AU2006202213A1

AU2006202213A1 - Bile acid containing prodrugs with enhanced bioavailability

Info

Publication number: AU2006202213A1
Application number: AU2006202213A
Authority: AU
Original assignee: University of Maryland at Baltimore
Current assignee: University of Maryland at Baltimore
Priority date: 2000-04-07
Filing date: 2006-05-25
Publication date: 2006-06-15
Also published as: CA2405151A1; JP2003530329A; AU2001253226B2; EP1267898A4; WO2001076531A2; WO2001076531A3; AU5322601A; EP1267898A2

Description

Our Ref: 12678241 P/00/011 Regulation 3:2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): University of Maryland, Baltimore 520 West Lombard Street Baltimore Maryland 21201 United States of America Address for Service: Invention Title: DAVIES COLLISON CAVE Patent Trade Mark Attorneys 255 Elizabeth Street Sydney, New South Wales, Australia, 2000 Bile acid containing prodrugs with enhanced bioavailability The following statement is a full description of this invention, including the best method of performing it known to me:- 5951 BILE ACID CONTAINING PRODRUGS WITH ENHANCED BIOAVAILABILITY Background of the Invention Field of Invention This invention relates to the method of increasing the bioavailability and reducing the bioavailability variability of compounds by conjugating or linking a bile acid to the compound. This invention also relates to the new composition of matter obtained by attaching a bile acid to another compound to generate a prodrug. This invention further relates to the usage of the bile acid transporter to actively move a to prodrug out of the lumen of the small intestine.

Description of the Related Art Insufficient or variable intestinal permeability is a reason for inadequate oral drug bioavailability. Many methods are available to increase bioavailability of various drugs While some of these methods improve the bioavailability of some drugs, not one method works for all compounds.

Some compounds that exhibit poor bioavailability, sub-optimal permeability, or variable bioavailability may have some or all of the following characteristics 1. Less than complete oral absorption.

2. Permeability less than a suitable reference marker metoprolol tartrate a permeability of 40 x 10- 6 cm/sec across Caco-2 monolayers]).

3. Molecular weight greater than 500 Daltons.

4. Hydrogen donors greater than five.

-1- Hydrogen bond acceptors greater than 6. Being substrates for P-glycoprotein efflux, Multi-drug Resistanceassociated Protein (MRP) efflux, or other efflux systems.

7. Not being substrates of or ligands for a carrier or transporter.

One potential method to increase the bioavailability of compounds with these characteristics is to conjugate a bile acid to the drug or compound to create a prodrug.

A bile acid conjugated prodrug allows for an increase in bioavailability and/or a reduction in the variability of the compound because of active transport of the prodrug by the intestinal bile acid transporter (IBAT). The intestinal absorption of bile acids is a sodium dependent process involving the human intestinal bile acid transporter (hlBAT) and Na'/K ATP-ase The bile acid transporter is an ideal candidate for drug targeting because the human IBAT has a high transport capacity of 10 grams per day and bile acids are one of the largest molecules taken up by a carrier mediated system In light of this biology, the bile acid transporter appears to be a promising mechanism to improve oral drug absorption by incorporating a bile acid moiety with an active drug in a prodrug fashion. The bile acid prodrug approach to targeting the bile acid transporter in various tissues has been investigated with peptides 8, HMG- CoA reductase inhibitors and chlorambucil This work was directed either at extremely small molecules or for targeting delivery of drugs to the liver. Other attempts at drug therapy involve inhibiting the bile acid transporter to reduce cholesterol synthesis in the liver [11].

-2- One compound that may benefit from bile acid conjugation to improve uptake in the small intestine is acyclovir. Acyclovir is an anti-viral compound, used to inhibit herpes virus proliferation. Its target is not the liver but all tissues within the body.

Typical treatment requires 200 mg doses administered five times daily, with a bioavailability after oral administration of 20% [12].

A different prodrug strategy has proved successful at improving the oral bioavailability of acyclovir [13, 14]. Valacyclovir, the L-valine ester prodrug of acyclovir, has an oral bioavailability of 54% This improved bioavailability for valacyclovir allows for a more convenient dosing regimen of 1000 mg, twice daily, with similar clinical efficacy as previously found for the acyclovir parent compound Valacyclovir is a substrate for the human intestinal peptide transporter (PepT1), with a Ki=4.08 mM in PepTI expressing Xenopus laevis oocytes [17] and

K

i =1.10 mM in stable lines of CHO/PepTI [18].

In comparison to PepTI, IBAT has the potential advantages of higher capacity and micromolar affinity. Therefore, it is possible to further enhance the oral bioavailability of acyclovir by synthesizing a cholic acid ester prodrug to target the IBAT. It is also possible to increase the bioavailability of other compounds by conjugating the compounds to a bile acid.

Furthermore, animals other than humans have an intestinal bile acid transporter. One can use the animal intestinal bile acid transport and a bile acid conjugated prodrug to increase the adsorption of the prodrug and bioavailability of the compound in animals.

P;\WPDOCS\CRAMMV7744590 new pIge 2 doc- Summary of the Invention

IND

In a first broad form, the present invention relates to increasing the bioavailability of a compound by conjugating a compound to a bile acid to create a prodrug.

Accordingly, in a first aspect, the invention provides a compound represented by formula IX: x/ R, x

R,

wherein R 1

R

2 and R 3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and betahydroxyl; x is a moiety containing a metabolically labile bond; and R 4 is selected from the group consisting of an agent having biological, activity and a metabolic precursor of an agent having biological activity; or a pharmaceutically acceptable salt or solvate thereof.

According to a second aspect, the invention further provides a compound represented by formula X: wherein R 2 and R 3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R 4 is a moiety that enhances binding of the compound to the intestinal bile acid transporter; X is a moiety containing a metabolically labile bond; -4- P:\WPDOCS\CRNAAMM\7744 909nw pags 2 docand Ri is selected from the group consisting of an agent having biological, activity or a metabolic precursor of an agent having biological activity; or a pharmaceutically acceptable salt or solvate thereof.

According to a third aspect, the invention further provides a compound represented by formula XI: R4 3 x R2 XI wherein RI and R 3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R 4 is a moiety that enhances binding of the compound to the intestinal bile acid transporter; X is a moiety containing a metabolically labile bond; and R 2 is selected from the group consisting of an agent having biological activity and a metabolic precursor of an agent having biological activity; or a pharmaceutically acceptable salt or solvate thereof.

According to a fourth aspect, the invention further provides a compound represented by formula XIII: R4XIII S2

XIII

P:.WPDOCS\CRN AMM\774459n n pags 2.ocwherein R 2 and R 3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R4 is a solubility enhancing moiety; X is a moiety containing a metabolically labile bond; and RI is selected from the group consisting of an agent having biological activity and a metabolic precursor of an agent having biological activity; or a pharmaceutically acceptable salt or solvate thereof.

According to a fifth aspect, the invention further provides a compound represented by formula XIV: 3 R2 XIV wherein RI and R 3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R 4 is a solubility enhancing moiety; X is a moiety containing a metabolically labile bond; and R 2 is selected from the group consisting of an agent having biological activity and a metabolic precursor of an agent having biological activity; or a pharmaceutically acceptable salt or solvate thereof.

According to a sixth aspect, the invention further provides a compound represented by formula XV: RR X R 4 RI XV p:\WPDOCS\CRNAMf7744590 fn page 2 doewherein R 1 and R 2 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R 4 is a solubility enhancing moiety; X is a moiety containing a metabolically labile bond; and R 3 is selected from the group consisting of an agent having biological activity and a metabolic precursor of an agent having biological activity; or a pharmaceutically acceptable salt or solvate thereof.

According to a s.eventh aspect, the invention further provides a method of increasing the bioavailability of an agent having biological activity or a metabolic precursor of an agent having biological activity or reducing the variability of said bioavailability, said method comprising: conjugating a bile acid to said agent having biological activity or said metabolic precursor of an agent having biological activity through a metabolically labile bond to form a prodrug, and orally administering said prodrug to a subject in need thereof, wherein said prodrug is selected from the compounds according to the present invention.

According to a eighth aspect, the invention further provides a method of eliminating adverse interactions between an agent having biological activity or a metabolic precursor of an agent having biological activity and a compound, wherein said adverse interactions result from intestinal absorption of at least one of said agent having biological activity or said metabolic precursor of an agent having biological activity and said compound, said method comprising: conjugating a bile acid to said agent having biological activity or said metabolic precursor of an agent having biological activity through a metabolically labile bond to form a prodrug, and orally administering said prodrug to a subject in need thereof, wherein said prodrug is selected from the compound according to the present invention.

According to a ninth aspect, the invention further provides a method of eliminating adverse interactions between an agent having biological activity or a metabolic precursor of an agent having biological activity and a compound, wherein said adverse interactions result from intestinal absorption of said compound or said agent having biological activity or metabolic precursor of an agent having biological activity, said method comprising: conjugating a bile acid to said agent having biological activity or said metabolic precursor of an agent having biological activity through a metabolically labile bond to form a prodrug, and orally administering said prodrug to a subject in need thereof, wherein said -4c- P:\WPDOCS\CRN\ MM\7744S90 ftw pagr 2 docprodrug is selected from the compounds according the present invention.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers or steps.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

In a preferred form, a compound of the invention is of the formula:

R,

R2 wherein Ri, R 2 and R 3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R4 is selected from the group consisting of an agent having biological activity and a metabolic precursor of an agent having biological activity; or a pharmaceutically acceptable salt, solvent, or polymorph thereof.

In a further preferred form, a compound of the invention is of the formula: P.\\VPDOCSXCRNV.NM77f44590 n paga 2 doe.

wherein R 2 and R 3 are independently selected from the group consisting of hydrogen, aipha-hydroxyl, and beta-hydroxyl; R, is selected from the group an agent having P "'I'DOCS CRN SIETSI 77-159T,, P a de.

biological activity and a metabolic precursor of an agent having biological activity; R 4 is any chemical moiety that enhances binding of the compound to The intestinal bile acid transporter; or a pharmaceutically acceptable salt, solvent or polymorph thereof.

In yet another preferred form, a compound of the invention is of the formula: wherein RI and R 3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl;

R

3 is selected from the group an agent having biological activity and a metabolic precursor of an agent having biological activity; R, is any chemical moiety that enhances binding of the compound to the intestinal bile acid transporter; or a pharmaceutically acceptable salt, solvent, or polymorph thereof.

Preferably, a further compound of the invention is of the formula:

R,

vherein R, and R 2 are independently selected from The group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl;

R

3 is selected from the group an agent having biological activity and a metabolic precursor of an agent having biological activity;

R

4 is P A.'Vr)OCS CRN.sFr ps7S any chemical moiety that enhances binding of the compound to the intestinal bile acid transporter; or a pharmaceutically acceptable salt, solvent, or polymorph thereof In yet another preferred form, a compound of the invention is of the formula: wherein R 2 and R 3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R, is selected from the group an agent having biological activity and a metabolic precursor of an agent having biological activity; R 4 is any chemical moiety that increases solubility of the compound; or a pharmaceutically acceptable salt solvent, or polymorph thereof.

In still yet another preferred form, a compound is of the formula: P AYPDOCYCRN Sr.'Spcc%7744j94),.- PXdudlc wherein R, and R 3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl;

R

2 is selected from the group an agent having biological activity and a metabolic precursor of an agent having biological activity;

R

4 is any chemical moiety that increases solubility of the compound; or a pharmaceutically acceptable salt, solvent, or polymorph thereof.

In another preferred form, a compound of the invention is of the formula: Ra C' R, wherein R, and R 2 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl;

R

In still yet another preferred form, a compound is of the formula: P \VP[t)(S*(KRNISEr Spc.77.5W- pryg d- RR R

X

Preferably, the prodrug is administered orally to an animal or human.

Even more preferably, the intestinal bile acid transporter binds to the prodrug and moves the prodrug from the lumen of the small intestine into brush border cells.

In yet another preferred form, the prodrug or compound moves from inside the brush border cells into the blood stream.

In another preferred form, the bioavailability of a compound is increased by conjugating a compound to a bile acid to create a prodrug.

Preferably, a metabolically labile bond exists between the compound and the bile acid.

Even more preferably, the prodrug is administered orally to an animal or human.

In another preferred form, the intestinal bile acid transporter binds to the prodrug and moves the prodrug from the lumen of the small intestine into brush border cells.

In still yet another preferred form, the bioavailability of a compound is increased by linking a compound to a bile acid via a linker group to create a prodrug.

In still another preferred form, the prodrug is administered orally to an animal or human.

Preferably, the intestinal bile acid transporter binds to the prodrug and moves the prodrug from the lumen of the small intestine into brush border cells.

P VRDOCSCRN'SF:' II'S1Cr71 771) 59n p, c d Even more preferably, the prodrug or compound moves from inside the brush border cells into the blood stream.

In still yet another preferred form, the linker group may be any bifunctional chemical moiety that achieves one or more of the following four functions: facilitates the synthesis of the prodrug, aid or enhance the binding of the prodrug to the intestinal bile acid transporter (IBAT), make it easier for the compound to disassociate from the bile acid after the prodrug has passed out of the lumen of the small intestine, enhance the solubility of the prodrug inside the body.

Preferably, the linker group may be any size, but more preferably be less than 200 daltons.

Even more preferably, a metabolically labile bond exists between the linker group and the compound, between the linker group and the bile acid, or within the linker group itself.

In a further preferred form, the bioavailability of a biologically active compound is increased by conjugating a biologically active compound to a bile acid to create a prodrug.

In another preferred form, a metabolically labile bond exists between the biologically active compound with the bile acid.

Preferably, the prodrug is administered orally to an animal or human.

In another preferred form, the prodrug or compound moves from inside the brush border cells into the blood stream.

In still yet another preferred form, a compound is conjugated to a bile acid to form a prodrug.

In another preferred form, the present invention relates to a phanraceutical compound containing a compound and a bile acid.

In still yet another preferred form, the present invention relates to a pharmaceutical compound containing a compound, a metabolically labile bond, and a bile acid.

In a further preferred form, the present invention relates to a pharmaceutical compound containing an agent, a linker group, and a bile acid.

P ETS1I, \T7.459D, .cq do- Preferably, the present invention relates to a pharmaceutical compound containing an agent, a linker group, a bile acid, and a metabolically labile bond.

In another preferred form, the present invention relates to a pharmaceutical compound containing an agent with biological activity and a bile acid.

In yet another preferred form, the present invention relates to a pharmaceutical compound containing an agent with biological activity, a metabolically labile bond, and a bile acid.

In a further preferred form, the present invention relates to a pharmaceutical compound containing an agent with biological activity, a linker group, and a bile acid.

In still yet another preferred form, the present invention relates to a pharmaceutical compound containing an agent with biological activity, a linker group, a bile acid, and a metabolically labile bond.

Preferably, the present invention utilizes the intestinal bile acid transporter to actively uptake and remove from the lumen of the small intestine a bile acid containing prodrug.

In another preferred form, the present invention relates to a method for increasing the bioavailability of a compound by using the intestinal bile acid transporter to actively uptake and remove from the lumen of the small intestine a bile acid containing prodrug.

Preferably, the inventions uses a linker group to link a compound to a bile acid to create a prodrug.

Even more preferably, the linker group may be any bifunctional chemical moiety that achieves one or more of the following four functions: facilitates the synthesis of the prodrug, aid or enhance the binding of the prodrug to the intestinal bile acid transporter (IBAT), make it easier for the compound to disassociate from the bile acid after the prodrug has passed out of the lumen of the small intestine, enhance the solubility of the prodrug inside the body.

Even more preferably, the linker group may be any size, and even more preferably, less than 200 daltons.

Preferably, the linker group, when attached to the compound or the bile acid, results in a metabolically labile bond being present.

P %IVPDOCSC RSr. 7s'P Ilr Even more preferably, the bioavailability variability of a compound is reduced by conjugating a compound to a bile acid to create a prodrug.

In a further preferred form, the prodrug is administered orally to an animal or human.

Even more preferably, the prodrug or compound moves from inside the brush border cells into the blood stream.

In yet another preferred form, the bioavailability variability of a compound is reduced by conjugating a compound to a bile acid to create a prodrug.

Even more preferably, the prodrug is administered orally to an animal or human.

In a further preferred form, the intestinal bile acid transporter binds to the prodrug and moves the prodrug from the lumen of the small intestine into brush border cells.

Preferably, the bioavailability variability of a compound is reduced by linking a compound to a bile acid via a linker group to create a prodrug.

Even more preferably, the prodrug is administered orally to an animal or human.

In still yet another preferred form, the linker group may be a bifunctional chemical moiety.

Even more preferably, the linker group may be any size, but more preferably is less than 200 daltons.

Preferably, a metabolically labile bond exists between the linker group and the compound, between the linker group and the bile acid, or within the linker group itself.

-lOa- P wI'pw k-4s 7 13 11() P..s doc- Even more preferably, the bioavailability variability of a biologically active compound is reduced by conjugating a biologically active compound to a bile acid to create a prodrug.

In a further preferred form, a metabolically labile bond exist between the biologically active compound with the bile acid.

In another preferred form, the prodrug is administered orally to an animal or human.

In still yet another preferred form, the intestinal bile acid transporter binds to the prodrug and moves the prodrug from the lumen of the small intestine into brush border cells.

In another preferred form, an adverse drug-drug interaction is reduced or prevented by linking or conjugating a bile acid to at least one of the compounds which is involved in the adverse drug-drug interaction to create a prodrug.

Preferably, the intestinal bile acid transporter is used to uptake the prodrug, thereby avoiding a transporter that is involved in the adverse drug-drug interaction.

Even more preferably, an adverse drug-nutrient interaction is reduced or prevented by linking or conjugating a bile acid to a compound which is involved in the adverse drugnutrient interaction to create a prodrug.

In a further preferred form, the intestinal bile acid transporter is used to uptake the prodrug, thereby avoiding a transporter that is involved in the adverse drug-nutrient interaction.

In yet another preferred form, the lipophilicity of a compound is increased by linking or conjugating a bile acid to the compound.

Preferably, the increased lipophilicity will increase the bioavailability and reduce the variability of the bioavailability of the compound.

Even more preferably, the compound component of the prodrug will be cleaved from the prodrug after the prodrug binds to the intestinal bile acid transporter.

In another preferred form, the prodrug is coated with a substance that protects the prodrug from the acidic environment of the stomach and that does not inhibit absorption of the prodrug in the intestine.

r.WVDOC'S CRNL; T.Sp4ci.7459l p> oC.j- In a further preferred form, the present invention relates to a pharmaceutical compound of acyclovir valyldeoxycholate.

In still another preferred form, the present invention relates to a pharmaceutical compound of acyclovir valylchenodeoxycholate.

Even more preferably, the present invention relates to a pharmaceutical compound of atenolol cholic acid amide.

Description of Several Views of the Drawings FigurelA illustrates the general structure of bile acids.

Figure 1B illustrates the general structure of the prodrug.

Figure 1C generalizes the synthesis of acyclovir valylchenodexycholate.

Figure 1D generalizes the synthesis of acyclovir valyldeoxycholate.

Figure IE generalizes the synthesis of atenolol cholic acid amide.

Figure 2 illustrates the competitive inhibition of uptake of 3 H-taurocholate by acyclovir valylchenodeoxycholate (acyclovir vCDC) chenodeoxycholate (CDC) and valacyclovir(A).

Figure 3 illustrates the competitive inhibition of uptake of 3 H-taurocholate by acyclovir valyldeoxycholate (acyclovir vDC) deoxycholate (DC) and valacyclovir Figure 4 illustrates the competitive inhibition of uptake of 3 H-taurocholate by atenolol cholic acid amide cholate and atenolol Figure 5 shows the concentration dependence of 3 H-taurocholate uptake in COShlBAT (COS cells transfected with hIBAT) in HBSS and in MHBSS (no sodium) Figure 6 illustrates the inhibition constant (Ki) of various bile acids and other agents by inhibiting 3 H-taurocholate uptake in COS cells transfected with hIBAT.

Detailed Description of the Invention In the preferred embodiment, this invention is a prodrug containing a bile acid attached to a compound. In an alternative embodiment, more than one bile acid can be attached to a compound. Alternatively, more than one compound can be attached to one bile acid. Alternatively, a complex of one or more bile acids can be attached to one or more compounds.

When used wherein, the word "compound" includes, but is not limited to, a pharmaceutical drug, a biologically active agent, a metabolic precursor to a pharmaceutical drug, a metabolic precursor to a biologically active agent, or any other agent which one would want to administer to an animal or human. A compound may be therapeutic or diagnostic in nature. A compound can also be nutritionally beneficial to an animal or human.

-11- It is preferable that a metabolically labile bond exist between a compound and the bile acid to which the compound is attached or conjugated. By way of example only, a metabolically labile bond can be an ester, amide, carbamate, carbonate, ether, urea, anhydride, or sulfur containing derivatives, such as thioamides, thioesters, thiocarbamates, and thioureas.

In an alternative embodiment, a linker group exists between a compound and the bile acid to which the compound is attached. The linker group can be any bifunctional chemical moiety but preferably has a molecular weight less than 200 daltons. Four reasons exist for using a linker group; any bifunctional chemical moiety that achieves any one of these reasons is considered a linker group. First, the linker group can facilitates the synthesis of the prodrug. Second, the linker group can aid or enhance the binding of the prodrug to the intestinal bile acid transporter (IBAT).

Third, the linker group can make it easier for the compound to disassociate from the bile acid after the prodrug has passed out of the lumen of the small intestine. Fourth, the linker group can enhance the solubility of the prodrug inside the body.

Different types of linker groups can be used. Linker groups can be, for example, natural and unnatural amino acids, di-acids, di-amines, di-alcohols, sulphate, phosphate, sulfur containing moieties, amino alcohols, hydroxyacids, and polymers.

Examples of the amino acids are valine, glycine, taurine, alanine, leucine, tyrosine, aspartate, glutamate, lysine, arginine, asparagine, cysteine. Examples of the di-acids are oxalic acid, fumaric acid, succinic acid, maleic acid, and tartaric acid. Examples of the di-amines include ethylenediamine, propylenediamine, 1, 3 -diaminopropane, 1,4- -12diaminobutane, 1,5-diaminopentane, piperazine, homopiperazine, and 3aminopiperidine. Examples of the di-alcohols are ethyleneglycol, propyleneglycol, C1 1,4-butanediol, polyethyleneglycol, and 1,5-pentanediol. Examples of the sulfur containing moieties are mercaptoacetic acid, mercaptopropanoic acid, mercaptobenzyl 5 alcohol, 2-mercaptoethanol, 3-mercaptopropanol, and 4-mercaptobutanol. Examples C7, of the amino alcohols are 2-aminoethanol, 3-aminopropanol, 4-aminobutanol, 4-

O

Shydroxypiperidine, and 3-hydroxypiperidine. Examples of the hydroxyacids include 3-hydroxypropanoic acid, 4-hydroxybutanoic acid, and 5-hydroxypentanoic acid.

One example of polymers is polyethylene glycol.

It is preferably that the linker group has a metabolically labile bond for easy cleavage of the prodrug into the compound and the bile acid. By way of example only, a metabolically labile bond can be an ester, amide, carbamate, carbonate, ether, urea, anhydride, or sulfur containing derivatives, such as thioamides, thioesters, thiocarbamates, and thioureas.

These bile acid containing prodrugs are administered orally and absorbed in the small intestine. The intestinal bile acid transporter actively transports the prodrug from inside the lumen of the small intestine into brush border cells. Once inside brush border cells, the prodrug may pass passively through the cell membrane down a concentration gradient into the blood stream or be actively transported out of the brush border cells into the blood stream. This active transport of the prodrug out of the lumen of the small intestine occurs because of the affinity of the intestinal bile acid transporter for its ligand, bile acids.

13- Intracellular or extracellular enzymes cleave one of the bonds between the bile acid and the compound either after the prodrug is inside the brush border cells, (2) CN attached to the outside of the brush border cells, located in proximity to the brush border cells, in the blood stream, or at other location inside the body, except

C

,5 cleavage should not occur in the stomach or lumen of the small intestine.

0 This active transport of a prodrug by the intestinal bile acid transport produces enhanced bioavailability of the compound when compared to the unconjugated compound. It also reduces bioavailability variability and provides for an alternative mechanism for compound permeation, including the avoidance of efflux pumps such as P-glycoprotein used by some drugs fexofenadine) and other drug transporters and/or nutrient transporters. By avoiding other drug transporters and/or nutrient transporters, drug-drug and/or drug-nutrient interactions can be reduced or eliminated.

Any bile acid may be conjugated or linked to a compound. More than one bile acid may be conjugated or linked to one compound. Also more than one compound may be conjugated or linked to one bile acid. The bile acids are, by way of example, cholate, glycocholate, taurocholate, deoxycholate, glycodeoxycholate, taurodeoxycholate, chenodeoxycholate, ursodeoxycholate, glycochenodeoxycholate, taurochenodeoxycholate, and lithocholate. The general structures of the bile acids are shown in Figure 1A.

The following structural requirements generally promote recognition of a bile acid by the intestinal bile acid transporter (IBAT): negatively charged side groups on -14the bile acid; at least one alpha oriented hydroxyl group at the steroid nucleus at position 3, 7, or 12; and a cis configuration of rings A and B of the steroid nucleus By way of example, compounds that have improved bioavailability as a result of conjugating or linking the compound to a bile acid are those compounds which contain (Group 1) an alcohol function which can be chemically coupled to the bile acid to give an ester; or (Group 2) a primary or secondary amine function which can be chemically coupled to the bile acid to give an amide; or (Group 3) an acid function which can be chemically coupled to the bile acid to give an anhydride.

Compounds which contain an alcohol function (Group 1) may include, but are not limited to, anti-viral agents 6-deoxyacyclovir, ganciclovir, dihydroxybutylguanine, foscamet, penciclovir, famciclovir, zidovudine, idoxuridine, trifluorothymidine, vidarabine, cytarabine, ribavirin). Compounds which contain a primary or secondary amine function (Group 2) may include, but are not limited to, H-2 antagonists derivatives of cimetidine, ranitidine, nizatidine, famotidine, roxatidine). Compounds which contain an acid function (Group 3) may include, but are not limited to, bisphosphonates alendronate, etidronate, pamidronate, tiludronate, clonronate) and ACE inhibitors enalapril, captopril, lisonopril). This list is not exhaustive and is not meant to limit the scope of this invention, but is provided by way of illustration only.

Any salts, solvates, isomeric compositions, and physical forms of these compounds and/or their derivatives can be conjugated or linked to a bile acid to form a prodrug. One can also use known in the art field enteric coating to protect prodrugs from the acidity of the stomach.

Figure 1A illustrates the general structure of bile acids. Bile acids can vary in their substituents at R 1

R

2 and R 3 positions 12, 7, and 3, respectively). For example, for chenodeoxycholate, R, is H, R 2 is a-OH, and R 3 is a-OH. For deoxycholate, R, is a-OH, R 2 is H, and R 3 is a-OH. For cholate, R 1

R

2 and R 3 are all a-OH. Many natural and synthetic bile acids exist and are well-known in the art field. Any of these natural or synthetic bile acids can be used to create a prodrug.

However, it may be preferable to have at least one alpha orientated hydroxyl group in the bile acid and this alpha orientated hydroxyl group can be located at R 1

R

2 or R 3 Figure 1B illustrates the general structure of bile acid component of the prodrug. Either directly or via a linker group, a compound can be attached to any natural or synthetic bile acid at either RI, R 2

R

3 or R4. While it may be preferable to have only one compound conjugated or linked to one bile acid, more than one compound can be conjugated or linked to the same bile acid. In addition, while it may be preferable to have the compound linked or conjugated to a bile acid at R4 (because of potential structural requirements necessary for recognition of a bile acid by the intestinal bile acid transporter), it is possible to link or conjugate compounds to a bile acid at R 1

R

2 or R 3 When a compound is linked or conjugated to either RI, R 2 or R 3 then it is preferable that R 4 be any chemical moiety which can aid or enhance the binding of the prodrug to the IBAT and/or can increase the solubility of the prodrug -16inside the body. Examples of such chemical moieties include hydroxyl, any amino acid (such as glycyl, valyl, alanyl, tauryl, and leucyl), any di-amino acid (such as glycyl-valyl, glycyl-glycyl, valyl-glycyl, alanyl-glycyl, alanyl-valyl, and leucyl-valyl), any tri-amino acid (such as glycyl-glycyl-glycyl, glycyl-valyl-glycyl, glycyl-glycylalanyl, valyl-glycyl-leucyl, alanyl-glycyl-glycyl, alanyl-valyl-glycyl, and leucyl-valylvalyl). It is preferable that this chemical moiety have a molecular weight less than 1500 daltons.

Figures IC, ID, and IE generalize the synthesis of three prodrugs, acyclovir valylchenodeoxycholate, acyclovir valyldeoxycholate, and atenolol cholic acid amide, 1o which have increased bioavailability and reduced bioavailability variability as a result of conjugating or linking the compounds, acyclovir and atenolol, to a bile acid. For these three prodrugs, the compounds are attached to a bile acid (chenodeoxycholate, deoxycholate, or cholic acid) at R4. For acyclovir valylchenodeoxycholate and acyclovir valyldeoxycholate, valine is utilized as a linker group. Furthermore, both acyclovir valylchenodeoxycholate and acyclovir valyldeoxycholate use an ester as a metabolically labile bond that can be cleaved to release acyclovir. For atenolol cholic acid amide, no linker group is used, but rather atenolol is conjugated directly to cholic acid. Furthermore, atenolol cholic acid uses an amide as a metabolically labile bond that can be cleaved to release atenolol.

Acyclovir Valvlchenodeoxvcholate Synthesis As in Figure 1C, to synthesize acyclovir valylchenodeoxycholate, 1, isobutylchloroformate (iBuOCOCl; 130 L, 1 mmol) is added dropwise to a cooled -17- OC) solution ofchenodeoxycholate, 2, (1 mmol) and triethylamine (140 pL, 1 mmol) in N,N-dimethylformamide (DMF) (10 mL) under an nitrogen (N 2 atmosphere. After 1.5 minutes, valacyclovir, 3, (0.42 g, 1.3 mmol) and triethylamine (NEt 3 280 pL, 2 mmol) are then added to the reaction mixture as a solution in DMF (5 mL). The reaction is kept at -15 OC for 0.5 hours, then is warmed to room temperature for 1 hour. The triethylammonium chloride formed during the reaction is filtered off, and the filtrate is concentrated by rotary evaporation. The crude material is then purified using silica gel flash chromatograpy with MeOH/CHCI 3 250 mL) as the eluent.

The acyclovir valylchenodeoxycholate, 1, prodrug synthesis is monitored using thin layer chromotography (TLC) plates coated with silica gel GHLF-0.25 mm plates (60 F 254 manufactured by Analtech, Inc. (Newark, DE). Fast-atom bombardment mass spectrometry (FAB-MS) and high resolution mass spectrometry (HRMS) spectra are obtained on a Jeol SX 102 mass spectrometer in the positive ion mode. Proton nuclear magnetic resonance (NMR) spectrometry is performed in d 6 dimethyl sulfoxide (DMSO) on a 300 MHz General Electric Aquerius model spectrometer controlled by a Macintosh Power Mac 7100 using MacNMR v. software. The purity of the bile acid conjugate is determined by analysis on a Beckman System Gold high pressure liquid chromotography (HPLC) system consisting of a model 126 solvent module, model 168 detector, and model 507 autosampler. The HPLC column used is a Vydac analytical column (C 1 l, 300 A, -18- 4.6 x 250 mm) equipped with a guard cartridge. Solvent A is aqueous 0.1% trifluoroacetic acid (TFA) and solvent B is acetonitrile containing 0.1% TFA. The conjugate is eluted using a linear gradient of 5 to 75% B over 50 minutes at a flow rate of 1.0 mL/min and detected at 214 nm.

The amount ofacyclovir valylchenodeoxycholate, 1, purified is 0.62 g Additionally, TLC RAMeOH/CHC 3 1:4) 0.46; HPLC Rt 32.1 min (99.3 purity); and ESI-MS 700.4. HRMS (calculated for C 37

H

59 0 7

N

6 699.4445.

found 699.4454. The NMR spectra contained peaks consistent with both chenodeoxychloate and valacyclovir portions. Coupling through the amino acid amine (and not the aniline) was confirmed through the presence of the NH 2 signal at 5.3 ppm.

Acyclovir Valyldeoxycholate Synthesis As in Figure ID, to synthesize acyclovir valyldeoxycholate, 4, isobutylchloroformate (iBuOCOCI; 130 jgL, I mmol) is added dropwise to a cooled (-15 OC) solution of deoxycholate, 5, (1 mmol) and triethylamine (140 gL, 1 mmol) in N,N-dimethylformamide (DMF) (10 mL) under an nitrogen (N 2 atmosphere. After minutes, valacyclovir, 3, (0.42 g, 1.3 mmol) and triethylamine (NEt 3 280 .tL, 2 mmol) are then added to the reaction mixture as a solution in DMF (5 mL). The reaction is kept at -15 OC for 0.5 hours, then is warmed to room temperature for 1 hour. The triethylammonium chloride formed during the reaction is filtered off, and -19the filtrate is concentrated by rotary evaporation. The crude material is then purified using silica gel flash chromatograpy with MeOH/CHCI 3 250 mL) as the eluent.

C1 The acyclovir valyldeoxycholate, 4, prodrug synthesis is monitored using thin layer chromotography (TLC) plates coated with silica gel GHLF-0.25 mm plates

F

25 4 manufactured by Analtech, Inc. (Newark, DE). Fast-atom bombardment mass spectrometry (FAB-MS) and high resolution mass spectrometry (HRMS) spectra are O obtained on a Jeol SX 102 mass spectrometer in the positive ion mode. Proton nuclear magnetic resonance (NMR) spectrometry is performed in d 6 -dimethyl sulfoxide (DMSO) on a 300 MHz General Electric Aquerius model spectrometer 0o controlled by a Macintosh Power Mac 7100 using MacNMR v. 5.0 software. The purity of the bile acid conjugate is determined by analysis on a Beckman System Gold high pressure liquid chromotography (HPLC) system consisting of a model 126 solvent module, model 168 detector, and model 507 autosampler. The HPLC column used is a Vydac analytical column (C 1 8 300 A, 5gm, 4.6 x 250 mm) equipped with a guard cartridge. Solvent A is aqueous 0.1% trifluoroacetic acid (TFA) and solvent B is acetonitrile containing 0.1% TFA. The conjugate is eluted using a linear gradient of to 75% B over 50 minutes at a flow rate of 1.0 mL/min and detected at 214 nm.

The amount of acyclovir valyldeoxycholate, 4, purified is 0.59 g Additionally, TLC R(MeOI/CHCl 3 1:4) 0.47; HPLC Rt 33.0 min (98.1 purity); FAB-MS 699.54; HRMS (calculated for C 37

H

59 0 6

N

7 699.4445, found: 699.4448. The NMR spectrum contained peaks consistent with both deoxycholic acid and valacyclovir portions. Coupling through the amino acid amine (and not the aniline) was confirmed through the presence of the NH 2 signal at 5.3ppm.

Atenolol Cholic Acid Amide Synthesis As in Figure IE, to synthesize atenolol cholic acid amide, 6, isobutylchloroformate (iBuOCOCI; 130 tL, 1 mmol) is added dropwise to a cooled OC) solution of cholic acid, 7, (0.5 mmol) and triethylamine (140 gpL, 1 mmol) in N,N-dimethylformamide (DMF) (10 mL) under an nitrogen (N 2 atmosphere. After minutes, atenolol, 8, (0.42 g, 1.3 mmol) and triethylamine (NEt 3 280 gL, 2 mmol) are then added to the reaction mixture as a solution in DMF (5 mL). The reaction is kept at -15 OC for 0.5 hours, then is warmed to room temperature for 1. hour. The triethylammonium chloride formed during the reaction is filtered off, and the filtrate is concentrated by rotary evaporation. The crude material is then purified using silica gel flash chromatograpy with MeOH/CHC1 3 250 mL) as the eluent.

The atenolol cholic acid amide, 6, prodrug synthesis is monitored using thin layer chromotography (TLC) plates coated with silica gel GHLF-0.25 mm plates

F

25 4 manufactured by Analtech, Inc. (Newark, DE). Fast-atom bombardment mass spectrometry (FAB-MS) and high resolution mass spectrometry (HRMS) spectra are obtained on a Jeol SX 102 mass spectrometer in the positive ion mode. Proton nuclear magnetic resonance (NMR) spectrometry is performed in d 6 -dimethyl sulfoxide (DMSO) on a 300 MHz General Electric Aquerius model spectrometer controlled by a Macintosh Power Mac 7100 using MacNMR v. 5.0 software. The -21 purity of the bile acid conjugate is determined by analysis on a Beckman System Gold high pressure liquid chromotography (HPLC) system consisting of a model 126 solvent module, model 168 detector, and model 507 autosampler. The HPLC column used is a Vydac analytical column (C 18 300 A, 5p.m, 4.6 x 250 mm) equipped with a guard cartridge. Solvent A is aqueous 0.1% trifluoroacetic acid (TFA) and solvent B is acetonitrile containing 0.1% TFA. The conjugate is eluted using a linear gradient of to 75% B over 50 minutes at a flow rate of 1.0 mL/min and detected at 214 nm.

The amount of atenolol cholic acid amide, 6, purified is 0.19 g Additionally, TLC RKAcOH/MeOH/CHC13, 1:1:4) 0.47; HPLC R 34.9 min (98.3 purity); FAB-MS [M+H] 657.6; HRMS (calculated for C 38

H

61

N

2 0 7 657.4479, found: 657.4470; IR (CHCI 3 3394, 2932, 2870, 1671, and 1610 cm-'.

Atenolol, 8, contains both a secondary alcohol and a secondary amine, and coupling to cholic acid, 7, through both of these nucleophiles could occur to give an ester or an amide, respectively. Only the amide is formed during the above reaction of cholic acid and atenolol which is confirmed through the presence of characteristic amide C=O stretching bands at 1671 cm'- and 1610 cm 1 in the IR spectrum. Also, NMR spectrum is consistent with that expected for a conjugate between cholic acid and atenolol the absence of the secondary amine proton signal at 4.92 ppm in the NMR). Coupling through the amine of atenolol (and not the alcohol) is also confirmed by a negative chloranil test, a test for secondary and primary amines. Atenolol is used as the positive control for the chloranil test.

-22- Bioavailability Assays To test the increase of bioavailability of acyclovir valylchenodeoxycholate, 1, acyclovir valyldeoxycholate, 4, and atenolol cholic acid amide, 6, the human intestinal bile acid transporter (hIBAT) cDNA (specifically, pCMV5-hIBAT expression plasmid) is transformed into competent DH5a cells according to the Life

O

STechnologies protocol (Grand Island, NY), using LipofectAMINE 2000 transfection

O

reagent (Life Technologies, Grand Island, NY). Cell dilutions are streaked on nutrient agar plates containing 50 gg/ml ampicillin, and incubated at 37 0 C overnight. Isolated colonies are selected aseptically, and are used to inoculate a 200 ml nutrient broth culture containing 50 gg/ml ampicillin. The culture is incubated for 24 hours at 225 RPM's and 37 0 C. cDNA is isolated from the broth cultures using a Quigan maxi-prep kit (DNA plasmid maxi kit #12162; Valencia, CA). After an isopropanol precipitation and ethanol wash, the DNA is reconstituted in 600 pl of sterile deionized water. DNA concentration is 1.18 g.g/pl, determined by spectrophotometry at 260 nm. The 260/280 absorbance ratio is 1.50, indicating the DNA is free from RNA contamination. pCMV5-hIBAT is also digested with the restriction endonucleases, BAMH1 and NDE, and results in bands of appropriate size (4238 bp and 1689 bp) when electrophoresed on a 1% agarose gel.

COS-7 cells are grown in T-75 flasks at 37 0 C, 5% CO 2 and 95% RH using Dulbecco's Modified Eagle's Medium (DMEM) supplemented with 10% FBS. Cells are passaged at 80-90% confluency using a 0.25% trypsin/0.20% EDTA solution, and -23are plated at a density of 8x10 4 cells per well (1.88 cm 2 Cells are transfected at 24 hours post seeding. For each well transfected, 0.8 Rg hlBAT cDNA is combined with LipofectAMINE 2000 reagent and incubated at room temperature for 20 minutes to allow complexes to form. A volume of 100 pl1 of hIBAT-lipid complex is added to each well of cells. Transfected cells are incubated at 37 0 C, 5% CO 2 and 95% RH for 24 hours, until ready for uptake assay.

Uptake studies are performed on COS-hIBAT cells at 24 hours posttransfection. Uptake buffer consists of either a Hank's Balanced Salts Solution (HBSS) containing 137 mM NaCI or a Modified Hank's Balanced Salts Solution (MHBSS) that replaced the sodium chloride with 137 mM tetraethylammonium chloride Because bile acid transport is sodium dependent, this MHBSS approach allows for the simple modification of the uptake buffer to exclude all sources of sodium, and thus enables for a control uptake assay under sodium-free conditions.

For the Km and Vmax studies oftaurocholate in the COS-hIBAT cells, cell culture medium is removed from each well and is replaced with 0.5 ml of uptake solution. 0.5 gM 3 H-taurocholate is investigated in HBSS. Cells are incubated at 37 0 C and 100 RPM's for 10 minutes. Uptake solution is removed, and the cells are washed three times with ice cold HBSS. Cells are lysed, neutralized, and counted for associated radioactivity. Each well is analyzed for protein content using the Lowry method This uptake assay is performed in triplicate, under both sodium and sodium-free conditions.

-24- The saturable uptake of H-taurocholate is determined using the following equation (Formula 1): dM V S kPS (Formula 1) dt K m

+S

where Vmax and Km represent the Michaelis-Menten constants, kp is the passive uptake rate constant, S is the concentration of taurocholate, and dM/dt is the uptake rate of taurocholate into the COS-hIBAT cells. This approach includes the contribution of passive uptake to the saturable kinetics of taurocholate uptake into the cells.

In the competitive inhibition studies (see Figures 2, 3, and the concentration of acyclovir valylchenodeoxycholate, 1, varies between 10 g.M and 400 i.M; the concentration of acyclovir valyldeoxycholate, 4, varies between 10 iM and 600 gM; and the concentration of atenolol cholic acid amide, 6, varies between 10 RM and 400 gM. Chenodeoxycholate, 2, deoxycholate, 5, and cholate inhibition studies are conduced as positive controls. Valacyclovir and atenolol inhibition studies are performed as negative controls.

Figure 2 illustrates the inhibition study ofvalacyclovir, 3, chenodeoxycholate (CDC), 2, and acyclovir valylchenodeoxycholate (acyclovir vCDC), 1, There is no inhibition of the bile acid transporter in COS-hIBAT cells after application of up to 600 gM valacyclovir, indicating that valacyclovir is not a substrate for hIBAT. A chenodeoxycholate inhibition study is performed as a positive control for this experiment, and results in Ki =5.4 gM, which indicates that the COS-hlBAT model is suitable for the inhibition study. The calculated Ki for c acyclovir valylchenodeoxycholate is Ki =35.6 gM, indicating a very strong C interaction of acyclovir valylchenodeoxycholate for the hIBAT transporter.

Similiarly for acyclovir valyldeoxycholate (Figure inhibition study of

O

IN valacyclovir, 3, deoxycholate 5, and acyclovir valyldeoxycholate p (acyclovir vDC), 4, are performed. Acyclovir valyldeoxycholate strongly interacts with hIBAT with a Ki=401 pM.

Likewise, in Figure 4, atenolol cholic acid amide, 6, strongly interacts with hIBAT with a Ki=160 gM, while atenolol, 8, itself does not interact. The natural bile acid cholate, 7, also strongly interacts with hIBAT [Ki=32.1 2.4) aM].

Figure 5 shows both the sodium dependence and saturation of 3 H-taurocholate uptake. The uptake rate is measured at 3H-taurocholate concentrations from 0.1 to 125 gM in HBSS with 137 mM NaCI and in MHBSS which contains no sodium. As expected, carrier mediated 3 H-taurocholate uptake is not present in the absence of sodium ions, thus establishing a baseline permeability due to the passive permeability of taurocholate into the cells. A passive uptake rate constant (kp) of 0.12 (pmoles/min mg protein)/pM is estimated using linear regression. Control uptake studies are also performed in untransfected COS-7 cells, and in COS-7 cells transfected with the antibiotic resistant vector, pcDNA3. The passive uptake of 3 H-taurocholate in these -26experiments is the same as that obtained under sodium-free conditions (data not shown). The kinetic parameters for carrier mediated uptake are estimated using WinNonlin (version and yields a Km=12.0(±2.2) PM and a Vmax=126.0(±5.9) pmoles/min/mg protein. These Michaelis-Menten parameters are in close agreement to those obtained previously [21].

Competitive inhibition studies are performed in HBSS containing 0.25 .tM 3Htaurocholate, and varying the concentration of unlabeled bile acid from 1 to 100 .M.

Glycine, taurine, acyclovir, and atenolol inhibition studies are performed as negative controls. Incubation conditions and analysis are performed as described for the Km o0 and Vmax studies. The following equation (Formula 2) is used to estimate the Ki for a series of naturally occurring bile acids: dM Vma. (S/K dt S+ I (Formula 2) K,

K,

where Vmax and Km are the Michaelis-Menten parameters for taurocholate uptake, S is 0.25 gM 3 H-taurocholate, dM/dt is the uptake rate of taurocholate, and I is the concentration of inhibitor applied to the cells.

The effect of various bile acids (cholate, glycocholate, taurocholate, deoxycholate, taurodeoxycholate, glycodeoxycholate, chenodeoxycholate, glycochenodeoxycholate, taurochenodeoxycholate, ursodeoxycholate, and lithocholate) on the uptake of H-taurocholate into COS-hIBAT cells is determined (see Figure 6).

Inhibition studies using glycine, taurine, valacyclovir, and atenolol are also performed -27as negative controls. Figure 6 shows the K, value SEM) for each compound tested.

All bile acids inhibit the uptake of 3 H-taurocholate into COS-hIBAT cells. However, the uptake of 3 H-taurocholate is not reduced in the presence of glycine or taurine.

Uptake of 3 H-taurocholate decreases in the presence of lithocholate, but never reaches 50% maximal velocity at a lithocholate concentration of 100 pM. Lithocholate concentrations above 100 gM were not investigated. All bile acids inhibit the uptake of 3 H-taurocholate in COS-hIBAT cells. Valacyclovir and atenolol do not inhibit the uptake of 3 H-taurocholate. In these inhibition studies, 3 H-taurocholate concentration is held constant at 0.25 LM and inhibitor concentration is varied between 1 and 100 L.M; except for glycine and taurine, which range in concentration from 50 to 200 g.M, valacyclovir which range from 10 to 600 gM, and atenolol which range from 10 to 200 gM. Inhibition studies are performed in triplicate. N/A denotes not applicable, because there was no evidence of inhibition.

Compounds can be conjugated or linked via a linker group to bile acids to improve the bioavailability and reduce the bioavailability variability of the compounds. It is preferable that a metabolically labile bond exist between the bile acid and the compound (with or without a linker group) for easy cleavage of the compound from the bile acid. While it is preferable that the compound or compound and linker group be attached to the R 4 of the bile acid, one can also attach the compound or compound and linker group at R 1

R

2 or R 3 Also, one can link or conjugate different -28-

I

or the same compounds to multiple positions on the bile acid. Furthermore, one may attach more than one bile acid to a compound.

The prodrugs can be coated with various coating compounds known in the art field to protect the prodrug from the acidic environment in the stomach. These coating compounds dissolve in the basic environment in the small intestine, thereby permitting the prodrug to be available for uptake by the IBAT.

The prodrugs can also be converted into a pharmaceutically acceptable salt or pharmaceutically acceptable solvate or other physical forms polymorphs by way of example only and not limitation) via known in the art field methods.

Pharmaceutically acceptable carriers can be used along with the prodrugs. In making the compositions of the present invention, the prodrug can be mixed with an excipient, diluted by an excipient or enclosed within such a carrier which can be in the form of a capsule, sachet, paper or other container. When the excipient serves as a diluent, it can be a solid, semi-solid, or liquid material, which acts as a vehicle, carrier, or medium for the prodrug. Thus, the compositions can be in the form of tablets, pills, powers, lozenges, sachets, cachets, elixirs, suspensions, emulsions, solutions, syrups, soft and hard gelatin capsules, and other orally ingestible formulations.

Some examples of suitable excipients include lactose, dextrose, sucrose, sorbitol, mannitol, starches, gum acacia, calcium phosphate, alginates, tragacanth, gelatin, calcium silicate, microcrystalline cellulose, polyvinylpyrrolidone, cellulose, water, syrup, and methyl cellulose. The formulations can additionally include lubricating agents such as talc, magnesium stearate, and mineral oil; wetting agents; -29- 1 emulsifying and suspending agents; preserving agents such as methyl- and propylhydroxybenzoates, sweetening agents; and flavoring agents. The compositions of the present invention can also be formulated so as to provide quick, sustained or delayed release of the prodrug after administration to the patient by employing procedures known in the art.

The compositions are preferably formulated in a unit dosage form, each dosage containing from about 0.005 mg to 100 mg, more usually about 1.0 mg to about 300 mg, of the prodrug. Unit dosage form generally refers to physically discrete units suitable as unitary dosages for human and animal patients, each unit containing a predetermined quantity of the prodrug calculated to produce the desired therapeutic effect, in association with a suitable pharmaceutical excipient.

A prodrug is used for treatment of human or animal patients which are in need of treatment with the compound that is contained in the prodrug. The specific purpose of the treatment, and the dose range to be administered, depends on the identity of the compound and the condition for which the patient is to be treated.

While a list of compounds for which this prodrug approach will work is too large to be contained here, below is a short list of compounds and their "drug" class: foscarnet, valacyclovir, acyclovir, ganciclovir, penciclovir, famciclovir (antivirals); alendronate, etidronate disodium, pamidronate, risedronate, tiludronate, clodronic acid (bisphosphonates); cimetidine, ranitidine (H-2 antagonists); enalaprilate, captopril, lisonopril (ACE inhibitors); losartan, E-3171 (angiotensin II antagonists); levofloxacin, norfloxacin (quinalone antibiotic which have decreased absorption with antacids); formycin B; acetbutalol, pindolol, aiprenolol, atenolol, nadolol (beta adrenergic blockers); bretylium tosylate (antiarrhythmic agents); cefuroxime sodium (cephalosporins); chiorothiazide, hydrochiorothiazide, furosemide (diuretic agents); gabapentin, lamotrigine (anticonvulsant); didanosine (nucleoside reverse transcriptase inhibitors); neviriapine (non-nucleoside reverse transcriptase inhibitors); ritinavir, saquinavir, amprinavir (HIV protease inhibitors); tacrolimus, cyclosporin (immunosuppresants); zafirlukast (leukotriene receptor antagonists); leuprorelin actetate (LHRH analogues); dDAVP (1-deamino-8-Darginine-vasopressin; desmopressin), calcitonin, thyrotropin releasing hormone (polypeptide hormones); loratidine, cetirizine (non-sedating antihistamines); penicillin V, amoxicillin, cefacor, cefixime, cefuroxime axetil, cefuroxime sodium, ampicillin (antibiotics); terbutaline hemisulfate (adrenergic agonist agents); metformin (anti-diabetics); celecoxib, refecoxib (COX-2 inhibitors); is sumatriptan, naratriptan, araztriptan, zolmitriptan (anti-migraines); 6mercaptopurine; ziprasidone; RGD mimetic (alpha IIb beta 3-antagonists); leuenkephalin analogues; aipha-methyldopa; 5-fluorouracil (fluoropoyrimidines); tacrine (acetylcholinesterase inhibitors); DZ-2640 (the ester-type oral carbapenem prodrug of an active parent compound, DU-6681, and other carbapenems); vitamin B12 (nutrients and minerals); 7-chiorokynurenic acid; oseltamivir or its active moiety; RGD (Arg-Gly-Asp) analogs (glycoprotein (GP) lIb/ITIa agonists and antagonists; platelet aggregation inhibitors); -31 sibrafiban (oral platelet aggregation inhibitors); nelarabine, 9-beta-Darabinofuranosyl guanine (ara-G), and ara-G; mycophenolate mofetil (MMF) and its active immunosuppressant mycophenolic acid (MPA); nabumetone and its active metabolite 6-methoxy-2-naphthylacetic acid (anti-osteoarthritis agents); adefovir (9-[2-phosphonylmethoxyethyl]-adenine [PMEA]) and adefovir dipivoxil [bis-(POM)-PMEA], and cidofovir (antiviral nucleotides); cromoglicate lisetil and cromoglycic acid (anti-arthritis agents); oseltamivir or its active moiety; its parent Ro 64-0802 (inhibitors of influenza virus neuraminidase); peptidomimetics; nucleic acids; This is for illustrative purposes only and is not meant to be exhaustive. Other compounds will have increased bioavailability and/or reduced bioavailability variability with bile acid conjugation.

All references cited herein are incorporated by reference in their entirety.

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[21] M.H. Wong, P. Oelkers and P.A. Dawson, Identification of a mutation in the ileal sodium-dependent bile acid transporter gene that abolishes transport activity, J Biol Chem 270 (1995) 27228-27234.

[22] F. Gaspari and M. Bonati, Correlation between n-octanol/water partition coefficient and liquid chromatographic retention for caffeine and its metabolites, and some structure-pharmacokinetic considerations, J Pharm Pharmacol 39 (1987) 252-60.

[23] K.A. Lentz, J. Hayashi, L.J. Lucisano and J.E. Polli, Development of a more rapid, reduced serum culture system for Caco-2 monolayers and application to the Biopharmaceutics Classification System, Int J Pharn 200 (2000) 41-51.

[24] G.A. Sawada, C.L. Barsuhn, B.S. Lutzke, M.E. Hooughton, G.E. Padbury, N.F.H. Ho and T.J. Raub, Increased lipophilicity and subsequent cell partitioning decrease passive transcellular diffusion of novel, highly lipophilic antioxidants, J Pharm Exp Ther 288 (1999) 1317-1326.

G.A. Sawada, L.R. Williams, B.S. Lutzke and T.J. Raub, Novel, highly lipophilic antioxidants readily diffuse across the blood-brain barrier and access intracellular sites, J Pharm Exp Ther 288 (1999) 1327-1333.

While the invention has been described in detail, and with reference to specific embodiments thereof, it will be apparent to one of ordinary skill in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof. The artisan will further acknowledge that the Examples recited herein are demonstrative only and are not meant to be limiting.

-36-

Claims

1. A method of increasing the bioavailability of a compound, said method comprising: conjugating a bile acid to said compound to form a prodrug, and orally administering said prodrug to an animal or human.

2. The method of Claim 1 further comprising the step of: coating said prodrug with a coating agent prior to orally administering said prodrug.

3. A method of reducing the bioavailability variability of a compound, said method comprising: conjugating a bile acid to said compound to form a prodrug, and orally administering said prodrug to an anirfial or human.

4. The method of Claim 3 further comprising the step of: coating said prodrug with a coating agent prior to orally administering said prodrug. A method of increasing the bioavailability of a compound, said method comprising: linking a bile acid to a compound to form a prodrug, and orally administering said prodrug to an animal or human.

6. The method of Claim 5 further comprising the step of: coating said prodrug with a coating agent prior to orally administering said prodrug. -37-

7. A method of reducing the bioavailability variability of a compound, said method comprising: linking a bile acid to a compound to form a prodrug, and orally administering said prodrug to an animal or human.

8. The method of Claim 7 further comprising the step of: coating said prodrug with a coating agent prior to orally administering said prodrug.

9. A method of eliminating adverse interactions between two compounds wherein said adverse interactions result from intestinal absorption of at least one of said compounds comprising: linking a bile acid to at least one of said compounds to form a prodrug, and orally administering said prodrug to an animal or human. A method of eliminating adverse interactions between a compound and a nutrient wherein said adverse interactions result from intestinal absorption of said compound comprising: linking a bile acid to said compound to form a prodrug, and orally administering said prodrug to an animal or human.

11. A method of eliminating adverse interactions between two compounds wherein said adverse interactions result from intestinal absorption of at least one of said compounds comprising: conjugating a bile acid to at least one of said compounds to form a prodrug, and orally administering said prodrug to an animal or human. -38-

12. A method of eliminating adverse interactions between a compound and a nutrient wherein said adverse interactions result from intestinal absorption of said compound comprising: conjugating a bile acid to said compound to form a prodrug, and orally administering said prodrug to an animal or human.

13. The method of Claims 9, 10, 11, and 12, further comprising: coating said prodrug with a coating agent prior to orally administering said prodrug.

14. A pharmaceutical compound comprising: acyclovir valyldeoxycholate. A pharmaceutical compound comprising: acyclovir valylchendeoxycholate.

16. A pharmaceutical compound comprising: atenolol cholic acid amide.

17. A pharmaceutical compound comprising: a compound; a linker group; and a bile acid.

18. The pharmaceutical compound of Claim 17 further comprising: wherein said pharmaceutical compound contains a metabolically labile bond.

19. The pharmaceutical compound of Claim 18 further comprising: -39- wherein said metabolically labile bond is selected from a group comprising an amide, ester, carbamate, carbonate, ether, thio, urea, anhydride, thioamide, thioester, thiocarbamate, and thiourea. The pharmaceutical compound of Claim 17 further comprising: wherein said linker group has a molecular weight of less than 200 daltons.

21. A pharmaceutical compound comprising: a compound; and a bile acid.

22. The pharmaceutical compound of Claim 21 further comprising: wherein said pharmaceutical compound contains a metabolically labile bond.

23. The pharmaceutical compound of Claim 22 further comprising: wherein said metabolically labile bond is selected from a group comprising an amide, ester, carbamate, carbonate, ether, thio, urea, anhydride, thioamide, thioester, thiocarbamate, and thiourea.

24. The pharmaceutical compound of Claims 17, 18, 19, 20, 21, 22, and 23 further comprising: wherein said bile acid is selected from the group comprising cholate, glycocholate, taurocholate, deoxycholate, glycodeoxycholate, taurodeoxycholate, chenodeoxycholate, glycochenodeoxycholate, taurochenodeoxycholate, ursodeoxycholate and lithocholate. A method of increasing the bioavailability of a compound, said method comprising: attaching a linker group to said compound; attaching a bile acid to said linker group to form a prodrug, and orally administering said prodrug to an animal or human.

26. The method of Claim 25 further comprising: wherein said linker group has a molecular weight of less than 200 daltons.

27. The method of Claim 25 further comprising: wherein said prodrug contains a metabolically labile bond.

28. The method of Claim 27 further comprising: wherein said metabolically labile bond is selected from a group comprising an amide, ester, carbamate, carbonate, ether, thio, urea, anhydride, thioamide, thioester, thiocarbamate, and thiourea.

29. A method of reducing the bioavailability variability of a compound, said method comprising: attaching a linker group to said compound; attaching a bile acid to said linker group to form a prodrug, and orally administering said prodrug to an animal or human. The method of Claim 29 further comprising: wherein said linker group has a molecular weight of less than 200 daltons.

31. The method of Claim 29 further comprising: wherein said prodrug contains a metabolically labile bond.

32. The method of Claim 31 further comprising: -41 wherein said metabolically labile bond is selected from a group comprising an amide, ester, carbamate, carbonate, ether, thio, urea, anhydride, thioamide, thioester, thiocarbamate, and thiourea.

33. A method of increasing the bioavailability of a compound, said method comprising: attaching a linker group to a bile acid; attaching said compound to said linker group to form a prodrug; and orally administering said prodrug to an animal or human.

34. The method of Claim 33 further comprising: wherein said linker group has a molecular weight of less than 200 daltons. The method of Claim 33 further comprising: wherein said prodrug contains a metabolically labile bond.

36. The method of Claim 35 further comprising: wherein said metabolically labile bond is selected from a group comprising an amide, ester, carbamate, carbonate, ether, thio, urea, anhydride, thioamide, thioester, thiocarbamate, and thiourea.

37. A method of reducing the bioavailability variability of a compound, said method comprising: attaching a linker group to a bile acid; attaching said compound to said linker group to form a prodrug; and orally administering said prodrug to an animal or human. -42-

38. The method of Claim 37 further comprising: wherein said linker group has a molecular weight of less than 200 daltons.

39. The method of Claim 37 further comprising: wherein said prodrug contains a metabolically labile bond.

40. The method of Claim 39 further comprising: wherein said metabolically labile bond is selected from a group comprising an amide, ester, carbamate, carbonate, ether, thio, urea, anhydride, thioamide, thioester, thiocarbamate, and thiourea.

41. The method of Claims 25,26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38 39, and further comprising the step of: coating said prodrug with a coating agent.

42. The method of Claims 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38 39, and 41 further comprising: wherein said bile acid is selected from the group comprising cholate, glycocholate, taurocholate, deoxycholate, glycodeoxycholate, taurodeoxycholate, chenodeoxycholate, glycochenodeoxycholate, taurochenodeoxycholate, ursodeoxycholate, and lithocholate.

43. A method for increasing the bioavailability of a compound comprising: administering a prodrug containing said compound and a bile acid to an animal or human; and -43- using the intestinal bile acid transporter to actively uptake and remove from the lumen of an intestine said prodrug.

44. A method for reducing the bioavailability variability of a compound comprising: administering a prodrug containing said compound and a bile acid to an animal or human; and using the intestinal bile acid transporter to actively uptake and remove from the lumen of an intestine said prodrug. A compound of the formula: R, RR4 wherein Ri, R 2 and R3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R4 is selected from the group consisting of an agent having biological activity and a metabolic precursor of an agent having biological activity; or a pharmaceutically acceptable salt, solvent, or polymorph thereof.

46. A compound of the formula: -44- IO O R1R O O, wherein R 2 and R 3 are independently selected from the group consisting of hydrogen, O alpha-hydroxyl, and beta-hydroxyl; R 1 is selected from the group an agent having biological activity and a metabolic precursor of an agent having biological activity; R4 is any chemical moiety that enhances binding of the compound to the intestinal bile acid transporter; or a pharmaceutically acceptable salt, solvent, or polymorph thereof.

47. A compound of the formula: RI R4 R2 R, wherein R, and R3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R 2 is selected from the group an agent having biological activity and a metabolic precursor of an agent having biological activity; R 4 is any chemical moiety that enhances binding of the compound to the intestinal bile acid transporter; or a pharmaceutically acceptable salt, solvent, or polymorph thereof.

48. A compound of the formula: R, R4 R' R2 wherein RI and R 2 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R 3 is selected from the group an agent having biological activity and a metabolic precursor of an agent having biological activity; R 4 is any chemical moiety that enhances binding of the compound to the intestinal bile acid transporter; or a pharmaceutically acceptable salt, solvent, or polymorph thereof.

49. A compound of the formula: -46- wherein R2 and R3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; RI is selected from the group an agent having biological activity and a metabolic precursor of an agent having biological activity; R 4 is any chemical moiety that increases solubility of the compound; or a pharmaceutically acceptable salt, solvent, or polymorph thereof. A compound of the formula: Ri R4 R R2 wherein R, and R3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R2 is selected from the group an agent having biological activity and a metabolic precursor of an agent having biological activity; -47- R 4 is any chemical moiety that increases solubility of the compound; or a pharmaceutically acceptable salt, solvent, or polymorph thereof.

51. A compound of the formula: R, R4 R 5 R 2 wherein R, and R 2 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R 3 is selected from the group an agent having biological activity and a metabolic precursor of an agent having biological activity; R 4 is any chemical moiety that increases solubility of the compound; or a pharmaceutically acceptable salt, solvent, or polymorph thereof.

52. A compound of the formula: -48- wherein RI, R2, and R3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; X is any chemical moiety resulting in a metabolically labile bond; and R 4 is selected from the group consisting of an agent having biological activity or a metabolic precursor of an agent having biological activity; or a pharmaceutically acceptable salt, solvent, or polymorph thereof.

53. The compound of Claim 52 wherein said metabolically labile bond is selected from the group consisting of amide, ester, carbamate, carbonate, ether, thio, urea, anhydride, thioamide, thioester, thiocarbamate, and thiourea.

54. A compound of the formula: R4 3 R2 wherein R2 and R3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R 4 is any chemical moiety that enhances binding of the compound to the intestinal bile acid transporter; X is any chemical moiety resulting in a metabolically labile bond; and RI is selected from the group consisting of an agent having biological activity or a metabolic precursor of an agent having biological activity; or a pharmaceutically acceptable salt, solvent, or polymorph thereof. -49- A compound of the formula: wherein R 1 and R 3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R 4 is any chemical moiety that enhances binding of the compound to the intestinal bile acid transporter; X is any chemical moiety resulting in a metabolically labile bond; and R 2 is selected from the group consisting of an agent having biological activity or a metabolic precursor of an agent having biological activity; or a pharmaceutically acceptable salt, solvent, or polymorph thereof.

56. A compound of the formula: R4 X R2 R 3 wherein R, and R 2 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R 4 is any chemical moiety that enhances binding of the compound to the intestinal bile acid transporter; X is any chemical moiety resulting in a metabolically labile bond; and R 3 is selected from the group consisting of an agent having biological activity or a metabolic precursor of an agent having biological activity; or a pharmaceutically acceptable salt, solvent, or polymorph thereof.

57. A compound of the formula: R--X2 R4 3e R2 wherein R 2 and R 3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R 4 is any chemical moiety that increases solubility of the compound; X is any chemical moiety resulting in a metabolically labile bond; and R 1 is selected from the group consisting of an agent having biological activity or a metabolic precursor of an agent having biological activity; or a pharmaceutically acceptable salt, solvent, or polymorph thereof.

58. A compound of the formula: -51 ;3 V R2 wherein R, and R 3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R 4 is any chemical moiety that increases solubility of the compound; X is any chemical moiety resulting in a metabolically labile bond; and R 2 is selected from the group consisting of an agent having biological activity or a metabolic precursor of an agent having biological activity; or a pharmaceutically acceptable salt, solvent, or polymorph thereof.

59. A compound of the formula: X R2 R3 wherein RI and R 2 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R 4 is any chemical moiety that increases solubility of the compound; X is any chemical moiety resulting in a metabolically labile bond; and -52- I R 3 is selected from the group consisting of an agent having biological activity or a metabolic precursor of an agent having biological activity; or a pharmaceutically acceptable salt, solvent, or polymorph thereof. The compound of Claim 54, 55, 56, 57, 58 and 59 wherein said metabolically labile bond is selected from the group consisting of amide, ester, carbamate, carbonate, ether, thio, urea, anhydride, thioamide, thioester, thiocarbamate, and thiourea. -53 -54-

61. A pharmaceutical compound comprising: an agent having biological activity or a metabolic precursor of an agent having biological activity conjugated to a bile acid through a metabolically labile bond.

62. The pharmaceutical compound of claim 61, wherein said an agent having biological activity or said metabolic precursor of an agent having biological activity is conjugated to said bile acid through a linker group.

63. The pharmaceutical compound of claim 62, wherein said linker group has a molecular weight of less than 200 daltons.

64. The pharmaceutical compound of claim 61, wherein said metabolically labile bond is selected from the group consisting of an amide, an ester, a carbamate, a carbonate, an ether, a thio, a urea, an anhydride, a thioamide, a thioester, a thiocarbamate, and a thiourea.

65. The pharmaceutical compound of claim 61, wherein said bile acid is selected from the group consisting of a cholate, a glycocholate, a taurocholate, a deoxycholate, a glycodeoxycholate, a taurodeoxycholate, a chenodeoxycholate, a glycochenodeoxycholate, a taurochenodeoxycholate, an ursodeoxycholate and a lithocholate.

66. A compound represented by formula I: X-R 1 X-R 4 X-R 2 X-R 3 wherein R 1 R 2 and R3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, beta-hydroxyl, an agent having biological activity and a metabolic precursor of an agent having biological activity, R 4 is an agent having biological activity, a metabolic precursor of an agent having biological activity, a moiety that enhances binding of the compound to the intestinal bile acid transporter or a solubility enhancing moiety, provided that one ofRi, R 2 R 3 and R 4 is said agent having biological activity or said a metabolic precursor of an agent having biological activity, each X is a single bond or three of the Xs are single bonds and the fourth X is a moiety containing a metabolically labile bond, wherein when X is a moiety containing a metabolically labile bond, X is linked to said agent having biological activity or said metabolic precursor of an agent having biological activity; or a pharmaceutically acceptable salt or solvate thereof.

67. The compound of claim 66, wherein each X is a single bond.

68. The compound of claim 67, wherein said compound is represented by formula 11: -56- r 3 "2 11 wherein R 1 R 2 and R 3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R4 is selected from the group consisting of an agent having biological activity and a metabolic precursor of an agent having biological activity; or a pharmaceutically acceptable salt or solvate thereof.

69. The compound of claim 67, wherein said compound is represented by formula III: R, R4 R3 R2 II wherein R 2 and R 3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R 1 is selected from the group consisting of an agent having biological activity and a metabolic precursor of an agent having biological activity; -57- R 4 is a moiety that enhances binding of the compound to the intestinal bile acid transporter; or a pharmaceutically acceptable salt or solvate thereof. The compound of claim 67, wherein said compound is represented by formula IV: R, R3. R2 IV wherein R, and R 3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R 2 is selected from the group consisting of an agent having biological activity and a metabolic precursor of an agent having biological activity; R 4 is a moiety that enhances binding of the compound to the intestinal bile acid transporter; or a pharmaceutically acceptable salt or solvate thereof.

71. The compound of claim 67, wherein said compound is represented by formula V: -58- R 4 R3-" R, V wherein R, and R 2 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R 3 is selected from the group consisting of an agent having biological activity and a metabolic precursor of an agent having biological activity; R4 is a moiety that enhances binding of the compound to the intestinal bile acid transporter; or a phannaceutically acceptable salt or solvate thereof.

72. The compound of claim 67, wherein said compound is represented by fornula VI: -59- R R2 V wherein R 2 and R 3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R 1 is selected from the group consisting of an agent having biological activity and a metabolic precursor of an agent having biological activity; R 4 is a solubility enhancing moiety; or a pharmaceutically acceptable salt or solvate thereof.

73. The compound of claim 67, wherein said compound is represented by formula VII: RR4 R3 R2 VII wherein RI and R 3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R 2 is selected from the group consisting of an agent having biological activity and a metabolic precursor of an agent having biological activity; R4 is a solubility enhancing moiety or a pharmaceutically acceptable salt or solvate thereof.

74. The compound of claim 67, wherein said compound is represented by formula VI1l: R" R VIII wherein R1 and R 2 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R3 is selected from the group consisting of an agent having biological activity and a metabolic precursor of an agent having biological activity; R 4 is a solubility enhancing moiety or a pharmaceutically acceptable salt or solvate thereof. The compound of claim 66, wherein three of the Xs are single bonds and the fourth X is a moiety containing a metabolically labile bond.

76. The compound of claim 75, wherein said metabolically labile bond is selected from the group consisting of an amide, an ester, a carbamate, a carbonate, an ether, a thio, a urea, an anhydride, a thioamide, a thioester, a thiocarbamate, and a thiourea. -61

77. The compound of claim 75, wherein said compound is represented by formula IX: o R, R4 x R2 Ix wherein Ri, R 2 and R 3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; X is a moiety containing a metabolically labile bond; and R 4 is selected from the group consisting of an agent having biological activity and a metabolic precursor of an agent having biological activity; or a pharmaceutically acceptable salt or solvate thereof.

78. The compound of claim 75, wherein said compound is represented by formula X: Ri- wherein R 2 and R 3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R4 is a moiety that enhances binding of the compound to the intestinal bile acid transporter; O S-62- X is a moiety containing a metabolically labile bond; and R is selected from the group consisting of an agent having biological activity or a metabolic precursor of an agent having biological activity; n 3 or a pharmaceutically acceptable salt or solvate thereof. N 5 79. The compound of claim 75, wherein said compound is represented by \0 formula XI: 3 R2 XI wherein RI and R 3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R 4 is a moiety that enhances binding of the compound to the intestinal bile acid transporter; X is a moiety containing a metabolically labile bond; and R 2 is selected from the group consisting of an agent having biological activity and a metabolic precursor of an agent having biological activity; or a pharmaceutically acceptable salt or solvate thereof. The compound of claim 75, wherein said compound is represented by formula XII: -63 R 3 XII wherein R, and R 2 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R4 is a moiety that enhances binding of the compound to the intestinal bile acid transporter; X is a moiety containing a metabolically labile bond; and R 3 is selected from the group consisting of an agent having biological activity and a metabolic precursor of an agent having biological activity; or a pharmaceutically acceptable salt or solvate thereof.

81. The compound of claim 75, wherein said compound is represented by formula XIII: R1j- 3 R2 XIII wherein R 2 and R 3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R 4 is a solubility enhancing moiety; X is a moiety containing a metabolically labile bond; and -64- R 1 is selected from the group consisting of an agent having biological activity and a metabolic precursor of an agent having biological activity; or a pharmaceutically acceptable salt or solvate thereof.

82. The compound of claim 75, wherein said compound is represented by fornula XIV: 3 I R2 XIV wherein RI and R 3 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R4 is a solubility enhancing moiety; X is a moiety containing a metabolically labile bond; and R2 is selected from the group consisting of an agent having biological activity and a metabolic precursor of an agent having biological activity; or a pharmaceutically acceptable salt or solvate thereof.

83. The compound of claim 75, wherein said compound is represented by formula XV: "3 XV wherein R, and R 2 are independently selected from the group consisting of hydrogen, alpha-hydroxyl, and beta-hydroxyl; R 4 is a solubility enhancing moiety; X is a moiety containing a metabolically labile bond; and R 3 is selected from the group consisting of an agent having biological activity and a metabolic precursor of an agent having biological activity; or a pharmaceutically acceptable salt or solvate thereof.

84. The compound of claim 66, wherein said compound is acyclovir valyldcoxycholate. The compound of claim 66, wherein said compound is acyclovir valylchendeoxycholate.

86. The compound of claim 66, wherein said compound is atenolol cholic acid amide.

87. A method of increasing the bioavailability of an agent having biological activity or a metabolic precursor of an agent having biological activity or reducing the variability of said bioavailability, said method comprising: conjugating a bile acid to said agent having biological activity or said metabolic precursor of an agent having biological activity to form a prodrug, and orally administering said prodrug to a subject in need thereof. -66-

88. The method of claim 87, wherein said bile acid is conjugated directly to said agent having biological activity or said metabolic precursor of an agent having biological activity.

89. The method of claim 87, wherein said bile acid is conjugated via a linker group to said agent having biological activity or said metabolic precursor of an agent having biological activity. The method of claim 89, wherein said linker group has a molecular weight of less than 200 daltons.

91. The method of claim 87, further comprising the step of coating said prodrug with a coating agent prior to orally administering said prodrug.

92. The method of claim 87, wherein said prodrug contains a metabolically labile bond between said agent having biological activity or said metabolic precursor of an agent having biological activity and said bile acid.

93. The method of claim 92, wherein said. metabolically labile bond is selected from the group consisting of an amide, an ester, a carbamate, a carbonate, an ether, a thio, a urea, an anhydride, a thioamide, a thioester, a thiocarbamate, and a thiourea.

94. A method of eliminating adverse interactions between an agent having biological activity or a metabolic precursor of an agent having biological activity and a compound, wherein said adverse interactions result from intestinal absorption of at least one of said agent having biological activity or said metabolic precursor of an agent having biological activity and said compound, said method comprising: conjugating a bile acid to said agent having biological activity or said metabolic precursor of an agent having biological activity to form a prodrug, and \O O -67- orally administering said prodrug to a subject in need thereof. The method of claim 94, wherein said bile acid is conjugated directly to Ssaid agent having biological activity or said metabolic precursor of an agent having biological activity.

96. The method of claim 94, wherein said bile acid is conjugated via a linker C group to said agent having biological activity or said metabolic precursor of an agent Shaving biological activity.

97. The method of claim 96, wherein said linker group has a molecular weight of less than 200 daltons.

98. The method of claim 94, further comprising the step of coating said prodrug with a coating agent prior to orally administering said prodrug.

99. The method of claim 94, wherein said prodrug contains a metabolically labile bond.

100. The method of Claim 99, wherein said metabolically labile bond is selected from the group consisting of an amide, an ester, a carbamate, a carbonate, an ether, a thio, a urea, an anhydride, a thioamide, a thioester, a thiocarbamate, and a thiourea.

101. A method of eliminating adverse interactions between an agent having biological activity or a metabolic precursor of an agent having biological activity and a compound, wherein said adverse interactions result from intestinal absorption of said compound or said an agent having biological activity or metabolic precursor of an agent having biological activity, said method comprising: conjugating a bile acid to said agent having biological activity or said metabolic precursor of an agent having biological activity to form a prodrug, and -68- orally administering said prodrug to a subject in need thereof.

102. The method of claim 101, wherein said bile acid is conjugated directly to said agent having biological activity or said metabolic precursor of an agent having biological activity.

103. The method of claim 101, wherein said bile acid is conjugated via a linker group to said agent having biological activity or said metabolic precursor of an agent having biological activity.

104. The method of claim 102, wherein said linker group has a molecular weight of less than 200 daltons.

105. The method of claim 101, further comprising the step of coating said prodrug with a coating agent prior to orally administering said prodrug.

106. The method of claim 103, wherein said linker group is attached to said agent having biological activity or said metabolic precursor of an agent having biological activity, then said bile acid is attached to said linker group to form the prodrug.

107. The method of claim 103, wherein said linker group is attached to said bile acid, then said agent having biological activity or said metabolic precursor of an agent having biological activity is attached to said linker group to form the prodrug.

108. The method of claim 101, wherein said prodrug contains a metabolically labile bond between said agent having biological activity or said metabolic precursor of an agent having biological activity and said bile acid.

109. The method of claim 108, wherein said metabolically labile bond is selected from the group consisting of an amide, an ester, a carbamate, a carbonate, an 69 ether, a thio, a urea, an anhydride, a thioamide, a thioester, a thiocarbamate, and a thiourea.

110. The method of claim 101, wherein said compound is a nutrient. DATED this twenty-fifth day of May 2006 University of Maryland, Baltimore By its Patent Attorneys DAVIES COLLISON CAVE