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Thr-211 is one of three different amino acid residues in the kinase domain of protein kinase B/Akt as compared to protein kinase A (PKA), a closely related analog in the same AGC family. In an attempt to improve the potency and selectivity of our indazole-pyridine series of Akt inhibitors over PKA, efforts have focused on the incorporation of a chemical functionality to interact with the hydroxy group of Thr-211. Several substituents including an oxygen anion, amino, and nitro groups have been introduced at the C-6 position of the indazole scaffold, leading to a significant drop in Akt potency. Incorporation of a nitrogen atom into the phenyl ring at the same position (i.e., 9f) maintained the Akt activity and, in some cases, improved the selectivity over PKA. The structure-activity relationships of the new pyridine-pyrazolopyridine series of Akt inhibitors and their structural features when bound to PKA are also discussed.

The crystal structure of ABT-378 (lopinavir), bound to the active site of HIV-1 protease is described. A comparison with crystal structures of ritonavir, A-78791, and BILA-2450 shows some analogous features with previous reported compounds. A cyclic urea unit in the P2 position of ABT-378 is novel and makes two bidentate hydrogen bonds with Asp 29 of HIV-1 protease. In addition, a previously unreported shift in the Gly 48 carbonyl position is observed. A discussion of the structural features responsible for its high potency against wild-type HIV protease is given along with an analysis of the effect of active site mutations on potency in in vitro assays.