Detection of the free acid of bimatoprost in aqueous humor samples from human eyes treated with bimatoprost before cataract surgery

Is fat the future for saving sight? Bioactive lipids and their impact on glaucoma

Glaucoma is characterized by a continuous loss of retinal ganglion cells. The cause of glaucoma is associated with an increase in intraocular pressure (IOP), but the underlying pathophysiology is diverse and, in most cases, unknown. There is an indisputable unmet need to identify new pathways involved in glaucoma pathogenesis. Increasing evidence suggests that bioactive lipids may be critical in the development and progression of glaucoma. Preclinical and clinical bioactive lipid targets exist and are being developed. In this review, we aim to shed light on the potential of bioactive lipids for the prevention, diagnosis, prognosis, and treatment of glaucoma by asking the question "is fat the future for saving sight".

Prostaglandin E2 and F2α Alter Expression of Select Cholesteryl Esters and Triacylglycerols Produced by Human Meibomian Gland Epithelial Cells

PURPOSE

PGF2α analogs are commonly used to treat glaucoma and are associated with higher rates of meibomian gland dysfunction (MGD). The purpose of this study was to evaluate the physiological effects of PGF2α and PGE2 on immortalized human meibomian gland epithelial cells (HMGECs).

METHODS

HMGECs were immunostained for the 4 PGE2 receptors (EP1, EP2, EP3, and EP4) and 1 PGF2α receptor (FP) and imaged. Rosiglitazone-differentiated HMGECs were exposed to PGF2α and PGE2 (10-9 to 10-6 M) for 3 hours. Cell viability was assessed by an adenosine triphosphate-based luminescent assay, and lipid extracts were analyzed for cholesteryl esters (CEs), wax esters (WEs), and triacylglycerols (TAGs) by ESI-MSMSALL in positive ion mode by a Triple TOF 5600 Mass Spectrometer using SCIEX LipidView 1.3.

RESULTS

HMGECs expressed 3 PGE2 receptors (EP1, EP2, and EP4) and the 1 PGF2α receptor (FP). Neither PGE2 nor PGF2α showed signs of cytotoxicity at any of the concentrations tested. WEs were not detected from any of the samples, but both CEs and TAGs exhibited a diverse and dynamic profile. PGE2 suppressed select CEs (CE 22:1, CE 26:0, CE 28:1, and CE 30:1). PGF2α dose dependently increased several CEs (CE 20:2, CE 20:1, CE 22:1, and CE 24:0) yet decreased others. Both prostaglandins led to nonspecific TAG remodeling.

CONCLUSIONS

PGE2 and PGF2α showed minimal effect on HMGEC viability. PGF2α influences lipid expression greater than PGE2 and may do so by interfering with meibocyte differentiation. This work may provide insight into the mechanism of MGD development in patients with glaucoma treated with PGF2α analogs.

Discovery to Launch of Anti-allergy (Emadine; Patanol/Pataday/Pazeo) and Anti-glaucoma (Travatan; Simbrinza) Ocular Drugs, and Generation of Novel Pharmacological Tools Such as AL-8810

The eye and eyesight are exquistly designed and are precious, and yet we often take them for granted. Good vision is critical for our long-term survival and for humanity's enduring progress. Unfortunately, since ocular diseases do not culminate in life-and-death scenarios, awareness of the plight of millions of people suffering from such eye ailments is not publicized as other diseases. However, losing eyesight or falling victim to visual impairment is a frightening outlook for most people. Glaucoma, a collection of chronic optic neuropathies, of which the most prevalent form, primary open-angle glaucoma (POAG), is the second leading cause of irreversible blindness. POAG currently afflicts >70 million people worldwide and is an insidious, progressive, silent thief of sight that is asymptomatic. On the other hand, allergic conjunctivitis (AC), and the associated rhinitis ("hay-fever"), frequently victimizes a huge number of people worldwide, especially during seasonal changes. While not life-threatening, sufferers of AC soon learn the value of drugs to treat their signs and symptoms of AC as they desire rapid relief to overcome the ocular itching/pain, redness, and tearing AC causes. Herein, I will describe the collective efforts of many researchers whose industrious, diligent, and dedicated team work resulted in the discovery, biochemical/pharmacological characterization, development and eventual launch of drugs to treat AC (e.g., olopatadine [Patanol/Pataday/Pazeo] and emedastine [Emedine]), and for treating ocular hypertension and POAG (e.g., travoprost [Travatan ] and Simbrinza). This represents a personal perspective.

Phase 3, Randomized, 20-Month Study of Bimatoprost Implant in Open-Angle Glaucoma and Ocular Hypertension (ARTEMIS 1)

PURPOSE

To evaluate the intraocular pressure (IOP)-lowering efficacy and safety of 10- and 15-μg bimatoprost implant in subjects with open-angle glaucoma (OAG) and ocular hypertension (OHT) after initial and repeated administrations.

DESIGN

Randomized, 20-month, multicenter, subject- and efficacy evaluator-masked, parallel-group, phase 3 clinical study.

PARTICIPANTS

Adults with OAG or OHT in each eye, open iridocorneal angle inferiorly in the study eye, and study eye baseline IOP (hour 0; 8 am) of 22-32 mmHg after washout.

METHODS

Study eyes received bimatoprost implant 10 μg (n = 198) or 15 μg (n = 198) on day 1 with readministration at weeks 16 and 32, or twice-daily topical timolol maleate 0.5% (n = 198). Intraocular pressure was measured at hours 0 and 2 at each visit.

MAIN OUTCOME MEASURES

Primary end points were IOP and change from baseline IOP through week 12. Safety measures included treatment-emergent adverse events (TEAEs) and corneal endothelial cell density (CECD).

RESULTS

Both dose strengths of bimatoprost implant were noninferior to timolol in IOP lowering after each administration. Mean diurnal IOP was 24.0, 24.2, and 23.9 mmHg at baseline and from 16.5-17.2, 16.5-17.0, and 17.1-17.5 mmHg through week 12 in the 10-μg implant, 15-μg implant, and timolol groups, respectively. The incidence of corneal and inflammatory TEAEs of interest (e.g., corneal endothelial cell loss, iritis) was higher with bimatoprost implant than timolol and highest with the 15-μg dose strength. Incidence of corneal TEAEs increased after repeated treatment; with 3 administrations at fixed 16-week intervals, incidence of ≥20% CECD loss was 10.2% (10-μg implant) and 21.8% (15-μg implant). Mean best-corrected visual acuity (BCVA) was stable; 3 implant-treated subjects with corneal TEAEs had >2-line BCVA loss at their last visit.

CONCLUSIONS

Both dose strengths of bimatoprost implant met the primary end point of noninferiority to timolol through week 12. One year after 3 administrations, IOP was controlled in most subjects without additional treatment. The risk-benefit assessment favored the 10-μg implant over the 15-μg implant. Ongoing studies are evaluating other administration regimens to reduce the potential for CECD loss. The bimatoprost implant has potential to improve adherence and reduce treatment burden in glaucoma.

Matrix Metalloproteinases and Glaucoma Treatment

Matrix metalloproteinases (MMPs) are a family of proteolytic enzymes that degrade extracellular matrix (ECM) components such as collagen and have important roles in multiple biological processes, including development and tissue remodeling, both in health and disease. The activity of MMPs is influenced by the expression of MMPs and tissue inhibitors of metalloproteinase (TIMPs). In the eye, MMP-mediated ECM turnover in the juxtacanalicular region of the trabecular meshwork (TM) reduces outflow resistance in the conventional outflow pathway and helps maintain intraocular pressure (IOP) homeostasis. An imbalance in the MMP/TIMP ratio may be involved in the elevated IOP often associated with glaucoma. The prostaglandin analog/prostamide (PGA) class of topical ocular hypotensive medications used in glaucoma treatment reduces IOP by increasing outflow through both conventional and unconventional (uveoscleral) outflow pathways. Evidence from in vivo and in vitro studies using animal models and anterior segment explant and cell cultures indicates that the mechanism of IOP lowering by PGAs involves increased MMP expression in the TM and ciliary body, leading to tissue remodeling that enhances conventional and unconventional outflow. PGA effects on MMP expression are dependent on the identity and concentration of the PGA. An intracameral sustained-release PGA implant (Bimatoprost SR) in development for glaucoma treatment can reduce IOP for many months after expected intraocular drug bioavailability. We hypothesize that the higher concentrations of bimatoprost achieved in ocular outflow tissues with the implant produce greater MMP upregulation and more extensive, sustained MMP-mediated target tissue remodeling, providing an extended duration of effect.

Effect of prostaglandin analogs: Latanoprost, bimatoprost, and unoprostone on matrix metalloproteinases and their inhibitors in human trabecular meshwork endothelial cells

Bimatoprost, latanoprost, and unoprostone are prostaglandin F_2α analogs (PGAs) and are used to lower intraocular pressure. We investigated the free acid effects of these three prostaglandin analogs: bimatoprost, latanoprost, and unoprostone on human matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMP) in the trabecular meshwork (TM) cells. Immunoblot results show that all three PGAs generally increased MMPs-1,9 and TIMPs-4. Additionally, bimatoprost and latanoprost both increased MMP-3 and TIMP-2, while unoprostone had an indeterminate effect on both. Zymography results show that all three PGAs except unoprostone increased intermediate MMP-1 activity while bimatoprost and latanoprost increased MMP-9 activity. Together, these data suggest that the balance between MMPs and TIMPs correlate to the relative intraocular pressure lowering effectiveness observed in clinical studies of these PGAs.

Nonclinical Pharmacokinetic and Pharmacodynamic Assessment of Bimatoprost Following a Single Intracameral Injection of Sustained-Release Implants

Purpose

To assess the pharmacokinetic (PK)/pharmacodynamic (PD) relationship following intracameral Bimatoprost sustained-release (SR) implants (8, 15, 30, and 60 µg) in dogs to determine the optimal investigative dose in humans.

Methods

Forty-four male normotensive beagle dogs were assigned to 1 of 8 groups receiving 8-, 15-, 30-, and 60-µg implants (PD assessment [n = 8/group, 4 groups]; PK assessment [n = 3/group, 4 groups]). Intraocular pressure (IOP) in PD animals and aqueous humor/blood concentrations of bimatoprost and its acid in PK animals were assessed. PK/PD correlation analysis was performed using steady-state data. Residual implants were recovered to assess polymer degradation.

Results

Dose-dependent IOP lowering was observed for all dose groups for at least 3 months postdose. Blood concentrations of bimatoprost and bimatoprost acid were below the limit of quantification (<0.25 ng/mL), whereas dose-dependent concentration-time profiles were observed in the aqueous humor. At steady state, observed and predicted correlation between aqueous humor drug concentration and IOP lowering was similar and translatable to findings in humans following topical bimatoprost eyedrop administration. Implants at all doses were well tolerated and polymer degradation was apparent.

Conclusions

Dose-dependent IOP lowering with Bimatoprost SR was maintained for at least 3 months in dogs, and the implants were well tolerated. The established PK/PD relationship appears to translate to humans. Doses between 8 and 15 µg appear to provide the best benefit/risk profile for clinical development of the implants.

Translational Relevance

The close PK/PD relationship between dog and human helps inform which bimatoprost dose should be investigated in clinical studies.

[Hypotensive efficacy of bimatoprost in monotherapy of primary open-angle glaucoma]

PURPOSE

To study the effectiveness of monotherapy with bimatoprost in patients with decompensated intraocular pressure (IOP).

MATERIAL AND METHODS

90 patients (132 eyes) with stage I-II glaucoma and decompensated IOP previously treated with timolol, latanoprost and travoprost were included in the study. Average IOP at the beginning of the study was 25.4±2.5 mmHg. All patients had their hypotensive medications substituted by bimatoprost. The patients were examined during the initial appointment, as well as after 4 and 12 weeks.

RESULTS

IOP decrease was highest in the group of patients who had been treated with timolol: initially IOP was 26.2±1.8 mmHg, after 4 weeks - 21.0±2.2 mmHg, after 12 weeks - 20.8±1.9 mmHg (p<0.001). The initial IOP of patients who had been treated with latanoprost was 24.8±2.9 mmHg, 21.8±2.4 mmHg after 4 weeks, and 21.6±2.3 mmHg after 12 weeks (p<0.001). Patients who had been treated with travoprost had 25.6±2.2 mmHg initially, 23.0±2.5 mmHg after 4 weeks, and 23.2±2.6 mmHg after 12 weeks (p<0.001). By the end of the study IOP has decreased by 5.4, 3.2 and 2.4 mmHg in the groups of patients who had been treated with timolol, latanoprost and travoprost, respectively.

CONCLUSION

Bimatoprost can be used as monotherapy if another hypotensive drug in monotherapy is insufficient for IOP compensation.

Analysis of pharmaceuticals and small molecules in aqueous humor

Aqueous humor (AH) is a transparent fluid found in the anterior chamber of the eye. The circulating AH nourishes the cornea and lens and removes the metabolic waste moving through the ocular chambers and drains from the eye to the venous blood. Analysis of drugs in AH is necessary to evaluate their pharmacokinetics parameters, which may be crucial to avoid potential adverse effects. Analysis of endogenous components of AH may help to understand its physiology as well as changes evoked by pathological situation. This review describes analytical methods used for determination of pharmaceuticals and small endogenous molecules in AH, focusing on sample preparation procedures and analytical techniques. Studies on human and animal samples are included. After inspection and filtering of records found in PubMed about 100 research papers were selected to review. In these articles AH samples of human and rabbit origin were studied most often. Sample evaporation and reconstitution in smaller solvent volume was the most popular method for analyte pre-concentration. Acetonitrile, methanol or mixture of both solvents were used most often for protein precipitation.

Prostaglandin FP receptor antagonists: discovery, pharmacological characterization and therapeutic utility

In contrast to the availability of potent and selective antagonists of several prostaglandin receptor types (including DP₁ , DP₂ , EP and TP receptors), there has been a paucity of well-characterized, selective FP receptor antagonists. The earliest ones included dimethyl amide and dimethyl amine derivatives of PGF_2α , but these have failed to gain prominence. The fluorinated PGF_2α analogues, AL-8810 and AL-3138, were subsequently discovered as competitive and non-competitive FP receptor antagonists respectively. Non-prostanoid structures, such as the thiazolidinone AS604872, the D-amino acid-based oligopeptide PDC31 and its peptidomimic analogue PDC113.824 came next, but the latter two are allosteric inhibitors of FP receptor signalling. AL-8810 has a sub-micromolar in vitro potency and ≥2 log unit selectivity against most other PG receptors when tested in several cell- and tissue-based functional assays. Additionally, AL-8810 has demonstrated therapeutic efficacy as an FP receptor antagonist in animal models of stroke, traumatic brain injury, multiple sclerosis, allodynia and endometriosis. Consequently, it appears that AL-8810 has become the FP receptor antagonist of choice. LINKED ARTICLES: This article is part of a themed section on Eicosanoids 35 years from the 1982 Nobel: where are we now? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.8/issuetoc.

Patient considerations in ocular hypertension: role of bimatoprost ophthalmic solution

Glaucoma is a leading cause of irreversible blindness worldwide. The reduction of intraocular pressure has been well established as an effective treatment to prevent both the development and the progression of all forms of glaucoma. Bimatoprost 0.03% ophthalmic solution, introduced in 2001, is a synthetic prostamide with the unique mechanism of improving both uveoscleral and trabecular outflow. Comparative studies with other pharmacotherapies have shown favorable results for bimatoprost as a potent ocular hypotensive agent that is generally well tolerated. Common side effects include conjunctival hyperemia, eyelash growth, iris pigmentation and periorbital changes. Hyperemia rates were reduced following the introduction of bimatoprost 0.01%. Bimatoprost should be used with caution in those with higher risk of developing ocular inflammation and macular edema. However, the perceived risk of bimatoprost in these patient populations is likely greater than the actual risk observed in practice. Bimatoprost is currently in the center of several clinical trials including its use for dermatologic applications and sustained-release therapies for the treatment of ocular hypertension and glaucoma.

Ocular Tolerability of Preservative-Free Tafluprost and Latanoprost: in vitro and in vivo Comparative Study

Objective:

Detrimental effects of the preserved prostaglandin analogs (PGAs) have been thoroughly documented in the published literature. The current work studied two preservative-free (PF) prostaglandin eye drops: PF tafluprost and PF latanoprost. The aim of the study was to compare these two PF formulations in vitro for viability of the human corneal epithelial (HCE-T) cells and in vivo for ocular tolerability of the rabbit eye.

Method:

Viability of the HCE-T cells was measured by the MTS assay. The SV40-immortalized HCE-T cells were exposed to 100 µL of the drug solutions (at their commercial concentrations) or the culture medium. Ocular irritation was evaluated after repeated instillation of the drug solutions in Japanese white rabbits (Kbl:JW).

Results:

A significant loss of HCE-T cell viability was observed in vitro immediately after the exposure to PF latanoprost formulation but not immediately after the exposure to PF tafluprost formulation. Congruently, PF latanoprost induced in vivo more irritation on the rabbit eye than PF tafluprost.

Conclusion:

Comparing these two PF formulations in vitro and in vivo, it is considered that ocular tolerability of PF tafluprost is better than PF latanoprost. Taking into account the composition of these two PF PGA formulations, the solubilizing agent macrogolglycerol hydroxystearate 40 (MGHS40) contained in PF latanoprost formulation is a plausible cause for the negative effects.

Bimatoprost, latanoprost, and tafluprost induce differential expression of matrix metalloproteinases and tissue inhibitor of metalloproteinases

Background

Differences in the increase in matrix metalloproteinase (MMP) and decrease in tissue inhibitor of metalloproteinase (TIMP) activity may contribute to the different characteristics observed clinically on decreased intraocular pressure in patients with glaucoma or ocular hypertension. The purpose of this study was to investigate differences in the expression profiles of MMPs and TIMPs induced by the prostaglandin analogs bimatoprost, latanoprost, and tafluprost in human non-pigmented ciliary epithelial cells (HNPCECs).

Methods

HNPCECs were cultured for 24 h with 0, 10, 100, or 1000 μM of the free acid forms of bimatoprost, latanoprost, and tafluprost. We measured the expression levels of MMPs and TIMPs using real-time polymerase chain reaction, and compared the results. Enzyme activities of MMP-2 and −9 in conditioned media were measured by gelatin zymography.

Results

All prostaglandin analogs we examined dose-dependently increased expression levels of MMP-1, −2, −3, −9, and −17, whereas expression levels of TIMP-1 and −2 decreased with increasing concentrations of each analog. Each prostaglandin analog induced different levels of increases in MMPs and decreases in TIMPs.

Conclusions

Unique expression profiles of MMPs and TIMPs induced by bimatoprost, latanoprost, and tafluprost, as shown in HNPCECs, may contribute to clinically different effects on intraocular pressure decreases in patients with glaucoma or ocular hypertension.

Latanoprost in the treatment of glaucoma

Prostaglandins are approved by the European Glaucoma Society guidelines as first-line treatment for glaucoma. This review focuses on latanoprost, an ester prodrug of prostaglandin (PG) F_2α, which was the first of the currently available topical PGF_2α analogs to be launched for glaucoma or ocular hypertension and which still accounts for the majority of prescriptions. It is better absorbed than the parent compound through the cornea, and peak concentration of the active drug is in the aqueous humor 1–2 hours after topical dosing (15–30 ng/mL). Metabolism occurs mainly in the liver. Latanoprost (0.005%) has been very well studied in clinical trials and meta-analyses that show it to be generally as effective as the other PG analogs (bimatoprost, travoprost, and tafluprost) and more effective than timolol, dorzolamide, and brimonidine. Latanoprost has good short- and long-term safety and tolerability profiles. In common with other prostaglandins, it lacks systemic effects, but can cause ocular adverse events such as conjunctival hyperemia, pigmentation of the iris, periocular skin or eyelashes, hypertrichosis, and ocular surface effects or irritation. Latanoprost is significantly better tolerated than either bimatoprost or travoprost. Patients treated with latanoprost have better compliance and persist with therapy longer than those that are given other drugs. An improved formulation of latanoprost without the preservative benzalkonium chloride has recently been developed. It is as effective as conventional latanoprost, has a lower incidence of hyperemia, and can be stored at room temperature. In conclusion, latanoprost has the best efficacy–tolerability ratio of the PG analogs available for glaucoma treatment, and has good compliance and persistence. These factors should be improved further by the recent development of preservative-free latanoprost.

Fixed-dose combination of tafluprost and timolol in the treatment of open-angle glaucoma and ocular hypertension: comparison with other fixed-combination products

A new preservative-free fixed-dose combination of 0.0015% tafluprost, a prostaglandin F_2α analog, and 0.5% timolol (TAF/TIM; Santen Oy, Tampere, Finland), a beta-adrenergic antagonist has recently been developed. The intraocular pressure (IOP) reduction with TAF/TIM in open-angle glaucoma and ocular hypertension is similar to that of other prostaglandin–timolol fixed-combination products. Patients with high IOP responded well to TAF/TIM with reductions of up to 40% (>13 mmHg) and beyond. Compared to previous controlled and double-masked clinical trials with DuoTrav^® (Alcon, Fort Worth, USA) and Ganfort^® (Allergan, Irvine, USA), TAF/TIM caused less superficial ocular side effects and less conjunctival hyperemia. Plausible explanations for the differences in side effects between the fixed-combination products are discussed.

Recent progress in prostaglandin F2α ethanolamide (prostamide F2α) research and therapeutics

Prostamide (prostaglandin ethanolamide) research emerged from two distinct lines of research: 1) the unique pharmacology of the antiglaucoma drug bimatoprost and 2) the discovery that endocannabinoid anandamide was converted by COX-2 to a series of electrochemically neutral prostaglandin (PG) ethanolamides. Bimatoprost pharmacology was found to be virtually identical to that of prostamide F2α. The earliest studies relied on comparison of agonist potencies compared with PGF2α and synthetic prostaglandin F2α (FP) receptor agonists. The subsequent discovery of selective and potent prostamide receptor antagonists (AGN 211334-6, as shown in Fig. 3) was critical for distinguishing between prostamide and FP receptor-mediated effects. The prostamide F2α receptor was then modeled by cotransfecting the wild-type FP receptor with an mRNA splicing variant (altFP4).Bimatoprost is now used therapeutically for treating both glaucoma and eyelash hypotrichosis. Bimatoprost also stimulates hair growth in isolated human scalp hair follicles. A strong effect is also seen in mouse pelage hair, where bimatoprost essentially halves the onset of hair regrowth and the time to achieve full hair regrowth in shaved mice. Beyond glaucoma and hair growth, bimatoprost has potential for reducing fat deposition. Studies to date suggest that preadipocytes are the cellular target for bimatoprost. The discovery of the enzyme prostamide/PGF synthase was invaluable in elucidating the anatomic distribution of prostamide F2α. High expression in the central nervous system provided the impetus for later studies that described prostamide F2α as a nociceptive mediator in the spinal cord. At the translational level, bimatoprost has already provided therapeutics in two distinct areas and the use of both prostamide agonists and antagonists may provide other useful medicaments.

Therapeutic uses of prostaglandin F(2α) analogues in ocular disease and novel synthetic strategies

The pharmacological management of glaucoma and ocular hypertension has significantly changed over the last 18 years with the introduction of PGF2α analogues, more specifically latanoprost (6), travoprost (8), bimatoprost (10) and tafluprost (12). Prostanoids are currently the first-line medicines among ocular antihypertensive drugs in terms of efficacy, safety, patient compliance and medical economy. Their ability to effectively reduce intraocular pressure with once-per-day dosing, ocular tolerability comparable to timolol and general lack of systemic adverse effects have made them the mainstay of pharmacological therapy for glaucoma and ocular hypertension all over the world. The present review reports a novel, convergent and highly diastereoselective method for the synthesis of PGF2α analogues from the structurally advanced prostaglandin phenylsulfone (5Z)-(+)-15 and new ω-chain synthons. The biochemistry, clinical efficacy and side effects of four commercially available PGF2α analogues, currently used as first-line agents for reducing intraocular pressure in patients with glaucoma or ocular hypertension, are also discussed.

Comparison of human ocular distribution of bimatoprost and latanoprost

PURPOSE

This study investigated the ocular distribution of bimatoprost, latanoprost, and their acid hydrolysis products in the aqueous humor, cornea, sclera, iris, and ciliary body of patients treated with a single topical dose of 0.03% bimatoprost or 0.005% latanoprost for understanding concentration-activity relationships.

METHODS

Thirty-one patients undergoing enucleation for an intraocular tumor not affecting the anterior part of the globe were randomized to treatment with bimatoprost or latanoprost at 1, 3, 6 or 12 h prior to surgery. Concentrations of bimatoprost, bimatoprost acid, latanoprost, and latanoprost acid in the human aqueous and ocular tissues were measured using liquid chromatography tandem mass spectrometry.

RESULTS

Following topical administration, intact bimatoprost was distributed in human eyes with a rank order of cornea/sclera >iris/ciliary body >aqueous humor. Bimatoprost acid was also detected in these tissues, where its low levels in the cornea relative to that of latanoprost acid indicated that bimatoprost hydrolysis was limited. Latanoprost behaved as a prodrug that entered eyes predominantly via the corneal route. Levels of latanoprost acid were distributed as cornea >>aqueous humor>iris>sclera>ciliary body.

CONCLUSIONS

Our study provided experimental evidence that levels of bimatoprost in relevant ocular tissues, and not only aqueous humor, are needed to understand the mechanisms by which bimatoprost lowers intraocular pressure (IOP) in human subjects. The data suggest that bimatoprost reached the target tissues favoring the conjunctival/scleral absorption route. Findings of intact bimatoprost in the target ciliary body indicated its direct involvement in reducing IOP. However, bimatoprost acid may have only a limited contribution on the basis that bimatoprost has greater/similar IOP-lowering efficacy than latanoprost, yet bimatoprost acid levels were a fraction of latanoprost acid levels in the aqueous humor and cornea and only sporadically detectable in the ciliary body. In this report, human ocular tissues were examined concurrently with aqueous humor for the in vivo distribution of bimatoprost, bimatoprost acid, latanoprost, and latanoprost acid.

Aqueous humor concentrations of bimatoprost free acid, bimatoprost and travoprost free acid in cataract surgical patients administered multiple topical ocular doses of LUMIGAN or TRAVATAN

PURPOSE

To quantify the aqueous humor (AH) concentrations of bimatoprost (amide), travoprost (isopropyl ester), and their hydrolysis products, bimatoprost free acid (BFA) and travoprost free acid (TFA), after multiple topical ocular doses of LUMIGAN and TRAVATAN, respectively, in patients awaiting cataract surgery.

METHODS

In 2 separate open-label, sparse-sampling trials, glaucoma patients with cataracts received LUMIGAN (bimatoprost ophthalmic solution, 0.03%) or TRAVATAN (travoprost ophthalmic solution, 0.004%) bilaterally once daily for at least 21 days prior to cataract surgery. Anterior chamber paracentesis was performed at selected times up to 5 h after the last dose and an AH sample was collected. AH samples were assayed by an independent bioanalytical laboratory using a sensitive and validated tandem LC-MS/MS method. The assay lower limits of quantitation were 0.59 nM for bimatoprost, 0.29 nM for BFA, and 0.44 nM for TFA.

RESULTS

AH concentrations of BFA (17-phenyl-trinor PGF(2alpha)) were quantifiable in all but one sample at 0.5 h. The maximum concentration achieved (C(max)) of BFA was 30.9 + or - 16.41 nM (n =5), observed at 2 h postdose. AH concentrations of bimatoprost amide were lower than BFA at all time points, with a C(max) of 6.81 + or - 1.36 nM (n = 7) at 1 h postdose. For TFA, measurable AH concentrations were obtained at all time points with a TFA C(max) of 3.91 + or - 2.27 nM (n = 5), which was observed at 3 h after the dose (all data are mean + or - SEM).

CONCLUSIONS

Once daily topical ocular administration of LUMIGAN or TRAVATAN for 3 weeks resulted in significant concentrations of BFA and TFA in the AH. Quantifiable levels of bimatoprost amide were also measured. Maximum concentrations of BFA (30.9 nM) and TFA (3.91 nM) in the anterior chamber are sufficient to fully activate the FP prostanoid receptors in the target cells of the ciliary muscle and trabecular meshwork. Both bimatoprost in LUMIGAN and travoprost in TRAVATAN are essentially prodrugs that are rapidly hydrolyzed to their respective free acids that induce the IOP-lowering effect observed with both drugs in vivo.

Clinical utility and differential effects of prostaglandin analogs in the management of raised intraocular pressure and ocular hypertension

Prostaglandin analogs (PGA) are powerful topical ocular hypotensive agents available for the treatment of elevated intraocular pressure (IOP). Latanoprost 0.005% and travoprost 0.004% are prodrugs and analogs of prostaglandin F2α. Bimatoprost 0.03% is regarded as a prostamide, and debate continues as to whether it is a prodrug. The free acids of all 3 PGAs reduce IOP by enhancing uveoscleral and trabecular outflow via direct effects on ciliary muscle relaxation and remodeling of extracellular matrix. The vast majority of clinical trials demonstrate IOP-lowering superiority of latanoprost, bimatoprost and travoprost compared with timolol 0.5%, brimonidine 0.2%, or dorzolamide 2% monotherapy. Bimatoprost appears to be more efficacious in IOP-lowering compared with latanoprost, with weighted mean difference in IOP reduction documented in one meta-analysis of 2.59% to 5.60% from 1- to 6-months study duration. PGAs reduce IOP further when used as adjunctive therapy. Fixed combinations of latanoprost, bimatoprost or travoprost formulated with timolol 0.5% and administered once daily are superior to monotherapy of its constituent parts. PGA have near absence of systemic side effects, although do have other commonly encountered ocular adverse effects. The adverse effects of PGA, and also those found more frequently with bimatoprost use include ocular hyperemia, eyelash growth, and peri-ocular pigmentary changes. Iris pigmentary change is unique to PGA treatment. Once daily administration and near absence of systemic side effects enhances tolerance and compliance. PGAs are often prescribed as first-line treatment for ocular hypertension and open-angle glaucoma.

Bimatoprost: a review of its use in open-angle glaucoma and ocular hypertension

Bimatoprost (Lumigan) is a synthetic prostamide that reduces intraocular pressure (IOP) by increasing the outflow of aqueous humour. In patients with open-angle glaucoma or ocular hypertension, long-term treatment (for up to 48 months) with once-daily bimatoprost 0.03% ophthalmic solution was more effective than timolol twice daily in providing a sustained and stable reduction in IOP. Bimatoprost 0.03% ophthalmic solution demonstrated efficacy similar to, or greater than, the prostaglandin analogues latanoprost and travoprost in reducing IOP and achieving target IOP levels. Switching to bimatoprost was as effective in maintaining diurnal IOP control as switching to a fixed combination of latanoprost/timolol (in patients with IOP levels controlled with a nonfixed combination of latanoprost plus timolol), and similarly, or more, effective in lowering IOP and providing overall diurnal IOP control than switching to a combination of dorzolamide/timolol (in patients with IOP inadequately controlled with other antiglaucoma agents including timolol). Treatment with bimatoprost was generally well tolerated, with conjunctival hyperaemia (mostly mild), growth of eyelashes and ocular pruritus being commonly reported. Other adverse events included increases in the pigmentation of the iris, perorbital areas and eyelashes.

Bimatoprost - a review

Bimatoprost is a synthetic prostamide analog that is efficacious in the treatment of open-angle glaucoma, ocular hypertension and other forms of glaucoma. It reduces intraocular pressure (IOP) by increasing uveoscleral and trabecular outflow. When used as a 0.03% topical preparation once daily, it demonstrates sustained lowering of IOP of 7 - 8 mmHg over a 24-h period. The drug has been found to be more effective than timolol. In some studies it has shown greater ability to lower IOP when compared with other prostaglandin analogs; whereas in others all three clinically used prostaglandin analogs were found to be equally effective. It shows good IOP reduction when used in combination with other glaucoma medications. A common side effect includes mild conjunctival hyperemia, which is generally reversible. Other side effects include periorbital pigmentation, discomfort, ocular surface hyperemia and skin changes. Pharmacoeconomic data indicate that bimatoprost is cost effective in the treatment of open-angle glaucoma.

Prostanoid receptor antagonists: development strategies and therapeutic applications

Identification of the primary products of cyclo-oxygenase (COX)/prostaglandin synthase(s), which occurred between 1958 and 1976, was followed by a classification system for prostanoid receptors (DP, EP(1), EP(2) ...) based mainly on the pharmacological actions of natural and synthetic agonists and a few antagonists. The design of potent selective antagonists was rapid for certain prostanoid receptors (EP(1), TP), slow for others (FP, IP) and has yet to be achieved in certain cases (EP(2)). While some antagonists are structurally related to the natural agonist, most recent compounds are 'non-prostanoid' (often acyl-sulphonamides) and have emerged from high-throughput screening of compound libraries, made possible by the development of (functional) assays involving single recombinant prostanoid receptors. Selective antagonists have been crucial to defining the roles of PGD(2) (acting on DP(1) and DP(2) receptors) and PGE(2) (on EP(1) and EP(4) receptors) in various inflammatory conditions; there are clear opportunities for therapeutic intervention. The vast endeavour on TP (thromboxane) antagonists is considered in relation to their limited pharmaceutical success in the cardiovascular area. Correspondingly, the clinical utility of IP (prostacyclin) antagonists is assessed in relation to the cloud hanging over the long-term safety of selective COX-2 inhibitors. Aspirin apart, COX inhibitors broadly suppress all prostanoid pathways, while high selectivity has been a major goal in receptor antagonist development; more targeted therapy may require an intermediate position with defined antagonist selectivity profiles. This review is intended to provide overviews of each antagonist class (including prostamide antagonists), covering major development strategies and current and potential clinical usage.

Commercially available prostaglandin analogs for the reduction of intraocular pressure: similarities and differences

Over the last 12 years, the pharmacological management of glaucoma and ocular hypertension has significantly changed with the introduction of the prostaglandin analogs, specifically, latanoprost, bimatoprost, and travoprost. Their ability to effectively reduce intraocular pressure with once-per-day dosing, their comparable ocular tolerability with timolol, and their general lack of systemic side effects have made them the mainstay of pharmacological therapy for glaucoma and ocular hypertension in most parts of the world. A review of their pharmacology reveals that they are all prodrugs that are converted to their respective free acids within the eye to activate the prostanoid FP receptor and to reduce intraocular pressure by enhancing the uveoscleral and the trabecular meshwork outflow pathways. A review of numerous prospective, randomized comparative studies indicates that no clinically significant differences exist among these agents regarding their ability to lower intraocular pressure.

Update on the mechanism of action of topical prostaglandins for intraocular pressure reduction

A decade has passed since the first topical prostaglandin analog was prescribed to reduce intraocular pressure (IOP) for the treatment of glaucoma. Now four prostaglandin analogs are available for clinical use around the world and more are in development. The three most efficacious of these drugs are latanoprost, travoprost, and bimatoprost, and their effects on IOP and aqueous humor dynamics are similar. A consistent finding is a substantial increase in uveoscleral outflow and a less consistent finding is an increase in trabecular outflow facility. Aqueous flow appears to be slightly stimulated as well. Prostaglandin receptors and their associated mRNAs have been located in the trabecular meshwork, ciliary muscle, and sclera, providing evidence that endogenous prostaglandins have a functional role in aqueous humor drainage. Earlier evidence found that topical PG analogs release endogenous prostaglandins. One well-studied mechanism for the enhancement of outflow by prostaglandins is the regulation of matrix metalloproteinases and remodeling of extracellular matrix. Other proposed mechanisms include widening of the connective tissue-filled spaces and changes in the shape of cells. All of these mechanisms alter the permeability of tissues of the outflow pathways leading to changes in outflow resistance and/or outflow rates. This review summarizes recent (since 2000) animal and clinical studies of the effects of topical prostaglandin analogs on aqueous humor dynamics and recent cellular and molecular studies designed to clarify the outflow effects.

Cat iris sphincter smooth-muscle contraction: comparison of FP-class prostaglandin analog agonist activities

The pharmacologic characteristics of a number of FP-class prostaglandin (PG) analogs were determined by using the cat iris sphincter smooth-muscle-contraction assay. Cumulative concentration-response curves were generated for each compound. The relative agonist potencies (EC(50)) of the compounds were: cloprostenol (0.0012 +/- 0.0004 nM) >> travoprost acid (0.46 +/- 0.13 nM) = bimatoprost acid (0.99 +/- 0.19 nM) > (+/-)-fluprostenol (15.8 +/- 2.6 nM) = PGF(2alpha) (18.6 +/- 1.8 nM) > latanoprost acid (29.9 +/- 1.6 nM) > bimatoprost (140 +/- 45 nM) > S-1033 (588 +/- 39 nM) > unoprostone (UF-021; 1280 +/- 50 nM; n = 4-14). The maximum response induced by travoprost acid (122% +/- 2.3% maximum response relative to PGF(2alpha)) was significantly greater than that induced by all the other PG compounds (P < 0.001 - P < 0.02). Interestingly, the FP-receptor antagonist, AL-8810, behaved as a moderate efficacy partial agonist (EC(50) = 2140 +/- 190 nM; 63 +/- 4.3% maximum response relative to PGF(2alpha)), indicating that the cat iris contains an extremely well-coupled FP-receptor population, and/or the tissue contains an extremely high density of the FP-receptor and/or spare receptors. The cat iris contraction data were well correlated with other FP-receptor-mediated signal-transduction processes, including FP-receptor binding in bovine corpus luteum (r = 0.86), FP-receptor binding in human iris (r = 0.61), phosphoinositide (PI) hydrolysis in human ciliary muscle and trabecular meshwork cells (r = 0.77 - 0.86), PI turnover in rat and mouse cells (r = 0.73 - 0.76) and via cloned human FP-receptor (r = 0.9), and rat uterus contraction (r = 0.84). These data confirm the presence of functional FP-receptors in the cat iris sphincter, which are exquisitely well coupled and which respond to a variety of FP-class PG analogs with differing potencies.

Bimatoprost, prostamide activity, and conventional drainage

PURPOSE

Despite structural similarity with prostaglandin F(2 alpha), the ocular hypotensive agent bimatoprost (Lumigan; Allergan, Inc., Irvine, CA) shows unique pharmacology in vitro and functional activity in vivo. Unfortunately, the precise mechanisms that underlie bimatoprost's distinctive impact on aqueous humor dynamics are unclear. The purpose of the present study was to investigate the effects of bimatoprost and a novel prostamide-selective antagonist AGN 211334 on human conventional drainage.

METHODS

Two model systems were used to test the consequences of bimatoprost and/or AGN 211334 treatment on conventional drainage. Human anterior segments in organ culture were perfused at a constant flow rate of 2.5 microL/min while pressure was recorded continuously. After stable baseline facilities were established, segments were treated with drug(s), and pressure was monitored for an additional 3 days. In parallel, the drugs' effects on hydraulic conductivity of human trabecular meshwork (TM) cell monolayers were evaluated. Pharmacological properties of AGN 211334 were characterized in isolated feline iris preparations in organ culture and heterologously expressed G-protein-coupled receptors were examined in vitro.

RESULTS

Bimatoprost increased outflow facility by an average of 40% +/- 10% within 48 hours of treatment (n = 10, P < 0.001). Preincubation or coincubation with AGN 211334 significantly blunted bimatoprost's effects by 95% or 43%, respectively. Similar results were obtained in cell culture experiments in which bimatoprost increased hydraulic conductivity of TM cell monolayers by 78% +/- 25%. Pretreatment with AGN 211334 completely blocked bimatoprost's effects, while coincubation decreased its effects on average by 74%. In both models, AGN 211334 alone significantly decreased fluid flux across trabecular tissues and cells.

CONCLUSIONS

The findings indicate that bimatoprost interacts with a prostamide receptor in the trabecular meshwork to increase outflow facility.

The side effects of the prostaglandin analogues

In the last decade topically applied prostaglandin F2alpha analogues (bimatoprost, latanoprost, travoprost and unoprostone) have become widely used as a means to reduce elevated intraocular pressure in patients with glaucoma and ocular hypertension. These molecules all have similar side-effect profiles, which include both side effects that occur frequently (e.g., conjunctiva hyperaemia, increase of iris pigmentation and eyelash changes) and rare adverse reactions (e.g., periocular pigmentation, damage to the blood-aqueous barrier and cystoid macular oedema). Conjunctiva hyperaemia, eyelash changes and cystoid macular oedema are reversible, but certain other side effects, such as increased iris pigmentation, are not. However, the systemic side-effect profile is favourable for all the prostaglandin analogues, and some of the local side effects are only of cosmetic significance. Numerous clinical studies suggest that discontinuing treatment with prostaglandin analogues on account of their side effects is rare in clinical practice.

Levels of bimatoprost acid in the aqueous humour after bimatoprost treatment of patients with cataract

AIM

To determine the aqueous humour concentration of the acid hydrolysis products of bimatoprost and latanoprost after a single topical dose of bimatoprost 0.03% or latanoprost 0.005% in humans.

METHODS

Randomised, controlled, double-masked, prospective study. 48 eyes of 48 patients scheduled for routine cataract surgery were randomised in an 8:2:2 ratio to treatment with a single 30 mul drop of bimatoprost 0.03%, latanoprost 0.005% or placebo at 1, 3, 6 or 12 h before the scheduled cataract surgery. Aqueous humour samples were withdrawn at the beginning of the surgical procedure and analysed using high-performance liquid chromatography-tandem mass spectrometry.

RESULTS

Bimatoprost acid (17-phenyl trinor prostaglandin F2alpha) was detected in aqueous samples at a mean concentration of 5.0 nM at hour 1, 6.7 nM at hour 3 and 1.9 nM at hour 6 after bimatoprost treatment. After latanoprost treatment, the mean concentration of latanoprost acid (13,14-dihydro-17-phenyl trinor prostaglandin F2alpha) in aqueous samples was 29.1 nM at hour 1, 41.3 nM at hour 3 and 2.5 nM at hour 6. Acid metabolites were below the limit of quantitation in all samples taken 12 h after dosing and in all samples from placebo-treated patients. None of the samples from latanoprost-treated patients contained quantifiable levels of non-metabolised latanoprost. Non-metabolised bimatoprost was detected in aqueous samples at a mean concentration of 6.6 nM at hour 1 and 2.4 nM at hour 3 after bimatoprost treatment.

CONCLUSIONS

Low levels of bimatoprost acid were detected in aqueous humour samples from patients with cataract treated with a single dose of bimatoprost. Latanoprost acid concentrations in samples from patients treated with latanoprost were at least sixfold higher. These results suggest that bimatoprost acid in the aqueous humour does not sufficiently account for the ocular hypotensive efficacy of bimatoprost.

Prostanoids in the therapy of glaucoma

Elevated intraocular pressure (IOP) is one of the most important risk factors for the development of glaucoma, which is a progressive optic neuropathy. Lowering IOP is currently the only therapeutic approach to the therapy of glaucoma. Since the use of pilocarpine eye drops for glaucoma treatment was reported in the late 1870s, academic researchers and pharmaceutical companies attempted to discover new drugs with more potent, prolonged, and safer IOP-reducing effects. These persistent efforts finally paid off, and prostanoids with FP-receptor agonist activity were found to be very potent IOP-lowering agents. To date, three prostanoids (latanoprost, travoprost and bimatoprost) have been launched in many countries, and now a new FP-receptor agonist, tafluprost, is entering clinical development. All of these prostanoids are superior to the beta-adrenoceptor antagonists in their IOP-lowering efficacy, and no severe side effects have been reported in their long-term clinical use. In addition, tafluprost may be expected to improve ocular blood flow. Hence, prostanoids currently occupy center stage among glaucoma medications. It cannot be denied that in terms of efficacy, safety, patient compliance, and medical economy prostanoids are currently the first-line medicines among ocular antihypertensive drugs.

Clinical pharmacology of bimatoprost

Bimatoprost (Lumigan), Allergan) is a highly efficacious ocular hypotensive agent that provides good diurnal control of intraocular pressure in glaucoma and ocular hypertensive patients. Bimatoprost is a synthetic molecule that is structurally and pharmacologically similar to prostamide F(2), and appears to mimic the activity of the prostamides. Consistent with prostamide-mimetic activity, bimatoprost has potent inherent pharmacological activity in prostamide-sensitive preparations and essentially remains intact in the living primate eye. This is sufficient to explain its potent and efficacious ocular hypotensive activity, and suggests that bimatoprost is a pharmacologically unique compound.