Schwartz, Gary K.

TPS11598 Background: Fibroblast Activation Protein (FAP) is expressed on the surface of cancer-associated fibroblasts and is involved in the formation, maintenance, and spread of tumors. Sarcoma frequently demonstrates high expression of FAP on the tumor cells themselves in contrast to other solid tumors, where it is mainly expressed on CAFs within the tumor stroma. Radioligand therapies utilizing alpha emitting isotopes such as Ac-225 have emerged as promising treatment strategies across multiple targets and indications in oncology. Ac-225 and its daughter radionuclides emit high-energy alpha particles capable of inducing double-stranded DNA breaks, leading to significant cytotoxic effects within cells. Early clinical data for other Ac-225-labeled compounds have shown promising outcomes, particularly in settings where traditional therapies have failed. [Ac-225] RTX-2358 (Ratio Therapeutics Inc, Boston, MA) is a novel FAP-targeted radioligand designed for specific high-affinity binding, resulting in prolonged tumor residence and limited normal tissue uptake. This sustained tumor retention leads to extended delivery of cytotoxic radiation to FAP-expressing tumors. A beta-emitting analog, [Lu-177]RTX-2358, has been administered to more than 25 patients under the German §13.2b compassionate use framework across multiple tumor types. Longitudinal SPECT imaging performed as late as 14 days after administration demonstrated persistent tumor retention with minimal washout. Based on time–activity curve analysis from these data, tumor biological half-time is estimated to be well in excess of 1,000 hours. Renal clearance was observed to be consistent with that reported for established lutetium-177–labeled radioligand therapies. Methods: This study is a seamless Phase 1 / 2 dose escalation study. The Phase 1 portion consists of a 3 x 3 dose escalation design, with patients treated in 3 planned dose escalation cohorts (7.5, 11.25 and 15 MBq) with up to 6, 8-week cycles of [Ac-225]RTX-2358. Backfill of phase 1 cohorts is permitted to facilitate selection of the recommended administered activity level for the subsequent Phase 2 expansion cohort. Dose escalation / de-escalation decisions will be made by a Safety Review Committee. Patients over 18yrs with a history of histologically confirmed relapsed or refractory soft tissue sarcoma (measurable disease per RECIST v1.1) are eligible if they have a positive [Cu-64]LNTH-1363S FAP PET, an ECOG PS 0 to 1, and adequate organ reserve and renal function. Recruitment of the first cohort was completed in December 2025. The ATLAS Study: NCT07156565 Clinical trial information: NCT07156565 .

We previously reported initial results of the pivotal phase II trial of atezolizumab for patients with alveolar soft part sarcoma (ASPS; ClinicalTrials.gov identifier: NCT03141684 ). Here, we report on three additional years of observation. Fifty-three patients with ASPS received atezolizumab. Median duration of response increased to 37.0 months. Objective response rate (ORR) and median progression-free survival (mPFS) remained essentially as previously reported (35.8% [95% CI, 23.1 to 50.2] and 20.8 months [IQR, 7.6-not reached], respectively). ASPSCR1::TFE3 fusion type was determined for 47/53 patients; ORR and mPFS were higher among the 41 patients expressing type 1 (43.9% [95% CI, 28.5 to 60.2] and 28.3 months [IQR, 9.2-not reached], respectively) than the six patients expressing type 2 (0% [95% CI, 0 to 45.9] and 7.5 months [IQR, 3.9-not reached], respectively, PFS HR, 3.2 [95% CI, 1.01 to 10.2]). Eleven patients chose a per-protocol drug holiday (range, 3.5-26.4 months) after ≥2 years of treatment; two experienced disease progression during the holiday. Nine eligible patients elected to receive bevacizumab plus atezolizumab after progressing on monotherapy; ORR was 0% and mPFS was 18.5 months (IQR, 7.9-21.1) in this small cohort. Long-term results support using atezolizumab to treat ASPS, even for several years; a drug holiday with careful monitoring may be an option for some patients.

PURPOSE Continued improvement in outcomes is needed for advanced cutaneous squamous cell carcinoma (cSCC). Methods Alliance A091802 is a randomized phase II trial of avelumab (800 mg IV once every 2 weeks) plus cetuximab (500 mg/m 2 IV once every 2 weeks) versus avelumab alone once every 2 weeks for up to 2 years. Cetuximab was given for 1 year in the avelumab + cetuximab arm. Crossover at progression to avelumab + cetuximab was allowed. Randomization was 1:1, stratified by PD-L1 and HIV status. Patients had distant metastatic or unresectable locally advanced cSCC, were anti–PD-1/PD-L1 monoclonal antibody–naive, had no previous cetuximab in the advanced setting, had an Eastern Cooperative Oncology Group performance status of 0-2, and could be HIV+ (CD4 >200, viral load <200). Patients with chronic lymphocytic leukemia, immunosuppression, or active autoimmune diseases were excluded. The primary end point was progression-free survival (PFS; null hypothesis: median = 12 months v alternative hypothesis: 21 months or a 75% improvement, power of 80% with one-sided alpha .2, n = 57, 37 PFS events required). Secondary end points were overall survival, objective response rates (ORRs), clinical benefit rate, and toxicity. RESULTS Sixty patients were enrolled; 57 patients were evaluable. The median age was 72 years, all were HIV–; 75.4% was PD-L1+, 84.2% had head/neck origin, 47.4% had distant metastasis, and there were no differences in baseline characteristics by arm. Avelumab + cetuximab significantly improved PFS versus avelumab (median, 11.1 [7.6-not reached (NR)] v 3.0 months [2.7-13.6] hazard ratio, 0.48 [95% CI, 0.23 to 0.97], P = .018). Avelumab patients who crossed over (n = 9) to combination had a median PFS after crossover of 11.3 months (5.8-NR). The confirmed ORR was 27.6% with avelumab + cetuximab and 21.4% with avelumab. Grade 3 treatment-related adverse events occurred in 48.3% and 21.5% of patients with avelumab + cetuximab (most common: rash [20.7%], infusion reaction [20.7%]) and avelumab, respectively. CONCLUSION Avelumab + cetuximab significantly improved PFS versus avelumab alone in patients with advanced cSCC. Alliance A091802 supports a larger confirmatory study with the combination of cetuximab and PD-1:PD-(L)1 blockade.

11507 Background: Advanced uterine leiomyosarcoma (uLMS) is an aggressive malignancy with poor prognosis. Standard-of-care treatments, including trabectedin (Tb) or pazopanib (P), provide median progression-free survival (PFS) of 3-4 months (mo) and objective response rates (ORR) of ~11%. Homologous recombination deficiency (HRD) in a subset of uLMS supports the use of PARP inhibitors combined with DNA-damaging agents. Preclinical studies demonstrated synergistic activity of olaparib and temozolomide (T+O), and a prior single-arm Phase II study of T+O showed promising efficacy independent of an established biomarker, warranting further investigation in a randomized setting. Methods: Alliance A092104 is a Phase II/III trial evaluating olaparib (200 mg BID) plus temozolomide (75 mg/m² daily, days 1-7, every 21 days) versus investigator’s choice of Tb or P in patients (pts) with advanced uLMS who progressed on ≥2 prior systemic therapies. Stratification factors included ECOG (0-1 vs. 2) and prior lines (2 vs. ≥3). The Phase II (Phase III) primary endpoint was PFS (OS), with a planned suspension of accrual at the end of Phase II. A total of 70 evaluable pts (58 PFS events) were needed to detect an improvement in PFS from 4 vs. 8 mo with power of 90% and 1-sided type I error of 10%, with futility assessed after 29 PFS events. Upon meeting the Phase II futility threshold for PFS, the trial was permanently closed. Data were released from the data and safety monitoring board. Pts continue to be followed for outcomes. Results: 74 pts enrolled (Arm 1: T+O, n = 37; Arm 2: investigator’s choice, n = 37 (Tb, 18; P, 13; 6 pts did not start treatment). The arms were balanced for baseline demographics except race, with the T+O arm having a higher proportion of black/African American (29.7% vs. 16.2%). 21 pts remain on treatment. Hematologic adverse events (AEs) were more frequent in the T+O arm, with Grade 4 neutropenia (19.5%) and thrombocytopenia (8.3%) both managed by dose reductions. Non-hematologic Grade 3 AEs were higher in the investigator’s choice arm (45.2% vs. 13.9%). No Grade 5 AEs were reported. In the first 70 pts, with a median follow-up of 5.9 mo, and 39 total PFS events, the median PFS was 3.2 mo (95% CI: 2.0-NE) for T+O versus 5.6 mo (95% CI: 2.8-NE) for investigator’s choice (HR = 1.00; 95% CI: 0.60-2.17; 1-sided stratified log rank p = 0.50). Within Arm 2, the median PFS for Tb and P were respectively 5.6 (95% CI: 3.1-NE) and 3.8 (95% CI: 1.5-NE) mo. 3 pts in the T+0 arm and 1 patient in the investigator’s choice arm (Tb) had a confirmed partial response. Conclusions: The trial did not meet its primary endpoint of PFS in Phase II. This suggests that a biomarker may be needed before there is further exploration of PARP inhibitor-based regimens in uLMS. Overall survival and analysis of tissue-based biomarkers will be presented. Clinical trial information: NCT05432791 .

6002 Background: There is a need for continued improvement in outcomes with systemic therapy for advanced cSCC. Pre-clinical data suggest immunologic synergy between IgG1 mAb therapy targeting EGFR and PD-1:PD-(L)1 blockade. Methods: Alliance A091802 is a randomized phase II trial of avelumab (AV) (800 mg) plus cetuximab (C) (500 mg/m2) vs. AV alone every 2 weeks for up to 2 years (yrs). C was given for 1 yr in the AV+C arm. Crossover at progression to AV+C was allowed in the AV arm. Randomization was 1:1 and stratified by PD-L1 [+(>1%) vs. -] and HIV status (+ vs. -). Eligible patients (pts) had distant metastatic or unresectable locally advanced cSCC, anti-PD-1/PD-L1 mAb naive, no prior cetuximab in the advanced setting, ECOG PS 0-2, HIV+ if CD4 >200 and VL <200. Pts with CLL, immunosuppression, or active autoimmune diseases were excluded. The primary endpoint was progression-free survival (PFS) (Ho: Median=12 mo vs Ha: 21 mo or a 75% improvement, power of 80% with one-sided alpha 0.2, n=57, 37 PFS events required). Secondary endpoints were overall survival (OS), confirmed response rate (ORR), clinical benefit rate, and toxicity. After 31/37 events, an early unplanned analysis (along with sensitivity analyses) was performed because it became apparent that 37 events would not be reached. These results were submitted to the Alliance Data and Safety Monitoring Board, which recommended releasing the data. Data cutoff was 1/16/25. Results: 60 pts were enrolled between 2019-2023; 57 pts were evaluable. Median age was 72 yrs (41‒93), 96.5% were white, 91.2% male, all HIV-; 75.4% PD-L1+. 84.2% were head/neck origin, 47.1% had distant metastasis, and there were no differences in baseline characteristics by arm. AV+C significantly improved PFS compared to AV [median 11.1 months (mo) (7.6‒not reached (NR)) vs. 4.8 mo (2.8‒NR) hazard ratio (HR) 0.53 95% CI (0.26‒1.09), one-sided p=0.041]. The median OS of AV+C vs. AV was NR (25.2‒NR) vs. 35.8 mo (18.6‒NR) HR 0.77 (0.33‒1.78) p=0.267. ORR was 31.0% in the AV+C arm and 21.4% in the AV arm. Treatment-related adverse events (TRAE) of any grade (G) occurred in 93% and 78.6%, respectively, and were G>3 in 48.3% and 21.5% of pts in the AV+C [most common G3 TRAEs were rash (20.7%) and infusion-related reaction (20.7%)] and AV arms, respectively. There were no G5 events. Outcomes after crossover and by PD-L1 status will be presented subsequently. Conclusions: Avelumab plus cetuximab significantly improved PFS vs. avelumab alone in advanced cSCC pts, without unexpected toxicity. Alliance A091802 supports a larger confirmatory study with combination cetuximab and PD-1:PD-(L)1 blockade. Support: U10CA180821, U10CA180882, U24CA196171; U10CA180868 (NRG Oncology); U10CA180888 (SWOG); https://acknowledgments.alliancefound.org . EMD Serono CrossRef Funder ID: 10.13039/100004755. Clinical trial information: NCT03944941 .

Background In this open-label, randomized, non-comparative, multicenter phase II study (Alliance A091401) we report on three expansion cohorts treated with nivolumab (N) with and without ipilimumab (N+I) and provide a multi-omic correlative analysis of actionable biomarkers. Methods Patients were randomized (non-comparative) to receive either N or N+I. The primary endpoint was a 6-month confirmed response rate (CRR) defined by Response Evaluation Criteria in Solid Tumors version 1.1. Secondary endpoints included treatment-related adverse events (TRAEs), progression-free survival, and overall survival. Multi-omic correlative analyses were conducted using samples from both the primary and expansion cohorts. Results A total of 66 patients were evaluated for the primary endpoint with disease including gastrointestinal stromal tumor (GIST, n=18), undifferentiated pleomorphic sarcoma (UPS, n=24), and dedifferentiated liposarcoma (DDLPS, n=24). Neither N nor N+I achieved a complete or partial response in the GIST expansion cohort. In DDLPS and UPS, the primary response endpoint of CRR was met with N+I (both 16.6%, 2/12) but not with N alone (both 8.3%, 1/12). In the GIST cohort, TRAE was higher with N+I treatment, halting enrollment as required per protocol. In a correlative analysis of patients for the expansion cohort and the original cohort (n=86), traditional biomarkers of immunotherapy response were not correlated with response in any histological subtype. Markers of genomic instability including the presence of gene fusions and increased subclonal mutations correlated with improved clinical outcomes. Conclusions This expansion cohort reaffirms the outcomes of A091401. There remains a pressing need to determine the role of and predictive biomarkers for immunotherapy in sarcoma. Trial registration number NCT02500797.

TPS4196 Background: Advanced BTC patients have poor prognosis. Up to 40% of BTCs have KRAS mutations and are associated with worse overall survival (OS). With a median OS of 7.7 months in KRAS wild-type compared to 1.7 months in KRAS mutated disease, these alterations are independent poor prognostic factors in BTC. Gemcitabine and cisplatin (GC) with or without immunotherapy are often used as 1st-line therapies. However, there is a lack of data on best 2nd-line regimens. mFOLFOX6 (5-fluorouracil [5-FU], leucovorin [LV], oxaliplatin) or liposomal irinotecan+5-FU+LV are options when no biomarkers are found (e.g., MSI-H, BRAFV600E, FGFR-fusions, IDH1-mutation, HER2-overexpression). Prior studies do not demonstrate benefit with MEK inhibitors (MEKi), but none of the studies had biomarker selection. Pre-clinical studies in BTC cell lines suggest synergy between MEKi and 5-FU. Thymidylate synthase (TS )levels induced by 5-FU are downregulated by addition of binimetinib. Early clinical studies show safety and tolerance of this combination. In this study, we will evaluate if the combination of mFOLFOX6+binimetinib improves OS for patients with BTC and MAPK mutations compared to mFOLFOX6 alone in 2nd-line therapy. Methods: EAY191-A6 is a treatment study arm of the NCI ComboMATCH master registration trial EAY191. The A6 trial has a randomized phase II design, enrolling a maximum of 66 patients. Patients with any MAPK pathway mutations except those with available therapies will be eligible. Patient must first enroll to the EAY191 master trial. Local molecular results may be used for enrollment. Submission of tissue at baseline is mandatory. Eligible patients will be randomized 1:1 to mFOLFOX6 vs mFOLFOX6 + binimetinib (45 mg oral twice a day every 14 days). Stratification factors include location and stage of disease. Primary efficacy analysis will compare OS in the intent-to-treat population. If the observed hazard ratio (HR) of experimental arm vs standard of care is < 0.545 (corresponding to an observed increase in OS by 5 months or longer), experimental treatment will be considered superior. An interim futility analysis at 50% of expected events will be conducted. If the observed HR is ≥ 1, experimental treatment will not be considered superior, and accrual maybe suspended. Secondary endpoints include progression-free survival, objective response rate, duration of response, disease control rate and toxicity of treatments. Exploratory objectives include prognostic modeling, correlations of genomic alterations with response or resistance and use of machine learning for outcome prediction. This study is active and open to accrual. Clinical trial information: NCT05564403 .

11526 Background: There are no FDA-approved treatments for advanced cCS. Chemotherapy provides limited benefit. IDH1/2 mutations (m) occur in 50% of cCS. Both IDHm and wild-type cCS harbor epigenetic dysregulation. In preclinical models, HDAC + DNMT inhibition (i) suppressed growth by inducing apoptosis, reversing the hypermethylated state, and upregulating expression of interferon (IFN) response genes including PDL1(1). This prompted a phase 2 study of HDACi + DNMTi in cCS, which failed to meet the 1° endpoint of ORR. The majority of pts had a best response of stable disease, with a trend towards improved mPFS in IDHm (2). Here we report correlative analysis of NCI 10330. Methods: NCI 10330 is a single-arm, multicenter, phase 2 study of belinostat with SGI-110 or ASTX727 in advanced cCS. All pts were required to have pre- and on-treatment (tx) biopsies (Cycle 2, Day 3-5). Tissue was evaluated with whole exome sequencing (WES) and RNA sequencing (RNAseq). From RNAseq, Tumor Inflammation Signature Scores (TISS) and Tumor Microenvironment functional Gene Set Enrichment Analysis scores (TME GSEA) were calculated as the mean of the log2 normalized counts of 18 signature genes (Danaher et al. J Imm Can 2018) and pre-defined gene sets (3), respectively. Wilcoxon rank sum test was used to analyze TME GSEA between pre- and on-tx samples. Differential expression was significant if |FC| > 1.33, adjusted P <0.01. Results: 19 pts were treated; all received paired biopsies. WES was adequate in 7/19 (37%) pts, with IDHm identified in 3/7 (43%) pts. All pts were MSI-stable, TMB: 1.01-3.57 mut/Mb. RNAseq was adequate in 7/19 (37%) pts at pre-tx and 5/19 (26%) pts at on-tx. TISS ranges trended higher for pre-tx (8.77-10.14) vs on-tx (7.36-9.51) samples. TME GSEA identified significantly enriched tumor immune infiltration (p < 0.05) in pre- vs on-tx samples. Differential analysis identified several gene sets related to inflammation overexpressed in pre-tx samples only, including IFN response. On-tx samples were enriched in myogenesis and coagulation gene sets. Conclusions: This is the first study to describe transcriptomic changes following epigenetic tx in cCS. Contradictory to our preclinical data, HDACi + DNTMi resulted in low expression of inflammation. Prior studies reported that the immune infiltrate of CS at progression is immunosuppressive; higher immune infiltrate is correlated with worse outcomes (4). Loss of inflammation may have implications for disease stability experienced by most pts on NCI 10330. Further analyses are planned to correlate TME (pro- vs anti-inflammatory infiltrates) and outcomes. Analyses are limited by small sample size, highlighting the challenges in collecting adequate CS specimens. 1. Sheikh, Schwartz et al. Mol Cancer Ther 2021. 2. Lacuna et al. ASCO 2023: #11531. 3. Bagaev et al. Can Cell 2021. 4. Richert et al. J Bone Onc 2020. Clinical trial information: NCT04340843 .

11514 Background: The role of immunotherapy remains uncertain in most sarcomas. We recently showed significant antitumor benefit for cabozantinib (C) with N in AS previously treated with a taxane. Since chemotherapy-immunotherapy combinations may synergize, and paclitaxel remains a standard of care option for advanced AS, we hypothesized that P+N would be more effective than P alone. Methods: We report Arm 1 (P+N) and Arm 2 (P) of this open label, multi-arm, phase II study. Pts all had locally advanced/metastatic AS, and no prior taxane (including adjuvant) or checkpoint inhibitor prior to entry. Pts were randomized 1:1 (stratified scalp/face vs other) to receive P 80 mg/m2 on days 1, 8, 15 every 4 weeks (wks), with (Arm 1) or without (Arm 2) N (480 mg intravenously every 4 wks). A pt could remain on study beyond disease progression (PD), after the initial 12 wk evaluation (4 wk confirmatory scan required), but responses were censored at 12 wks. Primary endpoint was progression-free survival (PFS) comparing P+N to P, with an assumed improvement from a median of 4 to 7 months with N added to P (power = 85.3%, alpha = 0.148, and one interim analysis (Wieand rule) for futility planned after 30 events). Secondary endpoints were overall response rate (ORR), adverse events (AEs), overall survival (OS), and pt reported outcomes (PRO). At PD, Arm 2 (P) pts were permitted to receive C+N. Results: 62 evaluable pts (P+N = 30, P = 32 pts) were balanced for age, race, ECOG PS 0 vs. 1, site of disease (including radiation related vs. not), while P+N had more females (60%) and P had more males (63%). Median PFS for P+N was 7.2 mo (5.3-17 mo), and 8.3 mo (4.0-18 mo) for P (hazard ratio (HR) 1.01 (95%CI: 0.55-1.9), p = 0.96). Median PFS for scalp/face was 16 mo (95%CI: 10-NR) for P+N and 8.3 mo (95%CI: 3.7-NR) for P. Median PFS for all others was 5.5 mo (95%CI 4.3-16) for P+N, and 6.0 mo (95%CI 4.1-NR) for P. Median OS was 18 mo (13-NR) in P+N, and 23 mo (15-NR) in P (HR 1.3 (95%CI: 0.63-2.7), p = 0.48). Overall confirmed ORR: P+N = 33% (10/30 pts, with 4 partial responses (PR) and 6 complete responses (CR) with scalp/face ORR = 73%, all others ORR = 11%). Overall ORR for P = 34% (11/32 pts, with 7 PR and 4 CR, with scalp/face ORR = 38%, all others ORR = 26%). Grade 3-4 AEs regardless of attribution occurred in 57% of P+N, and 44% of P, most commonly ( > 10%) fatigue, AST increase, and dyspnea for P+N (n = 3 each), and anemia (n = 4) for P. Conclusions: P alone can be an effective therapy in a subset of pts with AS. The combination of P+N failed to demonstrate improvement in median PFS over P alone, but may show benefit in scalp/face AS. OS trended better with P alone. No new safety signals were observed. The impact of weekly steroid premedication prior to P+N on these outcomes remains to be determined. PRO and exploratory analyses are ongoing. Support: U10CA180821, U10CA180882, U24 CA196171; NCT04339738. https://acknowledgments.alliancefound.org . Clinical trial information: NCT04339738 .

PURPOSE This multicenter, single-arm, open-label, phase Ib study was designed to determine the recommended phase II dose (RP2D) and to evaluate the safety and preliminary efficacy of unesbulin plus dacarbazine (DTIC) in patients with advanced leiomyosarcoma (LMS). PATIENTS AND METHODS Adult subjects with locally advanced, unresectable or metastatic, relapsed or refractory LMS were treated with escalating doses of unesbulin orally twice per week in combination with DTIC 1,000 mg/m2 intravenously (IV) once every 21 days. The time-to-event continual reassessment method was used to determine the RP2D on the basis of dose-limiting toxicities (DLTs) assessed during the first two 21-day treatment cycles. All explored doses of unesbulin (200 mg up to 400 mg) were in combination with DTIC. An expansion cohort was enrolled to evaluate the safety and efficacy of unesbulin at the RP2D. RESULTS Unesbulin 300 mg administered orally twice per week in combination with DTIC 1,000 mg/m2 IV once every 21 days was identified as the RP2D. On the basis of data from 27 subjects who were deemed DLT-evaluable, toxicity was higher in the unesbulin 400 mg group, with three of four subjects (75%) experiencing DLTs versus one of four subjects (25%) in the 200 mg group and three of 19 subjects (15.8%) in the 300 mg group. The most commonly reported DLTs and treatment-related grade 3 and 4 adverse events were thrombocytopenia and neutropenia. At the RP2D, seven subjects who were efficacy evaluable achieved partial response for an objective response rate of 24.1%. CONCLUSION Unesbulin 300 mg twice per week plus DTIC 1,000 mg/m2 once every 21 days was identified as the RP2D, demonstrating a favorable benefit-risk profile in a heavily pretreated population of adults with advanced LMS.