Search

Supplementary methods of tumor xenograft studies and light microscopic evaluation of tumor xenografts

Supplementary Figure S9 shows TIE2 and macrophage markers expression.

Supplementary Figure S10 additional data on TIE2 and macrophage marker expression.

AMG 337 KINOME scan binding data

BH3 mimetic drugs, which inhibit prosurvival BCL2 family proteins, have limited single-agent activity in solid tumor models. The potential of BH3 mimetics for these cancers may depend on their ability to potentiate the apoptotic response to chemotherapy and targeted therapies. Using a novel class of potent and selective MCL1 inhibitors, we demonstrate that concurrent MEK + MCL1 inhibition induces apoptosis and tumor regression in KRAS-mutant non–small cell lung cancer (NSCLC) models, which respond poorly to MEK inhibition alone. Susceptibility to BH3 mimetics that target either MCL1 or BCL-xL was determined by the differential binding of proapoptotic BCL2 proteins to MCL1 or BCL-xL, respectively. The efficacy of dual MEK + MCL1 blockade was augmented by prior transient exposure to BCL-xL inhibitors, which promotes the binding of proapoptotic BCL2 proteins to MCL1. This suggests a novel strategy for integrating BH3 mimetics that target different BCL2 family proteins for KRAS-mutant NSCLC.Significance:Defining the molecular basis for MCL1 versus BCL-xL dependency will be essential for effective prioritization of BH3 mimetic combination therapies in the clinic. We discover a novel strategy for integrating BCL-xL and MCL1 inhibitors to drive and subsequently exploit apoptotic dependencies of KRAS-mutant NSCLCs treated with MEK inhibitors.See related commentary by Leber et al., p. 1511.This article is highlighted in the In This Issue feature, p. 1494

Tumor cell line profiling data

The MET receptor tyrosine kinase is involved in cell growth, survival, and invasion. Clinical studies with small molecule MET inhibitors have shown the role of biomarkers in identifying patients most likely to benefit from MET-targeted therapy. AMG 337 is an oral, small molecule, ATP-competitive, highly selective inhibitor of the MET receptor. Herein, we describe AMG 337 preclinical activity and mechanism of action in MET-dependent tumor models. These studies suggest MET is the only therapeutic target for AMG 337. In an unbiased tumor cell line proliferation screen (260 cell lines), a closely related analogue of AMG 337, Compound 5, exhibited activity in 2 of 260 cell lines; both were MET-amplified. Additional studies examining the effects of AMG 337 on the proliferation of a limited panel of cell lines with varying MET copy numbers revealed that high-level focal MET amplification (>12 copies) was required to confer MET oncogene addiction and AMG 337 sensitivity. One MET-amplified cell line, H1573 (>12 copies), was AMG 337 insensitive, possibly because of a downstream G12A KRAS mutation. Mechanism-of-action studies in sensitive MET-amplified cell lines demonstrated that AMG 337 inhibited MET and adaptor protein Gab-1 phosphorylation, subsequently blocking the downstream PI3K and MAPK pathways. AMG 337 exhibited potency in pharmacodynamic assays evaluating MET signaling in tumor xenograft models; >90% inhibition of Gab-1 phosphorylation was observed at 0.75 mg/kg. These findings describe the preclinical activity and mechanism of action of AMG 337 in MET-dependent tumor models and indicate its potential as a novel therapeutic for the treatment of MET-dependent tumors. Mol Cancer Ther; 15(7); 1568–79. ©2016 AACR.

High-level focal amplification of MET is associated with sensitivity to AMG 337

Enzymatic and cellular potency of Amgen Compound 5

Western blot analysis in responsive PDX model (LI0612) after 14 days treatment. Total and phosphorylated levels of the indicated proteins were evaluated to assess the effects of AMG 337 on MET signaling. Five to twelve PDX samples were processed for each group.

Figure S1. Kinase interaction map for AMG 337; Figure S2. In a large unbiased cancer cell line viability screen only MET-amplified cell lines were sensitive to treatment with an analogue of AMG 337 (Compound 5); Figure S3: AMG 337 inhibits the phosphorylation of MET and but not its downstream effectors in MET-amplified, KRAS mutant NSCLC cell line NCI-H1573; Figure S4. Cell lines harboring MET FISH scores >3 exhibited sensitivity to AMG 337. MET FISH analysis was performed on a subset of cancer cell lines exhibiting elevated MET gene copy number; Figure S5. Selective inhibition of MET exhibits partial effects on the viability of U-87 MG glioblastoma cells harboring an HGF/MET autocrine loop; Figure S6. Increases in MET gene number correlate with high levels of total MET protein; Figure S7. AMG 337 inhibits Gab-1 phosphorylation in a concentration dependent manner in the TPR-MET mouse tumor model.

Supplementary Figure S4 shows the effect of combination on lung metastases.

Supplementary Figure S1 shows the chemical structure of compound 22.

Supplementary Figure S2 shows additional tumor growth data

Supplementary Figure S8 shows pTie expression in treated tumors.

Supplementary Figure S6 shows additional data on E-Cadherin protein expression.

Supplementary Figure S7 shows pathway alterations downstream of Tie2 and c-MET inhibition.

Receptor tyrosine kinase inhibitors have shown clinical benefit in clear cell renal cell carcinoma (ccRCC), but novel therapeutic strategies are needed. The angiopoietin/Tie2 and MET pathways have been implicated in tumor angiogenesis, metastases, and macrophage infiltration. In our study, we used trebananib, an angiopoietin 1/2 inhibitor, and a novel small-molecule MET kinase inhibitor in patient-derived xenograft (PDX) models of ccRCC. Our goal was to assess the ability of these compounds to alter the status of tumor-infiltrating macrophages, inhibit tumor growth and metastases, and prolong survival. Seven-week-old SCID mice were implanted subcutaneously or orthotopically with human ccRCC models. One month postimplantation, mice were treated with angiopoietin 1/2 inhibitor trebananib (AMG 386), MET kinase inhibitor, or combination. In our metastatic ccRCC PDX model, RP-R-02LM, trebananib alone, and in combination with a MET kinase inhibitor, significantly reduced lung metastases and M2 macrophage infiltration (P = 0.0075 and P = 0.0205, respectively). Survival studies revealed that treatment of the orthotopically implanted RP-R-02LM tumors yielded a significant increase in survival in both trebananib and combination groups. In addition, resection of the subcutaneously implanted primary tumor allowed for a significant survival advantage to the combination group compared with vehicle and both single-agent groups. Our results show that the combination of trebananib with a MET kinase inhibitor significantly inhibits the spread of metastases, reduces infiltrating M2-type macrophages, and prolongs survival in our highly metastatic ccRCC PDX model, suggesting a potential use for this combination therapy in treating patients with ccRCC.

Supplementary Figure 1-5, Supplementary Tables 1-3

Supplementary Figure S5 shows the effect of combination on E-Cadherin and Snail expression.

Supplementary Figure 1 from Context-Dependent Role of Angiopoietin-1 Inhibition in the Suppression of Angiogenesis and Tumor Growth: Implications for AMG 386, an Angiopoietin-1/2–Neutralizing Peptibody

Tissue expression datasets

Supplementary Figure 3 from Context-Dependent Role of Angiopoietin-1 Inhibition in the Suppression of Angiogenesis and Tumor Growth: Implications for AMG 386, an Angiopoietin-1/2–Neutralizing Peptibody

AMG 386 is an investigational first-in-class peptide-Fc fusion protein (peptibody) that inhibits angiogenesis by preventing the interaction of angiopoietin-1 (Ang1) and Ang2 with their receptor, Tie2. Although the therapeutic value of blocking Ang2 has been shown in several models of tumorigenesis and angiogenesis, the potential benefit of Ang1 antagonism is less clear. To investigate the consequences of Ang1 neutralization, we have developed potent and selective peptibodies that inhibit the interaction between Ang1 and its receptor, Tie2. Although selective Ang1 antagonism has no independent effect in models of angiogenesis-associated diseases (cancer and diabetic retinopathy), it induces ovarian atrophy in normal juvenile rats and inhibits ovarian follicular angiogenesis in a hormone-induced ovulation model. Surprisingly, the activity of Ang1 inhibitors seems to be unmasked in some disease models when combined with Ang2 inhibitors, even in the context of concurrent vascular endothelial growth factor inhibition. Dual inhibition of Ang1 and Ang2 using AMG 386 or a combination of Ang1- and Ang2-selective peptibodies cooperatively suppresses tumor xenograft growth and ovarian follicular angiogenesis; however, Ang1 inhibition fails to augment the suppressive effect of Ang2 inhibition on tumor endothelial cell proliferation, corneal angiogenesis, and oxygen-induced retinal angiogenesis. In no case was Ang1 inhibition shown to (a) confer superior activity to Ang2 inhibition or dual Ang1/2 inhibition or (b) antagonize the efficacy of Ang2 inhibition. These results imply that Ang1 plays a context-dependent role in promoting postnatal angiogenesis and that dual Ang1/2 inhibition is superior to selective Ang2 inhibition for suppression of angiogenesis in some postnatal settings. Mol Cancer Ther; 9(10); 2641–51. ©2010 AACR.

File contains Supplementary Methods

Supplementary Figure 3 Evaluation of DLL3 expression in tumor types other than SCLC.

Supplementary Figure 6 A, Expression of human CD25, CD69, PD-1, and 4-1BB on human CD4+ T cells isolated from mouse lungs harboring SHP-77 tumors 168 hours after treatment with AMG 757 or a control HLE BiTE® molecule. B, Expression of human CD25, CD69, PD-1, and 4-1BB on human CD8+ T cells isolated from mouse lungs harboring SHP-77 tumors 168 hours after treatment with either AMG 757 or a control HLE BiTE® molecule. *P < 0.05; **P < 0.01; *** P< 0.001

Purpose:Small-cell lung cancer (SCLC) is an aggressive neuroendocrine tumor with a high relapse rate, limited therapeutic options, and poor prognosis. We investigated the antitumor activity of AMG 757, a half-life extended bispecific T-cell engager molecule targeting delta-like ligand 3 (DLL3)—a target that is selectively expressed in SCLC tumors, but with minimal normal tissue expression.Experimental Design:AMG 757 efficacy was evaluated in SCLC cell lines and in orthotopic and patient-derived xenograft (PDX) mouse SCLC models. Following AMG 757 administration, changes in tumor volume, pharmacodynamic changes in tumor-infiltrating T cells (TILs), and the spatial relationship between the appearance of TILs and tumor histology were examined. Tolerability was assessed in nonhuman primates (NHPs).Results:AMG 757 showed potent and specific killing of even those SCLC cell lines with very low DLL3 expression (Conclusions:AMG 757 has a compelling safety and efficacy profile in preclinical studies making it a viable option for targeting DLL3-expressing SCLC tumors in the clinical setting.

This file contains Supplementary Tables 1-5

Supplementary Methods, Figure Legends, and References from Context-Dependent Role of Angiopoietin-1 Inhibition in the Suppression of Angiogenesis and Tumor Growth: Implications for AMG 386, an Angiopoietin-1/2–Neutralizing Peptibody

Supplementary Figure 1 DLL3 is differentially expressed in SCLC tumors and cell lines compared with normal tissues.

Supplementary Figure 2 Representative photomicrographs of DLL3 immunostaining (brown color) in normal human tissues using immunohistochemistry.

Supplementary Figure 5 A, DLL3 RNA expression levels in a panel of SCLC patient-derived xenograft (PDX) models compared with positive (NCI-H82) and negative (NCI-H460) control SCLC cell lines. Data are reported as relative quantification normalized to NCI-H460 cell line expression. B, DLL3 protein expression levels in a panel of SCLC PDX models compared with positive (NCI-H82) and negative (NCI-H460) control SCLC cell lines. GAPDH, glyceraldehyde 3-phosphate dehydrogenase.

Supplementary Figure 2 from Context-Dependent Role of Angiopoietin-1 Inhibition in the Suppression of Angiogenesis and Tumor Growth: Implications for AMG 386, an Angiopoietin-1/2–Neutralizing Peptibody

Supplementary Figure 4 from Context-Dependent Role of Angiopoietin-1 Inhibition in the Suppression of Angiogenesis and Tumor Growth: Implications for AMG 386, an Angiopoietin-1/2–Neutralizing Peptibody

Supplementary FIgure 4 AMG 757 demonstrated antitumor activity in the WM266-4 melanoma xenograft model.

The efficacy of molecularly targeted anti-cancer therapies may be limited by the presence of co-occurring mutations within a tumor.1-3 Conversely, these alterations may confer collateral vulnerabilities that can be leveraged for the development of novel therapeutic approaches. KRAS mutant lung cancers are distinguished by recurrent mutations in tumor suppressor genes such as TP53 and STK11/LKB1.4 However, clinically actionable targets associated with these alterations are largely undefined. BH3 mimetics targeting distinct pro-survival BCL-2 family proteins have been proposed to enhance the efficacy of targeted therapies, but no biomarkers exist that can predict which patients are most likely to respond. Here we show that inhibition of oncogenic signaling in KRAS-LKB1 mutant lung cancer cells creates a specific dependency on the anti-apoptotic protein MCL-1 for survival. We find that loss of the LKB1-NUAK signaling axis derepresses a JNK-mediated stress response to KRAS or MEK inhibition, allowing inhibitory phosphorylation of BCL-XL that alters BH3-protein interactions and makes cells vulnerable to concurrent MCL-1 inhibition. These results uncover a previously unknown role for LKB1 in regulating the mitochondrial apoptotic response of cancer cells independent of its tumor suppressor activity mediated by AMPK5-7 and SIK8,9 kinases and suggest a fundamental role for LKB1-NUAKs in suppressing the cellular stress response. Additionally, our study reveals a therapeutically targetable vulnerability in KRAS-LKB1 lung cancer cells and suggests a genotype-informed strategy for improving the efficacy of KRAS-targeted therapies.

The recently approved KRASG12C inhibitor sotorasib induces durable responses of KRASG12C-mutant non-small cell lung cancers (NSCLCs), however, some patients do not derive benefit. Identification of specific vulnerabilities conferred by co-occurring mutations may enable the development of biomarker-driven combination therapies in distinct subsets of patients. We report that co-occurring loss of STK11/LKB1 is associated with a drug-induced vulnerability of KRAS-mutant NSCLCs to MCL-1 inhibition. In LKB1-deficient cells, inhibition of KRAS-MAPK signaling leads to hyperactivated JNK, which phosphorylates BCL-XL and impairs its ability to sequester BIM, thus creating a dependency on MCL-1 for survival. In LKB1-proficient cells, LKB1 suppresses drug-induced JNK hyperactivation in a NUAK-dependent manner. Ex vivo treatment of tumors from LKB1-deficient but not LKB1 wild-type KRAS-mutant NSCLC patients with sotorasib or trametinib increased MCL-1 dependence. These results uncover a novel role for the LKB1-NUAK axis in regulation of apoptotic dependency and suggest a genotype-directed therapeutic approach for KRAS-LKB1 mutant NSCLC.

Purpose: Small-cell lung cancer (SCLC) is an aggressive neuroendocrine tumor with a high relapse rate, limited therapeutic options, and poor prognosis. We investigated the antitumor activity of AMG 757, a half-life extended bispecific T-cell engager molecule targeting delta-like ligand 3 (DLL3)—a target that is selectively expressed in SCLC tumors, but with minimal normal tissue expression. Experimental Design: AMG 757 efficacy was evaluated in SCLC cell lines and in orthotopic and patient-derived xenograft (PDX) mouse SCLC models. Following AMG 757 administration, changes in tumor volume, pharmacodynamic changes in tumor-infiltrating T cells (TILs), and the spatial relationship between the appearance of TILs and tumor histology were examined. Tolerability was assessed in nonhuman primates (NHPs). Results: AMG 757 showed potent and specific killing of even those SCLC cell lines with very low DLL3 expression ( Conclusions: AMG 757 has a compelling safety and efficacy profile in preclinical studies making it a viable option for targeting DLL3-expressing SCLC tumors in the clinical setting.

Receptor tyrosine kinase inhibitors have shown clinical benefit in clear cell renal cell carcinoma (ccRCC), but novel therapeutic strategies are needed. The angiopoietin/Tie2 and MET pathways have been implicated in tumor angiogenesis, metastases, and macrophage infiltration. In our study, we used trebananib, an angiopoietin 1/2 inhibitor, and a novel small-molecule MET kinase inhibitor in patient-derived xenograft (PDX) models of ccRCC. Our goal was to assess the ability of these compounds to alter the status of tumor-infiltrating macrophages, inhibit tumor growth and metastases, and prolong survival. Seven-week-old SCID mice were implanted subcutaneously or orthotopically with human ccRCC models. One month postimplantation, mice were treated with angiopoietin 1/2 inhibitor trebananib (AMG 386), MET kinase inhibitor, or combination. In our metastatic ccRCC PDX model, RP-R-02LM, trebananib alone, and in combination with a MET kinase inhibitor, significantly reduced lung metastases and M2 macrophage infiltration (P = 0.0075 and P = 0.0205, respectively). Survival studies revealed that treatment of the orthotopically implanted RP-R-02LM tumors yielded a significant increase in survival in both trebananib and combination groups. In addition, resection of the subcutaneously implanted primary tumor allowed for a significant survival advantage to the combination group compared with vehicle and both single-agent groups. Our results show that the combination of trebananib with a MET kinase inhibitor significantly inhibits the spread of metastases, reduces infiltrating M2-type macrophages, and prolongs survival in our highly metastatic ccRCC PDX model, suggesting a potential use for this combination therapy in treating patients with ccRCC.

Overexpression of the antiapoptotic protein Mcl-1 provides a survival advantage to some cancer cells, making inhibition of this protein an attractive therapeutic target for the treatment of certain types of tumors. Herein, we report our efforts toward the identification of a novel series of macrocyclic Mcl-1 inhibitors featuring an α-hydroxy phenylacetic acid pharmacophore or bioisostere. This work led to the discovery of

The recent approval of the KRAS G12C inhibitor sotorasib (AMG 510) for non-small cell lung cancer (NSCLC) marked a milestone in the development of targeted therapies for KRAS mutant cancers. While sotorasib and other KRAS G12C inhibitors have demonstrated rapid and durable responses in the clinic, some patients do not achieve responses. The identification of specific vulnerabilities conferred by recurrent co-occurring mutations may enable the development of biomarker-driven combination therapies with enhanced activity in distinct subsets of patients. We screened a panel of KRAS-mutant NSCLC cell lines as well as patient-derived xenograft (PDX) mouse models and observed that loss of the tumor suppressor STK11/LKB1 is associated with increased sensitivity to combined MAPK (either the KRAS G12C inhibitor sotorasib or MEK inhibitor trametinib) and MCL-1 inhibition (AMG 176). Restoration of LKB1 expression in LKB1-deficient cell lines and PDX tumors blunted the apoptotic response to MAPK + MCL-1 inhibition; conversely, deletion of LKB1 in LKB1 wild-type models increased sensitivity. Mitochondrial apoptotic cell death is regulated by interactions between pro- (e.g., BIM) and anti-apoptotic (e.g., MCL-1, BCL-XL) BCL-2 family members. MAPK inhibition increases BIM, while MCL-1 inhibition prevents BIM sequestration by MCL-1, resulting in apoptosis. LKB1 deficient cells exhibit increased association of BIM and MCL-1 upon MAPK inhibition, effectively priming cells for death upon inhibition of MCL-1. Mechanistically, LKB1 deficiency and associated loss of NUAK phosphorylation leads to hyperactivation of the JNK phospho-kinase network. JNK phosphorylates MCL-1 at S64 and T163, which enhances BIM: MCL-1 protein-protein interaction. Conversely, JNK phosphorylates BCL-XL at S62 and prevents sequestration of BIM. This series of phosphorylation events increases MCL-1 dependence and creates a specific vulnerability of KRAS-LKB1 tumors to MAPK + MCL-1 inhibition. Consistent with this mechanism, ex vivo treatment of tumor tissue from a KRAS-LKB1 mutant NSCLC patient with sotorasib or trametinib increased MCL-1 dependent priming. These results reveal a novel link between LKB1 and the regulation of BCL-2 family proteins and provide preclinical rationale for evaluation of combined KRAS G12C + MCL-1 inhibitors for KRAS-LKB1 mutant NSCLC. Citation Format: Chendi Li, Mohammed Usman Syed, Yi Shen, Audris Oh, Cameron Fraser, Johannes Kreuzer, Christopher Nabel, Kaitlyn Webster, Robert Morris, Sean Caenepeel, Anne Y. Saiki, Karen Rex, J. Russell Lipford, Wilhelm Hass, Kristopher Sarosiek, Paul E. Hughes, Aaron Hata. LKB1 loss rewires JNK-induced apoptotic protein dynamics through NUAKs and sensitizes KRAS-mutant non-small cell lung cancers to combined KRAS G12C + MCL-1 blockade [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2150.

Immuno-Oncology (IO) therapies provide remarkable clinical benefits. However, too few patients respond, and there are no diagnostic tools that predict IO response with high accuracy. Moreover, as more IO drugs and combinations are approved, selecting the best IO-based regimen for each patient will become more complex. To facilitate this selection, we are developing an ex vivo live tumor fragment (LTF) screening platform that retains representation of a patient’s tumor microenvironment (TME) including immune cells, enabling development of deep neural networks to predict IO response and thereby individualize therapy. Here we present preliminary data from our proof-of-concept platform that performs tissue fragmentation/sorting, liquid handling, drug treatment, high-resolution dynamic imaging, and multiplex immuno-assays. Human tumor excisions were obtained from the Univ. of Wisconsin (IRB approved), and CT26 tumors were grown in mice subcutaneously. Live tumors were cut into 300 x 300 µm fragments of 100 - 300 µm thickness, sorted into multi-well plates, and cultured for 48 or 72 h in the presence or absence of anti-PD1 (nivolumab or mouse equivalent), anti-PD1 plus anti-CTLA4 (ipilimumab or mouse equivalent), or concanavalin A (ConA) as a positive control. Cell viability was measured by ATP luminescence assay or flow cytometry. Motility of CD8+ cells was tracked in human LTF using camelid VHH anti-hCD8a-AF594 and 3D multiphoton microscopy for 30 min. Supernatant cytokines were measured using bead immunoassay and T cell markers by flow cytometry. T cells were retained within LTFs, and the proportion of lymphocytes in LTFs was independent of fragment thickness (1.6%/2.1% for 300 µm, 1.4%/2.3% for 200 µm and 1.4%/2.8% for 100 µm thickness, for CD4+ and CD8+ T cells, respectively). Total cell viability and T cell viability exceeded 80% at 48h, and 3D LTF structure remained intact for at least 48 h. We treated LTFs with anti-PD1, anti-PD1 plus anti-CTLA4, or ConA and confirmed the presence of IFN-γ and 10 (mouse) or 16 (human) other cytokines associated with immune activation in both the ConA and anti-PD1 treated samples, but not the control. In human LTFs, cytokine panel upregulation was observed for anti-PD1 vs. control (p=1.1e-5) and anti-PD1 plus anti-CTLA4 vs. anti-PD1 (p=3.7e-9). Using multiphoton microscopy and CD8-binding nanobodies, we observed vigorous CD8+ T cell motility in human LTFs, with a speed of 10 µm/min, which is comparable to that reported in vivo. Our LTF platform has an immuno-competent TME in which we can detect cellular and secreted immune response markers, compare alternative treatments, and track the surveillance activity of infiltrating T cells. Future work will further advance the platform, enabling clinical trials for training and validating deep neural networks to predict response to checkpoint inhibitors and other IO drugs. Citation Format: Tomasz Zal, Leung Kau Tang, Laura Hrycyniak, Anura Shrestha, Dinesh Joshi, Pichet Adstamongkonkul, Kelsey Tweed, Wesley A. Cox-Muranami, Sean Caenepeel, Hinco J. Gierman, Kevin Eliceiri, Kristina A. Matkowskyj, Sam J. Lubner, John Rafter, Mike Szulczewski, Maneesh Arora, Jonathan Oliner. A live tumor fragment (LTF) platform with real-time imaging for immune response assays [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2779.

BH3 mimetic drugs, which inhibit prosurvival BCL2 family proteins, have limited single-agent activity in solid tumor models. The potential of BH3 mimetics for these cancers may depend on their ability to potentiate the apoptotic response to chemotherapy and targeted therapies. Using a novel class of potent and selective MCL1 inhibitors, we demonstrate that concurrent MEK + MCL1 inhibition induces apoptosis and tumor regression in KRAS-mutant non–small cell lung cancer (NSCLC) models, which respond poorly to MEK inhibition alone. Susceptibility to BH3 mimetics that target either MCL1 or BCL-xL was determined by the differential binding of proapoptotic BCL2 proteins to MCL1 or BCL-xL, respectively. The efficacy of dual MEK + MCL1 blockade was augmented by prior transient exposure to BCL-xL inhibitors, which promotes the binding of proapoptotic BCL2 proteins to MCL1. This suggests a novel strategy for integrating BH3 mimetics that target different BCL2 family proteins for KRAS-mutant NSCLC. Significance: Defining the molecular basis for MCL1 versus BCL-xL dependency will be essential for effective prioritization of BH3 mimetic combination therapies in the clinic. We discover a novel strategy for integrating BCL-xL and MCL1 inhibitors to drive and subsequently exploit apoptotic dependencies of KRAS-mutant NSCLCs treated with MEK inhibitors. See related commentary by Leber et al., p. 1511. This article is highlighted in the In This Issue feature, p. 1494

Myeloid cell leukemia sequence 1 (MCL-1) is an antiapoptotic protein that plays a key role in promoting cell survival in multiple myeloma (MM), acute myeloid leukemia (AML), and non-Hodgkin lymphoma (NHL). Overexpression of MCL-1 is associated with treatment resistance and poor prognosis; thus, MCL-1 inhibitors are rational therapeutic options for malignancies depending on MCL-1. Several MCL-1 inhibitors have entered clinical trials, including AZD5991, S64315, AMG 176, and AMG 397. A key area of investigation is whether MCL-1 inhibitors will complement the activity of BCL-2 inhibitors, such as venetoclax, and synergistically enhance anti-tumor efficacy when given in combination with other anti-cancer drugs. Another important question is whether a safe therapeutic window can be found for this new class of inhibitors. In summary, inhibition of MCL-1 shows potential as a treatment for hematologic malignancies and clinical evaluation of MCL-1 inhibitors is currently underway.

Acute Myeloid Leukemia (AML) is the most common and aggressive acute leukemia in adults, with a 25% 5-year survival rate. FLT3 is the most frequently mutated gene in AML. About 25% of AML patients harbor FLT3 internal tandem duplication (ITD) mutations, and about 8 % of patients harbor FLT3 tyrosine kinase domain (TKD) mutations. Both FLT3-ITD and FLT3-TKD mutations constitutively activate the protein, which causes poor survival. Gilteritinib is a highly potent and selective oral FLT3 inhibitor recently approved by the FDA. Although gilteritinib showed strong single agent activity in AML patients with FLT3 mutations, the development of gilteritinib resistance limits the long-term efficacy of this treatment, indicating that combination therapy may be advantageous for AML patients with FLT3 mutations. FLT3 mutations are known to be anti-apoptotic. Myeloid cell leukemia-1 (MCL-1), an anti-apoptotic protein, expressed in a large percentage of the AML patient population, plays a critical role in AML cell survival and drug resistance. AMG 176 is a potent, selective and orally bioavailable MCL-1 inhibitor, which induces rapid commitment to apoptosis in AML. Here we demonstrated that AMG 176 and gilteritinib combination treatment synergistically targeted FLT3-ITD mutated AML. A strong synergistic effect (Combination index Citation Format: Xiaoyue Chen, Sean Caenepeel, Brian Belmontes, Patricia L. McElroy, Karen Rex, Tao Osgood, Paul Hughes. Efficacy of AMG 176 in combination with gilteritinib in preclinical models of acute myeloid leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1050.

Background: There are currently no approved targeted therapies for KRAS-mutant non-small cell lung cancers (NSCLC), which represent 25-30% of lung adenocarcinomas. The development of mutant-specific covalent inhibitors of KRAS G12C has invigorated hope that clinically effective KRAS-targeted therapies are within reach. While these agents have shown activity in early phase clinical trials, identification of specific vulnerabilities conferred by common co-occurring mutations in KRAS-mutant NSCLC may enable development of combination therapies with enhanced activity in distinct subsets of patients. Results: We screened a panel of KRAS-mutant NSCLC cell lines and observed that loss of the tumor suppressor STK11/LKB1 is associated with increased MCL-1 dependence and sensitivity to combined MAPK (either MEK inhibitor or KRAS G12C inhibitor AMG 510) and MCL-1 inhibition (AMG 176). Restoration of LKB1 expression in LKB1-deficient cell lines and mouse xenograft tumors blunted the apoptotic response to MAPK + MCL-1 inhibition; conversely, deletion of LKB1 in LKB1 wild-type models restored the sensitivity. Mechanistically, LKB1 deficiency is associated with an altered phosphoproteome and increased MCL-1-dependent apoptotic priming. LKB1 loss increased cellular stress leading to hyperactivation of JNK1, phosphorylation and stabilization of MCL-1 protein, and increased BIM sequestration by MCL-1. Upon suppression of MAPK signaling, LKB1-deficient cells exhibited greater levels of BIM bound to MCL-1 that could be liberated by AMG 176 to induce apoptosis. Consistent with these results, ex vivo treatment of tumor tissue from a KRAS-LKB1 mutant NSCLC patient with MEK inhibitor or AMG 510 increased MCL-1 dependent priming. Conclusion: These results uncover a novel link between LKB1, cellular stress, and the regulation of MCL-1. LKB1 loss confers a dependency on MCL-1 that can be exploited therapeutically. Moreover, our study provides preclinical rationale for the exploration of combined KRAS G12C + MCL-1 inhibitors, particularly for KRAS-LKB1 mutant patients who respond poorly to standard-of-care checkpoint inhibitor therapy. Citation Format: Chendi Li, Yi Shen, Mohammed Usman Syed, Audris Oh, Cameron Fraser, Johannes Kreuzer, Kaitlyn Webster, Robert Morris, Sean Caenepeel, Anne Y. Saiki, Karen Rex, James Lipford, Wilhelm Hass, Kristopher Sarosiek, Paul E. Hughes, Aaron N. Hata. LKB1 loss rewires stress signaling-induced apoptotic protein dynamics and sensitizes KRAS-mutant non-small cell lung cancers to combined MAPK + MCL-1 blockade [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 982.

Many advances in the treatment of cancer have been driven by the development of targeted therapies that inhibit oncogenic signaling pathways and tumor-associated angiogenesis, as well as by the recent development of therapies that activate a patient's immune system to unleash antitumor immunity. Some targeted therapies can have effects on host immune responses, in addition to their effects on tumor biology. These immune-modulating effects, such as increasing tumor antigenicity or promoting intratumoral T cell infiltration, provide a rationale for combining these targeted therapies with immunotherapies. Here, we discuss the immune-modulating effects of targeted therapies against the MAPK and VEGF signaling pathways, and how they may synergize with immunomodulatory antibodies that target PD1/PDL1 and CTLA4. We critically examine the rationale in support of these combinations in light of the current understanding of the underlying mechanisms of action of these therapies. We also discuss the available preclinical and clinical data for these combination approaches and their implications regarding mechanisms of action. Insights from these studies provide a framework for considering additional combinations of targeted therapies and immunotherapies for the treatment of cancer.

Aberrant hepatocyte growth factor (HGF)/MET signaling has been implicated in hepatocarcinogenesis, suggesting that MET may serve as an attractive therapeutic target in hepatocellular carcinoma. We sought to investigate the in vitro and in vivo antitumor activity of AMG 337, a potent and highly selective small molecule MET kinase inhibitor, in preclinical models of hepatocellular carcinoma. The antiproliferative activity of AMG 337 was evaluated across a panel of hepatocellular carcinoma cell lines in a viability assay. Daily oral administration was used to evaluate the in vivo antitumor activity of AMG 337 in two patient-derived xenograft (PDX) models of hepatocellular carcinoma (LI0612 and LI1078). AMG 337 exerted potent antiproliferative activity against 2 of 40 hepatocellular carcinoma cell lines, namely, MHCC97H (IC50, 0.015 μmol/L) and HCCLM3 (IC50, 0.025 μmol/L). Both sensitive cell lines showed MET amplification (MET/CEN-7 >2.0) assessed by FISH, and high MET expression (3+ IHC) assessed by IHC. AMG 337 potently inhibited p-MET in all cell lines with detectable levels of total MET. However, the dose-dependent inhibition of downstream effectors of HGF/MET signaling, including p-GAB1, p-AKT, and p-ERK, was limited to those cell lines sensitive to AMG 337 in a viability assay (MHCC97H and HCCLM3). AMG 337 significantly inhibited tumor growth at all doses tested in the MET-amplified and MET-high–expressing hepatocellular carcinoma PDX model LI0612 and had no effect on tumor growth in the non-MET–amplified and MET-low–expressing hepatocellular carcinoma PDX model LI1078. AMG 337 represents a promising and novel therapeutic strategy for targeting hepatocellular carcinomas with a dependence on HGF/MET signaling. Mol Cancer Ther; 15(6); 1227–37. ©2016 AACR.

SCLC is a highly aggressive neuroendocrine tumor with poor prognosis and limited therapeutic options. Delta-like ligand 3 (DLL3) is a tumor-associated antigen that is highly specific for SCLC; expression is elevated in tumors but minimal and mainly cytoplasmic in normal tissues. AMG 757 is an HLE BiTE® immune therapy that is designed to redirect T-cell cytotoxicity to cancer cells by binding to DLL3 on the surface of cancer cells and CD3 on T cells. AMG 757 is being evaluated in a phase 1 clinical trial in patients with relapsed/refractory SCLC (NCT03319940). We evaluated the efficacy and pharmacodynamic (PD) effects of AMG 757 in three preclinical models of SCLC that express DLL3. We used the LXFS 1129 patient-derived xenograft (PDX) model to assess AMG 757 efficacy in established, subcutaneously implanted tumors similar to human SCLC tumors with their associated stroma. We also developed two orthotopic models of SCLC (SHP-77 and H82) to assess AMG 757 efficacy and PD at biologically relevant sites. In the SHP-77 orthotopic model, cells injected intravenously trafficked to the lungs where they formed diffuse tumors similar to primary SCLC tumors. In the H82 orthotopic model, cells injected intravenously formed discrete metastatic lesions in the liver, mimicking a major site for SCLC metastasis. In each model, mice bearing established tumors received a single infusion of human T cells and were then dosed with AMG 757 or a control HLE BiTE molecule. In the LXFS 1129 PDX model, treatment with AMG 757 induced complete tumor regression in 8 out of 10 mice, whereas treatment with the control HLE BiTE molecule showed no tumor growth inhibition. In the orthotopic SHP-77 model, treatment with AMG 757 led to significant tumor growth inhibition in the lungs relative to treatment with a control HLE BiTE molecule; the bioluminescence (BLI) signal decreased to near the limit of detection 22 days after start of treatment. AMG 757 antitumor activity was associated with increased T-cell trafficking and expansion in tumors; a single dose of AMG 757 significantly increased the number of human CD4+ and CD8+ cells in lungs as assessed by flow cytometry. In the orthotopic H82 model, AMG 757 treatment completely cleared visible lesions from the liver, as assessed by a decrease in BLI to near-background levels and macroscopic analysis of the liver tissue. AMG 757 antitumor activity was associated with increased CD8+ T-cell infiltration as assessed by flow cytometry and IHC and upregulation of the T cell surface activation markers CD25, CD69, PD-1, and 4-1BB as assessed by flow cytometry. Together, these preclinical data demonstrate that AMG 757 can recruit and engage T cells to tumors, consistent with the BiTE® mechanism of action, and that AMG 757-mediated redirected T-cell lysis can drive significant antitumor activity in established SCLC tumor models. Citation Format: Keegan Cooke, Juan Estrada, Jinghui Zhan, Jonathan Werner, Sean Caenepeel, Mike Giffin, Julie M. Bailis, Angela Coxon, Paul E. Hughes, Jude Canon. Antitumor activity of AMG757, a half-life extended (HLE) bispecific T-cell engager (BiTE®) immune therapy targeting DLL3, in human PDX and orthotopic mouse models of small cell lung cancer (SCLC) [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 4558.