Browsing by Subject "Peptidi"

Diseases of the posterior eye segment, such as age-related macular degeneration (AMD), diabetic retinopathy, diabetic macular edema and glaucoma are the leading cause of blindness worldwide. Current therapy to treat these vision-threatening diseases relies on intravitreal injections to maintain a desired therapeutic drug concentration in the back of the eye. Frequent intravitreal injections are uncomfortable with poor patient compliance and causes major burden to the healthcare systems as well as to the patients. Small molecule drugs have shorter half-life in the vitreous and are eliminated rapidly. This requires frequent intravitreal dosing intervals that are not feasible in the clinical settings. Also, intravitreally injected small molecule drugs are often poorly and non-specifically distributed to the ocular tissues causing adverse effects. To address these issues, controlled and sustained drug delivery systems in the form of drug conjugates are desirable. Conjugating small molecule drugs with enzymatically cleavable peptide linkers increases the residence time in the vitreous. The peptide linker gets cleaved by vitreal enzyme and the released drug reaches the target in retina and choroid. Aim of this thesis was to screen a library of 25 peptide linkers for cleavage in the presence of porcine vitreal enzymes. The peptide linkers were chemically synthesized and the in vitro stability of the peptide linkers were studied in freshly isolated porcine vitreous. Ten time point samples were collected over a period of 45 days and the peptide cleavage in porcine vitreous was assessed by LC-MS method. A TQ-S liquid chromatography-mass spectrometer was used to study the linker cleavage. LC-MS method development for the peptide library was carried out using IntelliStart wizard function. Out of the 25 peptide linker in the library, stability of eight linkers were not included in the LC-MS analysis as a mass method could not be developed. Out of 17 peptide linkers studied, 14 were categorized as fast cleaving linkers (>90% of the linker cleaved in porcine vitreous after 5 h). Three linker peptides; P4, P5 and P25 were categorized as slow cleaving linkers. Conjugating slow cleaving peptide linkers to small molecule drugs will increase the half-life and enhance the duration of drug action upon intravitreal injection. In this study, linkers that are hydrolyzed by specific enzymes present in vitreous or ocular tissues are exploited to investigate their potential for delivering small molecule drugs.