Michel J. N. Cormier

Macroflux Microprojection Array Patch Technology: A New and Efficient Approach for Intracutaneous Immunization

AbstractPurpose. We evaluated the Macroflux® microprojection array patch technology as a novel system for intracutaneous delivery of protein antigens. Methods. Macroflux® microprojection array systems (330-μm microprojection length, 190 microprojections/cm2, 1- and 2-cm2 area) were coated with a model protein antigen, ovalbumin (OVA), to produce a dry-film coating. After system application, microprojection penetration depth, OVA delivery, and comparative immune responses were evaluated in a hairless guinea pig model. Results. Macroflux® microprojections penetrated into hairless guinea pig skin at an average depth of 100 μm with no projections deeper than 300 μm. Doses of 1 to 80 μg of OVA were delivered via 1- or 2-cm2 systems by varying the coating solution concentration and wearing time. Delivery rates were as high as 20 μg in 5 s. In a prime and boost dose immune response study, OVA-coated Macroflux® was most comparable to equivalent doses injected intradermally. Higher antibody titers were observed when OVA was administered with the microprojection array or intradermally at low doses (1 and 5 μg). Macroflux® administration at 1- and 5-μg doses gave immune responses up to 50-fold greater than that observed after the same subcutaneous or intramuscular dose. Dry coating an adjuvant, glucosaminyl muramyl dipeptide, with OVA on the Macroflux® resulted in augmented antibody responses. Conclusions. Macroflux® skin patch technology provides rapid and reproducible intracutaneous administration of dry-coated antigen. The depth of skin penetration targets skin immune cells; the quantity of antigen delivered can be controlled by formulation, patch wearing time, and system size. This novel needle-free patch technology may ultimately have broad applications for a wide variety of therapeutic vaccines to improve efficacy and convenience of use.

Transdermal Delivery of Antisense Oligonucleotides with Microprojection Patch (macroflux®) Technology

In recent years, antisense oligodeoxynucleotide (ODN) technology has emerged as one of the most promising functional genomic therapies. Several clinical trials have demonstrated its therapeutic value and low toxicity (1). To date, parenteral infusion has been the primary mode of ODN delivery. However, efforts to develop more convenient routes of administration are being explored. Transdermal iontophoresis increased ODNs across the skin; however, delivery of a therapeutically relevant dose was not achieved (2–5). The major barrier for transdermal delivery is the stratum corneum, the outermost “dead” layer of the skin. In human skin, the stratum corneum is 10–20 m thick, whereas in mice and rats it is significantly thinner. Removal of the stratum corneum by mechanical abrasion, tape stripping, or chemical treatment has been shown to significantly enhance permeation through the skin for a wide range of pharmaceuticals, including phosphorothioated (PS) ODNs (5–8). However, these approaches may be limited due to the lack of control and reproducibility, as well as the irritancy potential (9). Microprojection patch is a novel microfabrication technology for controlled transdermal drug delivery. The patch system incorporates a stainless steel or titanium microprojection array. When applied onto the skin manually or by an applicator, microprojections penetrate and create superficial pathways through the skin barrier layer to allow drug delivery. The array can be combined either with passive or iontophoretic delivery systems. In this study, we demonstrate that microprojection patch technology can facilitate the controlled transdermal ODN delivery. MATERIALS AND METHODS

Bioavailability following transdermal powdered delivery (TPD) of radiolabeled inulin to hairless guinea pigs

Abstract Transdermal powdered delivery (TPD) is a novel method for needle-free administration of drugs, vaccines, and other therapeutic compounds. In this study, the efficiency of the TPD method has been evaluated following delivery of radiolabeled inulin to hairless guinea pigs. The quantity of radioactive inulin excreted in the urine, as a percentage of the total amount delivered, has been used as a measure of bioavailability. Maximum urine recoveries of radiolabeled inulin (mean±SE) for TPD were 32.8±3.7% when the site was unwashed following injection and when large inulin particles (39–52 μ m) were used. Washing the injection site immediately following inulin administration resulted in decreased recovery levels (12.2±1.3%) for the same sized particles. Delivery of smaller inulin particles (21–24 μ m) with no post-injection washing of the site resulted in a reduced urine recovery levels (10.8±4.1%) over that obtained with the larger particles. For comparison, subcutaneous injection of a similar dose resulted in recovery levels of 88.9±3.6%. Inulin residue within the prototype PowderJect ® device used for these experiments was shown to be approximately 17% of the starting dose. A small but acceptable degree of skin damage (erythema) at the injection site was seen following administration of the compound.

In vitro cytotoxicity of eight β-blockers in human corneal epithelial and retinal pigment epithelial cell lines: Comparison with epidermal keratinocytes and dermal fibroblasts

beta-Blockers are a class of agents that have been used extensively in topical preparations for the treatment of glaucoma. Recent evidence indicates that they may also be useful in a number of retinal diseases. Because biocompatibility is of utmost importance in the treatment of ocular-related diseases, we compared the in vitro cytotoxicity, using the MTT assay, of eight clinically available beta-blockers (propranolol, alprenolol, atenolol, labetalol, metoprolol, pindolol, timolol, and bisoprolol) on human corneal epithelial and retinal pigment epithelial cell lines. Primary and immortalized corneal and retinal cell lines were compared for their susceptibility to the cytotoxic effect of the drugs. The cytotoxicity of beta-blockers was also evaluated on human skin keratinocytes and fibroblasts in order to investigate susceptibility differences as a function of the tissue of origin. Results demonstrated large differences in cytotoxicity (about 60-fold) for these closely related drugs on the same cell line. Conversely, only relatively small differences in cytotoxicity were observed between the different cell lines for the same drug, indicating that the mechanism of cytotoxicity is not cell-specific. Calculation of the ratio between the cytotoxicity of beta-blockers and their beta-blocking constant is presented as a potential tool to help identify the least irritating, most potent drug.

Reverse iontophoresis: monitoring prostaglandin E2 associated with cutaneous inflammation in vivo

Abstract In response to topical application of irritants, increased concentrations of prostaglandin E2 (PGE2) are found in human skin exudate and in cultured dermal fibroblasts. In this study, PGE2 generated in response to transdermal delivery of irritant drug compounds was monitored in hairless guinea pig (HOP) by a non‐invasive method, reverse iontophoresis. Reverse iontophoresis is the movement of molecules from the skin under the influence of an applied electric field. Irritant drug compounds were applied with iontophoresis (electrotransport), and reverse iontophoresis of PGE2 from skin was monitored by radioimmunoassay (RIA) after extraction from the delivery system. Chlorpromazine was used as a model drug irritant. When chlorpromazine and saline were applied over a range of current densities from 0 to 200 μA/cm2, visual scores of erythema and edema yielded a correlation with measured skin efflux of PGE2 (r=0.86). Delivery of chlorpromazine resulted in greater efflux of PGE2 than delivery of non‐irritant saline controls under the same delivery conditions. Five drug compounds, chloroquine, promazine, chlorpromazine, tetracaine, metoclopramide, and saline were applied to hairless guinea pig skin. The 6 agents were similarly rank ordered by visual erythema/edema scores and by PGE2 efflux, indicating that the quantity of PGE2 effluxed reflects the intensity of skin irritation. In contrast, vasoconstriction or vasodilation produced by the local delivery of vasoactive agents did not correlate with PGE2 skin efflux, indicating that this measurement is specific for an inflammatory response. In summary, PGE2 generated in response to transdermally applied drug irritants can be monitored non‐invasively in vivo by reverse iontophoresis.

Pharmacokinetic study of dexamethasone disodium phosphate using intravitreal, subconjunctival, and intravenous delivery routes in rabbits.

Dexamethasone is a corticosteroid with proven efficacy for treating both anterior- and posterior-segment ocular diseases. Delivery of drugs to the back of the eye has always been a challenge, with dexamethasone being no exception. There are multiple delivery routes to the retina, with each exhibiting different pharmacokinetics, depending on the drug molecule and specific route of administration. In this study, we used intravenous (IV), subconjunctival (SC), and intravitreal (IVT) injections in rabbits to determine the pharmacokinetics of dexamethasone phosphate and its metabolic product, dexamethasone, at low (25 microg/kg) and high (250 microg/kg) doses. Plasma samples were collected from each group of animals at different time points up to 24 h after the injection. Using a liquid chromatographic mass spectrometric method with a limit of detection of 0.5 ng/mL, the plasma concentration for dexamethasone and its prodrug compound were quantified. IV delivery showed the fastest plasma elimination, followed by SC delivery. IVT delivery exhibited a depot effect, with very low plasma levels throughout the 24-h time course. At 24 h postinjection, only the high-dose IVT and low- and high-dose SC dexamethasone injections were still detectable in the plasma.

Antiflammin 1 peptide delivered non‐invasively by iontophoresis reduces irritantinduced inflammation in vivo

Abstract The potential of an anti‐inflammatory peptide (antiflammin 1) to reduce irritation when delivered transdermally by iontophoresis was examined. A model drug irritant, chlorpromazine, was co‐delivered with and without antifiammin 1 by iontophoresis to hairless guinea pigs transdermally. Quantitative skin irritation measurements were obtained by monitoring erythema by skin color reflectance with the Minolta Chromameter. Antifiammin 1 delivered by iontophoresis significantly decreased, but did not eliminate, the erythema associated with co‐delivery of an irritating drug compound. Lesion formation was also reduced in the presence of antiflammin 1. In vitro flux across hairless guinea pig skin demonstrated no significant differences in flux of the irritant compound in the presence or absence of antiflammin 1. In vivo generation and efflux of the inflammation mediator Prostaglandin E2 increased during 24‐h application of irritant and was unchanged in the presence of antiflammin 1. This result is discussed with respect to recent evidence that antiflammins may act on the lipo‐oxygenase pathway. In summary, antiflammin 1, an antiflammatory peptide, can be delivered transdermally by iontophoresis with retention of its biological activity in vivo.

Predictive Toxicology Methods for Transdermal Delivery Systems

Predicting potential toxicologic responses to transdermal delivery is a complex procedure, involving both traditional toxicology protocols for evaluating results of systemic exposure and topical studies assessing skin-drug interactions and reactions. Evaluation of individual drug and system components is followed by final system testing to assess possible interactions. Risk is estimated by analyzing toxicologic data quantitatively, with estimation of human exposure based on dose-response extrapolations. Formulation or system changes designed to minimize risk are evaluated. In some instances local intolerance to a compound—due either to irritation or sensitization—may preclude development of a successful transdermal product despite efficacious plasma levels. For viable projects with acceptable toxicologic profiles, a strategy is implemented to manage risk of irritation and sensitization. In addition to the usual drug-specific systemic toxicology and regulatory issues, a toxicology evaluation plan for trans...

A minimally invasive jet injector for intravitreal and subconjunctival injection.

BACKGROUND AND OBJECTIVE To evaluate a minimally invasive injector for intravitreal and subconjunctival administration of medications. MATERIALS AND METHODS The device has a microneedle that communicates with an internal formulation chamber. A piercing depth-limiting flange restricts microneedle penetration to a depth of less than 1 mm and defines the location of the pars plana from the limbus. The jet injector creates a force of up to 1,000 psi, forcing the medication through the remaining sclera/choroid thickness. The device was tested in 28 enucleated rabbit eyes and 9 experimental and 4 control rabbit eyes to define jet pressure for subconjunctival and intravitreal injection. RESULTS Injection pressures of 76 to 156 psi were needed for subconjunctival injection and 974 psi for intravitreal injection. Clinical and histologic examinations did not reveal damage to intraocular structures. CONCLUSION The semi-automated jet injector facilitated intravitreal/subconjunctival injection. The microneedle-assisted jet injector minimized the risk of wet injection by anchoring the microneedle in the sclera.

Transdermal Delivery of Antisense Oligonucleotides

In recent years, antisense oligodeoxynucleotides (ODNs) have emerged as promising biopharmaceutical therapeutics. These agents specifically target genes or gene transcripts involved in pathogenesis. Several clinical trials have demonstrated the therapeutic value and low toxicity of ODNs (1–5). Because ODNs, like most biopharmaceuticals, are highly susceptible to degradation in the gastrointestinal environment and only poorly absorbed through biomembranes, they have been delivered primarily by parenteral infusion. This route of administration, however, is invasive and inconvenient, and repeated injections or lengthy infusions can be painful and disruptive to normal life. Therefore, transdermal delivery is being explored as a more patient-friendly alternative (6).