Structural effects of morpholine replacement in ZSTK474 on Class I PI3K isoform inhibition: Development of novel MEK/PI3K bifunctional inhibitors

Marcian E Van Dort; Youngsoon Jang; Christopher A Bonham; Kevin Heist; Dilrukshika S W Palagama; Lucas McDonald; Edward Z Zhang; Thomas L Chenevert; Gary D Luker; Brian D Ross

doi:10.1016/j.ejmech.2021.113996

Structural effects of morpholine replacement in ZSTK474 on Class I PI3K isoform inhibition: Development of novel MEK/PI3K bifunctional inhibitors

Eur J Med Chem. 2022 Feb 5:229:113996. doi: 10.1016/j.ejmech.2021.113996. Epub 2021 Nov 14.

Authors

Affiliations

¹ Center for Molecular Imaging, The University of Michigan Medical School, MI, 48109, USA; Department of Radiology, The University of Michigan Medical School, MI, 48109, USA. Electronic address: mvandort@umich.edu.
² Center for Molecular Imaging, The University of Michigan Medical School, MI, 48109, USA; Department of Radiology, The University of Michigan Medical School, MI, 48109, USA. Electronic address: jyoungso@umich.edu.
³ Center for Molecular Imaging, The University of Michigan Medical School, MI, 48109, USA; Department of Radiology, The University of Michigan Medical School, MI, 48109, USA. Electronic address: bonhachr@umich.edu.
⁴ Center for Molecular Imaging, The University of Michigan Medical School, MI, 48109, USA; Department of Radiology, The University of Michigan Medical School, MI, 48109, USA. Electronic address: heistka@umich.edu.
⁵ Center for Molecular Imaging, The University of Michigan Medical School, MI, 48109, USA; Department of Radiology, The University of Michigan Medical School, MI, 48109, USA. Electronic address: dilruksp@umich.edu.
⁶ Center for Molecular Imaging, The University of Michigan Medical School, MI, 48109, USA; Department of Radiology, The University of Michigan Medical School, MI, 48109, USA. Electronic address: mcdonalu@umich.edu.
⁷ Center for Molecular Imaging, The University of Michigan Medical School, MI, 48109, USA; Department of Radiology, The University of Michigan Medical School, MI, 48109, USA. Electronic address: edzhang@umich.edu.
⁸ Center for Molecular Imaging, The University of Michigan Medical School, MI, 48109, USA; Department of Radiology, The University of Michigan Medical School, MI, 48109, USA. Electronic address: tlchenev@umich.edu.
⁹ Center for Molecular Imaging, The University of Michigan Medical School, MI, 48109, USA; Department of Radiology, The University of Michigan Medical School, MI, 48109, USA. Electronic address: gluker@umich.edu.
¹⁰ Center for Molecular Imaging, The University of Michigan Medical School, MI, 48109, USA; Department of Radiology, The University of Michigan Medical School, MI, 48109, USA; Department of Biological Chemistry, The University of Michigan Medical School, MI, 48109, USA. Electronic address: bdross@umich.edu.

Abstract

Established roles for PI3K and MAPK signaling pathways in tumorigenesis has prompted extensive research towards the discovery of small-molecule inhibitors as cancer therapeutics. However, significant compensatory regulation exists between these two signaling cascades, leading to redundancy among survival pathways. Consequently, initial clinical trials aimed at either PI3K or MEK inhibition alone have proven ineffective and highlight the need for development of targeted and innovative therapeutic combination strategies. We designed a series of PI3K inhibitor derivatives wherein a single morpholine group of the PI3K inhibitor ZSTK474 was substituted with a variety of 2-aminoethyl functional groups. Analogs with pendant hydroxyl or methoxy groups maintained low nanomolar inhibition towards PI3Kα, PI3Kγ, and PI3Kδ isoforms in contrast to those with pendant amino groups which were significantly less inhibitory. Synthesis of prototype PI3K/MEK bifunctional inhibitors (6r, 6s) was guided by the structure-activity data, where a MEK-targeting inhibitor was tethered directly via a short PEG linker to the triazine core of the PI3K inhibitor analogs. These compounds (6r, 6s) displayed nanomolar inhibition towards PI3Kα, δ, and MEK (IC₅₀ ∼105-350 nM), and low micromolar inhibition for PI3Kβ and PI3Kγ (IC₅₀ ∼1.5-3.9 μM) in enzymatic inhibition assays. Cell viability assays demonstrated superior anti-proliferative activity for 6s over 6r in three tumor-derived cell lines (A375, D54, SET-2), which correlated with inhibition of downstream AKT and ERK1/2 phosphorylation. Compounds 6r and 6s also demonstrated in vivo tolerability with therapeutic efficacy through reduction of kinase activation and amelioration of disease phenotypes in the JAK2V617F mutant myelofibrosis mouse cancer model. Taken together, these results support further structure optimization of 6r and 6s as promising leads for combination therapy in human cancer as a new class of PI3K/MEK bifunctional inhibitors.

Keywords: Bifunctional MEK/PI3K inhibitor; PI3K isoform inhibition; ZSTK474.

MeSH terms

Animals
Binding Sites
Cell Line, Tumor
Cell Proliferation / drug effects
Disease Models, Animal
Humans
Mice
Mice, Transgenic
Mitogen-Activated Protein Kinase Kinases / antagonists & inhibitors*
Mitogen-Activated Protein Kinase Kinases / metabolism
Molecular Docking Simulation
Morpholines / chemistry*
Phosphatidylinositol 3-Kinases / chemistry*
Phosphatidylinositol 3-Kinases / metabolism
Phosphoinositide-3 Kinase Inhibitors / chemistry*
Phosphoinositide-3 Kinase Inhibitors / metabolism
Phosphoinositide-3 Kinase Inhibitors / therapeutic use
Primary Myelofibrosis / drug therapy
Protein Isoforms / antagonists & inhibitors
Protein Isoforms / metabolism
Structure-Activity Relationship
Triazines / chemistry*
Triazines / metabolism
Triazines / therapeutic use

Substances

Morpholines
Phosphoinositide-3 Kinase Inhibitors
Protein Isoforms
Triazines
ZSTK474
morpholine
Mitogen-Activated Protein Kinase Kinases

Abstract

MeSH terms

Substances

Grants and funding