Combination for lowering serum phosphate in subject

Abstract

To provide methods for lowering serum phosphate in a mammal, comprising administering an epithelial phosphate transport inhibitor, such as an NHE3 inhibitor, in combination with a phosphate binder as well as pharmaceutical compositions comprising such epithelial phosphate transport inhibitors and phosphate binders.SOLUTION: In an aspect of the present invention, there is provided a method for treating hyperphosphatemia in a subject, comprising administering an effective amount of an epithelial phosphate transport inhibitor in combination with a phosphate binder, wherein the amount of the phosphate binder administered is less than the amount that would be administered as a single agent.SELECTED DRAWING: None

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 62 / 851,099, filed May 21, 2019, and claims priority to U.S. Provisional Application No. 62 / 852,299, filed May 23, 2019. The entire contents of these applications referenced above are incorporated herein by reference.

[0002] The present invention relates to the use of epithelial phosphate transport inhibitors in combination with phosphate binders in lowering serum phosphate levels or preventing elevated serum phosphate. [Background technology]

[0003] Serum phosphate levels are normally maintained within a narrow physiological range, primarily through the regulation of renal phosphate excretion. As a consequence, hyperphosphatemia is common in end-stage renal disease (ESRD) patients on dialysis who have impaired or absent urinary phosphate excretion. Intestinal phosphate absorption is linearly dependent on the phosphate concentration gradient and does not saturate even at high luminal phosphate concentrations. Furthermore, despite impaired renal phosphate excretion in ESRD patients, intestinal phosphate absorption in hemodialysis patients is similar to healthy individuals and is further increased by vitamin D therapy, which is commonly used in ESRD to manage secondary hyperparathyroidism. Thus, persistence of intestinal phosphate absorption in the face of impaired renal phosphate excretion predicts the high prevalence of hyperphosphatemia observed in ESRD patients.

[0004] Tenapanor is a novel, minimally absorbed, small molecule inhibitor of sodium / hydrogen exchanger isoform 3 (NHE3) that acts locally in the gastrointestinal tract to inhibit intestinal phosphate absorption and has been shown to significantly reduce serum phosphate levels in hemodialysis patients. NHE3 is expressed on the luminal surface throughout the small intestine and proximal colon and functions as a transporter to take up luminal sodium in lieu of cellular protons. The mechanism by which inhibition of NHE3 by tenapanor reduces intestinal phosphate absorption by decreasing paracellular phosphate permeability has been reported by King et al (Sci Transl Med.2018 Aug 29;10(456)) by results of intracellular proton retention to modulate tight junctions and increase transepithelial electrical resistance.

[0005] Paracellular phosphate flux through tight junction complexes, driven by the electrochemical phosphate gradient, is quantitatively the most important mechanism of intestinal phosphate absorption under typical conditions of phosphate availability. This was confirmed by a recent study showing no effect of deletion of the major sodium-dependent phosphate transporter, NaPi2b (SLC34A2), on intestinal phosphate absorption in mice under physiological luminal phosphate concentrations. Paracellular phosphate flux in the intestine is determined by the predominant electrochemical phosphate gradient in combination with the simultaneous paracellular phosphate permeability.

[0006] Current medical management of hyperphosphatemia aims to reduce intestinal phosphate absorption by combining dietary phosphate restriction with administration of oral phosphate binders. Although restricting dietary phosphate intake can modestly reduce the severity of hyperphosphatemia, adherence is difficult and typically inadequate, due at least in part to the widespread use of high phosphate content additives in processed foods. Phosphate binders physically sequester dietary phosphate, making it unavailable for absorption, and can effectively lower serum phosphate. However, many ESRD patients are unable to maintain serum phosphate levels in the target range, due in part to non-adherence to the use of phosphate binders as a result of the high cost involved. Inadequate control of serum phosphate has important clinical implications, as elevated serum phosphate concentrations are associated with poor patient outcomes, including all-cause mortality, cardiovascular events, left ventricular hypertrophy, and CKD progression in patients not yet on dialysis. Thus, additional therapeutic approaches are needed to optimize serum phosphate management in hyperphosphatemic patients.

[0007] Therefore, it is desirable to control serum phosphate in CKD and ESRD patients using reduced amounts of phosphate binders. [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] King et al(Sci Transl Med.2018 Aug 29;10(456) Summary of the Invention [Means for solving the problem]

[0009] In one aspect of the invention, a method is provided for treating hyperphosphatemia in a patient comprising administering an effective amount of an epithelial phosphate transport inhibitor in combination with a phosphate binder, wherein the amount of phosphate binder administered is less than the amount administered as a single agent.

[0010] In another aspect of the invention, a pharmaceutical composition is provided comprising an epithelial phosphate transport inhibitor and a phosphate binder, wherein the amount of the phosphate binder is less than that administered as a single agent. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 shows the effect of the phosphate binder sevelamer with and without the NHE3 inhibitor tenapanor (also called Cp002) on urinary phosphate excretion. [Diagram 2] FIG. 1 shows the effect of tenapanor (Cpd 002) treatment on plasma phosphorus in a rat model of uremia-associated vascular calcification. [Figure 3A] Figure 1 shows that administration of tenapanor (Cpd 002) reduced both urinary phosphorus levels compared to vehicle-only controls in rats. Increasing doses of tenapanor also significantly reduced urinary phosphorus levels compared to 48 mg / kg Renvela®. [Figure 3B] Figure 1 shows that administration of tenapanor (Cpd 002) reduced both urinary phosphorus levels compared to vehicle-only controls in rats. Increasing doses of tenapanor also significantly reduced urinary phosphorus levels compared to 48 mg / kg Renvela®. [Figure 4A] 24-hour urinary phosphorus excretion in rats treated with tenapanor, sevelamer, or the combination of tenapanor and sevelamer over the last 4 treatment days (A) (final treatment day is shown separately for clarity (B)) is shown along with 24-hour urinary phosphorus excretion normalized to daily phosphorus intake over the last 4 treatment days (C) (final treatment day is shown separately for clarity (D)). Data are shown as mean ± SEM. *=significant from vehicle control, ****=p<0.0001, #=significant from tenapanor alone, ##=p<0.01; ####=p<0.0001, $=significant from equivalent dose of sevelamer alone, $=p<0.05; $$=p<0.01; $$$$=p<0.0001 [Figure 4B]24-hour urinary phosphorus excretion in rats treated with tenapanor, sevelamer, or the combination of tenapanor and sevelamer over the last 4 treatment days (A) (final treatment day is shown separately for clarity (B)) is shown along with 24-hour urinary phosphorus excretion normalized to daily phosphorus intake over the last 4 treatment days (C) (final treatment day is shown separately for clarity (D)). Data are shown as mean ± SEM. *=significant from vehicle control, ****=p<0.0001, #=significant from tenapanor alone, ##=p<0.01; ####=p<0.0001, $=significant from equivalent dose of sevelamer alone, $=p<0.05; $$=p<0.01; $$$$=p<0.0001 [Figure 4C] 24-hour urinary phosphorus excretion in rats treated with tenapanor, sevelamer, or the combination of tenapanor and sevelamer over the last 4 treatment days (A) (final treatment day is shown separately for clarity (B)) is shown along with 24-hour urinary phosphorus excretion normalized to daily phosphorus intake over the last 4 treatment days (C) (final treatment day is shown separately for clarity (D)). Data are shown as mean ± SEM. *=significant from vehicle control, ****=p<0.0001, #=significant from tenapanor alone, ##=p<0.01; ####=p<0.0001, $=significant from equivalent dose of sevelamer alone, $=p<0.05; $$=p<0.01; $$$$=p<0.0001 [Figure 4D] 24-hour urinary phosphorus excretion in rats treated with tenapanor, sevelamer, or the combination of tenapanor and sevelamer over the last 4 treatment days (A) (final treatment day is shown separately for clarity (B)) is shown along with 24-hour urinary phosphorus excretion normalized to daily phosphorus intake over the last 4 treatment days (C) (final treatment day is shown separately for clarity (D)). Data are shown as mean ± SEM. *=significant from vehicle control, ****=p<0.0001, #=significant from tenapanor alone, ##=p<0.01; ####=p<0.0001, $=significant from equivalent dose of sevelamer alone, $=p<0.05; $$=p<0.01; $$$$=p<0.0001 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention relates to the discovery that phosphate uptake from the gastrointestinal tract is synergistically inhibited by phosphate binders combined with epithelial phosphate transport inhibitors, i.e., the combination reduces phosphate absorption more than either agent alone. It has been observed that epithelial phosphate transport is mainly via epithelial tight junctions and controlled by epithelial cell pH. When cells are acidified, phosphate transport is inhibited. This phenomenon has been observed when epithelial cells are treated with, for example, NHE3 inhibitors, guanylate cyclase C receptor (GC-C) agonists, regardless of the mechanism by which they are acidified. Other targets that can be modulated to acidify epithelial cells are P2Y agonists, adenosine A2b receptor agonists, soluble guanylate cyclase agonists, adenylate cyclase receptor agonists, imidazoline-1 receptor agonists, cholinergic agonists, prostaglandin EP4 receptor agonists, dopamine D1 agonists, melatonin receptor agonists, 5HT4 agonists, atrial natriuretic peptide receptor agonists, carbonic anhydrase inhibitors, phosphodiesterase inhibitors, and downregulated in adenomas (DRA or SLC26A3) agonists.

[0013] Thus, in one aspect of the invention, there is provided a method for lowering serum phosphate in a patient, comprising administering an effective amount of an epithelial phosphate transport inhibitor in combination with a phosphate binder, wherein the amount of phosphate binder administered is less than that which would be administered as a single agent. In one embodiment, there is provided a method for treating hyperphosphatemia in a patient in need thereof, comprising administering to said patient an epithelial phosphate transport inhibitor and a phosphate binder, wherein the amount of phosphate binder is less than that which would be required to lower serum phosphate in the patient as a single agent. In one embodiment, there is a method for preventing phosphate uptake from the lumen of the gastrointestinal tract of a patient, comprising administering to said patient an epithelial phosphate transport inhibitor and a phosphate binder, wherein the amount of phosphate binder is less than that which would be required to lower serum phosphate in the patient as a single agent.

[0014] In another aspect of the invention, a composition is provided comprising an epithelial phosphate transport inhibitor and a phosphate binder, wherein the amount of the phosphate binder is less than the amount required to lower serum phosphate in a patient as a single agent. In one embodiment, a manufacture of a medicament for lowering serum phosphate in a patient is provided, the medicament comprising an epithelial phosphate transport inhibitor and a phosphate binder, wherein the amount of the phosphate binder is less than the amount required to lower serum phosphate in a patient as a single agent. In another embodiment, a composition for use in lowering serum phosphate in a patient is provided, the composition comprising an epithelial phosphate transport inhibitor and a phosphate binder, wherein the amount of the phosphate binder is less than the amount required to lower serum phosphate in a patient as a single agent. In certain embodiments, the epithelial phosphate transport inhibitor and the phosphate binder are administered as part of a single pharmaceutical composition. In some embodiments, the epithelial phosphate transport inhibitor and the phosphate binder are administered as separate pharmaceutical compositions. In some embodiments, the individual medicaments, pharmaceutical compositions are administered sequentially. In some embodiments, the individual pharmaceutical compositions are administered simultaneously. In one embodiment, the epithelial phosphate transport inhibitor is administered before the phosphate binder. In another embodiment, the epithelial phosphate transport inhibitor is administered after the phosphate binder.

[0015] In certain embodiments, a method for inhibiting phosphate uptake in the gastrointestinal tract of a patient in need of phosphate lowering comprises enterally administering to the patient a substantially systemically non-bioavailable epithelial transport inhibitor in combination with a reduced amount of a phosphate binder in accordance with the present invention to inhibit transport of phosphate ions (Pi) therein after administration to a patient in need thereof. In some embodiments, the method is selected from one or more of the following: (a) a method for treating hyperphosphatemia, optionally postprandial hyperphosphatemia; (b) a method for treating a renal disease, optionally chronic kidney disease (CKD) or end stage renal disease (ESRD); (c) a method for reducing serum creatinine levels; (d) a method for treating proteinuria; (e) Renal replacement therapy (RRT), a method for voluntarily delaying time to dialysis; (f) methods for reducing FGF23 levels; (g) A method for reducing the hyperphosphatemic effects of active vitamin D. (h) a method for reducing hyperparathyroidism, optionally secondary hyperparathyroidism; (i) Methods for reducing serum parathyroid hormone (PTH) (j) methods for reducing interdialytic weight gain (IDWG); (k) a method for improving endothelial dysfunction, optionally induced by postprandial serum phosphate; (l) A method for reducing vascular calcification, optionally intimal localized vascular calcification; (m) A method for reducing urinary phosphorus; (n) a method for normalizing serum phosphorus levels; (o) A method for reducing phosphate load in an elderly patient. (p) A method for reducing dietary phosphate intake. (q) a method for reducing renal hypertrophy; (r) a method for reducing cardiac hypertrophy, and (s) A method for treating obstructive sleep apnea.

[0016] In certain embodiments, administering the method or composition of the present invention to a patient in need thereof (a) reduces serum phosphate concentration or level to about 150% or less of normal serum phosphate level, and / or (b) reduces dietary phosphate intake by at least about 10% compared to an untreated state. In some embodiments, administering to a patient in need thereof reduces urinary phosphate concentration or level by at least about 10% compared to an untreated state. In certain embodiments, administering to a patient in need thereof increases fecal phosphate levels by at least about 10% compared to an untreated state.

[0017] In certain embodiments, the patient in need of administration has ESRD, and administration of the composition of the present invention to the patient (a) reduces serum phosphate concentration or level to about 150% or less of normal serum phosphate level, and (b) reduces interdialytic weight gain (IDWG) by at least about 10% compared to the untreated state. In one embodiment, the ESRD patient is on dialysis.

[0018] In some embodiments, the patient in need of administration has CKD, and administration to the patient (a) reduces FGF23 levels and serum intact parathyroid hormone (iPTH) levels by at least about 10% compared to an untreated state, and (b) reduces blood pressure and proteinuria by at least about 10% compared to an untreated state. In one embodiment, the CKD patient is on dialysis.

[0019] In one embodiment, the method is one of the following: (a) a method for treating hyperphosphatemia, optionally postprandial hyperphosphatemia; (b) a method for treating a renal disease, optionally chronic kidney disease (CKD) or end stage renal disease (ESRD); (c) a method for reducing serum creatinine levels; (d) a method for treating proteinuria; (e) Renal replacement therapy (RRT), a method for voluntarily delaying time to dialysis; (f) methods for reducing FGF23 levels; (g) A method for reducing the hyperphosphatemic effects of active vitamin D. (h) a method for reducing hyperparathyroidism, optionally secondary hyperparathyroidism; (i) Methods for reducing serum parathyroid hormone (PTH) (j) methods for reducing interdialytic weight gain (IDWG); (k) a method for improving endothelial dysfunction, optionally induced by postprandial serum phosphate; (l) A method for reducing vascular calcification, optionally intimal localized vascular calcification; (m) A method for increasing urinary phosphorus. (n) a method for normalizing serum phosphorus levels; (o) A method for reducing phosphate load in an elderly patient. (p) A method for reducing dietary phosphate intake. (q) a method for reducing renal hypertrophy; (r) a method for reducing cardiac hypertrophy, and (s) A method for treating obstructive sleep apnea.

[0020] Phosphate Binders In certain embodiments, the phosphate binder is sevelamer (e.g., Renvela® (sevelamer carbonate), Renagel® (sevelamer hydrochloride)), lanthanum carbonate (e.g., Fosrenol®), calcium carbonate (e.g., Calcichew®, Titralac®, Tums®), calcium acetate (e.g., PhosLo®, Phosex®), calcium acetate / magnesium carbonate (e.g., Renepho®, Os vaRen®), MCI-196, ferric citrate (e.g., Zerenex™), ferric magnesium hydroxycarbonate (e.g., Fermagate™), aluminum hydroxide (e.g., Alucaps®, Basaljel®), ferric citrate, e.g., tetraferric tricitrate (e.g., Auryxia®), sucroferric oxyhydroxide (e.g., Velphoro®), APS1585, SBR-759, and PA-21.

[0021] In one embodiment, the phosphate binder is sevelamer. In one embodiment, the phosphate binder is sevelamer carbonate. In one embodiment, the phosphate binder is sevelamer hydrochloride. In one embodiment, the single dose of sevelamer is about 800-1600 mg, once or twice per day. In one embodiment, the composition comprises about 30 mg tenapanor and about 200 mg sevelamer. In one embodiment, the composition comprises about 30 mg tenapanor and about 400 mg sevelamer. In one embodiment, the composition comprises about 30 mg tenapanor and about 800 mg sevelamer. In one embodiment, the composition comprises about 30 mg tenapanor and about 1,200 mg sevelamer. In one embodiment, the amount of sevelamer is about 100-200 mg.

[0022] In one embodiment, the amount of sevelamer is about 100-200 mg. In one embodiment, the amount of sevelamer is about 200-300 mg. In one embodiment, the amount of sevelamer is about 300-400 mg. In one embodiment, the amount of sevelamer is about 400-500 mg. In one embodiment, the amount of sevelamer is about 500-600 mg. In one embodiment, the amount of sevelamer is about 600-700 mg. In one embodiment, the amount of sevelamer is about 700-800 mg.

[0023] In one embodiment, the phosphate binder is ferric citrate, e.g., tetraferric tricitrate (e.g., Auryxia®). The single dose of Auryxia is up to 12 210 mg tablets per day, and an average of 8-9 tablets per day, to achieve a serum phosphate level of 3.5-5.5 mg / dL. The starting dose of Auryxia® is 2-3 210 mg tablets per day. In one embodiment, the amount of Auryxia® administered per dose according to the method of the invention or present in the composition of the invention is about 10-25 mg. In one embodiment, the amount of Auryxia® administered per dose according to the method of the invention or present in the composition of the invention is about 25-50 mg. In one embodiment, the amount of Auryxia® administered per dose according to the method of the invention or present in the composition of the invention is about 50-75 mg. In one embodiment, the amount of Auryxia® administered per dose according to the methods of the invention or present in the compositions of the invention is about 75-100 mg. In one embodiment, the amount of Auryxia® administered per dose according to the methods of the invention or present in the compositions of the invention is about 100-125 mg. In one embodiment, the amount of Auryxia® administered per dose according to the methods of the invention or present in the compositions of the invention is about 125-150 mg. In one embodiment, the amount of Auryxia® administered per dose according to the methods of the invention or present in the compositions of the invention is about 150-175 mg. In one embodiment, the amount of Auryxia® administered per dose according to the methods of the invention or present in the compositions of the invention is about 175-200 mg.

[0024] In one embodiment, the phosphate binder is sucroferric oxyhydroxide (e.g., Velphoro®). The starting dose of Velphoro® is one 500 mg tablet. The average maintenance dose of Velphoro® is one 500 mg tablet, 3-4 times per day. In one embodiment, the amount of Velphoro® administered per dose according to the methods of the invention or present in the compositions of the invention is about 25-50 mg. In one embodiment, the amount of Velphoro® administered per dose according to the methods of the invention or present in the compositions of the invention is about 50-100 mg. In one embodiment, the amount of Velphoro® administered per dose according to the methods of the invention or present in the compositions of the invention is about 100-150 mg. In one embodiment, the amount of Velphoro® administered per dose according to the methods of the invention or present in the compositions of the invention is about 200-50 mg. In one embodiment, the amount of Velphoro® administered per dose according to the methods of the invention or present in the compositions of the invention is about 250-300 mg. In one embodiment, the amount of Velphoro® administered per dose according to the methods of the invention or present in the compositions of the invention is about 300-350 mg. In one embodiment, the amount of Velphoro® administered per dose according to the methods of the invention or present in the compositions of the invention is about 350-400 mg.

[0025] In one embodiment, the amount of phosphate binder administered in combination with an epithelial phosphate transport inhibitor or present in a composition of the invention is 90-95% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with an epithelial phosphate transport inhibitor or present in a composition of the invention is 85-90% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with an epithelial phosphate transport inhibitor or present in a composition of the invention is 80-85% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with an epithelial phosphate transport inhibitor or present in a composition of the invention is 75-80% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with an epithelial phosphate transport inhibitor or present in a composition of the invention is 70-75% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with an epithelial phosphate transport inhibitor or present in a composition of the invention is 65-70% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with an epithelial phosphate transport inhibitor or present in a composition of the invention is 60-65% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with an epithelial phosphate transport inhibitor or present in a composition of the invention is 55-60% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with an epithelial phosphate transport inhibitor or present in a composition of the invention is 50-55% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with an epithelial phosphate transport inhibitor or present in a composition of the invention is 45-50% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with an epithelial phosphate transport inhibitor or present in a composition of the invention is 40-45% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with an epithelial phosphate transport inhibitor or present in a composition of the invention is 35-40% of the amount administered as a single agent.In one embodiment, the amount of phosphate binder administered in combination with an epithelial phosphate transport inhibitor or present in a composition of the invention is 30-35% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with an epithelial phosphate transport inhibitor or present in a composition of the invention is 25-30% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with an epithelial phosphate transport inhibitor or present in a composition of the invention is 20-25% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with an epithelial phosphate transport inhibitor or present in a composition of the invention is 15-20% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with an epithelial phosphate transport inhibitor or present in a composition of the invention is 10-15% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with an epithelial phosphate transport inhibitor or present in a composition of the invention is about 5-10% of the amount administered as a single agent.

[0026] In one embodiment, the amount of phosphate binder administered in combination with epithelial phosphate transport inhibitor or present in the composition of the present invention is about 95% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with epithelial phosphate transport inhibitor or present in the composition of the present invention is about 90% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with epithelial phosphate transport inhibitor or present in the composition of the present invention is about 85% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with epithelial phosphate transport inhibitor or present in the composition of the present invention is about 80% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with epithelial phosphate transport inhibitor or present in the composition of the present invention is about 75% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with epithelial phosphate transport inhibitor or present in the composition of the present invention is about 70% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with epithelial phosphate transport inhibitor or present in the composition of the present invention is about 65% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with epithelial phosphate transport inhibitor or present in the composition of the present invention is about 60% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with epithelial phosphate transport inhibitor or present in the composition of the present invention is about 55% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with epithelial phosphate transport inhibitor or present in the composition of the present invention is about 50% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with epithelial phosphate transport inhibitor or present in the composition of the present invention is about 45% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with epithelial phosphate transport inhibitor or present in the composition of the present invention is about 40% of the amount administered as a single agent.In one embodiment, the amount of phosphate binder administered in combination with epithelial phosphate transport inhibitor or present in the composition of the present invention is about 35% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with epithelial phosphate transport inhibitor or present in the composition of the present invention is about 30% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with epithelial phosphate transport inhibitor or present in the composition of the present invention is about 25% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with epithelial phosphate transport inhibitor or present in the composition of the present invention is about 20% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with epithelial phosphate transport inhibitor or present in the composition of the present invention is about 20% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with epithelial phosphate transport inhibitor or present in the composition of the present invention is about 15% of the amount administered as a single agent. In one embodiment, the amount of phosphate binder administered in combination with epithelial phosphate transport inhibitor or present in the composition of the present invention is about 10% of the amount administered as a single agent.

[0027] Epithelial phosphate transport inhibitors The epithelial phosphate transport inhibitor used in the method and composition of the present invention is any compound that can reduce the pH of epithelial cells.In one embodiment, the epithelial phosphate transport inhibitor is selected from the group consisting of NHE3 inhibitor, guanylate cyclase C receptor (GC-C) agonist, P2Y agonist, adenosine A2b receptor agonist, soluble guanylate cyclase agonist, adenylate cyclase receptor agonist, imidazoline-1 receptor agonist, cholinergic agonist, prostaglandin EP4 receptor agonist, dopamine D1 agonist, melatonin receptor agonist, 5HT4 agonist, atrial natriuretic peptide receptor agonist, carbonic anhydrase inhibitor, phosphodiesterase inhibitor, and agonist that is downregulated in adenoma (DRA or SLC26A3).

[0028] NHE3 Inhibitors In one embodiment, the epithelial phosphate transport inhibitor is an NHE3 inhibitor. In certain embodiments, the NHE3 inhibitor has the structure of formula (I) or (IX): [ka] During the ceremony, NHE is an NHE-linked small molecule comprising (i) a heteroatom-containing moiety and (ii) a cyclic or heterocyclic backbone or support moiety bonded directly or indirectly thereto, the heteroatom-containing moiety being selected from a substituted guanidinyl moiety and a substituted heterocyclic moiety, which may optionally be fused with the backbone or support moiety to form a fused bicyclic structure; Z is a moiety having at least one site thereon for attachment to an NHE-binding small molecule, and the resulting NHE-Z molecule has overall physicochemical properties that render it substantially impermeable or substantially systemically non-bioavailable; E is an integer having a value of 1 or greater.

[0029] In some embodiments, the backbone of the NHE-binding small molecule is linked to a moiety Z and the compound has the structure of formula (II): [ka] During the ceremony, Z is a core having one or more sites thereon for attachment to one or more NHE-binding small molecules, and the resulting NHE-Z molecule has overall physicochemical properties that render it substantially impermeable or substantially systemically non-bioavailable; B is a heteroatom-containing moiety of an NHE-linked small molecule selected from a substituted guanidinyl moiety and a substituted heterocyclic moiety, which can optionally be fused with a backbone moiety to form a fused bicyclic structure; The backbone is a cyclic or heterocyclic backbone or support moiety of an NHE-linked small molecule, which is directly or indirectly attached to a heteroatom-containing moiety B and is optionally substituted with one or more additional hydrocarbyl or heterohydrocarbyl moieties; X is a bond or a substituted or unsubstituted hydrocarbyl or heterohydrocarbyl moiety, and in particular a substituted or unsubstituted C 1-7 a spacer moiety selected from the group consisting of hydrocarbyl or heterohydrocarbyl, and substituted or unsubstituted, saturated or unsaturated, cyclic or heterocyclic moieties, which connects B to the backbone; and D and E are integers, each independently having a value of 1 or greater.

[0030] In some embodiments, the compound is an oligomer, dendrimer, or polymer, and further, Z is a core moiety having two or more moieties thereon for attachment to multiple NHE-binding small molecules, either directly, or indirectly through a linking moiety L, and the compound has the structure of formula (X): [ka] where L is a bond or linker connecting the core to the NHE-binding small molecule, n is an integer equal to or greater than 1, and further, each NHE-binding small molecule can be the same or different from the other.

[0031] In some embodiments, the NHE binding small molecule has the structure of formula (IV): [ka] or a stereoisomer, prodrug, or pharma- ceutically acceptable salt thereof; During the ceremony, each R, R, R, R, and R is independently selected from H, halogen, -NR(CO)R, -(CO)NR, -SO-NR, -NRSO, -NR, -OR, -SR, -O(CO)NR, -NR(CO)OR, and -NRSONR, where R and R are independently selected from H, or a bond linking an NHE-binding small molecule to L, provided that at least one is a bond linking an NHE-binding small molecule to L; R4 is selected from H, C1-C7 alkyl, or a bond linking an NHE-linked small molecule to L; R6 is absent or selected from H and C1-C7 alkyl; Ar1 and Ar2 independently represent an aromatic ring or a heteroaromatic ring.

[0032] In certain embodiments, the NHE binding small molecule has the following structure: [ka] or a stereoisomer, prodrug, or pharma- ceutically acceptable salt thereof; During the ceremony, Each R1, R2, and R3 is independently selected from H, halogen, -NR7(CO)R8, -(CO)NR7R8, -SO2-NR7R8, -NR7S02R8, -NR7R8, -OR7, -SR7, -O(CO)NR7R8, -NR7(CO)OR8, and -NR7S02NR8, where R7 and R8 are independently selected from H, or a bond linking an NHE-binding small molecule to L, provided that at least one is a bond linking an NHE-binding small molecule to L.

[0033] In some embodiments, the NHE binding small molecule has one of the following structures: [ka] or a stereoisomer, prodrug, or pharma- ceutically acceptable salt thereof. In certain embodiments, L is a polyalkylene glycol linker. In certain embodiments, L is a polyethylene glycol linker. In some embodiments, n is 2.

[0034] In certain embodiments, the core has the structure: [ka] During the ceremony, X is a bond, -O-, -NH-, -S-, or C 1-6selected from the group consisting of alkylene, -NHC(=O)-, -C(=O)NH-, -NHC(=O)NH-, -SO2NH-, and -NHSO2-; Y is a bond, an optionally substituted C 1-8 alkylene, optionally substituted aryl, optionally substituted heteroaryl, polyethylene glycol linker, -(CH2) 1-6 O(CH2) 1-6 - and -(CH2) 1-6 NY1(CH2) 1-6 - selected from the group consisting of Y1 is hydrogen, optionally substituted C 1-8 It is selected from the group consisting of alkyl, optionally substituted aryl, or optionally substituted heteroaryl.

[0035] In some embodiments, the core is selected from the group consisting of: [ka] where L is a bond or linking moiety, NHE is an NHE-linked small molecule, and n is a non-zero integer.

[0036] In some embodiments, the NHE3 inhibitor has the structure of formula (IH): [ka] or a stereoisomer, prodrug, or pharma- ceutically acceptable salt thereof; During the ceremony, (a) n is an integer of 2 or greater; (b) the core is a core moiety having two or more sites thereon for attachment to two or more NHE-binding small molecule moieties; (c) L is a bond or linker connecting the core moiety to two or more NHE-binding small molecule moieties; (d) NHE is an NHE-linked small molecule moiety having the structure of formula (XI-H): [ka] During the ceremony, B is selected from the group consisting of aryl and heterocyclyl; Each R5 is independently hydrogen, halogen, or optionally substituted C 1-4 Alkyl, optionally substituted C 1-4 Alkoxy, optionally substituted C 1-4 Thioalkyl, optionally substituted heterocyclyl, optionally substituted heterocyclylalkyl, optionally substituted aryl, optionally substituted heteroaryl, hydroxyl, oxo, cyano, nitro, -NR7R8, -NR7C(=O)R8, -NR7C(=O)OR8, -NR7C(=O)NR8R9, -NR7SO2R8, -NR7S(O)2NR8R9, -C(=O)OR7, -C(=O)R7, -C(=O)NR7R8, -S(O) 1-2 R7, R8, and R9 are independently selected from the group consisting of hydrogen, C 1-4 alkyl, or a bond linking an NHE-binding small molecule moiety to L, with the proviso that at least one is a bond linking an NHE-binding small molecule to L; R and R are independently hydrogen, optionally substituted C 1-4 selected from the group consisting of alkyl, optionally substituted cycloalkyl, optionally substituted cycloalkylalkyl, optionally substituted aryl, optionally substituted aralkyl, optionally substituted heterocyclyl, and optionally substituted heteroaryl; or R3 and R4 together with the nitrogen to which they are attached form an optionally substituted 4-8 membered heterocyclyl; Each R1 is independently hydrogen, halogen, or optionally substituted C 1-6 Alkyl, and optionally substituted C 1-6 In some embodiments, n is 2. In certain embodiments, L is a polyalkylene glycol linker. In certain embodiments, L is a polyethylene glycol linker.

[0037] In certain embodiments, the core has the structure: [ka] During the ceremony, X is a bond, -O-, -NH-, -S-, or C 1-6 selected from the group consisting of alkylene, -NHC(=O)-, -C(=O)NH-, -NHC(=O)NH-, -SO2NH-, and -NHSO2-; Y is a bond, an optionally substituted C 1-8 alkylene, optionally substituted aryl, optionally substituted heteroaryl, polyethylene glycol linker, -(CH2) 1-6 O(CH2) 1-6 - and -(CH2) 1-6 NY1(CH2) 1-6 - selected from the group consisting of Y1 is hydrogen, optionally substituted C 1-8 It is selected from the group consisting of alkyl, optionally substituted aryl, or optionally substituted heteroaryl.

[0038] In some embodiments, the core is selected from the group consisting of: [ka]

[0039] In certain embodiments, the NHE-binding small molecule moiety has the structure of formula (XII-H): [ka] During the ceremony, Each R and R is independently selected from hydrogen and optionally substituted C 1-4 alkyl, or R3 and R4 together with the nitrogen to which they are attached form an optionally substituted 4-8 membered heterocyclyl; Each R1 is independently hydrogen, halogen, or C 1-6 Alkyl, and C 1-6 haloalkyl; R5 is selected from the group consisting of -SO2-NR7- and -NHC(=O)NH-, where R7 is hydrogen or C 1-4 It is an alkyl.

[0040] In some embodiments, R3 and R4 together with the nitrogen to which they are attached form an optionally substituted 5- or 6-membered heterocyclyl. In certain embodiments, the optionally substituted 5- or 6-membered heterocyclyl is pyrrolidinyl or piperidinyl. In certain embodiments, the optionally substituted 5- or 6-membered heterocyclyl is pyrrolidinyl or piperidinyl, each of which is substituted with at least one amino or hydroxyl. In some embodiments, R3 and R4 are independently selected from C 1-4 In certain embodiments, R3 and R4 are alkyl. In certain embodiments, R3 and R4 are methyl. In some embodiments, each R1 is independently selected from the group consisting of hydrogen or halogen. In certain embodiments, each R1 is independently selected from the group consisting of hydrogen, F, and Cl.

[0041] In certain embodiments, the NHE3 inhibitor has the structure of formula (II): [ka] or a stereoisomer, prodrug, or pharma- ceutically acceptable salt thereof; During the ceremony, (a) NHE is an NHE-binding small molecule moiety having the structure of formula (AI): [ka] During the ceremony, Each R1, R2, R3, R5, and R9 is independently selected from H, halogen, -NR7(CO)R8, -(CO)NR7R8, -SO2-NR7R8, -NR7S02R8, -NR7R8, -OR7, -SR7, -O(CO)NR7R8, -NR7(CO)OR8, and -NR7S02NR8, wherein R7 and R8 are independently selected from H, C 1-6 Alkyl, -C 1-6alkyl-OH, or a bond linking an NHE-binding small molecule to L, provided that at least one is a bond linking an NHE-binding small molecule to L; R4 is selected from H, C1-C7 alkyl, or a bond linking an NHE-linked small molecule to L; R6 is absent or selected from H and C1-C7 alkyl; Ar1 and Ar2 each independently represent an aromatic ring or a heteroaromatic ring; (b) the core is a core moiety having the structure of formula (BI): [ka] During the ceremony, X is a function of C(X1), N, and N(C 1-6 alkyl), X1 is hydrogen, optionally substituted alkyl, -NX a X b , -NO2, -NX c -C(=O)-NX c -X a , -C(=O)NX c -X a , -NX c -C(=O)-X a , -NX c -SO2-X a , -C(=O)-X a , and -OX a is selected from each X a and X b is independently selected from hydrogen, optionally substituted alkyl, optionally substituted cycloalkyl, optionally substituted cycloalkylalkyl, optionally substituted heterocyclyl, optionally substituted heterocyclylalkyl, optionally substituted aryl, optionally substituted aralkyl, optionally substituted heteroaryl, and optionally substituted heteroarylalkyl; Y is C 1-6 is alkylene, Z is -NZ if X is CX1 a -C(=O)-NZ a -, -C(=O)NZa -, -NZ a -C(=O)-, and heteroaryl; Z is the number of times X is N or N(C 1-6 alkyl), -NZ a -C(=O)-NZ a -, -NZ a -C(=O)-, and heteroaryl; each X c and Z a are independently hydrogen and C 1-6 alkyl, (c) L is a bond or linker that connects the core moiety to the NHE-binding small molecule moiety.

[0042] In some embodiments, the NHE-binding small molecule moiety has the structure: [ka] During the ceremony, Each R1, R2, and R3 is independently selected from H, halogen, -NR7(CO)R8, -(CO)NR7R8, -SO2-NR7R8, -NR7S02R8, -NR7R8, -OR7, -SR7, -O(CO)NR7R8, -NR7(CO)OR8, and -NR7S02NR8, wherein R7 and R8 are independently selected from H, C 1-6 Alkyl, -C 1-6 or an alkyl-OH, or a bond linking an NHE-binding small molecule to L, provided that at least one is a bond linking an NHE-binding small molecule to L.

[0043] In some embodiments, the NHE-binding small molecule moiety has one of the following structures: [ka]

[0044] In some embodiments, L is a polyalkylene glycol linker. In certain embodiments, L is a polyethylene glycol linker. In some embodiments, X is C(X1). In some embodiments, each X c is hydrogen. In certain embodiments, X is N. In certain embodiments, each Z a is hydrogen.

[0045] In some embodiments, the NHE3 inhibitor has the structure of formula (II): [ka] (II-I) or a stereoisomer, prodrug, or pharma- ceutically acceptable salt thereof; During the ceremony, (a) NHE is an NHE-binding small molecule moiety having the structure of formula (AI): [ka] During the ceremony, Each R1, R2, R3, R5, and R9 is independently selected from H, halogen, -NR7(CO)R8, -(CO)NR7R8, -SO2-NR7R8, -NR7S02R8, -NR7R8, -OR7, -SR7, -O(CO)NR7R8, -NR7(CO)OR8, and -NR7S02NR8, wherein R7 and R8 are independently selected from H, C 1-6 Alkyl, -C 1-6 alkyl-OH, or a bond linking an NHE-binding small molecule to L, provided that at least one is a bond linking an NHE-binding small molecule to L; R4 is selected from H, C1-C7 alkyl, or a bond linking an NHE-linked small molecule to L; R6 is absent or selected from H and C1-C7 alkyl; Ar1 and Ar2 each independently represent an aromatic ring or a heteroaromatic ring; (b) the core is a core moiety having a structure of formula (CI): [ka] During the ceremony, W is selected from alkylene, polyalkylene glycol, -C(=O)-NH-(alkylene)-NH-C(=O)-, -C(=O)-NH-(polyalkylene glycol)-NH-C(=O)-, -C(=O)-(alkylene)-C(=O)-, -C(=O)-(polyalkylene glycol)-C(=O)-, and cycloalkyl; X is N; Y is C 1-6 is alkylene, Z is -NZ a -C(=O)-NZ a -, -C(=O)NZ a -, -NZ a -C(=O)-, and heteroaryl; each Z a are independently hydrogen and C 1-6 alkyl, (c) L is a bond or linker connecting the core moiety to the NHE-binding small molecule.

[0046] In certain embodiments, the NHE-binding small molecule moiety has the structure: [ka] During the ceremony, Each R1, R2, and R3 is independently selected from H, halogen, -NR7(CO)R8, -(CO)NR7R8, -SO2-NR7R8, -NR7S02R8, -NR7R8, -OR7, -SR7, -O(CO)NR7R8, -NR7(CO)OR8, and -NR7S02NR8, wherein R7 and R8 are independently selected from H, C 1-6 Alkyl, -C 1-6 or an alkyl-OH, or a bond linking an NHE-binding small molecule to L, provided that at least one is a bond linking an NHE-binding small molecule to L.

[0047] In certain embodiments, the NHE-binding small molecule moiety has one of the following structures: [ka]

[0048] In one embodiment, the NHE3 inhibitor is one disclosed in WO2010 / 078449. In an embodiment, the NHE3 inhibitor is TP0469711. In one embodiment, the NHE3 inhibitor is: [ka]

[0049] In one embodiment, the NHE3 inhibitor is: [ka]

[0050] In certain embodiments, the NHE3 inhibitor has the structure: [ka]

[0051] In one embodiment, the NHE3 inhibitor is an HCl salt. In one embodiment, the NHE3 inhibitor is a dihydrochloride salt.

[0052] In one embodiment, the NHE3 inhibitor is tenapanor. It will be understood that the amount of tenapanor administered may be specific to each individual patient. Furthermore, if the NHE3 inhibitor is other than tenapanor, the amount administered may vary depending on several factors, such as potency, stability, and exposure to NHE3 countertransport in the colon. In one embodiment, the NHE3 inhibitor is administered in an amount that achieves about the same degree of NHE3 inhibition in the patient as tenapanor. In one embodiment, the amount of tenapanor administered in combination with the phosphate binder is 30 mg. In one embodiment, tenapanor is administered twice a day in combination with the phosphate binder. In one embodiment, tenapanor is administered three times a day with meals in combination with the phosphate binder. In one embodiment, tenapanor is administered as three 10 mg tablets in combination with the phosphate binder. In one embodiment, tenapanor is administered twice a day and the phosphate binder is administered three times a day. In one embodiment, tenapanor is administered two times per day with food and the phosphate binder is administered three times per day when the patient eats meals.

[0053] Virtually systemically non-bioavailable NHE3 inhibitors: Some of the NHE3 inhibitors described herein are designed to be substantially active or localized in the lumen of the gastrointestinal tract of a human or animal subject. The term "lumen of the gastrointestinal tract" is used herein interchangeably with the term "lumen" which refers to the space or cavity in the gastrointestinal tract (GI tract, which may also be referred to as the digestive tract) bounded by the apical membrane of the GI epithelial cells of a subject. In some embodiments, the compound is not absorbed through the layer of epithelial cells of the GI tract (also known as GI epithelium). "Gastrointestinal mucosa" refers to the layer of cells that separates the lumen of the gastrointestinal tract from the rest of the body, including the gastric mucosa and intestinal mucosa, such as the mucosa of the small intestine. As used herein, "gastrointestinal epithelial cells" or "gastrointestinal epithelial cells" refers to any epithelial cells on the surface of the gastrointestinal mucosa that faces the lumen of the gastrointestinal tract, including, for example, gastric epithelial cells, intestinal epithelial cells, colonic epithelial cells, etc.

[0054] As used herein, "substantially systemically non-bioavailable" and / or "substantially impermeable" (and variations thereof) generally refer to a situation in which, in a statistically significant amount and in some embodiments, substantially all of the compound remains in the lumen of the gastrointestinal tract. For example, according to one or more embodiments of the present disclosure, preferably at least about 60%, about 70%, about 75%, about 80%, about 85%, about 90%, about 95%, about 96%, about 97%, about 98%, about 99%, or even about 99.5% of the compound remains in the lumen of the gastrointestinal tract. In such cases, localization to the lumen of the gastrointestinal tract refers to reducing the net movement of the compound across the gastrointestinal layer of epithelial cells, for example, by both transcellular and paracellular transport, and by active and / or passive transport. The compound in such embodiments is prevented from net permeating the layer of gastrointestinal epithelial cells in transcellular transport, for example, through the apical membrane of epithelial cells of the small intestine. The compounds in these embodiments also prevent net permeation through "tight junctions" in paracellular transport between gastrointestinal epithelial cells lining the lumen.

[0055] In this regard, it should be noted that in one particular embodiment, the NHE3 inhibitor compound is essentially not absorbed at all by the lumen of the GI tract or gastrointestinal tract.As used herein, the term "substantially impermeable" or "substantially systemically non-bioavailable" includes embodiments in which no detectable amount of the compound is absorbed, penetrated, or exposed to the whole body, using means generally known in the art.

[0056] However, in this regard, it is further noted that in alternative embodiments, "substantially impermeable" or "substantially systemically non-bioavailable" provides or allows some limited absorption in the GI tract, more specifically in the gastrointestinal epithelium (e.g., some detectable amount of absorption, e.g., at least about 0.1%, 0.5%, 1% or more, and less than about 30%, less than 20%, less than 10%, less than 5%, etc., with absorption ranging from, e.g., about 1% to 30% or 5% to 20%, etc.). In other words, "substantially impermeable" or "substantially non-bioavailable" may refer to a compound that exhibits some detectable permeability to the epithelial layer of cells in the GI tract of less than about 20% of the administered compound (e.g., less than about 15%, less than about 10%, or even less than about 5%, less than 4%, less than 3%, or less than 2%, and e.g., more than about 0.5% or 1%), but is then cleared by the liver (i.e., hepatic extraction) / kidneys (i.e., renal extraction).

[0057] In this regard, it is further noted that in certain embodiments, due to the substantial impermeability and / or substantial systemic bioavailability of NHE3 inhibitors, about 50%, 60%, 70%, 80%, 90%, or more than 95% of the compound of the present invention can be recovered from feces, for example, for 24, 36, 48, 60, 72, 84, or 96 hours after administration to a subject in need of administration.In this regard, it is understood that the recovered compound can include the sum of the parent compound and its metabolites derived from the parent compound, for example, by hydrolysis, conjugation, reduction, oxidation, N-alkylation, glucuronidation, acetylation, methylation, sulfation, phosphorylation, or any other modification that adds or removes atoms from the parent compound, and that the metabolites are generated through the action of any enzyme or exposure to any physiological environment, including pH, temperature, pressure, or interaction with food when present in the digestive environment.

[0058] Measurement of fecal recovery of NHE3 inhibitor compounds and metabolites can be carried out using standard methods. For example, compounds can be orally administered at a suitable dose (e.g., 10 mg / kg), and then feces are collected at a predetermined time (e.g., 24 hours, 36 hours, 48 ​​hours, 60 hours, 72 hours, 96 hours) after administration. Parent compounds and metabolites can be extracted with organic solvents and quantitatively analyzed using mass spectrometry. Mass balance analysis of parent compounds and metabolites (including parent=M, metabolite 1 [M+16], and metabolite 2 [M+32]) can be used to determine fecal recovery.

[0059] C max and I.C. 50 or EC 50 In some embodiments, the substantially systemically non-bioavailable NHE3 inhibitors detailed herein, when administered to a subject in need thereof (e.g., enterally), either alone or in combination with a phosphate binder, exhibit a phosphate ion (Pi) transport or uptake inhibitory concentration IC 50 Approximately equal to or smaller than C max In some embodiments, for example, C max IC for inhibiting Pi transport or uptake 50 In some embodiments, C is about or at least about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100% less than C. max IC for inhibiting Pi transport or uptake 50 Approximately 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9X (0.9 times).

[0060] In certain embodiments, one or more of the substantially systemically non-bioavailable NHE3 inhibitor compounds detailed herein, when administered (e.g., enterally) to a subject in need thereof, have an activity of about 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0 or less, or about 0.01 to 1.0, 0 C (to inhibit Pi transport or uptake) in the range of .01-0.9, 0.01-0.8, 0.01-0.7, 0.01-0.6, 0.01-0.5, 0.01-0.4, 0.01-0.3, 0.01-0.2, or 0.01-0.1, or in the range of about 0.1-1.0, 0.1-0.9, 0.1-0.8, 0.1-0.7, 0.1-0.6, 0.1-0.5, 0.1-0.4, 0.1-0.3, or 0.1-0.2 max :I C 50 and C max and I.C. 50 are expressed in the same units.

[0061] In some embodiments, the substantially systemically non-bioavailable NHE3 inhibitors detailed herein, either alone or in combination with one or more additional pharma- ceutical active compounds or agents, when administered (e.g., enterally) to a subject in need thereof, have an EC of the compound to increase fecal output of phosphate. 50 Approximately equal to or less than C max and stool volume is increased by about or at least about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%. max EC for increasing phosphate excretion 50 In some embodiments, C is about or at least about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100% less than C. max EC for increasing phosphate excretion 50Approximately 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9X (0.9 times).

[0062] In some embodiments, one or more of the substantially systemically non-bioavailable compounds detailed herein, either alone or in combination with one or more additional pharma- ceutical active compounds or agents, when administered (e.g., enterally) to a subject in need thereof or as measured in an animal model or cell-based assay, has an EC for increasing phosphate excretion of about 10 μM, 9 μM, 8 μM, 7 μM, 7.5 μM, 6 μM, 5 μM, 4 μM, 3 μM, 2.5 μM, 2 μM, 1 μM, 0.5 μM, 0.1 μM, 0.05 μM, or 0.01 μM or less. 50 and IC 50 is, for example, within the range of about 0.01 μM to about 10 μM, or about 0.01 μM to about 7.5 μM, or about 0.01 μM to about 5 μM, or about 0.01 μM to about 2.5 μM, or about 0.01 μM to about 1.0, or about 0.1 μM to about 10 μM, or about 0.1 μM to about 7.5 μM, or about 0.1 μM to about 5 μM, or about 0.1 μM to about 2.5 μM, or about 0.1 μM to about 1.0, or μM0.5 μM to about 10 μM, or about 0.5 μM to about 7.5 μM, or about 0.5 μM to about 5 μM, or about 0.5 μM to about 2.5 μM, or about 0.5 μM to about 1.0 μM.

[0063] In certain embodiments, the substantially systemically non-bioavailable NHE3 inhibitors detailed herein, either alone or in combination with one or more additional pharmacologic active compounds or agents, when administered (e.g., enterally) to a subject in need thereof, have an EC value of less than 100 mg / kg / day of the compound for reducing urinary levels of phosphate. 50 Approximately equal to or less than C maxand urinary volume is reduced by about or at least about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%. max EC for reducing urinary phosphate 50 In some embodiments, C is about or at least about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100% less than C. max EC for reducing urinary phosphate 50 Approximately 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9X (0.9 times).

[0064] In some embodiments, one or more of the substantially systemically non-bioavailable NHE3 inhibitors detailed herein, either alone or in combination with a phosphate binder, when administered (e.g., enterally) to a subject in need thereof or as measured in an animal model or cell-based assay, has an EC for reducing urinary phosphate of about 10 μM, 9 μM, 8 μM, 7 μM, 7.5 μM, 6 μM, 5 μM, 4 μM, 3 μM, 2.5 μM, 2 μM, 1 μM, 0.5 μM, 0.1 μM, 0.05 μM, or 0.01 μM or less. 50 and IC 50 is, for example, within the range of about 0.01 μM to about 10 μM, or about 0.01 μM to about 7.5 μM, or about 0.01 μM to about 5 μM, or about 0.01 μM to about 2.5 μM, or about 0.01 μM to about 1.0, or about 0.1 μM to about 10 μM, or about 0.1 μM to about 7.5 μM, or about 0.1 μM to about 5 μM, or about 0.1 μM to about 2.5 μM, or about 0.1 μM to about 1.0, or μM0.5 μM to about 10 μM, or about 0.5 μM to about 7.5 μM, or about 0.5 μM to about 5 μM, or about 0.5 μM to about 2.5 μM, or about 0.5 μM to about 1.0 μM.

[0065] In certain embodiments, one or more of the substantially systemically non-bioavailable NHE3 inhibitor compounds detailed herein, when administered (e.g., enterally) to a subject in need thereof, have an activity of about 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0 or less, or about 0.01-1.0, 0.01-0.9, 0. C in the range of .01-0.8, 0.01-0.7, 0.01-0.6, 0.01-0.5, 0.01-0.4, 0.01-0.3, 0.01-0.2, or 0.01-0.1, or in the range of about 0.1-1.0, 0.1-0.9, 0.1-0.8, 0.1-0.7, 0.1-0.6, 0.1-0.5, 0.1-0.4, 0.1-0.3, or 0.1-0.2 (e.g., to increase stool output of phosphate, decrease urinary output of phosphate) max :EC 50 and C max and E.C. 50 are expressed in the same units.

[0066] Additionally, or alternatively, one or more of the substantially systemically non-bioavailable NHE3 inhibitor compounds detailed herein, when administered (e.g., enterally) to a subject in need thereof, either alone or in combination with one or more additional pharmacologic active compounds or agents, have a C of about 10 ng / mL or less, about 7.5 ng / mL, about 5 ng / mL, about 2.5 ng / mL, about 1 ng / mL, or about 0.5 ng / mL. max C max is, for example, within the range of 1 ng / mL to about 10 ng / mL or about 2.5 ng / mL to about 7.5 ng / mL.

[0067] NHE3 inhibitors include known NHE-binding compounds, which may be monovalent or polyvalent, which bind to and / or modulate NHE3, which have activity as phosphate transport inhibitors, and which include small molecules that are substantially impermeable or substantially systemically non-bioavailable in the gastrointestinal tract, and which may be modified or functionalized in accordance with the present disclosure to change their physicochemical properties so as to render the overall compound substantially active in the GI tract.

[0068] Thus, the compounds of the present disclosure may be generally represented by formula (I): [ka] In the formula, (i) NHE represents an NHE-binding small molecule, (ii) Z represents a moiety having at least one site thereon for attachment to an NHE-binding small molecule, and the resulting NHE-Z molecule has an overall physicochemical property that makes it substantially impermeable or substantially systemically non-bioavailable. NHE-binding small molecules generally comprise a heteroatom-containing moiety and a cyclic or heterocyclic backbone or support moiety directly or indirectly bonded thereto. In particular, as further exemplified herein below, examination of the structures of small molecules previously reported to be NHE binders or inhibitors suggests that most comprise a cyclic or heterocyclic backbone or support moiety directly or indirectly bonded (e.g., by an acyl moiety, or a hydrocarbyl or heterohydrocarbyl moiety, e.g., an alkyl, alkenyl, heteroalkyl, or heteroalkenyl moiety) to a heteroatom-containing moiety, the heteroatom-containing moiety being capable of acting as a sodium atom or sodium ion mimic, which is typically selected from a substituted guanidinyl moiety and a substituted heterocyclic moiety (e.g., a nitrogen-containing heterocyclic moiety). Optionally, the heteroatom-containing moiety may be fused with the backbone or support moiety to form a fused bicyclic structure and / or may be capable of forming a positive charge at physiological pH.

[0069] In this regard, it should be noted that although the sodium atom or heteroatom-containing moiety that can act as an ion mimic may optionally form a positive charge, this should not be understood or interpreted as requiring the entire compound to have a net positive charge or only moieties with a single positive charge therein. Rather, in various embodiments, the compound may have no moieties with a charge or may have moieties with multiple charges therein (positive charges, negative charges, or a combination thereof, and the compound is a zwitterion). Furthermore, it should be understood that the entire compound may have a net neutral charge, a net positive charge (e.g., +1, +2, +3, etc.), or a net negative charge (e.g., -1, -2, -3, etc.).

[0070] The Z moiety may be attached to essentially any position on or within the NHE small molecule, in particular (i) to the backbone or support moiety, (ii) to a position on or within the heteroatom-containing moiety, and / or (iii) to a spacer moiety connecting the backbone to the heteroatom-containing moiety, provided that introduction of the Z moiety does not significantly adversely affect NHE binding activity. In one particular embodiment, Z may be in the form of an oligomer, dendrimer, or polymer bound to an NHE small molecule (e.g., bound to a backbone or spacer moiety), or alternatively, Z may be in the form of a linker that links multiple NHE small molecules together and thus acts to increase (i) the overall molecular weight and / or polar surface area of ​​the NHE-Z molecule, and / or (ii) the number of freely rotatable bonds in the NHE-Z molecule, and / or (iii) the number of hydrogen bond donors and / or acceptors in the NHE-Z molecule, and / or (iv) the Log P value of the NHE-Z molecule to a value of at least about 5 (or alternatively less than 1, or even about 0) (all as described herein), such that the entire NHE-binding compound (i.e., the NHE-Z compound) is substantially impermeable or substantially systemically non-bioavailable.

[0071] The present disclosure is more specifically directed to such substantially impermeable or substantially systemically non-bioavailable NHE-binding compounds, or pharmaceutical salts thereof, the compounds having the structure of formula (II): [ka] wherein (i) Z, as already defined above, is a moiety attached to or incorporated into an NHE-binding small molecule such that the resulting NHE-Z molecule has overall physicochemical properties that render it substantially impermeable or substantially systemically non-bioavailable; (ii) B is a heteroatom-containing moiety of an NHE-binding small molecule, which in one particular embodiment is selected from a substituted guanidinyl moiety and a substituted heterocyclic moiety, which may optionally be fused with a backbone moiety to form a fused bicyclic structure; and (iii) the backbone is bonded directly or indirectly to the heteroatom-containing moiety (e.g., a substituted guanidinyl moiety or a substituted heterocyclic moiety), B, and which comprises one or more additional hydrocarbyl or heterohydrogen groups. (iv) X is a bond or a spacer moiety selected from the group consisting of substituted or unsubstituted hydrocarbyl or heterohydrocarbyl moieties, and specifically substituted or unsubstituted C1-C7 hydrocarbyl or heterohydrocarbyl (e.g., C1-C7 alkyl, alkenyl, heteroalkyl, or heteroalkenyl), and substituted or unsubstituted, saturated or unsaturated, cyclic or heterocyclic moieties (e.g., C4-C7 cyclic or heterocyclic moieties), which connect B to the backbone; and (v) D and E are integers, each independently having a value of 1, 2, or greater.

[0072] In one or more particular embodiments, as further exemplified herein below, B may be selected from a moiety that is a guanidinyl moiety or a guanidinyl bioisostere selected from the group consisting of a substituted cyclobutenedione, a substituted imidazole, a substituted thiazole, a substituted oxadiazole, a substituted pyrazole, or a substituted amine. More specifically, B may be selected from a guanidinyl, an acylguanidinyl, a sulfonylguanidinyl, or a guanidine bioisostere, such as a cyclobutenedione, a substituted or unsubstituted 5- or 6-membered heterocycle, such as a substituted or unsubstituted imidazole aminoimidazole, an alkylimidazole, a thiazole, an oxadiazole, a pyrazole, an alkylthioimidazole, or optionally other functional groups that may become positively charged or function as a sodium mimetic at physiological pH, including amines (e.g., tertiary amines), alkylamines, and the like. In one particularly preferred embodiment, B is a substituted guanidinyl or substituted heterocyclic moiety that can optionally become positively charged at physiological pH to function as a sodium mimetic. In one exemplary embodiment, a compound of the present disclosure (or more specifically, a pharma- ceutically acceptable HCl salt thereof, as exemplified) can have the structure of formula (III): [ka] wherein Z may be optionally attached to any one of a number of sites on the NHE-binding small molecule, and further wherein the R1, R2, and R3 substituents on the aromatic ring are as detailed elsewhere herein and / or in U.S. Pat. No. 6,399,824, the entire contents of which are incorporated herein by reference for all relevant and consistent purposes.

[0073] However, in this regard, it should be noted that the substantially impermeable or substantially systemically non-bioavailable NHE-binding compounds of the present disclosure may have structures other than those exemplified above without departing from the scope of the present disclosure.For example, in various alternative embodiments, one or both of the terminal nitrogen atoms in the guanidine moiety may be replaced with one or more substituents, and / or the modified or functionalized moiety Z may be attached to the NHE-binding compound by (i) a backbone, (ii) a spacer X, or (iii) a heteroatom-containing moiety, B, generally as further illustrated in the structures provided below. [ka]

[0074] In this regard, it is further noted that, as used herein, "bioisomer" generally refers to a moiety that has similar physical and chemical properties to a guanidine moiety, which again confers biological properties to a given moiety that are similar to the guanidine moiety. (See, e.g., Ahmad, S. et al., Aminoimidazoles as See Bioisosteres of Acylguanidines: Novel, Potent, Selective and Orally Bioavailable Inhibitors of the Sodium Hydrogen Exchanger Isoform-1, Boorganic & Med. Chem. Lett., pp. 177-180 (2004), the entire contents of which are incorporated herein by reference for all relevant and consistent purposes.

[0075] As described in further detail below, known NHE-binding small molecules or species that can serve as suitable starting materials (for modification or functionalization to render the small molecule substantially impermeable or substantially systemically non-bioavailable, and / or for use in pharmaceutical preparations) can be generally organized into a number of subsets, such as, for example, the following: [ka] wherein the terminal ring (or "R" in the case of non-acyl guanidines) represents the backbone or support moiety, the guanidine moiety (or the substituted heterocycle, more specifically the piperidine ring, in the case of non-guanidine inhibitors) represents B, and X is an acyl moiety, or -AB-acyl- moiety (or a bond in the case of non-acyl guanidines and non-guanidine inhibitors). (See, e.g., Lang, HJ, "Chemistry of NHE Inhibitors" in See The Sodium-Hydrogen Exchanger, Harmazyn, M., Avkiran, M. and Fliegel, L., Eds., Kluwer Academic Publishers 2003. See also B. Masereel et al., An Overview of Inhibitors of Na+ / H+ Exchanger, European J. of Med. Chem., 38, pp. 547-554 (2003), the entire contents of which are incorporated herein by reference for all relevant and consistent purposes. Without being bound to any particular theory, it has been proposed that guanidine groups, or acylguanidine groups, or charged guanidine or acylguanidine groups (or in the case of non-guanidine inhibitors, heterocyclic or other functional groups that can reproduce the molecular interactions of the guanidinyl functional group, including but not limited to the protonated nitrogen atom in the piperidine ring) at physiological pH may mimic sodium ions at the binding sites of exchangers or antiporters (see, e.g., Vigne et al., J. Biol. Chem. 1982, 257, 9394).

[0076] Although the heteroatom-containing moiety may be capable of forming a positive charge, this should not be understood or interpreted as requiring that the entire compound has a net positive charge, or that it only has a single positively charged moiety therein, or that the heteroatom-containing moiety therein is even capable of forming a positive charge in all cases. Rather, in various alternative embodiments, the compound may have no charged moieties therein, or may have multiple charged moieties therein (which may have positive charges, negative charges, or combinations thereof). Furthermore, it should be understood that the entire compound may have a net neutral charge, a net positive charge, or a net negative charge.

[0077] In this regard, it should be noted that the U.S. patents and U.S. published applications cited above or elsewhere in this specification are hereby incorporated by reference in their entireties for all relevant and consistent purposes.

[0078] In addition to the structures exemplified above and elsewhere herein, it should be noted that bioisosteric replacements of guanidine or acylguanidine can also be used. Potentially viable bioisosteric "guanidine replacements" identified thus far have 5- or 6-membered heterocycles with similar donor / acceptor and pKa patterns as guanidine or acylguanidine (see, for example, Ahmad, S. et al., Aminoimidazoles as Bioisosteres of Acylguanidines: Novel, Potent, Selective and Orally Bioavailable Inhibitors of the Sodium Hydrogen Exchanger Isoform-1, Boorganic & Med. Chem. Lett., pp. 177-180 (2004) (the entire contents of which are incorporated herein by reference for all relevant and consistent purposes)), including the following: [ka]

[0079] The above bioisostere embodiments (i.e., the above group of structures) correspond to "B" in the structure of formula (II) in which the dashed bond is attached to "X" (e.g., the acyl moiety, or alternatively, the bond linking the bioisostere to the backbone), and the bond to Z in formula (III) is not shown here.

[0080] It should be noted that in many of the structures illustrated herein, not all of the various linkages or bonds are shown in all examples. For example, in one or more of the structures illustrated above, the bond or connection between the NHE-binding small molecule and the modifying or functionalizing moiety Z is not necessarily shown. However, this should not be seen in a limiting sense. Rather, it should be understood that the NHE-binding small molecule is bound or connected to Z in some way (e.g., by some type of bond or linker), such that the resulting NHE-Z molecule is suitable for use (i.e., substantially impermeable in the GI tract or substantially systemically non-bioavailable). Alternatively, Z may be incorporated into the NHE-binding small molecule, for example, by positioning it between the guanidine moiety and the backbone.

[0081] It is further noted that for substantially impermeable or substantially systemically non-bioavailable NHE-binding compounds and / or NHE-binding small molecules suitable for modification or functionalization according to the present disclosure, numerous structures are provided herein so that they are substantially impermeable or substantially systemically non-bioavailable. Many structures may allow various identifiers (e.g., atom identifiers in a chain or ring, identifiers of substituents on a ring or chain, etc.) to be used more than once. Thus, identifiers in one structure should not be assumed to have the same meaning in different structures unless otherwise stated (e.g., "R1" in one structure may or may not be identical to "R1" in another structure). It is further noted that in one or more of the structures further exemplified herein below, specific details of the structures including one or more of the identifiers therein may be provided in the cited references (the contents of which are specifically incorporated herein by reference for all relevant and consistent purposes).

[0082] Small molecules suitable for use (i.e., suitable for use as a substantially bioavailable compound and suitable for modification or functionalization to produce a substantially systemically non-bioavailable compound) include those exemplified below. In this regard, it should be noted that the binding or linking to Z (i.e., modification or functionalization that renders the small molecule substantially impermeable or substantially non-systemically bioavailable) is not specifically indicated. As stated, the Z moiety may be attached to or included within the small molecule at essentially any site or position that does not interfere (e.g., does not sterically interfere) with the ability of the resulting compound to effectively bind to the NHE countertransport of interest. More specifically, Z may be attached to substantially any site on the NHE-binding small molecule, for example, Z replaces all or a portion of the substituents originally or originally present thereon and as exemplified below, provided that the site of introduction of the Z moiety does not substantially adversely affect its NHE-binding activity. However, in one particular embodiment, the bond or linkage extends from Z to a site on the small molecule that effectively positions the point of attachment far away (e.g., based on the number of intervening atoms or bonds) from the atom(s) present in the resulting compound that effectively acts as a sodium ion mimetic (e.g., the atom(s) capable of forming a cation under physiological pH conditions). In a preferred embodiment, the bond or linkage extends from Z to a site in a ring, more preferably an aromatic ring within the small molecule that serves as the backbone.

[0083] In view of the foregoing, in one particular embodiment, the following small molecules disclosed in U.S. Patent Application No. 2005 / 0054705 (the entire contents of which (and in particular the text of pages 1-2 therein) are incorporated by reference herein for all relevant and consistent purposes) may be suitable for use or modification in accordance with the present disclosure (e.g., modified to be linked to or include Z, such that the resulting NHE-Z molecule is substantially impermeable or substantially systemically non-bioavailable): [ka]

[0084] The variables in the structure are defined in the cited patent applications, the details of which are incorporated herein by reference. In one particularly preferred embodiment, R6 and R7 are halogen (e.g., Cl), R5 is lower alkyl (e.g., CH3), R1-R4 are H, and the compound has, for example, the following structure: [ka]

[0085] In yet another specific embodiment, the following small molecules disclosed in Canadian Patent Application No. 2,241,531 (or International Patent Publication No. WO 97 / 24113), the entire contents of which (and in particular pages 1-2 therein) are incorporated herein for all relevant and consistent purposes, may be suitable for use or modification in accordance with the present disclosure (e.g., modified to be linked to or contain Z, such that the resulting NHE-Z molecule is substantially impermeable or substantially systemically non-bioavailable): [ka]

[0086] The variables in the structures are defined in the cited patent applications, the details of which are incorporated herein by reference.

[0087] In yet another specific embodiment, the following small molecules disclosed in Canadian Patent Application No. 2,241,531 (or International Patent Publication No. WO 97 / 24113), the entire contents of which (and in particular page 49 therein) are incorporated herein for all relevant and consistent purposes, may be suitable for use or modification in accordance with the present disclosure (e.g., modified to be linked to or contain Z, such that the resulting NHE-Z molecule is substantially impermeable or substantially systemically non-bioavailable): [ka]

[0088] The variables in the structures are defined in the cited patent applications, the details of which are incorporated herein by reference.

[0089] In yet another specific embodiment, the following small molecules disclosed in Canadian Patent Application No. 2,241,531 (or International Patent Publication No. WO 97 / 24113), the entire contents of which (and in particular pages 118-120 and 175-177 therein) are incorporated herein for all relevant and consistent purposes, may be suitable for use or modification in accordance with the present disclosure (e.g., modified to be linked to or contain Z, such that the resulting NHE-Z molecule is substantially impermeable or substantially systemically non-bioavailable): [ka]

[0090] The variables in the structures are defined in the cited patent applications, the details of which are incorporated herein by reference.

[0091] In yet another specific embodiment, the following small molecules disclosed in Canadian Patent Application No. 2,241,531 (or International Patent Publication No. WO 97 / 24113), the entire contents of which (and in particular pages 129-131 therein) are incorporated herein for all relevant and consistent purposes, may be suitable for use or modification in accordance with the present disclosure (e.g., modified to be linked to or contain Z, such that the resulting NHE-Z molecule is substantially impermeable or substantially systemically non-bioavailable): [ka]

[0092] The variables in the structures are defined in the cited patent applications, the details of which are incorporated herein by reference. (In this regard, it should be noted that the substituent Z in the structures illustrated above should not be confused with the moiety Z that is attached to the NHE-binding small molecule in accordance with the present disclosure to effectively render the resulting "NHE-Z" molecule substantially impermeable.)

[0093] In yet another specific embodiment, the following small molecules disclosed in Canadian Patent Application No. 2,241,531 (or International Patent Publication No. WO 97 / 24113), the entire contents of which (and in particular pages 127-129 thereof) are incorporated herein for all relevant and consistent purposes, may be suitable for use or modification in accordance with the present disclosure (e.g., modified to be linked to or contain Z, such that the resulting NHE-Z molecule is substantially impermeable or substantially systemically non-bioavailable): [ka]

[0094] The variables in the structures are defined in the cited patent applications, the details of which are incorporated herein by reference. (In this regard, it should be noted that the Z in the ring of the above illustrated structures should not be confused with the moiety Z attached to the NHE-binding small molecule in accordance with the present disclosure to effectively render the resulting "NHE-Z" molecule substantially impermeable.)

[0095] In yet another specific embodiment, the following small molecules disclosed in Canadian Patent Application No. 2,241,531 (or International Patent Publication No. WO 97 / 24113), the entire contents of which (and in particular pages 134-137 therein) are incorporated herein for all relevant and consistent purposes, may be suitable for use or modification in accordance with the present disclosure (e.g., modified to be linked to or contain Z, such that the resulting NHE-Z molecule is substantially impermeable or substantially systemically non-bioavailable): [ka]

[0096] The variables in the structures are defined in the cited patent applications, the details of which are incorporated herein by reference.

[0097] In yet another specific embodiment, the following small molecules disclosed in Canadian Patent Application No. 2,241,531 (or International Patent Publication No. WO 97 / 24113), the entire contents of which (and in particular pages 31-32 and 137-139 therein) are incorporated herein for all relevant and consistent purposes, may be suitable for use or modification in accordance with the present disclosure (e.g., modified to be linked to or contain Z, such that the resulting NHE-Z molecule is substantially impermeable or substantially systemically non-bioavailable): [ka]

[0098] The variables in the structures are defined in the cited patent applications, the details of which are incorporated herein by reference.

[0099] In yet another specific embodiment, the following small molecules disclosed in Canadian Patent Application No. 2,241,531 (or International Patent Publication No. WO 97 / 24113), the entire contents of which (and in particular pages 37-45 thereof) are incorporated herein for all relevant and consistent purposes, may be suitable for use or modification in accordance with the present disclosure (e.g., modified to be linked to or contain Z, such that the resulting NHE-Z molecule is substantially impermeable or substantially systemically non-bioavailable): [ka]

[0100] The variables in the structure are defined in the cited patent applications, the details of which are incorporated herein by reference. (In this regard, it should be noted that Z in the ring structures illustrated above should not be confused with the moiety Z attached to the NHE-binding small molecule in accordance with the present disclosure to effectively render the resulting "NHE-Z" molecule substantially impermeable.)

[0101] In yet another specific embodiment, the following small molecules disclosed in Canadian Patent Application No. 2,241,531 (or International Patent Publication No. WO 97 / 24113), the entire contents of which (and in particular pages 100-102 therein) are incorporated herein for all relevant and consistent purposes, may be suitable for use or modification in accordance with the present disclosure (e.g., modified to be linked to or contain Z, such that the resulting NHE-Z molecule is substantially impermeable or substantially systemically non-bioavailable): [ka]

[0102] The variables in the structures are defined in the cited patent applications, the details of which are incorporated herein by reference (in particular, the wavy bonds indicate variable lengths or numbers of atoms therein).

[0103] In yet another specific embodiment, the following small molecules disclosed in Canadian Patent Application No. 2,241,531 (or International Patent Publication No. WO 97 / 24113), the entire contents of which (and in particular pages 90-91 therein) are incorporated herein for all relevant and consistent purposes, may be suitable for use or modification in accordance with the present disclosure (e.g., modified to be linked to or contain Z, such that the resulting NHE-Z molecule is substantially impermeable or substantially systemically non-bioavailable): [ka]

[0104] The variables in the structures are defined in the cited patent applications, the details of which are incorporated herein by reference.

[0105] In yet another specific embodiment, the following small molecules disclosed in U.S. Pat. No. 5,900,436 (or EP 0822182 B1) (the entire contents of which (and in particular column 1, lines 10-55 therein) are incorporated by reference herein for all relevant and consistent purposes) may be suitable for use or modification in accordance with the present disclosure (e.g., modified to be linked to or contain Z, such that the resulting NHE-Z molecule is substantially impermeable or substantially systemically non-bioavailable): [ka]

[0106] The variables in the structures are defined in the cited patents, the details of which are incorporated herein by reference.

[0107] In yet another specific embodiment, the following small molecules disclosed in Canadian Patent Application No. 2,241,531 (or International Patent Publication No. WO 97 / 24113), the entire contents of which (and in particular pages 35-47 therein) are incorporated herein for all relevant and consistent purposes, may be suitable for use or modification in accordance with the present disclosure (e.g., modified to be linked to or contain Z, such that the resulting NHE-Z molecule is substantially impermeable or substantially systemically non-bioavailable): [ka]

[0108] The variables in the structures are defined in the cited patent applications, the details of which are incorporated herein by reference.

[0109] In yet another specific embodiment, the following small molecules disclosed in Canadian Patent Application No. 2,241,531 (or International Patent Publication No. WO 97 / 24113), the entire contents of which (and in particular pages 154-155 thereof) are incorporated herein for all relevant and consistent purposes, may be suitable for use or modification in accordance with the present disclosure (e.g., modified to be linked to or contain Z, such that the resulting NHE-Z molecule is substantially impermeable or substantially systemically non-bioavailable): [ka]

[0110] The variables in the structures are defined in the cited patent applications, the details of which are incorporated herein by reference.

[0111] In yet another specific embodiment, the following small molecules disclosed in Canadian Patent Application No. 2,241,531 (or International Patent Publication No. WO 97 / 24113), the entire contents of which (and in particular pages 132-133 therein) are incorporated herein for all relevant and consistent purposes, may be suitable for use or modification in accordance with the present disclosure (e.g., modified to be linked to or contain Z, such that the resulting NHE-Z molecule is substantially impermeable or substantially systemically non-bioavailable): [ka]

[0112] The variables in the structures are defined in the cited patent applications, the details of which are incorporated herein by reference.

[0113] In yet another specific embodiment, the following small molecules disclosed in Canadian Patent Application No. 2,241,531 (or International Patent Publication No. WO 97 / 24113), the entire contents of which (and in particular pages 58-65 and 141-148 therein) are incorporated herein for all relevant and consistent purposes, may be suitable for use or modification in accordance with the present disclosure (e.g., modified to be linked to or contain Z, such that the resulting NHE-Z molecule is substantially impermeable or substantially systemically non-bioavailable): [ka]

[0114] The variables in the structure are defined in the cited patent applications, the details of which are incorporated herein by reference. (In this regard, it should be noted that Z in the ring structures illustrated above should not be confused with the moiety Z attached to the NHE-binding small molecule in accordance with the present disclosure to effectively render the resulting "NHE-Z" molecule substantially impermeable.)

[0115] In yet another specific embodiment, the following small molecules disclosed in U.S. Pat. Nos. 6,911,453 and 6,703,405 (the entire contents of which (and in particular the sentences in paragraphs 1-7 and 46 of 6,911,453 and paragraphs 14-15 of 6,703,405) are incorporated herein by reference for all relevant and consistent purposes) may be suitable for use or modification in accordance with the present disclosure (e.g., modified to be linked to or contain Z, such that the resulting NHE-Z molecule is substantially impermeable or substantially systemically non-bioavailable): [ka]

[0116] The variables in the structure are defined in the cited patents, the details of which are incorporated herein by reference. Particularly preferred small molecules falling within the above-mentioned structure are further exemplified below (see, for example, Example 1 of the US6,911,453 patent, the entire contents of which are specifically incorporated herein by reference). [ka]

[0117] In yet another specific embodiment, the following small molecules disclosed in U.S. Patent Publication Nos. 2004 / 0039001, 2004 / 0224965, 2005 / 0113396, and 2005 / 0020612 (the entire contents of which are incorporated by reference into this specification for all relevant and consistent purposes) may be suitable for use or modification in accordance with the present disclosure (e.g., modified to be linked to or contain Z, such that the resulting NHE-Z molecule is substantially impermeable or substantially systemically non-bioavailable): [ka]

[0118] The variables in the structures are as defined above and / or in one or more of the cited patent applications (the details of which are incorporated herein by reference) and / or as exemplified above (wherein the dashed bond indicates the point of attachment of the Y moiety to the fused heterocycle). In particular, in various embodiments, combinations of X and Y may be as follows: [ka]

[0119] In particularly preferred embodiments of the above structures, the small molecule has the following general structure: [ka] wherein R1, R2, and R3 can be the same or different, but are preferably different and are independently selected from H, NR'R'', where R' and R'' are independently selected from H and hydrocarbyl, e.g., lower alkyl, as defined elsewhere herein, and the following structures: [ka]

[0120] In further particularly preferred embodiments of the above structures, particularly preferred small molecules falling within the above structures are further exemplified below (see, for example, compound I1 on page 5 of patent application 2005 / 0020612, the entire contents of which are specifically incorporated herein by reference). [ka]

[0121] In another particularly preferred embodiment, the following small molecules disclosed in U.S. Pat. No. 6,399,824 (the entire contents of which (and in particular the sentence of Example 1 therein) are incorporated by reference herein for all relevant and consistent purposes) may be particularly suitable for use or modification in accordance with the present disclosure (e.g., modified to be linked to or contain Z, such that the resulting NHE-Z molecule is substantially impermeable or substantially systemically non-bioavailable): [ka]

[0122] In the structures, R may preferably be selected from H and (CH3)2NCH2CH2-, with H being particularly preferred in various embodiments.

[0123] In yet another specific embodiment, the following small molecules disclosed in U.S. Pat. No. 6,005,010 (and particularly paragraphs 1-3 therein) and / or U.S. Pat. No. 6,166,002 (and particularly paragraphs 1-3 therein) (the entire contents of which are incorporated by reference herein for all relevant and consistent purposes) may be suitable for use or modification in accordance with the present disclosure (e.g., modified to be linked to or contain Z, such that the resulting NHE-Z molecule is substantially impermeable or substantially systemically non-bioavailable): [ka]

[0124] The variables ("R") in the structures are defined in the cited patent applications, the details of which are incorporated herein by reference.

[0125] In yet another particularly preferred embodiment, the following small molecules disclosed in U.S. Patent Application No. 2008 / 0194621 (the entire contents of which (and in particular the sentence of Example 1 therein) are incorporated by reference herein for all relevant and consistent purposes) may be particularly suitable for use or modification in accordance with the present disclosure (e.g., modified to be linked to or contain Z, such that the resulting NHE-Z molecule is substantially impermeable or substantially systemically non-bioavailable): [ka]

[0126] The variables in the structures ("R1", "R2", and "R3") are as defined above and / or in the cited patent applications, the details of which are incorporated herein by reference.

[0127] In yet another particularly preferred embodiment, the following small molecules disclosed in U.S. Patent Application No. 2007 / 0225323 (the entire contents of which (and in particular the sentence of Example 36 therein) are incorporated by reference herein for all relevant and consistent purposes) may be particularly suitable for use or modification in accordance with the present disclosure (e.g., modified to be linked to or contain Z, such that the resulting NHE-Z molecule is substantially impermeable or substantially systemically non-bioavailable): [ka]

[0128] In yet another particularly preferred embodiment, the following small molecules disclosed in U.S. Pat. No. 6,911,453 (the entire contents of which (and in particular the sentence of Example 35 therein) are incorporated by reference herein for all relevant and consistent purposes) may be particularly suitable for use or modification in accordance with the present disclosure (e.g., modified to be linked to or contain Z, such that the resulting NHE-Z molecule is substantially impermeable or substantially systemically non-bioavailable): [ka]

[0129] In one particularly preferred embodiment of the present disclosure, the small molecule may be selected from the group consisting of: [ka]

[0130] In these structures, a bond or linkage (not shown) may extend, for example, between the core and an amine-substituted aromatic ring (first structure), a heterocyclic or aromatic ring to which it is attached, or alternatively, a chloro-substituted aromatic ring (second structure), or a difluoro-substituted aromatic ring, or a sulfonamide-substituted aromatic ring (third structure).

[0131] In one or more specific embodiments, the "NHE-Z" molecule is monovalent, i.e., the molecule contains one moiety that effectively binds to and / or modulates NHE3 and inhibits phosphate transport in the GI tract or kidney. In such embodiments, the NHE-Z molecule may be selected from one of the following structures, e.g., of formula (IV), (V), (VI), or (VII): [ka] wherein each R, R, R, R, and R is independently selected from H, halogen (e.g., Cl), -NR(CO)R, -(CO)NR, -SO-NR, -NRSO, -NR, -OR, -SR, -O(CO)NR, -NR(CO)OR, and -NRSONR; wherein R and R are independently selected from H or Z; wherein Z is selected from substituted or unsubstituted hydrocarbyl, heterohydrocarbyl, polyalkylene glycol, and polyol; and wherein the substituents thereon are selected from hydroxyl, amine, amidine, carboxylate, phosphonate, sulfonate, sulphon ... R4 is selected from H, C1-C7 alkyl, or Z, where Z is selected from substituted or unsubstituted hydrocarbyl, heterohydrocarbyl, polyalkylene glycol and polyol, where the substituents thereon are selected from hydroxyl, amine, amidine, carboxylate, phosphonate, sulfonate, and guanidine, R6 is absent or selected from H and C1-C7 alkyl, Ar1 and Ar2 independently represent an aromatic ring or, alternatively, a heteroaromatic ring in which one or more of the carbon atoms are replaced with an N, O or S atom; [ka] wherein each R, R, R, and R is independently selected from H, -NR(CO)R, -(CO)NR, -SO-NR, -NRSO, -NR, -OR, -SR, -O(CO)NR, -NR(CO)OR, and -NRSONR; wherein R and R are independently selected from H or Z; wherein Z is selected from substituted or unsubstituted hydrocarbyl, heterohydrocarbyl, polyalkylene glycol, and polyol; wherein the substituents thereon are selected from hydroxyl, amine, amidine, carboxylate, phosphonate, sulfonate, and guanidine, optionally linked to the ring Ar by a heterocyclic linker; 12 is independently selected from H and R7, where R7 is as defined above, and R 10 and R 11 is, if present, independently selected from H and C1-C7 alkyl, and Ar1 and Ar2 independently represent an aromatic ring or, alternatively, a heteroaromatic ring in which one or more of the carbon atoms are replaced by an N, O or S atom; [ka] wherein each X is a halogen atom, which may be the same or different; R1 is selected from -SO2-NR7R8, -NR7(CO)R8, -(CO)NR7R8, -NR7S02R8, -NR7R8, -OR7, -SR7, -O(CO)NR7R8, -NR7(CO)OR8, and -NR7S02NR8; wherein R7 and R8 are independently selected from H or Z; wherein Z is selected from substituted or unsubstituted hydrocarbyl, heterohydrocarbyl, polyalkylene glycol, and polyol; wherein the substituents thereon are selected from hydroxyl, amine, amidine, carboxylate, phosphonate, sulfonate, and guanidine; R3 is selected from H or R7; wherein R7 is as described above; and R 13 is selected from substituted or unsubstituted C1-C8 alkyl, R2 and R 12 is independently selected from H or R7, where R7 is as defined above, and R10 and R 11は , if present, are independently selected from H and C1-C7 alkyl, Ar1 represents an aromatic ring or, alternatively, a heteroaromatic ring in which one or more of the carbon atoms are replaced with an N, O or S atom, and Ar2 represents an aromatic ring or, alternatively, a heteroaromatic ring in which one or more of the carbon atoms are replaced with an N, O or S atom.

[0132] In one particular embodiment of the structure of formula (V), one of R1, R2, and R3 is connected to ring Ar1, and / or R5 is connected to ring Ar2 by a heterocyclic linker having the following structure: [ka] In the formula, R represents R1, R2, R3, or R5 attached thereto.

[0133] In another particular embodiment, the NHE-Z molecule of the present disclosure may have the structure of formula (IV): [ka] wherein each R, R, R, R, and R is independently selected from H, halogen, NR(CO)R, -(CO)NR, -SO-NR, -NRSO, -NR, -OR, -SR, -O(CO)NR, -NR(CO)OR, and -NRSONR; wherein R and R are independently selected from H or Z; wherein Z is selected from a substituted hydrocarbyl, heterohydrocarbyl, or polyol, and / or a substituted or unsubstituted polyalkylene glycol; and wherein the substituents thereon are selected from phosphinate, phosphonate, phosphonoamidate, R4 is selected from H or Z, where Z is a substituted or unsubstituted hydrocarbyl, heterohydrocarbyl, polyalkylene glycol and polyol, where the substituents thereon are selected from hydroxyl, amine, amidine, carboxylate, phosphonate, sulfonate, and guanidine, R6 is selected from -H and C1-C7 alkyl, and Ar1 and Ar2 independently represent an aromatic ring or, alternatively, a heteroaromatic ring in which one or more of the carbon atoms are replaced with an N, O or S atom.

[0134] As mentioned above, certain embodiments relate to NHE-binding small molecules that are structurally modified or functionalized (by attachment or inclusion of a moiety Z) to alter their physicochemical properties, and more particularly, the physicochemical properties of the NHE-Z molecule, thereby rendering it substantially impermeable or substantially systemically non-bioavailable. In one particular embodiment, and as further detailed elsewhere herein, the NHE-Z compound may be multivalent (i.e., an oligomeric, dendrimeric, or polymeric moiety), Z may in this embodiment be generally referred to as the "core" moiety, to which the NHE-binding small molecule may be directly or indirectly bound (by a linking moiety), and the multivalent compound may have, for example, one of the following general structures of formulae (VIII), (IX), and (X): [ka] where the core (or Z) and NHE are as defined above, L is a bond or linker as further defined elsewhere herein, and E and n are both integers equal to or greater than 1. However, in various alternative embodiments, the NHE-binding small molecule may be made substantially impermeable or substantially systemically non-bioavailable by forming a polymeric structure from multiple NHE-binding small molecules, which may be the same or different (connected or linked by a series of linkers L, which may also be the same or different), such that the compound has, for example, the structure of formula (XI): [ka] wherein core (or Z) and NHE are as defined above, L is a bond or linker as further defined elsewhere herein, and m is an integer equal to or greater than 0 or 1. In this embodiment, the physicochemical properties of the NHE-binding small molecule, particularly the molecular weight or polar surface area, are modified (e.g., increased) by linking a series of NHE-binding small molecules together to make them substantially impermeable or substantially systemically non-bioavailable. In these or further alternative embodiments, the multivalent compound may be in dimeric, oligomeric, or polymeric form, e.g., Z or core is a backbone that is linked (e.g., by a linker) to multiple NHE-binding small molecules. Such compounds may, for example, have the structure of formula (XIIA) or (XIIB): [ka] wherein L is a linking moiety, NHE is an NHE-binding small molecule, each NHE is as described above and in further detail below, and n is a non-zero integer (i.e., an integer greater than or equal to 1).

[0135] The core moiety has one or more attachment sites to which the NHE-binding small molecule is attached, preferably covalently attached, via a bond or linker L. The core moiety can generally be anything (e.g., an atom, a small molecule, etc.) that serves to render the entire compound substantially impermeable or substantially systemically non-bioavailable, but in one or more preferred embodiments is an oligomeric, dendrimeric, or polymeric moiety, in each case having two or more attachment sites to L (and thus the NHE-binding small molecule). The combination of the core and the NHE-binding small molecule (i.e., the NHE-Z molecule) can have physicochemical properties that render the entire compound substantially impermeable or substantially systemically non-bioavailable.

[0136] In this regard, it should be noted that the repeating units of formula (XIIA) and (XIIB) generally encompass the repeating units of various polymeric embodiments, which may be produced by any of the methods referred to herein. It should be noted that in each polymer, or more generally in a multivalent embodiment, each repeating unit may be the same or different, and may or may not be linked to the NHE-binding small molecule by a linker (which, if present, may be the same or different). In this regard, it should be noted that as used herein, "multivalent" refers to a molecule having multiple (e.g., 2, 4, 6, 8, 10, or more) NHE-binding moieties therein.

[0137] The above-mentioned embodiments are further exemplified herein below. For example, the following first representation of an exemplary oligomeric compound, in which various portions of the compound corresponding to the structure of formula (X) are identified, is intended to provide a broad context for the disclosure provided herein. Note that while each "NHE" portion (i.e., NHE small molecule) in the following structure is the same, it is within the scope of the present disclosure that each is independently selected and may be the same or different. In the following example, the linker portion is a polyethylene glycol (PEG) motif. PEG derivatives are advantageous, in part, due to their aqueous solubility, which may help to avoid hydrophobic collapse (intramolecular interactions of hydrophobic motifs that may occur when hydrophobic molecules are exposed to an aqueous environment) (see, for example, Wiley, RA; Rich, DH Medical Research Reviews 1993, 13(3), 327-384). The core portion exemplified below is also intended to provide a broad context for the disclosure provided herein, in which it is a core-(L-NHE) n This is advantageous because it provides some rigidity to the molecule, allowing for increased distance between the NHE-bound compounds while minimally increasing rotational freedom. [ka]

[0138] In alternative embodiments (eg, Formula (XI) where m=0), the structure may be, for example: [ka]

[0139] Within the multivalent NHE3 inhibitor compounds utilized for treatment according to the present disclosure, n and m (when m is not zero) may be independently selected from the range of about 1 to about 10, more preferably from about 1 to about 5, and even more preferably from about 1 to about 2. However, in alternative embodiments, n and m may be independently selected from the range of about 1 to about 500, preferably from about 1 to about 300, more preferably from about 1 to about 100, and most preferably from about 1 to about 50. In these or other specific embodiments, n and m may both be within the range of about 1 to about 50 or about 1 to about 20.

[0140] The above structure is illustrative of one embodiment of a compound utilized for administration in which absorption is limited (i.e., the compound is rendered substantially impermeable or substantially systemically non-bioavailable) by increasing the molecular weight of the NHE-binding small molecule. In an alternative approach, as described elsewhere herein, NHE-binding small molecules can be rendered substantially impermeable or substantially systemically non-bioavailable by altering, and more specifically increasing, the topological polar surface area, as further exemplified by the following structure, in which substituted aromatic rings are attached to the "backbone" of the NHE-binding small molecule. The selection of ionizable groups, such as phosphonates, sulfonates, guanidines, etc., can be particularly advantageous in preventing paracellular permeability. Carbohydrates are also advantageous, being uncharged, but which increase molecular weight minimally while significantly increasing tPSA. [ka]

[0141] In one or more of the various embodiments exemplified herein, NHE-binding small molecules suitable for use (i.e., suitable for use as substantially bioavailable compounds and suitable for modification or functionalization to render them substantially impermeable or substantially systemically non-bioavailable) include, inter alia, small molecules described as benzoylguandines, heteroaroylguandines, "spacer-extended" aroylguandines, non-acylguanidines, and acylguanidine equivalents, as discussed above and in more detail below, and / or small molecules described in, for example, US5866610, US6399824, US6911453, US6703405, US6005010, US6887870, US6737423, US7326705, US 55824691(WO94 / 026709), US6399824(WO02 / 024637), US 2004 / 0339001(WO02 / 020496), US 2005 / 0020612(WO03 / 055490), WO01 / 072742, CA 2387529(WO01 / 021582), CA 02241531(WO97 / 024113), US US2005 / 0113396 (WO03 / 051866), US2005 / 0020612, US2005 / 0054705, US2008 / 0194621, US2007 / 0225323, US2004 / 0039001, US2004 / 0224965, US2005 / 0113396, US2007 / 0135383, US2007 / 0135385, US2005 / 0244367, US2007 / 0270414, and CA 2177007 (EP0744397), the entire contents of which are incorporated herein by reference for all relevant and consistent purposes. Again, it should be noted that when NHE-binding small molecules are said to be independently selected, it is intended that the oligomeric structures represented, for example, in formulas (X) and (XI) above, may include different structures of NHE small molecules within the same oligomer or polymer.In other words, each "NHE" within a given multivalent embodiment can independently be the same as or different from other "NHE" moieties within the same multivalent embodiment.

[0142] Guanylate biclase C receptor (GC-C) agonists In some embodiments, the GC-C agonist is a peptide, optionally a bacterial heat-stable enterotoxin, guanylin, proguanylin, uroguanylin, prouroguanylin, lymphoguanylin, or a variant or analog of any of the foregoing. In one embodiment, the GC-C agonist is disclosed in WO2015 / 021358, the entirety of which is incorporated herein by reference.

[0143] In some embodiments, the GC-C agonist peptide has the amino acid sequence (I): Xaa1Xaa2Xaa3Xaa4Xaa5Cys6Cys7Xaa8Xaa9Cys 10 Cys 11 Xaa 12 Xaa 13 Xaa 14 Cys 15 Xaa 16 Xaa 17 Cys 18 Xaa 19 Xaa 20 Xaa 21 (SEQ ID NO: ___), wherein Xaa1Xaa2Xaa3Xaa4Xaa5 is Asn Ser Ser Asn Tyr (SEQ ID NO: ____) or is absent, or Xaa1 Xaa2 Xaa3 Xaa4 is absent.

[0144] In certain embodiments, Xaa5 is Asn, Trp, Tyr, Asp, or Phe.

[0145] In certain embodiments, Xaa5 is Thr or Ile.

[0146] In certain embodiments, Xaa5 is Tyr, Asp, or Trp.

[0147] In certain embodiments, Xaa8 is Glu, Asp, Gln, Gly, or Pro.

[0148] In certain embodiments, Xaa9 is Leu, Ile, Val, Ala, Lys, Arg, Trp, Tyr, or Phe.

[0149] In certain embodiments, Xaa9 is Leu, Ile, Val, Lys, Arg, Trp, Tyr, or Phe.

[0150] In certain embodiments, Xaa 12 is Asn, Tyr, Asp, or Ala.

[0151] In certain embodiments, Xaa 13 is Ala, Pro, or Gly.

[0152] In certain embodiments, Xaa 14 is Ala, Leu, Ser, Gly, Val, Glu, Gln, Ile, Leu, Lys, Arg, or Asp.

[0153] In certain embodiments, Xaa 16 is Thr, Ala, Asn, Lys, Arg, or Trp.

[0154] In certain embodiments, Xaa 17 is Gly, Pro, or Ala.

[0155] In certain embodiments, Xaa 19 is Trp, Tyr, Phe, Asn, or Leu.

[0156] In certain embodiments, Xaa 19 is Lys or Arg.

[0157] In certain embodiments, Xaa 20 Xaa 21 is AspPhe or Xaa20 is Asn or Glu, and Xaa 21 In certain embodiments, Xaa is absent. 19 Xaa 20 Xaa 21 is missing.

[0158] In certain embodiments, the GC-C agonist peptide has the amino acid sequence: Asn Ser Ser Asn Tyr Cys Cys Glu Tyr Cys Cys Asn Pro Ala Cys Thr Gly Cys Tyr (SEQ ID NO: ___), or a variant thereof having 1, 2, 3, 4, or 5 deletions, insertions, and / or substitutions. In certain embodiments, the peptide comprises the amino acid sequence: Cys Cys Glu Tyr Cys Cys Asn Pro Ala Cys Thr Gly Cys Tyr (SEQ ID NO: ___), or a variant thereof having 1, 2, 3, 4, or 5 deletions, insertions, and / or substitutions.

[0159] In certain embodiments, the GC-C agonist peptide has the amino acid sequence (III): Xaa1Xaa2Xaa3Cys4Xaa5Xaa6Xaa7Xaa8Xaa9Xaa 10 Xaa 11 Cys 12 Xaa 13 Xaa 14 Xaa 15 Xaa 16Xaa1 is Ser, Asn, Tyr, Ala, Gln, Pro, Lys, Gly, or Thr or is absent, Xaa2 is His, Asp, Glu, Ala, Ser, Asn, Gly or is absent, Xaa3 is Thr, Asp, Ser, Glu, Pro, Val, or Leu, Xaa5 is Asp, Ile, or Glu, Xaa6 is Ile, Trp, or Leu, Xaa7 is Cys, Ser, or Tyr, Xaa8 is Ala, Val, Thr, Ile, Met or is absent, Xaa9 is Phe, Tyr, Asn, or Trp, and Xaa 10 is Ala, Val, Met, Thr, or Ile, and Xaa 11 is Ala or Val, and Xaa 13 is Thr or Ala, and Xaa 14 is Gly, Ala, or Ser, and Xaa 15 is Cys, Tyr, or absent, and Xaa 16 is His, Leu, or Ser.

[0160] In some embodiments, the peptide comprises the amino acid sequence: Asn Asp Glu Cys Glu Leu Cys Val Asn Val Ala Cys Thr Gly Cys Leu (SEQ ID NO: ___), or a variant thereof having 1, 2, 3, 4, or 5 deletions, insertions, and / or substitutions. In certain embodiments, the GC-C agonist is linaclotide. In certain embodiments, the GC-C agonist is plecanatide.

[0161] Additional examples of GC-C agonist peptides can be found in, e.g., U.S. Patent Nos. 7,041,786, 7,304,036, 7,371,727, 7,494,979, 7,704,947, 7,799,897, 7,745,409, 7,772,188, 7,879, ,802, 7,910,546, 8,034,782, 8,080,526, 8,101,579, 8,114,831, 8,110,553, 8,357,775, and 8,367,800; U.S. Application Nos. 2013 / 0096071, 2013 / 0096072, 2013 / 0096073, 2013 / 0096074, 2013 / 0096075, 2013 / 0096076, 2013 / 0096077, 2013 / 0096078, 2013 / 0096079 ... No. 0190238, No. 2012 / 0040892, No. 2012 / 0040025, No. 2012 / 0213846, No. 2012 / 02894 No. 60, No. 2011 / 0118184, No. 2010 / 0152118, No. 2010 / 0048489, No. 2010 / 0120694, No. Nos. 2010 / 0261877, 2009 / 0253634, 2009 / 0192083, 2009 / 0305993, and PCT Publication Nos. WO2006 / 086653 and WO2002 / 098912, each of which is incorporated by reference in its entirety.

[0162] P2Y agonists In certain embodiments, the epithelial phosphate transport inhibitor is a P2Y agonist. In one embodiment, the P2Y agonist is selected from the compounds disclosed in Figure 4 or Figures 5A-5C of WO2015 / 021358, which are incorporated herein by reference.

[0163] A2b receptor agonists In certain embodiments, the epithelial phosphate transport inhibitor is an A2b receptor agonist. In certain embodiments, the adenosine A2b receptor agonist is selected from the compounds of Figures 6A-6C of WO2015 / 021358.

[0164] Soluble guanylate cyclase agonists In certain embodiments, the epithelial phosphate transport inhibitor is a soluble guanylate cyclase agonist. In some embodiments, the soluble guanylate cyclase agonist is selected from the compounds of Figures 9A-9L disclosed in WO2015 / 021358. Non-limiting examples of sGC agonists include Bay 41-2271, Bay 58-2667, and the compounds shown in Figures 9A-9L. Additional structures of exemplary sGC agonists, along with methods of synthesis thereof, are described in U.S. Patent No. 7,087,644 and PCT Publication No. WO No. 2013 / 101830, each of which is incorporated by reference in its entirety.

[0165] Adenylyl cyclase receptor agonists In certain embodiments, the epithelial phosphate transport inhibitor is an adenylate cyclase receptor agonist. In certain embodiments, the adenylate cyclase receptor agonist is selected from the compounds in Figure 10. In some embodiments, the imidazoline-1 receptor agonist is selected from moxonidine and the compounds in Figure 11 of WO2015 / 021358.

[0166] Adenylate cyclase agonists such as forskolin have been shown to increase cAMP-mediated duodenal bicarbonate secretion (without increasing gastric bicarbonate secretion), optionally via CFTR signaling.See, for example, Takeuchi et al., Am.J.Physiol.272(3 Pt 1):G646-53,1997.Thus, in certain embodiments, adenylate cyclase agonists inhibit or reduce phosphate uptake in the gastrointestinal tract by stimulating bicarbonate secretion into the small intestine.

[0167] In certain embodiments, the compound is an agonist of adenylate cyclase III (AC-III), optionally an agonist of one or more of the AC-III isoforms ADCY1, ADCY2, ADCY3, ADCY4, ADCY5, ADCY6, ADCY7, ADCY8, ADCY9, and / or ADCY10.

[0168] Specific examples of adenylate cyclase agonists include labdane diterpenes, such as forskolin, and analogs / derivatives thereof, including water-soluble forskolin analogs, such as colforsin (NKH477). Forskolin is a tmAC Forskolin is a diterpene compound isolated from plants that activates all mammalian tmACs except IX (mammalian sACs are insensitive to forskolin). See, for example, Kamenetsky et al., J.Mol.Biol.362:623-639, 2006. Forskolin stimulation can produce strong and long-lasting cAMP changes. See, for example, Tresguerres et al., Kidney Int.79:1277-1288, 2011. The structures of forskolin and some forskolin analogs are shown in Figure 10. Water-soluble derivatives of forskolin include those acylated at C-6 or C-7 with polar aliphatic amines. These derivatives are typically more selective for ACs with less off-target activity. See, for example, Hartzell and Budnitz, Molecular Pharmacology 41:880-888, 1992. Thus, certain embodiments involve the use of soluble forskolin analogs that selectively activate adenylate cyclase in cells lining the gastrointestinal tract.

[0169] Specific examples of forskolin analogs / derivatives include aminoalkylcarbamyl derivatives of forskolin, including 1-aminoalkylcarbamate, 9-aminoalkylcarbamate, 7-aminoalkylcarbamate, 6-aminoalkylcarbamate, 6,7-diaminoalkylcarbamate, 1,6-diaminoalkylcarbamate, 1,7-diaminoalkylcarbamate, and 1,6,7-triaminoalkylcarbamate of forskolin, which can be used as intermediates in the synthesis of forskolin derivatives.See U.S. Patent No. 5,350,864.Further examples of forskolin analogs / derivatives include 12-halogenated forskolin derivatives, including 12-chlorodesacetylforskolin, 12-chloroforskolin, 12-bromodesacetylforskolin, 12-bromodesacetylforskolin, 12-fluorodesacetylforskolin, and 12-fluoroforskolin. See U.S. Patent No. 4,871,764.

[0170] In some embodiments, the forskolin analog / derivative is 6-acetyl-7-deacetyl-forskolin, 7-deacetyl-forskolin, 7-deacetyl-6-(N-acetylglycyl)-forskolin, 7-deacetyl-7-β-hemisuccunyl-forskolin, 7-deacetyl-7-(ON-methylpiperazino)-γ-butryl-dihydrochlonde-forskolin, 7-HPP-forskolin, 6-HPP-forskolin, or colforsin daropate hydrochloride (NKH477). For example, see US Application Nos. 2011 / 0171195, 2006 / 0004090, and 2011 / 0077292; Laurenza et al., Mol Pharmacol. 32: 133-9, 1987; Lal et al., Bioorg Med Chem. 6: 2075-83, 1998; Mori et al., J.Cardiovasc.Pharmacol. 24: 310-6, 2004. For exemplary methods of synthesizing forskolin analogs, see also Levin, Tetrahedon Letters. 37: 3079-3082, 1996, and for additional examples of water-soluble forskolin analogs and methods of synthesizing them, see Lal et al., Indian J.Chemistry. 45B: 232-246, 2006. Additional structures of exemplary adenylate cyclase agonists, along with methods for their synthesis, are disclosed in U.S. Patent No. 4,954,642 and Khandelwal et al., J Med Chem. 31:1872-9, 1988. See also Cunliffe et al., Electrophoresis. 28:1913-20, 2007 for exemplary methods / assays for detecting agonist-stimulated adenylate cyclase activity. These references are incorporated by reference in their entirety.

[0171] Cholinergic agonists In certain embodiments, the epithelial phosphate transport inhibitor is a cholinergic agonist. In certain embodiments, the cholinergic agonist is selected from the compounds in Figure 12 of WO2015 / 021358. Non-limiting examples of indirect acting cholinergic agonists include acetylcholinesterase inhibitors, such as carbamates (e.g., physostigmine, neostigmine, pyridostigmine), piperidines (e.g., donepidil), edrophonium, huperzine A, ladostigil, ungelemine, lactucopicrin, tacrine, galantamine, trans-delta-9-tetrahydrocannabinol, and phosphates (e.g., isoflurophate, echothiophate, parathion, malathion). Preferably, the methods provided herein use reversible acetylcholinesterase inhibitors.

[0172] Non-limiting examples of direct acting cholinergic agonists include acetylcholine, nicotine, succinylcholine, methacholine (acetyl-β-methylcholine), McN-A-343, carbachol (carbamoylcholine), bethanechol (carbamoyl-β-methlycholine), muscarine, pilocarpine, oxotremorine, lobeline, and dimethylphenylpiperazinium.

[0173] Prostaglandin EP4 receptor agonist In certain embodiments, the epithelial phosphate transport inhibitor is a prostaglandin EP4 receptor agonist.In certain embodiments, the prostaglandin EP4 receptor agonist is selected from PGE2 or its analogue / derivative, and the compound in Figure 7 or Figure 13 of WO2015 / 021358. Non-limiting examples of prostaglandin EP4 receptor agonists include PGE2, PGE2 analogs, AE1-329, AGN205203, APS-999 Na, Cay10598(19a), CP-044519-02, CJ-023,423, EP4RAG, ER-819762, L-902688, lubiprostone, ONO-4819CD, ONO AE1-329, ONO AE1-734, PGE1-OH, TCS2510, gamma-lactam PGE analog 3, 11-deoxy-PGE1, gamma-lactam PGE analog 2a, gamma-lactam PGE analog 4. See, e.g., Konya et al., Pharmacol Ther.138:485-502,2013. Non-limiting examples of PGE2 analogs include 16,16-dimethyl PGE2, 16-16 dimethyl PGE2, p-(p-acetamidobenzamido)phenyl ester, 11-deoxy-16,16-dimethyl PGE2, 9-deoxy-9-methylene-16,16-dimethyl PGE2, 9-deoxy-9-methylene PGE2, 9-ketofluprostenol, 5-trans PGE2, 17-phenyl-omega-triol PGE2, PGE2 serinolate, and the like. PGE2 methyl ester, PGE2 methyl ester, 16-phenyltetraol PGE2, 15(S)-15-methyl PGE2, 15(R)-15-methyl PGE2, 8-iso-15-keto PGE2, 8-iso PGE2 isopropyl ester, 20-hydroxy PGE2, 11-deoxy PGEi, nocloprost, sulprostone, butaprost, 15-keto PGE2, and 19(R) hydroxy PGE2.See, for example, US Application No. 2012 / 0202288.

[0174] Further examples of prostaglandin EP4 receptor agonists include those described in U.S. Patent Application Nos. 2001 / 0056060, 2002 / 0040149, 2005 / 0164949, and 2011 / 0098481. Also, U.S. Patent Nos. 4,219,479, 4,049,582, 4,423,067, 4,474,802, 4,692,464, 4,708,963, 5,010,065, 5,013,758, 6,747,037, and 7,776,896, European Patent No. EP0084856, Canadian Patent No. 1248525, U.S. Application Nos. 2004 / 0102499, 2005 / 049227, 2005 / 228185, 2006 / 106088, 2006 / 111430, 2007 / 0010495, 2007 / 0123568, 2007 / 0123569, 200 5 / 0020686, 2008 / 0234337, 2010 / 0010222, 2010 / 0216689, 2004 / 0198701, 2004 / 02 No. 04590, No. 2005 / 0227969, No. 2005 / 0239872, No. 2006 / 0154899, No. 2006 / 0167081, No. 2006 / 0258726 No. 2006 / 0270721, No. 2009 / 0105234, No. 2009 / 0105321, No. 2009 / 0247596, No. 2009 / 0258918, No. 2009 / 0270395, 2004 / 0087624, 2004 / 0102508, 2006 / 0252799, 2009 / 0030061, 2009 Nos. 2009 / 0312388, 2009 / 0318523, 2010 / 0069457, 2010 / 0076048, 2007 / 0066618, 2004 / 0259921, 2005 / 0065133, and 2007 / 0191319, and PCT Publication Nos. WO Nos. WO 2004 / 4071428, WO 2006 / 052630, WO 2006 / 047476, WO 2006 / 058080, WO 2004 / 065365, WO 2003 / 047513, WO 2004 / 085421, WO 2004 / 085430, WO 2005 / 116010, WO 2005 / 116010, WO 2007 / 014454, WO 2006 / 080323 and WO Also included are the prostaglandin EP4 receptor agonists (along with associated synthetic methods) described in US Pat. No. 6,200,233,200 (each of which is incorporated by reference in its entirety).

[0175] Dopamine D1 agonists In certain embodiments, the epithelial phosphate transport inhibitor is a dopamine D1 agonist. In certain embodiments, the dopamine D1 agonist is selected from the compounds in Figure 14 of WO2015 / 021358. Non-limiting examples of dopamine D1 receptor agonists include dopamine (e.g., dopamine hydrochloride, NPEC-caged dopamine), dihydrexidine (e.g., dihydrexidine hydrochloride), benzazepaine, and analogs / derivatives thereof. Specific examples of dihydrexidine derivatives include A86929, dinapsoline, dinoxyline, and doxantrin, and specific examples of benzazepine derivatives include SKF81297, SKF82958, SKF38393, fenoldopam, and 6-Br-APB. Also included are the dopamine D1 receptor agonists shown in FIG.

[0176] Additional non-limiting examples of dopamine D1 receptor agonists include A68930, A77636, (R)-(-)-apomorphine hydrochloride, CY208-243, SKF89145, SKF89626, 7,8-dihydroxy-5-phenyl-octahydrobenzo[h]isoquinoline, YM435, ABT-431, NNC01-0012, SCH23390, SKF7734, SKF81297, SKF38322, SKF83959, cabergoline, fenoldopam (e.g., fenoldapam hydrochloride), bromocriptine, ropinirole, pramipexole, entacapone, tolcapone, dihexazine, IPX-750, and pergolide. Zhang et al.,Med Res Rev.29:272-94,2009, Yvonne Connolly Martin,International See also Journal of Medicinal Chemistry, vol.2011, Article ID 424535, 8 pages, 2011.doi:10.1155 / 2011 / 424535; Salmi et al., CNS Drug Rev.10:230-42, 2004; Bourne, CNS Drug Rev.7:399-414, 2001. In addition, D1 receptor agonists can be identified using standard screening methods known in the art. As a non-limiting example, a cell-based functional assay for high-throughput drug screening for dopamine D1 receptor agonists is described in Jiang et al., Acta Pharmacol Sin.26:1181-6, 2005. These references are incorporated by reference in their entirety.

[0177] Melatonin receptor agonists In certain embodiments, the epithelial phosphate transport inhibitor is a melatonin receptor agonist. In some embodiments, the melatonin receptor agonist is selected from melatonin and the compound of Figure 15 of WO2015 / 021358. Examples of melatonin receptors include MT1 and MT2 receptors. In some aspects, the melatonin receptor agonist binds to both MT1 and MT2 receptors. In some embodiments, the melatonin receptor agonist selectively binds to MT1 or MT2 receptor, for example, binds to MT2 but not significantly to MT1, or binds to MT1 but not significantly to MT2.

[0178] Melatonin receptor agonists such as melatonin have been shown to stimulate duodenal bicarbonate secretion, for example, through the action of enterocyte MT2 receptor.See, for example, Sjoblom et al., J Clin Invest.108:625-33,2001; Sjoblom and Flemstrom, J.Pineal Res.34:288-293,2003.Therefore, in certain embodiments, melatonin receptor agonists inhibit or reduce phosphate uptake in the gastrointestinal tract by stimulating bicarbonate secretion into the small intestine.

[0179] Examples of melatonin receptor agonists include melatonin (N-acetyl-5-methoxytryptamine) and melatonin analogs, which bind to and activate melatonin receptors. The general structure of melatonin includes an indole ring with a methoxy group (5-methoxy group) at position 5 and an acylaminoethyl side chain at position 3, and the two side chains contribute to binding to and activating melatonin receptors. The indole ring has been evaluated at all positions by the effect of substitution. See, for example, Rivara et al., Curr Top Med Chem. 8:954-68, 2008, and Sugen et al., Pigment Cell Research. 17:454-460, 2004.

[0180] Specific examples of melatonin receptor agonists include 2-iodomelatonin, 6-chloromelatonin, 6,7-dichloro-2-methylmelatonin, and 8-hydroxymelatonin, all of which are also used in the treatment of chronic conditions such as circadin, agomelatine, ramelteon, tasimelteon, beta-methyl-6-chloromelatonin (TIK-301 or LY156735), TAK-375, VEC-162, GR1964, and the like. In addition to 29, S20242, S23478, S24268, S25150, GW290569, BMS-214778, 8-methoxy-2-chloroacetamidotetralin, 8-methoxy-2-propionamido-tetralin, N-acetyltryptamine, 6-chloromelatonin, 2-iodomelatonin, 8-M-PDOT, and 2-phenylmelatonin, they contain a 5-methoxyindole ring as a moiety.See, for example, US Application No. 2005 / 0164987 (incorporated by reference in its entirety).Also included are the exemplary melatonin receptor (MT2) agonists shown in FIG. 15.

[0181] Methods for screening for melatonin receptor agonists are described, for example, in US Application No. 2003 / 0044909, which is incorporated by reference in its entirety.

[0182] 5HT4 agonists In certain embodiments, the epithelial phosphate transport inhibitor is a 5HT4 agonist.In some embodiments, the 5HT4 agonist is selected from serotonin and its analogs, prucalopride, metoclopramide, cleobopride, mosapride, prucalopride, renzapride, tegaserod, zacopride, norcisapride, nalonopride, and velsetrag. Non-limiting examples of 5HT4 agonists include serotonin and its analogs, BIMU-8, cisapride, cleobopride, CL033466, ML10302, mosapride, prucalopride, renzapride, RS67506, RS67333, SL650155, tegaserod, zacopride, nalonopride (ATI-7505), velsetrag (TD-5108).

[0183] In some embodiments, the 5HT4 receptor agonist or partial agonist is a substituted benzamide such as cisapride, including cisapride enantiomers ((+)cisapride and (-)cisapride), mosapride, or renzapride, individually or in combination.In some embodiments, the 5HT4 receptor agonist is an indole such as prucalopride, tegaserod, or a benzofuran derivative such as benzimidazolone. Other non-limiting examples of 5HT4 receptor agonists or partial agonists include zacopride (CAS RN 90182-92-6), SC-53116 (CAS RN 141196-99-8) and its racemate SC-49518 (CAS RN 146388-57-0), BIMU1 (CAS RN 127595-43-1), TS-951 (CAS RN 174486-39-6), ML10302 (CAS RN 13161-37-6), TS-951 ... 148868-55-7), metoclopramide, 5-methoxytryptamine, RS67506, 2-[1-(4-piperonyl)piperazinyl]benzothiazole, RS66331, BIMU8, SB 205149 (an n-butyl quaternary analog of renzapride), and indolecarbazimidamide. Also, norcisapride, a metabolite of cisapride (CAS RN 102671-04-5); mosapride citrate; the maleate form of tegaserod (CAS RN 189188-57-6); zacopride hydrochloride (CAS RN 99617-34-2); mezacopride (CAS RN 89613-77-4); SK-951 ((+-)-4-amino-N-(2-(1-azabicyclo(3.3.0)octan-5-yl)ethyl)-5-chloro-2,3-dihydro-2-methylbenzo[b]furan-7-carboxamide hemifumarate); ATI-7505, a cisapride analog; and SDZ-216-454, a selective 5HT4 receptor agonist that stimulates cAMP formation in a concentration-dependent manner (e.g., Markstein et al. al., Naunyn-Schmiedebergs Arch Pharmacol. 359:454-9, 1999); SC-54750, or aminomethylazaadamantane; Y-36912, or 4-amino-N-[1-[3-(benzylsulfonyl)propyl]piperidin-4-ylmethyl]-5-chloro-2-methoxybenzamide (Sonda et al., Bioorg Med. Chem. 12:2737-47, 2004); TKS159, or 4-amino-5-chloro-2-methoxy-N-[(2S,4S)-1-ethyl-2-hydroxymethyl-4-pyrrolidinyl]benzamide; RS67333, or 1-(4-amino-5-chloro-2-methoxyphenyl)-3-(1-n-butyl-4-piperidinyl)-1-propanone; KDR-5169, or 4-amino-5-chloro-N-[1-(3-fluoro-4-methoxybenzyl)piperidin-4-yl]-2-(2-hydroxyethoxy)benzamide hydrochloride dihydrate (see Tazawa, et al., Eur J Pharmacol. 434:169-76, 2002); SL65.0155, or 5-(8-amino-7-chloro-2,3-dihydro-1,4-benzodioxin-5-yl)-3-[1-(2-phenylethyl)-4-piperidinyl]-1,3,4-oxadiazol-2(3H)-one monohydrochloride; and Y-34959, or 4-amino-5-chloro-2-methoxy-N-[1-[5-(1-methylindol-3-ylcarbonylamino)pentyl]piperidin-4-ylmethyl]benzamide.

[0184] Additional examples of 5HT4 receptor agonists and partial agonists include metoclopramide (CAS RN 364-62-5), 5-methoxytryptamine (CAS RN 608-07-1), RS67506 (CAS RN 168986-61-6), 2-[1-(4-piperonyl)piperazine]benzothiazole (CAS RN 155106-73-3), RS66331 (see Buccafusco et al., Pharmacology. 295:438-446, 2000); BIMU8 (endo-N-8-methyl-8-azabicyclo[3.2.1]oct-3-yl)-2,3-dehydro-2-oxo-3-(prop-2-yl)-1H-benzimidazole-1-carboxamide), or SB 205149 (an n-butyl quaternary analog of renzapride). Also included are metoclopramide dihydrochloride (CAS RN 2576-84-3), metoclopramide dihydrochloride (CAS RN 5581-45-3), and metoclopramide hydrochloride (CAS RN Also included are compounds related to metoclopramide, such as 54143-57-6 or 5432-21-5. See, for example, U.S. Application No. 2009 / 0325949; De Maeyer et al., Neurogastroenterology and Motility. 20:99-112, 2008; Manabe et al., Expert Opin Investig Drugs. 19:765-75, 2010; Tack et al., Alimentary Pharmacology & Ther. 35:745-767, 2012. These references are incorporated by reference in their entirety.

[0185] Atrial natriuretic peptide receptor agonists In certain embodiments, the epithelial phosphate transport inhibitor is an atrial natriuretic peptide receptor agonist. In some embodiments, the atrial natriuretic peptide receptor agonist is selected from the group consisting of Ser Leu Arg Arg Ser Ser Cys Phe Gly Gly Arg Ile Asp Arg Ile Gly Ala Gln Ser Gly Leu Gly Cys Asn Ser Phe Arg Tyr (SEQ ID NO: ), Cys Phe Gly Gly Arg Ile Asp Arg Ile Gly Ala Gln Ser Gly Leu Gly Cys (SEQ ID NO: ), and Ser Ser Cys Phe Gly Gly Arg Ile Asp Arg Ile Gly Ala Gln Ser Gly Leu Gly Cys Asn Ser Phe Arg (SEQ ID NO: __), including variants thereof having 1, 2, 3, 4, or 5 deletions, insertions, and / or substitutions. In certain embodiments, the NP receptor agonist comprises, consists, or consists essentially of the atrial natriuretic peptide amino acid sequence: Ser Leu Arg Arg Ser Ser Cys Phe Gly Gly Arg Ile Asp Arg Ile Gly Ala Gln Ser Gly Leu Gly Cys Asn Ser Phe Arg Tyr (SEQ ID NO: __), including active variants thereof having 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 deletions, insertions, and / or substitutions. Specific examples of deletion mutants include those with the sequences: Cys Phe Gly Gly Arg Ile Asp Arg Ile Gly Ala Gln Ser Gly Leu Gly Cys (SEQ ID NO: __), and Ser Ser Cys Phe Gly Gly Arg Ile Asp Arg Ile Gly Ala Gln Ser Gly Leu Gly Cys Asn Ser Phe Arg (SEQ ID NO: ). As described elsewhere herein, such peptides can be composed of any combination of natural and unnatural amino acids.

[0186] Dehydratase inhibitors In certain embodiments, the epithelial phosphate transport inhibitor is a carbonic anhydrase inhibitor. In certain embodiments, the carbonic anhydrase inhibitor is selected from the compounds in Figure 17 of WO2015 / 021358.

[0187] Phosphodiesterase inhibitors In certain embodiments, the epithelial phosphate transport inhibitor is a phosphodiesterase inhibitor. In certain embodiments, the phosphodiesterase inhibitor is selected from the compounds in Figure 18 of WO2015 / 021358. In some embodiments, the DRA agonist is selected from Figures 21A-B of WO2015 / 021358. Non-limiting example PDE inhibitors can include those disclosed in the following patent applications and patents: DE1470341, DE2108438, DE2123328, DE2305339, DE2305575, DE2315801, DE2402908, DE2413935, DE2451417, DE2459090, DE2646469, DE2727481, DE2825048, DE2837161, DE2845220, DE2847621 , DE2934747, DE3021792, DE3038166, DE3044568, DE3142982, DE1116676, DE2162096, EP000718, EP0008408, EP0010759 , EP0059948, EP0075436, EP0096517, EP0112987, EP0116948, EP0150937, EP0158380, EP0161632, EP0161918, EP0167121 , EP0199127, EP0220044, EP0247725, EP0258191, EP0272910, EP0272914, EP0294647, EP0300726, EP0335386, EP035778 8, EP0389282, EP0406958, EP0426180, EP0428302, EP0435811, EP0470805, EP0482208, EP0490823, EP0506194, EP051186 5, EP0527117, EP0626939, EP0664289, EP0671389, EP0685474, EP0685475, EP0685479, EP0293063, EP0463756, EP0482208, EP0579496, EP0667345, EP0163965, EP0393500, EP0510562, EP0553174, JP92234389, JP94329652, JP95010875, U.S. Patent Nos. 4,963,561, 5,141,931, and 6,331,543, International Patent Application Publication Nos. WO9117991, WO9200968, WO9212961, WO9307146, WO9315044, WO9315045, WO9318024, WO9319068, WO9319720, WO9319747, WO9319749, WO9319751, WO9325517, and WO940246 5, WO9406423, WO9412461, WO9420455, WO9422852, WO9425437, WO9427947, WO9500516, WO9501980, WO9503794, WO9504045, WO9504046, WO9505386, WO9508534, WO9509623, WO95 09624, WO9509627, WO9509836, WO9514667, WO9514680, WO9514681, WO9517392, WO951739 No. 9, WO9519362, WO9522520, WO9524381, WO9527692, WO9528926, WO9535281, WO9535282, Nos. WO9600218, WO9601825, WO9602541, WO9611917, WO9307124, WO9501338, and WO9603399, and U.S. Application No. 2005 / 0004222 (including Formulas I-XIII and those disclosed in paragraphs 37-39, 85-0545, and 557-577), each of which is incorporated by reference in its entirety.

[0188] Examples of PDE5 inhibitors include RX-RA-69, SCH-51866, KT-734, vesnarinone, zaprinast, SKF-96231, ER-21355, BF / GP-385, NM-702, and sildenafil (Viagra®). Examples of PDE4 inhibitors include RO-20-1724, MEM1414 (R1533 / R1500, Pharmacia Roche), denbufylline, rolipram, oxagrelate, nitraquazone, Y-590, DH-6471, SKF-94120, motapizone, lixazinone, indolidan, olprinone, atizolam, KS-506-G, zipamphylline, BMY-43351, atizolam, allofylline, filaminast, PDB-093, UCB-29646, CDP-840, SKF-107806, piclamilast, RS-17597, RS-2 5344-000, SB-207499, tibenelast, SB-210667, SB-211572, SB-211600, SB-212066, SB-212179, GW-3600, CDP-840, mopidamole, anagrelide, ibudilast, amrinone, pimobendan, cilostazol, quazinone, and N-(3,5-dichloropyrid-4-yl)-3-cyclopropylmethoxy 4-difluoromethoxybenzamide. Examples of PDE3 inhibitors include sulmazole, ampizon, cilostamide, carbazeran, piroximone, imazodan, CI-930, ciguazodan, azibendan, saterinone, SKF-95654, SDZ-MKS-492, 349-U-85, emoladan, EMD-53998, EMD-57033, NSP-306, NSP-307, revidinone, NM-702, WIN-62582 and WIN-63291, enoximone, and milrinone. Examples of PDE3 / 4 inhibitors include benafentrin, trequinsin, ORG-30029, zardaverine, L-686398, SDZ-ISQ-844, ORG-20241, EMD-54622, and trafentrin.Other examples of PDE inhibitors include cilomilast, pentoxifylline, roflumilast, tadalafil (Cialis®), theophylline, vardenafil (Levitra®), and zaprinast (PDE5 specific).

[0189] formulation For the purpose of administration, the compound of the present invention may be administered to a patient or subject as a raw chemical or may be formulated as a pharmaceutical composition. The pharmaceutical composition of the present invention generally comprises the compound of the present invention and a pharma- ceutically acceptable carrier, diluent, or excipient. The compound is present in the composition in an amount that is effective for treating the specific disease or condition of interest, as described herein, and preferably has an acceptable toxicity to the subject. The activity of the compound can be determined by those skilled in the art, for example, as described in the following examples. The appropriate concentration and dosage can be easily determined by those skilled in the art.

[0190] The compounds or compositions of the invention may be used in methods for treating essentially any disease or other condition in a subject that would benefit from inhibition of phosphate uptake in the gastrointestinal tract and / or kidney.

[0191] For example, and by way of illustration and not limitation, kidney damage reduces the production and activity of renal 1-alpha hydroxylase, resulting in a decline in 1,25-dihydroxyvitamin D. Decreased vitamin D levels limit calcium absorption in the gastrointestinal tract, resulting in a decline in serum calcium levels. The combination of lower 1,25-dihydroxyvitamin D and lower serum calcium synergistically stimulates parathyroid tissue to produce and secrete PTH. Loss of nephrons also impairs Pi excretion, but serum P levels are actively protected by the action of PTH and FGF-23 and by higher serum P levels, which significantly enhance urinary PO4 excretion. However, the tubular action of PTH and FGF-23 is unable to maintain serum P levels in the face of continued nephron loss. As renal insufficiency progresses to approximately 40-50% loss of renal function, the reduced amount of functioning renal tissue does not allow for the excretion of the full amount of ingested phosphate required to maintain homeostasis. As a result, hyperphosphatemia develops. Furthermore, elevated serum P levels impede renal 1-alpha hydroxylase activity, further suppressing activated vitamin D levels and further stimulating PTH, resulting in secondary hyperparathyroidism (sHPTH).

[0192] However, phosphorus imbalance does not necessarily equate to hyperphosphatemia. Rather, the majority of CKD patients not yet undergoing dialysis are normophosphatemic, but have a positive phosphorus balance, with excess phosphorus being placed in the blood vessels in the form of ectopic calcification, e.g., intimal-localized vascular calcification. Clinically, CKD patients have elevated FGF-23 levels that are significantly associated with worsening renal function and reduced calcitriol levels, and it has been hypothesized that the synthesis of FGF-23 is induced by the presence of excess P in the body following renal failure.

[0193] Additionally, an unrecognized effect on cardiovascular disease is postprandial phosphatemia, i.e., serum P fluctuations secondary to dietary intake. Furthermore, studies have investigated the acute effects of phosphorus loading on endothelial function in vitro and in vivo. Exposure of bovine aortic endothelial cells to phosphorus loading increased the production of reactive oxygen species and reduced nitric oxide, a known vasodilator. In the acute P loading study in healthy volunteers mentioned above, it was found that flow-mediated vasodilation was inversely related to postprandial serum P (Shuto et al., 2009b, J. Am. Soc. Nephrol., v. 20, no. 7, p. 1504-1512).

[0194] Thus, in certain embodiments, the compounds or compositions of the invention may be used in a method selected from one or more of the following: methods for treating hyperphosphatemia, optionally postprandial hyperphosphatemia, methods for treating renal disease (e.g., chronic kidney disease (CKD), end stage renal disease (ESRD)), methods for reducing serum creatinine levels, methods for treating proteinuria, methods for delaying time to renal replacement therapy (RRT) such as dialysis, methods for reducing FGF23 levels, methods for reducing the hyperphosphatemic effects of active vitamin D, methods for alleviating hyperparathyroidism, such as secondary hyperparathyroidism, methods for reducing serum parathyroid hormone (PTH or iPTH), methods for reducing interdialytic weight gain (IDWG), and optionally postprandial serum phosphate. Methods for improving salt-induced endothelial dysfunction, methods for reducing vascular calcification or attenuating intimal localized vascular calcification, methods for reducing urinary phosphorus (e.g., enterally administering a GI-acting substantially systemically non-bioavailable compound), methods for increasing urinary phosphorus (e.g., administering a substantially systemically bioavailable compound, administering a substantially systemically non-bioavailable compound via a route other than enteral administration), methods for normalizing serum phosphorus levels, methods for reducing phosphate load in elderly patients, methods for reducing dietary phosphate intake, methods for reducing postprandial calcium absorption, methods for reducing renal hypertrophy, methods for reducing cardiac hypertrophy, and methods for treating obstructive sleep apnea.

[0195] Hyperphosphatemia refers to a condition in which there is an elevated level of phosphate in the blood. The average serum phosphorus in human adults typically ranges from about 2.5 to 4.5 mg / dL (about 0.81 to 1.45 mmol / L). Levels are often about 50% higher in infants and about 30% higher in children due to growth hormone effects. Accordingly, certain methods include treating an adult human patient with hyperphosphatemia, where the patient has a serum phosphorus level of about or at least about 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, or 5.5 mg / dL. In some embodiments, the treatment reduces serum phosphate concentration or levels in a hyperphosphatemic subject to about 150%, 145%, 140%, 135%, 130%, 125%, 120%, 115%, 110%, 105%, or 100% (normalized) of normal serum phosphate levels (e.g., 2.5-4.5 mg / dL or 0.81-1.45 mmol / L for adults). In some embodiments, the treatment regimen provides for and / or includes monitoring of phosphate levels such that phosphate levels remain within the range of about 2.5-4.5 mg / dL (about 0.81-1.45 mmol / L). Also included are methods of treating a pediatric or adolescent human patient, wherein the patient has a serum phosphorus level of about or at least about 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, or 8.0 mg / dL. As noted herein, in these and related embodiments, administration of a compound or composition described herein may reduce serum phosphorus levels in a subject by about or at least about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 200%, or more.

[0196] Certain embodiments relate to a method for treating chronic kidney disease (CKD), a condition characterized by progressive loss of kidney function.Common causes of CKD include diabetes, hypertension, and glomerulonephritis.Therefore, certain methods include treating CKD subjects, which optionally also have one or more of the above conditions.

[0197] In some embodiments, the subject is administered 60 mL / min / 1.73 m for about 3 months, regardless of whether or not the subject also exhibits renal impairment. 2 A person is classified as having CKD if he or she has a glomerular filtration rate (GFR) of less than about 60, 55, 50, 45, 40, 30, 35, 20, 25, 20, 15, or 10 mL / min / 1.73 m. Thus, certain methods include 2 This includes treating a subject with a GFR (e.g., an initial GFR before treatment) that is about or at least about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 200%, or more.

[0198] CKD is most often characterized according to stages: 1, 2, 3, 4, and 5. Stage 1 CKD is characterized by kidney damage and kidney failure at approximately 90 mL / min / 1.73 m 2 Stage 2 CKD includes subjects with normal or relatively high GFR, or above 60–89 mL / min / 1.73 m. Stage 3 CKD includes subjects with normal or relatively high GFR, or above 60–89 mL / min / 1.73 m. 2 Stage 3 CKD is defined as kidney damage and a GFR of approximately 30–59 mL / min / 1.73 m 2 Stage 4 CKD is defined as kidney damage and a GFR of approximately 15–29 mL / min / 1.73 m 2 Stage 5 CKD includes subjects with established renal failure and a GFR of approximately 15 mL / min / 1.73 m 2The subject includes a subject with a GFR of less than 500 mg / kg. Stage 5 CKD is also called end-stage renal disease (ESRD). Thus, in certain methods, the subject has one or more of stage 1, 2, 3, 4 or 5 CKD and its associated clinical characteristics (e.g., defined GFR, kidney damage). In some embodiments, the subject has any one or more of ESRD and its associated clinical characteristics as described herein and known in the art.

[0199] CKD can be characterized according to the affected part of the kidney.For example, in certain embodiments, CKD includes vascular-related CKD, including macrovascular disease such as bilateral renal artery stenosis, and small vessel disease such as ischemic nephropathy, hemolytic uremic syndrome, and vasculitis.In certain embodiments, CKD includes glomerular-related CKD, including primary glomerular disease such as focal segmental glomerulosclerosis and IgA nephritis, and secondary glomerular disease such as diabetic nephropathy and lupus nephritis.Also includes tubulointerstitial-related CKD, including polycystic kidney disease, drug and toxin-induced chronic tubulointerstitial nephritis, and reflux nephropathy.Therefore, a certain subject who is treated for CKD may have one or more of the above-mentioned CKD-related characteristics.

[0200] Certain embodiments relate to methods for treating subjects with kidney damage or one or more symptoms / clinical signs of kidney damage.Examples of kidney damage (e.g., CKD-related kidney damage) and its associated symptoms include pathological abnormalities and markers of damage, including abnormalities identified in blood tests (e.g., high blood or serum creatinine levels, creatinine clearance), urinalysis (e.g., proteinuria), and / or imaging studies.

[0201] Creatinine is a breakdown product of creatine phosphate in muscle and provides an easily measured and useful indicator of kidney health. Normal human reference ranges for blood or serum creatinine range from about 0.5 to 1.0 mg / dL (about 45 to 90 μmol / L) for women and about 0.7 to 1.2 mg / dL (about 60 to 110 μmol / L) for men. Thus, a particular subject for treatment according to the methods described herein may have a blood or serum creatine level that is about 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0 mg / dL or greater (e.g., initially prior to treatment). In these and related embodiments, administration of a compound or composition described herein may reduce overall blood or serum creatinine levels in a subject by about or at least about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, or 200% or more.

[0202] Creatinine clearance rate (C Cr Creatinine clearance (CCL) refers to the volume of plasma from which creatinine is removed per unit time, and is measured by comparing blood creatinine levels to urine over a period of time (e.g., 24 hours). Creatine clearance is often measured as milliliters per minute (mL / min) or as a function of body weight (mL / min / kg). Depending on the test performed, normal values ​​range from about 97 to 137 mL / min for men and about 88 to 128 mL / min for women. A reduction in creatinine clearance provides a useful indication of kidney damage. Thus, certain male subjects for treatment according to the methods described herein may have (e.g., initially prior to treatment) a C of less than about 97, 96, 95, 94, 93, 92, 91, 90, 89, 88, 87, 86, 85, 84, 83, 82, 81, 80, 79, 78, 77, 76, 75, 74, 73, 72, 71, 70, 69, 68, 67, 66, 65, 64, 63, 62, 61, 60, 59, 58, 57, 56, 55, 54, 53, 52, 51, 50, or less. CrCertain female subjects for treatment according to the methods described herein may have a C of less than about 88, 87, 86, 85, 84, 83, 82, 81, 80, 79, 78, 77, 76, 75, 74, 73, 72, 71, 70, 69, 68, 67, 66, 65, 64, 63, 62, 61, 60, 59, 58, 57, 56, 55, 54, 53, 52, 51, 50, 49, 47, 46, 45, 44, 43, 42, 41, 40, or less (e.g., initially, before treatment). Cr In some embodiments, administration of a compound or composition described herein may result in an increase in C in a subject. Cr may be maintained or increased by about or at least about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, or 200% or more.

[0203] Proteinuria refers to the condition of excess protein in the urine. It is associated with a variety of disease states, including kidney damage. Proteinuria is often characterized as a urinary protein / creatinine ratio greater than about 45 mg / mmol, or an albumin / creatine ratio greater than about 30 mg / mmol in specific tests. Particular subjects for treatment according to the methods provided herein include those who have proteinuria (e.g., prior to treatment), either alone or in combination with CKD or other kidney damage, and have a urinary protein / creatinine ratio of about 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, or 120 mg / mmol or greater, or a urinary albumin / creatinine ratio of about 30, 35, 40, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, or 120 mg / mmol or greater. In these and related embodiments, administration of a compound or composition described herein may treat proteinuria, for example, by reducing urinary protein / creatinine and / or albumin / creatinine ratios by about or at least about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, or 200% or more.

[0204] CKD is associated with various clinical conditions. Examples include high blood pressure (hypertension), urea accumulation, hyperkalemia, anemia, hyperphosphatemia, hypocalcemia, metabolic acidosis, and atherosclerosis. Thus, in certain methods, CKD subjects may also have or be at risk of one or more of the aforementioned clinical conditions. In certain embodiments, CKD subjects have or are at risk of hyperphosphatemia as described herein.

[0205] Renal replacement therapy (RRT) refers to various life-sustaining treatments for kidney failure, including treatments initiated in late stage CKD and ESRD. Examples of RRT include dialysis, hemodialysis, hemofiltration, and kidney transplantation. In certain embodiments, the subject for treatment according to the methods provided herein is about to undergo, has undergone, or has undergone one or more types of RRT. In some embodiments, the subject has not yet undergone RRT, and administration of the compound described herein delays the time to begin RRT by about or at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 weeks, or about or at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 months, or about or at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 years or more.

[0206] Fibroblast growth factor 23 (FGF23) regulates phosphorus and vitamin D metabolism. It also promotes phosphaturia and reduces calcitriol production. Elevated FGF23 levels are associated with mortality, left ventricular hypertrophy (or left ventricular muscle mass index), myocardial performance, endothelial dysfunction, and CKD progression. In fact, FGF23 levels are progressively elevated in early CKD, presumably as a physiological adaptation to maintain normal serum phosphate levels or normal phosphorus balance. FGF23 levels may also directly contribute to tissue injury in the heart, blood vessels, and kidney. Thus, certain embodiments relate to the treatment of subjects with elevated FGF23 levels in blood or serum, including CKD subjects and subjects undergoing dialysis / hemodialysis (see, for example, Kirkpantur et al., Nephrol Dial Transplant. 26:1346-54, 2011). In some embodiments, administration of a compound or composition described herein reduces the log level of FGF23 in blood or serum by about or at least about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, or 200% or more.

[0207] Vitamin D stimulates the absorption of phosphate ions, especially in the small intestine.Therefore, excessive levels or activity of vitamin D can lead to elevated phosphate levels and hyperphosphatemia.Therefore, certain embodiments relate to methods for reducing the hyperphosphatemic effect of active vitamin D, for example, in subjects with elevated levels or activity of vitamin D.In some aspects, the subject has vitamin D toxicity due to over-intake of vitamin D.

[0208] Hyperparathyroidism is a disorder in which the parathyroid gland produces excess parathyroid hormone (PTH). Secondary hyperparathyroidism is characterized by hypersecretion of PTH in response to hypocalcemia and associated hypertrophy of the parathyroid gland. CKD is the most common cause of secondary hyperparathyroidism, which is generally due to the kidneys being unable to convert sufficient vitamin D into its active form and excrete sufficient phosphate. Insoluble calcium phosphate forms in the body, thus removing calcium from circulation and resulting in hypocalcemia. The parathyroid gland then further increases secretion of PTH in an attempt to raise serum calcium levels. Thus, certain subjects for treatment according to the methods provided herein may show hyperparathyroidism and / or elevated PTH levels (e.g., early on before treatment), optionally in combination with CKD, hyperphosphatemia, hypocalcemia, or other conditions or symptoms described herein. In some embodiments, administration of a compound or composition described herein may reduce hyperparathyroidism, including secondary hyperparathyroidism, in a subject in need thereof. In some embodiments, administration of a compound or composition described herein may reduce PTH levels by about or at least about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, or 200% or more, for example, by reducing serum phosphate levels and the associated formation of insoluble calcium phosphate, increasing available calcium, thereby reducing hypocalcemia-induced production of PTH.

[0209] In certain embodiments, administration of the compounds described herein, for example, dual activity compounds that inhibit both Pi and NHE3-mediated antiport transport of sodium and hydrogen ions, can provide multiple therapeutic effects to CKD subjects.In some cases, administration of dual activity compounds reduces the logarithm of FGF23 levels and serum parathyroid hormone (PTH) levels by about or at least about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, or 200% or more compared to untreated conditions, reduces blood pressure, and reduces proteinuria by at least about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, or 200% or more compared to untreated conditions.

[0210] In certain embodiments, administration of a compound described herein, for example a dual activity compound that inhibits both Pi and NHE3-mediated antiport of sodium and hydrogen ions, can provide multiple therapeutic benefits to ESRD (or stage 5 CKD) subjects. In certain cases, administration of a dual activity compound reduces serum phosphate concentration or level by about or at least about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, or 200% or more compared to untreated conditions, and reduces interdialytic weight gain (IDWG) by about or at least about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, or 200% or more compared to untreated conditions. IDWG is an easily measurable parameter that is routinely assessed before, during, or after dialysis (see Sarkar et al., Semin Dial. 19:429-33, 2006).

[0211] Hyperphosphatemia can lead to endothelial dysfunction in both healthy subjects and subjects with renal disease, independent of vascular calcification (see, for example, Di Marco et al., Kidney International. 83:213-222, 2013). Dietary phosphate restriction or management of serum phosphate levels by phosphate binders can prevent such subjects from developing cardiovascular disease. Research has also shown that dietary phosphate restriction can improve aortic endothelial dysfunction (e.g., in CKD with hyperphosphatemia) by increasing the phosphorylation of endothelial nitric oxide synthase and Akt (see, for example, Van et al., J Clin Biochem Nutr. 51:27-32, 2012). Particular subjects for treatment according to the methods provided herein may have or be at risk of endothelial dysfunction, optionally combined with hyperphosphatemia, renal disease, or any other condition described herein. By reducing postprandial or dietary phosphate intake, alone or in combination with dietary phosphate restriction, administration of a compound or composition described herein may reduce the risk of developing endothelial dysfunction or may improve existing endothelial dysfunction, including endothelial dysfunction induced by postprandial serum phosphate.

[0212] Hyperphosphatemia is a major inducer of vascular calcification (see Giachelli, Kidney Int. 75:890-897, 2009). Calcium phosphate deposition, primarily in the form of apatite, is a hallmark of vascular calcification and can occur in blood vessels, myocardium, and heart valves. Along with passive deposition of calcium phosphate in extraskeletal tissues, inorganic phosphate can also directly induce arterial calcification via "ossification" of the tunica media in blood vessels. Furthermore, vascular smooth muscle cells respond to elevated phosphate levels by undergoing an osteochondrogenic phenotypic change and calcifying their extracellular matrix via a mechanism that requires sodium-dependent phosphate cotransporters.

[0213] Intimal calcification is usually found in atherosclerotic lesions. Medial calcification is commonly observed in age-related arteriosclerosis and diabetes and is the predominant form of calcification observed in ESRD. Indeed, extensive calcification of the arterial wall and soft tissue is a common feature of CKD patients, including those with ESRD. In the valve, calcification is a defining feature of aortic stenosis, occurring in both the valve leaflets and annulus, primarily at sites of inflammation and mechanical stress. These mechanical changes are associated with increased arterial pulse wave velocity and pulse pressure, leading to impaired arterial distensibility, increased afterload favoring left ventricular hypertrophy, and impaired coronary perfusion (see Guerin et al., Circulation. 103:987-992, 2001). Thus, both intimal and medial calcification may contribute to morbidity and mortality associated with cardiovascular disease and are likely major contributors to the significantly increased risk of cardiovascular mortality observed in CKD and ESRD patients. Thus, controlling serum phosphate can reduce the formation of calcium / phosphate products, thereby reducing vascular calcification. Thus, certain subjects for treatment according to the methods provided herein may have or be at risk of developing vascular calcification, including intimal and / or medial calcification, optionally combined with any of hyperphosphatemia, CKD, and ESRD. In some embodiments, administering a compound or composition described herein reduces the risk of developing vascular calcification or reduces its formation or level in a subject in need thereof. In certain embodiments, administering a compound or composition described herein can reduce vascular calcification by about or at least about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, or 200% or more, for example, compared to untreated state.

[0214] Elderly patients may be particularly susceptible to increased phosphate. For example, dietary and genetic engineering studies provide in vivo evidence that phosphate toxicity accelerates the aging process, suggesting a new role for phosphate in mammalian aging (see, for example, Ohnishi and Razzaque, FASEB J.24:3562-71,2010). These studies show that excess phosphate is associated with many symptoms of premature aging, including kyphosis, uncoordinated movements, hypogonadism, infertility, skeletal muscle wasting, emphysema, and osteopenia, as well as general atrophy of the skin, intestine, thymus, and spleen. Thus, certain embodiments relate to reducing phosphate load in elderly patients, and include administering to elderly patients the compounds described herein, for example, to reduce any one or more symptoms of premature aging. In some cases, the elderly patient is about or at least about 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100 years of age or older.

[0215] Hypertrophy refers to the increase in the volume of an organ or tissue due to the enlargement of its constituent cells. Hyperphosphatemia is associated with myocardial hypertrophy, including left ventricular hypertrophy (Neves et al., Kidney Int.66:2237-44,2004, and Achinger and Ayus, Am Soc Nephrol.17(12 Suppl 3):S255-61,2006), and compensatory renal hypertrophy, including glomerular hypertrophy, the latter of which is frequently observed in CKD. Particular subjects for treatment according to the methods provided herein may have myocardial hypertrophy, renal hypertrophy, or both, either alone or in combination with CKD or renal injury (e.g., early before treatment). In some embodiments, administration of a compound described herein may reduce myocardial and / or renal hypertrophy by about or at least about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 200%, or more compared to an untreated condition.

[0216] Administration / form of administration: Administration of the compositions of the present invention may be carried out via any of the accepted modes of administration of drugs to provide similar benefits. The pharmaceutical compositions of the present invention may be prepared by combining the compounds of the present invention with suitable pharma- ceutically acceptable carriers, diluents, or excipients, and may be formulated into preparations in solid, semi-solid, liquid, or gaseous form, such as tablets, capsules, powders, granules, ointments, solutions, suppositories, injections, inhalants, gels, microspheres, and aerosols. Typical routes of administration of such pharmaceutical compositions include, but are not limited to, oral, topical, transdermal, inhalation, parenteral, sublingual, buccal, rectal, vaginal, and intranasal. As used herein, the term parenteral includes subcutaneous injection, intravenous, intramuscular, intrasternal injection, or infusion techniques. The pharmaceutical compositions of the present invention are formulated to allow the active ingredients contained therein to be bioavailable when the compositions are administered to a patient. The compositions administered to a subject or patient may take the form of one or more dosage units, for example, a tablet may be a single dosage unit, and a container of the compounds of the present invention in aerosol form may hold multiple dosage units. The actual method of preparing such dosage forms will be known or will be apparent to those skilled in the art. For example, see Remington: The Science and Practice of Pharmacy, 20th Edition (Philadelphia College of Pharmacy and Science, 2000). The composition to be administered will in each case contain a therapeutically effective amount of the compound of the present invention, or a pharma-ceutically acceptable salt thereof, for treating the disease or condition of interest according to the teachings of the present invention.

[0217] The pharmaceutical composition of the present invention may be in solid or liquid form.In one embodiment, the carrier is particulate, so that the composition is, for example, in tablet or powder form.The carrier may also be liquid, so that the composition is, for example, oral syrup, injectable liquid or aerosol, which is useful, for example, in inhalation administration.

[0218] When intended for oral administration, the pharmaceutical compositions are preferably either in a solid or liquid form, with semi-solid, semi-liquid, suspension, and gel forms being included within the forms considered herein as either solid or liquid.

[0219] As a solid composition for oral administration, pharmaceutical compositions can be formulated into powder, granules, compressed tablets, pills, capsules, chewing gum, wafers, or similar forms. Such solid compositions typically contain one or more inert diluents or edible carriers. In addition, one or more of the following may be present: binders such as carboxymethylcellulose, ethylcellulose, microcrystalline cellulose, gum tragacanth, or gelatin; excipients such as starch, lactose, or dextrin; disintegrants such as alginic acid, sodium alginate, Primogel, corn starch; lubricants such as magnesium stearate or Sterotex; glidants such as colloidal silicon dioxide; sweeteners such as sucrose or saccharin; flavors such as peppermint, methyl salicylate, or orange flavor; and colorants.

[0220] When the pharmaceutical composition is in the form of a capsule, for example, a gelatin capsule, it may contain, in addition to materials of the above type, a liquid carrier such as polyethylene glycol or oil.

[0221] The pharmaceutical composition may be in the form of a liquid, such as an elixir, syrup, solution, emulsion, or suspension. The liquid may be for oral administration or for delivery by injection, as two examples. When intended for oral administration, the preferred composition contains, in addition to the compound, one or more of a sweetener, a preservative, a dye / colorant, and a flavor enhancer. In the composition intended for administration by injection, one or more of a surfactant, a preservative, a wetting agent, a dispersing agent, a suspending agent, a buffer, a stabilizer, and an isotonic agent may be included.

[0222] The liquid pharmaceutical composition of the present invention, whether in solution, suspension, or other similar form, may contain one or more of the following adjuvants: water for injection, saline, preferably saline, Ringer's solution, sterile diluent such as isotonic sodium chloride, fixed oils such as synthetic mono- or diglycerides that can act as solvents or suspending media, polyethylene glycol, glycerin, propylene glycol, or other solvents; antibacterial agents such as benzyl alcohol or methylparaben; antioxidants such as ascorbic acid or sodium bisulfite; chelating agents such as ethylenediaminetetraacetic acid; buffers such as acetates, citrates, or phosphates, and agents for adjusting tonicity such as sodium chloride or dextrose. Parenteral preparations may be enclosed in ampoules, disposable syringes, or multiple dose vials made of glass or plastic. Saline is the preferred adjuvant. Pharmaceutical compositions for injection are preferably sterile.

[0223] A liquid pharmaceutical composition of the present invention intended for either parenteral or oral administration should contain an amount of a compound of the present invention such that a suitable dosage will be obtained.

[0224] The pharmaceutical composition of the present invention may be intended for topical administration, in which case the carrier may suitably comprise a solution, emulsion, ointment or gel base.The base may comprise, for example, one or more of the following: petrolatum, lanolin, polyethylene glycol, beeswax, mineral oil, diluents such as water and alcohol, and emulsifiers and stabilizers.Thickeners may be present in pharmaceutical compositions for topical administration.When intended for transdermal administration, the composition may comprise a transdermal patch or an iontophoresis device.

[0225] The pharmaceutical composition of the present invention may be for rectal administration, for example, in the form of suppository, which melts in the rectum and releases the drug.The composition for rectal administration may contain an oleaginous base as a suitable non-irritating excipient.Such bases include, but are not limited to, lanolin, cocoa butter, and polyethylene glycol.

[0226] The pharmaceutical composition of the present invention may contain various materials that modify the physical form of solid or liquid dosage units.For example, the composition may contain materials that form a coating shell around the active ingredient.The materials that form the coating shell are typically inert and may be selected from, for example, sugar, shellac, and other enteric coating agents.Alternatively, the active ingredient may be placed in a gelatin capsule.

[0227] The pharmaceutical compositions of the invention, in solid or liquid form, may include an agent that binds to the compounds of the invention and thereby aids in the delivery of the compounds. Suitable agents that may act in this capacity include monoclonal or polyclonal antibodies, proteins, or liposomes.

[0228] The pharmaceutical composition of the present invention may consist of a dosage unit that can be administered as an aerosol. The term aerosol is used to indicate a variety of systems ranging from those of colloidal nature to systems consisting of pressurized packages. Delivery may be by liquefied or compressed gas or by a suitable pump system that dispenses the active ingredient. Aerosols of the compounds of the present invention may be delivered in single-phase, two-phase, or three-phase systems to deliver the active ingredient. Delivery of the aerosol includes the necessary containers, activators, valves, subcontainers, etc., which together may form a kit. Those skilled in the art will be able to determine the preferred aerosol without undue experimentation.

[0229] The pharmaceutical composition of the present invention can be prepared by the methodology well known in the pharmaceutical art.For example, the pharmaceutical composition intended to be administered by injection can be prepared by combining the compound of the present invention with sterile distilled water to form a solution.Surfactant may be added to promote the formation of a homogeneous solution or suspension.Surfactant is a compound that non-covalently interacts with the compound of the present invention to promote the dissolution or homogeneous suspension of the compound in the aqueous delivery system.

[0230] The compounds of the present invention, or their pharma- ceutically acceptable salts, are administered in a therapeutically effective amount, which will vary depending on a variety of factors, including the activity of the particular compound employed, the metabolic stability and length of action of the compound, the patient's age, weight, general health, sex, and diet, the mode and time of administration, rate of excretion, drug combination, the severity of the particular disorder or condition, and the subject being treated.

[0231] In certain embodiments, a typical dosage of a substantially impermeable or substantially systemically non-bioavailable compound may be from about 0.2 mg per day to about 2 g per day, or from about 1 mg to about 1 g per day, or from about 5 mg to about 500 mg, or from about 10 mg to about 250 mg per day, administered to a subject in need of treatment.

[0232] The frequency of administration of the compounds and compositions described herein can vary, such as once daily (QD) to twice daily (BID) or three times daily (TID), with the exact frequency of administration depending, for example, on the condition of the patient, the dosage, etc.

[0233] The compound of the present invention, or its pharma- ceutically acceptable derivative, may also be administered simultaneously with, before, or after the administration of one or more other therapeutic or bioactive agents, dietary supplements, or any combination thereof.Such combination therapy includes administration of a single pharmaceutical dosage formulation containing the compound of the present invention and one or more additional active agents, as well as administration of the compound of the present invention and each active agent in their own separate pharmaceutical dosage formulation.For example, the compound of the present invention and the other active agents can be administered together to a patient in a single oral dosage composition such as a tablet or capsule, or each agent can be administered in a separate oral dosage formulation.When separate dosage formulations are used, the compound of the present invention and one or more additional active agents can be administered essentially at the same time, i.e., simultaneously, or at different staggered times, i.e., sequentially, and combination therapy is understood to include all these regimens.

[0234] For example, in certain embodiments, the additional bioactive agent included in the pharmaceutical compositions (or methods) of the invention is selected from, for example, vitamin D2 (ergocalciferol), vitamin D3 (cholecalciferol), active vitamin D (calcitriol), and active vitamin D analogs (e.g., doxercalciferol, paricalcitol).

[0235] In some embodiments, the additional bioactive agent is an inhibitor of intestinal sodium-dependent phosphate transporter (NaPi2b inhibitor). Examples of NaPi2b inhibitors can be found in, for example, International Application Nos. PCT / US2011 / 043267, PCT / US2011 / 043261, PCT / US2011 / 043232, PCT / US2011 / 043266 and PCT / US2011 / 043263, and U.S. Patent No. 8,134,015, each of which is incorporated by reference in its entirety.

[0236] In certain embodiments, the additional bioactive agent is niacin or nicotinamide.

[0237] It is understood that in this description, combinations of substituents and / or variables of the depicted formulae are permissible only if such contributions result in stable or reasonably stable compounds.

[0238] It will also be appreciated by those skilled in the art that in the processes described herein, functional groups of intermediate compounds may need to be protected by suitable protecting groups. Such functional groups include hydroxy, amino, mercapto, and carboxylic acid. Suitable protecting groups for hydroxy include trialkylsilyl or diarylalkylsilyl (e.g., t-butyldimethylsilyl, t-butyldiphenylsilyl, or trimethylsilyl), tetrahydropyranyl, benzyl, and the like. Suitable protecting groups for amino, amidino, and guanidino include t-butoxycarbonyl, benzyloxycarbonyl, and the like. Suitable protecting groups for mercapto include -C(O)-R" (wherein R" is alkyl, aryl, or arylalkyl), p-methoxybenzyl, trityl, and the like. Suitable protecting groups for carboxylic acid include alkyl, aryl, or arylalkyl esters. Protecting groups may be added or removed according to standard techniques known to those skilled in the art and as described herein. The use of protecting groups is described in detail in Green, T W and P G M Hutz, Protective Groups in Organic Synthesis (1999), 3rd Ed., Wiley. One of skill in the art will appreciate that the protecting group may be a polymeric resin, such as a Wang resin, a Rink resin, or a 2-chlorotrityl-chloride resin.

[0239] It will also be understood by those skilled in the art that such protected derivatives of the compounds of the present invention may not have pharmacological activity themselves, but may be administered to a mammal and subsequently metabolized in the body to form a compound of the present invention that is pharmacologically active. Thus, such derivatives may be described as "prodrugs." All prodrugs of the compounds of the present invention are included within the scope of the present invention.

[0240] Additionally, all compounds of the present invention that exist in free base or acid form can be converted to their pharma- ceutically acceptable salts by treatment with an appropriate inorganic or organic base or acid by methods known to those skilled in the art. Salts of the compounds of the present invention can be converted to their free base or acid form by standard techniques. EXAMPLES

[0241] Example 1 Rapid cell-based activity. Rat or human NHE3-mediated Na + Dependency H + Countertransport was measured using a modification of the pH-sensitive dye method originally reported by Paradiso (PNAS USA. 81:7436-7440, 1984). Opossum kidney (OK) cells were obtained from ATCC and grown according to their instructions. The rat NHE3 gene (GenBank M85300) or human NHE3 gene (GenBank NM_004174.1) was introduced into OK cells via electroporation, and the cells were seeded into 96-well plates and grown overnight. The medium was aspirated from the wells and the cells were washed twice with NaCl-HEPES buffer (100 mM NaCl, 50 mM HEPES, 10 mM glucose, 5 mM KCl, 2 mM CaCl2, 1 mM MgCl2, pH 7.4) and then incubated for 30 min at room temperature in NH4Cl-HEPES buffer (20 mM NH4Cl, 80 mM NaCl, 50 mM HEPES, 5 mM KCl, 2 mM CaCl2, 1 mM MgCl2, pH 7.4) containing 5 μM bis(acetoxymethyl) 3,3'-(3',6'-bis(acetoxymethoxy)-5-((acetoxymethoxy)carbonyl)-3-oxo-3H-spiro[isobenzofuran-1,9'-xanthene]-2',7'-diyl)dipropanoate (BCECF-AM).

[0242] The cells were treated with ammonium-free, Na +The cells were washed twice with free HEPES (100 mM choline, 50 mM HEPES, 10 mM glucose, 5 mM KCl, 2 mM CaCl2, 1 mM MgCl2, pH 7.4) and incubated in the same buffer for 10 min at room temperature to lower the intracellular pH. NHE3-mediated recovery of neutral intracellular pH was determined by the addition of Na-HEPES buffer containing 0.4 μM ethyl isopropyl amiloride (EIPA, a selective agonist of NHE-1 activity that does not inhibit NHE3) and 0-30 μM test compound, and the pH-insensitive BCECF fluorescence (λ ex 439nm, λ em BCECF fluorescence (λ) normalized to 538 nm ex 505nm, λ em The initial rates were plotted as the average of two or more replicates and pIC 50 Values ​​were estimated using GraphPad Prism.

[0243] Inhibition of Intestinal Sodium and Phosphate Absorption. Urinary sodium concentration and stool form were measured to assess the ability of selected exemplary compounds to inhibit sodium absorption from the lumen of the intestine. Eight-week-old Sprague-Dawley rats were cultured at Charles River Rats were purchased from Teklad Laboratories (Hollister, CA), housed two per cage, and allowed to acclimate for at least 3 days prior to the start of the study. Throughout the study, animals were provided with Harlan Teklad Global 2018 Rodent Chow (Indianapolis, IN) and water ad libitum and maintained on a standard light / dark cycle of 6 AM to 6 PM. On the day of the study, between 4 PM and 5 PM, groups of rats (n=6) were administered test compound or vehicle (water) by oral gavage in a volume of 10 mL / kg.

[0244] After dose administration, animals were placed in individual metabolic cages and were also provided with the same food in dietary form and water ad libitum. Sixteen hours after dosing, urine samples were collected and stool form was assessed by two independent observations. Stool form was scored according to a common scale related to the increase in fecal moisture to the wettest observation in the cage's collection funnel (1, normal clump; 2, clump adhering to the side of the collection funnel due to moisture; 3, loss of normal clump shape; 4, complete loss of shape with blotting pattern; 5, obvious liquid fecal flow). Stool form score (FFS) of rats was determined by averaging both observation scores for all rats in a group (n=6). The vehicle group average was 1.

[0245] For urine samples, the volume was determined gravimetrically and centrifuged at 3,600×g. The supernatant was diluted 100-fold in deionized Milli-Q water and then filtered through a 0.2 μM GHP Pall AcroPrep filter plate (Pall Life Sciences, Ann Arbor, MI) prior to analysis by ion chromatography. Ten microliters of each filtered extract was injected into a Dionex ICS-3000 ion chromatograph system (Dionex, Sunnyvale, CA). Cations were separated by isocratic method on an IonPac CS12A 2 mm id×250 mm, 8 μM particle size cation exchange column (Dionex) using 25 mM methanesulfonic acid as eluent. Li + , Na + , NH4 + , K + , Mg 2+ , and Ca 2+ Sodium was quantified using standards prepared from a cation standard mixture (Dionex) containing 100 mg sodium per 100 mg sodium per day. The average mass of sodium urinated for each group over a 16-hour period was determined, with the vehicle group typically urinating approximately 21 mg sodium. Urinary Na (uNa) for rats in the test groups was expressed as a percentage of the vehicle mean and compared to the vehicle group mean by utilizing one-way ANOVA with Dunnett's post-hoc test.

[0246] Example 2 Effects in a rat model of uremia-associated vascular calcification Chronic kidney disease (CKD) has multiple pathogenic mechanisms, and progressive CKD is often characterized by mineral metabolism disorders (e.g., hyperphosphatemia, hypercalcemia) and vascular calcification. Thus, a study was conducted to test the efficacy of Cpd 002 in a uremic rat model of CKD characterized by vascular calcification. This model is characterized by renal insufficiency and regular active vitamin D3 administration to promote hyperphosphatemia and vascular calcification (see Lopez et al., J. Am. Soc. Nephrol. 17:795-804, 2006). The study utilized Spraque-Dawley rats that were treated as follows: five-sixths nephrectomy by resection, regular calcitriol administration (active vitamin D3) 80 ng / kg intraperitoneally 3 / week, and feeding of purified 0.9% P diet (inorganic phosphorus).

[0247] Rats were stratified into two experimental groups by serum creatinine levels of 0.8-1.5 mg / dL and body weight, fed a powdered vehicle diet or the same diet mixed with Cpd 002 (0.065 mg / g sample) with in-diet drug, and monitored for weekly body weight and selected serum parameters, daily clinical observations, and endpoint calcification.

[0248] Selected experimental groups were fed vehicle (n=12) or Cpd002 (n=12) at the time of enrollment (day 0). Initial body weight and selected serum parameters such as serum phosphorus, serum calcium, serum creatinine, and blood urea nitrogen were comparable for both groups.

[0249] Selected end point plasma parameters from day 27 showed reduced plasma creatinine, reduced plasma phosphorus, and reduced plasma FGF-23.

[0250] End-point cardiac and renal remnant weights indicated that cardiac and renal remnant hypertrophy was reduced in rats treated with Cpd 002. Given the reduction in plasma creatinine, these results suggest that the renal remnants in Cpd 002-treated rats have less mass and greater functionality.

[0251] The endpoint of creatinine clearance (C Cr ) and plasma aldosterone levels suggest that treatment with Cpd 002 prevented loss of renal function, with the increase in aldosterone suggesting some degree of fluid loss consistent with the decrease in Na intake.

[0252] The endpoints of vascular and soft tissue calcification showed that treatment with Cpd 002 reduced calcium and phosphorus in the stomach, which is particularly susceptible to calcification, and also reduced vascular calcification as measured by aortic mineral content.

[0253] Overall, Cpd 002 was shown to improve renal function, reduce both cardiac and renal hypertrophy, exhibit antihyperphosphatemic effects, and reduce associated vascular calcification. These effects and reductions in moribundity were accompanied by a trend toward improved mortality outcomes observed in the treatment group. Although the benefit from 002 may be due in part to its effects on fluid overload and hemodynamics, vascular calcification in this model is highly sensitive to dietary phosphate, so the reduction in ectopic calcification points to a reduction in phosphate absorption.

[0254] Example 3 Effect on adenine-induced uremia rat model The effect of Cpd 002 was tested in an adenine-induced uremic rat model. Rats were fed a diet containing 0.75% adenine and 1.2% phosphorus during the nephritis induction phase. The basal diet during the treatment phase was normal chow containing 0.3% adenine and 0.6% phosphorus for 2 weeks. Rats were pair-fed for the first 5 days (groups 1 and 2 to group 3, with an interval of 4 days) and then fed ad libitum. Treatment groups were as follows: vehicle, n=10; Cpd 002, 2 mg / kg / day, drug in diet, n=10; and Cpd 002, 5 mg / kg / day, drug in diet, n=12. Weekly measurements of serum markers and renal function were performed.

[0255] Cpd 002 reduced serum phosphorus and serum creatinine at early time points, where this adenine-induced model is considered to be acute kidney injury characterized by gradual recovery of renal function, and therefore the effects at early time points are significant.

[0256] Organ weight collection data from week 3 indicated that treatment with Cpd 002 in this model showed a trend towards less cardiac and renal remodeling, as well as reduced cardiac and renal calcification at the highest dose.

[0257] Example 4 Effect of high-salt feeding on renal dysfunction in nephrectomized rats The effect of Cpd 002 was tested in a dietary salt-induced, partial renal ablation model of CKD. The study design is described in WO2014 / 169094, which shows the effect of Cpd 002 on urinary excretion of phosphorus. In this study, Cpd 002 improved blood pressure, fluid overload, albuminuria, and cardiac and renal hypertrophy, and also significantly reduced urinary excretion of phosphorus. These data suggest an additive contribution to the phosphorus-lowering effect of Cpd 002 on the improvement of renal and vascular function.

[0258] Example 5 Effect of phosphate and calcium on urinary excretion in rats The activity of Compound 002 was tested for its effect on urinary phosphorus and calcium levels in rats. Rats were dosed according to the schedule in Table E7. [Table 1]

[0259] Rats were kept in individual metabolic cages overnight for 16 hours (in the dark, typical feeding period) and urine was collected the following morning for analysis of phosphate and calcium levels. The study design is shown in WO2014 / 169094. Results are shown in Figures 3A and 3B. These results show that Cpd 002 reduced urinary phosphorus compared to vehicle only controls. Increasing doses of Cpd 002 also significantly reduced urinary phosphorus compared to 48 mg / kg Renvela®.

[0260] Example 6 Evaluating activity in reducing dietary phosphorus at doses of 15, 30, and 60 mg BID in a 7-day repeated-dose study in healthy volunteers A phase 1, single-center, randomized, double-blind, placebo-controlled study was designed to evaluate the safety, tolerability, and pharmacodynamic activity (PD) of different dosing regimens of Compound 002 (CPD002) on sodium and phosphorus excretion in healthy male and female subjects.

[0261] Subjects were screened within 3 weeks prior to enrollment and assigned sequentially to cohorts in the order in which they completed screening assessments. Each cohort of 15 subjects checked into the Clinical Pharmacology Center (CPU) before dinner on day -5. Subjects remained in the CPU and were provided with a Na+ standardized meal (approximately 1500 mg / meal).

[0262] In each cohort, 12 subjects were randomized to receive CPD002 and 3 to receive placebo. Subjects were administered a dose of CPD002 (twice daily, depending on the dose, immediately prior to the appropriate meal [bid, breakfast, dinner]) with approximately 240 mL of still water on days 1-7. Subjects were offered a standardized meal within 10 minutes of dosing.

[0263] Selection of Study Population - Inclusion Criteria. Subjects were eligible for inclusion in the study if they met all of the following criteria: 1. Healthy males or females aged 19-65 years (inclusive). 2.18~29.9kg / m 2 (Inclusive) Body Mass Index (BMI). 3. No clinically significant abnormalities in medical history, physical examination, or clinical laboratory evaluations at screening. 4. Able to understand and follow protocols. 5. Willing and able to sign informed consent. 6. Women were not pregnant, not breastfeeding, and either postmenopausal for at least 12 months as confirmed by follicle-stimulating hormone (FSH) testing, or surgically infertile for at least 90 days (e.g., tubal ligation, hysterectomy, bilateral oophorectomy with appropriate documentation), or agreed to use one of the following contraceptive methods from the time of signing the informed consent until 45 days after the end of the study: intrauterine device with spermicide, female condom containing spermicide, contraceptive sponge containing spermicide, diaphragm containing spermicide, cervical cap containing spermicide, male condom containing spermicide, infertile sexual partner, abstinence, intravaginal system containing spermicide (e.g., NuvaRing®), or oral, implantable, transdermal, or injectable contraceptives containing spermicide. 7. Men were either infertile, abstinent, or agreed to use one of the following approved contraceptive methods from check-in through 45 days after the last study visit: male condoms containing spermicide, infertile sexual partner, intrauterine device containing spermicide, female condoms containing spermicide, contraceptive sponge containing spermicide, intravaginal system containing spermicide (e.g., NuvaRing), diaphragm containing spermicide, cervical cap containing spermicide, or use of oral, implantable, transdermal, or injectable contraceptives by the female sexual partner.

[0264] Study Population Inclusion-Exclusion Criteria. Subjects were excluded from the study if they met any of the following criteria: 1. Diagnosis or treatment of clinically symptomatic biochemical or structural abnormalities of the gastrointestinal system. 2. Any surgery of the small intestine or colon, except appendectomy or cholecystectomy. 3. Clinical evidence of significant cardiovascular, respiratory, renal, hepatic, gastrointestinal, hematological, metabolic, endocrine, neurological, or psychiatric disease, or any condition that may prevent the subject from successfully completing the study. 4. Two or more days of loose stools in the past seven days (BSFS of 6 or 7). 5. Hepatic dysfunction (alanine aminotransaminase [ALT] or aspartate aminotransaminase [AST] greater than 1.5 times the upper limit of normal [ULN]) or renal impairment (serum creatinine greater than ULN). 6. Clinically significant laboratory results at screening as determined by the investigator. 7. Evidence of or treatment of any malignancy, except non-melanoma malignancies of the skin. 8. Subject is unable or unwilling, in the opinion of the Investigator, to comply with the requirements of the protocol or has a condition that makes the results uninterpretable. 9. Diet which, in the opinion of the investigator, may have influenced the outcome of the study. 10. Use of diuretics, medications known to affect stool consistency and / or gastrointestinal motility (including dietary fiber supplements (unless required by study), antidiarrheals, laxatives, antacids, opiates, anesthetics, prokinetics, enemas, antibiotics, probiotic medications or supplements), or salt or electrolyte supplements containing Na+, potassium, chloride, or bicarbonate preparations from CPU check-in (Day -5) to CPU check-out (Day 9). 11. Use of an investigational drug within 30 days prior to Day 5. 12. Positive virological test (active hepatitis B infection [HBsAg], hepatitis C infection [HCV], or human immunodeficiency virus [HIV]), alcohol, or drug abuse test during screening. 13. Use of any prescription medication within 7 days prior to admission to the CPU, or the need for long-term use of any prescription or non-prescription medication, except for hormone replacement therapy (HRT) and hormonal contraceptives for postmenopausal women. 14. History of tobacco use, alcohol abuse, illicit drug use, serious psychiatric illness, physical dependence on opioids, or drug abuse or dependence within 12 months of study enrollment. 15. Had significant blood loss (>450 mL) or donated 1 or more units of blood or plasma within 8 weeks prior to study enrollment.

[0265] Exclusion of Subjects from Therapy or Evaluation. Subjects were free to discontinue the study at any time, for any reason, and without compromising further treatment. Investigators could exclude subjects if, in the investigator's opinion, continued participation posed an unacceptable risk to the subject or the integrity of the study data. Subjects who withdrew early could be replaced during discussion with the sponsor.

[0266] Efficacy Assessments - Demographic and Other Baseline Characteristics. All subjects enrolled in the study received study treatment and all underwent at least one post-baseline PD assessment.

[0267] A summary of the overall and cohort-specific demographic characteristics of subjects enrolled in the study is provided below in Table E8. Some variability was observed across cohorts, particularly in terms of gender and race. However, the baseline characteristics of most cohorts reflected those of the overall population.

[0268] No clinically significant abnormal findings were noted in any of the subjects during the physical examination performed at screening. [Table 2]

[0269] The schedule of events for the screening and treatment periods is provided below in Table E9. [Table 3]

[0270] Investigational Medications. CPD002 capsules or matching placebo capsules were administered in multiples of 15 mg or placebo with approximately 240 mL of non-carbonated water. CPD002 is an amorphous off-white powder and was supplied as a white, size 0 hydroxypropyl methylcellulose (HPMC) capsule. Each capsule contained 15 mg of CPD002. Capsules were packaged in opaque white high density polyethylene (HDPE) bottles (10 / bottle). The formulation was formulated without excipients.

[0271] Placebo was supplied as white, size 0 HPMC capsules filled with methylcellulose. Capsules were packaged in opaque white HDPE bottles (10 / bottle).

[0272] Method of Allocating Subjects to Treatment Groups. The clinical research organization's statisticians prepared the randomization scheme according to their standard operating procedures (SOPs) and a randomization plan that reflected GCP standards.

[0273] After informed consent was obtained, subjects were sequentially assigned to cohorts in the order in which they completed the screening assessments.

[0274] Within each cohort, subjects were randomly assigned to active CPD002 or placebo in a 4:1 ratio using a computer-generated randomization schedule.

[0275] Once a subject was deemed eligible for randomization, they were assigned the next available randomization number sequentially and received the treatment indicated in the randomization schedule. Subjects who withdrew early could be replaced during discussion with the sponsor. Replacement subjects received the same blinded treatment as the original subject.

[0276] Dose selection and timing for each subject. Subjects were sequentially assigned to cohorts of 15 subjects each in the order in which they completed screening assessments and received either CPD002 or placebo based on random assignment. Table E10 provides the actual dosing regimen for each cohort. Because this was an adaptive design protocol, the dosing regimen for each cohort was based on blinded results from the previous cohort. [Table 4]

[0277] Dosing was performed immediately before breakfast and dinner. Subjects were not allowed to eat or drink anything for 8 hours prior to dosing at breakfast, except for water up to 2 hours prior. Subjects were provided with a standardized meal approximately 10 minutes after dosing.

[0278] The standardized diet contained a Na content of approximately 1500 mg for each meal. Dietary phosphorus was not measured or set at a predetermined value. It was expected to be within typical values, i.e., within the range of 750 mg to 1250 mg per day.

[0279] Subjects were not allowed to add salt to their diet. Fluid intake was ad libitum (and recorded) except as prescribed prior to drug administration. Subjects were to refrain from strenuous physical activity (e.g., contact sports) during study participation.

[0280] Blinding. Treatments were performed in a double-blind fashion. Only the study site pharmacist responsible for dispensing the products and the bioanalytical laboratory technician responsible for performing the bioanalysis of plasma CPD002 had knowledge of the assigned treatment.

[0281] The study was not unblinded for between-cohort safety review.

[0282] A third party maintained the randomization schedule in a secure location with appropriate controls in place to prevent unauthorized access.

[0283] One set of unblinded envelopes (sealed envelopes containing individual subject treatment assignments) was kept at the CPU.

[0284] The study was unblinded only after all data had been collected from the final cohort and the database was locked.

[0285] Previous and Concomitant Therapies. This was a study in healthy subjects. Subjects with previous therapies as defined in the exclusion criteria were not eligible to participate in the study.

[0286] Concomitant use of medications was prohibited during the study unless required for treatment of an AE, with the exception of HRT and hormonal contraceptives for postmenopausal women.

[0287] All previous medications (prescription and over-the-counter), vitamin and mineral supplements, and herbs taken by participants in the past 30 days were recorded on the CRF, including start and stop dates, dose and route of administration, frequency, and indication. Medications taken for procedures were also included.

[0288] Treatment Compliance. All doses of study drug were administered under the supervision of clinic staff, who recorded the time and dose on the CRF. Clinical staff inspected the subjects' mouths and hands after drug administration to ensure that the capsules were swallowed.

[0289] Efficacy variables. The study consisted of a 3-week screening period, followed by 5 days of baseline assessments, a 7-day double-blind treatment period, with a 2-day follow-up for safety and PD assessments. After 14 days of the treatment period, subjects were contacted by telephone for safety follow-up.

[0290] Subjects were admitted to the CPU 5 days prior to receiving the first dose of study drug, remained on site for the duration of the treatment period, and were released on the 9th day.

[0291] Safety assessments were performed from day -5 onwards and included physical examination, vital signs, 12-lead ECG, routine serum chemistry, hematology and urinalysis, and AE reporting. Pharmacodynamic assessments were performed daily from day -4 to day 9 and included urinary and fecal Na+ excretion, time to first bowel movement, and fecal parameters (consistency, weight, and frequency). Pharmacodynamic laboratory assessments (plasma renin, aldosterone, and NT-proBNP) were collected on days -4, -1, 3, 6, and 9.

[0292] Laboratory Evaluations. Blood and urine samples for clinical tests (hematology, chemistry, urinalysis) were collected during screening (to meet inclusion / exclusion criteria) and on days -4 and 9, upon awakening and before breakfast.

[0293] In addition, blood was drawn at screening and on day -5 for alcohol / drug screening, FSH testing (postmenopausal women only), and pregnancy testing (all women). Virological screening for HBsAg, HCV, and HIV was performed at screening.

[0294] Pharmacodynamic variables. The following PD parameters were monitored as signals of potential drug activity: ·Fecal Na+ excretion Fecal phosphorus excretion

[0295] Bowel movements. Study participants were instructed to notify study personnel immediately prior to a bowel movement. Study staff recorded the time of each bowel movement and assessed fecal parameters (e.g., consistency, weight). A bowel movement that occurred before leaving the restroom was considered a single bowel movement. All bowel movements were collected, weighed, and stored by the CPU for total Na+ and P analysis. Collections were at 24-h intervals.

[0296] Pharmacodynamic Analysis-Fecal Sodium and Phosphorus Analysis Method. Human fecal samples were treated with nitric acid to obtain predigested samples (hereafter predigest) prior to laboratory determination of sodium and phosphorus content. The predigest was further digested with nitric acid at 100°C, followed by hydrochloric acid at 100°C, and diluted with deionized water. Yttrium was added to the digest as an internal standard. Calibration standards and quality control samples were digested with the same procedure. Sodium and phosphorus concentrations were determined by inductively coupled plasma optical emission spectroscopy (ICP-OES) method. The light intensities of the analytes and yttrium were measured with an SCD (array) detector. The analyte-to-yttrium intensity ratios were converted to solution concentrations via the instrument software. The total sodium and phosphorus contents in each sample were calculated using the sample volume and measured concentrations obtained during the predigestion process.

[0297] Results. After unblinding of the data, pharmacodynamic measurements of fecal and urinary P and Na were performed for placebo (3 subjects enrolled in each cohort x 3 cohorts = 9 subjects) and three treatment groups, respectively. The data are illustrated in WO2014 / 169094, which shows the mean daily fecal excretion of Na (+ / - SE), averaged over a 7-day treatment period (days 1-7) and reported as mEq / day. The mean daily fecal excretion of phosphorus (+ / -), averaged over a 7-day treatment period (days 1-7) and reported as mEq / day. Statistical analysis was performed by one-way ANOVA; (*); p<0.05, (**); p<0.01, (***); p<0.001.

[0298] Example 7 Evaluating activity in reducing dietary phosphorus at a dose of 15 mg BID in a 7-day repeated-dose crossover study in healthy volunteers A phase 1, single-center, randomized, three-way crossover, open-label study was designed to evaluate the pharmacodynamics of CPD002 for three different formulations of CPD002 administered twice daily for 4 days in healthy male and female subjects receiving a proton pump inhibitor (omeprazole) utilizing a three-way crossover design. Many potential patients take either a PPI or an H2 antagonist for the treatment of gastroesophageal reflux disease (GERD). However, the in vitro dissolution profile of CPD002 formulations may be affected by high pH, ​​and slower and / or incomplete dissolution is sometimes observed. To evaluate the pharmacodynamic activity of the drug in relation to elevated intragastric pH, subjects in this study were required to receive omeprazole starting on day -5 and throughout the entire treatment period.

[0299] Subjects were screened within 3 weeks of enrollment. Each subject received omeprazole 20 mg twice daily beginning on day -5. Subjects checked into the Clinical Pharmacology Facility (CPU) before dinner on day -2. Each subject was fed a diet standardized for Na+ content while in the CPU. Subjects were administered one of three formulations of CPD002 BID with approximately 240 mL of non-carbonated water on days 1-4, 7-10, and 13-16 (a different formulation each time). Breakfast and / or dinner were provided to subjects within approximately 5 minutes of dosing. There was a 2-day washout period between each treatment period.

[0300] While on the CPU, they were provided with a Na+ standardized diet according to CPU procedures.Pharmacodynamic assessments included measurements of 24-hour urinary sodium and phosphorus, and fecal sodium and phosphorus.

[0301] At least 18 healthy male and female subjects were randomized in this study.

[0302] Subject Selection Criteria-Inclusion Criteria. 1. Healthy males or females aged 19-65 years (inclusive). Body mass index between 2.18 and 29.9 kg / m2 (inclusive). 3. No clinically significant abnormalities in medical history, physical examination, or clinical laboratory evaluations at screening. 4. Able to understand and follow protocols. 5. Willing and able to sign informed consent and have signed and dated written informed consent prior to any study-specific procedures. 6. Females of childbearing potential must have a negative pregnancy test at screening and upon admission to the facility and must not be lactating. 7. Women of childbearing potential who are enrolled in the study must use two effective methods to avoid pregnancy from screening to the follow-up visit (including use of oral, transdermal, or implantable contraceptives, intrauterine devices, female condoms containing spermicide, diaphragms containing spermicide, cervical caps, or condoms containing spermicide by sexual partners). 8. Women of non-childbearing potential identified at screening must meet one of the following criteria: a. Postmenopausal, defined as amenorrhea for at least 12 months; after cessation of all exogenous hormone therapy, and LH and FSH levels in the postmenopausal range; or b. Documentation of irreversible sterilization by hysterectomy, bilateral oophorectomy, or bilateral salpingectomy rather than tubal ligation. 9. Men must either be infertile, abstinent, or agree to use one of the following approved contraceptive methods from check-in until 45 days after the last study visit: male condoms containing spermicide; infertile sexual partner, and use by the female sexual partner of an IUD containing spermicide, female condom containing spermicide, contraceptive sponge containing spermicide, intravaginal system containing spermicide (e.g., NuvaRing®), diaphragm containing spermicide, cervical cap containing spermicide, or oral, implantable, transdermal, or injectable contraceptive. 10. To be included in any genetic study, patients must meet all of the inclusion criteria above and provide informed consent for genetic sampling and analysis.

[0303] Exclusion Criteria. Subjects were excluded from the study if they met any of the following criteria: 1. Diagnosis or treatment of clinically symptomatic biochemical or structural abnormalities of the gastrointestinal (GI) tract. 2. Any surgical procedure of the small intestine or colon, except appendectomy or cholecystectomy, or any other condition known to interfere with drug absorption, distribution, metabolism, or excretion. 3. Clinical evidence of significant cardiovascular, respiratory, renal, hepatic, gastrointestinal, hematological, metabolic, endocrine, neurological, or psychiatric disease, or any condition that may prevent the subject from successfully completing the study or that represents a safety risk to the subject. 4. History of severe or ongoing allergy / hypersensitivity as determined by the investigator, or history of hypersensitivity to any agent with a similar chemical structure or class to CPD002. 5. Two or more days of loose stools in the past seven days (Bristol stool form score of 6 or 7). 6. Hepatic dysfunction (alanine aminotransaminase [ALT] or aspartate aminotransaminase [AST] greater than 1.5 times the upper limit of normal [ULN]) or renal impairment (serum creatinine greater than ULN). 7. Clinically significant laboratory results at screening as determined by the investigator. 8. Evidence of or treatment of any malignancy, except non-melanoma malignancies of the skin. 9. Subject is unable or unwilling, in the opinion of the Investigator, to comply with the requirements of the protocol, which makes the results uninterpretable. 10. Use of diuretics, medications known to affect stool consistency and / or GI motility (including dietary fiber supplements (unless required by study), antidiarrheals, laxatives, antacids, opiates, anesthetics, prokinetics, enemas, antibiotics, probiotic medications or supplements), or salt or electrolyte supplements containing sodium, potassium, chloride, or bicarbonate preparations from CPU check-in (Day -2) to CPU check-out (Day 17). 11.- Use of an investigational drug within 30 days prior to Day 2. 12. Positive virological test (active hepatitis B infection, hepatitis C infection, or human immunodeficiency virus), alcohol, or drug abuse test during screening. 13. Use of any prescription medication within 7 days prior to admission to the CPU, or the need for long-term use of any prescription or non-prescription medication, except for hormone replacement therapy and hormonal contraceptives for postmenopausal women. 14. History of tobacco use, alcohol abuse, illicit drug use, serious psychiatric illness, physical dependence on opioids, or drug abuse or dependence within 12 months of study enrollment. 15. Had significant blood loss (>450 mL) or donated 1 or more units of blood or plasma within 8 weeks prior to study enrollment.

[0304] Investigational Medications. CPD002-HCl capsules, CPD002-HCl tablets, and CPD002 free base tablets. CPD002 bis-HCl salt is an amorphous off-white powder. CPD002 free base is a white crystalline solid. CPD002 is presented as either white, size 0 HPMC (hydroxypropyl methylcellulose) capsules or round, white tablets. Capsules were manufactured in a dosage strength of 15 mg based on the CPD002 dihydrochloride formula weight equivalent to 14 mg of CPD002 free base. To ensure comparable dosage strengths throughout the study, both the dihydrochloride and free base tablets were manufactured in a dosage strength reflecting 14 mg based on the free base. Capsules and tablets were packaged in white HDPE (high density polyethylene) bottles. CPD002 capsules and tablets were stored refrigerated (2-8°C) in their original packaging until use. The tablet components are listed in Table E11 below. [Table 5]

[0305] Dose and Route of Administration. CPD002 capsules or tablets, 15 mg (14 mg free base equivalent), were administered PO with approximately 240 mL of non-carbonated water twice daily before breakfast and dinner for 4 consecutive days per treatment period, with a 2-day washout period between treatments. Omeprazole 20 mg BID was administered to screened subjects beginning on day -5. All subjects received omeprazole 20 mg twice daily, 1 hour prior to ingestion of CPD002, daily until the last dose of study drug on day 16. See Table E12 below. [Table 6]

[0306] Once a subject was deemed eligible for randomization, they were assigned the next available randomization number sequentially and received the sequence of treatment outlined in the randomization schedule. All doses of study drug were administered under the supervision of clinic staff, who recorded the time and dose of administration on the case report form (CRF). Clinical staff examined the subject's mouth and hands after drug administration to ensure that the capsule was swallowed.

[0307] Fluid and food intake. Subjects participating in the study were fed a standardized diet with an approximate sodium content (approximately 1500 mg for each meal). Dietary phosphorus was not measured or set at a predetermined value. It was expected to be within typical values, i.e., 750 mg to 1250 mg per day. Subjects were not allowed to add salt or any other sodium containing spices or sauces to their meals.

[0308] Fluid intake was ad libitum, except as specified prior to drug administration. The daily menu (food and fluids) was similar during each treatment period.

[0309] Pharmacodynamic Variables. The following parameters were monitored as signals of potential drug activity: Urinary sodium excretion (daily) Fecal sodium excretion (daily)

[0310] Stool and urine collections were performed as described above (Example 8) and the pharmacodynamic activity of the three dosage forms was evaluated as follows: Baseline fecal excretion of phosphorus or sodium was established as the average daily fecal excretion of phosphorus or sodium between days -1 and 0, except for one subject whose baseline was established at the first washout period, i.e., days 6 and 7. Daily fecal excretion of phosphorus or sodium after treatment was measured by averaging fecal phosphorus or sodium excretion over the 4-day treatment period. The same method was used for urine.

[0311] Results. The results are presented in WO2014 / 169094. Statistical analysis was performed by one-way ANOVA; (*); p<0.05, (**); p<0.01, (***); p<0.001.

[0312] The median mean daily excretion of phosphorus (+ / -SE) is presented in WO2014 / 169094. Except for one subject in whom a baseline was established during the first washout period, i.e., days 6 and 7 (referred to as "pre-dose"), baseline fecal excretion of phosphorus or sodium was established as the mean daily fecal excretion of phosphorus or sodium between days -1 and 0. Daily fecal excretion of phosphorus following treatment with 15 mg BID HCl tablets was measured by averaging fecal phosphorus or sodium excretion over the 4-day treatment period.

[0313] Except for one subject for whom a baseline was established during the first washout period, i.e., days 6 and 7 (referred to as "pre-dose"), baseline fecal excretion of sodium was established as the average daily urinary excretion of sodium between days -1 and 0. Daily urinary excretion of sodium after treatment with the three forms of the formulation was measured by averaging urinary sodium excretion over the four-day treatment period.

[0314] Except for one subject for whom a baseline was established during the first washout period, i.e., days 6 and 7 (referred to as "pre-dose"), baseline fecal excretion of phosphorus was established as the average daily urinary excretion of phosphorus between days -1 and 0. Daily urinary excretion of phosphorus after treatment with the three forms of the formulation was measured by averaging urinary sodium excretion over the four-day treatment period.

[0315] Example 8 Effect of Renvela® on the pharmacodynamics of CP002 A Phase 1, single-center, randomized, open-label study was designed to evaluate the effect of Renvela® on the pharmacodynamic activity of CP002 administered PO twice daily for 4 days in healthy male and female subjects.

[0316] Subjects were screened within 3 weeks of enrollment. Eighteen subjects checked into the CPU before dinner on day -2. Each subject was fed a diet standardized for Na+ content while on the CPU. Subjects were administered 15 mg of CP002 BID on days 1-4 and 7-10. Breakfast and / or dinner were provided to subjects within approximately 5 minutes of administration. Subjects were administered one Renvela® 800 mg tablet with breakfast, lunch, and dinner (either days 1-4 or days 7-10) during one of two treatment periods (randomized). There was a 2-day washout period between each treatment period. While on the CPU, subjects were provided with a Na+ standardized diet according to CPU procedures. Pharmacodynamic assessments included 24-hour fecal sodium and phosphorus measurements.

[0317] Subject inclusion criteria and description of study medication were the same as those described in Example 9 (see above). The schedule of assessments and procedures is shown in Table E13 below. [Table 7]

[0318] Pharmacodynamic variables. Baseline fecal excretion of phosphorus or sodium was established as the average daily fecal excretion of phosphorus or sodium between days -1 and 0. Daily fecal excretion of phosphorus or sodium after treatment was measured by averaging fecal phosphorus or sodium excretion over the 4-day treatment period. Sodium and phosphorus analysis methods were performed as described in Example 8 (see above).

[0319] Results. Data are presented in WO2014 / 169094. Statistical analysis performed by one-way ANOVA followed by Tukey's multiple comparison test; (*); p<0.05, (**); p<0.01, (***); p<0.001. vs. pre-treatment.

[0320] Here, baseline fecal excretion of sodium was established as the average daily fecal excretion of phosphorus or sodium between days -1 and 0 (referred to as "pre-dose"). Daily fecal excretion of sodium following treatment with BID HCl tablets was determined by averaging fecal sodium excretion over the 4-day treatment period.

[0321] The median mean daily fecal excretion of phosphorus (+ / -SE) is presented in WO2014 / 169094. Baseline fecal excretion of phosphorus was established as the mean daily fecal excretion of phosphorus between days -1 and 0 (referred to as "pre-dose"). Daily fecal excretion of phosphorus after treatment with 15 mg BID HCl tablets was determined by averaging fecal phosphorus excretion over the 4-day treatment period.

[0322] Example 9 Tenapanor and sevelamer combination therapy animal A total of 48 male Sprague Dawley (SD) rats (Envigo, Livermore, CA), approximately 8 weeks of age weighing approximately 250 g on arrival, were housed two per cage in microisolator cages for a 48-h acclimation period before being assigned to study groups. Animals were housed in a temperature (65-75°F) and humidity (35-55%) controlled facility utilizing a reversed 12-h light / dark cycle (7 am to 7 pm dark cycle). Rats had free access to standard rodent chow (1:1 sodium:potassium salt, TD.160470, 1.1% w / w total phosphorus content, Harlan-Teklad, Madison, WI) with additional 0.4% inorganic phosphorus, and deionized drinking water for the duration of the study. Body weights were recorded at the start of the study and daily for the remainder of the study. Animals were maintained in accordance with the Guidelines for the Care and Use of Laboratory Animals (National Research Council, 2011). Studies were conducted according to protocols approved by the Institutional Animal Care and Use Committee.

[0323] research design Rats were randomly assigned to one of eight groups (n=6 / group) that received diets containing various amounts of sevelamer (0-3% w / w) and were orally gavaged twice daily with vehicle (0.01% Tween 80) or tenapanor (0.15 mg / kg) for 11 consecutive days according to the study allocation shown in the table below. [Table 8]

[0324] Rats orally administered vehicle and provided with diet without sevelamer (group 1) served as the control group. Treatment groups included groups treated with tenapanor alone (0.15 mg / kg, bid), sevelamer alone (0.75, 1, 5, or 3% w / w in diet), and combinations of tenapanor (0.15 mg / kg, bid) with each dose level of sevelamer (0.75, 1, 5, or 3% w / w in diet).

[0325] Animals were dosed in their home cages while pair-housed for the first five treatment days. On the sixth treatment day, all animals were individually housed in metabolic cages for the remainder of the study and continued to be provided with free access to diet containing 0-3% sevelamer w / w and were dosed with vehicle or tenapanor twice daily. After 2 days of acclimation to the metabolic cages, 24-h food intake, water intake, and urine volume were measured and recorded over the final four treatment days. Urinary sodium and phosphorus concentrations were measured by ion chromatography (IC). 24-h urinary sodium and phosphorus excretion was calculated by multiplying the ion concentration by the 24-h urine volume. Urinary ion excretion was also normalized to daily dietary ion intake to account for diurnal variations in food intake. Terminal blood samples were obtained by cardiac puncture under isoflurane anesthesia for serum sodium and phosphate measurements (Alera, Alpha Wassermann, West Caldwell, NJ) to allow calculation of renal clearance of sodium and phosphate to further assess renal ion handling.

[0326] Dosing solutions and dietary formulations Dosing solutions containing tenapanol (Ardelyx, Fremont CA) at a concentration of 0.03 mg / mL were made fresh weekly by adding the appropriate weight of tenapanol to a 0.1% Tween 80 vehicle. Dose volumes were 5 mL / kg for all groups. Standard rodent chow with phosphate was weighed into a mixing bowl. The appropriate amount of sevelamer carbonate (Renvela, Genzyme) was added to the powdered diet (sevelamer 0, 0.75, 1.5, or 3% w / w) in the mixing bowl and placed on a stand mixer (KitchenAid) and set to agitation speed 2 for 10 minutes.

[0327] Dose Administration Animals were dosed twice daily (bid) orally (po) just before lights out (7 am) and in the middle of the dark cycle (2 pm) using a standard gavage needle (38 mm, 20 G). Animals were removed from holding or metabolic cages for dosing and then immediately returned to their home cages.

[0328] Urinary ion analysis by ion chromatography Urine samples were analyzed for sodium and phosphorus content on an ion chromatography system (Thermo Fisher Scientific ICS-3000 or ICS-5000+) with a conductivity detector. Chromatographic separation of cations was performed using an IonPac HPLC system with isocratic elution using 25 mM methanesulfonic acid. Analytical separation was performed using a CS12A (Thermo Fisher) 2 x 250 mm analytical column. Chromatographic separation of anions was performed using an IonPac AS18 (Thermo Fisher) 2 x 250 mm analytical column with isocratic elution using 35 mM potassium hydroxide. Concentrations were interpolated from standard curves (prepared in 10 mM hydrochloric acid) for each analyte ion based on retention time and peak area.

[0329] statistical analysis All data sets for each group are presented by mean ± SEM. Statistical analysis was performed using one-way ANOVA followed by Tukey's post-hoc test to correct for multiple comparisons and allow comparison of individual groups. Statistical significance between groups was marked *, P<0.05; **, P<0.01; and ***, P<0.001 compared to the vehicle group. The BLISS independence model was used to statistically determine whether the combination of tenapanor and sevelamer was independent, synergistic, or antagonistic. The BLISS independence model is defined by the following equation, which compares the predicted response to the combination, calculated using full additivity of probability theory based on the observed effect of each individual drug administered alone, compared to the observed effect of the combination treatment: Y ab,P =Y a +Y b -Y a Y b In the formula, Y a = % efficacy of drug A at dose A, Y b = % efficacy of drug B at dose B, Y ab,P = predicted efficacy of the combination, and Y ab,O = observed efficacy of the combination.

[0330] Also, comparing predicted combination efficacy with observed combination efficacy, Y ab,O >Y ab,P = Synergy, Y ab,O =Y ab,P = independence (additivity), and Y ab,O <Y ab,P = antagonistic effect.

[0331] result Effects on body weight, food intake, and calculation of administered sevelamer dose Body weight and food intake were not significantly affected by tenapanor, sevelamer, or combination treatment compared to controls. When sevelamer was administered as a dietary admixture, the actual dose of sevelamer delivered in the food was calculated based on the food consumed. There was a linear increase in sevelamer dose with increasing sevelamer content in the food, the sevelamer dose was stable over time, and coadministration of tenapanor did not significantly affect the dose of sevelamer consumed in the food. As a result, the dose of sevelamer was well matched between the tenapanor-treated group consuming sevelamer and the non-tenapanor-treated group, allowing for a direct comparison of the combination effect. The sevelamer doses administered on the last day of the study are summarized in the table below, along with conversion to human equivalent dose based on body surface area conversion (1 / 7). [Table 9]

[0332] The recommended human starting dose of sevelamer is 2.4-4.8 g / day; therefore, based on dose conversion, the 0.75% sevelamer dose in rats is approximately equivalent to the recommended human starting dose of sevelamer.

[0333] Effect on urinary phosphorus excretion 24-hour urinary phosphorus excretion over the last 4 days of treatment is shown in FIG. 4A, and for clarity, the final treatment day is shown in FIG. 4B. Tenapanor treatment alone significantly reduced urinary phosphorus excretion compared to vehicle control. Sevelamer significantly and dose-dependently reduced urinary phosphorus excretion, and in combination with tenapanor, dose-dependently reduced urinary phosphorus excretion, such that reductions with the combination were significantly greater than either tenapanor or equivalent doses of sevelamer alone across all sevelamer dose levels. Normalization of urinary phosphorus excretion to dietary phosphorus intake to account for any variation in daily intake over the last 4 days of treatment is shown in FIG. 4C, and for clarity, the final treatment day is shown alone in FIG. 4D. The enhanced urinary phosphorus reduction of the combination of tenapanor and sevelamer compared to equivalent doses of tenapanor or sevelamer alone is confirmed by this analysis, ruling out variation in dietary phosphorus intake as a confounding effect.

[0334] The interaction between tenapanor and sevelamer was assessed using the BLISS independence model and is summarized in the table below. [Table 10]

[0335] The average urinary phosphorus excretion over the entire 4-day collection period for each treatment group was used in this analysis to ensure that all data points collected were included in the evaluation of combination effect. The observed reduction in urinary phosphorus excretion with combination treatment compared to the vehicle control (Group 1) was then compared to the predicted reduction in urinary phosphorus excretion with combination treatment based on the BLISS model. The observed reduction in urinary phosphorus excretion with combination treatment was greater than the predicted reduction based on the single-agent effect by the BLISS model for all sevelamer doses combined with tenapanor, indicative of a synergistic effect. The difference in the observed combination effect (64.8% reduction) from the predicted combination effect with tenapanor (47.2% reduction) was greatest at the lowest (0.75% w / w) sevelamer dose. This suggests that tenapanor and sevelamer act synergistically to reduce urinary phosphorus excretion, an index of intestinal phosphate absorption, especially at the lower, clinically relevant sevelamer doses.

[0336] Effect on urinary sodium excretion Tenapanor treatment significantly reduced urinary sodium excretion compared to vehicle controls, whereas sevelamer alone had no significant effect on urinary sodium excretion. Tenapanor also significantly reduced urinary sodium excretion compared to controls when coadministered with all doses of sevelamer. Sevelamer at doses of 0.75% and 1.5% w / w did not significantly affect the magnitude of the sodium-lowering effect of tenapanor. However, the highest dose of sevelamer (3% w / w) modestly but significantly attenuated the sodium-lowering effect of tenapanor. Normalization of urinary sodium excretion to dietary sodium intake to account for any variation in daily intake over the final 4 days of treatment demonstrated that the observations in urinary sodium excretion were not confounded by variation in sodium intake. The BLISS model confirmed that the urinary sodium reduction observed with the combination of tenapanor and sevelamer 3% w / w was less than that predicted based on the individual drug treatments (table below), indicating that high doses of sevelamer (3% w / w), equivalent to approximately 20 g / day of sevelamer in humans and likely of no clinical significance, attenuate the sodium-reducing pharmacodynamic effect of tenapanor. [Table 11]

[0337] Effect on renal clearance of phosphorus and sodium Tenapanor and sevelamer alone significantly reduced renal clearance of phosphorus, reflecting an appropriate renal response in the face of reduced intestinal phosphorus absorption. In combination with tenapanor, sevelamer further and dose-dependently reduced phosphorus clearance, such that the reduction with the combination was significantly greater than either tenapanor or equivalent doses of sevelamer alone. Tenapanor alone significantly reduced renal clearance of sodium, reflecting an appropriate renal response that conserves sodium in the face of reduced intestinal phosphorus absorption. Sevelamer alone did not affect intestinal sodium absorption and therefore did not affect renal sodium handling. Renal clearance of sodium was not significantly affected by sevelamer at 0.75% or 1.5% w / w when combined with tenapanor. However, compared with tenapanor alone, combination with sevelamer at 3% w / w resulted in significantly higher renal clearance of sodium, reflecting a weakening of the sodium-lowering pharmacodynamic effect of tenapanor when combined with this high dose of sevelamer. The present invention provides, for example, the following items. (Item 1) 1. A method for lowering serum phosphate in a patient comprising administering an effective amount of an epithelial phosphate transport inhibitor in combination with a phosphate binder, wherein the amount of the phosphate binder administered is less than the amount administered as a single agent. (Item 2) 2. The method of claim 1, wherein the phosphate binder is selected from the group consisting of sevelamer, lanthanum carbonate, calcium carbonate, calcium acetate, calcium acetate / magnesium carbonate, MCI-196, ferric citrate, sucroferric oxyhydroxide, magnesium ferric hydroxycarbonate, aluminum hydroxide, APS1585, SBR-759, and PA-21. (Item 3) 2. The method of claim 1, wherein the epithelial phosphate transport inhibitor is a compound that lowers the pH of epithelial cells. (Item 4) The method of claim 3, wherein the compound is selected from the group consisting of NHE3 inhibitors, guanylate cyclase C receptor (GC-C) agonists, P2Y agonists, adenosine A2b receptor agonists, soluble guanylate cyclase agonists, adenylate cyclase receptor agonists, imidazoline-1 receptor agonists, cholinergic agonists, prostaglandin EP4 receptor agonists, dopamine D1 agonists, melatonin receptor agonists, 5HT4 agonists, atrial natriuretic peptide receptor agonists, carbonic anhydrase inhibitors, phosphodiesterase inhibitors, and downregulated in adenomas (DRA or SLC26A3) agonists. (Item 5) the epithelial phosphate transport inhibitor is an NHE3 inhibitor having the structure of formula (I) or (IX), [ka] During the ceremony, NHE is an NHE-linked small molecule comprising (i) a heteroatom-containing moiety and (ii) a cyclic or heterocyclic backbone or support moiety bonded directly or indirectly thereto, said heteroatom-containing moiety being selected from a substituted guanidinyl moiety and a substituted heterocyclic moiety which may optionally be fused with said backbone or support moiety to form a fused bicyclic structure; Z is a moiety having at least one site thereon for attachment to said NHE-binding small molecule, and the resulting NHE-Z molecule has overall physicochemical properties that render it substantially impermeable or substantially systemically non-bioavailable; 5. The method according to any one of items 1 to 4, wherein E is an integer having a value of 1 or greater. (Item 6) the compound is an oligomer, dendrimer, or polymer, and further wherein Z is a core moiety having two or more moieties thereon for attachment to multiple NHE-binding small molecules, either directly, or indirectly through a linking moiety L, the compound having the structure of formula (X): [ka] 5. The method of any of items 1 to 4, wherein L is a bond or linker connecting the core to the NHE-binding small molecule, n is an integer equal to or greater than 1, and further wherein each NHE-binding small molecule can be the same or different from the other. (Item 7) The NHE-binding small molecule has the structure of formula (IV): [ka] or a stereoisomer, prodrug, or pharma- ceutically acceptable salt thereof; During the ceremony, each R, R, R, R, and R is independently selected from H, halogen, -NR(CO)R, -(CO)NR, -SO-NR, -NRSO, -NR, -OR, -SR, -O(CO)NR, -NR(CO)OR, and -NRSONR; wherein R and R are independently selected from H, or a bond connecting said NHE-binding small molecule to L, with the proviso that at least one is a bond connecting said NHE-binding small molecule to L; R4 is selected from H, C1-C7 alkyl, or a bond linking the NHE-binding small molecule to L; R6 is absent or selected from H and C1-C7 alkyl; 7. The method according to item 6, wherein Ar1 and Ar2 independently represent an aromatic ring or a heteroaromatic ring. (Item 8) The NHE binding small molecule has the following structure: [ka] or a stereoisomer, prodrug, or pharma- ceutically acceptable salt thereof; During the ceremony, The method of claim 6, wherein each R1, R2, and R3 is independently selected from H, halogen, -NR7(CO)R8, -(CO)NR7R8, -SO2-NR7R8, -NR7S02R8, -NR7R8, -OR7, -SR7, -O(CO)NR7R8, -NR7(CO)OR8, and -NR7S02NR8, wherein R7 and R8 are independently selected from H, or a bond connecting the NHE-binding small molecule to L, with the proviso that at least one is a bond connecting the NHE-binding small molecule to L. (Item 9) The NHE binding small molecule has one of the following structures: [ka] or a stereoisomer, prodrug, or pharma- ceutically acceptable salt thereof. (Item 10) The NHE3 inhibitor is [ka] or a pharma- ceutically acceptable salt thereof. (Item 11) A pharmaceutical composition comprising an epithelial phosphate transport inhibitor and a phosphate binder, wherein the amount of said phosphate binder administered is less than the amount administered as a single agent. (Item 12) 12. The composition of claim 11, wherein the epithelial phosphate transport inhibitor is tenapanor. (Item 13) 12. The composition according to item 11, wherein the amount of the phosphate binder is 50% of the amount administered as a single agent. (Item 14) 12. The composition according to item 11, wherein the amount of the phosphate binder is about 40% of the amount administered as a single agent. (Item 15) 12. The composition according to item 11, wherein the amount of the phosphate binder is about 30% of the amount administered as a single agent. (Item 16) 12. The composition according to item 11, wherein the amount of the phosphate binder is about 20% of the amount administered as a single agent.

Claims

[Claim 1] The invention described in this specification.

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