Prodrugs containing novel bio-cleavable linkers

1. A compound of formula (I), or pharmaceutically acceptable salts thereof:

wherein,

a is 0;

B is S—S;

A is CH 2 ;

A 1 is CH 2 ;

D 1 represents a therapeutic agent comprising one or more of the functional groups selected from the group consisting of —NHR 1 , CONHR 1 , —OC(═O)NHR 1 , —SO 2 NHR 1 , —OSO 2 NHR 1 , —N(R 1 )C(═O)NHR 1 and —N(R 1 )SO 2 NHR 1 ; wherein the N atom in said functional groups is either a part of or directly attached to L 1 ;

D 2 is selected from the group consisting of a peptide, a protein, a monoclonal antibody, a vitamin, R 2 , R 4 and a polymer; with the proviso that the derivatizable OH, SH, NH or CO 2 H groups of D 2 are involved in the formation of L 2 wherein the heteroatom of OH, SH or NH groups or C(═O) of the C(═O)OH group is either a part of or directly attached to L 2 ;

E represents CH 2 ;

L 1 is

wherein,

X represents at each occurrence O or NR 1 ;

Y represents at each occurrence C═O;

L 2 represents O;

R 1 represents H or a bond to the same drug residue at an atom other than the atom to which N is attached;

R 2 represents NH 2 ;

R 4 represents at each occurrence H or a group selected from the group consisting of:

R 6 represents at each occurrence H, Na + , K + or any other pharmaceutically acceptable metal ion and f is 0-6.

2. The compound according to claim 1 , wherein D 2 is a polymer.

3. The compound according to claim 2 , wherein the polymer is selected from the group consisting of dextran, amino-modified dextran, arabinogalactan, arabinolactone, polyamino acids, polyethylene glycol, polycaprolactone, polyglycolic acid, polylactic acid, polyacrylic acid, poly(2-hydroxyethyl 1-glutamine), dextran aldehyde, carboxymethyl dextran, arabinogalactane aldehyde, carboxymethyl arabinogalactane and hyaluronic acid or the polymer is selected from the group consisting of:

wherein, R 5 is represents H or (C 1 -C 8 )alkyl and i is 1-2000.

4. The compound according to claim 2 , wherein the polymer is a polyamino acid selected from group consisting of poly(l-glutamic acid), poly(d-glutamic acid), poly(dl-glutamic acid), poly(l-aspartic acid), poly(d-aspartic acid), and poly(dl-aspartic acid), copolymer of the polyamino acids and polyethylene glycol.

5. The compound according to claim 2 , wherein the polymer has a molecular weight of about 5000 to about 100,000 Daltons.

6. The compound according to claim 5 , wherein the polymer has a molecular weight of about 10,000 to about 50,000 Daltons.

7. The compound according to claim 1 , wherein said peptide is a dipeptide.

8. The compound according to claim 1 , wherein D 2 is a vitamin selected from the group consisting of vitamin A, vitamin C, thiamine, folic acid, biotin, inositol, nicotinic acid, riboflavin, pyridoxine, pyridoxal 5-phosphate, ergosterol, vitamin D2, vitamin D3, vitamin D4, vitamin E, menadoxime and menadiol.

9. The compound according to claim 1 selected from the group consisting of:

10. A pharmaceutical composition comprising a therapeutically effective amount of the compound of claim 1 or a pharmaceutically acceptable salt thereof; and one or more pharmaceutically acceptable carriers, vehicles or diluents.

11. A pharmaceutical composition comprising a therapeutically effective amount of the compound of claim 9 or a pharmaceutically acceptable salt thereof and one or more pharmaceutically acceptable carriers, vehicles or diluents.

12. The compound according to claim 1 , wherein D 1 is a therapeutic agent selected from the group consisting of: sedatives, hypnotics, antidepressants, antipsychotics, antimanics, analgesics, antipyretics, anti-migraine agents, anticonvulsants, drugs used in parkinsonism and movement disorders, drugs used for treating dementia, anti-emetics, drugs used for treating vertigo, CNS stimulants activators, antiinfective eye preparations, anti-inflammatory, anti-allergic preparations, antiglaucoma drugs, preparations to cure eye diseases, aural preparations, nasal preparations, oropharyngeal preparations, anti-arrhythemic drugs, antihypertensives, alfa/beta-blockers, ACE inhibitors, angiotensin II receptor antagonists, diuretics, anti-anginals, nitrates, calcium channel blockers, drugs for cardiac failure and shock, vasodilators, coagulants, anticoagulants, thrombolytics, antiplatelet drugs, respiratory stimulants, antitussives, expectorants, mucolytics, decongestants, antihistamine agents, anti-asthmatics; antiulcer, antisecretory drugs, H 2 receptor antagonists, proton pump inhibitors, prostaglandin analogues, antacids, antispasmodics, drugs modifying intestinal motility, antidiarrhoeals, antimotility drugs, antimicrobial drugs, drugs acting on gall bladder, urinary antiinfectives, diuretics, urinary analgesics, antispasmodics, antiinfective drugs acting on urethra and vagina, drugs acting on uterus, drugs for prostatic hypertrophy, alpha blockers, antiandrogens, drugs for erectile dysfunction, spermicidals, nonhormonal contraceptives, emollients, keratolytics, topical antiinfectives, topical antifungals, topical parasiticidals, topical steroids, topical drugs for acne vulgaris, drugs for psoriasis, pigmentation disorders, and antiseborrhoeics, non steroidal anti inflammatory drugs (NSAIDs), COX-2 inhibitors, antiarthritic agents, immunosuppressants, topical analgesics, muscle relaxants, neuromuscular drugs, antianaerobics, antitubercular drugs, antileprosy drugs, antifungals, antiprotozoals, anthelminthics, antiinfective drugs, antimalarials, antivirals, anabolics, androgenic steroids, corticosteroids, oestrogens, progestogens and hormonal contraceptives, fertility agents, trophic hormones and related drugs, thyroid and antithyroid drugs, antidiabetics and hyperglycaemics, vitamins, amino acids, anti-obesity drugs, hypolipidaemic drugs, fibric acid derivatives, statins, HMG CoA reductase inhibitors, drugs used for gout, drugs affecting bone metabolism, bisphosphonates, anticancer or antineoplastic drugs, cytotoxic antibiotics, antimetabolites, topoisomerase I inhibitors, cytotoxic immunosuppressants, immunostimulants, cytoprotectives, amifostine, oestrogens, progestogens, hormone antagonists, non-sedative antihistamines, sedative histamines, histamine receptor blockers, local anaesthetics, intravenous anaesthetics, inhalation anaesthetics and muscle relaxants.

13. The compound according to claim 1 , wherein D 1 is a therapeutic agent selected from the group consisting of: penicillin antibiotics, cephalosporin antibiotics, quinolone, fluoroquinolone antibiotics, chloramphenicol, tetracycline antibiotics, sulfonamides, alkylating agents, cytarabine, fludarabine, 5-fluorouracil, mercaptopurine, thioguanine, vinca alkaloids and desloratadine.

14. A method of treating a disease where a chronic, sustained and selective release of the constituent therapeutic agent is beneficial; comprising administering to a mammal or a human in need of the treatment a therapeutically effective amount of the compound of claim 1 .

15. A method of treating a disease where a chronic, sustained and selective release of the constituent therapeutic agent is beneficial; comprising administering to a mammal or a human in need of the treatment a therapeutically effective amount of the composition of claim 10 .

16. The method of claim 14 , wherein the disease is selected from the group consisting of: the diseases of central nervous system, eye, ear, nose and oropharynx, cardiovascular system, respiratory system, gastrointestinal tract system, genitourinary system, skin, musculoskeletal system, endocrine system, metabolism and neoplastic disorders, infectious diseases, allergy and immunology, and for anaesthetic, analgesic and surgical needs in a mammal.

17. The method of claim 15 , wherein the disease is selected from the group consisting of: the diseases of central nervous system, eye, ear, nose and oropharynx, cardiovascular system, respiratory system, gastrointestinal tract system, genitourinary system, skin, musculoskeletal system, endocrine system, metabolism and neoplastic disorders, infectious diseases, allergy and immunology, and for anaesthetic, analgesic and surgical needs in a mammal.

18. A process for the preparation of the compound of formula I according to claim 1 , wherein D 1 represents a therapeutic agent containing —NHR 1 group and D 2 is selected from a peptide, a protein, a monoclonal antibody, a vitamin, or a polymer with the proviso that when in the compound of formula I, D 1 -L 1 linkage represents D 1 -N(R 1 )—C(═O)—O—, then L 2 -D 2 linkage represents a group other than —O—C(═O)—N(R 1 )-D 2 ; wherein said process comprises the steps of:

(a) monoprotecting bis-(2-hydroxyethyl)disulphide (SL-1) with an appropriate hydroxyl protecting group (PG) to obtain the corresponding monoprotected intermediate LI-1x of the following formula,

(b) reacting the intermediate LI-1x obtained in step (a) above with phosgene or its equivalent to obtain an activated formyl intermediate LI-1xy of the following formula;

(c) reacting the intermediate LI-1xy obtained in the step (b) with an appropriate therapeutic agent D 1 to obtain a protected intermediate containing a hydroxyl protecting group (PG),

(d) subjecting the intermediate obtained in the step (c) to a deprotection step to remove the hydroxyl protecting group to yield a compound of formula I having a free hydroxyl group on the linker;

(e) treating the compound obtained in step (d) with phosgene or its equivalents to obtain the corresponding activated formyl halide or imidazolide derivative of the compound; and

(f) reacting the activated formyl halide or imidazolide derivative of the compound obtained in step (e) with a therapeutic agent D 2 selected from: a peptide or a protein or a monoclonal antibody or a vitamin or a polymer to obtain the compound of formula I as claimed in claim 1 .

19. A process for the preparation of the compound of formula (I) according to claim 1 , wherein D 1 represents a therapeutic agent containing —COOH group and D 2 represents a peptide or a protein or a monoclonal antibody or a vitamin or a polymer; said process comprising the steps of:

(a) converting the therapeutic agent D 1 containing —COOH group into its activated acyl halide or imidazolide or isocyanate derivative by known methods;

(b) reacting the intermediate obtained in step (a) with the monoprotected linker intermediate OH—(CH 2 ) 2 —S—S—(CH 2 ) 2 —O-PG (LI-1x) to obtain the corresponding D 1 -linker intermediate containing a hydroxyl protecting group (PG);

(c) subjecting the intermediate obtained in the step(b) to a deprotection step to remove the hydroxyl protecting group to yield the compound of formula I having a free hydroxyl group on the linker;

(d) treating the intermediate obtained in step (c) with phosgene or its equivalents to obtain its corresponding activated formyl halide or imidazolide derivative;

(e) reacting the intermediate obtained in the step (d) with D 2 selected from a peptide or a protein or a monoclonal antibody or a vitamin or a polymer to yield the compound of formula I, or

said process comprises the steps of:

(a) converting the therapeutic agent D 1 containing —COOH group into its activated acyl halide or imidazolide or isocyanate derivative by a known method;

(b) reacting the intermediate obtained in the step (a) with 1.5 to 3.0 equivalents of bis-(2-hydroxyethyl)disulphide (SL-1) to yield a compound of formula I having a free hydroxyl group on the linker;

(c) treating the intermediate obtained in step (b) with phosgene or its equivalents to obtain its corresponding activated formyl halide or imidazolide derivative; and

(d) reacting the intermediate obtained in the step (c) with D 2 selected from a peptide or a protein or a monoclonal antibody or a vitamin or a polymer to yield the compound of formula I.

20. A process for the preparation of the compound of formula (I) according to claim 1 , wherein D 1 represents a therapeutic agent containing —COOH or —CONHR 1 group wherein R 1 is as defined in claim 1 and D 2 represents a peptide or a protein or a monoclonal antibody or a vitamin or a dipeptide or a polymer; said process comprising the steps of:

(a) reacting bis-(2-hydroxyethyl)disulphide (SL-1) with cysteamine in the presence of a base and a solvent to yield the intermediate amino alcohol (SL-2) which is converted to its Boc-derivative (LI-2c);

(b) treating the Boc-derivative (LI-2c) with trifluoroacetic acid (TFA) to remove the Boc group and to yield its corresponding ammonium TFA salt;

(c) converting the therapeutic agent D 1 containing —COOH or —CONHR 1 group into its activated acyl halide or imidazolide or isocyanate derivative by known methods;

(d) reacting the TFA salt obtained in step (b) with the activated acyl halide or imidazolide or isocyanate derivative of the therapeutic agent D 1 obtained in step (c) in the presence of a base in a solvent to yield the compound of formula I containing free hydroxyl-group on the linker;

(e) treating the intermediate obtained in the step (d) with phosgene or its equivalents to obtain the corresponding formyl halide or imidazolide derivative of D 1 ;

(f) reacting the intermediate obtained in the step (e) with D 2 selected from a peptide or a protein or a monoclonal antibody or a vitamin or a polymer to yield the compound of formula I; or

said process comprises the steps of:

(a) converting the therapeutic agent D 1 containing —COOH or —CONHR 1 group (R 1 is as defined in claim 1 ) into its activated acyl halide or imidazolide or isocyanate derivative by known methods;

(b) reacting the intermediate obtained in step (a) with the Boc-derivative, HO—(CH 2 ) 2 —S—S—(CH 2 ) 2 —NH(Boc) (LI-2c) in the presence of a base in a solvent to yield an intermediate containing terminal Boc-amino group on the linker;

(c) treating the intermediate containing terminal Boc-amino group with trifluoroacetic acid (TFA) or hydrochloric acid (HCl) to remove the Boc group and to yield its corresponding ammonium TFA or HCl salt;

(d) reacting the intermediate obtained in step (c) with an appropriately protected or derivatized or activated D 2 , wherein D 2 represents a peptide or a protein or a monoclonal antibody or a vitamin or a polymer to yield the compound of formula I.