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.

Serotonin-2B/2C Receptors Mediate Bovine Ciliary Muscle Contraction: Role in Intraocular Pressure Regulation

PURPOSE

To study the pharmacological profile of the serotonin (5-hydroxytryptamine [5-HT]) receptor subtype mediating contractions in bovine isolated ciliary muscles.

METHODS

Ciliary muscle strips were isolated from bovine eyeballs and mounted in organ baths containing aerated (95% O₂, 5% CO₂) Krebs buffer solution maintained at 37°C. Each muscle strip was attached at 1 end to a Grass Force-displacement Transducer connected to a Polyview Computer System for recording changes in isometric tension. After an equilibration period, ciliary muscle strips were exposed to selective agonists and antagonists of 5-HT receptors.

RESULTS

Both selective and nonselective agonists for 5-HT produced concentration-dependent contractions of isolated ciliary muscles with the following rank order of potency: BW723C86>α-methyl-5-HT>MK-212>>8-hydroxy-DPAT>quipazine>R-DOI>>5-HT>>tryptamine. The selective 5-HT₂ receptor antagonists, M-100907 (5-HT_2A), RS-127445 (5-HT_2B), and RS-102221 (5-HT_2C), produced noncompetitive inhibition of the contractile effects of selective agonists yielding antagonist potency (pK_B) values of 251 ± 27.2 nM (n = 4), 52.5 ± 6.3 nM (n = 4), and 79.4 ± 9.5 nM (n = 4), respectively.

CONCLUSION

On the basis of the profile of activity of selective agonists and antagonists, we conclude that the 5-HT_2B and 5-HT_2C receptor subtypes appear to be the predominant serotonin receptors that mediate the contractile action of this amine in bovine isolated ciliary muscles.

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.