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Thymic mucoepidermoid carcinoma (MEC) is a rare tumor, and its characteristics remain to be clarified. Here we investigated 20 cases of thymic MEC to systematically characterize its clinical, histopathologic, and molecular features. The median age of the patients was 56 years (range, 19 to 80 y), there was a slight male predilection (3:2), and 44% of the patients were asymptomatic at diagnosis. The median tumor size was 6.8 cm in diameter, 55% were pT1 tumors, and 50% were TNM stage I tumors. When 4 tumor grading systems for salivary MEC (Armed Forces Institutes of Pathology, Brandwein, modified Healey, and the Memorial Sloan-Kettering) were employed, low-grade, intermediate-grade, and high-grade tumors accounted for 35% to 70%, 5% to 25%, and 25% to 50%, respectively. Many histologic variants were noted, and 70% of the cases were classified as nonclassic variants. MAML2 rearrangement was detected in 56% of cases, and the fusion partner was CRTC1 in all cases. CRTC1-MAML2 fusion was associated with lower pT classification and lower TNM stage. The overall survival rate of all patients was 69% and 43% at 5 and 10 years, respectively. Worse overall survival was associated with higher pT stage, higher TNM stage, residual tumors, greater tumor size, high-grade tumor histology (Armed Forces Institutes of Pathology and Memorial Sloan-Kettering, but not the other 2), and with the absence of CRTC1-MAML2 fusion. Of note, none of the patients with CRTC1-MAML2 fusion-positive tumors died during the follow-up. In conclusion, the clinicopathologic and molecular findings of thymic MEC presented here are expected to contribute to the management of this rare tumor.

Abstract Background Gastroesophageal reflux disease (GERD) and reflux esophagitis remain problems after peroral endoscopic myotomy (POEM). This study aimed to elucidate the risk factors and long-term course of reflux esophagitis and symptomatic GERD after POEM. Methods This multicenter cohort study involved 14 high volume centers. Overall, 2905 patients with achalasia-related esophageal motility disorders treated with POEM were analyzed for reflux esophagitis, severe reflux esophagitis (Los Angeles classification C or D), and symptomatic GERD. Results Reflux esophagitis was diagnosed in 1886 patients (64.9 %). Age ≥ 65 years (risk ratio [RR] 0.85), male sex (RR 1.11), posterior myotomy (RR 1.12), esophageal myotomy > 10 cm (RR 1.12), and gastric myotomy > 2 cm (RR 1.17) were independently associated with reflux esophagitis. Severe reflux esophagitis was diagnosed in 219 patients (7.5 %). Age ≥ 65 years (RR 1.72), previous treatments (RR 2.21), Eckardt score ≥ 7 (RR 0.68), sigmoid-type achalasia (RR 1.40), and esophageal myotomy > 10 cm (RR 1.59) were factors associated with severe reflux esophagitis. Proton pump inhibitors (PPIs) were more effective for reflux esophagitis at 5-year follow-up (P = 0.03) than after 1 year (P = 0.08). Symptomatic GERD was present in 458 patients (15.9 %). Symptom duration ≥ 10 years (RR 1.28), achalasia diagnosis (RR 0.68), integrated relaxation pressure ≥ 26 (RR 0.60), and posterior myotomy (RR 0.80) were associated with symptomatic GERD. The incidence of symptomatic GERD was lower at 5-year follow-up compared with that after 1 year (P = 0.04), particularly in PPI users (P < 0.001). Conclusions The incidence of severe reflux esophagitis was low after POEM, but excessive myotomy for older patients with previous treatments should be avoided. Early phase symptomatic GERD is non-acid reflux dependent and the natural course is favorable, basically supporting conservative treatment.

Extracellular vesicles (EVs) have gained considerable attention as vital circulating biomarkers since their structure and composition resemble the originating cells. The investigation of EVs’ biochemical and biophysical properties is of great importance to map them to their parental cells and to better understand their functionalities. In this study, a novel frequency-dependent impedance measurement system has been developed to characterize EVs based on their unique dielectric properties. The system is composed of an insulator-based dielectrophoretic (iDEP) device to entrap and immobilize a cluster of vesicles followed by utilizing electrical impedance spectroscopy (EIS) to measure their impedance at a wide frequency spectrum, aiming to analyze both their membrane and cytosolic charge-dependent contents. The EIS was initially utilized to detect nano-size vesicles with different biochemical compositions, including liposomes synthesized with different lipid compositions, as well as EVs and lipoproteins with similar biophysical properties but dissimilar biochemical properties. Moreover, EVs derived from the same parental cells but treated with different culture conditions were characterized to investigate the correlation of impedance changes with biochemical properties and functionality in terms of pro-inflammatory responses. The system also showed the ability to discriminate between EVs derived from different cellular origins as well as among size-sorted EVs harbored from the same cellular origin. This proof-of-concept approach is the first step towards utilizing EIS as a label-free, non-invasive, and rapid sensor for detection and characterization of pathogenic EVs and other nanovesicles in the future.

TPS489 Background: Tucatinib (TUC), a highly selective HER2-directed TKI approved in multiple regions for HER2+ metastatic breast cancer, is being investigated as a novel therapy for patients (pts) with metastatic colorectal cancer, gastric cancer, and other GI tumors. Preclinical and clinical data have shown HER2-targeted agents may improve clinical outcomes. In xenograft models of HER2+ and HER2-mutated tumors, dual targeting of HER2 with TUC + trastuzumab (Tras) showed superior activity to either agent alone (Kulukian 2020). Interim results from the MOUNTAINEER study have shown promising activity for TUC + Tras in HER2+ colorectal cancer. In 23 response-evaluable pts, an objective response rate (ORR) of 52% was observed with a median progression-free survival (PFS) of 8.1 months (mo) (Strickler 2019). The prognosis for pts with biliary tract cancers (BTCs) remain poor, and treatment options are limited. Given that approximately 12%-15% of BTC pts are HER2+, and 1%-8% have HER2 mutations, TUC + Tras warrants further evaluation in this patient population. The SGNTUC-019 basket study (NCT04579380) is evaluating TUC + Tras in pts with previously treated, locally advanced, unresectable or metastatic solid tumors including BTC that display HER2 overexpression/amplification or activating mutations. We describe the design of the BTC cohort. Methods: SGNTUC-019 is a multi-cohort, open-label, international Phase 2 study. Pts must be ≥18 years old; have an ECOG PS of ≤1; have adequate hepatic, hematological, renal, and cardiac functions; and have no previous exposure to HER2-directed therapy. BTC pts must have progressed on or after ≥1 previous line of treatment. The HER2+ BTC cohort will enroll 12 response-evaluable pts. If >2 responses are observed, the cohort will be expanded to 30 pts. HER2-mutated BTC patients may also be enrolled in a 30 pts cohort for other HER2-mutated solid tumors. The primary objective is antitumor activity with confirmed ORR as the primary endpoint. Secondary efficacy endpoints include disease control rate, duration of response, PFS, and OS. For eligibility, HER2 alterations can be demonstrated by HER2 overexpression/amplification in tumor tissue by prior IHC/ISH, or by HER2 amplification/mutation in a prior or on-study NGS assay of ctDNA or prior tissue NGS assay. Pts will receive TUC 300 mg orally twice a day and Tras 8 mg/kg intravenously on Cycle 1 Day 1 then 6 mg/kg every 21 days from Cycle 2 Day 1. Disease assessments per RECIST 1.1 are every 6 weeks for the first 24 weeks, then every 12 weeks. Quality of life will be evaluated every 2 cycles using EQ-5D-5L. Sites are currently enrolling within the US, EU and Asia-Pacific. Clinical trial information: NCT04579380.

TPS371 Background: Tucatinib (TUC), a highly selective HER2-directed tyrosine kinase inhibitor (TKI) approved in multiple regions for HER2+ metastatic breast cancer, is being developed as a novel therapy for patients (pts) with GI tumors including gastric or gastroesophageal junction adenocarcinoma (GEC). While trastuzumab (Tras) with chemotherapy is standard in the 1st-line setting for metastatic HER2+ GEC, no anti-HER2 therapy has demonstrated an OS benefit over chemotherapy as 2nd-line therapy, possibly due to loss of HER2 expression following Tras-based therapy. In GEC xenograft models, dual targeting of HER2 with TUC and Tras showed superior activity to either agent alone.(Kulukian 2020) Interim results from the MOUNTAINEER study have shown promising activity for TUC and Tras for HER2+ mCRC.(Strickler 2019) The MOUNTAINEER-02 study is evaluating the efficacy and safety of TUC with Tras, ramucirumab (Ram), and paclitaxel (Pac) in pts with HER2+ GEC in the 2nd-line setting. Methods: MOUNTAINEER-02 (NCT04499924) is a phase 2/3 study evaluating TUC + Tras with Ram and Pac. Pts receive TUC 300 mg or placebo PO BID, Tras (6 then 4 mg/kg) or placebo (IV on Days 1 and 15 of each 28-day cycle), Pac (IV on Days 1, 8, 15), and Ram (IV on Days 1 and 15). Eligible pts have locally-advanced unresectable or metastatic HER2+ GEC and have received a HER2-directed antibody and 1 prior line of therapy for advanced disease. Pts must be ≥18 years of age, with an ECOG ≤1, and have had no prior exposure to Ram, anti-HER2 or anti-EGFR TKI, HER2-directed antibody-drug conjugates, or taxanes ≤12 months before enrollment. Due to the potential impact of TUC on Pac metabolism, the study will include an initial Pac dose optimization stage. The open-label phase 2 part will determine the recommended dose of Pac (60 or 80 mg/m²) combined with TUC, Tras, and Ram in 6-18 pts, and evaluate safety and activity of the regimen in Cohorts 2A and 2B (30 pts each). The randomized, double-blind, phase 3 part will compare the efficacy and safety of TUC and Tras (Arm 3A; ̃235 pts) vs. placebo (Arm 3B; ̃235 pts), both in combination with Ram and Pac, and also evaluate activity of TUC with Ram and Pac (Arm 3C; ̃30 pts). The dual primary phase 3 endpoints are OS and PFS per investigator, with confirmed ORR as a key secondary endpoint. HER2 status is determined at baseline using a blood-based NGS assay, and IHC/ISH of fresh or archival tumor biopsies, if available. Pts must be HER2+ by blood-based NGS in Cohort 2A and phase 3; in Cohort 2B, pts must be HER2+ in a biopsy taken post-progression during/after 1st-line therapy, but HER2-negative by blood-based NGS. Disease assessments per RECISTv1.1 will occur q6 weeks for 36 weeks, then q9 weeks. The pharmacokinetics of TUC, Pac, and their metabolites will be evaluated in a subset of pts, including a cohort with gastrectomies. Enrollment in phase 2 is ongoing. Clinical trial information: NCT04499924.

Abstract Background: SUMOylation, a post-translational modification analogous to ubiquitination, attaches a small, ubiquitin-like modifier (SUMO) to target proteins. SUMOylation plays a central role in the immune system by regulating type I interferon (IFN-I) expression, thereby functioning to constrain the innate immune response (Decque Nat Immunol 2016), and limit tumor immune surveillance. The SUMOylation pathway is often overexpressed in multiple myeloma (MM) and is associated with poor outcomes (Driscoll Blood 2010). TAK-981 is a first-in-class, small-molecule inhibitor of SUMO-activating enzyme, which blocks the SUMOylation cascade (Langston J Med Chem 2021) and increases IFN-I production and signaling in innate immune cells (Nakamura AACR 2019). In ex vivo assays, TAK-981 activated the IFN-I pathway, increased phagocytic activity of monocyte-derived macrophages, and increased natural killer (NK) cell cytotoxicity via IFN-I signaling (Nakamura AACR 2019). The ability of TAK-981 to promote activation of macrophages and NK cells provides a mechanistic rationale for its use in combination with monoclonal antibodies (mAbs) reliant on antibody-dependent cellular cytotoxicity and phagocytosis; in vivo experiments have demonstrated synergistic activity between TAK-981 and rituximab, and between TAK-981 and the anti-CD38 mAbs daratumumab (dara) (Nakamura SITC 2020) or mezagitamab (meza; TAK-079; Figure 1). Patients with MM who have disease refractory to the three most effective classes of anti-myeloma therapies (proteasome inhibitors [PIs], immunomodulatory drugs [IMiDs], and anti-CD38 mAbs) have a poor prognosis, with median survival 9.2 months (Gandhi Leukemia 2019). Given the incurable nature of advanced MM and the highly complex mechanisms of resistance, continued efforts to better understand MM biology at the time of relapse and to translate this into effective treatment combinations are needed. Combination therapies that engage the immune system to treat MM may offer substantial clinical benefit. Methods: To be eligible for this multicenter, open-label, Phase 1b/2 trial (NCT04776018), patients must have failed at least 3 prior lines of anti-myeloma therapy, have MM disease that is triple-class refractory (defined as refractory/intolerant to ≥1 PI and ≥1 IMiD, and refractory to ≥1 anti-CD38 mAb), and have demonstrated disease progression on their last therapy. Prior CAR-T therapy is allowed. Patients will be assigned to TAK-981 plus subcutaneous (SC) meza (Phase 1 Part 1) or SC dara (dara and hyaluronidase-fihj; Phase 1 Part 2). The primary objectives of Phase 1b are to determine safety and tolerability, and to select the recommended Phase 2 dose (RP2D) and schedule for TAK-981 with each mAb; secondary objectives are to evaluate preliminary antitumor activity, to characterize TAK-981 pharmacokinetics (PK), and to explore pharmacodynamic (PD) markers of TAK-981 target engagement and SUMOylation pathway inhibition. Approximately 30 patients will participate in the Phase 1b Part 1 dose escalation of TAK-981 plus meza (~15 patients per dosing schedule), and ~15 patients will participate in the Phase 1b Part 2 dose escalation of TAK-981 plus SC dara. The primary objective of Phase 2 is to evaluate the efficacy of TAK-981 at the RP2D in combination with an anti-CD38 mAb; ~36 patients will be enrolled. In Phase 1b, patients will receive TAK-981 via a 1-hour intravenous infusion either on days 1, 4, 8, 11, and 15 (twice weekly; BIW) or on days, 1, 8, 15, and 22 (weekly; QW) for 2x 28-day cycles, then 8x every other week, then monthly. Meza 600 mg SC or dara 1800 mg SC will be given 8x weekly, 8x every other week, then monthly, in a 28-day cycle (Figure 2). Treatment will continue until disease progression or unacceptable toxicity (max. 24 cycles). TAK-981 dose escalation will proceed from 60 mg BIW, a dose shown to be pharmacologically active in a first-in-human, single-agent TAK-981 study (TAK-981-1002; data on file). Dose escalation will be guided by Bayesian Optimal Internal Design with Informative Prior (iBOIN) plus consideration of other safety, clinical, PK, and PD data. The iBOIN design selects the true maximum tolerated dose (if any) with high accuracy by allocating more patients to dose levels with a prior dose-limiting toxicity probability closest to the target of 0.3. This study is currently enrolling patients, with the first patient dosed in May 2021. Figure 1 Figure 1. Disclosures Lonial: AMGEN: Consultancy, Honoraria; Takeda: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; GlaxoSmithKline: Consultancy, Honoraria, Research Funding; TG Therapeutics: Membership on an entity's Board of Directors or advisory committees; BMS/Celgene: Consultancy, Honoraria, Research Funding; Merck: Honoraria; Abbvie: Consultancy, Honoraria. Boccia: BMS: Consultancy, Honoraria, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Speakers Bureau; Abbvie: Consultancy, Honoraria, Speakers Bureau; Takeda: Honoraria, Research Funding, Speakers Bureau; Amgen: Research Funding, Speakers Bureau; Epizyme: Honoraria, Speakers Bureau; Morphosis: Honoraria, Speakers Bureau. Yimer: Beigene: Speakers Bureau; Astrazeneca: Speakers Bureau; Karyopharm: Current equity holder in publicly-traded company, Speakers Bureau; Janssen: Speakers Bureau; GSK: Speakers Bureau; Sanofi: Speakers Bureau; Amgen: Speakers Bureau; Pharmacyclics: Speakers Bureau; Texas Oncology: Current Employment. Levy: Jazz Pharmaceuticals: Consultancy, Honoraria, Speakers Bureau; Morphosys: Consultancy, Honoraria, Other: Promotional speaker, Speakers Bureau; Karyopharm: Consultancy, Honoraria, Other: Promotional speaker, Speakers Bureau; Dova: Consultancy, Other: Promotional speaker; Janssen Pharmaceuticals: Consultancy, Honoraria, Other: Promotional speaker, Speakers Bureau; Amgen Inc.: Consultancy, Honoraria, Other: Promotional speaker, Speakers Bureau; GSK: Consultancy, Other: Promotional speaker; Epizyme: Consultancy, Other: Promotional speaker; Novartis: Consultancy, Other: Promotional speaker; AbbVie: Consultancy, Honoraria, Other: Promotional speaker, Speakers Bureau; Beigene: Consultancy, Honoraria, Speakers Bureau; Bristol Myers Squibb: Consultancy, Honoraria, Other: Promotional speaker, Speakers Bureau; AstraZeneca: Consultancy, Honoraria, Speakers Bureau; Gilead Sciences, Inc.: Consultancy, Honoraria, Speakers Bureau; Seattle Genetics: Consultancy, Honoraria, Other: Promotional speaker, Speakers Bureau; Takeda: Consultancy, Honoraria, Other: Promotional speaker, Speakers Bureau; TG Therapeutics: Consultancy, Honoraria, Speakers Bureau. Abonour: Takeda: Research Funding; GSK: Consultancy, Honoraria, Research Funding; Celgene-BMS: Membership on an entity's Board of Directors or advisory committees, Research Funding; Jensen: Honoraria, Research Funding. Mohan: Medical College of Wisconsin: Current Employment. Girnius: BMS: Honoraria, Speakers Bureau; Celgene: Speakers Bureau; Genentech: Honoraria; GSK: Honoraria, Speakers Bureau; Takeda: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Beigene: Speakers Bureau. Rosenbaum: Takeda: Honoraria; Akcea: Honoraria; Janssen: Honoraria. Nadeem: Karyopharm: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees; GSK: Membership on an entity's Board of Directors or advisory committees. Berg: Takeda: Current Employment, Current equity holder in publicly-traded company, Current holder of stock options in a privately-held company. Chao: Takeda: Current Employment. Berger: Takeda Development Center Americas, Inc.: Current Employment. Nakamura: Takeda Development Center Americas, Inc.: Current Employment. Zhang: Takeda: Current Employment. Song: Takeda Pharmaceuticals International Co.: Current Employment. Ward: Takeda: Current Employment. Proscurshim: Takeda Pharmaceuticals: Current Employment, Current holder of individual stocks in a privately-held company. Kumar: Novartis: Research Funding; Tenebio: Research Funding; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Antengene: Consultancy, Honoraria; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche-Genentech: Consultancy, Research Funding; Astra-Zeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Consultancy, Research Funding; Beigene: Consultancy; Bluebird Bio: Consultancy; KITE: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Research Funding; Oncopeptides: Consultancy; Amgen: Consultancy, Research Funding; Carsgen: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Adaptive: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sanofi: Research Funding. OffLabel Disclosure: Study of the investigational agent TAK-981 in combination with daratumumab and hyaluronidase-fihj or the investigational agent mezagitamab (TAK-079).