The medical treatment of glaucoma has recently advanced very little. The pharmaceuticals brought to market in the last 2 years addressed issues related to safety, not efficacy. These compounds include BAK-free travoprost (Travatan Z; Alcon Laboratories, Inc., Fort Worth, TX), which was approved in September 2006, and brimonidine tartrate (Alphagan P; Allergan, Inc., Irvine, CA), which was approved in August 2005 (see the point/counterpoint article on preservatives by Robert Noecker, MD, and Eve Higginbotham, MD, in this issue). Unlike in Europe and Canada, the fixed combinations using a prostaglandin base (ie, prostaglandin + beta blocker, prostaglandin + carbonic anhydrase inhibitor, or prostaglandin + alpha agonist) are unlikely to gain FDA approval. Furthermore, and perhaps more importantly, a new class of agents that lowers IOP has not been introduced in more than a decade, since the first prostaglandin, latanoprost (Xalatan; Pfizer Inc., New York, NY), was approved in 1996.
One cannot help but speculate why pharmaceutical progress has been so slow. Is the basic science of aqueous production and outflow so complex as to prevent further innovation? Is the cost of development too prohibitive, especially given the safety and efficacy of the current prostaglandin analogs? Are the regulatory hurdles too steep? Have we reached the limits of IOP reduction with topical medication?
Presentations at ophthalmic meetings and private conversations indicate that experimental compounds with unique and diverse mechanisms of action are in development by big and small pharmaceutical companies. Clinical trials are underway, but the commercial launch of these products appears to be years in the future. The current need for more options in treating glaucoma is obvious, and the slowness of pharmaceutical development is emphasized by the energetic research into surgical devices. Small, lean, startup companies are pushing the envelope with regard to the surgical control of IOP. Their technologies utilize the canal and suprachoroidal space, and some of these devices may even aid drug delivery.
What happens when the most commonly used medications are off patent like timolol? The patent for dorzolamide (Trusopt; Merck & Co., Inc., Whitehouse Station, NJ) expires in 2008, and that for Xalatan ends in 2011. Without new medications, the glaucoma market will shift to less expensive generics. The concurrent improvement in surgical options has profound implications for patients and the subspecialty of glaucoma.
