Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Peptide containing doai
Reexamination Certificate
1998-10-14
2003-07-08
Low, Christopher S. F. (Department: 1653)
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Peptide containing doai
C514S015800, C514S017400, C530S323000, C530S329000, C530S330000, C530S331000, C530S327000, C530S328000
Reexamination Certificate
active
06589937
ABSTRACT:
FIELDS OF INDUSTRIAL APPLICATION
The invention relates to a new peptide having an improved effect of the brain function and an anti-dementia effect, and to an anti-dementia drug.
BACKGROUND ART
Anti-dementia drugs are classified into the first, second and third generations according to their action mechanisms and their chronological development ages. In the first generation are included the drugs already marketed such as calcium hopantenate (trade name: Hopate), indeloxazine hydrochloride (trade name: Elen) and idebenone (trade name: Avan), expressing the protection of the brain function and a metabolic acceleration action. In the second generation are included a prolyl endopeptidase (PEP) inhibitor and a choline esterase inhibitor which is marketing. Furthermore, in recent years the application of a biological substance is tried as the third generation anti-dementia drug, and neuropeptides with neuron growth factor (NGF) as the head of the list, argine vasopressin (AVP), thyroid hormone releasing hormone (TRH), vasoactive intestinal peptide (VIP), etc., are noticed.
Among these AVP is classified as the third generation anti-dementia drug as described above, though, the history of its research is long, and it has been studied as a peptide hormone having a strong anti-dementia activity since the report of D. Weid in 1984 (see Nature, 308, 276-278, 1984). Additionally, the number of its reports' publications exceeds 100 annually since 1980s, hereby indicating that it is a notable substance in the field of neurophsiology. Furthermore, the above PEP inhibitors are developed aiming to inhibit the intracerebral metabolism of AVP. From these, it can be estimated that the expectation for the anti-dementia activity of AVP is extremely high.
On one hand, problems in case of applying AVP as an anti-dementia drug are (1) the intrinsic activity of AVP, that is to say, elevation of blood pressure and diuretic action, (2) the instability in body due to the proline cleavage by PEP, and (3) a low blood-brain barrier (BBB) permeability. Owing to these, a number of AVP derivatives have been synthesized to improve these points and to further strengthen the anti-dementia activities. Such a research like this has been undertaken at a drug development level, and a lot of patent applications have been made (for example, JP, A, S54-73133, JP, A, S55-55120, JP, A, S62-234095, JP, A, H2-53797, JP, A, H2-53800, JP, A, H2-273696, JP, A, H2-273694, JP, A, H2-273699, etc.).
By up-to-date reports, as to the above (1)-(3) problems the following solutions are found for (1) and (2).
(1) The side effects on blood pressure and urine volume can be reduced by using AVP as the 4-9 fragment pGlu-Asn-Cys-Pro-Arg-Gly-NH
2
(AVP 4-9)(SEQ ID NO:2).
(2) By converting the amino acid proline of AVP 4-9 into D form, the metabolism by PEP can be avoided keeping the anti-dementia activity.
On one hand, as to the increase of a BBB permeability as mentioned in the above (3), it has currently been tried to increase the BBB permeability by increasing lipophilicity. However, in case of increasing a drug lipophilicity, not only the BBB permeability but the transition to all tissues increase, resulting to the decreasing phenomenon of area under the blood concentration (AUC), whereby it results to a big amount of administration and virtually increases the side effect. Therefore, in case of developing AVP as an anti-dementia drug, it is considered most ideal to make a chemical modification for increasing the BBB transition specificity, maintaining a high anti-dementia activity and changing proline of AVP 4-9 to D form to reduce the toxicity.
BBB is known as a site where fundamentally the permeability for substances is extremely slow. Especially, a substance low in the lipophlicity or a substance whose molecular weight exceeds 1000 are said to barely permeate through BBB. Therefore, a kind of peptides or proteins are classified one of substances which are hardly permeable through BBB. However, it is necessary for a nutrient into brain or an exocrine hormone to permeate through BBB, and it is recognized that they actually permeate (Pharmacol. Rev. 46:269-291; 1994). Concerning this, Pardridge (UCLA) and Terasaki, Sugiyama, et al. (Tokyo Univ.) recently found two types of transition pathways and studied a drug delivery method into the central nerve by using these (see Pharmacol. Toxicol., 71:3-10:1992 and J. Control Release, 29:163-169:1994). The first is the receptor mediated endocytosis mechanism (RME) by each kind of hormone receptor. The second is the absorptive mediated endocytosis mechanism (AME) by which a cationic substance is specifically taken in BBB. As to RME the receptor expression of insulin, transferrin, etc. in BBB is apparent. Up to date, as a drug delivery method specific to the central nerve system by utilizing RME, conjugates between a target drug and insulin or anti-transferrin antibody are actively prepared. These conjugates are shown to relatively well permeate through BBB. However, in case of administering the insulin conjugate is expected the appearance of hypoglycemia as a side effect. Further, in case of the conjugate with anti-transferrin antibody there is the problem that it is necessary to make the conjugate with a human type IgG owing to the problem of allergy.
From these, it is considered that utilizing AME is most safe and realistic as a drug delivery method specific to the central nerve system. AME is recently well noticed among researchers of drug delivery system (DDS) and is considered to do the uptake of a cationic substance into the central nerve system by the mechanism which is frequently observed in the cerebrovascular endothelial cells which constitute BBB. Especially, it is said that a substance high in the isoelectric point (PI value) permeates through BBB with a high specificity (see Zoku-Iyakuhin no Kaihatsu (Development of Drugs, second series), Vol. 4, 1991, Hirokawa).
SUMMARY OF THE INVENTION
In the above circumstances, the inventors synthesized new AVP type compounds which are estimated to have the PI value around 10, and by investigating the anti-dementia effect for these compounds by a passive avoidance test, found them to have an excellent therapeutic effect. The invention has been made on the basis of these findings.
The invention is to provide new peptides represented by the following general formula
(wherein X is OH or NH
2
, R is an amino acid residue selected from Arg, His, Lys, Methyl-Arg or Methyl-Tyr, n is an integer of 1-4, and in the case that n is 2-4, R may be identical with or different from each other) and an anti-dementia drug containing one or more of these new peptides as an active ingredient.
In the following, the invention will be explained in detail.
The new peptide compounds (denoted as C-AVP 4-9) represented by the formula (I) according to the invention are peptides consisting of 9-amino acids, wherein the N-terminal of Cys in AVP (H-(R)
n
-Pro is removed in the above formula (I), X is a hydrogen atom; denoted as AVP 4-9) side chain is substituted with a various combination of basic amino acids such as Arg, His, Lys, Methyl-Arg or Methyl-Tyr, and they show an extremely excellent anti-dementia activity, having a high PI value and BBB permeability compared with AVP 4-9.
The peptide compounds of the invention can be synthesized by a conventional method generally used in a peptide synthesis, though, a method, in which two units cleaved at the S—S bond of Cys—Cys are each synthesized and then the S—S bonding is finally made, is convenient and preferable. In the following is illustrated C-AVP 4-9-000 (in the above formula (I), R=Arg-His) explaining its synthesis.
SYNTHETIC METHOD
1. Synthesis of unit A and unit B
The unit A (Arg-His-Pro-Cys;SEQ ID NO:3) and the unit B (pyro-Glu-Asn-Cys-Pro-Arg-Gly;SEQ ID NO:2) were synthesized according to a conventional method using Beckman 990 peptide synthesis apparatus. Namely, by using Boc-trisulfonylarginine, Boc-benzyloxymethylhistidine and 4-methylbenzylcysteine-Merrifield resin and repeating the following removal st
Furushiro Masayoshi
Hashimoto Shusuke
Kado Kunio
Shishido Yoshiyuki
Tanabe Shuichi
Gupta Anish
Kabushiki Kaisha Yakul't Honsha
Low Christopher S. F.
Wolf Greenfield & Sacks P.C.
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