Safety of parenteral hydroxypropyl beta-cyclodextrin

The counteracting influence of 2-hydroxypropyl substitution and the presence of a guest molecule on the shape and size of the β-cyclodextrin cavity

The aqueous solubility of β-cyclodextrin (β-CD), a cyclic carbohydrate comprising seven α-D-glucose molecules, is enhanced by 2-hydroxypropyl (2-HP) substitution of the hydroxyl groups at the CD rims. Our thorough analysis of the structural and solvation properties with different degrees of 2-hydroxypropyl substitution on β-CD using molecular dynamics simulations reveals that the solubility is enhanced at the cost of the structural distortion of the CD cyclic structure. Substitution at the secondary rim predominantly enhances the favourable interactions between CD and water by decreasing CD-CD hydrogen bonding and promoting CD-water hydrogen bonding. However, the effect of substitution at the primary rim on the CD-water interactions is minimal; the hydrogen bonds between water and the primary hydroxyl group in native CD merely get replaced by those between water and 2-HP, since the substitution makes the primary hydroxyl oxygen (O6 atom) inaccessible to water. In contrast, substitution at the primary rim maintains the structural integrity of CD, while substitution at the secondary rim results in structural distortion due to the disruption of the intramolecular hydrogen bond belt, even leading to cavity closure. Certain strategic substitutions of the primary hydroxyl groups can help in the reduction of structural distortion, depending upon the degree of substitution at the secondary hydroxyl rim. A detailed inspection of the simulation trajectory revealed that the tilting of glucose units with the primary hydroxyl oxygen (O6) pointing inward is the primary driver for cavity closure. Even though the dynamics of glucose tilting can influence the kinetics of host-guest complex formation, once the guest is well incorporated into the cavity, glucose tilting is inhibited and the cavity opens up as in native β-CD.

HP-β-CD for the formulation of IgG and Ig-based biotherapeutics

The main challenge to develop HCF for IgG and Ig-based therapeutics is to achieve essential solubility, viscosity and stability of these molecules in order to maintain product quality and meet regulatory requirement during manufacturing, production, storage, shipment and administration processes. The commonly used and FDA approved excipients for IgG and Ig -based therapeutics may no longer fulfil the challenge of HCF development for these molecules to certain extent, especially for some complex Ig-based platforms. 2-Hydroxypropyl beta-cyclodextrin (HP-β-CD) is one of the promising excipients applied recently for HCF development of IgG and Ig-based therapeutics although it has been used for formulation of small synthesized chemical drugs for more than thirty years. This review describes essential aspects about application of HP-β-CD as excipient in pharmaceutical formulation, including physico-chemical properties of HP-β-CD, supply chain, regulatory, patent landscape, marketed drugs with HP-β-CD, analytics and analytical challenges, stability and control strategies, and safety concerns. It also provides an overview of different studies, and outcomes thereof, regarding formulation development for IgGs and Ig-based molecules in liquid and solid (lyophilized) dosage forms with HP-β-CD. The review specifically highlights the challenges for formulation manufacturing of IgG and Ig-based therapeutics with HP-β-CD and identifies areas for future work in pharmaceutical and formulation development.

Technological evolution of cyclodextrins in the pharmaceutical field

We herein disclose how global cyclodextrin-based pharmaceutical technologies have evolved since the early 80s through a 1998 patents dataset retrieved from Derwent Innovation Index. We used text-mining techniques based on the patents semantic content to extract the knowledge contained therein, to analyze technologies related to the principal attributes of CDs: solubility, stability, and taste-masking enhancement. The majority of CDs pharmaceutical technologies are directed toward parenteral aqueous solutions. The development of oral and ocular formulations is rapidly growing, while technologies for nasal and pulmonary routes are emerging and seem to be promising. Formulations for topical, transdermal, vaginal, and rectal routes do not account for a high number of patents, but they may be hiding a great potential, representing opportunity research areas. Certainly, the progress in materials sciences, supramolecular chemistry, and nanotechnology, will influence the trend of that, apparently neglected, research. The bottom line, CDs pharmaceutical technologies are still increasing, and this trend is expected to continue in the coming years.

Patent monitoring allows the identification of relevant technologies and trends to prioritize research, development, and investment in both, academia and industry. We expect the scope of this approach to be applied in the pharmaceutical field beyond CDs technological applications.

MEF2D haploinsufficiency downregulates the NRF2 pathway and renders photoreceptors susceptible to light-induced oxidative stress

Gaining mechanistic insight into interaction between causative factors of complex multifactorial diseases involving photoreceptor damage might aid in devising effective therapies. Oxidative stress is one of the potential unifying mechanisms for interplay between genetic and environmental factors that contribute to photoreceptor pathology. Interestingly, the transcription factor myocyte enhancer factor 2d (MEF2D) is known to be important in photoreceptor survival, as knockout of this transcription factor results in loss of photoreceptors in mice. Here, using a mild light-induced retinal degeneration model, we show that the diminished MEF2D transcriptional activity in Mef2d^+/- retina is further reduced under photostimulation-induced oxidative stress. Reactive oxygen species cause an aberrant redox modification on MEF2D, consequently inhibiting transcription of its downstream target, nuclear factor (erythroid-derived 2)-like 2 (NRF2). NRF2 is a master regulator of phase II antiinflammatory and antioxidant gene expression. In the Mef2d heterozygous mouse retina, NRF2 is not up-regulated to a normal degree in the face of light-induced oxidative stress, contributing to accelerated photoreceptor cell death. Furthermore, to combat this injury, we found that activation of the endogenous NRF2 pathway using proelectrophilic drugs rescues photoreceptors from photo-induced oxidative stress and may therefore represent a viable treatment for oxidative stress-induced photoreceptor degeneration, which is thought to contribute to some forms of retinitis pigmentosa and age-related macular degeneration.

Comparison in toxicity and solubilizing capacity of hydroxypropyl-β-cyclodextrin with different degree of substitution

Hydroxypropyl-β-cyclodextrin (HP-β-CD) has been widely used as an effective solubilizing agent in pharmaceutical industry for many years. However, the effect of degree of substitution (D.S.) of HP-β-CD on solubilizing capacity and toxicity has not been concerned. In this study, solubilizing capacity of HP-β-CDs with three different D.S. (4.55, 6.16 and 7.76) for 16 drugs were measured and their toxicities were compared by a 7-day i.v. administration (q.d.) study in rats. Generally, HP-β-CD with high D.S. (7.76) showed weaker solubilizing capacity for steroids and BCS class II drugs, but lower hemolytic activity, compared with that of HP-β-CD with low (4.55) or medium (6.16) D.S. HP-β-CD with low D.S. resulted in more changes in hematological and biochemical parameters, but the effects were reversible after a 7-day recovery. Moreover, HP-β-CD with medium D.S. may have slightly greater nephrotoxicity than the other two HP-β-CDs. HP-β-CDs with different D.S. had similar urine excretion percentage after i.v. administration and none of them was found to affect glomerular filtration function of rats. The results suggest that HP-β-CD with low D.S. would be a better choice considering both the solubilizing capacity and toxicity. However, comparison in toxicity of HP-β-CDs with different D.S. should be carried out in human in view of its species-dependence property.

Current controversies in Niemann-Pick C1 disease: steroids or gangliosides; neurons or neurons and glia

There has been a recent explosion in research on Niemann-Pick type C disease. Much of the work has used mouse models or cells in culture to elucidate the pathophysiological mechanisms resulting in the phenotype of the disease. This work has generated several contrasting views on the mechanism, which are labeled 'controversies' here. In this review, two of these controversies are explored. The first concerns which stored materials are causative in the disease: cholesterol, gangliosides and sphingolipids, or something else? The second concerns which cells in the body require Npc1 in order to function properly: somatic cells, neurons only, or neurons and glia? For the first controversy, a clear answer has emerged. More research will be needed in order to definitively solve the second controversy.

Pulmonary function and pathology in hydroxypropyl-beta-cyclodextin-treated and untreated Npc1⁻/⁻ mice

Lung dysfunction is an important part of the pathology of the neurodegenerative disorder, Niemann-Pick C1 (NPC1). We have studied the pulmonary disease in the Npc1(NIH/NIH) mouse model. On histology, we find large numbers of alveolar foamy macrophages but no alveolar proteinosis. Lung weight as percent of body weight was markedly increased; using the flexiVent small animal ventilator (SCIREQ, Inc.), we find inspiratory capacity, elastance and hysterisivity to be increased while resistance was not changed. Cholesterol measurements show a doubling of lung cholesterol levels. Collagen is also increased. Treatment of Npc1(-/-) mice with hydroxypropyl-β-cyclodextrin (HPBCD), despite efficacious effects in brain and liver, results in little difference from age-matched controls (using a CNS-expressed transgene to extend the life expectancy of the Npc1(-/-) mice) for these variables.

Upregulation of endogenous neurotrophin levels in the brain by intranasal administration of carnosic acid

The potential of intranasally administered carnosic acid to enhance the endogenous levels of neurotrophins [nerve growth factor and brain-derived neurotrophic factor] in the brain was investigated. Hydroxypropyl-β-cyclodextrin (HP-β-CD) was used to enhance the aqueous solubility of carnosic acid. The effect of different concentrations of chitosan on the permeation of carnosic acid was investigated across the bovine olfactory mucosa using Franz diffusion cell setup. The formulations were administered [intranasal (i.n.)/subcutaneous route] in Sprague-Dawley rats, and the neurotrophins were sampled from the brain by microdialysis after the treatment period and measured by enzyme-linked immunosorbent assay. Phase solubility studies revealed that the solubility of carnosic acid was enhanced significantly with increase in the concentration of HP-β-CD. The neurotrophin levels were enhanced significantly upon i.n. administration of carnosic acid with chitosan, which was approximately 1.5-2-fold more over the parenteral route. Nose-to-brain delivery of carnosic acid along with chitosan is a potential approach for treating disorders associated with depletion of neurotrophins.

Review of the basic and clinical pharmacology of sulfobutylether-beta-cyclodextrin (SBECD)

Despite its use in commercially available drugs such as intravenous voriconazole, there is little known in the medical literature about the clinical pharmacology of the solubilizing agent, sulfobutylether-beta-cyclodextrin (SBECD). This paper summarizes all known data on SBECD pharmacokinetics and safety. In animals, volume of distribution approximates extracellular water volume and clearance is determined by the glomerular filtration rate. SBECD does not have any apparent effects on cardiovascular or respiratory systems, nor on autonomic and somatic functions in animals. In 1- and 6-month studies in rats and dogs, the most noteworthy findings were renal tubular vacuolation and foamy macrophages in the liver and lungs. Mild toxicity in the kidney and liver as a consequence of vacuolation occurred in rats at the maximum dose of 3000 mg/kg, which is approximately 50-fold greater than the SBECD dose typically administered in man. Doses up to 1500 mg/kg produced no histopathological evidence of toxicity in dog kidneys. SBECD has also been studied in healthy volunteers and subjects with renal dysfunction. Whereas plasma SBECD levels accumulate in those with renal compromise, there were no deleterious effects on renal function. Nonetheless, serum creatinine levels should be monitored in subjects with renal compromise receiving multiple doses of SBECD.

Cyclodextrins

beta-cyclodextrin (beta-CD) and other cyclodextrins (CDs) have utility for solubilizing and stabilizing drugs; however, some are nephrotoxic when administered parenterally. A number of workers have attempted to identify, prepare, and evaluate various CD derivatives with superior inclusion complexation and maximal in vivo safety for various biomedical uses. A systematic study led to SBE-beta-CD (Captisol), a polyanionic variably substituted sulfobutyl ether of beta-CD, as a non-nephrotoxic derivative and HP-beta-CD, a modified CD developed by Janssen. SBE-beta-CD and HP-beta-CD have undergone extensive safety studies and are currently used in six products approved by the Food and Drug Administration (four for Captisol and two for HP-beta-CD). They are also in use in numerous clinical and preclinical studies. This article will focus on the issues that led to the development of these two CDs, their safety, characterization, and applications, and especially their ability to improve drug delivery. SBE-beta-CD interacts very well with neutral drugs to facilitate solubility and chemical stability, and because of its polyanionic nature, it interacts particularly well with cationic drugs. Complexes between SBE-beta-CD and HP-beta-CD and various drugs have been shown to rapidly dissociate after parenteral drug administration, to have no tissue-irritating effects after intramuscular dosing, and to result in superior oral bioavailability of poorly water-soluble drugs. The pharmacokinetics, tissue distribution, and cellular effects of some representative CDs, including SBE-beta-CD and HP-beta-CD, are reviewed. The safety profiles of CDs are discussed, with emphasis on the biological effects of some CDs on the gastrointestinal tract, kidney, and reproduction and development and the carcinogenic potential of CDs. In addition, human experience with CD derivatives, specifically SBE-beta-CD and HP-beta-CD, indicates that these two CDs are well tolerated in humans and have no adverse effects on the kidneys or other organs following either oral or intravenous administration.

The anticancer activity of the transcription inhibitor terameprocol (meso-tetra-O-methyl nordihydroguaiaretic acid) formulated for systemic administration

Terameprocol (meso-tetra-O-methyl nordihydroguaiaretic acid, formerly known as EM-1421 and M4N) is a semi-synthetic small molecule with antitumor activity occurring via selective targeting of Sp1-regulated proteins, including survivin and cdc2 that control cell cycle and apoptosis. Terameprocol is in clinical development as a site-specific transcription inhibitor in solid refractory tumors. The present studies were designed to investigate the in-vitro and in-vivo anticancer activity of terameprocol in a novel hydroxypropyl beta-cyclodextrin and polyethylene glycol solvent formulation (designated CPE) designed for safe parenteral administration. Terameprocol powder was dissolved in CPE (20% hydroxypropyl beta-cyclodextrin and 50% polyethylene glycol 300 or 30% hydroxypropyl beta-cyclodextrin and 25% polyethylene glycol 300) or dimethyl sulfoxide and used for in-vitro cell proliferation assays, and in human carcinoma xenograft studies using female athymic nude mice injected with SW-780 human bladder cells. Terameprocol (50 and 100 mg/kg), paclitaxel (5 mg/kg), terameprocol and paclitaxel or vehicle was administered intraperitoneally daily for 21 days. Stock solutions of the CPE formulation were stable for up to 12 months. Terameprocol CPE formulation showed concentration-dependent inhibition of HeLa and C33A cell proliferation, and was less toxic than terameprocol dimethyl sulfoxide formulation. The terameprocol CPE formulation showed no overt toxicities in tumor-bearing mice. Terameprocol alone reduced the rate of tumor growth, and a combination of terameprocol/paclitaxel reduced both the rate and extent of tumor growth. These preclinical results confirm the tumoricidal activity of terameprocol formulated in a solvent suitable for parenteral administration and suggest that terameprocol has improved efficacy when coadministered with paclitaxel.

Phase I trial of phenoxodiol delivered by continuous intravenous infusion in patients with solid cancer

BACKGROUND

Phenoxodiol is a multi-pathway initiator of apoptosis with broad anti-tumor activity and high specificity for tumor cells. Its biochemical effects are particularly suited to reversal of chemo-resistance, and the drug is being developed as a chemo-sensitizer of standard chemotherapeutics in solid cancers. This phase I, single-center trial was conducted to test a continuous intravenous dosing regimen of phenoxodiol in patients with late-stage, solid tumors to determine toxicity, pharmacokinetics, and preliminary efficacy.

METHODS

Phenoxodiol given by intravenous infusion continuously for 7 days on 14-day cycles was dose-escalated on an inter-patient basis at dosages of 0.65,1.3, 3.3, 20.0, and 27.0 mg/kg/day (three to four patients per stratum). Treatment cycles continued until disease progression. Toxicity was based on standard criteria; efficacy was based on changes in tumor burden (WHO); pharmacokinetic analysis was conducted on plasma samples at specified time points during treatment cycles.

RESULTS

Nineteen heavily-pre-treated patients with solid tumors received a median of three cycles of treatment (range 1-13); two patients received >or= 12 cycles. No dose-limiting toxicities were encountered, with emesis and fatigue (one patient) and rash (one patient) the only significant toxicities. Stabilized disease was the best efficacy outcome, with one patient showing stable disease at 24 weeks. Pharmacokinetics suggested a linear relationship between dosage and mean steady-state plasma concentrations of phenoxodiol.

CONCLUSION

A 7-day continuous infusion of phenoxodiol given every 2 weeks is well tolerated up to a dose of 27.0 mg/kg/day.

Phase I and pharmacokinetic study of weekly NV06 (Phenoxodiol), a novel isoflav-3-ene, in patients with advanced cancer

BACKGROUND

We wished to define the maximum tolerated dose (MTD), toxicity, and pharmacokinetics of the novel isoflav-3-ene, NV06 (Phenoxodioltrade mark), a compound with a diphenolic structure related chemically and biologically to genistein and flavopiridol.

PATIENTS AND METHODS

Twenty-one patients with advanced cancers were treated with weekly intravenous administration of NV06 at escalating dose levels with 1-4 patients at each dose cohort. Plasma sampling was undertaken to characterize the pharmacokinetic (PK) profile of the compound.

RESULTS

Toxicity was minimal, with asymptomatic Grade 3 lymphocytopenia occurring in nine patients. Nine patients developed Grade 1 nausea, six patients developed Grade 1 increases in alkaline phosphatase, and six patients developed Grade 1 increases in transaminases. Two patients experienced hypersensitivity reactions. The MTD was not reached. Most patients had progressive disease on treatment but eight completed 12 weeks and two completed 24 weeks of treatment. The best response was stable disease of 6 months duration. The plasma half-life (T1/2), clearance (Cl), and volume of distribution (VD) were 304 (+/-91) min, 82 (+/-19) ml/min and 32,663 (+/-7,199) ml, respectively, for total NV06.

CONCLUSIONS

NV06 is well tolerated and can be given safely as an intravenous infusion over 1-2 h at a dose of at least 30 mg/kg.

Preparation of prostaglandin E1-hydroxypropyl-β-cyclodextrin complex and its nasal delivery in rats

The potential use of hydroxypropyl-beta-cyclodextrin (HP-betaCD) in the solubilization and stabilization of prostaglandin E(1) (PGE(1)) was investigated. The solubility and chemical stability of PGE(1) were significantly improved upon complexation with HP-betaCD. The nasal delivery of PGE(1) from the complex formulation was also studied in Wistar rats and compared with intravenous administration. PGE(1) complex after nasal administration caused a rapid decrease of blood pressure and exhibited an obvious dose-efficacy relationship, showing results nearly similar to those obtained for intravenous route. The time to reach the peak effect (T(max)) was approximately 3-4 min. Except T(max), other pharmacodynamic parameter values such as the maximal percent of blood pressure decrease (E(max), %), the lasting time of effect (T(d)), and the area under the curve (AUC, blood pressure decrease % min) were increased with increasing the administered doses. The E(max), T(d), and in particular AUC values between doses were significantly different (P < 0.01), but T(max) between doses were not significantly different (P < 0.05). The AUC values per unit dose of PGE(1) for nasal administration, however, were smaller than those for intravenous route, probably due to the incomplete absorption of nasally administered PGE(1). Besides, the in vitro effect of the PGE(1) complex on nasal mucociliary movement was also investigated with a toad palate model. The PGE(1) complex formulation exerted only minor effect on nasal mucociliary movement. These results indicate that the PGE(1)-HP-betaCD complex formulation for nasal delivery is a very promising preparation with advantages such as rapid and effective absorption, good chemical stability, ease of administration, and minor nasal ciliotoxicity.

Cyclodextrins and oligonucleotide delivery to solid tumours

Cyclodextrins (CyDs) have traditionally been used for dissolving hydrophobic chemicals into aqueous media, and more recently, for inducing cholesterol efflux from lipid-laden cells as a proposed mechanism for reversal of cardiovascular disease. This review discusses the potential of delivering therapeutic oligonucleotides to solid tumours using CyD molecules. The physicochemical properties of these oligosaccharide molecules, and the barriers posed by the solid tumour itself, factors that affect may affect the uptake of oligonucleotides by CyDs, are the major foci of this review.

Vehicles for oligonucleotide delivery to tumours

The vasculature of a tumour provides the most effective route by which neoplastic cells may be reached and eradicated by drugs. The fact that a tumour's vasculature is relatively more permeable than healthy host tissue should enable selective delivery of drugs to tumour tissue. Such delivery is relevant to carrier-mediated delivery of genetic medicine to tumours. This review discusses the potential of delivering therapeutic oligonucleotides (ONs) to tumours using cationic liposomes and cyclodextrins (CyDs), and the major hindrances posed by the tumour itself on such delivery. Cationic liposomes are generally 100-200 nm in diameter, whereas CyDs typically span 1.5 nm across. Cationic liposomes have been used for the introduction of nucleic acids into mammalian cells for more than a decade. CyD molecules are routinely used as agents that engender cholesterol efflux from lipid-laden cells, thus having an efficacious potential in the management of atherosclerosis. A recent trend is to employ these oligosaccharide molecules for delivering nucleic acids in cells both in-vitro and in-vivo. Comparisons are made with other ON delivery agents, such as porphyrin derivatives (< 1 nm), branched chain dendrimers (approximately 10 nm), polyethylenimine polymers (approximately 10 nm), nanoparticles (20-1,000 nm) and microspheres (> 1 microm), in the context of delivery to solid tumours. A discourse on how the chemical and physical properties of these carriers may affect the uptake of ONs into cells, particularly in-vivo, forms a major basis of this review.

BTS 72664-- a novel CNS drug with potential anticonvulsant, neuroprotective, and antimigraine properties

BTS 72664, (R)-7-[1-(4-chlorophenoxy)]ethyl]-1,2,4-triazolo(1,5-alpha)pyrimidine, was identified as a drug development candidate from a research program designed to discover novel, broad-spectrum, non-sedative anticonvulsant drugs. BTS 72664 antagonized bicuculline (BIC)- and maximal electroshock (MES)-induced convulsions with ED(50) values of 1.9 and 47.5 mg/kg p.o., respectively. In rodents, it has a wide spectrum of activity preventing seizures induced by picrotoxin, pentylenetetrazol, i.c.v. 4-aminopyridine or NMDA, and audiogenic seizures in DBA-2 mice and GEPR-9 rats. BTS 72664 was also effective in preventing convulsions in amygdala-kindled rats The lack of sedative potential was predicted on the basis of wide separation between ED(50) in anticonvulsant models and TD(50) for motor impairment in mice in rotating rod and inverted horizontal grid tests. BTS 72664 is likely to produce its anticonvulsant effect by enhancing chloride currents through picrotoxin-sensitive chloride channels, and by weak inhibition of Na(+) and NMDA channels. It does not act, however, at the benzodiazepine binding site. In addition to its potential use in the treatment of epilepsy BTS 72664 may be useful in the treatment of stroke. At 50 mg/kg p.o. x 4, given to rats at 12 hourly intervals, starting at 15 min after permanent occlusion of middle cerebral artery (MCA), it reduced cerebral infarct size by 31% (measured at 2 days after insult) and accelerated recovery in a functional behavioral model. BTS 72664 prevented increases in extraneuronal concentrations of glutamate, glycine and serine brain levels induced by a cortical insult to rats (cf. cortical spreading depression). It may, therefore, have also antimigraine activity.

Apolipoprotein A-I, cyclodextrins and liposomes as potential drugs for the reversal of atherosclerosis. A review

Several studies have revealed that high-density lipoprotein (HDL) is the most reliable predictor for susceptibility to cardiovascular disease. Since apolipoprotein A-I (apoA-I) is the major protein of HDL, it is worthwhile evaluating the potential of this protein to reduce the lipid burden of lesions observed in the clinic. Indeed, apoA-I is used extensively in cell culture to induce cholesterol efflux. However, while there is a large body of data emanating from in-vitro and cell-culture studies with apoA-I, little animal data and scant clinical trials examining the potential of this apolipoprotein to induce cholesterol (and other lipid) efflux exists. Importantly, the effects of oxysterols, such as 7-ketocholesterol (7KC), on cholesterol and other lipid efflux by apoA-I needs to be investigated in any attempt to utilise apoA-I as an agent to stimulate efflux of lipids. Lessons may be learnt from studies with other lipid acceptors such as cyclodextrins and phospholipid vesicles (PLVs, liposomes), by combination with other effluxing agents, by remodelling the protein structure of the apolipoprotein, or by altering the composition of the lipoprotein intended for administration in-vivo. Akin to any other drug, the usage of this apolipoprotein in a therapeutic context has to follow the traditional sequence of events, namely an evaluation of the biodistribution, safety and dose-response of the protein in animal trials in advance of clinical trials. Mass production of the apolipoprotein is now a simple process due to the advent of recombinant DNA technology. This review also considers the potential of cyclodextrins and PLVs for use in inducing reverse cholesterol transport in-vivo. Finally, the potential of cyclodextrins as delivery agents for nucleic acid-based constructs such as oligonucleotides and plasmids is discussed.

Apolipoprotein A-I, phospholipid vesicles, and cyclodextrins as potential anti-atherosclerotic drugs: delivery, pharmacokinetics, and efficacy

High-density lipoprotein (HDL) is a reliable predictor for susceptibility to cardiovascular disease. Since apolipoprotein A-I (apoA-I) is the major protein of HDL, it is worthwhile to evaluate the potential of this protein to reduce the lipid burden of lesions observed in the clinic. While a large body of data emanates from in vitro and cell culture studies with apoA-I, few animal and lesser clinical trials examining the potential of this apolipoprotein to induce cholesterol (and other lipid) efflux exist. Lessons may be learned from studies with other lipid acceptors such as phospholipid vesicles (PLVs, liposomes) and cyclodextrins (CDs). Additionally, the combination of apoA-I with other effluxing agents, alteration of the composition of the lipoprotein, or a remodeling of the protein structure of the apolipoprotein to be administered in vivo may result in increased efficacy. The usage of this apolipoprotein in a therapeutic context has to follow the conventional sequence of events: an evaluation of the biodistribution, safety, and dose-response of the protein in animal trials before clinical trials. The review also considers the potential of cyclodextrins and PLVs to induce reverse cholesterol transport in vivo and discusses the potential of CDs as delivery agents for genetic constructs, such as plasmids and oligonucleotides.

Complexation of the interferon inducer, bropirimine, with hydroxypropyl-beta-cyclodextrin

Bropirimine (ABPP) is an orally active immunomodulator that increases endogenous alpha-interferon and other cytokines used clinically against carcinoma in situ of the bladder. The oral absorption of ABPP is poor because its low solubility in water. The purpose of this study is to develop a technological procedure useful to increase the water solubility of ABPP. To this end, the interaction of ABPP with several cyclodextrin derivatives-alpha-, beta-, gamma- and hydroxypropyl-beta-cyclodextrin with a degree of substitution 2.7 (HPbetaCD) was studied and the effect of the complexation process on the water solubility of the drug was evaluated. The best results were obtained with the hydroxypropyl derivative, HPbetaCD, that interacts in a 1:1 drug:cyclodextrin molar ratio. The inclusion complex ABPP-HPbetaCD was characterized in solution by nuclear magnetic resonance (1H-NMR). The solid inclusion complex was obtained by freeze-drying and characterized by differential scanning calorimetry (DSC), X-ray diffractometry and mass spectrometry. The dissolution rate of ABPP from the HPbetaCD solid inclusion complex was increased compared to the powdered drug but not differences were found between the complex and a physical mixture with a similar molar ratio. The increase of the dissolution rate of the drug can be attributed to the breakdown in solution of the drug dimers in the presence of the cyclodextrin and to the complex formation.

Characterization of an inclusion complex of cholesterol and hydroxypropyl-beta-cyclodextrin

Interactions between endogenous cholesterol and cyclodextrins have been investigated by several researchers, and they found altered skin penetration of some drugs, membrane disruption, and extraction of cholesterol from the large lipoprotein particles or animal fat. In the present study, an inclusion complex composed of cholesterol and hydroxypropyl-beta-cyclodextrin (HPbetaCD) prepared by lyophilization was investigated and characterized in order to confirm these interactions. Five grams of cholesterol were dispersed in 50 ml of 73.2 mM HPbetaCD aqueous solution, mixed for 2 days, and the filtrate lyophilized. A phase solubility study was performed by mixing an excess amount of cholesterol with an aqueous solution containing increasing amounts of HPbetaCD. The amount of cholesterol in solution after mixing for 2 days at 25 degrees C was determined by HPLC. The inclusion complex was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry, and differential scanning calorimetry (DSC). An Ap-type Higuchi phase solubility diagram, DSC, FTIR, and X-ray diffraction demonstrated the formation of an inclusion complex. DSC thermograms indicated that the endothermic peaks of cholesterol and physical mixture of cholesterol with HPbetaCD due to the fusion of drug crystals, were absent in DSC thermograms obtained on the freeze dried inclusion complex. FTIR spectra indicated that some of the absorption peaks in the lyophilized inclusion complex were different from that of the physical mixture of cholesterol and HPbetaCD. X-ray diffraction patterns showed that the pure cholesterol and a physical mixture of cholesterol and HPbetaCD exhibited crystalline characteristics whereas the lyophilized inclusion complex and HPbetaCD displayed amorphous characteristics. The results indicated that the formation of a cholesterol/HPbetaCD inclusion complex is more water soluble than cholesterol alone.

Pharmacokinetics of the protease inhibitor KNI-272 in plasma and cerebrospinal fluid in nonhuman primates after intravenous dosing and in human immunodeficiency virus-infected children after intravenous and oral dosing

KNI-272 is a human immunodeficiency virus (HIV) protease inhibitor with potent activity in vitro. We studied the pharmacokinetics of KNI-272 in the plasma and cerebrospinal fluid (CSF) of a nonhuman primate model and after intravenous and oral administration to children with HIV infection. Plasma and CSF were sampled over 24 h after the administration of an intravenous dose of 50 mg of KNI-272 per kg of body weight (approximately 1,000 mg/m2) to three nonhuman primates. The pharmacokinetics of KNI-272 were also studied in 18 children (9 males and 9 females; median age, 9.4 years) enrolled in a phase I trial of four dose levels of KNI-272 (100, 200, 330, and 500 mg/m2 per dose given four times daily). The plasma concentration-time profile of KNI-272 in the nonhuman primate model was characterized by considerable interanimal variability and rapid elimination (clearance, 2.5 liters/h/kg; terminal half-life, 0.54 h). The level of drug exposure achieved in CSF, as measured by the area under the KNI-272 concentration-time curve, was only 1% of that achieved in plasma. The pharmacokinetics of KNI-272 in children were characterized by rapid elimination (clearance, 276 ml/min/m2; terminal half-life, 0.44 h), limited (12%) and apparently saturable bioavailability, and limited distribution (volume of distribution at steady state, 0.11 liter/kg). The concentrations in plasma were maintained above a concentration that is active in vitro for less than half of the 6-h dosing interval. There was no significant increase in CD4 cell counts or decrease in p24 antigen or HIV RNA levels. The pharmacokinetic profile of KNI-272 may limit the drug's efficacy in vivo. It appears that KNI-272 will play a limited role in the treatment of HIV-infected children.

Subchronic intravenous toxicity studies with gamma-cyclodextrin in rats

The toxicity of gamma-cyclodextrin (gamma-CD), a cyclic polymer of 8 alpha-1,4-linked glucopyranosyl units with potential applications in food and pharmaceutical preparations, was examined in two toxicity studies in rats with intravenous administration of gamma-CD for 1 and 3 months, respectively. Each study comprised four groups of 15 rats/sex each. In the 1-month study, gamma-CD was administered to the four groups at daily doses of 0 (controls), 200, 630, or 2000 mg/kg body wt, respectively. In the 3-month study, dose levels of 0, 60, 120, and 600 mg/kg body wt were tested. gamma-CD was administered by injection of an aqueous solution in the tail vein. At the end of the treatment period, 10 rats/sex/group were killed. The remaining 5 rats continued the study without treatment (recovery period) for 4 weeks (1-month study) or 5 weeks (3-month study). The treatment was generally well tolerated and there were no mortalities in either study. Mean body weights tended to be slightly reduced during the first and second week in the groups receiving gamma-CD at doses of >/=600 mg/kg body wt. Thereafter, body weights did not differ between treated groups and controls. Examination of standard hematological parameters at the end of the treatment period revealed decreased erythrocyte counts, hemoglobin, hematocrit values, and thrombocyte counts in both studies at gamma-CD doses of >/=600 mg/kg body wt. Concomitantly, the relative weight of the spleen was increased. In the high-dose group of the 1-month study, hemoglobin was detected in the urine. It is likely that a direct interaction of the injected gamma-CD with blood cells accounts for these effects. Examination of standard clinicochemical parameters at the end of the treatment period did not reveal any changes that would point to the liver as a target organ for gamma-CD toxicity. This was confirmed by the absence of histopathological changes in the liver. The only noteworthy observation was an increase of serum urea in the high-dose group (either sex) of the 1-month study and in males of the high-dose group of the 3-month study, suggesting a slight impairment of the renal function. On histopathological examination, reabsorptive vacuolation was seen in the renal tubular epithelium of some rats receiving gamma-CD at doses of 630 or 600 mg/kg body wt in the 1- and 3-month study, respectively. In the high-dose group of the 1-month study, all animals exhibited this morphological effect. However, degenerative changes were not observed in the kidneys, and the vacuolation was fully reversible on cessation of the treatment. The occurrence of absorptive vacuolation was attributed to the presence of gamma-CD in urine (parenterally administered gamma-CD is excreted unchanged in the urine). Simple or focal hyperplasia of the urinary bladder epithelium was observed in some animals of the high-dose group of the 3-month study. This hyperplasia was not seen at the end of the recovery period and, therefore, was considered to be a reactive response to the treatment. The most prominent morphological effect was an accumulation of phagocytosing alveolar macrophages (histiocytosis) in the lungs of rats receiving gamma-CD at a dose of >/=600 mg/kg body wt. This effect was associated with an increase of relative lung weights. However, degenerative changes (fibrosis) were not seen, and at the end of the recovery period only some small residual changes were noted in the lungs of a few animals. In conclusion, daily intravenous gamma-CD doses of 120-200 mg/kg body wt were tolerated without adverse effects. The changes observed at higher dose levels (>/=600-630 mg/kg body wt) were reversible on cessation of the treatment and are considered to be biochemical responses, without toxicological relevance, to the presence of transiently high concentrations of gamma-CD in the circulating blood.

Pharmaceutical applications of cyclodextrins. III. Toxicological issues and safety evaluation

The objective of this review is to summarize recent findings on the safety profiles of three natural cyclodextrins (alpha-, beta- and gamma-CDs) and several chemically modified CDs. To demonstrate the potential of CDs in pharmaceutical formulations, their stability against non-enzymatic and enzymatic degradations in various body fluids and tissue homogenates and their pharmacokinetics via parenteral, oral, transmucosal, and dermal routes of administration are outlined. Furthermore, the bioadaptabilities of CDs, including in vitro cellular interactions and in vivo safety profiles, via a variety of administration routes are addressed. Finally, the therapeutic potentials of CDs are discussed on the basis of their ability to interact with various endogenous and exogenous lipophiles or, especially for sulfated CDs, their effects on cellular processes mediated by heparin binding growth factors.

Pharmaceutical applications of cyclodextrins. 2. In vivo drug delivery

The objective of this Review is to summarize and critique recent findings and applications of both unmodified and modified cyclodextrins for in vivo drug delivery. This review focuses on the use of cyclodextrins for parenteral, oral, ophthalmic, and nasal drug delivery. Other routes including dermal, rectal, and pulmonary delivery are also briefly addressed. This Review primarily focuses on newer findings concerning cyclodextrin derivatives which are likely to receive regulatory acceptance due to improved aqueous solubility and safety profiles as compared to the unmodified cyclodextrins. Many of the applications reviewed involve the use of hydroxypropyl-beta-cyclodextrins (HP-beta-CDs) and sulfobutylether-beta-cyclodextrins (SBE-beta-CDs) which show promise of greater safety while maintaining the ability to form inclusion complexes. The advantages and limitations of HP-beta-CD, SBE-beta-CD, and other cyclodextrins are addressed.