Sustained-release Technologies Research Articles

Transgene expression of Stanniocalcin-1 provides sustained intraocular pressure reduction by increasing outflow facility.

Glaucoma is the leading cause of irreversible blindness worldwide. Therapies for glaucoma are directed toward reducing intraocular pressure (IOP), the leading risk factor and only reliable therapeutic target via topical medications or with procedural intervention including laser or surgery. Though topical therapeutics are typically first line, less than 50% of patients take drops as prescribed. Sustained release technologies that decrease IOP for extended periods of time are being examined for clinical use. We recently identified Stanniocalcin-1, a naturally occurring hormone, as an IOP-lowering agent. Here, we show that a single injection into the anterior chamber of mice with an adeno-associated viral vector containing the transgene of stanniocalcin-1 results in diffuse and sustained expression of the protein and produces IOP reduction for up to 6 months. As the treatment effect begins to wane, IOP-lowering can be rescued with a repeat injection. Aqueous humor dynamic studies revealed an increase in outflow facility as the mechanism of action. This first-in-class therapeutic approach has the potential to improve care and reduce the rates of vision loss in the 80 million people worldwide currently affected by glaucoma.

Sustained release of persulfate from inert inorganic materials for groundwater remediation

Groundwater has often been plagued by persistent contaminants such as dense nonaqueous phase liquids (DNAPLs). There is a need for sustained release technologies to ensure long-term treatment in these flow systems. Innovative methods involving sustained release of a selected reagent, persulfate, through pellets made from inorganic materials such as zeolite, diatomite, and silica flour are reported through a proof-of-concept study. Efficacy of the method relies on the preservation of the reagent without decreasing the treatment potential that would otherwise occur with organic matrices. Several methods and different matrix materials for pellet fabrication are described for sustained release of persulfate as a model reagent. Some pellets (diameter: 13 mm; thickness: 2.5–2.7 mm; mass: 0.5 g) show persulfate release of >25 h. Larger pellets are expected to provide longer release times. Different pellet types and fabrication methods offer a range of ease of pellet construction, as well as reagent release times for sustained release. Trichloroethylene (TCE), a DNAPL, was selected as the model contaminant for testing this sustained release approach. Treatment of 15 mg L−1 (ppm) TCE solutions showed 99% degradation, and the pellets remained intact afterwards. The current work demonstrates the potential feasibility of sustained persulfate release from inert matrices for groundwater treatment.

Protein Stability and Photostability under In Vitro Vitreal Conditions - Implications for Long Acting Delivery of Protein Therapeutics for Ocular Disease.

To evaluate the stability of a model Mab1 and Fab1 under in vitro vitreal conditions in the presence of various metabolites and in the presence of light at λ> 400nM. A full length IgG1 monoclonal antibody (Mab1) and a fab fragment (Fab1) were formulated with various metabolites typically found in the vitreous humor and subjected to visible light treatment. Both proteins were analyzed using a variety of biochemical techniques. Furthermore, Fab1 was also tested for antigen binding ability using surface plasmon resonance. Our data shows that some vitreal metabolites such as riboflavin and ascorbic acid affect protein stability, via formation of reactive oxygen species (ROS) and advanced glycation end products (AGE) s respectively. In contrast, metabolites such as glutathione may protect these proteins from light-induced degradation to some extent. Ascorbic acid and riboflavin were found to photosensitize therapeutic proteins especially when exposed to light. Ascorbic acid reacted with proteins even in the absence of light. Antioxidants such as glutathione helped limit photooxidation under ambient or blue light exposure. Since antioxidant capacity in the eye decreases with age we recommend understanding long term stability, including photooxidation and photosensitization, of new candidate proteins in the context of controlled or sustained release technologies for ocular diseases.

Sustained Release Technology and Its Application in Environmental Remediation: A Review.

Sustained release technology is a class of technology characterized by slowly-releasing specific active substances into a target medium to keep a certain concentration in the system within valid time. As a new of type technology, it has been extensively applied to medicine, chemical engineering, agriculture, environmental protection, etc. The principles and classification of sustained release technologies, as well as typical preparation methods of sustained release agents, were summarized in this paper; by introducing applied research progress of sustained release technologies into environmental fields like rainwater purification, sewage/drinking water treatment, and soil and atmosphere remediation, application features of these sustained release technologies were evaluated, and their application prospect in environmental remediation, especially in water treatment, was predicted.

New Generation of Orally Disintegrating Tablets for Sustained Drug Release: A Propitious Outlook.

Orally disintegrating tablets (ODTs) or orodispersible tablets are solid dosage forms that disintegrate within 3 minutes in the mouth into a paste that can be easily swallowed. ODTs have improved over the past years, in an attempt to produce a safe and efficient substitute to the conventional oral dosage forms, particularly for dysphagia patients. Since its introduction in the market in the 1980s, ODTs expanded rapidly and achieved revenues over $3 billion in 2006 and sustaining 20% annual growth. It is therefore evident that ODTs carry good commercial value, however there is potential for improvement. Current sustained-release technologies may be exploited and incorporated into an ODT to provide greater therapeutic value by reducing the need for multiple daily dosing regimens and improving patient adherence. A number of technologies such as polymer coated nanoparticles, stimuli-responsive polymers and ion-exchange resins have emerged to produce robust, sustained release orally disintegrating tablets (SR-ODT). The purpose of this review is to highlight these various approaches and techniques and how they have been utilised in an ODT formulation to extend differentiated line, market exclusivity and patent life. The review also explores future perspective and the potential challenges that SR-ODTs will face.

Exploring drug delivery for the DOT1L inhibitor pinometostat (EPZ-5676): Subcutaneous administration as an alternative to continuous IV infusion, in the pursuit of an epigenetic target

Protein methyltransferases are emerging as promising drug targets for therapeutic intervention in human cancers. Pinometostat (EPZ-5676) is a small molecule inhibitor of the DOT1L enzyme, a histone methyltransferase that methylates lysine 79 of histone H3. DOT1L activity is dysregulated in the pathophysiology of rearranged mixed lineage leukemia (MLL-r). Pinometostat is currently in Phase 1 clinical trials in relapsed refractory acute leukemia patients and is administered as a continuous IV infusion (CIV). The studies herein investigated alternatives to CIV administration of pinometostat to improve patient convenience. Various sustained release technologies were considered, and based on the required dose size as well as practical considerations, subcutaneous (SC) bolus administration of a solution formulation was selected for further evaluation in preclinical studies. SC administration offered improved exposure and complete bioavailability of pinometostat relative to CIV and oral administration. These findings warranted further evaluation in rat xenograft models of MLL-r leukemia. SC dosing in xenograft models demonstrated inhibition of MLL-r tumor growth and inhibition of pharmacodynamic markers of DOT1L activity. However, a dosing frequency of thrice daily (t.i.d) was required in these studies to elicit optimal inhibition of DOT1L target genes and tumor growth inhibition. Development of an extended release formulation may prove useful in the further optimization of the SC delivery of pinometostat, moving towards a more convenient dosing paradigm for patients.

Injectable and implantable sustained release naltrexone in the treatment of opioid addiction

Sustained release technologies for administering the opioid antagonist naltrexone (SRX) have the potential to assist opioid-addicted patients in their efforts to maintain abstinence from heroin and other opioid agonists. Recently, reliable SRX formulations in intramuscular or implantable polymers that release naltrexone for 1-7 months have become available for clinical use and research. This qualitative review of the literature provides an overview of the technologies currently available for SRX and their effectiveness in reducing opioid use and other relevant outcomes. The majority of studies indicate that SRX is effective in reducing heroin use, and the most frequently studied SRX formulations have acceptable adverse events profiles. Registry data indicate a protective effect of SRX on mortality and morbidity. In some studies, SRX also seems to affect other outcomes, such as concomitant substance use, vocational training attendance, needle use, and risk behaviour for blood-borne diseases such as hepatitis or human immunodeficiency virus. There is a general need for more controlled studies, in particular to compare SRX with agonist maintenance treatment, to study combinations of SRX with behavioural interventions, and to study at-risk groups such as prison inmates or opioid-addicted pregnant patients. The literature suggests that sustained release naltrexone is a feasible, safe and effective option for assisting abstinence efforts in opioid addiction.

Industry Update: the Latest Developments in Therapeutic Delivery

The present industry update covers the period 15 August–15 September 2012, with information sourced from company press releases, regulatory and patent agencies as well as scientific literature. The internationally rougher financial climate especially in the EU zone is also affecting investments in the medical drug and device industry including drug-delivery technology providers. Maybe not just coincidentally, one can observe a strive for public funding such as with the University of Liverpool (Liverpool, UK) and Penn State College (PA, USA) and precompetitive public–private partnerships as the recently announced by Capsugel. The first bioabsobable drug-eluting stent from Abbott was approved while successful clinical trials on sustained-release technologies for diabetes (University of Cambridge) and cancer treatment (Hospital Amaral Carvalho, Brazil) were reported.

Colloidal Carriers for Ophthalmic Drug Delivery

To achieve effective drug concentration at the intended site for a sufficient period of time is a requisite desired for many drug formulations. For drugs intended to ocular delivery, its poor bioavailability is due to pre-corneal factors. Most ocular diseases are treated by topical drug application in the form of solution, suspension and ointment. However, such dosage forms are no longer sufficient to combat some ocular diseases. Intravitreal drug injection is the current therapy for disorders in posterior segment. The procedure is associated with a high risk of complications, particularly when frequent, repeated injections are required. Thus, sustained-release technologies are being proposed, and the benefits of using colloidal carriers in intravitreal injections are currently under investigation for posterior drug delivery. This review will discuss recent progress and specific development issues relating to colloidal drug delivery systems, such as liposomes, niosomes, nanoparticles, and microemulsions in ocular drug delivery.

Time-release compression-coated core tablet containing nifedipine for chronopharmacotherapy

Compression-coated time-release tablets (CC tablets) containing nifedipine, dihydropyridine Ca channel blocker, in the core tablet were prepared by dry coating with different polyethylene oxide-polyethylene glycol mixtures. Each formulation showed a clear lag period before nifedipine release initiation, followed by sustained drug release lasting up to 24 h. The lag time of nifedipine release increased as the amount of polyethylene oxide in the outer layer increased. To investigate the applicability of such CC-tablets for chronopharmacotherapy, the pharmacokinetics of CC-1 and CC-2 tablets, with different in vitro lag times before drug release, were compared with the pharmacokinetics of a sustained-release (SR) tablet in dogs. The times of first nifedipine appearance (TFA) in plasma were 0.7 ± 0.3 h for SR, 2.5 ± 1.2 h for CC-1, and 5.3 ± 1.0 h for CC-2. These data show a significant difference in in vivo lag time ( P < 0.01) among the three formulations that correlates with the in vitro lag times. Thus, the in vivo lag time could be predicted from the in vitro lag time. Additionally, higher plasma nifedipine concentrations were observed at 8 h after administration of the CC-2 than that observed for the SR-tablet. These results indicate that a CC-tablet with a lag time before drug release is a potentially useful formulation for chronopharmacotherapy that can control the time and duration of plasma drug concentration better than existing SR technologies.

Amphiphilic block copolymers for drug delivery

Amphiphilic block copolymers (ABCs) have been used extensively in pharmaceutical applications ranging from sustained-release technologies to gene delivery. The utility of ABCs for delivery of therapeutic agents results from their unique chemical composition, which is characterized by a hydrophilic block that is chemically tethered to a hydrophobic block. In aqueous solution, polymeric micelles are formed via the association of ABCs into nanoscopic core/shell structures at or above the critical micelle concentration. Upon micellization, the hydrophobic core regions serve as reservoirs for hydrophobic drugs, which may be loaded by chemical, physical, or electrostatic means, depending on the specific functionalities of the core-forming block and the solubilizate. Although the Pluronics, composed of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide), are the most widely studied ABC system, copolymers containing poly(L-amino acid) and poly(ester) hydrophobic blocks have also shown great promise in delivery applications. Because each ABC has unique advantages with respect to drug delivery, it may be possible to choose appropriate block copolymers for specific purposes, such as prolonging circulation time, introduction of targeting moieties, and modification of the drug-release profile. ABCs have been used for numerous pharmaceutical applications including drug solubilization/stabilization, alteration of the pharmacokinetic profile of encapsulated substances, and suppression of multidrug resistance. The purpose of this minireview is to provide a concise, yet detailed, introduction to the use of ABCs and polymeric micelles as delivery agents as well as to highlight current and past work in this area.