As a result of our efforts to discover novel p53:MDM2 protein-protein interaction inhibitors useful for treating cancer, the potent and selective MDM2 inhibitor NVP-CGM097 (1) with an excellent in vivo profile was selected as a clinical candidate and is currently in phase 1 clinical development. This article provides an overview of the discovery of this new clinical p53:MDM2 inhibitor. The following aspects are addressed: mechanism of action, scientific rationale, binding mode, medicinal chemistry, pharmacokinetic and pharmacodynamic properties, and in vivo pharmacology/toxicology in preclinical species.

JAK inhibitors are being developed for the treatment of rheumatoid arthritis, psoriasis, myeloproliferative neoplasms and leukemias. Most of these drugs target the ATP-binding pocket and stabilize the active conformation of the JAK kinases. This type-I binding mode leads to an increase in JAK activation-loop phosphorylation, despite blockade of kinase function. Here we report that stabilizing the inactive state via type-II inhibition acts in the opposite manner, leading to a loss of activation-loop phosphorylation. We used X-ray crystallography to corroborate the binding mode and report for the first time the crystal structure of the JAK2 kinase domain in an inactive conformation. Importantly, JAK inhibitor-induced activation-loop phosphorylation requires receptor interaction, as well as intact kinase and pseudokinase domains. Hence, depending on the respective conformation stabilized by a JAK inhibitor, hyperphosphorylation of the activation-loop may or may not be elicited.

The recent discovery of an acquired activating point mutation in JAK2, substituting valine at amino acid position 617 for phenylalanine, has greatly improved our understanding of the molecular mechanism underlying chronic myeloproliferative neoplasms. Strikingly, the JAK2 V617F mutation is found in nearly all patients suffering from polycythemia vera and in roughly every second patient suffering from essential thrombocythemia and primary myelofibrosis. Thus, JAK2 represents a promising target for the treatment of myeloproliferative neoplasms and considerable efforts are ongoing to discover and develop inhibitors of the kinase. Here, we report potent inhibition of JAK2 V617F and JAK2 wild-type enzymes by a novel substituted quinoxaline, NVP-BSK805, which acts in an ATP-competitive manner. Within the JAK family, NVP-BSK805 displays more than 20-fold selectivity towards JAK2 in vitro, as well as excellent selectivity in broader kinase profiling. The compound blunts constitutive STAT5 phosphorylation in JAK2 V617F-bearing cells, with concomitant suppression of cell proliferation and induction of apoptosis. In vivo, NVP-BSK805 exhibited good oral bioavailability and a long half-life. The inhibitor was efficacious in suppressing leukemic cell spreading and splenomegaly in a Ba/F3 JAK2 V617F cell-driven mouse mechanistic model. Furthermore, NVP-BSK805 potently suppressed recombinant human erythropoietin-induced polycythemia and extramedullary erythropoiesis in mice and rats. Mol Cancer Ther; 9(7); 1945-55. ©2010 AACR.

Mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) is essential for immune responses triggered by antigen receptors but the contribution of its paracaspase activity is not fully understood. Here, we studied how MALT1 proteolytic function regulates T-cell activation and fate after engagement of the T-cell receptor pathway. We show that MLT-827, a potent and selective MALT1 paracaspase inhibitor, does not prevent the initial phase of T-cell activation, in contrast to the pan-protein kinase C inhibitor AEB071. However, MLT-827 strongly impacted cell expansion after activation. We demonstrate this is the consequence of profound inhibition of IL-2 production as well as reduced expression of the IL-2 receptor alpha subunit (CD25), resulting from defective canonical NF-jB activation and accelerated mRNA turnover mechanisms. Accordingly, MLT-827 revealed a unique transcriptional fingerprint of MALT1 protease activity, providing evidence for broad control of T-cell signaling pathways. Altogether, this first report with a potent and selective inhibitor elucidates how MALT1 paracaspase activity integrates several T-cell activation pathways and indirectly controls gammachain receptor dependent survival, to impact on T-cell expansion.

The interesting biological properties of the hamigerans wherein hamigeran B is a potent antiviral agent with low cytotoxicity to host cells make these deceptively simple looking structures challenging synthetic targets. A strategy to hamigeran B evolved wherein the three contiguous stereocenters are established ultimately from a Pd catalyzed asymmetric allylic alkylation (AAA). The latter involves an asymmetric allylation of a non-stabilized ketone enolate in 77 % yield and 93 % ee. By using this process, (S)-5-allyl-2-isopropyl-5-methyl-1-trifluoromethanesulfonyloxycyclopentene becomes available in four steps from 2-methylcyclopentanone. Introduction of the aryl unit by cross-coupling proceeded intermolecularly but failed intramolecularly. On the other hand, reductive removal of the triflate permitted a Heck reaction to effect intramolecular introduction of the aryl ring. The unusual conformational properties of this molecular architecture are revealed by the regioselectivity of the beta-hydrogen elimination in the Heck reaction and the diastereoselectivity of the reduction establishing the stereochemistry of the carbon bearing the isopropyl group. The successful route consists of 15 steps from 2-methylcyclopentanone and dimethylorcinol illustrating the efficiency of the route based upon the Pd AAA.