PEtOxylated Interferon-α2a Bioconjugates Addressing H1N1 Influenza A Virus Infection

Deciphering Polymer Interactions in Bioconjugates with Different Architectures by Structural Analysis via Time-Resolved Limited Proteolysis Mass Spectrometry

Therapeutic proteins are commonly conjugated with polymers to modulate their pharmacokinetics but often lack a description of the polymer-protein interaction. We deployed limited proteolysis mass spectrometry (LiP-MS) to reveal the interaction of polyethylene glycol (PEG) and PEG alternative polymers with interferon-α2a (IFN). Target conjugates were digested with the specific protease trypsin and a "heavy" 15N-IFN wild type (IFN-WT) for time-resolved quantification of the cleavage dynamics. Interactions between IFN-α2a and its high-affinity receptor were detailed by LiP-MS. Then, 10 kDa polymers of PEG, linear polyglycerol (LPG), and poly(2-oxazoline) (POX) with two different cyclooctyne linkers (BCN/DBCO) were used for site-specific bioconjugation to azide functionalized IFN-α2a. Tryptic events at each cleavage site and in different structural environments (loops/helices) were compared. PEG and LPG were similar, and POX showed a reduced interaction profile with the IFN-α2a surface. All-atom molecular dynamics simulations of IFN-DBCO-polymer conjugates revealed distinct and transient (below 50 ns) protein-interaction profiles for PEG, LPG, and POX. Cleavage dynamics of IFN-polymer conjugates from the BCN handle were homogeneous, pointing to a more conserved IFN structure than DBCO-polymer conjugates. In summary, time-resolved LiP-MS for quantification of cleavage events enhances the structural understanding of transient IFN-polymer interactions, which may be extended to other bioconjugate types.

Matrix Metalloproteinase-Responsive Delivery of PEGylated Fibroblast Growth Factor 2

Attachment of polyethylene glycol (PEG) chains is a common, well-studied, and Food and Drug Administration-approved method to address the pharmacokinetic challenges of therapeutic proteins. Occasionally, PEGylation impairs the activity of pharmacodynamics (PD). To overcome this problem, disease-relevant cleavable linkers between the polymer and the therapeutic protein can unleash full PD by de-PEGylating the protein at its target site. In this study, we engineered a matrix metalloproteinase (MMP)-responsive fibroblast growth factor 2 (FGF-2) mutant that was site-specifically extended with a PEG polymer chain. Using bioinspired strategies, the bioconjugate was designed to release the native protein at the desired structure/environment with preservation of the proliferative capacity in vitro on NIH3T3 cells. In vivo, hepatic exposure was diminished but not its renal distribution over time compared to unconjugated FGF-2. By releasing the growth factor from the PEG polymer in response to MMP cleavage, restored FGF-2 may enter hard-to-reach tissues and activate cell surface receptors or nuclear targets.

Mechanism of interferon alpha therapy for chronic hepatitis B and potential approaches to improve its therapeutic efficacy

Hepatitis B virus (HBV) chronically infects 296 million people worldwide and causes more than 820,000 deaths annually due to cirrhosis and hepatocellular carcinoma. Current standard-of-care medications for chronic hepatitis B (CHB) include nucleos(t)ide analogue (NA) viral DNA polymerase inhibitors and pegylated interferon alpha (PEG-IFN-α). NAs can efficiently suppress viral replication and improve liver pathology, but not eliminate or inactivate HBV covalently closed circular DNA (cccDNA). CCC DNA is the most stable HBV replication intermediate that exists as a minichromosome in the nucleus of infected hepatocyte to transcribe viral RNA and support viral protein translation and genome replication. Consequentially, a finite duration of NA therapy rarely achieves a sustained off-treatment suppression of viral replication and life-long NA treatment is most likely required. On the contrary, PEG-IFN-α has the benefit of finite treatment duration and achieves HBsAg seroclearance, the indication of durable immune control of HBV replication and functional cure of CHB, in approximately 5% of treated patients. However, the low antiviral efficacy and poor tolerability limit its use. Understanding how IFN-α suppresses HBV replication and regulates antiviral immune responses will help rational optimization of IFN therapy and development of novel immune modulators to improve the rate of functional cure. This review article highlights mechanistic insight on IFN control of HBV infection and recent progress in development of novel IFN regimens, small molecule IFN mimetics and combination therapy of PEG-IFN-α with new direct-acting antivirals and therapeutic vaccines to facilitate the functional cure of CHB.

PEG-Lipids: Quantitative Study of Unimers and Aggregates Thereof by the Methods of Molecular Hydrodynamics

Understanding the polymorphism of lipids in solution is the key to the development of intracellular delivery systems. Here, we study the dynamics of poly(ethylene glycol)-lipid (PEG-Lipid) conjugates aiming at a better understanding of their molecular properties and aggregation behavior in solution. Those PEG-Lipids are used as components of lipid nanoparticles (LNPs). LNPs are gaining increased popularity, e.g., by their utilization in modern vaccination strategies against SARS-CoV-2. Characterization of the systems is conducted by the classical methods of hydrodynamics in different solvents, such as ethanol and water, which are also commonly used for LNP formulation. We were able to elucidate the structurally associated hydrodynamic properties of isolated PEG-Lipids in ethanol, revealing the typically expected values of the hydrodynamic invariant for random coil polymers. By virtue of the same experimental setting, the PEG-Lipids' behavior in water was as well studied, which is a less good solvent than ethanol for the PEG-Lipids. Our experiments demonstrate that PEG-Lipids dissolved in water form well-defined micelles that can quantitatively be characterized in terms of their degree of aggregation of PEG-Lipid polymer unimers, their hydrodynamic size, and solvation, i.e., the quantitative determination of water contained or associated to the identified micelles. Quantitative results obtained from classical hydrodynamic analyses are fully supported by studies with standard dynamic light scattering (DLS). The obtained diffusion coefficients and hydrodynamic sizes are in excellent agreement with numerical results derived from analytical ultracentrifugation (AUC) data. Cryo-transmission electron microscopy (cryo-TEM) supports the structural insight from hydrodynamic studies, particularly, in terms of the observed spherical structure of the formed micelles. We demonstrate experimentally that the micelle systems can be considered as solvent-permeable, hydrated spheres.