CC-115, a selective dual inhibitor of the mammalian target of rapamycin (mTOR) kinase and DNA-dependent protein kinase (DNA-PK), is undergoing Phase 1 clinical studies. Here we report the ...characterization of DNA-PK inhibitory activity of CC-115 in cancer cell lines. CC-115 inhibits auto-phosphorylation of the catalytic subunit of DNA-PK (DNA-PKcs) at the S2056 site (pDNA-PK S2056), leading to blockade of DNA-PK-mediated non-homologous end joining (NHEJ). CC-115 also indirectly reduces the phosphorylation of ataxia-telangiectasia mutated kinase (ATM) at S1981 and its substrates as well as homologous recombination (HR). The mTOR kinase and DNA-PK inhibitory activity of CC-115 leads to not only potent anti-tumor activity against a large panel of hematopoietic and solid cancer cell lines but also strong induction of apoptosis in a subset of cancer lines. Mechanistically, CC-115 prevents NHEJ by inhibiting the dissociation of DNA-PKcs, X-ray repair cross-complementing protein 4 (XRCC4), and DNA ligase IV from DNA ends. CC-115 inhibits colony formation of ATM-deficient cells more potently than ATM-proficient cells, indicating that inhibition of DNA-PK is synthetically lethal with the loss of functional ATM. In conclusion, CC-115 inhibits both mTOR signaling and NHEJ and HR by direct inhibition of DNA-PK. The mechanistic data not only provide selection of potential pharmacodynamic (PD) markers but also support CC-115 clinical development in patients with ATM-deficient tumors.
Summary
Sotatercept (ACE‐011), a recombinant human fusion protein containing the extracellular domain of the human Activin receptor IIA, binds to and inhibits activin and other members of the ...transforming growth factor ‐β (TGF‐β) superfamily. Administration of sotatercept led to a rapid and sustained increase in red blood cell (RBC) count and haemoglobin (Hb) in healthy volunteers (phase I clinical trials), but the mechanism is not fully understood. Mice treated with RAP‐011 (murine ortholog of ACE‐011) respond with a rapid (within 24 h) increase in haematocrit, Hb, and RBC count. These effects are accompanied by an equally rapid stimulation of late‐stage erythroid precursors in the bone marrow (BM). RAP‐011 also induces a significant increase in erythroid burst‐forming units and erythropoietin, which could contribute to additional, sustained effects on RBC production. Further in vitro co‐culture studies demonstrate that BM accessory cells are required for RAP‐011 effects. To better understand which TGF‐β family ligand(s) mediate RAP‐011 effects, we evaluated the impact of several of these ligands on erythroid differentiation. Our data suggest that RAP‐011 may act to rescue growth differentiation factor 11/Activin A‐induced inhibition of late‐stage erythropoiesis. These data define the mechanism of action of a novel agent that regulates RBC differentiation and provide the rationale to develop sotatercept for the treatment of anaemia and ineffective erythropoiesis.
Cluster of differentiation 47 (CD47) is a transmembrane protein ubiquitously expressed on human cells but overexpressed on many different tumor cells. The interaction of CD47 with signal-regulatory ...protein alpha (SIRPα) triggers a “don’t eat me” signal to the macrophage, inhibiting phagocytosis. Thus, overexpression of CD47 enables tumor cells to escape from immune surveillance via the blockade of phagocytic mechanisms. We report here the development and characterization of CC-90002, a humanized anti-CD47 antibody. CC-90002 is unique among previously reported anti-CD47 bivalent antibodies that it does not promote hemagglutination while maintaining high-affinity binding to CD47 and inhibition of the CD47–SIRPα interaction. Studies in a panel of hematological cancer cell lines showed concentration-dependent CC-90002-mediated phagocytosis in acute lymphoblastic leukemia, acute myeloid leukemia (AML), lenalidomide-resistant multiple myeloma (MM) cell lines and AML cells from patients. In vivo studies with MM cell line-derived xenograft models established in immunodeficient mice demonstrated significant dose-dependent antitumor activity of CC-90002. Treatment with CC-90002 significantly prolonged survival in an HL-60-disseminated AML model. Mechanistic studies confirmed the binding of CC-90002 to tumor cells and concomitant recruitment of F4-80 positive macrophages into the tumor and an increase in expression of select chemokines and cytokines of murine origin. Furthermore, the role of macrophages in the CC-90002-mediated antitumor activity was demonstrated by transient depletion of macrophages with liposome-clodronate treatment. In non-human primates, CC-90002 displayed acceptable pharmacokinetic properties and a favorable toxicity profile. These data demonstrate the potential activity of CC-90002 across hematological malignancies and provided basis for clinical studies CC-90002-ST-001 (NCT02367196) and CC-90002-AML-001 (NCT02641002).
Summary
Pomalidomide is an IMiD® immunomodulatory agent, which has shown clinically significant benefits in relapsed and/or refractory multiple myeloma (rrMM) patients when combined with ...dexamethasone, regardless of refractory status to lenalidomide or bortezomib. (Schey et al, ; San Miguel et al, 2013; Richardson et al, 2014; Scott, ) In this work, we present preclinical data showing that the combination of pomalidomide with dexamethasone (PomDex) demonstrates potent anti‐proliferative and pro‐apoptotic activity in both lenalidomide‐sensitive and lenalidomide‐resistant MM cell lines. PomDex also synergistically inhibited tumour growth compared with single‐agent treatment in xenografts of lenalidomide‐resistant H929 R10‐1 cells. Typical hallmarks of IMiD compound activity, including IKZF3 (Aiolos) degradation, and the downregulation of interferon regulatory factor (IRF) 4 and MYC, seen in lenalidomide‐sensitive H929 MM cell lines, were also observed in PomDex‐treated lenalidomide‐resistant H929 MM cells. Remarkably, this resulted in strong, synergistic effects on the induction of apoptosis in both lenalidomide‐sensitive and resistant MM cells. Furthermore, gene expression profiling revealed a unique differential gene expression pattern in PomDex‐treated samples, highlighted by the modulation of pro‐apoptotic pathways in lenalidomide‐resistant cells. These results provide key insights into molecular mechanisms of PomDex in the lenalidomide‐resistant setting.
Historically, phenotypic-based drug discovery has yielded a high percentage of novel drugs while uncovering new tumor biology. CC-671 was discovered using a phenotypic screen for compounds that ...preferentially induced apoptosis in triple-negative breast cancer cell lines while sparing luminal breast cancer cell lines. Detailed
kinase profiling shows CC-671 potently and selectively inhibits two kinases-TTK and CLK2. Cellular mechanism of action studies demonstrate that CC-671 potently inhibits the phosphorylation of KNL1 and SRp75, direct TTK and CLK2 substrates, respectively. Furthermore, CC-671 causes mitotic acceleration and modification of pre-mRNA splicing leading to apoptosis, consistent with cellular TTK and CLK inhibition. Correlative analysis of genomic and potency data against a large panel of breast cancer cell lines identifies breast cancer cells with a dysfunctional G
-S checkpoint as more sensitive to CC-671, suggesting synthetic lethality between G
-S checkpoint and TTK/CLK2 inhibition. Furthermore, significant
CC-671 efficacy was demonstrated in two cell line-derived and one patient tumor-derived xenograft models of triple-negative breast cancer (TNBC) following weekly dosing. These findings are the first to demonstrate the unique inhibitory combination activity of a dual TTK/CLK2 inhibitor that preferably kills TNBC cells and shows synthetic lethality with a compromised G
-S checkpoint in breast cancer cell lines. On the basis of these data, CC-671 was moved forward for clinical development as a potent and selective TTK/CLK2 inhibitor in a subset of patients with TNBC.
.
mTOR pathway hyperactivation occurs in approximately 90% of glioblastomas, but the allosteric mTOR inhibitor rapamycin has failed in the clinic. Here, we examine the efficacy of the newly discovered ...ATP-competitive mTOR kinase inhibitors CC214-1 and CC214-2 in glioblastoma, identifying molecular determinants of response and mechanisms of resistance, and develop a pharmacologic strategy to overcome it.
We conducted in vitro and in vivo studies in glioblastoma cell lines and an intracranial model to: determine the potential efficacy of the recently reported mTOR kinase inhibitors CC214-1 (in vitro use) and CC214-2 (in vivo use) at inhibiting rapamycin-resistant signaling and blocking glioblastoma growth and a novel single-cell technology-DNA Encoded Antibody Libraries-was used to identify mechanisms of resistance.
Here, we show that CC214-1 and CC214-2 suppress rapamycin-resistant mTORC1 signaling, block mTORC2 signaling, and significantly inhibit the growth of glioblastomas in vitro and in vivo. EGFRvIII expression and PTEN loss enhance sensitivity to CC214 compounds, consistent with enhanced efficacy in strongly mTOR-activated tumors. Importantly, CC214 compounds potently induce autophagy, preventing tumor cell death. Genetic or pharmacologic inhibition of autophagy greatly sensitizes glioblastoma cells and orthotopic xenografts to CC214-1- and CC214-2-induced cell death.
These results identify CC214-1 and CC214-2 as potentially efficacious mTOR kinase inhibitors in glioblastoma, and suggest a strategy for identifying patients most likely to benefit from mTOR inhibition. In addition, this study also shows a central role for autophagy in preventing mTOR-kinase inhibitor-mediated tumor cell death, and suggests a pharmacologic strategy for overcoming it.
DNA-dependent protein kinase catalytic subunit (DNA-PK) is a pleiotropic kinase involved in DNA repair and transcriptional regulation. DNA-PK is deregulated in selected cancer types and is strongly ...associated with poor outcome. The underlying mechanisms by which DNA-PK promotes aggressive tumor phenotypes are not well understood. Here, unbiased molecular investigation in clinically relevant tumor models reveals novel functions of DNA-PK in cancer.
DNA-PK function was modulated using both genetic and pharmacologic methods in a series of
models,
xenografts, and patient-derived explants (PDE), and the impact on the downstream signaling and cellular cancer phenotypes was discerned. Data obtained were used to develop novel strategies for combinatorial targeting of DNA-PK and hormone signaling pathways.
Key findings reveal that (i) DNA-PK regulates tumor cell proliferation; (ii) pharmacologic targeting of DNA-PK suppresses tumor growth both
, and
; (iii) DNA-PK transcriptionally regulates the known DNA-PK-mediated functions as well as novel cancer-related pathways that promote tumor growth; (iv) dual targeting of DNA-PK/TOR kinase (TORK) transcriptionally upregulates androgen signaling, which can be mitigated using the androgen receptor (AR) antagonist enzalutamide; (v) cotargeting AR and DNA-PK/TORK leads to the expansion of antitumor effects, uncovering the modulation of novel, highly relevant protumorigenic cancer pathways; and (viii) cotargeting DNA-PK/TORK and AR has cooperative growth inhibitory effects
and
.
These findings uncovered novel DNA-PK transcriptional regulatory functions and led to the development of a combinatorial therapeutic strategy for patients with advanced prostate cancer, currently being tested in the clinical setting.
Mutations in α-synuclein have been linked to rare, autosomal dominant forms of Parkinson's disease. Despite its ubiquitous expression, mutant α-synuclein primarily leads to the loss of ...dopamine-producing neurons in the substantia nigra. α-Synuclein is a presynaptic nerve terminal protein of unknown function, although several studies suggest it is important for synaptic plasticity and maintenance. The present study utilized a new human mesencephalic cell line, MESC2.10, to study the effect of A53T mutant α-synuclein on dopamine homeostasis. In addition to expressing markers of mature dopamine neurons, differentiated MESC2.10 cells are electrically active, produce dopamine, and express wild-type human α-synuclein. Lentivirus-induced overexpression of A53T mutant α-synuclein in differentiated MESC2.10 cells resulted in down-regulation of the vesicular dopamine transporter (VMAT2), decreased potassium-induced and increased amphetamine-induced dopamine release, enhanced cytoplasmic dopamine immunofluorescence, and increased intracellular levels of superoxide. These results suggest that mutant α-synuclein leads to an impairment in vesicular dopamine storage and consequent accumulation of dopamine in the cytosol, a pathogenic mechanism that underlies the toxicity of the psychostimulant amphetamine and the parkinsonian neurotoxin 1-methyl-4-phenylpyridinium. Interestingly, cells expressing A53T mutant α-synuclein were resistant to amphetamine-induced toxicity. Because extravesicular, cytoplasmic dopamine can be easily oxidized into reactive oxygen species and other toxic metabolites, mutations in α-synuclein might lead to Parkinson's disease by triggering protracted, low grade dopamine toxicity resulting in terminal degeneration and ultimately cell death.
mTOR is a serine/threonine kinase that regulates cell growth, metabolism, proliferation, and survival. mTOR complex-1 (mTORC1) and mTOR complex-2 (mTORC2) are critical mediators of the PI3K-AKT ...pathway, which is frequently mutated in many cancers, leading to hyperactivation of mTOR signaling. Although rapamycin analogues, allosteric inhibitors that target only the mTORC1 complex, have shown some clinical activity, it is hypothesized that mTOR kinase inhibitors, blocking both mTORC1 and mTORC2 signaling, will have expanded therapeutic potential. Here, we describe the preclinical characterization of CC-223. CC-223 is a potent, selective, and orally bioavailable inhibitor of mTOR kinase, demonstrating inhibition of mTORC1 (pS6RP and p4EBP1) and mTORC2 pAKT(S473) in cellular systems. Growth inhibitory activity was demonstrated in hematologic and solid tumor cell lines. mTOR kinase inhibition in cells, by CC-223, resulted in more complete inhibition of the mTOR pathway biomarkers and improved antiproliferative activity as compared with rapamycin. Growth inhibitory activity and apoptosis was demonstrated in a panel of hematologic cancer cell lines. Correlative analysis revealed that IRF4 expression level associates with resistance, whereas mTOR pathway activation seems to associate with sensitivity. Treatment with CC-223 afforded in vivo tumor biomarker inhibition in tumor-bearing mice, after a single oral dose. CC-223 exhibited dose-dependent tumor growth inhibition in multiple solid tumor xenografts. Significant inhibition of mTOR pathway markers pS6RP and pAKT in CC-223-treated tumors suggests that the observed antitumor activity of CC-223 was mediated through inhibition of both mTORC1 and mTORC2. CC-223 is currently in phase I clinical trials.
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