Development of sulfonamide AKT PH domain inhibitors

Abstract

Disruption of the phosphatidylinositol 3-kinase/AKT signaling pathway can lead to apoptosis in cancer cells. Previously we identified a lead sulfonamide that selectively bound to the pleckstrin homology (PH) domain of AKT and induced apoptosis when present at low micromolar concentrations. To examine the effects of structural modification, a set of sulfonamides related to the lead compound was designed, synthesized, and tested for binding to the expressed PH domain of AKT using a surface plasmon resonance-based competitive binding assay. Cellular activity was determined by means of an assay for pAKT production and a cell killing assay using BxPC-3 cells. The most active compounds in the set are lipophilic and possess an aliphatic chain of the proper length. Results were interpreted with the aid of computational modeling. This paper represents the first structure-activity relationship (SAR) study of a large family of AKT PH domain inhibitors. Information obtained will be used in the design of the next generation of inhibitors of AKT PH domain function.

Figure 1

The structures of PI(3,4,5)P₃ and DPIEL

Figure 2

Extent of AKT phosphorylation at Ser⁴⁷³ in the presence of compounds 1–47 at 10 μM.

Figure 3

The best GOLD docking poses for IP₄ (green), 1 (magenta), 17 (blue), 29 (yellow), and 37 (salmon). The dashed lines represent hydrogen bonds, and the electrostatic surface is for the protein. The circled regions are those with synthetic modifications.

Figure 4

Structural alignment of AKT kinase-PH domain (PDB code 3O96, see reference 38) and PH domain (PDB code 1UNQ, see reference 37). Blue Ribbons: 1UNQ. Green sticks: PI(3,4,5)P₃ from 1UNQ. Red Ribbons: 3O96. Grey sticks: inhibitor VIII from 3O96.

Figure 5

The correlation between experimental pK_i values and GOLD scores. Compounds 31 and 32 are outliers, suggesting their binding mode might be different from the other compounds.