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A phase Ib trial evaluating the safety, efficacy, and immunologic effects of pembrolizumab plus paclitaxel or flat-dose capecitabine in 1st/2nd line metastatic triple-negative breast cancer

ABSTRACT: Chemoimmunotherapy with anti-programmed cell death 1/ligand 1 and cytotoxic chemotherapy is a promising therapeutic modality for women with triple-negative breast cancer, but questions remain regarding optimal chemotherapy backbone and biomarkers for patient selection. We report final outcomes from a phase Ib trial evaluating pembrolizumab (200mg IV every 3 weeks) with either weekly paclitaxel (80mg/m2 weekly) or flat-dose capecitabine (2000mg orally twice daily for 7 days of every 14-day cycle) in the 1st/2nd line setting. The primary endpoint is safety (receipt of 2 cycles without grade III/IV toxicities requiring discontinuation or ≥21-day delays). The secondary endpoint is efficacy (week 12 objective response). Exploratory aims are to characterize immunologic effects of treatment over time, and to evaluate novel biomarkers. The trial demonstrates that both regimens meet the pre-specified safety endpoint (paclitaxel: 87%; capecitabine: 100%). Objective response rate is 29% for pembrolizumab/paclitaxel (n=4/13, 95% CI: 10-61%) and 43% for pembrolizumab/capecitabine (n=6/14, 95% CI: 18-71%). Partial responses are observed in two subjects with chemo-refractory metaplastic carcinoma (both in capecitabine arm). Both regimens are associated with significant peripheral leukocyte contraction over time. Response is associated with clinical PD-L1 score, non-receipt of prior chemotherapy, and the H&E stromal tumor infiltrating lymphocyte score, but also by a novel 27 gene IO score and spatial biomarkers (lymphocyte spatial skewness). In conclusion, pembrolizumab with paclitaxel or capecitabine is safe and clinically active. Both regimens are lymphodepleting, highlighting the competing immunostimulatory versus lymphotoxic effects of cytotoxic chemotherapy. Further exploration of the IO score and spatial TIL biomarkers is warranted.

ORGANISM(S): Homo sapiens

PROVIDER: GSE225078 | GEO | 2023/02/17

REPOSITORIES: GEO

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Project description:Background: Although immunotherapy has not yet been as successful in ovarian cancer (OC), it remains a potential therapeutic strategy. Preclinical models of OC are necessary to evaluate the efficacy of immuno-oncology (IO) drugs targeting human cancer and immune components but have been underutilized. Developing mouse models with a humanized (Hu) immune system can help understand the human immune response to IO drugs, including immune checkpoint inhibitors (ICIs), which have demonstrated limited effectiveness in OC patients. Methods: We established OC xenograft Hu-mouse models by intraperitoneally injecting luciferase-expressing SKOV-3 Luc and OVCAR-3 Luc OC cells into CD34+ Hu-mice. Tumor growth was monitored through bioluminescence imaging (BLI). We assessed the efficacy of PD-1 blockade with pembrolizumab in the SKOV-3 Luc Hu-mouse model. The immune profiles of the tumors were characterized using colorimetric immunostaining and flow cytometry. Additionally, we analyzed RNA-seq data to investigate the gene expression signature of pembrolizumab refractory tumors. Results: We confirmed tumor development in both OC cell lines within CD34+ Hu-mice. In these models, human lymphocyte and myeloid cell subsets were present in the tumors, draining lymph nodes, blood, and spleens. The SKOV-3 Luc tumor-bearing Hu-mice did not respond to pembrolizumab monotherapy. These tumors exhibited a high presence of tumor-infiltrating macrophages. Tumors in Hu-mice unresponsive to pembrolizumab showed a lower abundance of CD8+ T-cells, memory B cells, plasma cells, and a higher proportion of naïve M0 macrophages and mast cells compared to the PBS control. Furthermore, we identified 43 significantly enriched gene sets in these tumors. The differentially expressed genes (DEGs) were predominantly enriched in HDAC class I, RB1, KLF1/3, TCF21, MYD88, SMARCE1 target genes, and genes associated with epithelial-mesenchymal transition (EMT) and fibroblasts. Conclusion: Our xenograft Hu-mouse model of OC provides a valuable tool for investigating the efficacy of IO drugs. The insights gained from this model offer potential avenues to explore mechanisms of resistance to PD-1/PD-L1 blockade in OC.

Project description:Despite decades of effort, pancreatic adenocarcinoma (PDAC) remains an intractable clinical challenge. An insufficient understanding of mechanisms underlying tumor cell responses to chemotherapy contributes significantly to the lack of effective treatment regimens. Here, paclitaxel, a first-line chemotherapeutic agent, was observed to interact synergistically with birinapant, a Second Mitochondrial-derived Activator of Caspases mimetic. Therefore, we investigated molecular-level drug interaction mechanisms using comprehensive, reproducible, and well-controlled ion-current-based MS1 quantification (IonStar). In a set of 40 biological samples, we compared temporal proteomic responses of PDAC cells treated with birinapant and paclitaxel, alone and combined. Using stringent criteria (e.g. strict false-discovery-rate FDR control, 2 peptides/protein), we quantified 4069 unique proteins confidently (99.8% without any missing data), and 541 proteins were significantly altered in the three treatment groups with a FDR of <1%. Interestingly, most of these proteins were altered only by combined birinapant/paclitaxel, and these predominantly represented three biological processes: mitochondrial function, cell growth and apoptosis, and cell cycle arrest. Proteins responsible for activation of oxidative phosphorylation, fatty acid β-oxidation, and inactivation of aerobic glycolysis were altered largely by combined birinapant/paclitaxel compared to single drugs, suggesting that the Warburg effect, which is employed by PDAC cells for survival and proliferation, was alleviated by the combination treatment. Metabolic profiling confirmed substantially greater suppression of the Warburg effect by the combined agents compared to either drug alone. Western blot analysis confirmed changes in apoptosis/survival signaling pathways, such as inhibition of PI3K/AKT, JAK/STAT, and MAPK/ERK signal transduction, as well as induction of G2/M arrest, and the drug combination induced much more apoptosis than did single agents. Overall, this in-depth, large-scale proteomics study provided novel insights into molecular mechanisms underlying synergy of combined birinapant/paclitaxel, and describes a proteomics/informatics pipeline that can be applied broadly to the development of cancer drug combination regimens.

Dataset Information

A phase Ib trial evaluating the safety, efficacy, and immunologic effects of pembrolizumab plus paclitaxel or flat-dose capecitabine in 1st/2nd line metastatic triple-negative breast cancer

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