Abstract 4033: Pan-exon mutant KIT inhibitor DCC-3009 demonstrates tumor regressions in preclinical gastrointestinal stromal tumor models

Introduction: Gastrointestinal stromal tumors (GISTs) are typically driven by primary mutations in KIT exons 9 or 11. Heterogeneous drug-resistant secondary mutations arise in patients treated with FDA approved KIT inhibitors, including imatinib and sunitinib. Drug resistant secondary mutations are found at multiple regions in the ATP pocket (encoded by exons 13 and 14) or activation switch (encoded by exons 17 and 18) of KIT kinase. In addition, multiple drug-resistant clones can arise within a tumor or in metastatic tumor sites. An inhibitor that can broadly and potently inhibit the spectrum of KIT mutations is highly sought. Ripretinib has been FDA approved as a 4th line treatment for GIST and has broad activity against KIT mutations, including clinical potency in patients with mutations in KIT exons 11, 17, or 18. DCC-3009 was designed as a next generation KIT inhibitor that broadly and potently inhibits primary KIT mutations in exons 9 and 11 and secondary drug-resistant mutations across exons 13, 14, 17, and 18. DCC-3009 is a potent and selective inhibitor in enzyme and cell-based assays, and has demonstrated efficacy in xenograft models driven by drug resistant KIT mutations.

Methods: DCC-3009 was tested for inhibition of KIT mutants using standard enzyme and cell-based assays. Levels of phosphorylated KIT were determined by Western blot or ELISA. Proliferation was measured using the fluorescent dye resazurin. KIT mutant xenograft or patient-derived xenograft models were performed at Crown Biosciences or Labcorp, AAALAC accredited facilities, with the approval of Animal Care and Use Committees.

Results: In BaF3 cells transfected with KIT mutants, DCC-3009 was shown to potently inhibit the spectrum of known primary and secondary drug-resistant mutations in GIST. The pan-mutant KIT profile of DCC-3009 was shown in vitro to be superior to 2nd and 3rd line standard of care therapies sunitinib and regorafenib. DCC-3009 was selective for KIT when screened against a large panel of kinases. DCC-3009 has optimized pharmaceutical properties for oral administration. In pharmacokinetic/pharmacodynamic studies DCC-3009 achieved sufficient free drug levels to significantly inhibit drug-resistant KIT mutants for 12 hr post dose. In xenograft studies, treatment with DCC-3009 twice daily led to tumor regression in drug-resistant models with KIT exon 9/13, 11/13 or 11/17 mutations.

Conclusions: DCC-3009 is a pan-exon mutant KIT inhibitor exhibiting high potency in KIT mutants in pre-clinical models spanning exons 9, 11, 13, 14, 17 and 18. In vivo, DCC-3009 exhibited efficacy in drug-resistant models with KIT exon 9/13, 11/13 or 11/17 mutations. Based on this profile, DCC-3009 has entered formal preclinical development.

Citation Format: Bryan D. Smith, Subha Vogeti, Timothy M. Caldwell, Hanumaiah Telikepalli, Yu Mi Ahn, Gada Al-Ani, Stacie L. Bulfer, Andrew Greenwood, Cale L. Heiniger, Joshua W. Large, Cynthia B. Leary, Wei-Ping Lu, Kylie Luther, William C. Patt, Max D. Petty, Yeni K. Romero, Forrest A. Stanley, Kristen L. Stoltz, Daniel C. Tanner, Sihyung Yang, Yu Zhan, Bertrand Le Bourdonnec, Daniel L. Flynn. Pan-exon mutant KIT inhibitor DCC-3009 demonstrates tumor regressions in preclinical gastrointestinal stromal tumor models. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4033.

Abstract 4045: DCC-3084, a RAF dimer inhibitor, broadly inhibits BRAF class I, II, III, BRAF fusions, and RAS-driven solid tumors leading to tumor regression in preclinical models

Background: Mutations in the RAS/MAPK pathway are a frequent driver of cancer, with oncogenic RAS or RAF mutations occurring in >30% of all cancers. First generation BRAF inhibitors are approved for use for tumors with Class I BRAF mutations (V600X). However, these drugs are not efficacious in RAF dimer mutant and RAS mutant cancers due to paradoxical activation of RAF dimers. Herein, we describe DCC-3084, a potent and selective investigational Switch Control inhibitor of BRAF and CRAF kinase dimers that targets Class I, II and III BRAF mutations, BRAF fusions, and BRAF/CRAF heterodimers. DCC-3084 combines with inhibitors of additional nodes in the MAPK pathway to potentially target a large unmet medical need in RAS and RAF mutant cancers.

Methods: Inhibition of RAF kinases, including off-rate analysis, was measured using recombinant enzymes. X-ray crystallography was used for structure-based drug design. Cellular proliferation was measured using resazurin to monitor cell viability. Synergy in cells was measured using BLISS scores and curve shift analysis. Inhibition of ERK or RSK phosphorylation was measured by AlphaLISA or ELISA. Pharmacokinetics (PK) in the plasma, brain and CSF compartments were measured following oral dosing in Wistar rats. RAF and RAS mutant mouse xenograft models were used to assess PK, pharmacodynamics (PD), and efficacy.

Results: DCC-3084 is a potent and selective Switch Control inhibitor of RAF dimers that was designed to target Class I, II, III BRAF mutants, BRAF fusions, and BRAF/CRAF heterodimers. DCC-3084 inhibits BRAF and CRAF, exhibiting slow off-rates (t1/2 >20 hr). Potent single-agent inhibition of MAPK pathway signaling and cellular proliferation was observed in a wide range of Class I, II, III BRAF and BRAF fusion altered cell lines. Synergy was observed in combination with inhibitors of other nodes in the RAS/MAPK pathway in RAS mutant cell lines. DCC-3084 was demonstrated to be CNS penetrable and exhibited dose dependent oral exposure with robust inhibition of the RAS/MAPK pathway in PK/PD models. DCC-3084 accumulated in tumor tissue relative to plasma, further demonstrating a favorable pharmaceutical profile. Oral treatment of DCC-3084 as a single agent resulted in tumor regression in BRAF mutant and KRAS Q61K mutant mouse xenograft models and tumor growth inhibition in KRAS G12C/D mutant models. Additionally, DCC-3084 in combination with a MEKi resulted in tumor regression in KRAS mutant models.

Conclusions: The Switch Control inhibitor DCC-3084 broadly inhibits Class I, II and III BRAF mutations, BRAF fusions, and BRAF/CRAF heterodimers leading to tumor regression in preclinical models. The overall preclinical profile of DCC-3084 supports IND-enabling activities towards clinical development in a key area of unmet medical need in RAS and RAF mutant cancers.

Citation Format: Stacie L. Bulfer, Bertrand Le Bourdonnec, Jeffery D. Zwicker, Yu Mi Ahn, Gada Al-Ani, Hikmat Al-Hashimi, Chase Crawley, Kristin M. Elliott, Saqib Faisal, Andrew M. Harned, Cale L. Heiniger, Molly M. Hood, Salim Javed, Michael Kennedy, Joshua W. Large, Cynthia B. Leary, Wei-Ping Lu, Kylie Luther, Max D. Petty, Hunter R. Picard, Justin T. Proto, Yeni K. Romero, Forrest A. Stanley, Kristen L. Stoltz, Daniel C. Tanner, Hanumaiah Telikepalli, Mary J. Timson, Lakshminarayana Vogeti, Subha Vogeti, Sihyung Yang, Lexy H. Zhong, Bryan D. Smith, Daniel L. Flynn. DCC-3084, a RAF dimer inhibitor, broadly inhibits BRAF class I, II, III, BRAF fusions, and RAS-driven solid tumors leading to tumor regression in preclinical models. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4045.

Discovery of vimseltinib (DCC-3014), a highly selective CSF1R switch-control kinase inhibitor, in clinical development for the treatment of Tenosynovial Giant Cell Tumor (TGCT)

Based on knowledge of kinase switch-control inhibition and using a combination of structure-based drug design and standard medicinal chemistry principles, we identified a novel series of dihydropyrimidone-based CSF1R kinase inhibitors displaying exquisite selectivity for CSF1R versus a large panel of kinases and non-kinase protein targets. Starting with lead compound 3, an SAR optimization campaign led to the discovery of vimseltinib (DCC-3014; compound 20) currently undergoing clinical evaluation for the treatment of Tenosynovial Giant Cell Tumor (TGCT), a locally aggressive benign tumor associated with substantial morbidity. 2021 Elsevier ltd. All rights reserved.

Vimseltinib: A Precision CSF1R Therapy for Tenosynovial Giant Cell Tumors and Diseases Promoted by Macrophages

Macrophages can be co-opted to contribute to neoplastic, neurologic, and inflammatory diseases. Colony-stimulating factor 1 receptor (CSF1R)-dependent macrophages and other inflammatory cells can suppress the adaptive immune system in cancer and contribute to angiogenesis, tumor growth, and metastasis. CSF1R-expressing osteoclasts mediate bone degradation in osteolytic cancers and cancers that metastasize to bone. In the rare disease tenosynovial giant cell tumor (TGCT), aberrant CSF1 expression and production driven by a gene translocation leads to the recruitment and growth of tumors formed by CSF1R-dependent inflammatory cells. Small molecules and antibodies targeting the CSF1/CSF1R axis have shown promise in the treatment of TGCT and cancer, with pexidartinib recently receiving FDA approval for treatment of TGCT. Many small-molecule kinase inhibitors of CSF1R also inhibit the closely related kinases KIT, PDGFRA, PDGFRB, and FLT3, thus CSF1R suppression may be limited by off-target activity and associated adverse events. Vimseltinib (DCC-3014) is an oral, switch control tyrosine kinase inhibitor specifically designed to selectively and potently inhibit CSF1R by exploiting unique features of the switch control region that regulates kinase conformational activation. In preclinical studies, vimseltinib durably suppressed CSF1R activity in vitro and in vivo, depleted macrophages and other CSF1R-dependent cells, and resulted in inhibition of tumor growth and bone degradation in mouse cancer models. Translationally, in a phase I clinical study, vimseltinib treatment led to modulation of biomarkers of CSF1R inhibition and reduction in tumor burden in TGCT patients.

Abstract C087: Phase 1 study of DCC-3014, an oral inhibitor of CSF1R, to assess the safety, tolerability, pharmacokinetics, and pharmacodynamics in patients with advanced solid tumors, including diffuse-type tenosynovial giant cell tumor

Background: DCC-3014 is an orally administered kinase inhibitor targeting the switch pocket of colony-stimulating factor 1 receptor (CSF1R). DCC-3014 exhibits approximately 100-fold selectivity from kinases homologous to CSF1R, such as KIT, and greater selectivity against 300 other human kinases. Tumor-associated macrophages (TAMs) are dependent on CSF1R kinase activity for proliferation and maintenance of the immunosuppressive phenotype. TAMs are known to enable tumor cells escape from immune surveillance. DCC-3014 is designed to exhibit an antitumor effect by inhibition of immunosuppressive TAMs or other CSF1R signaling-dependent pro-tumor activities. In addition, tenosynovial giant cell tumor (TGCT) is a rare, monoarticular disease known to be caused by the translocation in the CSF1 gene leading to overexpression of CSF1. Anti-CSF1R therapies have shown clinical activity in diffuse TGCT. Methods: This study is a multicenter, first-in-human study of DCC-3014 to determine a recommended Phase 2 dose (RP2D) or maximally tolerated dose (MTD) with a 3+3 dose escalation design and evaluate the safety, efficacy, pharmacokinetics (PK) and pharmacodynamics (PD) of DCC-3014 in advanced solid tumors, including diffuse-type TGCT [NCT03069469]. Results: As of June 2, 2019, the study is ongoing in the dose escalation phase and has enrolled 32 patients with advanced solid tumors in 7 cohorts. The first cohort was initiated at 10 mg daily. Based on preliminary PK analysis from the first cohort, subsequent cohorts utilized a loading dose followed by a maintenance dosing schedule to achieve steady-state exposures more rapidly. The median age of patients was 61 years old and 69% were female with the median of 4 lines of prior anti-cancer treatment. No dose limiting toxicities (DLTs) have been seen in the assessed cohorts. Most commonly seen treatment-emergent adverse events (TEAEs >20%) were constipation (38%), vomiting (34%), diarrhea (31%), nausea (31%), decreased appetite (25%), abdominal pain (22%), and dyspnea (22%) whereas diarrhea, nausea and fatigue were reported as treatment-related AEs seen in >10% of all patients (13%). TEAEs were mostly Grade 1 or 2. Serious AEs (SAEs) were seen in 16 patients, none of which were related to DCC-3014. Exposure was approximately dose proportional. PD effects were seen for dose levels at 10 mg and above, and induction of the CSF1R ligand, CSF-1, was seen up to 148-fold from baseline. The RP2D or MTD has not been selected or reached. Conclusion: DCC-3014 in this study was generally well tolerated in patients with advanced solid tumors and showed approximately dose-proportional exposure and PD changes as expected. Further evaluation is ongoing to determine the RP2D or MTD. Data from the TGCT cohort will be presented at a future meeting.

Citation Format: Matthew H Taylor, Stephen Leong, Ying Su, Cynthia B Leary, Xiaoyan Li, Keisuke Kuida, Rodrigo Ruiz-Soto, Todd Bauer. Phase 1 study of DCC-3014, an oral inhibitor of CSF1R, to assess the safety, tolerability, pharmacokinetics, and pharmacodynamics in patients with advanced solid tumors, including diffuse-type tenosynovial giant cell tumor [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr C087. doi:10.1158/1535-7163.TARG-19-C087

Abstract B129: Preclinical studies with DCC-3116, an ULK kinase inhibitor designed to inhibit autophagy as a potential strategy to address mutant RAS cancers

Background: Cancer cells activate autophagy, a catabolic process to resupply nutrients and recycle damaged organelles, in order to survive stresses such as limited nutrients and hypoxia, or chemotherapy treatments. RAS mutant cancers, in particular, have been found to require autophagy for tumor growth and survival.1,2 Treating RAS mutant tumors with inhibitors of the downstream MAPK pathway has been largely unsuccessful, as these drugs have been shown to further stimulate autophagy, allowing for tumor cell survival.3,4 Inhibiting autophagy in combination with MAPK pathway inhibition may represent a possible new treatment paradigm for RAS mutant cancers. Proof-of-concept for this strategy was obtained in cancer models and in a RAS mutant pancreatic cancer patient by blocking autophagy with derivatives of chloroquine, in combination with MAPK inhibitors.3,4 Chloroquines indirectly block autophagy via disruption of lysosomal function, which may also affect important normal cellular processes. Chloroquines accumulate in tissues, notably the brain, where autophagy may be vital for neuronal health. The potential exists to more selectively inhibit autophagy by targeting specific components of the autophagy pathway. ULK1/2 kinases initiate autophagy and provide the potential for a targeted approach for selectively inhibiting autophagy in RAS mutant cancers. Herein, we describe preclinical studies with the ULK inhibitor DCC-3116, designed as a potential inhibitor of autophagy in RAS mutant cancers. Methods: In vitro kinase assays were performed using cellular levels of ATP (1 mM) and a peptide substrate. In cell assays, ULK activity was assessed using an ELISA for phosphorylated ATG13. Autophagosome formation was measured using the dye, Cyto-ID. Autophagic flux was assessed using cells expressing the autophagy protein LC3 fused to luciferase. The synergy of DCC-3116 in combination with MAPK inhibitors was assessed in 2D or 3D cell growth assays. Xenograft models were used to assess pharmacokinetics (PK) and pharmacodynamics (PD), as well as efficacy in vivo. Results: DCC-3116 is a potent and selective inhibitor of ULK1/2, inhibiting no other kinases within 30-fold of ULK potency, and only 5 kinases within 100-fold. DCC-3116 inhibited phosphorylation of the ULK substrate ATG13 in cancer cell assays. DCC-3116 inhibited autophagosome formation, as well as degradation of the autophagy marker LC3. DCC-3116 exhibited synergy in vitro in combination with MAPK pathway inhibitors in inhibiting cancer cell growth. In PK/PD models, oral doses of DCC-3116 led to sustained inhibition of ATG13 phosphorylation. DCC-3116, in combination with MAPK inhibitors, exhibited additivity or synergy in inhibiting tumor growth in xenograft models. DCC-3116 exhibited low brain penetration in rats, minimizing inhibition of CNS autophagy. Conclusion: Selectively blocking autophagy via inhibition of ULK kinases, in combination with MAPK pathway inhibition, is a promising therapeutic approach for RAS mutant cancers. DCC-3116 warrants further study as an inhibitor of autophagy, and has been selected as a candidate for potential development in the treatment of RAS mutant cancers.

Guo et al., Genes and Dev. 2011; 25: 460

Yang et al., Genes and Dev. 2011; 25: 717

Bryant et al., Nature Med. 2019; 25: 628

Kinsey et al., Nature Med. 2019; 25: 620

Citation Format: Bryan D Smith, Lakshminarayana Vogeti, Anu Gupta, Jarnail Singh, Gada Al-Ani, Stacie L Bulfer, Timothy M Caldwell, Mary J Timson, Subha Vogeti, Yu Mi Ahn, Hikmat Al-Hashimi, Chase K Crawley, Cale L Heiniger, Cynthia B Leary, Justin T Proto, Quanrong Shen, Hanumaiah Telikepalli, Karen Yates, Wei-Ping Lu, Daniel L Flynn. Preclinical studies with DCC-3116, an ULK kinase inhibitor designed to inhibit autophagy as a potential strategy to address mutant RAS cancers [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr B129. doi:10.1158/1535-7163.TARG-19-B129

Ripretinib (DCC-2618) Is a Switch Control Kinase Inhibitor of a Broad Spectrum of Oncogenic and Drug-Resistant KIT and PDGFRA Variants

Ripretinib (DCC-2618) was designed to inhibit the full spectrum of mutant KIT and PDGFRA kinases found in cancers and myeloproliferative neoplasms, particularly in gastrointestinal stromal tumors (GISTs), in which the heterogeneity of drug-resistant KIT mutations is a major challenge. Ripretinib is a "switch-control" kinase inhibitor that forces the activation loop (or activation "switch") into an inactive conformation. Ripretinib inhibits all tested KIT and PDGFRA mutants, and notably is a type II kinase inhibitor demonstrated to broadly inhibit activation loop mutations in KIT and PDGFRA, previously thought only achievable with type I inhibitors. Ripretinib shows efficacy in preclinical cancer models, and preliminary clinical data provide proof-of-concept that ripretinib inhibits a wide range of KIT mutants in patients with drug-resistant GISTs.

Abstract 3925: Inhibition of oncogenic and drug-resistant PDGFRA and KIT alterations by DCC-2618

Introduction:

Activating mutations and other genetic alterations in KIT and PDGFRA receptor tyrosine kinases have been identified in certain cancers and proliferative diseases, including most cases of gastrointestinal stromal tumors (GIST) and systemic mastocytosis, and small percentages of gliomas, lung cancer, and leukemias. The treatment of metastatic GIST has been transformed with KIT inhibitors, but heterogeneous drug-resistant mutations arise during therapy, with individual patients often having multiple KIT mutations in different tumor sites. PDGFRA variants in GIST and other cancers also have a significant unmet medical need. DCC-2618 is a kinase switch control inhibitor that potently inhibits the spectrum of exon 9, 11, 13, 14, 17 and 18 mutations in KIT and exons 12, 14 and 18 mutations in PDGFRA. DCC-2618 has been designed to bind as a type II kinase inhibitor that forces the mutant kinases, including strongly activated mutants such as D816V KIT and D842V PDGFRA, into inactive conformations. DCC-2618 has been observed to be potent in enzyme and cell-based assays, and has demonstrated consistent efficacy in xenograft models driven by PDGFRA and KIT alterations.

Methods:

DCC-2618, and an active human metabolite, DP-5439, were tested for inhibition of PDGFRA and KIT mutants using standard enzyme and binding assays, and a variety of cell-based assays. Levels of phosphorylated PDGFRA and KIT were determined by Western blot or ELISA. Proliferation was measured using the fluorescent dye resazurin. An x-ray crystal structure of an analog of DCC-2618 was determined at Emerald Biostructures. The H1703 PDGFRA-amplified lung cancer and GIST T1 mutant KIT xenograft models were performed at MI Bioresearch. A GIST PDX exon 17 mutant KIT xenograft model was run at Molecular Response.

Results:

DCC-2618 and the metabolite DP-5439 inhibited KIT and PDGFRA variants with nanomolar potency. In CHO cells transfected with KIT or PDGFRA variants, DCC-2618 was shown to inhibit the full spectrum of the clinically relevant primary and refractory drug-resistant mutations tested. DCC-2618 also inhibited phosphorylation of KIT or PDGFRA in cell lines with various drug-resistant KIT mutations or PDGFRA alterations. DCC-2618 was compared to the FDA-approved KIT inhibitors imatinib, sunitinib, regorafenib, and midostaurin, as well as other KIT and PDGFRA inhibitors.

In vivo, treatment with DCC-2618 led to tumor regressions in KIT- and PDGFRA-driven xenograft models.

Conclusions:

DCC-2618 has been observed to be a potent inhibitor of KIT and PDGFRA alterations, including mutants, fusions, and amplifications. Based on this profile, DCC-2618 may have utility in the treatment of KIT and PDGFRA-driven cancers including GIST, systemic mastocytosis, and a subset of lung cancers, gliomas, and leukemias. DCC-2618 is currently in a Phase 1 clinical trial in KIT and PDGFRA driven cancers (ClinicalTrials.gov Identifier: NCT02571036).

Citation Format: Bryan D. Smith, Michael D. Kaufman, Anu Gupta, Cynthia B. Leary, Wei-ping Lu, Stacie L. Bulfer, Gada Al-Ani, Jarnail Singh, Subha Vogeti, Michael C. Heinrich, Daniel L. Flynn. Inhibition of oncogenic and drug-resistant PDGFRA and KIT alterations by DCC-2618 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3925.

The Selective Tie2 Inhibitor Rebastinib Blocks Recruitment and Function of Tie2Hi Macrophages in Breast Cancer and Pancreatic Neuroendocrine Tumors

Tumor-infiltrating myeloid cells promote tumor progression by mediating angiogenesis, tumor cell intravasation, and metastasis, which can offset the effects of chemotherapy, radiation, and antiangiogenic therapy. Here, we show that the kinase switch control inhibitor rebastinib inhibits Tie2, a tyrosine kinase receptor expressed on endothelial cells and protumoral Tie2-expressing macrophages in mouse models of metastatic cancer. Rebastinib reduces tumor growth and metastasis in an orthotopic mouse model of metastatic mammary carcinoma through reduction of Tie2⁺ myeloid cell infiltration, antiangiogenic effects, and blockade of tumor cell intravasation mediated by perivascular Tie2^Hi/Vegf-A^Hi macrophages in the tumor microenvironment of metastasis (TMEM). The antitumor effects of rebastinib enhance the efficacy of microtubule inhibiting chemotherapeutic agents, either eribulin or paclitaxel, by reducing tumor volume, metastasis, and improving overall survival. Rebastinib inhibition of angiopoietin/Tie2 signaling impairs multiple pathways in tumor progression mediated by protumoral Tie2⁺ macrophages, including TMEM-dependent dissemination and angiopoietin/Tie2-dependent angiogenesis. Rebastinib is a promising therapy for achieving Tie2 inhibition in cancer patients. Mol Cancer Ther; 16(11); 2486-501. ©2017 AACR.

Altiratinib Inhibits Tumor Growth, Invasion, Angiogenesis, and Microenvironment-Mediated Drug Resistance via Balanced Inhibition of MET, TIE2, and VEGFR2

Altiratinib (DCC-2701) was designed based on the rationale of engineering a single therapeutic agent able to address multiple hallmarks of cancer (1). Specifically, altiratinib inhibits not only mechanisms of tumor initiation and progression, but also drug resistance mechanisms in the tumor and microenvironment through balanced inhibition of MET, TIE2 (TEK), and VEGFR2 (KDR) kinases. This profile was achieved by optimizing binding into the switch control pocket of all three kinases, inducing type II inactive conformations. Altiratinib durably inhibits MET, both wild-type and mutated forms, in vitro and in vivo. Through its balanced inhibitory potency versus MET, TIE2, and VEGFR2, altiratinib provides an agent that inhibits three major evasive (re)vascularization and resistance pathways (HGF, ANG, and VEGF) and blocks tumor invasion and metastasis. Altiratinib exhibits properties amenable to oral administration and exhibits substantial blood-brain barrier penetration, an attribute of significance for eventual treatment of brain cancers and brain metastases.

Abstract 790: Altiratinib is a potent inhibitor of TRK kinases and is efficacious in TRK-fusion driven cancer models

Introduction:

TRK kinases have been implicated in a variety of cancers, wherein TRK gene fusions, amplifications and mutations have been shown to drive tumor growth. TRK kinases have also been shown to play key roles in metastasis. Recently, large-scale sequencing efforts have identified TRK fusions at a low but significant frequency across all major cancers. Altiratinib is a potent single-digit nanomolar inhibitor of TRK, MET, TIE2, and VEGFR2 kinases. Altiratinib inhibits TRKA, TRKB, and TRKC phosphorylation in both WT TRK and TRK-fusion cell lines and inhibits cell proliferation in these cell lines. In vivo, altiratinib suppressed TRK phosphorylation for >18 hr after a single oral dose and showed significant inhibition of tumor growth in TRKA and TRKC-fusion xenograft efficacy studies. Altiratinib is currently in a Phase 1 clinical trial for patients with advanced solid tumors.

Experimental procedures:

Altiratinib was tested for inhibition of various recombinant kinases using a standard PK/LDH coupled spectrophotometric continuous assay. In cell assays, cells were treated with a dose response of compound. Levels of phosphorylated TRK in cell lysates were determined Western blot. Cell proliferation was measured using the fluorescent dye resazurin. Experiments were performed in triplicate. In vivo xenograft models were performed at Molecular Imaging, Inc. (Ann Arbor, MI).

Summary of results:

Altiratinib potently inhibited TRK kinase activity in biochemical assays (IC50 values of 0.9 nM, 4.6 nM, and 0.8 nM for TRKA, B, and C, respectively). Altiratinib inhibited phosphorylation of TRKA in the TPM3-TRKA fusion cell line KM-12 (IC50 = 1.4 nM) and of TRKC in ETV6-TRKC transformed NIH-3T3 cells (IC50 = 0.5 nM). Altiratinib inhibited NGF-stimulated phosphorylation of wild-type TRKA in K562 (IC50 = 0.7 nM) and SK-N-SH cells (IC50 = 1.2 nM) and BDNF-stimulated phosphorylation of TRKB in ATRA-transformed SK-N-SH cells (IC50 = 0.24 nM). In compound washout experiments, altiratinib inhibited TRKA phosphorylation in KM-12 cells for > 24 hr after compound washout, due to its durable Type II switch pocket binding mode to the kinase. In cell lines driven by TRK fusions, altiratinib also inhibited cell proliferation (KM-12 IC50 = 3.8 nM; NIH-3T3 ETV6/TRKC IC50 = 0.5 nM). In vivo, altiratinib inhibited phosphorylation of TRK and downstream targets in the signaling pathway for >12 hr after a single oral dose. Altiratinib treatment led to tumor regression in TRK-fusion xenograft efficacy studies.

Conclusions:

Altiratinib exhibits potent inhibition of oncogenic TRK fusions in vitro and in vivo. Combined with its inhibition of the tumor and microenvironment targets MET, TIE2, and VEGFR2 kinases, altiratinib provides the potential to treat cancers driven by TRK fusions. Altiratinib is currently in a Phase 1 clinical trial in patients with solid tumors.

Citation Format: Bryan D. Smith, Cynthia B. Leary, Benjamin A. Turner, Michael D. Kaufman, Scott C. Wise, Maria E. R. Garcia-Rendueles, James A. Fagin, Daniel L. Flynn. Altiratinib is a potent inhibitor of TRK kinases and is efficacious in TRK-fusion driven cancer models. [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 790. doi:10.1158/1538-7445.AM2015-790

Abstract PR01: Rebastinib, a selective TIE2 kinase inhibitor, decreases TIE2-expressing macrophages, reduces metastasis, and increases survival in murine cancer models

In the tumor microenvironment, TIE2 expression on tissue macrophages, bone marrow derived TIE2-expressing monocytes (TEMs), osteoclasts, and vascular endothelial cells promotes tumor invasiveness, dissemination, and metastasis. Additionally, a subset of TIE2-expressing macrophages, located within specialized vascular structures known as tumor microenvironment for metastases (TMEMs), are linked to intravasation of cancer cells into circulation and dissemination to metastatic sites. Rebastinib is a picomolar inhibitor of TIE2 kinase, and exhibits an extraordinarily long off-rate from TIE2, measured to be over 24 hours in a cell-based assay. Herein, we examine the efficacy of rebastinib in the polyoma middle-T antigen (PyMT) syngeneic mouse breast cancer model. In this model, PyMT breast cancer cells are implanted in the mammary fat pad, and primary tumor growth leads to lung metastasis, which is known to be modulated by TEMs and TMEM vascular structures. We examined multiple dosing schedules of rebastinib in combination with anti-tubulin agents (ATAs). Rebastinib treatment in this model significantly ablated TEMs in the primary tumor stroma and caused a significant decrease in lung metastases. Furthermore, the combination of rebastinib with ATAs, even with once or twice weekly oral dosing of rebastinib, led to a significant further decrease in lung metastases compared to single-agent treatment with ATAs. Rebastinib also enhanced the activity of ATAs in reducing primary tumor growth and regrowth of tumor post-resection. TIE2 inhibition with targeted therapy represents a novel treatment approach for metastatic breast cancer and other cancers that rely on TEMs and TMEMs for growth and metastasis. As such, rebastinib has been selected for further clinical development in solid tumors with a Phase 1b trial being planned for 2014.

This abstract is also presented as Poster A5.

Citation Format: Daniel L. Flynn, Michael D. Kaufman, Cynthia B. Leary, Molly M. Hood, Wei-Ping Lu, Benjamin A. Turner, Scott C. Wise, Marc S. Rudoltz, Bryan D. Smith. Rebastinib, a selective TIE2 kinase inhibitor, decreases TIE2-expressing macrophages, reduces metastasis, and increases survival in murine cancer models. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr PR01. doi:10.1158/1538-7445.CHTME14-PR01

Abstract P4-15-12: Rebastinib in combination with eribulin ablates TIE2-expressing macrophages, reduces metastasis, and increases survival in the PyMT metastatic breast cancer model

In cancer models, TIE2 kinase plays an important role in angiogenesis, vasculogenesis, and tumor metastasis. TIE2 expression is largely restricted to vascular endothelial cells, tissue macrophages, and bone marrow derived TIE2-expressing monocytes (TEMs), which are proangiogenic, provasculogenic and enhance invasiveness. The hypoxic tumor environment engendered by damaging the vasculature with chemotherapy, radiation, or anti-angiogenic treatments leads to rebound tumor vascularization by an angiogenic switch from the VEGF pathway to the angiopoietin/TIE2 pathway. This leads to recruitment of provasculogenic TEMs from the bone marrow, leading to the growth of residual tumor cells and disease progression. Significantly, a subset of TIE2-expressing macrophages are located within specialized vascular structures known as tumor microenvironment for metastases (TMEMs). Recent observations have linked TIE2-expressing macrophages within TMEM structures to intravasation of cancer cells into circulation and subsequent dissemination to metastatic sites. We hypothesized that TIE2 inhibition should decrease migration and association of TEMs with blood vessels in the tumor stroma, therefore blocking their proangiogenic activity and leading to reduced tumor growth. TIE2 inhibition may also alter TMEM function, leading directly to a blockade of metastasis.

Rebastinib is a picomolar inhibitor of TIE2 kinase, and exhibits an extraordinarily long off-rate from TIE2, measured to be over 24 hours in a cell-based assay. Herein, we examine the efficacy of rebastinib in the polyoma middle-T antigen (PyMT) syngeneic mouse breast cancer model. In this model, PyMT breast cancer cells are implanted in the mammary fat pad, and primary tumor growth leads to metastasis, which is known to be modulated by TEMs and TMEM vascular structures. We examined dosing rebastinib in combination with eribulin, an inhibitor of microtubule dynamics that recently was FDA-approved for treatment-refractory metastatic breast cancer. Rebastinib treatment in this model significantly ablated TEMs in the primary tumor stroma and caused a significant decrease in lung metastases. Furthermore, the combination of rebastinib and eribulin led to a significant further decrease in lung metastases compared to treatment with eribulin alone (Table 1). Rebastinib also enhanced the activity of eribulin in reducing primary tumor growth and regrowth of tumor post-resection.

TIE2 inhibition represents a novel treatment approach for metastatic breast cancer and other cancers that rely on TEMs and TMEMs for growth and metastasis. As such, rebastinib has been selected for further clinical development in combination with eribulin for treatment-refractory metastatic breast cancer, with a Phase 1b trial being planned for late 2013.

Rebastinib reduces lung metastases in the PyMT breast cancer modelTreatmentLung Metastases (% of Control)Vehicle100%Eribulin 1 mg/kg three times/week71%Rebastinib 10 mg/kg twice/week + Eribulin 1 mg/kg23%Eribulin 0.3 mg/kg three times/week71%Rebastinib 10 mg/kg twice/week + Eribulin 0.3 mg/kg51%Eribulin 0.1 mg/kg three times/week72%Rebastinib 10 mg/kg twice/week + Eribulin 0.1 mg/kg43%

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-15-12.

Abstract P4-15-13: Rebastinib in combination with paclitaxel ablates TIE2-expressing macrophages, reduces metastasis, and increases survival in the PyMT metastatic breast cancer model

In cancer models, TIE2 kinase plays an important role in angiogenesis, vasculogenesis, and tumor metastasis. TIE2 expression is largely restricted to vascular endothelial cells, tissue macrophages, and bone marrow derived TIE2-expressing monocytes (TEMs), which are proangiogenic, provasculogenic and enhance invasiveness. The hypoxic tumor environment engendered by damaging the vasculature with chemotherapy, radiation, or anti-angiogenic treatments leads to rebound tumor vascularization by an angiogenic switch from the VEGF pathway to the angiopoietin/TIE2 pathway. This leads to recruitment of provasculogenic TEMs from the bone marrow, leading to the growth of residual tumor cells and disease progression. Significantly, a subset of TIE2-expressing macrophages are located within specialized vascular structures known as tumor microenvironment for metastases (TMEMs). Recent observations have linked TIE2-expressing macrophages within TMEM structures to intravasation of cancer cells into circulation and subsequent dissemination to metastatic sites. We hypothesized that TIE2 inhibition should decrease migration and association of TEMs with blood vessels in the tumor stroma, therefore blocking their proangiogenic activity and leading to reduced tumor growth. TIE2 inhibition may also alter TMEM function, leading directly to a blockade of metastasis.

Rebastinib is a picomolar inhibitor of TIE2 kinase, and exhibits an extraordinarily long off-rate from TIE2, measured to be over 24 hours in a cell-based assay. Herein, we examine the efficacy of rebastinib in the polyoma middle-T antigen (PyMT) syngeneic mouse breast cancer model. In this model, PyMT breast cancer cells are implanted in the mammary fat pad, and primary tumor growth leads to metastasis, which is known to be modulated by TEMs and TMEM vascular structures. We examined multiple dosing schedules of rebastinib in combination with paclitaxel. Rebastinib treatment in this model significantly ablated TEMs in the primary tumor stroma and caused a significant decrease in lung metastases (Table 1). Furthermore, the combination of rebastinib and paclitaxel led to a significant further decrease in lung metastases compared to treatment with paclitaxel or rebastinib alone. Rebastinib also enhanced the activity of paclitaxel in reducing primary tumor growth and regrowth of tumor post-resection.

TIE2 inhibition with targeted therapy represents a novel treatment approach for metastatic breast cancer and other cancers that rely on TEMs and TMEMs for growth and metastasis. As such, rebastinib has been selected for further clinical development for treatment-refractory metastatic breast cancer, with a Phase 1b trial being planned for late 2013.

Rebastinib reduces lung metastases in the PyMT breast cancer modelStudynTreatmentLung Metastases (% of Control)110Vehicle100%110Paclitaxel 10 mg/kg Q5D36%110Rebastinib 10 mg/kg BID28%110Rebastinib 10 mg/kg BID + Paclitaxel7%210Vehicle100%210Paclitaxel 10 mg/kg Q5D51%210Rebastinib 10 mg/kg QD + Paclitaxel21%33Vehicle100%33Paclitaxel 10 mg/kg Q5D58%33Rebastinib 10 mg/kg twice/week + Paclitaxel28%

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-15-13.