The ETS Inhibitors YK-4-279 and TK-216 Are Novel Antilymphoma Agents

PURPOSE

Transcription factors are commonly deregulated in cancer, and they have been widely considered as difficult to target due to their nonenzymatic mechanism of action. Altered expression levels of members of the ETS-transcription factors are often observed in many different tumors, including lymphomas. Here, we characterized two small molecules, YK-4-279 and its clinical derivative, TK-216, targeting ETS factors via blocking the protein-protein interaction with RNA helicases, for their antilymphoma activity.

EXPERIMENTAL DESIGN

The study included preclinical in vitro activity screening on a large panel of cell lines, both as single agent and in combination; validation experiments on in vivo models; and transcriptome and coimmunoprecipitation experiments.

RESULTS

YK-4-279 and TK-216 demonstrated an antitumor activity across several lymphoma cell lines, which we validated in vivo. We observed synergistic activity when YK-4-279 and TK-216 were combined with the BCL2 inhibitor venetoclax and with the immunomodulatory drug lenalidomide. YK-4-279 and TK-216 interfere with protein interactions of ETS family members SPIB, in activated B-cell-like type diffuse large B-cell lymphomas, and SPI1, in germinal center B-cell-type diffuse large B-cell lymphomas.

CONCLUSIONS

The ETS inhibitor YK-4-279 and its clinical derivative TK-216 represent a new class of agents with in vitro and in vivo antitumor activity in lymphomas. Although their detailed mechanism of action needs to be fully defined, in DLBCL they might act by targeting subtype-specific essential transcription factors.

Abstract 694: TK-216: a novel, first-in-class, small molecule inhibitor of EWS-FLI1 in early clinical development, for the treatment of Ewing Sarcoma

One of the most significant challenges in creating more potent, less toxic treatments for patients is to identify new cancer therapeutic targets that distinguish the malignant from normal cells. EWS-FLI1 is a well-established Ewing sarcoma (ES) oncogene that has the potential to be an ideal therapeutic target by directly impacting malignant cells. We have previously reported the discovery and characterization of YK-4-279, an enantiomer-specific inhibitor of EWS-FLI1, which has been demonstrated to induce apoptosis, inhibit EWS-FLI1 transcription, block RNA helicase A co-immunoprecipitation with EWS-FLI1, and result in alternative splicing to mimic EWS-FLI1 knockdown. Continuous efforts in structure-guided medicinal chemistry has yielded TK-216, an analog of YK-4-279 inhibitor of EWS-FLI1, which is 3-4 fold more potent with excellent drug-like properties. TK-216 potently inhibits the proliferation of ES cells. Induces apoptosis in a dose -dependent manner as measured by caspase-3 activity in multiple ES cell lines with distinct translocation variants. The effects of TK-216 on alternative splicing (AS) were further validated using genes including ARID1A, CLK1, CASP3, PPFIBP1 and RUNX2. The splicing pattern was similar between TK-216 and YK-4-279. In addition to the in vitro activity of TK-216 , we show that TK-216 displays anti-tumor activity in a number of ES xenograft models. In summary, TK-216, a novel, first-in-class therapeutic which directly inhibits EWS-FLI1, offers a promising approach for the treatment of Ewing Sarcoma and is currently in Phase 1 clinical trials in patients with relapsed or refractory Ewing Sarcoma (clinicaltrials.gov - NCT02657005).

Citation Format: Saravana P. Selvanathan, Eric Moseley, Garrett T. Graham, Katti Jessen, Brian Lannutti, Aykut Üren, Jeffrey A. Toretsky. TK-216: a novel, first-in-class, small molecule inhibitor of EWS-FLI1 in early clinical development, for the treatment of Ewing Sarcoma [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 694. doi:10.1158/1538-7445.AM2017-694

Abstract 5179: The first in class FLI1 inhibitor TK-216 presents both in vitro and in vivo anti-tumor activity in lymphoma

Background. ETS transcription factors, such as FLI1 and SPIB, are recurrently deregulated in human lymphomas (Bonetti et al, Blood 2013; Lenz et al, PNAS 2008). The small molecule YK-4-279 inhibits binding of EWS1-FLI1 fusion protein to RHA resulting in growth arrest and apoptosis in Ewing sarcoma cells (Erkizan et al, Nat Med 2009) and we previously showed that YK-4-279 has in vitro anti-lymphoma activity (Chung et al, AACR 2015). TK-216 is a YK-4-279 clinical derivative that is in phase 1 for patients with relapsed or refractory Ewing sarcoma (NCT02657005). Here, we present extensive preclinical results obtained with TK-216 in lymphoma models.

Methods. 56 cell lines [27 diffuse large B cell lymphoma (DLBCL); 10 mantle cell lymphoma; 6 marginal zone lymphoma; 5 anaplastic large T-cell lymphoma; 8 others] were exposed to TK-216 increasing doses for 72h using a Tecan D300e Digital Dispenser and 384well plates; cell proliferation was measured with MTT. In vivo studies were performed in NOD-SCID mice and treatments started with approximately sc 60mm3 tumor volumes.

Results. TK-216 displayed high activity: median IC50 was 449 nM (95%CI: 367-506). Sensitivity was not affected by the lymphoma cell of origin [B vs T; activated B cell type (ABC) vs germinal center type DLBCL] or MYC and TP53 status. There was a non-statistically significant trend for lower sensitivity in cell lines bearing BCL2 chromosomal translocation (P=0.07, DLBCL only; P=0.06, all cell lines). Anti-tumor activity was mainly cytotoxic as confirmed by performing cell cycle analysis and Annexin V staining in 6 DLBCL cell lines (TMD8, U2932, HBL1, OCI-LY-18, WSU-DLCL2, DOHH2 for 24, 48, 72h), in which a time-dependent apoptosis was preceded by G2/M arrest.

Antitumor activity was confirmed in DLBCL TMD8 xenografts. Compared with control group (n=10), mice treated with TK-216 (100 mg/Kg, BID; n=9) clearly presented a reduction in tumor growth, already evident at day 3 and becoming much stronger with time (D3, D5, D8, D11: P<0.01; D13, P not available since control group had to be stopped due to tumor volume) and a 4 times reduction in tumor volume at D11 (P<0.01).

TK-216 was tested in combination with other targeted agents in DLBCL cell lines. A benefit was observed with the combination of TK-216 with the immunomodulator lenalidomide (synergism in 2/2 ABC DLBCL), with the BET inhibitor OTX015 (MK-8628) (synergism in 2/4 cells and additive effect in 1/4), the anti-CD20 monoclonal antibody rituximab (synergism in 2/3 cells) and the BCL2 inhibitor venetoclax (synergism in 3/4 cells). The latter synergism could be linked to the previously mentioned negative trend between TK-216 IC50 values and the presence of BCL2 translocation.

Conclusions. The novel small molecule TK-216 presented strong preclinical anti-lymphoma activity, which provides evidence for further preclinical and clinical development as single agent and in combination.

Citation Format: Filippo Spriano, Chiara Tarantelli, Eugenio Gaudio, Elaine YL Chung, Alberto J. Arribas, Luciano Cascione, Sara Napoli, Ivo Kwee, Andrea Rinaldi, Davide Rossi, Emanuele Zucca, Anastasios Stathis, Katti Jessen, Brian Lannutti, Jeffrey Toretsky, Francesco Bertoni. The first in class FLI1 inhibitor TK-216 presents both in vitro and in vivo anti-tumor activity in lymphoma [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 5179. doi:10.1158/1538-7445.AM2017-5179

A phase I, first-in-human, dose escalation study of intravenous TK216 in patients with relapsed or refractory Ewing sarcoma

TPS11626

Background: Ewing sarcoma (ES) is a rare cancer that affects children and young adults. Patients with recurrent/refractory ES have a poor prognosis (5-year survival 10-15%) with no improvement despite advances in cytotoxic and targeted therapies. Genomic rearrangements resulting in fusion proteins and over-expression of ets family transcription factors occur in 95% of ES. In particular, the EWS-FLI1 oncogenic fusion creates a constitutively active transcription factor that drives the malignant ES phenotype. Strategies to target the EWS-FLI1 fusion protein have been limited by lack of specificity. A promising approach is to target the interaction of the ets transcription factor with its critical protein partner, RNA helicase A (RHA). TK216 is a novel small-molecule that directly binds to EWS-FLI1 and inhibits its function by blocking binding to RHA. TK216 demonstrates potent anti-proliferative effects on ES cell lines and xenografts. Methods: We initiated a Phase 1, first-in-human, open-label, multi-center, dose-escalation/dose-expansion trial of TK216 in patients with recurrent/refractory ES who are ≥12 years of age (ClinicalTrials.gov: NCT02657005). TK216 is dosed based on body surface area and administered as a continuous intravenous infusion for 7 days followed by 14 days rest every 21 days. Treatment may continue in the absence of disease progression. One intrapatient dose escalation is allowed. Enrollment of 6 to 8 cohorts using a 3+3 dose-escalation design is anticipated. During dose expansion, a total of 18 patients with ES will be accrued at the recommended Phase 2 dose (RP2D). The primary objective of the study is to determine the maximum tolerated dose and RP2D of TK216. Secondary objectives are to assess the safety profile, pharmacokinetics, pharmacodynamics, and antitumor activity of TK216. Molecular assays will be performed to characterize EWS-FLI or EWS-ets abnormalities in archival tumor tissue. The overall response rate, duration of response, progression-free survival, and overall survival will be determined in the expansion cohort. Nine patients have been enrolled since June 2016. Accrual to cohorts 1, 2, and 3 completed and cohort 4 opened in January 2017. Clinical trial information: NCT02657005.

Tetraspanin CD37 directly mediates transduction of survival and apoptotic signals

Tetraspanins are commonly believed to act only as "molecular facilitators," with no direct role in signal transduction. We herein demonstrate that upon ligation, CD37, a tetraspanin molecule expressed on mature normal and transformed B cells, becomes tyrosine phosphorylated, associates with proximal signaling molecules, and initiates a cascade of events leading to apoptosis. Moreover, we have identified two tyrosine residues with opposing regulatory functions: one lies in the N-terminal domain of CD37 in a predicted "ITIM-like" motif and mediates SHP1-dependent death, whereas the second lies in a predicted "ITAM motif" in the C-terminal domain of CD37 and counteracts death signals by mediating phosphatidylinositol 3-kinase-dependent survival.

Abstract 3555: Anti-tumor activity of CAL-101, a potent selective inhibitor of the p110Δ isoform of PI3K, in models of human glioblastoma

Phosphatidylinositol 3-kinase (PI3K) activation and Akt phosphorylation play a pivotal role in cell proliferation and survival, transducing signals from several cell surface receptors through PI3K isoforms (designated p110α, β, Δ, and γ). Our previous research has elucidated a significant role of the PI3K p110Δ (PI3KΔ) isoform in hematologic malignancies. Aberrant upregulation of the PI3K/Akt pathway is a frequently observed defect in human malignancies, including glioblastoma, but the role of the PI3KΔ isoform, has not been systematically evaluated. Selective inhibition of PI3KΔ with the orally bioavailable investigational drug, CAL-101, offers the potential for targeting PI3KΔ as a therapeutic approach to glioblastoma while avoiding undesirable side effects associated with pan-inhibitors that broadly block PI3K isoforms in multiple cell types. CAL-101 potently inhibits PI3KΔ (with an EC50 of 65 nM in a whole-blood assay) and shows >200-fold selectivity over other Class I PI3K isoforms and no activity against Class II and III PI3K family members or other PI3K-related proteins, including mTOR and DNA-PK. We examined expression levels of PI3KΔ and constitutive pathway activation in a panel of glioma cell lines (LN18, LN229, SF-539, U87MG, U138MG, and U251). PI3KΔ was consistently expressed and was functionally active, inducing high basal levels of phosphorylated-Akt (pAkt) in all tested cell lines. Treatment with CAL-101 decreased p-Akt levels in all cell lines and also reduced phosphorylation of the downstream pathway target, S6. Furthermore, PI3KΔ inhibition with CAL-101 resulted in an accumulation of cells in G1 and a decrease in the S phase population. Consistent with the effects of CAL-101 on G1 cell-cycle arrest, immunoblotting showed a decrease in cyclin D1 levels. In mice bearing U87MG xenografts, in vivo PI3KΔ inhibition resulted in significant anti-tumor effects, delaying time to tumor progression (tumor volume of >1000 mm3) by 30 days (p<0.001). Taken together, these data suggest that PI3KΔ overexpression and heightened functional activity contribute to glioblastoma proliferation, and that selective targeting of PI3KΔ may offer a novel therapeutic approach for patients with central nervous system tumors.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3555. doi:10.1158/1538-7445.AM2011-3555

Abstract B136: CAL-120, a novel dual p110β/p110δ phosphatidylinositol-3-kinase (PI3K) inhibitor, attenuates PI3K signaling and demonstrates potent in vivo antitumor activity against solid tumors

Phosphatidylinositide 3-kinases (PI3K) are a family of lipid kinases that are involved in signaling events which control a diverse number of cellular processes. The activation of the PI3K pathway by cell surface receptors is directly mediated by the class I isoforms (α, β, δ, and γ). Aberrant regulation of the PI3K signaling pathway is frequently observed in a wide range of human malignancies including gain-of-function mutations in PI3K p110α isoform and/or loss-of-function mutations in PTEN phosphatase, which is responsible for down regulation of PI3K signaling. In purified enzyme assays, CAL-120, a dual p110β/p110δ PI3K inhibitor, was inactive against class II and III PI3K family members,the PI3K-related protein kinases mTOR and DNA-PK as well as an additional ∼350 protein kinases in a genome wide screen. The ability of CAL-120 to block oncogenic transformation mediated by individual PI3K class Ia isoforms was evaluated in primary cells using viral transduction. Foci formation mediated by p110α and p110δ was inhibited at 15–200 nM whereas little or no inhibition was observed against oncogenic forms of p110α at 20-fold higher concentrations. To further demonstrate p110 isoform selectivity, AKT phosphorylation was induced in embryonic fibroblasts with PDGF or LPA that is mediated by p110α and p110β respectively. CAL-120 inhibited the p110β response with an IC50 of 1.2 µM whereas the p110α IC50 was greater than 20 µM. The antitumor activity of CAL-120 was evaluated in a panel of 23 human tumor cell lines representing different tissues and PI3K pathway mutations. Constitutive PI3K pathway activation as measured by AKT phosphorylation was observed in 50% of the cell lines and was highly correlated with PTEN mutations. In all cases, CAL-120 blocked AKT phosphorylation at concentrations of 0.1–1.0 µM. In most cases inhibition of the phosphorylation of downstream effectors Akt, GSK-3 , and S6 ribosomal protein was also observed over this concentration range. These effects of CAL-120 on PI3K pathway inhibition correlated with G1 cell cycle arrest leading to inhibition of tumor cell proliferation and in a number of cases induced apoptosis. Of note was a lack of PI3K pathway activation in cell lines with K-RAS mutations and their insensitivity to CAL-120 treatment. In mice bearing xenografts of MCF-7 breast adenocarcinoma (p110α mutation), PC-3 prostate adenocarcinoma (PTEN deficient), or OVCAR-3 ovarian adenocarcinoma (no pathway mutation), oral administration of CAL-120 significantly inhibited tumor growth or caused tumor regression in each of these models. These data are the first to demonstrate that p110β/δ inhibition in the absence of effects on p110α is an effective strategy for the treatment of solid tumors. The antitumor activity was not restricted to cells with PTEN loss and was surprisingly observed even when p110α mutations were present. Collectively, these preclinical data support clinical evaluation of CAL-120, an oral dual p110α/p110δ inhibitor, for the treatment of patients with solid tumors. (L. U. and P.K.V. are supported by grants from the National Cancer Institute. This is manuscript number 20362 of The Scripps Research Institute).

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):B136.