A new series of 4-[4-(N-substituted carbamoyl)-1-piperazinyl]-6,7-dimethoxyquinazoline derivatives were found to show potent and selective inhibition of platelet-dervied growth factor (PDGF) receptor phosphorylation. In this exploration of the structure-activity relationships (SARs) of the prototype inhibitor KN1022, the 4-nitrophenylurea moiety was probed. We found that 4-substitution on the phenyl ring was optimal and the introduction of more than two substituents on the phenyl ring decreased activities. Bulky substituents on the phenyl ring enhanced activities. Thiourea analogues were also prepared, and the SARs were found to be slightly different from those of the urea derivatives. Through this research, we obtained some potent KN1022 derivatives such as 4-(4-methylphenoxy)phenyl (36, IC(50) 0.02 micromol/L), 4-tert-butylphenyl (16, IC(50) 0.03 micromol/L), and 4-phenoxyphenyl (21, IC(50) 0.08 micromol/L) analogues, which had almost a 10-fold increase in activity against KN1022. These potent compounds retained their high selectivity against the PDGF receptor family similar to KN1022. We also observed that these compounds could inhibit the PDGF-BB-induced proliferation of porcine vascular smooth muscle cells without cell toxicity almost at the same IC(50) values observed for PDGF receptor phosphorylation. To evaluate the biological effects in vivo, we selected some analogues on the basis of the measurement of the plasma drug concentration after oral administration to rats. Oral administration of the 4-chlorophenyl (6), 4-bromophenyl (9), or 4-isopropoxyphenyl (20) analogue to Sprague-Dawley rats (30 mg/kg, twice daily) resulted in significant inhibition (24-38%) of neointima formation in the carotid artery of the balloon catheter deendothelialized vessel in the rats. Therefore, 4-[4-(N-substituted carbamoyl)-1-piperazinyl]-6,7-dimethoxyquinazoline derivatives, which are potent inhibitors of PDGFR phosphorylation, may be expected to represent a new therapeutic approach for the treatment of various aspects of atherosclerosis and other cellular proliferative disorders.

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RES-701-1, a novel cyclic peptide endothelin antagonist, was isolated from the culture broth of Streptomyces sp. RE-701. RES-701-1 selectively inhibited the ET-1 binding to type B endothelin receptor (ETB receptor) with an IC50 of 10 nM expressed in CHOcells and blocked the ET-1-induced elevation of intracellular free Ca2+ concentration in ETB receptor-expressing COS-7 cells. Characterization of producing strain, fermentation, isolation, structure, physico-chemical and biological properties of RES-701-1 are described. Endothelins (ETs) are a family of three related peptides, endothelin 1, 2, and 3 (ET-1, ET-2 and ET-3), which have a variety of biological activities in both vascular and non-vascular tissues, including hemodynamic, cardiac, pulmonary and renal effects. Circulating levels of ET-1 have been found to be elevated in some pathophysiological conditions such as systemic hypertension, cardiac ischemia, asthmatic attacks and cyclosporin-induced renal failure. These observations suggest that specific blockage of endothelin actions at receptor level can be potential treatment of disease states caused by elevated levels ofETs1'2*. In our microbial screening for endothelin antagonists using bovine lung membranes, we isolated a novel cyclic peptide RES-701-1 from the fermentation broth of Streptomyces sp. RE-701. RES-701-1 selectively inhibited ET-1 binding to type B endothelin receptor (ETB receptor) expressed in CHOcells and blocked the ET-1-induced elevation of intracellular free Ca2 + concentration in ETBreceptor-expressing COS-7cells. This paper describes the characterization and fermentation of the producing strain and the isolation, physico-chemical properties and biological activities of RES-701-1. Details of the structure determination are described in the succeeding paper3} Materials and Methods Materials (3-[125I]Iodotyrosyl13)endothelin-l was purchased from Amersham Japan. Endothelin-1 (ET-1) was purchased from Peptide Institute, Inc., Osaka, Japan. Bovine lung was obtained from a local slaughterhouse. The humanB type endothelin receptor gene was the generous gift of Dr. Hirose (

RES-1214-1 and -2, novel and non-peptidic endothelin antagonists, were isolated from the culture broth of a fungus, Pestalotiopsis sp. RE-1214. RES-1214-1 and -2 selectively inhibited the ET-1 binding to endothelin type A receptor (ETA receptor) with IC50 values of 1.5//m and 20/iM, respectively. RES-1214-1 and -2 inhibited the increase in intracellular Ca2+ concentration elicited by 1 nMET-1 in A10cells. Taxonomyof producing strains, fermentation, isolation, structural determination, and biochemical properties of RES-1214-1 and -2 are described. we report taxonomy of the producing strains, fermentation, isolation, structural elucidation and biochemical properties of RES-1214-1 and -2.

RES-701-2, -3 and -4, novel cyclic peptide endothelin antagonists, were isolated from the culture broths of Streptomyces sp. RE-701 and RE-896. RES-70Is selectively inhibited the ET-1 binding to endothelin type B receptor (ETB receptor) with IC50 values ranging from 5 to 20nM. Taxonomyof the producing strains, fermentation, isolation and biochemical properties of RES-70I s are described. Endothelins(ETs), which consist of 21 amino acid residues, are a family of potent vasoactive peptides termed endothelin -1, -2, and -3 (ET-1, ET-2 and ET-3)1}. ETs induce numerous biological responses in both vascular and non-vascular tissues by binding to at least two distinct receptor subtypes, ETAand ETB. The ETA receptor shows a high affinity for ET-1 and mediates vasoconstriction, whereas the ETBreceptor is nonselective for isopeptides and mediates vasoconstriction as well as vasodilatation2'3).In the course of screening of endothelin antagonists, wehave recently isolated a novel cyclic peptide RES-701-1 from the fermentation broth of Streptomyces sp. RE-7014'5).RES-701-1 selectively inhibited ET-1 binding to ETB receptor and blocked ETB receptor-mediated responces6). In the present investigation, we have found that many strains of Streptomyces produce RES-701-1-related compounds and isolated three novel compounds, designated RES-701-2, RES-701-3 and RES-701-4 from the culture broths. In this paper, we describe taxonomy of the producing strains, fermentation, isolation and biological properties of RES-701-2, -3 and -4. Studies on structural determination are described in the succeeding paper. (3-[125I]iodotyrosyl13)Endothelin-l was purchased from Du Pont-New England Nuclear. Other radioligands used for binding assays were purchased from Du Pont-New England Nuclear and Amersham. Endothelin-1 (ET-1) was purchased Materials and Methods Materials