Advanced Soft Tissue Sarcoma Research Articles

Incidence of cardiotoxicity after high cumulative dose of anthracyclines in adult patients with advanced soft tissue sarcomas: A systematic review and meta-analysis.

e24004 Background: The risk of anthracycline-related cardiotoxicity increases with cumulative dose, with most available literature based from studies on breast cancer patients. Although soft tissue sarcomas are heterogenous entities, anthracycline-based chemotherapy is considered the most active regimen. This study aims to clarify the incidence of cardiotoxicity among patients with advanced soft tissue sarcomas who receive a high cumulative dose of anthracyclines. Methods: We performed a systematic search across PubMed, Cochrane, Google Scholar, and ASCO and ESMO references. Studies were eligible if they (1) investigated soft tissue sarcoma patients, (2) receiving high cumulative doses of doxorubicin ( > 450mg/m2), lipodox ( > 550mg/m2) or epirubicin ( > 900mg/m2), and (3) reported the incidence of cardiotoxicity (clinical and subclinical). Three authors independently assessed validity of the articles using the Cochrane Tool for randomized trials and the Newcastle-Ottawa scale for cohorts. Pooled analysis was performed using MetaXL with the random effects model. Pooled incidence with 95% CI and heterogeneity (Cochran's Q) were determined. Results: For doxorubicin, 4 studies with 168 patients without pre-existing cardiomyopathy, and a mean age of 47 years were included. At a mean cumulative dose of 651.1mg/m2, clinical cardiotoxicity was seen in 2.6% (0.62–5.62%,Q3) while subclinical cardiotoxicity was seen in 23.8%(17.67%-30.53%,Q86). For epirubicin, we included 3 studies with 109 patients, without pre-existing cardiomyopathy, and mean age of 39 years. At a cumulative dose of 1128.33mg/m2, clinical cardiotoxicity was seen in 5.3% (1.74–10.38%,Q25), and subclinical cardiotoxicity was seen in 13.4% (7.62%-20.50%,Q37). Conclusions: The incidence of cardiotoxicity in patients with advanced soft tissue sarcomas receiving high cumulative dose of anthracyclines is comparable with existing data on breast, lymphoma and leukemia patients. Subclinical cardiotoxicity is more prominent. Majority of the patients received cardioprotective strategies during their treatment (dexrazoxane or continuous infusions of doxorubicin). Evidence with regard to lipodox is lacking.

Safety and efficacy of eribulin plus anlotinib in patients with advanced soft tissue sarcoma (ERAS): A multi-center phase II study.

11561 Background: Both the microtubule-dynamics inhibitor eribulin and the multi-targeted tyrosine kinase inhibitor anlotinib exhibit single-agent anti-tumor activity in previously treated soft tissue sarcoma (STS). This study aimed to evaluate the efficacy and safety of the combination treatment of eribulin and anlotinib in patients with advanced STS. Methods: In this multi-center phase II study (ERAS), patients with advanced soft tissue sarcoma who relapsed/progressed after anthracycline chemotherapy or were not candidates for such treatment were included. Patients received eribulin (1.1 mg/m² intravenously on days 1 and 8) and anlotinib (12mg orally once daily on days 1-14) every 21 days for 6-8 cycles, followed by anlotinib maintenance. The primary endpoint was progression-free survival rate at 24 weeks (PFR24w). Secondary endpoints included median progression-free survival (mPFS), median overall survival (mOS), objective response rate (ORR), disease control rate (DCR) and safety. Results: Thirty-one patients were enrolled. Twenty-eight (90.3%) patients had received anthracycline chemotherapy, and the remaining 3 (9.7%) were chemotherapy-naïve. Pathological types included L-type sarcomas (10 leiomyosarcomas and 6 dedifferentiated liposarcomas) and non-L-type sarcomas (n =15, with 8 subtypes). As of the cut-off date of Jan 28, 2024, the median follow-up time was 30.4 weeks. Response evaluation was feasible in 29 patients. The ORR, DCR and predicted PFR24w were 20.7%, 82.8% and 65.5%, respectively. The mPFS was 30.1 weeks, with no significant difference observed between patients with L-type sarcomas and non-L-type sarcomas. The mOS was not reached. Nineteen (61.3%) patients experienced at least one grade 3/4 adverse event. The most common grade 3/4 adverse events included neutropenia (35.5%), leukopenia (25.8%), hypertension (16.1%), hypertriglyceridemia (16.1%) and increased gamma-glutamyl transpeptidase (16.1%). Conclusions: The combination of eribulin and anlotinib shows promising efficacy with an acceptable toxicity profile in patients with advanced STS, irrespective of pathological type. Clinical trial information: ChiCTR2300067650.

Maintenance treatment with toripalimab and anlotinib after anthracycline-based chemotherapy in patients with advanced soft tissue sarcoma (TORAN): A single-arm, phase 2 trial.

11572 Background: In patients with advanced soft tissue sarcoma (STS) who have achieved disease control after anthracycline-based chemotherapy, maintenance therapy is being explored. This study evaluated the efficacy and safety of toripalimab (a monoclonal antibody against the programmed cell death-1 receptor) combined with anlotinib (a multitargeted tyrosine kinase inhibitor) as a maintenance treatment. Methods: Patients with advanced STS who have achieved disease control after at least four cycles of first-line anthracycline-based chemotherapy were enrolled in this single-arm, phase 2 trial. Fifty patients are planned to receive treatment with toripalimab and anlotinib. The primary endpoint was progression-free survival rate at 24 weeks (PFR24w) during maintenance therapy. Secondary endpoints were median progression-free survival (PFS), median overall survival (OS), objective response rate (ORR), disease control rate (DCR) and safety. Results: By the cut-off date of Jan 25, 2024, 22 patients were enrolled, including patients with leiomyosarcoma (n =5), synovial sarcoma (n =3), epithelioid sarcoma (n =3), dedifferentiated liposarcoma (n =2) and other different subtypes of sarcomas (n =9). The median follow-up time was 11 months. Response has been evaluated in 18 patients. The ORR and DCR were 22.2% and 100%. The PFR24w was 67%, the median PFS was 11.8 months, and the median OS was not reached. The grade 3 or higher adverse events were hypertension (n =4), hemorrhage (n =1), adrenal insufficiency (n =1) and hypertriglyceridemia (n =1). Conclusions: Maintenance therapy with toripalimab and anlotinib is a promising treatment option for patients with advanced STS after first-line anthracycline-based chemotherapy. Clinical trial information: ChiCTR2100054901.

Fragility index analysis of systemic therapy clinical trials in soft tissue sarcoma (STS).

11581 Background: The fragility index (FI) measures the robustness of randomized clinical trials (RCT) that have positive results based on statistical p-values. It estimates the minimum number of events that are needed to reverse the trial results from positive to negative. Here, we perform FI analysis on RCTs evaluating systemic treatments for STS. Methods: A systematic search of the Medline and Embase databases for RCTs in adults with advanced STS (Jan 1998 to Dec 2023) was conducted. Gastrointestinal stromal tumor trials were excluded. The FI framework was adapted to allow the use of time-to-event (TTE) outcomes – progression-free survival (PFS) or overall survival (OS) as previously described (Desnoyers et al 2021). Survival tables were reconstructed from published data on positive TTE outcomes, using the Parmar Toolkit. Positive secondary endpoints were used only if the primary endpoint was negative. The number of additional events that would result in a non-significant effect for the hazard ratio (HR) of the positive endpoint of each trial (FI) was calculated and expressed as a proportion of the size of the experimental arm (fragility quotient; FQ). The number of censored patients – those who withdrew consent or were lost to follow-up (Cn) was noted. Results: Among 47 RCTs, 16 (8 phase II; 8 phase III) trials had positive outcomes. The primary endpoint was positive and used for FI analysis in 11/16 trials (68.8%). PFS was the most common positive outcome, evaluated in 13 trials (81.3%). The median FI was 6 (range 2 – 52), with FI < 10 observed in 11 trials (68.8%). Median FQ was 7% (range 1 – 59%) and 10 trials (62.5%) had FQ < 10%. Among 14 trials that reported data, Cn was ≥ FI in 7 trials (50%). Only 2 of 4 trials (50%) that led to regulatory approval had FI > 10 or FQ > 10%. Of the other 2, one drug approval was subsequently withdrawn (Table). Conclusions: Most positive clinical trials in STS were fragile and their outcomes may be confounded by the level of censoring. Real-world evaluation of approved systemic therapies and value scales such as ESMO Magnitude of Clinical Benefit scale or ASCO value framework are needed to confirm clinical benefit of systemic treatments in STS.[Table: see text]

Correlation of ctDNA with hematologic ratios (NLR, MLR, PLR, ELR) in predicting disease progression in soft tissue sarcomas among non-Hispanic Whites and Hispanics: Single-center experience.

e23536 Background: Circulating tumor DNA (ctDNA) has gained prominence as a potential indirect marker for minimal residual disease (MRD) in various cancers, including soft tissue sarcomas (STS). Previous studies have suggested that indirect hematologic ratios – such as Neutrophil-Lymphocyte Ratio (NLR), Monocyte-Lymphocyte Ratio (MLR), Platelet-Lymphocyte Ratio (PLR), and Eosinophil-Lymphocyte Ratio (ELR) may correlate with worse outcomes. We sought to evaluate the correlation of NLR, MLR, PLR and ELR in a real world cohort of Non-Hispanic Whites (NHW) and Hispanics (H) with advanced STS. Methods: We performed a retrospective chart review at Dignity Health Cancer institute using our Electronic Medical Records (EMR) and Signatera™ assay to obtain our data points. Inclusion criteria were STS patients of all ages and stages of disease with complete records. We reviewed 33 patient charts, 14 NHW and 19 H patients. Of the NHW population, 11 were male (M) and 3 females (F). For the H population, 14 were M, and 5 were F. We utilized Spearman's rank correlation coefficient to assess monotonic relationships between ct-DNA levels and the hematologic ratios. ct-DNA was quantified through standardized assays per Protocol, with the resultant values treated as continuous variables in our statistical analyses. Power considerations, based on expected effect sizes and type I error rate adjustments were performed. Results: The Spearman’s correlation coefficients and p-values indicated varied associations across ethnic groups. For NHW, the correlations were generally weak and non-significant (NLR: r = 0.18, p = 0.54; MLR: r = -0.04, p = 0.89; PLR: r = 0.35, p = 0.21; ELR: r = 0.001, p = 1.00). Conversely, in the Hispanic cohort, stronger and statistically significant correlations were observed, particularly with NLR (r = 0.78, p < 0.0001) and MLR (r = 0.70, p < 0.001). Overall, the correlations across the entire study population did not reach statistical significance. Conclusions: This study revealed notable racial variations, particularly in the H population, in the relationship between ctDNA levels and hematologic ratios. The noteworthy associations found with NLR (r = 0.78, p < 0.0001) and MLR (r = 0.70, p < 0.001) highlight the possible usefulness of these ctDNA and these indirect biomarkers in assessing disease status in STS. These findings suggest the possibility of using hematologic ratios, particularly in the Hispanic population, as markers of disease progression similar as ctDNA. Hematologic ratios are more easily accessible to the general population compared to ctDNA in many underserved countries and communities. Future studies with larger cohorts are need to further analyze its validity.

A first-in-human phase 1 trial of T cell membrane-anchored tumor targeted IL12 (ATTIL12) -T cell therapy in advanced/metastatic soft tissue and bone sarcoma.

TPS11586 Background: Interleukin-12 (IL12) is a cytokine that induces antitumor immune response and immune memory by activation of NK cells, induction of IFNg, and maturation of DC cells in the tumor microenvironment (TME). However, prior clinical experience with IL12 has been limited by toxicities including cytokine release syndrome (CRS) and hepatotoxicity. We developed a novel tumor-targeted IL12 gene (ttIL12) that encodes the p35 and p40 VNTANST fusion subunits that targets cell surface vimentin (CSV). Vimentin is expressed intracellularly in many normal and neoplastic mesenchymal cells but our group discovered that intracellular vimentin is often flipped to the cell surface (referred to as CSV) across multiple tumor types.2 Preclinical studies demonstrated efficacy and induction of long-term memory of ttIL12 against metastatic osteosarcoma with reduced toxicity in immune competent models.3 However, ttIL12 had limited efficacy in treating large volume tumors and did not completely eliminate toxic peripheral cytokines. To address this, our team generated a membrane anchored ttIL12 to arm T cells known as attIL12-T cell therapy. We hypothesize attIL12 will minimize toxic cytokines in peripheral tissues but promote induction of INFg/TNFa in the TME to decrease the toxicity and boost efficacy. Methods: This is a phase 1 trial of attIL12-T cells in patients (pts) with locally advanced or metastatic soft tissue or bone sarcomas to assess safety, maximal tolerated dose (MTD) and recommended phase 2 dose (RP2D). Pts in part A (dose finding) will be enrolled using a Bayesian optimal interval (BOIN) design in up to 6 dose levels. Part B (dose expansion) will evaluate preliminary efficacy in 10 additional pts with osteosarcoma treated at the RP2D. Treatment:Pts will undergo leukapheresis to collect peripheral blood mononuclear cells (PBMCs) for generation of attIl12-T cells. Bridging therapy is permitted but not required. Pts will receive cyclophosphamide (Cy) IV prior to planned T cell administration. attIL12 T cells will be administered at the specified dose level IV in a single infusion (dose level 1 and 2) or 2 serial doses (dose level 3-6) on day 0 and day 14. Pts will be monitored for toxicity and response evaluation. Pts will also undergo pre-treatment/on-treatment tumor biopsies for translational and correlative analysis. Eligibility:Pts must be ≥ 12 years of age, have a confirmed diagnosis of locally advanced or metastatic sarcoma, evaluable disease, received at least 1 prior line of standard systemic therapy, ECOG PS 0-1, and adequate organ function to tolerate immune-effector cell therapy. Pts with known sensitivity to Cy, active/prior autoimmune disease, uncontrolled CNS disease, or other uncontrolled comorbidities that pose potential safety risk will be excluded. Enrollment to cohort 1 began in Dec 2023. Clinical trial information: NCT05621668 .

A multicenter real-world study on the efficacy and safety of anlotinib-based treatment for metastatic breast cancer.

e13120 Background: Anlotinib is a multi-targeted small molecule receptor tyrosine kinase (RTK) inhibitor that inhibits angiogenesis. There is only one phase II study on the use of anlotinib in advanced breast cancer (MBC). Therefore, this study aims to analyze its efficacy and safety in the treatment of BC in the real world. It has been approved for the treatment of advanced non-small cell lung cancer and soft tissue sarcoma. There is limited research on the use of anlotinib in advanced breast cancer (MBC). Methods: This study retrospectively analyzed the clinical data of MBC patients who received anlotinib treatment at four domestic centers from January 2021 to December 2023. The primary endpoint was progression-free survival (PFS), and secondary endpoints included overall survival (OS), objective response rate (ORR), disease control rate (DCR), and safety. Kaplan-Meier analysis was used to analyze PFS and OS, and Cox regression model was used to analyze the hazard ratios (HRs) of anlotinib-based treatment on PFS and OS in different subgroups of patients. A p-value <0.05 was considered statistically significant. Results: A total of 153 MBC patients receiving anlotinib-based treatment were included from four centers. The median age was 51 years (range: 22-76), and the median number of prior lines of therapy was 3. The median PFS was 7.7 months (range: 5.2-10.1 months), and the median OS was 28.0 months (range: 21.4-34.9 months). The median ORR and DCR were 19.6% and 60.1%, respectively. The ORR for HR+/HER2- and triple-negative breast cancer patients was 11.6% and 28.8%, respectively, DCR for HR+/HER2- and triple-negative breast cancer (TNBC) patients was 55.8% and 59.6%, respectively. The median PFS was 9.0 months (range: 6.0-11.9 months) for HR+/HER2- patients and 5.3 months (range: 3.5-7.0 months) for TNBC patients, while the median OS was 33.0 months (range: 24.4-41.5 months) and 14.0 months (range: 9.5-18.4 months), respectively. In the subgroup analysis, age <60 years, initial stage IV disease, Ki67≤60%, and treatment with PD-L1 monoclonal antibodies-based regimen were associated with PFS benefit. ECOG <2 and treatment with PD-L1 monoclonal antibodies-based regimen were associated with prolonged OS. Among the 31 patients with brain metastases receiving anlotinib treatment, 11 had active brain metastases and 20 had stable brain metastases. The median PFS was 8.0 months. The intracranial ORR was 12.9%, and the intracranial DCR was 61.3%. No serious adverse events or treatment-related deaths occurred. Grade I/II adverse reactions included hand-foot syndrome (22.2%) and fatigue (19.6%), while grade III/IV adverse reactions included fatigue (6.5%) and decreased neutrophil count (5.2%). Three patients required dose reduction due to intolerable adverse reactions, and nine patients discontinued treatment. Conclusions: Anlotinib demonstrates good antitumor activity and safety in the treatment of MBC. When combined with chemotherapy or immunotherapy, it can improve PFS and OS without significantly increasing toxicity. In particular, it shows promising intracranial ORR and PFS in patients with brain metastases. Clinical trial information: NCT04541420 .

Durvalumab and tremelimumab versus doxorubicin in previously untreated patients with advanced or metastatic soft tissue sarcoma: Patient-reported outcomes (PROs) of the randomized phase II MEDISARC study (AIO-STS-0415).

11519 Background: The randomized phase II MEDISARC trial (NCT03317457) tested durvalumab (DUR) and tremelimumab (TRE) vs. doxorubicin (DOX) in soft tissue sarcoma (STS) patients in first-line therapy. The study showed no PFS benefit (HR 1.22; 95%CI 0,90-1.64; P = .4049), but a trend in prolonged OS (HR 0.73; 95%CI 0.54-0.99; P = .185) in favor of DUR-TRE (Grünwald et al. ESMO 2024: LBA90). The current analysis reports on patient reported outcomes (PROs) under treatment. Methods: We utilized EORTC QLQ-C30 printed questionnaires in randomized patients. PRO were assessed during screening and under treatment every 12 weeks until progression, and 4 weeks after last dose. Time to deterioration (TTD; decrease by 5 points) and mean change from baseline was measured for QLQ-C30 domains. Formal statistic testing was not performed. Results: The median follow-up for DUR-TREM vs. DOX were 34.0 mo. (25.6-42.2) and 37.9 mo. (31.5-37.9). The median duration of therapy was 2.8 (0-13) and 2.1 (0-4) mo., respectively. 86 of 92 (93.5%) patients had ≥1 PRO assessments and were included into the analyses. The completion rate at week 12 was 41.3%. Mean baseline global health status (GHS) was 54.1 (SD: 25.64) and 56.5 (SD: 28.47), respectively. GHS above the median was associated with improved OS and PFS in both arms, indicating a possible predictive biomarker. Under treatment, changes in PRO domains at 12 weeks were noted. TTD favored DUR-TRE in selected functional and symptom domains. Details will be shown at the meeting. Conclusions: MEDISARC is the first study to compare check-point inhibitor and doxorubicin treatment in sarcoma patients. PRO measures from baseline to week 12 favored DUR-TRE. Overall, results indicated better symptom and quality of life in patients treated with DUR-TRE. Clinical trial information: NCT03317457. [Table: see text]

Effectiveness of online activities to reinforce multidisciplinary management of advanced soft tissue sarcoma and extend education globally.

e21013 Background: Soft tissue sarcoma is a heterogeneous group of rare tumors. The multidisciplinary team is integral to optimize patient care and prolong survival. Online video platforms provide a convenient and costless method to deliver content, but their ability to reach and teach clinicians has not been studied extensively. We investigated usage and pre/post-survey data from viewers of a continuing medical education (CME)/nursing continuing professional development (NCPD) Virtual Tumor Board (VTB) video activity. Methods: We developed Virtual Tumor Board: Multidisciplinary Management of Advanced Soft Tissue Sarcoma, for oncologists, pathologists, nurse practitioners, physician assistants, and nurses. The VTB discussed strategies to optimize treatment outcomes of patients with soft tissue sarcoma using case studies. It was made accessible on August 10, 2023, on the i3 Health website, YouTube, and VuMedi. Viewers can receive CME/NCPD. Responses were analyzed, with Fisher’s exact test used to compare responses. Results: At the 5-month follow-up, the VTB has been viewed 1,547 times: 459 views on i3 Health, 988 views on YouTube, and 150 views on VuMedi, representing viewers from across the US and internationally. Baseline assessment data revealed gaps in knowledge in areas addressed by the VTB. For learners who completed the assessments (N=422), the mean score for all topics combined rose by 56% (33% vs 89%). The activity resulted in significant gains in knowledge and competence, with P < 0.001 for all learning gains (Table).Upon completion, 92% of learners self-reported that knowledge acquired from this activity would be utilized to improve the outcomes of their patients, and 91% self-reported that, based on the information learned during the activity, they felt more confident in treating patients with soft tissue sarcoma. Conclusions: Over 1,500 viewers from both rural and urban areas have viewed this lecture, primarily on YouTube. Learners of i3 Health’s accredited activities have grown from 100,000 YouTube viewers in 2021 to over 600,000 by the end of 2023. In 2023, viewership extended to 60 countries, including 30 countries classified as low-to-middle income by The World Bank. The post-activity knowledge gains and improvements in competence show significant impact and the educational benefits of online video viewing. [Table: see text]

Randomized controlled, open-label, phase IIb/III study of lurbinectedin in combination with doxorubicin versus doxorubicin alone as first-line treatment in patients with metastatic leiomyosarcoma.

TPS11590 Background: Lurbinectedin (LUR) is a synthetic chemical entity structurally related to trabectedin that inhibits oncogenic transcription and is active in tumors addicted to transcription. Synergistic activity of the combination of LUR with Doxorubicin (DOX) was found in solid tumors. Preliminary results from two trials showed efficacy for LUR/DOX in anthracycline-naïve advanced Leiomyosarcoma (LMS) (1st or 2nd line) at different doses. In a phase 2 trial in soft tissue sarcoma (STS) patients (pts) (mostly with LMS: 12/20 pts), a combination of DOX 50 mg/m2 + LUR 2 mg/m2 Day (D)1 q3wk resulted in a response rate (RR) of 35% (4/7 LMS pts responding) and a disease control rate (DCR) at 24 wks of 40% (1). A phase 1b/2 trial in 10 advanced STS pts found a RR of 60% (5 were LMS, with 3 partial responses) treated at DOX 25 mg/m2 D1 or D1,D8 + LUR 3.2 mg/m2 D1 q3wk, (2). The promising results of these trials provide a rationale for further exploring this combination in a phase 2b/3 trial as first-line therapy for metastatic LMS (SaLuDo - NCT06088290). Methods: SaLuDo is a randomized, open-label study evaluating LUR in combination with DOX compared to DOX alone as first-line treatment of pts with metastatic LMS. The primary endpoint is progression-free survival (PFS) according to Independent Radiological committee (IRC). Secondary endpoints include overall survival, PFS according to Investigator assessment (IA), overall response rate, duration of response, and clinical benefit rate (according to IRC and IA), safety profile, patient-reported outcomes, pharmacokinetics, and exploratory pharmacogenomic analysis. Main inclusion criteria include age ≥ 18 years, confirmed diagnosis of metastatic LMS, and no prior systemic treatment for metastatic disease. Exclusion criteria include prior treatment with anthracyclines, lurbinectedin or trabectedin. The phase 2b part of the study will randomize approximately 120 pts into 3 arms (1:1:1): Control arm (DOX 75 mg/m2 D1 q3wk; experimental ARM A (DOX 50 mg/m2 D1 + LUR 2.2 mg/m2 D1 + 1ry GCSF prophylaxis q3wk), and experimental ARM B (DOX 25 mg/m2 D1 + LUR 3.2mg/m2 D1 + 1ry GCSF prophylaxis q3wk). Stratification will be done according to site of primary tumor (uterine vs. soft tissue), sites of metastatic disease (lung as unique site vs. other) and time from diagnosis to study entry (≤ 12 months vs. >12 months). One of the two experimental arms will be dropped out at the end of phase 2b. The study will then enter the phase 3 part and approximately 120 pts will be randomized 1:1 between the control arm and the selected experimental arm. An Independent Data Monitoring Committee will oversee the conduct of the study. The first patient was randomized in 09/2023. The phase 2b part of the study is ongoing and recruiting patients in Europe and the USA. 1. Cote EJC 2020; 126:21-32. 2. Cote. JCO 2023; 41: Abst 11507. Clinical trial information: NCT06088290 .

A Comprehensive Literature Review on Efficient Synthetic Approaches and Polymorphism of Pazopanib (Votrient), a Tyrosine Kinase Inhibitor

Angiogenesis involves the development of new blood vessels from the pre-existing vasculature. In cancer, an inappropriate or pathological angiogenesis reinforces tumor growth by feeding with nutrient and oxygen. Central to the process of angiogenesis is vascular endothelial growth factor (VEGF) and its receptor (VEGFR), as they regulate angiogenesis and vascular permeability. To stop tumor angiogenesis by cutting off the blood supply, a multitude of angiogenesis inhibitors (antiangiogenic agents or anticancer drugs) have been developed. In pursuit of developing an effective angiogenesis inhibitor, a novel pyrimidine derivative, an inhibitor of VEGFR-2 kinase activity later known as “VOTRIENT (Pazopanib)” was developed by GlaxoSmithKline and approved by the FDA in October 2009 for treatment of advanced renal cell cancer. Later, it was also approved by the FDA for the treatment of advanced soft tissue sarcoma in April 2012. In the literature, there are multiple synthetic pathways reported and the present work reviews the literature related to the synthesis of Pazopanib emphasizing applicability at a commercial scale. The main purpose of this review paper is to provide a comprehensive overview of different existing routes of synthesis with relevant comparison, reported polymorphs, and suggesting further development.

HMGA1 regulates trabectedin sensitivity in advanced soft-tissue sarcoma (STS): A Spanish Group for Research on Sarcomas (GEIS) study

HMGA1 is a structural epigenetic chromatin factor that has been associated with tumor progression and drug resistance. Here, we reported the prognostic/predictive value of HMGA1 for trabectedin in advanced soft-tissue sarcoma (STS) and the effect of inhibiting HMGA1 or the mTOR downstream pathway in trabectedin activity. The prognostic/predictive value of HMGA1 expression was assessed in a cohort of 301 STS patients at mRNA (n = 133) and protein level (n = 272), by HTG EdgeSeq transcriptomics and immunohistochemistry, respectively. The effect of HMGA1 silencing on trabectedin activity and gene expression profiling was measured in leiomyosarcoma cells. The effect of combining mTOR inhibitors with trabectedin was assessed on cell viability in vitro studies, whereas in vivo studies tested the activity of this combination. HMGA1 mRNA and protein expression were significantly associated with worse progression-free survival of trabectedin and worse overall survival in STS. HMGA1 silencing sensitized leiomyosarcoma cells for trabectedin treatment, reducing the spheroid area and increasing cell death. The downregulation of HGMA1 significantly decreased the enrichment of some specific gene sets, including the PI3K/AKT/mTOR pathway. The inhibition of mTOR, sensitized leiomyosarcoma cultures for trabectedin treatment, increasing cell death. In in vivo studies, the combination of rapamycin with trabectedin downregulated HMGA1 expression and stabilized tumor growth of 3-methylcholantrene-induced sarcoma-like models. HMGA1 is an adverse prognostic factor for trabectedin treatment in advanced STS. HMGA1 silencing increases trabectedin efficacy, in part by modulating the mTOR signaling pathway. Trabectedin plus mTOR inhibitors are active in preclinical models of sarcoma, downregulating HMGA1 expression levels and stabilizing tumor growth.

Abstract CT059: Phase 1b trial Mipasetamab Uzoptirine (ADCT-601-102) dose escalation in patients with advanced bone and soft tissue sarcomas

Abstract Background: AXL is a cell surface receptor tyrosine kinase widely expressed in solid tumors (ST), including sarcomas. ADCT-601 (Mipasetamab uzoptirine; Mipa) is an antibody-drug conjugate comprising a humanized anti-AXL antibody conjugated via a cleavable linker to SG3199 (pyrrolobenzodiazepine dimer cytotoxin). Mipa demonstrated antitumor activity in pre-clinical mice models of sarcoma, adrenocortical carcinoma and pancreatic cancer, and clinical activity in ST patients (pts) in its first-in-human trial. Here, we report initial clinical data in pts with advanced bone and soft tissue sarcomas treated in dose escalation with Mipa. Objective: To characterize the safety and tolerability of Mipa in pts with sarcoma indications who exhausted standard of care therapy. Method: This is a phase 1b, open-label, dose-escalation, dose expansion study of Mipa (NCT05389462; EudraCT: 2021-00566-18). Pts received Mipa every 3 weeks (Q3W) at escalating dose levels, in a 3+3 dose escalation design. Results: As of 04 December 2023, 18 sarcoma patients (15 [83%], soft tissue sarcoma [STS] and 3 [17%] bone sarcoma), unselected for AXL expression, with a median number of 3 prior lines of therapy (1-10), were enrolled in 4 different dose cohorts: 7.5mg, 11mg, 13mg and 15mg. Reasons for treatment discontinuation were disease progression (10 pts [55.6%]), adverse events (3 pts [16.7%]) and consent withdrawal (2 pts [11.1%]). Treatment emergent adverse events (TEAE) were seen in 17 pts (94.4%). Most common TEAE (all grades and relationship [≥20%]) were palmar-plantar erythrodysesthesia syndrome (7 pts [38.9%]); anemia (6 pts [33.3%]); rash maculopapular (5 pts [27.8%]); cheilitis and constipation (4 pts each [22.2%]). TEAE≥grade 3 were seen in 9 pts (50%). Most common TEAE≥grade 3 (≥10%) were GGT increase (2 pts [11.1%]). Two dose limiting toxicities were seen: cheilitis grade 2 and grade 3 at 15mg and 13mg respectively. Cutaneous reactions, all grades, are more prominent in higher doses. Maximum tolerated dose (MTD) has not been established. In 17 sarcoma pts evaluable per RECISTv1.1, best overall response was partial response (PR) (2 pts [11.8%]), including a confirmed PR; stable disease (SD) (8 pts [47.1%]); progressive disease (7 pts [41.2%]). Tumor reductions was observed at 7.5mg, 11mg and 13mg. By week 12, 6/17 pts (35.3%) did not demonstrate PD . Initial IHC staining showed AXL expression in all sarcoma baseline biopsies tested so far. Initial pharmacokinetic (PK) data indicate exposures with moderate to marked interpatient variability; rapid clearance with no accumulation by Cycle 2. Updated biomarkers and PK data will be presented. Conclusion: The MTD was not established. Due to the incidence of TEAE judged related to Mipa and the preliminary activity observed, 15mg was selected as the highest dose to be tested in a fixed dose Q3W regimen. The study continues to enroll to further optimize Mipa dosing regimen and in dose escalation with gemcitabine. Citation Format: Brian Andrew Van Tine, Christopher T. Chen, Victor Moreno, Elizabeth J. Davis, Maria J. de Miguel, Antoine Italiano, Esma Saada-Bouzid, Mohammed Milhem, Claudia Valverde, Sant P. Chawla, Abdul Rafeh Naqash, Louise Carter, Robin Jones, Ilaria Conti, Joe Boni, Karin Havenith, Yvan LeBruchec, Serafino Pantano, Jean-Yves Blay. Phase 1b trial Mipasetamab Uzoptirine (ADCT-601-102) dose escalation in patients with advanced bone and soft tissue sarcomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT059.

Abstract CT287: LINNOVATE: A Phase 1/2 study of safety/efficacy using lurbinectedin, combined with ipilimumab, and nivolumab for advanced soft tissue sarcomas (NCT05876715)

Abstract Background: Sarcoma cells are most immunogenic earlier in the course of the disease. Therefore, immune checkpoint inhibitors such as ipilimumab (ipi) and nivolumab (nivo), that promote sustained T-cell activation by suppressing T regs would be most effective when given as first line therapy, together with a tumoricidal agent, such as lurbinectedin, whose plausible mechanism of action is not only to destroy the cancer cells and expose the tumor neoantigens for immune recognition, but also to destroy growth promoting factors in the tumor microenvironment. In the SAINT phase 2 study using ipi, nivo and trabectedin as first line therapy for advanced soft tissue sarcomas (STS; n=79), there were 6 complete responses, 14 partial responses, 49 stable disease, 25.3% best response rate, 87.3% disease control rate; median PFS, 6.7 months, median OS, 24.6 months (Gordon et al, Cancers vol. 15, 906, 2023). Lurbinectedin is a synthetic marine-derived agent and an analog of trabectedin. Therefore, we expect that lurbinectedin will be as effective as trabectedin when used together with ipi and nivo as first line therapy for advanced STS. Methods: Objective 1: Assess MTD of lurbinectedin. Objective 2: Evaluate PFS, OS, incidence and severity of adverse events; Correlative: Correlate response with ctDNA using Signatera. This is an open label, dose-seeking phase 1/2 study. The phase 1 part employs standard “cohort of three” design with a DLT window of 6 weeks. Treatment schedule: Ipi 1 mg/kg IV q 12 weeks; Nivo 3 mg/kg IV q 2 weeks; escalating doses of lurbinectedin from 2.6 mg/m2 to 3.2 mg/m2 IV q 3 weeks. Phase 2 part follows completion of phase 1 part wherein additional 28-34 participants will receive lurbinectedin at the MTD with fixed doses of Ipi and Nivo. Participants may continue treatment until significant disease progression or unacceptable toxicity occurs. Eligible patients are 18 years of age or older, previously treated in phase 1 and previously untreated in phase 2 with confirmed diagnosis of advanced STS, adequate hematologic and organ function, and no history of autoimmune disorder. To date, 6 patients in phase 1 have been dosed. Citation Format: Erlinda M. Gordon, Nadezhda Omelchenko, Samantha Jeffrey, Vaishali Kumar, Neal S. Chawla, Mahesh Seetharam, Victoria Chua, Ania Moradkhani, Doris Quon, Steven Wong, Sant Chawla. LINNOVATE: A Phase 1/2 study of safety/efficacy using lurbinectedin, combined with ipilimumab, and nivolumab for advanced soft tissue sarcomas (NCT05876715) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT287.

Pazopanib attenuated bleomycin-induced pulmonary fibrosis via suppressing TGF-β1 signaling pathway.

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive interstitial lung disease with a high mortality rate and limited treatment efficacy. Nintedanib, a tyrosine kinase inhibitor, is clinically used to treat pulmonary fibrosis. At present, only nintedanib is on the market for the treatment of pulmonary fibrosis. Pazopanib is a drug for the treatment of renal cell carcinoma and advanced soft tissue sarcoma. In this study, we explored whether pazopanib can attenuate bleomycin (BLM)-induced pulmonary fibrosis and explored its antifibrotic mechanism. In vivo and in vitro investigations were carried out to investigate the efficacy and mechanism of action of pazopanib in pulmonary fibrosis. In vivo experiments showed that pazopanib can alleviate pulmonary fibrosis caused by BLM, reduce the degree of collagen deposition and improve lung function. In vitro experiments showed that pazopanib suppressed transforming growth factor-β1 (TGF-β1)-induced myofibroblast activation and promoted apoptosis and autophagy in myofibroblasts. Further mechanistic studies demonstrated that pazopanib inhibited the TGF-β1/Smad and non-Smad signaling pathways during fibroblast activation. In conclusion, pazopanib attenuated BLM-induced pulmonary fibrosis by suppressing the TGF-β1 signaling pathway. Pazopanib inhibits myofibroblast activation, migration, autophagy, apoptosis, and extracellular matrix (ECM) buildup by downregulating the TGF-β1/Smad signal route and the TGF-β1/non-Smad signal pathway. It has the same target as nintedanib and is a tyrosine kinase inhibitor.

Best Overall Response-Associated Signature to Doxorubicin in Soft Tissue Sarcomas: A Transcriptomic Analysis from ANNOUNCE.

This exploratory analysis evaluated the tumor samples of the patients treated with doxorubicin (with or without olaratumab) in a negative phase III ANNOUNCE trial to better understand the complexity of advanced soft tissue sarcomas (STS) and to potentially identify its predictive markers. RNA sequencing was performed on pretreatment tumor samples (n = 273) from the ANNOUNCE trial to evaluate response patterns and identify potential predictive treatment markers for doxorubicin. A BOR-associated signature to doxorubicin (REDSARC) was created by evaluating tumors with radiographic response versus progression. An external cohort of doxorubicin-treated patients from the Spanish Group for Research on Sarcomas (GEIS) was used for refinement and validation. A total of 259 samples from the trial were considered for analysis. Comparative analyses by the treatment arm did not explain the negative trial. However, there was an association between the BOR signature and histologic subtype (χ2P = 2.0e-7) and grade (P = 0.002). There were no associations between the BOR signature and gender, age, ethnicity, or stage. Applied to survival outcomes, REDSARC was also predictive for progression-free survival (PFS) and overall survival (OS). Using the GEIS cohort, a refined 25-gene signature was identified and applied to the ANNOUNCE cohort, where it was predictive of PFS and OS in leiomyosarcoma, liposarcoma, and other sarcoma subtypes, but not in undifferentiated pleomorphic sarcoma. The refined REDSARC signature provides a potential tool to direct the application of doxorubicin in sarcomas and other malignancies. Validation and further refinement of the signature in other potentially subtype specific prospective cohorts is recommended.

Abstract 1880: Ecubectedin and PM54 demonstrate antitumor activity in patient-derived xenograft models of soft tissue sarcoma

Abstract Objective: Soft tissue sarcoma (STS) is a heterogenous group of rare, malignant tumors arising from mesenchymal tissue. Doxorubicin (DOX)-based chemotherapy is the standard for advanced or metastatic STS, despite low response rates and poor disease control. We explored the antitumor activity of two novel compounds, ecubectedin (ECU; PM14) and PM54 (PharmaMar), in two patient-derived xenograft (PDX) models of STS, leiomyosarcoma (LMS) and CIC-rearranged sarcoma (CRS). Mode of action of ECU and PM54 is similar to lurbinectedin (LUR), inhibiting oncogenic transcription by eviction of oncogenic transcription factors from gene promotors’ recognition sequences, while inducing the generation of double strand breaks through DNA adduct formation. Methods: Female NMRI nu/nu mice (n=104) were transplanted bilaterally with STS PDX: UZLX-STS134 (CRS) and UZLX-STS22_2 (LMS). Xenografted mice were randomized to six treatment groups: 1) vehicle (VEH) (5% dextrose) 5 mL/kg once weekly (QW) intravenously (IV); 2) DOX 5 mg/kg QW IV; 3) trabectedin (TRA) 0.15 mg/kg QW IV; 4) LUR 0.18 mg/kg QW IV; 5) ECU 1.2 mg/kg QW IV; 6) PM54 1.2 mg/kg QW IV. Treatment lasted 16 days and antitumor activity was assessed by tumor volume (TV) analysis, histopathology and western blot. The Mann-Whitney U test was used to compare groups, the Wilcoxon test to compare to baseline. Results: ECU and PM54 caused TV shrinkage in UZLX-STS134, while TV in other groups grew significantly on day 16 (Table 1). VEH treatment led to the largest TV increase on day 16, compared to any treatment. PM54 treatment showed TV stabilization in UZLX-STS22_2, and significantly smaller tumors than VEH and TRA treated tumors (p<0.05 and p<0.01, respectively). Histopathological evaluation corroborate the results from the relative TV analysis. Conclusion: Novel drugs exhibit promising results in the PDX models tested, supporting ongoing exploration in additional PDX models of synovial sarcoma and dedifferentiated liposarcoma. Table 1: TV change on day 16 versus baseline, and comparison of proliferative and apoptotic activity Tumor volume change Proliferative activity (pHH3) Apoptotic activity (cPARP) Subtypes UZLX-STS134 UZLX-STS22_2 UZLX-STS134 UZLX-STS22_2 UZLX-STS134 UZLX-STS22_2 VEH(5 ML/kg) 387%*** 349%** n/a n/a n/a n/a DOX (5 mg/kg/QW IV) 177%*** 243%** ↓*** ↓ ↑** ↑ TRA(0.15 mg/kg/QW IV) 230%** 254%*** ↓** ↓** ↑** ↑*** LUR(0.18 mg/kg/QW IV) 202%** 232%** ↓*** ↓*** ↑*** ↑** ECU(1.2 mg/kg/QW IV) 41%*** 181%** ↓*** ↓*** ↑*** ↑*** PM54 (1.2 mg/kg/QW IV) 76%*** 162% ↓*** ↓*** ↑*** ↑ Citation Format: Daniël Gorgels, Agnieszka Wozniak, Chao-Chi Wang, Pablo M. Avilés, Maria J. Guillen, Carmen Cuevas, Patrick Schöffski. Ecubectedin and PM54 demonstrate antitumor activity in patient-derived xenograft models of soft tissue sarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1880.

Abstract 4606: Combinatorial effects of a sequence of trabectedin (T) and CD13-targeted tissue factor tTF-NGR on human vascular endothelial cells (HUVEC) and in soft tissue sarcoma (STS) models

Abstract Trabectedin represents a standard treatment option for relapsed or refractory soft tissue sarcomas. CD13 is a neutral aminopeptidase expressed on remodeling and invasive endothelial cells such as in the tumor vasculature. CD13-targeted tissue factor (tTF-NGR) is a recombinant pro-coagulatory fusion protein which accumulates in the tumor vasculature leading to tumor vascular occlusion and ultimately to tumor infarction. Giving both compounds in sequence could trap trabectedin inside tumors and thus increase its efficacy. This vice versa can optimize the activity of tTF-NGR. To prepare a multicenter clinical trial of a combination of trabectedin and tTF-NGR in patients with advanced soft tissue sarcomas refractory to 1st line systemic therapy (TRABTRAP), preclinical experiments on the mechanism of action of this combination, its efficacy and pharmacokinetics (PK) were performed. We first tested the pro-apoptotic function of trabectedin on human vascular endothelial cells (HUVEC) and human HT1080 sarcoma cells in vitro. Trabectedin significantly (p<.0001) increased the presence of phosphatidylserine (PS) on the outer leaflet of the phospholipid bilayer of the cell membrane in a dose- and time-dependent manner. The resulting optimized phospholipid milieu significantly potentiated the pro-coagulatory efficacy of tTF-NGR within the factor X:factor VIIa:tTF-NGR:CD13 complex on the outer cell membrane when compared to cultures without trabectedin (p<.05). This effect was specifically dependent on the presence of PS as it could be abolished by masking PS via preincubation with annexin V, whereas corticosteroids had no effect on the pro-coagulatory response of HUVEC in the presence of tTF-NGR. In an in vivo HT1080 human sarcoma xenograft model in athymic mice, systemic combination treatment of trabectedin followed by tTF-NGR (n=11) inhibited tumor growth to a greater extent than either compound alone (trabectedin n=9, tTF-NGR n=9) and compared to a saline control (n=8). The terminal half-life of tTF-NGR infused intravenously over 1 hour, was 9 hours (phase I trial). To further characterize the duration of tTF-NGR presence upon binding to the endothelial cell surface molecule CD13, we performed flow cytometry and fluorescence labeling experiments with tTF-NGR and HUVEC in vitro. After coincubation with HUVEC, the cells rapidly internalized the tTF-NGR:CD13 complex into the cytoplasm of the cells (approx. 50% of the labeled tTF-NGR after 3 h at 37oC), a process which exposed the protein to intracellular degradation. The multicenter TRABTRAP trial is actively recruiting patients (EudraCT 2020-005858-21). Citation Format: Caroline Brand, Stefanie Pavelka, Kathrin Hessling, Heike Hintelmann, Andrew F. Berdel, Sebastian Bäumer, Nicole Bäumer, Georg Lenz, Christoph Schliemann, Wolfgang E. Berdel, Christian Schwöppe. Combinatorial effects of a sequence of trabectedin (T) and CD13-targeted tissue factor tTF-NGR on human vascular endothelial cells (HUVEC) and in soft tissue sarcoma (STS) models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4606.

Abstract 2870: Analysis of cancer cells response to radiotherapy activated NBTXR3 nanoparticles

Abstract In 2011, NBTXR3 emerged as the first-in-class radioenhancer used in clinical practice for treating patients with locally advanced soft tissue sarcoma (LA-STS). NBTXR3 became the first radioenhancer to receive CE mark approval after successfully completing a phase II/III clinical study for LA-STS with a doubling of the pCR rate in the NBTXR3 arm compared with the control arm. NBTXR3 nanoparticles consist of a functionalized core of hafnium oxide, a high atomic number element, specifically designed to amplify the effects of radiotherapy (RT) within cells without additional side effects on healthy tissues. Leveraging this physical mechanism, RT-activated NBTXR3 (NBTXR3+RT) has demonstrated superior efficacy in destroying tumor cells and controlling tumor growth in numerous preclinical models and in human, surpassing the effects of RT alone, while maintaining a favorable safety profile. Preclinical studies have revealed that the benefits of NBTXR3 extend beyond mere radioenhancement and improved cancer cell destruction. Specifically, NBTXR3 has been reported to possess immunomodulatory properties through 1) improved induction of DNA damage, leading to better activation of the cGAS-STING pathway, 2) promotion of immunogenic cell death, 3) enhancement of immunopeptidome presentation, 4) generation of an antitumor immune response leading to the production of an abscopal effect mediated by CD8+ cytotoxic lymphocytes. Notably, a series of recent studies using a two-tumor mouse model of anti-PD1-resistant lung cancer that the addition of NBTXR3 significantly improved the efficacy of various treatment regimens (RT+anti-PD1 and combinations with other check-point inhibitors) in terms of tumor growth, abscopal effect, and survival. It has been demonstrated that same benefits can be achieved when NBTXR3 was combined with proton therapy. Moreover, all these studies (X-ray and proton) reported a robust activation of the antitumor immune response, restoration of the effectiveness of anti-PD1 therapy, and the induction of memory response in cured mice. However, our understanding of the biological events leading to these effects remains limited. To address this question, we conducted a series of in vitro studies that employed cytometry, microscopy, and RNA sequencing on various cancer models, both human and murine. We reported that NBTXR3 nanoparticles primarily accumulate within lysosomes following their uptake by tumor cells, leading to the activation of genes associated with the biogenesis, structure, and contents of these organelles. Upon activation by RT, NBTXR3 within lysosomes induces lysosomal membrane permeabilization (LMP), resulting in an increase in lipid peroxidation, inducing regulation of fatty acid oxidation genes, and impacting mitochondrial genes expression, such as respirasome. These findings provide a deeper insight into the early biological effects of NBTXR3+RT in comparison to RT alone. Citation Format: Jordan Da Silva, Celia Bienassis, Sebastien Paris. Analysis of cancer cells response to radiotherapy activated NBTXR3 nanoparticles [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2870.

Abstract 2973: Analysis of NBTXR3 nanoparticles recapture after release by dying cells

Abstract In 2011, NBTXR3 emerged as the pioneering radioenhancer used in clinical practice to treat patients with locally advanced soft tissue sarcoma (LA-STS). Following the successful completion of a phase II/III clinical study for LA-STS, with a doubling of the pCR rate in the NBTXR3 arm compared with the control arm. NBTXR3 became the first radioenhancer to receive CE mark approval. NBTXR3 nanoparticles are composed of a functionalized core made of hafnium oxide, a high atomic number element. They were designed to enhance the effects of radiotherapy (RT) within cells without causing additional side effects on healthy tissues. Exploiting this physical mechanism, radiation-activated NBTXR3 (NBTXR3+RT) has exhibited superior efficacy in eradicating tumor cells and managing tumor growth in various preclinical models and in human studies. It surpasses the effects of RT alone while maintaining a favorable safety profile. Recent preclinical investigations have uncovered that the advantages of NBTXR3 go beyond mere radioenhancement and improved cancer cell destruction. Notably, NBTXR3 has been reported to possess immunomodulatory properties through several mechanisms, including 1) improved induction of DNA damage, leading to enhanced activation of the cGAS-STING pathway, 2) promotion of immunogenic cell death, 3) enhancement of immunopeptidome presentation, 4) generation of an antitumor immune response that results in the production of an abscopal effect mediated by CD8+ cytotoxic lymphocytes. Significantly, a series of recent studies using a two-tumor mouse model of anti-PD1-resistant lung cancer demonstrated that the addition of NBTXR3 significantly improved the efficacy of various treatment regimens (combinations of RT plus anti-PD1 and other checkpoint inhibitors) in terms of tumor growth, abscopal effect, and overall survival. Furthermore, similar benefits can be achieved when NBTXR3 is combined with proton therapy (PBT). Moreover, all these studies (both X-ray and PBT) reported a robust activation of the antitumor immune response, the restoration of the effectiveness of anti-PD1 therapy, and the induction of a memory response in cured mice. But our knowledge of the underlying biological processes that lead to these effects remains rather limited. For example, no information is available about the fate of these nanoparticles once they are injected into a tumor or when they are released by dying cancer cells. To gain a better understanding of these issues, we conducted a series of in vitro and in vivo experiments. We demonstrate that the endocytosis occurs similarly both in vivo and in vitro, at the level of tumor cells. Furthermore, we demonstrate in vitro that nanoparticles taken up by these tumor cells and subsequently released upon their death can be reinternalized by other tumor cells, thus facilitating their destruction by RT. These initial findings provide a deeper insight into the behavior of NBTXR3. Citation Format: Jordan Da silva, Célia Bienassis, Sebastien Paris. Analysis of NBTXR3 nanoparticles recapture after release by dying cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2973.