In vivo efficacy of a dry powder formulation of ciprofloxacin-copper complex in a chronic lung infection model of bioluminescent Pseudomonas aeruginosa.

A significant limitation of locally delivered treatments for chronic pulmonary infections is often the short residence time within the airways. Ciprofloxacin (CIP), for example, undergoes rapid absorption from the airway lumen. Previously, we demonstrated that the complexation of CIP with copper (CIP-Cu) reduces its apparent epithelial permeability and pulmonary absorption rate without affecting antimicrobial activity against Pseudomonas aeruginosa grown planktonically or as biofilms. This study aimed to evaluate the in vivo efficacy of CIP-Cu, prepared as a dry powder, in a chronic lung infection model. The powders were prepared by jet milling (CIP-HCl) and by spray drying (CIP-Cu). A bioluminescent strain of P. aeruginosa (PAO1::p16Slux) was used to prepare bacteria-loaded agar beads that were inoculated intratracheally to rats. The dynamics of the infection were monitored using luminometry. The bacteria/beads ratio was optimized to allow the highest luminescence signal and animal survival for 8 days. The efficacy of the treatment was evaluated by luminometry in addition to the end-point (Day 8) where colony counting was performed after lung harvesting. Luminescent P. aeruginosa entrapped in agar beads were useful to monitor the spatial development of the chronic lung infection in rats. The rats were treated with the dry powders in a nose-only inhalation exposure system (NOIES). CIP-Cu and CIP-HCl powders showed similar aerodynamic properties and comparable CIP lung deposition. However, treatment with CIP-Cu significantly (p < 0.01) reduced by 4-log the number of CFU of P. aeruginosa per lung in the chronic infection model, whereas CIP-HCl effect was not different from the untreated control group.

Oxaliplatin Pt(IV) prodrugs conjugated to gadolinium-texaphyrin as potential antitumor agents.

Described here is the development of gadolinium(III) texaphyrin-platinum(IV) conjugates capable of overcoming platinum resistance by 1) localizing to solid tumors, 2) promoting enhanced cancer cell uptake, and 3) reactivating p53 in platinum-resistant models. Side by side comparative studies of these Pt(IV) conjugates to clinically approved platinum(II) agents and previously reported platinum(II)-texaphyrin conjugates demonstrate that the present Pt(IV) conjugates are more stable against hydrolysis and nucleophilic attack. Moreover, they display high potent antiproliferative activity in vitro against human and mouse cell cancer lines. Relative to the current platinum clinical standard of care (SOC), a lead Gd(III) texaphyrin-Pt(IV) prodrug conjugate emerging from this development effort was found to be more efficacious in subcutaneous (s.c.) mouse models involving both cell-derived xenografts and platinum-resistant patient-derived xenografts. Comparative pathology studies in mice treated with equimolar doses of the lead Gd texaphyrin-Pt(IV) conjugate or the US Food and Drug Administration (FDA)-approved agent oxaliplatin revealed that the conjugate was better tolerated. Specifically, the lead could be dosed at more than three times (i.e., 70 mg/kg per dose) the tolerable dose of oxaliplatin (i.e., 4 to 6 mg/kg per dose depending on the animal model) with little to no observable adverse effects. A combination of tumor localization, redox cycling, and reversible protein binding is invoked to explain the relatively increased tolerability and enhanced anticancer activity seen in vivo. On the basis of the present studies, we conclude that metallotexaphyrin-Pt conjugates may have substantial clinical potential as antitumor agents.

Caveolin-1-derived peptide limits development of pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a fatal fibrotic lung disease with a median 5-year survival of ~20%. Current U.S. Food and Drug Administration-approved pharmacotherapies slow progression of IPF, providing hope that even more effective treatments can be developed. Alveolar epithelial progenitor type II cell (AEC) apoptosis and proliferation, and accumulation of activated myofibroblasts or fibrotic lung fibroblasts (fLfs) contribute to the progression of IPF. Full-length caveolin-1 scaffolding domain peptide (CSP; amino acids 82 to 101 of Cav1: DGIWKASFTTFTVTKYWFYR) inhibits AEC apoptosis and fLf activation and expansion and attenuates PF in bleomycin (BLM)-induced lung injury in mice. Like full-length CSP, a seven-amino acid deletion fragment of CSP, CSP7 (FTTFTVT), demonstrated antifibrotic effects in murine models of lung fibrosis. When CSP7 was administered during the fibrotic phase in three preclinical models [single-dose BLM, repeated-dose BLM, and adenovirus expressing constitutively active transforming growth factor-ß1 (Ad-TGF-ß1)-induced established PF], CSP7 reduced extracellular matrix (ECM) markers characteristic of PF, increased AEC survival, and improved lung function. CSP7 is amenable to both systemic (intraperitoneal) or direct lung delivery in a nebulized or dry powder form. Furthermore, CSP7 treatment of end-stage human IPF lung tissue explants attenuated ECM production and promoted AEC survival. Ames testing for mutagenicity and in vitro human peripheral blood lymphocyte and in vivo mouse micronucleus transformation assays indicated that CSP7 is not carcinogenic. Together, these findings support the further development of CSP7 as an antifibrotic treatment for patients with IPF or other interstitial lung diseases.

Enhanced Aerosolization of High Potency Nanoaggregates of Voriconazole by Dry Powder Inhalation.

Invasive pulmonary aspergillosis is a deadly fungal infection with a high mortality rate, particularly in patients having undergone transplant surgery. Voriconazole, a triazole antifungal pharmaceutical product, is considered as a first-line therapy for invasive pulmonary aspergillosis, and exhibits efficacy even for patients who have failed other antifungal drug therapies. The objective of this study is to develop high potency nanoaggregates of crystalline voriconazole composition for dry powder inhalation using the particle engineering process, thin film freezing. In this study, mannitol at low concentrations acted as a surface texture-modifying agent, and we evaluated the physicochemical and aerodynamic properties of the voriconazole formulations containing different amounts of mannitol. In vitro aerosol performance data demonstrated that powder formulations consisting of 90 to 97% (w/w) voriconazole were the optimum for inhalation with a fine particle fraction (% of delivered dose) as high as 73.6 ± 3.2% and mass median aerodynamic diameter of 3.03 ± 0.17 µm when delivered by a commercially available device. The thin film freezing process enabled phase-separated submicron crystalline mannitol to be oriented such as to modify the surface texture of the crystalline voriconazole nanoaggregates, thus enhancing their aerosolization. Addition of as low as 3% (w/w) mannitol significantly increased the fine particle fraction (% of metered dose) of voriconazole nanoaggregates when compared to compositions without mannitol (40.8% vs 24.6%, respectively). The aerosol performance of the voriconazole nanoaggregates with 5% (w/w) mannitol was maintained for 13 months at 25 °C/60% RH. Therefore, voriconazole nanoaggregates having low amounts of surface texture-modifying mannitol made by thin film freezing are a feasible local treatment option for invasive pulmonary aspergillosis with high aerosolization efficiency and drug loading for dry powder inhalation.

Delivery Technologies for Orally Inhaled Products: an Update.

Orally inhaled products have well-known benefits. They allow for effective local administration of many drugs for the treatment of pulmonary disease, and they allow for rapid absorption and avoidance of first-pass metabolism of several systemically acting drugs. Several challenges remain, however, such as dosing limitations, low and variable deposition of the drug in the lungs, and high drug deposition in the oropharynx region. These challenges have stimulated the development of new delivery technologies. Both formulation improvements and new device technologies have been developed through an improved understanding of the mechanisms of aerosolization and lung deposition. These new advancements in formulations have enabled improved aerosolization by controlling particle properties such as density, size, shape, and surface energy. New device technologies emerging in the marketplace focus on minimizing patient errors, expanding the range of inhaled drugs, improving delivery efficiency, increasing dose consistency and dosage levels, and simplifying device operation. Many of these new technologies have the potential to improve patient compliance. This article reviews how new delivery technologies in the form of new formulations and new devices enhance orally inhaled products.

Manufacturing and ambient stability of shelf freeze dried bacteriophage powder formulations.

The severity of multidrug resistance to antibiotics has urged development of alternative treatment approaches, including bacteriophage therapy. Given the complexity of the bacteriophage structure, formulation and stability are primary concerns. Our present work optimized process and formulations of phage powder manufacturing and investigated the stability of lyophilized bacteriophage powders under ambient storage. The model phage M13 was formulated with trehalose, mannitol, sucrose and PEG6000 and lyophilized in different conditions. Bacteriophage viability was examined by titering and was considered as the assessment of phage stability. Less titer loss of trehalose and sucrose formulations were observed compared to mannitol and PEG groups both immediately after lyophilization and upon long term storage. When evaluating lyophilization conditions, an additional 1 log titer was preserved by reduction of product drying stress. Trehalose was stabilized in the amorphous state whereas mannitol stayed in crystalline state in lyophilized powders. Increased moisture content was demonstrated to have a positive impact on viability of phage after lyophilization and upon storage. Overall, 2% trehalose or sucrose (w/v) can sufficiently stabilize phage during lyophilization process and storage in ambient conditions. There is a positive correlation between residual water and stability of phage. These collective findings highlight the potential of long-term, ambient storage of bacteriophage towards their successful use in diverse healthcare settings.

An update on coating/manufacturing techniques of microneedles.

Recently, results have been published for the first successful phase I human clinical trial investigating the use of dissolving polymeric microneedles… Even so, further clinical development represents an important hurdle that remains in the translation of microneedle technology to approved products. Specifically, the potential for accumulation of polymer within the skin upon repeated application of dissolving and coated microneedles, combined with a lack of safety data in humans, predicates a need for further clinical investigation. Polymers are an important consideration for microneedle technology-from both manufacturing and drug delivery perspectives. The use of polymers enables a tunable delivery strategy, but the scalability of conventional manufacturing techniques could arguably benefit from further optimization. Micromolding has been suggested in the literature as a commercially viable means to mass production of both dissolving and swellable microneedles. However, the reliance on master molds, which are commonly manufactured using resource intensive microelectronics industry-derived processes, imparts notable material and design limitations. Further, the inherently multi-step filling and handling processes associated with micromolding are typically batch processes, which can be challenging to scale up. Similarly, conventional microneedle coating processes often follow step-wise batch processing. Recent developments in microneedle coating and manufacturing techniques are highlighted, including micromilling, atomized spraying, inkjet printing, drawing lithography, droplet-born air blowing, electro-drawing, continuous liquid interface production, 3D printing, and polyelectrolyte multilayer coating. This review provides an analysis of papers reporting on potentially scalable production techniques for the coating and manufacturing of microneedles.

Formulation of a novel fixed dose combination of salmeterol xinafoate and mometasone furoate for inhaled drug delivery.

Co-administration of an inhaled corticosteroid and long acting beta agonist for chronic obstructive pulmonary disease has reduced mortality compared to either drug alone. This combination reduces exacerbations, hospitalization, emergency department visits and health care costs. A novel fixed-dose combination of the long acting beta-2 agonist salmeterol xinafoate (SX) and the corticosteroid mometasone furoate (MF) were prepared in a composite particle formulation as brittle matrix powder (BMP) and investigated for suitability as an inhaled combination product. In this study, BMP fixed dose combinations of SX and MF with or without stabilizing excipients (lactose, mannitol, glycine and trehalose) were prepared and characterized with respect to their thermal properties, morphology, aerodynamic performance and physical stability. BMP combination formulations of SX and MF exhibited improved aerodynamic properties when delivered by dry powder inhalation as compared to the micronized blends of the same substances. Aerodynamic evaluation was carried out by next generation pharmaceutical impactor (NGI) with a marketed DPI device. Results demonstrated that co-deposition occurred when SX and MF were formulated together as composite particles in a BMP, while physical blends resulted in inconsistent deposition and dose uniformity. As a result of the bottom-up particle engineering approach, combination BMP formulations allow for dual API composite formulations to be dispersed as aerosolized particles. Aerosolized BMP combination formulations resulted in delivered dose uniformity and co-deposition of each API. Further, an excipient-free formulation, BMP SXMF, delivered approximately 50% of the loaded dose in the respirable range and demonstrated stability at ambient conditions for 6months. Single dose 24-h pharmacokinetic studies in rats demonstrated that lung tissue deposition and blood circulation (AUC0-24h) of two APIs were higher for the BMP combination group exhibiting a significantly higher lung concentration of drugs than for the crystalline physical blend. While high system drug levels are generally undesirable in lung targeted therapies, high blood levels in this rodent study could be indicative of increased pulmonary tissue exposure using BMP formulations.

Characterization and pharmacokinetic analysis of crystalline versus amorphous rapamycin dry powder via pulmonary administration in rats.

The pharmacokinetics of inhaled rapamycin (RAPA) is compared for amorphous versus crystalline dry powder formulations. The amorphous formulation of RAPA and lactose (RapaLac) was prepared by thin film freezing (TFF) using lactose as the stabilizing agent in the weight ratio 1:1. The crystalline formulation was prepared by wet ball milling RAPA and lactose and posteriorly blending the mixture with coarse lactose (micronized RAPA/micronized lactose/coarse lactose=0.5:0.5:19). While both powders presented good aerosolization performance for lung delivery, TFF formulation exhibited better in vitro aerodynamic properties than the crystalline physical mixture. Single-dose 24h pharmacokinetic studies were conducted in Sprague-Dawley rats following inhalation of the aerosol mist in a nose-only inhalation exposure system. Lung deposition was higher for the crystalline group than for the TFF group. Despite higher pulmonary levels of drug that were found for the crystalline group, the systemic circulation (AUC0₋24) was higher for the amorphous group (8.6 ngh/mL) than for crystalline group (2.4 ngh/mL) based on a five-compartmental analysis. Lung level profiles suggest that TTF powder stays in the lung for the same period of time as the crystalline powder but it presented higher in vivo systemic bioavailability due to its enhanced solubility, faster dissolution rate and increased FPF at a more distal part of the lungs.

In vitro and in vivo performance of dry powder inhalation formulations: comparison of particles prepared by thin film freezing and micronization.

Recently, inhaled immunosuppressive agents have attracted increasing attention for maintenance therapy following lung transplantation. The rationale for this delivery approach includes a more targeted and localized delivery to the diseased site with reduced systemic exposure, potentially leading to decreased adverse side effects. In this study, the in vitro and in vivo performance of an amorphous formulation prepared by thin film freezing (TFF) and a crystalline micronized formulation produced by milling was compared for tacrolimus (TAC). Despite the relatively large geometric size, the TFF-processed formulation was capable of achieving deep lung delivery due to its low-density, highly porous, and brittle characteristics. When emitted from a Miat® monodose inhaler, TFF-processed TAC formulations exhibited a fine particle fraction (FPF) of 83.3% and a mass median aerodynamic diameter (MMAD) of 2.26 µm. Single-dose 24-h pharmacokinetic studies in rats demonstrated that the TAC formulation prepared by TFF exhibited higher pulmonary bioavailability with a prolonged retention time in the lung, possibly due to decreased clearance (e.g., macrophage phagocytosis), compared to the micronized TAC formulation. Additionally, TFF formulation generated a lower systemic TAC concentration with smaller variability than the micronized formulation following inhalation, potentially leading to reduced side effects related to the drug in systemic circulation.

The impact of pulmonary diseases on the fate of inhaled medicines--a review.

The portfolio of compounds approved for inhalation therapy has expanded rapidly for treatment of lung diseases. To assess the efficacy and safety of inhaled medicines, a better understanding of their fate in the lungs is essential; especially in diseased lungs where changes in anatomical structure, ventilation parameters and breathing pattern may occur. In this article, the impact of lung pathophysiology factors on the fate of inhaled medicines is reviewed, and discussed in the context of aerosol deposition, dissolution, absorption and clearance. Special emphasis is given to computational modeling of aerosol deposition and clearance taking disease factors into consideration. In silico modeling can be used as a valuable tool to characterize the biopharmaceutics and pharmacodynamics of inhaled medicines, or assess risks associated with inhaled environmental pollutants for patients with pulmonary diseases. The deposition pattern of aerosol particles is greatly altered by different lung diseases based on both experimental data and model simulation. The fate of inhaled medicines after deposition primarily depends on the site of aerosol deposition. Therefore, when developing inhalation products for treatment of lung diseases, the dosing regimen, safety and pharmacokinetic studies should be conducted on patients with lung diseases, in addition to healthy subjects.

Respirable low-density microparticles formed in situ from aerosolized brittle matrices.

PURPOSE: Inhalation of low-density porous particles enables deep lung delivery with less dependence on device design and patient inspiration. The purpose of this study was to implement Thin Film Freezing (TFF) to investigate a novel approach to dry powder inhalation. METHODS: Powders produced by TFF were evaluated for aerodynamic and geometric particle size by cascade impaction and laser light scattering, respectively. Density measurements were conducted according to USP methods and calculated using data from particle size measurements. Excipient inclusion and its effect on moisture sorption was measured by Dynamic Vapor Sorption (DVS). RESULTS: TFF-produced brittle matrix powders were sheared apart into respirable microparticles using a passive DPI device, producing fine particle fractions (FPF) up to 69% and mass median aerodynamic diameters (MMAD) as low as 2.6 µm. Particles had a mean geometric diameter ranging from 25 µm to 50 µm and mass densities of approximately 0.01 g/cm(3). Powders were susceptible to moisture-induced matrix collapse, capillary forces and electrostatic charging; although formulations containing mannitol or no sugar excipient proved to be more robust. CONCLUSIONS: Aerosolized brittle matrices produced by TFF may prove to be a useful platform for highly efficient pulmonary delivery of thermally labile, highly potent, and poorly soluble drugs.

Preclinical evaluation of tacrolimus colloidal dispersion for inhalation.

Substantial improvements in transplant therapy have been made in the past four decades resulting in the acceptance of organ transplantation as a viable treatment for late-stage disease and organ failure. More recently, lung transplantation has gained acceptance; however, high incidence of chronic rejection and opportunistic infections has limited success rates in comparison with other transplant procedures. To achieve more targeted therapy, pulmonary administration of nebulized tacrolimus (TAC) colloidal dispersion once daily for 28 consecutive days in Sprague Dawley (SD) rats has been investigated for safety and systemic elimination. A liquid dispersion of colloidal TAC and lactose (1:1 ratio by weight) was aerosolized using a vibrating mesh nebulizer and administered via a nose-only dosing chamber. Blood chemistry and histological comparisons to saline-dosed animals showed no clinically significant differences in liver and kidney function or lung tissue damage. Maximum blood and lung concentrations sampled 1h after the final dose showed TAC concentrations of 10.1 ± 1.4 ng/mL and 1758.7 ± 80.0 ng/g, respectively. Twenty-four hours after the final dose, systemic TAC concentrations measured 1.0 ± 0.5 ng/mL, which is well below clinically accepted trough concentrations (5-15 ng/mL) for maintenance therapy, and therefore, would not be expected to induce toxic side effects. The propensity for pulmonary retention seen when compared to single dose lung levels may be due to macrophage uptake and the lipophilic nature of TAC. Additionally, three month stability testing of TAC powder for reconstitution showed no changes in amorphous nature or drug potency when stored at ambient conditions. TAC colloidal dispersion proved to be non-toxic when administered by pulmonary inhalation to SD rats over 28 days while providing therapeutic concentrations locally. This delivery strategy may prove safe and effective for the prevention of lung allograft rejection in lung transplant recipients.

Characterization and pharmacokinetic analysis of tacrolimus dispersion for nebulization in a lung transplanted rodent model.

Lung transplantation animal models have been well established and enabled the investigation of a variety of new pharmacotherapeutic strategies for prevention of lung allograft rejection. Direct administration of immunosuppressive agents to the lung is a commonly investigated approach; however, can prove challenging due to the poor solubility of the drug molecule, the tortuous pathways of the lung periphery, and the limited number of excipients approved for inhalation. In this study, we aimed to evaluate a solubility enhancing formulation of tacrolimus for localized therapy in a lung transplanted rat model and determine the extent of drug absorption into systemic circulation. Characterization of the nebulized tacrolimus dispersion for nebulization showed a fine particle fraction (FPF) of 46.1% and a mass median aerodynamic diameter (MMAD) of 4.06 microm. After single dose administration to transplanted and non-transplanted rats, a mean peak transplanted lung concentration of 399.8+/-29.2 ng/g and mean peak blood concentration of 4.88+/-1.6 ng/mL were achieved. It is theorized that enhanced lung retention of tacrolimus is due to lipophilic associations with bronchial tissue and phospholipid surfactants in lung fluid. These findings indicate that tacrolimus dispersion for nebulization can achieve highly localized therapy for lung transplant recipients.

Recent developments in drug delivery to prolong allograft survival in lung transplant patients.

Since the discovery of cyclosporine in 1971, calcineurin inhibitors have played a critical role in the therapeutic suppression of the immune response. Patients receiving solid organ transplants rely heavily on these medications to prevent the acute and chronic rejection of allografted tissue. These therapies can prove difficult because of potential toxicity, heightened risk of invasive infection, and erratic oral bioavailability, requiring frequent blood samples for monitoring of systemic levels. Added challenges are presented in immunosuppression of lung transplant patients owing to the increased susceptibility to invasive infection and extensive immune mechanisms inherent in lung tissue. With the introduction of tacrolimus, a more potent calcineurin inhibitor, clinical outcomes of transplants have continued to improve; however, little improvement has been noted in lung transplantation. While very effective upon arrival at the site of action, tacrolimus and cyclosporine present a variety of formulation challenges such as poor solubility, potential systemic toxicity, and extensive first pass metabolism. Initial attempts to improve solubility in both oral and intravenous formulations have resulted in variable drug absorption and increased systemic toxicity, respectfully, creating a need for formulation improvement. Through alternative routes of delivery and novel formulation techniques, researchers have addressed these issues and, in some cases, demonstrated improved clinical outcomes. Through enhanced solubilization, reduction in absorption variability, and more effective drug targeting with reduced systemic levels, improvements in outcomes and overall patient survival in lung and other solid organ transplantation can be expected.

Influence of polymeric subcoats on the drug release properties of tablets powder-coated with pre-plasticized Eudragit L 100-55.

The aim of the study was to investigate the properties of sodium valproate tablets that were dry powder-coated with pre-plasticized Eudragit L 100-55. Polyethylene glycol 3350 (PEG 3350) was used as primer to facilitate initial coating powder adhesion. Solubility parameters were employed to determine the wetting properties of the PEG 3350 primer. Additional PEG 3350 within the powder coating formulation was required to enable powder adhesion to the tablet cores. The application of a subcoat of either Eudragit E PO or Eudragit RL PO facilitated adhesion of the enteric polymer to the tablet cores and reduced the amount PEG 3350 required in the coating formulation. Since reduction of the PEG 3350 content produced less water-vapor permeable films, the enteric coating level necessary to control the drug release was decreased. PEG 3350 and Methocel K4M were incorporated in both Eudragit E PO and Eudragit RL PO subcoating formulations as pore forming agents. The influence of the pore forming excipients on physicochemical properties of free powder-cast films was investigated. The miscibility of the PEG 3350 and Methocel K4M in the film coating was correlated with their ability to function as pore forming agent.

Current therapies and technological advances in aqueous aerosol drug delivery.

Recent advances in aerosolization technology have led to renewed interest in pulmonary delivery of a variety of drugs. Pressurized metered dose inhalers (pMDIs) and dry powder inhalers (DPIs) have experienced success in recent years; however, many limitations are presented by formulation difficulties, inefficient delivery, and complex device designs. Simplification of the formulation process as well as adaptability of new devices has led many in the pharmaceutical industry to reconsider aerosolization in an aqueous carrier. In the acute care setting, breath-enhanced air-jet nebulizers are controlling and minimizing the amount of wasted medication, while producing a high percentage of respirable droplets. Vibrating mesh nebulizers offer advantages in higher respirable fractions (RFs) and slower velocity aerosols when compared with air-jet nebulizers. Vibrating mesh nebulizers incorporating formulation and patient adaptive components provide improvements to continuous nebulization technology by generating aerosol only when it is most likely to reach the deep lung. Novel innovations in generation of liquid aerosols are now being adapted for propellant-free pulmonary drug delivery to achieve unprecedented control over dose delivered and are leading the way for the adaptation of systemic drugs for delivery via the pulmonary route. Devices designed for the metered dose delivery of insulin, morphine, sildenafil, triptans, and various peptides are all currently under investigation for pulmonary delivery to treat nonrespiratory diseases. Although these devices are currently still in clinical testing (with the exception of the Respimat), metered dose liquid inhalers (MDLIs) have already shown superior outcomes to current pulmonary and systemic delivery methods.

The manufacture and characterisation of hot-melt extruded enteric tablets.

The aim of this highly novel study was to use hot-melt extrusion technology as an alternative process to enteric coating. In so doing, oral dosage forms displaying enteric properties may be produced in a continuous, rapid process, providing significant advantages over traditional pharmaceutical coating technology. Eudragit L100-55, an enteric polymer, was pre-plasticized with triethyl citrate (TEC) and citric acid and subsequently dry-mixed with 5-aminosalicylic acid, a model active pharmaceutical ingredient (API), and an optional gelling agent (PVP K30 or Carbopol 971P). Powder blends were hot-melt extruded as cylinders, cut into tablets and characterised using powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC) and dissolution testing conducted in both pH 1.2 and pH 6.8 buffers. Increasing the concentration of TEC significantly lowered the glass transition temperature (Tg) of Eudragit L100-55 and reduced temperatures necessary for extrusion as well as the die pressure. Moreover, citric acid (17% w/w) was shown to act as a solid-state plasticizer. HME tablets showed excellent gastro-resistance, whereas milled extrudates compressed into tablets released more than 10% w/w of the API in acidic media. Drug release from HME tablets was dependent upon the concentration of TEC, the presence of citric acid, PVP K30, and Carbopol 971P in the matrix, and pH of the dissolution media. The inclusion of an optional gelling agent significantly reduced the erosion of the matrix and drug release rate at pH 6.8; however, the enteric properties of the matrix were lost due to the formation of channels within the tablet. Consequently this work is both timely and highly innovative and identifies for the first time a method of producing an enteric matrix tablet using a continuous hot-melt extrusion process.