Seetharam, ­Mahesh

Background/Objectives: Chordoma, a rare slow-growing malignant bone tumor, remains therapeutically challenging due to its invasive nature. We examined institutional outcomes comparing imatinib and brachyury-directed vaccines. Methods: We used data from three sites of our quaternary care academic institution to analyze demographics, time to progression, overall survival, and adverse events in chordoma patients treated with imatinib or enrolled in a brachyury vaccine trial. Results: We included a total of 52 patients (8 in the brachyury vaccine cohort and 44 in the imatinib cohort) in the analysis. As expected, sacrococcygeal location was the most predominant in both cohorts: 62.5% in the brachyury cohort and 45.5% in the imatinib cohort. No demographic differences were present between the cohorts. ECOG was similar in both groups (p = 0.796). The primary outcome, time to progression (TTP), was shorter in the brachyury compared to the imatinib cohort (5.6 vs. 13 months, p = 0.0589), almost reaching statistical significance. Overall survival (OS) was comparable, 211 vs. 212 months for the brachyury and imatinib cohorts, respectively (p = 0.277). Although the brachyury vaccine cohort presented a higher incidence of adverse events than the imatinib cohort (75% vs. 31.8%, p = 0.021), the severity was milder. Conclusions: Imatinib showed longer disease control than the brachyury vaccine, though overall survival was similar. Future studies and deeper molecular insights are essential to develop better therapies and improve patient quality of life.

11506 Background: Catequentinib Hydrochloride (AL3818, Anlotinib, Catequentinib) is a novel, orally administered, small molecule tyrosine kinase inhibitor. There remains an unmet need for effective, well tolerated therapies for patients (pts) with advanced/ metastatic leiomyosarcoma (LMS). We performed a randomized, double blind trial of Catequentinib monotherapy versus placebo in advanced/metastatic LMS. Methods: Patients with a diagnosis of LMS requiring third or further line treatment were eligible. Catequentinib was administered in a 21-day cycle with 14 days on and 7 days off regimen. In this double blind phase 3 trial, patients were randomized 2:1 to Catequentinib or placebo, with the option of crossover to Catequentinib after confirmed Progression Disease (PD) on placebo. Progression-free survival (PFS) with Log Rank test was the primary endpoint and the trial was conducted at multiple sites in the US, UK and EU. Results: Total N = 111 patients were enrolled, and N = 110 were treated and evaluated, 74 randomized to Catequentinib (C), and 36 to placebo (P). In arms (C)/(P) median ages were 59.0/60.5 (range: 33-91) years respectively and 59/29 (79.7%/80.6%) were female. Median PFS by Blinded Independent Central Review (BICR) met the primary endpoint at 3.42 months (95% CI: 2.60, 6.83) for (C) and 1.41 months (95% CI: 1.35, 4.86) for (P) with a p-value of 0.0265 and a HR of 0.536 (95% CI: 0.307, 0.936). Median PFS for patients stratified at ≤ 3 prior lines was 4.86 months (95% CI: 2.04, 8.94) for (C) and 1.41 months (95% CI: 1.31, 4.86) for (P) with a p-value of 0.0046 and a HR of 0.386 (95% CI: 0.196, 0.760). The 6-month progression-free rate was 42.37% for (C) and 20.71% for (P). OS was 17.45 months (95% CI: 13.57, 19.32) for (C) and 16.33 months (95% CI: 11.27, NE) for crossover patients in the (P) arm. 30 (40.5%) of patients have experienced grade 3 treatment-related adverse events in the (C) arm compared to 3 (8.3%) of patients in the (P) arm. The most common TEAE for (C) vs (P) were diarrhea (50.0% vs 22.2%), stomatitis (31.1% vs 8.3%), fatigue (64.9% vs 41.7%), and hypertension (47.3% vs 19.4%). Conclusions: This phase 3 trial met the primary PFS endpoint and demonstrates superior PFS for Catequentinib vs placebo in metastatic/advanced LMS. This study confirms the acceptable benefit-risk profile of Catequentinib in LMS. Catequentinib is an effective and well tolerated treatment option for patients with LMS. Clinical trial information: NCT03016819 .

3116 Background: Pralsetinib is an oral tyrosine kinase inhibitor that selectively and potently targets oncogenic RET fusion and mutation proteins. RET fusions or mutations are present in various tumor types. We report the final results from the phase 2 portion of ARROW, a phase 1/2, open-label, multi-cohort, dose-expansion study evaluating the efficacy and safety of pralsetinib (NCT03037385) in patients with RET fusion-positive solid tumors other than non-small-cell lung cancer (NSCLC) and thyroid cancer. Methods: Eligible pts were ≥18 years of age with a pathologically documented, definitively diagnosed advanced solid tumor with an oncogenic RET fusion or mutation, had previously received standard of care appropriate for their tumor type, and were not eligible for any other study groups. Overall response rate (ORR) and safety were primary endpoints of the study. Key secondary endpoints included duration of response (DOR), progression-free survival (PFS), and overall survival (OS). The final database lock was May 20, 2024. Results: Twenty-nine patients were enrolled with 11 different solid tumor histologies. Twenty-six (90%) received prior systemic therapy. Median age was 58 years (range 25-75); 59% were female. Twenty-eight patients were included in the efficacy analysis. ORR (by RECIST) was 46.4% (13/28); 10.7% (3/28) achieved complete response (pancreatic cancer, n=2; cancer of unknown primary, n=1) and 35.7% (10/28) achieved partial response. Median PFS was 7 months (95% CI: 3.9, 12.8). Median DOR was 11.1 months (95% CI: 5.5, 25.1). Median OS was 10.3 months (95% CI: 6.8, 25.2). Twenty-five (86%) patients experienced treatment-related adverse events (TRAEs); 19/29 (66%) reported TRAEs ≥grade 3. The most common TRAEs included increased aspartate aminotransferase (11/29; 38%), increased alanine aminotransferase (10/29; 35%), and anemia (9/29; 31%). Four (13.8%) patients experienced hypertension, and 1 (3.4%) patient had ≥grade 3 hypertension. No new safety risks were identified; AEs remained manageable with supportive care and/or dose modifications. Conclusions: In the phase 2 portion of this trial, responses were observed in many tumor types (Table). Pralsetinib demonstrated robust and durable anti-tumor activity with an ORR of 46.4%. These data validate RET fusions as a tissue-agnostic target with sensitivity to RET inhibition and activity beyond NSCLC and thyroid cancer, further supporting the promising potential of pralsetinib to address the unmet medical need in these patients. Clinical trial information: NCT03037385 . Overall response rate by tumor type. Cancer Type (patient n) ORRn (%) Pancreatic (5) 5 (100) Cancer of unknown primary (1) 1 (100) Neuroendocrine (3) 2 (67) Sarcoma (3) 2 (67) Head and neck (2) 1 (50) Small cell lung (2) 1 (50) Hepatobiliary (4) 1 (25) Colorectal (5), gastric (1), ovarian (1), thymic (1) 0

Sarcomas are rare heterogenous mesenchymal tumors with over seventy-five different subtypes, with varying biology and outcomes, with no clear inciting factor in the vast majority. To determine the prevalence of pathogenic germline variants (PGV) in patients with sarcomas, we undertook a prospective multi-site study of germline sequencing using an 84-gene next-generation sequencing panel among patients receiving care at the four Mayo Clinic Cancer Centers. Of 115 patients with bone and soft tissue sarcoma, the median age was 60 years, 49.6% were female, 82.6% were White. The anatomical location of the primary tumor included extremities (34.8%), retroperitoneum (19.1%), trunk (13.0%), and head and neck (7.8%). Family history of cancer was present in 62.6% of the study population. Ten patients (8.7%) had a pathogenic/likely pathogenic variant (PGV). Of these, three had stage IV sarcoma, and seven had earlier-stage sarcoma (stages I–III). Among the 55 (48.7%) patients who had variant of uncertain significance (VUS), 41.1% (22/55) had stage IV sarcoma and 58.9% (33/55) had earlier-stage disease. Of the ten patients with PGV, high-to-moderate penetrance gene abnormalities were identified in eight patients (80%) involving TP53 (3), BRCA1 (1), SDHA (1), ATM (2), and NBN (1) genes. The vast majority of the PGVs (70%) would not have been detected using the current guidelines. Because of the paucity of sarcomas and lack of effective treatment options for advanced disease, germline testing in sarcomas represents a potentially impactful strategy to assess therapeutic options and for assessment of familial risk.

Melanoma is the deadliest form of skin cancer. The median age at diagnosis is 66. While most patients are treated with immunotherapy, the use of targeted therapy is a valid alternative for patients whose tumors harbor a BRAF or c-KIT driver mutation. These agents, while effective, come with a variety of side effects which limit their use, especially in older patients. We sought to assess the efficacy and toxicity of these agents in older melanoma patients. Melanoma patients over 65 treated with BRAF/MEK or c-KIT inhibitors were retrospectively identified, and their data were analyzed for treatment efficacy and toxicity. All data were compared using the Chi-square test for categorical comparisons and the Kruskal–Wallis method for median comparisons. One hundred and sixteen patients were identified. One hundred and six patients were treated with BRAF/MEK inhibitors. The assessed response rate (RR) was 83% and was comparable across different subgroups, including advanced line patients and those with a more aggressive disease. The median progression free survival (PFS) was 7.9 months, and the median overall survival (OS) was 15.7 months. Twenty-seven percent experienced grade 3–4 toxicity leading to a 24% treatment discontinuation rate. Another 10 patients were treated with the c-KIT inhibitor imatinib, for whom the assessed RR was 55%. The median PFS was 4.3 months, and the median OS was 22.6 months. Forty percent needed dose reductions, yet none had to stop treatment due to adverse effects. The use of targeted therapy in older patients is effective yet challenging due to toxicity. Deploying mitigation strategies can help maximizing their usefulness.

AbstractBackgroundThis was a single‐arm, phase 2 clinical trial of Bavarian Nordic (BN)‐Brachyury vaccine plus radiotherapy (RT) designed to determine the objective response rate (ORR), progression‐free survival (PFS), and safety of the combination in chordoma.MethodsA total of 29 adult patients with advanced chordoma were treated with two subcutaneous priming vaccine doses of modified vaccinia Ankara‐Bavarian Nordic (MVA‐BN)‐Brachyury and one vaccine dose of fowlpox virus (FPV)‐Brachyury before RT. After RT, booster vaccinations were given with FPV‐Brachyury every 4 weeks for 4 doses, then every 12 weeks (week 110). A minimum RT dose of >8 Gy in one fraction for each target was required. Response was evaluated by modified Response Evaluation Criteria in Solid Tumors 1.1 (mRECIST), where only radiated lesions were considered targets, and by standard RECIST 1.1 in a subset of patients.ResultsTwo of 26 evaluable patients experienced durable partial response (PR) (ORR of 7.7%; 90% confidence interval [CI], 2.6–20.8]) by mRECIST 1.1. A total of 21 patients (80.8%; 90% CI, 65.4–90.3) had stable disease, and three patients (11.5%; 90% CI, 4.7–25.6) had progressive disease as best response per mRECIST 1.1. Median PFS was not reached during the study.ConclusionsThis trial confirms the safety of BN‐Brachyury and RT. Although the study did not meet the predefined study goal of four responses in 29 patients, we did observe two PRs and a PFS of greater than 2 years. For a vaccine‐based study in chordoma, an ultra‐rare disease where response rates are low, a randomized study or novel trial designs may be required to confirm activity.

2598 Background: GI-102 (CD80-IL2v3) is a novel immunocytokine designed to direct IL-2v3 to immune cells and tumor cells. IL-2v3 of GI-102 abolished affinity to IL-2Rα minimizing the impact of IL-2 on Treg cells. Preferential targeting of immune cells and further inhibition of CTLA-4 and PD-L1 via CD80 synergize with potent activity of IL-2v3, resulting in robust proliferation and activation of CD8+ T and NK cells. Here we report preliminary safety and efficacy data of GI-102 from a phase 1/2a trial in patients with metastatic solid tumors. Methods: NCT05824975 is an ongoing, dose escalation (3+3 design) and expansion study to evaluate safety, tolerability, PK, PD and anti-tumor activity of GI-102. Each dose level allows to enroll additional 7 patients to fully inform the safety, PK and PD at that dose level. GI-102 was administered intravenously every 3 weeks until disease progression or unacceptable toxicities. Disease was assessed every 6 weeks using RECIST v1.1. Results: As of 12 Jan 2024, 32 patients were treated in dose escalation: 8 at dose level 0.06 mg/kg, 10 at 0.12 mg/kg, 9 at 0.24 mg/kg and 5 at 0.45 mg/kg. Patients had received median of 3 [1-7] prior lines of therapy, including 25.0% (8/32) who had received ≥ 5 lines and 68.8% (22/32) had experienced immune checkpoint blockade (ICB). No dose-limiting toxicities (DLTs) were observed until the highest dose of 0.45 mg/kg Q3W. The most common treatment-related adverse events (TRAEs, ≥ 10%) were pyrexia [43.8%] and chills [34.4%]. 5 patients [15.6%] had ≥ Grade 3 TRAEs and no patient reported TRAEs leading to discontinuation of GI-102. In 23 patients (7 cutaneous melanoma, 4 non-small cell lung cancer, 3 ovarian cancer and others) who had at least 1 post-treatment tumor assessment, objective responses were observed in 17.4% (4/23). In patients with metastatic melanoma who previously experienced ICB, overall response rate (ORR) and disease control rate (DCR) was 42.9% (3/7) and 85.7% (6/7), respectively, including 3 confirmed partial responses (cPR). The median time to response (TTR) was 6 weeks and duration of response (DoR) was 6.0+, 2.4+ and 1.7+ month, respectively. In patients with metastatic ovarian cancer, ORR and DCR were 33.3% (1/3) and 66.7% (2/3), respectively, including 1 cPR [TTR of 6 weeks; DoR 1.9+ month]. Preliminary PK profile showed target-mediated drug disposition with a half-life of ~48 hours. 0.24 mg/kg of GI-102 resulted in a significant expansion of peripheral lymphocytes, CD8+ T cells (effector & memory) and NK cells, by 4.4 [2.1-9.6], 3.9 [2.0–5.7] and 20.4 [9.5–32.6]-fold change from baseline, respectively. There was no meaningful increase in Treg cells. Conclusions: GI-102 was well tolerated up to dose of 0.45 mg/kg Q3W with meaningful monotherapy activity, regardless of previous ICB experience, in patients who failed on standard of care. The dose-escalation is currently ongoing to identify RP2D. Clinical trial information: NCT05824975 .

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 .

e23270 Background: Melanoma is the most lethal form of skin cancer which have seen drastic improvement in patient survival over the last decade. BRAF is the most common driver mutation in melanoma, seen in ≈50% of all patients (≈30% of patients > 65). The use of BRAF & MEK inhibitors yields high response rates, though it is limited by toxicity and development of acquired resistance. Acknowledging these limitations, we aimed at assessing the efficacy and toxicity of these agents in melanoma patients > 65. Methods: We identified electronic medical records of all melanoma patients > 65 that were treated with BRAF & MEK inhibitors at our institution over the years 2017-2023. Data was retrospectively collected including demographics, disease characteristics, treatment given, response patterns and toxicity. Results: 106 patients were identified. The median age was 71 (65-89), 55% were males. The median follow up was 28.9 months. 32 (30%) patients were treated at first line, 58 (55%) at second line and 16 (15%) at third line. 88 (83%) evaluable patients received treatment for unresectable/metastatic disease of which 84% had an objective response (60% partial response, 24% complete response). Response rate (RR) was 82%, 85% and 87% for first, second and third line respectively. RR was 86% for patients with an increased serum lactate dehydrogenase. 33% of patients had active central nervous system (CNS) metastases at treatment initiation, for whom the systemic RR was 80% and the CNS RR was 39%. The median progression free survival (PFS) was 7.9 months, with a PFS of 6, 8.3 and 13.4 months for first, second and third line respectively. The median PFS was 5.7 months for patients with active CNS disease. The median overall survival (OS) from treatment initiation was 15.7 months (12.5, 14.5, 31.9 for first, second & third line respectively). The median OS for patients with CNS disease was 9.8 months. 16 patients were treated in the adjuvant setting, of which 6 (37%) finished treatment as planned, 3 stopped due to disease progression (19%) and 6 stopped due to toxicity (37%). 88% of patients experienced adverse events (AEs) of any grade, with 27% having grade 3-4 toxicity. There were no grade 5 toxicities reported. 36% of patients experienced one AE, while 52% experienced two or more. 21% of patients stopped treatment due to toxicity, 28% needed a dose reduction and 20% changed to different BRAF/MEK inhibitors. 10% of patients needed systemic corticosteroids to treat AEs. The most common toxicities seen were fever (30%), fatigue (30%), skin rash (22%), elevated liver function tests (20%), arthralgia/myalgia (15%), nausea (14%) and diarrhea (11%). 7% had decrease in cardiac ejection fraction with one grade 3 leading to treatment discontinuation. Conclusions: Treatment with BRAF & MEK inhibitors is challenging in older patients, with a high prevalence of toxicity leading to treatment modifications and discontinuation. Efficacy seems to be the same as in the general population.

e23269 Background: Most cases of malignant melanoma are cutaneous, with ≈50% having a BRAF driver mutation that predicts response to MAPK pathway inhibitors. A small minority of melanoma cases harbor an activating KIT mutation, most notably in mucosal and acral melanomas (15-20%) and occasionally in those arising from chronic sun-damaged skin (2-3%). Only about a third of KIT mutated melanomas respond to targeted therapy with Imatinib, yet data is scarce and limited, especially in older patients. We sought to characterize the efficacy and toxicity of Imatinib in KIT-mutated melanoma patients over 65. Methods: We identified electronic medical records of patients over 65 that were treated with Imatinib for KIT mutated melanoma at our institution over the years 2017-2023. Data was retrospectively collected including demographics, disease characteristics, response patterns and toxicity. Results: 10 patients were identified, 50% were males. The median age at treatment initiation was 75 years (71-100). 3 patients had cutaneous primary, 3 had Vulvar/vaginal primary, 3 had acral primary and 1 had anal canal primary. All patients had normal Lactate dehydrogenase at treatment initiation and ECOG performance status was 0-2 (median 0). 9 patients received Imatinib for stage IV disease with an overall response rate (ORR) of 55% (44% partial response, 11% complete response). Median duration of response was 4 months. Responses were seen in acral melanoma (67%), vulvar/vaginal melanoma (67%) and cutaneous melanoma (33%). Median Progression free survival was 4.3 months (1.8-44), median overall survival from treatment initiation was 22.6 months (4-64). 6 patients were treated as 2nd line with an ORR of 67% and 3 were treated as 3rd line with an ORR of 33%. There was one patient with M1d disease who did not respond to treatment either systematically or intracranially. 6 patients had Exon 11 mutations (V560D/G/E, N564S and L576P) of which 4 responded (67%). 2 had Exon 17 mutations (N822C/K) of which 1 responded (50%) and the 2 others had an Exon 14 (F681I) and Exon 13 (K642E) mutation that did not respond to treatment at all. Toxicity was moderate with 90% of patients experiencing any grade AE, yet only 1 experienced toxicity requiring dose interruption with two Grade 3 toxicities - Pneumonitis and decreased neutrophil count, leading to temporary treatment interruption, dose reduction and a course of corticosteroids. The rest of the patients experienced only Grade 1-2 toxicity. 4 patients needed dose reductions, there were no treatment discontinuations due to toxicity. Conclusions: Treatment with Imatinib for elderly KIT mutated melanoma patients is safe and well tolerated with no treatment discontinuations recorded. The response rate is encouraging yet seems to vary according to the KIT mutation present as previously reported. The duration of response is usually short-lived and alternative/combination treatments are still needed for this patient population.