Binding interactions with sevelamer and polystyrene sulfonate in vitro.

This study explored the binding of 28 drugs, which were selected based on frequency of concomitant use and chemical properties, to sevelamer and polystyrene sulfonate in vitro. The relative binding was determined by dissolving the investigated drugs alone (=control), together with 800 mg of sevelamer and 15 g of polystyrene sulfonate at different pH levels (1.5, 5.5, and 7.4), respectively. After incubation at 37℃ and shaking for 60 min, the solutions were diluted and centrifuged, and the drug concentrations were quantified with validated analytical assays. The binding assays were performed in threefold. The mean relative binding (MRB) at each pH level was calculated, with a MRB >20% for at least one pH level to be considered as relevant binding. Fourteen and 23 potentially new binding interactions were identified with sevelamer and polystyrene sulfonate, respectively. These potentially new binding interactions have to be studied in vivo to assess their clinical relevance.

Bile acid sequestration reverses liver injury and prevents progression of nonalcoholic steatohepatitis in Western diet-fed mice.

Nonalcoholic fatty liver disease is a rapidly rising problem in the 21st century and is a leading cause of chronic liver disease that can lead to end-stage liver diseases, including cirrhosis and hepatocellular cancer. Despite this rising epidemic, no pharmacological treatment has yet been established to treat this disease. The rapidly increasing prevalence of nonalcoholic fatty liver disease and its aggressive form, nonalcoholic steatohepatitis (NASH), requires novel therapeutic approaches to prevent disease progression. Alterations in microbiome dynamics and dysbiosis play an important role in liver disease and may represent targetable pathways to treat liver disorders. Improving microbiome properties or restoring normal bile acid metabolism may prevent or slow the progression of liver diseases such as NASH. Importantly, aberrant systemic circulation of bile acids can greatly disrupt metabolic homeostasis. Bile acid sequestrants are orally administered polymers that bind bile acids in the intestine, forming nonabsorbable complexes. Bile acid sequestrants interrupt intestinal reabsorption of bile acids, decreasing their circulating levels. We determined that treatment with the bile acid sequestrant sevelamer reversed the liver injury and prevented the progression of NASH, including steatosis, inflammation, and fibrosis in a Western diet-induced NASH mouse model. Metabolomics and microbiome analysis revealed that this beneficial effect is associated with changes in the microbiota population and bile acid composition, including reversing microbiota complexity in cecum by increasing Lactobacillus and decreased Desulfovibrio The net effect of these changes was improvement in liver function and markers of liver injury and the positive effects of reversal of insulin resistance.

The Effect of Sevelamer on Serum Levels of Gut-Derived Uremic Toxins: Results from In Vitro Experiments and A Multicenter, Double-Blind, Placebo-Controlled, Randomized Clinical Trial.

High serum levels of gut-derived uremic toxins, especially p-cresyl sulfate (pCS), indoxyl sulfate (IS) and indole acetic acid (IAA), have been linked to adverse outcomes in patients with chronic kidney disease (CKD). Sevelamer carbonate could represent an interesting option to limit the elevation of gut-derived uremic toxins. The aim of the present study was to evaluate the adsorptive effect of sevelamer carbonate on different gut-derived protein-bound uremic toxins or their precursors in vitro, and its impact on the serum levels of pCS, IS and IAA in patients with CKD stage 3b/4. For the in vitro experiments, IAA, p-cresol (precursor of pCS) and indole (precursor of IS), each at a final concentration of 1 or 10 µg/mL, were incubated in centrifugal 30 kDa filter devices with 3 or 15 mg/mL sevelamer carbonate in phosphate-buffered saline at a pH adjusted to 6 or 8. Then, samples were centrifuged and free uremic toxins in the filtrates were analyzed. As a control experiment, the adsorption of phosphate was also evaluated. Additionally, patients with stage 3b/4 CKD (defined as an eGFR between 15 and 45 mL/min per 1.73 m2) were included in a multicenter, double-blind, placebo-controlled, randomized clinical trial. The participants received either placebo or sevelamer carbonate (4.8 g) three times a day for 12 weeks. The concentrations of the toxins and their precursors were measured using a validated high-performance liquid chromatography method with a diode array detector. In vitro, regardless of the pH and concentration tested, sevelamer carbonate did not show adsorption of indole and p-cresol. Conversely, with 10 µg/mL IAA, use of a high concentration of sevelamer carbonate (15 mg/mL) resulted in a significant toxin adsorption both at pH 8 (mean reduction: 26.3 ± 3.4%) and pH 6 (mean reduction: 38.7 ± 1.7%). In patients with CKD stage 3b/4, a 12-week course of treatment with sevelamer carbonate was not associated with significant decreases in serum pCS, IS and IAA levels (median difference to baseline levels: -0.12, 0.26 and -0.06 µg/mL in the sevelamer group vs. 1.97, 0.38 and 0.05 µg/mL in the placebo group, respectively). Finally, in vitro, sevelamer carbonate was capable of chelating a gut-derived uremic toxin IAA but not p-cresol and indole, the precursors of pCS and IS in the gut. In a well-designed clinical study of patients with stage 3b/4 CKD, a 12-week course of treatment with sevelamer carbonate was not associated with significant changes in the serum concentrations of pCS, IS and IAA.

Influence of pH and phosphate concentration on the phosphate binding capacity of five contemporary binders. An in vitro study.

AIM: Hyperphosphataemia is associated with increased mortality and morbidity in end stage renal disease. Despite phosphate binder therapy, a large proportion of patients do not reach the treatment target. In five contemporary binders we explored the influence of pH and phosphate concentration on phosphate binding. This interaction could be of relevance in clinical practice. METHODS: Phosphate binding was quantified in vitro in 25 mL of purified water containing phosphate concentrations of 10, 15 and 20 mM and baseline pH values of 3.0 or 6.0, with a binder over 6 h. Lanthanum carbonate, calcium acetate/magnesium carbonate, sevelamer carbonate, calcium carbonate and sucroferric oxyhydroxide, 67 mg of each, were used. The experiments were performed in duplicate. The primary outcome was the difference in the amount of bound phosphate for each binder after 6 h in solutions at two different pH values. Secondary outcomes were the influence of phosphate concentration on phosphate binding, next to binding patterns and phosphate binder saturation. RESULTS AND CONCLUSION: In this specific in vitro setting, lanthanum carbonate, sevelamer carbonate, calcium carbonate and sucroferric oxyhydroxide bound more phosphate in the solution with baseline pH of 3.0. Differences however were small except for lanthanum carbonate. Calcium acetate/magnesium carbonate was most effective in a solution with baseline pH of 6.0. All phosphate binders bound more phosphate in solutions with higher concentrations of phosphate. Sevelamer carbonate, calcium acetate/magnesium carbonate and sucroferric oxyhydroxide bound most phosphate in the first hour and reached maximum binding capacity in less than 6 h.

Phosphate Binders Derived from Natural Ores Contain Many Kinds of Metallic Elements Besides Their Active Ingredient Metals.

Most patients undergoing dialysis are required to take many phosphate binder pills to control hyperphosphatemia. Phosphate binders prescribed in Japan are classified into two types: metal-based binders (Ca carbonate, lanthanum carbonate, ferric citrate hydrate, and sucroferric oxyhydroxide) and chemically synthesized polymers (sevelamer hydrochloride and bixalomer). The raw materials of metal-based phosphate binders are natural ores; thus, such binders may contain several other metallic elements. We measured the elemental contents in six metal-based phosphate binders using an inductively coupled plasma mass - spectrometry (ICP-MS) method. As a result, despite being in small amounts, ore-derived phosphate binders contained various elements besides their active ingredient metals: Na, Mg, P, Mn, Fe, Sr, Y, Ba, La, Nd, and Pb in three Ca-based products; Mg, P, Se, Ce, and Gd in one La-based product; and Na, Mg, Al, P, Ca, Ti, Cr, Mn, Co, Ni, Ge, Ba, and La in two Fe-based products. These elements are considered to have originated from pharmaceutical bulk and from pharmaceutical additives. It is unlikely these elements are immediately harmful to patients. However, it should be emphasized that patients undergoing dialysis do not have a urinary excretion route and are administered many phosphate binder pills every day over a long period of time. In the future, pharmaceutical companies may have to disclose standard amounts and/or analytical values regarding the type and quantity of metallic elements in the final formulation or pharmaceutical bulk derived from natural ores.

Evaluation of the In Vitro Efficacy of Sevelamer Hydrochloride and Sevelamer Carbonate.

The objective of this project is to develop an in vitro approach that can be used to determine the phosphate binding capacity of sevelamer hydrochloride and carbonate for both drug products and active pharmaceutical ingredients (APIs). A simple and efficient inductively coupled plasma spectrometer method for analysis of phosphate at physiologically relevant pH conditions has been developed and validated. The method addresses each of the analytical validation characteristics such as linearity, accuracy, precision, stability, and selectivity, and meets the acceptance criteria defined in the United States Food and Drug Administration guidance (Food and Drug Administration, Center for Drug Evaluation and Research. 2001. Guidance for industry-Bioanalytical method validation, May). The in vitro phosphate binding efficacies were systematically evaluated and compared for two drug products and two APIs. The phosphate binding profiles appeared similar between the drug products. Under all conditions, the sevelamer-phosphate binding reached equilibrium at 6 h. The 90% confidence interval for the k2 ratio (sevelamer carbonate vs. sevelamer hydrochloride) was well within 80%-125% under all pH conditions. However, the k1 ratio varied, indicating that there exists difference in the binding affinity. Our findings will be useful in assisting with "in vivo" biowaiver for the approval of generic sevelamer drug products.

Gastrointestinal symptoms after the substitution of sevelamer hydrochloride with lanthanum carbonate in Japanese patients undergoing hemodialysis.

Lanthanum carbonate has the same phosphorus depressant effect as the other phosphorus adsorbents, and is expected to decrease digestive symptom onset such as constipation in Japanese patients undergoing hemodialysis compared to sevelamar hydrochloride. In this study, we investigated the short- and long-term changes in digestive symptoms in these patients after substituting sevelamar hydrochloride with lanthanum carbonate. We studied 16 patients (4 men, 12 women) and evaluated their gastrointestinal symptoms before administration, at the time of administration, and 2, 4, 8, and 12 weeks after administration, using the Gastrointestinal Symptom Rating Scale. In addition, we conducted repeat evaluations 52 weeks after administration for the patients in whom lanthanum carbonate was administered continuously for 52 weeks. Fourteen (87.5%) out of the 16 patients could tolerate continuous administration for 12 weeks. The constipation score was 3.21 ± 1.74 before administration, 2.07 ± 0.83 2 weeks after administration, 1.76 ± 0.83 4 weeks after administration, 1.57 ± 0.56 8 weeks after administration, and 11.41 ± 0.48 12 weeks after administration. The scores improved significantly 4 weeks after administration (p < 0.05) and even 12 weeks after continuous administration. Among the 16 study patients, 9 patients (1 men, 8 women) were received lanthanum carbonate continuously for 52 weeks. The constipation score was 3.74 ± 1.92 at the start of administration, 1.37 ± 0.56 12 weeks after administration, and 1.85 ± 0.63 52 weeks after administration, with significant improvement even 52 weeks after administration (p < 0.05). This study shows that substituting sevelamar hydrochloride with lanthanum carbonate improves constipation symptoms in hemodialysis patients from an early stage, which indicates its usefulness in improving constipation symptoms caused by sevelamar hydrochloride.

Novel oral phosphate binder with nanocrystalline maghemite-phosphate binding capacity and pH effect.

Hyperphosphatemia is one of the main risk factors contributing to morbidity and mortality in patients with end stage renal disease. The demand for a new phosphate binder is continuously increasing since the number of patients suffering under hyperphosphatemia is growing. However, side effects and high pill burden of currently available phosphate binders are the main reasons for low compliance and uncontrolled serum phosphate levels. Therefore, the aim of this study was to develop a novel phosphate binder with a high phosphate binding capacity over the entire gastrointestinal (GI) pH range. This novel phosphate binder C-PAM-10 is based on d-mannose coated nanocrystalline maghemite and belongs to the new class of phosphate binders, called the "iron based agents". It was possible to obtain a phosphate binding product that showed very high phosphate binding capacities with the characteristic of being pH independent at relevant pH ranges. The simulation of a GI passage ranging from pH 1.2 to pH 7.5 showed a 2.5 times higher phosphate binding capacity compared to the commonly used phosphate binder sevelamer carbonate. The simulation of a pH sensitive coating that releases the iron based phosphate binder at pH values ≥4.5 still showed a very high phosphate binding capacity combined with very low iron release which might decrease iron related side effects in vivo. Therefore, C-PAM-10 and its variations may be very promising candidates as a superior phosphate binder.

Alternative use of cross-linked polyallylamine (known as Sevelamer pharmaceutical compound) as biosorbent.

In this study, an alternative use of Sevelamer carbonate (SEV, a cross-linked polyallylamine which is a widely known pharmaceutical compound) was suggested. The existence of primary and secondary amino groups (with different ratios) in its molecule increases its adsorption potential and use as biosorbent material. SEV was tested as biosorbent material aiming the removal of heavy metals and dyes from simulated effluents. As heavy metals and dyes, hexavalent chromium (Cr(VI)) and Remazol Brilliant Blue RN (RB) were used, respectively. A full adsorption study was done confirming the strong adsorption capability of SEV. The maximum theoretical adsorption capacity (Qm) was 772 and 485mg/g for single-component solutions of RB and Cr(VI), respectively; the respective values for binary mixtures of the same concentration (200mg/L) were 445 and 309mg/g respectively (calculated after fitting to Langmuir-Freundlich isotherm model at 25°C). The same experiments were also done at increasing temperatures (45 and 65°C) concluding thermodynamic remarks (ΔH(0)>0; ΔG(0)<0; ΔS(0)>0). The effect of contact time was analyzed running kinetic adsorption experiments and fitting them to pseudo-second order kinetic equation. The reusability was evaluated completing successfully 20 cycles of reuse (adsorption/desorption). The adsorption mechanism among SEV molecules and Cr(VI) or/and RB was clarified using FTIR spectroscopy before and after adsorption in line with a detailed theoretical modeling which provided important calculations. SEV was also characterized using swelling experiments, BET, SEM, XRD, TGA techniques.