds. The applied amount of drugs used in the reported strategy ranged from 5 to 10 μg per formulation which were dispensed by an inkjet 2D printer directly into a 96-well plate. The selected polymer/drug formulations with high water solubility demonstrated improved cytotoxicity against a human lung adenocarcinoma cancer cell line (A549) compared to the free drugs. We attribute the enhanced efficacy to the improved apparent-solubility of the drug molecules achieved via this methodology. This novel miniaturized method showed promising results in terms of water solubility improvement of the highly hydrophobic pyrazolo[3,4-d]pyrimidine derivatives, requiring only a few micrograms of each drug per tested polymeric formulation. In addition, the reported experimental evidence may facilitate identification of suitable polymers for combination with drug, leading to investigations on biological properties or mechanisms of action in a single formulation.

Prodrugs of Pyrazolo[3,4-d]pyrimidines: From Library Synthesis to Evaluation as Potential Anticancer Agents in an Orthotopic Glioblastoma Model

Pyrazolo[3,4-d]pyrimidines are potent protein kinase inhibitors with promising antitumor activity but suboptimal aqueous solubility, consequently worth being further optimized. Herein, we present the one-pot two-step procedure for the synthesis of a set of pyrazolo[3,4-d]pyrimidine prodrugs (1a-8a and 9a-e) with higher aqueous solubility and enhanced pharmacokinetic and therapeutic properties. ADME studies demonstrated for the most promising prodrugs a better aqueous solubility, a favorable hydrolysis in human and murine serum, and an increased ability to cross cell membranes with respect to the parental drugs, explaining their better 24 h in vitro cytotoxicity against human glioblastoma U87 cell line. Finally, the 4-4a couple of drug/prodrug was also evaluated in vivo, revealing a profitable pharmacokinetic profile of the prodrug associated with a good efficacy. The application of the prodrug approach demonstrated to be a successful strategy for improving aqueous solubility of the parental drugs, determining a positive impact also in their biological efficacy.

Nanoparticle Functionalization and Its Potentials for Molecular Imaging

Functionalization enhances the properties and characteristics of nanoparticles through surface modification, and enables them to play a major role in the field of medicine. In molecular imaging, quality functional images are required with proper differentiation which can be seen with high contrast to obtain viable information. This review article discusses how functionalization enhances molecular imaging and enables multimodal imaging by which images with combination of functions particular to each modality can be obtained. This also explains how nanoparticles interacting at molecular level, when functionalized with molecules can target the cells of interest or substances with high specificity, reducing background signal and allowing simultaneous therapies to be carried out while imaging. Functionalization allows imaging for a prolonged period and enables to track the cells over a period of time. Recent researches and progress in functionalizing the nanoparticles to specifically enhance bioimaging with different modalities and their applications are reviewed in this article.

Novel pyrazolo[3,4-d]pyrimidine with 4-(1H-benzimidazol-2-yl)-phenylamine as broad spectrum anticancer agents: Synthesis, cell based assay, topoisomerase inhibition, DNA intercalation and bovine serum albumin studies

A series of new pyrazolo[3,4-d]pyrimidine possessing 4-(1H-benzimidazol-2-yl)-phenylamine moiety at C4 position and primary as well as secondary amines at C6 position has been designed and synthesized. Their antitumor activities were evaluated against a panel of 60 human cancer cell lines at National Cancer Institute (NCI). Six compounds displayed potent and broad spectrum anticancer activities at 10 μM. Compounds 8, 12, 14 and 17 proved to be the most active and efficacious candidate in this series, with mean GI₅₀ values of 1.30 μM, 1.43 μM, 2.38 μM and 2.18 μM, respectively against several cancer cell lines. Further biological evaluation of these compounds suggested that these compounds induce apoptosis and inhibit human topoisomerase (Topo) IIα as a possible intracellular target. UV-visible and fluorescence studies of these compounds revealed strong interaction with ct-DNA and bovine serum albumin (BSA).