Fragment-based hit discovery and structure-based optimization of aminotriazoloquinazolines as novel Hsp90 inhibitors

qFit-ligand reveals widespread conformational heterogeneity of drug-like molecules in X-ray electron density maps

“…In the course of structure-based optimization of Hsp90 inhibitors, Casale and coworkers observed a flipped binding mode of the ligand in the crystal structure, leading them to change the direction of design towards a low nanomolar compound (Figure 1B). 11 In PTR1, compounds that presumably could not be accommodated by the binding site ultimately led to a boost in affinity, owing to altered binding modes. 11,12 In human lipoprotein-associated phospholipase A2, two related ligands ( Figure 1C) that explored distinct subpockets were merged into a more potent ligand (Figure 1D).…”

“…11 In PTR1, compounds that presumably could not be accommodated by the binding site ultimately led to a boost in affinity, owing to altered binding modes. 11,12 In human lipoprotein-associated phospholipase A2, two related ligands ( Figure 1C) that explored distinct subpockets were merged into a more potent ligand (Figure 1D). 13 These selected examples highlight both the perils of design based solely on an i nitial ligand pose, but also how the fortuitous discovery of alternate poses can create new opportunities for design.…”

Establish an automated flow injection ESI-MS method for the screening of fragment based libraries: Application to Hsp90

“…Five of these ligands were classified as ATP-competitors, although at this point we cannot unequivocally rule out the possibility that AUY922 could displace them by an allosteric mechanism. Nevertheless most of these hits, previously identified by NMR FAXS experiments and X-ray crystallography studies performed at NMS, confirmed the binding to the ATP pocket of Hsp90 (Casale et al, 2014). Moreover, as reported in Table 2, a fluorescence polarization method was used to determine equilibrium dissociation constants for these compounds and K D values were aligned to %BP obtained by AFI-MS determinations over a wide range of affinities (7.5-181 lM, see Table 2).…”

“…Among the identified hits, the novel Hsp90 ligand FBA-12-062 (K D = 37.2 lM determined by FP) paved the way to the design of a class of potent [1,2,4]triazolo[1,5-c]pyrimidine derivatives as Hsp90 modulators (Casale et al, 2014).…”

“…The attractiveness of Hsp90 inhibitors for the management of oncological diseases, led to establishing a research project in Nerviano Medical Sciences (NMS) including a FAXS (Fluorine chemical shift Anisotropy and eXchange for Screening) NMR 19 F based screening (Dalvit et al, 2003) performed to support a fragment-based program (Brasca et al, 2010;Casale et al, 2014). The use of ESI-MS to investigate this target was previously reported by Vallée and coworkers in the medicinal chemistry optimization of tricyclic imidazo [4,5-c]pyridines as a new class of Hsp90 inhibitors (Vallee et al, 2011).…”