Methods to determine pharmacokinetic profiles of therapeutic proteins

Polyester-Based Nanoparticles for Delivery of Therapeutic Proteins

Therapeutic proteins are widely used to treat severe conditions, such as oncologic and metabolic diseases, and also for vaccination. They are recognized for its high biopotency, but their hydrophilicity and high molecular weight make its transport through membranes difficult to achieve. They may also suffer in vivo structural instability caused by a proteolytic cleavage, turning them biological inactive. Polyester-based nanoparticles are useful tools to overcome such problems, and deliver therapeutic proteins in a controlled and localized manner, decreasing the number of administrations needed and enhancing the therapeutic outcome. The biodegradable and biocompatible nature of such carriers makes them feasible to be administered by invasive and noninvasive routes. Since nanoparticles are produced in suspension form, they are usually lyophilized to increase its long-term storage stability. Therefore, the aim of this work is to propose an intuitive protocol for production and lyophilization of polyester-based nanoparticles for therapeutic proteins delivery. The characterization techniques to evaluate the nanoparticle and lyophilisate features, as well as the structural stability of the loaded protein are also described. For these purposes, PLGA nanoparticles and human insulin are used as models.

Chitosan-based nanoparticles as delivery systems of therapeutic proteins

Therapeutic proteins represent a significant part of the new pharmaceuticals coming on the market every year and are now widely spread in therapy to treat or relief symptoms related to many metabolic and oncologic diseases. The parenteral route remains as a primary strategy for protein administration essentially due to its specific physicochemical properties. However, the research on alternative nonparenteral delivery routes continues. The high molecular weight (MW), hydrophilicity, and charged nature of therapeutically valued proteins render transport through membranes very difficult. In this regard, chitosan arises as a promising candidate for the development of protein-containing drug formulations, due to its exceptional biological properties. Chitosan-based delivery systems have been proposed as valid approaches to provide protective conditions to proteins from denaturation and loss of activity, during preparation and delivery, as well as during long-term storage of the prepared formulation. In this chapter, one production method of a chitosan-based nanoparticle formulation is presented, as well as several characterization techniques to assess both nanoparticles and proteins characteristics and stability.

Investigation of the mechanism of clearance of AMG 386, a selective angiopoietin-1/2 neutralizing peptibody, in splenectomized, nephrectomized, and FcRn knockout rodent models

Purpose

To investigate the mechanisms of clearance of AMG 386, an investigational recombinant peptide-Fc fusion protein (peptibody) that blocks tumor angiogenesis by neutralizing the interaction between angiopoietin-1 and -2 and the Tie2 receptor.

Methods

The role of the neonatal Fc receptor (FcRn) in AMG 386 clearance was assessed in wild-type and FcRn-knockout mice; the roles of the spleen and kidneys were assessed in splenectomized and 5/6th nephrectomized rats, respectively, compared with sham-operated rats. Animals were administered AMG 386 as a single intravenous dose of 3 or 10 mg/kg. Blood samples for pharmacokinetic analysis were collected periodically throughout a 504-hour postdose period.

Results

Compared with wild-type mice, AMG 386 clearance in FcRn-knockout mice was 18-fold faster at the 3-mg/kg dose (FcRn knockout, 13.2 mL/h/kg; wild-type, 0.728 mL/h/kg) and 14-fold faster at the 10-mg/kg dose (FcRn knockout, 10.7 mL/h/kg; wild-type, 0.777 mL/h/kg). Clearance in nephrectomized rats was slower than in sham-operated rats at both the 3-mg/kg dose (nephrectomized, 1.23 mL/h/kg; sham-operated, 1.75 mL/h/kg) and the 10-mg/kg dose (nephrectomized, 1.14 mL/h/kg; sham-operated, 1.65 mL/h/kg). Splenectomy had no apparent effect on the pharmacokinetics of AMG 386.

Conclusions

The FcRn is integral to maintaining circulating levels of AMG 386 in mice. Renal clearance contributed approximately 30% to total AMG 386 clearance in rats.

Pitfalls in protein quantitation using acid-catalyzed O18 labeling: hydrolysis-driven deamidation

Proteolysis combined with O(18) labeling emerged recently as a powerful tool for quantitation of proteins for which suitable internal standards cannot be produced using molecular biology methods. Several recent reports suggested that acid-catalyzed O(18) labeling may be superior to the commonly accepted enzymatic protocol, as it may allow more significant spacing between the isotopic clusters of labeled and unlabeled peptides, thereby eliminating signal interference and enhancing the quality of quantitation. However, careful examination of this procedure reveals that the results of protein quantitation assisted by acid-catalyzed O(18) labeling are highly peptide-dependent. The inconsistency was found to be caused by deamidation of Asn, Gln, and carbamidomethylated Cys residues during prolonged exposure of the proteolytic fragments to the acidic environment of the labeling reaction, which translates into a loss in signal for these peptides. Taking deamidation into account leads to a significant improvement in the consistency of quantitation across a range of different proteolytic fragments.