Vinyl and methyl-ester groups in the insoluble polymer drug patiromer identified and quantified by solid-state NMR.

Patiromer (Veltassa®) is a crosslinked, insoluble co-polymer drug used as a nonabsorbent potassium binder, approved for treatment of hyperkalemia. Quantitative solid-state 13C nuclear magnetic resonance (NMR) analysis with comprehensive peak assignment, component quantification, and calculation of mole and weight fractions of monomer units was performed on three doses of patiromer. The workflow is documented in detail. Spectrally edited solid-state 13C NMR spectra of patiromer show =CHn peaks of matching intensity at 116 and 141 ppm, characteristic of -CH=CH2 vinyl groups. Similar spectral features can be observed in earlier studies but were previously ignored. In this study, the vinyl signals are well-resolved in a 2-s direct polarization (DP) spectrum without and with dipolar dephasing, which confirms that these sp2-hybridized carbons are bonded to hydrogen and partially mobile, consistent with vinyl side groups from incompletely reacted divinyl crosslinkers. The vinyl groups account for 1.6% of all carbon, 3% of the monomer units, and nearly 1/3 of the crosslinkers. Furthermore, an unexpected OCH3 moiety accounting for ∼1.2% of all carbons was identified by spectral editing; its chemical shift of 54 ppm is more consistent with a methyl ester than with a methyl ether. It can originate from incomplete hydrolysis of ∼6% of methyl-2-fluoroacrylate, the main monomer of patiromer. Characteristic cross peaks in two-dimensional 1H-13C heteronuclear correlation NMR confirm the presence of the vinyl and OCH3 groups. Trace amounts of xanthan gum are also detected. The quantitative 13C NMR spectrum of patiromer has been matched in a simulation using a model with five monomer units.

Newly Designed Cysteine-Based Self-Assembling Prodrugs for Sepsis Treatment.

Reactive oxygen species (ROS) are essential signaling molecules that maintain intracellular redox balance; however, the overproduction of ROS often causes dysfunction in redox homeostasis and induces serious diseases. Antioxidants are crucial candidates for reducing overproduced ROS; however, most antioxidants are less effective than anticipated. Therefore, we designed new polymer-based antioxidants based on the natural amino acid, cysteine (Cys). Amphiphilic block copolymers, composed of a hydrophilic poly(ethylene glycol) (PEG) segment and a hydrophobic poly(cysteine) (PCys) segment, were synthesized. In the PCys segment, the free thiol groups in the side chain were protected by thioester moiety. The obtained block copolymers formed self-assembling nanoparticles (NanoCys(Bu)) in water, and the hydrodynamic diameter was 40-160 nm, as determined by dynamic light scattering (DLS) measurements. NanoCys(Bu) was stable from pH 2 to 8 under aqueous conditions, as confirmed by the hydrodynamic diameter of NanoCys(Bu). Finally, NanoCys(Bu) was applied to sepsis treatment to investigate the potential of NanoCys(Bu). NanoCys(Bu) was supplied to BALB/cA mice by free drinking for two days, and lipopolysaccharide (LPS) was intraperitoneally injected into the mice to prepare a sepsis shock model (LPS = 5 mg per kg body weight (BW)). Compared with the Cys and no-treatment groups, NanoCys(Bu) prolonged the half-life by five to six hours. NanoCys(Bu), designed in this study, shows promise as a candidate for enhancing antioxidative efficacy and mitigating the adverse effect of cysteine.

Design of cysteine-based self-assembling polymer drugs for anticancer chemotherapy.

Reactive oxygen species (ROS) play essential roles in the body, such as the production of energy in oxidative phosphorylation and signal transduction for homeostasis. Redox balance in biological systems gradually collapses due to various environmental factors, including aging and disease, and induces oxidative stress in the body. None of the natural or synthetic antioxidants have been approved clinically, owing to their adverse effects. Herein, we developed L-cysteine (Cys)-based polymer micelles as new self-assembling antioxidants to reduce the adverse effects of conventional antioxidants. Poly(ethylene glycol)-block-poly(L-cysteine) (PEG-block-PCys) was synthesized via anionic ring-opening polymerization. Because the free SH groups in the side chains of the PCys segment were protected by disulfide bonds, the obtained block copolymers were amphiphilic and formed polymer micelles (NanoCyss) of tens of nanometers in size in aqueous media. The stability of NanoCyss in the presence of bovine serum albumin (BSA) was increased by increasing the molecular weight (MW) of the PCys segments, which was analyzed using dynamic light scattering (DLS). The size and coagulation tendency of NanoCyss were also analyzed using DLS measurements by changing the pH and NaCl concentration. NanoCyss were confirmed to be less toxic both in vitro and in vivo than N-acetylcysteine (NAC) because of their size and biocompatible PEG surface layer. Intraperitoneal (i.p.) administration of NanoCyss to the tumor xenograft mouse model successfully suppressed tumor growth. Interestingly, this effect depended on the MW of the PCys segments.