Non-peptidic quenched fluorescent imaging probes
Methods and materials for the imaging of cells and tissues containing active proteases such as cathepsin are disclosed. The present materials include activity based probes that bind to an enzyme and are subsequently cleaved. Cleavage results in covalent attachment of a fluorescent signal to a target protease due to removal of a quenching group which, when present on the probe causes altered or no fluorescence. The probes are non-peptidic, small molecule scaffolds linked to a reactive acyloxymethyl ketone group, a fluorophore and a quencher. The probes are cell permeable and may use, for example, a QSY21 (CAS 304014-13-9) quencher and a cyanine dye. The probes form covalent bonds with the active site of cysteine cathepsins, proteases that are upregulated at the tumor boundaries with normal tissue and at sites of inflammation.
1. A compound according to Formula I
where
R is either a 4-7 member aromatic ring or a 4-7 member cycloalkyl group, said aromatic ring or said cycloalkyl group having therein 0 to 5 heteroatoms which are one or more of N, O, S, Si, B or Ar;
R1 is lower alkyl;
R2 is selected from the group consisting of lower alkyl, alkoxy, alkyl amine and alkyl amide; and
R3 is selected from the group consisting of aryl, lower alkyl, alkoxy, alkyl amine and alkyl amide; provided that
at least one of R, R1, R2, and R3 is linked to a fluorophore; and R, R1, R2 and R3 are optionally linked to a quencher for said fluorphore, and said fluorophore and said quencher are present either as (i) only a fluorophore or (ii) a fluorophore and a quencher pair where one member of the pair is on R, R1, or R2 and another member of the pair is on R3.
2. The compound of claim 1 wherein R is selected from the group consisting of
where * indicates a point of attachment of the bond shown in Formula I.
3. The compound of claim 1 wherein R3 is dimethyl phenyl.
4. The compound of claim 1 wherein R3 is dimethyl phenyl linked to a quencher.
5. The compound of claim 1 comprising a Flu/Qu pair that is a bora-diaza-indecene and a diaryl rhodamine.
6. The compound of claim 1 comprising a Flu/Qu pair that is cyanine and QSY.
7. The compound of claim 1 comprising a Flu/Qu pair that is Cy5 and QSY21.
8. A composition useful for imaging one or more cells associated with cathepsin activity, comprising a compound according to claim 1 , in purified form.
9. The composition of claim 8 , further comprising excipients and suitable for in vivo administration.
10. The composition of claim 8 wherein R is selected from the group consisting of
where * indicates a point of attachment of the bond shown in Formula I.
11. The composition of claim 8 wherein R3 is dimethyl phenyl.
12. The composition of claim 8 wherein R3 is dimethyl phenyl linked to a quencher.
13. A composition according to claim 8 wherein said compound is according to Formula II below
wherein R2 is a linker to Flu/Qu, where Flu/Qu is either a fluorphore or a quencher, said linker selected from the group consisting of lower alkyl, lower alkoxy, lower alkyl amine and lower alkyl amide; or R2 is a capping group if Flu/Qu is absent; and R4 is H or Flu/Qu.
14. The compound of claim 13 comprising a Flu/Qu pair that is a bora-diaza-indecene and a diaryl rhodamine.
15. The compound of claim 13 comprising a Flu/Qu pair that is cyanine and QSY.
16. The compound of claim 13 comprising a Flu/Qu pair that is Cy5 and QSY21.
17. A composition according to claim 8 wherein said compound is according to Formula III below
wherein n is between 1 and 5 and Flu1 and Qu are a fluorophore-quencher pair.
18. The compound of claim 17 comprising a Flu1/Qu pair that is a bora-diaza-indecene and a diaryl rhodamine.
19. The compound of claim 17 comprising a Flu1/Qu pair that is cyanine and QSY.
20. The compound of claim 17 comprising a Flu1/Qu pair that is Cy5 and QSY21.
21. The compound of claim 1 comprising a Flu/Qu pair that is a bora-diaza-indecene and a diaryl rhodamine.
22. The compound of claim 1 comprising a Flu/Qu pair that is cyanine and QSY.
23. The compound of claim 1 comprising a Flu/Qu pair that is Cy5 and QSY21.
24. A compound according to Formula II below
wherein R2 is a linker to Flu/Qu, where Flu/Qu is either a fluorphore or a quencher, said linker selected from the group consisting of lower alkyl, lower alkoxy, lower alkyl amine and lower alkyl amide; or R2 is a capping group if Flu/Qu is absent; and R4 is H or Flu/Qu.
25. The compound of claim 24 comprising a Flu/Qu pair that is a bora-diaza-indecene and a diaryl rhodamine.
26. The compound of claim 24 comprising a Flu/Qu pair that is cyanine and QSY.
27. The compound of claim 24 comprising a Flu/Qu pair that is Cy5 and QSY21.
28. A compound according to Formula III below
wherein n is between 1 and 5 and Flu 1 and Qu are a fluorophore-quencher pair.
29. The compound of claim 28 comprising a Flu 1 /Qu pair that is a bora-diaza-indecene and a diaryl rhodamine.
30. The compound of claim 28 comprising a Flu 1 /Qu pair that is cyanine and QSY.
31. The compound of claim 28 comprising a Flu 1 /Qu pair that is Cy5 and QSY21.