Dirk Erdmann

Characterization of the novel and specific PI3Kα inhibitor NVP-BYL719 and development of the patient stratification strategy for clinical trials.

Somatic PIK3CA mutations are frequently found in solid tumors, raising the hypothesis that selective inhibition of PI3Kα may have robust efficacy in PIK3CA-mutant cancers while sparing patients the side-effects associated with broader inhibition of the class I phosphoinositide 3-kinase (PI3K) family. Here, we report the biologic properties of the 2-aminothiazole derivative NVP-BYL719, a selective inhibitor of PI3Kα and its most common oncogenic mutant forms. The compound selectivity combined with excellent drug-like properties translates to dose- and time-dependent inhibition of PI3Kα signaling in vivo, resulting in robust therapeutic efficacy and tolerability in PIK3CA-dependent tumors. Novel targeted therapeutics such as NVP-BYL719, designed to modulate aberrant functions elicited by cancer-specific genetic alterations upon which the disease depends, require well-defined patient stratification strategies in order to maximize their therapeutic impact and benefit for the patients. Here, we also describe the application of the Cancer Cell Line Encyclopedia as a preclinical platform to refine the patient stratification strategy for NVP-BYL719 and found that PIK3CA mutation was the foremost positive predictor of sensitivity while revealing additional positive and negative associations such as PIK3CA amplification and PTEN mutation, respectively. These patient selection determinants are being assayed in the ongoing NVP-BYL719 clinical trials. Mol Cancer Ther; 13(5); 1117–29. ©2014 AACR.

Genetic resistance to JAK2 enzymatic inhibitors is overcome by HSP90 inhibition

Hsp90 inhibition in B cell acute lymphoblastic leukemia overcomes resistance to JAK2 inhibitors.

Potent and Selective Inhibition of Polycythemia by the Quinoxaline JAK2 Inhibitor NVP-BSK805

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 JAK2V617F 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 JAK2V617F 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 JAK2V617F-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 JAK2V617F 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.

2-Amino-aryl-7-aryl-benzoxazoles as potent, selective and orally available JAK2 inhibitors

A series of novel benzoxazole derivatives has been designed and shown to exhibit attractive JAK2 inhibitory profiles in biochemical and cellular assays, capable of delivering compounds with favorable PK properties in rats. Synthesis and structure-activity relationship data are also provided.

Effect of the acylation of TEAD4 on its interaction with co-activators YAP and TAZ

The Hippo pathway is deregulated in various cancers, and the discovery of molecules that modulate this pathway may open new therapeutic avenues in oncology. TEA/ATTS domain (TEAD) transcription factors are the most distal elements of the Hippo pathway and their transcriptional activity is regulated by the Yes‐associated protein (YAP). Amongst the various possibilities for targeting this pathway, inhibition of the YAP:TEAD interaction is an attractive strategy. It has been shown recently that TEAD proteins are covalently linked via a conserved cysteine to a fatty acid molecule (palmitate) that binds to a deep hydrophobic cavity present in these proteins. This acylation of TEAD seems to be required for efficient binding to YAP, and understanding how it modulates the YAP:TEAD interaction may provide useful information on the regulation of TEAD function. In this report we have studied the effect of TEAD4 acylation on its interaction with YAP and the other co‐activator transcriptional co‐activator with PDZ‐binding motif (TAZ). We show in our biochemical and cellular assays that YAP and TAZ bind in a similar manner to acylated and non‐acylated TEAD4. This indicates that TEAD4 acylation is not a prerequisite for its interaction with YAP or TAZ. However, we observed that TEAD4 acylation significantly enhances its stability, suggesting that it may help this transcription factor to acquire and/or maintain its active conformation.

The Surprising Features of the TEAD4-Vgll1 Protein–Protein Interaction

The Hippo signaling pathway, which controls organ size in animals, is altered in various human cancers. The TEAD transcription factors, the most downstream elements in this pathway, are regulated by different cofactors, such as the Vgll (vestigial‐like) proteins. Having studied the interaction between Vgll1‐derived peptides and human TEAD4, we show that, although it lacks a key secondary structure element required for tight binding by two other TEAD cofactors (YAP and TAZ), Vgll1‐derived peptides bind to TEAD with nanomolar affinity. We identify a β‐strand:loop:α‐helix motif as the minimal Vgll binding site. Finally, we reveal an unexpected difference between mouse and human Vgll1‐derived peptides.

Kinetic Study of Human Full-Length Wild-Type JAK2 and V617F Mutant Proteins

The Janus kinase 2 (JAK2) is a drug target in particular because a missense mutation in this gene (V617F) has been identified in various human diseases. We report here the first kinetic study of the human full-length wild type and V617F JAK2 proteins and of their isolated kinase domain. The kinetic parameters of both full-length proteins are similar revealing that the mutation does not affect JAK2 catalytic activity suggesting that it has a more complex role in the regu- lation of JAK2 activity. Our study also shows that the domains located outside the kinase domain have little influence on JAK2 catalytical activity.

Dissection of the interaction between the intrinsically disordered YAP protein and the transcription factor TEAD

TEAD (TEA/ATTS domain) transcription factors are the most distal effectors of the Hippo pathway. YAP (Yes-associated protein) is a coactivator protein which, upon binding to TEAD proteins, stimulates their transcriptional activity. Since the Hippo pathway is deregulated in various cancers, designing inhibitors of the YAP:TEAD interaction is an attractive therapeutic strategy for oncology. Understanding the molecular events that take place at the YAP:TEAD interface is therefore important not only to devise drug discovery approaches, but also to gain knowledge on TEAD regulation. In this report, combining single site-directed mutagenesis and double mutant analyses, we conduct a detailed analysis on the role of several residues located at the YAP:TEAD interface. Our results provide quantitative understanding of the interactions taking place at the YAP:TEAD interface and give insights into the formation of the YAP:TEAD complex and more particularly on the interaction between TEAD and the Ω-loop found in YAP. DOI: http://dx.doi.org/10.7554/eLife.25068.001

Leveraging the Contribution of Thermodynamics in Drug Discovery with the Help of Fluorescence-Based Thermal Shift Assays

The development of new drugs with better pharmacological and safety properties mandates the optimization of several parameters. Today, potency is often used as the sole biochemical parameter to identify and select new molecules. Surprisingly, thermodynamics, which is at the core of any interaction, is rarely used in drug discovery, even though it has been suggested that the selection of scaffolds according to thermodynamic criteria may be a valuable strategy. This poor integration of thermodynamics in drug discovery might be due to difficulties in implementing calorimetry experiments despite recent technological progress in this area. In this report, the authors show that fluorescence-based thermal shift assays could be used as prescreening methods to identify compounds with different thermodynamic profiles. This approach allows a reduction in the number of compounds to be tested in calorimetry experiments, thus favoring greater integration of thermodynamics in drug discovery.

Study of the Selectivity of Insulin-Like Growth Factor-1 Receptor (IGF1R) Inhibitors

The insulin-like growth factor-1 receptor (IGF1R) is a drug target for oncology, and many studies are ongoing to identify compounds that inhibit its tyrosine kinase activity. IGF1R is highly homologous to the insulin receptor (IR) and IGF1R inhibition might be beneficial for patients, while IR inhibition may lead to limiting toxicity. Therefore selectivity for IGF1R over IR is the aim for drug design in this context. A few compounds that selectively inhibit IGF1R over IR in cells have been identified, but none of them show the same levels of selectivity in enzymatic assays. To deter- mine whether this discrepancy is linked to the conditions used in the enzymatic assays, we have studied the interaction be- tween known IGF1R inhibitors (NVP-AEW541, OSI906, AG538, NVP-TAE226) and phosphorylated/unphosphorylated IGF1R/IR proteins with both biophysical (isothermal calorimetry and surface plasmon resonance) and enzymatic methods. In this report, we describe the results of this study and comment on the different degrees of selectivity IGF1R versus IR measured in biochemical and cellular assays. Finally, our study provides new information on the biochemical and mechanism of action of these small molecular weight IGF1R inhibitors.