Abstract 3588: Discovery of potent and selective CSNK1A1 inhibitors for solid tumor therapy

CSNK1A1 is a serine/threonine kinase involved in multiple cellular processes, including cell division, beta catenin signaling, and TP53 activation. Inhibition of CSNK1A1 has previously been validated as a therapeutic strategy in hematologic malignancy, and degradation of CSNK1A1 protein is the downstream mechanism of action for lenalidomide in 5q- myelodysplasia (Krönke, et al. Nature. 2015.). However, lenalidomide is inactive in most solid tumor models, thus limiting the study of CSNK1A1 inhibition in other contexts. Analysis of genetic loss-of-function data from the Cancer Dependency Map reveals multiple sensitive models, including lineage-specific enrichment in colorectal and gastric cancer. In an academic-industry collaboration, we a) developed first-in-class potent and selective ATP-competitive CSNK1A1 small molecule inhibitors with preclinical anti-cancer efficacy in vivo, and b) identified FAM83 expression as a key determinant of inhibitor sensitivity.

We identified a tetrahydro-pyrrolopyridinone scaffold that was subsequently optimized to yield BAY-888 (CSNK1A1 IC50 4 nM @ 10 μM ATP; 63 nM @ 1 mM ATP) and BAY-204 (CSNK1A1 IC50 2 nM @ 10 μM ATP; 12 nM @ 1 mM ATP). The crystal structure of CSNK1A1 in complex with BAY-888 confirmed compound binding in the ATP binding pocket. Across the PRISM barcoded cell line panel of more than 500 solid tumor cell lines, inhibitors phenocopy the CSNK1A1 shRNA knockdown profile. To determine downstream mediators of CSNK1A1 inhibitor sensitivity, we performed co-IP mass spectrometry following CSNK1A1 pulldown and global phosphoproteomic assays following inhibitor treatment. We identified multiple interacting proteins that are also phosphorylation targets, including FAM83 family members. FAM83 was recently reported to mediate the subcellular localization of CSNK1A1 (Fulcher, et al. Sci Signal. 2018.). Excitingly, the baseline expression of FAM83B and FAM83H correlates with inhibitor and shRNA cell line sensitivity. Modulation of FAM83H expression altered CSNK1A1 localization and sensitivity to CSNK1A1 inhibition.

BAY-888 and BAY-204 are orally bioavailable and were evaluated in multiple murine cell line xenograft models. We observed promising efficacy in DLBCL (TMD8) in vivo as well as in multiple FAM83-high solid tumor models, including colorectal (HCT116 and HT29), gastric (IM95), and urothelial cancer (KU19-19). We identified RPS6 phosphorylation as one of the PD biomarkers correlating with efficacy in vivo. In summary, CSNK1A1 is a promising target with anti-tumor efficacy and achievable therapeutic index in preclinical models of FAM83-high solid tumors.

Citation Format: Steven M. Corsello, Huajia Zhang, Rajesha Rupaimoole, Volker K. Schulze, Clara Lemos, Kasia B. Handing, Douglas L. Orsi, Mrinal Shekhar, Ulrike Sack, Sven Christian, Wilhelm Bone, Ranad Humeidi, William Colgan, Stephanie Hoyt, Andrew Cherniack, Jens Schroder, Stefan Kaulfuss, Krzysztof Brzezinka, Oliver von Ahsen, Anne Mengel, Roman C. Hillig, Detlev Suelzle, Jeremie Mortier, Caitlin Harrington, Rohith Nagari, Justyna Wierzbinska, Derek Chiang, Georg Beckmann, Meagan Olive, Namrata Udeshi, Annie Apffel, Steven Carr, Philip Lienau, Christian Lechner, Ulf Boemer, Alisha Caliman, David McKinney, Florence Wagner, Dominik Mumberg, Marcus Bauser, Andrea Haegebarth, Knut Eis, Ashley Eheim, Todd R. Golub. Discovery of potent and selective CSNK1A1 inhibitors for solid tumor therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3588.

Abstract 1722: Enhancement of anti-tumor T-cell immunity by means of an oral small molecule targeting the intracellular immune checkpoint MAP4K1

Immune checkpoint blockade using antibodies targeting the cell surface expressed proteins CTLA-4, PD-1 and PD-L1 has revolutionized cancer care and its clinical impact in several indications has prompted a search for complementary immunostimulatory approaches that can further increase the efficacy of these drugs. Mitogen-activated protein kinase kinase kinase kinase 1 (MAP4K1; HPK1), a serine/threonine kinase expressed exclusively in hematopoietic cell lineages, mediates a negative feedback signal downstream of T-cell receptor stimulation. Its activity is enhanced by PGE2 and TGFβ, factors commonly present in the tumor microenvironment. Mice deficient for MAP4K1 or expressing a kinase-dead variant of MAP4K1 exhibit enhanced T-cell function, including increased anti-tumor immunity. We developed the small molecule inhibitor BAY-405 that displays potent nanomolar MAP4K1 inhibition in biochemical and cellular assays, good kinase selectivity, and in vivo exposure after oral dosing. Pharmacological inhibition of MAP4K1 enhances T-cell immunity and overcomes the suppressive impact of PGE2, TGFβ and CD4+ T-regulatory cells. Single agent treatment of tumor-bearing mice results in suppression of tumor outgrowth in several syngeneic models. This is accompanied by an increase in the anti-tumor T-cell response, dependent on an intact T-cell compartment, while not involving direct anti-tumor cytotoxicity. Inhibition of MAP4K1 in conjunction with PD-L1 blockade results in further suppression of tumor outgrowth. Moreover, we found that MAP4K1 is expressed in both PD-L1-high and PD-L1-low human cancers. In summary, our data show that selective inhibition of MAP4K1 by means of small molecule drugs may be used to expand the patient population responding to immune checkpoint inhibition.

Citation Format: Gabriele Leder, Rafael Carretero, Jeffrey Mowat, Sandra Berndt, Roland Neuhaus, Nuria Aiguabella Font, Ulf Boemer, Oliver von Ahsen, Uwe Eberspaecher, Judith Guenther, Mareike Grees, Corinna Link, Barbara Nicke, Daniel Baumann, Martina Schaefer, Mine Oezcan-Wahlbrink, Nicolas D. Werbeck, Ingo Hartung, Bertolt Kreft, Rienk Offringa. Enhancement of anti-tumor T-cell immunity by means of an oral small molecule targeting the intracellular immune checkpoint MAP4K1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1722.

Abstract 1470: Preclinical activity of the first reversible, potent and selective inhibitor of EGFR exon 20 insertions

Several targeted therapeutic options exist for non-small cell lung cancer (NSCLC) patients whose tumors harbor mutations of EGFR, including L858R, exon 19 deletions, and the acquired resistance mutation, T790M. However, there is no approved targeted therapy for patients with EGFR exon 20 insertions, highlighting an ongoing unmet medical need. Here, we describe a potent and selective inhibitor of EGFR exon 20 insertion mutants with decreased activity on the wild-type EGFR for an improved therapeutic window. Our compound, BAY-568, exhibits greater than 20-fold selectivity for EGFR exon 20 insertions compared to wild-type EGFR in isogenic Ba/F3 models and in cancer cell lines endogenously expressing EGFR exon 20 insertions. This activity is also observed in xenograft models in vivo, correlating with reductions in phospho-EGFR and phospho-Erk in tumors but not skin samples from treated mice. BAY-568 furthermore has even greater activity towards the “classical” erlotinib-sensitive mutations, L858R and exon 19 deletions. Importantly, our compound is reversible, differentiating it from other investigational compounds currently in clinical trials. Consistent with this, the presence of a C797S mutation, typically found in patients with acquired resistance to osimertinib, has no effect on the activity of BAY-568. Taken together, these results demonstrate the ability of BAY-568 to kill cancer cells harboring exon 20 insertions and other EGFR mutations with decreased activity on wild-type EGFR, irrespective of C797S mutation status.

Citation Format: Franziska Siegel, Stephan Siegel, Keith Graham, Bethany Kaplan, Kirstin Petersen, Ulf Boemer, Uwe Eberspaecher, Daniel Korr, Ursula Moenning, Detlev Suelzle, Jens Schroeder, Florian Prinz, Sabine Zitzmann-Kolbe, Gizem Karsli-Uzunbas, Timothy Lewis, Mario Hermsen, Andrew Cherniack, Franz von Nussbaum, Knut Eis, Matthew Meyerson, Heidi Greulich. Preclinical activity of the first reversible, potent and selective inhibitor of EGFR exon 20 insertions [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1470.

Rogaratinib: A potent and selective pan-FGFR inhibitor with broad antitumor activity in FGFR-overexpressing preclinical cancer models

Aberrant activation in fibroblast growth factor signaling has been implicated in the development of various cancers, including squamous cell lung cancer, squamous cell head and neck carcinoma, colorectal and bladder cancer. Thus, fibroblast growth factor receptors (FGFRs) present promising targets for novel cancer therapeutics. Here, we evaluated the activity of a novel pan‐FGFR inhibitor, rogaratinib, in biochemical, cellular and in vivo efficacy studies in a variety of preclinical cancer models. In vitro kinase activity assays demonstrate that rogaratinib potently and selectively inhibits the activity of FGFRs 1, 2, 3 and 4. In line with this, rogaratinib reduced proliferation in FGFR‐addicted cancer cell lines of various cancer types including lung, breast, colon and bladder cancer. FGFR and ERK phosphorylation interruption by rogaratinib treatment in several FGFR‐amplified cell lines suggests that the anti‐proliferative effects are mediated by FGFR/ERK pathway inhibition. Furthermore, rogaratinib exhibited strong in vivo efficacy in several cell line‐ and patient‐derived xenograft models characterized by FGFR overexpression. The observed efficacy of rogaratinib strongly correlated with FGFR mRNA expression levels. These promising results warrant further development of rogaratinib and clinical trials are currently ongoing (ClinicalTrials.gov Identifiers: NCT01976741, NCT03410693, NCT03473756).

What's new?

Deregulated fibroblast growth factor receptor (FGFR) signaling is involved in tumorigenesis and cancer progression. Here, the authors report on a novel pan‐FGFR inhibitor, rogaratinib, that potently and highly selectively prevents the activity of FGFRs 1, 2, 3, and 4. Rogaratinib inhibits cell proliferation in various FGFR‐addicted cancers in vitro, including colon, lung, and bladder cancer. Rogaratinib also exhibits strong in vivo efficacy in several cell line‐ and patient‐derived xenograft models characterized by FGFR mRNA overexpression with good tolerability. Altogether, these data warrant the further development of rogaratinib for treatment of cancers with FGFR alterations, and clinical trials are currently ongoing.

Discovery and Characterization of the Potent and Highly Selective (Piperidin-4-yl)pyrido[3,2- d]pyrimidine Based in Vitro Probe BAY-885 for the Kinase ERK5

The availability of a chemical probe to study the role of a specific domain of a protein in a concentration- and time-dependent manner is of high value. Herein, we report the identification of a highly potent and selective ERK5 inhibitor BAY-885 by high-throughput screening and subsequent structure-based optimization. ERK5 is a key integrator of cellular signal transduction, and it has been shown to play a role in various cellular processes such as proliferation, differentiation, apoptosis, and cell survival. We could demonstrate that inhibition of ERK5 kinase and transcriptional activity with a small molecule did not translate into antiproliferative activity in different relevant cell models, which is in contrast to the results obtained by RNAi technology.

Abstract 1887: Preclinical evaluation of a novel interleukin-1 receptor-associated kinase 4 (IRAK4) inhibitor in combination with PI3K inhibitor copanlisib or BTK inhibitors in ABC-DLBCL

Activated B-cell-like diffuse large B-cell lymphoma (ABC-DLBCL) is frequently characterized by aberrant activation of both B-Cell Receptor (BCR) & TLR/MYD88 signaling pathways. Constitutive BCR signaling via Bruton's tyrosine kinase (BTK) and PI3K pathways leads to downstream activation of NF-κB and AKT signaling. In addition, IRAK4 mediated activation of the TLR/MYD88 pathway further activates NF-κB signaling and pro-survival pathways. Simultaneous blockade of TLR/MYD88 signaling via IRAK4 inhibition in combination with pharmacological blockade of PI3K/BCR signaling pathways may therefore provide a novel treatment strategy in ABC-DLBCL.

BAY 1830839 is a novel small molecule inhibitor of IRAK4 identified by a medicinal chemistry optimization program. Key features of the compound are high potency (IC50 of 3 nM) in a biochemical assay, excellent kinase selectivity and a good overall PK profile making the compound a valuable tool for in vivo studies.

In vitro, treatment of IRAK4 inhibitor BAY 1830839 in combination with BTK inhibitors or copanlisib, a pan class I PI3K inhibitor with predominant activity towards PI3Kα and PI3Kδ, synergistically inhibited NF-κB activation and cell viability in human ABC-DLBCL cell lines. In vivo, IRAK4 inhibition alone did not exhibit anti-tumor effects but in combination treatment with ibrutinib, a covalent inhibitor of BTK, synergistic anti-tumor activity with significantly improved efficacy over ibrutinib monotherapy was observed in the human ABC-DLBCL xenograft models TMD-8 and OCI-LY10 (MYD88mut/CD79A/Bmut). Moreover, IRAK4 inhibitor BAY 1830839 showed synergistic anti-tumor activity in combination with copanlisib with significant improvement of copanlisib monotherapy efficacy in the ABC-DLBCL PDX models LY2988 and LY2266 (MYD88mut/CD79A/Bmut and MYD88wt/CD79A/Bwt, respectively). In addition, the combination of IRAK4 inhibition with pharmacological blockade of PI3K-/ BCR signaling led to reduced activity of the downstream pro-survival STAT3 pathway and IL-6/IL-10 production as detected in tumor xenografts, validating our biological rationale and the expected mechanism of action.

In summary, IRAK4 inhibition in combination with pharmacological blockade of PI3K or BCR signaling blocks pro-survival NF-κB & JAK-STAT pathway activation and subsequent IL-6/IL-10 production. Enhancing activity of clinically used PI3K or BTK inhibitors by combination with IRAK4 inhibition indicates a potential new treatment approach for ABC-DLBCL patients progressing on Standard of Care therapy.

Citation Format: Martin Lange, Antje Margret Wengner, Ulrich Bothe, Ulf Boemer, Reinhard Nubbemeyer, Holger Siebeneicher, Holger Steuber, Judith Guenther, Lisette Potze, Nicole Schmidt, Oliver Politz, Wolf-Dietrich Doecke, Eleni Lagkadinou, Thomas M. Zollner, Franz von Nussbaum, Dominik Mumberg, Andreas Steinmeyer, Michael Brands, Karl Ziegelbauer. Preclinical evaluation of a novel interleukin-1 receptor-associated kinase 4 (IRAK4) inhibitor in combination with PI3K inhibitor copanlisib or BTK inhibitors in ABC-DLBCL [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1887.

Abstract 341: Preclinical mode of action and anti-tumor efficacy of the selective MKNK1 inhibitor BAY 1143269 in NSCLC models

MKNK1 (MAP kinase-interacting serine/threonine-protein kinase, also known as Mnk1) is activated by the mitogen-activated protein kinases ERK1/2 and p38. Thus, MKNK1 signaling is involved in the cellular response to environmental stress factors and cytokines. Of particular interest, MKNK1 kinase regulates mRNA translation by phosphorylating the translation initiation factor eIF4E (eukaryotic translation initiation factor 4E), known to be critical for malignant transformation but shown to be dispensable for translation in normal cells. Phosphorylated eIF4E levels were found to be elevated in several cancer tissues, including lung cancer. MKNK1 is also involved in resistance mechanisms to cancer therapeutics. Thus, the inhibition of MKNK1 activity may provide an innovative approach for anti-cancer therapy, and in particular for lung cancer, the main cancer-related cause of death worldwide. BAY 1143269 is a potent and selective MKNK1 inhibitor and inhibits eIF4E phosphorylation and reduces MKNK1-regulated translational downstream targets in non-small cell lung cancer (NSCLC) cell lines. In this study, BAY 1143269-mediated effects on molecular mechanisms in lung cancer models were analyzed.

Epithelial-mesenchymal transition (EMT) is associated with the pathogenesis of numerous lung diseases including cancer progression, metastasis and resistance. BAY 1143269 reduced expression of EMT key regulators like Snail1 and cellular junction components, as well as reduced TGFβ1-induced EMT. Accumulating evidence suggests a role for proinflammatory cytokines in the development and progression of cancer; increased serum concentrations of cytokines like interleukin 6 (IL-6) are associated with diminished lung cancer survival rates. BAY 1143269 reduced the secretion of several proinflammatory cytokines, including TNFα and IL-6 in whole blood, and affected IFN-stimulated gene expression in cell lines.

Consistent with the observed effects in vitro, BAY 1143269 showed significant anti-tumor effects in vivo in cell line as well as patient derived NSCLC xenograft models in monotherapy. In combination with chemotherapeutics approved for treatment of NSCLC, BAY 1143269 improved anti-tumor effects in comparison to chemotherapy alone.

In conclusion, BAY 1143269 has the potential to provide therapeutic benefit in NSCLC. A phase I study of BAY 1143269 in combination with docetaxel for subjects with advance solid tumors is ongoing (NCT02439346).

Citation Format: Susann Santag, Franziska Siegel, Antje M. Wengner, Claudia Lange, Ulf Boemer, Knut Eis, Florian Puehler, Martin Michels, Franz von Nussbaum, Karl Ziegelbauer, Dominik Mumberg, Kirstin Petersen. Preclinical mode of action and anti-tumor efficacy of the selective MKNK1 inhibitor BAY 1143269 in NSCLC models. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 341.

Abstract 4332: Discovery of BAY 1163877 - A pan-FGFR inhibitor: De novo structure-based design and lead optimization of benzothiophenyl-pyrrolotriazines

Fibroblast growth factors (FGFs) orchestrate a variety of cellular functions by binding to their transmembrane tyrosine-kinase receptors (FGFR1-4) and activating downstream signaling pathways. Alterations in FGFR encoding genes are frequently observed in a variety of solid tumors including lung, gastric, breast and urothelial cancer. Therefore, targeting FGFRs using selective FGFR inhibitors is an attractive therapeutic approach to treat cancer patients.

BAY 1163877 is an orally active, highly potent and selective small molecule FGFR-1, -2 and -3 kinase inhibitor. We disclose for the very first time its discovery and chemical structure. BAY 1163877 was derived from a de novo structure-based design approach and medicinal chemistry optimization. Data on the structure activity relationship and the pharmacokinetic profile of the benzothiophenyl-pyrrolotriazine structure class will be presented. Based on its favorable preclinical profile, BAY 1163877 is currently being investigated in a Phase 1 clinical trial (NCT01976741).

Citation Format: Marie-Pierre L. Collin, Mario Lobell, Walter Huebsch, Dirk Brohm, Mélanie Héroult, Klemens Lustig, Sylvia Gruenewald, Ulf Boemer, Rolf Jautelat, Holger Hess-Stump, Stefan Jaroch, Michael Brands, Karl Ziegelbauer. Discovery of BAY 1163877 - A pan-FGFR inhibitor: De novo structure-based design and lead optimization of benzothiophenyl-pyrrolotriazines. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4332.

Abstract 379: Allosteric AKT1/2-inhibitor BAY 1125976 as potent inhibitor in luminal breast cancer resistant to antihormone therapy

The PI3K-AKT-mTOR signaling cascade is one of the major drivers in the development of cancer. It is constitutively activated in many types of cancers and is one of the prominent pathways that promote tumor cell survival and confers resistance to antihormonal therapies for patients with breast cancer.

Breast cancer has been classified into at least four distinct subtypes, based on molecular profiling. Luminal-B breast cancer, although still expressing the hormone receptor, has been identified as relatively insensitive to endocrine therapy and is an entity with highest need for novel treatments and combination approaches. Despite the notable improvements in endocrine therapy, the invariable appearance of endocrine resistance, either primary or secondary, remains an important issue in this type of tumor. Main cancer signaling pathways, including PI3K/Akt/mTOR and CCND1/CDK4-6, are thought to play an important role in development of this resistance.

Therefore AKT is considered an attractive drug target for the treatment of breast cancer. BAY 1125976, an orally active, potent, highly selective, allosteric AKT1/2 inhibitor is currently in phase I clinical development (NCT01915576). BAY 1125976 is particularly effective in preclinical models with PI3K-AKT pathway aberrations and luminal B status as shown by profiling in a panel of tumor cell lines as well as respective in vivo studies. The efficacy of BAY 1125976 in inhibition of cell proliferation is correlated with luminal status of the tumor as shown in several cell line panels. In vitro combination with anti-hormonal therapeutics showed synergistic anti-proliferative effects and rendered resistant cell lines sensitive towards tamoxifen or fulvestrant treatment. In the MCF-7 cell line tamoxifen combined with BAY 1125976 resulted in a 14 fold reduction of the IC50 for inhibition of cell proliferation compared to monotherapy. This translated into additive to synergistic activity in combination with tamoxifen in a ER+ MCF7 (PIK3CAE545K) BC model and enabled the use of alternative dosing schedules with improved efficacy versus monotherapy.

BAY 1125976 also showed potent inhibition of tumor cell growth in a tamoxifen- and fulvestrant-resistant derivate of MCF-7 enabling a reduction of the therapeutic dose of BAY 1125976 and thereby improving tolerability while keeping efficacy.

Combination of the allosteric AKT inhibitor BAY 1125976 therefore provides an interesting opportunity in improving efficacy of antihormonal therapy in luminal B type breast cancer.

Citation Format: Oliver Politz, Lars Baerfacker, Stuart Ince, Andrea Haegebarth, Ningshu Liu, Roland Neuhaus, Ulf Boemer, Martin Michels, Karl Ziegelbauer, Dominik Mumberg. Allosteric AKT1/2-inhibitor BAY 1125976 as potent inhibitor in luminal breast cancer resistant to antihormone therapy. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 379.

Abstract DDT02-02: BAY 1143572: A first-in-class, highly selective, potent and orally available inhibitor of PTEFb/CDK9 currently in Phase I, inhibits MYC and shows convincing anti-tumor activity in multiple xenograft models by the induction of apoptosis

PTEFb/CDK9 mediated transcription of short-lived anti-apoptotic survival proteins like MYC, a key oncogene in multiple tumors, plays a critical role in cancer cell growth and survival. In addition, these survival proteins exhibit important functions in the development of resistance to chemotherapy.

In contrast to pan-CDK inhibitors which are currently evaluated in Phase I and II clinical trials, to our knowledge PTEFb selective inhibitors have not been explored for clinical utility. We report for the first time the preclinical profile and structure of BAY 1143572, a novel selective PTEFb/CDK9 inhibitor currently being investigated in a Phase I clinical trial.

BAY 1143572 had potent and highly selective PTEFb-kinase inhibitory activity in the low nanomolar range against PTEFb/CDK9 and an at least 50-fold selectivity against other CDKs in enzymatic assays. Furthermore, BAY 1143572 showed a favorable selectivity against a panel of non-CDK kinases in vitro. The potent enzymatic activity on PTEFb translated into broad antiproliferative activity against a panel of tumor cell lines with sub-micromolar IC-50 values. In line with the proposed mode of action, a concentration-dependent inhibition of the phosphorylation of the RNA polymerase II and downstream reduction of MYC mRNA and protein levels was observed in vitro. This inhibition was accompanied by an induction of apoptosis in cellular assays.

BAY 1143572 also showed single agent in vivo efficacy at tolerated doses in various xenograft tumor models in mice and rats upon once daily oral administration. Potent anti-tumor activity characterized with partial or even complete remissions could be documented in models showing different MYC gene alterations like amplifications and translocations. Treatment with BAY 1143572 resulted in a transient inhibition of intratumoral MYC mRNA and protein levels and an induction of apoptosis in these models. The inhibition of MYC mRNA was also observed in blood cells of BAY 1143572-treated rats indicating the potential clinical utility of MYC in blood cells as a pharmacodynamic marker in clinical development. The in vivo efficacy of BAY 1143572 was significantly enhanced in combination with several chemotherapeutics in different solid tumor models. These pharmacology data provided the rationale for the initiation of clinical development of BAY 1143572 in advanced cancer patients (NCT01938638).

In conclusion, our data provide preclinical proof of concept for BAY 1143572 as a potent and highly selective inhibitor of PTEFb/CDK9 with first-in-class potential. Further clinical evaluation of BAY 1143572 for the treatment of cancers dependent on the transcription of the key oncogene MYC and other short-lived survival proteins is warranted.

Citation Format: Arne Scholz, Ulrich Luecking, Gerhard Siemeister, Philip Lienau, Ulf Boemer, Peter Ellinghaus, Annette O. Walter, Ray Valencia, Stuart Ince, Franz von Nussbaum, Dominik Mumberg, Michael Brands, Karl Ziegelbauer. BAY 1143572: A first-in-class, highly selective, potent and orally available inhibitor of PTEFb/CDK9 currently in Phase I, inhibits MYC and shows convincing anti-tumor activity in multiple xenograft models by the induction of apoptosis. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr DDT02-02. doi:10.1158/1538-7445.AM2015-DDT02-02

Abstract 3685: BAY 1125976, is a selective allosteric AKT1/2 inhibitor with high efficacy in AKT1-mutated cancers

The PI3K-AKT-mTOR signaling cascade is activated in human cancers by elevated membrane receptor activity, mutation, amplification, and deletion of genes encoding components of the pathway. An oncogenic, single hotspot mutation in the AKT1 gene, G49A:E17K, in the pleckstrin homology domain of AKT1, was described in human cancers with highest relative incidence in breast cancer. The E17K mutation in AKT1 results in PI3K-independent membrane recruitment of AKT1.

Recently we reported the development of a highly selective, potent allosteric AKT1/2 inhibitor BAY 1125976 with strong in vitro and in vivo activity in tumor models with activated AKT signaling and strong synergistic activity in combination.

The efficacy of BAY 1125976 was evaluated in tumor models carrying activation of the PI3K-AKT pathway by either deletion of PTEN or activating mutation in PI3K.

We investigated whether BAY 1125976 can also inhibit AKT signaling in cell lines carrying an activating mutation in AKT. To this extend, KU-19-19 (AKT1E17K; NRASQ61R) bladder cancer as well as LAPC4 (AKT1E17K) prostate cancer cell lines both bearing the AKT1E17K mutation were profiled. BAY 1125976 potently inhibited AKT activation as well as downstream signaling in KU-19-19 and LAPC4 cells.

Furthermore, anti-tumor efficacy of BAY 1125976 was tested in the patient-derived anal cancer xenograft AXF 984 (AKT1E17K). BAY 1125976 shows dose-dependent potent pathway activity in AKT1mut patient derived tumor model with inhibition of pAKT473 as well as downstream targets p- PRAS40 and p-FOXO3a compared to selected PI3K, AKT and mTOR inhibitors.

Continuous daily treatment of AXF 984 (AKT1E17K) mouse xenografts with 25 mg/kg and 50 mg/kg QD p.o. BAY 1125976 resulted in very potent statistically significant anti-tumor efficacy. All animals of these treatment groups exhibited tumor shrinkage or disease control with response rates of 88% and 83%, respectively. Furthermore, for animals treated with 50 mg/kg BAY 1125976 the delay of reaching a relative tumor volume of 600% was statically significant compared to the vehicle-treated control group.

In summary, BAY 1125976 showed superior anti-tumor activity in AKT1E17K mutated models compared to PI3K and mTOR inhibitors. These results indicate that the clinical development of BAY 1125976 in patients with activating mutation in AKT could result in an innovative and more effective alternative to current treatments.

Citation Format: Oliver Politz, Arne Scholz, Andrea Haegebarth, Ningshu Liu, Lars Baerfacker, Stuart Ince, Roland Neuhaus, Ulf Boemer, Martin Michels, Dominik Mumberg. BAY 1125976, is a selective allosteric AKT1/2 inhibitor with high efficacy in AKT1-mutated cancers. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3685. doi:10.1158/1538-7445.AM2014-3685

Abstract 2050: BAY 1125976, a highly selective and potent allosteric AKT1/2 inhibitor, for the treatment of cancers with aberrations in the PI3K-AKT-mTOR pathway

The PI3K/AKT/mTOR pathway is frequently activated in human cancer. AKT, a central element in the pathway, is essential for tumor growth, proliferation, survival, invasion and metastasis. Activation of AKT is a key mechanism in resistance to chemo-, radio- and targeted therapies. Thus, AKT is considered an attractive drug target. Herein, we report on the preclinical profile and combinability of BAY 1125976, a potent, highly selective, allosteric AKT1/2 inhibitor, which is particularly effective in models with PI3K-AKT pathway aberrations. In biochemical assays, BAY 1125976 demonstrates equal potency against AKT1 and AKT2 in the low nanomolar range (IC50 ∼ 10 nM) while it displays weaker activity against AKT3 (IC50 ∼ 500 nM) and is inactive against ∼230 other protein/ lipid kinases (IC50 > 1 μM). Mechanistically, BAY 1125976 blocks AKT signalling by inhibiting the phosphorylation of AKT at both Thr308 and Ser473 (IC50 < 1 nM), as well as downstream phosphorylation of 4E-BP1 (IC50 < 50 nM). The strong inhibition of cellular p-AKT and downstream signalling translates to a broad inhibition of tumor cell proliferation in vitro. In particular, tumor cell lines carrying defects in the tumor suppressor PTEN, or oncogenic mutations in PIK3CA are most sensitive to BAY 1125976 treatment. Daily oral dosing of BAY 1125976 in human xenograft tumor models induces strong pharmacodynamic inhibition of AKT phosphorylation that correlates with drug exposure. In vivo, BAY 1125976 demonstrates dose-dependent anti-tumor efficacy in multiple xenograft tumor models of different histological types with PIK3CA mutations or PTEN deletions while being well tolerated. BAY 1125976 can be effectively combined with various anti-cancer therapies. In vitro combination profiling shows synergistic anti-proliferative effects with anti-hormonal therapeutics in breast and prostate cancer cell lines, which translates to enhanced anti-tumor efficacy with durable tumor regressions in vivo. Furthermore, in vivo combination of BAY 1125976 with external beam radiation results in strong additive to synergistic efficacy and significant tumor growth delay. Moreover, the combination of BAY 1125976 with the bone-targeting agent Radium 223 in a breast cancer bone metastasis model results in reduced tumor and metastases burden and increased necrotic and fibrotic bone area. In conclusion, BAY 1125976 is a highly selective, potent allosteric AKT1/2 inhibitor with strong in vitro and in vivo activity in tumor models with activated AKT signalling and strong synergistic activity in combination. Targeting AKT might also provide a promising strategy for overcoming chemo/radio-resistance and increasing radio-sensitization and radio-potentiation.

Citation Format: Oliver Politz, Lars Baerfacker, Stuart Ince, William J. Scott, Roland Neuhaus, Ulf Boemer, Martin Michels, Dominik Mumberg, Franz von Nussbaum, Karl Ziegelbauer, Andrea Haegebarth. BAY 1125976, a highly selective and potent allosteric AKT1/2 inhibitor, for the treatment of cancers with aberrations in the PI3K-AKT-mTOR pathway. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2050. doi:10.1158/1538-7445.AM2013-2050

Preclinical characterization of a novel class of 18F-labeled PET tracers for amyloid-β

Imaging of amyloid-β (Aβ) plaques by PET is more and more integrated into concepts for Alzheimer disease (AD) diagnosis and drug development. The objective of this study was to find novel chemical entities that can be transformed into (18)F-labeled Aβ tracers with favorable brain washout kinetics and low background signal.

METHODS

High-throughput screening of a large chemical library was used to identify new ligands for fibrillar aggregates of Aβ(1-42) peptide. Thirty-two fluorinated derivatives were synthesized and tested for their affinity toward AD brain homogenate. Twelve ligands have been radiolabeled with (18)F. The pharmacokinetic properties of the radioligands were investigated in mouse and monkey biodistribution studies. Binding characteristics were determined by autoradiography of AD brain sections in vitro and using amyloid precursor protein transgenic mice in vivo.

RESULTS

The systematic search for Aβ imaging agents revealed several fluorinated derivatives with nanomolar affinity for Aβ. The fluoropyridyl derivative BAY 1008472 showed a high initial brain uptake (6.45 percentage injected dose per gram at 2 min) and rapid brain washout (ratio of percentage of injected dose per gram of tissue at 2 and 30 min after injection, 9.2) in mice. PET studies of healthy rhesus monkeys confirmed the high initial brain uptake of BAY 1008472 (2.52 standardized uptake value at peak) and a fast elimination of total radioactivity from gray and white matter areas (ratio of standardized uptake value at peak uptake and 60 min 11.0). In autoradiographic analysis, BAY 1008472 selectively detected Aβ deposits in human AD brain sections with high contrast and did not bind to τ- or α-synuclein pathologies. Finally, ex vivo autoradiography of brain sections from amyloid precursor protein-transgenic mice confirmed that BAY 1008472 is indeed suitable for the in vivo detection of Aβ plaques.

CONCLUSION

A new chemical class of Aβ tracers has been identified by high-throughput screening. The fluoropyridyl derivative BAY 1008472 shows a favorable preclinical profile including low background binding in gray and white matter. These properties might qualify this new tracer, in particular, to detect subtle amounts or changes of Aβ burden in presymptomatic AD and during therapy.

Abstract 3751: In vitro and in vivo pharmacological profile of BAY 1001931, a novel highly potent allosteric AKT1/2 inhibitor

The PI3K/AKT/mTOR pathway is essential for tumor growth, proliferation, survival, invasion and metastasis. AKT, a central switch in this pathway, is deregulated in a broad range of refractory and primary tumors. Importantly, activation of AKT is one of the major mechanisms by which tumors escape from and become resistant to chemo-, radio- and targeted therapies. We report on preclinical studies of BAY 1001931, a highly selective and potent allosteric AKT1/2 inhibitor. In biochemical assays, BAY 1001931 inhibits AKT1 and AKT2 with similar potency (IC50 = 16 nM) while it displays weak activity against AKT3 (IC50 ∼ 1 µM) and is inactive against ∼230 other protein/ lipid kinases. Mechanistically, BAY 1001931 blocks AKT signalling by inhibiting the phosphorylation of AKT at both Thr308 and Ser473 (IC50 = 3.3 / 5.5 nM) as well as downstream phosphorylation of 4E-BP1 (IC50 = 70 nM). The strong inhibition of cellular p-AKT translates to a selective inhibition of tumor cell proliferation in vitro. Cell lines carrying defects in the tumor suppressor PTEN or oncogenic mutations in PIK3CA are most sensitive to BAY 1001931 treatment. Moreover, characterization of BAY 1001931 in a broader breast and prostate cancer cell line panel indicated strongest anti-proliferative efficacy in luminal and HER2 positive breast cancer cell lines and in androgen sensitive prostate cancer cell lines. In vitro combination profiling showed synergistic anti-proliferative effects with anti-hormonal therapeutics in breast and prostate cancer cell lines. When dosed orally in human xenograft tumor models, BAY 1001931 induced strong pharmacodynamic inhibition of AKT phosphorylation that correlated with drug exposure. BAY 1001931 was highly efficacious in multiple xenograft tumor models of different histological types with PIK3CA mutations or PTEN deletions. In tumor models predicted to be dependent on activated AKT signalling such as the KPL4 breast tumor model (PIK3CA H1047R and HER2 overexpression), daily oral treatment with BAY 1001931 induced tumor stasis or regression at well tolerated doses. Most importantly, when combined with anti-hormonal therapies such as tamoxifen in PIK3CA breast cancer xenograft models or bicalutamide or abiraterone acetate in PTEN deleted prostate cancer xenograft models, enhanced anti-tumor efficacy with durable tumor regressions were observed. In conclusion, BAY 1001931 is a highly selective, potent allosteric AKT1/2 inhibitor with strong in vitro and in vivo activity in tumor models with activated AKT signalling and strong synergistic activity in combination with anti-hormonals in breast and prostate cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3751. doi:1538-7445.AM2012-3751

Abstract 2799: BAY 1082439, a highly selective and balanced PI3Kα/β inhibitor demonstrated potent activity in tumors with activated PI3Kα and loss-of-function of PTEN

The PI3K pathway plays critical roles in cancer cell growth and survival, as well as in intrinsic and acquired resistance to both chemotherapy and targeted agents. These essential roles have led to the clinical development of PI3K pathway inhibitors. Due to the complexity derived from the existence of various PI3K isoforms (≥,α,α,α), and their differential roles in signal transduction, as well as cancer pathology, development of PI3K inhibitors with differential pharmacological profiles would allow exploration in different indications, combinations and dosing regimens. Having identified BAY 80-6946, an intravenously dosed, highly potent and selective PI3K inhibitor which is particularly effective in PIK3CAmut and/or Her2+ tumors, we sought to develop a novel oral PI3K inhibitor particularly effective in PTEN-loss tumors with coexisting mutation or amplification of PIK3CA and/or activation of PI3Kα (e.g., through RTKs). Herein we report the pharmacological profile of a highly selective PI3Kα/α-balanced inhibitor, BAY 1082439. BAY 1082439 has an IC50 ratio of 1:3 in biochemical assays of PI3Kα (4.9 nM) vs. PI3Kα (15.0 nM), and >1000-fold selectivity against mTOR kinase. The balanced PI3Kα and PI3Kα activity of BAY 1082439 is also reflected in cellular mechanistic (p-AKT473) and proliferation assays in PI3Kα- (KPL4, BT474) vs. PI3Kα-driven (PC3, LNCaP) tumor cells. In vivo, BAY 1082439 showed clear advantages over the strong PI3Kα inhibitor BAY 80-6946 in PTEN/PI3Kα-driven tumor models (e.g., PC3 and HEC-1B), when the two compounds were compared at their MTDs. Furthermore, BAY 1082439 has unique pharmacokinetic (PK) properties with very high plasma free fractions across all species tested (33-50%), large Vss, high clearance and intermediate T1/2. The relationship of PK vs. PD and the efficacy vs. dosing regimens were investigated. BAY 1082439 showed strong p-AKT inhibition at 2 and 5 hours post-treatment while p-AKT returned to levels comparable to the vehicle group at 24 hours in all 4 tumor models tested. Interestingly, with once daily dosing, BAY 1082439 could induce tumor regression in KPL4 (PIK3CAmut and HER2+), and tumor stasis in HEC-1B (PTENdel) and in HEC-1A (PIK3CAmut) tumor models, suggesting that continuous inhibition of p-AKT may not be required for anti-tumor efficacy. In addition, comparison of different dosing regimens (QD, Q2D, D1-2/W, D1-3/W, D1-4/W to QW) at MTD indicated that QD and QW dosing produced optimal anti-tumor efficacy. These results support the hypothesis that strong pathway inhibition for a certain time period, rather than maintaining constant inhibition might lead to optimal anti-tumor efficacy along with a maximal therapeutic window. In conclusion, BAY 1082439 represents a new type of PI3K inhibitor with unique pharmacological and pharmacodynamic properties to be further explored in clinical development.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2799. doi:1538-7445.AM2012-2799