Robyn Fabrey

Bio: Robyn Fabrey is an academic researcher from Takeda Pharmaceutical Company. The author has contributed to research in topics: PI3K/AKT/mTOR pathway & Kinase. The author has an hindex of 3, co-authored 11 publications receiving 55 citations.

Biological Characterization of TAK-901, an Investigational, Novel, Multitargeted Aurora B Kinase Inhibitor

Abstract: Protein kinases Aurora A, B, and C play essential roles during mitosis and cell division, are frequently elevated in cancer, and represent attractive targets for therapeutic intervention. TAK-901 is an investigational, multitargeted Aurora B kinase inhibitor derived from a novel azacarboline kinase hinge-binder chemotype. TAK-901 exhibited time-dependent, tight-binding inhibition of Aurora B, but not Aurora A. Consistent with Aurora B inhibition, TAK-901 suppressed cellular histone H3 phosphorylation and induced polyploidy. In various human cancer cell lines, TAK-901 inhibited cell proliferation with effective concentration values from 40 to 500 nmol/L. Examination of a broad panel of kinases in biochemical assays revealed inhibition of multiple kinases. However, TAK-901 potently inhibited only a few kinases other than Aurora B in intact cells, including FLT3 and FGFR2. In rodent xenografts, TAK-901 exhibited potent activity against multiple human solid tumor types, and complete regression was observed in the ovarian cancer A2780 model. TAK-901 also displayed potent activity against several leukemia models. In vivo biomarker studies showed that TAK-901 induced pharmacodynamic responses consistent with Aurora B inhibition and correlating with retention of TAK-901 in tumor tissue. These preclinical data highlight the therapeutic potential of TAK-901, which has entered phase I clinical trials in patients within a diverse range of cancers.

Antitumor Activity of the MEK Inhibitor TAK-733 against Melanoma Cell Lines and Patient-Derived Tumor Explants

Abstract: The goal of this study was to investigate the activity of the selective MEK1/2 inhibitor TAK-733 in both melanoma cell lines and patient-derived melanoma xenograft models. In vitro cell proliferation assays using the sulforhodamine B assay were conducted to determine TAK-733 potency and melanoma responsiveness. In vivo murine modeling with eleven patient-derived melanoma explants evaluated daily dosing of TAK-733 at 25 or 10 mg/kg. Immunoblotting was performed to evaluate on-target activity and downstream inhibition by TAK-733 in both in vitro and in vivo studies. TAK-733 demonstrated broad activity in most melanoma cell lines with relative resistance observed at IC50 > 0.1 μmol/L in vitro. TAK-733 also exhibited activity in 10 out of 11 patient-derived explants with tumor growth inhibition ranging from 0% to 100% (P < 0.001-0.03). Interestingly, BRAF(V600E) and NRAS mutational status did not correlate with responsiveness to TAK-733. Pharmacodynamically, pERK was suppressed in sensitive cell lines and tumor explants, confirming TAK-733-mediated inhibition of MEK1/2, although the demonstration of similar effects in the relatively resistant cell lines and tumor explants suggests that escape pathways are contributing to melanoma survival and proliferation. These data demonstrate that TAK-733 exhibits robust tumor growth inhibition and regression against human melanoma cell lines and patient-derived xenograft models, suggesting that further clinical development in melanoma is of scientific interest. Particularly interesting is the activity in BRAF wild-type models, where current approved therapy such as vemurafenib has been reported not to be active.

Abstract C146: Combination treatment with the investigational RAF kinase inhibitor MLN2480 and the investigational MEK kinase inhibitor TAK-733 inhibits the growth of BRAF mutant and RAS mutant preclinical models of melanoma and CRC.

Abstract: Background: RAS mutant melanoma and colorectal cancer represent areas of significant unmet medical need. MLN2480 is an investigational class II RAF kinase inhibitor and TAK-733 is an investigational allosteric MEK kinase inhibitor; each of which is the subject of a single agent phase I clinical trial. The present studies have characterized the combination activity of these agents in BRAF mutant and RAS mutant preclinical models of melanoma and colorectal cancer. Methods: Combination effects of MLN2480 and TAK-733 on cell viability were studied using an ATP-based cell viability assay across a panel of BRAF and RAS mutant melanoma and CRC cell lines. Western blot analysis was used to compare effects on MAPK pathway signaling and response markers in cell lines showing a range of sensitivity to this combination. Pharmacodynamic responses and growth inhibitory effects of the combination were studied in xenografts of the same cell lines, as well as in primary human tumor xenografts, of RAS mutant melanoma and CRC. Results: MLN2480 inhibits MAPK pathway signaling in BRAF mutant and some RAS mutant preclinical cancer models at concentrations that are tolerated in vivo. MLN2480 is most potent in BRAF mutant melanoma models but also has single agent activity in some RAS mutant models. The combination of MLN2480 with TAK-733 inhibits the growth of a broader range of RAS mutant tumor models than single agent MLN2480, including primary human tumor xenograft models of melanoma and CRC. In vitro analysis of this drug combination in cell proliferation assays demonstrates synergistic activity. Western blot analysis demonstrated the effect of MLN2480 in reversing feedback activation of MEK in response to TAK-733, leading to more concerted MAPK pathway inhibition. Conclusions: The activity of the RAF kinase inhibitor MLN2480 in preclinical models of BRAF and RAS mutant melanoma and CRC provides a rationale for clinical testing. The combination of MLN2480 with the MEK inhibitor TAK-733 represents an additional strategy for clinical research within these tumor types. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C146. Citation Format: Elizabeth Grace Carideo Cunniff, Julie Zhang, Jouhara Chouitar, Jerome Mettetal, Kazuhide Nakamura, Takeo Arita, Akito Nakamura, Masanori Okaniwa, Tomoyasu Ishikawa, Sei Yoshida, Robyn Fabrey, Patrick Vincent, Kurt Eng, Khristofer Garcia, Deanna Borelli, Teena Vagrhese, Steve Stroud, Saurabh Menon, Mike Kuranda, Katherine Galvin. Combination treatment with the investigational RAF kinase inhibitor MLN2480 and the investigational MEK kinase inhibitor TAK-733 inhibits the growth of BRAF mutant and RAS mutant preclinical models of melanoma and CRC. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C146.

Abstract B189: MLN0128, an investigational mTORC1/2 inhibitor, demonstrates potent antitumor activity alone and in combination with paclitaxel in preclinical models of endometrial cancer.

Abstract: Endometrial cancers are the most common gynecologic cancers in the US, and are a heterogeneous group of malignancies with distinct molecular characteristics. The phosphatidylinositol-3-kinase (PI3K)-AKT-mammalian target of rapamycin (mTOR) pathway is frequently dysregulated, being activated in 70-80% of hormone-dependent endometrioid carcinomas (Type I) and 40% of non-endometrioid carcinomas (Type II). Loss of PTEN or activation of PIK3CA results in constitutive activation of AKT and up-regulation of mTOR. We evaluated MLN0128, an investigational catalytic mTORC1/2 inhibitor, in preclinical models of endometrial cancer to assess its activity as a single agent and in combination with paclitaxel across various dose schedules and sequences. In vitro MLN0128 showed antiproliferative activity with IC50 values of 5-100 nM across cell line models (n=9) with various genetic aberrations including complex combinations of PTEN loss and mutations in PIK3CA, KRAS and/or FGFR. This antiproliferative activity was associated with inhibition of pathway markers, including phosphorylated AKT, S6, and 4EBP1. In vivo MLN0128 demonstrated tumor growth inhibition (TGI) in a PIK3CA/KRAS model (HEC-1A) and a PTEN/FGFR model (AN3CA) with TGI values of 62% and 73%, respectively. Similar TGI values were achieved regardless of dosing schedule (once daily [QD], 3 days a week [QDx3D], or once weekly [QW]). TGI could be improved by using a combination approach. In the AN3CA model, the in vitro combination of MLN0128 and paclitaxel suppressed the PI3K pathway activation (phosphorylation of AKT, S6, and 4EBP1) that occurred when paclitaxel was administered alone; the combination also suppressed S6 phosphorylation at 24 hours. This finding correlated with an increase in the induction of cleaved PARP, a marker of apoptosis, and accumulation of cells in the sub-G1 phase of the cell cycle. The combination was also observed to add benefit in vivo, most prominently when tumor regrowth was assessed. In the HEC-1A model, TGI only increased by 10% with concomitant administration of MLN0128 and paclitaxel daily vs MLN0128 alone. However, when monitoring re-growth 18 days after administration, this difference in TGI (combination vs MLN0128 alone) increased to 44%. Furthermore pretreatment with paclitaxel before MLN0128 was also associated with significant enhancement of antitumor activity relative to the concomitant administration of both agents; this effect was observed with the QDx3D and QW MLN0128 schedules. Results from these preclinical studies support further investigation of MLN0128 in endometrial cancer, either as a single agent or in combination with current standards of care. Phase 1 studies are ongoing to investigate single-agent MLN0128 ([NCT01058707][1]) and MLN0128 plus paclitaxel ([NCT01351350][2]) in advanced solid tumors. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B189. Citation Format: Karuppiah Kannan, Robyn Fabrey, Jodi Cooper, Jessica Huck, Esha Gangolli, Eric Westin, Rachael Brake. MLN0128, an investigational mTORC1/2 inhibitor, demonstrates potent antitumor activity alone and in combination with paclitaxel in preclinical models of endometrial cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B189. [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT01058707&atom=%2Fmolcanther%2F12%2F11_Supplement%2FB189.atom [2]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT01351350&atom=%2Fmolcanther%2F12%2F11_Supplement%2FB189.atom

Abstract 2518: TAK-733 is a Potent and Selective Inhibitor of Mammalian MEK Kinases Capable of Inducing Apoptosis in BRAF Driven Cells Bothin vitroandin vivo

Abstract: Mutations in BRAF a serine/threonine protein kinase are frequently observed in human cancers. A valine to glutamic acid mutation at amino acid position 600 accounts for nearly 80% of all the activating mutations found for this kinase. This mutation (V600E) forces BRAF to become constitutively active and phosphorylate its substrates regardless of upstream signaling. Numerous cancers in tissues such as skin, colon, thyroid, and ovary have been attributed to uncontrolled proliferation driven by this mutation. TAK-733 represents a novel and distinct chemotype which is capable of allosteric inhibition of the BRAF substrates MEK-1 and MEK-2 at low nanomolar concentrations. Viability assays in established human cancer cell lines which bear the BRAF V600E mutation demonstrate this compound was also capable of lowering NADH levels with single digit nanomolar EC50s. Loss of NADH production can be attributed to the induction of programmed cell death pathways involving Caspases 3 and 7. Induction of these apoptosis markers was confirmed in vitro by a Caspase-GLO assay. TAK-733 induces apoptosis more potently in COLO 205 (BRAF V600E) human colo-rectal carcinoma cells when compared to other MEK inhibitors. Pharmacodynamic analysis of COLO 205 tumor bearing mice confirmed TAK-733, unlike other MEK inhibitors tested, is capable of inducing apoptosis 36 hours after a single oral administration. To determine whether the anti-tumor effect of TAK-733 is associated with apoptosis, A375 (BRAF V600E) human melanoma tumors were harvested at sacrifice and protein extracted to determine cleavage products of PARP. A single oral treatment with 1, 10, and 30 mg/kg TAK-733 increased protein expression of cleaved PARP in a dose and time dependent manner. Elevated cleaved PARP protein expression was detected as early as 0.5-hours in tumors following 30 mg/kg dose and detectable at all groups by 4-hours. The increase cleaved PARP protein levels persisted for at least 24-hours and returned to control expression levels by 48-hours. Daily oral administration of 1, 10, and 30 mg/kg/day TAK-733 for 14 days potently inhibited tumor growth resulting in tumor growth delay of 3.4, 10.8, and 26.6 days in A375 cell implanted mice. A 60% partial regression response rate (tumor volume reduced by more than 50% of initial volume) was observed in mice that received 30 mg/kg/day TAK-733. These data suggest a possible explanation as to why TAK-733 is capable of inducing regressions in COLO 205 and A375 tumor growth inhibition studies, and may represent a differentiation point from other MEK inhibitors currently in clinical trials. 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 2518.

Whole-exome sequencing identifies recurrent SF3B1 R625 mutation and comutation of NF1 and KIT in mucosal melanoma.

Abstract: Mucosal melanomas are a rare subtype of melanoma, arising in mucosal tissues, which have a very poor prognosis due to the lack of effective targeted therapies. This study aimed to better understand the molecular landscape of these cancers and find potential new therapeutic targets. Whole-exome seque

Current Advances in the Treatment of BRAF-Mutant Melanoma

Abstract: Melanoma is the most lethal form of skin cancer. Melanoma is usually curable with surgery if detected early, however, treatment options for patients with metastatic melanoma are limited and the five-year survival rate for metastatic melanoma had been 15–20% before the advent of immunotherapy. Treatment with immune checkpoint inhibitors has increased long-term survival outcomes in patients with advanced melanoma to as high as 50% although individual response can vary greatly. A mutation within the MAPK pathway leads to uncontrollable growth and ultimately develops into cancer. The most common driver mutation that leads to this characteristic overactivation in the MAPK pathway is the B-RAF mutation. Current combinations of BRAF and MEK inhibitors that have demonstrated improved patient outcomes include dabrafenib with trametinib, vemurafenib with cobimetinib or encorafenib with binimetinib. Treatment with BRAF and MEK inhibitors has met challenges as patient responses began to drop due to the development of resistance to these inhibitors which paved the way for development of immunotherapies and other small molecule inhibitor approaches to address this. Resistance to these inhibitors continues to push the need to expand our understanding of novel mechanisms of resistance associated with treatment therapies. This review focuses on the current landscape of how resistance occurs with the chronic use of BRAF and MEK inhibitors in BRAF-mutant melanoma and progress made in the fields of immunotherapies and other small molecules when used alone or in combination with BRAF and MEK inhibitors to delay or circumvent the onset of resistance for patients with stage III/IV BRAF mutant melanoma.

Stamping out RAF and MEK1/2 to inhibit the ERK1/2 pathway: an emerging threat to anticancer therapy.

Abstract: The RAS-RAF-MEK1/2-ERK1/2 pathway is a key signal transduction pathway in the cells. Critically, it remains constitutively active in approximately 30% of human cancers, having key roles in cancer development, maintenance and progression, while being responsible for poorer prognosis and drug resistance. Consequently, the inhibition of this pathway has been the subject of intense research for >25 years. The advent of better patient screening techniques has increasingly shown that upstream regulators like RAS and RAF remain persistently mutated in many cancer types. These gain-of-function mutations, such as KRAS-4B(G12V/G13D/Q61K), NRAS(Q61L/Q61R) or BRAF(V600E), lead to tremendous increase in their activities, resulting in constitutively active extracellular signal-regulated kinase 1/2 (ERK1/2). They were not efficiently targeted by the first-generation inhibitors such as Lonafarnib or Sorafenib, which were essentially broad spectrum inhibitors targeting pan-RAS and pan-RAF, respectively. This triggered the development of the second-generation inhibitors selective against the mutated proteins. Second generation inhibitors such as Vemurafenib (Zelboraf) and Dabrafenib (Tafinlar) targeting BRAF(V600E), Trametinib (Mekinist) targeting MEK1/2 and the first generation pan-RAF inhibitor Sorafenib (Nexavar) have already been approved for treating renal, hepatocellular, thyroid cancers and BRAF(V600E/K) harboring metastatic melanoma. Others against RAF and MEK1/2 are presently undergoing clinical trials. Their success would depend on the better understanding of the acquired resistance mechanisms to these drugs in the cancer cells and the identification of predictive biomarkers for the proper administration of suitable inhibitor(s).