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Bart Jonckx, Peter Stalmans, Joachim Van Calster, Marc Vanhove, Bernard Noppen, Frans Aerts, Jean Marie Stassen, Marc D. de Smet; Determination Of The Inactivation Of Ocriplasmin In The Vitreous. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6684.
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To determine the pharmacokinetics of ocriplasmin enzyme in ex vivo vitreous, vitreous humor or buffer.
Residual ocriplasmin activity was determined in vitreous samples taken from porcine eyes 0, 5, 15, 30, 60, 120 and 180 minutes following intravitreal injection of ocriplasmin; and in ocriplasmin mixed with phosphate buffered saline (PBS), porcine or human vitreous humor, at specific time points (up to 24 hours) after mixing. Ocriplasmin (50, 125, 175 and 250 µg) in a citrate buffer was added to each sample, and residual enzymatic activity was determined based on the release of p-nitroaniline (pNA) from the substrate Glu-Phe-Lys-pNA, measured on a spectrophotometer at 405 nm.
Degradation in ex vivo porcine eyes closely resembles degradation in in vitro vitreous humor or buffer. Ocriplasmin degradation most closely matches a reaction of second order kinetics. A rapid decline in activity was noted during the first 5 hours of incubation at 37°C in porcine vitreous or PBS, with 35.4 ± 3.5% and 17.3 ± 2.3% of the initial concentration remaining, respectively. Subsequent inactivation occurred at a slower rate. After 72 hours, only 0.6% of the initial dose was present in human vitreous. These second order processes were characterized by rate constants of 81 ± 15 M-1.s-1, 195 ± 21 M-1.s-1 and 207 ± 15 M-1.s-1, for porcine and human vitreous humor, and PBS, respectively.
Ocriplasmin undergoes rapid, concentration-dependent, auto-proteolytic degradation, as previously described for plasmin, which is most closely described by second order kinetics. Previous investigation has shown that, despite this rapid degradation, residual activity at 72 hours is sufficient for biologic activity. These data demonstrate that ocriplasmin exerts activity in the vitreous for several hours, and are consistent with previous findings for plasmin.Acknowledgements: Ashraf Gad El Kareem for technical support/training
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