Closed gateways--can neuroprotectants shield the retina in glaucoma?

Neuroprotection for glaucoma is a therapeutic approach that aims to prevent optic nerve damage or cell death. An appropriate drug that reaches an adequate concentration across the blood retinal barrier is expected to shield the retina in glaucoma. Several in vitro and in vivo attempts in experimental models indicate the possibility of successful neuroprotection. However, clinical trials might not show the same level of neuroprotection as a result of subtherapeutic concentrations of the drug in the eye. The study by Zhong et al. in this issue of Drugs in R&D could not attribute the observed improvement in visual field indices to any one of the individual active constituents of Erigeron breviscapus (vant.) Hand. Mazz. (EBHM). One of the major constituents of EBHM is scutellarin, which is known to have poor oral bioavailability and an unclear ability to penetrate inside the eye. Therefore, before recognizing EBHM as a neuroprotectant in glaucoma for further clinical studies and practice, its active constituents and their pharmacokinetics (systemic as well as ocular) need to be explored.