Biomedical subjects
E Buchdunger
Publications and source records attributed to E Buchdunger.
Prevention of cardiac allograft arteriosclerosis by protein tyrosine kinase inhibitor selective for platelet-derived growth factor receptor.
BACKGROUND: Increased immunoreactivity of platelet-derived growth factor (PDGF)-AA, -Ralpha, and -Rbeta in intimal cells correlates with the development of cardiac allograft arteriosclerosis, a condition for which there is little or no current therapy. Therefore, we hypothesized that PDGF may have a rate-limiting role in the development of this disease. METHODS AND RESULTS: The hypothesis was tested in a rat model of heterotopic cardiac and aortic allografts using dark agouti (AG-B4, RT1(a)) donors and Wistar-Furth (AG-B2, RT1(u)) recipients. The recipients received CGP 53716, a selective PDGF-R protein tyrosine kinase inhibitor, 50 mg. kg-1. d-1, or vehicle for 60 days. Cardiac allograft recipients also received background cyclosporin A immunosuppression. Our results demonstrate that CGP 53716 significantly reduced the incidence and intensity of arteriosclerotic lesions in rat cardiac and aortic allograft recipients. When rat coronary smooth muscle cells were stimulated in vitro with PDGF-AA or -BB in the presence of interleukin-1beta or tumor necrosis factor-alpha, CGP 53716 significantly inhibited only AA-ligand-induced but not BB-ligand-induced replication. Concomitantly, in quantitative reverse transcriptase-polymerase chain reaction, interleukin-1beta or tumor necrosis factor-alpha stimulation specifically upregulated the expression of PDGF-Ralpha mRNA but not of other ligand or receptor genes in cultured smooth muscle cells. CONCLUSIONS: We conclude that a PDGF-AA/Ralpha-dependent cycle is induced in the generation of allograft arteriosclerosis that may be inhibited by blocking of signaling downstream of PDGF-R.
In vivo eradication of human BCR/ABL-positive leukemia cells with an ABL kinase inhibitor.
BACKGROUND: The leukemia cells of approximately 95% of patients with chronic myeloid leukemia and 30%-50% of adult patients with acute lymphoblastic leukemia express the Bcr/Abl oncoprotein, which is the product of a fusion gene created by a chromosomal translocation [(9:22) (q34;q11)]. This oncoprotein expresses a constitutive tyrosine kinase activity that is crucial for its cellular transforming activity. In this study, we evaluated the antineoplastic activity of CGP57148B, which is a competitive inhibitor of the Bcr/Abl tyrosine kinase. METHODS: Nude mice were given an injection of the Bcr/Abl-positive human leukemia cell lines KU812 or MC3. Tumor-bearing mice were treated intraperitoneally or orally with CGP57148B according to three different schedules. In vitro drug wash-out experiments and in vivo molecular pharmacokinetic experiments were performed to optimize the in vivo treatment schedule. RESULTS: Treatment schedules administering CGP57148B once or twice per day produced some inhibition of tumor growth, but no tumor-bearing mouse was cured. A single administration of CGP57148B caused substantial (>50%) but short-lived (2-5 hours) inhibition of Bcr/Abl kinase activity. On the basis of the results from in vitro wash-out experiments, 20-21 hours was defined as the duration of continuous exposure needed to block cell proliferation and to induce apoptosis in these two leukemia cell lines. A treatment regimen assuring the continuous block of the Bcr/Abl phosphorylating activity that was administered over an 11-day period cured 87%-100% of treated mice. CONCLUSION: These data indicate that the continuous block of the oncogenic tyrosine kinase of Bcr/Abl protein is needed to produce important biologic effects in vivo.
Favorable therapeutic index of a p210(BCR-ABL)-specific tyrosine kinase inhibitor; activity on lineage-committed and primitive chronic myelogenous leukemia progenitors.
PURPOSE: In order to assess the effect of the tyrosine kinase inhibitor CGP57148B on lineage-committed and primitive chronic myelogenous leukemia (CML) progenitor cells, peripheral blood progenitor cells (PBPC) mobilized in chronic phase CML were exposed to this compound in vitro. METHODS: Both short-term (</=1 week) and long-term exposure (>/=2 weeks) to CGP57148B were investigated using suspension culture, semisolid (methylcellulose) assay or stroma-dependent long-term culture (LTC). The proportion of bcr/abl-positive progenitors was determined after direct plating [2 weeks in colony-forming cell (CFC) assay] as well as after 2 or 6 weeks LTC (LTC always followed by CFC replates). RESULTS: Incubation of CML PBPC over 48 h in suspension culture with 100 microM CGP57148B reduced the proportion of bcr/abl-positive colonies to 4.4 +/- 4.3% (n = 5) after direct plating, 6.6 +/- 4.2% (n = 5) after 2 weeks LTC and 5 +/- 5.6% (n = 2) after 6 weeks LTC. At this dose, survival of drug-exposed normal PBPC was 53 +/- 4.2%, 51 +/- 2.8% and 54.5 +/- 4.9% (n = 2), respectively. Incubation with CGP57148B at a concentration of 10 microM over 1 week under LTC conditions reduced the number of bcr/abl-positive colonies to 11.8 +/- 6.1% (n = 5) after direct plating, 12 +/- 6.4% (n = 4) after 2 weeks LTC and 14.3 +/- 11.4% (n = 3) after 6 weeks LTC; survival of normal PBPC was 84.5 +/- 2.1%, 93 +/- 4.2% and 86 +/- 1.4% (n = 2), respectively. Following long-term exposure to CGP57148B at a concentration of 1 microM, the proportion of remaining bcr/abl-positive colonies was 35%, 9% and 25% of untreated CML samples after direct plating as well as after 2 and 6 weeks LTC, respectively. The respective values for 10 microM CGP57148B were 10%, 11% and 19%. Long-term exposure of normal progenitors to CGP57148B yielded a survival of 98%, 100% and 93% (1 microM) or 77%, 86% and 80% (10 microM), respectively. CONCLUSION: The results support the use of CGP57148B either for short-term exposure in vitro (e.g. purging) or for continuous treatment of CML in vivo.
Selective tyrosine kinase inhibitor for the platelet-derived growth factor receptor in vitro inhibits smooth muscle cell proliferation after reinjury of arterial intima in vivo.
The long-term success of coronary angioplasty is limited by restonosis. This study was undertaken to investigate whether and to what extent the enhanced proliferative response observed in a balloon reinjury model of rat aorta is regulated by the PDGF receptor (PDGF-R). Balloon injury was performed to 14-day-old pre-existing neointimal lesion in rat aorta. PDGF receptor and ligand immunoreactivity were measured at several time points after the first and second injury, and PDGF-R signaling was blocked with a selective inhibitor of PDGF-R tyrosine kinase. In the neointima, after repeated injury, upregulation of PDGF-AA was seen to coincide with a prompt proliferative response of smooth muscle cells (SMC). Administration of the PDGF-R tyrosine kinase inhibitor in vivo, tested and found to inhibit the proliferation of SMC induced by PDGF-AA and PDGF-BB, but not by IGF-1, EGF, or bFGF, resulted in a 60% reduction in the absolute number and percentage of BrdU + cells after the second balloon injury to pre-existing neointima, but had no significant effect on proliferation after the first injury. Endpoint lesion area was reduced by 50% in the treated group at 14 days after the second injury. The results suggest that systemic administration of a tyrosine kinase inhibitor specific for the PDGF-R can be useful in the prevention of restenosis.
Role of platelet-derived growth factor in obliterative bronchiolitis (chronic rejection) in the rat.
The role of platelet-derived growth factor (PDGF) in the development of obliterative bronchiolitis (OB) as a manifestation of chronic rejection was investigated in the heterotopic rat tracheal allograft model. An increase in intragraft PDGF-Ralpha and -Rbeta mRNA expression, and in PDGF-AA and -Ralpha immunoreactivity, was demonstrated during the progressive loss of respiratory epithelium and airway occlusion in nontreated allografts compared with syngeneic grafts. Treatment with CGP 53716, a protein-tyrosine kinase inhibitor selective for PDGF receptor, alone and in combination with suboptimal doses of cyclosporin A, significantly reduced myofibroproliferation and the degree of OB by more than 50%. CGP 53716 did not affect airway wall inflammatory cell proliferation, the number of graft-infiltrating CD4(+) or CD8(+) T cells, ED3(+) macrophages, or the level of immune activation determined as IL-2R and MHC class II expression. This study suggests a regulatory role for PDGF, especially for PDGF-AA and -Ralpha, in the development of obliterative bronchiolitis in this model, and demonstrates that inhibition of PDGF receptor protein-tyrosine kinase activation prevents these obliterative changes. Thus, receptor protein-tyrosine kinase inhibitors may provide a novel therapeutic strategy for the prevention of chronic rejection.
A potent protein-tyrosine kinase inhibitor which selectively blocks proliferation of epidermal growth factor receptor-expressing tumor cells in vitro and in vivo.
A calculated 3-D model of the kinase domain of the epidermal growth factor receptor (EGF-R) protein-tyrosine kinase (PTK) was used to develop a pharmacophore model for ATP-competitive inhibitors and, subsequently, a new class of selective EGF-R kinase inhibitors. CGP 59326A, a highly selective and potent inhibitor of the EGF-R in vitro, inhibited the proliferation of EGF-R-expressing epithelial lines, while having little anti-proliferative activity against EGF-R-negative lines. In contrast to previously described inhibitors, CGP 59326A had potent and selective in vivo anti-tumor activity at well-tolerated doses against EGF-R-expressing tumors (e.g., ED50 of 0.78 to 1.5 mg/kg for inhibition of A431 tumor growth). CGP 59326A inhibited growth of human tumor xenografts expressing the EGF-R but showed little activity against EGF-R-negative xenografts. Combination of CGP 59326A with cytotoxic agents resulted in tumor regression and cures. The high selectivity and attractive biological profile of CGP 59326A suggest that it could have therapeutic value in the treatment of proliferative diseases which involve mitogenic signaling from the EGF-R.
Bcr-Abl kinase promotes cell cycle entry of primary myeloid CML cells in the absence of growth factors.
Cell cycle control of both immature and differentiated primary myeloid normal and chronic-phase chronic myeloid leukaemia (CML) cells to growth factor deprivation was studied. CD34+ cells were cultured in liquid culture. After removal of growth factors for 48 h normal cells were very efficiently arrested with the fraction of cells in S phase reduced by 70.8 +/- 6.5% in CD34+ and 50.5 +/- 4.2% in CD34- cells. In contrast, a significantly higher proportion of leukaemic cells remained in S phase. The fraction of S-phase cells was reduced by only 29.3 +/- 5.7% in CD34+ CML cells and 21.2 +/- 3.8% in CD34- cells. This abnormal negative cell cycle control in leukaemic cells was specific for growth factor deprivation. Reaction to IFN-alpha and TNF-alpha treatment was identical both in normal and CML cells. Equal quantities of the cytokines TNF-alpha, IL-1alpha, IL-1RA and IL-6 were produced by CML and normal cells. However, production of GM-CSF, with a median of 11 +/- 5 pg/ml, was found only in the supernatants of CML cells. But antibodies to GM-CSF did not restore growth factor dependence of the leukaemic cells. The defect was completely corrected by the abl-specific tyrosine kinase inhibitor CGP 57148 without effecting cell cycle control of normal cells. Our results demonstrate a directly Bcr-Abl-dependent defective response of both immature and differentiated primary myeloid CML cells to growth factor deprivation.
CGP 57148, a tyrosine kinase inhibitor, inhibits the growth of cells expressing BCR-ABL, TEL-ABL, and TEL-PDGFR fusion proteins.
CGP 57148 is a compound of the 2-phenylaminopyrimidine class that selectively inhibits the tyrosine kinase activity of the ABL and the platelet-derived growth factor receptor (PDGFR) protein tyrosine kinases. We previously showed that CGP 57148 selectively kills p210BCR-ABL-expressing cells. To extend these observations, we evaluated the ability of CGP 57148 to inhibit other activated ABL tyrosine kinases, including p185BCR-ABL and TEL-ABL. In cell-based assays of ABL tyrosine phosphorylation, inhibition of ABL kinase activity was observed at concentrations similar to that reported for p210BCR-ABL. Consistent with the in vitro profile of this compound, the growth of cells expressing activated ABL protein tyrosine kinases was inhibited in the absence of exogenous growth factor. Growth inhibition was also observed with a p185BCR-ABL-positive acute lymphocytic leukemia (ALL) cell line generated from a Philadelphia chromosome-positive ALL patient. As CGP 57148 inhibits the PDGFR kinase, we also showed that cells expressing an activated PDGFR tyrosine kinase, TEL-PDGFR, are sensitive to this compound. Thus, this compound may be useful for the treatment of a variety of BCR-ABL-positive leukemias and for treatment of the subset of chronic myelomonocytic leukemia patients with a TEL-PDGFR fusion protein.
Use of a pharmacophore model for the design of EGF-R tyrosine kinase inhibitors: 4-(phenylamino)pyrazolo[3,4-d]pyrimidines.
In the course of the random screening of a pool of CIBA chemicals, the two pyrazolopyrimidines 1 and 2 have been identified as fairly potent inhibitors of the EGF-R tyrosine kinase. Using a pharmacophore model for ATP-competitive inhibitors interacting with the active site of the EGF-R protein tyrosine kinase (PTK), the class of the pyrazolo[3,4-d]pyrimidines was then optimized in an interactive process leading to a series of 4-(phenylamino)-1H-pyrazolo[3,4-d]-pyrimidines as highly potent inhibitors of the EGF-R tyrosine kinase. The most potent compounds 13, 14, 15, 17, 19, 22, 26, 28, and 30 of this series inhibited the EGF-R PTK with IC50 values below 10 nM. High selectivity toward a panel of nonreceptor tyrosine kinases (c-Src, v-Abl and serine/threonine kinases (PKC alpha, CDK1) was observed. In cells, EGF-stimulated cellular tyrosine phosphorylation was inhibited by compounds 13, 15, 19, 22, and 23 at IC50 values below 50 nM, whereas PDGF-induced tyrosine phosphorylation was not affected by concentrations up to 10 microM, thus indicating high selectivity for the inhibition of the ligand-activated EGF-R signal transduction pathway. Compounds 15 and 19 inhibited proliferation of the EGF-dependent MK cell line with IC50 values below 0.5 microM. In addition, two compounds, 9 and 11, showing satisfactory oral bioavailability in mice after oral administration, exhibited good in vivo efficacy at doses of 12.5 and 50 mg/kg in a nude mouse tumor model using xenografts of the EGF-R overexpressing A431 cell line. From SAR studies, a binding mode for 4-(phenylamino)-1H-pyrazolo[3,4-d]pyrimidines, especially for compound 15, at the ATP-binding site of the EGF-R tyrosine kinase is proposed. 4-(Phenylamino)-1H-pyrazolo[3,4-d]pyrimidines represent a new class of highly potent tyrosine kinase inhibitors which preferentially inhibit the EGF-mediated signal transduction pathway and have the potential for further evaluation as anticancer agents.
Inhibition of platelet-derived growth factor receptor tyrosine kinase inhibits vascular smooth muscle cell migration and proliferation.
Platelet-derived growth factors (PDGFs) and their receptors (PDGFRs) have been linked to vascular smooth muscle cell (SMC) migration and proliferation leading to atherosclerosis, restenosis, and chronic allograft rejection. This study describes the effect of CGP 53716, a specific PDGFR tyrosine kinase inhibitor on SMC proliferation and migration in vitro and in neointimal formation in vivo. CGP 53716 inhibited dose dependently tyrosine phosphorylation of both the known PDGFRs: the PDGFR-alpha and PDGFR-beta. In primary rat SMC cultures, a dose-dependent inhibition of PDGF-AA and PDGF-BB induced migration, and tritiated thymidine incorporation of SMC was seen at nontoxic concentrations. After rat carotid artery ballooning injury in vivo, the migration of alpha-actin-positive cells on the luminal side of internal elastic lamina was decreased with 50 mg x kg(-1) x day(-1) of CGP 53716 from 38 +/- 10 (control group) to 4 +/- 2 (P<0.0001, Mann-Whitney U test, N=18). CGP 53716 did not inhibit the number of replicating bromodeoxyuridine (BrdU)-incorporating cells in the intima, media, or adventitia during BrdU labeling at 0-96 postoperative h, though it inhibited significantly (P<0.01) the replication of medial and intimal cells from 93 h onward. Intima/media ratio was inhibited by 40% after 14 days in the CGP 53716-treated group (P=0.028) after rat aortic denudation. The results indicate that inhibition of the PDGFR tyrosine kinase inhibits SMC migration and proliferation in vitro, SMC migration, and, to a lesser extent, proliferation after ballooning injury in vivo, confirming a causal role for activation of the PDGFR and the formation of neointimal lesions.
4-(Phenylamino)pyrrolopyrimidines: potent and selective, ATP site directed inhibitors of the EGF-receptor protein tyrosine kinase.
Using a pharmacophore model for ATP-competitive inhibitors interacting with the active site of the EGF-R protein tyrosine kinase (PTK), 4-(phenylamino)-7H-pyrrolo[2,3-d]pyrimidines have been identified as a novel class of potent EGF-R protein tyrosine kinase inhibitors. In an interactive process, this class of compounds was then optimized. 13, 14, 28, 36, 37, and 44, the most potent compounds of this series, inhibited the EGF-R PTK with IC50 values in the low nanomolar range. High selectivity toward a panel of nonreceptor tyrosine kinases (c-Src, v-Abl) and serine/threonine kinases (PKC alpha, PKA) was observed. Kinetic analysis revealed competitive type kinetics relative to ATP. In cells, EGF-stimulated cellular tyrosine phosphorylation was inhibited by compounds 13, 36, 37, and 44 at IC50 values between 0.1 and 0.4 microM, whereas PDGF-induced tyrosine phosphorylation was not affected by concentrations up to 10 microM. In addition, these compounds were able to selectively inhibit c-fos mRNA expression in EGF-dependent cell lines with IC50 values between 0.1 and 2 microM, but did not affect c-fos mRNA induction in response to PDGF or PMA (IC50 >100 microM). Proliferation of the EGF-dependent MK cell line was inhibited with similar IC50 values. From SAR studies, a binding mode for 4-(phenylamino)-7H-pyrrolo[2,3-d]pyrimidines as well as for the structurally related 4-(phenylamino)quinazolines at the ATP-binding site of the EGF-R tyrosine kinase is proposed. 4-(Phenylamino)7H-pyrrolo[2,3-d]pyrimidines therefore represent a new class of highly potent tyrosine kinase inhibitors which preferentially inhibit the EGF-mediated signal transduction pathway and have the potential for further evaluation as anticancer agents.
Inhibition of the Abl protein-tyrosine kinase in vitro and in vivo by a 2-phenylaminopyrimidine derivative.
Oncogenic activation of Abl proteins due to structural modifications can occur as a result of viral transduction or chromosomal translocation. The tyrosine protein kinase activity of oncogenic Abl proteins is known to be essential for their transforming activity. Therefore, we have attempted to identify selective inhibitors of the Abl tyrosine protein kinase. Herein we describe an inhibitor (CGP 57148) of the Abl and platelet-derived growth factor (PDGF) receptor protein-tyrosine kinases from the 2-phenylaminopyrimidine class, which is highly active in vitro and in vivo. Submicromolar concentrations of the compound inhibited both v-Abl and PDGF receptor autophosphorylation and PDGF-induced c-fos mRNA expression selectively in intact cells. In contrast, ligand-induced growth factor receptor autophosphorylation in response to epidermal growth factor (EGF), insulin-like growth factor-I, and insulin showed no or weak inhibition by high concentrations of CGP 57148. c-fos mRNA expression induced by EGF, fibroblast growth factor, or phorbol ester was also insensitive to inhibition by CGP 57148. In antiproliferative assays, the compound was more than 30-100-fold more potent in inhibiting growth of v-abl-transformed PB-3c cells and v-sis-transformed BALB/c 3T3 cells relative to inhibition of EGF-dependent BALB/MK cells, interleukin-3-dependent FDC-P1 cells, and the T24 bladder carcinoma line. Furthermore, anchorage-independent growth of v-abl- and v-sis-transformed BALB/c 3T3 cells was inhibited potently by CGP 57148. When tested in vivo, CGP 57148 showed antitumor activity at tolerated doses against tumorigenic v-abl- and v-sis-transformed BALB/c 3T3 cells. In contrast, CGP 57148 had no antitumor activity when tested using src-transformed BALB/c 3T3 cells. These findings suggest that CGP 57148 may have therapeutic potential for the treatment of diseases that involve abnormal cellular proliferation induced by Abl protein-tyrosine kinase deregulation or PDGF receptor activation.
Effects of a selective inhibitor of the Abl tyrosine kinase on the growth of Bcr-Abl positive cells.
The bcr-abl oncogene, present in 95% of patients with chronic myelogenous leukemia (CML), has been implicated as the cause of this disease. A compound, designed to inhibit the Abl protein tyrosine kinase, was evaluated for its effects on cells containing the Bcr-Abl fusion protein. Cellular proliferation and tumor formation by Bcr-Abl-expressing cells were specifically inhibited by this compound. In colony-forming assays of peripheral blood or bone marrow from patients with CML, there was a 92-98% decrease in the number of bcr-abl colonies formed but no inhibition of normal colony formation. This compound may be useful in the treatment of bcr-abl-positive leukemias.
[(Alkylamino)methyl]acrylophenones: potent and selective inhibitors of the epidermal growth factor receptor protein tyrosine kinase.
[(Alkylamino)methyl]acrylophenones and (alkylamino)propiophenones, bearing a spacer moiety such as the benzyloxy or (benzoylsulfonyl)oxy group in the 4-position, represent a novel class of inhibitors of the epidermal growth factor (EGF) receptor protein tyrosine kinase with a high degree of selectivity versus other tyrosine and serine/threonine kinases. The most active compounds inhibited the EGF receptor protein tyrosine kinase from A431 cell membranes with IC50 values of < 0.5 microM. Derivatives with a benzyloxy substituent in the 4-position of the aromatic ring inhibited both the EGF receptor kinase and the proliferation of an EGF-dependent mouse epidermal keratinocyte cell line (BALB/MK) but were only marginally active in the inhibition of the cellular EGF-dependent tyrosine phosphorylation. Compound 18 inhibited ligand-induced tyrosine phosphorylation and BALB/MK cell proliferation with IC50 values of approximately 100 and 1.21 microM, respectively, and showed antitumor activity in vivo in a nude mouse model. However, the discrepancy between the IC50 values for antiproliferative activity and cellular tyrosine phosphorylation as well as the relatively low tolerability in animals suggests a second site of action of this class of inhibitors. Nevertheless, [(alkylamino)methyl]acrylophenones and (alkylamino)propiophenones may prove to be interesting tools for studying the action of tyrosine kinases.
Selective inhibition of the platelet-derived growth factor signal transduction pathway by a protein-tyrosine kinase inhibitor of the 2-phenylaminopyrimidine class.
The platelet-derived growth factor (PDGF) receptor is a member of the transmembrane growth factor receptor protein family with intrinsic protein-tyrosine kinase activity. We describe a potent protein-tyrosine kinase inhibitor (CGP 53716) that shows selectivity for the PDGF receptor in vitro and in the cell. The compound shows selectivity for inhibition of PDGF-mediated events such as PDGF receptor autophosphorylation, cellular tyrosine phosphorylation, and c-fos mRNA induction in response to PDGF stimulation of intact cells. In contrast, ligand-induced autophosphorylation of the epidermal growth factor (EGF) receptor, insulin receptor, and the insulin-like growth factor I receptor, as well as c-fos mRNA expression induced by EGF, fibroblast growth factor, and phorbol ester, was insensitive to inhibition by CGP 53716. In antiproliferative assays, the compound was approximately 30-fold more potent in inhibiting PDGF-mediated growth of v-sis-transformed BALB/c 3T3 cells relative to inhibition of EGF-dependent BALB/Mk cells, interleukin-3-dependent FDC-P1 cells, and the T24 bladder carcinoma line. When tested in vivo using highly tumorigenic v-sis- and human c-sis-transformed BALB/c 3T3 cells, CGP 53716 showed antitumor activity at well-tolerated doses. In contrast, CGP 53716 did not show antitumor activity against xenografts of the A431 tumor, which overexpresses the EGF receptor. These findings suggest that CGP 53716 may have therapeutic potential for the treatment of diseases involving abnormal cellular proliferation induced by PDGF receptor activation.
Protein tyrosine kinase and protein kinase C inhibition by fungal anthraquinones related to emodin.
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