Abstract 1361: Fragment based drug discovery of selective inhibitors of Fibroblast Growth Factor Receptor (FGFR)

Recent data in a number of tumour types has implicated Fibroblast Growth Factor (FGF) and Fibroblast Growth Factor receptor (FGFR) signalling as being key to the molecular pathology of cancer.

A fragment screening campaign was conducted against the tyrosine kinase domain of FGFR1 to detect low molecular weight compounds that bound to the hinge region of the kinase. The screening produced several fragment inhibitors (molecular weight <250 Da) in the micromolar range and their binding modes were confirmed by X-ray crystallography. We selected an imidazo[1,2-a]pyridine fragment that was 120 uM versus FGFR3 in the kinase inhibition bioassay. Subsequently, in the fragments-to-leads stage a detailed structural understanding of the binding interactions between the fragment and its protein kinase target, using X-ray crystallography, led to the identification of a 0.003 uM inhibitor of FGFR3 in the kinase bioassay, with significant selectivity versus VEGFR2 and FLT3.

The poster will focus on the description of previously undescribed compounds bearing an imidazo[1,2-a]pyridine core scaffold where selectivity versus other protein kinases, for example FLT3, is obtained using the X-ray crystal structure and structure-based design. In summary we will illustrate how X-ray crystallography and fragment-based drug design (FBDD) can be used to discover compounds with activity in an FGFR driven xenograft model when dosed by the oral route.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1361. doi:10.1158/1538-7445.AM2011-1361

Abstract 5778: Fragment-based drug discovery of selective inhibitors of fibroblast growth factor receptor (FGFr)

Recent data in a number of tumour types has implicated Fibroblast Growth Factor (FGF) and Fibroblast Growth Factor receptor (FGFr) signalling as being key to the molecular pathology of cancer. This poster will describe fragment based drug discovery using biophysical screening to identify initial fragments. Subsequently, in the fragments-to-leads stage a detailed structural understanding of the binding interactions between the fragment and its target protein utilised X-ray crystallography and NMR. Starting with different fragments allows several lead series to be identified, often by synthesizing only small numbers of compounds.

A fragment screening campaign was conducted against the FGFr-1 to detect very low molecular weight compounds that bound to the hinge region of the kinase. The screening produced several fragment molecules (Molecular Weight <250 Da) which were in the micromolar range and confirmed binding mode in X-ray crystallography. One X-ray hit series that was 120 uM verse FGFr-3 will be described. Several iterations of structure-guided medicinal chemistry led to the identification of a lead compound with 3 nM affinity for FGFr-3, good cell activity and 30-fold selectivity verse VEGFr-2 with good oral activity. The lead was optimised to afford a compound that showed good PK/PD and efficacy.

This poster represents first disclosure of the structure of the lead series and illustrates how a fragment-based drug discovery approach can be efficiently used to discover compounds advanced nanomolar compounds with oral bioavailability.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5778.

Characterization of the antitumor effects of the selective farnesyl protein transferase inhibitor R115777 in vivo and in vitro

R115777 [(B)-6-[amino(4-chlorophenyl)(1-methyl-1H-imidazol-5-yl)-methyl]-4-(3-chlorophenyl)-1-methyl-2(1H)-quinolinone] is a potent and selective inhibitor of farnesyl protein transferase with significant antitumor effects in vivo subsequent to oral administration in mice. In vitro, using isolated human farnesyl protein transferase, R115777 competitively inhibited the farnesylation of lamin B and K-RasB peptide substrates, with IC50s of 0.86 nM and 7.9 nM, respectively. In a panel of 53 human tumor cell lines tested for growth inhibition, approximately 75% were found to be sensitive to R115777. The majority of sensitive cell lines had a wild-type ras gene. Tumor cell lines bearing H-ras or N-ras mutations were among the most sensitive of the cell lines tested, with responses observed at nanomolar concentrations of R115777. Tumor cell lines bearing mutant K-ras genes required higher concentrations for inhibition of cell growth, with 50% of the cell lines resistant to R115777 up to concentrations of 500 nM. Inhibition of H-Ras, N-Ras, and lamin B protein processing was observed at concentrations of R115777 that inhibited cell proliferation. However, inhibition of K-RasB protein-processing could not be detected. Oral administration b.i.d. of R115777 to nude mice bearing s.c. tumors at doses ranging from 6.25-100 mg/kg inhibited the growth of tumors bearing mutant H-ras, mutant K-ras, and wild-type ras genes. Histological evaluations revealed heterogeneity in tumor responses to R115777. In LoVo human colon tumors, treatment with R115777 produced a prominent antiangiogenic response. In CAPAN-2 human pancreatic tumors, an antiproilferative response predominated, whereas in C32 human melanoma, marked induction of apoptosis was observed. The heterogeneity of histological changes associated with antitumor effects suggested that R115777, and possibly farnesyl protein transferase inhibitors as a class, alter processes of transformation related to tumor-host interactions in addition to inhibiting tumor-cell proliferation.

Glass-forming tendency and stability of the amorphous state in the aqueous solutions of linear polyalcohols with four carbons. I. Binary systems water-polyalcohol

All the aqueous solutions of linear saturated polyalcohols with four carbons have been investigated at low temperature. Only ice has been observed in the solutions of 1,3-butanediol and 1,2,3- and 1,2,4-butanetriol. For same solute concentration, the glass-forming tendency on cooling is highest with 2,3-butanediol, where it is comparable to that with 1,2-propanediol, the best solute reported to date. However, the quantity of ice and hydrate crystallized is particularly high on slow cooling or on subsequent rewarming. The highest stability of the amorphous state is observed on rewarming the 1,2-butanediol and 1,3-butanediol solutions. With respect to this property, these compounds come just after 1,2-propanediol and before all the other compounds studied so far. They are followed by dimethylsulfoxide and 1,2,3-butanetriol. The glass-forming tendency of the 1,3-butanediol solutions is also very high; it is third only to that of 1,2-propanediol and 2,3-butanediol. The glass-forming tendency is a little smaller with 1,2-butanediol, but it is cubic instead of ordinary hexagonal ice which crystallizes on cooling rapidly with 35% 1,2-butanediol. Cubic ice is thought to be innocuous. A gigantic glass transition is observed with 45% of this strange solute. 1,4-Butanediol, 45% also favors cubic ice greatly. Therefore, 1,2- and 1,3-butanediol with comparable physical properties are perhaps as interesting as 1,2-propanediol for cryopreservation of cells or organs by complete vitrification. Together with 1,2-propanediol, 1,2- and 1,3-butanetriol, 1,2,3-butanetriol, and perhaps 2,3-butanediol provide an interesting battery of solutions for cryopreservation by vitrification.