Pharmacokinetic characterization and tissue distribution of the new glucocorticoid soft drug loteprednol etabonate in rats and dogs

Comparison of ophthalmic loteprednol etabonate and prednisolone acetate effects on adrenocortical response to ACTH in dogs

OBJECTIVE

This study served to compare the degree of adrenocortical suppression following a 2-week administration of loteprednol etabonate (LE) and prednisolone acetate (PA) ophthalmic drops.

PROCEDURES

In this prospective double-masked triple-crossover study, 21 clinically healthy dogs were randomized to receive loteprednol etabonate ophthalmic suspension 0.5%, prednisolone acetate ophthalmic suspension 1%, or artificial tears (AT). Each group (LE, PA, and AT) received one drop in each eye every 12 h for 2 weeks, followed by a 3-week washout period between treatment blocks. ACTH stimulation tests were performed before and after each treatment block. Serum cortisol samples were drawn before and 60 min after administration of 1 μg/kg cosyntropin IV. Repeated-measurement ANOVA followed by a Tukey's multiple comparisons test (or a Friedman test followed by a Dunn's multiple comparisons test) were used to compare pre- and post-treatment cortisol values between each group. A p-value of ≤.05 was considered significant.

RESULTS

A total of 18 dogs completed the study. Prestimulation cortisol values were lower in the PA group compared to the LE (p = .0106), but not AT (p = .0589) groups, and post-stimulation cortisol values were lower in the PA group than either LE (p = .0005) or AT (p = .0002) groups. There was no significant difference detected in pre- or post-stimulation cortisol values after the treatment periods between LE and AT.

CONCLUSIONS

Based on the reduced suppression of cortisol values, LE caused significantly less hypothalamic-pituitary-adrenal axis suppression than PA. A topical steroid with minimal adrenocortical suppression, such as LE, may be favorable in patients where systemic glucocorticoid effects should be avoided.

A retrospective analysis of the use of loteprednol etabonate ophthalmic suspension 0.5% following canaloplasty

Background

While loteprednol etabonate (LE) suspension 0.5% is approved for the treatment of postoperative ocular inflammation, there have been no reported studies of its use in glaucoma patients undergoing canaloplasty.

Methods

This was a retrospective medical chart review conducted at a single US center. Data were collected on patients with glaucoma who underwent canaloplasty with or without cataract surgery, and were prescribed LE suspension 0.5% postoperatively. Outcomes evaluated included postsurgical inflammation (anterior chamber [AC] cells and flare), intraocular pressure (IOP), number of IOP-lowering medications, and postsurgical complications.

Results

Data were collected on 204 patients (262 eyes) with a mean (SD) age of 71.6 (11.3) years. The most frequent LE dosing regimens at day 1, week 1, and month 1 postsurgery were QID (92.3%; 241/261), TID (52.6%; 133/253), and QD (65.5%; 78/119), respectively. Inflammation (AC flare and cells), mostly mild, was noted in 33.2% (86/259) of eyes on postoperative day 1 and 8.6% (21/244) of eyes at month 1. Mean IOP and mean number of IOP-lowering medications were significantly reduced from baseline (P<0.001) at all time points postoperatively. Complete (no IOP-lowering medication) or qualified (use of ≤2 IOP-lowering medications) surgical success was achieved in 78.8% and 90.6% of eyes, respectively, at month 6 and 63.4% and 92.7% of eyes at month 36. The most frequently observed postoperative complication was hyphema in 48.7% (126/259) eyes at day 1, which decreased to 0.4% (1/244) of eyes by month 1. IOP ≥30 mmHg was noted in 13 (5.3%) eyes at postoperative week 1 and rarely thereafter, and no patient discontinued therapy because of an IOP increase.

Conclusion

These real-world data suggest that canaloplasty with or without cataract surgery managed postoperatively with LE suspension 0.5% is effective and safe in the glaucoma patient.

Rho Kinase (ROCK) Inhibitors and Their Therapeutic Potential

Rho kinases (ROCKs) belong to the serine-threonine family, the inhibition of which affects the function of many downstream substrates. As such, ROCK inhibitors have potential therapeutic applicability in a wide variety of pathological conditions including asthma, cancer, erectile dysfunction, glaucoma, insulin resistance, kidney failure, neuronal degeneration, and osteoporosis. To date, two ROCK inhibitors have been approved for clinical use in Japan (fasudil and ripasudil) and one in China (fasudil). In 1995 fasudil was approved for the treatment of cerebral vasospasm, and more recently, ripasudil was approved for the treatment of glaucoma in 2014. In this Perspective, we present a comprehensive review of the physiological and biological functions for ROCK, the properties and development of over 170 ROCK inhibitors as well as their therapeutic potential, the current status, and future considerations.

Chemical delivery systems and soft drugs: Retrometabolic approaches of drug design

Inclusion of metabolic considerations in the drug design process leads to significant development in the field of chemical drug targeting and the design of safer drugs during past few years which is a part of an approach now designated as Retro metabolic drug design (RMDD). This approach represents systematic methodologies that integrate structure-activity and structure-metabolism relationships and are aimed to design safe, locally active compounds with an improved therapeutic index. It embraces two distinct methods, chemical delivery systems and a soft drug approach. Present review recapitulates an impression of RMDD giving reflections on the chemical delivery system and the soft drug approach and provides a variety of examples to embody its concepts. Successful application of such design principles has already been applied to a number of marketed drugs like esmolol; loteprednol etc., and many other candidates like beta blockers, ACE inhibitors, alkylating agents, antimicrobials etc., are also under investigation.

Intranasal Loteprednol Etabonate in Healthy Male Subjects: Pharmacokinetics and Effects on Endogenous Cortisol

Loteprednol etabonate (LE) is a glucocorticoid soft drug that is currently in development for intranasal use. The main objectives of this study were to examine the pharmacokinetics and potential effects on systemic cortisol of two intranasal suspension formulations of LE and to compare these findings with placebo and fluticasone propionate (FP, Flonase) control treatments. In this randomized, double-blind (except for FP), parallel-group study (n = 8/group), all subjects received for 14 days once daily in the morning two puffs of the following nasal spray formulations into each nostril: LE 0.1% (400 microg/day), LE 0.2% (800 microg/day), FP 0.05% (200 microg/day), and placebo. Drug trough levels were determined on days 1, 5, 12, 13, and 14, and a full pharmacokinetic profile was established on day 14, and 24-hour serum cortisol profiles were assessed prior to treatment (i.e., at baseline) and after the last dose. All subjects completed the protocol without treatment-emergent adverse findings. All formulations were rapidly absorbed (t(max) less than 1 h). The rather short mean terminal half-lives of 2.2 +/- 1.5 hours and 1.8 +/- 1.0 hours for LE 400 microg and LE 800 microg, respectively, and 4.2 +/- 1.8 hours for the 200-microg FP treatment explained the lack of any accumulation. Mean peak concentrations (C(max)) were 139 +/- 57 pg/mL with LE 400 microg and 164 +/- 54 pg/mL with LE 800 microg and thus fairly independent from dose. The 200-microg FP treatment resulted in a C(max) of only 15.5 +/- 5.9 pg/mL. Mean measured AUC(0-t) values (193 +/- 87 pg/h/mL(-1), 300 +/- 183 pg/h/mL(-1), and 40 +/- 34 pg/h/mL(-1) for LE 400 microg, LE 800 microg, and FP 200 microg, respectively) showed high variability and suggested nonlinear pharmacokinetics for the LE formulations, indicative of a less complete systemic uptake of LE from the 0.2% concentration. None of the treatments (LE 400 microg, LE 800 microg, and FP 200 microg) showed evidence for serum cortisol suppression when compared with placebo, respectively. The uptake and systemic exposure appears less complete from the 0.2% LE concentration, which principally favors this formulation for further clinical development.

Recent developments in the treatment of posterior uveitis

Uveitis is an intraocular inflammation that can be caused by infection, autoimmune disease, trauma or malignancy. It is a serious cause of visual handicap and therapy is targeted at: removal of possible infectious agents, the immunological processes that lead to or sustain the inflammation and finally to prevent or treat the destructive effects of the inflammation on the delicate ocular structures. In this review the latest developments concerning the treatment of posterior uveitis are illuminated, e. g., new approaches concerning the treatment of infectious uveitis including the therapy of herpes virus (VZV, HSV and CMV), bacterial and toxoplasma infections of the eye. Several new ways to influence the immune response and inflammation are described including the use of interferons, modulation of cytokines, soft steroids, other new immunosuppressive drugs and treatment of autoimmune uveitis by oral tolerization. An overview is given to illustrate new ways to administer drugs into eyes, such as intravitreal devices. Finally new developments in the field of the treatment of the various complications of uveitis (cystoid macular edema) are described.

Advances in corticosteroid therapy for ocular inflammation: loteprednol etabonate

Topical corticosteroids are effective in reducing anterior segment inflammation but are associated with adverse drug reactions (ADRs) including elevation of intraocular pressure (IOP) and cataract formation. Retrometabolic drug design has advanced the development of new corticosteroids with improved therapeutic indices. Engineered from prednisolone, loteprednol etabonate (LE) has a 17α-chloromethyl ester, in lieu of a ketone group, and a 17β-etabonate group. LE is highly lipophilic and binds with high affinity to the glucocorticoid receptor; any unbound LE is metabolized to inactive metabolites. LE has been studied in several anterior segment inflammatory conditions (giant papillary conjunctivitis, allergic conjunctivitis, anterior uveitis, and keratoconjunctivitis sicca), and in postoperative ocular inflammation and pain. Combined with tobramycin, it is effective in blepharokeratoconjunctivitis. Elevations in IOP are infrequent with LE, and the absence of a C-20 ketone precludes formation of Schiff base intermediates with lens proteins, a common first step implicated in cataract formation with ketone steroids.

Pharmacokinetics of the sequential metabolites of loteprednol etabonate in rats

Pharmacokinetics, metabolism and excretion of two sequential inactive metabolites of the soft corticosteroid loteprednol etabonate (LE), Delta1-cortienic acid etabonate (AE) and Delta1-cortienic acid (A), have been investigated in rats. Pharmacokinetic studies (two-compartment model, 10 mg kg(-1) intra-venous bolus of AE or A) found the elimination of both AE (t(1/2)(beta), 12.46 +/- 1.18 min; CL total, 101.94 +/- 5.80 mL min(-1) kg(-1); and K el, 0.24 +/- 0.02 min(-1)) and A (t(1/2)(beta), 14.62 +/- 0.46 min; CL total, 53.80 +/- 1.40 mL min(-1) kg(-1); and K el, 0.18 +/- 0.02 min(-1)) to be significantly faster than that previously determined for the parent LE (t(1/2)(beta), 43.41 +/- 7.58 min; CL total, 67.40 +/- 11.60 mL min(-1) kg(-1); and K el, 0.071 +/- 0.024 min(-1)). For metabolism and excretion evaluations, 1 and 10 mg kg(-1) of either AE or A were intravenously administered, and the urine and bile were collected. AE and A rapidly reached their peak concentrations in the bile and urine, and most of them were eliminated within one hour. Total cumulative excretions at 4 h after 1 and 10 mg kg(-1) injections were 85.51 +/- 3.38% and 67.50 +/- 2.67% for AE, and 71.90 +/- 3.72% and 37.73 +/- 2.69% for A in bile; and 4.84 +/- 1.87% and 13.85 +/- 3.27% for AE, and 24.28 +/- 8.44% and 22.35 +/- 1.12% for A in urine, respectively. After AE administration, the excretion of AE was > 90%, and A was < 10% in all cases, indicating that the elimination of AE was much faster than its metabolism (to A). In a manner similar to that seen for LE, dose-dependent elimination was observed both in AE and A. These results suggested that both AE and A were ideal leads for the design of soft steroids based on the inactive metabolite approach.

Allergic diseases of the eye

The prevalence of ocular allergy is clearly underappreciated; it has been an underdiagnosed and undertreated area in primary care medicine. The ocular symptoms associated with the most common ocular allergy conditions,such as seasonal and perennial AC, are twice as likely to affect the allergy sufferer as nasal symptoms alone. The emergence of new medications for the specific treatment of ocular symptoms over the course of the past 15 years offers a new field for improved patient care by the primary and sub-specialty health care providers.

Pharmacokinetic/pharmacodynamic evaluation of inhalation drugs: application to targeted pulmonary delivery systems

Inhaled therapy with either glucocorticoids and/or beta(2)-adrenergic drugs remains the mainstay of asthma treatment. In the last few years, a number of new products have been introduced into the market with the goal of improving efficacy and safety. This review article summarises the pharmacokinetic and pharmacodynamic properties of inhaled drugs for topical delivery necessary to achieve this goal. Pharmacokinetic properties include a high pulmonary deposition, low oral bioavailability, optimised pulmonary residence time and a very high systemic clearance. Optimisation of pharmacodynamic properties, such as receptor selectivity, may also yield drugs with improved pulmonary selectivity. As existing drugs also provide high efficacy and safety profiles, future developments will represent only slight improvements and quantum leap improvements are unlikely to occur.

Ophthalmic drug design based on the metabolic activity of the eye: soft drugs and chemical delivery systems

Despite its apparent easy accessibility, the eye is, in fact, well protected against the absorption of foreign materials, including therapeutic agents, by the eyelids, by the tear-flow, and by the permeability barriers imposed by the cornea on one side and the blood-retinal barrier on the other. Most existing ophthalmic drugs were adapted from other therapeutic applications and were not specifically developed for the treatment of eye diseases; hence, they are not well suited to provide eye-specific effects without causing systemic side effects. A real breakthrough in the area of ophthalmic therapeutics can be achieved only by specifically designing new drugs for ophthalmic applications to incorporate the possibility of eye targeting into their chemical structure. Possibilities provided along these lines by designing chemical delivery systems (CDSs) and soft drugs within the framework of retrometabolic drug design are reviewed here. Both are general concept applicable in almost any therapeutic area. This review will concentrate on beta-adrenergic agonists and anti-inflammatory corticosteroids, where clinical results obtained with new chemical entities, such as betaxoxime, adaprolol, loteprednol etabonate, and etiprednol dicloacetate, exist to support the advantages of such metabolism-focused, ophthalmic-specific drug design approaches.

Effect of loteprednol etabonate nasal spray suspension on seasonal allergic rhinitis assessed by allergen challenge in an environmental exposure unit

BACKGROUND

Loteprednol etabonate (LE) is a novel soft steroid that was designed to improve the benefit/risk ratio of topical corticosteroid therapy. This study assesses the clinical efficacy and safety of three different doses of LE nasal spray in seasonal allergic rhinitis (SAR).

METHODS

In this single-center, double-blind, placebo-controlled, parallel-group trial 165 subjects with SAR to grass pollen received daily single doses of either 100, 200, 400 microg LE nasal spray, or placebo for 14 days. The patients underwent three 4-h allergen challenges with grass pollen in an environmental exposure unit at a screening visit (baseline) and on days 7 and 14 of treatment. Standardized nasal symptom scores were obtained every 20 min. Nasal flow, nasal secretions, and FEV(1) were measured every hour during allergen challenges.

RESULTS

After 14 days of treatment, patients who received 400 microg LE had significantly lower total nasal symptom scores compared with those receiving placebo (P = 0.007). LE400 reduced rhinorrhea, nasal congestion, nasal itching, the amount of nasal secretions, and improved nasal flow as compared with placebo (P < 0.05). LE100 and LE200 were not significantly different from placebo. All treatments were well tolerated.

CONCLUSIONS

Loteprednol 400 microg once daily is superior to placebo and the only effective dose tested in improving nasal symptoms and objective parameters in patients with SAR.

An HPLC method to evaluate purity of a steroidal drug, loteprednol etabonate

Validation of an analytical method for impurities and degradation products in an active pharmaceutical ingredient is important to assessment of quality and safety in a new pharmaceutical product. In the present study, a high-performance liquid chromatographic method was validated to evaluate purity of loteprednol etabonate (LE). LE and its four related substances, major process impurities and degradation products (PJ-90, PJ-91, LE-11-keto and LE-methyl ester) were well resolved using a phenyl-stationary phase under isocratic conditions. Two photo-degradation products were identified as chloromethyl 17alpha-ethoxycarbonyloxy-11beta-hydroxy-5alpha-methyl-2-oxo-19-norandrosta-1(10),3-diene-17beta-carboxylate and chloromethyl 17alpha-ethoxycarbonyloxy-11beta-hydroxy-1-methyl-3-oxo-6(5-->10alpha)-abeo-19-norandrosta-1,4-diene-17beta-carboxylate. A photo-degradation product, chloromethyl 1beta,11beta-epoxy-17alpha-ethoxycarbonyloxy-2-oxo-10alpha-androsta-4-ene-17beta-carboxylate, was not abundant by ultraviolet detector. The risk depending on only ultraviolet detection should be noted. Calibration curves for PJ-90, PJ-91, LE-11-keto and LE-methyl ester showed linearity over the range of 0.05-2.0% levels in LE with correlation coefficient of 0.999. Accuracy (n = 3) at the concentration of 0.5% level in LE for PJ-90, PJ-91, LE-11-keto and LE-methyl ester were 2.0, 2.0, 2.3 and 2.0%, respectively. Intra-day repeatability (n = 6) at the concentration of 0.5% level in LE for PJ-90, PJ-91, LE-11-keto and LE-methyl ester were 1.4, 1.4, 1.8 and 1.4%, respectively. The lower limits of detection for PJ-90, PJ-91, LE-11-keto and LE-methyl ester were 0.002, 0.001, 0.004 and 0.003% levels in LE, respectively.

Ocular allergy guidelines: a practical treatment algorithm

The treatment of ocular allergy requires a better understanding of the spectrum of clinical disorders involving various components of the immune system, and of interactions at the conjunctival surface. The immune response focuses primarily on the different levels of activity of Th2 lymphocytes and various other immune cells associated with allergic disorders, including mast cells, eosinophils, fibroblasts, and epithelial and endothelial cells. Ocular allergic disorders include seasonal allergic conjunctivitis (SAC), perennial allergic conjunctivitis (PAC), vernal keratoconjunctivitis (VKC), giant papillary conjunctivitis (GPC) and atopic keratoconjunctivitis (AKC), which, through immunopathological and molecular immunological techniques, can all be better appreciated as being part of a larger spectrum of an atopic disease state. In SAC, pathological changes, such as increased mast-cell activation, the presence of migratory inflammatory cells, and early signs of cellular activation at the molecular level, are minimal. In PAC, these changes are more pronounced in line with the increased duration of allergenic stimulation. In more chronic forms of allergic conjunctivitis, such as VKC in children and AKC in adults, the following changes are evident: a persistent state of mast cell, eosinophil and lymphocyte activation; noted switching from connective-tissue to mucosal-type mast cells; increased involvement of corneal pathology; and follicular development and fibrosis. The treatment of acute and more chronic forms of allergic conjunctivitis has focused in the past on symptomatic relief of symptoms, but with a better understanding of the mechanisms involved we can now provide interventional therapeutic strategies and symptomatic relief. Our advances in the basic understanding of these conditions are providing the foundation for guidelines that improve the ocular health of patients with ocular allergies.

Soft drug design: general principles and recent applications

Soft drug design represents a new approach aimed to design safer drugs with an increased therapeutic index by integrating metabolism considerations into the drug design process. Soft drugs are new therapeutic agents that undergo predictable metabolism to inactive metabolites after exerting their therapeutic effect. Hence, they are obtained by building into the molecule, in addition to the activity, the most desired way in which the molecule is to be deactivated and detoxified. In an attempt to systematize and summarize the related work done in a number of laboratories, including ours, the present review presents an overview of the general soft drug design principles and provides a variety of specific examples to illustrate the concepts. A number of already marketed drugs, such as esmolol, remifentanil, or loteprednol etabonate, resulted from the successful application of such design principles. Many other promising drug candidates are currently under investigation in a variety of fields including possible soft antimicrobials, anticholinergics, corticosteroids, beta-blockers, analgetics, ACE inhibitors, antiarrhythmics, and others. Whenever possible, pharmacokinetic and pharmacodynamic properties are briefly summarized and compared to those of other compounds used in the same field.

Recent advances in retrometabolic design approaches

The retrometabolic drug design approaches simultaneously incorporate structure activity (SAR) and structure metabolism (SMR) relationships in the design process. Two major approaches were developed, the chemical delivery systems (CDS), which allow chemical-enzymatic targeting of drugs via strategic sequential enzymatic activation of the inactive CDSs. On the opposite end of the retrometabolic design loop are the soft drugs (SD), which are designed to have highly improved therapeutic indeces by controlling their metabolism, after they achieve their therapeutic role. One of the most successful SD class is the 'inactive metabolite approach', where the design starts from an inactive metabolite of a drug. Its strategic manipulation yields an isosteric/isoelectronic drug analog, which is enzymatically deactivated to the very inactive metabolite at the desired compartment and with controlled rate. Overall, retrometabolic approaches represent a complex collection of chemical-enzymatic means for the design of safer drugs and for their controlled release. Most recent advances involve FDA approval of a soft steroid, as well as the first successful brain targeting of various neuropeptides and their brain-targeted analogs.

Soft drugs based on hydrocortisone: the inactive metabolite approach and its application to steroidal antiinflammatory agents

PURPOSE

The soft drug approach was applied to the design of analogs of highly potent synthetic steroids but with a metabolically labile ester group which at the same time served as an activating group.

METHODS

Several structural modifications of soft antiinflammatory steroids were synthesized and tested in several assays of biological activity. The hydrolytic stability of the compounds was also determined.

RESULTS

One of the compounds synthesized was determined to be a very potent steroid and had a highly significant separation of topical from systemic activity. However, the compound demonstrated greater than expected stability in the hydrolysis studies.

CONCLUSIONS

The goal of the soft drug approach has been achieved with the development of a highly potent drug which displays little or no systemic activity as measured in the tests presented here. The anticipated hydrolytic instability of the compounds was not corroborated; however, in view of other results, the interpretation is allowed that the rapid hydrolysis of the unbound fraction of the drug is an important factor in its lack of systemic effects.

Structural studies of loteprednol etabonate and other analogs of prednisolone using NMR techniques

Several structural analogs of prednisolone, prepared by esterification of the carboxylic and/or the C(17)-hydroxy group of 11 beta, 17 alpha-dihydroxy-3-oxo-androsta-1,4-diene-17 beta-carboxylic acid, were investigated by NMR. Step-by-step analysis of the 1H and 13C NMR spectra of these steroids, including proton-proton selective decoupling, nuclear Overhauser effect difference spectra, attached proton test, proton-carbon correlation (HETCOR), proton-proton correlation (COSY), and long-range proton-carbon decoupling (INAPT) techniques, led to unequivocal assignments of all their proton and carbon resonances. The stereochemical structure of loteprednol etabonate (chloromethyl 17 alpha-ethoxycarbonyloxy-11 beta-hydroxy-3-oxoandrosta-1,4-diene-17 beta-carboxylate, 1), a soft corticosteroid antiinflammatory drug, was proved to be analogous to prednisolone.