Design, synthesis, and structure-activity relationship studies of a potent PACE4 inhibitor.

PACE4 plays an important role in the progression of prostate cancer and is an attractive target for the development of novel inhibitor-based tumor therapies. We previously reported the design and synthesis of a novel, potent, and relatively selective PACE4 inhibitor known as a Multi-Leu (ML) peptide. In the present work, we examined the ML peptide through detailed structure-activity relationship studies.

Design, synthesis and structure-activity relationship of new arginine vasopressin analogues containing proline derivatives in position 2.

In this study, we present the synthesis and pharmacological properties of new analogues of arginine vasopressin modified in the N-terminal part of the molecule with proline derivatives: indoline-2-carboxylic acid (Ica) and (2S,4R)-4-(naphthalene-2-ylmethyl)pyrrolidine-2-carboxylic acid. All the peptides were tested for pressor, antidiuretic and in vitro uterotonic activities. We also determined their binding affinity to the human oxytocin receptor.

The Multi-Leu peptide inhibitor discriminates between PACE4 and furin and exhibits antiproliferative effects on prostate cancer cells.

The proprotein convertases (PCs) play an important role in protein precursor activation through processing at paired basic residues. However, significant substrate cleavage redundancy has been reported between PCs. The question remains whether specific PC inhibitors can be designed.

Novel Bradykinin Analogues Modified in the N-Terminal Part of the Molecule with a Variety of Acyl Substituents.

In the current work we present some pharmacological characteristics of ten new analogues of bradykinin (Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg) modified in the N-terminal part of the molecule with a variety of acyl substituents. Of the many acylating agents used previously with B(2) receptor antagonists, the following residues were chosen: 1-adamantaneacetic acid (Aaa), 1-adamantanecarboxylic acid (Aca), 4-tert-butylbenzoic acid (t-Bba), 4-aminobenzoic acid (Aba), 12-aminododecanoic acid (Adc), succinic acid (Sua), 4-hydroxybenzoic acid, 4-hydroxy-3-methoxybenzoic acid, 3-(4-hydroxyphenyl)propionic acid and 6-hydroxy-2-naphthoic acid. Biological activity of the compounds was assessed in the in vivo rat blood pressure test and the in vitro rat uterus test.

Design, synthesis and biological activity of new neurohypophyseal hormones analogues conformationally restricted in the N-terminal part of the molecule. Highly potent OT receptor antagonists.

In this study we present the synthesis and some pharmacological properties of fourteen new analogues of neurohypophyseal hormones conformationally restricted in the N-terminal part of the molecule. All new peptides were substituted at position 2 with cis-1-amino-4-phenylcyclohexane-1-carboxylic acid (cis-Apc). Moreover, one of the new analogues: [cis-Apc(2), Val(4)]AVP was also prepared in N-acylated forms with various bulky acyl groups.

Novel analogues of bradykinin conformationally restricted in the C-terminal part of the molecule.

In the present work, achiral non-coded amino acids, N-(Bzl)-Gly, X(1) or X(2) , were substituted at position 7 of the model B(2) receptor antagonist [D-Arg(0) , Hyp(3) , Thi(5, 8) , D-Phe(7) ]-BK. The N-terminal amino group of the analogues was either free or acylated with 1-Aca or Aaa. Biological activity of the compounds was assessed in the in vitro rat uterus test and the in vivo rat blood pressure test.

Novel analogues of arginine vasopressin containing alpha-2-indanylglycine enantiomers in position 2.

Continuing our efforts to obtain potent and selective analogues of AVP we synthesized and pharmacologically evaluated ten new compounds modified at position 2 with alpha-2-indanylglycine or its D-enantiomer (Igl or D-Igl, respectively). All the peptides were tested for pressor, antidiuretic, and in vitro uterotonic activities. We also determined the binding affinity of these compounds to human OT receptor.

Arginine vasopressin and its analogues--the influence of position 2 modification with 3,3-diphenylalanine enantiomers. Highly potent V2 agonists.

Eleven new analogues of arginine vasopressin (AVP) modified in position 2 by 3,3-diphenyl-L-alanine or its D-enantiomer (Dip or D-Dip) were synthesized and pharmacologically evaluated for their pressor, antidiuretic and in vitro uterotonic activities. Both the Dip and D-Dip modifications at position 2 of AVP are sufficient to completely change the pharmacological profile of the peptides. They preserve or increase antidiuretic activity, cause its prolongation, transform uterotonic property in antagonistic one and cancel the effect on blood pressure.

Structure-activity relationships of novel peptide agonists of the human bradykinin B2 receptor.

The nonapeptide bradykinin (BK) is involved in the genesis of inflammation, edema and in pain mediation. As such, much effort has gone into the development of peptide/non-peptide antagonists to counteract these processes. However, there is an increasing awareness of the potential value of chemically stable BK agonists in the treatment of diabetes and cardiovascular diseases.

Analogues of AVP modified in the N-terminal part of the molecule with Pip isomers: TFA-catalysed peptide bond hydrolysis.

Using SPPS techniques, six new analogues of AVP and some of its agonists were synthesised. The peptides were designed by substitution of Phe at position 3 of AVP, [Mpa(1)] AVP (dAVP) and [Mpa(1),Val(4),D-Arg(8)]VP (dVDAVP) with L- or D-Pip, a non-coded alpha-imino acid, also called homoproline. Surprisingly enough, both the analogues of AVP and [Mpa(1)]AVP with identical substituents at position 2 turned out to be highly sensitive to TFA used for deprotection and cleavage of the synthesised peptides from the resin and it was the reason why we were not able to obtain these four peptides.

The effects of N-terminal part modification of arginine vasopressin analogues with 2-aminoindane-2-carboxylic acid: a highly potent V2 agonist.

In this study we present the synthesis and some pharmacological properties of nine new analogues of arginine vasopressin modified in the N-terminal part of the molecule with 2-aminoindane-2-carboxylic acid (Aic). The peptides were tested for their in vitro uterotonic and in vivo pressor and antidiuretic activities. One of the new peptides, [Mpa1,Aic2,Val4,D-Arg8]VP, exhibited an antidiuretic activity similar to that of [Mpa1,D-Arg8]VP, thus being one of the most potent antidiuretic vasopressin analogues reported to date.

Influence of conformationally constrained amino acids replacing positions 2 and 3 of arginine vasopressin (AVP) and its analogues on their pharmacological properties.

Synthesis of thirteen new analogues of arginine vasopressin (AVP) has been described. Amino acid residues at positions 2 and 3 of AVP, [3-mercaptopropionic acid (Mpa)(1)]AVP (dAVP), [Mpa(1),d-Arg(8)]VP (dDAVP) and [Mpa(1),Val(4),d-Arg(8)]VP (dVDAVP) were replaced with one amino acid residue using sterically constrained non-proteinogenic amino acids, 4-aminobenzoic acid (Abz), cis-4-aminocyclohexanecarboxylic acid (ach) or its trans-isomer (Ach). In the case of a potent V(1a) antagonist, [1-mercaptocyclohexaneacetic acid (Cpa)(1)]AVP, only one similar analogue has been prepared by replacing positions 2 and 3 with Abz.

Analogs of arginine vasopressin modified in the N-terminal part of the molecule with a conformationally constrained cis-peptide bond motif.

The present work is part of our studies aimed at clarifying the influence of steric constraints in the N-terminal part of arginine vasopressin (AVP) and its analogs on the pharmacological activity of the resulting peptides. We describe the synthesis of eight new analogs of AVP or [3-mercaptopropionic acid (Mpa)]AVP (dAVP) substituted at positions 2 and 3 or 3 and 4 with two diastereomers of 4-aminopyroglutamic acid. The steric constraints provided by this modification turned out, however, so strong that all the peptides were inactive in all of the bioassays (pressor, antidiuretic and uterotonic tests).

Raman and surface-enhanced Raman spectroscopy investigation of vasopressin analogues containing 1-aminocyclohexane-1-carboxylic acid residue.

In this work, Raman spectroscopy (RS) was employed to characterize molecular structures of [Arg8]vasopressin (AVP) and its [Acc2,D-Arg8]AVP, [Acc3]AVP, and [Cpa1, Acc3]AVP analogues. The RS band assignments have been proposed. To determine the mechanism of adsorption of the above-mentioned compounds adsorbed on a colloidal silver surface, surface-enhanced Raman spectra (SERS) were measured.

Conformational studies of vasopressin analogues modified with N-methylphenylalanine enantiomers in dimethyl sulfoxide solution.

The conformations of [Arg8]vasopressin (AVP) analogues substituted at positions 2 and 3 with N-methylphenylalanine (MePhe) enantiomers were earlier investigated by using nuclear magnetic resonance (NMR) spectroscopy in aqueous solution. A comparison of the results obtained in H2O/D2O (9:1) and DMSO-d6 has shown the structures in the first solution to be more flexible than those in DMSO-d6. This is manifested by a higher percentage of minor conformations in H2O/D2O.

Analogues of neurohypophyseal hormones, oxytocin and arginine vasopressin, conformationally restricted in the N-terminal part of the molecule.

It is generally accepted that the conformation of the N-terminal part of neurohypophyseal hormones analogues is important for their pharmacological activity. In this work, we decided to investigate how the substitution of positions 2 and 3 with the ethylene-bridged dipeptide would alter the pharmacological properties of OT, [Mpa1]OT, and [Cpa1]OT (OT=oxytocin; Mpa=3-mercaptopropionic acid; Cpa=1-mercaptocyclohexaneacetic acid) and to investigate how a bulky 3,3-diphenyl-L-alanine residue incorporated in position 2 of AVP, [Mpa1]AVP, and [Cpa1]AVP (AVP=arginine vasopressin) would change the pharmacological profile of the compounds. The next analogues, [Val4]AVP, [Mpa1,Val4]AVP, and [Cpa1,Val4]AVP, had N-benzyl-L-alanine introduced at position 3.

The influence of modification at position 2 on the side-chain conformation in oxytocin analogs.

The nonapeptide oxytocin (OT) is used in medicine to help begin and/or continue childbirth. Its analogs can be also used to control bleeding following fetus delivery. The main function of oxytocin is to stimulate contraction of uterus smooth muscle and the smooth muscle of mammary glands, thus regulating lactation.

New bradykinin analogues modified in the C-terminal part with sterically restricted 1-aminocyclohexane-1-carboxylic acid.

In the present work, a sterically constrained noncoded amino acid, 1-aminocyclohexane-1-carboxylic acid (Acc), was substituted in position 8 of the peptide chain of bradykinin (BK) and position 6, 7, or 8 of its B2 receptor antagonist [D-Arg0,Hyp3,Thi,(5,8)D-Phe7]BK, previously synthesized by Stewart's group, to reduce the flexibility of the peptides, thus forcing the peptide backbone and side chains to adopt specific orientations. Knowing that acylation of the N-terminus of several known B2 blockers with a variety of bulky groups has consistently improved their antagonistic potency in the rat blood pressure assay, the Acc substituted analogues were also synthesized in the N-acylated form with 1-adamantaneacetic acid (Aaa). The activity of eight new analogues was assayed in isolated rat uterus and in rat blood pressure tests.

Conformational studies of two bradykinin antagonists by using two-dimensional NMR techniques and molecular dynamics simulations.

The solution conformations of two potent antagonists of bradykinin (Arg1-Pro2-Pro3-Gly4-Phe5-Ser6-Pro7-Phe8-Arg9), [Aca(-1),DArg0,Hyp3,Thi5,DPhe7,(N-Bzl)Gly8]BK (1) and [Aaa(-1),DArg0,Hyp3,Thi5,(2-DNal)7,Thi8]BK (2), were studied by using 2D NMR spectroscopy in DMSO-d6 and molecular dynamics simulations. The NMR spectra of peptide 1 reveals the existence of at least two isomers arising from isomerization across the DPhe7-(N-Bzl)Gly8 peptide bond. The more populated isomer possesses the cis peptide bond at this position.

Investigation of cis/trans ratios of peptide bonds in AVP analogues containing N-methylphenylalanine enantiomers.

The solution conformation of vasopressin analogues, modified at positions 2 and 3 with N-methylphenylalanine or its enantiomer, [D-MePhe2,MePhe3]AVP and [MePhe2,D-MePhe3]AVP, were studied by 2D NMR spectroscopy in H2O/D2O and theoretical calculations (EDMC/ANALYZE). In the case of [MePhe2,D-MePhe3]AVP, the synthesis afforded two products, A and B, which had identical molecular ions and similar retention times on HPLC. This finding was explained by racemization of Cys1, which gave an additional analogue, [D-Cys1,MePhe2,D-MePhe3]AVP (B).

Analogues of arginine vasopressin and its agonist and antagonist modified in the N-terminal part of the molecule with l-beta-homophenylalanine.

In continuation of our efforts to elucidate the role of positions 2 and 3 in arginine vasopressin (AVP) and its analogues, we designed and synthesized peptides modified in these positions with l-beta-homophenylalanine (beta-Hph). Two of them had just this single modification, the next two peptides are analogues of the V2 agonist, namely [3-mercaptopropionic acid (Mpa)1]AVP (dAVP). The last two compounds were designed by substitution of positions 2 or 3 of a potent V(1a) antagonist, [1-mercaptocyclohexaneacetic acid (Cpa)1]AVP, with beta-Hph.

The influence of 1-aminocyclopentane-1-carboxylic acid at position 2 or 3 of AVP and its analogues on their pharmacological properties.

This study describes the synthesis and some pharmacological properties of eight new analogues of arginine vasopressin (AVP) substituted at position 2 or 3 with cycloleucine (1-aminocyclopentane-1-carboxylic acid, Apc). All new peptides were tested for their pressor, antidiuretic and uterotonic in vitro potency. The Apc3 modification resulted in an almost complete loss of potency in all three tests, which is interpreted as a loss of interaction with all three neurohypophyseal hormone receptors.

New acylated bradykinin analogues: effect on rat blood pressure and rat uterus.

It was previously reported that acylation of the N-terminus of several known B(2) antagonists with various types of bulky acyl groups consistently improved their antagonistic potency in the rat blood pressure assay. On the other hand, earlier results seem to suggest that the effects of acylation on the contractility of isolated rat uterus depend substantially on the chemical character of the acyl group, as it was observed that this modification may either change the range of antagonism or even transform it into agonism. Bearing all this in mind, three new analogues of bradykinin were designed by modifying the moderately potent B(2) antagonist, previously synthesized by Stewart's group, D-Arg-Arg-Pro-Hyp-Gly-Thr-Ser-D-Phe-Thi-Arg.