Folate mimetics and folate-receptor binding conjugates thereof

1. A ligand-agent conjugate having the formula

wherein X and Y are each independently selected from the group consisting of halo, R 2 , OR 2 , SR 3 , and NR 4 R 5 ;

U, V, and W represent divalent moieties wherein U and W are —N═ or —N(R 4″ )— and V is —(R 6′ )C═ or —(R 6′ )C—(R 7′ )—;

Q is selected from the group consisting of C and CH;

T is selected from the group consisting of S, O, N and —C═C— such that the ring structure of which T is a member is aromatic;

A 1 and A 2 are each independently selected from the group consisting of —C(S)—, —C(Z)O—, —OC(Z)—, —N(R 4″ )—, —C(Z)—N(R 4″ )—, —N(R 4″ )—C(Z), —O—C(Z)—N(R 4″ )—, —N(R 4″ )—C(Z)—O—, —N(R 4″ )—C(Z)—N(R 5″ )—, —O—, —S—, —S(O)—, —S(O) 2 —, —N(R 4″ )S(O) 2 —, —C(R 6″ )(R 7″ )—, —N(C≡CH)—, —N(CH 2 —C≡CH)—, —C 1 -C 12 alkyl and C 1 -C 12 alkoxy; where Z is oxygen or sulfur provided that A 2 does not represent —C(O)NH—;

R 1 is selected from the group consisting of hydrogen, halo, C 1 -C 12 alkyl, and C 1 -C 12 alkoxy;

R 2 , R 3 , R 4 , R 4′ , R 4″ , R 5 , R 5″ , R 6 and R 7 are each independently selected from the group consisting of hydrogen, halo, C 1 -C 12 alkyl, C 1 -C 12 alkoxy, C 1 -C 12 alkanoyl, C 1 -C 12 alkenyl, C 1 -C 12 alkynyl, (C 1 -C 12 alkoxy)carbonyl, and (C 1 -C 12 alkylamino)carbonyl;

R 6 and R 7 are each independently selected from the group consisting of hydrogen, halo, C 1 -C 12 alkyl, and C 1 -C 12 alkoxy; or R 6 and R 7 are taken together to form O═;

R 6′ and R 7′ are each independently selected from the group consisting of hydrogen, halo, C 1 -C 12 alkyl, and C 1 -C 12 alkoxy; or R 6 and R 7 are taken together to form O═;

L is a divalent linker;

n, p, r and s are each independently either 0 or 1 provided when n=1, then r=1;

q is an integer ≧1;

D is diagnostic agent or a therapeutic agent; and

provided that the linker L does not include a naturally occurring amino acid covalently linked to A 2 at its α-amino group through an amide bond.

2. The ligand-agent conjugate of claim 1 comprising a metabolically labile linker L.

3. The ligand-agent conjugate of claim 2 wherein the metabolically labile linker L is hydrolytically or reductively cleaved in the cell to release the diagnostic or therapeutic agent D.

4. A pharmaceutical composition comprising the ligand agent conjugate of claim 1 and at least one component selected from the group consisting of a pharmaceutically acceptable carrier, excipient, or diluent.

5. A method for delivering a diagnostic agent or a therapeutic agent to a target cell population comprising a folate receptor, the method comprising: providing a ligand-agent conjugate having the formula

wherein X and Y are each independently selected from the group consisting of halo, R 2 , OR 2 , SR 3 , and NR 4 R 5 ;

U, V, and W represent divalent moieties wherein U and W are —N═ or —N(R 4″ )— and V is —(R 6′ )C═ or —(R 6′ )C(R 7′ )—;

Q is selected from the group consisting of C and CH;

T is selected from the group consisting of S, O, N and —C═C— such that the ring structure of which T is a member is aromatic;

A 1 and A 2 are each independently selected from the group consisting of —C(S)—, —C(Z)O—, —OC(Z)—, —N(R 4″ )—, —C(Z)—N(R 4″ )—, —N(R 4″ )—C(Z), —O—C(Z)—N(R 4″ )—, —N(R 4″ )—C(Z)—O—, —N(R 4″ )—C(Z)—N(R 5″ )—, —O—, —S—, —S(O)—, —S(O) 2 —, —N(R 4″ )S(O) 2 —, —C(R 6″ )(R 7″ )—, —N(C≡CH)—, —N(CH 2 —C≡CH)—, C 1 -C 12 alkyl and C 1 -C 12 alkoxy; where Z is oxygen or sulfur provided that A 2 does not represent —C(O)NH—;

R 1 is selected from the group consisting of hydrogen, halo, C 1 -C 12 alkyl, and C 1 -C 12 alkoxy;

R 2 , R 3 , R 4 , R 4′ , R 4″ , R 5 , R 5″ , R 6 , and R 7 are each independently selected from the group consisting of hydrogen, halo, C 1 -C 12 alkyl, C 1 -C 12 alkoxy, C 1 -C 12 alkanoyl, C 1 -C 12 alkenyl, C 1 -C 12 alkynyl, (C 1 -C 12 alkoxy)carbonyl, and (C 1 -C 12 alkylamino)carbonyl;

R 6 and R 7 are each independently selected from the group consisting of hydrogen, halo, C 1 -C 12 alkyl, and C 1 -C 12 alkoxy; or R 6 and R 7 are taken together to form O═;

R 6′ and R 7′ are each independently selected from the group consisting of hydrogen, halo, C 1 -C 12 alkyl, and C 1 -C 12 alkoxy; or R 6 and R 7 are taken together to form O═;

L is a divalent linker;

n, p, r and s are each independently either 0 or 1 provided when n=1, then r=1; and;

provided that the linker L does not include a naturally occurring amino acid covalently linked to A 2 at its α-amino group through an amide bond;

q is an integer ≧1; and

D is diagnostic agent or a therapeutic agent; and

contacting the target cell population with an effective amount of ligand-agent conjugate to permit binding of the ligand-conjugate to the folate receptor.

6. The method of claim 5 wherein D is a diagnostic agent comprising a contrast agent for use in medical imaging.

7. The method of claim 5 wherein the ligand-agent conjugate binds to the cell surface and is not internalized by the cells of the cell population.

8. The method of claim 5 wherein the diagnostic or therapeutic agent D is internalized by the cells of the cell population.

9. A ligand-agent conjugate having the formula

wherein

X and Y are each independently selected from the group consisting of halo, R 2 , OR 2 , SR 3 , and NR 4 R 5 ;

U, V, and W represent divalent moieties wherein U and W are —N═ or —N(R 4″ )— and V is —(R 6′ )C═ or —(R 6′ )C—(R 7′ )—;

Q is selected from the group consisting of C and CH;

T is selected from the group consisting of S, O, N and —C═C— such that the ring structure of which T is a member is aromatic;

A 1 and A 2 are each independently selected from the group consisting of —C(Z)—, —C(Z)O—, —OC(Z)—, —N(R 4″ )—, —C(Z)—N(R 4″ )—, —N(R 4″ )—C(Z), —O—C(Z)—N(R 4″ ), —N(R 4″ )—C(Z)—O—, —N(R 4″ )—C(Z)—N(R 5″ )—, —O—, —S—, —S(O)—, —S(O) 2 —, —N(R 4″ )S(O) 2 —, —C(R 6″ )(R 7″ )—, —N(C≡CH)—, —N(CH 2 —C≡CH)—, C 1 -C 12 alkyl and C 1 -C 12 alkoxy; where Z is oxygen or sulfur provided that A 2 does not represent —C(O)NH—;

R 1 is selected from the group consisting of hydrogen, halo, C 1 -C 12 alkyl, and C 1 -C 12 alkoxy;

R 2 , R 3 , R 4 , R 4′ , R 4″ , R 5 , R 5″ , R 6 and R 7 are each independently selected from the group consisting of hydrogen, halo, C 1 -C 12 alkyl, C 1 -C 12 alkoxy, C 1 -C 12 alkanoyl, C 1 -C 12 alkenyl, C 1 -C 12 alkynyl, (C 1 -C 12 alkoxy)carbonyl, and (C 1 -C 12 alkylamino)carbonyl;

R 6 and R 7 are each independently selected from the group consisting of hydrogen, halo, C 1 -C 12 alkyl, and C 1 -C 12 alkoxy; or R 6 and R 7 are taken together to form O═;

R 6′ and R 7′ are each independently selected from the group consisting of hydrogen, halo, C 1 -C 12 alkyl, and C 1 -C 12 alkoxy; or R 6 and R 7 are taken together to form O═;

L is a divalent linker;

n, p and r are each independently either 0 or 1 provided when n=1, then r=1; and;

q is an integer ≧1; and

D is diagnostic agent or a therapeutic agent

provided that the linker L does not include a naturally occurring amino acid covalently linked to A 2 at its α-amino group through an amide bond.

10. The ligand-agent conjugate of claim 9 comprising a metabolically labile linker L.

11. The ligand-agent conjugate of claim 10 wherein the metabolically labile linker L is hydrolytically or reductively cleaved in the cell to release the diagnostic or therapeutic agent D.

12. The ligand-agent conjugate of claim 10 wherein the metabolically labile linker L comprises a disulfide or an ester.

13. A pharmaceutical composition comprising the ligand-agent conjugate of claim 9 and at least one component selected from the group consisting of a pharmaceutically acceptable carrier, excipient, or diluent.

14. A ligand-agent conjugate having the formula

wherein

X and Y are each independently selected from the group consisting of halo, R 2 , OR 2 , SR 3 , and NR 4 R 5 ;

U, V, and W represent divalent moieties wherein U and W are —N═ or —N(R 4″ )— and V is —(R 6′ )C═ or —(R 6′ )C—(R 7′ )—;

Q is selected from the group consisting of C and CH;

T is selected from the group consisting of S, O, N and —C═C— such that the ring structure of which T is a member is aromatic;

A 1 and A 2 are each independently selected from the group consisting of —C(Z)—, —C(Z)O—, —OC(Z)—, —N(R 4″ )—, —C(Z)—N(R 4″ )—, —N(R 4″ )—C(Z), —O—C(Z)—N(R 4″ )—, —N(R 4″ )—C(Z)—O—, —N(R 4″ )—C(Z)—N(R 5″ )—, —O—, —S—, —S(O)—, —S(O) 2 —, —N(R 4″ )S(O) 2 —, —C(R 6″ )(R 7″ )—, —N(C≡CH)—, —N(CH 2 —C≡CH)—, C 1 -C 12 alkyl and C 1 -C 12 alkoxy; where Z is oxygen or sulfur provided that A 2 does not represent —C(O)NH—;

R 1 is selected from the group consisting of hydrogen, halo, C 1 -C 12 alkyl, and C 1 -C 12 alkoxy;

R 2 , R 3 , R 4 , R 4′ , R 4″ , R 5 , R 5″ , R 6 and R 7 are each independently selected from the group consisting of hydrogen, halo, C 1 -C 12 alkyl, C 1 -C 12 alkoxy, C 1 -C 12 alkanoyl, C 1 -C 12 alkenyl, C 1 -C 12 alkynyl, (C 1 -C 12 alkoxy)carbonyl, and (C 1 -C 12 alkylamino)carbonyl;

R 6 and R 7 are each independently selected from the group consisting of hydrogen, halo, C 1 -C 12 alkyl, and C 1 -C 12 alkoxy; or R 6 and R 7 are taken together to form O═;

R 6′ and R 7′ are each independently selected from the group consisting of hydrogen, halo, C 1 -C 12 alkyl, and C 1 -C 12 alkoxy; or R 6 and R 7 are taken together to form O═;

L is a metabolically labile divalent linker comprising a disulfide or an ester;

n, p, r and s are each independently either 0 or 1 provided when n=1, then r=1;

q is an integer ≧1;

D is diagnostic agent or a therapeutic agent; and

provided that the linker L does not include a naturally occurring amino acid covalently linked to A 2 at its α-amino group through an amide bond.

15. The ligand-agent of claim 14 wherein the metabolically labile linker L is hydrolytically or reductively cleaved in the cell to release the diagnostic or therapeutic agent D.

16. A ligand-agent conjugate having the formula

wherein

X and Y are each independently selected from the group consisting of halo, R 2 , OR 2 , SR 3 , and NR 4 R 5 ;

U, V, and W represent divalent moieties wherein U and W are —N═ or —N(R 4″ )— and V is —(R 6′ )C═ or —(R 6′ )C(R 7′ )—;

Q is selected from the group consisting of C and CH;

T is selected from the group consisting of S, O, and N such that the ring structure of which T is a member is aromatic;

A 1 and A 2 are each independently selected from the group consisting of —C(Z)—, —C(Z)O—, —OC(Z)—, —N(R 4″ )—, —C(Z)—N(R 4″ )—, —N(R 4″ )—C(Z), —O—C(Z)—N(R 4″ )—, —N(R 4″ )—C(Z)—O—, —N(R 4″ )—C(Z)—N(R 5″ )—, —O—, —S—, —S(O)—, —S(O) 2 —, —N(R 4″ )S(O) 2 —, —C(R 6″ )(R 7″ )—, —N(C≡CH)—, —N(CH 2 —C≡CH)—, C 1 -C 12 alkyl and C 1 -C 12 alkoxy; where Z is oxygen or sulfur provided that A 2 does not represent —C(O)NH—;

R 1 is selected from the group consisting of hydrogen, halo, C 1 -C 12 alkyl, and C 1 -C 12 alkoxy;

R 2 , R 3 , R 4 , R 4′ , R 4″ , R 5 , R 5″ , R 6 and R 7 are each independently selected from the group consisting of hydrogen, halo, C 1 -C 12 alkyl, C 1 -C 12 alkoxy, C 1 -C 12 alkanoyl, C 1 -C 12 alkenyl, C 1 -C 12 alkynyl, (C 1 -C 12 alkoxy)carbonyl, and (C 1 -C 12 alkylamino)carbonyl;

R 6 and R 7 are each independently selected from the group consisting of hydrogen, halo, C 1 -C 12 alkyl, and C 1 -C 12 alkoxy; or R 6 and R 7 are taken together to form O═;

R 6′ and R 7′ are each independently selected from the group consisting of hydrogen, halo, C 1 -C 12 alkyl, and C 1 -C 12 alkoxy; or R 6 and R 7 are taken together to form O═;

L is a divalent linker;

n, p, r and s are each independently either 0 or 1 provided when n=1, then r=1;

q is an integer ≧1;

D is diagnostic agent or a therapeutic agent; and

provided that the linker L does not include a naturally occurring amino acid covalently linked to A 2 at its α-amino group through an amide bond.

17. A pharmaceutical composition comprising the ligand agent conjugate of claim 16 and at least one component selected from the group consisting of a pharmaceutically acceptable carrier, excipient, or diluent.