Efficacy of a novel synthetic topically applied tetrapeptide on eliciting corneal analgesia subsequent to experimentally induced chemical corneal injury Bruce I. Gaynes, OD, Pharm D, Michael Russo, David Goldmeier Loyola University Chicago, Stritch School of Medicine, Department of Ophthalmology, Maywood, IL IntroductionReferences Methods Results Summary Currently, only limited medical alternatives are available to obtain adequate corneal analgesia following various corneal insults, either iatrogenic, traumatic or disease related. Effective corneal analgesics must provide adequate pain relief without compromise of corneal sensitivity. Interestingly, viper venom appears to demonstrate marked analgesic properties. Chromatographic fractionation of venoms demonstrated that low molecular weight fractions consist of peptides that impart significant analgesics properties. Here we describe the action of the synthetic analogue of the low molecular weight venom fraction pGlu- Asn-Trp-Thr-OH (SIS-ZEP04) for topical use as a potential corneal analgesic.  Study Purpose: To ascertain efficacy of SIS-ZEP04 in reducing pain in a rat model of experimentally induced chemical corneal injury. SIS-ZEP04 appears to demonstrate efficacy in reducing pain and modifying pathways of nociception following chemical irritation in a capsaicin model of corneal insult. As analgesic action was apparent in both treated and control eyes, it is unclear what effect, if any, the vehicle exerted in minimizing ocular pain or rather if a central action induced by systemic absorption of the peptide is in place. The analgesic action appears to be a delayed action and occurs without reduction in corneal sensitivity. Further study is required to clarify the mechanism by which this novel peptide appears to exert analgesia in the mammalian eye as well as ramifications of potential systemic absorption. Five adult Sprague Dawley rats were utilized for study. All procedures were approved by the local animal use committee. The capsaicin eye wipe test was employed as a mechanism to ascertain analgesic efficacy. 1,2 Methods Administration of 20 µL of 0.01 mg/mL of tetrapeptide in 0.01% ethanol vehicle was applied to the right eye for 14 days. A negative control was employed in the fellow eye. Capsaicin testing was performed at baseline, day 7 and 14. The time required for recovery from capsaicin induced corneal insult, defined as blepharospasm, eye wiping, and squinting was recorded as a surrogate indicator of analgesic efficacy in relation to the control eye. Mean time (seconds) for recovery from capsaicin induced irritation in both right and left eyes at baseline was /- 7.8 and /- 9.8 seconds respectively. Following SIS-ZEP04 treatment (at day 14) mean (SD) time for capsaicin induced irritation recovery was /- 5.6 and / seconds for right and left eyes respectively (Tables 1 and 2). A statistically significant reduction in mean time of capsaicin recovery was found for both right and left eyes (paired one way t test, p= and respectively, Figure 1 + ). Cochet-Bonnet aesthesiometry measurements did not deviate from baseline levels at day 7 or 14 for either eye. Intermediate day 7 capsaicin results did not differ significantly between treatment and control groups. Table 1. Descriptive values, blepharospasm recovery time (seconds + ) Acknowledgments: We would like to acknowledge the support of the Shulov Institute of Science (SIS) Ltd. Rehovot, Israel and the Richard A. Perritt Charitable Foundation in the conduct of this work. SIS ZEP04 was kindly provided by Dr. Naftali Primor of Shulov Institute of Science Ltd. 1.Farazifard R. Safarpour F, Sheibani V, Javan M. Eye-wiping test: a sensitive animal model for acute trigeminal pain studies. Brain Research Protocols. 2005;16: Bates, BD, Mitchell K, Keller MM, Chan CC, Swaim WD, Yaskovich R, Mannes AJ, Iadarola MJ. Prolonged analgesic response of cornea to topical resiniferatoxin., a potent TRPV1 agonist. Pain. 2010;149: right eye baseline right eye 2 weeks left eye baseline left eye 2 weeks Number of values4455 Minimum Maximum Mean Std. Deviation T testmatched pairs AnalysisPost-hoc Inputone tailed Calculated effect size Total sample size 4 Power (1-β) Table 2. Power analysis * * G*Power v GraphPad Prism v5.00