(190bp) Proteins Covalently Conjugated to Phenylpiperazine-Containing Polymers Experience Selectively Enhanced Intestinal Epithelial Transport

Oral delivery of protein drugs remains a crucial challenge facing the field of drug delivery (1). Protein drugs are critical for the treatment of many diseases, ranging from daily insulin for diabetes management to antibody immunotherapies for cancer. The current gold standard for delivery of protein drugs is injection; however, the pain and inconvenience associated with injections decreases patient compliance, leading to detrimental effects on their health (2). Oral delivery is generally more accepted by patients, but is less conducive to systemic protein delivery due, in part, to the barrier function of the intestinal epithelium. The large size and hydrophilic nature of proteins precludes their absorption across the intestinal epithelium, limiting the bioavailability, and thus the efficacy, of orally delivered protein drugs. The use of chemical permeation enhancers to improve protein transport across the intestinal epithelium has been studied extensively, but their impact has been limited because strong permeation enhancing activity is often accompanied by toxicity (3). To reduce the harmful effects of chemical permeation enhancers, it is advantageous to have a drug delivery system that co-localizes the enhancer and the drug, thus reducing the amount of enhancer required to improve transport.

Here, we present a novel approach for increasing protein permeability across the intestine using chemical permeation enhancers that are incorporated into polymers conjugated from the protein surface. Based on previous studies showing the potential of 1-phenylpiperazine as an intestinal permeation enhancer (3), we synthesized protein-polymer conjugates with polymers containing phenylpiperazine. A novel phenylpiperazine acrylamide monomer was synthesized and incorporated into polymers grown from bovine serum albumin, a model protein, via atom transfer radical polymerization. Using Caco-2 monolayers as a model for the intestinal epithelium, the protein-polymer conjugates induced dose-dependent and reversible reductions in the trans-epithelial electrical resistance, a measurement previously shown to correlate with permeability (3). Conjugation with phenylpiperazine-containing polymers enabled an approximately 30-fold increase in protein permeability, while limiting the increase in permeability of calcein, a small molecule co-administered with the conjugates, to approximately 5-fold. This selectivity is promising because non-selective increases in intestinal permeability can lead to infection and inflammation if pathogens from the intestine can pass into the bloodstream (4). Importantly, at equivalent phenylpiperazine concentrations, the conjugates were significantly less toxic than the small molecule 1-phenylpiperazine. These results highlight the potential of conjugating permeation enhancing polymers to proteins as a strategy to facilitate selective intestinal absorption of protein drugs and address one of the major barriers to oral protein delivery (5).

References:

(1) Moroz, E., Matoori, S., and Leroux, J.-C. (2016) Adv. Drug Deliv. Rev. 101, 108–121.

(2) Sokolowski, C. J., Giovannitti, J. A., and Boynes, S. G. (2010) Dent. Clin. North Am. 54, 731–744.

(3) Whitehead, K., Karr, N., and Mitragotri, S. (2008) Pharm. Res. 25, 1782-1788.

(4) Mccartney, F., Gleeson, J. P., and Brayden, D. J. (2016) Tissue Barriers 4, 1–13.

(5) Cummings, C. S., Fein, K., Murata, H., Ball, R. L., Russell, A. J., and Whitehead, K. A. (2017) J. Control. Release 255, 270–278.