ABSTRACT The objective of this NIH R01 proposal is to develop a non-immunogenic, injectable depot of a PEG-like conjugate of a peptide drug for systemic drug delivery. This proposal is motivated by the fact that many peptide and protein drugs have a short plasma half-life on the order of minutes to a few hours. PEGylation —the conjugation of polyethylene glycol (PEG) moieties to biologics— is commonly used to overcome these limitations. Unfortunately, PEG is antigenic, which has led to the early termination of a Phase III clinical trial of a PEGylated drug candidate and withdrawal of several PEGylated drugs from the market because of severe allergic reactions in some patients. These problems have been traced to circulating anti-PEG antibodies that are found even in individuals who have not previously received a PEGylated drug. Furthermore, the improvement in pharmacokinetics (PK) and pharmacodynamics (PD) conferred by PEG and its branched derivatives are now at an asymptote. This proposal addresses the urgent, unmet need to develop the next-generation of PEGylation that overcomes these limitations. We hypothesize that we can solve the immunogenicity problem of PEG conjugates and further extend the half-life of PEG conjugates by a next generation PEG-like “stealth” polymer, poly[oligo(ethylene glycol) methyl ether methacrylate] (POEGMA) that presents short oligomeric ethylene glycol (OEG) side-chains on a backbone. This hypothesis is validated by our preliminary data that shows that reactivity towards patient-derived anti-PEG antibodies is eliminated by shortening the OEG side-chain length to ≤3 without compromising PK or PD, and that a copolymer with a mixture of two and three EG long side-chains also allows POEGMA to reversibly transition from a solution into an insoluble coacervate between 25-37 ºC, thereby enabling the creation of a sustained release depot. We will demonstrate the utility of this non-immunogenic, injectable drug depot by synthesizing POEGMA conjugates of exendin —a potent but short-acting clinically approved peptide drug for type 2 diabetes— and show that exendin-POEGMA conjugates are pharmacologically active, form a depot upon subcutaneous (s.c.) injection in diabetic mice, show zero-order release kinetics into the bloodstream from the depot, leading to sustained glucose control in diabetic (db/db) mice, while simultaneously eliminating PEG immunogenicity and antigenicity. The overall significance of this research is that it will solve the problem of PEG antigenicity and will also improve upon the PK and PD of PEG conjugates by creating an injectable PEG conjugate that forms a s.c. depot with sustained release of the drug. By doing so, it will breathe new life into an established drug delivery technology that is now beginning to show its age. More specifically, it will also enable improved management of type diabetes for the ~30 million Americans who are diabetic. Because the POEGMA conjugate technology can likely be applied ...