title: Toxin binding of tolevamer, a polyanionic drug that protects against antibiotic-associated diarrhea.
abstract: Tolevamer, (GT160-246), is a sodium salt of styrene sulfonate polymer that is under development for the treatment of diarrhea caused by infection with Clostridium difficile. Pulsed ultrafiltration binding experiments in phosphate buffer containing 0.15 M Na(+) provide per polymer chain dissociation constants of 133 nM and 8.7 microM for the binding of tolevamer to C. difficile toxins A and B, respectively. At 0.05 M Na(+), the binding of toxin A to tolevamer is irreversible, whereas the dissociation constant to toxin B under these conditions is 120 nM. Binding constants obtained from fluorescence polarization data for toxin A binding to tolevamer at 0.15 M Na(+) agree substantially with those obtained by pulsed ultrafiltration. The binding activity of tolevamer reported here correlates well with previously reported results for the inhibition of the biological activity of C. difficile toxins A and B. From the fluorescence polarization data, it is estimated that one toxin A molecule interacts with between 600 to 1000 monomer units on tolevamer at 0.15 M Na(+). Thus, the data suggest a very large interaction surface between polymer and toxin A.
authors.affiliation: Genzyme Corporation, Waltham, Massachusetts 02451, USA.
authors.forename: William
authors.initials: W
authors.lastname: Braunlin
authors.forename: Qiuwei
authors.initials: Q
authors.lastname: Xu
authors.forename: Patrick
authors.initials: P
authors.lastname: Hook
authors.forename: Richard
authors.initials: R
authors.lastname: Fitzpatrick
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Klinger
authors.forename: Robert
authors.initials: R
authors.lastname: Burrier
authors.forename: Caroline B
authors.initials: CB
authors.lastname: Kurtz
mesh_terms: D001427:Bacterial Toxins / Q000737:chemistry*; D016360:Clostridioides difficile / Q000737:chemistry*; D004347:Drug Interactions; D005454:Fluorescence Polarization / Q000379:methods*; D007477:Ions / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D013451:Sulfonic Acids; D014462:Ultrafiltration / Q000379:methods
chemical_list: D001427:Bacterial Toxins; D007477:Ions; D011108:Polymers; D013451:Sulfonic Acids; C077114:styrenesulfonic acid polymer