Standard Of Care Chemotherapy Research Articles

AMPLIFY-7P: Phase 1 and randomized phase 2 study of amphiphile immunotherapy ELI-002 7P as adjuvant treatment for subjects with G12D, G12R, G12V, G12C, G12A, G12S and G13D Kirsten rat sarcoma (KRAS)-mutated pancreatic ductal adenocarcinoma.

TPS720 Background: KRAS mutations occur in 25% of human tumors, frequently in pancreatic where over 85% relapse after locoregional treatment. ELI-002 7P is a lymph node targeted immunotherapy comprised of Amphiphile (Amph)-modified G12D, G12R, G12V, G12C, G12A, G12S and G13D mutant KRAS peptides together with an Amph-modified CpG oligonucleotide adjuvant. In the first in human AMPLIFY-201 study, a two peptide G12D/G12R formulation increased KRAS-specific T cells in 87% of patients, and T cell responses 13-fold or higher over baseline correlated with outcomes including reduction in risk of relapse or death. The AMPLIFY-7P study hypothesizes that adjuvant administration of ELI-002 7P will be safe and will delay relapse compared to observation in patients with KRAS mutated pancreatic cancers who have completed curative intent locoregional treatment. Methods: This open-label, phase 1 and randomized phase 2 study is evaluating ELI-002 7P in patients with KRAS mutated pancreatic adenocarcinoma following standard of care chemotherapy and surgery. In phase 2, patients are randomized 2:1 to ELI-002 7P versus observation with crossover of the observation arm permitted at the time of confirmed radiographic relapse via iRECIST. Eligible patients must be within 6 months of completion of locoregional treatment for up-front resectable pathologically confirmed pancreatic cancer (Stage I-III) with radiographic NED (no evidence of disease). Phase 2 patients are included regardless of biomarker evidence of recurrent disease, however, those who have not recovered absolute lymphocytes to the normal range following cytotoxic therapy are excluded. The primary phase 2 objective is to compare the efficacy of ELI-002 7P versus observation, with primary endpoint disease-free survival per investigator. Secondary objectives compare biomarker response (reduction or clearance of ctDNA or if ctDNA was not detectable, serum tumor antigen CA19-9) in the subset with positive baseline values, OS, safety, and iRECIST response rate in the crossover subset. Exploratory endpoints include immunogenicity, the association of immunogenicity with high resolution HLA typing, and evaluation of tumor-infiltrating T cells and the tumor microenvironment in the event biopsy tissue is available. An Independent Data Monitoring Committee reviewed phase 1 data and recommended opening phase 2. Subsequent patients will receive up to 10 doses of Amph-peptides 7P 700 mcg each (4.9 mg total), together with Amph-CpG-7909 (10.0 mg) administered over a five-month treatment period. In Phase 2, approximately 135 patients will be enrolled in the United States. An interim analysis is planned using group sequential design for control of overall alpha 0.10. Clinical trial information: NCT05726864 .

A phase 1b/2 trial of pepinemab and avelumab as second line therapy for patients with metastatic pancreatic adenocarcinoma.

TPS712 Background: Pancreatic adenocarcinoma (PDAC) is a leading cause of cancer-related mortality with poor prognosis despite maximal therapy and is unresponsive to immune checkpoint blockade (ICB). This failure of response is hypothesized to be driven in part by the characteristic immunosuppressive tumor microenvironment. In PDAC, Semaphorin 4D (SEMA4D) expression is prognostic in patients who have undergone surgical resection and correlates with tumor infiltration of activated CD8+ T-cells. Additionally, preclinical models suggest that antibody-mediated SEMA4D blockade promotes tumoral infiltration and activation of CD8+ T-cells and sensitizes PDAC to ICB, with improved overall survival with standard of care chemotherapy and ICB in combination with pepinemab (humanized anti-SEMA4D). Thus, we hypothesized that pepinemab may improve clinical outcomes in PDAC by sensitizing tumors to ICB. Methods: We designed a phase Ib/II single-arm clinical trial to evaluate the safety, tolerability, and efficacy of humanized anti-SEMA4D (pepinemab) with anti-PD-L1 (avelumab) in patients with chemotherapy-refractory PDAC. Patients must have failed first-line 5-fluorouracil or gemcitabine-based combination chemotherapy. The study follows a dose de-escalation schema starting at a dose combination of 20mg/kg pepinemab and 800mg avelumab every two weeks. Patient accrual for phase 1b utilizes the Bayesian Optimal Interval Design (BOIN) targeting a dose-limiting toxicity rate of 30% or less. After 16 subjects receive a given combination dose, a Simon’s two stage assessment of futility will be undertaken with expansion to phase 2 if 2 or more subjects demonstrate response. The trial is designed to evaluate a total cohort of 40 subjects and powered to detect a response rate of 23% or greater, with alpha set at 0.1% and 80% power. Treatment response is assessed via RECIST 1.1 criteria with surveillance CT prior to enrollment and after completion of two cycles (8 weeks). Baseline and on-treatment tumor biopsies (after completion of one cycle, 4 weeks) are performed to analyze changes in immune, stromal, and genomic profiles to elucidate mechanisms of treatment response and failure. Patient reported outcomes are incorporated (FACT-Hep and FAACT subdomains) to assess disease-specific symptoms. To date, 7 patients have been enrolled (Clinical Trial NCT05102721). Clinical trial information: NCT05102721 .

Abstract A091: The RAF/MEK clamp avutometinib as the backbone of therapy for pancreatic cancer: Novel combinations with standard of care chemotherapy, FAK inhibitors, KRAS G12D inhibitors and/or autophagy inhibitors

Abstract KRAS mutations (mt) occur in up to 98% of pancreatic ductal adenocarcinoma (PDAC) and represent a key initiating event in PDAC carcinogenesis. Therapeutic efforts targeting the RAS/RAF/MEK/ERK (MAPK) pathway with MEK-only inhibitors have been unsuccessful in substantially modifying PDAC prognosis. Thus, novel strategies are needed to overcome putative mechanisms of resistance to MEK inhibition such as focal adhesion kinase (FAK) pathway activation. Another hallmark of PDAC is its high stromal density, which is thought to limit the penetration of cytotoxic drugs and T cells into the tumor and has been shown to be correlated with FAK hyperactivation, altogether supporting co-targeting the MAPK and FAK pathways to achieve deep and durable responses for patients with PDAC. Avutometinib is a RAF/MEK clamp that potently inhibits MEK kinase activity and induces dominant negative RAF-MEK complexes preventing phosphorylation of MEK by ARAF, BRAF and CRAF. This unique mechanism allows avutometinib to block MEK signaling without the compensatory re-activation of MEK that appears to limit the efficacy of MEK-only inhibitors. Preclinically, avutometinib has shown strong anti-proliferative potency across tumor cell lines carrying KRAS mt including PDAC cell lines. Clinically, avutometinib in combination with the FAK inhibitor (FAKi) defactinib received breakthrough therapy designation for the treatment of patients with recurrent low-grade serous ovarian cancer. Here, we tested the combination of avutometinib and FAK inhibition with standard of care chemotherapy in PDAC mouse models. In a KRAS/p53 pancreatic cancer mouse model, we found that whereas the combination of avutometinib + FAKi induced tumor inhibition and increased survival, addition of chemotherapy (gemcitabine + paclitaxel as a surrogate for nab-paclitaxel) to avutometinib/FAKi induced tumor regression. These results support the ongoing clinical study of avutometinib and defactinib in combination with standard of care chemotherapy (gemcitabine/nab-paclitaxel) for patients with front-line metastatic PDAC (NCT05669482). Other combinations being explored preclinically include avutometinib with G12D inhibition (G12Di) in KRAS G12D PDAC, which accounts for 28% of patients with PDAC. In 3D culture, avutometinib was synergistic with the G12Di MRTX1133 in reducing viability of a panel of KRAS G12D PDAC cell lines. In mouse models, avutometinib enhanced anti-tumor efficacy of MRTX1133 in a KRAS G12D pancreatic cancer patient-derived xenograft model. Furthermore, in KRAS mt PDAC cell lines, avutometinib was synergistic with the autophagy inhibitors chloroquine or apilimod. Indeed, dual treatment with avutometinib + MRTX1333 synergistically decreased proliferation and increased autophagic flux in KRAS G12D PDAC cell lines, supporting testing the triple combination of avutometinib + G12Di + autophagy inhibitor in patients with KRAS G12D pancreatic cancers. In conclusion, we show that avutometinib is a unique RAF/MEK clamp with the potential to become the backbone of therapy for pancreatic cancers. Citation Format: Silvia Coma, Xiuting Liu, Noah L. Pieper, Wen-Hsuan Chang, Kirsten L. Bryant, Channing J. Der, David G. DeNardo, Jonathan A. Pachter. The RAF/MEK clamp avutometinib as the backbone of therapy for pancreatic cancer: Novel combinations with standard of care chemotherapy, FAK inhibitors, KRAS G12D inhibitors and/or autophagy inhibitors [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr A091.

Abstract C038: Interim pharmacodynamic analyses of mitazalimab in combination with FOLFIRINOX in first-line metastatic pancreatic ductal adenocarcinoma (mPDAC) identify CD4 effector T cells as a correlate of treatment outcomes

Abstract CD40 agonists are being investigated in combination with standard of care chemotherapy as an approach to trigger anti-tumor immunity and improve outcomes for patients with cancer. Preclinical models suggest the importance of appropriate sequencing of chemotherapy and a CD40 agonist. Herein, we report interim pharmacodynamic analyses and their association with outcomes from a Phase 2 study evaluating mitazalimab, a CD40 agonist, in combination with modified (m) FOLFIRINOX chemotherapy as first line therapy in patients with metastatic pancreatic ductal adenocarcinoma (mPDAC). Patients with newly diagnosed mPDAC were treated with mitazalimab on day 1 prior to beginning an every 2-week regimen on day 8 of mFOLFIRINOX followed by mitazalimab 48 hours later. Tumor response was determined by RECIST v1.1 imaging. Peripheral blood was analyzed for selected cytokines and chemokines and by flow cytometry to assess changes in leukocyte subsets including B cells, monocytes, T cells, and NK cells. The neutrophil-to-lymphocyte ratio was determined from complete blood counts. The analysis included 23 patients with associated response data and indicated a mitazalimab-specific contribution to tumor response. Mitazalimab triggered an expected immune response characterized by transient cytokine (IL-8, IP-10, MCP-1, and MIP1b) release and B cell depletion. Chemotherapy provoked a reduction in classical monocytes and proliferating CD4+ T cells. Both mitazalimab and chemotherapy caused a transient reduction in circulating dendritic cells and NK cells. Tumor response was associated with an expansion in the frequency of effector CD4 T cells (p < 0.0001) at day 8 after receiving mitazalimab but did not correlate with neutrophil-to-lymphocyte ratio (p = 0.851). In conclusion, mitazalimab and FOLFIRINOX modulate immune responses in patients with mPDAC in different ways. Interim results of pharmacological analyses identify CD4 effector T cells as a correlate of treatment outcomes suggesting the contribution of mitazalimab to tumor responses. Citation Format: Max M. Wattenberg, Karin Enell Smith, Yago Pico de Coana, David Gomez Jimenez, Malin Carlsson, Sumeet Vijay Ambarkhane, Peter Ellmark, Gregory L. Beatty. Interim pharmacodynamic analyses of mitazalimab in combination with FOLFIRINOX in first-line metastatic pancreatic ductal adenocarcinoma (mPDAC) identify CD4 effector T cells as a correlate of treatment outcomes [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr C038.

Abstract LB_C02: A phase 1b dose escalation study of AV-380 in combination with standard of care chemotherapy in metastatic cancer patients (pts) with cachexia and elevated GDF-15 levels

Abstract Background: Cancer cachexia is a complex metabolic syndrome characterized by involuntary weight loss, muscle wasting and weakness leading to resistance to therapy and high mortality. Elevated levels of circulating GDF-15, an inflammatory cytokine involved in stress response and body weight regulation, are common in cancer pts with cachexia. Furthermore, GDF-15 expression increases in proportion to disease severity, and preclinical models have shown that elevated levels of circulating GDF-15 elicit cachexia. AV-380 is an antibody that binds with high affinity to GDF-15 resulting in its elimination from circulation. It has been shown to reverse weight loss and increase recovery of muscle in animal cancer models and was well tolerated without serious AEs in a phase 1 study in healthy subjects. The current study is designed to determine if adding AV-380 to standard-of-care (SoC) chemotherapy will confer additional clinically meaningful benefits in metastatic cancer pts with cachexia. Methods: This is an open-label, dose escalation, multicenter phase 1b study to assess the safety, PK, and PD of AV-380. Eligible pts must be ≥18 years of age, have confirmed metastatic colorectal or pancreatic cancer, actively receiving 1st-line SoC chemotherapy (>2 cycles of FOLFOX/FOLFOXIRI±bevacizumab for colorectal, FOLFOX/FOLFIRINOX for pancreatic), have cachexia defined by Fearon criteria (weight loss >5% over past 6 months w/o simple starvation, or BMI <20 kg/m2 or sarcopenia plus any degree of weight loss >2%), life expectancy ≥3 months, GDF-15 >1200 pg/mL, and ECOG PS 0/1. Those with brain metastases (unless treated and stable for ≥2 weeks prior to study treatment), significant cardiovascular disease, corrected QT interval >460 ms, uncontrolled pleural or pericardial effusion, parenteral nutrition, or non-cancer related cachexia are excluded. Primary endpoints are AE characterization, serum PK parameters, and serum levels of GDF-15; secondary endpoints include assessments of weight/BMI, cachexia measures, and anti-AV-380 antibodies; and exploratory endpoints include best objective response and biomarkers. Five escalating dose cohorts of AV-380 are planned (50, 100, 200, 400, 800 mg IV) with 4-6 pts in each and following a standard 3+3 design. Dose de-escalation will be performed if the lowest dose cohort is successful. The study is structured into 28-day courses with Course 1 being the single-dose phase of AV-380 and Course 2 starting the multiple-dose phase where AV-380 is administered every 14 days. Pts will remain enrolled until they start 2nd-line systemic anticancer therapy, have unacceptable toxicity related to AV-380, complete 4 courses of AV-380, withdraw consent, or sponsor terminates study. Statistical analyses will be done by cohort and summarized descriptively. Clinicaltrials.gov: NCT05865535 Encore abstract. Originially accepted at the annual Cancer Cachexia Society meeting, 28-30 September 2023, Edinburgh Scotland. Citation Format: Arvind Chaudhry, RIchard Zuniga, J. Eva Selfridge, Bruno Bastos, Vipin Lohiya, Martin Birkhofer. A phase 1b dose escalation study of AV-380 in combination with standard of care chemotherapy in metastatic cancer patients (pts) with cachexia and elevated GDF-15 levels [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr LB_C02.

Proteogenomics Coupled with Ex Vivo Profiling for Therapeutic Targeting in AML

AML is the most common acute leukaemia in adults and incidence is on the rise, partly due to population ageing. Despite the emergence of new targeted therapies for AML patients, survival rates remain dismal (~27% at 5 years). Current challenges include the rapid development of resistance and the inability to predict which therapy is optimal for each patient, especially for those without ‘actionable’ mutations. These challenges are compounded by the lack of complete testing platforms for capturing critical patient-specific molecular profiles beyond somatic mutations, such as changes in the proteome and phosphoproteome. Due to the heterogeneous nature of AML, individualised screening and personalised treatment plans are likely required to improve treatment and survival outcomes for AML patients. By combining genetic profiling, phosphoproteomic and proteomic analysis, we have developed a pipeline for profiling AML patient samples. Using this pipeline, we have identified novel therapies for different leukaemia subtypes ( Leukemia, 2021). In this study, we have integrated genomic, proteomic, and phosphoproteomic profiling together with ex vivo drug sensitivity profiling for a functional read-out of drug sensitivity or resistance, to identify optimal therapeutic regimes for individual AML patients. Ex vivo drug sensitivity profiling has been performed on 71 patients. Genomic profiling was performed using the SOPHiA Genetics Myeloid Panel. The mutation frequency identified was similar to previous reports ( TCGA, N Engl J Med 2013). The drug screen panel included AML standard of care treatments (e.g., cytarabine, midostaurin) as well as investigational agents. Cell survival was measured at 24 hours using an ATPlite assay or Annexin V staining. Results identified both known and novel associations with mutation subgroups. Consistent with previous reports ( Jawhar, Blood 2017), IDH2 mutations were associated with reduced sensitivity to midostaurin (p=0.0039). Samples with NPM1 mutation were significantly more sensitive to Aurora kinase/CDK inhibitor JNJ7706621 compared to NPM1 wildtype (p=0.0007). This association also held true in the BeatAML cohort (Vizome, p<0.0001). NPM1 has documented roles in cell cycle regulation, and these results suggest that mutant NPM1 may sensitise to cell cycle targeted therapies. Multi-omic analyses of 23 intermediate/high risk patients, 9 of which had no actionable mutations, identified further drug vulnerabilities, with >2 therapies identified for each patient. Validation of this approach is exemplified by individual case studies where our profiling platform correlates with clinical outcome. In the first case, the patient presented with a KRAS mutation, predictive of resistance to midostaurin. Proteomic profiling identified low expression of BCL2, predictive of resistance to venetoclax. Phosphoproteomic profiling however identified activation of DNA repair and CDK proteins, suggesting sensitivity to DNA repair and CDK inhibitors. Ex vivo drug sensitivity profiling of the patient blasts identified resistance to midostaurin and venetoclax, but sensitivity to PARP and CDK inhibitors. Concurrently, the patient received a combination of standard chemotherapy and targeted therapy (cytarabine, midostaurin, venetoclax) and was primary refractory to treatment. In a second case, proteogenomics and ex vivo screening predicted sensitivity to midostaurin and venetoclax. The patient received cytarabine, midostaurin, and venetoclax therapy and achieved remission. In our third case study, ex vivo screening predicted sensitivity to standard of care agents (cytarabine, midostaurin, venetoclax). While the patient achieved remission with standard of care chemotherapy, they subsequently relapsed. At relapse, ex vivo screening identified reduced sensitivity to cytarabine but a high level of venetoclax sensitivity. The patient was placed on FLAG with venetoclax and was bridged to transplant. Therefore, our approach can predict treatment sensitivities and resistance to standard of care therapies, and may also identify alternative clinically available therapies. The results of these and further case studies will be presented at the meeting.

EXTH-32. SYNERGISTIC EFFICACY OF Y BOX BINDING PROTEIN 1 (YBX1) INHIBITION COMBINED WITH CHEMOTHERAPY FOR THE TREATMENT OF MYC-AMPLIFIED MEDULLOBLASTOMA

Abstract Medulloblastoma is the most common pediatric brain tumor in children. Patients diagnosed with MYC-amplified group 3 (G3) have a dismal prognosis with a 5 year survival rate of < 50%. Standard of care consists of maximal resection surgery followed by craniospinal irradiation and chemotherapy, but patients experience diminished quality of life from these extensive treatment regimens. Recent observations have shown that Y-box binding protein 1 (YBX1) is upregulated across human medulloblastoma subgroups compared to normal cerebellum. G3 patient tumors have the highest expression of YBX1, possibly due to an oncogenic feedback loop. We utilized an orthogonal pharmacogenetic approach to target YBX1. Knockdown/out of YBX1 significantly inhibits proliferation of G3 MB cells in vitro and in vivo. We next investigated the therapeutic potential of a novel YBX1 inhibitor, which displays single agent efficacy at decreasing the proliferation of medulloblastoma cell line derived xenografts (CDX). Since YBX1 targeting downregulated ABC transporter expression, we hypothesize that inhibition of YBX1 may sensitize medulloblastoma cells to chemotherapeutic agents. We performed drug synergy experiments combining YBX1 inhibition and commonly used standard of care chemotherapy. We identify that combining YBX1 inhibition sensitizes to both gemcitabine and vincristine in vitro and in vivo. We are currently evaluating this YBX1 inhibitor in an “anchor-probe” screen combining with all currently FDA approved drugs. Our findings impart an alluring prospect of targeting YBX1 in combination with chemotherapy, and possibly other compounds could improve patients’ outcomes.

Pooled Analysis of Safety from Birtamimab Phase 1-3 Studies in Patients with Light Chain (AL) Amyloidosis

Introduction: SystemicAL amyloidosis is a progressive and often fatal disease caused by misfolded light chains that aggregate into amyloid fibrils and deposit in vital organs, leading to organ dysfunction. Current standard of care (SoC) therapies for AL amyloidosis target the plasma cell clone to reduce or eliminate light chain production, but do not remove soluble toxic light chain aggregates or insoluble amyloid deposits. Early mortality remains high for patients with advanced disease (e.g., Mayo 2012 Stage IV disease, median overall survival <6 months). Birtamimab - a humanized monoclonal antibody that neutralizes soluble, toxic light chain aggregates and depletes insoluble amyloid deposits by inducing phagocytosis - is under investigation for the treatment of AL amyloidosis. Here, we present a pooled safety analysis from previous Phase 1-3 clinical trials, with a focus on the 2 double-blind randomized controlled trials (RCTs): PRONTO (NCT02632786) and VITAL (NCT02312206). Methods: Patients with AL amyloidosis were treated with intravenous birtamimab up to 24 mg/kg every 28 daysin the non-placebo-controlled Phase 1/2 open-label trial (NCT01707264) with open-label extension (OLE; NCT02613182) and 2 RCTs (Phase 2 PRONTO with OLE [NCT03154047] and Phase 3 VITAL). In PRONTO, patients had received ≥1 previous systemic therapy with at least a partial hematologic response and persistent cardiac dysfunction, and received birtamimab or placebo. In VITAL, newly diagnosed treatment-naïve patients with cardiac involvement received birtamimab + SoC or placebo + SoC (where SoC was a bortezomib-containing chemotherapy regimen). The analysis included all patients who received ≥1 dose of birtamimab. Pooled median exposure times were calculated, and baseline characteristics and demographics were summarized. For VITAL and PRONTO, pooled rates and severity of treatment-emergent adverse events (TEAEs) with birtamimab were compared with rates in the placebo arms. In addition, safety data from the non-placebo-controlled studies were summarized. Results: The median (range) exposure to birtamimab among 302 patients pooled from the Phase 1-3 trials was 12.24 (0.03-57.72) months. Of the 302 patients exposed to birtamimab, 295 received at least one 24-mg/kg infusion, up to 2500 mg. Analysis of the 2 randomized, placebo-controlled trials included data from 196 patients treated with birtamimab from the PRONTO (n=66) and VITAL (n=130) trials and 193 patients who received placebo (PRONTO, n=63; VITAL, n=130). Both trials had comparable treatment durations overall. The rates of TEAEs, serious and grade ≥3 TEAEs were similar between birtamimab and placebo arms within each trial and between treatment arms in the placebo-controlled pooled analysis set (PRONTO and VITAL; Table 1). Higher rates of treatment-related, serious, and grade ≥3 TEAEs were reported in VITAL compared with PRONTO, presumably due to the treatment-naïve population and receipt of concomitant SoC therapy in VITAL. In the pooled analysis set, the most common TEAEs that occurred with greater frequency in the birtamimab vs placebo arms in either trial were, respectively, fatigue (36.2%, 34.2%), diarrhea (33.2%, 33.7%), nausea (31.6%, 30.1%), constipation (31.1%, 31.6%), and dyspnea (25.0%, 24.9%). The most commonly reported (≥5%) serious and grade ≥3 TEAEs were primarily cardiac disorders (cardiac failure, syncope, cardiac arrest), consistent with the underlying disease. Infusion-associated TEAE rates were low in the pooled birtamimab and placebo arms (5.1% vs 3.6%, respectively) and were generally mild to moderate. The safety profile observed in the non-placebo-controlled Phase 1/2 trial plus OLE and PRONTO OLE (n=106) was consistent with the safety data reported in the placebo-controlled studies. Conclusions: Birtamimab was well tolerated in patients with AL amyloidosis when administered as monotherapy and did not demonstrate additive toxicity when given with SoC chemotherapy. Rates of TEAEs in the birtamimab arm were similar to rates in the placebo arm in the PRONTO and VITAL trials. The safety and efficacy of birtamimab is being further investigated in an ongoing confirmatory Phase 3 double-blind RCT in patients with Mayo Stage IV AL amyloidosis (AFFIRM-AL; NCT04973137), which is currently enrolling.

Abemaciclib plus trastuzumab with or without fulvestrant versus trastuzumab plus standard-of-care chemotherapy in women with HR+, HER2+ advanced breast cancer: plain language summary of the monarcHER study.

This article summarizes the results of a study called monarcHER. The study included participants with a certain type of aggressive breast cancer called HR+, HER2+ advanced breast cancer (ABC) that had their disease worsen or return after multiple previous therapies. This summary intends to help you understand the impact of a non-chemotherapy treatment called abemaciclib in people with HR+, HER2+ ABC. When the study was planned, HER2-targeted therapy (ie trastuzumab) was standard treatment and was typically combined with chemotherapy and endocrine therapy (ie fulvestrant). However drug resistance can develop when HER2+ targeted therapy is used for a long time, making it less effective and allowing cancer to grow or spread to other parts of the body. When this happens, few chemotherapy-free options are available. Because of the chemotherapy side effects, this is not desirable. There is an urgent need to develop new, effective, safe, and tolerable treatment options for patients with HR+, HER2+ ABC. The monarcHER study compared the effects of abemaciclib plus trastuzumab with or without fulvestrant compared to the standard of care treatment. Participants were randomly assigned to 1 of 3 groups: Group A (abemaciclib, trastuzumab and fulvestrant), Group B (abemaciclib and trastuzumab), or Group C (trastuzumab and standard of care chemotherapy). The study compared the length of time patients took study treatments without worsening or dying from their breast cancer. This is called the progression free survival (PFS). Participants in Group A had a longer median PFS than those in groups B and C (8.3months, 5.7months and 5.7months respectively). There was no notable difference in PFS between participants in Groups B and C. Additionally, the study looked at the side effects with each treatment group. The most common side effect which is considered severe or lifethreatening was neutropenia, defined as decreased white blood cell levels. Neutropenia may lead to an increased risk of getting infections. However, the percentage of patients experiencing neutropenia was similar in all groups A, B and C (27%, 22% and 26%, respectively). Patients in groups A (79%) and B (78%) who received abemaciclib experienced similar rates of diarrhea. The data from the monarcHER study suggest that the combination of abemaciclib, trastuzumab, and fulvestrant may offer a chemotherapy-free option for patients with HR+, HER2+ ABC who have experienced worsening of disease despite multiple prior therapies.

746MO Randomized phase II trial of durvalumab in combination with olaparib and cediranib (DOC) compared to olaparib and cediranib (OC) or durvalumab and cediranib (DC) or standard of care chemotherapy (SOC) in platinum-resistant ovarian cancer with prior bevacizumab (NRG-GY023)

746MO Randomized phase II trial of durvalumab in combination with olaparib and cediranib (DOC) compared to olaparib and cediranib (OC) or durvalumab and cediranib (DC) or standard of care chemotherapy (SOC) in platinum-resistant ovarian cancer with prior bevacizumab (NRG-GY023)

1536P HERIZON: A phase II study of HER-Vaxx (IMU-131), a HER2-targeting peptide vaccine plus standard of care chemotherapy in patients with HER2+ advanced stomach cancer - Dose-dependent anti-cancer antibodies correlating with improved clinical outcome

1536P HERIZON: A phase II study of HER-Vaxx (IMU-131), a HER2-targeting peptide vaccine plus standard of care chemotherapy in patients with HER2+ advanced stomach cancer - Dose-dependent anti-cancer antibodies correlating with improved clinical outcome

BREAKWATER: An open-label, multicenter, randomized, phase 3 study, with a safety lead-in (SLI), of first-line (1L) encorafenib (E) + cetuximab (C) ± chemotherapy (CT) vs standard-of-care (SOC) CT for BRAF V600E-mutant metastatic colorectal cancer (mCRC).

TPS3627 Background: Globally, 8-12% of patients (pts) with mCRC have BRAF V600E mutations, which confer poor prognosis. Based on BEACON (NCT02928224), EC was approved for the treatment (tx) of previously treated pts with BRAF V600E-mutant mCRC. BREAKWATER (NCT04607421) is evaluating EC ± CT vs SOC CT in pts with BRAF V600E-mutant mCRC. In the BREAKWATER SLI (N = 57), EC + CT showed encouraging antitumor activity. Confirmed ORR by BICR (95% CI) with EC + mFOLFOX6 and EC + FOLFIRI, respectively, was 68.4% (46.0, 84.6) and 75.0% (46.8, 91.1) in 1L, and 37.5% (13.7, 69.4) and 44.4% (24.6, 66.3) in 2L. mPFS by BICR (95% CI) with EC + mFOLFOX6 and EC + FOLFIRI, respectively, was 11.1 months [mo] (8.5, NE) and NE (13.8, NE) in 1L, and 10.8 mo (4.3, NE) and 12.6 mo (6.9, NE) in 2L. These results support the continued evaluation of EC + CT. Based on the SLI, EC + mFOLFOX6 was selected for the phase 3 portion. Here we present the updated study design. Methods: BREAKWATER is an ongoing, open-label, multicenter, randomized, phase 3 study evaluating 1L EC ± CT vs SOC CT alone in pts with BRAF V600E-mutant mCRC. Approximately 620 pts will be enrolled in the phase 3 portion and an additional 135 in cohort 3 (Table). Phase 3 and cohort 3 inclusion criteria are age ≥16 (or ≥18 based on country); no prior systemic tx for metastatic disease; measurable disease (RECIST 1.1); BRAF V600E-mutant mCRC (blood or tumor tissue); ECOG PS 0 or 1; and adequate bone marrow, hepatic, and renal function. Pts who received prior BRAF or EGFR inhibitors, those with symptomatic brain metastases (unless stable for ≥4 weeks prior to randomization), or with MSI-H/dMMR tumors (unless ineligible to receive immune checkpoint inhibitors due to a pre-existing medical condition) are excluded. Study treatments and endpoints are shown in the Table. Phase 3 enrollment began in November 2021. Clinical trial information: NCT04607421 . [Table: see text]

LOGGIC/FIREFLY-2: A phase 3, randomized trial of tovorafenib vs. chemotherapy in pediatric and young adult patients with newly diagnosed low-grade glioma harboring an activating RAF alteration.

TPS10067 Background: Pediatric low-grade gliomas (pLGGs) are the most common CNS tumors of childhood. Genomic alterations of BRAF are oncogenic drivers in almost all pLGGs. Approximately 50%‒60% of pLGGs harbor a KIAA1549-BRAF fusion and 5%‒15% a BRAF V600E mutation. Tovorafenib is an investigational, oral, selective, CNS-penetrant, small molecule, type II pan-RAF inhibitor. The registrational, phase 2 FIREFLY-1 (NCT04775485) study of tovorafenib in pediatric patients with recurrent/progressive LGG is ongoing and interim analysis has shown encouraging anticancer activity. Methods: LOGGIC/FIREFLY-2 (NCT05566795) is a registrational, 2-arm, randomized, multicenter, global (~100 sites across Australia, Canada, Europe, New Zealand, Singapore, South Korea, and USA), phase 3 trial being conducted in collaboration with the SIOPe Brain Tumor Group LOGGIC Consortium. The study is evaluating the efficacy, safety, and tolerability of tovorafenib vs. standard of care (SoC) chemotherapy in patients < 25 years old with pLGG harboring an activating RAF-alteration and requiring first-line systemic therapy. Approximately 400 patients will be randomized 1:1 to receive oral tovorafenib, 420 mg/m2 (≤600 mg) once weekly (tablet or liquid suspension), or an investigator’s choice of SoC chemotherapy: COG-V/C regimen (60 weeks), SIOPe-LGG-V/C regimen (81 weeks), or single-agent vinblastine (70 weeks). Tovorafenib will be continued until the occurrence of radiographic progression (based on Response Assessment in Neuro-Oncology [RANO] criteria as determined by the investigator and confirmed by independent review) or unacceptable toxicity; patients with radiographic progression may be allowed to continue tovorafenib if, in the opinion of the treating investigator, they are deriving clinical benefit from study treatment. Patients who progress in the SoC arm during or after completion of chemotherapy are eligible to cross-over to receive tovorafenib. The primary endpoint is the objective response rate based on RANO criteria, as determined by independent review. Key secondary endpoints are progression-free survival and duration of response per RANO criteria by independent review and overall survival. Other secondary endpoints include efficacy assessments per Response Assessment in Pediatric Neuro-Oncology (RAPNO) criteria, changes in neurological and visual function, and safety and tolerability. Exploratory endpoints include efficacy assessments per investigator, tumor volume, adaptive behavior and quality of life. Prognostic and predictive molecular biomarkers, including senescence profiles for treatment outcome, response prediction, and treatment resistance, will be explored in parallel studies. Clinical trial information: NCT05566795 .

ASCEND: A randomised, double-blinded, phase II study of gemcitabine and nab‐paclitaxel with CEND‐1/LSTA1 or placebo in patients with untreated metastatic pancreatic ductal adenocarcinoma.

TPS4197 Background: LSTA1 is a novel cyclic peptide with high tumor vascular endothelium specificity that activates an endocytotic/exocytotic transport pathway on stroma and tumor. LSTA1 potentiates greater intratumoral access for co-administered or tethered anti-cancer agents, including small molecules, antibodies, and nanoparticles, leading to increased anti-neoplastic activity. Preclinical studies in solid tumor models have shown co-administrating LSTA1 is effective in augmenting the delivery and activity of multiple anti-cancer agents. LSTA1 has been evaluated in 31 patients in a Phase I study in metastatic pancreatic ductal adenocarcinoma (mPDAC) demonstrating an objective response in 59% of patients, a 79% disease control rate at 16 weeks with a median progression free survival (PFS) of ~9.9 months. No dose limiting toxicities were observed. The ASCEND study will determine whether LSTA1 when added to SOC chemotherapy is active and safe as first-line treatment of mPDAC, and whether an additional dose of LSTA1 administered approximately 4 hours after chemotherapy further improves anti-cancer activity. Methods: ASCEND is a randomized, double-blind, placebo-controlled phase II trial evaluating the safety and efficacy of LSTA1 3.2 mg/kg in combination with standard of care chemotherapy (nab-paclitaxel 125mg/m2 and gemcitabine 1000mg/m2 on days 1, 8, and 15, every 28 days) in patients with histologically proven, previously untreated mPDAC. A total of 155 subjects will be randomized 2:1 in favor of study intervention in two cohorts and stratified by age, ECOG status, presence of liver metastasis, and study site. Patients in cohort A receive single doses of LSTA1 or placebo, and for cohort B, two doses of LSTA1 or placebo spaced 4 hours apart. Tumour assessment occurs every 8-weeks from randomization until disease progression or commencement of a new anti-cancer therapy. The primary endpoint is PFS. Secondary endpoints include objective tumour response safety, overall survival, and patient reported outcomes. At 14 Feb 2023, 70 participants have been enrolled from Australian sites. Sites in Ireland and New Zealand are anticipated to open this year. Clinical trial information: NCT05042128 .

Therapeutic potential of dual CDK12 and 13 inhibition in colorectal cancer.

e15601 Background: To date, studies on cyclin-dependent kinase inhibitors in colorectal cancer (CRC), such as targeting CDK4/6 with Palbociclib, have shown little to no clinical benefit. However, tumor profiling of CRC has shown that mutations and amplifications in CDK 12 and 13 are prevalent in 5 to 10% of CRC patients, suggesting that CDK12/13 inhibition may be a potential target for patients with CRC. Methods: To study the effects of inhibiting CDK12 and 13 in CRC, a total of 11 patient-derived organoids (PDO) were first established from patients undergoing biopsy or resection of their primary or metastatic CRC. In vitro drug sensitivity assays were performed by treating each PDO with THZ531, a selective dual CDK12/13 inhibitor; 5-flurouracil, oxaliplatin and SN38 as a standard of care; or Palbociclib (CDK 4/6 inhibitor) at seven different drug concentrations (0.0064 μM - 100 μM) with five replicates at each concentration. Viability was assessed 72 hours following the addition of each drug using CellTiter-Glo (Promega) and IC50s were calculated. Results: Targeting CDK12/13 with THZ531 demonstrated dose dependent activity in the majority of CRC PDOs, with IC50 values ranging from 0.06 μM to 4.2 μM. In comparison, targeting CDK4/6 with Palbociclib was ineffective, with IC50 values ranging from 2.5 μM to 17 μM (p = 0.0003, 95% CI 3.7 to 10.4). Inhibition of CDK12/13 was also more effective than standard of care chemotherapy with either 5- FU or oxaliplatin (mean IC50 values were 4.2 μM and 21.4 μM for 5-fluorouracil and oxaliplatin, p < 0.05) and was comparable to irinotecan (mean IC50 was 0.07 μM for SN38). Finally, no significant correlation was found between sensitivity to THZ531 and microsatellite status, mutations in RAS and BRAF, or grade of the original patient tumor. Conclusions: We identify dual CDK12/13 inhibition as a promising therapy to treat CRC. Further studies will focus on characterizing mechanisms of action, evaluating efficacy and toxicity in vivo, and determining biomarkers of response based on actionable genomic alterations.

ARTISTRY-7: A phase 3, multicenter study of nemvaleukin alfa in combination with pembrolizumab versus chemotherapy in patients with platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal cancer (GOG-3063; ENGOT-OV68).

TPS5612 Background: ARTISTRY-7 will evaluate the novel engineered cytokine nemvaleukin alfa (nemvaleukin, ALKS 4230) in patients (pts) with gynecologic cancers. Ovarian cancer (OC) is the 8th most common cause of cancer mortality in women. OC is an area of high unmet need, as many pts become resistant/refractory to frontline platinum-based chemotherapy. In the platinum-resistant setting, standard of care chemotherapy and anti-PD-1 therapy in clinical trials have modest response rates ranging from ~6% to 20% and ~7% to 12%, respectively. Nemvaleukin was designed to selectively bind to the intermediate-affinity interleukin-2 (IL-2) receptor, preferentially activating antitumor CD8+ T and natural killer cells with minimal regulatory T cell expansion. This selectivity may provide enhanced tumor killing and improved safety/tolerability vs high-dose IL-2. In clinical studies, nemvaleukin, as monotherapy and in combination with pembrolizumab, has shown clinical benefit in multiple tumor types, including OC. In ARTISTRY-1, in 14 evaluable patients with OC, 4 responses were observed with nemvaleukin + pembrolizumab, including 2 complete responses and 2 partial responses (ORR 28.6%; DCR 71.4%; median DOR 53.4 wks). Nemvaleukin monotherapy activity was also observed (6 melanoma and 4 renal cell carcinoma responses). Methods: ARTISTRY-7 (NCT05092360) is an ongoing phase 3, multicenter, randomized study of nemvaleukin and/or pembrolizumab vs chemotherapy. Eligible pts are women (≥18 y) with histologically confirmed epithelial OC (high-grade serous, endometrioid, clear cell), fallopian tube cancer, or primary peritoneal cancer. Pts must have had ≥1 prior line of systemic therapy (platinum-sensitive setting), ≤5 prior lines (platinum-resistant setting), and prior bevacizumab, with radiographic progression on most recent therapy. Pts with primary platinum-refractory disease (progression on first-line platinum therapy) or primary platinum resistance (progression <3 months after first-line platinum therapy completion) are excluded. Approximately 376 pts will be randomized (3:1:1:3) to receive nemvaleukin 6 μg/kg IV (days 1-5) + pembrolizumab 200 mg IV (day 1) of each 21-day cycle, pembrolizumab or nemvaleukin monotherapy, or chemotherapy, and stratified by PD-L1 status, histologic subtype, and chemotherapy (paclitaxel vs other). Pts will continue treatment until disease progression or intolerable toxicity (maximum 35 pembrolizumab cycles; nemvaleukin can be continued). The primary endpoint is investigator-assessed PFS (RECIST v1.1) in the nemvaleukin + pembrolizumab vs chemotherapy arms. Secondary/exploratory endpoints include overall survival, other antitumor measures, safety, health-related quality of life, and PK/PD effects. Clinical trial information: NCT05092360 .

Abstract CT222: Multimodal mechanism of action of the GSK-3 inhibitor 9-ING-41 (elraglusib) includes an immunomodulatory component: preliminary results from the 1801 phase 1/2 trial

Abstract 9-ING-41 (elraglusib) is a potent and selective GSK-3 inhibitor that has shown anti-tumor activity in patient-derived xenograft models and phase1/2 clinical studies in patients (pts) with advanced solid tumors. Preclinical studies have demonstrated that elraglusib downregulates PD-1, TIGIT and LAG-3, upregulates expression of MHC class I proteins in tumor cells from “cold tumors”, and shows synergy when combined with PD-1 blockade in mouse xenografts. Clinical activity has been observed both as a single agent and in combination with standard of care chemotherapies in several advanced cancer histologies. Here we present initial ‘omics data from our phase 1/2 study (NCT03678883; ACT1801) spanning >100 pts with advanced cancer evaluating both single agent and chemotherapy combinations. The patients (pts) included in this study received elraglusib as a ≥3rd line therapy for advanced disease. Most pts with melanoma treated with elraglusib monotherapy (8/9; 89%) stayed on study for >2 cycles. One patient with melanoma refractory to checkpoint inhibitors achieved a confirmed and durable CR. Clinical benefit was also observed among pts with colorectal cancer with 4/12 (33.3%) pts treated with monotherapy and 12/15 (80%) that received elraglusib plus irinotecan rechallenge stayed on study >2 cycles reaching median overall survival of 106 and 211 days, respectively. Based on emerging in vivo and in vitro results demonstrating that elraglusib activates T and NK cells promoting anti-tumor immune responses, we hypothesize immunomodulation by elraglusib may be contributing to anti-tumor immune response in the 1801 trial. We have acquired TCRseq and RNAseq profiles of PBMC samples from seven patients in 1801 during the first two weeks of treatment with elraglusib monotherapy. In these pts, reduced TCR clonality was observed and specific TCR clonotypes expanded after treatment, indicating T cell activation and expansion. These pts also showed changes in PBMC populations during elraglusib therapy as measured by immune deconvolution of PBMC RNAseq. Taken together, these data support a novel, previously unrecognized immunomodulatory mechanism of action for elraglusib and could provide rationale for future clinical development of elraglusib in pts with advanced malignancies. Additional analysis from TCRseq, immune profiling and cytokine analysis from expanded cohort of pts is ongoing. Citation Format: Taylor Weiskittel, Joseph McDermott, Daniel Billadeau, Hu Li, Anwaar Saeed, Devalingam Mahalingam, Solmaz Sahebjam, Pamela Munster, Ludimila Cavalcante, Frank J. Giles, Andrew Mazar, Benedito Carneiro. Multimodal mechanism of action of the GSK-3 inhibitor 9-ING-41 (elraglusib) includes an immunomodulatory component: preliminary results from the 1801 phase 1/2 trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT222.

Abstract 6246: The MTA-cooperative PRMT5 inhibitor AM-9747 exhibits robust antitumor activity in combination with clinically relevant chemotherapies and targeted agents in MTAP null tumor models

Abstract Homozygous deletion of chr9p21, containing genes CDKN2A and MTAP, occurs in about 15% of cancers. MTAP loss, a key enzyme in the methionine and adenine salvage pathways, leads to the accumulation of its substrate MTA. MTA competes with the methyl donor SAM for binding to type II arginine methyltransferase PRMT5, placing PRMT5 in a hypomorphic state and vulnerable to further PRMT5 inhibition. MTA-cooperative PRMT5 inhibitors are an emerging class of therapeutics targeting MTAP null tumors. AMG 193, currently in Phase 1 trials, and its representative analog AM-9747 have broad spectrum activity in MTAP null tumor models across hematologic and solid tumor indications. Mechanistically, AM-9747 induces DNA damage, shown by increased phosphorylated H2AX, resulting in cell cycle arrest and senescence. Exploration of clinically relevant therapeutic combinations with standard of care (SOC) chemotherapies or targeted agents that could potentiate this DNA damage or target orthogonal pathways is a rational therapeutic approach. Here, we evaluated AM-9747 in combination with SOC chemotherapies and assessed synergy using the Chou-Talalay Method to generate Combination Index (CI) scores. SOC agents representing a variety of mechanisms of action (paclitaxel, carboplatin, gemcitabine, pemetrexed, irinotecan, 5-FU) were evaluated and results ranged from strongly synergistic (CI<0.3) to additive (CI=1) in a panel of non-small cell lung carcinoma (NSCLC) and pancreatic cancer cell lines. The SOC combinations augmented AM-9747 induced DNA damage resulting in increased cell cycle arrest and nuclear count assays confirmed the synergistic antiproliferative effects of the combinations. Combinations of AM-9747 and one strongly synergistic agent (carboplatin) and one moderately synergistic agent (paclitaxel) were evaluated in H292 NSCLC xenografts. Significant reductions in tumor burden compared to single agent treatments were observed with AM-9747 + paclitaxel (67% TGI) and AM-9747 + carboplatin (82% TGI). Additionally, roughly 2-3% of NSCLC tumors harbor both MTAP loss and a KRAS G12C mutation. To target both pathways we combined the FDA-approved KRAS G12C inhibitor sotorasib with AM-9747 and observed synergy (CI<0.6) in MIAPACA2 cells. Nuclear counts confirmed a greater cell growth inhibition in the combination and immunoblots confirmed on target inhibition of both pathways. Combination treatment of AM-9747 and sotorasib in LU99 NSCLC xenografts resulted in significant tumor regression compared to each single agent with 10/10 mice tumor free. This combination is being tested in additional MTAP null KRAS G12C mutant models. Overall, our data suggests that combining MTA-cooperative inhibitor AM-9747 with SOC or clinically relevant targeted agents is a compelling therapeutic strategy for the treatment of MTAP null cancers. Citation Format: Katherine Slemmons, Brian Belmontes, Siyuan Liu, Jodi Moriguchi, Antonia Policheni, Paul E. Hughes. The MTA-cooperative PRMT5 inhibitor AM-9747 exhibits robust antitumor activity in combination with clinically relevant chemotherapies and targeted agents in MTAP null tumor models. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6246.

Abstract 1667: Elimusertib shows stronger antitumor activity than standard of care chemotherapy in pediatric solid tumor models

Abstract Elimusertib is a small molecule inhibitor of ataxia telangiectasia and Rad3-related protein (ATR) currently being tested in clinical trials. Despite the known anti-tumor activity in various cancer entities, its effect on many pediatric malignancies remains unknown. We assessed the preclinical activity of elimusertib in a cohort of over 40 cell lines and 30 patient-derived xenograft (PDX) models derived from pediatric solid tumors. Elimusertib reduced tumor growth in all PDX models, with 50% of them achieving stable disease, partial or total response, even in those derived from relapsed tumors. Moreover, elimusertib outperformed the effect of standard of care chemotherapy, particularly in alveolar rhabdomysarcoma. Molecular characterization of the models provide information on response biomarkers with diagnostic potential. In summary, elimusertib shows strong preclinical anti-tumor activity in pediatric solid tumor models, that may translate to clinically meaningful responses in patients. Citation Format: Fabian Fadi Pusch, Heathcliff Dorado García, Robin Xu, Dennis Guergen, Yi Bei, Lotte Brueckner, Claudia Roeefzaad, Jennifer von Stebut, Victor Bardinet, María del Rocío Chamorro Gonzalez, Angelika Eggert, Johannes H. Schulte, Patrick Hundsdoerfer, Georg Seifert, Kerstin Haase, Beat Schaefer, Marco Wachtel, Anja A. Kühl, Michael Ortiz, Antje M. Wengner, Monika Scheer, Anton G. Henssen. Elimusertib shows stronger antitumor activity than standard of care chemotherapy in pediatric solid tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1667.

Abstract 6252: HDAC inhibition increases Ewing sarcoma sensitivity to chemotherapy

Abstract Purpose: The survival rate of those with Ewing sarcoma (ES) has seen very little improvement over the past several decades and remains dismal for those with recurrent or metastatic disease. Current treatment for Ewing sarcoma includes a combination of cytotoxic chemotherapeutic agents and local control with radiation and/or surgery. The purpose of this study is to identify currently available targeted agents which may be combined with chemotherapy for use in Ewing sarcoma to improve patient outcomes. Methods: Novel targeted approaches for the treatment of ES were identified using RNA sequencing performed on ES patient tumors with bioinformatic analysis of gene expression. HDAC inhibitors were tested on patient cell lines at escalating doses and cell viability was assessed with CellTiter-Glo 2.0 and analyzed with GraphPad Prism to determine the IC50. Cells were treated with Panobinostat for 12 and 24 hours and RNA sequencing was performed. Cell cycle analysis was performed using Incucyte® Cell Cycle Lentivirus Reagent and analyzed using an Incucyte® S3. At 24- and 48-hours western blot analysis was performed to evaluate the effect on cell cycle and apoptosis. Combination studies with standard chemotherapy were performed and viability was assessed with CellTiter-Glo 2.0. At 24 hours of treatment with a combination of doxorubicin and HDAC inhibition western blot analysis was performed to evaluate changes in DNA damage and repair. Results: RNA analysis identified HDAC2 as a potential therapeutic target. The pan-HDAC inhibitors, Panobinostat and Belinostat, and the HDAC1/2 inhibitor, Romidepsin, were cytotoxic to all Ewing sarcoma cell lines tested with clinically relevant IC50s. Mechanistically, pathways involved in cell cycle progression and DNA repair were repressed by Panobinostat as shown by RNA sequencing and western blotting (Cyclin D1, pRb, CHK1). Additionally, cell cycle analysis has shown a G1 arrest in response to HDAC inhibition. HDAC inhibitors significantly decrease cell viability when combined with standard chemotherapy (upfront and relapse therapy) compared to that of chemotherapy alone. When combined with doxorubicin, CHK1 and CHK2 were significantly decreased and pH2AX was significantly increased indicating an accumulation of DNA damage. Conclusion: This work highlights that combining HDAC inhibitors with standard of care chemotherapy may be an effective treatment and improve outcomes for Ewing sarcoma patients. Future studies of HDAC inhibitors combined with chemotherapy drugs will aim to determine efficacy in xenograft models. Citation Format: Kaitlyn H. Smith, Chloe Sholler, Divya Gandra, Kimberly McKinney, Karl Dykema, Abhinav Nagulapally, Erin Trovillion. HDAC inhibition increases Ewing sarcoma sensitivity to chemotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6252.