This document summarizes newer treatment modalities for glaucoma. It discusses how lowering intraocular pressure remains the primary treatment but may not stop disease progression. It then outlines several novel treatment approaches being investigated, including cannabinoids, cellular cytoskeletal modulators, memantine, and Rho kinase inhibitors. Clinical trials have been conducted or are ongoing for some of these alternative therapies to potentially treat glaucoma through neuroprotective mechanisms rather than solely lowering pressure. However, many of these novel agents have shown toxicity or failed to meet efficacy endpoints to date.

1. Newer treatment modalities of glaucoma
Dr. ATIF RAHMAN RAINI

2. Glaucoma
 Glaucoma is a chronic optic neuropathy involving damage to the retinal
ganglion cells and their axons.
 Hypothesised that the retinal ganglion cells and their axons become damaged
through various, specific insults.
 However, the pathogenesis of glaucoma is still largely unknown.
 IOP is a major risk factor

3. Increased intraocular pressure risk
factors and therapies
 Lowering intraocular pressure remains the only currently approved medical
course of treatment.
 Conventional therapy has focused on affecting the balance of aqueous humor
production and outflow, as a decrease in net aqueous humor volume results in
decreased intraocular pressure.

4. Current therapies to reduce IOP
 includes medication eye drops, laser treatment to the trabecular meshwork,
or surgery.
 Six classes of drug currently approved for lowering IOP
 miotics,
 beta-blockers
 alpha-agonists
 epinephrine derivatives
 carbonic anhydrase inhibitors
 prostaglandin analogues

5.  Although reducing IOP is often efficacious, in many cases
achieving an appropriate target IOP for an individual
patients may not halt the progression.

6.  Primary goal of glaucoma therapy is to stop
the loss of retinal ganglionic cells by
rescuing injured cells or regenerating new,
functional cells to replace those that are
lost.

7.  A number of mechanisms have been proposed to explain
retinal ganglion cell death in glaucoma, including
ischemia, oxidative stress, excitotoxicity, defective axonal
transport, trophic factor withdrawal, and
neuroinflammation.

8.  Broader therapeutic concept – NEUROPROTECTION

9. Novel medical therapy
 Includes
 Anecortave
 Cannabinoids
 Cellular cytoskeletal modulators
 Memantine
 Rho kinase inhibitors

10. Anecortave
 Angiostatic steroid without glucocorticoid activity
 Evaluated for therapeutic potential in glaucoma and ARMD
 No longer being persued for glaucoma treatment studies
(Robin AL, Clark AF, Covert DW et al. anterior juxtascleral delievery of
anecortave acetate in eyes with POAG: a pilot investigation. Am J
Ophthalmology. 2009;147(1):45-50.)

11. Cannabinoids
 Marijuana
 Acts on cannabinoid receptors – CB1 and CB2
 CB1 – present in the ciliary body of human
 Evidence for its use in glaucoma came from the observation – smoking
marijuana decreases IOP.
 Primary active ingredient- tetrahydrocannabinol (THC)
 THC effectively lower IOP when given orally or I.V. but not effective
topically

12.  Ocular side effect – conjunctival hyperemia, slight miosis, reduced tear production
 Systemic side effect- tachycardia, hypotension, euphoria
 Long term side effect- pulmonary fibrosis, impaired neurological behaviour
 SYSTEMIC HYPOTENSION may leads to reduced optic nerve
perfusion, limit their usefulness in Glaucoma

13. Cellular cytoskeletal Modulators
 Ethacrynic Acid- diuretic
 Change actin, alpha- actinin,vinculin and vimentin in cultured trabecular
meshwork
 Altering trabecular meshwork shape – main mechanism to decrease IOP
 Human clinical trial – though there is IOP reduction but corneal toxicity and
trabecular toxicity precluded its clinical application
(Tingey DP, Ozment RR, Schoeder A et al. the effect of intracameral ethacrynic acid
on IOP in patients with glaucoma. Am J Ophthalmology. 1992;113(6):706-711.)
( Jhonson Dh, Tschumper RC. Ethacrynic acid:outflow effects and toxicity in human
trabecular meshwork in perfusion organ culture. Curr Eye Res. 1993:12(5):385-396.)

14.  Latrunculins
 Disrupt the actin cytoskeleton
 Selective effects on trabecular meshwork
 Compound INS115644- now in clinical trials
(Sabanay I, Tian B, Gabelt BT et al. latrunculin B effect on trabecular meshwork
and cornel endothelial morphology in monkeys. Exp Eye Res.2006;82(2):236-246.)

15. memantine
 N-methyl-D-aspartate receptor antagonist
 Used for treatment of Parkinson disease, vascular dementia, Alzheimer
disease
 NMDA an ion channel is activated by glutamate and coagonist glycine leads to
extracellular calcium to enter cells.
 Excess activation of NMDA signaling cascade leads to “ EXCITOTOXICITY” leads
to overloads of intracellular ions in neuron causes apoptosis.
 The concept of excitotoxicity is based on the observation that subcutaneous
glutamate injection causes inner retinal damage.
(Lucas Dr, Newhouse JP. The toxic effect of Sodium l- glutamate on the inner
layers of retina. AMA Arch Ophthalmol.1957;58(2):193-201)

16.  After completing phase 3 clinical trial in United States, memantine did meet
glaucoma end points of efficacy.
(danesh- Mayer HV, Levin LA.neuroprotection :extrapolating from neurologic
diseases to eye. Am J Ophthalmol. 1996;114(3):299-305.)

17. Rho kinase inhibitors
 Two types of rho kinases- ROCK1 and ROCK2
 Serine – threonine kinases downstream effectors of Rho GTPase
 Regulate smooth muscle contraction in a calcium independent manner
 By selectively inhibiting ROCK activity, aqueous humor drainage through the
trabecular meshwork can be increased
 INS117548, DE-104, RKI983 in clinical trials
( RaoVP, Epstein DL. Rho GTPase/Rhokinase inhibition as a novel target for the
treatment for glaucoma. BioDrugs.2007;21(3):239-348.)

18. Thank You…….