Phase 3 Clinical Trial Comparing the Safety and Efficacy of Netarsudil to Ripasudil in Patients with Primary Open-Angle Glaucoma or Ocular Hypertension: Japan Rho Kinase Elevated Intraocular Pressure Treatment Trial (J-ROCKET)

INTRODUCTION

A clinical trial evaluated ocular hypotensive efficacy and safety of netarsudil 0.02% once daily (QD) relative to ripasudil 0.4% twice daily (BID).

METHODS

This was a single-masked, randomized, phase 3, superiority study. Japanese patients were randomized to either the netarsudil 0.02% group or the ripasudil 0.4% group in a 1:1 ratio and treated for 4 weeks. The primary efficacy variable was mean diurnal intraocular pressure (IOP) (average of diurnal time points at 09:00, 11:00, and 16:00) at Week 4.

RESULTS

A total of 245 patients were included in the primary analysis. At Week 4, least squares (LS) mean of diurnal IOP adjusted for baseline was 15.96 and 17.71 mmHg in the netarsudil 0.02% and ripasudil 0.4% groups, respectively, demonstrating the superiority of netarsudil 0.02% QD over ripasudil 0.4% BID by a margin of - 1.74 mmHg (p < 0.0001). Mean reduction from baseline in mean diurnal IOP at Week 4 was 4.65 and 2.98 mmHg, respectively. Adverse events (AEs) occurred less frequently in netarsudil 0.02% than in ripasudil 0.4%, with the incidence of ocular AEs being 59.8% and 66.7%, respectively. The most frequently reported AE was conjunctival hyperemia in both groups, with an incidence of 54.9% and 62.6%, respectively. No serious eye-related AEs were reported.

CONCLUSION

Netarsudil ophthalmic solution 0.02% dosed QD (p.m.) was well tolerated and more effective in reducing IOP than ripasudil ophthalmic solution 0.4% dosed BID. Netarsudil 0.02% QD may become an important option for the treatment of Japanese patients with primary open-angle glaucoma (POAG) or ocular hypertension (OHT).

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT04620135.

Eyes on Topical Ocular Disposition: The Considered Design of a Lead Janus Kinase (JAK) Inhibitor That Utilizes a Unique Azetidin-3-Amino Bridging Scaffold to Attenuate Off-Target Kinase Activity, While Driving Potency and Aqueous Solubility

An unmet medical need remains for patients suffering from dry eye disease (DED). A fast-acting, better-tolerated noncorticosteroid anti-inflammatory eye drop could improve patient outcomes and quality of life. Herein, we describe a small-molecule drug discovery effort to identify novel, potent, and water-soluble JAK inhibitors as immunomodulating agents for topical ocular disposition. A focused library of known 3-(4-(2-(arylamino)pyrimidin-4-yl)-1H-pyrazol-1-yl)propanenitriles was evaluated as a molecular starting point. Structure-activity relationships (SARs) revealed a ligand-efficient (LE) JAK inhibitor series, amenable to aqueous solubility. Subsequent in vitro analysis indicated the potential for off-target toxicity. A KINOMEscan selectivity profile of 5 substantiated the likelihood of widespread series affinity across the human kinome. An sp²-to-sp³ drug design strategy was undertaken to attenuate off-target kinase activity while driving JAK-STAT potency and aqueous solubility. Tactics to reduce aromatic character, increase fraction sp³ (Fsp³), and bolster molecular complexity led to the azetidin-3-amino bridging scaffold in 31.

Fixed-Dose Combination of Netarsudil and Latanoprost in Ocular Hypertension and Open-Angle Glaucoma: Pooled Efficacy/Safety Analysis of Phase 3 MERCURY-1 and -2

INTRODUCTION

New open-angle glaucoma (OAG) and ocular hypertension (OHT) therapies that reduce treatment burden and improve outcomes relative to currently available agents are needed. Netarsudil, a novel Rho kinase inhibitor approved by the US Food and Drug Administration, reduces intraocular pressure (IOP) by increasing trabecular outflow. Two phase 3 superiority studies compared a fixed-dose combination (FDC) of netarsudil and the prostaglandin latanoprost with each active component for IOP-lowering efficacy.

METHODS

Pooled efficacy and safety data were analyzed from MERCURY-1 and -2 studies in patients with OAG or OHT. Patients instilled one drop of netarsudil (0.02%)/latanoprost (0.005%) FDC (n = 483), netarsudil (0.02%, n = 499), or latanoprost (0.005%, n = 486) into each eye once-daily between 20:00 and 22:00. IOP was measured at 08:00, 10:00, and 16:00 at weeks 2, 6, and the primary endpoint at month 3.

RESULTS

Baseline mean diurnal IOP was 23.6, 23.6, and 23.5 mmHg in netarsudil/latanoprost FDC, netarsudil, and latanoprost groups, respectively. Mean diurnal IOP in each group was 15.3, 18.1, and 17.5 mmHg at week 2, 15.7, 18.4, and 17.4 mmHg at week 6, and 15.8, 18.4, and 17.3 mmHg at week 12. The netarsudil/latanoprost FDC met criteria for superiority compared with each active component (p < 0.0001 for all nine time points). At month 3, among patients randomized to netarsudil/latanoprost FDC or latanoprost, 58.4% vs 37.3% (p < 0.0001) achieved IOP ≤ 16 mmHg. Among patients randomized to netarsudil/latanoprost FDC or netarsudil or latanoprost, 30.9% vs 5.9% (p < 0.0001) vs 8.5% (p < 0.0001) achieved at least a 40% reduction from baseline in mean diurnal IOP. Pooled safety results were consistent with individual MERCURY studies.

CONCLUSION

Once-daily netarsudil/latanoprost FDC produced statistically significant and clinically relevant reductions in mean IOP that were statistically superior to IOP reductions achieved by netarsudil and latanoprost monotherapy. Results of the pooled efficacy and safety analyses were consistent with the individual studies.

TRIAL REGISTRATION

ClinicalTrials.gov identifiers, NCT02558400 and NCT02674854.

Netarsudil/Latanoprost Fixed-Dose Combination for Elevated Intraocular Pressure: Three-Month Data from a Randomized Phase 3 Trial

PURPOSE

To compare the ocular hypotensive efficacy and safety of a fixed-dose combination (FDC) of the Rho kinase inhibitor netarsudil and latanoprost vs monotherapy with netarsudil or latanoprost.

DESIGN

Three-month primary endpoint analysis of a randomized, double-masked, phase 3 clinical trial.

METHODS

Adults with open-angle glaucoma or ocular hypertension (unmedicated intraocular pressure [IOP] >20 and <36 mm Hg at 8:00 AM) were randomized to receive once-daily netarsudil/latanoprost FDC, netarsudil 0.02%, or latanoprost 0.005% for up to 12 months. The primary efficacy endpoint was mean IOP at 8:00 AM, 10:00 AM, and 4:00 PM at week 2, week 6, and month 3.

RESULTS

Mean treated IOP ranged from 14.8-16.2 mm Hg for netarsudil/latanoprost FDC, 17.2-19.0 mm Hg for netarsudil, and 16.7-17.8 mm Hg for latanoprost. Netarsudil/latanoprost FDC met the criteria for superiority to each active component at all 9 time points (all P < .0001), lowering IOP by an additional 1.8-3.0 mm Hg vs netarsudil and an additional 1.3-2.5 mm Hg vs latanoprost. At month 3, the proportion of patients achieving mean diurnal IOP ≤15 mm Hg was 43.5% for netarsudil/latanoprost FDC, 22.7% for netarsudil, and 24.7% for latanoprost. No treatment-related serious adverse events were reported; treatment-related systemic adverse events were minimal. The most frequent ocular adverse event was conjunctival hyperemia (netarsudil/latanoprost FDC, 53.4%; netarsudil, 41.0%; latanoprost, 14.0%), which led to treatment discontinuation in 7.1% (netarsudil/latanoprost FDC), 4.9% (netarsudil), and 0% (latanoprost) of patients.

CONCLUSIONS

Once-daily netarsudil/latanoprost FDC demonstrated IOP reductions that were statistically and clinically superior to netarsudil and latanoprost across all 9 time points through month 3, with acceptable ocular safety.

Once-Daily Netarsudil Versus Twice-Daily Timolol in Patients With Elevated Intraocular Pressure: The Randomized Phase 3 ROCKET-4 Study

PURPOSE

To compare the intraocular pressure (IOP)-lowering efficacy and safety of netarsudil once daily (QD) and timolol twice daily (BID).

DESIGN

Double-masked, randomized, phase 3, noninferiority study.

METHODS

Patients with open-angle glaucoma or ocular hypertension (unmedicated baseline IOP >20 to <30 mm Hg at 8:00 AM) were randomized to netarsudil ophthalmic solution 0.02% QD (PM) or timolol ophthalmic solution 0.5% BID. The primary endpoint was mean IOP at 8:00 AM, 10:00 AM, and 4:00 PM at week 2, week 6, and month 3 in patients with baseline IOP <25 mm Hg (per-protocol population). Safety was recorded over the 6-month treatment period.

RESULTS

A total of 186 patients from each treatment arm were included in the primary efficacy analysis. Netarsudil QD met the criteria for noninferiority to timolol BID. Mean treated IOP ranged from 16.3 to 17.9 mm Hg for netarsudil and 16.7 to 17.6 for timolol, with mean reductions from baseline of 3.9 to 4.7 mm Hg and 3.8 to 5.2 mm Hg, respectively. In prespecified secondary analyses, netarsudil demonstrated noninferiority to timolol in patients with baseline IOP <27 mm Hg and <30 mm Hg. The IOP-lowering effects of netarsudil were sustained over 6 months of treatment. No treatment-related serious adverse event (AE) was reported for either study drug. However, statistically significant reductions in mean heart rate were recorded at all study visits for the timolol group. The most frequent ocular AE among netarsudil-treated patients was conjunctival hyperemia (47.9%), which was predominately mild.

CONCLUSIONS

Netarsudil QD (PM), a first-in-class IOP-lowering medication, was noninferior to timolol BID and was associated with tolerable ocular AEs.

Long-term Safety and Ocular Hypotensive Efficacy Evaluation of Netarsudil Ophthalmic Solution: Rho Kinase Elevated IOP Treatment Trial (ROCKET-2)

PURPOSE

To evaluate netarsudil 0.02% ophthalmic solution in patients with open-angle glaucoma (OAG) and ocular hypertension (OHT).

DESIGN

Double-masked, randomized, multicenter, parallel-group, noninferiority clinical study.

METHODS

After a washout of all prestudy ocular hypotensive medications, 756 eligible patients with elevated IOP were randomized to receive netarsudil 0.02% once a day (q.d.) (251); netarsudil 0.02% twice a day (b.i.d.) (254); or timolol 0.5% b.i.d. (251) for 12 months, as well as a noninterventional Corneal Observation Study (COS) for patients manifesting cornea verticillata.

RESULTS

On treatment, mean IOP at 8:00 AM decreased from a baseline IOP of 22.5-22.6 mm Hg to 17.9-18.8 mm Hg, 17.2-18.0 mm Hg, and 17.5-17.9 mm Hg for netarsudil q.d., netarsudil b.i.d., and timolol, respectively, over 12 months. The most frequently reported adverse events (AEs) were ocular, with the most frequent ocular AE being conjunctival hyperemia, with an incidence of 61%, 66%, and 14%, respectively. The next most frequent AEs were corneal deposits (corneal verticillata), with an incidence of 26%, 25%, and 1%, respectively, and conjunctival hemorrhage (typically petechial), with an incidence of 20%, 19%, and 1%, respectively. All 3 AEs were generally scored as mild, with conjunctival hyperemia and/or hemorrhage appearing sporadically during the study. In the observational follow-up component of this study, there was no clinically meaningful impact of corneal verticillata on visual function in affected patients.

CONCLUSIONS

In this randomized, double-masked trial, once-daily dosing of netarsudil 0.02% was effective, consistently lowering IOP through 12 months, and was tolerated by the majority of patients.

Netarsudil ophthalmic solution 0.02% for the treatment of patients with open-angle glaucoma or ocular hypertension

Once-daily (p.m.) netarsudil ophthalmic solution 0.02% (Rhopressa) is approved in the United States for lowering elevated intraocular pressure (IOP) in patients with open-angle glaucoma or ocular hypertension. Netarsudil, a Rho kinase (ROCK) inhibitor that lowers IOP primarily by increasing trabecular outflow, produces statistically and clinically significant reductions in mean IOP from baseline, with comparable effects on nocturnal and diurnal IOP. In three phase III trials of patients with elevated IOP, the ocular hypotensive efficacy of once-daily netarsudil 0.02% met the criteria for noninferiority to twice-daily timolol 0.5% at all time points over 3 months in patients with baseline IOP less than 25 mmHg. The most frequent adverse event (AE) was generally mild conjunctival hyperemia, the severity of which did not increase with continued dosing. Netarsudil was associated with minimal treatment-related serious or systemic AEs, likely due to the lack of systemic exposure. This report summarizes the available preclinical and clinical data on netarsudil.

Consensus recommendations for trabecular meshwork cell isolation, characterization and culture

Cultured trabecular meshwork (TM) cells are a valuable model system to study the cellular mechanisms involved in the regulation of conventional outflow resistance and thus intraocular pressure; and their dysfunction resulting in ocular hypertension. In this review, we describe the standard procedures used for the isolation of TM cells from several animal species including humans, and the methods used to validate their identity. Having a set of standard practices for TM cells will increase the scientific rigor when used as a model, and enable other researchers to replicate and build upon previous findings.

The Effects of Netarsudil Ophthalmic Solution on Aqueous Humor Dynamics in a Randomized Study in Humans

PURPOSE

Netarsudil, an inhibitor of Rho kinase and a norepinephrine transporter, has been shown to lower elevated intraocular pressure (IOP) in controlled studies of patients with open-angle glaucoma and ocular hypertension, and in healthy volunteers. The mechanism of this ocular hypotensive effect in humans is unknown.

METHODS

The objective of this study was to evaluate the effect of netarsudil 0.02% on aqueous humor dynamics (AHD) parameters. In this double-masked, vehicle-controlled, paired-eye comparison study, 11 healthy volunteers received topical netarsudil ophthalmic solution 0.02% or its vehicle once daily for 7 days (morning dosing). The primary endpoints were the change in AHD parameters, compared between active and vehicle-treated eyes.

RESULTS

In netarsudil-treated eyes, diurnal outflow facility increased from 0.27 ± 0.10 μL/min/mmHg to 0.33 ± 0.11 μL/min/mmHg (+22%; P = 0.02) after 7 days of treatment. In placebo-treated eyes, diurnal outflow facility did not significantly change (P = 0.94). The difference between netarsudil and placebo eyes in diurnal change of outflow facility was 0.08 μL/min/mmHg (P < 0.001). Diurnal episcleral venous pressure (EVP) in netarsudil-treated eyes decreased from 7.9 ± 1.2 mmHg to 7.2 ± 1.8 (-10%; P = 0.01). Diurnal EVP was not significantly different between netarsudil- and placebo-treated eyes. There was a trend toward decreasing aqueous humor flow rate (-15%; P = 0.08). No treatment changes were seen in uveoscleral outflow rate.

CONCLUSIONS

Once-daily dosing of netarsudil ophthalmic solution 0.02% lowered IOP through increasing trabecular outflow facility and reducing EVP. This suggests a combination of mechanisms that affect both the proximal and distal outflow pathways.

Two Phase 3 Clinical Trials Comparing the Safety and Efficacy of Netarsudil to Timolol in Patients With Elevated Intraocular Pressure: Rho Kinase Elevated IOP Treatment Trial 1 and 2 (ROCKET-1 and ROCKET-2)

PURPOSE

To evaluate the efficacy and ocular and systemic safety of netarsudil 0.02% ophthalmic solution, a rho-kinase inhibitor and norepinephrine transporter inhibitor, in patients with open-angle glaucoma and ocular hypertension.

DESIGN

Double-masked, randomized noninferiority clinical trials: Rho Kinase Elevated IOP Treatment Trial 1 and 2 (ROCKET-1 and ROCKET-2).

METHODS

After a washout of all pre-study ocular hypotensive medications, eligible patients were randomized to receive netarsudil 0.02% once daily (q.d.), timolol 0.5% twice a day (b.i.d.), and (ROCKET-2 only) netarsudil 0.02% b.i.d. Data through 3 months from both studies are provided in this report.

RESULTS

Enrolled into the 2 studies were 1167 patients. Treatment with netarsudil q.d. produced clinically and statistically significant reductions from baseline intraocular pressure (P < .001), and was noninferior to timolol in the per-protocol population with maximum baseline IOP < 25 mm Hg in both studies (ROCKET-2, primary outcome measure and population, ROCKET-1, post hoc outcome measure). Netarsudil b.i.d. was also noninferior to timolol (ROCKET-2). The most frequent adverse event was conjunctival hyperemia, the incidence of which ranged from 50% (126/251, ROCKET-2) to 53% (108/203, ROCKET-1) for netarsudil q.d., 59% (149/253, ROCKET-2) for netarsudil b.i.d., and 8% (17/208, ROCKET-1) to 11% (27/251, ROCKET-2) for timolol (P < .0001 for netarsudil vs timolol).

CONCLUSIONS

In 2 large, randomized, double-masked trials reported here, once-daily dosing of netarsudil 0.02% was found to be effective and well tolerated for the treatment of patients with ocular hypertension and open-angle glaucoma. The novel pharmacology and aqueous humor dynamic effects of this molecule suggest it may be a useful addition to the armamentarium of ocular hypotensive medications.

Discovery and Preclinical Development of Netarsudil, a Novel Ocular Hypotensive Agent for the Treatment of Glaucoma

PURPOSE

Rho-associated protein kinase (ROCK) inhibitors lower intraocular pressure (IOP) by increasing aqueous outflow through the trabecular meshwork (TM). The preclinical characterization of netarsudil, a new ROCK/norepinephrine transporter (NET) inhibitor currently in clinical development, is presented herein.

METHODS

The kinase inhibitory activity of netarsudil was compared to its esterase metabolite, netarsudil-M1, and 3 other ROCK inhibitors using a commercially available kinase assay kit. Disruption of actin stress fibers was measured in primary porcine TM cells and disruption of focal adhesions in transformed human TM (HTM) cells. Induction of fibrosis markers after exposure to transforming growth factor-β2 (TGF-β2) was conducted in primary HTM cells. Ocular hypotensive activity and tolerability of topical formulations were evaluated in normotensive Dutch Belted rabbits and Formosan Rock monkeys. In vitro corneal metabolism assays were conducted using dog, pig, rabbit, monkey, and human corneas. In vivo ocular pharmacokinetics was studied in Dutch Belted rabbits.

RESULTS

Netarsudil inhibited kinases ROCK1 and ROCK2 with a Ki of 1 nM each, disrupted actin stress fibers and focal adhesions in TM cells with IC50s of 79 and 16 nM, respectively, and blocked the profibrotic effects of TGF-β2 in HTM cells. Netarsudil produced large reductions in IOP in rabbits and monkeys that were sustained for at least 24 h after once daily dosing, with transient, mild hyperemia observed as the only adverse effect.

CONCLUSION

Netarsudil is a novel ROCK/NET inhibitor with high potency in biochemical and cell-based assays, an ability to produce large and durable IOP reductions in animal models, and favorable pharmacokinetic and ocular tolerability profiles.

Visualization of conventional outflow tissue responses to netarsudil in living mouse eyes

Visual impairment due to glaucoma currently impacts 70 million people worldwide. While disease progression can be slowed or stopped with effective lowering of intraocular pressure, current medical treatments are often inadequate. Fortunately, three new classes of therapeutics that target the diseased conventional outflow tissue responsible for ocular hypertension are in the final stages of human testing. The rho kinase inhibitors have proven particularly efficacious and additive to current therapies. Unfortunately, non-contact technology that monitors the health of outflow tissue and its response to conventional outflow therapy is not available clinically. Using optical coherence tomographic (OCT) imaging and novel segmentation software, we present the first demonstration of drug effects on conventional outflow tissues in living eyes. Topical netarsudil (formerly AR-13324), a rho kinase/ norepinephrine transporter inhibitor, affected both proximal (trabecular meshwork and Schlemm's Canal) and distal portions (intrascleral vessels) of the mouse conventional outflow tract. Hence, increased perfusion of outflow tissues was reliably resolved by OCT as widening of the trabecular meshwork and significant increases in cross-sectional area of Schlemm's canal following netarsudil treatment. These changes occurred in conjunction with increased outflow facility, increased speckle variance intensity of outflow vessels, increased tracer deposition in conventional outflow tissues and decreased intraocular pressure. This is the first report using live imaging to show real-time drug effects on conventional outflow tissues and specifically the mechanism of action of netarsudil in mouse eyes. Advancements here pave the way for development of a clinic-friendly OCT platform for monitoring glaucoma therapy.

Discovery of the ROCK inhibitor netarsudil for the treatment of open-angle glaucoma

Inhibition of Rho kinase (ROCK) to improve fluid outflow through the trabecular meshwork and lower intraocular pressure is a strategy for the development of new anti-glaucoma agents. Alpha-aryl-beta-amino isoquinoline analogs were identified as potent ROCK inhibitors. Compounds that provided a longer duration of intraocular pressure reduction in Dutch Belted rabbits also inhibited norepinephrine transporter. Ester 60 improved bioavailability of its parent ROCK inhibitor, 29 (Ki=0.2nM) and demonstrated an effective and sustained IOP reduction for 24h after dosing. From these studies, netarsudil (a.k.a. AR-13324) was discovered and is currently in clinical trials for the treatment of glaucoma and ocular hypertension.

Fixed-dose combination of AR-13324 and latanoprost: a double-masked, 28-day, randomised, controlled study in patients with open-angle glaucoma or ocular hypertension

BACKGROUND/AIMS

To evaluate the ocular hypotensive efficacy of fixed-dose combinations of the Rho kinase inhibitor and norepinephrine transport inhibitor AR-13324 (0.01% and 0.02%) and latanoprost (PG324 Ophthalmic Solution) relative to the active components AR-13324 0.02% and latanoprost 0.005%, used bilaterally at night.

METHODS

This was a double-masked, randomised, parallel comparison study in patients with open-angle glaucoma or ocular hypertension. After washout, patients were randomised to one of four treatment arms and treated for 28 days. The primary efficacy variable was mean diurnal intraocular pressure (IOP) at day 29.

RESULTS

We randomised 298 patients, of whom 292 (98%) completed the study. Mean unmedicated diurnal IOPs (study eye) was 25.1, 25.1, 26.0 and 25.4 in the PG324 0.01%, PG324 0.02%, latanoprost and AR-13324 0.02% groups, respectively. On day 29, mean diurnal IOP decreased to 17.3, 16.5, 18.4 and 19.1 mm Hg, respectively. For the primary efficacy variable of mean diurnal IOP at day 29, PG324 0.02% met the criterion for statistical superiority relative to both latanoprost and AR-13324 0.02% (p<0.0001), providing additional IOP lowering of 1.9 and 2.6 mm Hg, respectively. PG324 0.01% also met the criterion for superiority. The most frequently reported adverse event was conjunctival hyperaemia with an incidence of 41% (30/73), 40% (29/73), 14% (10/73) and 40% (31/78) in the PG324 0.01%, PG324 0.02%, latanoprost and AR-13324 0.02% groups, respectively.

CONCLUSIONS

In this short-term study, the fixed-dose combination of AR-13324 0.02% and latanoprost 0.005% in PG324 Ophthalmic Solution provides clinically and statistically superior ocular hypotensive efficacy relative to its individual active components at the same concentrations. The only safety finding of note was transient asymptomatic conjunctival hyperaemia which was typically of mild severity.

TRIAL REGISTRATION NUMBER

NCT02057575.

Effect of AR-13324 on episcleral venous pressure in Dutch belted rabbits

PURPOSE

AR-13324 is a potential new drug for the treatment of patients with glaucoma that has been shown to lower intraocular pressure (IOP) by increasing trabecular outflow facility and decreasing aqueous production. The present study tested the hypothesis that AR-13324 also lowers IOP by reducing episcleral venous pressure (EVP).

METHODS

In Dutch Belted (DB) rabbits (n=11), arterial pressure (AP), IOP, carotid blood flow (BFcar), heart rate (HR), and EVP were measured invasively. Animals were dosed with AR-13324 (0.04%, topical, n=6) once daily for 3 days. On day 3, the animals were anesthetized, and then, measurements were obtained before dosing with AR-13324 or vehicle (n=5) and for 3 h after dosing. The data (mean±standard error of the mean) were analyzed by repeated measures ANOVA with post hoc testing. Retrospective baseline data from prior similar studies in New Zealand White rabbits were also compiled.

RESULTS

Baseline values were as follows: AP, 101±3 mmHg; IOP; 33±3 mmHg; EVP, 16±1 mmHg; BFcar, 41±4 mL/min; and HR, 330±6 bpm. Three hours after AR-13324 dosing, IOP was reduced by 39%±7% (P<0.001) and EVP decreased by 35%±4% (P<0.05); after vehicle dosing, IOP was reduced by 24%±4% (P<0.05) and EVP increased by 25%±5% (P<0.05). AP, BFcar, and HR were unchanged.

CONCLUSIONS

AR-13324 produces statistically significant lowering of EVP in DB rabbits. In addition, the baseline values for AP, IOP, EVP, BFcar, and HR in the DB rabbit are higher than those previously reported in the New Zealand rabbit.

Wrapper, a novel member of the Ig superfamily, is expressed by midline glia and is required for them to ensheath commissural axons in Drosophila

The midline glia are specialized, nonneuronal cells at the midline of the Drosophila central nervous system (CNS). During development, the midline glia provide guidance cues for extending axons. At the same time, they migrate and help separate the two axon commissures. They then wrap around and ensheath the commissural axons. In many segments, a few of the glia do not enwrap the axons, and these cells die. The wrapper gene encodes a novel member of the immunoglobulin (Ig) superfamily. Wrapper protein is expressed specifically on the surface of midline glia. In wrapper mutant embryos, the midline glia express their normal guidance cues and migrate normally. However, they do not ensheath the commissural axons, and as a result, the glia die. In the absence of Wrapper, the two axon commissures are not properly separated.

A high throughput screen to identify secreted and transmembrane proteins involved in Drosophila embryogenesis

Secreted and transmembrane proteins play an essential role in intercellular communication during the development of multicellular organisms. Because only a small number of these genes have been characterized, we developed a screen for genes encoding extracellular proteins that are differentially expressed during Drosophila embryogenesis. Our approach utilizes a new method for screening large numbers of cDNAs by whole-embryo in situ hybridization. The cDNA library for the screen was prepared from rough endoplasmic reticulum-bound mRNA and is therefore enriched in clones encoding membrane and secreted proteins. To increase the prevalence of rare cDNAs in the library, the library was normalized using a method based on cDNA hybridization to genomic DNA-coated beads. In total, 2,518 individual cDNAs from the normalized library were screened by in situ hybridization, and 917 of these cDNAs represent genes differentially expressed during embryonic development. Sequence analysis of 1,001 cDNAs indicated that 811 represent genes not previously described in Drosophila. Expression pattern photographs and partial DNA sequences have been assembled in a database publicly available at the Berkeley Drosophila Genome Project website (). The identification of a large number of genes encoding proteins involved in cell-cell contact and signaling will advance our knowledge of the mechanisms by which multicellular organisms and their specialized organs develop.

A neural tetraspanin, encoded by late bloomer, that facilitates synapse formation

Upon contacting its postsynaptic target, a neuronal growth cone transforms into a presynaptic terminal. A membrane component on the growth cone that facilitates synapse formation was identified by means of a complementary DNA-based screen followed by genetic analysis. The late bloomer (lbl) gene in Drosophila encodes a member of the tetraspanin family of cell surface proteins. LBL protein is transiently expressed on motor axons, growth cones, and terminal arbors. In lbl mutant embryos, the growth cone of the RP3 motoneuron contacts its target muscles, but synapse formation is delayed and neighboring motoneurons display an increase in ectopic sprouting.

Introns excised from the Delta primary transcript are localized near sites of Delta transcription

Introns excised from the primary transcript of Delta (Dl), a Drosophila neurogenic gene, accumulate to unusually high levels in embryos. High resolution in situ hybridization reveals a striking localization of the excised introns to two foci per embryonic nucleus. The number of foci can be altered by varying the number of Dl genes present in the embryonic nucleus, suggesting that the excised introns are localized near sites of Dl transcription. This conclusion is supported by the observation that larval and imaginal disc nuclei containing two copies of Dl exhibit only one focus of intron accumulation, as expected for nuclei in which homologous chromosomes are paired. Interestingly, the excised introns do not appear to diffuse away from the foci until late prophase, at which time the foci disperse into numerous small dots of hybridization. These results suggest that the excised Dl introns may be associated with a structural element within the nucleus that is dissociated during cell division.

Complex spatio-temporal accumulation of alternative transcripts from the neurogenic gene Delta during Drosophila embryogenesis

Delta (Dl) function is required for proper specification of epidermal and neural lineages within the neurogenic ectoderm of Drosophila melanogaster. We have determined the spatial accumulation of five Dl transcripts that arise as the result of alternative RNA processing during embryogenesis. We find that these transcripts accumulate in all cells of the neurogenic ectoderm immediately preceding neuroblast segregation, indicating that transcription of Dl does not differ between presumptive neuroblasts and presumptive dermoblasts. Dl transcripts also accumulate transiently in mesodermal and endodermal cells, suggesting that Dl may function in developmental processes in addition to differentiation of the neurogenic ectoderm. We find that three of the Dl transcripts are localized to the base of the nucleus during cellularization. The apparent association of these three transcripts with polysomes suggests that they accumulate within the cytoplasm at the nuclear periphery and is consistent with the hypothesis that Dl encodes multiple translational products.

Molecular genetics of Delta, a locus required for ectodermal differentiation in Drosophila

Delta (Dl) is one of the six known zygotic neurogenic genes, each of which is essential for proper segregation of the embryonic ectoderm into neural and epidermal lineages. Molecular analysis of Dl reveals that it is a transcriptionally complex locus that yields multiple maternal and zygotic transcripts. DNA sequence analysis suggests that the predominant product of the locus is a putative transmembrane protein exhibiting homology to blood coagulation factors and epidermal growth factor of vertebrates. The structure of this product is consistent with the hypothesis that Dl participates in cell-cell interactions that are central to establishment of the epidermal lineage within the developing ectoderm. Genetic analyses demonstrate that Dl mutations can modify the imaginal phenotypes that result from heterozygosity for Notch (N) mutations as well as the interaction between particular alleles of Notch (N) and Enhancer of split [E(spl)], two other members of the neurogenic gene set. Vital interactions also occur between Dl and N. Given the structures of products encoded by N, Dl, and E(spl), we suggest that the synergistic phenotypic interactions observed among mutations in these three loci result from physical, as opposed to regulatory, interactions.

Delta, a Drosophila neurogenic gene, is transcriptionally complex and encodes a protein related to blood coagulation factors and epidermal growth factor of vertebrates

Delta (D1) is required for normal segregation of the embryonic ectoderm into neural and epidermal cell lineages in Drosophila melanogaster. Loss-of-function mutations in D1 and other zygotic neurogenic loci lead to expansion of the neuroblast population at the expense of the dermoblast population within the ectoderm. Characterization of the transcriptional organization and maternal/embryonic expression within the chromosomal interval corresponding to D1 reveals that the locus encodes multiple transcripts: a minimum of two maternal transcripts, approximately 4.5 and 3.6 kb in length, and four zygotic transcripts, approximately 5.4 (two distinct species), 3.5, and 2.8 kb in length. These transcripts differ on the bases of differential splicing and differential polyadenylation site choice. The DNA sequence of a cDNA clone representing the predominant transcripts of the locus indicates that D1 encodes a transmembrane protein homologous to blood coagulation factors and epidermal growth factor. The relationship between coding sequences and transcript-specific exons within the locus suggests that D1 encodes multiple translational products.

Cat-2 gene expression. Developmental control of translatable CAT-2 mRNA levels in maize scutellum

Poly(A)+ RNA was isolated from maize scutella of different stages of post-germinative development and translated in vitro in a rabbit reticulocyte translation system. Immunoprecipitation of the translation products with CAT-2-specific antibody was used to quantitate the relative levels of translatable CAT-2 mRNA at each stage. The results show a close correlation between the developmental profile of Cat2 gene expression and the profile of CAT-2 mRNA levels. Evidence that the levels of CAT-2 mRNA are regulated by a temporal regulatory gene (Car1) is presented and the possible mechanism(s) of this regulation discussed.