ROS1 Inhibitor Research Articles

Abstract 2986: E-cadherin/ROS1 inhibitor synthetic lethality in breast cancer

Abstract The E-cadherin (CDH1) tumour suppressor gene encodes a calcium-dependent cell-cell adhesion glycoprotein, which has roles in maintaining cell polarity, differentiation, cell migration and survival. E-cadherin dysfunction is a feature common to many epithelial tumours, with the highest incidence occurring in diffuse gastric cancer (50%) and lobular breast cancer (63%) and can occur via CDH1 mutation, deletion or epigenetic silencing. Although E-cadherin dysfunction is relatively common, precision medicine approaches that exploit this pathogenic alteration are not yet available. Using genetic and small-molecule perturbation screens in breast tumour cells with CRISPR-Cas9 engineered CDH1 mutations, we identified a synthetic lethal interaction between E-cadherin deficiency and inhibition of the tyrosine kinase ROS1. Using data from large-scale genetic screens in molecularly diverse breast tumour cell lines, we found that the E-cadherin/ROS1 synthetic lethality was not only robust in the face of considerable molecular heterogeneity but was also elicited with clinical ROS1 inhibitors including foretinib and crizotinib. ROS1 inhibitors induced mitotic abnormalities and multinucleation in E-cadherin defective cells, phenotypes that were associated with a defect in cytokinesis and aberrant p120-catenin phosphorylation and localisation. In vivo, ROS1 inhibitors produced profound anti-tumour effects in multiple, distinct, models of E-cadherin defective breast cancer. This data therefore provides the pre-clinical rationale for assessing ROS1 inhibitors such as the licensed drug crizotinib in appropriately stratified patients. Citation Format: Ilirjana Bajrami, Rebecca Marlow, Marieke van de Ven, Rachel Brough, Helen N. Pemberton, Jessica Frankum, Fei Fei Song, Rumana Rafiq, Asha Konde, Malini Menon, James Campbell, Aditi Gulati, Rahul Kumar, Stephen J. Pettitt, Mark D. Gurden, Marta Llorca Cardenosa, Irene Chong, Patrycja Gazinska, Fredrik Wallberg, Elinor J. Sawyer, Lesley-Ann Martin, Mitch Dowsett, Spiros Linardopoulos, Colm Ryan, Patrick W. Derksen, Jos Jonkers, Andrew N.J. Tutt, Alan Ashworth, Christopher J. Lord. E-cadherin/ROS1 inhibitor synthetic lethality in breast cancer [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 2986.

Phase 1 study of entrectinib (RXDX-101), a TRK, ROS1, and ALK inhibitor, in children, adolescents, and young adults with recurrent or refractory solid tumors.

10536Background: Entrectinib (RXDX-101) inhibits TRKA/B/C, ROS1, and ALK tyrosine kinases with IC50 < 2 nM. In vivo, entrectinib is active in several fusion-driven solid tumor and TRKB-expressing n...

GEINO 1402: A phase Ib dose-escalation study followed by an extension phase to evaluate safety and efficacy of crizotonib in combination with temozolomide (TMZ) and radiotherapy (RT) in patients with newly diagnosed glioblastoma (GB): Results of the dose-escalation phase.

2054Background: Crizotinib is an ALK, ROS-1 and c-MET inhibitor with an interesting rationale to be tested in NDGB due to the role of MET signaling in gliomagenesis and stem cell maintenance and capability of midkine, a recently discovered ALK ligand, to promote resistance of glioma cells to anticancer therapies such as RT and TMZ. Primary objective of this trial was to determine maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D) of crizotinib in combination with RT and TMZ. Methods: Eligible patients received crizotinib with standard RT and TMZ and afterwards continued crizotinib daily with sequential adjuvant TMZ. Additional treatment with crizotinib beyond 6 TMZ cycles was allowed at the discretion of physician. Crizotinib MTD was determined using a standard “3+3” dose escalation design. Dose-limiting toxicities were observed during the first 12 weeks of therapy. Results: 12 patients (median age: 53,5 (33-60 y)) were enrolled in 3 crizotinib cohorts (200 mg/QD, 250 mg/QD and 200 mg/BID). ...

3D culture system containing gellan gum restores oncogene dependence in ROS1 rearrangements non-small cell lung cancer

The ROS1 fusion gene has been identified in approximately 1% of non-small cell lung cancer (NSCLC) cases. Several clinical studies have highlighted ROS1 as a promising therapeutic target because crizotinib, a multi-targeted drug against ROS1, ALK, and the MET proto-oncogene, has elicited remarkable responses in ROS1-rearrangements NSCLC. However, acquired resistance mediated by ROS1 kinase domain mutations has been identified and a system to assess ROS1 inhibitors for these resistant mutations is necessary for the promotion of drug development. Publicly available NSCLC cell lines harboring the ROS1 fusion gene are limited to only HCC78 cells carrying SLC34A2-ROS1. This cell line exhibits resistance to ROS1 inhibitors through activation of the EGFR pathway, although the cells were established from ROS1-TKI naïve pleural effusion. Here, we demonstrate that 3D culture with gellan gum can restore the ROS1 oncogene dependence of HCC78 cells by upregulating the expression of the ROS1 fusion gene and reducing the activity of the EGFR pathway. Moreover, we established the HCC78xe3 cell line, a subclone of the HCC78 cell line, by repeated in vitro cultures from tumor xenografts and created xenograft tumors three times using in vitro cultured cells. This eventually enabled us to engraft and stably grow the cells in vivo, and subsequently evaluate various ROS1 inhibitors against HCC78xe3 cells by overexpressing crizotinib-resistant mutations in the ROS1 kinase domain including G2032R and D2033 N. We newly found that lorlatinib, a next generation ROS1/ALK inhibitor, remain the activity against D2033 N mutation. Furthermore, we demonstrated that HCC78xe3 cells expressing SLC34A2-ROS1 G2032R, and D2033 N, but not wild type (WT) cells, were resistant to crizotinib in vivo. Taken together, our data suggested that 3D cultures of HCC78 might reflect the features in patients and this new system will be a useful tool for evaluating ROS1 inhibitors.

A (synthetic) lethal weapon for cancer

ROS1 inhibition in E-cadherin–deficient tumors leads to synthetic lethality, which could be exploited for the selective treatment of breast cancer patients.

E-Cadherin/ROS1 Inhibitor Synthetic Lethality in Breast Cancer.

The cell adhesion glycoprotein E-cadherin (CDH1) is commonly inactivated in breast tumors. Precision medicine approaches that exploit this characteristic are not available. Using perturbation screens in breast tumor cells with CRISPR/Cas9-engineered CDH1 mutations, we identified synthetic lethality between E-cadherin deficiency and inhibition of the tyrosine kinase ROS1. Data from large-scale genetic screens in molecularly diverse breast tumor cell lines established that the E-cadherin/ROS1 synthetic lethality was not only robust in the face of considerable molecular heterogeneity but was also elicited with clinical ROS1 inhibitors, including foretinib and crizotinib. ROS1 inhibitors induced mitotic abnormalities and multinucleation in E-cadherin-defective cells, phenotypes associated with a defect in cytokinesis and aberrant p120 catenin phosphorylation and localization. In vivo, ROS1 inhibitors produced profound antitumor effects in multiple models of E-cadherin-defective breast cancer. These data therefore provide the preclinical rationale for assessing ROS1 inhibitors, such as the licensed drug crizotinib, in appropriately stratified patients.Significance: E-cadherin defects are common in breast cancer but are currently not targeted with a precision medicine approach. Our preclinical data indicate that licensed ROS1 inhibitors, including crizotinib, should be repurposed to target E-cadherin-defective breast cancers, thus providing the rationale for the assessment of these agents in molecularly stratified phase II clinical trials. Cancer Discov; 8(4); 498-515. ©2018 AACR.This article is highlighted in the In This Issue feature, p. 371.

Preclinical evaluation of a new ROS1 inhibitor to overcome resistance to EGFR therapy in glioblastoma

Glioblastoma Multiforme (GBM) is the most aggressive brain tumor in adults and remains incurable despite multimodal intensive treatment regimens. The majority of GBM tumors show a mutated or overexpressed Epidermal Growth Factor Receptor EGFR; however, tumors treated with EGFR inhibitors such as gefitinib or erlotinib inevitably recur. This recurrence highlights the need to identify signaling pathways involved in GBM resistance to EGFR therapy that may serve as targets for intervention. In our recently published work, we found that activation of the ROS1 pathway is a primary mechanism by which glioma cells become resistant to EGFR‐targeted therapy. ROS1 is a proto‐oncogene receptor tyrosine kinase activated by chromosomal rearrangement in several human cancers, including non‐small‐cell lung cancer (NSCLC), cholangiocarcinoma, gastric cancer, ovarian cancer, and glioblastoma. We therefore, designed, synthesized and screened a series of new ROS1 inhibitors. The lead compound, ROS‐Ic, is very potent (IC50 = 24nM) and highly specific to ROS1 protein. Treatment of gefitinib‐resistant GBM cells with ROS1‐lc sensitized the resistant cells to low concentrations of gefitinib resulting in apoptosis following a prolonged S phase cell cycle arrest. When compared to Crizotinib, an FDA‐approved small‐molecule tyrosine kinase inhibitor currently used to treat ALK‐ and ROS1+ NSCLC patients, ROS‐Ic showed superior cytotoxic activity in vitro towards ROS1‐positive GBM cells. Crizotinib resistance is thought to be due to diminished Crizotinib binding, due to ROS1 mutations in Crizotinib binding pocket. Interestingly, our initial analysis suggests that our lead compound ROS1‐Ic might not be affected by these mutations, highlighting the potential therapeutic value of this compound.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

CD74-ROS1 G2032R mutation transcriptionally up-regulates Twist1 in non-small cell lung cancer cells leading to increased migration, invasion, and resistance to crizotinib

The c-ros oncogene 1 (ROS1) is a receptor tyrosine kinase, which has been identified as an oncogene driver of non-small-cell lung cancer (NSCLC). Although crizotinib has a prominent effect on ROS1, resistance is inevitable. Development of the acquired ROS1 G2032R mutation has been reported as a resistant mechanism to ROS1 inhibitors in ROS1-rearranged (ROS1+) NSCLC patients. To explore the mechanism of drug resistance, we constructed the crizotinib resistance cell line, A549-CD74-ROS1 G2032R mutation cells, by the methods of fusion polymerase chain reaction (PCR), plasmid construction and cell transfection in vitro. The results showed that the expression of CD74-ROS1 or CD74-ROS1 G2032R mutation in A549 cells induced epithelial-mesenchymal transition (EMT), dramatically enhanced the ability of invasion and migration, and increased expression of matrix metalloproteinase (MMP)-9 and Twist1 transcription factor. Moreover, we found that inhibition of Twist1 could reverse EMT induced by CD74-ROS1 G2032R mutation. Combination of Twist1 siRNA and crizotinib significantly reduced cell vitality, inhibited cell invasion and migration, and promoted apoptosis in A549-CD74-ROS1 G2032R mutation cells. Taken together, these results suggested that CD74-ROS1 G2032R mutation mediated EMT phenotype by increasing the expression of Twist1, resulting in drug resistance. Combination of Twist1 silence and ROS1 inhibitor may provide a potent strategy to treat the ROS1+ NSCLC patients with crizotinib resistance.

Clinical benefit of entrectinib for patients with metastatic pancreatic cancer who harbor NTRK and ROS1 fusions.

521 Background: Despite recent improvements in chemotherapy for pancreatic cancer that have demonstrated improvements in survival, response rates remain at less than 50%. Distinct molecular subgroups of pancreatic cancer that harbor specific actionable molecular alterations have recently been identified. These include gene fusions of the receptor tyrosine kinases NTRK and ROS1. Entrectinib is a CNS-active, potent, and selective TRK and ROS1 inhibitor that has shown substantial clinical activity in patients with locally advanced or metastatic solid tumors that have NTRK or ROS1 fusions (Drilon A, et al. Cancer Discov. 2017;7[4]:400-409). Methods: We examined 3 cases of pancreatic cancer where an actionable gene rearrangement was identified: 2 with a TPR-NTRK gene fusion, and 1 with an SCL4-ROS1 gene fusion. All 3 patients were treated with entrectinib 600 mg daily in a phase 2 trial (NCT02568267). Results: Entrectinib was well tolerated with mostly grade 1-2 adverse events consisting primarily of arthralgias, myalgias, and fatigue. All 3 patients showed evidence of clinical improvement, with normalization of the tumor biomarker CA19-9 and confirmed partial responses as per RECIST v1.1 in the 2 patients with a TPR-NTRK fusion, 1 of which was associated with a significant decrease in metabolic activity as assessed by PET/CT scan. The patient with the SCL4-ROS1 fusion had stable disease for at least 6 months. All 3 patients had an improvement to, or maintenance of, a high quality of life while on study. At the time of data cutoff, 1 of the patients with a TPR-NTRK fusion remained on treatment &gt; 1 year. Conclusions: Entrectinib treatment was associated with response and prolonged disease control in these 3 patients with NTRK or ROS1 fusion-positive pancreatic cancer. NTRK and ROS1 gene fusions are rare in pancreatic cancer. The true incidence is unknown, as routine testing for gene fusions in pancreatic cancer is not yet standard practice. Given the benefit seen here with entrectinib and the clinical need for improved therapeutics, there may be value in broader and earlier molecular testing of patients with pancreatic cancer for these actionable fusions. Clinical trial information: NCT02568267.

Antitumor Activity of Entrectinib, a Pan-TRK, ROS1, and ALK Inhibitor, in ETV6-NTRK3-Positive Acute Myeloid Leukemia.

Activation of tropomyosin receptor kinase (TRK) family tyrosine kinases by chromosomal rearrangement has been shown to drive a wide range of solid tumors and hematologic malignancies. TRK fusions are actionable targets as evidenced by recent clinical trial results in solid tumors. Entrectinib (RXDX-101) is an investigational, orally available, CNS-active, highly potent, and selective kinase inhibitor against TRKA/B/C, ROS1, and ALK kinase activities. Here, we demonstrate that TRK kinase inhibition by entrectinib selectively targets preclinical models of TRK fusion-driven hematologic malignancies. In acute myelogenous leukemia (AML) cell lines with endogenous expression of the ETV6-NTRK3 fusion gene, entrectinib treatment blocked cell proliferation and induced apoptotic cell death in vitro with subnanomolar IC50 values. Phosphorylation of the ETV6-TRKC fusion protein and its downstream signaling effectors was inhibited by entrectinib treatment in a dose-dependent manner. In animal models, entrectinib treatment at clinically relevant doses resulted in tumor regression that was accompanied by elimination of residual cancer cells from the bone marrow. Our preclinical data demonstrate the potential of entrectinib as an effective treatment for patients with TRK fusion-driven AML and other hematologic malignancies. Mol Cancer Ther; 17(2); 455-63. ©2017 AACR.

Abstract B185: TPX-0005, a supreme ROS1 inhibitor, overcomes crizotinib-resistant ROS1 mutations including solvent front mutation G2032R and gatekeeper mutation L2026M

Abstract The fusion kinases of ROS1 and ALK have been identified as oncogene drivers in small portions of many malignancies, especially in non-small cell lung cancer (NSCLC). ALK/ROS1/MET inhibitor crizotinib has been approved by the US Food and Drug Administration for the treatment of ALK or ROS1-positive non-small cell lung cancer in 2011 and 2016, respectively. The emergence of drug resistance presents a major issue for targeted therapy. Although ceritinib, alectinib, and brigatinib have been approved for crizotinib-refractory ALK+ patients with NSCLC, treatment options for patients with ROS1+ NSCLC are limited, especially for crizotinib-refractory patients. Ceritinib and entectinib demonstrated clinical efficacy only in crizotinib-naïve ROS1+ patients. The most common resistance mechanisms to crizotinib treatment in ROS1+ NSCLC is the solvent front mutation ROS1 G2032R and gatekeeper mutation ROS1 L2026M. TPX-0005, a novel three-dimensional macrocycle with a much smaller size than current ROS1 inhibitors in the clinic, was designed to overcome clinical resistance mutations systematically. TPX-0005 potently inhibited both wild type and mutant ROS1s including solvent front mutations and gatekeeper mutations. TPX-0005 showed pico-molar activity against ROS1 kinase (IC50 0.076 nM) in Reaction Biology kinase assay. The comparison of TPX-0005 with other ROS1 inhibitors in Ba/F3 cell proliferation assays is presented in the table. In the xenograft tumor model studies, TPX-0005 dramatically caused tumor regression in the tumors carrying WT or solvent-front mutated ROS1 fusion gene. Overall, TPX-0005 demonstrated desired drug-like properties, good safety profile, and is a supreme ROS1 inhibitor against WT and various mutated ROS1s. A phase 1/2 clinical trial of TPX-0005 is actively being pursued (NCT03093116). CD74-ROS1 Ba/F3 Cell Proliferation Assay IC50 (nM)InhibitorWTG2032RD2033NL2026MS1986FS1986YTPX-0005&amp;lt;0.28.40.210&amp;lt;0.2&amp;lt;0.2Crizotinib9.71402139606.420.919Lorlatinib0.5262.42.4ND0.30.3Entrectinib25.42404ND2026NDNDCeritinib131.92000NDND14.226.9Brigatinib28.61385167.1211527.724.6Cabozantinib1.060.70.129.1NDND ND: not determined. Citation Format: J. Jean Cui, Dayong Zhai, Wei Deng, Evan Rogers, Zhongdong Huang, Jeffrey Whitten, John Lim, Yishan Li. TPX-0005, a supreme ROS1 inhibitor, overcomes crizotinib-resistant ROS1 mutations including solvent front mutation G2032R and gatekeeper mutation L2026M [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B185.

Abstract A141: Preclinical evaluation of a new ROS1 inhibitor to overcome resistance to EGFR therapy in glioblastoma

Abstract Glioblastoma (GBM) is the most aggressive brain tumor in adults and remains incurable despite multimodal intensive treatment regimens. The majority of GBM tumors show a mutated or overexpressed epidermal growth factor receptor (EGFR); however, tumors treated with EGFR inhibitors such as gefitinib or erlotinib inevitably recur. This recurrence highlights the need to identify signaling pathways involved in GBM resistance to EGFR therapy that may serve as targets for intervention. In our recently published work, we found that activation of the ROS1 pathway is a primary mechanism by which glioma cells become resistant to EGFR-targeted therapy. ROS1 is a proto-oncogene receptor tyrosine kinase activated by chromosomal rearrangement in several human cancers, including non-small cell lung cancer (NSCLC), cholangiocarcinoma, gastric cancer, ovarian cancer, and glioblastoma. We therefore designed, synthesized, and screened a series of new ROS1 inhibitors. The lead compound, ROS-Ic, is very potent (IC50 = 24nM) and highly specific to ROS1 protein. Treatment of gefitinib-resistant GBM cells with ROS1-lc sensitized the resistant cells to low concentrations of gefitinib, resulting in apoptosis following a prolonged S-phase cell cycle arrest. When compared to crizotinib, an FDA-approved small-molecule tyrosine kinase inhibitor currently used to treat ALK- and ROS1+ NSCLC patients, ROS-Ic showed superior cytotoxic activity in vitro towards ROS1-positive GBM cells. Crizotinib resistance is thought to be due to abolished crizotinib binding by ROS1 mutations in crizotinib binding pocket. Interestingly, the binding of our leading compound ROS1-Ic was not affected by these mutations and crizotinib-resistant cells harboring these mutations were still sensitive to ROS1-Ic, highlighting the potential therapeutic value of this compound. Citation Format: Hashim M. Aljohani, Mohamed Aittaleb, Byung Sun Park, So Ha Lee, El Mustapha Bahassi. Preclinical evaluation of a new ROS1 inhibitor to overcome resistance to EGFR therapy in glioblastoma [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A141.

The role of brigatinib in crizotinib-resistant non-small cell lung cancer.

Despite the advances in new targeted therapies in ALK positive population, most patients progress under ALK inhibitors within first 2 years; being the brain the most frequent site of relapse. ALK mutations, in ~30% of patients, are the main known mechanism of resistance. Classically, second-generation ALK inhibitors have been the standard of care in the crizotinib-resistant population; however, each ALK inhibitor has a different spectrum of sensitivity to ALK mutations, complicating the optimal treatment strategy for the resistant population. Brigatinib (AP26113) is a novel highly selective and potent inhibitor of ALK and ROS1 with a high degree of selectivity. In vitro, brigatinib not only inhibited ALK with 12-fold higher potency compared to crizotinib, but also inhibited IGF-1R, FLT3 and EGFR mutants, with some activity against the EGFRT790M resistance mutation. In xenograft models, brigatinib overcomes resistance to ALK inhibitors, including the ALK G1202R mutation, which is resistant to first- and second-generation inhibitors. The efficacy of brigatinib in crizotinib-resistant, ALK-positive patients has been demonstrated in two early studies, which led to its approval in this setting, and it is currently being investigated as the first-line therapy versus crizotinib in tyrosine kinase inhibitor-naïve patients. Brigatinib demonstrates not only promising whole-body activity, but also an impressive improvement of intracranial outcomes in terms of both objective response rate and progression-free survival in the crizotinib-resistant population, with optimal efficacy at 180 mg (following a 90 mg run-in for 7 days) and good tolerance. These data confirm brigatinib as an excellent therapeutic strategy after crizotinib failure, particularly in the setting of central nervous system involvement. In this review, we summarize the two main clinical studies reported to date with brigatinib in ALK-positive advanced NSCLC patients, in particular, in the crizotinib-resistant population. We also address the mechanism of action for development of resistance and the challenging issues of optimal implementation for sequences of administration for ALK inhibitors.

Abstract B184: TPX-0005, a highly potent TRK inhibitor, effectively overcomes clinical-resistance TRK mutations including solvent front mutants TRKA G595R, TRKB G639R, and TRKC G623R

Abstract The tropomyosin receptor kinases (TRKs), including TRKA/B/C encoded by NTRK1/2/3 genes, are high-affinity receptors for neurotrophins. Oncogenic rearrangement of NTRK1, NTRK2, and NTRK3 have been identified in many solid malignancies. The use of TRK inhibitors entrectinib and larotrectinib has led to clinical benefit in patients with solid malignancies harboring oncogenic NTRK fusions. Similar to ALK and ROS1 inhibitor treatment, the solvent front mutations TRKA G595R and TRKC G623R (both analog to ALK G1202R) were reported in clinic from treatment-resistant patients. A new generation of TRK inhibitors targeting both wild type and mutated TRKs is highly needed for effectively treating patients harboring fusion TRKs. TPX-0005, a novel three-dimensional macrocycle with a much smaller size than current TRK inhibitors in the clinic, was designed to overcome clinical resistance mutations systematically. TPX-0005 potently inhibited both wild type and mutant TRKs including solvent front mutations. TPX-0005 showed pico-molar activity against TRK kinases (IC50s 0.83 nM, 0.05 nM, and 0.10 nM for TRKA/B/C, respectively) in Reaction Biology kinase assay. TPX-0005 is the most potent TRK inhibitor in clinic and effectively overcomes clinical resistance TRK mutations as shown in the table in cell proliferation assays. It was recently reported that LOXO-195 inhibited the phosphorylation of TRKA and ERK kinases in NIH3T3 cell line expressing ΔTRKA G595R or ETV6-TRKC G623R with IC50s of 7 nM and 45.5 nM, respectively. TPX-0005 is more than 10-fold more potent than LOXO-195. In the xenograft tumor model studies including human PDX model, TPX-0005 dramatically caused tumor regression in the tumors carrying WT or solvent-front mutated TRK fusion gene. Overall, TPX-0005 demonstrated desired drug-like properties, good safety profile, and is a supreme TRK inhibitor against WT and mutated TRKs. A phase 1/2 clinical trial of TPX-0005 is actively being pursued (NCT03093116). KM-12 IC50 (nM)Ba/F3 Cell Proliferation Assay IC50 (nM)InhibitorTPM3-TRKAWTLMNA-TRKA WTLMNA-TRKA G595RETV6-TRKB WTETV6-TRKB G639RETV6-TRKC WTETV6-TRKC G623RTPX-0005&amp;lt;0.2&amp;lt;0.20.4&amp;lt;0.20.6&amp;lt;0.23Entrectinib9.20.3705&amp;lt;0.513840.61000Larotrectinib12.33.5102410.9300010.21500 Citation Format: J. Jean Cui, Dayong Zhai, Wei Deng, Evan Rogers, Zhongdong Huang, Jeffrey Whitten, John lim, Yishan Li. TPX-0005, a highly potent TRK inhibitor, effectively overcomes clinical-resistance TRK mutations including solvent front mutants TRKA G595R, TRKB G639R, and TRKC G623R [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B184.

Abstract 52: Antitumor activity of entrectinib, a highly potent pan-TRK, ROS1, and ALK inhibitor, in NTRK-fusion positive acute myeloid leukemia

Abstract Acute myeloid leukemia (AML) is the most common form of acute leukemia in adults and comprises a heterogeneous group of diseases. A number of recurrent leukemogenic gene mutations or chromosomal rearrangements have been identified and clinically validated in AML. However, nearly 50% of AML patient samples lack any known canonical AML driver mutations. Advances in molecular diagnostics have resulted in the identification of novel and actionable gene mutations or chromosomal rearrangements in a subset of these AML samples. The ETV6-NTRK3 fusion gene is one such rearrangement identified in samples from patients with AML. Fusion of ETV6 to the tyrosine kinase domain of TRKC (encoded by NTRK3) results in constitutive activation of the TRKC kinase, and ETV6-TRKC fusion protein expression has been shown to be sufficient for leukemogenesis. Constitutive activation of TRK family tyrosine kinases has also been detected in a wide range solid tumor and hematologic malignancies including lung, colorectal, salivary gland, sarcoma, thyroid, glioblastoma, melanoma, anaplastic large cell lymphoma, and Philadelphia-like acute lymphoblastic leukemia. Entrectinib (RXDX-101) is an investigational, orally available, CNS-active, highly potent, and selective kinase inhibitor with low nanomolar potency against TRKA/B/C, ROS1 and ALK kinase activities (encoded by NTRK1/2/3, ROS1, and ALK genes, respectively). In these studies, we have demonstrated sensitivity to entrectinib in AML cell lines with endogenous expression of the ETV6-NTRK3 fusion gene. Entrectinib treatment blocked cell proliferation and induced apoptotic cell death in vitro with sub-nanomolar IC50 values. Phosphorylation of the ETV6-TRKC fusion protein, as well as phosphorylation of known TRKC downstream signaling effectors, was inhibited by entrectinib treatment in a dose-dependent manner. Sensitivity to entrectinib was dependent on expression of the TRKC fusion protein. In xenograft models, entrectinib treatment at clinically relevant doses resulted in tumor regression, which was accompanied by elimination of residual cancer cells from the bone marrow. The clinical relevance of activated oncogenic tyrosine kinases resulting from chromosomal rearrangements has been validated by the efficacy of selective tyrosine kinase inhibitors. Entrectinib is currently the subject of STARTRK-2, an ongoing global phase 2 basket study enrolling patients across multiple tumor histologies containing TRK, ROS1, or ALK fusions. Our preclinical data demonstrate the potential of entrectinib as an effective treatment for patients with NTRK rearranged acute myeloid leukemia and provide a rationale for the clinical development of entrectinib in molecularly defined hematologic malignancies. Citation Format: Patrick Fagan, Maria Barrera, Colin Walsh, Danielle Murphy, Ian Silverman, Robert Shoemaker, Ge Wei, Zachary Hornby, Gary Li, Kristen M. Smith. Antitumor activity of entrectinib, a highly potent pan-TRK, ROS1, and ALK inhibitor, in NTRK-fusion positive acute myeloid leukemia [abstract]. In: Proceedings of the Second AACR Conference on Hematologic Malignancies: Translating Discoveries to Novel Therapies; May 6-9, 2017; Boston, MA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(24_Suppl):Abstract nr 52.

Design, synthesis, biological evaluation and molecular modeling of novel 2-amino-4-(1-phenylethoxy) pyridine derivatives as potential ROS1 inhibitors

With the aim of discovering potential and selective inhibitors targeting ROS1 kinase, we rationally designed, synthesized and evaluated two series of novel 2-amino-pyridine derivatives with 1-phenylethoxy at C-3 and C-4 position. The enzymic assays results indicated that six of the new compounds 13b-13d and 14a-14c showed remarkably higher inhibitory activities against ROS1 kinase. The most promising compounds, 13d and 14c displayed the most desired ROS1 inhibitory activity with IC50 values of 440 nM and 370 nM respectively. Furthermore, 13d and 14c displayed ROS1 inhibitory selectivity of about 7-fold and 12-fold, relative to that of ALK sharing about 49% amino acid sequence homology in the kinase domains. They also showed good anti-proliferative effects against ROS1-addicted HCC78 cell lines with the IC50 values of 8.1 μM and 65.3 μM, respectively. Moreover, molecular docking and molecular dynamics simulation studies disclosed that compound 14c and 13d shared similar binding poses with Crizotinib except the selective binding site of ROS1. It also gave a probable molecular explanation for their activity and selectivity, which the methoxyl group in benzene ring was the crucial to the selectivity to ROS1 versus ALK.

Acral Lentiginous Melanoma Harboring a ROS1 Gene Fusion With Clinical Response to Entrectinib.

ROS1 gene fusions demonstrate oncogenic activity, and patients with non-small-cell lung cancer (NSCLC) harboring a ROS1 fusion benefit from the use of a ROS1 inhibitor; however, clinical response to ROS1 inhibitors remains largely uncharacterized outside of NSCLC. ROS1 fusions have been identified in multiple tumor types but have not been reported in cutaneous melanoma. Tumors from 22 patients with acral lentiginous melanoma (ALM) were analyzed with targeted RNA sequencing to detect fusions in ROS1, NTRK1, NTRK2, NTRK3, and ALK genes. A patient harboring a ROS1 fusion was enrolled in a phase I basket trial of a ROS1/TRK/ALK inhibitor (entrectinib). An additional 78 tumors with different subtypes of melanoma were screened by ROS1 immunohistochemistry. Targeted sequencing identified a GOPC-ROS1 fusion in a patient with ALM. The patient underwent a dramatic and durable response to entrectinib, with a RECIST (version 1.1) partial response of -38% at 3 months and -55% at 11 months. The response is ongoing, and the patient has not developed any new lesions. No additional ROS1 fusions were identified by immunohistochemistry, resulting in a frequency of 3.0% in ALM and 1.3% in all melanomas. ROS1 fusions occur and can respond to targeted therapy in cutaneous melanoma; however, they may be specific to ALM subtype. This report expands knowledge of ROS1 inhibitor response outside of NSCLC and identifies new therapeutic options for a subset of patients with ALM.

P1.01-016 Next-Generation Sequencing Shows Mechanisms of Intrinsic Resistance in ALK-Positive NSCLC Patients Treated with Crizotinib

Crizotinib (XALKORI®) is a small molecule ALK, ROS1, and c-MET tyrosine kinase inhibitor approved for the treatment of patients with ALK-positive or ROS1-positive metastatic NSCLC. PROFILE 1005 was a single arm phase 2 study of the safety and efficacy of crizotinib in previously treated patients with advanced NSCLC that is ALK-positive as determined by the investigational use only FISH test or on a case-by-case basis using a local FISH, IHC or RT-PCR laboratory developed test. In this study 54.1% of patients exhibited a confirmed complete or partial response to crizotinib (responders) by investigator assessment, while 9.9% had a best overall tumor response of progressive disease (progressors).

MS 25.05 Novel Fusions

Chromosomal rearrangements or deletions can generate novel gene fusions that lead to the expression of chimeric proteins with oncogenic activity in lung and other cancers. The paradigm for gene fusions in lung cancer is the EML4-ALK gene fusion which is found in approximately 5% of lung adenocarcinomas.1 Once identified, drug development for this target proceeded rapidly and crizotinib was the first approved tyrosine kinase inhibitor for patients with ALK+ non-small cell lung cancer based on its ability to generate substation objective response rates and prolonged progression free survival (NSCLC).3,4 The development of CNS penetrant and/or next generation ROS1 inhibitors including lorlatinib, entrectinib and TPX-0005 is ongoing. RET gene fusions are also found in 1-2% of NSCLC, but the use of multiple different RET inhibitors have failed to reproduce the success of targeting ALK or ROS1 fusions.5 The development of more selective RET inhibitors such as LOXO-292, BLU-667, and RXDX-105 are currently in clinical trials for RET+ lung and other cancers. NTRK1 fusions were recently identified in NSCLC and homologous NTRK2 and NTRK3 fusions are found in multiple tumor types.6,7, Early clinical trials of larotrectinib showed an impressive objective response rate of 76% for 12 different tumor histologies harboring NTRK1/2/3 fusions and the CNS-penetrant entrectinib is similarly being evaluated in a basket trial. Other rare, novel fusions have recently been identified in NSCLC including EGFR fusions or MET fusions.7 Early evidence suggests that these fusions may also respond to cognate TKIs. EGFR fusions break the paradigm of ALK and ROS1 fusions in which the 5’ end of ALK or ROS1 is replaced with the 5’ portion of another gene. EGFR fusions retain most of the EGFR gene, with the unrelated gene sequencing fusing at the 3’ end of EGFR. A related oncogenic EGFR mutation in which the kinase domain of EGFR is duplicated in tandem has also been described and appears responsive to EGFR TKIs.7 Additional fusions involving the receptor tyrosine kinase (RTK) encoding genes AXL, PDGFRA, and ERBB4 fusions have been described, but little is known about the true incidence in lung cancer.8,9 The fusions described thus far all involve genes that encode RTKs, but additional gene fusions have also been identified in lung cancer including BRAF fusions.7,9 BRAF fusions replace the 5’ region of BRAF, including the Ras-binding domain (RBD), with sequences from another gene. Anecdotal evidence suggests that these alterations may be responsive to MEK inhibition. Analogous splice alteration which remove a region including the RBD have also been described in cancer and are oncogenic. Finally, gene fusions involving NRG1, which encodes the HER3/4 ligand neuregulin-1, have been described, mostly in invasive mucinous adenocarcinomas of the lung.9,10 Several challenges exist to the development of targeted therapies for these novel fusions. Even in the era of next-generation sequencing tests these alterations may go undetected due to limited testing of genes to those with approved therapies (ALK, ROS1, EGFR, and BRAF) and not all assays are designed to detect all of these alterations. Furthermore, the rarity of some of these alterations may make clinical trials for these novel fusions less appealing, although amalgamating some of these alterations with analogous mutations, e.g., MET gene fusions with MET exon 14 splice alterations or MET gene amplification, may allow for a more rapid path to approval.

Investigation on the binding mechanism of loratinib with the c-ros oncogene 1 (ROS1) receptor tyrosine kinase via molecular dynamics simulation and binding free energy calculations

The c-ros oncogene 1 (ROS1) has proven to be an important cancer target for the treatment of various human cancers. The anaplastic lymphoma kinase inhibitor crizotinib has been granted approval for the treatment of patients with ROS1 positive metastatic non-small-cell lung cancer by the Food and Drug Administration on 2016. However, serious resistance due to the secondary mutation of glycine 2032 to arginine (G2032R) was developed in clinical studies. Loratinib (PF-06463922), a macrocyclic analog of crizotinib, showed significantly improved inhibitory activity against wild–type (WT) ROS1 and ROS1G2032R mutant. To provide insights into the inhibition mechanism, molecular dynamics simulations and free energy calculations were carried out for the complexes of loratinib with WT and G2032R mutated ROS1. The apo-ROS1WT and apo-ROS1G2032R systems showed similar RMSF distributions, while ROS1G2032R-loratinib showed significantly higher than that of WT ROS1-loratinib, which revealed that the binding of loratinib to ROS1G2032R significantly interfered the fluctuation of protein. Calculations of binding free energies indicate that G2032R mutation significantly reduces the binding affinity of loratinib for ROS1, which arose mostly from the increase of conformation entropy and the decrease of solvation energy. Furthermore, detailed per-residue binding free energies highlighted the increased and decreased contributions of some residues in the G2032R mutated systems. The present study revealed the detailed inhibitory mechanism of loratinib as potent WT and G2032R mutated ROS1 inhibitor, which was expected to provide a basis for rational drug design.