Small Molecule Tyrosine Kinase Inhibitors Research Articles

FGFR inhibitors: Emerging treatments in advanced or metastatic cholangiocarcinoma

Cholangiocarcinoma (CCA) is an aggressive cancer with poor prognosis, where the median overall survival remains less than 1 year with standard treatment for unresectable or metastatic disease. This highlights the need for new therapeutic approaches. The fibroblast growth factor receptor (FGFR) family of transmembrane receptors, which are implicated in tumorigenesis, may represent one such target. In this article, we summarize the therapeutic rationale for targeting these receptors in CCA and the role of molecular testing to identify potential responders to treatment. We examine the current available safety and efficacy data on the several small molecule tyrosine kinase inhibitors under investigation for this disease. With a move toward identifying and targeting tumor specific mutations, FGFR inhibitors represent an exciting development which may be available for patients in the near future.

Current treatments and future potential of surufatinib in neuroendocrine tumors (NETs).

Neuroendocrine tumors (NETs) are rare, heterogeneous, often indolent tumors that predominantly originate in the lungs and gastrointestinal tract. An understanding of the biology and tumor microenvironment of NETs has led to the development of molecularly targeted treatment options including somatostatin analogs, tyrosine kinase inhibitors, mammalian target of rapamycin inhibitors and peptide receptor radionuclide therapy. Although increases in progression-free survival have been demonstrated, most currently approved NET therapies are limited by the development of tumor resistance. Surufatinib (HMPL-012, previously known as sulfatinib) is a new, oral, small-molecule tyrosine kinase inhibitor that potently inhibits vascular endothelial growth-factor receptor 1–3, fibroblast growth-factor receptor 1, and colony-stimulating-factor-1 receptor. This unique combination of molecular activities inhibits tumor angiogenesis, regulates tumor-immune evasion, and may decrease tumor resistance. Surufatinib demonstrated statistically significant, clinically meaningful antitumor activity, including tumor shrinkage, in two phase III studies recently completed in China in advanced pancreatic NETs and advanced extrapancreatic NETs. The safety profile of surufatinib in neuroendocrine tumors studies was consistent with previous surufatinib clinical studies. In an ongoing study in United States (US) patients with NETs of pancreatic origin and NETs of extrapancreatic origin previously treated with everolimus or sunitinib, surufatinib has also demonstrated promising efficacy. Furthermore, the pharmacokinetic and safety profile of surufatinib in US patients is similar to data collected in studies done in China. These positive phase III results support the efficacy of surufatinib in patients with advanced, progressive, well-differentiated NETs regardless of tumor origin.

Combined crizotinib and endocrine drugs inhibit proliferation, migration, and colony formation of breast cancer cells via downregulation of MET and estrogen receptor

Hormone-dependent breast cancer is the most abundant molecular subtype of the disease. Despite the availability of endocrine treatments, the use of these drugs is limited by their serious adverse reactions and development of acquired resistance often mediated by growth factor receptors. The hepatocyte growth factor receptor, MET, is a receptor tyrosine kinase known for its oncogenic activity and mediating resistance to targeted therapies. Crizotinib is a small-molecule tyrosine kinase inhibitor of MET. In this study, the anticancer effects of combined crizotinib and endocrine drugs were investigated in breast cancer cells in vitro along with the molecular mechanisms associated with these effects. Results showed that crizotinib inhibited growth of MCF7 and T-47D breast cancer cells in a dose-dependent manner with IC50 values of 2.88 μM and 0.93 μM, respectively. Combined treatment of crizotinib and 4-hydroxytamoxifen resulted in synergistic growth inhibition of MCF7 and T-47D cells with combination index values of 0.39 and 0.8, respectively. The combined treatment significantly suppressed migration and colony formation of MCF7 and T-47D cells. Immunofluorescence showed a significant reduction of the expression of the nuclear protein Ki-67 with the combination of crizotinib and 4-hydroxytamoxifen in both cell lines. Western blotting indicated that the combination treatment reduced the levels of active and total MET, estrogen receptor α (ERα), total and active levels of AKT, ERK, c-SRC, NFĸB p65, GSK-3β, and the anti-apoptotic BCL-2 protein. Findings from this study suggest a potential role of MET inhibitors in breast cancer treatment as monotherapy or combination with endocrine drugs.

Lenvatinib: A narrative drug review

The discovery and clinical efficacy of imatinib in chronic myeloid leukemia opened a new and interesting avenue of oral small-molecule tyrosine kinase inhibitors. Thereafter, several such molecules with efficacy across multiple tumor types have been discovered. One of the oral multi-kinase inhibitors is lenvatinib, which started its journey in 2008 when it showed efficacy on stem cells in the laboratory setting and was first approved by the United States Food and Drug Administration in August 2015 for the management of radioiodine-refractory differentiated thyroid cancer. Since then, it has been approved for hepatocellular, endometrial, and renal cell carcinomas, and many more trials are underway for lenvatinib in multiple solid tumors, either alone or in combination with immunotherapy. In addition to the robust data on the efficacy of this drug, it is known for its tolerability with different dosing schedules in different tumor types, a feature unique to this drug. Therefore, an in-depth understanding of its mechanism of action, pharmacokinetics, pharmacodynamics, dosage in different tumor types, expected side effects, and predictors of response will go a long way in its safe and appropriate use in the clinics. In this review, we aim to summarize and collate these data in a reader-friendly manner, thus making it a ready reckoner for lenvatinib. We searched the PubMed database for full-text articles on lenvatinib published in the last 10 years using the search terms “lenvatinib,” “hepatocellular carcinoma,” renal cell carcinoma,” “thyroid carcinoma,” “and “endometrial carcinoma”. A total of 1053 studies were identified, of which 60 were included in this review.

Determination of Crizotinib in Mouse Tissues by LC-MS/MS and Its Application to a Tissue Distribution Study.

Toxicity induced by crizotinib, a small-molecule tyrosine kinase inhibitor, is a significant clinical issue during treatment. A tissue distribution study is required to explore the organs affected by this molecule. In this study, a simple liquid chromatography tandem mass spectrometry method was developed and validated for the determination of crizotinib in various mouse tissues. Mouse tissue homogenates were processed by protein precipitation with methanol, and apatinib was chosen as the internal standard. The analytes were separated on a Phenomenex Kinetex C18 (50 mm × 2.1 mm, 2.6 μm) column with gradient elution using methanol and 0.3% formic acid water solution. Tandem mass spectrometric detection was conducted using multiple reaction monitoring via an electrospray ionization source in the positive mode. The monitored ion transitions were m/z 450.1 ⟶ 260.2 for crizotinib and m/z 398.2 ⟶ 212.0 for apatinib. The problem of the severe carryover effect was successfully resolved. The method was validated and applied to a tissue distribution study of crizotinib in mice, which was reported for the first time. The results of the study showed that the main target organs of crizotinib were the lung, liver, and spleen, and a high concentration of crizotinib was found in the gastrointestinal tract. This study offers a reliable method for quantifying crizotinib and provides a basis for further research on crizotinib toxicity.

FLT3 Ligand-DM1 Conjugate Selectively Targets Acute Myeloid Leukemia Cells with FLT3 Expression

Acute myeloid leukemia (AML) is a malignant hematopoietic neoplasm featured by impaired differentiation and uncontrolled proliferation of myeloid progenitors. Gain-of-function mutations of FMS-like tyrosine kinase 3 (FLT3) present in 30-40% of patients with AML. In addition, more than 90% of AML blasts aberrantly express FLT3, making FLT3 an attractive therapeutic target for AML. Currently, several small molecule tyrosine kinase inhibitors (TKIs) targeting FLT3 have been approved in the treatment of AML, but they need to be used in combination with chemotherapy because of their limited potency to eliminate leukemic cells as single agents, largely due to the development of secondary inhibitor-resistant FLT3 mutations. Therefore, novel therapeutic strategies targeting FLT3 are needed. In the present study, we developed a FLT3 ligand-emtansine drug conjugate (FL-DM1) that targeted FLT3-positive AML cells with high potency and selectivity. We expressed recombinant human FLT3 ligand (rhFL) in the periplasm of recombinant E. Coli. The protein was purified by a two-step purification system containing Ni-NTA and Phenyl Sepharose. Our purified rhFL was bioactive to stimulate phosphorylation of FLT3 and proliferation of THP-1 cells. Next, we conjugated purified rhFL and emtansine (DM1) with SPDP linker. Reducing and non-reducing SDS-PAGE revealed that rhFL and DM1 were successfully conjugated, evidenced by a band with higher molecular weight of the conjugation product. Previous studies show that DM1 is a drug preferentially targeting proliferating cells by depolymerizing microtubules through binding at the vinca binding site of tubulin. We found that FL-DM1 reserved the physiological function of FLT3 ligand to stimulate proliferation of AML cells by inducing phosphorylation of FLT3 and the downstream signaling protein AKT in immunoblot, potentially enhancing the potency of FL-DM1 to inhibit FLT3-positive AML cells. Furthermore, flow cytometry showed that the surface expression of FLT3 significantly decreased on cells treated by FL-DM1 within two hours, which indicated the internalization of FL-DM1/FLT3 complex on these FLT3-positive AML cells, providing a mechanism of FL-DM1 entering target cells. In cell viability assay, we found that FL-DM1 effectively inhibited FLT3-positive AML cells THP-1 and MV-4-11 with IC50 around 10-30 nM. Also, FL-DM1 induced apoptosis and cell cycle arrest at G2/M phase in these cells detected by flow cytometry. In our previous studies, we generated FLT3-ITD transformed HCD-57 cells. HCD-57 cells are FLT3-negative erythroleukemia cells that depend on erythropoietin for survival. When infected with recombinant retroviruses carrying FLT3-ITD, they acquired ability to proliferate in the absence of EPO. We found that FL-DM1 inhibited HCD-57 cells transformed by FLT3-ITD, but not parental HCD-57 cells without FLT3 expression, indicating the selectivity of FL-DM1 to target FLT3-positive AML cells. In conclusion, our data demonstrated that FL-based drug conjugate can serve as an effective drug to target FLT3-expressing AML cells. Further studies will focus on in-vivo evaluation of FL-DM1 in animal models, the production of uncleavable SMCC linked FL-DM1 with improved in-vivo pharmacokinetic properties, and screening of FL muteins-DM1 conjugates with desired pharmacological properties. Disclosures No relevant conflicts of interest to declare.

Targeting HER2 Alterations in Non-Small-Cell Lung Cancer: A Comprehensive Review.

HER2 is a critical gene that drives various solid tumors in addition to those of breast cancer. For example, HER2 plays a role in non-small-cell lung cancer (NSCLC). Overexpression, amplification, and point mutations in HER2 have been described in patients with NSCLC; however, the potential roles of these alterations remain unclear. We summarize the evidence regarding the distinct impacts of different HER2 aberrations on antitumor agents. Also, we update the therapeutic efficacy of HER2-targeted agents, including anti-HER2 antibodies, antibody-drug conjugates, and small-molecule tyrosine kinase inhibitors, tested in HER2-aberrant NSCLC. Although these drugs are not yet standard treatments, certain patients may benefit from these therapies. In this review, we aim to provide an improved understanding of HER2 aberrations in NSCLC, including NSCLC biology and the impacts of each aberration on prognosis and standard treatment. We also highlight the potential of novel anti-HER2 therapies approved by regulatory bodies and those in clinical development. Compared with HER2 amplification or overexpression, HER2 mutations, especially HER2 exon 20 mutations, are emerging as the most clear targetable driver for HER2-directed therapies in lung cancer. De novo and inducible HER2 pathway activation need to be differentially managed. Further investigations with new strategies are needed.

Clinical Efficacy and Safety of Apatinib for the Treatment of Patients with Metastatic, Recurrent Cervical Cancer after Failure of Radiotherapy and First-Line Chemotherapy: A Prospective Study

Purpose: As a small-molecule tyrosine kinase inhibitor of vascular endothelial growth factor receptor 2 (VEGFR2), apatinib has shown a survival benefit in multiple solid tumors. This study aims to evaluate the efficacy and safety of apatinib in patients with metastatic, recurrent cervical cancer after failure of radiotherapy and first-line chemotherapy. Methods: A total of 42 patients between June 2018 and March 2019 were involved in this study. All patients orally received apatinib once daily in a 4-week cycle until disease progression or adverse events that prohibit further therapy. The primary endpoint was progression-free survival (PFS), the secondary endpoints were overall survival (OS), objective response rate (ORR), disease control rate (DCR), health-related quality of life (HRQoL) and adverse events. Results: During a median follow-up of 13 months, 8 patients achieved a partial response and 24 cases achieved stable disease. None of them reported a complete response. The ORR and DCR were 19.0 and 76.2%, respectively. The median PFS was 6.0 months (95% CI 4.9–7.1), and the median OS was 12.0 months (95% CI 10.1–13.9). The global health score/HRQoL improved significantly following 3-cycle treatment (50.4 ± 12.5 vs. 60.1 ± 11.8; p < 0.01). The most frequent grade 3–4 adverse events were hand-foot syndrome, hypertension and fatigue. Conclusion: Apatinib should be an effective and tolerable treatment option for patients with metastatic, recurrent cervical cancer after failure of radiotherapy and first-line chemotherapy.

Choosing between isotretinoin and acitretin for epidermal growth factor receptor inhibitor and small molecule tyrosine kinase inhibitor acneiform eruptions

Choosing between isotretinoin and acitretin for epidermal growth factor receptor inhibitor and small molecule tyrosine kinase inhibitor acneiform eruptions

A Comprehensive Review of Contemporary Literature for Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors in Non-Small Cell Lung Cancer and Their Toxicity.

Mutations in the epidermal growth factor receptor (EGFR) are common amongst those with non-small cell lung cancer and represent a major factor in treatment decisions, most notably in the advanced stages. Small molecule tyrosine kinase inhibitors (TKIs) that target the EGFR, such as erlotinib, gefitinib, icotinib, afatinib, dacomitinib and osimertinib, have all shown to be effective in this setting. Osimertinib, a third-generation EGFR TKI, is a favorable option, but almost all patients develop resistance at some time point. There are no effective treatment options for patients who progress on osimertinib, but ongoing trials will hopefully address this unmet need. The aim of this review is to provide a comprehensive review of the data with EGFR TKIs, management of the toxicities and the ongoing trials with this class of agents.

Current perspectives on novel systemic therapeutic agents beyond immune checkpoint inhibition in metastatic urothelial carcinoma.

Treatment strategies for metastatic urothelial carcinoma (mUC) have evolved dramatically over the last decade. The emergence of immunotherapeutic agents, especially immune checkpoint inhibitors, has been the most significant development. Immunotherapy increased the overall survival rate of patients with mUC and provided a durable response. The success of immune checkpoint inhibitors further led to the development of novel agents that regulate the immune system within the tumor microenvironment. However, despite some success with immune checkpoint inhibitors, researchers are still developing new agents, including small molecule tyrosine kinase inhibitors, mammalian target of rapamycin (mTOR) inhibitors, and novel fusion proteins, tailored for targets other than immune checkpoint inhibitors. Novel treatment strategies are being developed rapidly with ongoing pre-clinical trials. Here, we outline promising new therapies that are expected to improve survival rates for patients with mUC.

A novel small molecule tyrosine kinase inhibitor (GUtinib) preferentially targets discoidin domain receptors and reduces toxic proteins in neurodegeneration

Tyrosine kinase inhibition (TKi) is a potential new strategy to target misfolded protein degradation in neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD) and Lewy Body Dementia (DLB). Our laboratory demonstrated that multi-kinase inhibitors like nilotinib and bosutinib are optimal agents since they target both Abl and Discoidin Domain Receptors (DDR1/2) and Abl and SRC tyrosine kinases, respectively. These two agents are currently in phase II in DLB (nilotinib and bosutinib), PD and AD (nilotinib). Profiling the tyrosine kinase targets of several FDA-approved drugs shows that agents with high potency to Abl alone are ineffective and cannot clear toxic proteins, but a multikinase inhibition like Abl/SRC and DDRs is optimal for misfolded protein clearance. Here we report a novel tyrosine kinase inhibitor (GUtinib) that has the highest specificity to DDR1/2 and exhibits a high efficacy to clear human alpha-Synuclein, amyloid-beta and hyper-phosphorylated tau in several animal models of neurodegeneration. Our data indicate that GUtinib preferentially targets DDR1 and 2, but not Abl, and induces autophagy at very low concentrations and higher efficacy than other multikinase inhibitors. Further toxicology experiments will be conducted to obtain pre-investigational new drug (pre-IND) status, and if the safety of GUtinib is acceptable this agent will be tested in first-in-human early development clinical trials.

FGF Expression in HPV16-positive and -negative SCC After Treatment With Small-molecule Tyrosine Kinase Inhibitors and Everolimus

Targeted therapies in the treatment of head and neck squamous cell carcinoma (HNSCC) are subject to extensive research. Different mutations of genes belonging to the fibroblast growth factor (FGF) family have been detected in HNSCC. In this study, we examined the expression of FGF1 and FGF2 after treatment with small-molecule tyrosine kinase inhibitors (TKIs) and an inhibitor of mechanistic target of rapamycin (mTOR) in vitro using human papillomavirus (HPV)-positive and -negative SCC lines. Cells of two human HPV-negative cell lines (UMSCC-11A/-14C) and one HPV-positive cell line (CERV196) were incubated with 20 μmol/l of erlotinib, gefitinib, nilotinib, dasatinib, or everolimus for 24-96 h. Cell proliferation was assessed by proliferation assay and the protein concentrations of FGF1 and FGF2 by sandwich enzyme-linked immunosorbent assay. For statistical analysis, the results were compared with those for untreated HPV-negative SCC cells. FGF1 and FGF2 were detected in all three tested cell lines. The tested TKIs significantly (p<0.05 reduced) FGF1 expression in the UMSCC-11A cell line within the first 24 h. At later time points, the tested TKIs and everolimus significantly (p<0.05) increased FGF1 and FGF2 expression in HPV-negative and -positive cancer cell lines. The effect was stronger in the HPV-positive cell line. Alterations in FGF signalling are considered to be relevant drivers of tumourigenesis in some HNSCCs. Our results show that the expression of FGF1 and -2 can be influenced effectively by small-molecule TKIs and everolimus. Based on our data, future research should include combinations of specific FGF inhibitors, mTOR inhibitors and other TKIs in the treatment of HNSCC and research on FGF-mediated drug escape mechanisms.

Prevention and treatment of FGFR inhibitor-associated toxicities.

Fibroblast growth factor receptor (FGFR) inhibitors have shown promising results in terms of objective response rates in phase I/II trials in various malignancies that harbor FGFR genetic aberrations. The class of medications brings in the concept of 'personalized' treatment by targeting susceptible FGFR genetic alterations in some rare but dismal cancers such as cholangiocarcinoma. Despite the fact that FGFR inhibitors are well-tolerated, these drugs are associated with toxicities that are distinct from that of other small-molecule tyrosine kinase inhibitors. These toxicities can result in dose reductions, interruptions, and even drug discontinuation as reported in the clinical trials. The prevention and effective management of the FGFR inhibitor-associated toxicities will allow patients to stay on these medications without the therapy interruptions. The current work is focused on summarizing the available literature on unique FGFR inhibitor-associated toxicities with a special emphasis in managing the unique adverse events.

Avelumab and axitinib combination therapy for the treatment of advanced renal cell carcinoma.

Owing to an improved understanding of the immunobiological profile of renal cell carcinoma (RCC), the past few years have ushered in significant changes in systemic therapies for advanced stage RCC. First-line treatment with single-agent tyrosine kinase inhibitors (TKI) has been virtually replaced for most patients by immunotherapy combinations. The first ofsuch treatments was the dual immune checkpoint inhibitor combination of ipilimumab and nivolumab. More recently, the combination of an immune checkpoint inhibitor and a TKI has also moved into the first-line setting. This review summarizes the pharmacologic properties, evidence for use and safety of avelumab, a PD-L1inhibitor and axitinib a small-molecule TKI, each as monotherapy, and in combination for the management of metastatic RCC.

Rola neratynibu w terapii przedłużonej u chorych na wczesnego, HER2-dodatniego raka piersi

HER2 overexpression is found in approximately 20% of patients with breast cancer and is associated with an unfavorable prognosis. The use of chemotherapy and targeted therapies blocking HER2 function in patients with early HER2 positive breast cancer has led to significant clinical benefits. Despite this, approximately 25% of patients initially treated with trastuzumab experience recurrence of invasive disease within 5 years of completion of adjuvant treatment. Neratinib is an oral, irreversible, small molecule tyrosine kinase inhibitor blocking the intracellular domain of the HER1, HER2 and HER4 receptor, whose activity in extended anti-HER2 adjuvant treatment in HER2-positive early breast cancer patients has been confirmed in ExteNET trial. It has been shown that the use of extended therapy with neratinib after adjuvant trastuzumab treatment in patients with early HER2-positive breast cancer led to a 33% reduction in the risk of invasive disease recurring, with a greater effect observed in ER/PgR positive patients and those with involvement 4 and more lymph nodes.

Abstract 4222: Tucatinib, a selective small molecule HER2 inibitor, is active in HER2 mutant driven tumors

Abstract Tucatinib is an investigational, orally dosed, small molecule tyrosine kinase inhibitor that is highly selective for the kinase domain of HER2 without significant inhibition of EGFR. In this report, we describe the activity of tucatinib alone and in combination with trastuzumab in multiple HER2 mutant driven PDX models. Tucatinib was tested in 6 HER2 mutant PDX tumor models derived from colorectal, non-small cell lung cancer, gall bladder and gastric cancers with L755S, V77L or S310Y mutations. MCF-10A cells were engineered to express the L755S and V777L HER2 activating point mutations and the potency of tucatinib was evaluated in each of these cell lines using HER2 autophosphorylation as an endpoint. The activity of tucatinib was also evaluated in G776V_G/C and G776_YVMA in frame exon 20 insertion mutations, including the G776V_G/C mutant non-small cell lung cancer line NCI-H1781 using both cellular signaling and cell proliferation as endpoints. Tucatinib significantly inhibited tumor growth in 5 of the 6 HER2 point mutant PDX models, whereas trastuzumab alone significantly inhibited tumor growth in 1 of 6 models and the combination of both drugs was significantly active in all HER2 mutant models. Tucatinib inhibited the phosphorylation of HER2 in a L755S mutant MCF-10A cell line and inhibited the growth of 3 L755S mutant tumor models derived from colorectal, gastric and non-small cell lung cancer. Tucatinib also potently inhibited the phosphorylation of HER2 in a V777L mutant MCF-10A cell line, and in a colorectal PDX model containing a V777L mutation, tucatinib alone or in combination with trastuzumab induced tumor regressions. In two PDX models containing the S310Y extracellular domain mutation of HER2, tucatinib alone, or in combination with trastuzumab, resulted in tumor growth delays. In exon 20 insertion mutant derived cell lines, tucatinib inhibited HER2 phosphorylation, but not EGFR phosphorylation, and inhibited the phosphorylation of HER2, HER3, Erk1/2, MEK1 and AKT in the G776V_G/C HER2 mutant NCI-H1781 cell line. These data demonstrate that tucatinib, a highly potent and selective inhibitor of HER2 signaling without significant inhibition of EGFR, is active in multiple HER2 mutant driven tumor models. Importantly, tucatinib is active in models containing the L755S HER2 mutation which has been associated with lapatinib resistance preclinically (1), and trastuzumab resistance clinically (2). Taken together, these results support the idea that HER2 selective inhibition by tucatinib can block oncogenic signaling elicited by mutant HER2, and that it could potentially provide clinical benefit in patients with cancers with activating HER2 mutations.

Abstract 1877: Hypoxia induces EGFR inhibitor resistance in lung cancer cells by upregulation of fibroblast growth factor receptor 1 (FGFR1) via MAPK pathway

Abstract The development of small molecule tyrosine kinase inhibitors (TKIs) specific for epidermal growth factor receptors (EGFRs) with activating mutations has led to a new paradigm in the treatment of non-small cell lung cancer (NSCLC) patients. However, most patients eventually develop resistance. Hypoxia is a key micro-environmental stress in solid tumors that is associated with poor prognosis due in part to acquired resistance to conventional therapy. In our previous study, we showed that long-term, moderate hypoxia promotes resistance to the EGFR TKI, gefitinib, in the NSCLC cell line, HCC827, which harbors an activating EGFR mutation. In this study, we found that hypoxia also induces third generation EGFR TKI, osimertinib (AZD9291), resistance in the NSCLC cell line, H1975, which had developed resistance to first and second generation of EGFR TKIs by harboring second EGFR mutation, T790M. Following growth in hypoxia, hypoxia-induced gefitinib resistant HCC827 clones and hypoxic H1975 cells show increased N-cadherin expression and decreased E-cadherin expression, characteristics of an epithelial-mesenchymal transition (EMT), coordinated by an increased expression of ZEB1, an EMT activator. Mechanistically, we show that hypoxia induces increased fibroblast growth factor receptor 1 (FGFR1) expression in HCC827 and H1975 cells, and that knockdown of the FGFR1 by shRNA can attenuate hypoxia induced EGFR TKI resistance in both HCC827 and H1975 cells. We also found the upregulated expression of FGFR1 by hypoxia is mediated through the MAPK pathway to lead to EGFR TKI resistance. In keeping with this, inhibition of FGFR1 function by the selective small molecular inhibitor, BGJ398, attenuates hypoxia-induced EGFR TKI resistance and promotes upregulation of BIM levels. Similarly, inhibition of MEK activity by the inhibitor, trametinib, shows similar effects. In vivo in tumor xenografts in mice, BGJ398 treatment or trametinib treatment suppresses tumor growth and enhances AZD9291 response. These results suggest that hypoxia is a driving force for acquired resistance to EGFR TKIs through increased FGFR1 expression and coordination of EMT in NSCLC. The combination of EGFR TKIs and FGFR1 or MEK inhibitors may offer an attractive therapeutic strategy for NSCLCs. Citation Format: Yuhong Lu, Yanfeng Liu, Sebastian Oeck, Gary J. Zhang, Peter M. Glazer. Hypoxia induces EGFR inhibitor resistance in lung cancer cells by upregulation of fibroblast growth factor receptor 1 (FGFR1) via MAPK pathway [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1877.

Abstract 1962: Preclinical characterization of tucatinib in HER2-amplified xenograft and CNS implanted tumors

Abstract Tucatinib is an investigational, oral, small molecule tyrosine kinase inhibitor that is highly selective for the kinase domain of HER2, without significant inhibition of EGFR. Recently, HER2CLIMB (NCT02614794), a pivotal, randomized, international, double-blind trial that evaluated tucatinib or placebo in combination with trastuzumab and capecitabine in patients with HER2+ metastatic breast cancer (MBC) with or without brain metastases, after progression with trastuzumab, pertuzumab, and ado-trastuzumab emtansine (T-DM1), showed superior progression-free and overall survival in patients treated on the tucatinib arm. Adverse events in the tucatinib arm were primarily low grade and occurred at rates similar to what was observed in the placebo arm. In this report, we characterize the in vitro and in vivo activity of tucatinib alone and in combination with T-DM1 in HER2-amplified preclinical models. In vitro assays demonstrate that tucatinib potently suppresses HER2-meditated signaling pathways, including phosphorylation of HER2, HER3, AKT and ERK. Ex vivo analysis of tucatinib-treated xenografts shows similar suppression of signal transduction pathways. Tucatinib inhibits the proliferation of HER2+ breast cancer (BC) cell lines in vitro with single digit nanomolar potencies, but was inactive in blocking cell proliferation of BC cell lines lacking amplified HER2. In HER2-amplified BC cell line derived- and patient-derived xenograft models, tucatinib suppresses growth of tumors as a single agent and shows improved activity when combined with T-DM1. To evaluate activity and drug penetration in HER2+ metastatic CNS tumors, we developed and characterized a red-shifted luciferase-expressing BT-474 BC cell line which was stereotaxically implanted into the brain. In vivo bioluminescence imaging was used to evaluate the efficacy of tucatinib and T-DM1 in CNS tumors as single agents and in combination. Histological assessment of treated tumors suggests that tucatinib can penetrate the blood-brain tumor barrier to suppress HER2 signaling. These data are further supported by a drug penetration study of CNS-implanted BT-474 tumors. Quantitative autoradiography analysis demonstrates that 14C-labeled tucatinib penetrates the CNS tumor mass with drug concentration levels exceeding measurements in normal brain regions. These data demonstrate that tucatinib is a uniquely selective and highly potent inhibitor of HER2 signaling, with activity against HER2+ breast cancer xenograft and brain metastasis models. Tucatinib is effective against implanted CNS tumors, suggesting that therapeutically relevant drug concentrations are achievable. These preclinical findings are consistent with clinical data showing tucatinib activity in patients with HER2+ MBC with brain metastases and support the continued development of tucatinib in patients with HER2+ BC. Citation Format: Devra J. Olson, Anita Kulukian, Janelle D. Taylor, Margo C. Zaval, Albina Nesterova, Kelly M. Hensley, Michelle L. Ulrich, Nicole S. Stevens, Scott R. Peterson. Preclinical characterization of tucatinib in HER2-amplified xenograft and CNS implanted tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1962.

Effects of Food on the Pharmacokinetic Properties of Surufatinib: A Phase I, Single-dose, Randomized, Open-label Crossover Study in Healthy Subjects

PurposeSurufatinib is a potent and orally active small-molecule tyrosine kinase inhibitor targeting VEGFRs 1 to 3, FGFR-1, and CSF-1R, and thus may exert antitumor and antiangiogenic effects. The objective of this study was to determine the tolerability and effects of food intake on the pharmacokinetic properties of surufatinib in healthy Chinese subjects. MethodsA total of 24 healthy Chinese male subjects aged between 18 and 55 years were enrolled. Subjects were administered a single dose of surufatinib 250–mg capsules in the fasted and fed states in succession. Pharmacokinetic analysis was performed through the collection of blood samples at predose and at several time points after surufatinib administration. Tolerability assessments comprised physical examination including vital sign measurements, laboratory testing, and ECG to determine adverse events (AEs). FindingsThe 90% CIs of the geometric mean ratios of AUC0–t and AUC0–∞ in the fasted and fed states was within 0.80 to 1.25; and for Cmax, within 0.70 to 1.43, indicating that food had no effect on the bioavailability of surufatinib in these healthy Chinese male subjects. Food intake delayed the time to peak absorption of surufatinib, as the median Tmax in the fed state was longer than that in the fasted state (4.0 vs 2.0 h). Surufatinib was marginally excreted from urine (mean [SD] cumulative excretion fraction, 1.2% [0.4%]). AEs occurred in 7 of the 24 subjects (29.2%) and included upper respiratory tract infection, dizziness, merycism, intervertebral disc protrusion, influenza-like disease, hematuria, prostatitis, and elevated blood urea nitrogen. All AEs were grade 1 or 2. ImplicationsThe bioavailability of surufatinib was not affected by food intake prior to dosing. However, food intake led to delated Tmax of surufatinib. The tolerability of a single oral dose of surufatinib 250 mg in the fasted and fed states was favorable in these healthy Chinese male subjects. These results indicate that surufatinib capsules could be administered before or after meals. ClinicalTrials.gov identifier: NCT02320409.