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Heikkinen EM, Ruponen M, Jasper LM, Leppänen J, Hellinen L, Urtti A, Auriola S, Rautio J, Vellonen KS. Prodrug Approach for Posterior Eye Drug Delivery: Synthesis of Novel Ganciclovir Prodrugs and in Vitro Screening with Cassette Dosing. Mol Pharm 2020; 17:1945-1953. [PMID: 32320251 DOI: 10.1021/acs.molpharmaceut.0c00037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Because of poor ocular drug bioavailability, intravitreal injections have become the gold standard for drug delivery to the posterior eye. The prodrug approach can be used for optimizing the biopharmaceutical properties of intravitreal drugs. The preclinical screening of prodrugs' properties, such as hydrolysis and bioconversion, should be conducted in a resource-efficient way for an extensive set of synthesized compounds with validated methods. Our objective was to explore cassette dosing in in vitro prodrug hydrolysis and bioconversion studies in buffer, vitreous, and retinal pigment epithelium (RPE) homogenate for rapid medium-throughput screening. Moreover, our aim was to correlate the prodrug structure with hydrolytic behavior. We synthesized 18 novel ganciclovir prodrugs and first studied their hydrolysis in aqueous buffer and porcine vitreous in vitro with cassette dosing for 35 h. A method for vitreous homogenate pH equilibration to a physiological level by using buffer and incubation under 5% carbon dioxide was validated. The hydrolysis of the prodrugs was evaluated in porcine RPE homogenate in vitro with cassette dosing, and five prodrugs were assayed individually to examine their bioconversion into ganciclovir in RPE after 2 h. Lastly, the prodrugs' binding to melanin was studied in vitro. The prodrugs showed a wide spectrum of hydrolysis rates, ranging from a few percentages to 100% in the vitreous and RPE; in general, hydrolysis in RPE was faster than in vitreous. Prodrugs with long carbon chains and disubstitution showed lability in the tissue homogenates, whereas prodrugs with branched carbon chains and aromatic groups were stable. All five prodrugs chosen for the bioconversion study in RPE were hydrolyzed into ganciclovir, and their hydrolytic behavior matched results from the cassette mix experiment, supporting the cassette mix approach for hydrolysis and bioconversion studies. None of the prodrugs bound highly to melanin (<50% bound). In conclusion, cassette dosing proved useful for the rapid screening of prodrug hydrolysis and bioconversion properties. Analyzing several compounds simultaneously can complicate the analytics, and thus, choosing the compounds of the cassette mix should be done carefully to avoid mutual interference of the compounds with the results. The methodology and results of the work are applicable in ocular drug research and prodrug design.
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Affiliation(s)
- Emma M Heikkinen
- School of Pharmacy, University of Eastern Finland, Yliopistonranta 1, Kuopio 70211, Finland
| | - Marika Ruponen
- School of Pharmacy, University of Eastern Finland, Yliopistonranta 1, Kuopio 70211, Finland
| | - Lisa-Marie Jasper
- School of Pharmacy, University of Eastern Finland, Yliopistonranta 1, Kuopio 70211, Finland
| | - Jukka Leppänen
- School of Pharmacy, University of Eastern Finland, Yliopistonranta 1, Kuopio 70211, Finland
| | - Laura Hellinen
- School of Pharmacy, University of Eastern Finland, Yliopistonranta 1, Kuopio 70211, Finland
| | - Arto Urtti
- School of Pharmacy, University of Eastern Finland, Yliopistonranta 1, Kuopio 70211, Finland.,Helsingin Yliopisto, Faculty of Pharmacy, Division of Pharmaceutical Biosciences, Viikinkaari 5E, Helsinki 00014, Finland.,Institute of Chemistry, Saint Petersburg State University, Universitetskii Prospect 26, Sankt-Peterburg 198504, Finland
| | - Seppo Auriola
- School of Pharmacy, University of Eastern Finland, Yliopistonranta 1, Kuopio 70211, Finland
| | - Jarkko Rautio
- School of Pharmacy, University of Eastern Finland, Yliopistonranta 1, Kuopio 70211, Finland
| | - Kati-Sisko Vellonen
- School of Pharmacy, University of Eastern Finland, Yliopistonranta 1, Kuopio 70211, Finland
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