Uridine 5'-Diphospho-glucuronosyltransferase 1A3 (UGT1A3) Prediction of Hepatic Clearance of Organic Anion Transporting Polypeptide 1B3 (OATP1B3) Substrate Telmisartan by Glucuronidation Using In Vitro-In Vivo Extrapolation (IVIVE)

BACKGROUND AND OBJECTIVE

The prediction of pharmacokinetic parameters for drugs metabolised by cytochrome P450 enzymes has been the subject of active research for many years, while the application of in vitro-in vivo extrapolation (IVIVE) techniques for non-cytochrome P450 enzymes has not been thoroughly evaluated. There is still no established quantitative method for predicting hepatic clearance of drugs metabolised by uridine 5'-diphospho-glucuronosyltransferases (UGTs), not to mention those which undergo hepatic uptake. The objective of the study was to predict the human hepatic clearance for telmisartan based on in vitro metabolic stability and hepatic uptake results.

METHODS

Telmisartan was examined in liver systems, allowing to estimate intrinsic clearance (CLint, in vitro) based on the substrate disappearance rate with the use of liquid chromatography tandem mass spectrometry (LC-MS/MS) technique. Obtained CLint, in vitro values were corrected for corresponding unbound fractions. Prediction of human hepatic clearance was made from scaled unbound CLint, in vitro data with the use of the well-stirred model, and finally referenced to the literature value of observed clearance in humans, allowing determination of the essential scaling factors.

RESULTS

The in vitro scaled CLint, in vitro by UGT1A3 was assessed using three systems, human hepatocytes, liver microsomes, and recombinant enzymes. Obtained values were scaled and hepatic metabolism clearance was predicted, resulting in significant clearance underprediction. Utilization of the extended clearance concept (ECC) and hepatic uptake improved prediction of hepatic metabolism clearance. The scaling factors for hepatocytes, assessing the in vitro-in vivo difference, changed from sixfold difference to only twofold difference with the application of the ECC.

CONCLUSIONS

The study showed that taking into consideration hepatic uptake of a drug allows us to obtain satisfactory scaling factors, hence enabling the prediction of in vivo hepatic glucuronidation from in vitro data.

Novel method of measurement of in vitro drug uptake in OATP1B3 overexpressing cells in the presence of dextran

BACKGROUND

In predictions about hepatic clearance (CLH), a number of studies explored the role of albumin and transporters in drug uptake by liver cells, challenging the traditional free-drug theory. It was proposed that liver uptake can occur for transporter substrate compounds not only from the drug's unbound form but also directly from the drug-albumin complex, a phenomenon known as uptake facilitated by albumin. In contrast to albumin, dextran does not exhibit binding properties for compounds. However, as a result of its inherent capacity for stabilization, it is widely used to mimic conditions within cells.

METHODS

The uptake of eight known substrates of the organic anion-transporting polypeptide 1B3 (OATP1B3) was assessed using a human embryonic kidney cell line (HEK293), which stably overexpresses this transporter. An inert polymer, dextran, was used to simulate cellular conditions, and the results were compared with experiments involving human plasma and human serum albumin (HSA).

RESULTS

This study is the first to demonstrate that dextran increases compound uptake in cells with overexpression of the OATP1B3 transporter. Contrary to the common theory that highly protein-bound ligands interact with hepatocytes to increase drug uptake, the results indicate that dextran's interaction with test compounds does not significantly increase concentrations near the cell membrane surface.

CONCLUSIONS

We evaluated the effect of dextran on the uptake of known substrates using OATP1B3 overexpressed in the HEK293 cell line, and we suggest that its impact on drug concentrations in liver cells may differ from the traditional role of plasma proteins and albumin.

Abstract 1280: New generation of STING agonists: Development and characterization of a novel series of systemic immunomodulators with improved potency

Background. Stimulator of interferon genes, known as STING, is an intracellular sensor of nucleic acids and one of key regulators in activating the innate immune response. Employing synthetic STING agonists has been shown to promote immune-mediated antitumor response in preclinical animal models. Ryvu is developing small-molecule STING agonists suitable for systemic administration. Herein we present unpublished results from characterization of the new generation of our agonist series with significantly improved potency on human immune cells.

Methods. Binding to recombinant STING protein was examined using Fluorescence Thermal Shift and Fluorescence Polarisation and was confirmed by X-ray crystallography. Primary screen was performed in THP-1 Dual reporter cells and selectivity was confirmed in THP-1 reporter cells with knocked out STING or expressing varying STING variants. T cell viability and proliferation was assessed by flow cytometry using activated, human T cells exposed to STING agonists. STING pathway activation pattern in cells treated with Ryvu's molecules was confirmed using Western blot analysis. BALB/c mice were injected with compounds and the levels of cytokine release were measured in the plasma. Mice were inoculated with CT26 or EMT6 tumor cells and the compound was administered intravenously followed by the regular monitoring of tumor growth.

Results. New generation Ryvu STING agonists are strong binders of human STING protein. Ryvu's compounds show high cellular potency inducing cytokine production in human immune cells at low nM range. Moreover, high activity of developed agonists is maintained irrespective of the natural human STING variant as seen in THP-1 reporter cells as well as in human primary immune cells. High cellular potency of developed compounds also translates into efficacy observed in vivo, where systemic intravenous administration leads to significant tumor growth inhibition and complete tumor regressions in mouse syngeneic models.

Conclusion. Ryvu has developed a new generation of potent, direct and selective small-molecule STING agonists. The compounds are characterized by drug-like properties and high in vitro potency on par or outperforming known references. Ryvu agonists are suitable for systemic administration and allow to achieve excellent antitumor efficacy. Taken together, the promising results suggest that the developed series holds high potential for improving immunotherapy in cancer patients.

Citation Format: Maciej Krzysztof Rogacki, Stefan Chmielewski, Jolanta Mazurek, Magdalena Zawadzka, Katarzyna Wnuk-Lipińska, Kamil Kuś, Katarzyna Wójcik-Jaszczyńska, Aleksandra Poczkaj, Łukasz Dudek, Wojciech Schonemann, Urszula Głowniak-Kwitek, Marcin Leś, Marek Wronowski, Tushar Mahajan, Urszula Kulesza, Magdalena Zastawna, David Synak, Karol Zuchowicz, Karolina Gluza, Katarzyna Banaszak, Karolina Wiatrowska, Izabela Strojny, Mirosława Gładysz, Justyna Jabłońska, Ewelina Gabor-Worwa, Monika Dobrzańska, Raghuram Tangirala, Peter Littlewood, Krzysztof Brzózka. New generation of STING agonists: Development and characterization of a novel series of systemic immunomodulators with improved potency [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 1280.

Discovery of indazole-pyridinone derivatives as a novel class of potent and selective MNK1/2 kinase inhibitors that protecting against endotoxin-induced septic shock

The mitogen-activated protein kinase (MAPK)-interacting kinases 1 and 2 (MNKs 1/2) and their downstream target eIF4E, play a role in oncogenic transformation, progression and metastasis. These results provided rationale for development of first MNKs inhibitors, currently in clinical trials for cancer treatment. Inhibitors of the MNKs/eIF4E pathway are also proposed as treatment strategy for inflammatory conditions. Here we present results of optimization of indazole-pyridinone derived MNK1/2 inhibitors among which compounds 24 and 26, selective and metabolically stable derivatives. Both compounds decreased levels of eIF4E Ser206 phosphorylation (pSer209-eIF4E) in MOLM16 cell line. When administered in mice compounds 24 and 26 significantly improved survival rates of animals in the endotoxin lethal dose challenge model, with concomitant reduction of proinflammatory cytokine levels - TNFα and IL-6 in serum. Identified MNK1/2 inhibitors represent a novel class of immunomodulatory compounds with a potential for the treatment of inflammatory diseases including sepsis.

Abstract 4532A: Development of selective small molecule STING agonists suitable for systemic administration

Background: Stimulator of Interferon Genes (STING) is a major player in the activation of robust innate immune response leading to initiation and enhancement of tumor-specific adaptive immunity. Several clinical and pre-clinical programs are developing cyclic dinucleotides - analogues of endogenous STING ligands. However their chemical nature and stability limit their use as systemic immuno-therapeutics. Herein, we present potent and selective non-nucleotide, non-macrocyclic, small molecule direct STING agonists, structurally unrelated to known chemotypes and suitable for systemic administration.

Methods: Binding to recombinant STING protein was examined using FTS, MST, FP and crystallography studies. Phenotypic screen was performed in THP-1 Dual reporter cells. Human macrophages (HMDM) and dendritic cells (HMDC) were differentiated from monocytes (obtained from PBMC) in the presence of M-CSF and GM-CSF/IL-4 for HMDM and HMDC, respectively. Mouse bone marrow-derived dendritic cells (BMDC) were obtained from C57BL/6 or STING KO mice and differentiated with mIL-4 and mGM-CSF. STING agonists were administered into BALB/c mice and cytokine release was measured in plasma. Additionally, mice were inoculated with CT26 murine colon carcinoma cells and the compound was administered, followed by the regular tumor growth monitoring. Finally, the compound was administered to C57BL/6 WT and STING KO mice in several escalating doses.

Results: Ryvu's agonists demonstrate a strong binding affinity to recombinant STING proteins across tested species. They trigger pro-inflammatory cytokine release from human PBMC and HMDC and induce dendritic cell maturation regardless of the STING haplotype. Systemic in vivo administration leads to dose-dependent upregulation of STING-dependent pro-inflammatory cytokines, suggesting immune activation which translates into efficacy in vivo in CT26 mouse colorectal cancer model and complete tumor remissions. Furthermore, cured animals develop lasting immunological response demonstrated by diminished tumor growth or lack of palpable tumors in re-challenged mice.

Conclusion: Ryvu's STING agonists selectively activate STING-dependent signaling in both mouse and human immune cells promoting anti-tumor immunity. Treatment with Ryvu's STING agonists leads to engagement of the immune system which results in complete tumor remission and development of immunological memory against cancer cells. The compounds show good selectivity and ADME properties enabling development for systemic administration as a single agent or in combinations with immunotherapies or targeted agents.

Citation Format: Stefan Chmielewski, Magdalena Zawadzka, Jolanta Mazurek, Maciej K. Rogacki, Karolina Gluza, Katarzyna Wójcik-Jaszczyńska, Aleksandra Poczkaj, Grzegorz Ćwiertnia, Grzegorz Topolnicki, Maciej Kujawa, Eliza Zimoląg, Urszula Głowniak-Kwitek, Magdalena Mroczkowska, Agnieszka Gibas, Marcin Leś, Sylwia Sudoł, Marek Wronowski, Kinga Michalik, Katarzyna Banaszak, Katarzyna Wiklik, Federico Malusa, Michał Combik, Karolina Wiatrowska, Łukasz Dudek, Jose Alvarez, Anna Rajda, Faustyna Gajdosz, Aniela Gołas, Katarzyna Wnuk-Lipińska, Kamil Kuś, Ewelina Gabor-Worwa, Charles Fabritius, Luigi Stasi, Peter Littlewood, Krzysztof Brzózka, Monika Dobrzańska. Development of selective small molecule STING agonists suitable for systemic administration [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4532A.

SEL120-34A is a novel CDK8 inhibitor active in AML cells with high levels of serine phosphorylation of STAT1 and STAT5 transactivation domains

Inhibition of oncogenic transcriptional programs is a promising therapeutic strategy. 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. X-ray crystallography has shown SEL120-34A to be a type I inhibitor forming halogen bonds with the protein's hinge region and hydrophobic complementarities within its front pocket. SEL120-34A inhibits phosphorylation of STAT1 S727 and STAT5 S726 in cancer cells in vitro. Consistently, regulation of STATs- and NUP98-HOXA9- dependent transcription has been observed as a dominant mechanism of action in vivo. Treatment with the compound resulted in a differential efficacy on AML cells with elevated STAT5 S726 levels and stem cell characteristics. In contrast, resistant cells were negative for activated STAT5 and revealed lineage commitment. In vivo efficacy in xenotransplanted AML models correlated with significant repression of STAT5 S726. Favorable pharmacokinetics, confirmed safety and in vivo efficacy provide a rationale for the further clinical development of SEL120-34A as a personalized therapeutic approach in AML.

Abstract 4087: Development of a potent, dual pan-PIM/FLT3 inhibitor for the treatment of heme malignancies

Despite huge effort spent on understanding the pathogenesis of acute myeloid leukemia (AML), current standards of care are still based on the same chemotherapy agents as two decades ago - combinational treatment of cytarabine with an anthracycline. Fms-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) is one of the most common genetic lesions in AML. Although FLT3 inhibitors initially exhibit clinical activity, resistance to treatment inevitably occurs within months. PIM kinases are thought to be major drivers of the resistance phenotype and their inhibition in relapsed samples restores cell sensitivity to FLT3 inhibitors. Thus, simultaneous PIM and FLT3 inhibition represents a promising strategy in AML therapy. Selvita has developed a potent and selective first-in-class, dual PIM/FLT3 kinase inhibitor, the SEL24-B489 compound, and profiled its activity for in vitro and in vivo AML models showing significantly broader anti-tumor activity of SEL24-B489 than selective FLT3-ITD or PIM inhibitors. We compared SEL24-B489 head-to-head with a selective PIM inhibitor (AZD1208) and a selective FLT3-ITD inhibitor (AC220) in a panel of AML cell lines with FLT3-ITD or unmutated kinase (FLT3-WT) as well as peripheral AML cells and CD34+ bone marrow blasts. SEL24-B489 exhibited a significantly broader activity, irrespective of FLT3 status, than either of the selective inhibitors. Since PIM kinases have emerged as important mediators of FLT3-inhibitor resistance, we hypothesized that the dual specificity of SEL24-B489 might overcome the phenotype of resistance. We utilized previously developed MOLM-14 cells transduced with either FLT3-WT or FLT3 alleles containing TKD point mutations to show that neither of the these mutations decreased the cellular sensitivity to SEL24-B489. Higher cellular activity and biomarker response of SEL24-B489 than competitive inhibitors was shown by inhibition of specific biomarkers such as S6 and STAT5 phosphorylation at nanomolar concentrations in both FLT3-ITD positive and FLT3-WT cell lines in vitro. We have also demonstrated SEL24-B489 superior potency of SEL24-B489 in xenograft models in vivo. Consistent with the experiments in vitro showing marked synergy between SEL24-B489 and AraC, a combination of these agents resulted in almost completely blocked tumor growth in vivo. Most importantly, SEL24-B489 has been selected as a clinical candidate and is currently in phase I clinical trials.

Citation Format: Wojciech Czardybon, Renata Windak, Aniela Gołas, Michał Gałęzowski, Aleksandra Sabiniarz, Izabela Dolata, Magdalena Salwińska, Paweł Guzik, Magdalena Zawadzka, Ewelina Gabor-Worwa, Bożena Winnik, Małgorzata Żurawska, Ewa Kolasińska, Ewelina Wincza, Marta Bugaj, Monika Danielewicz, Grzegorz Dubin, Ewa Jabłońska, Maciej Szydłowski, Tomasz Sewastianik, Bartosz Puła, Anna Szumera-Ciećkiewicz, Monika Prochorec-Sobieszek, Elżbieta Mądro, Ewa Lech-Marańda, Krzysztof Warzocha, Jerome Tamburini, Przemysław Juszczyński, Krzysztof Brzózka. Development of a potent, dual pan-PIM/FLT3 inhibitor for the treatment of heme malignancies [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 4087. doi:10.1158/1538-7445.AM2017-4087

Abstract 5394: First-in-class dual PIM/FLT3 kinase inhibitor SEL24-B489 for the treatment of hematological malignancies

Despite huge effort spent on understanding acute myeloid leukemia (AML), current standards of care are still based on the same chemotherapy agents as two decades ago - typically based on cytarabine chemotherapy with an anthracycline. Although patients aged <60 years may achieve remission to induction therapy, most patients will relapse. One of primary reasons for that is high heterogeneity of the disease. Recently one of the most extensively investigated approaches to the treatment of AML, are targeted therapies, especially inhibition of certain kinases. Probably mostly investigated up to date are inhibitors of FLT3 with most advanced clinical compound - AC220 (Quizartinib). FLT3 inhibitors are very effective in killing cancer lines with a major drawback of the therapy being fast development of resistance.

PIM kinases are expressed in various cancers including AML but also other liquid tumors as well as in some solid tumors. Inhibition of PIM kinases which are downstream in the FLT3 signaling cascade have already shown influence on cancer cell survival. In addition there are great hopes related to the fact that PIM kinases were shown to contribute in resistance to FLT3 inhibitors. This leads to the conclusion that combined inhibition of PIM and FLT3 may be a rational strategy.

Selvita has developed series of inhibitors combining activity against PIM and FLT3 kinases. Selected clinical candidate SEL24-B489 - has shown excellent anticancer efficacy. It is active against broad panel of AML cell lines and primary blasts, but also against other hematological cancers: DLBCL, CLL, HL - both in vitro on cell lines, patient samples and in vivo. Head to head comparison of SEL24-B489 with PIM (AZD1208) and FLT3 (AC220) inhibitors currently in clinical development will be presented. Comparison shows strong activity of SEL24-B489 against broader panel of cell lines in vitro and in vivo (in xenograft models) than AZD1208 or AC220. SEL24-B489 is currently in preclinical development and details of toxicology profile will also be discussed.

Citation Format: Krzysztof Brzózka, Wojciech Czardybon, Aniela Gołas, Renata Windak, Michał Gałęzowski, Ewelina Gabor-Worwa, Bożena Winnik, Agnieszka Przybyłowicz, Maciej Szydłowski, Emilia Białopiotrowicz, Tomasz Sewastianik, Elżbieta Mądro, Ewa Lech-Marańda, Krzysztof Warzocha, Przemysław Juszczyński. First-in-class dual PIM/FLT3 kinase inhibitor SEL24-B489 for the treatment of hematological malignancies. [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 5394. doi:10.1158/1538-7445.AM2015-5394