Design of Redispersible High-Drug-Load Amorphous Formulations: Impact of Ionic vs Nonionic Surfactants on Processing and Performance.

Amorphous solid dispersions (ASDs) are an enabling formulation approach used to enhance bioavailability of poorly water-soluble molecules in oral drug products. Drug-rich amorphous nanoparticles generated in situ during ASD dissolution maintain supersaturation that drives enhanced absorption. However, in situ formation of nanoparticles requires large quantities of polymers to release drugs rapidly, resulting in an ASD drug load <25%. Delivering directly engineered drug-rich amorphous nanoparticles can reduce the quantities of polymers significantly without sacrificing bioavailability. Preparation of 90% drug-load amorphous nanoparticles (ANPs) of <300 nm diameter using solvent/antisolvent nanoprecipitation, organic solvent removal, and spray drying was demonstrated previously on model compound ABT-530 with Copovidone and sodium dodecyl sulfate (anionic). In this work, nonionic surfactant d-α-tocopheryl polyethylene glycol succinate (Vitamin E TPGS, or TPGS) was used to prepare ANPs as a comparison. Characterization of ANPs by dynamic light scattering, filtrate potency assay, scanning electron microscopy, and differential scanning calorimetry revealed differences in surface properties of nanoparticles afforded by surfactants. This work demonstrates the importance of understanding the impact of the stabilizing agents on nanoparticle behavior when designing a high-drug-load amorphous formulation for poorly water-soluble compounds as well as the impact on redispersion.

Human Mesofluidic Intestinal Model for Studying Transport of Drug Carriers and Bacteria Through a Live Mucosal Barrier.

The intestinal mucosal barrier forms a critical interface between lumen contents such as bacteria, drugs, and drug carriers and the underlying tissue. Current in vitro intestinal models, while recapitulating certain aspects of this barrier, generally present challenges with respect to imaging transport across mucus and uptake into enterocytes. A human mesofluidic small intestinal chip was designed to enable facile visualization of a mucosal interface created by growing primary human intestinal cells on a vertical hydrogel wall separating channels representing the intestinal lumen and circulatory flow. Type I collagen, fortified via cross-linking to prevent deformation and leaking during culture, was identified as a suitable gel wall material for supporting primary organoid-derived human duodenal epithelial cell attachment and monolayer formation. Addition of DAPT and PGE2 to culture medium paired with air-liquid interface culture increased the thickness of the mucus layer on epithelium grown within the device for 5 days from approximately 5 mm to 50 µm, making the model suitable for revealing intriguing features of interactions between luminal contents and the mucus barrier using live cell imaging. Time-lapse imaging of nanoparticle diffusion within mucus revealed a zone adjacent to the epithelium largely devoid of nanoparticles up to 4.5 hr after introduction to the lumen channel, as well as pockets of dimly lectin-stained mucus within which particles freely diffused, and apparent clumping of particles by mucus components. Multiple particle tracking conducted on the intact mucus layer in the chip revealed significant size-dependent differences in measured diffusion coefficients. E. coli introduced to the lumen channel were freely mobile within the mucus layer and appeared to intermittently contact the epithelial surface over 30 minute periods of culture. Mucus shedding into the lumen and turnover of mucus components within cells were visualized. Taken together, this system represents a powerful tool for visualization of interactions between luminal contents and an intact live mucosal barrier.

LHRH-targeted nanogels as a delivery system for cisplatin to ovarian cancer.

Targeted drug delivery using multifunctional polymeric nanocarriers is a modern approach for cancer therapy. Our purpose was to prepare targeted nanogels for selective delivery of chemotherapeutic agent cisplatin to luteinizing hormone-releasing hormone (LHRH) receptor overexpressing tumor in vivo. Building blocks of such delivery systems consisted of innovative soft block copolymer nanogels with ionic cores serving as a reservoir for cisplatin (loading 35%) and a synthetic analogue of LHRH conjugated to the nanogels via poly(ethylene glycol) spacer. Covalent attachment of (D-Lys6)-LHRH to nanogels was shown to be possible without loss in either the ligand binding affinity or the nanogel drug incorporation ability. LHRH-nanogel accumulation was specific to the LHRH-receptor positive A2780 ovarian cancer cells and not toward LHRH-receptor negative SKOV-3 cells. The LHRH-nanogel cisplatin formulation was more effective and less toxic than equimolar doses of free cisplatin or untargeted nanogels in the treatment of receptor-positive ovarian cancer xenografts in mice. Collectively, the study indicates that LHRH mediated nanogel-cisplatin delivery is a promising formulation strategy for therapy of tumors that express the LHRH receptor.

Design of a Re-Dispersible High Drug Load Amorphous Formulation.

Amorphous solid dispersions (ASD) are a commonly used enabling formulation technology to drive oral absorption of poorly soluble drugs. To ensure adequate solid-state stability and dissolution characteristics, the ASD formulation design typically has ≤ 25% drug loading. Exposed to aqueous media, ASD formulations can produce drug-rich colloidal dispersion with particle size < 500 nm. This in situ formation of colloidal particles requires incorporation of excess excipients in the formulation. The concept of using engineered drug-rich particles having comparable size as those generated by ASDs in aqueous media is explored with the goal of increasing drug loading in the solid dosage form. Utilizing ABT-530 as model compound, a controlled solvent-antisolvent precipitation method resulted in a dilute suspension that contained drug-rich (90% (w/w)) amorphous nanoparticles (ANP). The precipitation process was optimized to yield a suspension containing < 300 nm ANP. A systematic evaluation of formulation properties and process variables resulted in the generation of dry powders composed of 1-8 µm agglomerates of nanoparticles which in contact with water regenerated the colloidal suspension having particle size comparable to primary particles. Thus, this work demonstrates an approach to designing a re-dispersible ANP based powder containing ≥90% w/w ABT-530 that could be used in preparation of a high drug load solid dosage form.

PEG modified liposomes containing CRX-601 adjuvant in combination with methylglycol chitosan enhance the murine sublingual immune response to influenza vaccination.

The mucosa is the primary point of entry for pathogens making it an important vaccination site to produce a protective mucosal immune response. While the sublingual (SL) mucosa presents several barriers to vaccine penetration, its unique anatomy and physiology makes it one of the best options for mucosal vaccination. Efficient and directed delivery of adjuvants and antigens to appropriate immune mediators in the SL tissue will aid in development of effective SL vaccines against infectious diseases. Herein we demonstrate a robust immune response against influenza antigens co-delivered sublingually with engineered liposomes carrying the synthetic Toll-like receptor-4 agonist, CRX-601. Liposome modification with PEG copolymers (Pluronics), phospholipid-PEG conjugates and chitosan were evaluated for their ability to generate an immune response in a SL murine influenza vaccine model. Phospholipid-PEG conjugates were more effective than Pluronic copolymers in generating stable, surface neutral liposomes. SL vaccination with surface modified liposomes carrying CRX-601 adjuvant generated significant improvements in flu-specific responses compared with unmodified liposomes. Furthermore, the coating of modified liposomes with methylglycol chitosan produced the most effective flu-specific immune response. These results demonstrate efficient SL vaccine delivery utilizing a combination of a muco-adhesive and surface neutral liposomes to achieve a robust mucosal and systemic immune response.

Methylglycol chitosan and a synthetic TLR4 agonist enhance immune responses to influenza vaccine administered sublingually.

Influenza is a vaccine-preventable contagious respiratory illness caused by influenza (flu) viruses which can lead to hospitalization and sometimes even death. Current flu vaccines delivered intramuscularly (IM) or intradermally (ID) are less effective at eliciting protective mucosal immune responses and vaccines delivered intranasally (IN) possess potential safety concerns. Sublingual (SL) vaccination is a promising alternative route for vaccine delivery which has been indicated as safe and effective at inducing protective immune responses in both systemic and mucosal compartments. We evaluated the efficacy of methylglycol chitosan (MGC) and a synthetic toll-like receptor 4 agonist (CRX-601), alone or in combination, for improving systemic and mucosal immune responses to a monovalent detergent-split flu virus vaccine delivered SL. SL vaccination of mice with split-flu vaccine formulated with either MGC or CRX-601 resulted in specific serum IgG and mucosal IgA titers that were significantly greater than titers from non-adjuvanted vaccination and equivalent to or greater than titers in mice vaccinated IM. Our results demonstrate that SL vaccination utilizing MGC or CRX-601 as adjuvants is a viable alternative route of vaccination for flu which can elicit systemic immune responses equivalent to or greater than IM vaccination with the added benefit of stimulating a robust specific mucosal immune response.

Polypeptide nanogels with hydrophobic moieties in the cross-linked ionic cores: synthesis, characterization and implications for anticancer drug delivery.

Polymer nanogels have gained considerable attention as a potential platform for drug delivery applications. Here we describe the design and synthesis of novel polypeptide-based nanogels with hydrophobic moieties in the cross-linked ionic cores. Diblock copolymer, poly(ethylene glycol)-b-poly(L-glutamic acid), hydrophobically modified with L-phenylalanine methyl ester moieties was used for controlled template synthesis of nanogels with small size (ca. 70 nm in diameter) and narrow particle size distribution. Steady-state and time-resolved fluorescence studies using coumarin C153 indicated the existence of hydrophobic domains in the ionic cores of the nanogels. Stable doxorubicin-loaded nanogels were prepared at high drug capacity (30 w/w%). We show that nanogels are enzymatically-degradable leading to accelerated drug release under simulated lysosomal acidic pH. Furthermore, we demonstrate that the nanogel-based formulation of doxorubicin is well tolerated and exhibit an improved antitumor activity compared to a free doxorubicin in an ovarian tumor xenograft mouse model. Our results signify the point to a potential of these biodegradable nanogels as attractive carriers for delivery of chemotherapeutics.

Nanocarriers for delivery of platinum anticancer drugs.

Platinum based anticancer drugs have revolutionized cancer chemotherapy, and continue to be in widespread clinical use especially for management of tumors of the ovary, testes, and the head and neck. However, several dose limiting toxicities associated with platinum drug use, partial anti-tumor response in most patients, development of drug resistance, tumor relapse, and many other challenges have severely limited the patient quality of life. These limitations have motivated an extensive research effort towards development of new strategies for improving platinum therapy. Nanocarrier-based delivery of platinum compounds is one such area of intense research effort beginning to provide encouraging preclinical and clinical results and may allow the development of the next generation of platinum chemotherapy. This review highlights current understanding on the pharmacology and limitations of platinum compounds in clinical use, and provides a comprehensive analysis of various platinum-polymer complexes, micelles, dendrimers, liposomes and other nanoparticles currently under investigation for delivery of platinum drugs.

Preparation and In Vivo Evaluation of Dichloro(1,2-Diaminocyclohexane)platinum(II)-Loaded Core Cross-Linked Polymer Micelles.

The therapeutic performance of oxaliplatin can be improved by incorporating the central cis-dichloro(1,2-diaminocyclohexane)platinum(II) (DACHPt) motif into the core cross-linked block copolymer micelles. We describe here the preparation, cellular uptake, and in vivo evaluation of core cross-linked micelles loaded with DACHPt. Stable drug-loaded micelles were prepared at high drug loading (~25 w/w%) and displayed a considerably increased in vitro cytotoxicity compared to free oxaliplatin against A2780 ovarian cancer cells. The DACHPt-loaded micelle formulation was well tolerated in mice and exhibited improved antitumor activity than oxaliplatin alone in an ovarian tumor xenograft model.

Cisplatin-loaded core cross-linked micelles: comparative pharmacokinetics, antitumor activity, and toxicity in mice.

Polymer micelles with cross-linked ionic cores are shown here to improve the therapeutic performance of the platinum-containing anticancer compound cisplatin. Biodistribution, antitumor efficacy, and toxicity of cisplatin-loaded core cross-linked micelles of poly(ethylene glycol)-b-poly(methacrylic acid) were evaluated in a mouse ovarian cancer xenograft model. Cisplatin-loaded micelles demonstrated prolonged blood circulation, increased tumor accumulation, and reduced renal exposure. Improved antitumor response relative to free drug was seen in a mouse model. Toxicity studies with cisplatin-loaded micelles indicate a significantly improved safety profile and lack of renal abnormalities typical of free cisplatin treatment. Overall, the study supports the fundamental possibility of improving the potential of platinum therapy using polymer micelle-based drug delivery.