752 Novel, orally administered HPK1 inhibitors demonstrate anti-tumor efficacy and enhanced immune response

Background

Hematopoietic progenitor kinase 1 (HPK1, MAP4K1) is emerging as a well-renowned, druggable target for T cell-based immunotherapies. HPK1 is a member of the serine/threonine MAP4K family, predominantly expressed in hematopoietic cell lineages and shown to be a negative regulator of the T cell receptor (TCR) signaling pathway. Upon TCR activation, HPK1 is recruited to the proximity of the cell membrane and phosphorylates an adaptor protein SLP-76 at the Ser376 residue which, in turn, abrogates TCR signaling. Other studies point to a potential role of HPK1 in T cell exhaustion as well as in functional re-programming of regulatory T cells. Moreover, mounting evidence suggest that HPK1 kinase activity suppresses the immune functions of a wide range of other immune cell subsets like B cells and dendritic cells. Taken together, these observations support small-molecule HPK1 inhibitors as an attractive modality in cancer immunotherapy either as single agents or in combination with immune checkpoint inhibitors.

Methods

Activity of compounds against HPK1 and selected off- and anti-targets was assessed in biochemical assays. Phosphorylation of SLP-76 was measured either by flow cytometry or TR-FRET. Jurkat and primary T cells were activated and cultured in the presence of tested compounds and immunosuppressive agents. Impact on TCR selectivity and T cell function was measured by AlphaLISA and flow cytometry. Target engagement was measured in splenocytes of mice administered orally with tested compounds followed by IP injection of aCD3 antibody. Anti-tumor efficacy of HPK1 inhibitors was assessed in a syngeneic tumor model.

Results

Ryvu's proprietary small molecule HPK1 inhibitors exhibit sub-nanomolar activity against human and mouse HPK1 proteins and good selectivity against other TCR pathway kinases. Tested compounds efficiently block phosphorylation of SLP-76 upon TCR engagement. TCR selectivity of Ryvu's inhibitors, measured as a ratio between CD69 and pSer376 SLP-76 inhibition, is on par or superior to reference molecules. Tested compounds are not only able to overcome PGE-2 induced resistance following TCR activation in human PBMCs, inducing elevated IL-2 release but also affect T cell function in co-culture assay. Developed molecules have favorable PK profiles, allowing for sustained target coverage in proposed dosing regimens and demonstrate efficacy in a mammary carcinoma syngeneic model.

Conclusions

Ryvu has developed potent and selective HPK1 inhibitors with favorable PK and PD profiles, whose activity in vitro translates to in vivo efficacy. Further preclinical work is warranted to select a lead candidate for IND-enabling studies and subsequently clinical studies across a variety of solid tumors.

Discovery of a series of ester-substituted NLRP3 inflammasome inhibitors

The NLRP3 inflammasome is a component of the innate immune system involved in the production of proinflammatory cytokines. Aberrant activation by a wide range of exogenous and endogenous signals can lead to chronic, low-grade inflammation. It has attracted a great deal of interest as a drug target due to the association with diseases of large unmet medical need such as Alzheimer's disease, Parkinson's disease, arthritis, and cancer. To date, no drugs specifically targeting inhibition of the NLRP3 inflammasome have been approved. In this work, we used the known NLRP3 inflammasome inhibitor CP-456,773 (aka CRID3 or MCC 950) as our starting point and undertook a Structure-Activity Relationship (SAR) analysis and subsequent scaffold-hopping exercise. This resulted in the rational design of a series of novel ester-substituted urea compounds that are highly potent and selective NLRP3 inflammasome inhibitors, as exemplified by compounds 44 and 45. It is hypothesized that the ester moiety acts as a highly permeable delivery vehicle and is subsequently hydrolyzed to the carboxylic acid active species by carboxylesterase enzymes. These molecules are greatly differentiated from the state-of-the-art and offer potential in the treatment of NLRP3-driven diseases, particularly where tissue penetration is required.

Inhibitory effects of SEL201 in acute myeloid leukemia

MAPK interacting kinase (MNK), a downstream effector of mitogen-activated protein kinase (MAPK) pathways, activates eukaryotic translation initiation factor 4E (eIF4E) and plays a key role in the mRNA translation of mitogenic and antiapoptotic genes in acute myeloid leukemia (AML) cells. We examined the antileukemic properties of a novel MNK inhibitor, SEL201. Our studies provide evidence that SEL201 suppresses eIF4E phosphorylation on Ser209 in AML cell lines and in primary patient-derived AML cells. Such effects lead to growth inhibitory effects and leukemic cell apoptosis, as well as suppression of leukemic progenitor colony formation. Combination of SEL201 with 5'-azacytidine or rapamycin results in synergistic inhibition of AML cell growth. Collectively, these results suggest that SEL201 has significant antileukemic activity and further underscore the relevance of the MNK pathway in leukemogenesis.

Abstract 1306: SEL120, a potent and specific inhibitor of CDK8 induces complete remission in human patient derived xenograft models of acute myeloid leukemia

Cyclin-dependent kinase 8 inhibitors (CDK8i) have anti-cancer activity in human acute myeloid leukaemia (AML) cell lines both in vitro and in vivo. Activity of CDK8i often involves deregulation of super-enhancer-associated genes in AML cell lines. Previous studies established SEL120 as a specific CDK8 inhibitor active in AML cells with increased STAT1/5 signalling pathways. Differential gene expression analysis demonstrated high enrichment of leukaemia stem cell (LSC) signatures in responding cells, linked to resistance to standard therapies and relapsed disease. Cells sensitive to SEL120 treatment were positive for CD34 and negative for lineage commitment surface markers. SEL120 markedly reduced STAT5 phosphorylation on serine 726 (STAT5 pS726) in sensitive cell lines. Prolonged SEL120 treatment led to significant downregulation of CD34 and induction of lineage commitment markers. Transcriptomic analysis revealed that SEL120 regulated many genes involved in differentiation and apoptosis. We observed synergistic effects of SEL120 with standard of care cytotoxic drugs such as cytarabine. Treatment of AML cells with cytarabine spared many CD34+ cells, which could be effectively eradicated by subsequent treatment with SEL120. Many cell lines which were resistant to SEL120 treatment could be sensitized by concomitant treatment with BH3 mimetic agent ABT-199. Combination of both compounds resulted in potent induction of apoptosis in AML cells in vitro and in vivo. Treatment of mice bearing subcutaneously implanted human leukaemia cell lines resulted in significant tumour growth inhibition, whereas cotreatment with ABT-199 led to complete regressions at doses which were vey well tolerated by animals. Next we have selected patient derived primary AML cells using gene expression signatures identifying SEL120 -responder cell lines. In these cells SEL120 significantly reduced viability, induced apoptosis and lineage commitment. Further, the same cells were implanted into NOD scid gamma mice. Animals succumbed to AML, diagnosed by a significant presence of human CD45/CD34 positive leukaemia cells in a peripheral blood and splenomegaly. Stand-alone treatment with SEL120 resulted in the complete remission of AML cells in a peripheral blood and bone marrow, and reduced spleen weight, without symptoms of compound-related toxicity. These results validate SEL120 as a promising agent in the treatment of AML.

Citation Format: Milena Mazan, Eliza Majewska, Michal Mikula, Katarzyna Wiklik, Michal Combik, Aniela Golas, Magdalena Masiejczyk, Elzbieta Fiedor, Anna Polak, Magdalena Cybulska, Aleksandra Grochowska, Michal Kopczynski, Urszula Kuklinska, Zuzanna Sandowska-Markiewicz, Malgorzata Statkiewicz, Agnieszka Paziewska, Michalina Dabrowska, Arkadiusz Bialas, Maciej Mikulski, Renata Windak, Jerzy Ostrowski, Przemyslaw Juszczynski, Krzysztof Brzozka, Tomasz Rzymski. SEL120, a potent and specific inhibitor of CDK8 induces complete remission in human patient derived xenograft models of acute myeloid leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1306.

CLI24-001: First-in-human study of SEL24/MEN1703, an oral dual PIM/FLT3 kinase inhibitor, in patients with acute myeloid leukemia

TPS7062

Background: FLT3-ITD is one of the most common genetic lesions in acute myeloid leukemia (AML). PIM kinases are oncogenic FLT3-ITD targets expressed in AML cells and increased PIM kinase expression is found in relapse samples from AML patients treated with FLT3 inhibitors. In addition, inhibition of PIM kinases restores sensitivity to FLT3 inhibitors and dual FLT3/PIM inhibition eradicates FLT3-ITD+ cells including primary AML cells. SEL24/MEN1703, a potent PIM/FLT3 dual inhibitor, demonstrates a significantly broader spectrum of activity in AML cell lines and primary AML blasts, irrespective of FLT3 status, compared to monotherapy with either FLT3 or PIM inhibitors such as quizartinib or AZD1208. Methods: CLI24-001 is a First in Human, open label, non-randomized, multi-center, Phase I/II dose-escalation and cohort expansion study of SEL24/MEN1703 in AML patients (excluding APL) not suitable for chemotherapy. SEL24/MEN1703 is given orally, QD, for 14 days in a 21-day cycle with cycles repeated until disease progression or unacceptable toxicity. Dose escalation follows a 3+3 design to identify the recommended phase 2 dose (RP2D). In the phase 2 part/cohort expansion, subjects will receive SEL24/MEN1703 at the RP2D, to further investigate the safety profile and signs of antileukemic activity. In both study parts, patients are eligible regardless of mutational status and/or prior exposure to FLT3 inhibitors; prior treatment with PIM inhibitors is not allowed. Main inclusion criteria comprise a white blood count (WBC) of ≤30 x 109/L (hydroxyurea/leukoapheresis permitted to lower WBC). Key secondary objectives include pharmacokinetics (PK) and single agent efficacy. The study is enrolling at 5 US sites and will be extended, both in US and EU, in the cohort expansion part. This is the first trial testing a dual PIM/FLT3 inhibitor with the potential to be active in AML regardless of FLT3 status andwith a potential to overcome FLT3 inhibitor resistance. (Sci Adv. 2015;1:e1500221; Oncotarget. 2018 Mar 30;9(24):16917-16931) Clinical trial information: NCT03008187.

Abstract 3516: Discovery of novel SHMT small molecule inhibitors for cancer treatment

Over-activation of the serine synthesis pathway, upregulation of SHMT2 has been described in over 20% of solid tumors (e.g. breast, lung, colorectal cancers). Such cancer cells are highly dependent on serine. Serine hydroxymethyltransferase (SHMT) plays a key role in a so-called one-carbon pathway, a group of biochemical reactions involved in amino acid metabolism. SHMT catalyzes the conversion of serine to glycine and also plays a role in the folate (vitamin B9) cycle. Antagonists of folate metabolism or antifolates are an established chemotherapy in certain cancers. Folate antagonism disrupts cell division, DNA/RNA synthesis and protein synthesis. Pemetrexed (for non-small cell lung carcinoma, mesothelioma) and methotreaxate (for autoimmune conditions like rheumatoid arthritis and certain cancers) are two well established and effective antifolates. The main drawback with antifolates in cancer treatment, however, is the development of resistance. In this study we report development of a series of small molecule SHMT1/2 inhibitors. Synthetized compounds exert potency in SHMT1/2 biochemical assay as well as in cellular assay (measured by the C13 serine to glycine conversion) with the low nanomolar range. Therapeutic effect of the compounds was investigated in the panel of cancer cell lines with different genetic background as well as with different SHMT2 levels. We identified several cell lines in which tested compounds inhibited cancer cell grow with nM GI50 values. Taken together, presented data supports our rationale for using SHMT1/2 inhibitors as a novel and interesting approach for the cancer therapy.

Citation Format: Anna Bartosik, Pawel Guzik, Marta Sowinska, Karolina Gluza, Marcin Krol, Anna Wrobel, Agnieszka Dreas, Faustyna Iwanska, Magdalena Zastawna, Urszula Kulesza, Nicolas Boutard, David Schultz, Justyna Wujkowska, Karolina Pyziak, Agnieszka Sroka-Porada, Agnieszka Przybylowicz, Agnieszka Adamus, Magdalena Sieprawska-Lupa, Przemyslaw Golik, Piotr Kowalczyk, Krzysztof Brzozka, Tomasz Rzymski, Mateusz Nowak. Discovery of novel SHMT small molecule inhibitors for cancer treatment [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 3516.

Abstract 5829: CDK8 inhibitor SEL120-34A targets CD34 positive AML cells by regulation of various transcriptional programs involved in maintenance of leukemia stem cells

Despite heterogeneity deregulated transcription is one of the universal features of leukemia cells. This has paved the way for the development of active compounds targeting epigenetic and transcriptional factors. A substituted tricyclic benzimidazole, SEL120-34A, is a novel inhibitor of Cyclin-dependent kinase 8 (CDK8), which regulates transcription by associating with the Mediator complex. In many cancer cells SEL120-34A regulates expression of STAT1- dependent genes as a major transcriptional effect. In AML cells regulation of NUP98-HOXA9 - dependent transcription and other transcriptional programs involved in maintenance of leukemia stem cells have been observed as a dominant mechanism of action. Treatment with the compound resulted in a differential efficacy on CD34 positive AML cells with elevated STAT5 S726 levels and stem cell characteristics. In contrast, resistant cells were negative for activated STAT5 and revealed lineage commitment. Prolonged exposure of AML cells lines to chemotherapy led to the enrichment in population of resistant CD34 positive cells, which proved to be oversensitive to SEL120-34A treatment, providing rationale for rational combinations with approved drugs. Further clinical development of SEL120-34A is warranted as a novel therapeutic approach in relapsed and refractory AML.

Citation Format: Eliza Majewska, Milena Mazan, Michal Mikula, Agnieszka Dreas, Katarzyna Wiklik, Aniela Golas, Katarzyna Wojcik, Magdalena Masiejczyk, Malgorzata Statkiewicz, Urszula Kuklinska, Krzysztof Goryca, Aleksandra Grochowska, Aleksandra Cabaj, Michal Combik, Jerzy Ostrowski, Krzysztof Brzozka, Tomasz Rzymski. CDK8 inhibitor SEL120-34A targets CD34 positive AML cells by regulation of various transcriptional programs involved in maintenance of leukemia stem cells [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 5829.

Abstract 442: Small molecule inhibitors of SHMT1/2 validate serine metabolism as a target in the treatment of c-Myc positive solid tumors

Many oncogenes modulate metabolic pathways and altered metabolism is one of the hallmarks of cancer. In order to sustain proliferation, cell growth and adopt to a very specific tumor microenvironment, cancer cells have to undergo metabolic reprogramming. Increased uptake of glucose, consumed in anaerobic manner, allows to maintain essential bioenergetic and biosynthetic pathways. Various reports indicated that many cancers cells are crucially dependent on serine, which could be either imported or synthesized by the serine synthesis pathway (SSP) branched from glycolysis. Serine can be converted to glycine by Serine Hydroxymethyltransferases isoforms 1 and 2 (SHMT1/2), which provide also carbon for the folate cycle. There is a growing interest in targeting SSP and SHMT1/2 have been proposed as druggable targets for the treatment of various cancers. One of the major challenges is validation of these concepts by high quality pharmacological and genetic tools, particularly in the context of high tumor heterogeneity, artificial tissue culture conditions and many branching points of tumor metabolism, which eventually result in acquired resistance. We have identified and characterized a series of sub micromolar dual SHMT1/2 inhibitors. Affinity of these compounds to protein targets has been confirmed in biochemical and binding assays and further corroborated by X-ray crystallography studies. In order to confirm efficacy of these compounds in cancer cells, both sensitive and resistant cells to the inhibition of SSP have been identified by using conditioned serine and glycine depleted media. Moreover functional roles of both paralogs: SHMT1, which fuels cytoplasmic folate cycle and SHMT2, which is responsible for the mitochondrial branch, were further confirmed by gene knockdown studies. Cell lines resistant to depletion of serine in cell culture media were characterized by elevated levels of proteins involved in the synthesis of serine, namely PHGDH, PSAT1, SHMT2, c-Myc amplification and increased 13C flux from glucose to serine and glycine. Metabolic flux analysis further indicated that treatment with presented SHMT1/2 inhibitors effectively blocked the production of glycine from glucose and serine in cancer cells. Viability studies confirmed anti-cancer efficacy of SHMT1/2 inhibitors at concentrations consistent with metabolic flux studies in the same cells. Moreover rescue experiments with media supplemented with glycine and formate, which is a crucial intermediate between mitochondrial and cytoplasmic branches of folate cycle, were sufficient to reduce activity of SHMT1/2 inhibitors. Finally synergistic studies with antifolates provided an insight how efficacy of SHMT1/2 could be exploited therapeutically also in rational combinations with approved drugs.

Citation Format: Tomasz Rzymski, Anna Wrobel, Karolina Pyziak, Agnieszka Sroka, Marta Sowinska, Agnieszka Dreas, Marcin Krol, Pawel Guzik, Agnieszka Adamus, Agnieszka Przybylowicz, Katarzyna Hamara, Magdalena Sieprawska-Lupa, Artur Biela, Krzysztof Brzozka. Small molecule inhibitors of SHMT1/2 validate serine metabolism as a target in the treatment of c-Myc positive solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 442. doi:10.1158/1538-7445.AM2017-442

Abstract 2174: Inhibition of CDK8 kinase with SEL120-34A allows for a personalized approach in AML

Inhibition of oncogenic transcriptional programs is recognized to be a promising therapeutic strategy. SEL120-34A is a novel inhibitor of Cyclin- dependent kinase 8 (CDK8), which regulates transcription by associating with the Mediator complex. SEL120-34A interacts with the ATP binding site of CDK8 in type I inhibitor fashion and forms several types of interactions, including halogen bonds with the protein’s hinge region and hydrophobic complementarities within its front pocket. Although the compound was only modestly active in solid tumor cell lines, it repressed phosphorylation of STAT5 Ser726 and could differentially inhibit viability of AML and ALL cell lines in vitro and in vivo, along with other type I CDK8 inhibitors. Transcriptomic analysis identified major transcriptional programs altered in responder cell lines, which strongly indicated that apart from repression of survival pathways, CDK8 inhibitors could induce differentiation in cell lines with leukemia stem cells characteristics. Further studies on a large panels of responder and non-responder cell lines identified robust biomarkers which could be used with high confidence for stratification and personalized approach in CDK8-dependent AML cases. Favorable pharmacokinetics, confirmed safety and in vivo efficacy in leukemia models provide the rationale for further clinical development of SEL120-34A.

Citation Format: Tomasz Rzymski, Michal Mikula, Eliza Zylkiewicz, Agnieszka Dreas, Katarzyna Wiklik, Aniela Golas, Katarzyna Wojcik, Magdalena Masiejczyk, Iga Dudzicz, Katarzyna Kucwaj, Malgorzata Statkiewicz, Krzysztof Goryca, Aleksandra Grochowska, Aleksandra Cabaj, Jerzy Ostrowski, Urszula Kukliniska, Krzysztof Brzozka. Inhibition of CDK8 kinase with SEL120-34A allows for a personalized approach in AML [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2174. doi:10.1158/1538-7445.AM2017-2174

Abstract 5063: Epigenetic modulators show differential activity on lung adenocarcinoma cells with loss-of-function mutations of SWI/SNF protein SMARCA4

SWI/SNF is a multiprotein chromatin remodeler with ATP-dependent activities leading to selective gene expression, DNA repair, recombination and replication. Various sequencing efforts indicated that nearly 20% of cancers bear mutations in at least one subunit of the complex. One of the crucial regulators of the complex is SMARCA4, a member of SWI/SNF family of helicases with ATPase activities, which are thought to regulate transcription of certain genes by altering the chromatin structure. SMARCA4 is mutated in virtually all cases of small cell carcinoma of the ovary and SMARCA4 is fourth the most frequently mutated gene in lung adenocarcinoma. High occurrence of inactivating mutations prompted several screenings projects focused on synthetic lethality interactions with other proteins, which led to the identification of SMARCA2 as an essential gene in SMARCA4 mutated cancers. This vulnerability could be potentially exploited therapeutically and several groups managed to identify potent ligands of SMARCA2 bromodomain. Surprisingly these molecules were inactive in SMARCA4 mutant cells, however additional studies indicated that ATPase rather than bromodomain is a target for novel compounds with anticancer activities. Overall, these results revealed functional complexity of SMARCA2 and SMARCA4 in cancer cells. In order to characterize molecular consequences of SMARCA2 silencing in SMARCA4 mutant lung adenocarcinoma cells, we have carried out a series of gene knockdown experiments, followed by transcriptional profiling by RNAseq and analysis of posttranslational histone modifications. These studies indicated rapid and irreversible loss of viability in SMARCA4 mutant cells after SMARCA2 gene silencing. Interestingly double SMARCA2/SMARCA4 knockdown in SMARCA4 WT cells has not resulted in lowered viability. Transcriptional profiling of SMARCA2 knockdown in SMARCA4 mutated cells revealed broad, predominantly repressory effects on gene expression levels. Gene set enrichment analysis showed significant inhibitory effects of SMARCA2 knockdown, particularly on transcripts which could be induced after reintroduction of SMARCA4. Furthermore MS/MS analysis indicated global rearrangements in histone epigenetic marks. These results prompted us to test activity of small-molecule epigenetic modulators, including DNA Methyltransferases (DNMTs), Histone Acetyltransferases (HATs), Histone Deacetylases (HDACs), Histone Methyltransferases (HMTs), Histone Demethylases (HDMs) and a distinct set of chromatin readers, bromodomains. Differential activity of these compounds provides a strong basis for novel strategies for the treatment of cancers with loss-of-function mutations of SMARCA4.

Citation Format: Tomasz Rzymski, Anna Wrobel, Michal Mikula, Karolina Pyziak, Anna Bartosik, Agnieszka Sroka, Agnieszka Paziewska, Aleksandra Grochowska, Malgorzata Statkiewicz, Katarzyna Paczkowska, Michalina Dabrowska, Jerzy Ostrowski, Krzysztof Brzozka. Epigenetic modulators show differential activity on lung adenocarcinoma cells with loss-of-function mutations of SWI/SNF protein SMARCA4 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5063. doi:10.1158/1538-7445.AM2017-5063

High temperature oxidation of iron–iron oxide core–shell nanowires composed of iron nanoparticles

The thermal oxidation of iron nanowires causes their breakdown due to void coalescence and formation of α-Fe₂O₃microparticles and microrods.

Abstract 755: Repression of tumor survival pathways by novel and selective inhibitors of MNK1 and MNK2 kinases in glioblastoma and colorectal cancer

Herewith, we report development of small molecule inhibitors of MNK1 and MNK2 kinases and their cellular activity. MNK1 and 2 are MAP kinase-interacting kinases that are activated by RAS and MAPK signaling pathways and are involved in regulation of translation. Both kinases phosphorylate translation initiation factor eIF4e on a conserved serine 209 residue. eIF4E can contribute to the oncogenic transformation both in vitro and in vivo and is highly expressed in various tumor types. Interestingly, mice that lack both MNK1 and MNK2 do not have any apparent phenotype, which is promising for the therapeutic window of MNK1/2 inhibitors. SEL201 is a series of small molecule inhibitors which inhibit activity of both MNK1 and MNK2 in a low nM range. Selected compounds were tested on the kinome panels and indicated MNK1 and MNK2 as primary kinase targets. SEL201 compounds caused dose dependent inhibition of phosphorylation of eIF4e at Ser209 in various cancer cell lines at concentrations <100nM, which were lower when compared with other reported MNK1/2 inhibitors such as Cercosporamid and CGP57380. Consistently, potent inhibition of eIF4e Ser209 was observed also in vivo after oral administration of the inhibitors in xenograft models. High potency, selectivity and favorable ADME/PK profile indicates that SEL201 inhibitors would be useful tools in probing molecular consequences of eIF4e Ser209 inhibition in cancer cells alone and in combination with other inhibitors targeting PI3K/mTOR or RAS/MEK pathway. SEL201 in vitro and in vivo activities on viability and metastasis will be presented in cellular and in vivo models of colorectal cancer and glioblastoma. SEL201 series is further developed as a promising anticancer therapy with potentially wide therapeutic window.

Citation Format: Tomasz Rzymski, Malgorzata Szajewska-Skuta, Adrian Zarebski, Kamil Sitarz, Lukasz Sapala, Malgorzata Zurawska, Magdalena Salwinska, Renata Windak, Ewa Trebacz, Joanna Daniel-Wojcik, Radoslaw Obuchowicz, Bozena Winnik, Ewelina Wincza, Urszula Kulesza, Katarzyna Kucwaj-Borysz, Mariusz Milik, Agnieszka Dreas, Krzysztof Brzozka. Repression of tumor survival pathways by novel and selective inhibitors of MNK1 and MNK2 kinases in glioblastoma and colorectal cancer. [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 755. doi:10.1158/1538-7445.AM2014-755

Abstract A49: Repression of tumor survival pathways by novel, selective inhibitors of MNK1 and MNK2 kinases

MNK1 and MNK2 are MAP kinase-interacting kinases involved in regulation of translation. Both kinases phosphorylate translation initiation factor eIF4E on a conserved serine 209. eIF4E can contribute to the oncogenic transformation both in vitro and in vivo and is highly expressed in diverse types of cancer. Interestingly, mice that lack both MNK1 and MNK2 do not have any apparent phenotype and therefore represent interesting possibility to develop targeted and safe anticancer therapies.

Herewith, we report the development of first selective small molecule inhibitors of MNK1 and MNK2 kinases and their in vitro cellular activity. Selvita developed a series of small molecule type I, ATP-competitive inhibitors targeting both MNK1 and MNK2 with mid nM activity range. Selected compounds were tested on a panel of 456 kinases and showed very high selectivity. Additionally, in cellular models such as serum stimulated SW480 cells, synthesized MNK1/2 inhibitors caused dose dependent inhibition of phosphorylation of eIF4e at Ser209 in line with the kinase activity profile. The observed cellular activity on biomarker inhibition was more potent than observed for reported in the literature MNK1/2 inhibitors such as cercosporamide and CGP57380. High activity of MNK1/2 inhibitors on in vitro biomarkers correlated with efficacy on cancer cells challenged with various stress conditions, typical for tumor microenvironment. These initial findings confirm that selective inhibition of MNK1/2 may repress major tumor survival pathways induced under stress and support further development of this class of compounds as a novel anticancer therapy with a promising therapeutic window.

Citation Format: Tomasz Rzymski, Agnieszka Dreas, Mariusz Milik, Katarzyna Kucwaj, Adrian Zarebski, Malgorzata Szajewska Skuta, Anna Cierpich, Charles Fabritius, Krzysztof Brzozka. Repression of tumor survival pathways by novel, selective inhibitors of MNK1 and MNK2 kinases. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr A49.

Abstract 3845: Antitumor activity of SEL120: An orally available dual inhibitors of Haspin/CDK9, for standalone and combination therapy with AuroraB inhibitors in solid tumors and hematopoietic malignancies

The mitotic machinery is a validated target for potential drug therapies in cancer. However, anti-mitotic agents are not without complications from various side effects, notably neurological and hematological toxicities. There is much interest in identifying new drug targets in mitosis which could lead to safer and more efficacious treatments of cancer. Recently, Haspin has been identified as another important kinase involved in mitosis. Similar to other mitotic kinases such as Polo-like kinase-1 and the Aurora kinases, inhibition of Haspin represents a novel approach in anti-mitotic cancer therapeutics. In this study we report the development of SEL120, series of novel ATP competitive inhibitors of Haspin kinase. These compounds have binding affinities towards Haspin kinase in the low nM range. Several compounds in the series exerted significant activity on CDK9 (selectively over other CDK kinases), a part of positive transcription elongation factor b (P-TEFb) involved in the expression of survival proteins during progression of cancer. SEL120 inhibited proliferation and clonogenic survival of a number of tumor cell lines with particularly good cytostatic activity in colon, lung (NSCLS) and B cell lymphoma cell lines. The only substrate of Haspin reported in literature to date is histone H3. During mitosis Haspin targets a single site in this protein, namely threonine at position T3 (H3T3ph). By using siRNA, we have confirmed that Thr3 phosphorylation of histone H3 could be completely repressed by the knockdown of Haspin in HCT116 colon and A549 (NSCLC) lung cancer cell lines. We also consistently observed decreased phosphorylation of histone H3 (Thr3) in both synchronized and asynchronous cell lines treated with SEL120 inhibitor. In addition SEL120-1 treatment decreased levels of CDK9 biomarkers- phosphorylation of pol II CTD (Ser2) and expression of the pro-survival protein Mcl-1 Treatment with SEL120 consistently resulted in mitotic cell cycle arrest in A549 cell line confirming inhibition of Haspin as the mechanism of action. Remarkably, inhibitory activity on CDK9 correlated with levels of cell death. Furthermore, co-administration of SEL120 with an AuroraB inhibitors, resulted in strong synergistic cytostatic effects. Treatment with both compounds increased the number of cells arrested in mitosis, notably without any signs of polyploidy typically observed after inhibition of AuroraB. Oral administration of SEL120 (25mg/kg BID) revealed excellent potency in colon and B-cell lymphoma xenograft models. Analysis of pharamcokinetic, ADMET and histopathological parameters afforded encouraging results towards potential development of new therapeutics emerging from our SEL120 program.

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 3845. doi:1538-7445.AM2012-3845

Abstract B242: Antitumor activity of SEL120: An orally available small-molecule inhibitor of Haspin kinase for standalone and combination therapy with AuroraB inhibitors in colorectal cancer

The mitotic machinery is a validated target for potential drug therapies in cancer. Anti-mitotic drugs like vinca alkaloids and taxanes interfering with microtubules are important classes of chemotherapeutical agents. However, these agents are not without complications from various side effects, notably neurological and hematological toxicities. There is much interest in identifying new drug targets in mitosis which could lead to safer and more efficacious treatments of cancer. Recently, Haspin has been identified as another important kinase involved in mitosis. Similar to other mitotic kinases such as Polo-like kinase-1 and the Aurora kinases, inhibition of Haspin represents a novel approach in anti-mitotic cancer therapeutics.

In this study we report the development of SEL120, a novel ATP competitive inhibitor of Haspin kinase. These small-molecule compounds have binding affinities towards Haspin kinase in the low nM range. SEL120 inhibited proliferation and clonogenic survival of a number of tumor cell lines with particularly good cytostatic activity in colon, lung (NSCLS) and B cell lymphoma cell lines.

The only substrate of Haspin reported in literature to date is histone H3. During mitosis Haspin targets a single site in this protein, namely threonine at position T3 (H3T3ph). By using siRNA, we have confirmed that Thr3 phosphorylation of histone H3 could be completely repressed by the knockdown of Haspin in HCT116 colon and A549 (NSCLC) lung cancer cell lines. We also consistently observed decreased phosphorylation of histone H3 (Thr3) in both synchronized and asynchronous cell lines treated with SEL120 inhibitor. Haspin-depleted cells were arrested in the prometaphase as a result of chromosome alignment defects and activation of the mitotic checkpoint. Treatment with SEL120 consistently resulted in mitotic cell cycle arrest in HCT116 and A549 cell lines confirming inhibition of Haspin as the mechanism of action. Furthermore, co-administration of SEL120 with an AuroraB inhibitor, AZD1152, resulted in strong synergistic cytostatic effects. Treatment with both compounds increased the number of cells arrested in mitosis, notably without any signs of polyploidy (cells with >4n) typically observed after inhibition of AuroraB.

Oral administration of SEL120 (25mg/kg BID) revealed excellent potency in the HCT116 xenograft model; observed tumor growth inhibition was over 80%. Analysis of pharamcokinetic, ADMET and histopathological parameters afforded encouraging results towards potential development of new therapeutics emerging from our SEL120 program. Presented data validates Haspin as a promising target for anticancer treatments, particularly for colon cancer, lung cancer and lymphomas.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B242.

Abstract A243: Novel Pim kinase inhibitors for treatment of hematological malignancies and solid tumors

The family of Pim kinases emerged as a novel and interesting target with significant potential for therapeutic intervention in cancer. All three members of the family Pim-1, Pim-2 and Pim-3 were shown to be prevent apoptosis, promote protein translation and cell survival thereby enhancing proliferation of malignant cells. Pim kinases seem to be crucial downstream effectors various important oncogenes like Jak, Flt3 or Ras kinases. Multiple targets phosphorylated by Pim kinases play important roles in intracellular signaling and contribute to pathways involved in cell survival, proliferation, stress response and cellular motility. Moreover, the significance and relevance of Pim kinases as valid therapeutic targets is further confirmed by their expression levels in variety of cancer types of both hematological origin. For example Pim kinase overexpression contributes to the development of diffuse B cell lymphoma, mantle cell lymphoma, B-cell chronic lymphocytic leukemia and Flt3-mediated acute myelogenous leukemia. Interestingly, accumulating literature data point towards emerging role of Pim kinases also in development of malignancies that originate from epithelial cells, especially gastric, colon and hepatocellular cancers, but also prostate and pancreatic cancers.

In this study we are reporting the results for novel small molecule Pim kinase inhibitors that were developed by Selvita. in Currently, we are performing a lead optimization program of novel, small molecule pan-Pim kinase inhibitors. Compounds developed within the SEL24 series exert high potency in vitro both on all three Pim kinases as well as on a large panel of cancer cell lines. Among synthesized compounds we have identified most selective Pim kinase inhibitors described so far with selectivity scores on a panel of 290 kinases inhibited over 90% at 1 μM concentration was equal to 1.8%. Mechanism of action for selected compounds was confirmed both in vitro in variety of cell lines and in vivo in xenograft models by downregulation of c-Myc and 4EBP1 phosphorylation inhibition. Further experiments indicated that our compounds induced both apoptotic cell death and cell cycle arrest at G0/G1, consistently with the predicted Pim kinase inhibition phenotype. SEL24 compounds showed mostly synergistic effects in a range of combinations with standard anti-cancer therapeutics in both leukemias and solid tumor cell lines. Strong synergies were observed not only for cytotoxic agents like docetaxel, gemcitabine or cyratabine, but also for targeted therapies like the PI3K/Akt pathway inhibitors or Jak kinase inhibitors. Data will be presented on in vivo efficacy of SEL24 lead compounds examined in xenograft models of leukemias, lymphomas and solid tumors (lung and colon cancer). Apart from excellent efficacy in in vivo xenograft models, SEL24 compounds show preferable safety profile with no effect on ion channel mediated cardiotoxicity and favorable pharmacokinetic profile. Taken together, presented data supports the rationale of using Pim kinase inhibition as a novel approach to standalone cancer therapy, and in combination with other targeted and cytotoxic therapies, especially to overcome developing drug resistance.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A243.

Abstract 4499: In vitro and in vivo evaluation of novel Pim kinase inhibitors with potent anticancer activity

The Pim serine-threonine kinase family is composed of three members that play an important role in intracellular signaling and contribute to pathways involved in cell survival, proliferation, stress response and cellular motility. Out the three family members, Pim-1 has been studied most extensively and was shown to be a crucial downstream effector of several oncogenes such as Jak2 and FLT3 kinases. Pim-1 overexpression has been also reported in a variety of cancers such as diffuse B cell lymphoma, chronic lymphocytic leukemia, Flt3-mediated acute myelogenous leukemia and solid tumors including prostate and pancreatic cancers. For this reason, Pim-1 kinase emerged as a novel and interesting target of significant potential for therapeutic intervention.

In the current study, the optimization of the initial lead compound - which presented moderate potency in Pim kinase inhibition, low solubility and bioavailability - led to the identification of a group of new compounds. Among the newly synthesized compounds several derivatives exerted increased potency in Pim kinase inhibition with IC50 values below 5 nM. Profiling of best inhibitors on a KINOMEscanTM Max kinase panel revealed superior selectivity towards Pim kinases.

Anticancer activity of these new derivatives was investigated in various neoplastic cell lines of hematological and solid tumor origin where the compounds were shown to induce apoptosis both as a single agent, but also synergistically with standard therapies, such as docetaxel and cytarabine. FACS analyses revealed accumulation of subG0 phase, indicating apoptosis in time and concentration dependant manner. In the living cells, two phenotypes could be observed, namely a cell cycle arrest of the cells either in the G0/G1 or G2/M phases, depending on the cell line.

In order to confirm that the observed cytotoxic and cell cycle effects were due to inhibition of the Pim kinases, we performed analyses of direct downstream substrates of these kinases. Pim kinases were shown to phosphorylate p27KIP1, 4E-BP1 and Bad proteins, and treatment of cells in vitro with our new compounds caused a dramatic reduction in the phosphorylation levels of these targets. Best performing compounds were then chosen for an efficacy screen in a mouse xenograft model, proving their anticancer activity. Treatment of the animals also led to in vivo biomarker inhibition after single administration of the compounds.

Results of Selvita's Pim kinase inhibitor optimization efforts are shown and discussed, supporting further development of this class of inhibitors in oncology indications.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4499.

Abstract A242: Identification of novel and specific Pim-1 kinase inhibitors with potent anticancer activity in hematological and solid tumor malignancies

The Pim serine-threonine kinase family is composed of three members which play an important role in intracellular signaling and contribute to pathways involved in cell survival, proliferation, stress response and cellular motility. Out the three family members, Pim-1 has been studied most extensively and was shown to be a crucial downstream effector of several oncogenes like Jak2 and FLT3 kinases. Pim-1 overexpression has been also reported in a variety of cancers such as diffuse B cell lymphoma, chronic lymphocytic leukemia, Flt3-mediated acute myelogenous leukemia and solid tumors such as prostate and pancreatic cancers. For this reason, Pim-1 kinase emerged as a novel and interesting target of significant potential for therapeutic intervention.

In the current study we have performed lead optimization of a new small molecule Pim-1 kinase inhibitor. Initial compound exerted moderate potency in Pim-1 kinase inhibition accompanied by high selectivity for the Pim kinase family. In parallel to biochemical characterization, the original compound had been extensively tested in vitro and in vivo for anticancer activity. In order to improve potency and selectivity of the original compound a series of new derivatives was synthesized and screened for Pim-1 inhibition. Among the newly synthesized compounds several exerted increased potency in Pim-1 inhibition with IC50 values as low as 4,8 nM. Further biochemical profiling of best inhibitors on a 440 KINOMEscanTM Max kinase panel revealed superior selectivity in binding and inhibition of the Pim-1 kinase with over 20-fold off-target selectivity. Anticancer effect of new derivatives was investigated in several cancer cell lines of hematological and solid tumor origin where the compounds was shown to induce of apoptosis. As Pim-1 kinase was shown to regulate cell cycle progression by phosphorylation of several key proteins such as p27 and cdc25A in the G1/S checkpoint and cdc25C and c-TAK-1 in the G2/M checkpoint, we investigated cell cycle effects after compounds administration. We could observe two phenotypes in cell that did not undergo apoptosis, namely a time and dose dependent arrest of the cells either in the G0/G1 or G2/M phase, depending on the cell line. To confirm that the observed cytotoxic and cell cycle effects were due to inhibition of the Pim-1 kinase by the new derivatives, a biomarker analysis was performed. Pim-1 kinase was shown to phosphorylate p27KIP1 at threonine 198 both in vitro and in the cells. As soon as 1h after treatment with the compounds, a dramatic inhibition of phospho-p27KIP1 was observed on K562 cells proving the expected mechanism of action of Pim-1 kinase inhibiting compounds in the cells. Results of the Selvita's Pim-1 inhibitor lead optimization efforts are shown and discussed, supporting further development of this class of inhibitors in oncology indications.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A242.