Single-agent Treatment Research Articles

A phase 2 study of dasatinib in recurrent clear cell carcinoma of the ovary, fallopian tube, peritoneum or endometrium: NRG oncology/gynecologic oncology group study 0283

ObjectiveGynecologic cancers are traditionally managed according to their presumed site of origin, without regard to the underlying histologic subtype. Clear cell histology is associated with chemotherapy refractoriness and poor survival. Mutations in SWI/SNF chromatin remodeling complex member ARID1A, which encodes for BAF250a protein, are common in clear cell and endometriosis-associated endometrioid carcinomas. High-throughput cell-based drug screening predicted activity of dasatinib, a tyrosine kinase inhibitor, in ARID1A-mutant clear cell carcinoma. MethodsWe conducted a phase 2 clinical trial of dasatinib 140 mg once daily by mouth in patients with recurrent or persistent ovarian and endometrial clear cell carcinoma. Patients with measurable disease were enrolled and then assigned to biomarker-defined populations based on BAF250a immunohistochemistry. The translational endpoints included broad next-generation sequencing to assess concordance of protein expression and treatment outcomes. ResultsTwenty-eight patients, 15 of whom had tumors with retained BAF250a and 13 with loss of BAF250a were evaluable for treatment response and safety. The most common grade 3 adverse events were anemia, fatigue, dyspnea, hyponatremia, pleural effusion, and vomiting. One patient had a partial response, eight (28%) had stable disease, and 15 (53.6%) had disease progression. Twenty-three patients had next-generation sequencing results; 13 had a pathogenic ARID1A alteration. PIK3CA mutations were more prevalent in ARID1A-mutant tumors, while TP53 mutations were more prevalent in ARID1A wild-type tumors. ConclusionsDasatinib was not an effective single-agent treatment for recurrent or persistent ovarian and endometrial clear cell carcinoma. Studies are urgently needed for this rare gynecologic subtype.

Treatment of Nodular Lymphocyte-Predominant Hodgkin Lymphoma: Where Do We Stand? Where Do We Go?

Nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL) is a rare B cell-derived lymphoma entity accounting for ≈5% of all Hodgkin lymphoma (HL) cases. In recent decades, patients with newly diagnosed NLPHL have usually been treated very similarly to classical HL (cHL). The 10-year overall survival rates with HL-directed approaches are in excess of 90%. However, pathological and clinical characteristics of NLPHL resemble indolent B-cell non-Hodgkin lymphoma (B-NHL) in some aspects. Thus, nodular lymphocyte-predominant B-cell lymphoma has been proposed as an alternative name, and the use of B-NHL-directed treatment strategies has become more common in NLPHL despite limited data. Given the often indolent clinical course of NLPHL, even in the case of relapse, the majority of patients with disease recurrence do not require high-dose chemotherapy and autologous stem cell transplantation but are treated sufficiently with low-intensity approaches such as single-agent anti-CD20 antibody treatment. The establishment of novel prognostic scores for NLPHL patients may optimize risk group and treatment allocation in newly diagnosed and relapsed disease.

PRMT5 inhibition drives therapeutic vulnerability to combination treatment with BCL-2 inhibition in mantle cell lymphoma

AbstractMantle cell lymphoma (MCL) is an incurable B-cell malignancy that comprises up to 6% of non-Hodgkin lymphomas diagnosed annually and is associated with a poor prognosis. The average overall survival of patients with MCL is 5 years, and for most patients who progress on targeted agents, survival remains at a dismal 3 to 8 months. There is a major unmet need to identify new therapeutic approaches that are well tolerated to improve treatment outcomes and quality of life. The protein arginine methyltransferase 5 (PRMT5) enzyme is overexpressed in MCL and promotes growth and survival. Inhibition of PRMT5 drives antitumor activity in MCL cell lines and preclinical murine models. PRMT5 inhibition reduced the activity of prosurvival AKT signaling, which led to the nuclear translocation of FOXO1 and modulation of its transcriptional activity. Chromatin immunoprecipitation and sequencing identified multiple proapoptotic BCL-2 family members as FOXO1-bound genomic loci. We identified BAX as a direct transcriptional target of FOXO1 and demonstrated its critical role in the synergy observed between the selective PRMT5 inhibitor, PRT382, and the BCL-2 inhibitor, venetoclax. Single-agent and combination treatments were performed in 9 MCL lines. Loewe synergy scores showed significant levels of synergy in most MCL lines tested. Preclinical, in vivo evaluation of this strategy in multiple MCL models showed therapeutic synergy with combination venetoclax/PRT382 treatment with an increased survival advantage in 2 patient-derived xenograft models (P ≤ .0001, P ≤ .0001). Our results provide mechanistic rationale for the combination of PRMT5 inhibition and venetoclax to treat patients with MCL.

ATRT-12. HYPERACTIVATING THE INTEGRATED STRESS RESPONSE WITH PROTEASOME INHIBITION IN AT/RT

Abstract Atypical teratoid/rhabdoid tumor (AT/RT) is an aggressive pediatric brain tumor with a poor prognosis. AT/RT has increased baseline activation of the integrated stress response (ISR), an evolutionarily conserved system that enables cells to tolerate various forms of stress. Elevated expression of ATF4 indicates activation of the ISR. Transient or low-level expression of this transcription factor protects cells from stress, while sustained, high-level activation results in cell death. Ixazomib is an orally bioavailable proteasome inhibitor that causes endoplasmic reticulum stress, which is a major upstream activator of the ISR. Because AT/RT has a high baseline level of ATF4, we hypothesized that this tumor would be susceptible to ISR activators such as ixazomib. After determining the IC50 of ixazomib, AT/RT cell lines were treated with increasing concentrations of the drug. Cleaved caspase-3 immunofluorescence showed a significant increase of apoptosis (CHLA06 p<0.0001 by ANOVA). We are currently testing ixazomib in combination with idarubicin, a brain-penetrant anthracycline, and gemcitabine, a brain-penetrant nucleoside analog. Synergy testing in CHLA06 showed an overall zero-interaction-potency (ZIP) synergy score of 23.464 with inhibitory concentrations of ixazomib and idarubicin in the low nanomolar range (scores of 10 or above indicate synergy). Similarly, ixazomib and gemcitabine synergized to suppress CHLA06 growth and induce apoptosis (67% Annexin V+ cells in combination compared to 14 and 24% Annexin V+ with single agent treatment). In the future, we will determine if ixazomib selectively kills AT/RT while sparing normal cells in iPSC brain organoids. We will also test ixazomib in orthotopic xenografts of AT/RT. These results suggest that ixazomib, especially in combination with idarubicin, gemcitabine or other ISR activators, has the potential to serve as an effective therapy for AT/RT.

HGG-25. TARGETED DRUGS SYNERGIZE WITH DOUBLE ALKYLATOR THERAPY IN H3.3 G34R/V PEDIATRIC HIGH-GRADE GLIOMA

Abstract Diffuse hemispheric H3 G34R/V mutant gliomas (G34R/V DHG) are lethal brain malignancies occurring in the cerebral hemisphere of adolescent patients with no effective treatment options. To date, standard care is adapted from adult treatment protocols which include maximal tumor resection, radiotherapy, and chemotherapy with temozolomide (TMZ). In a recent study led by the Children’s Oncology Group (COG, ACNS0423), the combination of the alkylators TMZ and lomustine (CCNU) showed improved event-free survival for pediatric high-grade glioma patients. Still, patient benefits remain limited and thus demand further improvement of treatment protocols. Therefore, the aim of this study is to identify FDA-approved blood-brain-barrier crossing compounds that specifically targeting known vulnerabilities of pediatric high-grade glioma that achieve synergistic treatment results when combined with the double alkylator approach. We conducted a compound screen in combination with TMZ and CCNU on G34R/V-tumor derived gliomaspheres to identify synergies based on cell viability assays in vitro. We identified three candidate agents - Fimepinostat, trametinib, and avapritinib, which inhibit different key oncogenic targets in pediatric high-grade glioma - Pi3K and histone-deacetylases, MAPKs, and PDGFRA, respectively. Our ongoing in vivo study elaborates the translatability of the identified combinatorial therapies in patient derived G34R/V DHG orthotopic xenograft models. We are comparing different study arms of single agent treatment and double as well as triple combinations of alkylators and the candidate agents. This study will serve to determine (i) treatment efficacy, as measured by tumor growth and survival, (ii) occurring side effects, especially alkylator-induced suppression of platelet counts, and (iii) molecular changes upon different treatments using single cell transcriptomics and immunohistochemistry. In summary, we present valuable pre-clinical data supporting the combination of alkylators with targeted agents as a novel treatment strategy in G34R/V DHG, which might be translated into a promising strategy of a new comparative study based on COG trial ACNS0423.

Single-agent activity of the anti-GD2 antibody dinutuximab beta given as a long-term infusion in relapsed and refractory neuroblastoma (APN311-304).

10034 Background: Severe pain is a common side effect associated with short-term infusions of anti-GD2 antibodies in combination with cytokines and isotretinoin and was reduced by the long-term infusison (LTI) strategy. We investigated efficacy and tolerability of a single-agent dinutuximab beta (DB)-LTI in patients with primary refractory or relapsed (R/R) stage 4 neuroblastoma (NB). Methods: Patients with R/R-NB were enrolled into an open label phase II trial. Previous anti-GD2 antibody therapies were allowed, if anti-DB antibody could not be detected. Patients received 5 cycles of DB-LTI (100 mg/m2/10 days). The primary endpoint was objective INRC response 24 weeks after the end of cycle 5. A sample size of 40 patients provides at least 80% power to reject the null hypothesis of an objective response in < 10% of patients if the true objective response rate observed was 25% (overall 1-sided significance level 0.05, exact binomial test). Secondary endpoints included safety, morphine use, best response and duration of response, pharmacodynamics and pharmacokinetics, 3-year progression-free (PFS) and overall survival (OS). Results: 40 patients were treated and 38 patients had evaluable response. The objective response rate 24 weeks after the end of cycle 5 was 26% (10/38) (CR/PR) (p = 0.0034) and 32% (12/38) (CR/PR/MR), with a higher response rate in refractory vs. relapsed patients (50% vs 25%; p = 0.0159). The best response rate was 53% (20/38). Of 14 patients with bone marrow involvement, 13 patients responded (93%) (12 CR, 1 PR). The median duration of response (CR/PR) was 238 days (95% CI [108-290d]). The 3-year probability of PFS was 31% (95% CI [0.17–0.47]) and of OS was 66% (95% CI [0.47–0.79]). Survival was higher for patients with refractory compared to relapsed disease (PFS 47% vs 19%, OS 93% vs 50%; p = 0.015). Grade 3 treatment emergent adverse events (TEAE) were pain (18%), diarrhea (5%), and hypokalemia (5%) and grade 3 hypotension, capillary leak and neurotoxicity were not observed. In patients who experienced pain, mean pain scores (scale 0–10, where 0 is no pain) were low and decreased between cycles 1 and 2: pain score at rest decreased from 1.01 to 0.30, and at stress from 1.45 to 0.28. There were no grade 4 or 5 TEAEs. The morphine usage decreased from cycle 2 to 5 (C2 95%; C3 12%; C4 0%; C5 0%). DB peak serum concentration in cycle 1 was 10.8±0.7 µg/ml and patients showed 7- and 11-fold increase of antibody-dependent cell-mediated (ADCC) and complement-dependent cytotoxicity (CDC), respectively. Anti-DB antibodies were found in 24% of patients. There was no association and no trend between exposure to DB (area under the curve, peak ot trough level) and response rate or survival in this cohort. Conclusions: Single-agent treatment with single agent dinutuximab beta given as long LTI without cytokines and without isotretinoin is effective and highly tolerable in R/R-NB. Clinical trial information: NCT02743429 .

Effect of MYC-targeting programmable epigenetic mRNA therapeutics on TME and immunotherapy responses.

4116 Background: c-MYC is a master transcription factor (TF) critical for multiple cell physiologies. As a pleiotropic TF, MYC regulates the tumor microenvironment (TME) and impacts cancer cell initiation, growth, and survival. Although MYC expression is normally tightly controlled in normal cells, its activity is frequently dysregulated in cancer (e.g., HCC, NSCLC, Burkitt’s lymphoma). A direct MYC targeting anti-cancer agent has remained elusive, largely due the absence of a drug binding pocket and tight autoregulation. The MYC gene and its regulatory elements reside alone within an insulated genomic domain and represents a potential target for gene regulation via an epigenetic approach. Methods: We are developing programmable epigenetic mRNA medicines designed to controllably tune gene expression pre-transcriptionally with high specificity and durability. We have rationally designed MYC-targeted Omega Epigenomic (MYC-OEC: clinical candidate OTX-2002; MYC Lung OEC; mouse surrogate muMYC-OEC) to downregulate MYC expression, thereby selectively killing cancer cells while sparing normal cells. We investigated the role of MYC-OECs in the modulation of the TME and demonstrated in human and mouse tumor models that MYC-OECs enhanced the host immune response. Results: In HCC and NSCLC cell lines (Hep 3B, SKHEP1, H2009 and H460), treatment with MYC-OECs in vitro significantly inhibited PD-L1 surface expression. Using the muMYC-OEC in vivo, we demonstrated tumor growth inhibition (TGI) in Hepa1-6 liver cancer syngeneic tumor models with 70% of the mice exhibiting complete tumor response with good tolerability. Cancer cells used to rechallenge the cured mice failed to grow, demonstrating that muMYC-OEC monotherapy induced immune memory. In addition to inhibiting tumor growth with either muMYC-OEC or checkpoint blockade immunotherapy (CBI; anti-PD-1 or anti-PD-L1) treatment, combination therapy further enhanced TGI. Tumor-infiltrating lymphocyte profiling demonstrated an increase in activated T cells and a reduction in Tregs following combination treatment, resulting in an increased effector T cell to Treg ratio over monotherapy. Depletion of CD4+, CD8+ and NK cells in vivo prior to single agent or combination treatment demonstrated a requirement for both CD4+ and CD8+ T cell activity for TGI. NK cells were dispensable. Taken together, these data demonstrate that the improved CBI/MYC-OEC combination activity is mediated through the recruitment of activated T cells and reduction of immune suppressive Tregs. Conclusions: These efficacy and tolerability data support the combination of MYC-OEC and CBI treatment in patients with solid tumors. OTX-2002 is currently being evaluated in a Phase 1/2 clinical trial as a monotherapy and in combination with SoC (i.e., TKI and CBIs) for patients with HCC and other solid tumor types known for an association with MYC.

Phase II study combining an anti-core 1 O-glycans targeting humanized monoclonal antibody NEO-201 with pembrolizumab in adults with chemo-resistant solid tumors.

e14515 Background: NEO-201 is a humanized IgG1 mAb which binds to Core 1 and/or extended Core 1 O-glycans expressed by solid and hematological cancers. NEO-201 reacts against cancer tissues but not most normal tissues. NEO-201 can identify and kill immune suppressor cells (iSCs), such as regulatory T cells (Tregs), neutrophils, and granulocytic myeloid-derived suppressor cells (gMDSCs) in human PBMCs via antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC). We observed a reduction in the percentage of circulating Tregs in subjects with stable disease (SD) following single-agent NEO-201 treatment in our Phase 1 study. Resistance to PD-1/PD-L1 blockade in solid cancers may be due to the activity of iSCs in the tumor microenvironment (TME). Based on this, we launched a Phase II study with a safety lead-in combining NEO-201 with pembrolizumab in adults who have progressed on prior checkpoint therapy. Methods: The recommended phase 2 dose (RP2D) of NEO-201 was determined to be 1.5 mg/kg IV every 2 weeks. Cohorts consisting of advanced non-small cell lung cancer (NSCLC), head and neck squamous cell carcinoma (HNSCC), uterine or cervical cancer who progressed during or after one front-line standard of care treatment, including chemotherapy, checkpoint therapy and/or targeted therapy were eligible. Three patients received NEO-201 at the RP2D with pembrolizumab 400 mg IV every 6 weeks (1 cycle) and were evaluated for safety 2 weeks following the 1st cycle of the therapy. DLTs were defined as specific Grade 3 or 4 toxicities related to NEO-201. Results: Safety lead-in was successfully completed at RP2D with no DLTs. Four subjects were enrolled in the safety lead-in; one subject electively discontinued after the first infusion and was not evaluable for DLT. Of the 3 evaluable subjects, 1 subject with refractory cervical cancer remained on study with SD for 8.5 months, electively coming off study for surgical debulking. The other 2 subjects developed progressive disease. All subjects had grade 3-4 transient neutropenia, which was expected. Other common toxicities included grade 3-4 decreased white blood cells and lymphocytes, grade 3 anemia and grade 2 infusion reactions. Conclusions: NEO-201 has demonstrated the ability to bind and kill iSCs in vitro and this phenomenon was observed in the initial first in human clinical study. This Phase II study was designed to determine if NEO-201 can reactivate the effectiveness of checkpoint inhibitor therapy in subjects who previously progressed on check point therapy. The safety of combining NEO-201 with pembrolizumab has been successfully established and all 4 disease cohorts are now open to accrual with response rate as the primary endpoint. The maximum accrual on this study will be 126 patients. Clinical trial information: NCT03476681 .

Betulinic acid, a major therapeutic triterpene of Celastrus orbiculatus Thunb., acts as a chemosensitizer of gemcitabine by promoting Chk1 degradation.

Celastrus orbiculatus Thunb., also called as oriental bittersweet vine or climbing spindle berry, a traditional Chinese herbal medicine has been used to treat a spectrum of painful and inflammatory diseases for centuries. Explored for their unique medicinal properties, C.orbiculatus offers additional therapeutic effects on cancerous diseases. The effect of single-agent gemcitabine on survival has not long been encouraging, combination therapies provide patients multiple chances of benefit for improved clinical response. This study aims at expounding the chemopotentiating effects and underlying mechanisms of betulinic acid, a primary therapeutic triterpene of C. orbiculatus in combination with gemcitabine chemotherapy. The preparation of betulinic acid was optimized using ultrasonic-assisted extraction method. Gemcitabine-resistant cell model was established by induction of the cytidine deaminase. MTT, colony formation, EdU incorporation and Annexin V/PI staining assays were used to evaluate cytotoxicity, cell proliferation and apoptosis in BxPC-3 pancreatic cancer cell line and H1299 non-small cell lung carcinoma cell line. Comet assay, metaphase chromosome spread and γH2AX immunostaining were applied for DNA damage assessment. Western blot and co-immunoprecipitation was used to detect the phosphorylation and ubiquitination of Chk1. Mode of action of gemcitabine in combination with betulinic acid was further captured in BxPC-3-derived mouse xenograft model. We noticed that the extraction method had an impact on the thermal stability of C. orbiculatus. Ultrasound-assisted extraction at room temperature in shorter processing time could maximize the overall yields and biological activities of C. orbiculatus. The major constituent was identified as betulinic acid, and the pentacyclic triterpene represented the prominent anticancer activity of C. orbiculatus. Forced expression of cytidine deaminase conferred acquired resistance to gemcitabine, while betulinic acid displayed equivalent cytotoxicity toward gemcitabine-resistant and sensitive cells. A combination therapy of gemcitabine with betulinic acid produced synergistic pharmacologic interaction on cell viability, apoptosis and DNA double-strand breaks. Moreover, betulinic acid abrogated gemcitabine-triggered Chk1 activation by destabilizing Chk1 loading via proteasomal degradation. The combination of gemcitabine and betulinic acid significantly retarded BxPC-3 tumor growth in vivo compared to single-agent gemcitabine treatment alone, accompanied with reduced Chk1 expression. These data provide evidence that betulinic acid is a potential candidate for chemosensitization as a naturally occurring Chk1 inhibitor and warrants further preclinical evaluation.

Approach to relapsed CLL including Richter Transformation

Approach to relapsed CLL including Richter Transformation

Alternating 17β-Estradiol and Aromatase Inhibitor Therapies Is Efficacious in Postmenopausal Women with Advanced Endocrine-Resistant ER+ Breast Cancer.

Strategies to implement estrogen therapy for advanced estrogen receptor-positive (ER+) breast cancer are underdeveloped. Preclinical data suggest that cycling treatment with 17β-estradiol followed by estrogen deprivation can control tumor growth long-term. Postmenopausal women with advanced ER+/HER2- breast cancer with recurrence or progression on ≥ 1 antiestrogen or aromatase inhibitor (AI)-based therapy were eligible. Patients received 17β-estradiol (2 mg orally, three times a day) for 8 weeks followed by AI (physician's choice) for 16 weeks, alternating treatments on an 8-week/16-week schedule until disease progression. Patients then optionally received continuous single-agent treatment until a second instance of disease progression. Endpoints included 24-week clinical benefit and objective response per RECIST, and tumor genetic alterations. Of 19 evaluable patients, clinical benefit rate was 42.1% [95% confidence interval (CI), 23.1%-63.9%] and objective response rate (ORR) was 15.8% (95% CI, 5.7%-37.9%). One patient experienced a grade 3 adverse event related to 17β-estradiol. Among patients who received continuous single-agent treatment until a second instance of disease progression, clinical benefit was observed in 5 of 12 (41.7%) cases. Tumor ER (ESR1) mutations were found by whole-exome profiling in 4 of 7 (57.1%) versus 2 of 9 (22.2%) patients who did versus did not experience clinical benefit from alternating 17β-estradiol/AI therapy. The only two patients to experience objective responses to initial 17β-estradiol had tumor ESR1 mutations. Alternating 17β-estradiol/AI therapy may be a promising treatment for endocrine-refractory ER+ breast cancer, including following progression on CDK4/6 inhibitors or everolimus. Further study is warranted to determine whether the antitumor activity of 17β-estradiol differs according to ESR1 mutation status.

Synergistic inhibitory effects of clopidogrel and rivaroxaban on platelet function and platelet-dependent thrombin generation in cats.

Dual antithrombotic treatment (DAT) with clopidogrel and rivaroxaban sometimes is prescribed to cats with hypertrophic cardiomyopathy at risk of thromboembolism. To date, no studies have evaluated their combined effects on platelet function. Evaluate the safety of DAT in healthy cats and compare, ex vivo, platelet-dependent thrombin generation and agonist-induced platelet activation and aggregation in cats treated with clopidogrel, rivaroxaban, or DAT. We hypothesized that DAT would safely modulate agonist-induced platelet activation and aggregation more effectively than single agent treatment. Nine apparently healthy 1-year-old cats selected from a research colony. Unblinded, nonrandomized ex vivo cross-over study. All cats received 7 days of rivaroxaban (0.6 ± 0.1 mg/kg PO), clopidogrel (4.7 ± 0.8 mg/kg PO), or DAT with defined washout periods between treatments. Before and after each treatment, adenosine diphosphate (ADP)- and thrombin-induced platelet P-selectin expression was evaluated using flow cytometry to assess platelet activation. Platelet-dependent thrombin generation was measured by fluorescence assay. Platelet aggregation was assessed using whole blood impedance platelet aggregometry. No cats exhibited adverse effects. Of the 3 treatments, only DAT significantly decreased the number of activated platelets (P = .002), modulated platelet activation in response to thrombin (P = .01), dampened thrombin generation potential (P = .01), and delayed maximum reaction velocity (P = .004) in thrombin generation. Like clopidogrel, DAT inhibited ADP-mediated platelet aggregation. However, rivaroxaban alone resulted in increased aggregation and activation in response to ADP. Treatment combining clopidogrel and rivaroxaban (DAT) safely decreases platelet activation, platelet response to agonists, and thrombin generation in feline platelets more effectively than monotherapy with either clopidogrel or rivaroxaban.

190MO Association of 18-Gene expression profile (GEP) with clinical outcomes in patients with metastatic triple-negative breast cancer (mTNBC) treated with pembrolizumab (Pembro) or chemotherapy (Chemo) in KEYNOTE-119

In the phase III, randomized, open-label KEYNOTE-119 (NCT02555657) study, second- or third-line treatment with pembro monotherapy did not significantly improve OS vs single-agent chemo treatment of physician’s choice (TPC) in patients (pts) with mTNBC, although the pembro treatment effect increased with increasing PD-L1 enrichment. In this exploratory analysis, we evaluated the association of T-cell-inflamed gene expression profile (GEP) with clinical outcomes from KEYNOTE-119. Pts with centrally confirmed mTNBC, ECOG PS ≤1, and 1-2 prior systemic treatments for metastatic breast cancer were randomized 1:1 to pembro 200 mg Q3W for up to 35 cycles or TPC (capecitabine, eribulin, gemcitabine, or vinorelbine) per local guidelines. Tumor RNA profiling was conducted on the RNA-seq platform (Illumina, San Diego, CA). Association of GEP with clinical outcomes was evaluated by logistic regression (best objective response [BOR] per RECIST v1.1) and Cox proportional hazards models (PFS and OS) with baseline adjustment for ECOG PS; 95% CIs for BOR were estimated using the Clopper and Pearson method. As of April 11, 2019, GEP data for 333 pts (pembro, n=177; TPC, n=156) were available for analysis. GEP was significantly associated with improved BOR, PFS, and OS in pts treated with pembro but not TPC (Table). HR for OS was 0.77 (95% CI, 0.58–1.04) in pts with GEP non-low (≥1st tertile) and 1.72 (1.15–2.55) in pts with GEP low (<1st tertile). No association was seen between BRCA/HRD status and treatment response. These findings suggest a positive association between GEP and clinical outcomes in pts with mTNBC who are treated with pembro, with a more favorable treatment effect in the GEP-enriched population. Results may help inform future analyses of outcomes by biomarker status in this population.

Surgical Site and Blood Stream Infections in Children with Delayed Sternal Closure after Cardiopulmonary Bypass Surgery: A Single-Center Experience

Abstract Objective Delayed sternal closure (DSC) is a frequent strategy for optimizing hemodynamics for patients after complicated cardiac surgery. However, this practice is associated with increased risk for infection and mortality. Despite the importance of antibiotic prophylaxis during open chest management, no clear recommendations are available. We sought to describe our practice with single-agent prophylactic antibiotic treatment for children with DSC. Methods We retrospectively reviewed the electronic medical record of children with delayed chest closure after stage 1 palliative surgery, between January 2009 and December 2020. Demographics, antibiotic treatment, and data regarding postoperative infection occurrence were collected. The primary outcomes were surgical site infection (SSI) and blood stream infection (BSI) rates within 28 days of repair. Results Sixty-eight patients were identified with single ventricle physiology, who underwent Damus–Kaye–Stansel or a modified Norwood procedure, remained with an open chest postoperatively, and were treated with prophylactic cefazolin. Sixty-three percent (43/68) of the children were male with a median (interquartile range) age of 9 (6–16) days. Eleven patients (16%) had an SSI or BSI identified postoperatively. Those with infections were significantly older (8 vs. 14 months, p = 0.037), had longer central line time (11 vs. 7 days, p = 0.004), had a central line location other than internal jugular (p = 0.022), and had a dialysis line (p = 0.022). Conclusion Our study demonstrates a relatively low occurrence rate of postoperative SSIs and bacteremia with prophylactic cefazolin therapy among children with DSC suggesting that single-agent, narrow antimicrobial treatment may be sufficient in this high-risk population.

Neutrophils Extracellular Traps (NETs) Inhibition Improves PD-1 Blockade Immunotherapy in Triple-Negative Breast Cancer

Abstract Introduction: Despite significant advances using immune checkpoint blockade therapy for patients with advanced cancer, 40–85% of patients fail to respond to therapy. Increasing evidence suggests that the tumor immune microenvironment plays a critical role in rendering the immune checkpoint blockade ineffective. As such, targeting the tumor immune microenvironment is an attractive strategy for the treatment of solid tumors and an important approach to improve the efficacy of checkpoint inhibitors. Our study explores the combination therapy of DNase I and PD-1 antibody to prevent tumor growth. We demonstrate that this combination treatment for triple-negative breast (TNBC) cancer shows superior efficacy in comparison to a single-agent treatment, both in vivoand in vitro. Methods: For 4T1 tumor models, 0.1-ml sample containing 10 4tumors was injected into the mammary fat pad of female BALB/c mice. Tumor diameters were measured using calipers. The tumor volume was calculated. Anti-PD-1 or IgG2a isotype Ab (10mg/kg, every 3 days) and DNase I (5 mg/kg, daily) were administered intraperitoneally starting from day 5 after tumor cell inoculation. Results: DNase I plays a pivotal role in the degradation of NETs, significantly dampening the resistance to anti-PD-1 blockade in a mouse TNBC model by attenuating tumor growth. Remarkably, DNase I decreases tumor-associated neutrophils and the formation of NETs in vivo. Mechanistically, the inhibition of NETs with DNase I results in the reversal of anti-PD-1 blockade resistance through increasing CD8+ T cell infiltration and cytotoxicity. These findings signify a novel approach to targeting the tumor microenvironment using DNase I alone or in combination with immune checkpoint inhibitors. R01CA214865-06 (Renewal) Surgery triggered immune response and liver metastases. NIH/NCI 1R01 CA214865-01. Surgery triggered immune response and liver metastases.

Combination of Everolimus and Bortezomib Inhibits the Growth and Metastasis of Bone and Soft Tissue Sarcomas via JNK/p38/ERK MAPK and AKT Pathways.

The combination of the mammalian target of rapamycin and proteasome inhibitors is a new treatment strategy for various tumors. Herein, we investigated the synergistic effect of everolimus and bortezomib on tumor growth and metastasis in bone and soft tissue sarcomas. The antitumor effects of everolimus and bortezomib were assessed in a human fibrosarcoma (FS) cell line (HT1080) and mouse osteosarcoma (OS) cell line (LM8) by MTS assays and Western blotting. The effects of everolimus and bortezomib on HT1080 and LM8 tumor growth in xenograft mouse models were evaluated using tumor volume and the number of metastatic nodes of the resected lungs. Immunohistochemistry was used to evaluate cleaved PARP expression. The combination therapy decreased FS and OS cell proliferation compared with either drug alone. This combination induced more intense p-p38, p-JNK, and p-ERK and activated apoptosis signals, such as caspase-3, compared with single-agent treatment. The combination treatment reduced p-AKT and MYC expression, decreased FS and OS tumor volumes, and suppressed lung metastases of OS. The combination therapy inhibited tumor growth in FS and OS and metastatic progression of OS via the JNK/p38/ERK MAPK and AKT pathways. These results could aid in the development of new therapeutic strategies for sarcomas.

MYC drives platinum resistant SCLC that is overcome by the dual PI3K-HDAC inhibitor fimepinostat

BackgroundSmall cell lung cancer (SCLC) is an aggressive neuroendocrine cancer with an appalling overall survival of less than 5% (Zimmerman et al. J Thor Oncol 14:768-83, 2019). Patients typically respond to front line platinum-based doublet chemotherapy, but almost universally relapse with drug resistant disease. Elevated MYC expression is common in SCLC and has been associated with platinum resistance. This study evaluates the capacity of MYC to drive platinum resistance and through screening identifies a drug capable of reducing MYC expression and overcoming resistance.MethodsElevated MYC expression following the acquisition of platinum resistance in vitro and in vivo was assessed. Moreover, the capacity of enforced MYC expression to drive platinum resistance was defined in SCLC cell lines and in a genetically engineered mouse model that expresses MYC specifically in lung tumors. High throughput drug screening was used to identify drugs able to kill MYC-expressing, platinum resistant cell lines. The capacity of this drug to treat SCLC was defined in vivo in both transplant models using cell lines and patient derived xenografts and in combination with platinum and etoposide chemotherapy in an autochthonous mouse model of platinum resistant SCLC.ResultsMYC expression is elevated following the acquisition of platinum resistance and constitutively high MYC expression drives platinum resistance in vitro and in vivo. We show that fimepinostat decreases MYC expression and that it is an effective single agent treatment for SCLC in vitro and in vivo. Indeed, fimepinostat is as effective as platinum-etoposide treatment in vivo. Importantly, when combined with platinum and etoposide, fimepinostat achieves a significant increase in survival.ConclusionsMYC is a potent driver of platinum resistance in SCLC that is effectively treated with fimepinostat.

Abstract LB233: Preclinical analysis identifies predictive biomarker and potential pathways of resistance to lurbinectedin treatment in small cell lung cancer

Abstract Background: Small cell lung cancer (SCLC) is an exceptionally aggressive disease with limited treatment options that typically result in transient responses. SCLC is responsible for approximately 250,000 deaths globally per year. Major hurdles to improving SCLC treatment include the development of rapid chemo-resistance and limited second-line therapies. Lurbinectedin is FDA approved as a second-line treatment for SCLC but shows a response in a subset of patients. Therefore, improved mechanistic understanding and identifying predictive biomarkers of lurbinectedin treatment is a major unmet clinical need. Methods: We treated SCLC cell lines and patient-derived xenograft (PDX) models from all major SCLC subtypes with lurbinectedin. Lurbinectedin-mediated changes in signaling pathways were studied by bulk RNA sequencing, western blot, and flow cytometry. Anti-tumor efficacy and toxicity studies were performed in vivo. Result: All human and PDX-derived SCLC cell lines showed sensitivity to lurbinectedin at a nano-molar concentration ranging from 1.905 to 30 nM. Bulk RNA-seq analysis showed lurbinectedin induced changes in neuroendocrine phenotype, DNA damage response and tumor progression markers in vitro. Single agent treatment of lurbinectedin showed remarkable anti-tumor efficacy in an ASCL1-driven PDX model. RNA sequencing analysis identified modulation of genes in multiple signaling pathways including PI3K-AKT, apoptosis and EMT to be significantly associated with the lurbinectedin response in PDX models. Conclusion: There is an immediate need to understand the subsets of SCLC that would be most sensitive to lurbinectedin and identify predictive biomarkers. We demonstrate MYC as a predictive biomarker for lurbinectedin response. We are the first to show that single agent lurbinectedin shows remarkable anti-tumor efficacy in a ASCL1-driven PDX models of SCLC. Furthermore, our pre and post-lurbinectedin treatment transcriptomic analysis identify the pathways that may contribute to primary or acquired resistance to lurbinectedin in SCLC. Finally, we identity candidate targets that would guide the design of future combination clinical trials with lurbinectedin in SCLC. Citation Format: Subhamoy Chakraborty, Charles Coleman, Deniz Demircioglu, Dan Hasson, Triparna Sen. Preclinical analysis identifies predictive biomarker and potential pathways of resistance to lurbinectedin treatment in small cell lung cancer [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 LB233.

Synergistic Action of MCL-1 Inhibitor with BCL-2/BCL-XL or MAPK Pathway Inhibitors Enhances Acute Myeloid Leukemia Cell Apoptosis and Differentiation.

Acute myeloid leukemia (AML) is a hematological malignancy characterized by excessive proliferation of abnormal myeloid precursors accompanied by a differentiation block and inhibition of apoptosis. Increased expression of an anti-apoptotic MCL-1 protein was shown to be critical for the sustained survival and expansion of AML cells. Therefore, herein, we examined the pro-apoptotic and pro-differentiating effects of S63845, a specific inhibitor of MCL-1, in a single-agent treatment and in combination with BCL-2/BCL-XL inhibitor, ABT-737, in two AML cell lines: HL-60 and ML-1. Additionally, we determined whether inhibition of the MAPK pathway had an impact on the sensitivity of AML cells to S63845. To assess AML cells' apoptosis and differentiation, in vitro studies were performed using PrestoBlue assay, Coulter electrical impedance method, flow cytometry, light microscopy and Western blot techniques. S63845 caused a concentration-dependent decrease in the viability of HL-60 and ML-1 cells and increased the percentage of apoptotic cells. Combined treatment with S63845 and ABT-737 or MAPK pathway inhibitor enhanced apoptosis but also induced differentiation of tested cells, as well as altering the expression of the MCL-1 protein. Taken together, our data provide the rationale for further studies regarding the use of MCL-1 inhibitor in combination with other pro-survival protein inhibitors.

Systematic Review of Single-Agent vs. Multi-Agent Chemotherapy for Advanced Pancreatic Adenocarcinoma in Elderly vs. Younger Patients.

To systematically review all studies comparing multi-agent to single-agent chemotherapy in the first and second-line setting for unresectable pancreatic adenocarcinoma, so as to compare the outcomes of young and elderly patients. This review searched three databases for relevant studies. The inclusion criteria were diagnosis of locally advanced or metastatic pancreatic adenocarcinoma, comparison of an elderly versus young population, comparison of single-agent versus multi-agent chemotherapy, data on survival outcomes, and randomised controlled trials. The exclusion criteria were phase I trials, incomplete studies, retrospective analyses, systematic reviews, and case reports. A meta-analysis was performed on second-line chemotherapy in elderly patients. Six articles were included in this systematic review. Three of these studies explored first-line treatment and three explored second-line treatment. In the subgroup analysis, the meta-analysis showed statistically improved overall survival for elderly patients receiving single-agent second-line treatment. This systematic review confirmed that combination chemotherapy improved survival in the first-line treatment of advanced pancreatic adenocarcinoma, regardless of age. The benefit of combination chemotherapy in second-line studies for elderly patients with advanced pancreas cancer was less clear.