Labadie, Brian

TPS4208 Background: Metastatic pancreatic ductal adenocarcinoma (mPDAC) carries a 5-year relative survival of 3%. Immune checkpoint inhibitors have thus far failed to improve outcomes due to an immunosuppressive tumor microenvironment (TME). Signaling through the C-X-C motif chemokine receptor 4 (CXCR4)/C-X-C motif chemokine ligand 12 (CXCL12) axis results in exclusion of anti-tumor immune cells in mouse PDAC models. Longitudinal survival studies testing combinations of CXCR4i, aPD-1, and gemcitabine in the KPC mouse model of PDAC demonstrated a survival benefit with the combination of all three agents. Results from a multicenter, investigator-initiated, single arm pilot study evaluating the preliminary safety and efficacy ofMotixafortide (CXCR4i), Cemiplimab (aPD1), Gemcitabine, and Nab-paclitaxel (MCGN) in 11 patients with treatment-naïve mPDAC were recently presented. Seven patients (64%) achieved a partial response, including 6 confirmed partial responses, and 10 patients (91%) had disease control, compared to historic partial response and disease control rates of 23% and 48%, respectively, with gemcitabine and nab-paclitaxel (GN). Preliminary median progression-free survival (PFS) was 9.6 months compared to historic median PFS of 5.5 months with GN. Analysis of paired pre- and on-treatment biopsy samples from demonstrated an increase in CD8+ T-cell density in tumors from all 11 patients treated with MCGN (p=0.007). Based on these promising results, the protocol was amended from a single arm expansion totaling 40 patients to a randomized phase 2 study. Methods: This is an open-label, multicenter, investigator-initiated phase 2 clinical trial. Patients are randomized 2:1 to receive MCGN or GNalone (N=108). The primary endpoint is progression free survival. The study has 80% power to detect an improvement in PFS from 6 to 9.2 months (HR 0.65) with a one-sided alpha of 0.20. One interim analysis for futility is planned when 50% of the PFS events are observed. Secondary objectives include response rate, disease control rate, duration of clinical benefit and overall survival. Patients will undergo optional paired biopsies which will be analyzed in conjunction with samples collected from the phase I pilot study. Exploratory studies include interrogation of the TME using quantitative multiplex immunofluorescence and single-cell RNA sequencing. The randomized phase 2 trial is open to enrollment and one patient has been randomized as of 1/29/2024. Clinical trial information: NCT04543071 .

Uveal melanoma is a rare form of melanoma with particularly poor outcomes in the metastatic setting. In contrast with cutaneous melanoma, uveal melanoma lacks BRAF mutations and demonstrates very low response rates to immune-checkpoint blockade. Our objectives were to study the transcriptomics of metastatic uveal melanoma with the intent of assessing gene pathways and potential molecular characteristics that might be nominated for further exploration as therapeutic targets. We initially analyzed transcriptional data from The Cancer Genome Atlas suggesting PI3K/mTOR and glycolysis as well as IL6 associating with poor survival. From tumor samples collected in a prospective phase II trial (A091201), we performed a transcriptional analysis of human metastatic uveal melanoma observing a novel role for epithelial-mesenchymal transition associating with survival. Specifically, we nominate and describe initial functional validation of neuropillin-1 from uveal melanoma cells as associated with poor survival and as a mediator of proliferation and migration for uveal melanoma in vitro. These results immediately nominate potential next steps in clinical research for patients with metastatic uveal melanoma.

Abstract Purpose: The surface receptor MET is highly expressed on primary uveal melanoma; MET inhibitors demonstrated early clinical signals of efficacy in slowing uveal melanoma growth. The primary objective of our study was to compare the progression-free survival rate at 4 months (PFS4) of patients with uveal melanoma treated with cabozantinib or chemotherapy. Patients and Methods: Patients with metastatic uveal melanoma and RECIST measurable disease were randomized 2:1 to receive either cabozantinib (arm 1) versus temozolomide or dacarbazine (arm 2) with restaging imaging every two cycles. Cross-over from arm 2 to cabozantinib after progression was allowed (arm 2X). Available tumor specimens were analyzed by whole-exome sequencing (WES) and results were correlated with outcome. Results: Forty-six eligible patients were accrued with 31, 15, and 9 in arms 1, 2, and 2X, respectively. Median lines of prior therapy, including hepatic embolization, were two. Rates of PFS4 in arm 1 and arm 2 were 32.3% and 26.7% (P = 0.35), respectively, with median PFS time of 60 and 59 days (P = 0.964; HR = 0.99). Median overall survival (OS) was 6.4 months and 7.3 months (P = 0.580; HR = 1.21), respectively. Grade 3–4 Common Terminology Criteria for Adverse Events were present in 61.3%, 46.7%, and 37.5% in arms 1, 2, and 2X, respectively. WES demonstrated a mean tumor mutational burden of 1.53 mutations/Mb and did not separate OS ≤ or >1 year (P = 0.14). Known mutations were identified by WES and novel mutations were nominated. Conclusions: MET/VEGFR blockade with cabozantinib demonstrated no improvement in PFS but an increase in toxicity relative to temozolomide/dacarbazine in metastatic uveal melanoma.

9506 Background: Survival is poor in mUM and treatment options are limited. MET kinase is over-expressed on UM and the MET inhibitor cabo showed activity in an early trial. Methods: A091201 was a 2:1 randomized phase II study testing progression-free survival (PFS) of cabo (60 mg daily) vs chemo (DTIC/TMZ). We studied baseline metastatic tumor samples (n = 19; 1 lung, 18 liver) by whole exome sequencing (WES) and RNAseq. We correlated data with OS and made comparisons for mUM vs. primary tumors from TCGA (n = 80). Results: 46 patients were accrued with 96% and 63% with liver metastases and elevated LDH, respectively. Toxicities were similar to prior reports of cabo and chemo. The trial stopped at interim analysis due to no difference in PFS (p = 0.964; HR = 0.99) or OS (p = 0.580; HR = 1.21). WES showed tumor mutational burden of 46±4 (mean±SEM) and did not separate OS at 1 year (p = 0.14, two-sided Wilcoxon rank sum test) in A091201. Recurrent known mutations included GNAQ/11, SF3B1, BAP1; novel mutations included GOLGA6L10, PKD1L3, and FAM228B. Gene expression signatures differed significantly between A091201 and TCGA cohorts including MET signaling (p = 7.87e-22), T cell-inflamed (p = 0.004), homologous recombination deficiency (p = 0.004), proliferation (p = 0.009) and hypoxia (p = 5.2e-10) (two-sided Student’s t-test). Tumor immune cell enrichment analysis revealed significant differences with lower M1:M2 macrophage (p = 1.2e-10) and higher Tregs (p = 6.0E-21) in mUM relative to TCGA (two-sided Wilcoxon rank sum test). Epithelial-mesenchymal transition gene expression signature was significantly associated with worse OS in A091201 (p = 0.02) with angiogenesis signature trending toward significance (p = 0.21) (log-rank test). OS separated by differentially expressed genes with OS ≤ 1 year associating with increased expression of the angiogenesis/immune-associated molecule neuropilin 1. Conclusions: These results provide insights between primary and mUM indicating potential novel therapeutic approaches. Support: U10CA180821, U10CA180882, T32GM007019, Exelixis. https://acknowledgments.alliancefound.org ; Clinical trial information: NCT01835145.