Synthetic peptide amides
The invention relates to synthetic peptide amide ligands of the kappa opioid receptor and particularly to agonists of the kappa opioid receptor that exhibit low P 450 CYP inhibition and low penetration into the brain. The synthetic peptide amides of the invention conform to the structure of formula I: Pharmaceutical compositions containing these compounds are useful in the prophylaxis and treatment of pain and inflammation associated with a variety of diseases and conditions. Such treatable pain includes visceral pain, neuropathic pain and hyperalgesia. Inflammation associated with conditions such as IBD and IBS, ocular and otic inflammation, other disorders and conditions such as pruritis, edema, hyponatremia, hypokalemia, ileus, tussis and glaucoma are treatable or preventable with the pharmaceutical compositions of the invention.
1. A synthetic peptide amide having the formula:
wherein
Xaa 1 Xaa 2 is D-Phe-D-Phe;
Xaa 3 is D-Leu or D-Nle;
Xaa 4 is selected from the group consisting of: (ε-Me)D-Lys, D-Lys, (ε-iPr)D-Lys, D-Nar, D-Har, D-Arg, (β-amidino)D-Dap, and D-Dbu; and
is selected from the group consisting of:
provided that when Xaa 3 is D-Nle, then Xaa 4 is not D-Arg;
or a stereoisomer, pharmaceutically acceptable salt, hydrate, acid salt hydrate or N-oxide thereof, wherein said stereoisomers are stereoisomeric with respect to said formula only at one or more chiral centers other than the alpha carbon of Xaa 1 , Xaa 2 , Xaa 3 and Xaa 4 .
2. The synthetic peptide amide of claim 1 having the structure of Compound (2):
D-Phe-D-Phe-D-Leu-D-Lys-[ω(4-aminopiperidine-4-carboxylic acid)]-OH (SEQ ID NO: 2).
3. The synthetic peptide amide according to claim 1 , having an EC 50 of less than about 500 nM for a kappa opioid receptor.
4. The synthetic peptide amide according to claim 1 , which at an effective concentration exhibits no more than about 50% inhibition of any of P 450 CYP1A2, CYP2C9, CYP2C19 or CYP 2D6 by the synthetic peptide amide at a concentration of 10 uM after 60 minutes incubation with human liver microsomes.
5. The synthetic peptide amide according to claim 1 , which at a dose of about 3 mg/kg in rat reaches a peak plasma concentration of the synthetic peptide amide and exhibits at least about a five-fold lower peak concentration in brain than such peak plasma concentration.
6. The synthetic peptide amide according to claim 1 , having an ED 50 for a sedative effect in a locomotion-reduction assay in a mouse at least about ten times the ED 50 of the synthetic peptide amide for an analgesic effect in a writhing assay in a mouse.
7. The synthetic peptide amide according to claim 1 , having at least about 50% of maximum efficacy at about 3 hours post-administration of a dose of about 3 mg/kg of the synthetic peptide amide in a rat.
8. A composition comprising a mixture of stereoisomers of the synthetic peptide amides of claim 1 .
9. A pharmaceutical composition comprising the synthetic peptide amide according to claim 1 and a pharmaceutically acceptable excipient or carrier.
10. A method of treating or inhibiting a kappa opioid receptor-associated disease or condition in a mammal, the method comprising administering to the mammal a composition comprising an effective amount of a synthetic peptide amide according to claim 1 , wherein the kappa opioid receptor-associated disease or condition is selected from the group consisting of pain, pancreatitis and pruritus.