Enzyme‐Triggered l‐α/d‐Peptide Hydrogels as a Long‐Acting Injectable Platform for Systemic Delivery of HIV/AIDS Drugs

Abstract

AbstractEradicating HIV/AIDS by 2030 is a central goal of the World Health Organization. Patient adherence to complicated dosage regimens remains a key barrier. There is a need for convenient long‐acting formulations that deliver drugs over sustained periods. This paper presents an alternative platform, an injectable in situ forming hydrogel implant to deliver a model antiretroviral drug (zidovudine [AZT]) over 28 days. The formulation is a self‐assembling ultrashort d or l‐α peptide hydrogelator, namely phosphorylated (naphthalene‐2‐ly)‐acetyl‐diphenylalanine‐lysine‐tyrosine‐OH (NapFFKY[p]‐OH), covalently conjugated to zidovudine via an ester linkage. Rheological analysis demonstrates phosphatase enzyme instructed self‐assembly, with hydrogels forming within minutes. Small angle neutron scattering data suggest hydrogels form narrow radius (≈2 nm), large length fibers closely fitting the flexible cylinder elliptical model. d‐Peptides are particularly promising for long‐acting delivery, displaying protease resistance for 28 days. Drug release, via hydrolysis of the ester linkage, progress under physiological conditions (37 °C, pH 7.4, H2O). Subcutaneous administration of Napffk(AZT)Y[p]G‐OH in Sprague Dawley rats demonstrate zidovudine blood plasma concentrations within the half maximal inhibitory concentration (IC50) range (30–130 ng mL−1) for 35 days. This work is a proof‐of‐concept for the development of a long‐acting combined injectable in situ forming peptide hydrogel implant. These products are imperative given their potential impact on society.