title: Substituted Polyesters by Thiol-Ene Modification: Rapid Diversification for Therapeutic Protein Stabilization.
abstract: Many proteins, especially those used as therapeutics, are unstable to storage and shipping temperatures, leading to increased costs in research and industry. Therefore, the design and synthesis of novel stabilizers is an important area of investigation. Herein we report new degradable polymers that stabilize proteins to environmental stressors such as refrigeration and elevated temperature. Specifically, polycaprolactones with different pendant groups were synthesized and surveyed for their ability to stabilize an important therapeutic protein to storage and shipping conditions. Ring-opening polymerization (ROP) of an allyl-substituted caprolactone monomer was carried out using the organocatalyst 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) to yield a well-defined, alkene-substituted degradable polymer, which was used as a common backbone to control for the degree of polymerization. Relevant side chains such as trehalose, lactose, glucose, carboxybetaine, and oligo(ethylene glycol) were installed via postpolymerization thiol-ene reactions. These degradable polymers were then employed as excipients for the stabilization of the therapeutic protein granulocyte colony-stimulating factor (G-CSF) against storage at 4 °C and shipping temperatures of 60 °C. The best stabilization was observed using the trehalose- and zwitterion- substituted polyesters. Both the trehalose- and carboxybetaine-substituted pCL were further investigated with regard to molecular weight dependence, and it was found that the molecular weight was minimally important for stabilization to refrigeration, but critical for G-CSF stabilization at elevated temperatures. Both high performing zwitterionic and trehalose polyesters were also degraded, and the polymers and degradation products were shown to be noncytotoxic. This work provides potential biocompatible polymers for stabilization of the important therapeutic G-CSF, as well as a general platform for the future discovery of new polymeric protein stabilizers.
authors.affiliation: Department of Chemistry and Biochemistry and California NanoSystems Institute, University of California, Los Angeles , 607 Charles E. Young Drive East, Los Angeles, California 90095, United States.
authors.forename: Emma M
authors.initials: EM
authors.lastname: Pelegri-O'Day
authors.affiliation: Department of Chemistry and Biochemistry and California NanoSystems Institute, University of California, Los Angeles , 607 Charles E. Young Drive East, Los Angeles, California 90095, United States.
authors.forename: Samantha J
authors.initials: SJ
authors.lastname: Paluck
authors.affiliation: Department of Chemistry and Biochemistry and California NanoSystems Institute, University of California, Los Angeles , 607 Charles E. Young Drive East, Los Angeles, California 90095, United States.
authors.forename: Heather D
authors.identifier: 0000-0003-3692-6289
authors.initials: HD
authors.lastname: Maynard
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D016179:Granulocyte Colony-Stimulating Factor / Q000737:chemistry*; D006801:Humans; D008958:Models, Molecular; D008968:Molecular Conformation; D011091:Polyesters / Q000138:chemical synthesis / Q000737:chemistry*; D055550:Protein Stability; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: D000475:Alkenes; D011091:Polyesters; D013438:Sulfhydryl Compounds; D016179:Granulocyte Colony-Stimulating Factor