Efficacy of cobalt chelates in the rabbit eye model for epithelial herpetic keratitis

A new class of antiviral agent, cobalt chelates (the CTC series), was evaluated for treating epithelial herpetic keratitis, consequent stromal disease being the major infectious cause of blindness in industrial nations.

Effects of CTC complexes were monitored in cell cultures and in a rabbit eye model, either infected with herpes simplex virus type 1 (HSV-1) or uninfected. Several antiviral concentrations of CTC complexes nontoxic to Vero cells were administered to rabbit eyes with HSV-1-induced keratitis. Corneal surface virus titers were measured, and corneal lesions of epithelial keratitis were monitored by slit-lamp microscopy and scored. Recovery rates and incidence were compared in eyes treated with CTC complexes, placebo, or clinically formulated trifluorothymidine (Viroptic), using nonparametric statistics.

All CTC complexes inhibited HSV-1 replication in vitro, CTC-96 being best. CTC-96, CTC-23, and CTC-67 eliminated (<1 plaque-forming unit[pfu]) corneal surface HSV-1 (otherwise >10(5) pfu) in order of descending potency, but CTC-82 was ineffective. CTC-96 (either 5 microg/ml six times daily or 10 microg/ml five times daily) accelerated herpetic dendritic keratitis recovery better than or the same as trifluorothymidine (10 mg/ml nine times daily). CTC complexes were nontoxic to Vero cells continuously exposed to < or =25 microg/ml; 50 microg/ml of CTC 96 nine times daily did not irritate uninfected rabbit eyes.

Topical CTC-96 applications were at least as effective as Viroptic in diminishing disease signs and corneal surface virus at concentrations less than one-thousandth that of Viroptic.