Pharmacological induction of membrane lipid poly-unsaturation sensitizes melanoma to ROS inducers and overcomes acquired resistance to targeted therapy

BACKGROUND

One of the key limitations of targeted cancer therapies is the rapid onset of therapy resistance. Taking BRAF-mutant melanoma as paradigm, we previously identified the lipogenic regulator SREBP-1 as a central mediator of resistance to MAPK-targeted therapy. Reasoning that lipogenesis-mediated alterations in membrane lipid poly-unsaturation lie at the basis of therapy resistance, we targeted fatty acid synthase (FASN) as key player in this pathway to evoke an exquisite vulnerability to clinical inducers of reactive oxygen species (ROS), thereby rationalizing a novel clinically actionable combination therapy to overcome therapy resistance.

METHODS

Using gene expression analysis and mass spectrometry-based lipidomics of BRAF-mutant melanoma cell lines, melanoma PDX and clinical data sets, we explored the association of FASN expression with membrane lipid poly-unsaturation and therapy-resistance. Next, we treated therapy-resistant models with a preclinical FASN inhibitor TVB-3664 and a panel of ROS inducers and performed ROS analysis, lipid peroxidation tests and real-time cell proliferation assays. Finally, we explored the combination of MAPK inhibitors, TVB-3664 and arsenic trioxide (ATO, as a clinically used ROS-inducer) in Mel006 BRAF mutant PDX as a gold model of therapy resistance and assessed the effect on tumor growth, survival and systemic toxicity.

RESULTS

We found that FASN expression is consistently increased upon the onset of therapy resistance in clinical melanoma samples, in cell lines and in Mel006 PDX and is associated with decreased lipid poly-unsaturation. Forcing lipid poly-unsaturation in therapy-resistant models by combining MAPK inhibition with FASN inhibition attenuated cell proliferation and rendered cells exquisitely sensitive to a host of ROS inducers. In particular, the triple combination of MAPK inhibition, FASN inhibition, and the clinical ROS-inducing compound ATO dramatically increased survival of Mel006 PDX models from 15 to 72% with no associated signs of toxicity.

CONCLUSIONS

We conclude that under MAPK inhibition the direct pharmacological inhibition of FASN evokes an exquisite vulnerability to inducers of ROS by increasing membrane lipid poly-unsaturation. The exploitation of this vulnerability by combining MAPK and/or FASN inhibitors with inducers of ROS greatly delays the onset of therapy resistance and increases survival. Our work identifies a clinically actionable combinatorial treatment for therapy-resistant cancer.

FASN inhibition targets multiple drivers of NASH by reducing steatosis, inflammation and fibrosis in preclinical models

Fatty acid synthase (FASN) is an attractive therapeutic target in non-alcoholic steatohepatitis (NASH) because it drives de novo lipogenesis and mediates pro-inflammatory and fibrogenic signaling. We therefore tested pharmacological inhibition of FASN in human cell culture and in three diet induced mouse models of NASH. Three related FASN inhibitors were used; TVB-3664, TVB-3166 and clinical stage TVB-2640 (denifanstat). In human primary liver microtissues, FASN inhibiton (FASNi) decreased triglyceride (TG) content, consistent with direct anti-steatotic activity. In human hepatic stellate cells, FASNi reduced markers of fibrosis including collagen1α (COL1α1) and α-smooth muscle actin (αSMA). In CD4+ T cells exposed to NASH-related cytokines, FASNi decreased production of Th17 cells, and reduced IL-1β release in LPS-stimulated PBMCs. In mice with diet induced NASH l, FASNi prevented development of hepatic steatosis and fibrosis, and reduced circulating IL-1β. In mice with established diet-induced NASH, FASNi reduced NAFLD activity score, fibrosis score, ALT and TG levels. In the CCl4-induced FAT-NASH mouse model, FASN inhibition decreased hepatic fibrosis and fibrosis markers, and development of hepatocellular carcinoma (HCC) tumors by 85%. These results demonstrate that FASN inhibition attenuates inflammatory and fibrotic drivers of NASH by direct inhibition of immune and stellate cells, beyond decreasing fat accumulation in hepatocytes. FASN inhibition therefore provides an opportunity to target three key hallmarks of NASH.

Targeting de novo lipogenesis and the Lands cycle induces ferroptosis in KRAS-mutant lung cancer

Mutant KRAS (KM), the most common oncogene in lung cancer (LC), regulates fatty acid (FA) metabolism. However, the role of FA in LC tumorigenesis is still not sufficiently characterized. Here, we show that KMLC has a specific lipid profile, with high triacylglycerides and phosphatidylcholines (PC). We demonstrate that FASN, the rate-limiting enzyme in FA synthesis, while being dispensable in EGFR-mutant or wild-type KRAS LC, is required for the viability of KMLC cells. Integrating lipidomic, transcriptomic and functional analyses, we demonstrate that FASN provides saturated and monounsaturated FA to the Lands cycle, the process remodeling oxidized phospholipids, such as PC. Accordingly, blocking either FASN or the Lands cycle in KMLC, promotes ferroptosis, a reactive oxygen species (ROS)- and iron-dependent cell death, characterized by the intracellular accumulation of oxidation-prone PC. Our work indicates that KM dictates a dependency on newly synthesized FA to escape ferroptosis, establishing a targetable vulnerability in KMLC.

TVB-2640 (FASN Inhibitor) for the Treatment of Nonalcoholic Steatohepatitis: FASCINATE-1, a Randomized, Placebo-Controlled Phase 2a Trial

BACKGROUND & AIMS

Increased de novo lipogenesis creates excess intrahepatic fat and lipotoxins, propagating liver damage in nonalcoholic steatohepatitis. TVB-2640, a fatty acid synthase inhibitor, was designed to reduce excess liver fat and directly inhibit inflammatory and fibrogenic pathways. We assessed the safety and efficacy of TVB-2640 in patients with nonalcoholic steatohepatitis in the United States.

METHODS

3V2640-CLIN-005 (FASCINATE-1) was a randomized, placebo-controlled, single-blind study at 10 US sites. Adults with ≥8% liver fat, assessed by magnetic resonance imaging proton density fat fraction, and evidence of liver fibrosis by magnetic resonance elastography ≥2.5 kPa or liver biopsy were eligible. Ninety-nine patients were randomized to receive placebo or 25 mg or 50 mg of TVB-2640 (orally, once-daily for 12 weeks). The primary end points of this study were safety and relative change in liver fat after treatment.

RESULTS

Liver fat increased in the placebo cohort by 4.5% relative to baseline; in contrast TVB-2640 reduced liver fat by 9.6% in the 25-mg cohort (n = 30; least squares mean: -15.5%; 95% confidence interval, -31.3 to -0.23; P = .053), and 28.1% in the 50-mg cohort (n = 28; least squares mean: -28.0%; 95% confidence interval, -44.5 to -11.6; P = .001). Eleven percent of patients in the placebo group achieved a ≥30% relative reduction of liver fat compared to 23% in the 25-mg group, and 61% in the 50-mg group (P < .001). Secondary analyses showed improvements of metabolic, pro-inflammatory and fibrotic markers. TVB-2640 was well tolerated; adverse events were mostly mild and balanced among the groups.

CONCLUSIONS

TVB-2640 significantly reduced liver fat and improved biochemical, inflammatory, and fibrotic biomarkers after 12 weeks, in a dose-dependent manner in patients with nonalcoholic steatohepatitis. ClinicalTrials.gov, Number NCT03938246.

Fatty acid synthase (FASN) regulates the mitochondrial priming of cancer cells

Inhibitors of the lipogenic enzyme fatty acid synthase (FASN) have attracted much attention in the last decade as potential targeted cancer therapies. However, little is known about the molecular determinants of cancer cell sensitivity to FASN inhibitors (FASNis), which is a major roadblock to their therapeutic application. Here, we find that pharmacological starvation of endogenously produced FAs is a previously unrecognized metabolic stress that heightens mitochondrial apoptotic priming and favors cell death induction by BH3 mimetic inhibitors. Evaluation of the death decision circuits controlled by the BCL-2 family of proteins revealed that FASN inhibition is accompanied by the upregulation of the pro-death BH3-only proteins BIM, PUMA, and NOXA. Cell death triggered by FASN inhibition, which causally involves a palmitate/NADPH-related redox imbalance, is markedly diminished by concurrent loss of BIM or PUMA, suggesting that FASN activity controls cancer cell survival by fine-tuning the BH3 only proteins-dependent mitochondrial threshold for apoptosis. FASN inhibition results in a heightened mitochondrial apoptosis priming, shifting cells toward a primed-for-death state "addicted" to the anti-apoptotic protein BCL-2. Accordingly, co-administration of a FASNi synergistically augments the apoptosis-inducing activity of the dual BCL-X_L/BCL-2 inhibitor ABT-263 (navitoclax) and the BCL-2 specific BH3-mimetic ABT-199 (venetoclax). FASN inhibition, however, fails to sensitize breast cancer cells to MCL-1- and BCL-X_L-selective inhibitors such as S63845 and A1331852. A human breast cancer xenograft model evidenced that oral administration of the only clinically available FASNi drastically sensitizes FASN-addicted breast tumors to ineffective single-agents navitoclax and venetoclax in vivo. In summary, a novel FASN-driven facet of the mitochondrial priming mechanistically links the redox-buffering mechanism of FASN activity to the intrinsic apoptotic threshold in breast cancer cells. Combining next-generation FASNis with BCL-2-specific BH3 mimetics that directly activate the apoptotic machinery might generate more potent and longer-lasting antitumor responses in a clinical setting.

First-in-human study of the safety, pharmacokinetics, and pharmacodynamics of first-in-class fatty acid synthase inhibitor TVB-2640 alone and with a taxane in advanced tumors

BACKGROUND

We conducted a first-in-human dose-escalation study with the oral FASN inhibitor TVB-2640 to determine the maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D), as monotherapy and with a taxane.

METHODS

This completed open-label outpatient study was conducted at 11 sites in the United States and United Kingdom. Patients with previously-treated advanced metastatic solid tumors and adequate performance status and organ function were eligible. TVB-2640 was administered orally daily until PD. Dose escalation initially followed an accelerated titration design that switched to a standard 3 + 3 design after Grade 2 toxicity occurred. Disease-specific cohorts were enrolled at the MTD. Statistical analyses were primarily descriptive. Safety analyses were performed on patients who received at least 1 dose of study drug. (Clinicaltrials.gov identifier NCT02223247).

FINDINGS

The study was conducted from 21 November 2013 to 07 February 2017. Overall, 136 patients received TVB-2640, 76 as monotherapy (weight-based doses of 60 mg/m² to 240 mg/m² and flat doses of 200 and 250 mg) and 60 in combination, (weight-based doses of 60 mg/m² to 100 mg/m² and flat dose of 200 mg) (55 paclitaxel, 5 docetaxel). DLTs with TVB-2640 were reversible skin and ocular effects. The MTD/RP2D was 100 mg/m². The most common TEAEs (n,%) with TVB-2640 monotherapy were alopecia (46; 61%), PPE syndrome (35; 46%), fatigue (28; 37%), decreased appetite (20; 26%), and dry skin (17; 22%), and with TVB-2640+paclitaxel were fatigue (29 ; 53%), alopecia (25; 46%), PPE syndrome (25; 46%), nausea (22; 40%), and peripheral neuropathy (20; 36%). One fatal case of drug-related pneumonitis occurred with TVB-2640+paclitaxel; no other treatment-related deaths occurred. Target engagement (FASN inhibition) and inhibition of lipogenesis were demonstrated with TVB-2640. The disease control rate (DCR) with TVB-2640 monotherapy was 42%; no patient treated with monotherapy had a complete or partial response (CR or PR). In combination with paclitaxel, the PR rate was 11% and the DCR was 70%. Responses were seen across multiple tumor types, including in patients with KRAS^MUT NSCLC, ovarian, and breast cancer.

INTERPRETATION

TVB-2640 demonstrated potent FASN inhibition and a predictable and manageable safety profile, primarily characterized by non-serious, reversible adverse events affecting skin and eyes. Further investigation of TVB-2640 in patients with solid tumors, particularly in KRAS^MUT lung, ovarian, and breast cancer, is warranted.

FUNDING

This trial was funded by 3-V Biosciences, Inc. (now known as Sagimet Biosciences Inc.).

Fatty Acid Synthase Inhibitor TVB-2640 Reduces Hepatic de Novo Lipogenesis in Males With Metabolic Abnormalities

BACKGROUND AND AIMS

Elevated hepatic de novo lipogenesis (DNL) is a key distinguishing characteristic of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis. In rodent models of NAFLD, treatment with a surrogate of TVB-2640, a pharmacological fatty acid synthase inhibitor, has been shown to reduce hepatic fat and other biomarkers of DNL. The purpose of this phase I clinical study was to test the effect of the TVB-2640 in obese men with certain metabolic abnormalities that put them at risk for NAFLD.

APPROACH AND RESULTS

Twelve subjects (mean ± SEM, 42 ± 2 years, body mass index 37.4 ± 1.2 kg/m² , glucose 103 ± 2 mg/dL, triacylglycerols 196 ± 27 mg/dL, and elevated liver enzymes) underwent 10 days of treatment with TVB-2640 at doses ranging from 50-150 mg/day. Food intake was controlled throughout the study. Hepatic DNL was measured before and after an oral fructose/glucose bolus using isotopic labeling with 1-¹³ C₁ -acetate intravenous infusion, followed by measurement of labeled very low-density lipoprotein palmitate via gas chromatography mass spectometry. Substrate oxidation was measured by indirect calorimetry. Across the range of doses, fasting DNL was reduced by up to 90% (P = 0.003). Increasing plasma concentrations of TVB-2640 were associated with progressive reductions in the percent of fructose-stimulated peak fractional DNL (R²  = -0.749, P = 0.0003) and absolute DNL area under the curve 6 hours following fructose/glucose bolus (R²  = -0.554, P = 0.005). For all subjects combined, alanine aminotransferase was reduced by 15.8 ± 8.4% (P = 0.05). Substrate oxidation was unchanged, and safety monitoring revealed that the drug was well tolerated, without an increase in plasma triglycerides. Alopecia occurred in 2 subjects (reversed after stopping the drug), but otherwise no changes were observed in fasting glucose, insulin, ketones, and renal function.

CONCLUSION

These data support the therapeutic potential of a fatty acid synthase inhibitor, TVB-2640 in particular, in patients with NAFLD and nonalcoholic steatohepatitis.

Abstract 708: Targeting fatty acid synthase induces apoptosis and senescence

Fatty acid synthase (FASN) is a novel therapeutic target for cancer as it has increased expression in many different types of cancers. There has been significant understanding that cancer cells can hijack and modify tightly regulated metabolic pathway for its own survival. FASN is the enzyme that synthesizes palmitate from malonyl-CoA for energy storage, structure and biomolecules. FASN expression is low to undetectable in normal cells with the exception of liver and adipose tissue. In this study, we investigated the role of FASN in breast cancer cells. We observed that in highly expressing FASN breast cancer cells, TVB-3166, FASN inhibitor, results in a decrease in cellular proliferation and an increase in cellular death. FASN inhibition increased reactive oxygen species (ROS) and altered NADPH/NADP+ ratio. Increase in ROS and NADPH have been linked to the intrinsic apoptosis pathway. Additionally, there is an increase in expression of the BH3-only proteins Bim, Puma and Noxa, leading to the permeabilization of the mitochondria and the release of cytochrome c. Furthermore, after prolong exposure to TVB-3166 a number of cells enter into a senescent state. This was observed the in detection of β-galactosidase and confirmed by the expression of senescent markers including ARF, INK4A, and CIP. Additionally, when the cells were treated with a CDK4/6 inhibitor in combination with the FASN inhibitor TVB-3166, an increase in stress induced premature senescence was observed. Our data demonstrates that inhibition of FASN induces intrinsic apoptosis while it stimulates cellular senescence to the apoptotic resistant cells. Therefore, the ability for TVB-3166 to both eradicate and overturn cell growth makes it potential therapeutic modality.

Citation Format: Travis Van der Steen, George Kemble, Ruth Lupu. Targeting fatty acid synthase induces apoptosis and senescence [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 708.

Abstract 3723: Fatty acid synthase: A new therapeutic target for pancreatic cancer

Pancreatic cancer is the fourth leading cause of cancer related deaths in the United States and continues to be hindered with limited treatment options. One of the current therapeutic regimens for pancreatic cancer often include the nucleoside analog gemcitabine (Gem), while it has been used for many years, the overall survival rate lingers around 6%. New therapies are needed to treat this disease. Fatty acid synthase (FASN) has received increased attention as a potential target for cancer therapy in the last decade. FASN is the key enzyme in the de novo synthesis of palmitate from malonyl-CoA. Palmitate is the precursor other long-chain fatty acids (FA). However, the precise mechanism by which pharmacological interference with endogenous FA biogenesis might facilitate apoptosis in tumor cells remains unresolved. We herein explored the molecular relationship between FASN activity, oxidative stress/redox balance, and the intrinsic apoptotic pathway in FASN overexpressing-dependent pancreatic cancer cells. About 68% of Pancreatic Ductal Carcinomas (PDA) expresses high levels of Fatty acid synthase (FASN), and its expression is correlated with disease free survival. A newly developed FASN inhibitor with excellent pharmaceutical properties was used for our studies TVB-3166 (in vitro) and TVB-3664 (in vivo) and ten different PDX derived cells were used for the studies. Pharmacological blockade of FASN activity significantly increased the NADPH/NADP+ ratio, promoted the production of reactive oxygen species (ROS). Accordingly, the inhibition of endogenous FA synthesis promoted mitochondrial membrane permeabilization, cytochrome c release, and apoptotic cell death. Each step of the FASN inhibition/BH3-only protein axis could be reversed with a ROS scavenger or the FASN end-product palmitate, thus confirming that the delineated pro-apoptotic cascade likely reflects on-target effects of FASN inhibition. Most importantly, the in vivo studies using PaCa-PDX reveal a significant decrease in tumor growth and furthermore a synergistic effect of between TVB-3664 and Gem. In conclusion, our findings uncover a novel FASN-dependent mitochondrial priming that links de novo FA biosynthesis with the intrinsic apoptotic threshold in cancer cells. The discovery that FASN-inhibited cancer cells exist in an apoptosis-prone state highly sensitive to BH3 mimetics warrants clinical exploration in FASN-overexpressing pancreatic cancer patients.

Citation Format: Travis Vander Steen, Li Ding, Yu Zhang, George Kemble, Daniel Billadeau, Ruth Lupu. Fatty acid synthase: A new therapeutic target for pancreatic cancer [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 3723.

Abstract CT153: First in human study of the first-in-class fatty acid synthase (FASN) inhibitor TVB-2640

Introduction

FASN inhibition causes selective disruption of palmitate biosynthesis that, in tumor cells, leads to apoptosis. TVB-2640 is an oral, first-in-class, small molecule reversible inhibitor of FASN that demonstrated in vivo antitumor effects. We previously reported the results of dose escalation and now present evidence of activity in patients (pts) treated in the dose expansion cohorts.

Methods

This fully enrolled multicenter phase I trial included pts with advanced solid tumors. TVB-2640 was given PO once daily at the MTD (100 mg/m2) as monotherapy (mono) or in combination (combo) with weekly IV paclitaxel (80 mg/m2).

Results

The most common related AEs observed in both groups (mono, N=44, combo, N=43) included alopecia (41%), palmar-plantar erythrodysesthesia (PPE) (47%), and decreased appetite (13%). Additional common AEs in the mono group included dry skin (19%) and in the combo group included nausea (28%). Gr3 related AEs included decreased appetite (8%) and PPE (9%); all other related AEs were ≤ Gr2. All related AEs were reversible on dose interruption. No enhancement of paclitaxel toxicity was observed with TVB-2640. Pneumonitis in the combo arm was observed uncommonly (9%), but the contribution of TVB-2640 to this effect is uncertain.

Pharmacokinetic analyses showed that TVB-2640 had a similar half-life whether given alone or in combo with paclitaxel. Clearance rates were similar on days 1 and 8 (or day 15 for combo). Multiple pharmacodynamic markers demonstrated potent inhibition of FASN and lipogenesis in pts.

With respect to clinical activity, overall, 5 confirmed RECIST partial responses (cPR) were seen. Among pts with NSCLC, 18 of 31 were KRASmut, and KRASmut pts achieved longer progression-free survival on TVB-2640 monotherapy, with 60% of KRASmut pts vs. 0% of KRASwt pts on study &gt; 12 wks. Among 18 KRASmut pts, 11 achieved prolonged SD (≥16 wks), including 6 mono pts (SD=19-46 wks) and 5 combo pts (SD=23-54 wks), whereas no KRASwt pts achieved prolonged SD. One NSCLC combo pt achieved cPR at wk 12 and remained on study for 39 wks. Of 14 breast cancer pts, 3 pts achieved cPR and 8 pts achieved prolonged SD (≥16 wks), despite extensive previous treatment, including taxane resistance. One ongoing breast cancer pt with SD, entering her 78th wk of treatment, discontinued paclitaxel at wk 35 and remains on monotherapy . One pt with peritoneal carcinoma (combo) achieved cPR and a 58% decrease in CA125. Reductions in CA125 were seen in 5 out of 12 ovarian cancer pts, who were typically heavily pretreated and taxane-resistant.

Summary

TVB-2640 demonstrated antitumor activity, including objective responses when combined with weekly paclitaxel, as well as prolonged SD as monotherapy or in combination with paclitaxel. Further studies are planned to evaluate the efficacy of TVB-2640 in NSCLC and breast cancer pts.

Citation Format: Gerald Falchook, Manish Patel, Jeffrey Infante, Hendrik-Tobias Arkenau, Emma Dean, Andrew Brenner, Erkut Borazanci, Juanita Lopez, Kathleen Moore, Peter Schmid, Arthur Frankel, Suzanne Jones, William McCulloch, George Kemble, Howard Burris. First in human study of the first-in-class fatty acid synthase (FASN) inhibitor TVB-2640 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr CT153. doi:10.1158/1538-7445.AM2017-CT153

Abstract 452: Activation of Akt pathway and autophagy promotes resistance to FASN inhibition in colorectal cancer patient-derived xenograft models

Fatty Acid Synthase (FASN), a key enzyme of de novo lipogenesis, is upregulated in many cancers including colorectal cancer (CRC); increased FASN expression is associated with poor prognosis. Potent FASN inhibitors developed by 3-V Biosciences demonstrate anti-tumor activity in vitro and in vivo and a favorable tolerability profile in a Phase I clinical trial in solid tumor patients. However, CRC characteristics associated with responsiveness to FASN inhibition are not fully understood. The purpose of our study was: (i) to determine the effect of FASN inhibition on tumor growth in CRC patient-derived xenografts (PDXs); (ii) to identify potential biomarkers associated with CRC responsiveness to FASN inhibition; and (iii) to explore new combination strategies with FASN inhibitors. METHODS. Tumor growth was assessed in 9 PDXs established in NSG mice using freshly resected specimens. Once the xenografts grew to ~100 mm3, mice were randomized into two groups (n=5) to receive either vehicle or TVB-3664 or four groups (n=10) for TVB-3664 treatment in combination with either MK2206 or Chloroquine (CQ). Tumor volume and animal weights were measured weekly. Western blot analysis and immunohistochemistry staining were used to identify FASN-mediated changes in signaling pathways. Changes in metabolites and lipids were analyzed by nuclear magnetic resonance and mass spectrometry in plasma and tumor tissues. Next Generation Sequencing was used to assess the mutation profile of 198 oncogenes in patient tumors and PDXs. RESULTS. PDXs showed a wide range of sensitivity to FASN inhibition: TVB-3664 treatment attained significant response (reduced tumor volume) in 3 PDXs, significant response followed by developed resistance in one PDX, and no response in 5 PDXs. Activation of Akt and AMPK pathways was associated with resistance to FASN inhibition and combination of TVB-3664 with either MK2206 or CQ led to a significant reduction in tumor volume as compared to either drug alone. Moreover, TVB-3664 treatment significantly decreased the total palmitate level in plasma and the levels of triglycerides, diglycerides, phosphatidylserines, phosphatidylethanolamines, and phosphatidylcholines in tumor tissues. Furthermore, a significant decrease in the levels of AXP-1, AXP-2 and myo-Inositol-2 was observed in tumors responsive to FASN inhibition. CONCLUSIONS. Our studies demonstrate that TVB-3664 shows anti-tumor activity in CRC. Importantly, our results suggest that activation of Akt and autophagy are major mechanisms of resistance to FASN inhibition and demonstrate that combine inhibition of these pathways and FASN may be a new therapeutic approach in CRC. Ongoing studies of correlation between mutation and metabolic profiles of tumors and tumor response to FASN inhibition aim to identify a subset of CRC patients that are likely to respond to FASN-targeted therapy.

Citation Format: Yekaterina Y. Zaytseva, Piotr G. Rychahou, Anh-Thu Le, Robert M. Flight, Timothy L. Scott, Jennifer W. Harris, Sally Hodges, Brent J. Hallahan, Dana L. Napier, Jinpeng Liu, Chi Wang, Manjula Sunkara, Andrew Morris, Ji Tae Kim, Sivakumaran Theru Arumugam, Andrew Lane, Teresa W. Fan, Hunter Moseley, Tianyan Gao, Eun Y. Lee, Heidi L. Weiss, Timothy S. Heuer, George Kemble, B Mark Evers. Activation of Akt pathway and autophagy promotes resistance to FASN inhibition in colorectal cancer patient-derived xenograft models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 452. doi:10.1158/1538-7445.AM2017-452

A phase 2 study to determine the efficacy and safety of TVB-2640 in combination with bevacizumab in patients with first relapse of high grade astrocytoma

TPS2080

Background: The mainstay of treatment for Glioblastoma Multiforme (GBM) remains surgical removal followed by combined chemotherapy with temozolomide and radiation therapy. Second line Bevacizumab (Bev) is indicated upon progression, but unfortunately the responses are not very long lasting, and there are no therapeutic options available at that point. We have learned that antiangiogenic resistance in GBM is promoted by hypoxia; moreover, metabolomic profile of GBM under such conditions reveals an increased presence of long chain fatty acids. On second hand, tumor cells compared to normal cells depend more on palmitate, and is Fatty Acid Synthase (FASN) the enzyme capable of catalyzing its biosynthesis. Further studies have shown how GBM overexpress FASN and how its inhibition selectively inhibits growth and viability of tumor cells by inducing tumor cell apoptosis. TVB-2640 emerges as a novel agent that selectively inhibits FASN. This study represents a phase 2 clinical investigation of TVB-2640, which is to be conducted in patients with Recurrent High Grade Astrocytoma. Methods: This is a prospective, randomized, phase 2 study of TVB-2640 in combination with Bev or Bev alone in patients with GBM in first relapse. Primary end point is progression free survival (PFS). Patients 18 years or older, with ECOG 0 to 2 and GBM progression following standard combined modality treatment will qualify for the study. Patients will be randomized into 2 separate arms. Patients in arm number one will receive Bev every 2 weeks in combination with TVB-2640 while patients in arm number two will receive Bev alone every 2 weeks. MR-Spectroscopy will be obtained on all patients at day 1 and 28 of first cycle. Starting on cycle 2 day 1, all patients will converge to a single arm and will continue to receive Bev in combination with TVB-2640. A total sample size of 24 patients will provide 90% power to detect a 4 months difference in PFS (3 months for Bev alone (historic controls) versus 7 months for TVB-2640 in combination with Bev, i.e., a hazard ratio of 0.43) using a one-sided log-rank test with alpha = 0.1. The trial is open and enrollment will begin in Feb 2017. Clinical trial information: NCT03032484.

FASN Inhibition and Taxane Treatment Combine to Enhance Anti-tumor Efficacy in Diverse Xenograft Tumor Models through Disruption of Tubulin Palmitoylation and Microtubule Organization and FASN Inhibition-Mediated Effects on Oncogenic Signaling and Gene Expression

Palmitate, the enzymatic product of FASN, and palmitate-derived lipids support cell metabolism, membrane architecture, protein localization, and intracellular signaling. Tubulins are among many proteins that are modified post-translationally by acylation with palmitate. We show that FASN inhibition with TVB-3166 or TVB-3664 significantly reduces tubulin palmitoylation and mRNA expression. Disrupted microtubule organization in tumor cells is an additional consequence of FASN inhibition. FASN inhibition combined with taxane treatment enhances inhibition of in vitro tumor cell growth compared to treatment with either agent alone. In lung, ovarian, prostate, and pancreatic tumor xenograft studies, FASN inhibition and paclitaxel or docetaxel combine to inhibit xenograft tumor growth with significantly enhanced anti-tumor activity. Tumor regression was observed in 3 of 6 tumor xenograft models. FASN inhibition does not affect cellular taxane concentration in vitro. Our data suggest a mechanism of enhanced anti-tumor activity of the FASN and taxane drug combination that includes inhibition of tubulin palmitoylation and disruption of microtubule organization in tumor cells, as well as a sensitization of tumor cells to FASN inhibition-mediated effects that include gene expression changes and inhibition of β-catenin. Together, the results strongly support investigation of combined FASN inhibition and taxane treatment as a therapy for a variety of human cancers.

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FASN inhibition decreases tubulin palmitoylation and disrupts microtubules in tumor cells but not non-tumor cells

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Combined FASN inhibition and taxane treatment increases inhibition of in vitro tumor cell colony growth

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FASN inhibition does not affect intracellular paclitaxel concentrations

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Combined FASN inhibition and taxane treatment significantly increases inhibition of tumor growth or causes regression of diverse xenograft tumors

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Taxane treatment sensitizes xenograft tumors to FASN inhibition-mediated beta-catenin blockade and gene expression changes

Fatty acid synthase (FASN) is a vital enzyme in tumor cell biology; the over-expression of FASN is associated with diminished patient prognosis and resistance to many cancer therapies. Our data demonstrate that selective and potent FASN inhibition combines with taxane treatment to enhance tumor growth inhibition and induce tumor regression in varied preclinical tumor models. Mechanism-of-action studies indicate that the increased activity of the combination results from the effects of both drugs. The results support clinical investigation of combined FASN inhibition and taxane treatment as an anti-cancer therapy.

A Phase 1 Study of 4 Live, Recombinant Human Cytomegalovirus Towne/Toledo Chimera Vaccines in Cytomegalovirus-Seronegative Men

BACKGROUND

 Human cytomegalovirus (HCMV) infection causes disease in newborns and transplant recipients. A HCMV vaccine (Towne) protects transplant recipients.

METHODS

 The genomes of Towne and the nonattenuated Toledo strain were recombined, yielding 4 Towne/Toledo chimera vaccines. Each of 36 HCMV-seronegative men received 1 subcutaneous dose of 10, 100, or 1000 plaque-forming units (PFU) in cohorts of 3. Safety and immunogenicity were evaluated over 12 weeks after immunization and for 52 weeks for those who seroconverted.

RESULTS

 There were no serious local or systemic reactions. No subject had HCMV in urine or saliva. For chimera 3, none of 9 subjects seroconverted. For chimera 1, 1 of 9 seroconverted (the seroconverter received 100 PFU). For chimera 2, 3 subjects seroconverted (1 received 100 PFU, and 2 received 1000 PFU). For chimera 4, 7 subjects seroconverted (1 received 10 PFU, 3 received 100 PFU, and 3 received 1000 PFU). All 11 seroconverters developed low but detectable levels of neutralizing activity. CD4⁺ T-cell responses were detectable in 1 subject (who received 100 PFU of chimera 4). Seven subjects receiving chimera 2 or 4 had detectable CD8⁺ T-cell responses to IE1; 3 responded to 1-2 additional antigens.

CONCLUSIONS

 The Towne/Toledo chimera vaccine candidates were well tolerated and were not excreted. Additional human trials of chimeras 2 and 4 are appropriate.

CLINICAL TRIALS REGISTRATION

 NCT01195571.

Abstract 4743: Preclinical studies characterize tumor type sensitivity to FASN inhibition and the mechanism and efficacy of novel drug combinations with TVB-2640

Tumor cells have an increased dependence on FASN-synthesized palmitate compared to non-tumor cells, which obtain many of their required lipids from the extracellular milieu. Palmitate and palmitate-derived lipids comprise diverse cellular components and function in processes required for tumor cell proliferation and survival. Previously we showed that FASN inhibition results in tumor cell apoptosis in vitro and xenograft tumor growth inhibition in vivo. Our studies demonstrated that diverse tumor types exhibit sensitivity to FASN inhibition and characterized mechanisms of action that associate with the antitumor activity of highly selective small molecule FASN inhibitors. In vitro studies with diverse tumor cell types elucidated a mechanism of action that includes plasma membrane remodeling, signal transduction pathway inhibition, and gene expression reprogramming.

TVB-2640, TVB-3166, and TVB-3664 belong to a series of orally available, reversible, potent, and selective FASN inhibitors discovered and developed by 3-V Biosciences. Analysis of gene expression data from tumor cell lines and human tumors, both primary and patient-derived xenografts, has allowed for the classification of FASN sensitivity by tumor type, histology, and molecular genetic markers. Discoveries from these analyses are being characterized further using in vitro and in vivo studies.

Combined inhibition of FASN and microtubule function with taxane treatment, e.g. paclitaxel, results in synergistic inhibition of tumor growth. Indeed, in Phase I clinical investigation, TVB-2640 combined with paclitaxel has shown promising early signs of clinical activity. Previous in vitro studies revealed that FASN inhibition causes changes in beta-tubulin expression and disrupts the organization of cellular microtubule structures in varied tumor cell types such as CALU-6 non-small-cell lung and 22Rv1 prostate tumor cell lines. Extending our investigation of the mechanism of FASN/taxane synergy, we now show that FASN inhibition prevents beta-tubulin palmitoylation. This likely plays a significant role in the observed effects on beta-tubulin expression and microtubule architecture. As disruption of protein palmitoylation is believed to contribute significantly to the anti-tumor activity of FASN inhibition in general, we expanded the analysis of protein palmitoylation following inhibition of FASN with TVB-3166 and TVB-3664 to include key oncogenic drivers of cell growth, proliferation, and survival such as K-Ras and EGFR. Additionally, the efficacy of FASN inhibition in combination with additional, non-taxane approved cancer therapies, including immunomodulatory agents and bevacizumab, is being investigated.

Citation Format: Timothy S. Heuer, Richard Ventura, Julie Lai, Joanna Waszczuk, Claudia Rubio, Glenn Hammonds, Marie O’ Farrell, Douglas Buckley, George Kemble. Preclinical studies characterize tumor type sensitivity to FASN inhibition and the mechanism and efficacy of novel drug combinations with TVB-2640. [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 4743.

Abstract LB-214: FASN inhibitor TVB-2640 shows pharmacodynamic effect and evidence of clinical activity in KRAS-mutant NSCLC patients in a phase I study

TVB-2640 is an oral, first-in-class, selective and reversible inhibitor of fatty acid synthase (FASN) in Phase 1 testing in solid tumor patients (study 3V2640-CLIN-002).

FASN is a central mediator of neoplastic lipogenesis and uniquely catalyzes the production of palmitate, a key signaling molecule and the building block for long chain fatty acids. Tumor cells frequently increase FASN expression compared to normal cells to support an increased dependence on de novo lipogenesis to produce palmitate, phospholipids, lipid second messengers, membranes and lipid rafts for oncogenic signaling. High FASN correlates with poor prognosis in several tumor types including NSCLC. Palmitoylation, the reversible attachment of palmitate to proteins regulates membrane interactions and dynamically alters protein trafficking and function. RAS proteins require palmitoylation for plasma membrane localization and signaling, and KRAS4A mutated at G12 specifically requires palmitoylation for oncogenic activity. FASN inhibitors may therefore provide a novel approach to target KRAS which to date has eluded many drug development approaches.

In vitro viability assays showed that KRAS mutant NSCLC cell lines show greater sensitivity to FASN inhibitors than KRAS WT. Furthermore gene expression analysis of TCGA NSCLC tumors and PDX models showed that KRAS mutant cases are associated with a higher incidence of lipogenic features than KRAS WT.

The ongoing Phase 1 study includes 2 NSCLC expansion cohorts; TVB-2640 as monotherapy or in combination with paclitaxel. Several biomarker approaches are ongoing to investigate pharmacodynamic activity and patient enrichment strategies. Metabolomic profiling of serum from 12 NSCLC patients showed increased serum malonyl carnitine and decreased palmitate- derived lipids after 8 or 15 days of TVB-2640 treatment. These changes are consistent with FASN inhibition, and also observed in preclinical models. A novel non-invasive approach using Sebutape patches to collect forehead sebum showed inhibition of de novo lipogenesis in 7/7 patients including 2 NSCLC. Decreases in wax esters, saturated and monounsaturated triglycerides were observed, indicating that these lipids are not restored by diet.

To date, 16 NSCLC patients are considered evaluable for clinical activity; 6 have KRAS mutant tumors, 2 have wild type KRAS and 8 are unknown. Of the 6 known KRAS mutant patients, 3 are in the monotherapy cohort and all 3 have stable disease for 20, &gt;25 and &gt;37 weeks respectively. The remaining 3 KRAS mutant patients are on combination therapy; one achieved a partial response and remains on therapy (&gt;22 weeks), 1 had stable disease (24 weeks), and 1 progressed.

This study shows that TVB-2640 1) inhibits palmitate production and lipogenesis, and 2) shows evidence of clinical activity in KRAS mutant NSCLC patients. Additional biomarker and clinical analyses are ongoing in NSCLC and other tumor types.

Citation Format: Marie O’Farrell, Tim Heuer, Katharine Grimmer, Richard Crowley, Joanna Waszczuk, Marina Fridlib, Richard Ventura, Claudia Rubio, Julie Lai, Doug Buckley, William McCulloch, George Kemble. FASN inhibitor TVB-2640 shows pharmacodynamic effect and evidence of clinical activity in KRAS-mutant NSCLC patients in a phase I study. [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 LB-214.

Abstract 1010: Evaluation of small-molecule FASN inhibitors in preclinical models of colorectal cancer

Fatty Acid Synthase (FASN), a key enzyme of de novo lipid synthesis, is upregulated in many cancers including colorectal cancer (CRC); increased FASN activity is associated with decreased survival and increased disease recurrence. Recently, a first-in-class, oral FASN inhibitor (TVB-2640) entered a Phase I clinical trial (3V2640-CLIN-002) in solid tumor patients demonstrating a favorable tolerability profile with no significant adverse events; however, tumor characteristics that would indicate responsiveness to FASN inhibition are not fully understood. The purpose of our study was: (i) to determine the effect of novel, selective and reversible FASN inhibitors on proliferation of primary CRC cell cultures, established CRC cell lines, and CRC patient-derived xenografts (PDXs); and (ii) to identify potential biomarkers associated with CRC responsiveness to FASN inhibition. METHODS. The effect of TVB-3166, TVB-3664, and TVB-3693 (all developed by 3-V Biosciences) on the proliferation of primary cells (established from 1st generation PDX tumors) and CRC cell lines was assessed by cell count; apoptosis was assessed by Cell Death ELISA. In addition, tumor growth was assessed in PDX models established in NOD SCID gamma mice using freshly resected CRC specimens (either primary CRC or metastasis) from our patient population. Once the xenografts grew to ∼100 mm3, mice were randomized into two groups (n = 5) to receive either vehicle or TVB-3664 (3mg/kg) by gavage daily. Tumor volume and animal weights were measured weekly. Western blot analysis, immunohistochemistry and immunofluorescent staining were used to identify FASN-mediated changes in β-catenin, Akt and AMPK pathways. RESULTS. TVB compounds tested showed similar efficacy in primary and established CRC cells with a wide range of sensitivity to FASN inhibition. The 5 cell lines that were most responsive to FASN inhibition demonstrated a low basal level of pAMPK and pAkt as compared to the 5 least responsive cells. Moreover, we noted that increased FASN protein expression was also associated with increased sensitivity to FASN inhibition. Inhibition of proliferation by TVB compounds was associated with decreased expression of active β-catenin, c-MYC, pAkt, and survivin, while an increase in apoptosis was noted by induction of PARP cleavage. Consistent with our in vitro studies, TVB-3664 treatment significantly reduced tumor volume in vivo with no weight changes or toxicity observed. CONCLUSIONS. Our studies show that the novel FASN inhibitors, as a single agent, significantly inhibit CRC growth both in vitro and in vivo. Importantly, our results suggest that basal activation of AMPK and Akt may be predictive of responsiveness to FASN inhibition and may function as potential biomarkers to allow a more personalized treatment approach.

Citation Format: Yekaterina Y. Zaytseva, Piotr G. Rychahou, Tianyan Gao, Eun Y. Lee, Heidi L. Weiss, Timothy S. Heuer, George Kemble, B. Mark Evers. Evaluation of small-molecule FASN inhibitors in preclinical models of colorectal cancer. [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 1010.

Abstract A75: Translational studies of a first-in-class FASN Inhibitor, TVB-2640, linking preclinical studies to clinical laboratory observations in solid tumor patients

Dysregulated expression of FASN is a central mediator of neoplastic lipogenesis. FASN catalyzes the production of palmitate, the building block of long chain fatty acids, providing a mechanism to convert glucose and other carbon sources into lipids needed for production of phospholipids, formation of lipid rafts and the subsequent assembly of receptor tyrosine kinases and other signaling molecules in microdomains juxtaposed to the membrane. Inhibition of FASN in tumor cells leads to disruption of PI3K/Akt/mTOR and other important pathways leading to apoptosis. Targeting this critical nexus between lipogenesis and cellular survival/proliferation signaling pathways makes inhibition of FASN a novel therapeutic approach with a strong biological rationale and 3-V Biosciences has initiated clinical studies with its first-in-class FASN inhibitor.

3-V Bio has developed a series of orally available, reversible, potent, and selective FASN inhibitors that remodel tumor cell membranes, disrupt pAkt and Wnt/beta-catenin pathways, and reprogram gene expression. These effects lead to apoptosis of tumor cells in culture, inhibition of anchorage-independent cell growth under lipid-rich conditions and inhibition of in vivo xenograft tumor growth in mice and rats. We are currently using transcriptomic and metabolomic analyses, including lipidmomic profiling, to explore the fundamental mechanisms resulting in sensitivity to the FASN inhibitor, TVB-3166. These same platforms are used to examine the changes in response to FASN inhibition in tumor and surrogate tissues of xenograft models as well as surrogate tissues of cancer patients.

A panel of tumor and normal cell lines was assembled and lipids were assessed prior to and 72 hours after treatment with TVB-3166. A reduction of saturated fatty acids was observed in all cell lines indicative of FASN inhibition. A similar extent of reduction was observed in media in the presence of 1% or 10% serum; these results demonstrated that the tumor cells did not compensate for FASN inhibition by increasing uptake of saturated fatty acids from the extracellular milieu. An inverse correlation was observed between the pretreatment quantities of saturated fatty acids and the induction of apoptosis resulting from FASN inhibition with TVB-3166; low levels of saturated fatty acids in cell lines such as COLO-205, correlated with a high level of cell killing. Normal, untransformed cells had significantly higher levels of pretreatment saturated fatty acids and a commensurate insensitivity to TVB-3166. These in vitro observations were extended to a COLO-205 rat xenograft model. Significant tumor growth inhibition was measured in these animals in response to FASN inhibition by TVB-3166. Tumor tissues were isolated and a reduction in pAkt and c-Myc expression were observed, the latter consistent with a reduction of Wnt/beta-catenin driven transcription. Further metabolomic analyses of surrogate and tumor tissues from this model continue.

The power of the metabolomic/lipidomic and transcriptomic analyses to evaluate drug responsiveness was applied to surrogate tissues of a small number of cancer patients treated with the FASN inhibitor, TVB-2640. Following 8 days of oral dosing, a preliminary evaluation of aqueous metabolites and lipids in patients' sera demonstrated changes consistent with the mechanism of FASN inhibition. Larger numbers of patients are being evaluated in order better characterize the extent of these changes. Preclinical evaluations of the molecular transformations caused by 3-V Bio's FASN inhibitors are being translated into clinical assessments that may ultimately lead to a more complete understanding of the impact of FASN inhibition in cancer patients and potentially the identification of tumor types that are likely to respond to treatment.

Citation Format: Doug Buckley, Tim Heuer, Marie O'Farrell, Bill McCulloch, George Kemble. Translational studies of a first-in-class FASN Inhibitor, TVB-2640, linking preclinical studies to clinical laboratory observations in solid tumor patients. [abstract]. In: Proceedings of the AACR Special Conference: Metabolism and Cancer; Jun 7-10, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(1_Suppl):Abstract nr A75.

Direct Inhibition of Cellular Fatty Acid Synthase Impairs Replication of Respiratory Syncytial Virus and Other Respiratory Viruses

Fatty acid synthase (FASN) catalyzes the de novo synthesis of palmitate, a fatty acid utilized for synthesis of more complex fatty acids, plasma membrane structure, and post-translational palmitoylation of host and viral proteins. We have developed a potent inhibitor of FASN (TVB-3166) that reduces the production of respiratory syncytial virus (RSV) progeny in vitro from infected human lung epithelial cells (A549) and in vivo from mice challenged intranasally with RSV. Addition of TVB-3166 to the culture medium of RSV-infected A549 cells reduces viral spread without inducing cytopathic effects. The antiviral effect of the FASN inhibitor is a direct consequence of reducing de novo palmitate synthesis; similar doses are required for both antiviral activity and inhibition of palmitate production, and the addition of exogenous palmitate to TVB-3166-treated cells restores RSV production. TVB-3166 has minimal effect on RSV entry but significantly reduces viral RNA replication, protein levels, viral particle formation and infectivity of released viral particles. TVB-3166 substantially impacts viral replication, reducing production of infectious progeny 250-fold. In vivo, oral administration of TVB-3166 to RSV-A (Long)-infected BALB/c mice on normal chow, starting either on the day of infection or one day post-infection, reduces RSV lung titers 21-fold and 9-fold respectively. Further, TVB-3166 also inhibits the production of RSV B, human parainfluenza 3 (PIV3), and human rhinovirus 16 (HRV16) progeny from A549, HEp2 and HeLa cells respectively. Thus, inhibition of FASN and palmitate synthesis by TVB-3166 significantly reduces RSV progeny both in vitro and in vivo and has broad-spectrum activity against other respiratory viruses. FASN inhibition may alter the composition of regions of the host cell membrane where RSV assembly or replication occurs, or change the membrane composition of RSV progeny particles, decreasing their infectivity.

Abstract A54: First-in-human study of the first-in-class fatty acid synthase (FASN) inhibitor, TVB-2640 as monotherapy or in combination - final results of dose escalation

Introduction

FASN inhibition is a novel approach to cancer treatment involving the selective disruption of palmitate biosynthesis that, in tumor cells, leads to apoptosis. TVB-2640 is an oral, first-in-class, small-molecule reversible inhibitor of FASN that demonstrates in vitro and in vivo anti-tumor effects. We previously reported (EORTC-NCI-AACR 2014: 3 LBA, AACR/ASCO 2015: CT203/ TPS2615) on the design of this trial (NCT02223247) and now report on the final results of the dose escalation phase.

Methods

Patients from 7 US and 4 UK sites with adequate bone marrow, hepatic and renal function were enrolled. Patients with significant cardiovascular or ophthalmological disease and any conditions that might interfere with oral absorption were excluded. In addition to standard safety assessments and pharmacokinetic (PK) sampling, ophthalmological examinations and 24-hour Holter monitoring for QTc assessments were performed. Blood and tumor tissue (archival and/or fresh) for various pharmacodynamic (PD) assessments were obtained.

Results

Thirty-one patients were enrolled in 6 monotherapy cohorts (60 mg/m2 to 250 mg flat dose) and 13 patients were enrolled in 2 combination cohorts (200 and 250 mg flat dose) in combination with weekly paclitaxel (80 mg/m2, days 1, 8 and 15 q 28 days). Plasma TVB-2640 drug levels increased with dose, with a half-life of approximately 15 hr. The MTD was declared at 100 mg/m2 for both schedules. DLTs observed in both mono- and combination patients were reversible and consisted of corneal edema (Grade 3, n = 2), keratitis and iritis (Grade 2 and 3, n = 1 each), probably a consequence of disrupted tear film lipid metabolism, and palmar-plantar erythrodysesthesia or skin peeling (Grade 3, n = 3 and Grade 1, n = 1). Other toxicities were mild (≤ Grade 2) and only minor GI symptoms were observed; alopecia was reported by 63% of patients overall. No enhancement of known paclitaxel toxicity was observed when given in combination with TVB-2640. Of the 7 NSCLC patients accrued so far, 1 achieved SD for 17 weeks with monotherapy and 2 patients treated in combination with paclitaxel had SD for 24 and 21 weeks respectively. One of three breast cancer patients (histology: triple negative) treated in combination had SD for 20 weeks. One confirmed PR was seen in a combination-treated patient who had peritoneal serous carcinoma with a 42% reduction in tumor load and 58% reduction in CA-125 levels. PD biomarkers have been identified in tumor and in serum. In all four patients with paired tumor biopsies, decreased pAKT S473 was observed after 1 cycle compared to pretreatment biopsies. Global metabolic profiling of serum showed increased levels of malonyl carnitine, a malonyl coA derivative, and decreased tripalmitin, a palmitate derivative, in 9 of 10 patients tested, after 8 days of TVB-2640 treatment. These changes are consistent with FASN inhibition.

Summary

Continuously administered, oral TVB-2640 demonstrated a tolerated dose and schedule with a manageable toxicity profile in association with encouraging signs of preliminary activity both as monotherapy and in combination with paclitaxel. PD analyses reveal engagement of the target in both tumor and surrogate tissue. Further exploration of biological activity in various specific tumor types is now underway in expansion cohorts at the MTD using both schedules.

Citation Format: Andrew Brenner, Jeffrey Infante, Manish Patel, Hendrik-Tobias Arkenau, Mark Voskoboynik, Erkut Borazanci, Gerald Falchook, L.R. Molife, Shubham Pant, Emma Dean, Lorraine Pelosof, Suzanne Jones, Chris Rubino, William McCulloch, Valentina Zhukova-Harrill, George Kemble, Marie O'Farrell, Howard A. Burris, III. First-in-human study of the first-in-class fatty acid synthase (FASN) inhibitor, TVB-2640 as monotherapy or in combination - final results of dose escalation. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr A54.

Abstract B13: Biomarker Analyses from Dose Escalation Phase of FASN Inhibitor TVB-2640 Phase 1 Study Shows Target Engagement in Solid Tumor Patients

TVB-2640 is a potent, reversible and selective fatty acid synthase (FASN) inhibitor currently in Phase 1 in solid tumor patients (study 3V2640-CLIN-002). This study includes biomarker assays to assess pharmacodynamic activity and refine strategies for patient selection. This report focuses on biomarker results from the dose escalation phase to assess pharmacodynamic activity for this first in class agent.

FASN is a central mediator of neoplastic lipogenesis, and uniquely catalyzes the production of palmitate, the building block of long chain fatty acids. Unlike most normal cells, tumor cells frequently have high FASN expression, which correlates with poor prognosis in several tumor types. Tumor cells rely on de novo lipogenesis to produce phospholipids, lipid second messengers, membranes and lipid rafts needed for oncogenic signaling, survival and proliferation, via many pathways including activated RTKs and hormone receptors.

In Phase 1 study 3V2640-CLIN-002 (NCT02223247), 31 patients were enrolled on TVB-2640 monotherapy (oral, once daily) and 13 patients were enrolled in combination with weekly paclitaxel. Plasma TVB-2640 drug levels increased with dose with a half-life of approximately 15 hr. Several complementary biomarker approaches were pursued to investigate FASN pathway inhibition in tumor and surrogate tissues.

(i) Serum was assessed by mass spectrometry-based global metabolomic profiling to screen for changes following TVB-2640 administration. Increased levels of malonyl carnitine were observed after 8 days of TVB-2640 treatment in 9/10 patients tested. The degree of change of malonyl carnitine increased with greater exposure to the drug. Decreased levels of tripalmitin were also observed in 9/10 patients. These changes are consistent with the expected consequences of FASN inhibition. Serum metabolite profiles from rats administered a FASN inhibitor for 5 to 7 days showed similar trends. These data provide evidence of FASN inhibition by TVB-2640, a first in class agent, in the clinic.

(ii) Fresh tumor biopsies were analyzed by immunohistochemistry (IHC) for markers relevant to FASN engagement. In all 4 patients to date with evaluable biopsies, pAKT S473 decreased by 30-50% after 1 cycle of TVB-2640 treatment relative to predose. Total AKT did not change in either of the 2 patients tested. pAKT inhibition has also been observed in preclinical rat xenografts treated with TVB-2640.

(iii) Gene expression analysis by RNA Seq has been initiated in pre and post dose macro-dissected tumor biopsies in a limited number of patients, and in whole blood for up to 13 patients. Preliminary bioinformatics analyses show modulation of several lipid metabolism pathways consistent with preclinical studies.

In conclusion, FASN pathway inhibition has been demonstrated at well tolerated dose levels of TVB-2640 in both tumor and serum from cancer patients. Increased serum malonyl carnitine and decreased levels of palmitate derivatives provide easily accessible biomarkers and show target inhibition. Early tumor biopsy analysis provides evidence of FASN inhibition in the target tissue by IHC and gene expression analysis. These and additional biomarker studies will be conducted in the expansion phase of this study and help guide clinical development of this first in class FASN inhibitor.

Citation Format: Marie O'Farrell, Richard Crowley, Timothy Heuer, Marina Fridlib, Doug Buckley, William McCulloch, George Kemble. Biomarker Analyses from Dose Escalation Phase of FASN Inhibitor TVB-2640 Phase 1 Study Shows Target Engagement in Solid Tumor Patients. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B13.

Abstract C175: FASN inhibition studies in preclinical tumor models identify biomarkers that align with in vitro and in vivo sensitivity to TVB-2640

Tumor cells have an increased dependence on FASN-synthesized palmitate compared to non-tumor cells, which obtain many of their required lipids from the extracellular milieu. Palmitate and palmitate-derived lipids comprise diverse cellular components and function in processes required for tumor cell proliferation and survival. Previously we showed that FASN inhibition results in tumor cell apoptosis in vitro and xenograft tumor growth inhibition in vivo. Our studies demonstrated that diverse tumor types exhibit sensitivity to FASN inhibition and characterized mechanisms of action that associate with the antitumor activity of highly selective small molecule FASN inhibitors. In vitro studies with diverse tumor cell types elucidated a mechanism of action that includes plasma membrane remodeling, signal transduction pathway inhibition, and gene expression reprogramming.

TVB-2640 and TVB-3166 belong to a series of orally available, reversible, potent, and selective FASN inhibitors discovered and developed by 3-V Biosciences. Tumor xenograft studies were conducted in rats and mice to examine the in vitro and in vivo relationship of tumor cell sensitivity to FASN inhibition. Pharmacodynamic analyses of tumor and serum samples from these studies characterized the mechanism of action and biomarkers of sensitivity to in vivo FASN inhibition.

Once daily oral dosing of TVB-2640 or TVB-3166 caused inhibition of xenograft tumor growth for varied tumor models that included COLO-205 and HCT-116 colon adenocarcinoma cell lines. In vivo sensitivity to FASN inhibition was in agreement with in vitro data. Analysis of lipid, metabolite, protein, and RNA expression in tumor, blood or serum samples showed drug-induced modulation that was consistent with independent in vitro or in vivo studies. Lipid and metabolite changes included decreased palmitate and palmitate-associated lipids as well as increased expression of acylcarnitine species. Decreased expression of pAkt (S473), β-catenin, pβ-catenin (S675), and Myc proteins were found to associate quantitatively with xenograft tumor growth inhibition. Additionally, mRNA expression was modulated in a manner that revealed coordinated changes in the mRNAs from fatty acid, metabolism, cell survival, and cell growth-associated pathways. Expression changes in lipids, metabolites, proteins, and RNA species are leading to the development of a biomarker panel that describes FASN inhibitor target engagement and tumor sensitivity in both in vitro and in vivo studies. These mechanism-based marker panels will be evaluated in current and upcoming clinical studies of TVB-2640.

Citation Format: Timothy S. Heuer, Richard Ventura, Kasia Mordec, Julie Lai, Joanna Waszczuk, Claudia Rubio, Marie O' Farrell, Douglas Buckley, George Kemble. FASN inhibition studies in preclinical tumor models identify biomarkers that align with in vitro and in vivo sensitivity to TVB-2640. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C175.

Abstract 4446: Discovery of tumor types highly susceptible to FASN inhibition and biomarker candidates for clinical analysis

Inhibition of de novo palmitate synthesis by fatty acid synthase (FASN) is a novel cancer therapeutic approach with strong biological rationale. Tumor cells have an increased dependence on FASN-synthesized palmitate compared to non-tumor cells, which obtain many of their required lipids from the extracellular milieu. FASN expression increases with tumor progression in human tumors and associates with chemoresistance, metastasis, and diminished patient survival in many tumor types. Palmitate and palmitate-derived lipids comprise diverse cellular components and function in processes required for tumor cell proliferation and survival.

TVB-2640 and TVB-3166 belong to a series of orally available, reversible, potent, and selective FASN inhibitors discovered and developed by 3-V Biosciences that exhibit anti-tumor activity in diverse preclinical tumor models. FASN inhibition induces tumor cell apoptosis by remodeling tumor cell membranes, blocking signal transduction, and reprogramming gene expression. These effects lead to inhibition of anchorage-independent tumor cell growth under lipid-rich conditions and inhibition of in vivo xenograft tumor growth in mice and rats.

Studies to understand the mechanisms of action and biological consequences of FASN inhibition are guiding the discovery of tumors highly dependent on FASN activity and biomarkers for assessment of pharmacodynamic activity and patient selection. Using quantitative genomics and a variety of directed analytical approaches, we identified lipid, mRNA, and protein profiles in tumor cells that change in response to FASN inhibition. Subsets of the changes show correlation with FASN inhibitor sensitivity. Marker candidates, such as gene expression signatures that classify in vitro sensitivity to FASN inhibition, are being investigated for detection in clinical human tumor data sets. Our studies also identified FASN inhibitor-mediated mechanisms of action that function in specific tumor types and biomarkers with potential utility for selecting responsive patients and measuring tumor response. Inhibition of the Wnt/b-catenin pathway and expression of TCF-promoter-regulated genes such as c-Myc are examples. Tumors dependent on Wnt/b-catenin activity or with lower intracellular palmitate stores prior to drug treatment may be susceptible to FASN inhibitor treatment. Pairing MYC expression with additional markers improves the performance of MYC as a marker to select tumor cell lines highly sensitive to FASN inhibition. Biomarker candidates from in vitro studies have been examined in vivo using xenograft tumor studies. These preclinical data support 3-V Biosciences’ ongoing Phase I clinical study of a first-in-class FASN inhibitor TVB-2640, and help guide the next steps in its development.

Citation Format: Timothy S. Heuer, Richard Ventura, Kasia Mordec, Julie Lai, Joanna Waszczuk, Glenn Hammonds, Marina Fridlib, Russell Johnson, Lily Hu, Allan Wagman, Marie O' Farrell, Douglas Buckley, George Kemble. Discovery of tumor types highly susceptible to FASN inhibition and biomarker candidates for clinical analysis. [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 4446. doi:10.1158/1538-7445.AM2015-4446

Abstract 2675: Biomarker and PK/PD analyses of first in class FASN inhibitor TVB-2640 in a first-in-human phase 1 study in solid tumor patients

TVB-2640 is a potent, reversible and selective fatty acid synthase (FASN) inhibitor currently in its first Phase 1 study (3V2640-CLIN-002) in solid tumor patients. This study includes biomarker assays for this first in class agent to assess pharmacodynamic activity and refine strategies for patient selection. We describe translational approaches and report early Phase 1 data on FASN biomarkers, in tumor, serum and surrogate tissues such as PBMC and whole blood.

FASN is a central mediator of neoplastic lipogenesis. FASN uniquely catalyzes the production of palmitate, the building block of long chain fatty acids, providing a mechanism to convert glucose into lipids needed to support cancer cell signaling and proliferation. Tumor cells have increased dependence on de novo lipogenesis than normal cells, and express higher levels of FASN. Several studies have shown a correlation between high levels of FASN expression and both advanced disease stage and poorer prognosis in patients. FASN plays several roles in cancer cell signaling, including production of phospholipids, alteration of membrane architecture, formation of lipid rafts and the subsequent assembly of signaling molecules in microdomains juxtaposed to the membrane. FASN is upregulated by RTK signaling and also by androgen and estrogen signaling.

The profile of FASN expression was characterized by IHC across several hundred archival human tumors and sera (unmatched) across 8 different tumor types. Highest FASN expression by IHC was observed in colorectal, prostate and bladder tumors, with a similar rank ordering for serum with NSCLC and endometrial also among the highest. Normal donors had significantly lower serum levels. Follow up studies are being conducted to investigate the effect of FASN inhibitors on secreted FASN, and its use as a biomarker.

Seventeen patients have been enrolled in 3V2640-CLIN-002, and four dose levels of TVB-2640 have been tested to date as monotherapy. PK data show a mean half-life of approximately 16.5 hours following oral administration. Plasma Cmax and AUC increase with dose on day 1, with some overlap between the two highest dose levels at steady state. Several exploratory biomarker analyses have been initiated. Tumor IHC data are available for one patient, and decreased pS6 S240/244 and pAKTS473 were observed after TVB-2640 administration. Secreted proteins such as FASN, VEGF and related proteins in serum are being assessed by ELISA and PK/PD analysis will be shown. A serum metabolomics screen has been initiated to assess changes in lipids and related metabolites.

These translational and clinical biomarker assessments inform on FASN biology and clinical development of the first in class FASN inhibitor TVB-2640.

Citation Format: Marie O'Farrell, Richard Crowley, Timothy S. Heuer, Doug Buckley, Chris M. Rubino, William McCulloch, George Kemble. Biomarker and PK/PD analyses of first in class FASN inhibitor TVB-2640 in a first-in-human phase 1 study in solid tumor patients. [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 2675. doi:10.1158/1538-7445.AM2015-2675

Diacylglycerol Metabolism and Signaling Is a Driving Force Underlying FASN Inhibitor Sensitivity in Cancer Cells

Fatty acid synthase (FASN) generates the de novo source of lipids for cell proliferation and is a promising cancer therapy target. Development of FASN inhibitors, however, necessitates a better understanding of sensitive and resistant cancer types to optimize patient treatment. Indeed, testing the cytotoxic effects of FASN inhibition across human cancer cells revealed diverse sensitivities. We show here that metabolic incorporation of glucose into specific complex lipid species strongly predicts FASN inhibitor sensitivity. We also show that the levels of one of these lipid classes, protein kinase C (PKC) stimulator diacylglycerols, are lowered upon FASN inhibitor treatment in sensitive compared to resistant cells and that PKC activators and inhibitors rescue cell death in sensitive cells and sensitize resistant cells, respectively. Our findings not only reveal a biomarker for predicting FASN sensitivity in cancer cells but also a put forth a heretofore unrecognized mechanism underlying the anticancer effects of FASN inhibitors.

Inhibition of de novo Palmitate Synthesis by Fatty Acid Synthase Induces Apoptosis in Tumor Cells by Remodeling Cell Membranes, Inhibiting Signaling Pathways, and Reprogramming Gene Expression

Inhibition of de novo palmitate synthesis via fatty acid synthase (FASN) inhibition provides an unproven approach to cancer therapy with a strong biological rationale. FASN expression increases with tumor progression and associates with chemoresistance, tumor metastasis, and diminished patient survival in numerous tumor types. TVB-3166, an orally-available, reversible, potent, and selective FASN inhibitor induces apoptosis, inhibits anchorage-independent cell growth under lipid-rich conditions, and inhibits in-vivo xenograft tumor growth. Dose-dependent effects are observed between 20–200 nM TVB-3166, which agrees with the IC₅₀ in biochemical FASN and cellular palmitate synthesis assays. Mechanistic studies show that FASN inhibition disrupts lipid raft architecture, inhibits biological pathways such as lipid biosynthesis, PI3K–AKT–mTOR and β-catenin signal transduction, and inhibits expression of oncogenic effectors such as c-Myc; effects that are tumor-cell specific. Our results demonstrate that FASN inhibition has anti-tumor activities in biologically diverse preclinical tumor models and provide mechanistic and pharmacologic evidence that FASN inhibition presents a promising therapeutic strategy for treating a variety of cancers, including those expressing mutant K-Ras, ErbB2, c-Met, and PTEN. The reported findings inform ongoing studies to link mechanisms of action with defined tumor types and advance the discovery of biomarkers supporting development of FASN inhibitors as cancer therapeutics.

Research in context

Fatty acid synthase (FASN) is a vital enzyme in tumor cell biology; the over-expression of FASN is associated with diminished patient prognosis and resistance to many cancer therapies. Our data demonstrate that selective and potent FASN inhibition with TVB-3166 leads to selective death of tumor cells, without significant effect on normal cells, and inhibits in vivo xenograft tumor growth at well-tolerated doses. Candidate biomarkers for selecting tumors highly sensitive to FASN inhibition are identified. These preclinical data provide mechanistic and pharmacologic evidence that FASN inhibition presents a promising therapeutic strategy for treating a variety of cancers.

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TVB-3166 is an orally available, reversible, potent, and selective FASN inhibitor.

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TVB-3166 inhibition of FASN induces apoptosis in tumor cells but not normal cells.

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TVB-3166 inhibits in vivo xenograft tumor growth.

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Candidate biomarkers to select tumors sensitive to FASN inhibition are identified.

Abstract 1815: Efficacy of FASN-selective small molecule inhibitors in preclinical tumor models

Fatty acid synthase (FASN) expression increases with tumor progression and is associated with impaired response to chemotherapy and diminished patient survival in many solid and hematopoietic tumor types. Palmitate, the product of FASN enzymatic activity, functions in vital cellular processes including energy metabolism and cell growth, cellular membrane biosynthesis and architecture, and protein localization and function. 3-V Biosciences has discovered and developed a series of potent, selective, orally available, and reversible FASN inhibitors with excellent pharmaceutical properties. Single agent FASN inhibition has been shown to cause anti-tumor activities in preclinical models of human cancer, including inhibition of AKT and mTOR signal transduction, induction of tumor cell apoptosis, and tumor growth inhibition and regression in pancreatic, ovarian, and lung cancer xenograft tumor models of human cancer. Current studies are supporting the active clinical development of TVB-2640, 3-V Biosciences' first-in-class FASN inhibitor, as an oncology therapeutic. These studies have multiple objectives: (1) characterizing a wide range of tumor types for responsiveness to FASN inhibition using tumor cell line and Champions TumorGraftTM efficacy models; (2) investigating the benefit of FASN combination therapy with chemotherapeutic or targeted anti-cancer agents; (3) developing biomarkers that characterize efficacy response; and (4) further elucidating the mechanisms of action that emanate from the inhibition of palmitate synthesis and lead to tumor cell apoptosis and in vivo anti-tumor efficacy. The results of these investigations show that FASN inhibition causes tumor growth inhibition or regression in diverse tumor types; and moreover, that tumor growth inhibition additivity or synergy is observed when FASN inhibition is combined with chemotherapy agents. Genomics and directed analysis of mRNA, proteins, and lipids following FASN inhibition have identified biomarker candidates and provided insights into the tumor growth inhibition mechanisms of action. For example, genome-wide gene expression analysis shows FASN inhibition to significantly increase the expression of many genes in biosynthetic (sterol, lipid, etc.) and apoptosis pathways while significantly reducing the expression of many genes in cell growth and proliferation pathways (DNA replication, cell cycle progression, mitosis, etc.). These data strongly support the clinical development of TVB-2640 as a first-in-class single and combination oncology therapeutic and are advancing the discovery and validation of biomarkers to inform clinical utility and response.

Citation Format: Timothy S. Heuer, Richard Ventura, Joanna Waszczuk, Kasia Mordec, Julie Lai, Russell Johnson, Lilly Hu, Haiying Cai, Allan Wagman, Douglas Buckley, Stanley T. Parish, Elizabeth Bruckheimer, George Kemble. Efficacy of FASN-selective small molecule inhibitors in preclinical tumor 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 1815. doi:10.1158/1538-7445.AM2014-1815

Abstract 2713: Small-molecule FASN inhibitors promote growth inhibition growth and apoptosis of breast cancer

Increased de novo lipogenesis due to enhanced expression of several lipogenic enzymes has been found in many types of human cancers. Fatty acid synthase (FASN), the key enzyme in the de novo lipogenesis pathway, is one of the most commonly over-expressed lipogenic enzymes. Studies in the past decade have recognized FASN overexpression as a molecular marker for poor prognosis and malignant phenotype of many cancers. Tumor-associated FASN, by conferring growth and survival advantages rather than functioning as an anabolic energy-storage pathway, has also been suggested to play an active part in the development, maintenance, and metastatic progression of human cancers. More recently, FASN has been implicated in contributing to cellular resistance to several anticancer treatments. A variety of agents have been developed to target lipogenic enzymes and the key regulators involved in lipid metabolism in cancer cell for therapeutic purposes. The development of several FASN inhibitors has been reported from both academic labs and industries. When used in in vitro, xenograft and genetically induced mouse model studies, these inhibitors have supported FASN as an excellent target. A new generation of FASN inhibitors was developed at 3-V Biosciences that are highly specific, reversible inhibitors of FASN. One compound in this series, TVB-2640, is orally bioavailable and has progressed into Phase 1 clinical studies. The effect of two anti-FASN drugs in this series, TVB-3150 and TVB-3199 were tested for their effect on breast cancer cells. We demonstrated that the EC50 is between 9-50 nM, depending on the drug and the tested cell line. We then demonstrated that the drugs inhibited the anchorage-dependent and -independent growth of FASN expressing cells in a dose dependent manner. The apparent mechanism by which the FASN inhibitors promote inhibition of growth is by inducing apoptotic cell death in a time- and dose-dependent manner that involves regulation of apoptotic and pro-apoptotic proteins. Furthermore, the combination of the anti-FASN drugs with small molecule inhibitors of the antiapoptotic proteins Bcl-2 and Bcl-xL significantly increased the apoptotic effect in a synergistic manner compared to either of the synthetic inhibitors alone. In vivo studies demonstrate tumor growth inhibition without toxicity. Clinical development of a first-in-class, orally active, potent, and reversible FASN inhibitor as a novel cancer therapeutic is ongoing.

Citation Format: Ruth Lupu, Anatilde Gonzalez Guerrico, Ashwani Khurana, Timothy Heuer, George Kemble, Chandra Mohan KVP. Small-molecule FASN inhibitors promote growth inhibition growth and apoptosis of breast 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 2713. doi:10.1158/1538-7445.AM2014-2713

Abstract B261: Characterization of FASN-selective small-molecule inhibitors in preclinical tumor models

The purpose of this study is to characterize the activity of small-molecule FASN inhibitors in preclinical models of human cancer to evaluate their potential utility as novel cancer therapeutics. FASN-synthesized palmitate is required for vital cellular processes that include energy metabolism, cellular membrane biosynthesis, and protein localization and function. Many solid and hematopoietic tumors overexpress FASN. Moreover, tumor expression of FASN is increased in a stage-dependent manner that is correlated with patient survival. FASN activity can promote the tumorigenic capacity of cells by multiple mechanisms that include: activating cell growth and survival signal transduction pathways such as PI3K-AKT and enhancing cellular processes such as macromolecular biosynthesis, cellular stress response, and energy metabolism. 3-V Biosciences has discovered and developed a series of selective, reversible FASN inhibitors that have been optimized and characterized using in vitro and in vivo assays. These molecules are highly active in both in vitro and in vivo studies, and selected FASN inhibitors demonstrate excellent biochemical (&lt; 10 nM) and cell-based (&lt;100 nM) IC50 values. In vitro, inhibitory activity of cell-based palmitate synthesis aligns with activity in cell phenotypic (e.g. growth and viability) and mechanistic (e.g. AKT phosphorylation and PARP cleavage) assays in cell lines derived from pancreas, breast, lung, colon, and other tumor tissues. Moreover, pharmacologic supplementation of palmitate to cell culture medium rescues cells from cell death in FASN-inhibition cell viability assays. Together, these data show that in vitro FASN inhibition is associated with growth-inhibitory and apoptosis-inducing effects. These novel FASN inhibitors show oral bioavailability, dose dependent plasma exposure, and demonstrate excellent in vivo pharmacodynamic activity. Tumor xenograft studies in mice have been conducted with the FASN inhibitor TVB-3166, and the results demonstrate in vivo tumor growth inhibition both as a single agent and in combination with standard of care chemotherapy agents. TVB-3166 in combination with different chemotherapy agents shows synergistic or additive anti-tumor efficacy in these xenograft studies. In conclusion, these data support continued investigation of FASN inhibition as an approach for the development of a novel cancer therapeutic with the potential for anti-tumor activity in multiple tumor types. Further characterization of FASN inhibitor activity as a single agent and in combination with chemotherapeutics is ongoing using cell-based mechanistic and phenotypic assays as well as tumor xenograft studies.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B261.

Citation Format: Timothy S. Heuer, Minchao Chen, Richard Ventura, Joanna Waszczuk, Satya Yendluri, Julie Lai, Samnang Tep, Shirley Feng, Russell Johnson, Cristiana Zaharia, Douglas Buckley, George Kemble. Characterization of FASN-selective small-molecule inhibitors in preclinical tumor models. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B261.

Genetic engineering of live attenuated influenza viruses

The first live attenuated influenza vaccine (LAIV) was licensed in the USA in 2003; it is a trivalent vaccine composed of two type A (H1N1 and H3N2) and one type B influenza virus each at 10(7) fluorescent focus units (FFU). Each influenza vaccine strain is a reassortant virus that contains the hemagglutinin (HA) and neuraminidase (NA) gene segments from a wild-type influenza virus and the six internal protein gene segments from a master donor virus (MDV) of either cold-adapted A/Ann Arbor/6/60 or B/Ann Arbor/1/66. MDV confers the cold-adapted, temperature-sensitive, and attenuation phenotypes to the vaccine strains. The reassortant vaccine seeds are currently produced by reverse genetics and amplified in specific pathogen-free (SPF) 9-11 days old embryonated chicken eggs for manufacture. In addition, MDCK cell culture manufacture processes have been developed to produce LAIV for research use and with modifications for clinical and/or commercial grade material production.

An open label Phase I trial of a live attenuated H6N1 influenza virus vaccine in healthy adults

BACKGROUND

We describe the results of an open label Phase I trial of a live attenuated H6N1 influenza virus vaccine (ClinicalTrials.gov Identifier: NCT00734175).

METHODS AND FINDINGS

We evaluated the safety, infectivity, and immunogenicity of two doses of 10(7) TCID(50) of the H6N1 Teal HK 97/AA ca vaccine, a cold-adapted and temperature sensitive live, attenuated influenza vaccine (LAIV) in healthy seronegative adults. Twenty-two participants received the first dose of the vaccine, and 18 received the second dose of vaccine 4 weeks later. The vaccine had a safety profile similar to that of other investigational LAIVs bearing avian hemagglutinin (HA) and neuraminidase (NA) genes. The vaccine was highly restricted in replication: two participants had virus detectable by rRT-PCR beyond day 1 after each dose. Antibody responses to the vaccine were also restricted: 43% of participants developed a serum antibody response as measured by any assay: 5% by hemagglutination-inhibition assay, 5% by microneutralization assay, 29% by ELISA for H6 HA-specific IgG and 24% by ELISA for H6 HA specific IgA after either 1 or 2 doses. Following the second dose, vaccine specific IgG and IgA secreting cells as measured by ELISPOT increased from a mean of 0.6 to 9.2/10(6) PBMCs and from 0.2 to 2.2/10(6) PBMCs, respectively.

CONCLUSION

The H6N1 LAIV had a safety profile similar to that of LAIV bearing other HA and NA genes, but was highly restricted in replication in healthy seronegative adults. The H6N1 LAIV was also not as immunogenic as the seasonal LAIV.

Comparison of a live attenuated 2009 H1N1 vaccine with seasonal influenza vaccines against 2009 pandemic H1N1 virus infection in mice and ferrets

The role of seasonal influenza vaccination in pandemic influenza A H1N1 disease is important to address, because a large segment of the population is vaccinated annually. We administered 1 or 2 doses of pandemic H1N1 vaccine (CA/7 ca), a seasonal trivalent inactivated (s-TIV), or live attenuated influenza vaccine (s-LAIV) to mice and ferrets and subsequently challenged them with a pandemic H1N1 virus. In both species, CA/7 ca was immunogenic and conferred complete protection against challenge. s-TIV did not confer protection in either animal model, and s-LAIV did not confer any protection in ferrets. In mice, 2 doses of s-LAIV led to complete protection in the upper respiratory tract and partial protection in the lungs. Our data indicate that vaccination with the seasonal influenza vaccines did not confer complete protection in the lower respiratory tract in either animal model, whereas the CA/7 ca vaccine conferred complete protection in both animal models.

Nasal Turbinate Enlargement Due to Cartilage and Bone Proliferation

Toxicity studies of intranasally administered, live attenuated influenza virus vaccine candidates conducted in male and female ferrets led to the microscopic observation of individual differences in the size of nasal turbinates, especially in the dorsal aspect of the nasal cavity. The association of these enlarged turbinates with acute to subacute inflammation, which is sometimes common in ferrets given live attenuated influenza virus vaccine candidates, led to this detailed microscopic evaluation of turbinate enlargement (cartilaginous and osseous thickening, or COT) in control animals dosed intranasally with saline. Results of this evaluation led to the conclusion that COT is a normal developmental feature of growing ferrets, irrespective of inflammation in nasal tissues or inflammatory exudate in the nasal cavity.

Genetic sequence analysis of influenza viruses and illness severity in ill children previously vaccinated with live attenuated or inactivated influenza vaccine

In a large comparative study in 2004-2005, children aged 6-59 months vaccinated with live attenuated influenza vaccine (LAIV) experienced 55% fewer cases of culture-confirmed influenza illness compared with trivalent inactivated influenza vaccine (TIV) recipients. To better understand the characteristics of the breakthrough influenza illnesses, we analyzed the HA1 genetic sequence for all available samples and examined disease severity by strain and treatment group. All 48 A/H1N1 viruses were well-matched to the vaccine, whereas all 276 A/H3N2 viruses and 349 (96%) influenza B viruses were mismatched to the vaccine. The incidence of fever or lower respiratory illness did not differ by strain; however, LAIV recipients had less febrile disease and fewer lower respiratory illnesses than TIV recipients. Viruses of each influenza B lineage caused more illnesses than A/H1N1 viruses; strategies to enhance protection against multiple influenza B lineages should be pursued.

Safety, immunogencity, and efficacy of a cold-adapted A/Ann Arbor/6/60 (H2N2) vaccine in mice and ferrets

We studied the attenuation, immunogenicity and efficacy of the cold-adapted A/Ann Arbor/6/60 (AA ca) (H2N2) virus in mice and ferrets to evaluate its use in the event of an H2 influenza pandemic. The AA ca virus was restricted in replication in the respiratory tract of mice and ferrets. In mice, 2 doses of vaccine elicited a >4-fold rise in hemagglutination-inhibition (HAI) titer and resulted in complete inhibition of viral replication following lethal homologous wild-type virus challenge. In ferrets, a single dose of the vaccine elicited a >4-fold rise in HAI titer and conferred complete protection against homologous wild-type virus challenge in the upper respiratory tract. In both mice and ferrets, the AA ca virus provided significant protection from challenge with heterologous H2 virus challenge in the respiratory tract. The AA ca vaccine is safe, immunogenic, and efficacious against homologous and heterologous challenge in mice and ferrets, supporting the evaluation of this vaccine in clinical trials.

The influence of the multi-basic cleavage site of the H5 hemagglutinin on the attenuation, immunogenicity and efficacy of a live attenuated influenza A H5N1 cold-adapted vaccine virus

A recombinant live attenuated influenza virus DeltaH5N1 vaccine with a modified hemagglutinin (HA) and intact neuraminidase genes from A/Vietnam/1203/04 (H5N1) and six remaining genome segments from A/Ann Arbor/6/60 (H2N2) cold-adapted (AA ca) virus was previously shown to be attenuated in chickens, mice and ferrets. Evaluation of the recombinant H5N1 viruses in mice indicated that three independent factors contributed to the attenuation of the DeltaH5N1 vaccine: the attenuating mutations specified by the AA ca loci had the greatest influence, followed by the deletion of the H5 HA multi-basic cleavage site (MBS), and the constellation effects of the AA genes acting in concert with the H5N1 glycoproteins. Restoring the MBS in the H5 HA of the vaccine virus improved its immunogenicity and efficacy, likely as a consequence of increased virus replication, indicating that removal of the MBS had a deleterious effect on the immunogenicity and efficacy of the DeltaH5N1 vaccine in mice.

Evaluation of two live attenuated cold-adapted H5N1 influenza virus vaccines in healthy adults

BACKGROUND

Development of live attenuated influenza vaccines (LAIV) against avian viruses with pandemic potential is an important public health strategy.

METHODS AND FINDINGS

We performed open-label trials to evaluate the safety, infectivity, and immunogenicity of H5N1 VN 2004 AA ca and H5N1 HK 2003 AA ca. Each of these vaccines contains a modified H5 hemagglutinin and unmodified N1 neuraminidase from the respective wild-type (wt) parent virus and the six internal protein gene segments of the A/Ann Arbor/6/60 cold-adapted (ca) master donor virus. The H5N1 VN 2004 AA ca vaccine virus was evaluated at dosages of 10(6.7) TCID(50) and 10(7.5) TCID(50), and the H5N1 HK 2003 AA ca vaccine was evaluated at a dosage of 10(7.5) TCID(50). Two doses were administered intranasally to healthy adults in isolation at 4-8 week intervals. Vaccine safety was assessed through daily examinations and infectivity was assessed by viral culture and by realtime reverse transcription-polymerase chain reaction testing of nasal wash (NW) specimens. Immunogenicity was assessed by measuring hemagglutination-inhibition (HI) antibodies, neutralizing antibodies, and IgG or IgA antibodies to recombinant (r)H5 VN 2004 hemagglutinin (HA) in serum or NW. Fifty-nine participants were enrolled: 21 received 10(6.7) TCID(50) and 21 received 10(7.5) TCID(50) of H5N1 VN 2004 AA ca and 17 received H5N1 HK 2003 AA ca. Shedding of vaccine virus was minimal, as were HI and neutralizing antibody responses. Fifty-two percent of recipients of 10(7.5) TCID(50) of H5N1 VN 2004 AA ca developed a serum IgA response to rH5 VN 2004 HA.

CONCLUSIONS

The live attenuated H5N1 VN 2004 and HK 2003 AA ca vaccines bearing avian H5 HA antigens were very restricted in replication and were more attenuated than seasonal LAIV bearing human H1, H3 or B HA antigens. The H5N1 AA ca LAIV elicited serum ELISA antibody but not HI or neutralizing antibody responses in healthy adults. (ClinicalTrials.gov Identifiers: NCT00347672 and NCT00488046).

A live attenuated H7N3 influenza virus vaccine is well tolerated and immunogenic in a Phase I trial in healthy adults

BACKGROUND

Live attenuated influenza vaccines (LAIVs) are being developed and tested against a variety of influenza viruses with pandemic potential. We describe the results of an open-label Phase I trial of a live attenuated H7N3 virus vaccine.

METHODS AND FINDINGS

The H7N3 BC 2004/AA ca virus is a live attenuated, cold-adapted, temperature-sensitive influenza virus derived by reverse genetics from the wild-type low pathogenicity avian influenza virus A/chicken/British Columbia/CN-6/2004 (H7N3) and the A/AA/6/60 ca (H2N2) virus that is the Master Donor Virus of the live, intranasal seasonal influenza vaccine. We evaluated the safety, infectivity, and immunogenicity of two doses of 10(7.5)TCID(50) of the vaccine administered by nasal spray 5 weeks apart to normal healthy seronegative adult volunteers in an inpatient isolation unit. The subjects were followed for 2 months after one dose of vaccine or for 4 weeks after the second dose. Twenty-one subjects received the first dose of the vaccine, and 17 subjects received two doses. The vaccine was generally well tolerated. No serious adverse events occurred during the trial. The vaccine was highly restricted in replication: 6 (29%) subjects had virus recoverable by culture or by real-time reverse transcription polymerase chain reaction (rRT-PCR) after the first dose. Replication of vaccine virus was not detected following the second dose. Despite the restricted replication of the vaccine, 90% of the subjects developed an antibody response as measured by any assay: 62% by hemagglutination inhibition assay, 48% by microneutralization assay, 48% by ELISA for H7 HA-specific serum IgG or 71% by ELISA for H7 HA-specific serum IgA, after either one or two doses. Following the first dose, vaccine-specific IgG secreting cells as measured by ELISPOT increased from a mean of 0.1 to 41.6/10(6) PBMCs; vaccine-specific IgA secreting cells increased from 2 to 16.4/10(6) PBMCs. The antibody secreting cell response after the second dose was less vigorous, which is consistent with the observed low replication of vaccine virus after the second dose and consequent lower antigenic stimulation.

CONCLUSION

The live attenuated H7N3 vaccine was generally well tolerated but was highly restricted in replication in healthy seronegative adults. Despite the restricted replication, the vaccine was immunogenic, with serum IgA being the most sensitive measure of immunogenicity. Further development of this vaccine is warranted (ClinicalTrials.gov Identifier: NCT00516035).

A live attenuated H9N2 influenza vaccine is well tolerated and immunogenic in healthy adults

Development of live attenuated influenza vaccines (LAIV) against avian strains with pandemic potential is an important public-health strategy. Either 1 or 2 10(7)-TCID(50) doses of H9N2 LAIV A/chicken/Hong Kong/G9/97 were administered intranasally to 50 adults in isolation; 41 participants were H9N2 seronegative, 24 of whom received 2 doses. The vaccine was well tolerated; vaccine shedding was minimal. After 2 doses, 92% of H9-seronegative participants had > or = 4-fold increases in hemagglutination-inhibition antibody, and 79% had > or = 4-fold increases in neutralizing antibody; 100% had responses detected by at least 1 assay. Although replication of the H9N2 LAIV was restricted, 2 doses were immunogenic in H9N2-seronegative adults. Trial registration. ClinicalTrials.gov identifier: NCT00110279 .

Molecular studies of temperature-sensitive replication of the cold-adapted B/Ann Arbor/1/66, the master donor virus for live attenuated influenza FluMist vaccines

Cold-adapted (ca) B/Ann Arbor/1/66 is the master donor virus for influenza B (MDV-B) vaccine component of live attenuated influenza FluMist vaccine. The six internal protein gene segments of MDV-B confer the characteristic cold-adapted (ca), temperature-sensitive (ts) and attenuated (att) phenotypes to the reassortant vaccine strains that contain the HA and NA RNA segments from the circulating wild type strains. Previously, we have mapped the loci in the NP, PA and M genes that determine the ca, ts and att phenotypes of MDV-B. In this report, the ts mechanism of MDV-B was described by comparing replication of MDV-B with its wild type counterpart at permissive and restricted temperatures. We showed that the PA and NP proteins of MDV-B are defective in RNA polymerase function at the restricted temperature of 37 degrees C resulting in greatly reduced viral RNA and protein synthesis. In addition, the two M1 residues, Q159 and V183 that are unique to MDV-B, contribute to reduced virus replication at temperatures greater than 33 degrees C, possibly due to the reduced M1 membrane association and its reduced virion M1 incorporation. Thus, the previously identified MDV-B loci not only reduce viral polymerase function at the restricted temperature but also affect virus assembly and release.

The cold adapted and temperature sensitive influenza A/Ann Arbor/6/60 virus, the master donor virus for live attenuated influenza vaccines, has multiple defects in replication at the restrictive temperature

We have previously determined that the temperature sensitive (ts) and attenuated (att) phenotypes of the cold adapted influenza A/Ann Arbor/6/60 strain (MDV-A), the master donor virus for the live attenuated influenza A vaccines (FluMist), are specified by the five amino acids in the PB1, PB2 and NP gene segments. To understand how these loci control the ts phenotype of MDV-A, replication of MDV-A at the non-permissive temperature (39 degrees C) was compared with recombinant wild-type A/Ann Arbor/6/60 (rWt). The mRNA and protein synthesis of MDV-A in the infected MDCK cells were not significantly reduced at 39 degrees C during a single-step replication, however, vRNA synthesis was reduced and the nuclear-cytoplasmic export of viral RNP (vRNP) was blocked. In addition, the virions released from MDV-A infected cells at 39 degrees C exhibited irregular morphology and had a greatly reduced amount of the M1 protein incorporated. The reduced M1 protein incorporation and vRNP export blockage correlated well with the virus ts phenotype because these defects could be partially alleviated by removing the three ts loci from the PB1 gene. The virions and vRNPs isolated from the MDV-A infected cells contained a higher level of heat shock protein 70 (Hsp70) than those of rWt, however, whether Hsp70 is involved in thermal inhibition of MDV-A replication remains to be determined. Our studies demonstrate that restrictive replication of MDV-A at the non-permissive temperature occurs in multiple steps of the virus replication cycle.