Bis(1H-2-indolyl)methanones as a Novel Class of Inhibitors of the Platelet-Derived Growth Factor Receptor Kinase

Abstract

The novel lead bis(1H-2-indolyl)methanone inhibits autophosphorylation of platelet-derived growth factor (PDGF) receptor tyrosine kinase in intact cells. Various substituents in the 5- or 6-position of one indole ring increase or preserve potency, whereas most modifications of the ring structures and of the methanone group as well as substitution at both indoles result in weak or no activity. An ATP binding site model, derived by homology from the FGFR-1 tyrosine kinase crystal structure suggesting hydrogen bonds of one indole NH and the methanone oxygen with the backbone carbonyl and amide, respectively, of Cys684, explains why only one indole moiety is open for substitution and locates groups in the 5- or 6-position outside the pocket. The hitherto most active derivatives, 39, 53 and 67, inhibit both isoforms of the PDGF receptor kinase in intact cells, with IC(50) of 0.1-0.3 microM, and purified PDGFbeta-receptor in vitro, with IC(50) of 0.09, 0.1, or 0.02 microM, respectively. PDGF-stimulated DNA synthesis is inhibited by these derivatives with IC(50) values of 1-3 microM. Kinetic analysis of 53 showed an ATP-competitive mode of inhibition. The compounds are inactive or weakly active toward a number of other tyrosine kinases, including the FGF receptor 1, EGF receptor, and c-Src kinase, as well as toward serine-threonine kinases, including different PKC isoforms and GRK2, and appear therefore selective for PDGF receptor inhibition.

Bis(1H-2-indolyl)-1-methanones as inhibitors of the hematopoietic tyrosine kinase Flt3

“…37 Bis(1H-2-indolyl)-1-methanones are a novel class of tyrosine kinase inhibitors with selectivity for the PDGF receptor family. 38 Here, we show that compounds from this class of tyrosine kinase inhibitors are effective inhibitors of Flt3, block Flt3-dependent transformation and sensitize Flt3-transformed cells for radiationinduced apoptosis.…”

“…In vitro kinase assays with this protein were carried out as described previously, except that kinase activity was assayed as autophosphorylation at a kinase concentration of approximately 100 ng/ml. 38 …”

“…These data further support the relatively narrow selectivity of the bis(1H-2-indolyl)-1-methanones. PDGF receptors (␣ and ␤-subtype) 38 and Flt3 are susceptible kinases whereas little sensitivity was found for a panel of tyrosine and serine-threonine kinases including FGF receptor-1, c-Kit, EGF receptor, insulin and IGF1 receptors and different PKC isoforms. 38 We also wished to know whether bis(1H-2-indolyl)-1-methanones act by direct inhibition of Flt3.…”

The protein-tyrosine phosphatase DEP-1 modulates growth factor-stimulated cell migration and cell–matrix adhesion

“…It is possible that the PDGFb-receptor plays an important role. This is indicated by inhibition of FCS-stimulated migration with D-65495 and AG1296, two potent and selective PDGF-receptor tyrosine kinase inhibitors of different structural families (Kovalenko et al, 1994;Mahboobi et al, 2002). Alternatively, or in addition, DEP-1 may affect migration by dephosphorylating other substrates, for example, other involved receptor tyrosine kinases, substrates downstream of the PDGF receptor, or substrates downstream of other surface receptors.…”

“…Interestingly, migration was also attenuated by DEP-1 when FCS was used for stimulation (Figure 2a,c). We recently described a novel selective PDGF receptor tyrosine kinase inhibitor D-65495 (Mahboobi et al, 2002), which potently inhibits PDGFa-and b-receptor and Flt3, but has little activity toward a large panel of other protein kinases. D-65495 suppressed FCS-stimulated migration of PAE cells to a large extent (Figure 2b), suggesting that much of the migration stimulation by FCS requires activation of PDGF receptor.…”