(12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (19) World Intellectual Property Organization International Bureau (10) International Publication Number (43) International Publication Date WO 2012/174731 Al 27 December 2012 (27.12.2012) P O P C T

(51) International Patent Classification: CA, CH, CL, CN, CO, CR, CU, CZ, DE, DK, DM, DO, A61K 31/215 (2006.01) A61K 31/4365 (2006.01) DZ, EC, EE, EG, ES, FI, GB, GD, GE, GH, GM, GT, HN, A61K 31/216 (2006.01) A61K 31/497 (2006.01) HR, HU, ID, IL, IN, IS, JP, KE, KG, KM, KN, KP, KR, A61K 31/4178 (2006.01) A61K 47/14 (2006.01) KZ, LA, LC, LK, LR, LS, LT, LU, LY, MA, MD, ME, MG, MK, MN, MW, MX, MY, MZ, NA, NG, NI, NO, NZ, (21) International Application Number: OM, PE, PG, PH, PL, PT, RO, RS, RU, SC, SD, SE, SG, PCT/CN201 1/076256 SK, SL, SM, ST, SV, SY, TH, TJ, TM, TN, TR, TT, TZ, (22) International Filing Date: UA, UG, US, UZ, VC, VN, ZA, ZM, ZW. 24 June 201 1 (24.06.201 1) (84) Designated States (unless otherwise indicated, for every (25) Filing Language: English kind of regional protection available): ARIPO (BW, GH, GM, KE, LR, LS, MW, MZ, NA, SD, SL, SZ, TZ, UG, (26) Publication Language: English ZM, ZW), Eurasian (AM, AZ, BY, KG, KZ, MD, RU, TJ, (72) Inventor; and TM), European (AL, AT, BE, BG, CH, CY, CZ, DE, DK, (71) Applicant : CHENG, Haiyung [US/CN]; 2F.-9, No.36, EE, ES, FI, FR, GB, GR, HR, HU, IE, IS, ΓΓ, LT, LU, LV, Taiyuan St., Zhubei, Hsinchu County 302, Taiwan (CN). MC, MK, MT, NL, NO, PL, PT, RO, RS, SE, SI, SK, SM, TR), OAPI (BF, BJ, CF, CG, CI, CM, GA, GN, GQ, GW, (74) Agent: SHANGHAI PATENT & TRADEMARK LAW ML, MR, NE, SN, TD, TG). OFFICE, LLC; 435 Guiping Road, Shanghai 200233 (CN). Published: — with international search report (Art. 21(3)) (81) Designated States (unless otherwise indicated, for every kind of national protection available): AE, AG, AL, AM, AO, AT, AU, AZ, BA, BB, BG, BH, BR, BW, BY, BZ,

(54) Title: METHOD AND IMPROVED PHARMACEUTICAL COMPOSITION FOR IMPROVING THE ABSORPTION OF AN ESTER PRODRUG (57) Abstract: The present invention relates to a method and an improved composition for improving the absorption of an ester prodrug in a subject. The method includes co-administering to the subject an effective amount of the ester prodrug or a pharmaceut - ical acceptable salt thereof, and a sufficient amount of adjuvant to impede a carboxylesterase-mediated hydrolysis of the ester prod - rug in vivo, wherein the adjuvant is selected from the group consisting of triacetin, triethyl citrate and a combination of both. The present invention also relates to a method for impeding carboxylesterase-mediated hydrolysis of esters, including ester prodrugs. METHOD AND IMPROVED PHARMACEUTICAL COMPOSITION FOR IMPROVING THE ABSORPTION OF AN ESTER PRODRUG

BACKGROU ND O F THE INVENTION

[0001 ] 1. FIELD O F THE INVENTION

The present disclosure relates t o a method and an improved composition for improving the absorption of ester prodrugs; and a method for impeding carboxylesterase-mediated hydrolysis of esters, including ester prodrugs. More particularly, the present disclosure relates t o a method and an improved composition for improving the absorption of ester prodrugs by use of an adjuvant that impedes carboxylesterase-mediated hydrolysis of ester prodrugs.

2. DESCRIPTION O F RELATED ART

[0002] Almost all drugs are metabolized by cytochrome P450 (CYP) isozymes.

Some drugs are rapidly degraded by esterase enzymes in the gastrointestinal (Gl) tract, liver and/or central circulation before arriving at their target sites or reaching certain levels in the central circulation t o confer therapeutic effect. Two pharmacokinetic parameters, i.e., the area under the plasma concentration versus time curve (AUC) and peak plasma

concentration (Cmax) are commonly used t o assess the absorption pharmacokinetics of a drug. The degree of improvement of absorption kinetics and the availability of a drug in the central circulation ( i .e., bioavailability), however, are assessed mainly by using AUC of the drug. The absorption kinetics and oral bioavailability of some drugs, which are therapeutically active but are poorly absorbed, can be improved by the synthesis of their ester prodrugs which are more readily absorbed from the Gl tract. Ester prodrugs are prodrugs having ester moieties. Once absorbed, ester prodrugs undergo hydrolysis t o

generate active drugs under the action of the esterase. Thus, the AUC and Cmax values of prodrugs and/or their active drugs are commonly used t o assess the absorption kinetics and oral bioavailability of ester prodrugs.

[0003] Esterase is a hydrolase enzyme which catalyzes the hydrolysis of an ester into its acid and alcohol . Esterase activity is found in various human tissues and organs including the liver, Gl track, kidney, large intestine, lung, placenta, skeletal muscles, uterus, heart, and blood. As such, some ester prodrugs undergo premature hydrolysis in the Gl tract even before it can be absorbed or premature hydrolysis in the liver after intestinal absorption, leading t o poor oral bioavailability and the need for more frequent and higher doses than are most desirable. In particular, the majority of intestinal esterase is present in the absorption sites of small intestine thereby offsetting the increased efficiency of prodrugs t o pass the intestinal barrier. Thus, methods and compositions are sought and a number of approaches have been tried t o overcome this problem and t o improve the absorption kinetics and, thus, t o enhance the oral bioavailability of ester prodrugs.

[0004] For example, esterase inhibitors including organophosphates (e.g., p-nitrophenyl phosphate), carbamates (e.g., neostigmine), p-hydroxymercuribenzoate, derivatives of nitrophenol and sulfonamide, trifluoromethyl ketones, benzil, isatins (or lH-indole-2,3-dione), and aryl ureas have been utilized or synthesized t o inhibit the esterase-mediated hydrolysis of ester prodrugs. However, organophosphates, carbamates, and p-hydroxymercuribenzoate are regarded as highly toxic poisons.

[0005] Another approach utilizes formulations containing substrates for the esterase t o impede esterase-mediated hydrolysis of ester prodrugs; examples of substrates include fruit extracts and phospholipids such as lecithin. Among a multitude of other substances, fruit extracts contain several flavoring esters. It is postulated that inhibition of the metabolism of the drug by these esters and/or by other compounds could at least partially explain the absorption enhancement observed in the presence of the fruit extract. However, it is not feasible t o incorporate the fruit extract in a pharmaceutical formulation, since it contains a broad variety of other compounds other than the esters, which makes it difficult t o control its absorption enhancing effect. In view of this, Gelder et al. investigated the effect of discrete esters and ester mixtures on the intestinal stability and absorption of tenofovir disoproxil fumarate (tenofovir DF, an esterase-sensitive prodrug of the antiviral tenofovir). However, their research indicated that the extent of inhibition of the enzymatic conversion of the prodrug t o the monoester varies from one ester t o another.

Specifically, the effect of discrete esters on metabolism of tenofovir D F ranged from a negligible effect t o almost complete inhibition (See, J. van Gelder et al., Drug Metabolism and Disposition, 2002, 30:924-930.)

[0006] In view of the foregoing, there still exists in this art a need of suitable esters, which are not only safe t o use in a live subject, but may also impede enzymatic conversion of ester prodrugs in vivo; such esters are suitable substrates for human esterase, hence may act as a pharmacological adjuvant of ester prodrugs in vivo t o improve absorption kinetics of the ester prodrugs. Accordingly, improved methods and pharmaceutical compositions that increase absorption and, thus, enhance the oral bioavailability of ester prodrugs, would represent a significant advancement in the art.

SUMMARY

[0007] The following presents a simplified summary of the disclosure in order t o provide a basic understanding t o the reader. This summary is not an extensive overview of the disclosure and it does not identify key/critical elements of the present invention or delineate the scope of the present invention. Its sole purpose is t o present some concepts disclosed herein in a simplified form as a prelude t o the more detailed description that is presented later. [0008] The present invention is based on the unexpected discovery that when triacetin, triethyl citrate, or a combination of both is co-administered with an ester prodrug susceptible t o carboxylesterase 1 (CEl)-mediated and/or carboxylesterase 2 (CE2)-mediated hydrolysis, hydrolysis of the ester prodrug is greatly impeded. Surprisingly, it is discovered that well known pharmaceutical excipients including triacetin and triethyl citrate, when applied alone or in combination, retards CE-mediated hydrolysis of ester prodrugs such as olmesartan medoxomil and clopidogrel more than lecithin does. In view of this discovery, one can use triacetin, triethyl citrate, or a combination of both t o improve absorption kinetics and, thus, enhance the oral bioavailability of an ester prodrug. The ester prodrug may belong t o any therapeutic class, including anti-thrombogenic agents, peroxisome proliferator-activated receptor alpha (PPARa) agonists, HMG-CoA reductase inhibitors (or statins), angiotensin I I (All) antagonists, angiotensin-converting enzyme (ACE) inhibitors, anti-coagulant, antibiotics, reverse transcriptase inhibitors, mitotic inhibitors, topoisomerase 1 inhibitors, DNA synthesis inhibitors, neuraminidase inhibitors, immunosuppressants, chemotherapy agents, gamma-aminobutyric acid (GABA) analogues,

and GABA B receptor agonists.

[0009] In one aspect, the present disclosure is directed t o a method for improving the absorption of an ester prodrug in a subject. According t o embodiments of the present disclosure, the method comprises the step of co-administering t o the subject an effective amount of the ester prodrug or a pharmaceutical acceptable salt thereof, and an adjuvant selected from the group consisting of triacetin, triethyl citrate and a combination of both, wherein the adjuvant is administered in an amount sufficient t o improve the absorption kinetics and, thus, enhance the bioavailability of the ester prodrug (i.e., t o increase the AUC values of the ester prodrug and/or the active drug). [001 0] In another aspect, the present disclosure is directed t o an improved pharmaceutical composition for improving absorption of an ester prodrug in a subject.

The improved pharmaceutical composition comprises an effective amount of an ester prodrug or a pharmaceutically acceptable salt thereof and a pharmaceutically acceptable excipient; and the improvement according t o embodiments of the present disclosure comprises an adjuvant selected from the group consisting of triacetin, triethyl citrate and a combination of both; wherein the adjuvant is capable of impeding carboxylase-mediated hydrolysis of the ester prodrug in vivo. According t o optional embodiments of the present disclosure, the improved pharmaceutical composition may further comprise a second ester prodrug and/or additional components such as other pharmaceutically acceptable carriers, adjuvants, and vehicles thereof as desired.

[001 1] Also within the scope of the present disclosure is the use of the above-mentioned pharmaceutical composition for treating conditions such as (1) cardiovascular disease (the ester prodrug being olmesartan medoxomil, candesartan cilexetil, ramipril, delapril, trandolapril, temocapril, cilazapril, quinapril, imidapril, aspirin, clopidogrel or prasugrel), (2) hypercholesterolemia, hypertriglyceridemia or both diseases

(the ester prodrug being lovastatin, simvastatin, clofibrate or fenofibrate), (3) fever and rheumatic arthritis (the ester prodrug being aspirin), (4) infections including HIV and

Hepatitis B infections (the ester prodrug being cefpodoxime proxetil, cefditoren pivoxil, tenofovir disoproxil, or adefovir dipivoxil), (5) cancer (the ester prodrug being paclitaxel, docetaxel, isotaxel, irinotecan or capecitabine), (6) Influenza virus A and Influenza virus B infection ( the ester prodrugs being oseltamivir or A-322278), (7) spasticity and GERD (the ester prodrug being arbaclofen placarbil), and (8) sleep loss caused by restless legs syndrome and pain associated with post-herpetic neuralgia (the ester prodrug being gabapentin enacarbil), and for manufacture of a medicament for that treatment. [001 2] Further within the scope of the present disclosure is the use of the above-mentioned pharmaceutical composition for reducing the risk of conditions such as cardiovascular disease (the ester prodrug being olmesartan medoxomil, candesartan cilexetil, ramipril, delapril, trandolapril, temocapril, cilazapril, quinapril, imidapril, lovastatin, simvastatin, clofibrate or fenofibrate), Influenza virus A and Influenza virus B infection (the ester prodrugs being oseltamivir or A-322278), organ rejection (the ester prodrug being mycophenolate mofetil), blood clots (the ester prodrug being dabigatran etexilate), and atherothrombotic events (the ester prodrug being aspirin, clopidogrel or prasugrel), and for the manufacture of a medicament for reducing that risk.

[001 3] The details of many embodiments of the invention are set forth in the detailed description and the claims below. Other features, objects, and advantages of the invention will become better understood with reference t o the following detailed description and the appended claims.

DESCRI PTION

[001 4] The detailed description provided below is intended as a description of the present examples and is not intended t o represent the only forms in which the present example may be constructed or utilized. The description sets forth the functions of the example and the sequence of steps for constructing and operating the example. However, the same or equivalent functions and sequences may be accomplished by different examples.

[001 5] For convenience, certain terms employed in the specification, examples and appended claims are collected here. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of the ordinary skill in the art t o which the present disclosure belongs. [001 6] The singular forms "a", "an", and "the" are used herein t o include plural referents unless the context clearly dictates otherwise.

[001 7] As used herein, the term "about" generally means within 10%, 5%, 1%, or

0.5% of a given value or range. Alternatively, the term "about" means within an acceptable standard error of the mean, when considered by one of ordinary skill in the art.

[001 8] The term "prodrug", as used herein, refers t o any compound that when administered t o a biological system yields the "drug" substance either as a result of spontaneous chemical reaction(s) or by enzyme catalyzed or metabolic reaction(s). "Ester prodrugs" are compounds that contain ester groups imparting the prodrug nature of the drug. For example, an ester prodrug of a compound containing a carboxyl group may be convertible by hydrolysis in vivo t o the corresponding carboxylic acid.

[001 9] The terms "oral bioavailability" and "bioavailability" are used interchangeably t o refer t o the amount or portion of an orally administered drug that reaches the systemic circulation.

[0020] As used herein, a "pharmaceutically acceptable" component is one that is suitable for use with humans and/or animals without undue adverse side effects (such as toxicity, irritation, and allergic response) commensurate with a reasonable benefit/risk ratio.

[0021 ] The term "effective amount" or "sufficient amount" as used herein refers t o the quantity of a component which is sufficient t o yield a desired therapeutic response.

The specific effective or sufficient amount will vary with such factors as the particular condition being treated, the physical condition of the patient (e.g., the patient's body mass, age, or gender), the type of mammal or animal being treated, the duration of the treatment, the nature of concurrent therapy (if any), and the specific formulations employed and the structure of the compounds or its derivatives. Effective amount may be expressed, for exa mple, as t he tota l mass of este r prod rug (e .g., in gra ms, millig rams or mic rog rams) or a rat io of mass of este r prod rug t o body mass, e.g., as milligra ms per kilogra m (mg/kg) .

[0022] The t erm "exci pie nt" as used here in mea ns any ine rt substa nce (suc h as a powde r or liq uid ) t hat forms a vehicle/ca rrie r for t he este r prod rug(s) and/o r adj uva nt.

The exc ipie nt is ge ne ra lly safe, non-toxic, and in a broad se nse, may also incl ude any known substa nce in t he pha rma ce utica l ind ust ry usefu l for pre pa ring pha rmace utica l com posit io ns such as, f ille rs, diluents, aggl uti na nts, binders, lubricat ing age nts, glida nts, sta bilize r, co lo ra nts, wett ing age nts, dis integra nts, and etc.

[0023] The t erm "adj uva nt" as used he rein is defi ned as a substa nce t hat, whe n added t o t he pharmace ut ica l co mposit ion, enha nces the absorpt io n kinetics, he nce, the bioava ila bility of the este r prod rug, w hile having few or none of direct the ra peut ica lly effects whe n give n by itse lf.

[0024] As used in the prese nt d isc losu re, t he t erm " Cmax" refe rs t o the maxim um conce ntrat ion of an active com pou nd or drug (e.g., clo pidog re l or capecita bine) in t he blood

plasma, whe reas the t erm "Tmax" mea ns t he t ime t o achieve t he maxim um plasma

conce ntrat ion of sa id act ive com pou nd or drug. The t erm "AUC 0 -t" refe rs t o an area unde r the curve from t ime ze ro t o the last measu red t ime poi nt of a meas urable drug conce ntrat ion .

[0025] The t erm "treati ng" as used he re in refe rs t o applicat ion or ad minist rat ion of t riacet in, t riet hyl cit rate or bot h pha rma ce ut ica l adj uva nts and at least one este r prod rugs t o a subject, who has a med ica l co nd itio n, a sym ptom of the co nd it io n, a disease or diso rde r seconda ry t o the co nd it io n, or a pred ispos ition towa rd t he cond it ion, with the purpose t o pa rt ia lly or co mplete ly allev iate, amelio rate, re lieve, delay onset of, inhibit progress io n of, red uce seve rity of, and/o r red uce inc ide nce of one or more sym ptoms or featu res of a part icu la r disease, diso rder, and/o r cond ition . Treatme nt may be ad ministe red t o a subject who does not exh ibit signs of a disease, diso rde r, and/o r cond itio n and/or t o a su bject who exh ibits only ea rly signs of a disease, diso rde r, and/o r cond itio n for t he purpose of dec reas ing the risk of deve lop ing pat ho logy assoc iated with the disease, diso rde r, and/o r co nd it io n.

[0026] The pract ices of t his inve ntio n are he re inafte r desc ribed in deta il wit h respect t o a met hod and a pha rma ce ut ica l com posit ion for improvi ng t he abso rption kinet ics and, t hus, enhanci ng the bioava ila bility of an este r prod rug in a su bject. Resu lts of pha rmacoki net ic st ud ies, as descri bed he rein below, show t hat the prese nt pha rma ce ut ica l com posit ion, pa rticu la rly, a co mpos it io n that conta ins an este r prod rug and an adj uva nt cons isti ng of tria cet in and/or t riet hyl cit rate, may im ped e t he ca rboxylase-med iated hyd rolysis of the este r prod rug in vivo the re by improv ing t he abso rpt ion kinet ics and, t hus, enhancing the bioava ila bility of t he este r prod rug in the subject.

[0027] Este rases are a group of hyd rolyt ic enzymes occ urri ng in mult iple forms with broad subst rate spec ific ity. Ca rboxyleste rase (CE) is t he most abundant este rase in the live r and sma ll intesti ne of humans, monkeys, dogs, ra bbits and rats. It plays an importa nt ro le in biot ra nsformatio n of a variety of este r prod rugs such as anti-th rom boge nic age nts (e .g., asp irin, clo pidog re l and prasug re l), peroxisome pro life rato r-act ivated rece pto r alpha (PPARa) ago nists (e.g., fenofi brate and clofib rate ),

HMG-CoA red uctase inhibito rs (or stat ins, e.g., lovastat in and simvastati n), angiote nsi n II

(Al l) antagon ists (e .g., olmesa rta n medoxom il and ca ndesa rta n cilexet il), angiote nsin-co nvert ing enzyme (ACE) inhibitors (e .g., ramipri l, de la pril, t rando la pril, t emoca pril, cilaza pril, quina pril and im ida pri l), ant i-coag ula nts (e .g., dabigat ran etexilate), anti biot ics (e.g., cefpod oxime proxet il and cefd itore n pivoxi l), reve rse t ra nscri ptase inhibito rs (e .g., t enofov ir diso proxi l and adefovi r dipivoxi l), mitot ic inhibito rs (e.g., paclitaxel, docetaxel and isotaxel), DNA synthesis inhibitors (e.g., capecitabine), topoisomerase 1 inhibitors (e.g., irinotecan), neuraminidase inhibitors (e.g., oseltamivir and

A-322278), immunosuppressants (e.g., mycophenolate mofetil), gamma-aminobutyric acid

(GABA) analogues (e.g., gabapentin enacarbil), and GABAB receptor agonists (e.g., arbaclofen placarbil).

[0028] In humans and laboratory animals, the majority of C E isozymes belong t o the carboxylesterase 1 (CEl) and carboxylesterase 2 (CE2) families. The liver contains both

CEl and CE2 isozymes in all these species. In human liver, the CEl level exceeds the CE2 level. The human and rat small intestines contain only CE2 isozymes, while in rabbits and monkeys, both CEl and CE2 isozymes are present. Therefore, bioconversion rates of orally administered prodrugs are affected by expression levels of CEl and CE2 in human liver and small intestine. Although human CEl and CE2 have overlapping substrate recognition, clear evidence of ester-based substrate specificity has been observed. Two products, an alcohol and an acyl moiety, are generated from ester hydrolysis. In general, human CEl prefers substrates with a large acyl moiety, whereas human CE2 prefers substrates with a large alcohol group. For example, prodrugs with a large acyl moiety such as oseltamivir, clopidogrel, lovastatin, temocapril, trandolapril, cilazapril, quinapril, delapril, and imidapril are hydrolyzed predominately or solely by human CEl, whereas prodrugs with a large alcohol group such as aspirin, prasugrel, arbaclofen placarbil, and gabapentin enacarbil are hydrolyzed mainly by human CE2. Based on this substrate specificity, it can be predicted that fenofibrate, clofibrate, ramipril, A-322278, and simvastatin are the preferred substrates for human CEl, while olmesartan medoxomil, candesartan cilexetil, tenofovir disoproxil, mycophenolate mofetil, adefovir dipivoxil, cefpodoxime proxetil, cefditoren pivoxil, and isotaxel are the preferred substrates for human CE2. Moreover, it can be concluded that, besides expression levels of CEl and CE2 in humans, bioconversion of ester prodrugs is also affected by the substrate specificity of human CE1 and CE2. Thus, one purpose of the present disclosure is t o provide a compound or composition which can retard not only CEl-mediated hydrolysis but also CE2-mediated hydrolyses of ester prodrugs t o improve the absorption kinetics and, thus, enhance oral bioavailability of these prodrugs.

[0029] Triacetin is affirmed as a generally recognized as safe (GRAS) human food additive by the Food and Drug Administration (FDA, USA). It is also used in pharmaceutical industry as an excipient, such as a humectant, a plasticizer, and a solvent. Likewise, triethyl citrate is commonly used as a food additive and in pharmaceutical coatings.

Triethyl citrate has also been used t o stabilize E-type prostaglandin compounds and t o prevent lipase hydrolysis of triglycerides. Both triacetin and triethyl citrate are safe t o be used in animals including human, and up t o 10 mg/Kg body weight may be used in man without exerting any toxicity. In the present disclosure, triacetin and triethyl citrate are evaluated and compared t o lecithin in terms of their effectiveness in impeding CE-mediated hydrolysis of ester prodrugs.

[0030] According t o embodiments of the present disclosure, the improved pharmaceutical composition comprises an effective amount of an ester prodrug or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable excipient; and the improvement comprises an adjuvant selected from the group consisting of triacetin, triethyl citrate and a combination of both; wherein the adjuvant is present in an amount sufficient t o impede carboxylase-mediated hydrolysis of the ester prodrug in vivo.

[0031 ] In optional embodiments of the present disclosure, the improved pharmaceutical composition may further comprise a second ester prodrug and/or additional components such as other pharmaceutically acceptable carriers, adjuvants, and vehicles thereof as desired. [0032] Accord ing t o embod ime nts of the prese nt disc losu re, t he method for improvi ng abso rpt io n of este r prod rugs com prises ad ministe ring t he improved pha rma ce ut ica l com posit io n d isc losed here in t o a su bject. Specifica lly, t he met hod com prises the ste p of co-a dministe ring t o the su bject an effect ive amount of the este r prod rug or a pha rma ce ut ica l acce pta ble sa lt t hereof; and a sufficie nt amount of an adj uva nt se lected from the group co nsist ing of t riacet in, t riethyl cit rate and a co mbinat ion of bot h, t o impede carboxylase-med iated hyd rolysis of t he este r prod rug in vivo and the re by improves t he abso rption kinet ics and, t hus, enhance t he bioava ila bility of t he este r prod rug.

[0033] Test resu lts su mmarized he re inbe low evide nce t hat tria ceti n, t riethyl cit rate, and a co mbination of bot h of these pharma ce ut ica l adj uva nts, whe n used wit h one or two este r prod rug(s), impede CE-med iated hyd rolysis of the prod rug(s) . Thus, t his co-ad ministe ring of este r prod rugs wit h adj uva nts ide nt ified by t his inve ntio n resu lts in an improve ment in absorpt io n kinetics (i.e ., t o increase t he AUC values of the este r prod rug(s) and/o r the act ive drug(s) of t he este r prod rug(s)) and, t hus, an enhance ment in o ra l bioava ila bility of the este r prod rug(s) .

[0034] Accord ing t o various embod ime nts of the prese nt disclosu re, suita ble este r prod rugs include t hose exemplified hereinabove and any othe r known or futu re este r prod rugs, as lo ng as t he abso rpt io n kinet ics may be improved and, t hus, bioava ila bility of such este r prod rug may be increased by t he prese nt met hod and/o r im proved com pos itio n.

[0035] Este r prod rugs used t o pract ice the prese nt d isc losu re are eit her com mercia lly ava ila ble or can be read ily pre pa red by methods well known in the art.

These prod rugs may occ ur as race mic mixtu res, sing le enant iome rs, ind ivid ual diaste reome rs, diaste reome ric mixtu res, and cis- or t rans-isome ric forms. Addit iona lly, the ir pha rmace ut ica lly acce pta ble sa lts are also with in t he sco pe of t he prese nt d isc los ure.

Suc h sa lts ca n be formed betwee n a pos itive ly cha rged ion ic grou p in a the ra pe utic age nt (e.g., ammonium) and a negatively charged counterion (e.g., acetate, citrate, aspartate, benzoate, fumarate, chloride, bromide, lactate, maleate, oxalate, phosphate, succinate, sulfate, or tartrate). Likewise, a negatively charged ionic group in a therapeutic agent (e.g., carboxylate) can also form a salt with a positively charged counter ion (e.g., sodium, potassium, calcium, or magnesium). Non-exhaustive examples of acids which may be employed t o form pharmaceutically acceptable acid addition salts include such inorganic acids as sulfuric acid, hydrochloric acid, and phosphoric acid and such organic acids as oxalic acid, maleic acid, and succinic acid. For example, clopidogrel also refers t o its corresponding bisulfate salt.

[0036] In embodying the present disclosure, ester prodrug(s) and the pharmaceutically acceptable adjuvant(s) may be administered orally. A composition for oral administration may be any orally acceptable dosage form including capsules, tablets, emulsions and aqueous suspensions, dispersions, and solutions. In the case of tablets, commonly used carriers include, but are not limited to, lactose and corn starch.

Lubricating agents, such as magnesium stearate, are also typically added. Tablets can additionally be prepared with enteric coatings. For oral administration in a capsule form, useful diluents include lactose and dried corn starch. When aqueous suspensions or emulsions are administered orally, the active ingredient can be suspended or dissolved in an oily phase combined with emulsifying or suspending agents. If desired, certain sweetening, flavoring, or coloring agents can be added.

[0037] The optimal amount in a given dosage form or formulation can be estimated or determined by experimentation such as that described in the examples of this application. As shown in these examples, the amount of triacetin, triethyl citrate or a combination of both in oral dosing solutions is in the range of about 10-90% by weight.

Thus, the amount of triacetin, triethyl citrate or a combination of both in an orally acceptable dosage form is generally ranged, for example, from about 1% t o about 99.9% by weight; and preferably from about 10% t o about 90 % by weight. The examples also show that the ratio of the amount of prodrug drug t o the amount of adjuvant (triacetin and/or triethyl citrate) is in the range of about 1:3-1:27. Thus, the ratio of the amount of prodrug drug t o the amount of adjuvant (triacetin and/or triethyl citrate) in an oral dosage form is generally ranged, for example, from about 1:1 t o about 1:50, and preferably from about 1:2 t o about 1:40.

[0038] In optional embodiments where two ester prodrugs are administered in combination, the two ester prodrugs can be formulated as a single composition or separate compositions.

[0039] Some of the ester prodrugs mentioned above (i.e., olmesartan medoxomil and candesartan cilexetil) are All antagonists and some (i.e., ramipril, delapril, trandolapril, temocapril, cilazapril, quinapril and imidapril) are ACE inhibitors. All antagonists and ACE inhibitors and their combinations are commonly used t o treat cardiovascular disease (e.g., hypertension and heart failure). Thus, also within the scope of the present disclosure is a method of treating cardiovascular disease using an All antagonist, an ACE inhibitor, or both therapeutic agents with an adjuvant identified in the present disclosure, which is triacetin, triethyl citrate, or a combination of both.

[0040] Some of the ester prodrugs (i.e., aspirin, clopidogrel, and prasugrel) are anti-thrombogenic agents. Anti-thrombogenic agents are commonly used t o inhibit blood clots in coronary artery disease, peripheral vascular disease, and cerebrovascular disease.

Aspirin is also commonly used t o reduce fever and treat rheumatic arthritis. Some of the ester prodrugs (i.e., dabigatran etexilate) are anti-coagulants. Anti-coagulants are commonly used t o prevent formation of blood clots in the veins after knee or hip replacement surgery. Thus, also within the scope of the present disclosure is a method of inhibiting blood clots using an anti-thrombogenic agent or anti-coagulant with triacetin, triethyl citrate or both; or reducing fever and treating rheumatic arthritis using aspirin with triacetin, triethyl citrate, or a combination of both.

[0041 ] Some of the ester prodrugs (i.e., fenofibrate and clofibrate) are PPARa agonists. Some are statins (e.g., lovastatin and simvastatin). Statins are commonly used t o treat hypercholesterolemia. PPARa agonists are commonly used alone or in conjunction with statins in the treatment of hypercholesterolemia and hypertriglyceridemia.

Thus, also within the scope of the present disclosure is a method of treating hypercholesterolemia, hypertriglyceridemia, or both diseases using a PPARa agonist, a stain, or both therapeutic agents with triacetin, triethyl citrate, or a combination of both.

[0042] Some of the ester prodrugs (i.e., cefpodoxime proxetil and cefditoren pivoxil) are antibiotics. Antibiotics are commonly used t o treat infections. Thus, also within the scope of the present disclosure is a method of treating infections using an antibiotic with triacetin, triethyl citrate, or a combination of both.

[0043] Some of the prodrugs (e.g., oseltamivir and A-322278) are neuraminidase inhibitors. Neuraminidase inhibitors are commonly used t o treat Influenza virus A and

Influenza virus B infection. Thus, also within the scope of the present disclosure is a method of treating Influenza virus A and Influenza virus B infection using a neuraminidase inhibitor with triacetin, triethyl citrate, or a combination of both.

[0044] Some of the ester prodrugs (i.e., tenofovir disoproxil, adefovir dipivoxil, arbaclofen placarbil, and gabapentin enacarbil) are reverse transcriptase inhibitors, GABAB receptor agonist, and GABA analogue, respectively. They are commonly used t o treat HIV infection, Hepatitis B infection, spasticity, and GERD, sleep loss caused by restless legs syndrome and pain associated with post-herpetic neuralgia, respectively. One of the ester prodrugs (i.e., mycophenolate mofetil) is an immunosuppressant and used t o prevent rejection in organ transplantation. Thus, also within the scope of the present disclosure is a method of treating the above diseases using these ester prodrugs with triacetin, triethyl citrate, or a combination of both.

[0045] Some of the ester prodrugs (i.e., paclitaxel, isotaxel, docetaxel, irinotecan, and capecitabine) are mitotic inhibitors, topoisomerase 1 inhibitor, and DNA synthesis inhibitor, respectively. They are commonly used t o treat cancer. Thus, also within the scope of the present disclosure is a method of treating cancer using these ester prodrugs with triacetin, triethyl citrate, or a combination of both.

[0046] In preferred embodiments of the present disclosure, the prodrug is clopidogrel, olmesartan medoxomil, tenofovir disoproxil, adefovir dipivoxil, mycophenolate mofetil, paclitaxel, docetaxel, isotaxel, irinotecan, capecitabine, arbaclofen placarbil, or gabapentin enacarbil.

[0047] The following Examples are provided t o elucidate certain aspects of the present invention and t o aid those of skilled in the art in practicing this invention. These

Examples are in no way t o be considered t o limit the scope of the invention in any manner.

Without further elaboration, it is believed that one skilled in the art can, based on the description herein, utilize the present invention t o its fullest extent. All publications cited herein are hereby incorporated by reference in their entirety.

[0048] Effectiveness of a pharmaceutical adjuvant such as triacetin or triethyl citrate in impeding hydrolysis of an ester prodrug by C E can be preliminarily screened by an in vitro assay. For example, a mixture of triacetin or triethyl citrate is incubated with an ester prodrug (e.g., olmesartan medoxomil) in the presence of CE, and the concentration of prodrug in the mixture after the incubation is then compared with that of a blank control containing neither triacetin nor triethyl citrate. See Example 1 below. In Example 1, the respective effect of triacetin, triethyl citrate, and lecithin in impeding hydrolysis of olmesartan medoxomil by C E was also documented. Further, the effect of triacetin and triethyl citrate in impeding CE-mediated hydrolysis of clopidogrel was also observed. See

Example 2 below. Moreover, as shown in Examples 1 and 2, a combination of triacetin and triethyl citrate is also effective in greatly impeding CE-mediated hydrolysis of olmesartan medoxomil and clopidogrel. In vivo assays can be conducted t o ascertain the effectiveness of triacetin, triethyl citrate or a combination of both adjuvants in improving the absorption kinetics of ester prodrugs. See Examples 3-5 below.

EXAMPLES

EXAMPLE 1: Influence of various ester excipients on in vitro CE-mediated hydrolysis of olmesartan medoxomil

[0049] Various known pharmaceutical ester excipients including triacetin, glyceryl tristearate, triethyl citrate, lecithin, tri-n-butyl citrate, acetyl triethyl citrate, and acetyl tri-n-butyl citrate were respectively tested t o determine whether any of them impedes hydrolysis of olmesartan medoxomil by CE in vitro. Preliminary results indicated that triacetin and triethyl citrate were promising candidates, hence further experiments were conducted below t o compare the effect of triacetin, triethyl citrate or a combination of both on CE-mediated hydrolysis of olmesartan medoxomil, as compared with that of lecithin.

[0050] Test solutions (a) t o (f) were prepared respectively as follows: (a) 10 µΜ of olmesartan medoxomil dissolved in 10% DMSO (dimethyl sulfoxide)/90% PEG400 (w/w, stability control); (b) 10 µΜ of olmesartan medoxomil dissolved in 10% DMSO/90% PEG400

(w/w, blank control) (c) 10 µΜ of olmesartan medoxomil dissolved in 10% DMSO/12% triacetin/78% PEG400 (w/w/w); (d) 10 µΜ of olmesartan medoxomil dissolved in 10%

DMSO/12% triethyl citrate/78% PEG400 (w/w/w); (e) 10 µΜ of olmesartan medoxomil dissolved in 10% DMSO/12% lecithin/78% PEG400 (w/w/w); and (f) 10 µΜ of olmesartan medoxomil dissolved in 10% DMSO/6% triacetin/6% triethyl citrate/78% PEG400

(w/w/w/w).

[0051 ] CE from porcine liver (17 units/mg, available from Sigma-Aldrich) was dissolved in simulated intestinal fluid (SIF, pH = 6.8) t o yield a C E solution (17 units/ml).

SIF was prepared by dissolving 0.6805 g of KH2P0 4 and 0.0896 g of NaOH in 100 ml of de-ionized water.

[0052] Each 70 µ Ι of olmesartan medoxomil solution (i.e., solutions (a)-(f)) was mixed with 70 µ Ι of SIF and thereby forming mixtures (a) t o (f). Each of the mixtures (a) t o

(f) was transferred t o one well of a 96-well plate, and 60 µ Ι each of the C E solution was added t o respective wells containing mixtures (b) t o (f) t o initiate the reaction. In addition, sixty (60) µ Ι of SIF without C E was added t o mixture (a). This incubation mixture without

CE was used as a stability control t o determine the chemical stability of olmesartan medoxomil in the incubation mixture. The mixtures were incubated for 20 minutes under the air at 37°C with constant shaking on a temperature-controlled heating block.

[0053] At the end of the 20-minute incubation, 100 µ Ι of ice-cold acetonitrile was added t o each well t o terminate the reaction. Each mixture was vortexed and centrifuged at 15,000xg for 20 min at room temperature. The supernatants were tested in HPLC/UV analysis, in which the concentration of olmesartan medoxomil in each mixture was measured. Percentages (%) of olmesartan medoxomil remaining in the mixtures were calculated based on the obtained data. Table 1 summarizes the results of this example.

[0054] As shown in Table 1, triacetin, triethyl citrate or a combination of both, retards CE-mediated hydrolysis of olmesartan medoxomil, which is predicted t o be a preferred substrate of CE2, better than lecithin. Table 1 : Influence of Various Ester Excipients on CE-Mediated Hydrolysis of Olmesartan Medoxomil. % Remaining of Olmesartan Medoxomil Olmesartan Medoxomil Solution 0 min 20 min (a) 10%DMSO + 90%PEG400 (Without CE) 100 94.2 (b) 10%DMSO + 90%PEG400 (With CE) 100 69.4 (c) 10%DMSO + 12%Triacetin + 78%PEG400 (With CE) 100 87.4 (d) 10%DMSO + 12%Triethyl citrate + 78%PEG400 (With CE) 100 82.2 (e) 10%DMSO + 12%Lecithin+78°/oPEG400 (With CE) 100 74.9 (f) 10%DMSO + 6%Triacetin +6%Triethyl Citrate + 78%PEG400 100 84.9 (With CE)

EXAMPLE 2 : Influence of Triacetin, triethyl citrate or both on in vitro CE-mediated hydrolysis of clopidogrel

[0055] The ability of triacetin and triethyl citrate t o impede CE-mediated hydrolysis of clopidogrel, which is a preferred substrate of CE1, is demonstrated in accordance with the in vitro test method described in Example 1 . Results are summarized in Table 2 . The results show that triethyl citrate, triacetin and lecithin retard CE-mediated hydrolysis of clopidogrel. Surprisingly, triethyl citrate and a combination of triethyl citrate and triacetin are more effective in impeding CE-mediated hydrolysis of clopidogrel than triacetin and lecithin. Table 2 : Influence of Triacetin, Triethyl Citrate or Both on CE-Mediated Hydrolysis of

Clopidogrel.

% Remaining of Clopidogrel Clopidogrel Solution 0 min 20 min (a) 10%DMSO + 90%PEG400 (Without CE) 100 97.8

(b) 10%DMSO + 90%PEG400 (With CE) 100 52.1 (c) 10%DMSO + 10%Triacetin + 80%PEG400 (With CE) 100 74.9 (d) 10%DMSO + 10%Triethyl citrate + 80%PEG400 (With CE) 100 89.1 (e) 10%DMSO + 10%Lecithin +80°/oPEG400 (With CE) 100 79.2 (f) 10%DMSO + 5%Triacetin+5%Triethyl Citrate + 80%PEG400 100 86.9 (With CE)

EXAMPLE 3 : Improvement of absorption kinetics of olmesartan medoxomil

[0056] Male rats (Sprague-Dawley, 300-400 g) were surgically implanted with jugular-vein cannulas one day prior t o dosing and fasted overnight (about 18-20 hours) prior t o dosing. Water was available ad libitum throughout the experiment. Dosing solutions of olmesartan medoxomil (5 mg/ml) were prepared in a vehicle of DMSO/PEG400 (10/90, v/v) or DMSO/PEG400/triacetin (10/80/10, v/v). Single oral doses of the olmesartan medoxomil and olmesartan medoxomil/triacetin were each administered separately t o a group of 3 male rats by gavage. Each rat received olmesartan medoxomil (5 mg/kg) in

DMSO/PEG400 (10/90, v/v) or olmesartan medoxomil (5 mg/kg) in DMSO/PEG400/triacetin

(10/80/10, v/v).

[0057] Blood samples (0.15 ml/rat) were collected from each rat via the jugular-vein cannula at 0, 0.25, 0.5, 1, 2, 4, 6 , 8, and 24 hours after dosing. Plasma was separated from blood cells by centrifugation and frozen at -20 C until analysis. The concentrations of olmesartan (active drug) and olmesartan medoxomil in the plasma samples were determined by LC-MS/MS. A plasma concentration-time curve was plotted

based on the obtained data. From the curve, the Cmax and the time of maximum concentration (Tmax) values were measured and the AUC value from t = 0 hour t o t = 24

hours (AUC0 -24hr) was calculated using the trapezoidal rule (see Altamn, Practical Statistics or Medical Research, CRC Press, 1991, pp. 432-433 and Khan and Reddy, Pharmaceutical and Clinical Calculations, CRC Press, 2000, pp. 235-236). As expected, olmesartan medoxomil was completely hydrolyzed t o olmesartan after absorption following oral administration of olmesartan medoxomil or olmesartan medoxomil/triacetin t o rats. Table

3 lists the mean (n = 3) values of AUC0 -24hr, Cmax and Tmax of olmesartan. The results indicate that triacetin increases AUC0 -24hr and Cmax of olmesartan by 64% and 108%, respectively; and thus improves the absorption kinetics of olmesartan medoxomil.

Table 3 : Improvement of Absorption Kinetics of Olmesartan Medoxomil.

Cmax T (hr) Treatment AUC 0 -24hr (ng-hr/ml) (ng/ml) max Olmesartan Medoxomil 1704 825 0.5 Olmesartan Medoxomil + Triacetin 2800 1720 0.5

EXAM PLE 4 : Improvement of absorption kinetics of clopidogrel bisulfate

[0058] Clopidogrel is a prodrug that is metabolized mainly by cytochrome P450

2C19 (CYP2C19) in the liver into an active drug. Being an ester prodrug, clopidogrel is also rapidly hydrolyzed by carboxylesterase, mainly in the liver, t o form an inactive carboxylic acid metabolite (clopidogrel acid). Thus, ester hydrolysis and hepatic metabolism by

CYP2C19 represent two competing pathways that determine the efficiency of clopidogrel.

A study similar t o the olmesartan medoxomil study described above in Example 3 was conducted in rats (n = 3) t o ascertain the effect of triethyl citrate in enhancing the oral bioavailability of clopidogrel. Each rat received clopidogrel bisulfate (30 mg/kg) in

DMSO/PEG400 (10/90, w/w) or 30 mg/kg of clopidogrel bisulfate in DMSO/PEG400/triethyl citrate (10.1/77.5/12.4, w/w/w). Serial plasma samples were obtained from each rat and concentrations of clopidogrel, its active drug, and clopidogrel acid in the plasma samples were determined by LC-MS/MS. It was found that in this study, concentrations of the active drug of clopidogrel were too low (< 1 ng/ml) t o be measured.

[0059] Table 4 lists the mean (n = 3) values of AUC0 -24hr, Cmax and Tmax of clopidogrel and clopidogrel acid. As evidenced from Table 4, triethyl citrate increases

values of AUC0 -24hr and Cmax of clopidogrel by 171% and 156%, respectively. Thus, it is fair to conclude that triethyl citrate retards esterase hydrolysis and improves the absorption kinetics of clopidogrel bisulfate in rats.

Table 4 : Mean (n = 3) Values of AUC0 -24hr, Cmax and Tmax of Clopidogrel and Clopidogrel

Acid.

Dose Clopidogrel Bisulfate + Clopidogrel Bisulfate Triethyl Citrate Parameter Clopidogrel Clopidogrel Acid Clopidogrel Clopidogrel Acid AUCo-24hr (ng-hr/ml) 28 12580 76 36810

Cmax (ng/ml) 7.3 2762 18.7 7851

Tmax (hr) 4.1 8.0 6.0 8.0

[0060] In a rat study similar t o the study described above, each rat received clopidogrel bisulfate (3 mg/kg) in DMSO/PEG400 (10/90, w/w) or 3 mg/kg of clopidogrel bisulfate in DMSO/PEG400/triethyl citrate/triacetin (10/78/6/6, w/w/w/w). Serial plasma samples were obtained from each rat and concentrations of clopidogrel and clopidogrel acid in the plasma samples were determined by LC-MS/MS.

[006 1 ] Table 5 lists the mean (n = 3) values of AUC0 -24hr, Cmax and Tmax of clopidogrel and clopidogrel acid. As shown in Table 5, a combination of triethyl citrate and

triacetin increases mean values of AUC0 -24hr and Cmax of clopidogrel by 650% and 638%, respectively. Thus, a combination of triethyl citrate and triacetin effectively improves the absorption kinetics of clopidogrel bisulfate in rats.

Table 5 : Mean (n = 3) Values of AUC0 -24hr, Cmax and Tmax of Clopidogrel and Clopidogrel

Acid.

Dose Clopidogrel Bisulfate + Clopidogrel Bisulfate Triethyl Citrate + Triacetin Parameter Clopidogrel Clopidogrel Acid Clopidogrel Clopidogrel Acid 2 8616 15 4910 AUC0 -2 hr (ng-hr/ml)

Cmax (ng/ml) 0.8 485 5.9 242 2.9 5.3 0.8 10 Tmax (hr)

EXAMPLE 5 : Improvement of absorption kinetics of Capecitabine

[0062] Capecitabine is an ester prodrug, which is hydrolyzed mainly by CE2 in the

Gl track and CEl in the liver and then converted by two enzymes t o its active drug

(5-fluorouracil) in the tumor after oral administration of capecitabine t o cancer patients.

A study similar t o the clopidogrel study described above was conducted in rats (n = 3) t o ascertain the effect of triethyl citrate in improving the absorption kinetics and enhancing the bioavailability of capecitabine. Each rat received capecitabine (5 mg/kg) in DMSO or capecitabine (5 mg/kg) in DMSO/triethyl citrate (45 mg/kg). Serial plasma samples were obtained from each rat and concentrations of capecitabine in the plasma samples were determined by LC-MS/MS.

[0063] Table 6 lists the mean (n = 3) values of AUC0 -24hr, Cmax and Tmax of capecitabine. As shown in Table 6, triethyl citrate increases values of AUC0 -24hr and Cmax of capecitabine by 2,050% and 964%, respectively. Thus, triethyl citrate effectively retards esterase hydrolysis and improves the absorption kinetics of capecitabine in rats.

Table 6 : Improvement of Absorption Kinetics of Capecitabine. Treatment AUC 0 -24hr (ng-hr/ml) Cmax (ng/ml) Tmax (hr) Capecitabine 34 11.8 0.8 Capecitabine + Triethyl Citrate 731 125.5 8.5

[0064] In a rat study similar t o the study described above, each rat received capecitabine (5 mg/kg) in DMSO or capecitabine (5 mg/kg) in DMSO/triethyl citrate (22.5 mg/kg)/triacetin (22.5 mg/kg). Serial plasma samples were obtained from each rat and concentrations of capecitabine in the plasma samples were determined by LC-MS/MS.

Table 7 : Improvement of Absorption Kinetics of Capecitabine by a Combination of

Triethyl Citrate and Triacetin.

Treatment AUC 0 -24hr (ng-hr/ml) Cmax (ng/ml) T, ax (hr) Capecitabine 15 8.9 0.4 Capecitabine + Triethyl Citrate + Triacetin 39 4.4 3.5

[0065] Table 7 lists the mean (n = 3) values of AUC0 -24hr, Cmax and Tmax of capecitabine. As shown in Table 7, a combination of triethyl citrate and triacetin increases

mean values of AUC0 -24hr of capecitabine by 160%. Thus, a combination of triethyl citrate and triacetin effectively improves the absorption kinetics of capecitabine in rats.

[0066] All of the features disclosed in this specification may be combined in any combination. Each feature disclosed in this specification may be replaced by an alternative feature serving the same, equivalent, or similar purpose. Thus, unless expressly stated otherwise, each feature disclosed is only an example of a generic series of equivalent or similar features.

[0067] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in the respective testing measurements.

[0068] It will be understood that the above description of embodiments is given by way of example only and that various modifications may be made by those with ordinary skill in the art. The above specification, examples, and data provide a complete description of the structure and use of exemplary embodiments of the invention.

Although various embodiments of the invention have been described above with a certain degree of particularity, or with reference t o one or more individual embodiments, those with ordinary skill in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of the present disclosure. CLAIMS

1. A method for improving the absorption of an ester prodrug in a subject comprising,

co-administering t o the subject an effective amount of the ester prodrug or a pharmaceutical acceptable salt thereof; and

an adjuvant in an amount effective t o impede a carboxylase-mediated hydrolysis of the ester prodrug in the subject, wherein the adjuvant is selected from the group consisting of triacetin, triethyl citrate and a combination of both.

2. The method of claim 1, wherein the ester prodrug is an angiotensin II (All) antagonist, an angiotensin-converting enzyme (ACE) inhibitor, an anti-thrombogenic agent, an anti-coagulant, a peroxisome proliferator-activated receptor alpha (PPARa) agonist, a

3-hydroxy-3-methyl-glutaryl-coenzyme A (HMG-CoA) reductase inhibitor, an antibiotic, a reverse transcriptase inhibitor, a mitotic inhibitor, a DNA synthesis inhibitor, a topoisomerase 1 (TOPI) inhibitor, a neuraminidase inhibitor, an immunosuppressant, a gamma-aminobutyric acid (GABA)

analogue, or a GABAB receptor agonist.

3. The method of claim 2, wherein the All antagonist is olmesartan medoxomil or candesartan cilexetil.

4 . The method of claim 2, wherein the ACE inhibitor is ramipril, delapril, trandolapril, temocapril, cilazapril, quinapril, or imidapril.

5. The method of claim 2, wherein the anti-thrombogenic agent is clopidogrel, prasugrel, or aspirin.

6. The method of claim 2, wherein the anti-coagulant is dabigatran etexilate.

7. The method of claim 2, wherein the PPARa is fenofibrate or clofibrate.

8. The method of claim 2, wherein the HMG-CoA reductase inhibitor is simvastatin or lovastatin. 9. The method of cla im 2, where in the antibiotic is cefpodoxime proxetil or cefd itoren pivoxil.

10. The method of cla im 2, whe rein the mitotic inhibitors is pacl itaxel, docetaxel, or isotaxel.

11. The method of cla im 2, where in the TOPI inh ibitor is irinoteca n.

12. The method of cla im 2, where in the DNA synthesis inhibitor is ca pecita bine.

13. The method of cla im 2, where in the neura minidase inhibitor is oselta mivir or

A-322278.

14. The method of cla im 2, whe rein the ester prod rug is clopidogre l, olmesa rta n medoxomil, tenofovir disoproxil, adefovir dipivoxil, mycophenolate mofetil, pacl itaxel, docetaxel, isotaxel, irinoteca n, ca pecita bine, arbaclofen placa rbil, or gabapentin enaca rbil.

15. In an improved pha rmaceutica l composition comprising an effective amount of an ester prod rug or a pha rmaceutica lly accepta ble sa lt thereof and a pha rmaceutica lly accepta ble excipient, wherein the improvement comprises,

an adjuva nt selected from the group consisting of triacetin, triethyl citrate and a combination of both, and the adj uva nt is present in an amount effective t o impede a ca rboxylase-med iated hyd rolysis of the ester prod rug in vivo.

16. The improved pha rmaceutica l composition of cla im 15, wherein the ester prod rug is clopidogre l, olmesa rta n medoxomil, or ca pecita bine.

17. A method for im ped ing ca rboxylesterase-med iated hyd rolysis of esters comprising contacting the ca rboxylesterase with triacetin, triethyl citrate, or both, in an amount effective t o impede ester hyd rolysis. International application No. INTERNATIONAL SEARCH REPORT PCT/CN201 1/076256

A. CLASSIFICATION OF SUBJECT MATTER

See the extra sheet According to International Patent Classification (IPC) or to both national classification and IP C

B . FIELDS SEARCHED

Minimum documentation searched (classification system followed by classification symbols)

IPC: A61K

Documentation searched other than minimum documentation to the extent that such documents are included in the fields searched

Electronic data base consulted during the international search (name of data base and, where practicable, search terms used)

WPI, EPODOC, CNPAT,CNKI, REGISTRY, CAPLUS: triacetin, triethyl citrate, carboxylase, absorption, ester prodrug, angiotensin II antagonist, angiotensin-converting enzyme inhibitor, anti-thrombogenic agent, anti-coagulant, PPARa agonist, HMG-CoA reductase inhibitor, antibiotic, reverse transcriptase inhibitor, mitotic inhibitor, DNA synthesis inhibitor, TOPI inhibitor, neuraminidase inhibitor, immunosuppressant, GABA analogue, GABA receptor agonist,clopidogrel, olmesartan medoxomil, capecitabine, tenofovir disoproxil, adefovir dipivoxil, mycophenolate mofetil, paclitaxel, docetaxel, isotaxel, irinotecan, capecitabine, arbaclofen placarbil, gabapentin enacarbil etc.

C. DOCUMENT S CONSIDERED TO BE RELEVANT

Category' Citation of document, with indication, where appropriate, of the relevant passages Relevant to claim No.

X WO2005026174 Al (GENERICS UK LTD [GB]) 24 Mar. 2005 (24.03.2005) see description 15, 16 page 5 lines 21-29.

X CN 101171006 A (SANKYO CO [ P]) 30 Apr. 2008 (30.04.2008) see claims 1, 7, 8, 10, 15, 16 description pages 1-5.

l~~l Further documents are listed in the continuation of Box C . patent family annex.

Special categories of cited documents: "T" later document published after the international filing date or priority date and not in conflict with the application but document defining the general state of the art which is not cited to understand the principle or theory underlying the considered to be of particular relevance invention earlier application or patent but published on or after the "X" document of particular relevance; the claimed invention international filing date cannot be considered novel or cannot be considered to involve an inventive step when the document is taken alone document which may throw doubts on priority claim (S) or "Y" document of particular relevance; the claimed invention which is cited to establish the publication date of another cannot be considered to involve an inventive step when the citation or other special reason (as specified) document is combined with one or more other such document referring to an oral disclosure, use, exhibition or documents, such combination being obvious to a person other means skilled in the art 'P document published prior to the international filing date " & "document member of the same patent family but later than the priority date claimed Date of the actual completion of the international search Date of mailing of the international search report 14 March 2012 (14.03.2012) 05 Apr. 2012 (05.04.2012) Name and mailing address of the ISA/CN Authorized officer The State Intellectual Property Office, the P.R.China 6 Xitucheng Rd., Jimen Bridge, Haidian District, Beijing, China XIAO, Ying 100088 Telephone No. (86-10)62411195 Facsimile No. 86-10-62019451 Form PCT ISA /210 (second sheet) (July 2009) International application No. INTERNATIONAL SEARCH REPORT PCT/CN201 1/076256

C (Continuation). DOCUMENTS CONSIDERED TO BE RELEVANT

Category' Citation of document, with indication, where appropriate, of the relevant passages Relevant to claim No.

CN101321478A(GIANFRANCO DE PAOLIAMBROSI [IT]) 10 Dec.2008 (10.12.2008)

X see claims 1, 4, 6, description page 1 paragraph 5 - page 4 line 13, preparation 8. 15, 17

A see the whole document. 1-14, 16

Form PCT SA /210 (continuation of second sheet ) (July 2009) International application No. INTERNATIONAL SEARCH REPORT PCT/CN201 1/076256

Box No. II Observations where certain claims were found unsearchable (Continuation of item 2 of first sheet)

This international search report has not been established in respect of certain claims under Article 17(2)(a) for the following reasons: 1. Claims Nos.: 1-14,17 because they relate to subject matter not required to be searched by this Authority, namely: human or animal body by therapy (Article 17(2) (a) (i) and Rule 39.1 (iv) PCT). The search has been carried out and based on the subject matters of claims when redrafted into "use of an ester prodrug or a pharmaceutically acceptable salt thereof and an adjuvant in manufacturing medicaments, characterized in that an adjuvant in an amount effective to impede carboxylase-mediated hydrolysis of the ester prodrug in the subject for improving the absorption of the ester prodrug, wherein the adjuvant is selected from the group consisting of triacetin, triethyl citrate and a combination of both" and "use of triacetin, triethyl citrate or both and esters in manufacturing medicaments, characterized in that contacting the carboxylesterase with triacetin, triethyl citrate, or both to impede carboxylase- mediated hydrolysis of esters".

2 . □ Claims Nos.: because they relate to parts of the international application that do not comply with the prescribed requirements to such an extent that no meaningful international search can be carried out, specifically:

3. Claims Nos.: because they are dependent claims and are not drafted in accordance with the second and third sentences of Rule 6.4(a).

Box No. Ill Observations where unity of invention is lacking (Continuation of item 3 of first sheet)

This International Searching Authority found multiple inventions in this international application, as follows:

1. As all required additional search fees were timely paid by the applicant, this international search report covers all searchable claims.

2 . As all searchable claims could be searched without effort justifying an additional fees, this Authority did not invite payment of additional fee.

3. As only some of the required additional search fees were timely paid by the applicant, this international search report covers only those claims for which fees were paid, specifically claims Nos. :

4 . No required additional search fees were timely paid by the applicant. Consequently, this international search report is restricted to the invention first mentioned in the claims; it is covered by claims Nos. :

The additional search fees were accompanied by the applicant's protest and, where applicable, the payment of a protest fee.

The additional search fees were accompanied by the applicant's protest but the applicable protest fee was not paid within the time limit specified in the invitation.

No protest accompanied the payment of additional search fees.

Form PCT ISA /210 (continuation of first sheet (2)) (July 2009) INTERNATIONAL SEARCH REPORT International application No. Information on patent family members PCT/CN201 1/076256

Patent Documents referred Publication Date Patent Family Publication Date in the Report

WO2005026174A1 24.03.2005 EP161 8 113A1 25.01 .2006

AU2004272337A1 24 .03 .2005

EP1772456A1 11.04 .2007

EP1 837337A1 26 .09.2007

US2007281964A1 06 .12 .2007

AU2004272337B2 14 .02.2008

AU2008200919A1 20 .03 .2008

AU2008200919B2 2 1.05 .2009

EP2149578A1 03.02.2010

EP161 8 113B1 10 .11.2010

DE602004029999E 23.12 .2010

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CN101 171006A 30.04.2008 WO2006123765A1 23.11.2006

KR2008001 1394A 04 .02.2008

JP2007516344T2T2 25.12 .2008

TW20071 9891A 0 1.06.2007

CN101 17 1006B 0 1.12 .2010

CN101 321478A 10.12.2008 WO200706637 1A1 14 .06.2007

EP1 962622A1 03.09.2008

US2008287377A1 20 .11.2008

JP200951 8388A 07 .05 .2009

INKOLNP200802026E 16 .01 .2009

IT1 360887B 19 .05 .2009

RU2008126721A 20 .01 .2010

Form PCT/ISA /210 (patent family annex) (July 2009) INTERNATIONAL SEARCH REPORT International application No.

PCT/CN201 1/076256

A. CLASSIFICATION OF SUBJECT MATTER: A61K31/215 (2006.01)i A61K31/216 (2006.01)i A61K3 1/4178 (2006.01)i A61K31/4365 (2006.01)i A61K3 1/497 (2006.01)i A61K47/14 (2006.01)i

Form PCT/ISA /210 (extra sheet) (July 2009)