ORIGINAL ARTICLE: Solubilization of vorinostat by cyclodextrins

Alkaline phosphatase (ALP) activatable small molecule-based prodrugs for cancer theranostics

Highly water-soluble small molecule-based prodrugs (5-FUPD and SAHAPD) are formulated. They comprise a phosphate group to lock the active drug payload (5-fluorouracil and SAHA) along with a turn-on fluorophore consisting of a glutathione (GSH) depletory feature. Installation of the phosphate group along with purification of final product has been accomplished in an operationally facile manner. Activation of the prodrugs is facilitated by alkaline phosphatase (ALP)-mediated hydrolysis of the phosphate group followed by 1,8-elimination. The prodrugs were found to be highly effective against ALP flared human cervical cancer (HeLa) and liver cancer (HepG2) cell lines. Most notably, they were found to be innocuous to normal liver cells (WRL-68).

Cyclodextrin-Based Arsenal for Anti-Cancer Treatments

Anti-cancer drugs are mostly limited in their use due to poor physicochemical and biopharmaceutical properties. Their lower solubility is the most common hurdle limiting their use upto their potential. In the recent years, the cyclodextrin (CD) complexation have emerged as existing approach to overcome the problem of poor solubility. CD-based nano-technological approaches are safe, stable and showed well in vivo tolerance and greater payload for encapsulation of hydrophobic drugs for the targeted delivery. They are generally chosen due to their ability to get self-assembled to form liposomes, nanoparticles, micelles and nano-sponges etc. This review paper describes a birds-eye view of the various CD-based nano-technological approaches applied for the delivery of anti-cancer moieties to the desired target such as CD based liposomes, niosomes, niosoponges, micelles, nanoparticles, monoclonal antibody, magnetic nanoparticles, small interfering RNA, nanorods, miscellaneous formulation of anti-cancer drugs containing CD. Moreover, the author also summarizes the various shortcomings of such a system and their way ahead.

Improved oral bioavailability of poorly water-soluble vorinostat by self-microemulsifying drug delivery system

Background

Vorinostat is a histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA) with anticancer properties. However, it is plagued by low water solubility, low permeability (BCS class IV drug), and suboptimal pharmacokinetics. The purpose of the present study was to develop a self-microemulsifying drug delivery system (SMEDDS) to enhance the oral bioavailability of vorinostat. Capryol 90, labrasol, and polyethylene glycol (PEG 400) were selected as oil phase, surfactant, and co-surfactant, respectively. The vorinostat self-microemulsifying drug delivery systems were tested for self-microemulsifying time, phase separation, effect of pH, droplet size, zeta potential, dilution study, Fourier-transform infrared (FT-IR) spectroscopy analysis, and field emission scanning electron microscopy (FESEM). A rat model in vivo pharmacokinetic study was conducted for the optimized formulation against vorinostat pure drug powder.

Results

The results from the characterization studies showed that the optimized formulation (F7) self-microemulsification time was 1.4 ± 0.05 min and no precipitation or phase separation was observed. The mean droplet size, polydispersity index (PDI), and zeta potential of the optimized formulation (F7) were found to be 272.9 ± 82.7 nm, 0.415, and − 57.2 mV, respectively. The pharmacokinetic parameters of the optimized formulation (F7) showed a 1.6-fold increase in maximum concentration (Cmax) and a 3.6-fold increase in area under the curve (AUC(0−∞)), in comparison with pure drug in suspension.

Conclusions

The findings suggest that SMEDDS formulation could be an effective method for increasing the oral bioavailability of vorinostat, which is poorly water soluble.

Selenium-Based Novel Epigenetic Regulators Offer Effective Chemotherapeutic Alternative with Wider Safety Margins in Experimental Colorectal Cancer

Colorectal cancer (CRC) is a major cause of morbidity and mortality worldwide. Despite the critical involvement of epigenetic modifications in CRC, the studies on the chemotherapeutic efficacy of various epigenetic regulators remain limited. Considering the key roles of histone deacetylases (HDACs) in the regulation of diverse cellular processes, several HDAC inhibitors are implied as effective therapeutic strategies. In this context, suberoylanilide hydroxamic acid (SAHA), a 2^nd-generation HDAC inhibitor, showed limited efficacy in solid tumors. Also, side effects associated with SAHA limit its clinical application. Based on the redox-modulatory and HDAC inhbitiory activities of essential trace element selenium (Se), the anti-carcinogenic potential of Se substituted SAHA, namely, SelSA-1 (25 mg kg^-1), was screened for it enhanced anti-tumorigenic role and wider safety profiles in DMH-induced CRC in Balb/c mice. A multipronged approach such as in silico, biochemical, and pharmacokinetics (PK) has been used to screen, characterize, and evaluate these novel compounds in comparison to existing HDAC inhibitor SAHA. This is the first in vivo study indicating the chemotherapeutic potential of Se-based novel epigenetic regulators such as SelSA-1 in any in vivo experimental model of carcinogenesis. Pharmcological and toxicity data indicated better safety margins, bioavailability, tolerance, and elimination rate of SelSA-1 compared to classical HDAC inhibitor SAHA. Further, histological and morphological evidence demonstrated enhanced chemotherapeutic potential of SelSA-1 even at lower pharmacological doses than SAHA. This is the first in vivo study suggesting Se-based novel epigenetic regulators as potential chemotherapeutic alternatives with wider safety margins and enhanced anticancer activities.

Improving the solubility of vorinostat using cyclodextrin inclusion complexes: The physicochemical characteristics, corneal permeability and ocular pharmacokinetics of the drug after topical application

Vorinostat (suberoylanilide hydroxamic acid, SAHA), an FDA-approved drug for cutaneous T cell lymphoma, has antiangiogenic and anti-inflammatory activity and thus has therapeutic potential for inflammatory corneal neovascularization (CNV). However, its practical administration is limited due to its poor aqueous solubility and permeability. This study aimed to enhance the corneal permeability of SAHA by promoting its inclusion into a complex with hydroxypropyl-β-CD (HPβCD) for topical application. In phase-solubility studies, the solubility of SAHA with HPβCD and sulfobutyl ether-β-CD (SEβCD) was assessed at different temperatures, and complexation efficiencies (K) were calculated. The inclusion complexes (ICs) were prepared and characterized by differential scanning calorimetry (DSC), infrared spectrometry (IR), scanning electron microscopy (SEM), and X-ray diffraction (XRD) after freeze-drying. The phase-solubility study showed that the complexation efficiencies of SAHA were higher in HPβCD solutions (297.35 M^-1, 115.28 M^-1 and 122.75 M^-1) than in SEβCD solutions (169.75 M^-1, 91.33 M^-1 and 96.49 M^-1) at 4 °C, 25 °C and 37 °C. HPβCD was selected for SAHA-IC preparation, and characterization revealed IC formation. SAHA existed in an amorphous state in the ICs. The ex vivo corneal permeability of SAHA was also evaluated and found to be greater when formulated as an HPβCD solution than as a suspension. Irritation assays in rabbit eyes showed that the SAHA-IC solution was not irritating after topical application. The ocular pharmacokinetics of SAHA in New Zealand White rabbits were assessed following topical administration (0.2%), and a 0.2% SAHA suspension was used as the control. Compared to its formulation as a suspension, the formulation of SAHA as an HPβCD solution increased its corneal bioavailability by more than 3-fold and its conjunctival bioavailability by more than 2-fold. Thus, IC formation was effective at improving the ocular bioavailability of SAHA. This study provides an important alternative approach for developing liquid pharmaceutical formulations of SAHA for topical ocular applications.

Redox-sensitive iodinated polymersomes carrying histone deacetylase inhibitor as a dual-functional nano-radiosensitizer for enhanced radiotherapy of breast cancer

Radiotherapy (RT) is a frequently used means in clinical tumor treatment. The outcome of RT varies, however, to a great extent, due to RT resistance or intolerable dose, which might be resolved by the development of radio-sensitizing strategies. Here, we report redox-sensitive iodinated polymersomes (RIP) carrying histone deacetylase inhibitor, suberoylanilide hydroxamic acid (SAHA, vorinostat), as a new dual-functional nano-radiosensitizer for breast cancer radiotherapy. SAHA-loaded RIP (RIP-SAHA) with a size of about 101 nm exhibited good colloidal stability while the reduction-activated release of SAHA, giving rise to better antitumor effect to 4T1 breast carcinoma cells than free SAHA. Accordingly, RIP-SAHA combined with a 4 Gy dose of X-ray radiation led to significantly enhanced suppression of 4T1 cells compared with SAHA combined 4 Gy of X-ray radiation, as a result of enhanced DNA damage and impeded DNA damage repair. The pharmacokinetics and biodistribution studies by single-photon emission computed tomography (SPECT) with 125I-labeled SAHA (125I-SAHA) showed a 17.3-fold longer circulation and 237.7-fold better tumor accumulation of RIP-SAHA over SAHA. The systemic administration of RIP-SAHA greatly sensitized radiotherapy of subcutaneous 4T1 breast tumors and brought about significant inhibition of tumor growth, without causing damages to major organs, compared with radiotherapy alone. RIP not only enhanced SAHA delivery but also acted as a radiosensitizer. RIP-SAHA emerges as a smart dual-functional nano-radiosensitizer to effectively enhance tumor radiotherapy.

Vorinostat (SAHA) and Breast Cancer: An Overview

Vorinostat (SAHA), an inhibitor of class I and II of histone deacetylases, is the first histone deacetylase inhibitor (HDI) approved for the treatment of cutaneous T-cell lymphoma in 2006. HDIs are promising anticancer agents that inhibit the proliferation of many types of cancer cells including breast carcinoma (BC). BC is a heterogeneous disease with variable biological behavior, morphological features, and response to therapy. Although significant progress in the treatment of BC has been made, high toxicity to normal cells, serious side effects, and the occurrence of multi-drug resistance limit the effective therapy of BC patients. Therefore, new active agents which improve the effectiveness of currently used regimens are highly needed. This manuscript analyzes preclinical and clinical trials data of SAHA, applied individually or in combination with other anticancer agents, considering different histological subtypes of BC.

Ultrasonic Atomizer-Driven Development of Biocompatible and Biodegradable Poly(d,l-lactide-co-glycolide) Nanocarrier-Encapsulated Suberoylanilide Hydroxamic Acid to Combat Brain Cancer

The path to the discovery of anticancer drugs and investigating their potential activity has remained a quest for several decades. Suberoylanilide hydroxamic acid (SAHA), also known as "Vorinostat", is a well-known histone deacetylase inhibitor (HDACi) and has the potential to act as a therapeutic agent against tumorigenesis. Herein, we have fabricated SAHA incorporated into biocompatible and biodegradable poly(d,l-lactide-co-glycolide) PLGA nanoparticles (NPs) using a facile method of ultrasonic atomization and evaluated their anticancer property. We have explored their characteristics using dynamic light scattering (DLS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), encapsulation efficiency, and in vitro drug release and have investigated their efficacy on U87 glioblastoma (GBM) cells. SAHA-PLGA NPs synthesized were of average mean size of 80 ± 23 and 105 ± 6.0 nm observed through cryo-field-emission gun SEM and HR-TEM with a polydispersity index of 0.068 and a ζ-potential value of -13.26 mV. The encapsulation efficiency was 53%, with a sustained in vitro release up to 48 h. The in vitro assessment of SAHA-PLGA NPs for their anticancer activity on U87 GBM cells showed cellular cytotoxicity with an IC₅₀ of 19.91 μM. SAHA-PLGA NP-treated cells also showed suppression in migration with 8.77 μM concentration, and cell growth inhibition was observed in the wound scratch assay for up to 24 h. The cellular uptake studies have been utilized by time-dependent experiments, revealing their cellular internalization. Taking this into account, our present experimental findings indicate that SAHA-PLGA NPs could play a significant role in enhancing the effectiveness and bioavailability and reducing adverse effects of cancer chemotherapy. It also highlights the inherent potential of these biocompatible entities for chemotherapeutic applications in biomedical and pharmaceutics.

Recent advances in prodrug-based nanoparticle therapeutics

Extensive research into prodrug modification of active pharmaceutical ingredients and nanoparticle drug delivery systems has led to unprecedented levels of control over the pharmacological properties of drugs and resulted in the approval of many prodrug or nanoparticle-based therapies. In recent years, the combination of these two strategies into prodrug-based nanoparticle drug delivery systems (PNDDS) has been explored as a way to further advance nanomedicine and identify novel therapies for difficult-to-treat indications. Many of the PNDDS currently in the clinical development pipeline are expected to enter the market in the coming years, making the rapidly evolving field of PNDDS highly relevant to pharmaceutical scientists. This review paper is intended to introduce PNDDS to the novice reader while also updating those working in the field with a comprehensive summary of recent efforts. To that end, first, an overview of FDA-approved prodrugs is provided to familiarize the reader with their advantages over traditional small molecule drugs and to describe the chemistries that can be used to create them. Because this article is part of a themed issue on nanoparticles, only a brief introduction to nanoparticle-based drug delivery systems is provided summarizing their successful application and unfulfilled opportunities. Finally, the review's centerpiece is a detailed discussion of rationally designed PNDDS formulations in development that successfully leverage the strengths of prodrug and nanoparticle approaches to yield highly effective therapeutic options for the treatment of many diseases.

Synthesis and in vitro evaluation of cyclodextrin hyaluronic acid conjugates as a new candidate for intestinal drug carrier for steroid hormones

Steroid hormones became increasingly interesting as active pharmaceutical ingredients for the treatment of endocrine disorders. However, medical applications of many steroidal drugs are inhibited by their very low aqueous solubilities giving rise to low bioavailabilities. Therefore, the prioritized oral administration of steroidal drugs remains problematic. Cyclodextrins are promising candidates for the development of drug delivery systems for oral route applications, since they solubilize hydrophobic steroids and increase their rate of transport in aqueous environments. In this study, the synthesis and characterization of polymeric β-cyclodextrin derivates is described, which result from the attachment of a hydrophilic β-CD-thioether to hyaluronic acid. Host-guest complexes of the synthesized β-cyclodextrin hyaluronic acid conjugates were formed with two poorly soluble model steroids (β-estradiol, dexamethasone) and compared to monomeric β-cyclodextrin derivates regarding solubilization and complexation efficiency. The β-cyclodextrin-drug (host-guest) complexes were evaluated in vitro for their suitability (cytotoxicity and transport rate) as intestinal drug carriers for steroid hormones. In case of β-estradiol, higher solubilities could be achieved by complexation with both synthesized β-cyclodextrin derivates, leading to significantly higher intestinal transport rates in vitro. However, this success could not be shown for dexamethasone, which namely solubilized better, but could not enhance the transport rate significantly. Thus, this study demonstrates the biocompatibility of the synthesized and characterized β-cyclodextrin derivates and shows their potential as new candidate for intestinal drug carrier for steroid hormones like β-estradiol.

Stabilized Peptide HDAC Inhibitors Derived from HDAC1 Substrate H3K56 for the Treatment of Cancer Stem-Like Cells In Vivo

FDA-approved HDAC inhibitors exhibit dose-limiting adverse effects; thus, we sought to improve the therapeutic windows for this class of drugs. In this report, we describe a new class of peptide-based HDAC inhibitors derived from the HDAC1-specific substrate H3K56 with improved nonspecific toxicity compared with traditional small-molecular inhibitors. We showed that our designed peptides exerted superior antiproliferation effects on cancer stem-like cells with minimal toxicity to normal cells compared with the small-molecular inhibitor SAHA, which showed nonspecific toxicity to normal and cancer cells. These peptide inhibitors also inactivated cellular HDAC1 and HDAC6 and disrupted the formation of the HDAC1, LSD1, and CoREST complex. In ovarian teratocarcinoma (PA-1) and testicular embryonic carcinoma (NTERA-2) cell xenograft animal models (5 mice/group, 50 mg/kg, every other day, intraperitoneal injection), these peptides inhibited tumor growth by 80% to 90% with negligible organ (heart, liver, spleen, lung, kidney, brain) lesions. These results represent the first attempt to design chemically stabilized peptide inhibitors to investigate HDAC inhibition in cancer stem-like cells. These novel peptide inhibitors have significantly enhanced therapeutic window and offer promising opportunities for cancer therapy. SIGNIFICANCE: Selective antiproliferative effects of stabilized peptide HDAC inhibitors toward cancer stem-like cells provide a therapeutic alternative that avoids high nonspecific toxicity of current drugs.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/79/8/1769/F1.large.jpg.

Advances and Challenges of HDAC Inhibitors in Cancer Therapeutics

Since the identification and cloning of human histone deacetylases (HDACs) and the rapid approval of vorinostat (Zolinza®) for the treatment of cutaneous T-cell lymphoma, the field of HDAC biology has met many initial successes. However, many challenges remain due to the complexity involved in the lysine posttranslational modifications, epigenetic transcription regulation, and nonepigenetic cellular signaling cascades. In this chapter, we will: review the discovery of the first HDAC inhibitor and present discussion regarding the future of next-generation HDAC inhibitors, give an overview of different classes of HDACs and their differences in lysine deacylation activity, discuss different classes of HDAC inhibitors and their HDAC isozyme preferences, and review HDAC inhibitors' preclinical studies, their clinical trials, their pharmacokinetic challenges, and future direction. We will also discuss the likely reason for the failure of multiple HDAC inhibitor clinical trials in malignancies other than lymphoma and multiple myeloma. In addition, the potential molecular mechanism(s) that may play a key role in the efficacy and therapeutic response rate in the clinic and the likely patient population for HDAC therapy will be discussed.

Histone Deacetylase Inhibitor Induced Radiation Sensitization Effects on Human Cancer Cells after Photon and Hadron Radiation Exposure

Suberoylanilide hydroxamic acid (SAHA) is a histone deacetylase inhibitor, which has been widely utilized throughout the cancer research field. SAHA-induced radiosensitization in normal human fibroblasts AG1522 and lung carcinoma cells A549 were evaluated with a combination of γ-rays, proton, and carbon ion exposure. Growth delay was observed in both cell lines during SAHA treatment; 2 μM SAHA treatment decreased clonogenicity and induced cell cycle block in G1 phase but 0.2 μM SAHA treatment did not show either of them. Low LET (Linear Energy Transfer) irradiated A549 cells showed radiosensitization effects on cell killing in cycling and G1 phase with 0.2 or 2 μM SAHA pretreatment. In contrast, minimal sensitization was observed in normal human cells after low and high LET radiation exposure. The potentially lethal damage repair was not affected by SAHA treatment. SAHA treatment reduced the rate of γ-H2AX foci disappearance and suppressed RAD51 and RPA (Replication Protein A) focus formation. Suppression of DNA double strand break repair by SAHA did not result in the differences of SAHA-induced radiosensitization between human cancer cells and normal cells. In conclusion, our results suggest SAHA treatment will sensitize cancer cells to low and high LET radiation with minimum effects to normal cells.

Co-delivery of Vorinostat and Etoposide Via Disulfide Cross-Linked Biodegradable Polymeric Nanogels: Synthesis, Characterization, Biodegradation, and Anticancer Activity

Treatment regimens for cancer patients using single chemotherapeutic agents often lead to undesirable toxicity, drug resistance, reduced uptake etc. Combination of two or more drugs is therefore becoming an imperative strategy to overcome these limitations. A step forward can be taken through delivery of the drugs used in combination via nanoparticles. Co-administration of chemotherapeutic drugs encapsulated in nanoparticles has been shown to result in synergistic effects and enhanced therapeutic efficacy. In present study, we explored the combination treatment of histone deacetylase inhibitor vorinostat (VOR) and topoisomerase II inhibitor etoposide (ETOP). The concurrent combination treatment of VOR and ETOP resulted in synergistic effect on human cervical HeLa cancer cells. VOR and ETOP were encapsulated into poly(ethylene glycol) monomethacrylate (POEOMA)-based disulfide cross-linked nanogels. The nanogels were synthesized using atom transfer radical polymerization (ATRP) via cyclohexane/water inverse mini-emulsion and were degradable in presence of intracellular glutathione (GSH) concentration. Both the drugs were loaded into the nanogels by physical encapsulation method and characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray diffraction (XRD), dynamic light scattering (DLS), and differential scanning calorimetry (DSC). Both VOR- and ETOP-loaded nanogels showed sustained release profile. Furthermore, combination treatment drugs encapsulated of POEOMA nanogel demonstrated enhanced synergistic cytotoxic effect compared with combination of free drugs. Enhanced synergistic cell killing efficiency of drug-loaded POEOMA nanogels was due to increased apoptosis via caspase 3/7 activation. Therefore, combination of VOR- and ETOP-loaded PEG-based biodegradable nanogels may provide a promising therapy with enhanced anticancer effect.

A physiologically based pharmacokinetic and pharmacodynamic (PBPK/PD) model of the histone deacetylase (HDAC) inhibitor vorinostat for pediatric and adult patients and its application for dose specification

PURPOSE

This study aimed at recommending pediatric dosages of the histone deacetylase (HDAC) inhibitor vorinostat and potentially more effective adult dosing regimens than the approved standard dosing regimen of 400 mg/day, using a comprehensive physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) modeling approach.

METHODS

A PBPK/PD model for vorinostat was developed for predictions in adults and children. It includes the maturation of relevant metabolizing enzymes. The PBPK model was expanded by (1) effect compartments to describe vorinostat concentration-time profiles in peripheral blood mononuclear cells (PBMCs), (2) an indirect response model to predict the HDAC inhibition, and (3) a thrombocyte model to predict the dose-limiting thrombocytopenia. Parameterization of drug and system-specific processes was based on published and unpublished in silico, in vivo, and in vitro data. The PBPK modeling software used was PK-Sim and MoBi.

RESULTS

The PBPK/PD model suggests dosages of 80 and 230 mg/m² for children of 0-1 and 1-17 years of age, respectively. In comparison with the approved standard treatment, in silico trials reveal 11 dosing regimens (9 oral, and 2 intravenous infusion rates) increasing the HDAC inhibition by an average of 31%, prolonging the HDAC inhibition by 181%, while only decreasing the circulating thrombocytes to a tolerable 53%. The most promising dosing regimen prolongs the HDAC inhibition by 509%.

CONCLUSIONS

Thoroughly developed PBPK models enable dosage recommendations in pediatric patients and integrated PBPK/PD models, considering PD biomarkers (e.g., HDAC activity and platelet count), are well suited to guide future efficacy trials by identifying dosing regimens potentially superior to standard dosing regimens.

Enhanced in vitro cytotoxicity and anti-tumor activity of vorinostat-loaded pluronic micelles with prolonged release and reduced hepatic and renal toxicities

Vorinostat is the first histone deacetylase inhibitor approved by US FDA for use in cancer therapy. However, its limited aqueous solubility, low permeability, and suboptimal pharmacokinetics hinder its delivery. Thus, in this study, micelles of vorinostat with each of pluronic F68 (PF68) and pluronic F127 (PF127) were developed and optimized based on drug loading and entrapment. The optimized micelles were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), differential scanning calorimetry (DSC), zeta analyzer, and electron transmission microscopy. Their in vitro release, stability, in vitro cytotoxicity against HepG2, Caco-2, and MCF-7 cell lines, and finally, in vivo antitumor activity in mice bearing Ehrlich Ascites Carcinoma (EAC) were assessed. The highest entrapment efficiency was 99.09±2.16% and 94.19±2.37% for micelles of 1:50 drug to polymer ratio with each of PF127 and PF68, respectively. These micelles were nearly spherical with nanoscopic mean diameters of 72.61±10.66nm for PF68 and 91.88±10.70nm for PF127 with narrow size distribution. The micelles provided prolonged release at phosphate buffer saline pH7.4 up to 24h for PF68 and 72h for PF127. Potentiation of in vitro cytotoxicity of vorinostat was more pronounced with PF127 micelles particularly against MCF-7 cells. Compared with free vorinostat, the micelles with PF127 were more effective in inhibiting tumor growth as well as exhibiting significantly (p<0.05) diminished hepatic and renal toxicities. In conclusion, 1:50 vorinostat-PF127 micelles may facilitate i.v. formulations and can be suggested as a promising stable and safe nanoparticulate delivery system with prolonged release and potentiated cytotoxicity.

A Comprehensive Review on Cyclodextrin-Based Carriers for Delivery of Chemotherapeutic Cytotoxic Anticancer Drugs

Most of the cytotoxic chemotherapeutic agents have poor aqueous solubility. These molecules are associated with poor physicochemical and biopharmaceutical properties, which makes the formulation difficult. An important approach in this regard is the use of combination of cyclodextrin and nanotechnology in delivery system. This paper provides an overview of limitations associated with anticancer drugs, their complexation with cyclodextrins, loading/encapsulating the complexed drugs into carriers, and various approaches used for the delivery. The present review article aims to assess the utility of cyclodextrin-based carriers like liposomes, niosomes, nanoparticles, micelles, millirods, and siRNA for delivery of antineoplastic agents. These systems based on cyclodextrin complexation and nanotechnology will camouflage the undesirable properties of drug and lead to synergistic or additive effect. Cyclodextrin-based nanotechnology seems to provide better therapeutic effect and sustain long life of healthy and recovered cells. Still, considerable study on delivery system and administration routes of cyclodextrin-based carriers is necessary with respect to their pharmacokinetics and toxicology to substantiate their safety and efficiency. In future, it would be possible to resolve the conventional and current issues associated with the development and commercialization of antineoplastic agents.

Development of lipid nanoparticles for a histone deacetylases inhibitor as a promising anticancer therapeutic

BACKGROUND

Vorinostat (VRS), a histone deacetylases inhibitor, has significant cytotoxic potential in a large number of human cancer cell lines.

OBJECTIVE

To clarify its promising anticancer potential and to improve its drawback related to physical properties and in vivo performance of VRS.

METHODS

VRS was successfully incorporated into nanostructured lipid carriers (NLCs) by the hot microemulsion method using sonication following a homogenization technique.

RESULTS

After the optimization process, VRS-loaded NLCs (VRS-NLCs) were obtained as ideal quality nanoparticles with a spherical shape, small size (∼150 nm), negative charge (∼-22 mV), and narrow size distribution. In addition, the high entrapment efficiency (∼99%) and sustained drug release profile were recorded. Cytotoxicity study in three different cell lines (A549, MCF-7, and SCC-7) demonstrated higher cytotoxicity of VRS-NLCs than free drug. Finally, the AUC of VRS (118.16 ± 17.35 µgh/mL) was enhanced ∼4.4 times compared with that of free drug (27.03 ± 3.25 µgh/mL).

CONCLUSION

These results suggest the potential of NLCs as an oral delivery system for enhancement of cellular uptake, in vitro cytotoxicity in cancer cell lines and the oral bioavailability of VRS.

Development of vorinostat-loaded solid lipid nanoparticles to enhance pharmacokinetics and efficacy against multidrug-resistant cancer cells

PURPOSE

To investigate whether delivery of a histone deacetylase inhibitor, vorinostat (VOR), by using solid lipid nanoparticles (SLNs) enhanced its bioavailability and effects on multidrug-resistant cancer cells.

METHODS

VOR-loaded SLNs (VOR-SLNs) were prepared by hot homogenization using an emulsification-sonication technique, and the formulation parameters were optimized. The cytotoxicity of the optimized formulation was evaluated in cancer cell lines (MCF-7, A549, and MDA-MB-231), and pharmacokinetic parameters were examined following oral and intravenous (IV) administration to rats.

RESULTS

VOR-SLNs were spherical, with a narrowly distributed average size of ~100 nm, and were physically stable for 3 months. Drug release showed a typical bi-phasic pattern in vitro, and was independent of pH. VOR-SLNs were more cytotoxic than the free drug in both sensitive (MCF-7 and A549) and resistant (MDA-MB-231) cancer cells. Importantly, SLN formulations showed prominent cytotoxicity in MDA-MB-231 cells at low doses, suggesting an ability to effectively counter the P-glycoprotein-related drug efflux pumps. Pharmacokinetic studies clearly demonstrated that VOR-SLNs markedly improved VOR plasma circulation time and decreased its elimination rate constant. The areas under the VOR concentration-time curve produced by oral and IV administration of VOR-SLNs were significantly greater than those produced by free drug administration. These in vivo results clearly highlighted the remarkable potential of SLNs to augment the bioavailability of VOR.

CONCLUSIONS

VOR-SLNs successfully enhanced the oral bioavailability, circulation half-life, and chemotherapeutic potential of VOR.

Toxicological and metabolic considerations for histone deacetylase inhibitors

INTRODUCTION

Vorinostat and romidepsin were the first histone deacetylase (HDAC) inhibitors (HDi) that fulfilled the preclinical promise of anticancer potential in clinical trials. Nevertheless, they merely opened a new chapter in the history of cancer therapy. Demonstration of their antitumor activity was a straightforward task in in vitro setting. Proving their efficacy in vivo was much more difficult, since the effects of an administrated drug strongly depend on its absorption, distribution, metabolism and excretion.

AREAS COVERED

This article summarizes clinical data on the pharmacokinetic properties of HDi that are currently at more advanced stages of clinical development. Specific attention is paid to the metabolic pathways. Moreover, a comprehensive overview of HDi-related adverse effects is given.

EXPERT OPINION

At this moment, HDi form one of the most interesting classes of therapeutics, yet their efficacy and safety profiles could still be improved by i) designing better formulations, ii) more extensive characterization of their disposition at the preclinical stage, iii) targeting of individual disease-related deacetylase isoforms and/or their complexes, iv) selecting a target patient population with the highest probability of response based on molecular signatures.

Vorinostat with sustained exposure and high solubility in poly(ethylene glycol)-b-poly(DL-lactic acid) micelle nanocarriers: characterization and effects on pharmacokinetics in rat serum and urine

The histone deacetylase inhibitor suberoylanilide hydroxamic acid, known as vorinostat, is a promising anticancer drug with a unique mode of action; however, it is plagued by low water solubility, low permeability, and suboptimal pharmacokinetics. In this study, poly(ethylene glycol)-b-poly(DL-lactic acid) (PEG-b-PLA) micelles of vorinostat were developed. Vorinostat's pharmacokinetics in rats was investigated after intravenous (i.v.) (10 mg/kg) and oral (p.o.) (50 mg/kg) micellar administrations and compared with a conventional polyethylene glycol 400 solution and methylcellulose suspension. The micelles increased the aqueous solubility of vorinostat from 0.2 to 8.15 ± 0.60 and 10.24 ± 0.92 mg/mL at drug to nanocarrier ratios of 1:10 and 1:15, respectively. Micelles had nanoscopic mean diameters of 75.67 ± 7.57 and 87.33 ± 8.62 nm for 1:10 and 1:15 micelles, respectively, with drug loading capacities of 9.93 ± 0.21% and 6.91 ± 1.19%, and encapsulation efficiencies of 42.74 ± 1.67% and 73.29 ± 4.78%, respectively. The micelles provided sustained exposure and improved pharmacokinetics characterized by a significant increase in serum half-life, area under curve, and mean residence time. The micelles reduced vorinostat clearance particularly after i.v. dosing. Thus, PEG-b-PLA micelles significantly improved the p.o. and i.v. pharmacokinetics and bioavailability of vorinostat, which warrants further investigation.

Discovery and extensive in vitro evaluations of NK-HDAC-1: a chiral histone deacetylase inhibitor as a promising lead

Herein, further SAR studies of lead compound NSC746457 (Shen, J.; Woodward, R.; Kedenburg, J. P.; Liu, X. W.; Chen, M.; Fang, L. Y.; Sun; D. X.; Wang. P. G. J. Med. Chem. 2008, 51, 7417-7427) were performed, including the replacement of the trans-styryl moiety with a 2-substituted benzo-hetero aromatic ring and the introduction of a substituent onto the central methylene carbon. A promising chiral lead, S-(E)-3-(1-(1-(benzo[d]oxazol-2-yl)-2-methylpropyl)-1H-1,2,3-triazol-4-yl)-N-hydroxyacrylamide (12, NK-HDAC-1), was discovered and showed about 1 order of magnitude more potency than SAHA in both enzymatic and cellular assays. For the in vitro safety tests, NK-HDAC-1 was far less toxic to nontransformed cells than tumor cells and showed no significant inhibition activity against CYP-3A4. The pharmaceutical properties (LogD, solubility, liver micrsomal stability (t1/2), plasma stability (t1/2), and apparent permeability) strongly suggested that NK-HDAC-1 might be superior to SAHA in bioavailability and in vivo half-life.