Association between gene expression signatures and clinical outcomes of pembrolizumab versus paclitaxel in advanced gastric cancer: exploratory analysis from the randomized, controlled, phase III KEYNOTE-061 trial

BACKGROUND

In the randomized, controlled, phase III KEYNOTE-061 trial, second-line pembrolizumab did not significantly prolong overall survival (OS) versus paclitaxel in patients with PD-L1-positive (combined positive score ≥1) advanced gastric/gastroesophageal junction (G/GEJ) cancer but did elicit a longer duration of response and offered a favorable safety profile. This prespecified exploratory analysis was conducted to evaluate associations between tumor gene expression signatures and clinical outcomes in the phase III KEYNOTE-061 trial.

METHODS

Using RNA sequencing data obtained from formalin-fixed, paraffin-embedded baseline tumor tissue samples, we evaluated the 18-gene T-cell-inflamed gene expression profile (TcellinfGEP) and 10 non-TcellinfGEP signatures (angiogenesis, glycolysis, granulocytic myeloid-derived suppressor cell (gMDSC), hypoxia, monocytic MDSC (mMDSC), MYC, proliferation, RAS, stroma/epithelial-to-mesenchymal transition/transforming growth factor-β, WNT). The association between each signature on a continuous scale and outcomes was analyzed using logistic (objective response rate (ORR)) and Cox proportional hazards regression (progression-free survival (PFS) and OS). One-sided (pembrolizumab) and two-sided (paclitaxel) p values were calculated for TcellinfGEP (prespecified α=0.05) and the 10 non-TcellinfGEP signatures (multiplicity-adjusted; prespecified α=0.10).

RESULTS

RNA sequencing data were available for 137 patients in each treatment group. TcellinfGEP was positively associated with ORR (p=0.041) and PFS (p=0.026) for pembrolizumab but not paclitaxel (p>0.05). The TcellinfGEP-adjusted mMDSC signature was negatively associated with ORR (p=0.077), PFS (p=0.057), and OS (p=0.033) for pembrolizumab, while the TcellinfGEP-adjusted glycolysis (p=0.018), MYC (p=0.057), and proliferation (p=0.002) signatures were negatively associated with OS for paclitaxel.

CONCLUSIONS

This exploratory analysis of tumor TcellinfGEP showed associations with ORR and PFS for pembrolizumab but not for paclitaxel. TcellinfGEP-adjusted mMDSC signature was negatively associated with ORR, PFS, and OS for pembrolizumab but not paclitaxel. These data suggest myeloid-driven suppression may play a role in resistance to PD-1 inhibition in G/GEJ cancer and support a strategy of considering immunotherapy combinations which target this myeloid axis.

TRIAL REGISTRATION NUMBER

NCT02370498.

Abstract 4528: Evaluation of plasma circulating tumor DNA (ctDNA)-based whole genome sequencing (pWGS) and whole exome sequencing (pWES) and concordance with tumor tissue whole exome sequencing (tWES): a pilot study in patients with recurrent or metastatic head and neck squamous cell carcinoma or metastatic urothelial carcinoma

Background: The genetic heterogeneity and clonal evolution of tumors is hypothesized to influence disease response and acquisition of resistance during treatment. However, comprehensive analysis of the changing tumor molecular landscape to support evaluation of such a hypothesis is often difficult to quantify due to the lack of accessibility to longitudinal biopsy samples in a large number of patients (pts). Longitudinal analyses using pWGS or pWES may allow the delineation of the genetic evolution of tumors and its impact on treatment outcomes. We conducted a pilot study to evaluate the feasibility of obtaining pWGS and pWES data from ctDNA in pretreatment samples from pts enrolled in 2 phase 3 trials that evaluated second-line pembrolizumab versus chemotherapy/standard-of-care therapy: KEYNOTE-040 (recurrent or metastatic head and neck squamous cell carcinoma; NCT02252042) and KEYNOTE-045 (metastatic urothelial carcinoma, NCT02256436). Concordance between pWES and tWES was also evaluated.

Methods: Cell-free DNA was isolated from 1-3 mL of plasma; pWGS (via low-pass WGS) and pWES were performed on samples from pts with available tWES data generated as part of planned tissue biomarker analyses for the respective studies. Tumor burden in ctDNA was estimated from pWES data using single nucleotide variant (SNV)-based maximum somatic allele frequency (MSAF) and from pWGS data using a copy number variation-based measure of mutational burden in the tumor fraction. Concordance between the pWES and tWES mutational spectrum was determined using the Jaccard index. Concordance of key driver somatic events (FGFR3, TP53, and HPV status) was evaluated.

Results: Plasma samples from 47 pts (KEYNOTE-040, n = 24; KEYNOTE-045, n = 23) were analyzed. Tumor burden estimates from pWGS (median coverage, 5.84; range, 4.28-8.18) and pWES (median coverage, 1806; range, 1038-2413) data were highly correlated (Spearman ρ = 0.94). A range of 0 to 956 nonsynonymous SNVs (median, 50) per pt was identified in ctDNA. When the ctDNA tumor burden was high (MSAF ≥5%, observed in two-thirds of pts), a relatively high concordance was observed for individual alterations in TP53, FGFR3, and HPV status (overall agreement: 0.87, 0.97, and 0.96, respectively); between tissue- and plasma-based tumor mutational burden (R = 0.49); and in overall mutational landscape overlap (Jaccard index: median, 0.30; range, 0.002-0.53).

Conclusions: These data show that pWES exhibits reasonably high concordance with tWES when the tumor burden in ctDNA is relatively high and may be informative regarding tumor genomic characteristics. Extensive longitudinal studies are still needed to understand tumor genetic evolution using plasma ctDNA.

Citation Format: Razvan Cristescu, Andrew Albright, Steven Townson, Cai Chen, Blanca Homet Moreno, Nati Lerman, Z. Alexander Cao, Carol Peña. Evaluation of plasma circulating tumor DNA (ctDNA)-based whole genome sequencing (pWGS) and whole exome sequencing (pWES) and concordance with tumor tissue whole exome sequencing (tWES): a pilot study in patients with recurrent or metastatic head and neck squamous cell carcinoma or metastatic urothelial carcinoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4528.

Society for Immunotherapy of Cancer (SITC) consensus definitions for resistance to combinations of immune checkpoint inhibitors with chemotherapy

Although immunotherapy can offer profound clinical benefit for patients with a variety of difficult-to-treat cancers, many tumors either do not respond to upfront treatment with immune checkpoint inhibitors (ICIs) or progressive/recurrent disease occurs after an interval of initial control. Improved response rates have been demonstrated with the addition of ICIs to cytotoxic therapies, leading to approvals from the US Food and Drug Administration and regulatory agencies in other countries for ICI-chemotherapy combinations in a number of solid tumor indications, including breast, head and neck, gastric, and lung cancer. Designing trials for patients with tumors that do not respond or stop responding to treatment with immunotherapy combinations, however, is challenging without uniform definitions of resistance. Previously, the Society for Immunotherapy of Cancer (SITC) published consensus definitions for resistance to single-agent anti-programmed cell death protein 1 (PD-1). To provide guidance for clinical trial design and to support analyses of emerging molecular and cellular data surrounding mechanisms of resistance to ICI-based combinations, SITC convened a follow-up workshop in 2021 to develop consensus definitions for resistance to multiagent ICI combinations. This manuscript reports the consensus clinical definitions for combinations of ICIs and chemotherapies. Definitions for resistance to ICIs in combination with targeted therapies and with other ICIs will be published in companion volumes to this paper.

Abstract 2140: Association between gene expression signatures and outcomes of pembrolizumab (pembro) and paclitaxel (pac) in advanced gastric cancer (GC): Exploratory analysis from KEYNOTE-061

Background: In the phase 3 KEYNOTE-061 study (NCT02370498), second-line pembro did not significantly prolong OS vs pac in patients with PD-L1-positive (CPS ≥1) GC (N = 395) but did elicit a longer DOR and offered a favorable safety profile. We explored the association between tumor gene expression signatures and clinical outcomes.

Methods: In patients with tumor RNA-sequencing data, we analyzed the association of the 18-gene T-cell-inflamed gene expression profile (TcellinfGEP) and 10 other signatures (angiogenesis, glycolysis, gMDSC, hypoxia, mMDSC, MYC, proliferation, RAS, stroma/EMT/TGFβ, WNT) on a continuous scale with outcomes using logistic (ORR) and Cox proportional hazards (PFS; OS) regression. For TcellinfGEP, 1-sided (pembro) and 2-sided (pac) P values were calculated (prespecified significance, α = 0.05). For the 10 non-TcellinfGEP signatures, 1-sided (pembro) and 2-sided (pac) multiplicity-adjusted P values were calculated (prespecified significance, α = 0.10). Clinical data cutoff was October 26, 2017.

Results: There were 274 patients with tumor RNA-sequencing data (n = 137 in each arm). Association with clinical outcomes for gene expression signatures are reported in the Table.

Conclusions: In this exploratory analysis of patients with previously treated GC from KEYNOTE-061, tumor TcellinfGEP showed some association with clinical outcomes for pembro (ORR and PFS) but not pac (ORR, PFS, and OS). The TcellinfGEP-adjusted mMDSC signature was negatively associated with clinical outcomes for pembro (ORR, PFS, and OS), while the TcellinfGEP-adjusted glycolysis, MYC, and proliferation signatures were negatively associated with OS for pac. This exploratory biomarker analysis suggests that myeloid-driven suppression may play a role in resistance to PD-1 inhibition and supports a strategy of considering immunotherapy combinations intended to target this myeloid axis.

Association between clinical outcomes and TcellinfGEP and non-TcellinfGEP signatures adjusted for TcellinfGEP Pembrolizumabn = 137 Paclitaxeln = 137 ORR PFS OS ORR PFS OS TcellinfGEPa 0.041 0.026 0.178 0.822 0.207 0.644 Angiogenesisb 0.077 0.298 0.623 0.220 0.462 0.263 Glycolysisb 0.934 0.861 0.956 0.223 0.097 0.018 gMDSCb 0.626 0.573 0.623 0.694 0.352 0.263 Hypoxiab 0.934 0.861 0.956 0.223 0.220 0.440 mMDSCb 0.077 0.057 0.033 0.694 0.932 0.263 MYCb 0.934 0.861 0.956 0.223 0.327 0.057 Proliferationb 0.934 0.861 0.956 0.223 0.071 0.002 RASb 0.934 0.861 0.956 0.223 0.327 0.440 Stroma/EMT/TGFβb 0.306 0.366 0.522 0.694 0.462 0.263 WNTb 0.934 0.861 0.956 0.097 0.327 0.440 aBolded P values (1-sided for pembrolizumab with hypothesized positive association and 2-sided for paclitaxel with no hypothesized association) indicate nominal statistical significance (α = 0.05); model includes additional covariates of ECOG PS. bBolded P values (1-sided for pembrolizumab with hypothesized negative association except for proliferation and 2-sided for paclitaxel with no hypothesized association) indicate multiplicity-adjusted statistical significance (α = 0.10); model includes additional covariates of ECOG PS and TcellinfGEP.

Citation Format: Kohei Shitara, Maria Di Bartolomeo, Mario Mandala, Min-Hee Ryu, Christian Caglevic, Tomasz Olesinski, Hyun C. Chung, Kei Muro, Eray Goekkurt, Raymond S. McDermott, Wasat Mansoor, Zev A. Wainberg, Chie-Schin Shih, Julie Kobie, Michael Nebozhyn, Razvan Cristescu, Z. Alexander Cao, Andrey Loboda, Mustafa Özgüroğlu. Association between gene expression signatures and outcomes of pembrolizumab (pembro) and paclitaxel (pac) in advanced gastric cancer (GC): Exploratory analysis from KEYNOTE-061 [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 2140.

Association of Tumor Mutational Burden with Efficacy of Pembrolizumab{plus minus}Chemotherapy as First-Line Therapy for Gastric Cancer in the Phase III KEYNOTE-062 Study

PURPOSE

This prespecified exploratory analysis evaluated the association between tumor mutational burden (TMB) status and outcomes of first-line pembrolizumab{plus minus}chemotherapy versus chemotherapy in KEYNOTE-062.

EXPERIMENTAL DESIGN

In patients with advanced gastric cancer and evaluable TMB data, we evaluated the association between TMB (continuous variable; square root scale) assessed with FoundationOne® CDx and clinical outcomes [ORR, PFS, and OS] using logistic (ORR) and Cox proportional hazards (PFS, OS) regression models. Clinical utility of TMB was assessed using the prespecified cutoff of 10mut/Mb.

RESULTS

TMB data were available for 306 of 763 patients (40.1%; pembrolizumab, 107; pembrolizumab+chemotherapy, 100; chemotherapy, 99). TMB was significantly associated with clinical outcomes in patients treated with pembrolizumab and pembrolizumab+chemotherapy (ORR, PFS, and OS; all P<0.05) but not with chemotherapy (all P>0.05). The overall prevalence of TMB {greater than or equal to}10mut/Mb was 16% across treatment groups; 44% of patients who had TMB {greater than or equal to}10mut/Mb had high microsatellite instability (MSI-H) tumors. Improved clinical outcomes (ORR, PFS, and OS) were observed in pembrolizumab-treated patients (pembrolizumab monotherapy and pembrolizumab+chemotherapy) with TMB {greater than or equal to}10mut/Mb. When the analysis was limited to the non-MSI-H subgroup, both the positive association between clinical outcomes with pembrolizumab or pembrolizumab+chemotherapy and TMB as a continuous variable and the clinical utility of pembrolizumab (with or without chemotherapy) versus chemotherapy by TMB cutoff were attenuated.

CONCLUSIONS

This exploratory analysis of KEYNOTE-062 suggests an association between TMB and clinical efficacy with first-line pembrolizumab-based therapy in patients with advanced gastric/gastroesophageal junction adenocarcinoma. However, after the exclusion of patients with MSI-H tumors, the clinical utility of TMB was attenuated.

Evolution of predictive and prognostic biomarkers in the treatment of advanced gastric cancer

Despite new therapeutic options, advanced gastric cancer remains associated with a poor prognosis compared with other cancers. Recent gains in the treatment of gastric cancer were accompanied by the identification of novel biomarkers associated with various cellular pathways and corresponding diagnostic technologies. It is expected that the standardization of clinical workflow and technological refinements in biomarker assessment will support greater personalization and further improve treatment outcomes. In this article, we review the current state of prognostic and predictive biomarkers in gastric cancer.

Transcriptomic Determinants of Response to Pembrolizumab Monotherapy across Solid Tumor Types

PURPOSE

To explore relationships between biological gene expression signatures and pembrolizumab response.

EXPERIMENTAL DESIGN

RNA-sequencing data on baseline tumor tissue from 1,188 patients across seven tumor types treated with pembrolizumab monotherapy in nine clinical trials were used. A total of 11 prespecified gene expression signatures [18-gene T-cell-inflamed gene expression profile (TcellinfGEP), angiogenesis, hypoxia, glycolysis, proliferation, MYC, RAS, granulocytic myeloid-derived suppressor cell (gMDSC), monocytic myeloid-derived suppressor cell (mMDSC), stroma/epithelial-to-mesenchymal transition (EMT)/TGFβ, and WNT] were evaluated for their relationship to objective response rate (per RECIST, version 1.1). Logistic regression analysis of response for consensus signatures was adjusted for tumor type, Eastern Cooperative Oncology Group performance status, and TcellinfGEP, an approach equivalent to evaluating the association between response and the residuals of consensus signatures after detrending them for their relationship with the TcellinfGEP (previously identified as a determinant of pembrolizumab response) and tumor type. Testing of the 10 prespecified non-TcellinfGEP consensus signatures for negative association [except proliferation (hypothesized positive association)] with response was adjusted for multiplicity.

RESULTS

Covariance patterns of the 11 signatures (including TcellinfGEP) identified in Merck-Moffitt and The Cancer Genome Atlas datasets showed highly concordant coexpression patterns in the RNA-sequencing data from pembrolizumab trials. TcellinfGEP was positively associated with response; signatures for angiogenesis, mMDSC, and stroma/EMT/TGFβ were negatively associated with response to pembrolizumab monotherapy.

CONCLUSIONS

These findings suggest that features beyond IFNγ-related T-cell inflammation may be relevant to anti-programmed death 1 monotherapy response and may define other axes of tumor biology as candidates for pembrolizumab combinations. See related commentary by Cho et al., p. 1479.

Association between biomarkers and clinical outcomes of lenvatinib + pembrolizumab in advanced renal cell carcinoma (RCC): Results from Study 111/KEYNOTE-146

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Background: In the Study 111/KEYNOTE-146 trial (NCT02501096; N=147), lenvatinib (lenva) + pembrolizumab (pembro) showed encouraging antitumor activity and a manageable safety profile in treatment-naive (n=23) or previously treated metastatic RCC (n=105, previously treated with immune checkpoint inhibitor [ICI]; n=19, previously treated ICI naive); 145 had clear cell RCC and 2 had non-clear cell RCC. In this exploratory analysis, we evaluated the association between clinical outcomes and gene expression signatures and DNA variants for individual RCC-specific driver genes of interest based on published reports. Methods: Patients (pts) with metastatic RCC were treated with lenva 20 mg orally once daily + pembro 200 mg intravenously once every 3 weeks. The analysis population included pts with treatment-naive (n=10) and ICI pretreated (n=70) disease with evaluable RNA-sequencing data for the 18-gene T-cell–inflamed gene expression profile (TcellinfGEP) and for 11 other signatures (angiogenesis; glycolysis; gMDSC; hypoxia; mMDSC; MVD; MYC; proliferation; RAS; stroma/EMT/TGFβ; WNT) and whole exome sequencing (WES) data for DNA variants for individual genes ( VHL, PBRM1, BAP1, and SETD2). Specimens were collected prior to the start of treatment. The associations between each signature score and ORR and PFS per immune-related RECIST were evaluated using logistic regression and Cox proportional hazards, respectively. One-sided P values for TcellinfGEP (hypothesized positive association) and two-sided P values for all other signatures (no hypothesized association) were adjusted for multiplicity using the Hochberg step-up procedure; significance was prespecified at α=0.05. The association between DNA variants for individual genes and ORR was evaluated descriptively. Clinical data cutoff was August 18, 2020. Results: Of 147 treated pts, RNA sequencing and WES data were available for 80 (54%) and 60 (41%), respectively. TcellinfGEP was not associated with ORR ( P=0.827) or PFS ( P=0.741), nor were the other 11 signatures before or after adjustment for TcellinfGEP. ORR for DNA variants reported in the table. Conclusions: In this exploratory analysis of pts with metastatic RCC enrolled in Study 111/KEYNOTE-146 treated with lenva + pembro, responses were observed regardless of biomarker status. There were no statistically significant associations between gene signatures and clinical outcomes. Clinical benefit was observed regardless of VHL, PBRM1, BAP1, or SETD2 mutation status. Analyses in larger randomized datasets will provide additional information on the role of biomarkers in RCC. Clinical trial information: NCT02501096. [Table: see text]

Current strategies for intratumoural immunotherapy - Beyond immune checkpoint inhibition

Immunotherapy has revolutionised cancer treatment through restoration of host antitumour immune response. Immune checkpoint inhibitors (ICIs) confer durable responses in only a subset of patients. Mechanisms of ICI resistance to improve durable response rates and overall survival are an area of intense clinical research. Robust clinical development is ongoing to evaluate novel combination therapies to overcome ICI resistance, including targeting immunoregulatory pathways in the tumour microenvironment. Intratumoural (IT) immunotherapies such as toll-like receptor agonists, stimulator of interferon-induced gene agonists, retinoic-inducible gene I-like receptor agonists and oncolytic viruses may represent potential combination treatment options to overcome ICI resistance. Use of IT immunotherapies in combination with ICIs may alter the tumour microenvironment to address resistance mechanisms and improve antitumour response. Optimisation of IT immunotherapy clinical trials will elucidate resistance mechanisms, facilitate clinical trial design, define pharmacodynamic predictors that identify patients who may most benefit and inform clinical development of combination immunotherapy regimens. Here we provide an overview of IT immunotherapy principles, mechanisms of action, categories of IT immunotherapeutics, emerging data, clinical development strategies, response assessment, dose and schedule determination, clinical trial design and translational study design.

Molecular determinants of clinical outcomes with pembrolizumab versus paclitaxel in a randomized, open-label, phase III trial in patients with gastroesophageal adenocarcinoma

BACKGROUND

In the phase III KEYNOTE-061 trial (NCT02370498), pembrolizumab did not significantly improve overall survival versus paclitaxel as second-line therapy for gastric/gastroesophageal junction (GEJ) adenocarcinoma with programmed death-ligand 1 (PD-L1) combined positive score (CPS) ≥1 tumors. The association of tissue tumor mutational burden (tTMB) status and clinical outcomes was determined, including the relationship with CPS and microsatellite instability-high (MSI-H) status.

PATIENTS AND METHODS

In patients with whole exome sequencing (WES) data [420/592 (71%); pembrolizumab, 218; paclitaxel, 202], the association of tTMB with objective response rate (ORR; logistic regression), progression-free survival (PFS; Cox proportional hazards regression), and overall survival (OS; Cox proportional hazards regression) were measured using one-sided (pembrolizumab) and two-sided [paclitaxel] P values. tTMB was also evaluated using FoundationOne®CDx [205/592 (35%)]. Prespecified equivalent cut-offs of 175 mut/exome for WES and 10 mut/Mb for FoundationOne®CDx were used.

RESULTS

WES-tTMB was significantly associated with ORR, PFS, and OS in pembrolizumab-treated (all P < 0.001) but not paclitaxel-treated patients (all P > 0.6) in univariate analysis. The area under the receiver operating characteristics curve for WES-tTMB and response was 0.68 [95% confidence interval (CI) 0.56-0.81] for pembrolizumab and 0.51 (95% CI 0.39-0.63) for paclitaxel in univariate analysis. There was low correlation between WES-tTMB and CPS in both treatment groups (r ≤ 0.16). WES-tTMB remained significantly associated with all clinical endpoints with pembrolizumab after adjusting for CPS and with PFS and OS after excluding known MSI-H tumors (n = 26). FoundationOne®CDx-tTMB demonstrated a positive association with ORR, PFS, and OS in pembrolizumab-treated patients (all P ≤ 0.003) but not PFS or OS in paclitaxel-treated patients (P > 0.1).

CONCLUSION

This exploratory analysis from KEYNOTE-061 is the first to demonstrate a strong association between tTMB and efficacy with pembrolizumab but not paclitaxel in patients with gastric/GEJ adenocarcinoma in a randomized setting. Data further suggest tTMB is a significant and independent predictor beyond PD-L1 status.

The association of tissue tumor mutational burden (tTMB) using the Foundation Medicine genomic platform with efficacy of pembrolizumab versus paclitaxel in patients (pts) with gastric cancer (GC) from KEYNOTE-061

4537

Background: KEYNOTE-061 (NCT02370498) was a randomized, open-label, phase 3 study of pembrolizumab vs paclitaxel in pts with advanced gastric or gastroesophageal junction (GEJ) adenocarcinoma with tumor progression after first-line therapy (N = 592). In this analysis, we evaluated tTMB using FoundationOne CDx (F1CDx; Foundation Medicine) in pts with gastric or GEJ cancer in KEYNOTE-061. Methods: In pts with evaluable F1CDx tTMB data (n = 204), we analyzed the association of tTMB with confirmed objective response rate (ORR), progression-free survival (PFS), and overall survival (OS) within each treatment arm using one-sided (pembrolizumab) and two-sided (paclitaxel) Wald test nominal P for logistic regression (ORR) and Cox proportional hazards regression (PFS; OS) adjusted for ECOG performance status; significance was prespecified at 0.05. The clinical utility of tTMB was assessed using the prespecified cutoff of 10 mut/Mb for F1CDx. Clinical data cutoff: Oct 26, 2017. Results: tTMB was positively associated with ORR ( P < 0.001; AUROC, 0.68), PFS ( P < 0.001), and OS ( P = 0.003) with pembrolizumab but not paclitaxel (ORR, P = 0.047; AUROC, 0.30; PFS, P = 0.605; OS, P = 0.084). Pt outcomes by tTMB cutoff are reported in the Table; prevalence of TMB ≥10 mut/Mb was 17%. In pts with microsatellite stable disease-only, HRs (95% CI) by treatment arm for OS by F1CDx cutoff were 0.40 (0.14-1.17) for tTMB ≥10 mut/Mb (n = 21) vs 0.97 (0.70-1.34) for tTMB <10 mut/Mb (n = 168). Conclusions: In this exploratory analysis from KEYNOTE-061, tTMB as determined by F1CDx demonstrated a positive association with clinical outcomes with pembrolizumab, but not paclitaxel, in pts with GC; these findings are consistent with those reported with whole exome sequencing. Pembrolizumab demonstrated an OS benefit vs paclitaxel in the subgroup with tTMB ≥10 mut/Mb, which remained when pts with microsatellite instability-high disease were excluded. Clinical trial information: NCT02370498 . [Table: see text]

The association of molecular biomarkers with efficacy of pembrolizumab versus paclitaxel in patients with gastric cancer (GC) from KEYNOTE-061

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Background: KEYNOTE-061 (NCT02370498) was a randomized, open-label, phase 3 study of pembrolizumab vs paclitaxel in patients with advanced gastric or gastroesophageal junction adenocarcinoma with tumor progression after first-line therapy (N =592). We explored the association of tissue tumor mutational burden (tTMB) status and clinical outcomes in patients with GC enrolled in KEYNOTE-061, including the relationship with PD-L1 combined positive score (CPS) and microsatellite instability-high (MSI-H) status. Methods: In patients from KEYNOTE-061 with evaluable tumor and matched normal whole exome sequencing (WES) data (N = 420; pembrolizumab, 218; paclitaxel, 202), the association of tTMB (continuous log10 scale) with confirmed ORR and PFS by blinded central radiology review per RECIST v1.1, and OS was evaluated within each treatment arm using logistic regression (ORR) and Cox proportional hazards regression (PFS; OS). The clinical utility of tTMB was assessed using the prespecified cutoff of 175 mut/exome. Clinical data cutoff: October 26, 2017. Results: tTMB was significantly associated (α=0.05) with ORR, PFS, and OS in patients treated with pembrolizumab (one-sided P<0.001) but not paclitaxel (two-sided P>0.600). The area under the receiver operating characteristics curve for tTMB and response (pembrolizumab vs paclitaxel) was 0.68 (95% CI, 0.56-0.81) vs 0.51 (95% CI, 0.39-0.63). Patient outcomes by tTMB cutoff are reported in Table. There was low correlation between tTMB and PD-L1 CPS in both treatment arms (r<0.18). tTMB remained significantly associated with all clinical end points with pembrolizumab after adjusting for PD-L1 CPS and with PFS and OS after excluding MSI-H patients. Conclusions: This exploratory analysis from KEYNOTE-061 is the first to demonstrate a strong association between tTMB and response to pembrolizumab in patients with GC. Data further suggest tTMB is a significant and independent predictor beyond PD-L1 status. Clinical trial information: NCT02370498 . [Table: see text]

KEYNOTE-811 pembrolizumab plus trastuzumab and chemotherapy for HER2+ metastatic gastric or gastroesophageal junction cancer (mG/GEJc): A double-blind, randomized, placebo-controlled phase III study

TPS463

Background: Combination therapy with the anti-HER2 antibody trastuzumab plus fluoropyrimidine and platinum is the current standard of care for patients with HER2+ mG/GEJc. We hypothesize that combination anti–PD-1 and anti-HER2 therapy will result in T-cell activation, augment antibody-dependent, cell-mediated cytotoxicity, and potentiate antitumor immune response in HER2+ patients. A phase 2 study in HER2+ mG/GEJc demonstrated the safety and preliminary efficacy of trastuzumab/pembrolizumab/chemotherapy; the objective response rate was 87%, and the disease control rate was 100% (Janjigian YY, ASCO GI 2019). KEYNOTE-811 (ClinicalTrials.gov, NCT03615326), a global, multicenter, randomized, placebo-controlled, phase 3 study, is underway. Methods: Key eligibility criteria are age ≥18 years; previously untreated unresectable or metastatic HER2+ (centrally confirmed IHC 3+ or IHC 2+/ISH > 2.0) G/GEJ cancer; life expectancy > 6 months with RECIST v1.1 measurable disease; and adequate organ function and performance status (ECOG PS of 0 or 1). Patients will be randomly assigned 1:1 to receive chemotherapy with pembrolizumab 200 mg intravenously (IV) or placebo with trastuzumab 6 mg/kg (after 8 mg/kg load) every 3 weeks (Q3W) up to 2 years or until intolerable toxicity or disease progression. Investigator-choice chemotherapy will include day 1 cisplatin 80 mg/m2 IV and 5-fluorouracil 800 mg/m2/day IV (days 1-5) or oxaliplatin 130 mg/m2 IV and capecitabine 1000 mg/m2 BID days 1-14 (Q3W). Primary end points are progression-free survival and overall survival. Secondary end points are objective response rate, duration of response, and safety and tolerability. Adverse events are graded per CTCAE v4.0 and will be monitored for 30 or 90 days after treatment. Patients will be followed up for survival. Planned enrollment is approximately 692 patients. Clinical trial information: NCT03615326.

KEYNOTE-811 pembrolizumab plus trastuzumab and chemotherapy for HER2+ metastatic gastric or gastroesophageal junction cancer (mG/GEJC): A double-blind, randomized, placebo-controlled phase 3 study

TPS4146

Background: Combination therapy with the anti-HER2 antibody trastuzumab with fluoropyrimidine and platinum is the current standard for patients with HER2+ mG/GEJc. We hypothesize that combination anti–PD-1 and anti-HER2 therapy will result in T-cell activation, augment ADCC, and potentiate antitumor immune response in HER2+ patients. This phase 2 study in HER2+ mG/GEJc demonstrated the safety and preliminary efficacy of trastuzumab/pembrolizumab/chemotherapy; the overall response rate was 87%, and the disease control rate was 100% Janjigian YY, ASCO GI 2019). KEYNOTE 811, a global, multicenter, randomized, placebo-controlled, phase 3 study, is underway. Methods: Key eligibility criteria are age ≥18 years; previously untreated unresectable or metastatic HER2+ (centrally confirmed IHC 3+ or IHC 2+/ISH >2.0) G/GEJ adenocarcinoma; life expectancy >6 months with RECIST v1.1 measurable disease; adequate organ function and performance status. Patients will be randomly assigned 1:1 to receive chemotherapy with pembrolizumab 200 mg IV flat dose or placebo with trastuzumab 6 mg/kg (after 8 mg/kg load) Q3W up to 2 years or until intolerable toxicity or disease progression. Investigator choice chemotherapy will include day 1 cisplatin 80 mg/m2 IV and /5-fluorouracil 800 mg/m2/day IV (days 1-5) or oxaliplatin 130 mg/m2 IV and capecitabine 1000 mg/m2 BID days 1-14 (Q3W). Primary end points are progression-free survival and overall survival. Secondary end points are objective response rate, duration of response, and safety and tolerability. Adverse events are graded per NCI CTCAE v4.0 and will be monitored for 30 or 90 days after treatment. Patients will be followed up for survival. Planned enrollment is approximately 692 patients. Clinical trial information: NCT03615326.

The brain microenvironment mediates resistance in luminal breast cancer to PI3K inhibition through HER3 activation

Although targeted therapies are often effective systemically, they fail to adequately control brain metastases. In preclinical models of breast cancer that faithfully recapitulate the disparate clinical responses in these microenvironments, we observed that brain metastases evade phosphatidylinositide 3-kinase (PI3K) inhibition despite drug accumulation in the brain lesions. In comparison to extracranial disease, we observed increased HER3 expression and phosphorylation in brain lesions. HER3 blockade overcame the resistance of HER2-amplified and/or PIK3CA-mutant breast cancer brain metastases to PI3K inhibitors, resulting in marked tumor growth delay and improvement in mouse survival. These data provide a mechanistic basis for therapeutic resistance in the brain microenvironment and identify translatable treatment strategies for HER2-amplified and/or PIK3CA-mutant breast cancer brain metastases.

Nivolumab + ipilimumab combination in patients with DNA mismatch repair-deficient/microsatellite instability-high (dMMR/MSI-H) metastatic colorectal cancer (mCRC): First report of the full cohort from CheckMate-142

553

Background: Nivolumab (NIVO) provided durable responses (investigator-assessed [INV] ORR, 31%) and disease control (DCR, 69%) in pretreated pts with dMMR/MSI-H mCRC in CheckMate-142 (NCT02060188; Overman et al Lancet Oncol 2017). An interim analysis of the NIVO + ipilimumab (IPI) combination cohort of CheckMate-142 reported a preliminary ORR of 55% and manageable safety profile in a subset of pts (n = 84) with dMMR/MSI-H mCRC and ≥ 6 mo of follow-up (André et al ASCO 2017). Here we report for the first time efficacy and safety from the complete population (N = 119) of the NIVO + IPI cohort of CheckMate-142, which is the largest single-study report of an immunotherapy regimen in pts with dMMR/MSI-H mCRC. Methods: Pts with dMMR/MSI-H mCRC received NIVO 3 mg/kg + IPI 1 mg/kg Q3W for 4 doses followed by NIVO 3 mg/kg Q2W. Primary endpoint was ORR (INV; RECIST 1.1). Other endpoints were DOR, PFS, OS, and safety/tolerability. Results: Of 119 treated pts, 76% had ≥ 2 prior lines of therapy. Median follow-up was 13.4 mo. The ORR was 55% and DCR was 80% (Table). Notably, ORR in pts with a BRAF mutation was 55%. Among all responders, median DOR was not reached (NR), with 94% of responses ongoing at data cutoff. Tumor burden was reduced from baseline in 77% of pts. The 9-mo PFS and OS rates were 76% and 87%, respectively. Gr 3–4 TRAEs occurred in 32% of pts; 13% (any gr) and 10% (gr 3–4) of pts had TRAEs that led to discontinuation. No treatment-related deaths were reported. Results including a similar follow-up of the NIVO arm will also be presented. Conclusions: In the largest cohort of dMMR/MSI-H pts treated with an immunotherapy regimen, NIVO + IPI built on the efficacy reported with NIVO monotherapy, demonstrating enhanced clinical benefit and manageable safety, and may represent a new standard of care in pts with dMMR/MSI-H mCRC. Clinical trial information: NCT02060188. [Table: see text]

Nivolumab in patients with DNA mismatch repair-deficient/microsatellite instability-high (dMMR/MSI-H) metastatic colorectal cancer (mCRC): Long-term survival according to prior line of treatment from CheckMate-142

554

Background: Nivolumab (NIVO) provided durable responses (ORR, 32% per central assessment) and disease control (DCR, 64%) in pre-treated pts with dMMR/MSI-H mCRC (NCT02060188; Overman MJ et al Lancet Oncol 2017). NIVO was approved in the US for pts with dMMR/MSI-H mCRC who progress after standard chemotherapy (SC) with a fluoropyrimidine (F), oxaliplatin (Ox), and irinotecan (Iri). Here we present long-term survival and outcomes by prior chemotherapy with NIVO in CheckMate-142. Methods: Pts with dMMR/MSI-H mCRC received NIVO 3 mg/kg Q2W. The primary endpoint was ORR per RECIST 1.1. Other endpoints were DCR, DOR, PFS, OS, and safety/tolerability. Results: Of 74 pts evaluated, 53 had received F, Ox and Iri (group A); 21 pts had ≤ 2 SC regimens (group B). Median follow-up was 21 mo. Efficacy by central assessment is shown in the Table. In the 74 pts, ORR was 34%; CRs increased from 3% in prior database lock (DBL) to 9%. Numerically higher responses were noted in group B vs group A (Table). Grade 3–4 TRAEs were reported in 20% (all pts), 25% (group A), and 10% (group B) of pts. No treatment-related deaths were reported. Conclusions: NIVO continued to provide clinically meaningful durable responses and long-term overall survival in pts with dMMR/MSI-H mCRC. Of note, CR rate increased with longer follow-up. No new safety signals were reported with long-term follow-up. Enhanced responses in pts with ≤ 2 SC regimens support ongoing evaluation of NIVO combinations in first-line setting. Clinical trial information: NCT02060188. [Table: see text]

Durable Clinical Benefit With Nivolumab Plus Ipilimumab in DNA Mismatch Repair-Deficient/Microsatellite Instability-High Metastatic Colorectal Cancer

Purpose Nivolumab provides clinical benefit (objective response rate [ORR], 31%; 95% CI, 20.8 to 42.9; disease control rate, 69%; 12-month overall survival [OS], 73%) in previously treated patients with DNA mismatch repair-deficient (dMMR)/microsatellite instability-high (MSI-H) metastatic colorectal cancer (mCRC); nivolumab plus ipilimumab may improve these outcomes. Efficacy and safety results for the nivolumab plus ipilimumab cohort of CheckMate-142, the largest single-study report of an immunotherapy combination in dMMR/MSI-H mCRC, are reported. Patients and Methods Patients received nivolumab 3 mg/kg plus ipilimumab 1 mg/kg once every 3 weeks (four doses) followed by nivolumab 3 mg/kg once every 2 weeks. Primary end point was investigator-assessed ORR. Results Of 119 patients, 76% had received ≥ two prior systemic therapies. At median follow-up of 13.4 months, investigator-assessed ORR was 55% (95% CI, 45.2 to 63.8), and disease control rate for ≥ 12 weeks was 80%. Median duration of response was not reached; most responses (94%) were ongoing at data cutoff. Progression-free survival rates were 76% (9 months) and 71% (12 months); respective OS rates were 87% and 85%. Statistically significant and clinically meaningful improvements were observed in patient-reported outcomes, including functioning, symptoms, and quality of life. Grade 3 to 4 treatment-related adverse events (AEs) occurred in 32% of patients and were manageable. Patients (13%) who discontinued treatment because of study drug-related AEs had an ORR (63%) consistent with that of the overall population. Conclusion Nivolumab plus ipilimumab demonstrated high response rates, encouraging progression-free survival and OS at 12 months, manageable safety, and meaningful improvements in key patient-reported outcomes. Indirect comparisons suggest combination therapy provides improved efficacy relative to anti-programmed death-1 monotherapy and has a favorable benefit-risk profile. Nivolumab plus ipilimumab provides a promising new treatment option for patients with dMMR/MSI-H mCRC.

Nivolumab in patients with metastatic DNA mismatch repair-deficient or microsatellite instability-high colorectal cancer (CheckMate 142): an open-label, multicentre, phase 2 study

BACKGROUND

Metastatic DNA mismatch repair-deficient (dMMR)/microsatellite instability-high (MSI-H) colorectal cancer has a poor prognosis after treatment with conventional chemotherapy and exhibits high levels of tumour neoantigens, tumour-infiltrating lymphocytes, and checkpoint regulators. All of these features are associated with the response to PD-1 blockade in other tumour types. Therefore, we aimed to study nivolumab, a PD-1 immune checkpoint inhibitor, in patients with dMMR/MSI-H metastatic colorectal cancer.

METHODS

In this ongoing, multicentre, open-label, phase 2 trial, we enrolled adults (aged ≥18 years) with histologically confirmed recurrent or metastatic colorectal cancer locally assessed as dMMR/MSI-H from 31 sites (academic centres and hospitals) in eight countries (Australia, Belgium, Canada, France, Ireland, Italy, Spain, and the USA). Eligible patients had progressed on or after, or been intolerant of, at least one previous line of treatment, including a fluoropyrimidine and oxaliplatin or irinotecan. Patients were given 3 mg/kg nivolumab every 2 weeks until disease progression, death, unacceptable toxic effects, or withdrawal from study. The primary endpoint was investigator-assessed objective response as per Response Evaluation Criteria in Solid Tumors (version 1.1). All patients who received at least one dose of study drug were included in all analyses. This trial is registered with ClinicalTrials.gov, number NCT02060188.

FINDINGS

Of the 74 patients who were enrolled between March 12, 2014, and March 16, 2016, 40 (54%) had received three or more previous treatments. At a median follow-up of 12·0 months (IQR 8·6-18·0), 23 (31·1%, 95% CI 20·8-42·9) of 74 patients achieved an investigator-assessed objective response and 51 (69%, 57-79) patients had disease control for 12 weeks or longer. Median duration of response was not yet reached; all responders were alive, and eight had responses lasting 12 months or longer (Kaplan-Meier 12-month estimate 86%, 95% CI 62-95). The most common grade 3 or 4 drug-related adverse events were increased concentrations of lipase (six [8%]) and amylase (two [3%]). 23 (31%) patients died during the study; none of these deaths were deemed to be treatment related by the investigator.

INTERPRETATION

Nivolumab provided durable responses and disease control in pre-treated patients with dMMR/MSI-H metastatic colorectal cancer, and could be a new treatment option for these patients.

FUNDING

Bristol-Myers Squibb.

An open-label, multicohort, phase I/II study of nivolumab in patients with virus-associated tumors (CheckMate 358): Efficacy and safety in recurrent or metastatic (R/M) cervical, vaginal, and vulvar cancers

5504

Background: Treatment options for cervical, vaginal, and vulvar (GYN) cancers are limited after first-line therapy. Human papillomavirus (HPV) infection is associated with squamous cell carcinomas of the cervix (≥90%) and vulva/vagina (40–70%), and may elicit an immune reaction. Programmed death (PD)-1 and its major ligand PD-L1 are expressed in GYN cancers and inhibit immune responses. Nivolumab disrupts PD-1–mediated signaling, restoring antitumor immunity. Methods: In CheckMate 358 (NCT02488759), an ongoing multicohort study of 5 virus-associated cancers, PD-L1–unselected adults with R/M GYN cancers, ECOG PS 0–1, and ≤2 prior systemic therapies for R/M disease were eligible to receive nivolumab 240 mg every 2 weeks until progression or unacceptable toxicity. Primary endpoints were objective response rate (ORR) and safety; secondary endpoints were duration of response (DoR), progression-free survival (PFS), and overall survival (OS). Results: Of 24 treated patients (pts), 19 had cervical and 5 had vaginal or vulvar cancer; median age was 51 y. At a median follow-up of 31 wks (range: 6–38), ORR was 20.8% (Table), and disease control rate (ORR + SD) was 70.8%. All responses were in pts with cervical cancer (ORR, 26.3%) and were observed regardless of PD-L1 or HPV status or number of prior R/M therapies. Median PFS was 5.5 mo (95% CI: 3.5, NR); median OS was NR. Conclusions: Nivolumab demonstrated encouraging clinical activity in pts with cervical cancer and a manageable safety profile in virus-associated GYN cancers, supporting further evaluation in these pts. Updated clinical and biomarker data to be presented. Clinical trial information: NCT02488759. [Table: see text]

An open-label, multicohort, phase I/II study to evaluate nivolumab in patients with virus-associated tumors (CheckMate 358): Efficacy and safety in recurrent or metastatic (R/M) nasopharyngeal carcinoma (NPC)

6025

Background: Treatment options for patients (pts) with R/M NPC are limited to palliative chemotherapy. NPC is often associated with the Epstein–Barr virus (EBV), a potential antigen for immune recognition, and high expression levels of the immune checkpoint receptor programmed death-1 (PD-1) and its major ligand PD-L1. Nivolumab disrupts PD-1–mediated signaling, restoring T-cell antitumor function. Methods: In CheckMate 358 (NCT02488759), PD-L1–unselected adults with R/M NPC, ECOG PS of 0–1, and ≤2 prior systemic therapies in the R/M setting were eligible to receive nivolumab 240 mg every 2 weeks until progression or unacceptable toxicity, as part of an ongoing multicohort study of 5 virus-associated cancers. Human papillomavirus-associated NPC and keratinizing squamous cell carcinoma (WHO Type 1) were excluded. Primary endpoints were objective response rate (ORR) and safety; secondary endpoints were duration of response (DoR), progression-free survival (PFS), and overall survival (OS). Results: Of 24 treated pts with R/M NPC, median age was 51 years, 88% were male, 62% were white, 88% were European, and 88% had EBV+ tumors. At a median follow-up of 26 weeks (range: 4–40), ORR was 20.8% and appeared to be higher in pts with no prior R/M therapy (Table). The disease control rate (ORR + SD) was 45.8%. Responses were observed regardless of PD-L1 or EBV status. Median PFS was 2.4 mo (95% CI: 1.5, NR); median OS was NR. Conclusions: Nivolumab demonstrated clinical activity and a manageable safety profile in R/M NPC, supporting ongoing research with nivolumab in this disease. Updated efficacy and biomarker data will be presented. Clinical trial information: NCT02488759. [Table: see text]

Concordance of DNA mismatch repair deficient (dMMR)/microsatellite instability (MSI) assessment by local and central testing in patients with metastatic CRC (mCRC) receiving nivolumab (nivo) in CheckMate 142 study

3548

Background: MMR or MSI testing is recommended for mCRC pts and is often done locally by IHC or PCR testing, respectively (NCCN V1.2017) Nivo, a fully human anti-PD-1 mAb, demonstrated durable responses and a 12-mo OS rate of 73.8% in pts with mCRC locally assessed for dMMR/MSI-H status in the CheckMate 142 study (NCT02060188; Overman M, et al. 2017). Here we describe the results of local and central testing with respect to MMR/MSI status and clinical outcomes in the CheckMate 142 study. Methods: MMR/MSI status was assessed locally on archival tumor using IHC/PCR at screening and confirmed centrally by PCR (modified Bethesda panel) testing of tumor biopsy at enrollment. dMMR was defined by IHC as a loss of expression in ≥1 mismatch repair proteins. Stable microsatellite (MSS), low MSI (MSI-L), and high MSI (MSI-H), were defined as instability in 0, 1, or ≥2 markers, respectively. Pts with dMMR/MSI-H mCRC who progressed on or were intolerant of ≥1 prior line of therapy received nivo 3 mg/kg Q2W. Results: 74 pts were dMMR/MSI-H by local testing. Of these pts, 53 (72%) were centrally confirmed as MSI-H, 7 pts had insufficient tissue sample for PCR testing, and 14 pts had a central test that did not match local test results. Of the 14 pts, 3 pts with a clinical history of LS were identified locally as dMMR but centrally as MSS (Table). INV-reported ORR was 31.1% in 74 pts locally determined as dMMR/MSI-H, 35.8% in 53 pts locally and centrally confirmed as MSI-H, and 21.4% in 14 pts not centrally confirmed as MSI-H. Conclusions: The similar clinical activity between pts locally confirmed as MSI-H and pts who were centrally confirmed as MSI-H suggest local testing is appropriate for identifying the dMMR/MSI-H pts who may benefit from nivo monotherapy. Clinical trial information: NCT02060188. [Table: see text]

Combination of nivolumab (nivo) + ipilimumab (ipi) in the treatment of patients (pts) with deficient DNA mismatch repair (dMMR)/high microsatellite instability (MSI-H) metastatic colorectal cancer (mCRC): CheckMate 142 study

3531

Background: Nivo, a fully human anti-PD-1 mAb, provided an ORR of 31%, durable responses (median DOR not reached), and a 12-mo OS rate of 73.8% in pts with dMMR/MSI-H mCRC (Overman M, et al. 2017). Preliminary analysis of nivo + ipi, a humanized anti-CTLA-4 mAb, demonstrated manageable safety and promising efficacy in pts with dMMR/MSI-H mCRC (Overman M, et al . 2016). Here we report interim safety and efficacy of nivo + ipi in this pt population from the Checkmate 142 study (NCT02060188). Methods: Pts with dMMR/MSI-H mCRC who progressed on or were intolerant of ≥1 prior line of therapy received nivo 3 mg/kg + ipi 1 mg/kg q3w × 4 doses followed by nivo 3 mg/kg q2w until discontinuation due to disease progression or other reason. Primary endpoint was investigator-reported ORR by RECIST 1.1. Other endpoints included DOR, PFS, OS, safety, and tolerability. Results: 27 pts with dMMR/MSI-H mCRC treated with nivo + ipi received the first dose ≥6 mo prior to the database lock (DBL; Sept 2016). Of these pts, 93% received ≥2 prior lines of therapy. At the time of DBL, 44% of pts remained on treatment, and 14 pts had discontinued therapy due to disease progression (n=8) or TRAEs (n=6). ORR was 41% and disease control rate (DCR) was 78% (Table). The median time to response was 2.7 mo, and 82% of responses (9/11) were ongoing at 6 mo. The medians for DOR, PFS and OS had not been reached. Grade 3–4 TRAEs occurred in 10 pts (37%).TRAEs leading to discontinuation included acute kidney injury, increased transaminases, necrotizing myositis, sarcoidosis, dyspnea, and thrombocytopenia (1 each). No deaths were attributed to therapy. Conclusions: Initial analysis ofnivo + ipi in pts with ≥6-mo follow-up demonstrated a manageable safety profile and clinical activity characterized by a high DCR and encouraging survival benefit. This study is ongoing, and updated efficacy and biomarker analyses of ≈80 pts with ≥6-mo follow-up will be presented. Clinical trial information: NCT02060188. [Table: see text]

Nivolumab in patients with DNA mismatch repair deficient/microsatellite instability high metastatic colorectal cancer: Update from CheckMate 142

519

Background: Approximately 4% of metastatic colorectal cancers (mCRCs) are associated with high microsatellite instability (MSI-H), indicating a deficient DNA mismatch repair (dMMR) system. dMMR/MSI-H CRC exhibits an increased tumor neoantigen load and immune cell infiltration and is hypothesized to be targetable by immune checkpoint inhibitors. CheckMate 142 (NCT02060188) evaluates the efficacy and safety of nivolumab (nivo) in patients (pts) with dMMR/MSI-H mCRC. Methods: Pts with dMMR/MSI-H mCRC who progressed on/were intolerant to ≥1 prior line of therapy received nivo 3 mg/kg (nivo 3) every 2 weeks (Q2W). The primary endpoint was objective response rate (ORR) per investigator (INV). The secondary endpoint was ORR per independent radiology review committee (IRRC); exploratory endpoints included safety, PFS, OS, and efficacy in biomarker-defined populations. Results: Among pts treated with nivo 3 Q2W (N = 74), 84% had received ≥2 prior lines of therapy. ORRs were 31% (INV) and 27% (IRRC); disease control rates were 69% (INV) and 62% (IRRC). The median time to response was ≈2.7 mo (INV/IRRC). PFS rates at 12 mo were 48.4% (INV) and 45.6% (IRRC). The duration of response and OS medians were not yet reached; OS rates were 83.4% (6 mo) and 73.8% (12 mo). Responses were observed in pts regardless of tumor programmed death-1 ligand 1 (PD-L1) expression level or BRAF or KRAS mutation status and were observed in pts with or without a history of Lynch syndrome (Table). Grade 3–4 treatment-related adverse events (TRAEs) occurred in 20% of pts. TRAEs leading to discontinuation included acute kidney injury, increased ALT, colitis, and stomatitis (1 each). No treatment-related deaths occurred in this arm. Conclusions: Nivo showed durable responses and disease control in heavily pretreated pts with dMMR/MSI-H mCRC. Treatment was well tolerated, with no new safety signals. Clinical trial information: NCT02060188. [Table: see text]

Abstract PR03: Molecular characterization of in vitro exhausted T cells

In previous work we observed that restimulating human PBMCs with anti-CD3/28 beads 4 days after a primary stimulation resulted in an exhausted phenotype, as characterized by loss of T cells' ability to secrete IL-2, TNFa, and IFNg. To further characterize the molecular phenotype of these cells, we isolated CD4+ and CD8+ T cells from our exhausted and non-exhausted samples and performed Nanostring gene expression analysis. Both exhausted CD4+ and CD8+ T cells exhibited upregulation of a 25-gene exhaustion gene signature, as compared to non-exhausted control cells. In addition, a number of immunologically important molecules are modulated in the exhausted cells. For example, MIF (macrophage migration inhibitory factor) mRNA is induced in the exhausted T cells. Closer examination of MIF expression in TCGA suggests that MIF level is inversely correlated to survival in indications such as HCC and H/N cancer. Furthermore, pathway analysis of differential gene expression revealed the JAK/STAT signaling pathway as significantly upregulated in the exhausted cells. Treatment of exhausted cells with a JAK inhibitor resulted in a partial reversal of the exhausted phenotype, as shown by restored cytokine secretion. Thus we show for the first time the involvement of JAK signaling in human T cell exhaustion, which may provide rationale for combining JAK inhibitors with other immune therapies for cancer. In summary, the in vitro T cell exhaustion model system has yielded intriguing activity nodes during T cell function. Future exploration in such immunological states may identify novel therapeutic targets and combination opportunities for immuno-oncology.

This abstract is also being presented as Poster B17.

Citation Format: William Hastings, Kenzie MacIsaac, Wei Guan, Pamela Shaw, Glenn Dranoff, Z Alexander Cao. Molecular characterization of in vitro exhausted T cells. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Targeting the Vulnerabilities of Cancer; May 16-19, 2016; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(1_Suppl):Abstract nr PR03.

Abstract 854: Mutation load measured using a 315 gene panel predicts genome-wide mutation load

High tumor mutation load has been associated with better response to immunotherapy. Measuring mutation load via whole-genome DNA sequencing can be cost prohibitive and requires extensive analysis and data management. Targeted genomic, on the other hand, are an appealing alternative. However it is unclear how mutation load assessed using a sample of hundreds of genes relates to genome-wide mutation burden. Here we use mutation data from The Cancer Genome Atlas (TCGA) to investigate if the exonic mutation load in a small set of genes can be used to predict the genome-wide exonic mutation load.

Using a gene panel composed of 315 genes, we observed a strong (R = 0.72) positive correlation between the total mutation burden and the gene panel mutation burden. To determine whether these genes allow high and low mutation burden samples to be accurately identified, we derived various classifiers on a training set of TCGA samples and evaluated their performance on held-out test data. High mutation load was defined as greater than 181 non-synonymous mutations. This threshold best distinguished microsatellite instable (MSI) high training set samples from MSI low and microsatellite stable (MSS) samples (95% true positive rate and 15% false positive rate).

Receiver operating characteristic (ROC) curve analysis revealed that the 315-gene panel had excellent power to discriminate high and low mutation samples, with the area under the ROC curve evaluated on held-out test data ranging from 0.85 to 0.97 across indications. Our analysis suggests that the optimal threshold for identifying high mutation load samples may vary by indication.

Our models were trained and tested using data generated by the TCGA consortium on pre-treatment patient biopsies. Direct application of our classifiers to clinical data would assume similar mutation calling sensitivity between platforms and similar underlying patient populations. To test these assumptions, we compared the mutational loads between TCGA and clinical samples within the same indication. We further performed a sensitivity analysis using a simulation-based approach which showed how deviations from these underlying assumptions would be expected to affect classification performance.

These results demonstrate the feasibility of using mutation burden in a cancer related gene panel as a biomarker for genome-wide mutation load. This approach may be useful in identifying patients more likely to respond to cancer immunotherapies, but may require development be tailored to the specific sequencing platform and patient-population of interest.

Citation Format: Artur Veloso, Z. Alexander Cao, Derek Y. Chiang, Hans Bitter, Kenzie D. MacIsaac. Mutation load measured using a 315 gene panel predicts genome-wide mutation load. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 854.

The identification and characterization of a STAT5 gene signature in hematologic malignancies

BACKGROUND

The JAK-STAT pathway is an important signaling pathway downstream of multiple cytokine and growth factor receptors. Dysregulated JAK-STAT signaling has been implicated in the pathogenesis of multiple human malignancies.

OBJECTIVE

Given this pivotal role of JAK-STAT dysregulation, it is important to identify patients with an overactive JAK-STAT pathway for possible treatment with JAK inhibitors.

METHODS

We developed a gene signature assay to detect overactive JAK-STAT signaling. The cancer cell line encyclopedia and associated gene-expression data were used to correlate the activation status of STAT5 with the induction of a set of STAT5 target genes.

RESULTS

Four target genes were identified (PIM1, CISH, SOCS2, and ID1), the expression of which correlated significantly with pSTAT5 status in 40 hematologic tumor cell lines. In pSTAT5-positive models, the expression of the gene signature genes decreased following ruxolitinib treatment, which corresponded to pSTAT5 downmodulation. In pSTAT5-negative cell lines, neither pSTAT5 modulation nor a change in signature gene expression was observed following ruxolitinib treatment.

CONCLUSIONS

The gene signature can potentially be used to stratify or enrich for patient populations with activated JAK-STAT5 signaling that might benefit from treatments targeting JAK-STAT signaling. Furthermore, the 4-gene signature is a predictor of the pharmacodynamic effects of ruxolitinib.

Abstract 5320: Targeting HER3 and EGFR in NRG1 positive and HER3 mutated lung squamous cell carcinoma

HER3 is a member of the ErbB family of receptor tyrosine kinases. Aberrant activation of HER3 as a result of HER2 amplification or neuregulin 1 (NRG1) over-expression has been demonstrated to mediate constitutive activation of downstream oncogenic signals. LJM716 is a fully human IgG1 anti-HER3 monoclonal antibody. It locks HER3 in an inactive conformation and prevents HER3 dimerization with other ErbB family members. This unique mode of action enables LJM716 to block both ligand dependent and ligand independent HER3 activation. In search of new indications that may benefit from anti-HER3 therapies, we noted that squamous cell carcinomas (SCC) tend to have relatively higher NRG1 expression as compared to their adenocarcinoma counterparts. Highest NRG1 expression was observed in the lung SCC cell lines in cell line encyclopedia (CLE). A subset of the lung SCC cell lines with high NRG1 expression are moderately sensitive to LJM716, with HER3 activation detected in all of the sensitive lines. Additionally, EGFR activation is consistently observed in our panel of squamous lung carcinoma models. In some cases, activation of HER2 and/or HER3 is also noted. We hypothesize that squamous lung carcinomas may be dependent on signaling through EGFR, HER2 and HER3. To completely block EGFR, HER2-HER3 signaling, we set to test the treatment of LJM716 and Cetixumab in a number of NGR 1 positive squamous lung carcinomas tumor models. Enhanced anti tumor activity of LJM716 and Cetixumab is observed in four out nine tumor models. Analysis of broad activation status of receptor tyrosine kinases (RTK) reveals that a subset of responsive models have activated pEGFR, pHER2 and pHER3. These data suggest that activated HER3 signaling may be important in a subset of lung squamous cell carcinoma. Combination of anti-HER3 and anti EGFR treatment is effective at inhibiting growth in these tumors.

Note: This abstract was not presented at the meeting.

Citation Format: Maria C. Pinzon-Ortiz, Xianhui Rong, Richard Versace, Qing Sheng, Z. Alexander Cao. Targeting HER3 and EGFR in NRG1 positive and HER3 mutated lung squamous cell carcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5320. doi:10.1158/1538-7445.AM2015-5320

Abstract 782: Modulation of receptor tyrosine kinase signaling by cMET inhibitor, INC280, in cMETmut/amp gastric carcinoma cell line Hs746.T

Aberrant Receptor Tyrosine Kinase (RTK) activity is one of the hallmarks of cancer. The genetic alternations of ABL and EGFR are classical examples of RTK-dependent oncogenesis. Recent data suggest that non mutated RTK signaling can form feedback pathways to serve as resistant mechanism against targeted therapies. Here, we examined the regulation of RTK signaling by a potent cMET inhibitor, INC280 (enzymatic EC50 against c-MET = 0.13 nM), in a cMET-dependent human gastric tumor model Hs746.T.

Hs746.T is a heavily cMET dependent cell line with both cMET amplication (12.9 copies) and mutation (G-T mutation at slice donor site to cause juxtamembrane domain deletion). This model is exquisitely sensitive to cMET inhibitor, INC280 in vitro (GI50 = 9 nM) and in vivo. The treatment of INC280 lead to significant inhibition of pcMET. Furthermore, the treatment of INC280 resulted in the suppression of pEGFR, though INC280 does not actively inhibit EGFR (enzymatic EC50 against EGFR &gt; 10 microM). This result supports prior reports that cMET and EGFR can form physical complex, with cMET modulating EGFR activation. Consequently, INC280 inhibited downstream signaling nodes of pAKT, pS6RP, pMEK and pERK in Hs746.T.

To examine the RTK signaling underlying possible treatment relapse, we treated Hs746.T cells chronically in vitro under increasing concentrations of INC280. After 8 weeks of treatment, Hs746.T-R cells were generated that grew at 600 nM of INC280. RTK signaling was examined in Hs746.T-R cells under treatment of INC280. As expected, cMET signaling was significantly curtailed in Hs746.T-R cells, as was pEGFR. Interestingly, pPDGFRb was elevated in Hs746.T-R, compared to the parental cell line. We hypothesize that the increased signaling through PDGFRb may serve as resistance mechanism to INC280 in Hs746.T-R cells.

In summary, we have examined RTK signaling in the cMET-dependent Hs746.T cell line. Our finding supported the notion of RTK cross-talk between cMET and EGFR in this setting. Additionally, our data reveal that additional RTK signaling (PDGFRb) can be induced under chronic treatment of INC280 to possibly mediate resistance to cMET inhibition.

Citation Format: Maria C. Pinzon-Ortiz, Xianhui Rong, Jinsheng Liang, Hui Qin Wang, Alan Huang, Robert Schlegel, Z. Alexander Cao. Modulation of receptor tyrosine kinase signaling by cMET inhibitor, INC280, in cMETmut/amp gastric carcinoma cell line Hs746.T. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 782. doi:10.1158/1538-7445.AM2015-782

Abstract 2140: Dual Wnt and EGFR-MAPK dependency of BRAFV600E-mutant colorectal cancer

Aberrant Wnt pathway activation due to inactivating mutations in the gene encoding RNF43 (an E3 ubiquitin ligase that promotes degradation of the Wnt receptors Frizzled and LRP6) may contribute to the unresponsiveness of BRAFV600E-mutant colorectal cancer (CRC) to BRAF inhibitors. Analysis of The Cancer Genome Atlas (TCGA) CRC data set reveals a striking co-occurrence of the BRAFV600E mutation and truncating mutations in RNF43. RNF43 mutations are likely to be functionally significant, as RNF43 mutations and mutations in the β-catenin destruction complex component APC are almost completely mutually exclusive. The vast majority of BRAFV600E;RNF43-mutant CRCs are hypermutable [microsatellite instability (MSI)-high phenotype]. The mismatch repair deficiency in these tumors may directly contribute to RNF43 mutagenesis, as RNF43 mutations tend to be small insertions/deletions in homopolymeric tracts. To determine if RNF43 mutations confer Wnt dependency in BRAFV600E-mutant CRC, we treated three BRAFV600E;RNF43-mutant CRC patient-derived xenograft (PDX) models with the porcupine inhibitor WNT974 (formerly LGK974), which blocks the palmitoylation and secretion of Wnt ligands. Single agent WNT974 anti-tumor activity was observed in 2/3 PDX models, and correlated with decreased tumor cell proliferation and mucinous differentiation. Single agent anti-tumor activity with the BRAF inhibitor LGX818 was also observed in 2/3 PDX models. No single agent anti-tumor activity was observed with the EGFR inhibitor cetuximab. The double combinations of WNT974+LGX818 and LGX818+cetuximab, and the triple combination of WNT974+LGX818+cetuximab were efficacious in all three BRAFV600E;RNF43-mutant CRC PDX models. In summary, the Wnt pathway and the EGFR-MAPK pathway may jointly promote tumorigenesis of BRAFV600E-mutant CRC, providing a strong rationale to treat patients with BRAFV600E-mutant CRCs harboring upstream Wnt pathway mutations with combinations of WNT974, LGX818 and/or cetuximab.

Citation Format: Youzhen Wang, Michael Palmer, Savina Jaeger, Linda Bagdasarian, Shumei Qiu, Steve Woolfenden, Ronald Meyer, Guizhi Yang, John Green, Shifeng Pan, Jun Liu, Hui Gao, Z. Alexander Cao, Andrea Myers, Margaret E. McLaughlin. Dual Wnt and EGFR-MAPK dependency of BRAFV600E-mutant colorectal cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2140. doi:10.1158/1538-7445.AM2015-2140

Abstract 2522: Molecular and cellular mechanisms underlying the therapeutic efficacy of the combination of JAK inhibitor, ruxolitinib, PIM inhibitor, LGH447, and CDK4/6 inhibitor, LEE011, in a preclinical model of myeloproliferative neoplasia

The JAK-STAT pathway is an important signaling pathway downstream of multiple cytokine and growth factor receptors. The genetic aberration of JAK2V617F and the associated activation of STAT in myeloproliferative neoplasia (MPN) is one example of the involvement of this pathway in human cancer. We have previously shown the combination benefits of combining ruxolitinib (Jak1,2 inhibitor), with LGH447 (PIM inhibitor) and LEE011 (CDK4/6 inhibitor) in a Ba/F3-JAK2V617F-driven MPN model. Here, we set to explore the molecular and cellular mechanisms underlying this combination benefit in the JAK2V617F UKE-1 model of MPN.

The triple combination of ruxolitinib, LGH447 and LEE011 resulted in sustained tumor regression in the UKE-1 model. Ruxolitinib, LGH447 and LEE011 inhibited pSTAT5, pBAD and pRb respectively. The monotherapies and the combination of ruxolitinib + LGH447 did not affect G1-S cycle. In contrast, the combination of ruxolitinib+LEE011, LGH447+LEE011 and the triple combination resulted in significant inhibition of G1-S progression. Consequently, after 72 hours of treatment, the percentage of cells in S phase decreased from 67% under DMSO to 15.8% under ruxolitinib+LEE011, and to 1.6% under the triple combination. Furthermore, monotherapies of LGH447 or LEE011 did not affect cell viability. Ruxolitinib monotherapy and ruxolitinib+LGH447 combination reduced viable cell% by 47% and 86%, respectively. The triple combination reduced it by 91%.

Our data suggest that the triple combination efficacy is the result of both cell killing and cell cycle blockade. The inhibition of JAK-PIM pathway significantly reduced cell viability. And the inclusion of CDK4/6 inhibition by LEE011 lead to more potent cell killing and cell growth arrest. Taken together, the triple combination achieves sustained tumor regression in preclinical models of MPN.

Citation Format: Maria Pinzon-Ortiz, Tyler Longmire, Xianhui Rong, Giordano Caponigro, Gary Vanasse, Benjamin H. Lee, Z. Alexander Cao. Molecular and cellular mechanisms underlying the therapeutic efficacy of the combination of JAK inhibitor, ruxolitinib, PIM inhibitor, LGH447, and CDK4/6 inhibitor, LEE011, in a preclinical model of myeloproliferative neoplasia. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2522. doi:10.1158/1538-7445.AM2015-2522

Abstract 2692: High allele frequency of KRAS functional mutations predicts resistance to MEK inhibitors: Evidence from cell lines and human tumor xenograft models

Introduction

KRAS mutant tumors represent a high unmet need for effective therapy. Even though there is no targeted therapy for KRAS, inhibitors of downstream targets like MEK have shown efficacy in preclinical studies. However, clinical trials of MEK inhibitors in KRAS-mutant tumors have not been successful, although there have been some responders. We sought to understand resistance to MEK inhibition in KRAS-mutant tumors and to develop biomarkers for patient stratification.

Results

Using DNA and RNA sequencing data from cell lines, we found that high variant allele frequency (&gt;50%) of KRAS functional mutations (G12, G13, Q61) was associated with baseline resistance to MEK inhibitors AZD6244 and MEK162 across multiple tumor types. Low allele frequency of KRAS mutation was found to be necessary but not sufficient for sensitivity to MEK inhibitors, suggesting the existence of additional resistance mechanisms. Comparison of copy number and variant allele frequency of KRAS showed that MEK inhibitor-resistant cell lines have either amplified mutant alleles or lost WT alleles.

This prediction of high KRAS mutant allele frequency being associated with MEKi resistance was successfully validated in vivo in 19 primary colorectal tumor xenograft models treated with MEK162. High KRAS mutant allele frequency and high KRAS expression were also associated with acquired resistance to BKM120+MEK162 combination treatment in an in vivo model of HeyA8, an ovarian cell line with a KRAS G12D mutation.

This prediction was also supported by the observation in a Phase II clinical trial with MEK inhibitor refametinib + gemcitabine in pancreatic cancer [1]. Patients with disease progression had a significantly higher KRAS mutant allele frequency compared to partial responders and stable disease.

Conclusion

High allele frequency of KRAS functional mutations is associated with resistance to MEK inhibitors. Excluding patients with high KRAS mutant allele frequency has the potential to improve clinical trial outcomes and benefit patients, with the added benefit that it may not require any additional screening or novel biomarkers.

References

[1] Reiss et al., J Clin Oncol 32:5s, 2014 (suppl; abstr 4129)

Citation Format: Anupama Reddy, Maria Pinzon-Ortiz, Adnan Derti, Joshua Korn, David Ruddy, Guizhi Yang, John Green, Hui Gao, Joseph Lehar, Giordano Caponigro, Z. Alexander Cao. High allele frequency of KRAS functional mutations predicts resistance to MEK inhibitors: Evidence from cell lines and human tumor xenograft models. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2692. doi:10.1158/1538-7445.AM2015-2692

Abstract 3489: Novel translational pharmacology approaches on dose reduction and alternative scheduling for the combination of JAK inhibitor, ruxolitinib, PIM inhibitor, LGH447, and CDK4/6 inhibitor, LEE011 in a preclinical model of myeloproliferative neoplasia

The JAK-STAT pathway is an important signaling pathway downstream of multiple cytokine and growth factor receptors. It has been implicated in the pathogenesis of multiple human diseases. The genetic aberration of JAK2V617F and the associated activation of STAT in myeloproliferative neoplasia (MPN) is one example of the involvement of this pathway in human cancer. We have shown the combination benefits of combining ruxolitinib (Jak1, 2 inhibitor), with LGH447 (PIM inhibitor) and LEE011 (CDK4/6 inhibitor) in a Ba/F3-JAK2V617F-driven MPN model. This triple combination resulted in ∼99% reduction of total tumor burden and a ∼96% reduction of spleen weight. Furthermore, the triple combination of ruxolitinib, LGH447 and LEE011 reduced JAK2V617F allele burden by &gt; 80%. To translate this combination from preclinical setting to the clinic, it is critical to evaluate dose to efficacy relationship for each agents and scheduling to efficacy correlation for this combination. Here, the preclinical doses for ruxolitinib, LGH447 and LEE011 were determined, based on their clinically achieved exposure. We then examined “intermittent dosing” of this combination in the same preclinical model. Our data suggest that the combination efficacy of ruxolitinib-LGH447-LEE011 is dependent on continuous administration of the agents. Finally, we examined the effect of dose reduction for each of the three agents on the combination efficacy in the Ba/F3-JAK2V617F-driven MPN model. By modifying the doses for ruxolitinib, LGH447 and LEE011 separately in the combination, our study reveals that the triple combination efficacy is most sensitive to LEE011 dose reduction, and it is least sensitive to LGH447 dose reduction. In summary, our studies aim to design novel preclinical approaches to inform and the design of clinical dose escalation in novel combination therapies.

Citation Format: Maria Pinzon-Ortiz, Xianhui Rong, Gary Vanasse, Z. Alexander Cao. Novel translational pharmacology approaches on dose reduction and alternative scheduling for the combination of JAK inhibitor, ruxolitinib, PIM inhibitor, LGH447, and CDK4/6 inhibitor, LEE011 in a preclinical model of myeloproliferative neoplasia. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3489. doi:10.1158/1538-7445.AM2015-3489

Abstract 3684: The combination of JAK inhibitor, ruxolitinib, pan-PIM inhibitor, LGH447, and CDK4/6 inhibitor, LEE011, in a preclinical mouse model of myeloproliferative neoplasia

The JAK/STAT axis is a critical component downstream of multiple cytokine and growth factor receptor signaling pathways. The genetic aberration of JAK2V617F and the associated activation of STAT in myeloproliferative neoplasia (MPN) is one example of the involvement of this pathway in human cancer. Activated JAKs phosphorylate STAT proteins, which then up-regulate the transcription of STAT target genes such as PIM1. Pim kinases are involved in the regulation of cell cycle and proliferation. The inhibition of JAK1/2 by the JAK inhibitor, ruxolitinib (RUX), results in the suppression of the JAK-STAT pathway and promotes significant clinical benefit in patients with myelofibrosis. Our previous preclinical studies in a Ba/F3-JAK2V617F-driven MPN model demonstrate that the combination of RUX and the pan-PIM inhibitor, LGH447, exhibits greater inhibition of spleen weight and some reduction of JAK2V617F allele burden, compared with the RUX monotherapy. Mutant JAK2V617F has been shown to increase CDC25A transcription through activated STAT5. It also regulates p27 at both the gene expression and phosphorylation levels. The activation of CDC25A and the modulation of p27 have been postulated to trigger the activation of cyclin dependent kinases (CDK), such as CDK4, to initiate cell cycle progression. Additionally, activated STATs and Pims have been shown to activate D cyclins that are upstream of CDK4/6. Here, we explored the hypothesis that CDK4/6 inhibition, in conjunction with JAK and PIM inhibition, would enhance therapeutic efficacy against MPN. LEE011 is a potent and selective inhibitor of CDK4/6. The combination of RUX and LEE011 was tested in an MPN model with Ba/F3 cells harboring EPOR-JAK2V617F. While RUX monotherapy reduced spleen weight and total tumor burden by more than 50%, it had marginal effect on JAK2V617F allele burden in this model. The combination of RUX and LEE011 resulted in an additional 2 to 3 fold reduction in spleen weight and total tumor burden. Yet, no clear modulation of JAK2V617F allele burden was observed. To further enhance the anti-tumor activity, we tested the triple combination of RUX, LGH447 and LEE011 in this MPN model. This triple combination resulted in &gt;99% reduction of total tumor burden and a ∼96% reduction of spleen weight. Furthermore, the triple combination of RUX, LGH447 and LEE011 significantly down-modulated JAK2V617F allele burden by &gt; 80%. Our preclinical data indicate that the triple combination of RUX, CDK4/6 inhibitor, LEE011, and pan-PIM inhibitor, LGH447, may preferentially impact the JAK2V617F mutant MPN clones. This combination also achieves greater reductions in tumor burden and spleen weight in our preclinical MPN model. Therefore, potentially greater therapeutic benefit in subgroups of MPN patients may be achieved with the triple combination of RUX, LEE011 and LGH447.

Citation Format: Maria Pinzon-Ortiz, Xianhui Rong, Abdel Saci, Robert Schlegel, Gary Vanasse, Giordano Caponigro, Z. Alexander Cao. The combination of JAK inhibitor, ruxolitinib, pan-PIM inhibitor, LGH447, and CDK4/6 inhibitor, LEE011, in a preclinical mouse model of myeloproliferative neoplasia. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3684. doi:10.1158/1538-7445.AM2014-3684

Abstract 5466: The Mdm2 inhibitor, NVP-CGM097, in combination with the BRAF inhibitor NVP-LGX818 elicits synergistic antitumor effects in melanoma

RAF kinase inhibitors have shown substantial therapeutic effects in patients with BRAF-mutant melanoma. However, despite impressive initial responses, therapeutic effects are often temporary due to acquired resistance. This resistance highlights the need to identify therapeutic approaches to improve the durability of responses to RAF inhibitors. In this study, we demonstrate that a novel inhibitor of p53-Mdm2 interaction, NVP-CGM097, causes marked reduction of melanoma cell viability. The activation of p53 signaling and consequent reduction in cell viability required wild-type p53, but was independent of BRAF status. Moreover, combined inhibition of Mdm2, using NVP-CGM097, and BRAF using NVP-LGX818, synergistically inhibited the viability of BRAF mutant melanoma cells in vitro and tumor growth in vivo. NVP-CGM097 caused induction of p21 and Bax, while NVP-LGX818 did not. Instead, NVP-LGX818 caused induction of p27 and Bim. Therefore, together they induced a complementary set of anti-proliferative and apoptosis stimulating molecules, which resulted in strong synergistic antitumor effects. In vivo, the combination treatment resulted in sustained tumor regressions and markedly prolonged survival relative to either single agent. Collectively, these data show that activation of p53, through inhibition of Mdm2, leads to antitumor effects in melanoma. Furthermore, the data show that concomitant activation of tumor suppressor p53 and inhibition of BRAF synergistically suppresses melanoma growth. Therefore, combined inhibition of Mdm2 and BRAF in melanoma may provide an effective therapeutic modality capable of overcoming the resistance observed with the BRAF inhibitor monotherapy and thus lead to more durable responses in the clinic.

Citation Format: Hui Qin Wang, Matthew Zubrowski, Erling Emerson, Elina Pradhan, Sébastien Jeay, Marion Wiesmann, Giordano Caponigro, Jens Wuerthner, Robert Schlegel, Z. Alexander Cao, Alan Huang, Ensar Halilovic. The Mdm2 inhibitor, NVP-CGM097, in combination with the BRAF inhibitor NVP-LGX818 elicits synergistic antitumor effects in melanoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5466. doi:10.1158/1538-7445.AM2014-5466

Abstract LB-237: Targeting HER3 and IGF1R in NRG1 high lung squamous cell carcinoma

HER3 is a member of the ErbB family of receptor tyrosine kinases. Aberrant activation of HER3 as a result of HER2 amplification or neuregulin 1 (NRG1) over-expression has been demonstrated to mediate constitutive activation of downstream oncogenic signals. LJM716 is a fully human IgG1 anti-HER3 monoclonal antibody. It locks HER3 in an inactive conformation and prevents HER3 dimerization with other ErbB family members. This unique mode of action enables LJM716 to block both ligand dependent and ligand independent HER3 activation. In search of new indications that may benefit from anti-HER3 therapies, we noted that squamous cell carcinomas (SCC) tend to have relatively higher NRG1 expression as compared to their adenocarcinoma counterparts. Highest NRG1 expression was observed in the lung SCC cell lines in cell line encyclopedia (CLE). A subset of the lung SCC cell lines with high NRG1 expression are moderately sensitive to LJM716, with HER3 activation detected in all of the sensitive lines. Surprisingly, phosphorylation of IGF1R rather than other HER family members tracked closely to HER3 phosphorylation in the lung SCC lines. Consistent with this finding, co-treatment with either IGF1R inhibitor, OSI-906, or anti-IGF1R antibody, Figitumumab, with LJM716 further enhanced LJM716 activity in the three NRG1-high lung SCC lines in vitro. The enhanced anti-tumor activity of LJM716 and Figitumumab is also observed in mouse xenografts generated from these lung SCC lines. Furthermore, pharmacodynamic analysis revealed increased inhibition of PI3K/mTOR signaling with the combined treatment of LJM716 and Figitumumab. These data suggest that NRG1- driven HER3 activation is a common feature in a subset of lung squamous cell carcinoma. Combination of anti-HER3 and anti-IGF1R is effective at suppressing PI3K/mTOR signaling and inhibit growth in these tumors.

Citation Format: Qing Sheng, Maria Pinzon-Ortiz, Rita Das, Alan Huang, Xianhui Rong, Z. Alexander Cao. Targeting HER3 and IGF1R in NRG1 high lung squamous cell carcinoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-237. doi:10.1158/1538-7445.AM2014-LB-237

Abstract 3683: Targeting PIK3CA mutant breast cancer with the combination of PIK3CA-specific inhibitor, BYL719, and IGF1-R antibody, ganitumab

Background: PI3K/AKT signaling is a critical growth and survival pathway in many human cancers. PI3Ks are lipid kinases that are important in controlling signaling pathways involved in cell proliferation, motility, cell death and cell invasion. The α isoform of PI3K (PIK3CA) is linked upstream mainly to receptor tyrosine kinases. Various solid tumor types such as colorectal cancers, gastric cancers, brain cancers, glioblastomas, breast and lung cancers have been found to contain gain-of-function mutations of PIK3CA. The existing scientific evidence strongly supports the concept of targeting PIK3CA in human cancers, especially those harboring PIK3CA mutations. Sustained PIK3CA inhibition may lead to aberrant RTK signaling to attenuate PIK3CA inhibition. IGF1R is a RTK commonly expressed in human neoplasia. Its signaling, primarily through AKT, has been implicated in tumor cell survival. Additionally, IGF1R/IRS signaling has been shown to be a feedback pathway to down-modulate mTOR inhibition by RAD001 in cancer cells. We speculate that the efficacy of PIK3CA inhibition might be enhanced if PIK3CA inhibitor is combined with a targeted agent against a key RTK in pAKT signaling.

Methods: With pATK signaling closely linked to mTOR signaling, we set out to examine whether PIK3CA inhibition would also trigger IGF1-R/IRS signaling. In addition, we explored the combination of PIK3CA-specific inhibitor, BYL719, and a fully human antibody against IGF1-R, AMG 479 (ganitumab), preclinically against a PIK3CA mutant breast cancer model, MCF7.

Results: Our data indicate that IGF1-R/IRS signaling is activated upon PIK3CA inhibition. BYL719 exhibited concentration-dependent tumor growth inhibition in vitro. Ganitumab alone had modest inhibitory activity. The combination of BYL719 and ganitumab inhibited MCF7 growth synergistically in vitro. This combination was further tested in an MCF7 xenograft in mice. BYL719 monotherapy resulted in tumor stasis. Ganitumab alone had marginal growth inhibition. The combination of BYL719 and ganitumab led to tumor regression. Further more, the combination of BYL719 and Ganitumumab lead to increased suppression of pS6RP in vivo.

Conclusions: Our data suggest that the combination of BYL719 and ganitumab would act synergistically to inhibit PIK3CA mutant breast cancer cells by blocking two inter-connected pathways. The combination of BYL719 and ganitumab has now entered into clinical trial (NCT01708161). It represents a promising approach against PI3KCA mutant breast cancers.

Citation Format: Z. Alexander Cao, Maria Pinzon-Ortiz, Yan Chen, Xiaoyan Li, Pedro J. Beltran, Jennifer Gansert, Malte Peters, Robert Schlegel, Karl M. Schumacher, Alan Huang. Targeting PIK3CA mutant breast cancer with the combination of PIK3CA-specific inhibitor, BYL719, and IGF1-R antibody, ganitumab. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3683. doi:10.1158/1538-7445.AM2014-3683

Abstract 2612: ljm716, an anti her3 antibody that inhibits her3 dimerization, displays anti-tumor activity in esophageal squamous cell cancer

Background: Esophageal cancer is the eighth most common cancer and the sixth most common cause of cancer related death in the world. Squamous cell carcinoma is the predominant histologic subtype of esophageal cancer, particularly in Asia. Currently, no targeted therapy has been approved for treating this type of disease. Platinum-based combination chemotherapy remains to be the standard care for first line treatment of advanced or metastatic esophageal cancer with limited efficacy. Activation of EGFR/HER3/PI3K pathway is frequently observed in esophageal cancer, however, their therapeutic value remains to be further tested.

Methods: In this study, we evaluated the anti-tumor activity of LJM716, a fully human anti-HER3 antibody, either alone or in combination with anti-EGFR antibody cetuximab or PI3K alpha subunit inhibitor BYL719 in esophageal squamous cancer. LJM716, cetuximab and BYL719 single agent as well as their pair-wised combination activity were assessed in 24 esophageal squamous cancer cell (ESCC) lines using the CellTiter-Glo® Luminescent Cell Viability Assay. Single agent and combination anti-tumor activities of these reagents were also tested in selected cell line xenograft and patient derived xenograft mouse models.

Results: NRG1 expression (60%), PIK3CA mutation (8%), moderate PIK3CA (30%) and EGFR (30%) amplification were detected in a panel of 24 ESCC lines. Anti-HER3 antibody LJM716 potently inhibited HER3 phosphorylation and decreased pAKT level in these cell lines. In vitro, LJM716 inhibited proliferation of a sub-set of ESCC lines. LJM716 further enhanced and broadened the anti-tumor activities of both BYL719 and cetuximab in ESCC lines. In mouse xenograft models, LJM716 single agent treatment induced tumor stasis while combination with either BYL719 or cetuximab induced model dependent tumor regression.

Conclusion: NRG1-HER3-PI3K pathway activation is commonly observed in esophageal squamous cell cancer. Activation of HER3 is a potential mechanism leading to resistance to EGFR or PI3K targeted therapies, and combining anti-HER3 therapies with therapies targeting PI3K/EGFR may provide new therapeutic strategy for patients with esophageal squamous cell cancer.

Citation Format: Qing Sheng, Hui-Qin Wang, rita das, yan chen, jinsheng liang, Fiona Xu, zongyao Wang, Z. Alexander Cao, youzhen Wang, alan huang. ljm716, an anti her3 antibody that inhibits her3 dimerization, displays anti-tumor activity in esophageal squamous cell cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2612. doi:10.1158/1538-7445.AM2014-2612

Abstract 2929: The Mdm2 inhibitor NVP-CGM097 enhances the anti-tumor activity of NVP-LDK378 in ALK mutant neuroblastoma models

Neuroblastoma is the most common cancer in infancy, accounting for 15% of all childhood cancer-related death. MYCN amplification is the major genetic aberration in high-risk neuroblastoma and is associated with poor outcome. Genome-wide association studies have identified activation mutations and high-level amplification of ALK in approximately 10% of neuroblastoma patients. In addition, ALK mutations can coexist with MYCN amplification, which defines a subset of ultra-high-risk neuroblastoma patients. In contrast to the high frequency of p53 mutations observed in many human cancers of adults, mutations of p53 are less common in childhood cancers and have been reported in less than 2% of neuroblastomas. Wild-type (WT) p53 is required for the activation of p53 signaling by Mdm2 inhibitors. This suggests that neuroblastoma could be amenable to intervention with Mdm2 inhibitors. In this study, we demonstrated that the ALK inhibitor, NVP-LDK378, in combination with a novel Mdm2 inhibitor, NVP-CGM097, promoted apoptosis in ALK mutant and p53 WT neuroblastoma cell lines. NVP-LDK378 inhibited ALK phosphorylation and NVP-CGM097 caused induction of p53 and its downstream target genes in these cell lines. Meanwhile, Mdm2 inhibition in MYCN-amplified neuroblastoma cell lines significantly decreased the levels of Mycn protein. In addition, NVP-LDK378 and NVP-CGM097 combination resulted in complete tumor regression and markedly prolonged survival in neuroblastoma xenograft models. Overall, NVP-LDK378 and NVP-CGM097 combination may provide an effective treatment for ALK mutant and p53 WT neuroblastoma patients.

Citation Format: Hui Qin Wang, Linda Battalagine, Jinsheng Liang, Ensar Halilovic, Robert Schlegel, Alan Huang, Z. Alexander Cao, John Monahan, Fang Li. The Mdm2 inhibitor NVP-CGM097 enhances the anti-tumor activity of NVP-LDK378 in ALK mutant neuroblastoma models. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2929. doi:10.1158/1538-7445.AM2014-2929

CDK 4/6 inhibitors sensitize PIK3CA mutant breast cancer to PI3K inhibitors

Activation of the phosphoinositide 3-kinase (PI3K) pathway occurs frequently in breast cancer. However, clinical results of single-agent PI3K inhibitors have been modest to date. A combinatorial drug screen on multiple PIK3CA mutant cancers with decreased sensitivity to PI3K inhibitors revealed that combined CDK 4/6-PI3K inhibition synergistically reduces cell viability. Laboratory studies revealed that sensitive cancers suppress RB phosphorylation upon treatment with single-agent PI3K inhibitors but cancers with reduced sensitivity fail to do so. Similarly, patients' tumors that responded to the PI3K inhibitor BYL719 demonstrated suppression of pRB, while nonresponding tumors showed sustained or increased levels of pRB. Importantly, the combination of PI3K and CDK 4/6 inhibitors overcomes intrinsic and adaptive resistance leading to tumor regressions in PIK3CA mutant xenografts.

RAD001 enhances the potency of BEZ235 to inhibit mTOR signaling and tumor growth

The mammalian target of rapamycin (mTOR) is regulated by oncogenic growth factor signals and plays a pivotal role in controlling cellular metabolism, growth and survival. Everolimus (RAD001) is an allosteric mTOR inhibitor that has shown marked efficacy in certain cancers but is unable to completely inhibit mTOR activity. ATP-competitive mTOR inhibitors such as NVP-BEZ235 can block rapamycin-insensitive mTOR readouts and have entered clinical development as anti-cancer agents. Here, we show the degree to which RAD001 and BEZ235 can be synergistically combined to inhibit mTOR pathway activation, cell proliferation and tumor growth, both in vitro and in vivo. RAD001 and BEZ235 synergized in cancer lines representing different lineages and genetic backgrounds. Strong synergy is seen in neuronal, renal, breast, lung, and haematopoietic cancer cells harboring abnormalities in PTEN, VHL, LKB1, Her2, or KRAS. Critically, in the presence of RAD001, the mTOR-4EBP1 pathway and tumorigenesis can be fully inhibited using lower doses of BEZ235. This is relevant since RAD001 is relatively well tolerated in patients while the toxicity profiles of ATP-competitive mTOR inhibitors are currently unknown.

Abstract 1066: Combination synergy of JAK inhibitor, BVB808, and FGFR inhibitor, BGJ398, in an FGFR3-driven multiple myeloma model

Multiple myeloma is a genetically heterogenous malignancy. Several clinical studies have indicated that the t(4:14)(p16:q32) translocation is associated with poor clinical prognosis. Two key target genes in this translocation are FGFR3 and MMSET. Additionally, activating mutations of FGFR3 have been identified, further implicating the involvement of this target in multiple myeloma. Recent advances have shed more light on the interaction between tumor cells and their microenvironment. The bone marrow stroma, endothelial cells, osteoclasts and others could promote the proliferation, survival and resistance to therapies of the malignant plasma cells. IL-6 is one of the major cytokines implicated in the tumor microenvironment. IL-6 signaling, mediated through receptor-coupled JAK-STAT pathway, has been reported to play an important role in cancer cell survival. Here we examine the combination effects of JAK inhibitor BVB808 and FGFR inhibitor BGJ398 against multiple myeloma in the preclinical setting. Combination of BVB808 and BGJ398 was tested in vitro in a panel of multiple myeloma models across broad drug concentrations. Significant synergy is noted in OPM II, a cell line harboring both t(4:14) translocation and FGFR3 K650E mutation. This combination benefit is further confirmed in the xenograft model bearing OPM II. We propose 2 hypotheses for this combination effect: 1) FGFR3 and IL-6/JAK-STAT may represent 2 parallel survival pathways in MM. When one pathway is inhibited, tumor cells would rely on the other axis as the alternative survival pathway. Synergy is noted only when both pathways are inhibited. 2) JAK-STAT may cooperate with FGFR3 to promote its activity. Synergy is achieved when potent and sustained inhibition of FGFR3 signaling is achieved with the combination of BVB808 and BGJ398. While it is an intriguing finding, the combination benefit is not observed across other MM models harboring FGFR3 lesions. Elucidation of the underlying molecular mechanism would enable more targeted therapies against two important targets in multiple myeloma.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1066. doi:1538-7445.AM2012-1066

A human monoclonal anti-ANG2 antibody leads to broad antitumor activity in combination with VEGF inhibitors and chemotherapy agents in preclinical models

Localized angiopoietin-2 (Ang2) expression has been shown to function as a key regulator of blood vessel remodeling and tumor angiogenesis, making it an attractive candidate for antiangiogenic therapy. A fully human monoclonal antibody (3.19.3) was developed, which may have significant pharmaceutical advantages over synthetic peptide-based approaches in terms of reduced immunogenicity and increased half-life to block Ang2 function. The 3.19.3 antibody potently binds Ang2 with an equilibrium dissociation constant of 86 pmol/L, leading to inhibition of Tie2 receptor phosphorylation in cell-based assays. In preclinical models, 3.19.3 treatment blocked blood vessel formation in Matrigel plug assays and in human tumor xenografts. In vivo studies with 3.19.3 consistently showed broad antitumor activity as a single agent across a panel of diverse subcutaneous and orthotopic xenograft models. Combination studies of 3.19.3 with cytotoxic drugs or anti-vascular endothelial growth factor agents showed significant improvements in antitumor activity over single-agent treatments alone with no apparent evidence of increased toxicity. Initial pharmacokinetic profiling studies in mice and nonhuman primates suggested that 3.19.3 has a predicted human half-life of 10 to 14 days. These studies provide preclinical data for 3.19.3 as a potential new antiangiogenic therapy as a single agent or in combination with chemotherapy or vascular endothelial growth factor inhibitors for the treatment of cancer.

CRA-026440: a potent, broad-spectrum, hydroxamic histone deacetylase inhibitor with antiproliferative and antiangiogenic activity in vitro and in vivo

CRA-026440 is a novel, broad-spectrum, hydroxamic acid-based inhibitor of histone deacetylase (HDAC) that shows antitumor and antiangiogenic activities in vitro and in vivo preclinically. CRA-026440 inhibited pure recombinant isozymes HDAC1, HDAC2, HDAC3/SMRT, HDAC6, HDAC8, and HDAC10 in the nanomolar range. Treatment of cultured tumor cell lines grown in vitro with CRA-026440 resulted in the accumulation of acetylated histone and acetylated tubulin, leading to an inhibition of tumor cell growth and the induction of apoptosis. CRA-026440 inhibited ex vivo angiogenesis in a dose-dependent manner. CRA-026440 parenterally given to mice harboring HCT116 or U937 human tumor xenografts resulted in a statistically significant reduction in tumor growth. CRA-026440, when used in combination with Avastin, achieved greater preclinical efficacy in HCT 116 colorectal tumor model. Inhibition of tumor growth was accompanied by an increase in the acetylation of alpha-tubulin in peripheral blood mononuclear cells and an alteration in the expression of many genes in the tumors, including several involved in angiogenesis, apoptosis, and cell growth. These results reveal CRA-026440 to be a novel HDAC inhibitor with potent antitumor activity.

CRA-024781: a novel synthetic inhibitor of histone deacetylase enzymes with antitumor activity in vitro and in vivo

CRA-024781 is a novel, broad spectrum hydroxamic acid-based inhibitor of histone deacetylase (HDAC) that shows antitumor activity in vitro and in vivo preclinically and is under evaluation in phase I clinical trials for cancer. CRA-024781 inhibited pure recombinant HDAC1 with a K(i) of 0.007 mumol/L, and also inhibited the other HDAC isozymes HDAC2, HDAC3/SMRT, HDAC6, HDAC8, and HDAC10 in the nanomolar range. Treatment of cultured tumor cell lines grown in vitro with CRA-024781 resulted in the accumulation of acetylated histone and acetylated tubulin, resulting in an inhibition of tumor cell growth and the induction of apoptosis. CRA-024781 parenterally administered to mice harboring HCT116 or DLD-1 colon tumor xenografts resulted in a statistically significant reduction in tumor growth at doses that were well tolerated as measured by body weight. Inhibition of tumor growth was accompanied by an increase in the acetylation of alpha-tubulin in peripheral blood mononuclear cells, and an alteration in the expression of many genes in the tumors, including several involved in apoptosis and cell growth. These results reveal CRA-024781 to be a novel HDAC inhibitor with potent antitumor activity.

[The chemical decomposition of glutamine and its effect on hybridoma cell culture]

The chemical decomposition of glutamine is a first-order reaction. Its reaction constants under storage and culture conditions were determined as 0.0009 h-1 and 0.0032 h-1 respectively. Batch culture of hybridoma cell C50 with different initial contents of glutamine helped to understand its real metabolic characteristic. The results show that when the initial concentration of glutamine is lower than 5 mmol/L, more than 80% is used by cells. And the lower the initial content, the more being used. As the initial glutamine concentration increases, the ratio of its utilization decreases. When it reaches 10 nmol/L, the ratio decreases dramatically.

[The measurement of intra-cellular AOX in recombinant Pichia pastoris]

The activities of intracellular alcohol oxidase(AOX) in recombinant P. pastoris expressing Pro-UK were determined by a self-designed dissolved oxygen measuring equipment. The enzyme vitality and specific enzyme vitality were defined nd the condition for detecting the enzyme vitality was also established. The experimental results showed that with a certain quantity of biomass in a phosphate buffer containing methanol, the consuming rate of dissolved-oxygen reflected the enzyme vitality of intracellular AOX. It was also found that the pH of the buffer could be very freely between 4.7 and 7.4 and the suitable optical dersity of cell concentration at 600 nm was between 0.5 and 2.0. Furthermore, the values of qo2max and Km of AOX versus oxygen consumption, which were 0.409 s-1 and 0.16 respectively, were calculated. It is a simple and sensitive and feasible method for quick measuring of AOX.