Tumor Treating Fields (TTFields) for Newly Diagnosed Glioblastoma in the Real World: A Systematic Review and Survival Meta-Analysis

PURPOSE/OBJECTIVE(S)

Tumor Treating Fields (TTFields) are electric fields that exert forces on cancer cells, disrupting processes critical for cancer cell viability and tumor progression. TTFields therapy is FDA-approved for patients with newly diagnosed glioblastoma (GBM) on the basis of the randomized controlled EF-14 study (NCT00916409). Subsequent approvals and increased worldwide adoption of TTFields has led to the question of whether or not a consistent survival benefit has been observed in the real-world setting, and whether device usage has played a role.

MATERIALS/METHODS

PubMed, Embase, and the Cochrane Library were searched using pre-defined terms, to identify clinical studies (including comparative and single-cohort studies) evaluating overall survival (OS) in adult patients with GBM treated with TTFields therapy added to radiochemotherapy. The Cochran Q test was used to assess inter-study heterogeneity, and results were quantified using the Higgins I2 statistic. Data were pooled, and a survival curve created using a distribution-free random-effects method.

RESULTS

Records identified from the literature search were screened and distilled using pre-specified methods, down to 8 studies evaluating the clinical efficacy of TTFields therapy in newly diagnosed GBM (spanning diverse geographic regions). Six studies (reporting on a total of 1378 patients) compared the addition of TTFields therapy to standard of care (SOC) vs SOC alone, and were included in a pooled analysis for OS. Meta-analysis of data from the 6 studies indicated a significant OS benefit for patients receiving TTFields therapy vs those who did not (hazard ratio [HR]: 0.62; 95% CI, 0.52-0.73; P < 0.001). Sensitivity analysis confirmed the pooled effect was robust and not dependent on any individual study. Of the 6 included in the analysis, 5 were post-approval for which the pooled median OS was 22.2 months (95% CI, 17.3-42.6) vs 17.3 months (95% CI, 13.6-22.0) for the TTFields/SOC group and the SOC group, respectively. Rates of gross total resection were numerically higher in the real-world setting, irrespective of TTFields use. Among studies reporting data on TTFields device usage, an average device usage rate of 75% or higher was found to consistently correlate with prolonged OS when compared to an average usage rate < 75% (pooled HR: 0.63; 95% CI, 0.48-0.83; P = 0.001).

CONCLUSION

Meta-analysis of comparative studies suggests a significant OS benefit when TTFields therapy is added to standard radiochemotherapy for patients with newly diagnosed GBM, and that a ≥ 75% usage rate may translate to clinical benefit in the real-world setting.

Association of Tumor Treating Fields (TTFields) therapy with survival in newly diagnosed glioblastoma: a systematic review and meta-analysis

PURPOSE

Tumor Treating Fields (TTFields) therapy, an electric field-based cancer treatment, became FDA-approved for patients with newly diagnosed glioblastoma (GBM) in 2015 based on the randomized controlled EF-14 study. Subsequent approvals worldwide and increased adoption over time have raised the question of whether a consistent survival benefit has been observed in the real-world setting, and whether device usage has played a role.

METHODS

We conducted a literature search to identify clinical studies evaluating overall survival (OS) in TTFields-treated patients. Comparative and single-cohort studies were analyzed. Survival curves were pooled using a distribution-free random-effects method.

RESULTS

Among nine studies, seven (N = 1430 patients) compared the addition of TTFields therapy to standard of care (SOC) chemoradiotherapy versus SOC alone and were included in a pooled analysis for OS. Meta-analysis of comparative studies indicated a significant improvement in OS for patients receiving TTFields and SOC versus SOC alone (HR: 0.63; 95% CI 0.53-0.75; p < 0.001). Among real-world post-approval studies, the pooled median OS was 22.6 months (95% CI 17.6-41.2) for TTFields-treated patients, and 17.4 months (95% CI 14.4-21.6) for those not receiving TTFields. Rates of gross total resection were generally higher in the real-world setting, irrespective of TTFields use. Furthermore, for patients included in studies reporting data on device usage (N = 1015), an average usage rate of ≥ 75% was consistently associated with prolonged survival (p < 0.001).

CONCLUSIONS

Meta-analysis of comparative TTFields studies suggests survival may be improved with the addition of TTFields to SOC for patients with newly diagnosed GBM.

Tumor Treating Fields (TTFields) increase the effectiveness of temozolomide and lomustine in glioblastoma cell lines

PURPOSE

Tumor Treating Fields (TTFields) are electric fields that disrupt cellular processes critical for cancer cell viability and tumor progression, ultimately leading to cell death. TTFields therapy is approved for treatment of newly-diagnosed glioblastoma (GBM) concurrent with maintenance temozolomide (TMZ). Recently, the benefit of TMZ in combination with lomustine (CCNU) was demonstrated in patients with O⁶-methylguanine DNA methyltransferase (MGMT) promoter methylation. The addition of adjuvant TTFields to TMZ plus CCNU further improved patient outcomes, leading to a CE mark for this regimen. The current in vitro study aimed to elucidate the mechanism underlying the benefit of this treatment protocol.

METHODS

Human GBM cell lines with different MGMT promoter methylation statuses were treated with TTFields, TMZ, and CCNU, and effectiveness was tested by cell count, apoptosis, colony formation, and DNA damage measurements. Expression levels of relevant DNA-repair proteins were examined by western blot analysis.

RESULTS

TTFields concomitant with TMZ displayed an additive effect, irrespective of MGMT expression levels. TTFields concomitant with CCNU or with CCNU plus TMZ was additive in MGMT-expressing cells and synergistic in MGMT-non-expressing cells. TTFields downregulated the FA-BRCA pathway and increased DNA damage induced by the chemotherapy combination.

CONCLUSIONS

The results support the clinical benefit demonstrated for TTFields concomitant with TMZ plus CCNU. Since the FA-BRCA pathway is required for repair of DNA cross-links induced by CCNU in the absence of MGMT, the synergy demonstrated in MGMT promoter methylated cells when TTFields and CCNU were co-applied may be attributed to the BRCAness state induced by TTFields.

Correction: Davidi et al. Tumor Treating Fields (TTFields) Concomitant with Sorafenib Inhibit Hepatocellular Carcinoma In Vitro and In Vivo. Cancers 2022, 14, 2959

The authors wish to make minor corrections to Figure 1 and Figure 2 of the following paper [...].

Tumor treating fields (TTFields) in combination with sorafenib inhibit hepatocellular carcinoma in vitro and in vivo

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Background: Hepatocellular carcinoma (HCC) is a highly malignant liver cancer and a leading cause of cancer related mortality. Sorafenib was the first approved systemic treatment for HCC, and remains one of few front-line treatments for this malignancy. Tumor treating fields (TTFields) are low intensity (1-3 V/cm), intermediate frequency (100-500 kHz), alternating electric fields that exert antimitotic effects on cancerous cells. Results of the phase 2 HEPANOVA study of TTFields (150 kHz) plus sorafenib for advanced HCC support investigation of TTFields in a randomized controlled phase 3 study. The current research aimed to describe the in vitro and in vivo efficacy of this combination and to elucidate details regarding the underlying mechanism of action. Methods: In vitro examinations were performed in HepG2 and Huh-7D12 human HCC cell lines, to which TTFields at a frequency of 150 kHz were applied using the inovitro system. Autophagy was examined by western blot and fluorescence detection of microtubule-associated protein light chain 3 (LC3) levels, an accepted autophagy marker. The effect of TTFields in combination with sorafenib was evaluated using cytotoxic, clonogenic, and apoptotic assays. In vivo, SD rats were inoculated orthotopically into the left hepatic lobe with N1S1 HCC cells. 7 days later, TTFields or sham (heat) were applied to the abdominal region of the rats, continuously for 6 days. Daily intraperitoneal injections of sorafenib (10 mg/kg/day) or vehicle were performed during this time. To determine tumor volume growth, MRI images were acquired before and after treatment. Levels of autophagy and apoptosis were examined in tumor sections by immunohistochemistry for LC3 and cleaved PARP, respectively. Results: Application of TTFields induced autophagy in HCC cells. TTFields delivery was cytotoxic to the cells, reduced their colony forming ability, and induced apoptosis while combination with sorafenib elevated these effects. In vivo, tumor volume increased 6-fold in control animals vs 1.6-fold in animals treated with TTFields plus sorafenib. This effect was accompanied by significantly elevated levels of cleaved PARP and LC3 within the tumors of treated relative to control rats. Conclusions: The results demonstrate induction of autophagy and apoptosis in HCC following treatment with TTFields. Concomitant application of TTFields with sorafenib enhanced efficacy via a mechanism that may involve overwhelming autophagy, in vitro and in vivo.

Tumor Treating Fields (TTFields) downregulate the Fanconi Anemia-BRCA pathway and increase the efficacy of chemotherapy in malignant pleural mesothelioma preclinical models

OBJECTIVES

Tumor Treating Fields (TTFields) are low intensity, intermediate frequency, alternating electric fields with antimitotic effects on cancerous cells. TTFields concomitant with pemetrexed and a platinum agent are approved in the US and EU as first line therapy for unresectable, locally advanced or metastatic malignant pleural mesothelioma (MPM). The goal of the current study was to characterize the mechanism of action of TTFields in MPM cell lines and animal models.

METHODS

Human MPM cell lines MSTO-211H and NCI-H2052 were treated with TTFields to determine the frequency that elicits maximal cytotoxicity. The effect of TTFields on DNA damage and repair, and the cytotoxic effect of TTFields in combination with cisplatin and/or pemetrexed were examined. Efficacy of TTFields concomitant with cisplatin and pemetrexed was evaluated in orthotopic IL-45 and subcutaneous RN5 murine models.

RESULTS

TTFields at a frequency of 150 kHz demonstrated the highest cytotoxicity to MPM cells. Application of 150 kHz TTFields resulted in increased formation of DNA double strand breaks, elevated expression of DNA damage induced cell cycle arrest proteins, and reduced expression of Fanconi Anemia (FA)-BRCA DNA repair pathway proteins. Co-treatment of TTFields with cisplatin or pemetrexed significantly increased treatment efficacy versus each modality alone, with additivity and synergy exhibited by the TTFields-pemetrexed and TTFields-cisplatin combinations, respectively. In animal models, tumor volume was significantly lower for the TTFields-cisplatin-pemetrexed combination compared to control, accompanied by increased DNA damage within the tumor.

CONCLUSION

This research demonstrated that the efficacy of TTFields for the treatment of MPM is associated with reduced expression of FA-BRCA pathway proteins and increased DNA damage. This mechanism of action is consistent with the observed synergism for TTFields-cisplatin vs additivity for TTFields-pemetrexed, as cisplatin-induced DNA damage is repaired via the FA-BRCA pathway.

Abstract 1063: Effectiveness of Tumor Treating Fields (TTFields) in combination with sorafenib for treatment of hepatocellular carcinoma in vitro and in vivo

Purpose/Objective(s): Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer and it is one of the leading causes of related mortality worldwide. Sorafenib is an oral multikinase inhibitor that targets the Raf/MEK/ERK signaling pathway, thus inducing autophagy and blocking angiogenesis. Sorafenib is approved for advanced HCC and is the main first-line chemotherapy, yet its survival benefits are limited. Tumor Treating Fields (TTFields) therapy is an anticancer treatment that is non-invasively and locoregionally delivered to tumor bed via low intensity (1-3 V/cm), intermediate frequency (100-500 kHz), alternating electric fields. Since HCC is a complex, heterogeneous tumor with exhibited aberrant signaling pathways, sorafenib combined with additional chemotherapy agents and other types of treatment modalities, such as TTFields, may be a feasible option for targeting HCC. The purpose of this study was to explore the use of TTFields, alone and in combination with sorafenib, for HCC treatment.

Materials/Methods: HCC cell lines (HepG2 and Huh-7D12) were treated for 72 hours with TTFields at various frequencies. Efficacy of TTFields and sorafenib combination was tested by applying optimal frequency TTFields in the presence of various concentrations of sorafenib. Cytotoxicity, apoptosis, and clonogenicity were determined, and overall effect was calculated as the product of the cytotoxic and clonogenic effects. Changes in autophagy levels were also examined. In vivo, N1S1 HCC cells (50,000) were orthotopically injected into the left hepatic lobe of SD rats. After 1 week, TTFields at the optimal frequency were continuously applied for 6 days to the abdominal region of rat torsos, and sorafenib (10 mg/kg/day) was injected daily. Tumor volume growth was determined by MRI.

Results: The TTFields frequency assessed for optimally treating HCC cell lines was 150 kHz. Cells were sensitive to sorafenib in a dose-dependent manner, and concomitant addition of TTFields augmented this effect. The effect of TTFields, like that of sorafenib, was demonstrated to be related to increases in autophagic flux. In the animal model, tumor growth was significantly reduced in the combination group compared to other treatment groups.

Conclusion: These results demonstrate that TTFields are effective for the treatment of HCC and may further enhance effectiveness in combination with standard of care chemotherapy. The ongoing phase 2 HEPANOVA (NCT03606590) clinical trial will investigate the safety and efficacy of TTFields plus sorafenib combination in patients with unresectable, locally advanced HCC.

Citation Format: Shiri Davidi, Anna Shteingauz, Sara Jacobovitch, Karnit Gotlib, Catherine Tempel-Brami, Mijal Munster, Einav Zeevi, Eyal Dor-On, Rosa S. Schneiderman, Tali Voloshin, Adi Haber, Moshe Giladi, Adrian Kinzel, Uri Weinberg, Yoram Palti. Effectiveness of Tumor Treating Fields (TTFields) in combination with sorafenib for treatment of hepatocellular carcinoma in vitro and in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1063.

Abstract 1186: Efficacy of Tumor Treating Fields (TTFields) in mesothelioma is associated with reduced capacity for DNA damage repair

Introduction: Malignant pleural mesothelioma (MPM) is an aggressive thoracic cancer with a poor prognosis and limited treatment options. Tumor Treating Fields (TTFields) are a noninvasive, locoregionally, antineoplastic treatment, delivering low intensity (1-3 V/cm), intermediate frequency (100-500 kHz), alternating electric fields, that has demonstrated a promising median overall survival in patients with MPM without increases in systemic toxicity (STELLAR clinical trial). Accordingly, TTFields with pemetrexed and a platinum-based chemotherapy agent received FDA-approval as first line therapy for MPM. While efficacy of TTFields for MPM treatment is well-established, the underlying mechanism of action needs further elucidation.

Methods: Human MPM cell lines (NCI-H2052 and MSTO-211H) were treated using various TTFields frequencies to assess the most effective frequency. The effect of optimal frequency TTFields on levels of DNA double strand breaks (DSB) was examined by fluorescent microscopy detection of γH2AX foci, and the levels of DNA damage repair proteins was evaluated by immunoblotting. The combined cytotoxic effect of TTFields with cisplatin or pemetrexed was tested in vitro, and efficacy of TTFields in combination with both chemotherapeutic agents was examined in C57BL/6 mice injected subcutaneously with RN-5 cells, by measuring tumor volume and through detection for DNA damage within the tumor.

Results: The optimal TTFields frequency in both MPM cell lines was 150 kHz, demonstrating significant cytotoxicity and increases in formation of DNA DSB. These effects were associated with reduced expression of proteins from the Fanconi Anemia (FA) repair pathway for DNA repair - FANCA, FANCD2, FANCJ, and BRCA1. Co-treatment of TTFields with cisplatin or pemetrexed significantly increased treatment efficacy versus each treatment alone, with an additive effect shown by the TTFields-pemetrexed combination, and a tendency towards synergism displayed for TTFields-cisplatin co-administration. In animal models, tumor volume fold increase was significantly decreased for co-treatment with TTFields and chemotherapy (cisplatin + pemetrexed) versus the control, showing also increased DNA damage within the tumor bed in comparison to control or chemotherapy alone.

Conclusions: The results presented here demonstrate that the efficacy of TTFields for treatment of MPM is associated with reduced expression of FA pathway proteins and increased DNA DSB. This effect may account for the synergistic effect seen for TTFields-cisplatin co-treatment, as cisplatin is known to cause DNA damage that requires the FA pathway for repair. This research provides further insights on the mechanism of action of TTFields in MPM, a treatment already approved against this malignancy.

Citation Format: Helena Mumblat, Antonia Martinez, Ori Braten, Mijal Munster, Eyal Dor-On, Rosa S. Schneiderman, Yaara Porat, Tali Voloshin, Shiri Davidi, Roni Blatt, Anna Shteingauz, Catherine Tempel-Brami, Einav Zeevi, Carolina Lajterer, Yuval Shmueli, Shiri Danilov, Adi Haber, Moshe Giladi, Adrian Kinzel, Uri Weinberg, Yoram Palti. Efficacy of Tumor Treating Fields (TTFields) in mesothelioma is associated with reduced capacity for DNA damage repair [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1186.

In Vivo Safety of Tumor Treating Fields (TTFields) Applied to the Torso

Background

Tumor Treating Fields (TTFields) therapy is a non-invasive, loco-regional, anti-mitotic treatment modality that targets rapidly dividing cancerous cells, utilizing low intensity, alternating electric fields at cancer-cell-type specific frequencies. TTFields therapy is approved for the treatment of newly diagnosed and recurrent glioblastoma (GBM) in the US, Europe, Israel, Japan, and China. The favorable safety profile of TTFields in patients with GBM is partially attributed to the low rate of mitotic events in normal, quiescent brain cells. However, specific safety evaluations are warranted at locations with known high rates of cellular proliferation, such as the torso, which is a primary site of several of the most aggressive malignant tumors.

Methods

The safety of delivering TTFields to the torso of healthy rats at 150 or 200 kHz, which were previously identified as optimal frequencies for treating multiple torso cancers, was investigated. Throughout 2 weeks of TTFields application, animals underwent daily clinical examinations, and at treatment cessation blood samples and internal organs were examined. Computer simulations were performed to verify that the targeted internal organs of the torso were receiving TTFields at therapeutic intensities (≥ 1 V/cm root mean square, RMS).

Results

No treatment-related mortality was observed. Furthermore, no significant differences were observed between the TTFields-treated and control animals for all examined safety parameters: activity level, food and water intake, stools, motor neurological status, respiration, weight, complete blood count, blood biochemistry, and pathological findings of internal organs. TTFields intensities of 1 to 2.5 V/cm RMS were confirmed for internal organs within the target region.

Conclusions

This research demonstrates the safety of therapeutic level TTFields at frequencies of 150 and 200 kHz when applied as monotherapy to the torso of healthy rats.

Abstract 2411: Cancer cell lines meta-analysis according to both short-term and long-term responses to Tumor Treating Fields (TTFields)

Tumor Treating Fields (TTFields) therapy is an approved modality for the treatment of glioblastoma. These alternating electric fields were shown to exert an inhibitory effect in numerous cancer cell lines with some variability in the response of different cell lines. The goal of the present study is to compare characteristics of cell lines based on their response pattern to TTFields.

Forty one different human cancerous cell lines were treated for 72 hours with TTFields at their optimal frequency with the same nominal intensity (1.7 V/cm). Two response values were quantified. The first cytotoxic response, is considered a short-term quantification of the response. The second clonogenic response, is considered a long-term response to TTFields.

Genomic analysis of 26 cell lines was performed based on the Cancer Cell Line Encyclopedia (CCLE) database. Association of mutated genes, mutations and copy number variations with cell lines response to TTFields was investigated.

TTFields application demonstrated varying degree of cytotoxic effect in all cell lines tested. The inhibitory response to TTFields was found to be distributed around an average of 50% with a cytotoxic effects ranging between 14% and 86% reductions in cell counts, and a clonogenic effect ranging between no effect and 88% reduction in the number of colonies. The “Overall response” was considered as the multiplication of the two values and represents the response both in short-term and long-term effects of TTFields. Lower values of all response quantifications indicate a better

response to TTFields. Cell lines were partitioned to responding and non-responding cell lines according to their “Overall response”.

Response to treatment doesn't seem to be affected by the number of mutations in each of the cell lines, and not by the type of the cancer the cell lines originated from. Mutations in genes that associate with the response to TTFields are enriched in GO terms that include muscle function and the intracellular organelle compartment. Mutation association with response to TTFields revealed mutations in genes related to the cytoskeleton, mitotic spindle, receptors and membrane transporters.

This multi parameter, large scale comparison of cancerous cell line response to TTFields demonstrate the broad effectiveness of TTFields in various cell lines and define the optimal frequency to be applied for each cell line. The data presented in this work, suggest that beside their anti-mitotic properties, TTFields may have effects on other cellular pathways.

Citation Format: Kerem Wainer Katsir, Gitit Lavy Shahaf, Moshe Giladi, Rosa S. Schneiderman, Noa Urman, Karnit Gotlieb, Einav Zeevi, Yaara Porat, Mijal Munster, Adrian Kinzel, Uri Weinberg, Eilon D. Kirson, Yoram Palti. Cancer cell lines meta-analysis according to both short-term and long-term responses to Tumor Treating Fields (TTFields) [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2411.

Abstract 572: In vitro and in vivo evidence for the safety and efficacy of Tumor Treating Fields (TTFields) in combination with sorafenib

Objective: Hepatocellular carcinoma (HCC) is the third cause of cancer related mortality. Sorafenib, an oral multikinase inhibitor, is approved for patients with advanced HCC, however its survival benefit is limited. Tumor Treating Fields (TTFields) therapy is an effective, anti-neoplastic treatment modality delivered via noninvasive application of low intensity, intermediate frequency, alternating electric fields. The aim of this work is to explore the potential use of TTFields alone and in combination with sorafenib as a treatment for HCC.

Methods: HepG2 and Huh-7D12 HCC cells were treated with various TTFields frequencies (100-400 kHz) for 72 hours using the inovitroTM system. Efficacy of the combined treatment of TTFields and sorafenib was tested by applying TTFields at the optimal frequency together with various sorafenib concentrations. Cell counts, induction of apoptosis, and clonogenic potential were determined. Moreover, N1S1 HCC cells were injected into the left lobe of the liver of Sprague Dawley rats. After 1 week, TTFields (1.2 V/cm) and sorafenib (10 mg/kg) were applied for 6 days and tumor growth was evaluated, using MRI. Healthy rats were used to study the safety of TTFields (150 kHz) application to the abdomen.

Results: The optimal frequency of TTFields was 150 kHz for both HCC cell lines. TTFields application (1.0 - 1.7 V/cm, 72 hours) at 150 kHz led to a 53-55% reduction in cell counts and to an additional reduction (65-69%) in clonogenic potential. The combination of TTFields and sorafenib led to a significant reduction in cell count (2-way ANOVA, P &lt;0.05) as compared to either treatment alone. HCC tumor growth was significantly reduced in the combined group compared to the control group (student t-test, P &lt;0.01). On average, the HCC tumor volume (fold-increase) in the combination treatment group (1.6-times) was significantly lower than in the control group (5.9-times, P &lt;0.0001), TTFields alone group (3.3-times, P &lt;0.01), and sorafenib alone group (2.3-times, P &lt;0.05). Histological analysis of the KI67 proliferation marker in HCC tumors showed reduced proliferation in all treated groups. Based on preliminary analysis of autophagy marker (LC3) in tumors, we hypothesized the involvement of autophagy as 1 of the mechanisms underlying increased treatment efficacy. Safety studies did not reveal any adverse events associated with TTFields application to the rat abdomen.

Conclusions: These results demonstrate that TTFields can be a safe and effective in the treatment of HCC, and that the combination with sorafenib leads to further enhancements in treatment effectiveness. Based on these results, a Phase 2 clinical trial evaluating the effects of TTFields and sorafenib treatment in patients with HCC is planned (HEPANOVA; NCT03606590).

Citation Format: Shiri Davidi, Catherine Tempel-Brami, Mijal Munster, Anna Shteingauz, Einav Zeevi, Rosa Schneiderman, Tali Voloshin, Moshe Giladi, Adrian Kinzel, Uri Weinberg, Yoram Palti. In vitro and in vivo evidence for the safety and efficacy of Tumor Treating Fields (TTFields) in combination with sorafenib [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 572.

Abstract 573: Efficacy of Tumor Treating Fields (TTFields) in combination with cisplatin or pemetrexed for the treatment of mesothelioma in vitro and in vivo

Objective: Malignant pleural mesothelioma (MPM) is an aggressive thoracic cancer, linked to asbestos exposure. The prognosis of patients with MPM is poor, with a median overall survival (OS) of ~12 months reported with historical, standard of care (SOC) cisplatin or carboplatin plus pemetrexed. Tumor Treating Fields (TTFields) is an anti-neoplastic treatment delivered via noninvasive application of low intensity, intermediate frequency, alternating electric fields and was shown to increase OS to 18.2 months in combination with SOC. Based on these data, TTFields were approved for treatment of unresectable MPM. The aim of this study was to further evaluate the effectiveness and safety of TTFields alone and in combination with SOC for MPM treatment, utilizing in vitro and in vivo models.

Methods: NCI-H2052 and MSTO-211H human MPM cells were treated at various TTFields frequencies (100-400 kHz) for 72 hours using the inovitroTM system to determine optimal frequency. The combination of TTFields with cisplatin or pemetrexed was tested by applying TTFields at the optimal frequency in combination with various concentrations of the chemotherapeutic agents. For TTFields alone, cell counts, clonogenic potential, and induction of apoptosis were determined. Also, cytotoxic, apoptotic, and overall (cytotoxic plus clonogenic) effects were evaluated for cisplatin or pemetrexed alone (at various concentration) and in combination with TTFields. TTFields (1.2 V/cm) were applied for 8 days to rats injected with IL-45 MPM cells to the intrapleural cavity and tumor volume was measured.

Results: The optimal frequency of TTFields was 150 kHz in both MPM human cell lines. TTFields application (1.0 V/cm, 72 hours) alone at 150 kHz led to a 45-51% reduction in cell counts and a 64-76% additional reduction in clonogenic potential. The combined treatment of TTFields with cisplatin or pemetrexed led to a significant reduction in cell count, induction of apoptosis, and reduced clonogenic potential as compared to each modality alone. In vivo, TTFields in combination with pemetrexed plus cisplatin significantly decreased the MPM tumor volume in the rat model compared to the control group (P &lt; 0.006). Safety studies did not reveal any adverse events associated with 150 kHz TTFields application to the rat torso.

Conclusions: These preclinical data demonstrate that TTFields are an effective treatment against MPM and the combination with cisplatin or pemetrexed enhanced treatment effectiveness. Results are consistent with the recent phase 2 STELLAR study (EF-23 trial; NCT02397928) that reported improved OS with TTFields in combination with pemetrexed plus platinum-based chemotherapeutic (cisplatin or carboplatin) as compared to historical control for front-line treatment of unresectable MPM, with no increases in systemic toxicity.

Citation Format: Mijal Munster, Helena Mumblat, Shiri Davidi, Rosa Schneiderman, Yaara Porat, Anna Shteingauz, Tali Voloshin, Noa Kaynan, Einav Zeevi, Moshe Giladi, Uri Weinberg, Adrian Kinzel, Yoram Palti. Efficacy of Tumor Treating Fields (TTFields) in combination with cisplatin or pemetrexed for the treatment of mesothelioma in vitro and in vivo [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 573.

Tumor treating fields (TTFields; 150 kHz) and FOLFOX combination treatment effects on gastric cancer in vitro

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Background: Gastric cancer is the third most common cause of cancer mortality worldwide, yet long-term survival in gastric cancer remains poor despite systemic therapeutic advances. FOLFOX (oxaliplatin, fluorouracil [5-FU], and leucovorin) is an approved chemotherapy regimen for gastric cancer treatment. Tumor Treating Fields (TTFields) are an antimitotic, loco-regional anticancer treatment delivered via non-invasive application of low intensity (1-3V/cm), intermediate frequency (100-500 kHz), alternating electrical fields. TTFields targets rapidly dividing cancer cells by disrupting microtubules leading to mitotic catastrophe, abnormal chromosome segregation, and apoptosis induction. We investigated the potential use of TTFields alone and in combination with FOLFOX for gastric carcinomas. Methods: Gastric cells (AGS and KATO III) were treated for 72 hours with TTFields (1.1 and 1.7 V/cm, respectively) at frequencies of 100-400 kHz using the inovitro system. Efficacy of TTFields and FOLFOX and its individual components was tested by applying TTFields at the optimal frequency in combination with various drug concentrations. Cell counts, apoptosis induction, clonogenic potential, and overall effect were determined. Results: The optimal TTFields frequency that led to the greatest cell count reduction (AGS, 55%; KATO III, 52%) was 150 kHz. The clonogenic potential was reduced by > 70% in both cell lines. TTFields combined with each FOLFOX component (oxaliplatin, 5-FU, or leucovorin) led to a significant reduction in AGS and KATO III cell survival (2-way ANOVA, P < 0.001 for each cell line) versus each treatment alone. In AGS, TTFields plus FOLFOX combination treatment led to a further reduction in the overall effect (cytotoxic and clonogenic; 79%) versus TTFields alone (65%) and FOLFOX alone (34%). Similar results were observed in KATO III cells. Conclusions: These results suggest that TTFields (150 kHz; optimal frequency) are an effective gastric cancer treatment; and combining TTFields with FOLFOX may further enhance efficacy. There is a strong rational to continue exploring the use of TTFields in combination with standard of care for gastric cancer treatment in the clinical settings.

Immunomodulatory effects of tumor treating fields (TTFields) on colon cancer models

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Background: Tumor Treating Fields (TTFields) are clinically approved in glioblastoma and malignant pleural mesothelioma as an anti-mitotic treatment modality delivered via noninvasive application of low intensity (1-3 V/cm), intermediate frequency (100-500 kHz), alternating electric fields. We evaluated whether TTFields (150 kHz) induced colon cancer cell death can be perceived as immunogenic and suitable for combination with anti-programmed cell death protein 1 (anti-PD-1; immune checkpoint inhibitor) therapy. Methods: Murine colorectal carcinoma cells (CT-26) were treated with TTFields using the inovitro system. Immunogenic cell death was evaluated by assessing changes in the levels of calreticulin (CRT) on the surface of treated cells, phosphorylation of eukaryotic translation initiation factor alpha (eIF2α), and secretion of ATP and high-mobility group box 1 (HMGB1). For in-vivo studies, CT-26 cells were subcutaneously implanted in BALB/c mice. The mice were treated with TTFields (150 kHz), anti-PD-1 (200 μg/mouse), or a combination of the 2 modalities. Tumor volume was monitored and flow cytometry analyses performed for phenotypic characterization of infiltrating immune cells. Results: We demonstrate that cancer cell death under TTFields application exhibited release of HMGB1, ATP secretion from cells, and ER stress leading to CRT translocation to the cell surface, all of which are signs of immunogenic cell death. The combined treatment of colon tumor-bearing mice with TTFields plus anti-PD-1 led to a significant decrease in tumor volume compared to anti-PD-1 alone or to the control group. Significant increases in CD45+ tumor infiltrating cells were observed in the TTFields plus anti-PD-1 group. We demonstrate significant increases in both CD8 and CD4 T-cells in tumors treated with combination therapy, and in CD8 in tumors treated with anti-PD-1 alone. Conclusions: Our results establish the potential of TTFields therapy to induce immunogenic cell death. We also demonstrate efficacy of concurrent application of TTFields and anti PD-1 therapy in mouse cancer models. These data suggest that TTFields plus anti-PD-1 combination treatment may achieve tumor control by further enhancing anti-tumor immunity.

In vitro and in vivo efficacy and safety of tumor treating fields (TTFields) and sorafenib combination in hepatocellular carcinoma

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Background: Hepatocellular carcinoma (HCC) is a leading global cause of cancer-related mortality. Sorafenib (oral multikinase inhibitor) is approved in patients with advanced HCC, yet survival benefit is limited. Tumor Treating Fields (TTFields) are an effective, anti-neoplastic treatment modality delivered via noninvasive, low intensity (1-3 V/cm), intermediate frequency (100-500 kHz), alternating electric fields. The study aim was to explore in vitro and in vivo effects of TTFields alone and combined with sorafenib for HCC treatment. Methods: HCC (HepG2 and Huh-7D12) cells were TTFields treated with at frequencies of 100-400 kHz for 72 hr using the inovitro system. Efficacy of TTFields and sorafenib combined treatment was tested at optimal frequency with various sorafenib concentrations. Cell counts, apoptosis induction, and clonogenic potential were determined. Healthy rats were used to assess safety of TTFields applied to the abdomen. N1S1 HCC cells were injected into the left hepatic lobe of Sprague Dawley rat; after 1 week, TTFields (1.2 V/cm) and sorafenib (10 mg/kg) were applied for 6 days. Tumor growth was evaluated using MRI. Results: The optimal TTFields frequency was 150 kHz in HepG2 and Huh-7D12 HCC cells. TTFields 150 kHz treatment (1.0 - 1.7 V/cm, 72 hr) led to cell count reductions (53-55%) and further decreases in clonogenic potential (65-69%). TTFields and sorafenib combination treatment led to a significant reduction in cell count (2-way ANOVA, P < 0.05) vs either treatment alone. Also, tumor growth was significantly reduced in the combined treatment group vs the control group (student t test, P < 0.01). Tumor volume (fold increase) in the combination treatment group (1.6) was significantly lower vs control (5.9, P < 0.0001), TTFields alone (3.3, P < 0.01), and sorafenib alone (2.3, P < 0.05) groups. Safety studies did not reveal any TTFields related adverse events with delivery to the rat abdomen. Conclusions: In vitro and in vivo data demonstrated efficacy and safety of TTFields in HCC; and improved efficacy in combination with sorafenib. A phase 2 study (HEPANOVA; NCT03606590) will explore the clinical potential of TTFields 150 kHz plus sorafenib.

CBMT-13. 3DEP SYSTEM TO TEST THE ELECTRICAL PROPERTIES OF DIFFERENT CELL LINES AS PREDICTIVE MARKERS OF OPTIMAL TUMOR TREATING FIELDS (TTFIELDS) FREQUENCY AND SENSITIVITY

BACKGROUND

Tumor Treating Fields (TTFields; approved anti-neoplastic treatment modality) are delivered via application of low intensity, intermediate frequency, alternating electrical fields. The electrical properties of cells (eg, permittivity and conductivity) determine the optimal TTFields frequency that would elicit the greatest cell count reduction. Currently, no predictive markers exist to determine TTFields response and optimal frequency for individual patient application. The study goal was to evaluate the correlation between electrical properties of cells and TTFields’s optimal frequency and sensitivity. The 3DEPTM reader (LabTech) determines cellular electrical properties, including permittivity and conductivity, by using dielectrophoresis (DEP) force. DEP is a physical effect that generates a force on polarizable particles, such as cells, subjected to non-uniform electric fields.

METHODS

Utilizing the 3DEP reader, baseline electrical properties (permittivity and conductivity) of 17 cell lines from different tumor-types were determined. Curves were analyzed using 2-way ANOVA. The optimal TTFields frequency of each cell line was determined by evaluating TTFields cytotoxicity at various frequencies using the inovitroTM system. Electrical properties of each cell line were compared with the optimal TTFields frequency and sensitivity.

RESULTS

Significant differences (P< 0.001) were demonstrated between the lower frequency range of the 3DEP curves that correspond to cellular membrane capacitance at TTFields optimal frequencies of 150 kHz (9 cell lines) and 200 kHz (8 cell lines). Also, membrane capacitance was a good predictor of TTFields sensitivity based on curve differences within the low-frequency range.

CONCLUSIONS

These results demonstrate that cell membrane capacitance correlates with TTFields optimal frequency and sensitivity. Based on these data, there is a strong rational to further explore the potential of measuring the electrical properties of cells as predictive markers to help determine the optimal TTFields frequency for individual patient application and to identify ideal treatment-responders to TTFields.

P11.18 Tumor treating fields (TTFields) treatment of spinal cord metastases

BACKGROUND

Tumor Treating Fields (TTFields) is an anti-mitotic cancer treatment approved for the treatment of Glioblastoma multiforme (GBM) and is currently also investigated in a phase III trial in 1–10 brain metastases from non-small cell lung cancer (METIS). Apart from spread to the brain, some cancer types, such as breast cancer, lung cancer, and melanoma, may lead to metastatic spread to the spinal cord. Previous studies have shown that reported transducer array layouts for the treatment of abdominal/pelvic tumors (e.g. pancreatic cancer), with one pair of arrays positioned on the anterior and posterior of the patient, and the second pair of arrays placed on each side of the thorax, yield therapeutically insufficient field intensities of <1 V/cm in the spinal cord. This finding probably results from the anatomical structure of the spine, consisting of the cerebrospinal fluid as a highly conductive layer, encased by a resistive bone structure that shunts the current delivered across the body by the arrays away from the spine. This simulation-based study aimed at resolving this challenge by identifying novel array layouts on the body that effectively deliver TTFields to the spine.

MATERIAL AND METHODS

For the simulations of the TTFields delivery to the spine, a human male 34 years old realistic computational model (DUKE v3.1 by ITI’S, Zurich) and the ZMT’s Sim4Life v4.0 electro-quasi-static solver was utilized. TTFields were simulated by imposing an alternating current with a current density of 200 mA/disk and a frequency of 150 kHz on the outer surfaces of the disks of each pair of arrays.

RESULTS

For one of the tested array layouts, a high electric field was shown to be induced within the spinal cord and surrounding CSF: Our calculations of mean field intensity within the spine and nerves from vertebrae T8-T9 at the top to L3-L4 at the bottom added up to 1.77 V/cm. This layout consisted of the placement of a pair of arrays on the back of the patient, with one array positioned above the section in the spine to which treatment would be delivered, and the other array positioned below the target section. Notably, the resulting electric field is directed along the spine in this setting (ie, vertically).

CONCLUSION

Our results demonstrate that treatment of the whole spinal cord and nerves in a single direction can be achieved by placing a pair of transducer arrays on the patient’s back: one array on the neck, and one at the bottom of the spine. For the development of an active treatment in the perpendicular direction, further studies need to be conducted.

P11.25 Assessing electrical properties of cells as predictive marker for patient-specific TTFields response and optimal frequency

BACKGROUND

Tumor treating fields (TTFields) are currently approved for the treatment of glioblastoma multiforme (GBM, using 200 kHz), and being tested in other tumor types such as non-small cell lung cancer and brain metastases occurring in this indication (LUNAR and METIS trials, using 150 kHz). Response to TTFields in cancer cells was empirically shown to be frequency-dependent specific for cell type; however, there are no markers available predicting optimal frequency or response in different cancer types or individual patients to date. There is evidence indicating electrical properties determine the optimal anti-mitotic frequency. This study analyzed the correlation of electrical properties of cells with their optimal TTFields frequency and sensitivity using the 3DEP reader (LabTech) to determine the electrical properties with the help of Dielectrophoresis (DEP) force. With this technique, cell movements within electric fields of different frequencies can by analyzed based on the physical effect of DEP, exercising a force on polarizable particles inside a non-homogeneous electric field.

MATERIAL AND METHODS

We used the 3DEP reader to obtain baseline properties (permittivity and conductivity) of 17 different cell lines of several tumor types. The resulting curves were analyzed by a 2-way ANOVA. Additionally, we determined the optimal frequency for maximum cytotoxic effect for each cell line using the inovitroTM system and eventually compared with the detected electrical properties.

RESULTS

We found cell lines with an optimal TTFields frequency of 150 kHz (corresponding to cells with a membrane capacitance in the lower range of the observed 3DEP curves, n=9) to possess significantly different (p<0.001) electrical properties from cells with an optimal TTFields frequency of 200 kHz (n=8). According to the curve differences in the lower frequency range, the measure of membrane capacitance served as a good predictor for TTFields response.

CONCLUSION

This study showed a correlation of cell membrane capacitance and optimal TTFields frequency and response. Our results provide a substantial rationale for further studies investigating the predictive potential of electrical properties of tumor cells as a measure for the optimal frequency and sensitivity to TTFields in individual patients.

P11.20 Assessing TTFields-response and associated gene expression in various human cancer cell lines

BACKGROUND

Various cancer cell lines were reported to be affected in an inhibitory manner of varying magnitude by tumor treating fields (TTFields). Here, we aimed to detect response markers for TTFields treatment by analyzing specific properties of cell lines according to their response pattern to these alternating electric fields of intermediate frequency and low intensity.

MATERIAL AND METHODS

We treated 45 cell lines of diverse types of human cancer with TTFields at their specific optimal frequency and equal nominal intensity of 1.7 V/cm for 72 h. In addition to investigating cytotoxicity and clonogenic potential, we used the Cancer Cell Line Encyclopedia (CCLE) database for further analysis: First, to functionally examine patterns of differentially expressed genes or mutations associated with response to TTFields; and second, to compare sensitivity to TTFields using pharmacological profiling (CCLE).

RESULTS

TTFields had a cytotoxic effect on tested cell lines of 50 % on average (range: 14–86% reduced cell counts), whereas the clonogenic effect varied between no effect and 88 % reduction in the number of colonies. With regard to differential gene expression and mutation analysis, our analysis detected upregulated pathways associated with migration, DNA damage repair response, oxidative stress, and hypoxia. Further, cells identified as having a better response to TTFields were also more sensitive to lapatinib, PHA-665752 and PLX-4720.

CONCLUSION

In this study, we determined the optimal frequency for maximum response to TTFields in numerous human cancer cell lines. Our results argue strongly for a vast effectiveness of TTFields treatment in cancer cells, and synergistic effects in combination with other therapeutic agents might be revealed in future studies using pharmacological profiling. Beyond that, further research is needed on the role of identified response-associated mutations.

Abstract 3961: Alternating electric fields (TTFields) induce immunogenic cell death resulting in enhanced antitumor efficacy when combined with anti-PD-1 therapy

Tumor Treating Fields (TTFields) are a clinically applied anti-neoplastic treatment modality delivered via noninvasive application of low intensity, intermediate frequency, alternating electric fields. In this study we evaluated whether TTFields-induced cell death is immunogenic. For evaluation of immunogenic cell death (ICD), cultured murine cells were treated with TTFields using the inovitro system. ICD was characterized by the pre-apoptotic exposure of calreticulin (CRT) on the cell surface, secretion of adenosine triphosphate (ATP), and release of the chromatin-binding protein high mobility group B1 (HMGB1). For detection of ER stress, phosphorylation of the translation initiation factor eIF2α was assessed. TTFields effect on autophagy was evaluated using electron microscopy and immunoblot and immunofluorescence evaluation of LC3. For evaluation of the effect of TTFields on dendritic cells (DCs), bone marrow derived dendritic cells were co-incubated with TTFields treated LLC-1 cells and phagocytosis by DCs and DCs maturation were evaluated using flow cytometry. For in-vivo studies, mice orthotopically implanted with LLC cells were treated with TTFields, the immune checkpoint inhibitor anti-PD-1 or a combination of the two modalities. Tumor volume was monitored and flow cytometry analysis was performed for phenotypic characterization of infiltrating immune cells. We demonstrate that cancer cells that die under TTFields application exhibit release of HMGB1, ATP depletion from cells, and ER stress leading to CRT translocation to the cell surface. Moreover, we show that TTFields treated cells promote phagocytosis by DCs, DC maturation in vitro, and initiate inflammation in vivo. We also show that the combined treatment of lung tumor-bearing mice with TTFields plus the immune checkpoint inhibitor anti-PD-1 led to a significant decrease in tumor volume compared to anti-PD-1 alone or to the control group. Significant increases in CD45+ tumor infiltrating cells were observed in the TTFields plus anti-PD-1 group. These infiltrating cells, specifically macrophages and DCs, demonstrated upregulation of surface PD-L1 expression. Correspondingly, cytotoxic T-cells isolated from these tumors have shown higher levels of IFN-γ production relative to untreated mice. Our results demonstrate the potential of TTFields therapy to induce ICD. We also demonstrate robust efficacy of concurrent application of TTFields and anti PD-1 therapy in a mouse model of lung cancer. These data suggest that combining TTFields with anti-PD-1 might achieve tumor control by further enhancing antitumor immunity.

Citation Format: Tali Voloshin, Noa Kaynan, Shiri Davidi, Yaara Porat, Anna Shteingauz, Mijal Munster, Rosa S. Schneiderman, Catherine Tempel Brami, Einav Zeevi, Karnit Gotlib, Shay Cahal, Aviran Itzhaki, Moshe Giladi, Eilon D. Kirson, Uri Weinberg, Adrian Kinzel, Yoram Palti. Alternating electric fields (TTFields) induce immunogenic cell death resulting in enhanced antitumor efficacy when combined with anti-PD-1 therapy [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 3961.

Abstract 307: The combined treatment of 150 kHz Tumor Treating Fields (TTFields) and Cisplatin or Pemetrexed inhibit mesothelioma cells in vitro

Malignant pleural mesothelioma (MPM) is a rare thoracic solid tumor cancer that has been strongly linked to asbestos exposure. The standard of care treatment for unresectable mesothelioma is cisplatin plus pemetrexed chemotherapy which offer short and insufficient efficacy. Furthermore, no validated treatment beyond first-line therapy is available. Thus, there is an urgent need to identify more effective treatments for mesothelioma patients. Tumor Treating Fields (TTFields) therapy is an effective anti-neoplastic treatment modality delivered via noninvasive application of low intensity, intermediate frequency, alternating electric fields. TTFields are employed as a local treatment with the intent to target dividing cells by disrupting microtubules leading to mitotic catastrophe, abnormal chromosome segregation and the induction of different forms of cancer cell death. The aim of this work is to explore the potential of the use of TTFields alone and in combination with cisplatin or pemetrexed as a treatment for Mesothelioma. MSTO-211H and NCI-H2052 cells were treated with various TTFields frequencies for 72 hours using the inovitro system. Efficacy of the combined treatment of TTFields and Cisplatin or Pemetrexed was tested by applying TTFields at the optimal frequency together with various drug concentrations. Cell counts, induction of apoptosis, and clonogenic potential were determined at the end of treatment. The optimal TTFields frequency leading to the highest reduction in cell counts was found to be 150 kHz for both MSTO-211H and NCI-H2052 cells. TTFields application (1.1 V/cm, 72 hours) at 150 kHz led to 51%, 65% reduction in cell counts, 40%, 55% reduction in the clonogenic potential in NCI-H2052 and MSTO-211H cells, respectively. The combined treatment of TTFields and Cisplatin or Pemetrexed led to a significant reduction in cell count, induction of apoptosis and reduced clonogenic potential as compared to each modality alone. (2-way ANOVA, p&lt0.0001). Safety studies did not reveal any adverse event associated with 150 kHz TTFields application to the rat torso. The results presented in this work demonstrate that TTFields can be an effective treatment against Mesothelioma cells and that the combination with cisplatin or pemetrexed may further enhance treatment efficacy. In accordance with these results, it was recently reported that patients treated by the combined treatment of TTFields with pemetrexed and cisplatin experienced improved overall survival as compared to historical control with no increase in systemic toxicity.

Citation Format: Mijal Munster, Rosa Schneiderman, Yaara Porat, Tali Voloshin, Shiri Davidi, Anna Shteingauz, Noa Kaynan, Einav Zeevi, Karnit Gotlib, Moshe Giladi, Eilon Kirson, Uri Weinberg, Adrian Kinzel, Yoram Palti. The combined treatment of 150 kHz Tumor Treating Fields (TTFields) and Cisplatin or Pemetrexed inhibit mesothelioma cells in vitro [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 307.

Abstract 306: The efficacy of the combined treatment of 150 KHz tumor treating fields (TTFields) and Sorafenib in hepatocellular carcinoma in vitro and in vivo

Hepatocellular carcinoma (HCC) is the third cause of cancer related mortality and the primary cause of cancer death. Sorafenib, an oral multikinase inhibitor is approved for patients with advanced HCC, yet its survival benefit is still limited. Tumor Treating Fields (TTFields) therapy is an effective anti-neoplastic treatment modality delivered via noninvasive application of low intensity, intermediate frequency, alternating electric fields. The aim of this work is to explore the potential of the use of TTFields alone and in combination with Sorafenib as a treatment for HCC. HepG2 and Huh-7D12 cells were treated with various TTFields frequencies for 72 hours using the inovitro system. Efficacy of the combined treatment of TTFields and Sorafenib (36-3000 nM) was tested by applying TTFields at the optimal frequency together with various drug concentrations. Cell counts, induction of apoptosis, cell cycle and clonogenic potential were determined. N1S1 HCC cells were injected to the left lobe of the liver of SD rats. After 1 week, TTFields (1.2 V/cm) and Sorafenib (10 mg/kg) were applied for 6 days and tumor growth was followed using MRI. Healthy rats were used to study safety of the use of TTFields (150 kHz) applied to the abdomen. The optimal TTFields frequency was found to be 150 kHz for both cell lines. TTFields application (1.0 - 1.7 V/cm, 72 hours) at 150 kHz led to 53-64% reduction in cell counts and to additional reduction of over 70% in the clonogenic potential. The combined treatment of TTFields and Sorafenib led to a significant reduction in the number of cells (2-way ANOVA, p&lt;0.001) as compared to each treatment alone. Tumor growth was significantly reduced by the combined group compared to the control group (student t test, p&lt;0.01). Moreover, the averaged tumor volume fold increase of the combination treatment group (1.6) was significantly lower than the one observed in the : control group (5.9, p &lt;0.0001), the TTFields group (3.3, p &lt;0.01) and the Sorafenib group (2.3, p &lt;0.05). Safety studies did not reveal any adverse event associated with TTFields application to the rat abdomen. The results presented in this work demonstrate that TTFields can be a safe and effective treatment against HCC cells and that the combination with Sorafenib may further enhance treatment efficacy.

Citation Format: Tali Voloshin, Shiri Davidi, Catherine Tempel-Brami, Mijal Munster, Karnit Gotlib, Einav Zeevi, Rosa S. Schneiderman, Moshe Giladi, Adrian Kinzel, Eilon D. Kirson, Uri Weinberg, Yoram Palti. The efficacy of the combined treatment of 150 KHz tumor treating fields (TTFields) and Sorafenib in hepatocellular carcinoma in vitro and in vivo [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 306.

Abstract 303: The efficacy of the combined treatment of 150 kHz Tumor Treating Fields (TTFields) and FOLFOX in gastric cancer in vitro

Background: Gastric cancer is the fourth most common cancer and the second most common cause of cancer death worldwide. Despite systemic therapies improvement in recent era, long-term survival rates for patients with advanced gastric cancer remains poor. FOLFOX (Oxaliplatin, 5-FU and Leucovorin) is an approved chemotherapy regimen for treatment of gastric cancer. Tumor Treating Fields (TTFields) therapy is an effective anti-neoplastic treatment modality delivered via noninvasive application of low intensity, intermediate frequency, alternating electric fields. The aim of this work is to explore the potential of the use of TTFields alone and in combination with FOLFOX as a treatment for gastric carcinomas.

Methods: AGS and KATO III cells were treated for 72 hours with TTFields (1.1 and 1.7 V/cm, respectively) at various frequencies, using the inovitro system. Efficacy of the combined treatment of TTFields and FOLFOX was tested by applying TTFields at the optimal frequency together with various drug concentrations. Cell counts, induction of apoptosis, clonogenic potential and overall effect were determined at the end of treatment.

Results: The optimal TTFields frequency leading to the highest reduction in cell counts was found to be 150 kHz for both cell lines resulting in 55% and 52% reduction in cell counts for AGS and KATO III, respectively. In addition, clonogenic potential of both cell lines was reduced by more than 70%. The combined treatment of TTFields with each chemotherapy (Oxaliplatin, 5-FU or Leucovorin), led to a significant reduction in the survival of AGS and KATO III cells (2-way ANOVA, p&lt;0.001 for both cell lines) as compared to each treatment alone. The combined treatment of TTFields with FOLFOX led to further reduction in the overall effect (cytotoxic and clonogenic) of AGS (79%) compared to TTFields alone (65%) and FOLFOX alone (34%). Similar results were observed for the combined treatment of TTFields and FOLFOX in KATO III cells.

Conclusions: The results presented in this work demonstrate that TTFields can be an effective treatment against gastric carcinoma and that the combination with FOLFOX may further enhance treatment efficacy. Based on the above, there is a strong rational to continue exploring the potential of the use of TTFields together with standard of care for the treatment of gastric cancer in the clinical settings.

Citation Format: Tali Voloshin, Einav Zeevi, Karnit Gotlib, Rosa S. Schneiderman, Mijal Munster, Yaara Porat, Shiri Davidi, Anna Shteingauz, Noa Kaynan, Moshe Giladi, Eilon D. Kirson, Uri Weinberg, Adrian Kinzel, Yoram Palti. The efficacy of the combined treatment of 150 kHz Tumor Treating Fields (TTFields) and FOLFOX in gastric cancer in vitro [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 303.

Abstract 239: Aurora kinase inhibition to enhance Tumor Treating Fields efficacy in glioblastoma treatment

Tumor Treating Fields (TTFields) have shown to be effective in prolonging progression-free and overall-survival and increasing the rate of two- and five-year survivors of patients with primary glioblastoma. However, the two-year survival rate is still below 50%. A promising approach to enhance the efficiency of TTFields is the use of drugs which extend metaphase-anaphase transition and telophase. In a previous study we tested the efficacy of the combined treatment of TTFields and the Aurora B kinase inhibitor AZD1152 in different established glioma cell lines: U87-MG, U87-MGshP53 and U-251. We found that the combined treatment of TTFields and AZD1152 led to a significant reduction in the number of glioma cells in all three cell lines as compared to each treatment alone.

In the present study we analyzed primary tumor-cell-lines to validate these data. In addition, we tested MLN8237, an Aurora A kinase inhibitor, to confirm that Aurora kinase inhibition is a valuable target for a combination therapy with TTFields.

Primary tumor-cell lines were established from glioblastoma tissue taken intraoperatively. TTFields (1.6 V/cm RMS, 200 kHz) were applied for 72 hours using the inovitro system. AZD1152 was added to the media in concentrations of up to 100 nmol/l. Cell counts, cell cycle and clonogenic potential were determined at the end of treatment. Formation of multinuclear cells was determined using microscopic images of cells stained with crystal violet. MLN8237 was used in concentrations up to 50 nmol/l for the treatment of U87 MG cells.

The combined treatment of TTFields and AZD1152 led to a significant reduction in the number of primary glioblastoma cells (Mann-Whitney-U-test, p&lt;0.001) as compared to each treatment alone. Microscopy images of glioblastoma cells stained with crystal violet after treatment, revealed high prevalence of multi nuclear cells in cells exposed to TTFields and AZD1152 (25nM) as compared to cells treated with AZD1152 (25nM) alone. Cells treated with TTFields and higher doses of AZD1152 (50-100nM) demonstrated increased rates of pyknosis. The combined treatment of MLN8237 and TTFields also resulted in a significant decrease of U87 MG cell numbers compared to each treatment alone (Mann-Whitney-U-test, p&lt;0.01).

The results presented in this work demonstrate that the combination of TTFields and aurora kinase inhibition can be an effective treatment against glioma cells. Based on the above, there is a strong rational to continue exploring the potential of combining TTFields and aurora kinase inhibition in early clinical trials.

Citation Format: Paula Bartmann, Silvia Roosz, Achim Temme, Moshe Giladi, Eilon D. Kirson, Yoram Plati, Uri Weinberg, Adrian Kinzel, Verena Leidgens, Dietmar Krex. Aurora kinase inhibition to enhance Tumor Treating Fields efficacy in glioblastoma treatment [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 239.

Abstract 2168: Testing the electrical properties of different cell lines using 3DEP reader and compare to TTFields response

Background: Tumor Treating Fields (TTFields) are an approved anti-neoplastic treatment modality delivered via application of low intensity, intermediate frequency, alternating electric fields. The electrical properties of cells (such as permittivity and conductivity) determine the optimal frequency of TTFields that incurs the highest reduction in cell counts. Currently, there are no predictive markers for determining TTFields response or the optimal frequency to be applied for individual patient. The goal of this study is to determine the correlation between electrical properties of cells and TTFields’s optimal frequency and sensitivity. The 3DEP reader (LabTech) determines the electrical properties of cells, including permittivity and conductivity, by using Dielectrophoresis (DEP) force. DEP is a physical effect that generates a force on polarizable particles experiencing a non-homogeneous electric field and can therefore be used as a technique to analyse the way cells move within electric fields at different frequencies. Methods: The baseline electrical properties (permittivity and conductivity) of 17 cell lines from different tumor types were determined using the 3DEP reader (LabTech). The curves were analyzed using 2-way ANOVA. The optimal TTFields frequency for each cell line was determined by testing the cytotoxic effect of TTFields at various frequencies using the inovitro system. The electrical properties of cells were compared with the optimal TTFields frequency and sensitivity of each cell line. Results: The results demonstrate significant differences (p&lt;0.001) between the lower frequency range of the 3DEP curves that corresponds to membrane capacitance of cells with TTFields optimal frequency of 150kHz (9 cell lines) and cells with TTFields optimal frequency of 200kHz (8 cell lines). Membrane capacitance was also a good predictor for TTFields sensitivity based on the differences in the curves in the low frequency range. Conclusions: The results presented in this study demonstrate that cell membrane capacitance correlates with TTFields optimal frequency and sensitivity. Based on the above, there is a strong rational to further explore the potential of measuring the electrical properties of cells as a predictive marker to help determine which patient will respond better to TTFields and the optimal TTFields frequency to be applied for each patient.

Citation Format: Moshe Giladi, Einav Zeevi, Karnit Gotlib, Cornelia Wenger, Ariel Naveh, Zeev Bomzon, Eilon D. Kirson, Uri Weinberg, Adrian Kinzel, Yoram Palti. Testing the electrical properties of different cell lines using 3DEP reader and compare to TTFields response [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 2168.

The combined treatment of 150 kHz tumor treating fields (TTFields) and cisplatin or pemetrexed inhibits mesothelioma cells in vitro and in vivo

e20069

Background: Malignant pleural mesothelioma (MPM) is an aggressive thoracic cancer mostly linked to asbestos exposure. The standard of care (SOC) therapy for unresectable MPM is cisplatin plus pemetrexed. Treating Fields (TTFields) therapy is an effective anti-neoplastic treatment modality delivered via noninvasive application of low intensity, intermediate frequency, alternating electric fields. We explored the potential use of TTFields alone and in combination with SOC as a treatment for MPM. Methods: NCI-H2052 and MSTO-211H cells were treated at various TTFields frequencies for 72 hours using the inovitro system. The combined treatment of TTFields and cisplatin or pemetrexed was tested by applying TTFields at the optimal frequency together with various drug concentrations. Cell counts, clonogenic potential and induction of apoptosis were determined. TTFields (1.2 V/cm) were applied for 8 days to rats injected to the intrapleural cavity with IL-45 cells, and overall survival was tested. Results: TTFields optimal frequency was 150 kHz for both human cell lines. TTFields application (1.1 V/cm, 72 hours) at 150 kHz led to 45%-51% reduction in cell counts and 46-64%% additional reduction in clonogenic potential. The combined treatment of TTFields and cisplatin or pemetrexed led to a significant reduction in cell count, induction of apoptosis and reduced clonogenic potential as compared to each modality alone (p < 0.0001(. TTFields significantly prolonged the survival of rats compared to control group. Safety studies did not reveal any adverse events associated with 150 kHz TTFields application to the rat torso. Conclusions: These results demonstrate that TTFields can be an effective treatment against mesothelioma and the combination with cisplatin or pemetrexed may further enhance treatment efficacy. These results are in consistency with the recent phase 2 study (EF-23 trial) that showed improved overall survival for combined treatment as compared to historical control with no increase in systemic toxicity.

The combined treatment of 150 kHz tumor treating fields (TTFields) and sorafenib inhibits hepatocellular carcinoma in vitro and in vivo

e15653

Background: Hepatocellular carcinoma (HCC) is the third cause of cancer related mortality and the primary cause of cancer death. Tumor Treating Fields (TTFields) therapy is an effective anti-neoplastic treatment modality delivered via noninvasive application of low intensity, intermediate frequency, alternating electric fields. Sorafenib, an oral multikinase inhibitor is approved for patients with advanced HCC, yet its survival benefit is still limited. In this work we explored the potential of the use of TTFields alone and in combination with Sorafenib as a treatment for HCC. Methods: HepG2 and Huh-7D12 cells were treated with various TTFields frequencies for 72 hours using the inovitro system. Efficacy of the combined treatment of TTFields and Sorafenib (36-3000 nM) was tested by applying TTFields at the optimal frequency together with various drug concentrations. Cell counts, induction of apoptosis, cell cycle and clonogenic potential were determined. TTFields (1.2 V/cm) and Sorafenib (10 mg/kg) were applied for 6 days to rats injected to the liver with N1S1 HCC cells. Tumor growth was followed using MRI. Results: The optimal TTFields frequency was 150 kHz for both cell lines. TTFields application (1.0 - 1.7 V/cm, 72 hours) at 150 kHz led to 36-40% reduction in cell counts and to additional reduction of over 70% in the clonogenic potential. The combined treatment of TTFields and Sorafenib led to a significant reduction in the number of cells (p < 0.001) as compared to each treatment alone. The averaged tumor volume fold increase of the combination treatment group was significantly lower than the one observed in the: control group, the TTFields group and the Sorafenib group. Conclusions: The results presented in this work demonstrate that TTFields can be an effective treatment against HCC cells and that the combination with Sorafenib may further enhance treatment efficacy.

In vitro and in vivo efficacy of the combined treatment of 150 khz tumor treating fields (TTFields) and sorafenib in hepatocellular carcinoma

333

Background: Hepatocellular carcinoma (HCC) is the third cause of cancer related mortality and the primary cause of cancer death. Sorafenib, an oral multikinase inhibitor is approved for patients with advanced HCC, yet its survival benefit is still limited. Tumor Treating Fields (TTFields) therapy is an effective anti-neoplastic treatment modality delivered via noninvasive application of low intensity, intermediate frequency, alternating electric fields. The aim of this work is to explore the potential of the use of TTFields alone and in combination with Sorafenib as a treatment for HCC. Methods: HepG2 and Huh-7D12 cells were treated with various TTFields frequencies for 72 hours using the inovitro system. Efficacy of the combined treatment of TTFields and Sorafenib (36-3000 nM) was tested by applying TTFields at the optimal frequency together with various drug concentrations. Cell counts, induction of apoptosis, cell cycle and clonogenic potential were determined. N1S1 HCC cells were injected to the left lobe of the liver of SD rats. After 1 week, TTFields (1.2 V/cm) and Sorafenib (10 mg/kg) were applied for 6 days and tumor growth was followed using MRI. Healthy rats were used to study safety of the use of TTFields (150 kHz) applied to the abdomen. Results: The optimal TTFields frequency was found to be 150 kHz for both cell lines. TTFields application (1.0 - 1.7 V/cm, 72 hours) at 150 kHz led to 53-64% reduction in cell counts and to additional reduction of over 70% in the clonogenic potential. The combined treatment of TTFields and Sorafenib led to a significant reduction in the number cells (2-way ANOVA, p < 0.001) as compared to each treatment alone. Tumor growth was significantly reduced by the combined group compared to the control group (student t test, p < 0.01). Safety studies did not reveal any adverse event associated with TTFields application to the rat abdomen. Conclusions: The results presented in this work demonstrate that TTFields can be a safe and effective treatment against HCC cells and that the combination with Sorafenib may further enhance treatment efficacy.

Tumor Treating Fields for Glioblastoma Treatment: Patient Satisfaction and Compliance With the Second-Generation Optune® System

Background:

Tumor treating fields (TTFields) are a non-invasive antimitotic therapy that delivers alternating electric fields via the Optune^® system. The Phase III EF-14 trial in newly diagnosed glioblastoma multiforme (GBM) showed significantly improved progression-free, overall and long-term survival when Optune was used together with maintenance temozolomide (TMZ) compared with TMZ alone. Compliance (average monthly use) was associated with better clinical outcome. The first-generation Optune system weighed approximately 6 pounds (~2.7 kg). The second-generation redesigned Optune system weighs 2.7 pounds (~1.2 kg). We tested and compared GBM patient experience with the second-generation system versus the first-generation system.

Methods:

Ten newly diagnosed and recurrent GBM patients in Germany (median age: 52.9 years [31-79]) were prospectively monitored over the first month of transitioning from the first-generation to the second-generation Optune system. Questionnaires using a numerical analog scale assessed feedback at baseline (first generation) and after 1 month of second-generation use.

Results:

After transitioning to the second-generation system, compliance improved by more than 10% in four patients, was maintained in five patients and decreased by more than 10% in one patient. Following transition, eight out of nine patients reported a reduction in the triggering of malfunction alarms. Self-reported patient feedback showed improved handling and portability (weight, mobility) of the second- versus the first-generation Optune system.

Conclusions:

This patient user survey suggests that patient satisfaction with the second-generation Optune system is improved versus the first-generation system. Improved features of the new system help patients achieve and maintain a higher rate of treatment compliance.

AMPK-dependent autophagy upregulation serves as a survival mechanism in response to Tumor Treating Fields (TTFields)

Tumor Treating Fields (TTFields), an approved treatment modality for glioblastoma, are delivered via non-invasive application of low-intensity, intermediate-frequency, alternating electric fields. TTFields application leads to abnormal mitosis, aneuploidy, and increased cell granularity, which are often associated with enhancement of autophagy. In this work, we evaluated whether TTFields effected the regulation of autophagy in glioma cells. We found that autophagy is upregulated in glioma cells treated with TTFields as demonstrated by immunoblot analysis of the lipidated microtubule-associated protein light chain 3 (LC3-II). Fluorescence and transmission electron microscopy demonstrated the presence of LC3 puncta and typical autophagosome-like structures in TTFields-treated cells. Utilizing time-lapse microscopy, we found that the significant increase in the formation of LC3 puncta was specific to cells that divided during TTFields application. Evaluation of selected cell stress parameters revealed an increase in the expression of the endoplasmic reticulum (ER) stress marker GRP78 and decreased intracellular ATP levels, both of which are indicative of increased proteotoxic stress. Pathway analysis demonstrated that TTFields-induced upregulation of autophagy is dependent on AMP-activated protein kinase (AMPK) activation. Depletion of AMPK or autophagy-related protein 7 (ATG7) inhibited the upregulation of autophagy in response to TTFields, as well as sensitized cells to the treatment, suggesting that cancer cells utilize autophagy as a resistance mechanism to TTFields. Combining TTFields with the autophagy inhibitor chloroquine (CQ) resulted in a significant dose-dependent reduction in cell growth compared with either TTFields or CQ alone. These results suggest that dividing cells upregulate autophagy in response to aneuploidy and ER stress induced by TTFields, and that AMPK serves as a key regulator of this process.