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.

Comparison of Antiplatelet Effect and Tolerability of Clopidogrel Resinate With Clopidogrel Bisulfate in Patients With Coronary Heart Disease (CHD) or CHD-Equivalent Risks: A Phase IV, Prospective, Double-Dummy, Parallel-Group, 4-Week Noninferiority Trial

“…21 The VerifyNow assay is a rapid whole-blood assay and was used according to the manufacturer's instructions. The VerifyNow P2Y 12 assay reports the results as P2Y 12 reaction units (PRU). This assay correlates with the gold standard turbidimetric aggregation assay and uses disposable cartridges containing 20 M adenosine diphosphate and 22 nM prostaglandin E 1 (PGE 1 ).…”

“…This assay correlates with the gold standard turbidimetric aggregation assay and uses disposable cartridges containing 20 M adenosine diphosphate and 22 nM prostaglandin E 1 (PGE 1 ). Aggregation testing using adenosine diphosphate as the sole agonist activates both P2Y 1 and P2Y 12 purinergic signaling, whereas adding PGE 1 increases the specificity of the test for P2Y 12 signaling. 21 The percent P2Y 12 inhibition was calculated as (baseline PRU -posttreatment PRU)/baseline PRU ϫ 100.…”

“…Aggregation testing using adenosine diphosphate as the sole agonist activates both P2Y 1 and P2Y 12 purinergic signaling, whereas adding PGE 1 increases the specificity of the test for P2Y 12 signaling. 21 The percent P2Y 12 inhibition was calculated as (baseline PRU -posttreatment PRU)/baseline PRU ϫ 100. 22 The evaluation of the antiplatelet effect included the comparison of percent P2Y 12 inhibition in the 3 groups after taking the study medications.…”

“…9 -11 Resinate has also been used in soluble or insoluble pharmaceutical ingredients for adsorption and excretion of inorganic ions or microbials from the gastrointestinal tract. [12][13][14] Clopidogrel resinate was determined to be physiochemically stable in gastrointestinal stability tests and to be safe in toxicity studies. 7 Clopidogrel resinate also showed good in vitro and in vivo absorption profiles of clopidogrel without absorption of resin and had demonstrated ex vivo and in vivo pharmacodynamics activity.…”

“…There were no significant differences in baseline clinical characteristics among the groups except for the frequency of a history of CHD (group A, 85.4%; group B, 73.0%; and group C, 88.3%; P ϭ 0.01). Patients treated with either type of clopidogrel showed significant inhibition (mean [SD]) of P2Y 12 12 did not exceed the predetermined value for inferiority (P for noninferiority, 0.02; 90% CI, Ϫ0.9 to 10.3). In the tolerability analysis, there was no mortality during the study period and no significant differences between groups in the frequency of AEs and serious AEs (AEs: group A, 33.0%; group B, 26.0%; and group C, 23.3% [P ϭ 0.27]; serious AEs: group A, 1.0%; group B, 3.0%; and group C, 1.0% [P ϭ 0.42]).…”