Development of a Topical Cell Penetrating Peptide Therapeutic for Inflammatory Eye Diseases
Bruce Littman
CEO, Portage Pharmaceuticals LTD
PPL licensed the Antennapedia cell penetrating peptide (CPP) technology and also developed its own proprietary CPP sequences derived from human Hox genes. Using the same cargo, a peptide that blocks NFκB transcription factor activation, the biological activities of these CPP platforms were compared in vitro and in animal endotoxin challenge models using synthetically made peptide conjugates. One 71 amino acid peptide, named PPL-003, was found to have superior biological anti-inflammatory activity as well physicochemical properties that would facilitate development as a biological therapeutic. A synthetic PPL-003 solution was also active as a topical eye drop in a mouse endotoxin-induced uveitis model. Recombinant (E. coli) PPL-003 was manufactured and found to be active in a rabbit endotoxin induced uveitis model and it was well tolerated in a 7 day rabbit safety study at a dose approximately 10-fold higher than the lowest efficacious dose in the uveitis study. During efforts to develop a specific topical eye formulation recombinant PPL-003 was found to be a mixture of two peptides, about 44% full length PPL-003 and about 56% inactive truncated peptide that lost its cargo sequence. Full length PPL-003 was purified from this mixture using reverse phase preparative HPLC methods and a precise extinction coefficient was determined using data from an amino acid analysis to confirm peptide identity. Pure PPL-003 was dosed for 14 days in a rabbit mycobacterial antigen-induced uveitis model thought to be more representative of human uveitis and for 14 days in a rat model of dry eye disease. Topical PPL-003 reduced inflammation in the anterior chamber and vitreous in the rabbit uveitis model and was well tolerated. Topical PPL-003 was also efficacious in the rat dry eye study, reducing corneal pathology at the lowest dose tested. Using the newly determined PPL-003 extinction coefficient and knowledge of PPL-003 content, the actual doses of PPL-003 were recalculated in all studies that utilized recombinant PPL-003. A topical dose <23μg/day in the endotoxin model and between 5-68μg/day in the mycobacterial model had anterior chamber anti-inflammatory activity in rabbits and a daily dose between 68-250μg/day was active in the vitreous. The lowest dose tested, 0.45μg/day, was active in the rat dry eye model. PPL is planning to develop an ocular formulation of PPL-003 for development in various inflammatory eye disease indications.
Other contributors: Jeffrey A. Jamison4, Frank L. Marcoux1, Keith G. Inman2, and Christopher A. Rhodes3
(Portage Pharmaceuticals Ltd. (PPL), Toronto, Ontario, Canada, 2Pargon Bioservices Inc., Baltimore, MD, USA
3Drug Delivery Experts, San Diego, CA, USA, 4 Ophthy-DS, Inc., Kalamazoo, MI USA)
Dr. Littman is the CEO and President of Portage Pharmaceuticals Ltd. He is a rheumatologist and immunologist by training and spent 13 years in academia as a professor at VCU School of Medicine in Richmond, VA and 19 years at Pfizer Research and Development prior to starting a consulting business focused on translational research and drug development. He is an author of many scientific publications and co-editor of "Translational Medicine and Drug Discovery" (Cambridge University Press). His expertise in early drug development and translational research led to his selection to lead PPL.