Date Published: September 18, 2013
Publisher: Public Library of Science
Author(s): Anthony S. Ham, William Lustig, Lu Yang, Ashlee Boczar, Karen W. Buckheit, Robert W. Buckheit Jr, Cheryl A. Stoddart.
The aim of this study was to investigate the physicochemical and in vitro/ex vivo characteristics of the pyrmidinedione IQP-0410 formulated into transdermal films. IQP-0410 is a potent therapeutic anti-HIV nonnucleoside reverse transcriptase inhibitor that would be subjected to extensive first pass metabolism, through conventional oral administration. Therefore, IQP-0410 was formulated into ethyl cellulose/HPMC-based transdermal films via solvent casting. In mano evaluations were performed to evaluate gross physical characteristics. In vitro release studies were performed in both Franz cells and USP-4 dissolution vessels. Ex vivo release and permeability assays were performed on human epidermal tissue models, and the permeated IQP-0410 was collected for in vitro HIV-1 efficacy assays in CEM-SS cells and PBMCs. Film formulation D3 resulted in pliable, strong transdermal films that were loaded with 2% (w/w) IQP-0410. Composed of 60% (w/w) ethyl cellulose and 20% (w/w) HPMC, the films contained < 1.2% (w/w) of water and were hygroscopic resulting in significant swelling under humid conditions. The water permeable nature of the film resulted in complete in vitro dissolution and drug release in 26 hours. When applied to ex vivo epidermal tissues, the films were non-toxic to the tissue and also were non-toxic to HIV target cells used in the in vitro efficacy assays. Over a 3 day application, the films delivered IQP-0410 through the skin tissue at a zero-order rate of 0.94 ± 0.06 µg/cm2/hr with 134 ± 14.7 µM collected in the basal media. The delivered IQP-0410 resulted in in vitro EC50 values against HIV-1 of 2.56 ± 0.40 nM (CEM-SS) and 0.58 ± 0.03 nM (PBMC). The film formulation demonstrated no significant deviation from target values when packaged in foil pouches under standard and accelerated environmental conditions. It was concluded that the transdermal film formulation was a potentially viable method of administering IQP-0410 that warrants further development.
With over 25 million deaths attributed to AIDS since the first cases in 1981, 33 million individuals worldwide living with HIV, and over 2.5 million new infections yearly, HIV/AIDS continues to be a global emergency . To combat this epidemic, combinations of nucleoside, nucleotide and nonnucleoside reverse transcriptase inhibitors and protease inhibitors have been effectively used in highly active anti-retroviral therapies (HAART) to significantly reduce HIV virus load in infected individuals for prolonged periods of time. The utilization of HAART has dramatically changed the therapeutic landscape of HIV treatment and the application of cocktails of antiretroviral agents is now the standard of care for HIV patients . Currently over thirty antiviral therapies have been approved for use in HIV-infected patients . However, HAART still suffers from complications with the emergence of multi-drug resistant virus strains, toxicity, drug-drug interactions, difficult treatment regimens, and inadequate pharmacology (bioavailability and tissue distribution) [4,5,6]. Thus, the prevailing belief is that the addition of new anti-HIV agents to HAART regimens will provide additional clinical benefit with the development of new anti-HIV strategies and therapies.
The pyrimidinedione IQP-0410 has been identified as a potent antiretroviral therapeutic for HIV treatment. In developing the NNRTI as a potential therapeutic product, transdermal films were investigated as a formulation to systematically deliver IQP-0410 over extended periods of time to avoid bolus administration and first-pass metabolism. However, in considering transdermal drug delivery, the barrier properties of epidermal tissue must be considered. Transport through the epidermis is primarily diffusion driven, governed by the physicochemical properties of the API and the barrier itself . The drug released from the patches diffuses through the boundary layer (stratum corneum) to the underlying dermal layer and into the blood vessels. The rate and ultimate success of a drug to diffuse through the skin is largely dependent upon its molecular weight, partition coefficient (Log P), solubility, and polarity. IQP-0410 is practically insoluble and has a molecular weight of 352.43 g/mol. With a calculated Log P of 3-4, IQP-0410 is non-polar and thus lipophilic. Compounds with Log P values of 2-3 show optimal permeability across the stratum corneum as well as moderate partitioning out of the stratum corneum. However, compounds with Log P values > 3 show a high diffusion into the stratum corneum with little transport into the systemic circulation . The lipophilicty of IQP-0410 may result in increased residence times in the stratum corneum, limiting systemic delivery. In vitro studies show that IQP-0410 is efficacious at sub-nanomolar concentrations against HIV-1 (0.28 nM) with a resulting therapeutic index of greater than 500,000 . However, in vivo PK and bioavailability studies in mice have shown that IQP-0410 only has a 24% oral bioavailability with a half-life of 5.37 hours and an intravenous half-life of 30 minutes. This short systemic residence time can be attributed by extensive first-pass metabolism by the liver. Therefore, by-passing oral first-pass metabolism via dermal delivery may not be an issue with IQP-0410 having limited diffusion from the stratum corneum into the underlying circulation. In this study, the NNRTI IQP-0410 was formulated into a transdermal film formulation and evaluated for potential ARV drug delivery.
The pyrimidinedione IQP-0410 is a potent NNRTI that has significant potential as an anti-HIV therapeutic agent. Its product profile suggests it will experience many of the absorption, distribution, metabolism, and excretion (ADME) issues observed in other molecules of this class. Therefore, transdermal drug delivery was investigated as a potential dosage form to overcome these issues. A polymeric based transdermal film was formulated to hold and deliver IQP-0410 that was composed of non-toxic excipients. Our in vitro and ex vivo studies successfully demonstrated that IQP-0410 could be released from the transdermal films and delivered through a full thickness epidermal tissue model. The subsequent successful in vitro reduction of HIV-1 activity from the delivered drug over a 3 day application suggests the potential of IQP-0410 to be administered via transdermal patches. Further studies investigating the transdermal delivery of IQP-0410 will potentially result in transdermal patches that would offer an easier option for patients to comply with their medication regimes as compared to current treatments.