Challenges for PEGylated Proteins and Alternative Half-Life Extension Technologies Based on Biodegradable Polymers. In: Scholz C, Kressler J, editors. Tailored Polymer Architectures for Pharmaceutical and Biomedical Applications. Washington: American Chemical Society; 2013. pp. 215-33. [DOI: 10.1021/bk-2013-1135.ch013]

Pharmacological and clinical monitoring in children with acute lymphoblastic leukemia treated with a biogeneric PEG-l-asparaginase product

BACKGROUND

l-Asparaginase (ASP) plays a crucial role in the treatment of childhood acute lymphoblastic leukemia (ALL). Currently, different ASP products are available in the market, including both native and pegylated drugs. Several biogeneric Escherichia coli ASP (GEN-ASP) products have been developed in response to shortages and expensiveness of the native E. coli ASP innovator compounds, but some concerns have been raised about their quality. Recently, a number of generic pegylated ASP products (GEN-PEG-ASP) have been marketed to substitute for the innovator product (PEG-ASP).

METHODS

Clinical courses and serum asparaginase activity (SAA) levels were monitored in 12 children with ALL, who were treated in our institution with two doses of a GEN-PEG-ASP product, given IV at 2500 IU/m² during the remission induction phase. Results were compared with those obtained in a reference cohort of 35 patients treated in our institution, who received the innovator PEG-ASP product at same dosage and within the same chemotherapy background.

RESULTS

Compared to the reference cohort treated with PEG-ASP, SAA levels were significantly lower in the 12 patients receiving GEN-PEG-ASP (p < .0001); a higher proportion of ASP-associated hypersensitivity reactions (2/12 vs. 0/35; p = .061) and silent inactivation (3/12 vs. 0/35; p = .014) were observed in comparison with the reference cohort.

CONCLUSIONS

Our results highlighted different pharmacological profiles and different rates of hypersensitivity reactions and silent inactivation in the GEN-PEG-ASP cohort compared to those treated with the innovator product. Our findings suggest that a rigorous clinical attention and a thorough pharmacological monitoring are advisable in patients treated with GEN-PEG-ASP products.

Structural similarity, characterization of Poly Ethylene Glycol linkage and identification of product related variants in biosimilar pegfilgrastim

The approval of biosimilars requires demonstration of biosimilarity, which rests on the base of thorough analytical characterization of the biosimilar product. In addition to demonstration of biosimilarity, the product related impurities need to be thoroughly characterized and controlled at minimal levels. Pegylation of peptides and proteins creates significant challenges for detailed structural characterization, such as PEG (Poly Ethylene Glycol) heterogeneity, site of addition and number of attached pegylated moieties. A combination of several methods including circular dichroism, FTIR (Fourier-transform Infrared Spectroscopy), fluorescence spectroscopy, DSC (Differential Scanning Calorimetry), 1D and 2D NMR (Nuclear Magnetic Resonance), Edman degradation and peptide mapping by LC-MS (Liquid Chromatography Mass Spectrometry) were used for characterization of N-terminally pegylated filgrastim. Product related impurities such as oxidized, reduced, deamidated, dipegylated variants and monopegylated positional isomers have been characterized in detail using various HPLC (High Performance Liquid Chromatography) based methods and LC-MS techniques. The functional characterization in terms of receptor binding and cell proliferation assay was conducted for the similarity assessment and the potential impact of the product variants on the in vitro biological activity has also been assessed. In summary, this study presents, for the first time, a detailed structural and molecular level characterization of a biosimilar pegfilgrastim providing a strong base for the demonstration of overall biosimilarity of the product with the innovator product.

Synthesis and Biological Evaluation of a Degradable Trehalose Glycopolymer Prepared by RAFT Polymerization

There is a significant need for new biodegradable protein stabilizing polymers. Herein, the synthesis of a polymer with trehalose side chains and hydrolytically degradable backbone esters and its evaluation for protein stabilization and cytotoxicity are described. Specifically, an alkene-containing parent polymer is synthesized by reversible addition-fragmentation chain transfer polymerization, and thiolated trehalose is installed using a radical-initiated thiol-ene reaction. The stabilizing properties of the polymer are investigated by thermally stressing granulocyte colony-stimulating factor (G-CSF), which is expressed and purified using a custom-designed G-CSF fusion protein with a polyhistidine-tagged maltose binding protein. The degradable polymer is shown to stabilize G-CSF to 66% after heating at 40 °C. Poly(5,6-benzo-2-methylene-1,3-dioxepane (BMDO)-co-butyl methacrylate-trehalose) is degraded and its cellular compatibility is investigated. While the polymer is noncytotoxic, cytotoxic effects are observed from the degraded products in fibroblasts and murine myeloblasts. These data provide important information for future use of BMDO-containing trehalose glycopolymers for biomedical applications.

Peptide chemistry toolbox - Transforming natural peptides into peptide therapeutics

The development of solid phase peptide synthesis has released tremendous opportunities for using synthetic peptides in medicinal applications. In the last decades, peptide therapeutics became an emerging market in pharmaceutical industry. The need for synthetic strategies in order to improve peptidic properties, such as longer half-life, higher bioavailability, increased potency and efficiency is accordingly rising. In this mini-review, we present a toolbox of modifications in peptide chemistry for overcoming the main drawbacks during the transition from natural peptides to peptide therapeutics. Modifications at the level of the peptide backbone, amino acid side chains and higher orders of structures are described. Furthermore, we are discussing the future of peptide therapeutics development and their impact on the pharmaceutical market.

Poly(amidoamine)–BSA conjugates synthesised by Michael addition reaction retained enzymatic activity

A bioconjugate synthesised using a “grafted to” method and Michael addition reaction retained the activity of the native protein.