Combination Of CB-839 Research Articles

The glutaminase inhibitor CB-839 targets metabolic dependencies of JAK2-mutant hematopoiesis in MPN

AbstractHyperproliferation of myeloid and erythroid cells in myeloproliferative neoplasms (MPN) driven by the JAK2-V617F mutation is associated with altered metabolism. Given the central role of glutamine in anabolic and catabolic pathways, we examined the effects of pharmacologically inhibiting glutaminolysis, that is, the conversion of glutamine (Gln) to glutamate (Glu), using CB-839, a small molecular inhibitor of the enzyme glutaminase (GLS). We show that CB-839 strongly reduced the mitochondrial respiration rate of bone marrow cells from JAK2-V617F mutant (VF) mice, demonstrating a marked dependence of these cells on Gln-derived ATP production. Consistently, in vivo treatment with CB-839 normalized blood glucose levels, reduced splenomegaly and decreased erythrocytosis in VF mice. These effects were more pronounced when CB-839 was combined with the JAK1/2 inhibitor ruxolitinib or the glycolysis inhibitor 3PO, indicating possible synergies when cotargeting different metabolic and oncogenic pathways. Furthermore, we show that the inhibition of glutaminolysis with CB-839 preferentially lowered the proportion of JAK2-mutant hematopoietic stem cells (HSCs). The total number of HSCs was decreased by CB-839, primarily by reducing HSCs in the G1 phase of the cell cycle. CB-839 in combination with ruxolitinib also strongly reduced myelofibrosis at later stages of MPN. In line with the effects shown in mice, proliferation of CD34+ hematopoietic stem and progenitor cells from polycythemia vera patients was inhibited by CB-839 at nanomolar concentrations. These data suggest that inhibiting GLS alone or in combination with inhibitors of glycolysis or JAK2 inhibitors represents an attractive new therapeutic approach to MPN.

Targeting Metabolic Reprogramming to Improve Breast Cancer Treatment: An In Vitro Evaluation of Selected Metabolic Inhibitors Using a Metabolomic Approach.

Characteristic metabolic adaptations are recognized as a cancer hallmark. Breast cancer, like other cancer types, displays cellular respiratory switches—in particular, the Warburg effect—and important fluctuations in the glutamine and choline metabolisms. This cancer remains a world health issue mainly due to the side effects associated with chemotherapy, which force a reduction in the administered dose or even a complete discontinuation of the treatment. For example, Doxorubicin is efficient to treat breast cancer but unfortunately induces severe cardiotoxicity. In the present in vitro study, selected metabolic inhibitors were evaluated alone or in combination as potential treatments against breast cancer. In addition, the same inhibitors were used to possibly potentiate the effects of Doxorubicin. As a result, the combination of CB-839 (glutaminase inhibitor) and Oxamate (lactate dehydrogenase inhibitor) and the combination of CB-839/Oxamate/D609 (a phosphatidylcholine-specific phospholipase C inhibitor) caused significant cell mortality in both MDA-MB-231 and MCF-7, two breast cancer cell lines. Furthermore, all inhibitors were able to improve the efficacy of Doxorubicin on the same cell lines. Those findings are quite encouraging with respect to the clinical goal of reducing the exposure of patients to Doxorubicin and, subsequently, the severity of the associated cardiotoxicity, while keeping the same treatment efficacy.

Abstract PO-094: Glutaminase inhibition increases ionizing radiation induced oxidative stress and DNA damage in head and neck squamous cell carcinoma models

Abstract Ionizing radiation (IR) is a pillar of head and neck cancer treatment, the 6th most common cancer worldwide. However, its efficacy is limited by radioresistance, resulting in locoregional failure rates of ~50%. The mechanisms that tumor cells use to evade IR-induced cellular damage are poorly understood. Our initial proteomics analysis indicated that IR induced metabolic pathways, including those involving the Krebs cycle. Glutamate is a key substrate of the Krebs cycle. Glutaminase is the enzyme that converts glutamine to glutamate. Analysis of The Cancer Genome Atlas’s transcriptome database revealed that glutaminase overexpression (upper 25%) in patients with HNSCC was associated with reduced patient survival (p≤0.03). In this study, we therefore aimed to identify whether glutaminase inhibition with CB-839 (currently in Phase 1/2 trials) could enhance cellular response to IR. To do this, we used three representative human-derived HNSCC cell lines: CAL-27, FaDu, and HN5. First, we established that proliferation of all 3 HNSCC cell lines was glutamine dependent (20-50% increase, n=3 per line, p≤0.01). Second, a synergistic decrease in cell survival was observed in clonogenic assays with HNSCC cell lines treated with IR and CB-839 relative to either treatment alone (n=3 per line, p≤0.05). Thirdly, in 3D cell culture, which better represents the host microenvironment, combinatorial treatment significantly reduced HNSCC spheroid size (11-26% decrease, n=3 per line, p≤0.0001). The functional effect of CB-839 on cellular metabolism was examined using Seahorse MitoStress test assays. CB-839 significantly reduced spare respiratory capacity and OCR/ECAR ratio in HNSCC cell lines examined (p≤0.001, p≤2.0 × 10−6, n>3). To understand the mechanism behind this reduced cell growth and survival, we examined whether CB-839 enhanced oxidative stress and DNA damage when combined with IR using immunofluorescence. Oxidative stress marker, 8-oxoguanine, was ~2 fold higher with combined treatment as compared to CB-839 or IR alone in CAL-27 cells (p≤0.01, p≤0.05; respectively). Additionally, increased levels of y-H2AX were observed in CAL-27 cells treated with both CB-839 and IR relative to independent treatment. Combination of CB-839 with IR significantly inhibited tumor growth in CAL-27 xenograft mice relative to vehicle (p≤0.01), CB-839 (p≤0.05) or IR (p≤0.01) (p values, day 19). To summarize, successful treatment of HNSCC is impeded by adaptive resistance to IR and locoregional failure. Overall, these data suggest that the rational combination of IR and glutaminase inhibitor (CB-839) enhances cellular response and tumor control relative to independent treatment and provides pre-clinical data in support of additional investigation in patients with HNSCC. Citation Format: Christina A. Wicker, Brian G. Hunt, Sarah Palackdharry, William R. Elaban, Trisha M. Wise-Draper, Gordon B. Mills, Susan E. Waltz, Vinita Takiar. Glutaminase inhibition increases ionizing radiation induced oxidative stress and DNA damage in head and neck squamous cell carcinoma models [abstract]. In: Proceedings of the AACR Virtual Special Conference on Radiation Science and Medicine; 2021 Mar 2-3. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(8_Suppl):Abstract nr PO-094.

The Glutaminase Inhibitor CB-839 (Telaglenastat) Enhances the Antimelanoma Activity of T-Cell-Mediated Immunotherapies.

Immune-checkpoint inhibitors and adoptive tumor-infiltrating lymphocyte (TIL) therapies have profoundly improved the survival of patients with melanoma. However, a majority of patients do not respond to these agents, and many responders experience disease relapse. Although numerous innovative treatments are being explored to offset the limitations of these agents, novel therapeutic combinations with immunotherapies have the potential to improve patient responses. In this study, we evaluated the antimelanoma activity of immunotherapy combinations with Telaglenastat (CB-839), a potent glutaminase inhibitor (GLSi) that has favorable systemic tolerance. In in vitro TIL:tumor coculture studies, CB-839 treatment improved the cytotoxic activity of autologous TILs on patient-derived melanoma cells. CB-839 treatment decreased the conversion of glutamine to alpha-ketoglutarate (αKGA) more potently in tumor cells versus TILs in these cocultures. These results suggest that CB-839 may improve immune function in a tumor microenvironment by differentially altering tumor and immune cell metabolism. In vivo CB-839 treatment activated melanoma antigen-specific T cells and improved their tumor killing activity in an immune-competent mouse model of adoptive T-cell therapy. Additionally, the combination of CB-839 with anti-PD1 or anti-CTLA4 antibodies increased tumor infiltration by effector T cells and improved the antitumor activity of these checkpoint inhibitors in a high mutation burden mouse melanoma model. Responsiveness to these treatments was also accompanied by an increase of interferon gamma (IFNγ)-associated gene expression in the tumors. Together, these results provide a strong rationale for combining CB-839 with immune therapies to improve efficacy of these treatments against melanoma.

AZA + Glutaminase Inhibition with Telaglenastat (CB-839) for Advanced MDS: An Updated Interim Analysis

AZA + Glutaminase Inhibition with Telaglenastat (CB-839) for Advanced MDS: An Updated Interim Analysis

5-Fluorouracil Enhances the Antitumor Activity of the Glutaminase Inhibitor CB-839 against PIK3CA-Mutant Colorectal Cancers

PIK3CA encodes the p110α catalytic subunit of PI3K and is frequently mutated in human cancers, including ∼30% of colorectal cancer. Oncogenic mutations in PIK3CA render colorectal cancers more dependent on glutamine. Here we report that the glutaminase inhibitor CB-839 preferentially inhibits xenograft growth of PIK3CA-mutant, but not wild-type (WT), colorectal cancers. Moreover, the combination of CB-839 and 5-fluorouracil (5-FU) induces PIK3CA-mutant tumor regression in xenograft models. CB-839 treatment increased reactive oxygen species and caused nuclear translocation of Nrf2, which in turn upregulated mRNA expression of uridine phosphorylase 1 (UPP1). UPP1 facilitated the conversion of 5-FU to its active compound, thereby enhancing the inhibition of thymidylate synthase. Consistently, knockout of UPP1 abrogated the tumor inhibitory effect of combined CB-839 and 5-FU administration. A phase I clinical trial showed that the combination of CB-839 and capecitabine, a prodrug of 5-FU, was well tolerated at biologically-active doses. Although not designed to test efficacy, an exploratory analysis of the phase I data showed a trend that PIK3CA-mutant patients with colorectal cancer might derive greater benefit from this treatment strategy as compared with PIK3CA WT patients with colorectal cancer. These results effectively demonstrate that targeting glutamine metabolism may be an effective approach for treating patients with PIK3CA-mutant colorectal cancers and warrants further clinical evaluation. SIGNIFICANCE: Preclinical and clinical trial data suggest that the combination of CB-839 with capecitabine could serve as an effective treatment for PIK3CA-mutant colorectal cancers.

A powerful drug combination strategy targeting glutamine addiction for the treatment of human liver cancer.

The dependency of cancer cells on glutamine may be exploited therapeutically as a new strategy for treating cancers that lack druggable driver genes. Here we found that human liver cancer was dependent on extracellular glutamine. However, targeting glutamine addiction using the glutaminase inhibitor CB-839 as monotherapy had a very limited anticancer effect, even against the most glutamine addicted human liver cancer cells. Using a chemical library, we identified V-9302, a novel inhibitor of glutamine transporter ASCT2, as sensitizing glutamine dependent (GD) cells to CB-839 treatment. Mechanically, a combination of CB-839 and V-9302 depleted glutathione and induced reactive oxygen species (ROS), resulting in apoptosis of GD cells. Moreover, this combination also showed tumor inhibition in HCC xenograft mouse models in vivo. Our findings indicate that dual inhibition of glutamine metabolism by targeting both glutaminase and glutamine transporter ASCT2 represents a potential novel treatment strategy for glutamine addicted liver cancers.

Abstract PR09: Targeting glutamine addiction of PIK3CA mutant colorectal cancers: From preclinical models to clinical trials

Abstract Glutamine addiction is a major metabolic reprogramming event that occurs in cancer cells. Many tumors exhibit oncogene-dependent addiction to glutamine. As a metabolite, glutamine is first converted to glutamate by glutaminase (GLS) and then to α-ketoglutarate (α-KG) by either a transaminase or a glutamate dehydrogenase. PIK3CA, which encodes the p110α catalytic subunit of phosphatidylinositol 3-kinase α, is frequently mutated in human cancers, including 20-30% of colorectal cancer (CRC). We found that oncogenic PIK3CA mutations render CRCs addicted to glutamine through an upregulation of glutamate pyruvate transaminase 2 (GPT2), thereby facilitating conversion of glutamate to α-KG. Here, we report that CB-839, a potent GLS inhibitor developed by Calithera Biosciences, inhibits xenograft tumor growth of PIK3CA mutant, but not WT, colorectal cancers. Remarkably, combination of CB-839 with 5-fluorouracil (5-FU) induces regression of xenograft tumors in four different PIK3CA mutant CRC models. These exciting preclinical data prompted us to perform a phase I and phase II clinical trial to assess combination of CB-839 with capecitabine, an oral prodrug of 5-FU. For the phase I trial, patients with advanced solid tumors and disease progression on standard treatment, or for whom capecitabine is an acceptable treatment option, were enrolled. A standard 3+3 design was used to assess escalating doses of CB-839 (400-800 mg) and capecitabine (500-1000 mg/m2) in four dose levels. CB-839 was given orally twice daily continuously and capecitabine was given orally twice daily on days 14/21 of a 21-day treatment cycle. Dose-limiting toxicity period was 21 days. Restaging CT scans were obtained every 9 weeks with response assessment per RECIST. Adverse events were assessed per CTCAEv4. Sixteen patients were enrolled, with 7 patients being treated at the final dose level (CB-839 800 mg and capecitabine 1000 mg/m2). No dose-limiting toxicity was observed. Ten patients achieved stable disease as their best response with 9 being fluoropyrimidine resistant. Among the 16 patients, 12 were CRC patients who were 5-FU resistant. Consistent with our preclinical data, the median progress-free survival (PFS) of seven PIK3CA mutant CRC patients was 26 weeks, whereas the median PFS of five PIK3CA WT CRC patients was 16 weeks. Notably, the PFS of three PIK3CA mutant CRC patients was over six months (8, 9 and 13 months, respectively). A phase II trial of the drug combination in metastatic PIK3CA mutant CRC patients is ongoing. In summary, our preclinical and clinical studies suggest that targeting glutamine metabolism may be a promising approach to treat CRCs with PIK3CA mutations. This abstract is also being presented as Poster A06. Citation Format: Jennifer Eads, Yiqing Zhao, David Bajor, Zhenghe John Wang. Targeting glutamine addiction of PIK3CA mutant colorectal cancers: From preclinical models to clinical trials [abstract]. In: Proceedings of the AACR Special Conference on Targeting PI3K/mTOR Signaling; 2018 Nov 30-Dec 8; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(10_Suppl):Abstract nr PR09.

Abstract 6278: Glutaminase inhibition in combination with ionizing radiation improves treatment response in head and neck squamous cell carcinoma models

Abstract Head and neck cancer is the 6th most common cancer worldwide. Ionizing radiation (IR) is an important aspect of cancer treatment. However, its efficacy is limited by radioresistance, resulting in locoregional failure rates as high as 50%. The pathways used by cells to evade the cellular damage caused by IR are poorly understood. Initial Reverse Phase Protein Array analyses in our laboratory demonstrated that IR induced metabolic pathways, including those involving the Krebs cycle. Glutamate is a key substrate of the Krebs cycle, and essential for the production of biomolecules necessary for tumor proliferation. Glutaminase is the enzyme that converts glutamine to glutamate. Analysis of The Cancer Genome Atlas's transcriptome database revealed that glutaminase overexpression (upper 25%) in patients with HNSCC was associated with significantly reduced patient survival (p<0.03). In this study, we aimed to identify whether glutaminase inhibition with CB-839 could enhance cellular response to IR. To do this, we used three representative human-derived HNSCC cell lines: CAL-27, FaDu, and HN5. We first established that proliferation of all 3 HNSCC cell lines was glutamine dependent (20-50% increase, n=3 per line, p<0.01). Moreover, a synergistic decrease in cell survival was observed in clonogenic assays with HNSCC cell lines treated with IR and CB-839 relative to either treatment alone (n=3 per line, p<0.05). In 3D cell culture, which better represents the host microenvironment, combinatorial treatment significantly reduced HNSCC spheroid size (11-26% decrease, n=3 per line, p<0.0001). To understand the mechanism behind this reduced cell growth and survival, we examined CB-839's effect on cellular metabolism using Seahorse MitoStress test assays. CB-839 significantly reduced spare respiratory capacity and OCR/ECAR ratio in HNSCC cell lines examined (p<0.001, p<2.0 × 10−6, n>3). Combination of CB-839 with IR significantly inhibited tumor growth in Cal-27 xenograft mice relative to vehicle (p<0.01), CB-839 (p<0.05) or IR (p<0.01) (p values representative of day 20). In summary, adaptive resistance to IR and locoregional failure is a major hurdle in the successful treatment of HNSCC. Overall, these data suggest that combinatorial treatment with IR and the glutaminase inhibitor, CB-839, lead to an enhanced response over either treatment alone and provide pre-clinical data to justify further investigation for clinical use in patients with HNSCC. Citation Format: Christina A. Wicker, Brian G. Hunt, Sarah Palackdharry, William R. Elaban, Gordon B. Mills, Trisha Wise-Draper, Susan Waltz, Vinita Takiar. Glutaminase inhibition in combination with ionizing radiation improves treatment response in head and neck squamous cell carcinoma models [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6278.

Interim Analysis of a Phase II Study of the Glutaminase Inhibitor Telaglenastat (CB-839) in Combination with Azacitidine in Advanced Myelodysplastic Syndrome (MDS)

Interim Analysis of a Phase II Study of the Glutaminase Inhibitor Telaglenastat (CB-839) in Combination with Azacitidine in Advanced Myelodysplastic Syndrome (MDS)

Abstract 3870: The addition of CB-839 to temozolomide significantly reduces glioma aspartate and glutamate in an IDH mutated patient derived glioma xenograft model

Abstract Background: IDH mutated gliomas are critically dependent on glutaminase for glutamate biosynthesis. CB-839 is a novel glutaminase-1 inhibitor which has demonstrated efficacy in both genetically engineered and patient derived IDH mutated glioma cells, especially in combination with radiation. These preclinical studies evaluate the pharmacodynamic and pharmacokinetic impact of combining CB-839 with TMZ in patient derived xenograft (PDX) glioma models. Methods: GBM164 is a PDX model derived from an IDH1 mutant, 1p/19q non-codeleted glioma. D- and L-2HG levels in untreated GBM164 tumors were compared to GBM6 tumors (IDH wildtype glioma PDX) by GC/MS. Athymic nude mice bearing GBM164 flank tumors were treated with CB-839 (200 mg/kg PO BID x 9 doses) and/or temozolomide (50 mg/kg PO daily x 5 doses) and sacrificed four hours after the last dose to harvest plasma, normal brain and flank tumor. Tumor metabolomics were assessed by GC/MS. DNA damage signaling in tumors was assessed by Western blotting for KAP1 / Chk1 / Chk2 phosphorylation and H2AX / Rad51. Tumor, plasma and brain pharmacokinetics were assessed by LC/MS/MS. Results: Total 2HG levels in GBM164 were 18-fold higher than GBM6. CB-839 monotherapy reduced tumor glutamate (18% reduction, p = 0.15) and aspartate (30% reduction, p = 0.06) when compared to vehicle, however these changes did not reach statistical significance. The combination of CB-839 and TMZ more significantly reduced both tumor glutamate (30% reduction, p = 0.03) and aspartate (34% reduction, p < 0.001) when compared to TMZ monotherapy. CB-839 did not significantly increase DNA damage compared to vehicle, and the combination of CB-839 and TMZ did not significantly increase DNA damage compared to TMZ monotherapy. The mean tumor: plasma ratios of CB-839 concentrations were 0.68 and 0.58 in mice treated with CB-839 monotherapy and CB-839/TMZ, respectively. The mean brain: plasma ratios of CB-839 concentrations were 0.07 and 0.12 in mice treated with CB-839 monotherapy and CB-839/TMZ, respectively. Conclusion: The addition of CB-839 to TMZ significantly reduces glioma aspartate and glutamate in an IDH1 mutant PDX glioma model, without any impact on DNA damage. Survival studies are in progress to assess the efficacy of CB-839 when used in combination with RT and/or TMZ. Citation Format: Sani Haider Kizilbash, Danielle M. Burgenske, Samuel McBrayer, Sandhya Devarajan, Shiv K. Gupta, Taro Hitosugi, Lihong He, Mark A. Schroeder, Brett L. Carlson, Marina Gelman, Charles A. Kunos, Joel M. Reid, Alex A. Adjei, Jann N. Sarkaria. The addition of CB-839 to temozolomide significantly reduces glioma aspartate and glutamate in an IDH mutated patient derived glioma xenograft model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3870.

Abstract LB-294: Targeting glutamine addiction of PIK3CA mutant colorectal cancers: From preclinical models to clinical trials

Abstract Glutamine addiction is a major metabolic reprogramming event that occurs in cancer cells. Many tumors exhibit oncogene-dependent addiction to glutamine. As a metabolite, glutamine is first converted to glutamate by glutaminase (GLS) and then to α-ketoglutarate (α-KG) by either a transaminase or a glutamate dehydrogenase. PIK3CA, which encodes the p110α catalytic subunit of phosphatidylinositol 3-kinase α, is frequently mutated in human cancers including 20 to 30% of colorectal cancer (CRC). We found that oncogenic PIK3CA mutations render CRCs addicted to glutamine through an upregulation of glutamate pyruvate transaminase 2 (GPT2), thereby facilitating conversion of glutamate to α-KG. Here, we report that CB-839, a potent GLS inhibitor developed by Calithera Biosciences, inhibits xenograft tumor growth of PIK3CA mutant, but not WT, colorectal cancers. Remarkably, combination of CB-839 with 5-fluorouracil (5-FU) induces regression of xenograft tumors in four different PIK3CA mutant CRC models. These exciting preclinical data prompted us to perform a Phase I and Phase II clinical trial to assess combination of CB-839 with capecitabine, an oral prodrug of 5-FU. For the Phase I trial, patients with advanced solid tumors and disease progression on standard treatment, or for whom capecitabine is an acceptable treatment option, were enrolled. A standard 3+3 design was used to assess escalating doses of CB-839 (400-800 mg) and capecitabine (500-1000 mg/m2) in four dose levels. CB-839 was given orally twice daily continuously and capecitabine was given orally twice daily on days 14/21 of a 21 day treatment cycle. Dose-limiting toxicity period was 21 days. Restaging CT scans were obtained every 9 weeks with response assessment per RECIST. Adverse events were assessed per CTCAEv4. Sixteen patients were enrolled with 7 patients being treated at the final dose level (CB-839 800 mg and Capecitabine 1000 mg/m2). No dose-limiting toxicity were observed. Ten patients achieved stable disease as their best response with 9 being fluoropyrimidine resistant. Among the 16 patients, 12 were CRC patients who were 5-FU resistant. Consistent with our preclinical data, the median progress-free survival (PFS) of seven PIK3CA mutant CRC patients was 25 weeks, whereas the median PFS of five PIK3CA WT CRC patients was 16 weeks. Notably, the PFS of three PIK3CA mutant CRC patients was over six months (8, 9 and 13 months respectively). A Phase II trial of the drug combination in metastatic PIK3CA mutant CRC patients is ongoing. In summary, our preclinical and clinical studies suggest that targeting glutamine metabolism may be a promising approach to treat CRCs with PIK3CA mutations. Citation Format: Yiqing Zhao, Jennifer Eads, David Bajor, zhenghe wang. Targeting glutamine addiction of PIK3CA mutant colorectal cancers: From preclinical models to clinical trials [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-294.

Interim results from a phase Ib/II clinical study of the glutaminase inhibitor telaglenastat (CB-839) in combination with azacitidine in patients with advanced myelodysplastic syndrome (MDS).

7037 Background: Glutaminase (GLS) is an enzyme that catalyzes conversion of glutamine to glutamate, providing key metabolic fuel for tumor cells. GLS is highly expressed in AML and high-risk MDS, particularly in the setting of complex cytogenetics. Preclinical studies of primary AML cells demonstrate dependence on glutamine; glutaminase inhibition led to reduced cell growth and induced apoptosis. This study was designed to evaluate the safety and efficacy of the oral glutaminase inhibitor CB-839 in combination with azacitidine for MDS. Methods: This is a single arm Phase Ib/II trial of CB-839, evaluating the dose of 600 mg BID orally daily in combination with azacitidine (AZA) for intermediate and high-risk MDS in 28-day cycles. The primary outcome for the Phase 1 portion was to confirm the safety and recommended Phase 2 dose of CB-839 in combination with AZA. Secondary endpoints evaluate efficacy and clinical activity using IWG response criteria for MDS including hematological improvement (HI), complete response (CR), marrow CR (mCR), stable disease (SD) and no response (NR). Results: A total of 10 pts with MDS were enrolled; the Phase I portion is now complete, confirming CB-839 600 mg BID with standard AZA. Median age was 71 [47-76], 90% were men. 7 pts were treatment naïve, 3 pts had prior HMA exposure. 6 pts were intermediate-2, and 4 pts intermediate-1 by IPSS with high-risk mutations. 3 pts had complex cytogenetics. The most frequent mutations were ASXL1 (n = 5), TET2 (n = 4) and TP53 (n = 4). Median number of cycles was 3 [1-9]. The most common non-hematological AEs were grade 1-3 nausea (60%) and constipation (50%). No DLTs were identified; one pt experienced grade 3 transaminitis requiring dose reduction of CB-839 (to 400 mg BID) with resolution. Seven pts (70%) achieved mCR/CR with HI, 2 pts had SD, and 1 pt had NR. The median time to mCR was 3 months [1-3]. 4 pts proceed to hematologic stem cell transplant (HSCT) after 2-4 cycles. 1 pt progressed to AML after 3 cycles of therapy, and 3 pts remain on study. Conclusions: 600 mg BID CB-839 is safe and well tolerated in combination with azacitidine in pts with MDS. The Phase II portion is ongoing. Clinical trial information: NCT03047993.

CB-839 in Combination With Niraparib in Platinum Resistant Breast Cancer (BRCA) -Wild-type Ovarian Cancer Patients

CB-839 in Combination With Niraparib in Platinum Resistant Breast Cancer (BRCA) -Wild-type Ovarian Cancer Patients

Abstract B28: Targeted inhibition of EGFR and glutaminase induces metabolic crisis in EGFR-mutant lung cancer

Abstract Cancer cells exhibit increased use of nutrients, including glucose and glutamine, to support the bioenergetic and biosynthetic demands of proliferation. We tested the small-molecule inhibitor of glutaminase CB-839 in combination with erlotinib on epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer (NSCLC) as a therapeutic strategy to simultaneously impair cancer glucose and glutamine utilization and thereby suppress tumor growth. Here, we show that CB-839 cooperates with erlotinib to drive energetic stress and activate the AMP-activated protein kinase (AMPK) pathway in EGFR (del19) lung tumors. Tumor cells undergo metabolic crisis and cell death, resulting in rapid tumor regression in vivo in mouse NSCLC xenografts. Consistently, positron emission tomography (PET) imaging with 18F-fluoro-2-deoxyglucose (18F-FDG) and 11C-glutamine (11C-Gln) of xenografts indicated reduced glucose and glutamine uptake in tumors following treatment with CB-839 + erlotinib. Therefore, PET imaging with 18F-FDG and 11C-Gln tracers can be used to noninvasively measure metabolic response to CB-839 and erlotinib combination therapy. Citation Format: Milica Momcilovic, Sean T. Bailey, Jason T. Lee, Clara Magyar, Daniel Braas, Thomas Graeber, Francesco Parlati, Susan Demo, Konstyantyn Krysan, Tonya C. Walser, Steven M. Dubinett, Saman Sadeghi, Heather R. Christofk, David B. Shackelford. Targeted inhibition of EGFR and glutaminase induces metabolic crisis in EGFR-mutant lung cancer [abstract]. In: Proceedings of the Fifth AACR-IASLC International Joint Conference: Lung Cancer Translational Science from the Bench to the Clinic; Jan 8-11, 2018; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(17_Suppl):Abstract nr B28.

Abstract 3509: The glutaminase inhibitor CB-839 synergizes with CDK4/6 and PARP inhibitors in pre-clinical tumor models

Abstract Many tumor cells utilize the amino acid glutamine to meet the elevated bioenergetic and biosynthetic demands of rapid cell growth. The enzyme glutaminase converts glutamine to glutamate, which is used to fuel the TCA cycle, synthesize amino acids and nucleotides, and balance cellular oxidative stress. We developed CB-839, a potent and orally bioavailable small molecule inhibitor of glutaminase, that blocks production of glutamate and generation of downstream metabolites glutathione, malate and aspartate. Mice treated with CB-839 had decreased levels of nucleotides in their tumors, likely due to glutamine-derived aspartate being required for nucleotide biosynthesis. Consistent with our finding that CB-839 decreases nucleotide pools, CB-839 treatment delayed cancer cells from either entry into S-phase or progression through S-phase. Based on this observation, the ability of CB-839 to synergize with therapies that block cell cycle progression was tested. CB-839 synergized with the CDK4/6 inhibitor palbociclib in colorectal carcinoma (CRC), triple negative breast cancer (TNBC) and ER+ breast cancer cell lines resulting in anti-proliferative activity. The combination of CB-839 with palbociclib also led to decreased cell cycle progression through S-phase and caused an accumulation of cells in G1 as measured by an EdU DNA incorporation assay. In vivo, the combination of CB-839 with palbociclib resulted in enhanced anti-tumor activity in both an ER+ breast cancer and CRC xenograft tumor model. We next investigated whether CB-839 treatment would enhance the anti-tumor effects of DNA repair inhibitors, given the ability of CB-839 treatment to decrease nucleotide pools. CB-839 treatment in combination with the PARP inhibitors niraparib and talazoparib led to synergistic anti-proliferative activity in TNBC, CRC, non-small cell lung carcinoma, ovarian and prostate cancer cells. In vivo, the combination of CB-839 with PARP inhibitors showed enhanced anti-tumor activity compared to single agent treatment in a CRC tumor xenograft model. CB-839 is currently undergoing evaluation for efficacy in the treatment of cancer in several phase I/II clinical trials. These encouraging pre-clinical results support the testing of CB-839 with CDK4/6 or PARP inhibitors in cancer patients. Citation Format: Ethan D. Emberley, Mark Bennett, Jason Chen, Matthew Gross, Tony Huang, Amani Makkouk, Gisele Marguier, Alison Pan, Sandra M. Spurlock, Susanne Steggerda, Francesco Parlati. The glutaminase inhibitor CB-839 synergizes with CDK4/6 and PARP inhibitors in pre-clinical tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3509.

Novel PET/CT imaging biomarkers of CB-839 in combination with panitumumab and irinotecan in patients with metastatic and refractory RAS wildtype (WT) colorectal cancer: A phase I/II study.

TPS3616Background: Irinotecan plus panitumumab is active in RAS WT metastatic CRC (mCRC) patients who progress on 5-FU based regimens. Inevitably, patients develop resistance to EGFR inhibition; on...

CANTATA: A randomized phase 2 study of CB-839 in combination with cabozantinib vs. placebo with cabozantinib in patients with advanced/metastatic renal cell carcinoma.

TPS4601Background: Glutamine utilization is a metabolic pathway upregulated in renal cell carcinoma (RCC) and important for RCC tumor cell proliferation and survival. CB-839 is a first-in-class, po...

Phase 1 study of glutaminase (GLS) inhibitor CB-839 combined with either everolimus (E) or cabozantinib (Cabo) in patients (pts) with clear cell (cc) and papillary (pap) metastatic renal cell cancer (mRCC).

603 Background: CB-839 is a first-in-class inhibitor of GLS that targets tumor glutamine utilization, a pathway upregulated in kidney cancer. CB-839 combines with E or Cabo in pre-clinical RCC models to inhibit metabolic pathways resulting in enhanced anti-tumor activity. The CX-839-001 study includes cohorts evaluating the safety, efficacy and recommended Phase 2 dose (RP2D) of CB-839 in combination with E (CBE) or Cabo (CB-Cabo) in pts with mRCC. Here we report results from the CBE and CB-Cabo cohorts. Methods: Eligibility criteria included mRCC with cc or pap histology, ECOG 0-1, RECIST measurable disease and, for cc pts, treatment with at least 1 prior anti-VEGF therapy. Pts received escalating doses of CB-839 (PO BID) in a 3+3 design, either 400-800 mg with E (10 mg PO QD) or 600-800 mg with Cabo (60 mg PO QD). Tumor response (RECIST 1.1) was assessed every 8 wks. Results: 27 pts (22 cc, 3 pap, 2 other) were enrolled in CB-E escalation (n = 17) and expansion (n = 10) cohorts (7 at 400 mg, 13 at 600 mg, 7 at 800 mg) and 11 pts (9 cc, 2 pap) in CB-Cabo escalation cohorts (6 at 600 mg, 5 at 800 mg). Median prior lines of therapy was 2 for CBE (including 64% of cc pts with ≥2 prior anti-VEGF therapies) and 3 for CB-Cabo (range 0-6). A maximum tolerated dose was not reached; 800 mg was selected as the RP2D for CB-839. The most common treatment-related Gr≥3 AEs were fatigue (11%), anemia, hyperglycemia, and neutropenia (7% each) for CBE (N = 27) and diarrhea (14%) and platelet count decreased (14% including 1 DLT at 600 mg) for CB-Cabo (N = 7). Of 24 evaluable CBE pts there was 1 PR and 21 SD for a disease control rate (DCR = CR + PR + SD) of 92% with a median PFS of 7.1 mo (95% CI 4 - 11). For 9 evaluable CB-Cabo pts the ORR and DCR were 44% (4 PR) and 100%, respectively. Conclusions: The tumor metabolism inhibitor CB-839 combines with full dose of RCC targeted therapies, E and Cabo, with good tolerability and encouraging clinical activity in heavily-pretreated mRCC pts. CB-Cabo ORR and DCR of 44% and 100% are promising, and CBE DCR of 92% and PFS of 7.1 mo compare favorably to historical E monotherapy. Randomized Phase 2 studies have been initiated (CBE) or are planned (CB-Cabo). Clinical trial information: NCT02071862.

Abstract PD3-13: Phase 1 study of CB-839, a first-in-class oral inhibitor of glutaminase, in combination with paclitaxel in patients with advanced triple negative breast cancer

Abstract Background: CB-839 is a first-in-class oral highly selective inhibitor of glutaminase (GLS), a mitochondrial enzyme that plays a key role in cancer cell metabolism. Triple negative breast cancer (TNBC) has high GLS expression and demonstrates high glutamine utilization and glutamine dependence in clinical and preclinical studies. CB-839 has monotherapy antitumor activity in vitro and in vivo in preclinical models of TNBC, and also demonstrates synergistic anti-cancer activity with the standard of care agent paclitaxel (Pac). In an ongoing Phase 1 study, CB-839 combined with Pac (Pac-CB) is being evaluated in patients (pts) with metastatic TNBC. We previously reported that Pac-CB was well-tolerated and active in heavily pre-treated TNBC pts, including those previously refractory to taxane treatment for metastatic disease. We report here updated results from this ongoing study. Methods: Pts with refractory metastatic TNBC (prior taxane therapy allowed) received escalating doses of CB-839 (400-800 mg BID) in combination with full dose Pac of 80 mg/m2 Days 1, 8, 15 every 28 days. After demonstration of safety and tolerability, an expansion cohort was opened at the CB-839 recommended phase 2 dose of 800 mg PO BID. Results: As of the May 2017 data cut, 45 pts have enrolled across the dose escalation and expansion cohorts (7 pts at 400 mg, 12 at 600 mg, and 26 at 800 mg). 15 pts (33%) have received ≥5 prior lines of systemic therapy for metastatic disease (median 3 prior lines), and 39 pts (87%) have received prior taxane therapy. The Pac-CB regimen has been well tolerated with the most frequent treatment-related Grade ≥3 AEs being neutropenia (24%), anemia (7.6%), fatigue (2.6%), WBC decreased (2.6%), and peripheral neuropathy (2.6%). At CB-839 doses ≥600 mg BID (n=27 RECIST-evaluable), the ORR has been 22% and disease control rate (DCR=CR+PR+SD) 59%; in the subgroup of pts refractory to previous taxane therapy (n=19) the ORR has been 21% (4 pts) and DCR 47% (9 pts). The highest ORR in this study has been seen in pts of African ancestry (AA, n=11 RECIST evaluable) with an ORR of 36% (4 pts) and DCR 55% (6 pts), with all 4 AA responders being refractory to prior taxane treatment for advanced/metastatic disease. Conclusions: TNBC has elevated glutamine metabolism that requires mitochondrial GLS. In TNBC pts with heavy pretreatment and previous taxane exposure, the combination of CB-839 with Pac has demonstrated clinical activity including a 21% ORR in pts refractory to taxane. Notably, in patients of African ancestry, a population reported to have especially high glutamine utilization in TNBC tumors, the encouraging ORR of 36% suggests a potential genetic association with treatment response. The Pac-CB regimen has been well tolerated in late line TNBC pts, including a Gr 3 neuropathy signal of only 2.6%. A Phase 2 study, CX-839-007, has been initiated to further evaluate the activity and safety of Pac-CB in pts with TNBC, including defined cohorts of pts with 1st line and 3rd line+ metastatic disease in pts of African and non-African ancestry. Responses in relation to genetic background, molecular subtype of TNBC and glutamine biology will be studied. Citation Format: Kalinsky K, Harding JJ, DeMichele A, Infante JR, Gogineni K, Owonikoko TK, Isakoff S, Iliopoulos O, Patel MR, Munster P, Telli ML, Jenkins Y, Fiji GP, Whiting SH, Meric-Bernstam F. Phase 1 study of CB-839, a first-in-class oral inhibitor of glutaminase, in combination with paclitaxel in patients with advanced triple negative breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD3-13.