Antitumor Efficacy In Xenograft Model Research Articles

Red blood cell membrane-coated FLT3 inhibitor nanoparticles to enhance FLT3-ITD acute myeloid leukemia treatment

FMS-like tyrosine kinase 3 (FLT3) is a viable and important therapeutic target for acute myeloid leukemia (AML). FLT3 internal tandem duplication (FLT3-ITD) mutations have been identified in approximately 30% of AML patients, and are associated with unfavorable prognosis, higher risk of relapse, drug resistance, and poor clinical outcome. Even FLT3 inhibitors have demonstrated promising efficacy, they cannot cure AML or even significantly extend the lives of patients with FLT3-ITD mutations. This is partly because of poor water solubility, insufficient membrane penetration and short half-life of small molecule inhibitors. Besides, the presence of enzymes like CYP3A4 in bone marrow accelerate the elimination and metabolism of FLT3 inhibitors, resulting in low plasma concentrations and side effects. Here we report the erythrocyte membrane-camouflaged FLT3 inhibitor nanoparticles to enhance FLT3-ITD AML treatment. Briefly, we physically coextruded red blood cell (RBC) membrane vesicles with nanoparticles derived from FLT3 inhibitor F30 to obtain F30@RBC-M, which exhibited comparable potent FLT3-ITD inhibitory effects compared to free F30in vitro, while displaying a higher potent antitumor efficacy in xenograft models due to the prolonged circulation properties. Furthermore, administration of F30@RBC-M significantly extended the survival of mice in a transplanted mouse model than F30 free drug. These findings suggest that RBC membrane-coated nanoparticles derived from FLT3 inhibitors hold promise as a tool to enhance the therapeutic efficacy to treat FLT3-ITD AML.

Discovery of novel and potent dual-targeting AXL/HDAC2 inhibitors for colorectal cancer treatment via structure-based pharmacophore modelling, virtual screening, and molecular docking, molecular dynamics simulation studies, and biological evaluation

Colorectal cancer (CRC) is one of the most common cancers worldwide. Nowadays, owing to the complex mechanism of tumorigenesis, simultaneous inhibition of multiple targets is an important anticancer strategy. Recent studies have demonstrated receptor tyrosine kinase AXL (AXL) and histone deacetylase 2 (HDAC2) are closely associated with colorectal cancer. Herein, we identified five hit compounds concurrently targeting AXL and HDAC2 using virtual screening. Inhibitory experiments revealed these hit compounds potently inhibited AXL and HDAC2 in the nanomolar range. Among them, Hit-3 showed the strongest inhibitory effects which were better than that of the positive control groups. Additionally, MD assays showed that Hit-3 could bind stably to the AXL and HDAC2 active pockets. Further MTT assays demonstrated that Hit-3 showed potent anti-proliferative activity. Most importantly, Hit-3 exhibited significant in vivo antitumor efficacy in xenograft models. Collectively, this study is the first discovery of dual-targeting AXL/HDAC2 inhibitors for colorectal cancer treatment.

Abstract LB316: A next-generation KRASG12C inhibitor ABSK071 demonstrated broad synergy with other therapeutic agents in KRASG12C mutated cancer models

Abstract Background: KRAS is frequently mutated in human cancers, including pancreatic (~90%), colorectal (~35%), and lung cancer (~25%). The KRASG12C mutation (single amino acid substitution of cysteine for glycine at position 12) accounts for ~14% of lung cancer, ~4% of colorectal cancer, and ~2% of pancreatic cancer. Currently, two covalent KRASG12C inhibitors, namely sotorasib (AMG-510) and adagrasib (MRTX-849), have been approved as monotherapy to treat locally advanced or metastatic NSCLC with KRASG12C mutation through accelerated approval process. Despite the beneficial effects of KRASG12C inhibitors in clinic for certain patients, the limited antitumor efficacy in most patients and potential drug resistance are major concerns. A next-generation inhibitor with better inhibitory activity may improve anti-tumor efficacy. Combination with other therapeutic agents may also improve the single-agent activity of KRASG12C inhibitors. These approaches could both overcome the limitations of sotorasib and adagrasib and provide additional benefits to patients. Materials and methods: KRASG12C inhibitory activity of ABSK071 was examined in vitro and in vivo in comparison with sotorasib and adagrasib. To identify potential targeted agents synergizing with ABSK071, we tested a set of inhibitors that targeting signaling components of KRAS pathways, including EGFRi, FGFRi, SHP2i and SOS1i, in combination with ABSK071 in cellular experiments using KRASG12C mutant cell lines. Cell growth inhibition was measured and synergistic effect was analyzed. In vivo efficacy study was also conducted to confirm the synergistic anti-tumor effect in animal models. A set of immuno-oncology reagents, including anti-PD-1/L1, CSF-1R inhibitor (ABSK021) and CD73 inhibitor (ABSK051) were also tested in combination with ABSK071 in vivo using mouse syngeneic models. Results: ABSK071 demonstrated much stronger inhibitory activity than sotorasib and adagrasib against a variety of cell lines harboring KRASG12C, as well as significantly better in vivo anti-tumor efficacy in xenograft models that were less sensitive to sotorasib. Synergistic effects on cell growth inhibition were observed in vitro with ABSK071 in combination with several agents including cetuximab, afatinib, AZD4547, TNO-155, RMC-4630 and BI3406. Superior anti-tumor activities were observed in vivo when these agents were combined with ABSK071 than in combination with sotorasib. In mouse syngeneic models harboring KrasG12C mutations, ABSK071 also demonstrated synergy with anti PD-1/L1 antibody or other IO reagents. Conclusions: ABSK071 is a next-generation KRASG12C inhibitor with greater activity and anti-tumor efficacy in vitro and in vivo. It also demonstrated broad synergistic effects with a large set of targeted agents and immuno-oncology agents, indicating its strong potential in combinatory therapy in treating a wider range of KRASG12C-dependent cancers. Citation Format: Haiyan Ying, Fushen Guo, Juan Peng, Jie Wang, Jie Zhang, Manqi Liu, Zhixuan Zhu, Zhui Chen. A next-generation KRASG12C inhibitor ABSK071 demonstrated broad synergy with other therapeutic agents in KRASG12C mutated cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB316.

Abstract 6376: Effect of MET tyrosine kinase inhibitors on MET amplified gastro-esophageal cancer cells

Abstract Background: Many studies have suggested that MET protein overexpression or MET amplification plays a critical role in the progression of gastro-esophageal cancer (GC) and negatively affects survival in patients with GC. However, the criteria used to define overexpression of MET protein have differed among many studies, and in contrast to the initial phase II studies, the phase III trials failed to show any clinical benefit from anti-MET therapies in GCs, even in patients with MET-positive disease. Several studies have used consistent criteria to define MET amplification on FISH, and recent MET inhibitor trials for MET amplified cancers have been successful. Furthermore, hyperactivation of MET pathway are known to reduce the growth-inhibitory effect of trastuzumab in HER2 positive GC. Currently, there is no FDA approved MET inhibitors for GC. Capmatinib and savolitinib, which are selective MET inhibitors, has been evaluated for various MET positive cancers. The aim of this study was to test these MET inhibitors on MET amplified gastro-esophageal cancer (GC) cells. Material and Methods: Among a total of 37 GC cells in our lab, the following cells were positive for MET by copy number amplification (CNV > 10): SNU-620, ESO51, MKN-45, SNU-5 and OE-33. We assessed cytotoxic response of these GC cells to capmatinib or savolitinib alone by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) assay and anchorage independent growth in soft agar. Western blots were performed to assess the cellular activity of capmatinib or savolitinib in MET signal pathway. Xenograft studies were performed to evaluate in vivo therapeutic efficacy of savolitinib with MKN-45 cells. Results: Savolitinib and capmatinib showed anti-proliferative activity against MET amplified GC cell lines in dose-dependent manner. There was no inhibitory effect on GC cells without MET amplification, such as SNU-216 and SNU-1750. Savolitinib inhibited phosphorylation of MET and down-stream signaling pathway, such as AKT or ERK, in MET amplified GC cells. We observed that treatment with savolitinib induced a significant decrease in the number of colonies formed in soft agar. In addition, Savolitinib exhibited dose-responsive anti-tumor efficacy in xenograft model with MKN-45 GC cells. Furthermore, the combination of Trastuzumab and capmatinib exhibited enhanced inhibition of AKT and ERK activation in OE-33 cells, which is positive for both HER2 and MET, and resistant to trastuzumab alone. Conclusion: Collectively, these data support that targeting MET with Savolitinib and capmatinib efficiently suppresses the growth of MET amplified GC cells. Moreover, MET inhibitor could synergize with trastuzumab to induce the therapeutic effect on the HER2 and MET amplified GC cells. Further studies are warranted to test this concept in clinical setting. Citation Format: Jin-Soo Kim, Sungyoul Hong, Mi Young Kim. Effect of MET tyrosine kinase inhibitors on MET amplified gastro-esophageal cancer cells [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 6376.

Discovery of Clinical Candidate NTQ1062 as a Potent and Bioavailable Akt Inhibitor for the Treatment of Human Tumors.

Akt has emerged as an exciting target in oncology due to its critical roles in proliferation, survival, metabolism, metastasis, and invasion in tumor cells. Herein, we describe the discovery and optimization of a series of ATP-competitive Akt inhibitors that possess new chemical scaffolds and exhibit potent enzymatic activities and improved in vivo pharmacokinetic profiles. Remarkably, NTQ1062 (compound 22b) exhibited potent antitumor efficacies in vitro and in vivo, which was accomplished through the optimization of the hinge binder region and the linkage. Subsequent studies of NTQ1062 demonstrated that it possesses good oral pharmacokinetic characteristics and dose-dependent pharmacodynamic effects on downstream biomarkers. In addition, NTQ1062 exhibits a robust antitumor efficacy in xenograft models in which the PI3K-Akt-mTOR pathway was activated. Based on its ideal druglike properties, NTQ1062 is currently being evaluated in a phase I clinical trial for the treatment of advanced solid tumors (CTR20211999).

Resistance to obinutuzumab-induced antibody-dependent cellular cytotoxicity caused by abnormal Fas signaling is overcome by combination therapies

BackgroundObinutuzumab, a Type II anti-CD20 antibody, is used to treat follicular lymphoma. A major mode of action of obinutuzumab is antibody-dependent cellular cytotoxicity (ADCC). Knowledge of the mechanisms of resistance to obinutuzumab is important for the development of next-line strategies to follow obinutuzumab-containing therapy, including obinutuzumab retreatment. Unfortunately, the mechanisms by which tumor cells acquire resistance to ADCC are still poorly understood. To address this, we examined the mechanisms of resistance to obinutuzumab-induced ADCC and the combination efficacy of obinutuzumab and clinically available agents in the established resistant cells.Methods and resultsWe established cells resistant to obinutuzumab-induced ADCC using the non-Hodgkin lymphoma cell line RL and examined their mechanisms of resistance and the combination efficacy of obinutuzumab and clinically available agents. Comprehensive analysis by RNA sequencing of resistance mechanisms revealed that abnormal Fas signaling decreased sensitivity to ADCC in resistant clones. Combination treatment with prednisolone, a component of CHOP and CVP, was found to enhance ADCC sensitivity of RL cells and resistant clones and to significantly suppress tumor growth in xenograft models. Treatment with prednisolone upregulated expression of CD20 and an apoptosis-inducing protein BIM, which might augment perforin/granzyme B-mediated cell death. Furthermore, pretreatment of the effector cells with bendamustine enhanced ADCC activity, and treatment with obinutuzumab plus bendamustine showed significant antitumor efficacy in xenograft models. It was speculated that bendamustine upregulates ADCC activity by potentiating granules-mediated cell killing.ConclusionsOur study revealed a novel mechanism underlying obinutuzumab-induced ADCC resistance and indicated that ADCC resistance could be overcome by combining obinutuzumab with prednisolone or bendamustine. This study provides a scientific rationale for obinutuzumab-retreatment in combination with clinically available chemotherapeutic agents for obinutuzumab resistant follicular lymphoma.

Preliminary Results from a Phase I Study of HMPL-523, a Selective Oral Syk Inhibitor, in Patients with Relapsed or Refractory Lymphoma

Background: Spleen tyrosine kinase (Syk) plays an integral role in B-cell receptor signaling critical in the development and survival of several subtypes of lymphoma. HMPL-523 is a selective, oral Syk inhibitor that has shown strong anti-tumor efficacy in xenograft models of B-cell and T-cell lymphoma. HMPL-523 had a manageable safety profile and demonstrated anti-tumor activity in a phase I study of lymphoma patients in China (NCT02857998). Here, we report the safety and preliminary anti-tumor activity of HMPL-523 in the dose escalation phase of a phase 1 study of relapsed/refractory lymphoma patients in the United States and Europe (NCT03779113).Methods: The primary objectives of the phase I study were to evaluate the safety and tolerability of HMPL-523 and to determine the maximum tolerated dose (MTD)/recommended phase 2 dose (RP2D). Secondary objectives were to assess the pharmacokinetics (PK) and evaluate the preliminary efficacy of HMPL-523. Eligible patients had histologically confirmed lymphoma, exhausted all approved therapy options, and had good organ function, including creatinine clearance ≥ 40 ml/min by Cockcroft-Gault, absolute neutrophil count ≥ 1000/µL, platelet count ≥ 50,000/µL, and hemoglobin ≥ 8.0 g/dL. Dose escalation was performed according to a 3+3 study design. Treatment emergent adverse events (AEs) were assessed per NCI CTCAE v5.0. Treatment responses were assessed by Lugano criteria at weeks 8, 16, and 24, and then every 12 weeks. Patients received HMPL-523 treatment daily in 28-day cycles until disease progression or unacceptable toxicity.Results: As of July 15, 2021, 21 patients had been enrolled and dosed with HMPL-523 at one of six dose levels (100 to 800 mg once daily). Baseline tumor subtypes included Hodgkin lymphoma (HL; n=5); diffuse large B-cell lymphoma (DLBCL; n=4); follicular lymphoma (FL; n=4); marginal zone lymphoma (MZL; n=2); and 1 patient each with mantle cell lymphoma (MCL), small lymphocytic lymphoma (SLL), peripheral T-cell lymphoma (PTCL), cutaneous T-cell lymphoma (CTCL), mixed HL/DLBCL, and Richter's transformation. Patients were predominantly Caucasian (90.5%) and male (71.4%). The median age was 61 years (range 27 to 89 years) and 71.4% had an ECOG performance status of 1. The median lines of prior therapy was 4 (range 2 to 17). The majority of patients had prior anti-CD20 antibody exposure (71.4%), and four patients (19%) received prior Bruton tyrosine kinase inhibitors.Five patients continue to receive study treatment. The most frequently reported treatment emergent AEs were aspartate aminotransferase increase (23.8%), anemia (23.8%), neutropenia (19%), hyponatremia (19%), creatinine increase (19%), and nausea (19%). The most common grade ≥ 3 AEs were neutropenia (14.3%), hyponatremia (14.3%), and anemia (9.5%). Three dose limiting toxicities were observed: 1 in the 100 mg cohort (grade 3 confusion) and 2 in the 800 mg cohort (grade 3 fever and grade 3 alanine aminotransferase increase). The dose was deescalated to 700 mg, which was determined to be the MTD and RP2D.Among 17 efficacy evaluable patients, 2 patients (1 HL, 1 FL) dosed at 600 mg and 800 mg (reduced to 600 mg due to toxicity) achieved complete response, and 1 patient (dose increased from 400 to 600 mg) achieved partial response (FL). Stable disease was observed in 5 (29.4%) patients (2 DLBCL, 1 MCL, 1 SLL, 1 PTCL). At steady state, HMPL-523 showed approximately dose proportional PK over the daily dose range of 100 to 700 mg.Conclusions: HMPL-523 was well tolerated at all dose levels within the range of 100 mg to 700 mg and demonstrated proof of activity at dose levels of 400 mg or higher in heavily pre-treated patients. The dose expansion phase of the study will evaluate safety and efficacy in patients with multiple subtypes of B-cell and T-cell lymphoma at the RP2D of 700 mg. Updated safety, PK, and anti-tumor activity will be presented. DisclosuresStrati: Astrazeneca-Acerta: Research Funding; Roche-Genentech: Consultancy. González-Barca: Roche: Honoraria, Other: Travel; Kyowa Kirin: Consultancy; EUSA Pharma: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Other: Travel; Takeda. Abbvie: Honoraria. Taszner: Roche, Takeda: Consultancy, Other: Travel. Pillai: HUTCHMED: Current Employment. Chien: HUTCHMED: Current Employment, Current equity holder in publicly-traded company. Nanda: HUTCHMED: Current Employment, Current equity holder in publicly-traded company, Other: Travel. Rudinski: HUTCHMED: Current Employment. Jayaprakash: HUTCHMED, Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company, Ended employment in the past 24 months; Astrazeneca: Current equity holder in publicly-traded company. Hahka-Kemppinen: HUTCHMED: Current Employment, Current holder of individual stocks in a privately-held company; Eli Lilly: Current holder of individual stocks in a privately-held company. Kania: HUTCHMED: Current Employment, Current equity holder in publicly-traded company.

A subset of cytotoxic effector memory T cells enhances CAR T cell efficacy in a model of pancreatic ductal adenocarcinoma.

In humans, the natural killer (NK) cell marker CD161 identifies several subsets of T cells, including a polyclonal CD8 αβ T cell receptor-expressing subset with characteristic specificity for tissue-localized viruses. This subset also displays enhanced cytotoxic and memory phenotypes. Here, we characterized this unique T cell subset and determined its potential suitability for use in chimeric antigen receptor (CAR) T cell therapy. In mice, gene expression profiling among the CD161-equivalent CD8+ T cell populations (CD8+NK1.1+) revealed substantial up-regulation of granzymes, perforin, killer lectin-like receptors, and innate signaling molecules in comparison to CD8+NK1.1- T cells. Adoptive transfer of CD8+NK1.1+ cells from previously exposed animals offered substantially enhanced protection and improved survival against melanoma tumors and influenza infection compared to CD8+NK1.1- cells. Freshly isolated human CD8+CD61+ T cells exhibited heightened allogeneic killing activity in comparison to CD8+CD61- T cells or total peripheral blood mononuclear cells (PBMCs). To determine whether this subset might improve the antitumor efficacy of CAR T cell therapy against solid tumors, we compared bulk PBMCs, CD8+CD161-, and CD8+CD161+ T cells transduced with a human epidermal growth factor receptor-2 (HER2)-specific CAR construct. In vitro, CD8+CD161+ CAR-transduced T cells killed HER2+ targets faster and with greater efficiency. Similarly, these cells mediated enhanced in vivo antitumor efficacy in xenograft models of HER2+ pancreatic ductal adenocarcinoma, exhibiting elevated expression of granzymes and reduced expression of exhaustion markers. These data suggest that this T cell subset presents an opportunity to improve CAR T cell therapy for the treatment of solid tumors.

43P Pre-clinical evaluation of potent and orally bioavailable next-generation inhibitors targeting the family of mutants that drive oncogenic BRAF dimer formation

The canonical BRAF V600E (class I) mutation is a potent oncogene which is uniquely active as a RAS-independent monomer, and which has been successfully targeted by several FDA-approved inhibitors. While active against monomeric BRAF V600E, these first generation BRAF inhibitors induce paradoxical activation of RAS-driven BRAF dimers in cells expressing wild-type RAF, and this can lead to secondary malignancies. More recently, numerous non-canonical BRAF oncogenic mutations including BRAF-fusions have been described as oncogenes that drive RAS-independent (class II) or RAS-dependent (class III) dimers. These non-canonical dimeric BRAF oncogenes are resistant to the first-generation drugs, effective only against the monomeric BRAF V600E mutation. Discovery of an inhibitor directed against the family of dimeric BRAF oncogenic mutations which avoids paradoxical activation is a major unmet need. We applied our proprietary Mutation-Allostery-Pharmacology (MAP) platform technology developed by Black Diamond Therapeutics to identify and validate a group of previously uncharacterized non-canonical oncogenic class II and class III BRAF mutation clusters. We further demonstrate that this ensemble of both novel and previously validated non-canonical oncogenic BRAF mutants can form the basis of a differentiated drug discovery program aimed at identifying small molecules that potently and selectively target this family of dimeric BRAF mutations. Herein, we describe a series of small molecule inhibitors with potent anti-proliferative activity directed against tumor cells harboring dimer-inducing BRAF oncogenic mutations and which are devoid of paradoxical RAF activation. Leading exemplars of BDTX compounds are orally available inhibitors that achieve target engagement of BRAF dimer oncogenes in vivo and robust anti-tumor efficacy in xenograft models in mice. These data support continued development of rationally designed molecules targeting a broad range of non-canonical BRAF dimer-promoting mutations to extend the prospect of precision medicine in patients with BRAF mutant tumors.

Abstract PS17-11: Her2-xpat, a novel protease-activatable prodrug t-cell engager (tce), exhibits potent t-cell activation and efficacy in her2 tumors, yielding large predicted safety margins based on non-human primate (nhp)

Abstract Background TCEs are effective at inducing remissions in hematologic cancers but have been challenging in solid tumors due to on-target, off-tumor toxicity. Attempts to circumvent CRS include fractionated or step-up dosing and/or complex molecular designs, but these have been unsuccessful due to toxicity and/or enhanced immunogenicity. Amunix has developed a conditionally active TCE, XPAT or XTENylated Protease-Activated bispecific T-Cell Engager, that exploits the protease activity present in tumors vs. healthy tissue to expand the therapeutic index (TI). The core of the HER2-XPAT (PAT) consists of 2 tandem scFVs targeting CD3 and HER2. Two unstructured polypeptide masks (XTEN) are attached to the core that sterically reduce target engagement and extend T1/2. Protease cleavage sites at the base of the XTEN masks enable proteolytic activation of XPATs in the tumor microenvironment, unleashing a highly potent TCE with a short T1/2 and further improving the TI. Although checkpoint inhibitors have been ineffective in HER2+ or HR+ breast cancer, TCEs can co-opt T-cells regardless of their antigenic specificity, providing the potential to introduce effective T-cell immunity against tumors expressing HER2. HER2-XPAT, as a tumor protease-activatable prodrug with a wide safety margin, offers the potential to induce effective T-cell cytotoxicity against HER2hi tumors and HR+/HER2 1-2+ tumors. Methods Preclinical studies were conducted to characterize the activity of HER2-XPAT, HER2-PAT (cleaved XPAT), and HER2-NonClv (a non-cleavable XPAT) for cytolytic activity in vitro, for anti-tumor efficacy in xenograft models, and for stability and safety in NHPs. Results HER2-PAT (cleaved XPAT) demonstrated potent in vitro tumor-directed T-cell cytotoxicity (EC50 1-2pM) and target-dependent T-cell activation and production of cytokines by PBMCs. HER2-PAT also exhibited cytotoxicity in HR+, HER2 1+ MCF7s at higher doses (EC50 0.13nM). HER2-XPAT provided up to 14,000-fold protection against killing of HER2 tumor cells and exhibited no cytotoxicity against cardiomyocytes at concentrations up to 1uM. In vivo, HER2-XPAT induced complete tumor regressions in BT-474 tumor models with equimolar dosing to HER2-PAT, whereas non-cleavable HER2-NonClv had no efficacy, supporting tumor protease cleavage requirement for T-cell activity. In NHP, HER2-XPAT has been dose-escalated safely up to 42mg/kg (MTD) but was not tolerated at 50mg/kg. HER2-XPAT demonstrated early T-cell margination at 2mg/kg but largely spared CRS, cytokine production, and tissue toxicity at doses up to 42mg/kg. PK profiles of HER2-XPAT and HER2-NonClv were comparable in NHP, indicating minimal systemic cleavage of XPAT, consistent with its ex vivo stability when incubated in the plasma of cancer pts for 7 days at 37°C. Given by continuous infusion, HER2-PAT induced lethal CRS and cytokine spikes at 0.3mg/kg/d, but was tolerated at 0.2mg/kg/d, providing HER2-XPAT with >3000-fold protection in tolerated Cmax versus HER2-PAT, >4 logs over cytotoxicity EC50s for HER2 and HR+ cell lines, and a 20-fold margin of safety over the dose required for pharmacodynamic activity. Conclusions HER2-XPAT is a potent prodrug T-cell engager with promising evidence of activity at low doses while exhibiting minimal CRS and a potentially wide TI based on NHP tolerability at doses up to 42mg/kg. With XTEN’s prior clinical data demonstrating low immunogenicity, the XPAT TCEs provide a promising solution. IND studies are currently ongoing. Additional PK, PD, cytokines, safety, and efficacy data will be presented. Citation Format: Fiore Cattaruzza, Ayesha Nazeer, Zachary Lange, Caitlin Koski, Mikhail Hammond, Angela Henkensiefken, Trang Dao-Pick, Mika K Derynck, Bryan Irving, Volker Schellenberger. Her2-xpat, a novel protease-activatable prodrug t-cell engager (tce), exhibits potent t-cell activation and efficacy in her2 tumors, yielding large predicted safety margins based on non-human primate (nhp) [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS17-11.

51 Poster Discussion - Vertical pathway inhibition with a SOS1::KRAS inhibitor enhances the efficacy of KRAS G12C inhibitors, delays feedback resistance and demonstrates durable response

BI 1701963 is the first SOS1::KRAS inhibitor, which has entered Phase I clinical trials both as a mono-therapy as well as in combination with MEK inhibitors in patients with KRAS mutated advanced solid tumors. Both, BI 1701963 as well as the previously reported probe compound BI-3406 are orally bioavailable small molecules, designed to bind to the catalytic domain of SOS1, thereby preventing the interaction with GDP-loaded KRAS. In KRAS-dependent cancers, both SOS1::KRAS inhibitors potently reduce the formation of GTP-loaded KRAS and inhibit MAPK pathway signaling. SOS1:: KRAS inhibitors exhibit activity on a broad spectrum of KRAS alleles, including all major G12D/V/C and G13D oncoproteins, while sparing the interaction of KRAS with SOS2. This increases the targetable patient population beyond tumors with a KRAS G12C mutation and suggests a favorable therapeutic window to enable rational combinations. We previously showed that combining the SOS1::KRAS inhibitor BI-3406 with a MEK inhibitor blocks the negative feedback relief induced by MAPK inhibition. Combining SOS1::KRAS inhibition with MEK inhibitor treatment enhances pathway blockade leading to stronger anti-tumor efficacy in xenograft models driven by mutant KRAS such as G12D/V/C, G13D as well as Q61 K.

Single Chain Variable Fragment Linker Length Regulates CAR Biology and T Cell Efficacy

Single Chain Variable Fragment Linker Length Regulates CAR Biology and T Cell Efficacy

Abstract 4477: MIK665/S64315, a novel Mcl-1 inhibitor, in combination with Bcl-2 inhibitors exhibits strong synergistic antitumor activity in a range of hematologic malignancies

Abstract One of the hallmarks of cancer is evasion of apoptosis. The B-cell lymphoma-2 (Bcl-2) family of proteins represents a crucial point of control of apoptosis. The Bcl-2 family comprises both pro- and anti-apoptotic members, the latter of which (Bcl-2, Bcl-xL, Bcl-w, Mcl-1 and Bcl-2A1) are often overexpressed in cancer cells, supporting their aberrant survival. Thus, these anti-apoptotic proteins have become an attractive target for cancer therapy. BH3 mimetics have been shown to bind to the BH3 binding groove of anti-apoptotic Bcl-2 family members and inhibit their function, resulting in apoptotic cell death, and one such BH3 mimetic, ABT-199 (venetoclax), has recently been approved for treatment of relapsed or refractory Chronic Lymphocytic Leukemia. We have developed two novel and potent BH3 mimetics: MIK665/S64315, a highly selective inhibitor of Mcl-1 and BCL201/S55746, a selective Bcl-2 inhibitor. Both compounds, individually induce apoptosis in hematological cancer cell lines, primary patient samples and demonstrate anti-tumor efficacy in xenograft models. MIK665/S64315 is currently in phase 1 clinical development in AML and MDS (NCT 02979366) and in MM and lymphoma (NCT02992483). Here, we describe the activity of the combination of MIK665/S64315 with BCL201/S55746 or venetoclax, both in vitro and in vivo, across a range of hematological indications (AML, MM and DLBCL). In vitro, a strong synergy was observed with these combinations, resulting in a remarkable induction of cell death in majority of cell lines tested. In vivo, MIK665/S64315 and BCL201/S55746 combinations lead to complete and durable antitumor responses in many different xenograft models in mice and rats. Taken together, these data demonstrate that a combination of MIK665/S64315 and BCL201/S55746 provide strong therapeutic benefit over either monotherapy, and support a rationale for testing Mcl-1 and Bcl-2 inhibitor combinations in patients with hematological malignancies. Citation Format: Ensar Halilovic, Maïa Chanrion, Prakash Mistry, Markus Wartmann, Shumei Qiu, Sneha Sanghavi, Yan Chen, Gaëlle Lysiak, Ana Leticia Maragno, Ulrike Pfaar, Felix Huth, Marie Schoumacher, Audrey Claperon, Laurence Kraus-Berthier, Sébastien Banquet, Alix Derreal, Heiko Maacke, Frédéric Colland, Olivier Geneste, Erick Morris, Youzhen Wang. MIK665/S64315, a novel Mcl-1 inhibitor, in combination with Bcl-2 inhibitors exhibits strong synergistic antitumor activity in a range of hematologic malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4477.

Preliminary Results from a Phase 1 Study of HMPL-523, a Highly Selective Syk Inhibitor, in Chinese Patients with Mature B-Cell Lymphomas

Background: Spleen tyrosine kinase (Syk) is a key component of B-cell receptor (BCR) signaling and is an established therapeutic target in multiple subtypes of B-cell lymphomas. HMPL-523 is an oral, selective Syk inhibitor, and has shown strong anti-tumor efficacy in xenograft models of B-cell malignancies. Here we report the safety, pharmacokinetics (PK) and preliminary anti-tumor activity results of the dose escalation stage in a Phase 1 study in patients with relapsed/refractory (R/R) B-cell lymphomas treated with HMPL-523 monotherapy (NCT02857998).Methods: This study comprised a dose escalation stage and a dose expansion stage. The primary objectives for the dose escalation stage were to evaluate the safety, tolerability, and to determine maximum tolerated dose (MTD) and /or recommended Phase 2 dose (RP2D) of HMPL-523. Secondary objectives were to assess the PK and preliminary anti-tumor activity. Treatment responses were assessed by the Lugano criteria, modified International Workshop on Chronic Lymphocytic Leukemia (CLL) guideline, or the consensus of international workshops on Waldenstrom Macroglobulinemia (WM), at weeks 8, 16, 24, and then every 12 weeks.Results: As of May 3rd 2018, 27 patients had been enrolled and dosed with one of the five dose levels of 200-800 mg once daily (QD) or 200 mg twice daily (BID) under the conventional “3+3” dose escalation design. Baseline tumor subtypes included follicular lymphoma (FL; n=10), diffuse large B cell lymphoma (DLBCL; n=5), CLL / small lymphocytic lymphoma (SLL; n=4), mantle cell lymphoma (MCL; n=4), marginal zone lymphoma (MZL; n=3) and WM (n=1). All patients (median age was 57 years [range 31-73]) were Asian, and 55.6% of the patients were male, with a median prior lines of therapy of 3 (range 1-6). All patients had received prior systemic chemotherapies and/or antibodies, including alkylating agents (100%), anti-CD20 antibodies (75%), and anthracyclines (95.8%). Three patients (8.3%) had received prior ibrutinib/placebo from clinical trials.Median follow-up time was 98 days (range, 8-427), and 70.4% of patients had discontinued therapy, mostly due to disease progression (25.9%) and adverse events (AEs) (14.8%). The AEs of any cause reported in more than 10% patients were leukopenia (44.4%), neutropenia (44.4%), alkaline phosphatase (ALT) increased (40.7%), aspartate aminotransferase (AST) increased (40.7%), thrombocytopenia (29.6%), blood bilirubin increased (29.6%), anaemia (25.9%), proteinuria (18.5%), amylases increased (18.5%), yellow skin (18.5%), hypokalaemia (14.8%), lung infection (14.8%), influenza syndrome (14.8%), hyperuricaemia (11.1%), cough (11.1%), and bilirubin conjugated increased (11.1%). The ≥ Grade 3 AEs of any cause reported in more than 5% patients were neutropenia (18.5%), lung infection (7.4%), and blood bilirubin increased (7.4%). Serious AEs were reported in 8 patients with 9 events, of which 5 events were considered to be related to HMPL-523 (i.e., interstitial pneumonia, febrile neutropenia, kidney failure, lung infection, and bilirubin conjugated increased). No fatal AE was reported. Five dose limiting toxicities (DLTs) were observed: 1 in the 200 mg QD cohort (Grade 3 amylase increased), 2 in the 800 mg QD cohort (Grade 3 febrile neutropenia; Grade 3 kidney failure), and 2 in the 200 mg BID cohort (Grade 3 bilirubin conjugated increased; Grade 4 hyperuricaemia and blood creatine phosphokinase increased). The MTD was reached at the 600 mg QD dose level which was determined as the RP2D.Preliminary PK data indicated that the exposures of HMPL-523 increased with the increase in dose from 200 mg QD to 800 mg QD. The geometric mean exposures indicated as AUCtau and Cmax at 600 mg QD at steady state were approximately 4,000 h•ng/mL and 300 ng/mL, respectively, and the t1/2 was in the range of 7-15 hours across all dose levels.Among 21 efficacy evaluable patients with at least one post treatment efficacy assessment, best tumor response was seen in 4 (19.0%) patients who achieved partial response (3/10 FL, and 1/3 CLL/SLL), and 9 (40%) patients who achieved stable disease (3/4 MCL, 3/10 FL, 1/3 CLL/SLL, 1/2 MZL, and 1/1 WM).Conclusions: HMPL-523 is well tolerated as a single agent in Chinese patients with R/R B-cell lymphomas. MTD was reached and RP2D was determined to be 600 mg QD. Preliminary anti-tumor activity was observed in indolent lymphomas, including CLL/SLL and FL. DisclosuresZhu:Beijing Cancer Hospital: Employment. Song:Peking University Cancer Hospital (Beijing Cancer Hospital): Employment. Hua:Hutchison Medipharma: Employment. Yang:Hutchison Medipharma: Employment. Yu:Hutchison Medipharma: Employment. Wang:Hutchison Medipharma: Employment. Dai:Hutchison Medipharma: Employment. Su:Hutchison Medipharma: Employment.

Abstract 4780: A novel, potent and selective FGFR4 inhibitor, HM81422 in hepatocellular carcinoma with FGFR4-driven pathway activation

Abstract Introduction: Hepatocellular carcinoma (HCC) is the sixth most prevalent cancer and the second most frequent cause of cancer-related death, however, treatment options are very limited. In recent studies, aberrant signaling through FGFR4 and its ligand, FGF19 have been identified as the oncogenic driver in a subset of HCCs and reported to be associated with poor prognosis. About 30% of HCC patients have altered FGF19/FGFR4 pathway signaling, therefore, the treatment with FGFR4 inhibitor may produce benefit. Materials and Method: Using the structure-based design, we have generated a novel, potent and selective FGFR4 inhibitor, HM81422 with irreversible-covalent binding mode, and evaluated its anti-tumor activity in a variety of HCC cell lines, HCC cell line xenografts and orthotopic grafts. Results: Biochemical selectivity assays demonstrated that HM81422 is highly selective towards FGFR4 compared to other FGFR isotypes as well as a panel of several kinases. The treatment of HM81422 to FGF19 amplified and overexpressed HCC cell lines led to suppression of FGF19/FGFR4 signaling pathway and concomitant reduction in cell viability in dose-dependent manner. Oral administration of HM81422 to mice bearing FGF19 altered HCC cells showed dose-dependent pharmacokinetics, pharmacodynamic modulation of FGFR4 signaling and antitumor efficacy in xenograft models. And HM81422 demonstrated inhibition of tumor growth in an orthotopic liver xenograft model of FGF19 altered HCC in nude mice. Conclusion: In conclusion, the treatment of HCC patients with a potent and selective FGFR4 inhibitor, HM81422, can be an attractive approach targeting approximately 30% of HCC patients by inhibiting altered FGF19-mediated signaling cascade. Further preclinical studies with HM81422 will be performed and reported soon. Citation Format: JaeHo Lee, Hyunjeong Kang, Kyounghwa Koo, Youngeun Ha, Sun Young Lim, Joo-Yun Byun, Hyunkyung Yu, Taehun Song, Moonsub Lee, Seung Hyun Jung, Taewoo Kim, Hyojeong Bang, Eunyoung Kim, Jahoon Kang, Ho Jeong Lee, YoungHoon Kim, YoungGil Ahn, KweeHyun Suh, Sun-Jin Kim. A novel, potent and selective FGFR4 inhibitor, HM81422 in hepatocellular carcinoma with FGFR4-driven pathway activation [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 4780.

Abstract 5071: Preclinical characterization of the potent and selective BET inhibitor INCB057643 in models of hematologic malignancies

Abstract Inhibitors of the Bromodomain and Extra-Terminal (BET) family of bromodomain containing proteins regulate expression of key cell fate, cell cycle, and survival genes including c-myc. In preclinical models, BET inhibitors have demonstrated significant efficacy in a variety of different oncology indications, including hematological malignancies. Here we describe the preclinical profile of the novel, orally bioavailable BET inhibitor INCB057643 in preclinical models of hematologic malignancies. INCB057643 inhibited binding of BRD2/BRD3/BRD4 to an acetylated histone H4 peptide in the low nM range, and was selective against other bromodomain containing proteins. In vitro analyses showed that INCB057643 inhibited proliferation of human AML, DLBCL, and multiple myeloma cell lines, with a corresponding decrease in MYC protein levels. Cell cycle analyses indicated that G1 arrest and a concentration-dependent increase in apoptosis were seen within 48 hours of treatment with INCB057643. BRD proteins also regulate the expression of many pro-inflammatory genes. Production of several cytokines, including IL-6, IL-10 and MIP-1α, was repressed by INCB057643 in human and mouse whole blood stimulated ex vivo with LPS. Consistent with these effects, analyses of gene expression in cells treated with INCB057643 revealed that pathways involved in cell cycle progression, apoptosis, and IL-6 were among the most significantly altered in vitro. Oral administration of INCB057643 resulted in significant anti-tumor efficacy in xenograft models of AML, myeloma, and DLBCL. Additionally, combining INCB057643 with standard of care agents used for the treatment of DLBCL including rituximab and bendamustine resulted in enhanced anti-tumor efficacy relative to that achieved with single agent therapies at doses that were well tolerated. In addition, many B cell malignancies are reliant on the PI3Kδ pathway for proliferation and survival, suggesting that the combination of INCB057643 with the clinical stage PI3Kδ specific inhibitor INCB050465 may be a rational therapeutic strategy for DLBCL. Compared with single agent BETi or PI3Kδi therapy, the combination significantly potentiated tumor growth inhibition in DLBCL models representative of the ABC subtype (HBL-1), and the double hit GCB subtype (WILL2). These data suggest that clinical exploration of INCB057643 as a monotherapy or in combination in hematologic malignancies is warranted. Citation Format: Matthew C. Stubbs, Thomas Maduskuie, Timothy Burn, Sharon Diamond-Fosbenner, Nikoo Falahatpisheh, Alla Volgina, Nina Zolotarjova, Xiaoming Wen, Patricia Feldman, Mark Rupar, Robert Collins, Cindy Marando, Bruce Ruggeri, Maryanne Covington, Xuesong Mike Liu, Richard Wynn, Swamy Yeleswaram, Wenqing Yao, Reid Huber, Gregory Hollis, Peggy Scherle, Andrew P. Combs, Phillip C. Liu. Preclinical characterization of the potent and selective BET inhibitor INCB057643 in models of hematologic malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5071. doi:10.1158/1538-7445.AM2017-5071

Abstract 34: A MET x MET bispecific antibody that induces receptor degradation potently inhibits the growth of MET-addicted tumor xenografts

Abstract Aberrant regulation of MET receptor tyrosine kinase signaling is associated with development and progression of various human tumors. Elevated MET signaling during tumorigenesis results from MET amplification, mutation or up-regulation of the ligand, HGF. MET amplification is thought to be a key driver of oncogenesis in non-small cell lung cancers (NSCLC) and oesophagogastric malignancies. In addition, mutations resulting in exon 14 deletion of MET have been described as oncogenic drivers in a subset of NSCLC. Both preclinical and recent clinical results indicate that tumors harboring these genetic alterations respond to MET inhibitors, validating MET as a cancer driver. We have developed a novel bispecific antibody that binds to two distinct epitopes on MET. The METxMET bispecific antibody blocks HGF binding and exhibits very low agonist activity (much weaker than either of its parental antibodies). Furthermore, the METxMET bispecific antibody effectively promotes MET degradation, thereby inhibiting ligand-independent signaling in MET-amplified tumor cells. The METxMET bispecific antibody exhibits strong anti-tumor efficacy in xenograft models harboring MET genetic alterations, either completely inhibiting tumor growth (EBC1 MET-amplified NSCLC) or promoting substantial tumor regression (SNU5 MET-amplified gastric cancer, Hs746T MET-amplified/MET exon 14 skip gastric cancer). Analysis of lysates from SNU5 tumors treated with the METxMET bispecific antibody confirms its ability to effectively promote MET degradation in vivo. Finally, the METxMET bispecific antibody strongly inhibits the growth of a glioblastoma xenograft model (U118) driven by autocrine HGF signaling. In summary, we have generated a novel METxMET bispecific antibody that potently inhibits the growth of MET-dependent tumor xenografts. Our data suggest that antibody-mediated MET degradation may be an effective clinical strategy in tumors harboring MET genetic alterations. Citation Format: John DaSilva. A MET x MET bispecific antibody that induces receptor degradation potently inhibits the growth of MET-addicted tumor xenografts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 34. doi:10.1158/1538-7445.AM2017-34

Imaging the delivery of drug-loaded, iron-stabilized micelles

Nanoparticle drug carriers hold potential to improve current cancer therapy by delivering payload to the tumor environment and decreasing toxic side effects. Challenges in nanotechnology drug delivery include plasma instability, site-specific delivery, and relevant biomarkers. We have developed a triblock polymer comprising a hydroxamic acid functionalized center block that chelates iron to form a stabilized micelle that physically entraps chemotherapeutic drugs in the hydrophobic core. The iron-imparted stability significantly improves the integrity of the micelle and extends circulation pharmacokinetics in plasma over that of free drug. Furthermore, the paramagnetic properties of the iron-crosslinking exhibits contrast in the tumors for imaging by magnetic resonance. Three separate nanoparticle formulations demonstrate improved anti-tumor efficacy in xenograft models and decreased toxicity. We report a stabilized polymer micelle that improves the tolerability and efficacy of chemotherapeutic drugs, and holds potential for non-invasive MRI to image drug delivery and deposition in the tumor.

Characterization and antitumor efficacy of poly(L-lactid acid)-based etoposide-loaded implants

Etoposide is widely used in the chemotherapy of a variety of malignancies. But the strong lipophilicity, poor bioavailability, and severe side effects of etoposide limit its clinical application. The aim of this study was to develop sustained-release etoposide-loaded implants and evaluate antitumor activity of the implants after intratumoral implantation. We prepared the implants containing etoposide, poly(L-lactid acid) and polyethylene glycol 4000 by the direct compression method. The implants were characterized regarding drug-excipient compatibility, content uniformity, morphology, sterility, in vitro, and in vivo release profiles. Then the antitumor activity of the implants was tested in xenograft model of A549 human non-small cell lung cancer. SEM images displayed smooth surface of the implant and indicated that etoposide was homogeneously dispersed in the polymeric matrix. The results of content uniformity met the requirements of the Chinese Pharmacopoeia. Both in vitro and in vivo release profiles of the implants were characterized by high burst release followed by sustained release of etoposide. Intratumoral implantation of etoposide-loaded implants could efficiently delay the tumor growth. Furthermore, increasing the dose of implants led to higher tumor suppression rate without adding systemic toxicity. These results indicated that etoposide-loaded implants have significant antitumor efficacy in xenograft model without dose-limiting side effects and they possess a strong potential to be used as an intratumoral chemotherapy option for lung cancer treatment.

Combination of the Glycoengineered Type II CD20 Antibody Obinutuzumab (GA101) and the MDM2 Selective Antagonist RG7388 Results in Superior Anti-Tumor Activity

Abstract Introduction: Obinutuzumab (GA101) is a novel glycoengineered type II, anti-CD20 monoclonal antibody that strongly induces direct cell death. As a result of glycoengineering, obinutuzumab has increased affinity for FcgRIII on innate immune effector cells resulting in enhanced induction of ADCC and ADCP. Obinutuzumab has been approved for first line treatment of CLL patients in combination with chlorambucil in the US and Europe and is currently in pivotal clinical trials in indolent NHL and DLCBL. RG7112, a Nutlin imidazoline-based compound, and RG7388, a pyrrolidine-based compound are novel, orally bioavailable, selective MDM2 antagonists which reactivate p53 and thereby mediate cell cycle arrest and subsequent apoptotic cell death in solid and hematologic tumors. RG7388 is currently in clinical trials for the treatment of AML and prostate cancer. Based on the fact that the majority of B lymphoid malignancies including NHL and CLL bear wildtype p53, and the complementary mechanisms of action involving increased apoptosis (MDM2 antagonist) or direct cell death (obinutuzumab), the combination of both compounds has the potential for superior efficacy in treating B lymphoid malignancies. Experimental methods: The combination of obinutuzumab and RG7388 (or obinutuzumab and rituximab with RG7112, the frontrunner compound with identical mode of action) was studied in vitro utilizing assays that measure direct cell death induction/apoptosis (Annexin V/PI positivity) on p53 wildtype Z138 Mantle cell lymphoma (MCL) and DoHH-2 Diffuse large B-Cell lymphoma (DLBCL) cells by FACS and the impact of MDM2 inhibition on ADCC induction and whole blood B cell depletion. In vivo efficacy of the combination of obinutuzumab or rituximab with RG7122 and RG7388 was evaluated in the s.c. Z138 MCL xenograft model in immunodeficient SCID beige mice. Results: RG7338 induced concentration-dependent cell death of Z-138 and DOHH-2 cell lines. At concentrations > 10-100 nM RG7388 resulted in enhanced cell death induction of DOHH-2 and Z-138 cells in combination with obinutuzumab. Notably, RG7388 did not influence obinutuzumab mediated ADCC during 4 h up to concentrations of 1000 nM and did not affect obinutuzumab mediated NK cell activation (CD16 downregulation, CD107a upregulation). Similarly, addition of RG7388 did not interfere with obinutuzumab mediated B cell depletion in healthy human whole blood at concentrations up to 1000 nM. In the Z-138 xenograft model, the combination of suboptimal doses of 0.5 mg/kg obinutuzumab or 1 mg/kg rituximab with 150 mg/kg RG7112 (three times a week p.o. for 3 weeks) resulted in superior tumor growth inhibition by obinutuzumab as compared to rituximab including the induction of complete tumor remission. In a second Z-138 study, the combination of the suboptimal dose of 0.5 mg/kg obinutuzumab with 80 mg/kg RG7388 yielded similar anti-tumor activity. In summary, the combination of either obinutuzumab or rituximab with RG7112 or the combination of obinutuzumab with RG7388 showed superior in vivo efficacy with no clinical signs of toxicity. Conclusions: The combination of obinutuzumab with MDM2 antagonists results in enhanced cell death of p53 wildtype NHL tumor cells while not affecting obinutuzumab mediated ADCC of tumor cells or B cell depletion in whole blood from healthy donors. In vivo the combination of obinutuzumab with MDM2 inhibitors RG7112 and RG7388 results in robust combined anti-tumor efficacy in xenograft models. Taken together, these preclinical data strongly support the investigation of obinutuzumab and RG7388 combination therapy in clinical trials. Disclosures Herting: Roche: Employment, Patents & Royalties. Herter:Roche: Employment. Friess:Roche: Employment, Patents & Royalties. Lehmann:Roche: Employment. Bacac:Roche: Employment. Dangl:Roche: Employment, Patents & Royalties. Klein:Roche: Employment, Equity Ownership, Patents & Royalties.