SSTR1-selective analogs

• US 20020173618A1
• Filed: 03/15/2002
• Published: 11/21/2002
• Est. Priority Date: 03/16/2001
• Status: Active Grant

• Current Assignee: The SALK Institute For Biological Studies
• Original Assignee: The SALK Institute For Biological Studies
• Inventors: Reubi, Jean Claude, Rivier, Jean E.F.
• Granted Patent: US 7,019,109 B2
• Time in Patent Office: Days
• US Class Current: 530/311
• CPC Class Codes: A61K 51/083 the peptide being octreotide or a somatostatin-receptor-binding peptide
• CPC Class Codes: A61K 51/088 conjugates with carriers being peptides, polyamino acids or proteins antibodies A61K51/10
• CPC Class Codes: C07K 14/6555 at least 1 amino acid in D-form

Abstract

Analogs of SRIF which are selective for SSTR1 in contrast to the other cloned SRIF receptors. These analogs are useful in determining the tissue and cellular expression of the receptor SSTR1 and its biological role in the endocrine, exocrine and nervous system, as well as in regulating tumor growth. SRIF analog peptides, such as des-AA^1,2,5[D-Trp⁸, NMeIAmp⁹, Tyr¹¹]-SRIF and counterparts incorporating Cbm at the N-terminus and/or N^αSer¹³, inhibit the binding of a universal SRIF radioligand to the cloned human receptor SSTR1, but they do not bind with significant affinity to human SSTR2, SSTR3, SSTR4 or SSTR5. By incorporating an iodinated tyrosine in position-2 or in position-11 in these SSTR1-selective SRIF analogs, a labeled compound useful in drug-screening methods is provided. The N-terminus accommodates bulky moieties without loss of selectivity, and a carbamoyl moiety or a conjugating agent that will accept a radioactive nuclide or will link to a cytotoxin may be present at the N-terminus.

Claims

1. A cyclic somatostatin(SRIF) analog peptide which selectively binds the SRIF receptor SSTR1, which peptide has the amino acid sequence (cyclo)Xaa₁-Xaa₂-Xaa₃-Lys-Phe-Xaa₇-D-Xaa₈-Xaa₉-Thr-Xaa₁₁-Thr-Xaa₁₃-Cys wherein Xaa₁ is H, Ala, D-Ala, Cbm, Biu, (lower alkyl)Cbm, L-Hor, an acyl group having up to 20 carbon atoms, lower alkyl or a conjugating/complexing agent;

Xaa₂ is Tyr, ITyr, D-Tyr, D-ITyr, Gly or des-Xaa;

Xaa₃ is Cys or D-Cys;

Xaa₇ is (A)Phe wherein A is H, Cl, F, Br, NO₃, Me, or NH(Q) where Q is H, Cbm or L-Hor;

D-Xaa₈ is a D-isomer amino acid having an aromatic side chain;

Xaa₉ is an aminomethyl Phe wherein the side chain is (C₂ to C₅)alkylated and which is optionally C^α

methylated;

Xaa₁l is Phe, Tyr or ITyr; and

Xaa₁₃ is Ser, N^α

MeSer or D-Ser;

provided that either Xaa₁l is Tyr or ITyr or Xaa₁ is Cbm, Biu or (lower alkyl)Cbm.

2. The peptide according to claim 1 wherein Xaa₁ is H, D-Ala, Ala, Cbm, Biu, L-Hor or an acyl group having up to 7 carbon atoms;

Xaa₂ is Tyr, ITyr, D-Tyr or des-Xaa;

Xaa₃ is Cys or D-Cys;

Xaa7 is (A)Phe wherein A is H, 4C1, 4F or 4NO₂;

D-Xaa₈ is an aromatic D-amino acid; and

Xaa₉ is IAmp.

3. The peptide according to claim 2 wherein D-Xaa₈ is D-Trp.

4. The peptide according to claim 2 wherein D-Xaa₈ is D-2Nal.

5. The peptide according to claim 2 wherein Xaa₁ and Xaa₂ are des-Xaa and Xaa₁₁ is Tyr or ITyr.

6. The peptide according to claim 1 wherein Xaa₁ is a conjugating/complexing agent capable of linking to a cytotoxin or complexing to a radioactive nuclide.

7. The peptide according to claim 6 wherein D-Xaa₈ is D-Trp or D-2Nal and Xaa₁₁ is Tyr.

8. The peptide according to claim 6 wherein Xaa₁ is a polyaminopolycarboxylic conjugating agent.

9. The peptide combination of claim 6 wherein said conjugating/complexing agent is DOTA, DTPA, HYNIC or P₂S₂-COOH.

10. A method for destroying SSTR1-containing cells, which method comprises administering thereto an amount of the peptide according to claim 6 which includes a radioactive nuclide or a cytotoxin, which amount is effective to destroy such cells.

11. The peptide according to claim 1 having the amino acid sequence:

(cyclo)Xaa₁-Xaa₂-Xaa₃-Lys-Phe-Xaa₇-D-Xaa₈-N^α

MeIAmp-Thr-Xaa₁₁-Thr-Xaa₁₃-Cys wherein Xaa₁ is Cbm;

Xaa₂ is des-Xaa;

D-Xaa₈ is D-Trp or D-2Nal; and

Xaa₁₁ is Tyr or ITyr.

12. The peptide according to claim 1 having the amino acid sequence:

(cyclo)Xaa₁-Cys-Lys-Phe-Xaa₇-D-Xaa₈-N^α

MeIAmp-Thr-Xaa₁₁-Thr-Xaa₁₃-Cys, wherein Xaa₁ is Cbm or des-Xaa;

Xaa₇ is Phe or 4NO₂Phe; and

Xaa₁₁ is Tyr or ITyr.

13. A pharmaceutical composition comprising a mixture of the peptide according to claim 1 and at least one pharmaceutically acceptable carrier.

14. A method of treating IH or another SSTR1-mediated physiopathology, which method comprises administering an amount of the composition according to claim 13, which amount is effective to reach tissue affected thereby having SSTR1 receptors and activate said receptors.

15. A method for detecting the presence of cells having SSTR1 by administering an effective amount of the peptide according to claim 1 which is labelled with a signal-providing moiety so as to selectively bind to such cells and provide a detectable signal at the location thereof.

16. A method for screening for ligands that bind with high affinity to SSTR1, which method comprises carrying out a competitive binding assay with SSTR1, the peptide according to claim 1 labelled with a signal-producing moiety and a candidate ligand, and determining the ability of the said candidate ligand to displace said labelled peptide.

18. The peptide of claim 17 wherein ITyr is radioactive.

20. The peptide according to claim 19 wherein D-Xaa₈ is D-Trp or D-2Nal and Cbm is present at the N-terminus of said peptide.

17. A cyclic somatostatin (SRIF) analog peptide having the amino acid sequence:

(cyclo)Xaa₁-Tyr-Xaa₃-Lys-Phe-Phe-D-Trp-N^α

MelAmp-Thr-Xaa₁₁-Thr-Ser-Cys, where Xaa₁ is Cbm or des-Xaa, Xaa₂ is Tyr, ITyr, D-Tyr or desXaa;

Xaa₃ is Cys or D-Cys, and Xaa₁l is Phe, Tyr or ITyr provided that either Xaa₂ or Xaa¹¹ is Tyr or ITyr.

19. A cyclic somatostatin(SRIF) analog peptide having specific affinity for the SRIF receptor SSTR1, which peptide has an amino acid sequence at least 11 residues in length, contains a Cys-Cys disulfide bond with a sequence of at least 9 residues located between said Cys residues as a ring, and contains Lys-Phe-Phe-D-Xaa8-Xaa₉-Thr-Xaa¹¹ or its equivalent linked to the Cys residue near the N-terminus, which analog peptide is characterized by D-Xaa₈ being an aromatic D-isomer amino acid, by Xaa₉ being IAmp or N^α

MeIAmp, and by Xaa₁l being Tyr or ITyr.