Narayan P. S. Cheruvu

Effect of eye pigmentation on transscleral drug delivery.

PURPOSE To determine the influence of eye pigmentation on transscleral retinal delivery of celecoxib. METHODS Melanin content in ocular tissues of both the strains was determined by sodium hydroxide solubilization METHOD The affinity of celecoxib to synthetic and natural melanin was estimated by co-incubating celecoxib and melanin in isotonic phosphate-buffered saline. The binding affinity (k) and the maximum binding (r(max)) for celecoxib to both natural and synthetic melanin were estimated. Suspension of celecoxib (3 mg/rat) was injected periocularly into one eye of Sprague-Dawley (SD, albino) and Brown Norway (BN, pigmented) rats. The animals were euthanatized at the end of 0.25, 0.5, 1, 2, 3, 4, 8, or 12 hours after the drug was administered, and celecoxib levels in ocular tissues (sclera, choroid-RPE, retina, vitreous, lens, and cornea) were estimated with an HPLC assay. In addition, celecoxib-poly(lactide) microparticles (750 microg drug/rat) were administered periocularly in SD and BN rats, and celecoxib levels in these eye tissues were assessed on day 8, to determine the effectiveness of the sustained release system. RESULTS The r(max) and k for celecoxibs binding to natural melanin were (3.92 +/- 0.06) x 10(-7) moles/mg of melanin and (0.08 +/- 0.01) x 10(6) M(-1), respectively. The affinity and the extent of celecoxibs binding to natural melanin were not significantly different from those observed with synthetic melanin. The concentrations of melanin in choroid-RPE, sclera, and retina of BN rats were 200 +/- 30, 12 +/- 4, and 3 +/- 0.2 mug/mg tissue, respectively. Melanin was not detectable in the vitreous, lens, and cornea of BN rats. In SD rats, melanin was not detected in all tissues assessed except in the choroid-RPE, wherein melanin-like activity was 100-fold less than in BN rats. The area under the curve (AUC) for tissue concentration versus time profiles for animals administered with celecoxib suspension was not significantly different between the two strains for sclera, cornea, and lens. However, the retinal (P = 0.001) and vitreal (P = 0.001) AUCs of celecoxib in the treated eyes were approximately 1.5-fold higher in SD rats than in BN rats. Further, the choroid-RPE AUC in the treated and untreated eyes, respectively, were 1.5-fold (P = 0.001) and 2-fold (P = 0.0001) higher in BN rats than in SD rats. With celecoxib-poly(lactide) microparticles, choroid-RPE, retina, and vitreous concentrations on day 8 exhibited similar trends in differences between the two strains, with the differences being greater than those recorded for the celecoxib suspension. CONCLUSIONS Transscleral retinal and vitreal drug delivery of lipophilic celecoxib is significantly lower in pigmented rats than in albino rats. This difference may be attributable to significant binding of celecoxib to melanin and its accumulation/retention in the melanin-rich choroid-RPE of pigmented rats. The hindrance of retinal and vitreal drug delivery by the choroid-RPE in pigmented rats is also true of sustained-release microparticle systems.

Pulmonary Delivery of Deslorelin: Large-Porous PLGA Particles and HPβCD Complexes

AbstractPurpose. To compare the systemic delivery of deslorelin following intratracheal administration of different deslorelin formulations. The formulations included dry powders of deslorelin, large-porous deslorelin-poly(lactide-co-glycolide) (PLGA) particles, and small conventional deslorelin-PLGA particles. Also, solution formulations of deslorelin and deslorelin-hydroxy-propyl-beta-cyclodextrin (HPβCD) complexes were tested. Methods. Dry powders of deslorelin, large-porous (mean diameter, 13.8 μm; density, 0.082 g/cc), and small conventional (mean diameter, 2.2 μm; density, 0.7 g/cc) deslorelin-PLGA particles and solutions of deslorelin with or without HPβCD were administered intratracheally to Sprague-Dawley rats. Blood samples were collected at 3 h, 1, 3, and 7 days postdosing, and plasma deslorelin concentrations were determined using enzyme immunoassay. At the end of 7 days, lungs were isolated, and bronchoalveolar lavage fluid was collected and analyzed for deslorelin. Results. At the end of 7 days, deslorelin plasma concentrations in the large-porous deslorelin-PLGA particle group were 120-fold and 2.5-fold higher compared to deslorelin powder and small conventional deslorelin-PLGA particles, respectively. Co-administration of HPβCD resulted in 2-, 3-, and 3-fold higher plasma deslorelin concentrations at 3 h, 1 and 3 days, respectively, compared to deslorelin solution. On day 7, deslorelin concentrations in bronchoalveolar lavage fluid as well as plasma were in the order: large porous particles > small conventional particles > deslorelin-HPβCD solution > deslorelin powder > deslorelin solution. Conclusions. Large-porous deslorelin PLGA particles can sustain deslorelin delivery via the deep lungs. Co-administration of HPβCD enhances the systemic delivery of deslorelin. The pulmonary route is useful as a noninvasive alternative for the systemic delivery of deslorelin.

Sclera-Choroid-RPE Transport of Eight β-Blockers in Human, Bovine, Porcine, Rabbit, and Rat Models

PURPOSE To determine the influence of drug lipophilicity, ocular pigmentation, and species differences on transscleral solute transport. METHODS The transport of eight β-blockers across excised sclera/sclera-choroid-RPE (SCRPE) of albino rabbit, pigmented rabbit, human, porcine, and bovine eyes was determined over 6 hours. The ex vivo transscleral β-blocker transport to the vitreous at the end of 6 hours was determined in euthanatized, pigmented Brown Norway rats. The thicknesses of the sclera and SCRPE and the melanin content in choroid-RPE (CRPE) were measured to determine whether species differences in drug transport can be explained on this basis. RESULTS Solute lipophilicity inversely correlated with the SCRPE cumulative percentage of transport in all species (R(2) ≥ 0.80). The CRPE impeded the SCRPE transport of all β-blockers (51%-64% resistance in the rabbits; 84%-99.8% in the bovine and porcine eyes) more than the sclera, with the impedance increasing with lipophilicity. SCRPE transport followed the trend albino rabbit > pigmented rabbit > human > porcine > bovine, and a cross-species comparison showed good Spearmans rho correlation (R(2) ≥ 0.85). Bovine (R(2) = 0.84), porcine (R(2) = 0.84), and human (R(2) = 0.71) SCRPE transport was more predictive than that in the rabbit models (R(2) = 0.60-0.61) of transscleral solute transport to the vitreous in rats. The CRPE concentrations were higher in pigmented rabbits than in albino rabbits. The melanin content of the CRPE exhibited the trend albino rabbit ≪ pigmented rabbit < porcine ∼ bovine < rat. Normalization to scleral thickness abolished the species differences in scleral transport. Normalization to SCRPE thickness and melanin content significantly reduced species differences in SCRPE transport. CONCLUSIONS Owing to the presence of pigment and drug binding, choroid-RPE is the principal barrier to transscleral β-blocker transport, with the barrier being more significant for lipophilic β-blockers. Although different in magnitude between species, sclera/SCRPE transport can be correlated between species. Tissue thickness accounts for the species differences in scleral transport. Differences in tissue thickness and melanin content largely account for the species differences in SCRPE transport.

Hydrophilic prodrug approach for reduced pigment binding and enhanced transscleral retinal delivery of celecoxib.

Transscleral retinal delivery of celecoxib, an anti-inflammatory and anti-VEGF agent, is restricted by its poor solubility and binding to the melanin pigment in choroid-RPE. The purpose of this study was to develop soluble prodrugs of celecoxib with reduced pigment binding and enhanced retinal delivery. Three hydrophilic amide prodrugs of celecoxib, celecoxib succinamidic acid (CSA), celecoxib maleamidic acid (CMA), and celecoxib acetamide (CAA) were synthesized and characterized for solubility and lipophilicity. In vitro melanin binding to natural melanin (Sepia officinalis) was estimated for all three prodrugs. In vitro transport studies across isolated bovine sclera and sclera-choroid-RPE (SCRPE) were performed. Prodrug with the highest permeability across SCRPE was characterized for metabolism and cytotoxicity and its in vivo transscleral delivery in pigmented rats. Aqueous solubilities of CSA, CMA, and CAA were 300-, 182-, and 76-fold higher, respectively, than celecoxib. Melanin binding affinity and capacity were significantly lower than for celecoxib for all three prodrugs. Rank order for the % in vitro transport across bovine sclera and SCRPE was CSA > CMA ~ CAA ~ celecoxib, with the transport being 8-fold higher for CSA than celecoxib. CSA was further assessed for its metabolic stability and in vivo delivery. CSA showed optimum metabolic stability in all eye tissues with only 10-20% conversion to parent celecoxib in 30 min. Metabolic enzymes responsible for bioconversion included amidases, esterase, and cytochrome P-450. In vivo delivery in pigmented BN rats showed that CSA had 4.7-, 1.4-, 3.3-, 6.0-, and 4.5-fold higher delivery to sclera, choroid-RPE, retina, vitreous, and lens than celecoxib. CSA has no cytotoxicity in ARPE-19 cells in the concentration range of 0.1 to 1000 μM. Celecoxib succinamidic acid, a soluble prodrug of celecoxib with reduced melanin binding, enhances transscleral retinal delivery of celecoxib.

Lung Gene Therapy: Clinical and Regulatory Issues

Lung gene therapy is a promising therapeutic approach for several difficult to treat disorders such as cystic fibrosis, α1‐antitrypsin deficiency, and cancers. Although several gene therapy protocols have proven success in preclinical studies, when moved to the clinical stages, they have met with limited success. Thus, there is a need to carefully assess the developmental approaches undertaken with gene therapy products intended for lung disorders. This review summarizes the advances made in lung gene therapy, discusses the limitations of the existing approaches including the lack of reliability of preclinical studies, immunogenecity and toxicity of the gene therapy vectors, and the poor efficiency of nonviral vectors, and invokes the role of ethics and the regulatory agencies in better developing the gene therapy products.

Retraction of “Hydrophilic Prodrug Approach for Reduced Pigment Binding and Enhanced Transscleral Retinal Delivery of Celecoxib”

T authors retract the article “Hydrophilic Prodrug Approach for Reduced Pigment Binding and Enhanced Transscleral Retinal Delivery of Celecoxib”, Mol. Pharmaceutics 2012, 9 (3), 605−614, following a scientific misconduct investigation by the University of Colorado Denver Anschutz Medical Campus, which concluded that the LC−MS data supporting Figures 3, 5, 6, and 7 were falsified by Rajendra Kadam to reduce variability in measurements, to produce smooth kinetics, or to create statistical differences. The fabrication of data related to these figures raises questions about the conclusions within the paper.