High-strength and fibrous capsule-resistant zwitterionic elastomers.

The high mechanical strength and long-term resistance to the fibrous capsule formation are two major challenges for implantable materials. Unfortunately, these two distinct properties do not come together and instead compromise each other. Here, we report a unique class of materials by integrating two weak zwitterionic hydrogels into an elastomer-like high-strength pure zwitterionic hydrogel via a "swelling" and "locking" mechanism. These zwitterionic-elastomeric-networked (ZEN) hydrogels are further shown to efficaciously resist the fibrous capsule formation upon implantation in mice for up to 1 year. Such materials with both high mechanical properties and long-term fibrous capsule resistance have never been achieved before. This work not only demonstrates a class of durable and fibrous capsule-resistant materials but also provides design principles for zwitterionic elastomeric hydrogels.

Zwitterionic Polymer Conjugated Glucagon-like Peptide-1 for Prolonged Glycemic Control.

Glucagon-like peptide-1 (GLP-1) is of particular interest for treating type 2 diabetes mellitus (T2DM), as it induces insulin secretion in a glucose-dependent fashion and has the potential to facilitate weight control. However, native GLP-1 is a short incretin peptide that is susceptible to fast proteolytic inactivation and rapid clearance from the circulation. Various GLP-1 analogs and bioconjugation of GLP-1 analogs have been developed to counter these issues, but these modifications are frequently accompanied by the sacrifice of potency and the induction of immunogenicity. Here, we demonstrated that with the conjugation of a zwitterionic polymer, poly(carboxybetaine) (pCB), the pharmacokinetic properties of native GLP-1 were greatly enhanced without serious negative effects on its potency and secondary structure. The pCB conjugated GLP-1 further provided glycemic control for up to 6 days in a mouse study. These results illustrate that the conjugation of pCB could realize the potential of using native GLP-1 for prolonged glycemic control in treating T2DM.

Enhanced pulmonary systemic delivery of protein drugs via zwitterionic polymer conjugation.

Pulmonary delivery of protein drugs into the systemic circulation is highly desirable as the lung provides a large absorption surface area and a more favorable environment for biologics compared to other delivery routes. However, pulmonary systemic delivery of proteins presents several challenges such as poor protein stability and limited bioavailability, especially for large proteins (molecular weight > 50 kDa), which exhibit an average bioavailability of 1% to 5% when delivered via the pulmonary route. Here, we demonstrated that with the conjugation of zwitterionic poly(carboxybetaine) (pCB) polymer, the bioavailability of organophosphate hydrolase (OPH) was significantly increased from 5% to 53%. OPH conjugated with pCB delivered through intubation-assisted intratracheal instillation (IAIS) into the lung exhibited improved pharmacokinetic properties and prophylactic efficacy against organophosphate poisoning, showing its application potential. Zwitterionic polymer conjugation provides the possibility for a favorable, non-invasive delivery of biological therapeutics into the systemic circulation.

Nanoscavenger provides long-term prophylactic protection against nerve agents in rodents.

Nerve agents are a class of organophosphorus compounds (OPs) that blocks communication between nerves and organs. Because of their acute neurotoxicity, it is extremely difficult to rescue the victims after exposure. Numerous efforts have been devoted to search for an effective prophylactic nerve agent bioscavenger to prevent the deleterious effects of these compounds. However, low scavenging efficiency, unfavorable pharmacokinetics, and immunological problems have hampered the development of effective drugs. Here, we report the development and testing of a nanoparticle-based nerve agent bioscavenger (nanoscavenger) that showed long-term protection against OP intoxication in rodents. The nanoscavenger, which catalytically breaks down toxic OP compounds, showed a good pharmacokinetic profile and negligible immune response in a rat model of OP intoxication. In vivo administration of the nanoscavenger before or after OP exposure in animal models demonstrated protective and therapeutic efficacy. In a guinea pig model, a single prophylactic administration of the nanoscavenger effectively prevented lethality after multiple sarin exposures over a 1-week period. Our results suggest that the prophylactic administration of the nanoscavenger might be effective in preventing the toxic effects of OP exposure in humans.

Proactively Reducing Anti-Drug Antibodies via Immunomodulatory Bioconjugation.

Although PEGylation reduces the immunogenicity of protein drugs to some extent, its limitations for highly immunogenic biotherapeutics have been demonstrated. Herein, a proactive strategy to alleviate the development of anti-drug antibodies (ADAs) against protein drugs by immunomodulatory bioconjugation is reported. Rapamycin was conjugated to a PEGylated protein therapeutic via a cleavable disulfide linker. The conjugated rapamycin can be released from the bioconjugate and prevent immune responses once the bioconjugate is uptaken by antigen-presenting cells. The immunomodulatory bioconjugate significantly reduced the titers of ADAs compared with a PEGylated protein. The inhibition of immune responses was specific to the conjugated antigen, avoiding systemic immune suppression and the risk of increased susceptibility to infections. The reported approach breaks the limitations of PEGylation by the proactive prevention of ADAs.

Revealing the Immunogenic Risk of Polymers.

Poly(ethylene glycol) (PEG) conjugation has been the gold standard to ameliorate the pharmacokinetic (PK) and immunological profiles of proteins. PEG polymer does become immunogenic once attached to proteins, evoking PEG-specific antibody (Ab) responses. The anti-PEG Abs could cause PEGylated biologic treatments to fail and even result in lethal adverse reactions. Thus the zwitterionic poly(carboxybetaine) (PCB) has been introduced as a PEG substitute for protein modification. Addressed herein is anti-polymer Ab induction by conjugating PEG and PCB polymers to a series of carrier proteins with escalating immunogenicity. Results indicate that titers of PEG-specific Abs were quantitatively correlated to the immunogenicity of carrier proteins, whereas the generation of PCB-specific Abs was minimal and insensitive to increased protein immunogenicity. This work provides insight into the immunological properties of PEG and PCB and has far-reaching implications for the development of polymer-protein conjugates.

Polypeptides with High Zwitterion Density for Safe and Effective Therapeutics.

The commonly used "stealth material" poly(ethylene glycol) (PEG) effectively promotes the pharmacokinetics of therapeutic cargos while reducing their immune response. However, recent studies have suggested that PEG could induce adverse reactions, including the emergence of anti-PEG antibodies and tissue histologic changes. An alternative stealth material with no or less immunogenicity and organ toxicity is thus urgently needed. We designed a polypeptide with high zwitterion density (PepCB) as a stealth material for therapeutics. Neither tissue histological changes in liver, kidney, or spleen, nor abnormal behavior, sickness or death was induced by the synthesized polymer after high-dosage administration for three months in rats. When conjugated to a therapeutic protein uricase, the uricase-PepCB bioconjugate showed significantly improved pharmacokinetics and immunological properties compared with uricase-PEG conjugates.

Zwitterionic Nanocages Overcome the Efficacy Loss of Biologic Drugs.

For biotherapeutics that require multiple administrations to fully cure diseases, the induction of undesirable immune response is one common cause for the failure of their treatment. Covalent binding of hydrophilic polymers to proteins is commonly employed to mitigate potential immune responses. However, while this technique is proved to partially reduce the antibodies (Abs) reactive to proteins, it may induce Abs toward their associated polymers and thus result in the loss of efficacy. Zwitterionic poly(carboxybetaine) (PCB) is recently shown to improve the immunologic properties of proteins without inducing any antipolymer Abs against itself. However, it is unclear if the improved immunologic profiles can translate to better clinical outcomes since improved immunogenicity cannot directly reflect amelioration in efficacy. Here, a PCB nanocage (PCB NC) is developed, which can physically encase proteins while keeping their structure intact. PCB NC encapsulation of uricase, a highly immunogenic enzyme, is demonstrated to eradicate all the immune responses. To bridge the gap between immunogenicity and efficacy studies, the therapeutic performance of PCB NC uricase is evaluated and compared with its PEGylated counterpart in a clinical-mimicking gouty rat model to determine any loss of efficacy evoked after five administrations.

A Coating-Free Nonfouling Polymeric Elastomer.

Medical devices face nonspecific biofouling from proteins, cells, and microorganisms, which significantly contributes to complications and device failure. Imparting these devices with nonfouling capabilities remains a major challenge, particularly for those made from elastomeric polymers. Current strategies, including surface coating and copolymerization/physical blending, necessitate compromise among nonfouling properties, durability, and mechanical strength. Here, a new strategy is reported to achieve both high bulk mechanical strength and excellent surface nonfouling properties, which are typically contradictory, in one material. This is realized through a nonfouling polymeric elastomer based on zwitterionic polycarboxybetaine derivatives. By hiding both charged moieties of the zwitterionic compounds with hydrocarbon ester and tertiary amine groups, the bulk polymer itself is elastomeric and hydrophobic while its superhydrophilic surface properties are restored upon hydrolysis. This coating-free nonfouling elastomer is a highly promising biomaterial for biomedical and engineering applications.

Butyrylcholinesterase nanocapsule as a long circulating bioscavenger with reduced immune response.

Butyrylcholinesterase (BChE) is the most promising bioscavenger candidate to treat or prevent organophosphate (OP) poisoning. However, the clinical application of BChE is limited by two obstacles: an inadequate circulation half-life and limited sources for production. Although several modification technologies including glycosylation and PEGylation have been developed to improve its pharmacokinetics, none of them have been able to outperform blood-derived native BChE. In this work, we designed a long-circulating bioscavenger nanogel by coating equine serum-derived BChE with a zwitterionic polymer gel layer. This zwitterionic gel coating protected BChE from denaturation and degradation under harsh conditions. Notably, the nanocapsule exhibited a long circulation half-life of ~45h, a three-fold increase from the unmodified native version, enabling both therapeutic and prophylactic applications. In addition, the gel coating reduced the immunogenicity of equine BChE, unlocking the possibility to use non-human derived BChE as an OP bioscavenger in humans.

Zwitterionic gel encapsulation promotes protein stability, enhances pharmacokinetics, and reduces immunogenicity.

Advances in protein therapy are hindered by the poor stability, inadequate pharmacokinetic (PK) profiles, and immunogenicity of many therapeutic proteins. Polyethylene glycol conjugation (PEGylation) is the most successful strategy to date to overcome these shortcomings, and more than 10 PEGylated proteins have been brought to market. However, anti-PEG antibodies induced by treatment raise serious concerns about the future of PEGylated therapeutics. Here, we demonstrate a zwitterionic polymer network encapsulation technology that effectively enhances protein stability and PK while mitigating the immune response. Uricase modified with a comprehensive zwitterionic polycarboxybetaine (PCB) network exhibited exceptional stability and a greatly prolonged circulation half-life. More importantly, the PK behavior was unchanged, and neither anti-uricase nor anti-PCB antibodies were detected after three weekly injections in a rat model. This technology is applicable to a variety of proteins and unlocks the possibility of adopting highly immunogenic proteins for therapeutic or protective applications.