Potent and selective inhibitors of PI3Kδ: obtaining isoform selectivity from the affinity pocket and tryptophan shelf.

A potent inhibitor of PI3Kδ that is ≥ 200 fold selective for the remaining three Class I PI3K isoforms and additional kinases is described. The hypothesis for selectivity is illustrated through structure activity relationships and crystal structures of compounds bound to a K802T mutant of PI3Kγ. Pharmacokinetic data in rats and mice support the use of 3 as a useful tool compound to use for in vivo studies.

Discovery of novel PI3-kinase δ specific inhibitors for the treatment of rheumatoid arthritis: taming CYP3A4 time-dependent inhibition.

PI3Kδ is a lipid kinase and a member of a larger family of enzymes, PI3K class IA(α, ß, δ) and IB (γ), which catalyze the phosphorylation of PIP2 to PIP3. PI3Kδ is mainly expressed in leukocytes, where it plays a critical, nonredundant role in B cell receptor mediated signaling and provides an attractive opportunity to treat diseases where B cell activity is essential, e.g., rheumatoid arthritis. We report the discovery of novel, potent, and selective PI3Kδ inhibitors and describe a structural hypothesis for isoform (α, ß, γ) selectivity gained from interactions in the affinity pocket. The critical component of our initial pharmacophore for isoform selectivity was strongly associated with CYP3A4 time-dependent inhibition (TDI). We describe a variety of strategies and methods for monitoring and attenuating TDI. Ultimately, a structure-based design approach was employed to identify a suitable structural replacement for further optimization.

The identification of 2-(1H-indazol-4-yl)-6-(4-methanesulfonyl-piperazin-1-ylmethyl)-4-morpholin-4-yl-thieno[3,2-d]pyrimidine (GDC-0941) as a potent, selective, orally bioavailable inhibitor of class I PI3 kinase for the treatment of cancer .

Phosphatidylinositol-3-kinase (PI3K) is an important target in cancer due to the deregulation of the PI3K/ Akt signaling pathway in a wide variety of tumors. A series of thieno[3,2-d]pyrimidine derivatives were prepared and evaluated as inhibitors of PI3 kinase p110alpha. The synthesis, biological activity, and further profiling of these compounds are described. This work resulted in the discovery of 17, GDC-0941, which is a potent, selective, orally bioavailable inhibitor of PI3K and is currently being evaluated in human clinical trials for the treatment of cancer.

Studies on pyrrolopyrimidines as selective inhibitors of multidrug-resistance-associated protein in multidrug resistance.

Multidrug resistance mediated by P-glycoprotein (Pgp) or multidrug-resistance-associated protein (MRP) remains a major obstacle for successful treatment of cancer. Inhibition of Pgp and MRP transport is important for high efficacy of anticancer drugs. While several Pgp inhibitors have entered clinical trials, the development of specific MRP1 inhibitors is still in its infancy. In our screening program, we have identified a pyrrolopyrimidine (4) as a novel and selective MRP1 inhibitor. Subsequent SAR work on the 4-position of the template revealed the phenethylpiperazine side chain as a potent replacement of the benzylthio group of the lead molecule. Introduction of groups at the 2-position seems to have no detrimental effect on activity. Modifications to the nitrile group at the 7-position resulted in the identification of analogues with groups, such as amides, with superior pharmacokinetic profiles. In vivo efficacy has been demonstrated by xenograft studies on selected compounds.

Design and synthesis of new templates derived from pyrrolopyrimidine as selective multidrug-resistance-associated protein inhibitors in multidrug resistance.

In our continued effort to identify selective MRP1 modulators, we have developed two novel templates, 3 and 4, through rational drug design by identifying the key pharmacophore interaction at the 7-position of the pyrrolopyrimidine template 1. Further synthesis and SAR work on these novel templates gave a number of potent MRP1 modulators with great selectivity against Pgp. Additional studies to reduce the CYP3A4 inhibition are also reported. Several compounds of these classes were subjected to in vivo xenograft studies and in vivo efficacies were demonstrated.

Novel angular benzophenazines: dual topoisomerase I and topoisomerase II inhibitors as potential anticancer agents.

A series of substituted angular benzophenazines were prepared using a new synthetic route via a novel regiocontrolled condensation of 1,2-naphthoquinones and 2,3-diaminobenzoic acids. The synthesis and biological activity of this new series of substituted 8,9-benzo[a]phenazine carboxamide systems are described. The analogues were evaluated against the H69 parental human small cell lung carcinoma cell line and H69/LX4 resistant cell line which overexpresses P-glycoprotein. Selected analogues were evaluated against the COR-L23 parental human non small cell lung carcinoma cell line and the COR-L23/R resistant cell line which overexpresses multidrug resistance protein. This series of novel angular benzophenazines were potent cytotoxic agents in these cell lines and may be able to circumvent multidrug resistance mechanisms which result in the lack of efficacy of many drugs in cancer chemotherapy. These compounds show dual inhibition of topoisomerase I and topoisomerase II and thus target two key enzymes responsible for the topology of DNA that are active at different points in the cell cycle. The introduction of chirality into the carboxamide side chain of these novel benzophenazine carboxamides has resulted in the discovery of a potent enantiospecific series of cytotoxic agents, exemplified by 4-methoxy-benzo[a]phenazine-11-carboxylic acid (2-(dimethylamino)-1-(R)-methyl-ethyl)-amide, XR11576 ((R)-4j' '). In vivo activity has been demonstrated for 4-methoxy-benzo[a]phenazine-11-carboxylic acid (2-(dimethylamino)-1-(R)-methyl-ethyl)-amide, XR11576, after intravenous administration to female mice, and this compound has been selected as a development candidate for further evaluation.

Structure-activity relationships for pyrido-, imidazo-, pyrazolo-, pyrazino-, and pyrrolophenazinecarboxamides as topoisomerase-targeted anticancer agents.

Heterocyclic phenazinecarboxamides were prepared by condensation of aminoheterocycles and 2-halo-3-nitrobenzoic acids, followed by reductive ring closure and amidation. They showed similar inhibition of paired cell lines that underexpressed topo II or overexpressed P-glycoprotein, indicating a non topo II mechanism of cytotoxicity and indifference to P-glycoprotein mediated multidrug resistance. Compounds with a fused five-membered heterocyclic ring were generally less potent than the pyrido[4,3-a]phenazines. A 4-methoxypyrido[4,3-a]phenazine (IC(50)s 2.5-26 nM) gave modest (ca. 5 day) growth delays in H69/P xenografts with oral dosing.