Abstract CT204: High cytotoxic T-cell or polymorphonuclear cell infiltrates in the tumor microenvironment correlate with responses to BL8040 plus pembrolizumab combination therapy in metastatic pancreatic tumors: Scientific correlates of a phase II clinical trial

Background: We recently conducted a clinical trial assessing Pembrolizumab (P) and BL-8040 (BL) in patients with pancreatic cancer. We prospectively collected serial biopsies to help understand the impact of this treatment on the tumor microenvironment (TME). Methods: Twenty patients were enrolled and were treated with BL8040 (1.25mg/kg) monotherapy for 2 weeks followed by dual therapy with BL8040 (d1, 4, 8, 11) plus Pembrolizumab (200 mg IV, d1) every 3 weeks. Biopsies were collected at baseline (T0) and during therapy. Some patients had biopsies after BL monotherapy (Tm) and some after combined therapy (Tc) due to a protocol change mid-study. Malignant cells expressing PD-L1 were assessed using immunohistochemistry (IHC) and TME was studied using 3 multiplex immunofluorescence panels including one each for T-cells subpopulations, macrophages and myeloid-derived suppressor cells (MDSCs). Median densities of the different phenotypes were analyzed in tumor and stromal compartments and correlated with serial biopsies. Results: Of 20 patients enrolled and 15 were evaluable for response of whom 2 had stability and 1 had a partial response. 17 patients had at least one viable biopsy; 4 had biopsies at T0 and Tm, 3 had biopsies at T0, Tm, and Tc, and 2 had biopsies at T0 and Tc. In general, we noted that cytotoxic T cells increased from baseline when measured at Tm or Tc. In contrast, MDSC counts and overall T cells decreased at Tm or Tc from baseline. Additionally, we saw an increase in CD 68+ and PD-L1 expressing macrophages (P=0.059 and P=0.046, respectively). Patients who had clinical benefit (PR/SD) had greater numbers of cytotoxic T-cells (CD3+CD8+, median, 226.08 cells/mm2) and regulatory T cells (CD3+FOXP3+, median, 48.20 cells/mm2) at baseline than PD patients (median, 26.15 cells/mm2, P=0.03; 13.31 cells/mm2, P=0.016, respectively). Conversely, at T0, the lowest numbers of tumor cytotoxic T-cells activated CD3+CD8+GB+ (median, 0.34 cells/mm2) and highest numbers of PMN-cells (CD66b+CD11b+, median, 16.66 cells/mm2) were observed in patients with PD when compared with PR or SD (median, 4.54 cells/mm2, P=0.097; 3.38 cells/mm2, P=0.023, respectively), suggesting that highest densities of PMN-cells may contribute to downregulation of T-cells in those cases. Conclusions: Higher cytotoxic T-cells or PMN-cell counts at T0 may predict changes in the TME and radiologic response to treatment with BL8040+Pembrolizumab therapy in metastatic pancreatic cancer. PMN-cells may play a role promoting immune suppression of T-cells, increase the risk of metastasis and interfering with the treatment. Trial Registration: NCT02907099, Ethics Approval: This study was approved by the M.D. Anderson Institutional Review Board, approval number 2016-0410.

Citation Format: Carmelia M. Noia Barreto, Debora A. Ledesma, Swati Gite, Luisa M. Solis, Mei Jiang, Renganayaki K. Pandurengan, Robert Wolff, Milind Javle, Shubham Pant, Gauri Varadhachary, Rachna Shroff, Abi Vainstein-Haras, Ella Sorani, Tzipora M. Lustig, Osnat Kashtan, Yosi Gozlan, Steven M. Townson, Jeanne M. Fahey, James Yao, Ignacio I. Wistuba, Michael Overman, David Fogelman, Edwin R. Parra. High cytotoxic T-cell or polymorphonuclear cell infiltrates in the tumor microenvironment correlate with responses to BL8040 plus pembrolizumab combination therapy in metastatic pancreatic tumors: Scientific correlates of a phase II clinical trial [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT204.

BL-8040, a CXCR4 antagonist, in combination with pembrolizumab and chemotherapy for pancreatic cancer: the COMBAT trial

Programmed cell death 1 (PD-1) inhibitors have limited effect in pancreatic ductal adenocarcinoma (PDAC), underscoring the need to co-target alternative pathways. CXC chemokine receptor 4 (CXCR4) blockade promotes T cell tumor infiltration and is synergistic with anti-PD-1 therapy in PDAC mouse models. We conducted a phase IIa, open-label, two-cohort study to assess the safety, efficacy and immunobiological effects of the CXCR4 antagonist BL-8040 (motixafortide) with pembrolizumab and chemotherapy in metastatic PDAC (NCT02826486). The primary outcome was objective response rate (ORR). Secondary outcomes were overall survival (OS), disease control rate (DCR) and safety. In cohort 1, 37 patients with chemotherapy-resistant disease received BL-8040 and pembrolizumab. The DCR was 34.5% in the evaluable population (modified intention to treat, mITT; N = 29), including nine patients (31%) with stable disease and one patient (3.4%) with partial response. Median OS (mOS) was 3.3 months in the ITT population. Notably, in patients receiving study drugs as second-line therapy, the mOS was 7.5 months. BL-8040 increased CD8+ effector T cell tumor infiltration, decreased myeloid-derived suppressor cells (MDSCs) and further decreased circulating regulatory T cells. In cohort 2, 22 patients received BL-8040 and pembrolizumab with chemotherapy, with an ORR, DCR and median duration of response of 32%, 77% and 7.8 months, respectively. These data suggest that combined CXCR4 and PD-1 blockade may expand the benefit of chemotherapy in PDAC and warrants confirmation in subsequent randomized trials.

Evaluation of pharmacodynamic (PD) biomarkers in patients with metastatic pancreatic cancer treated with BL-8040, a novel CXCR4 antagonist

88

Background: BL-8040 is a novel CXCR4 antagonist being developed for multiple oncology indications. Preclinical studies demonstrated that BL-8040 increases the number of immune cells in peripheral blood and promotes CD8+ T cell infiltration into orthotropic pancreatic mouse tumors, reducing tumor load. BL-8040 is being evaluated in a Phase 2a, multicenter, open label trial in patients with metastatic pancreatic cancer (the COMBAT study). Patients are undergoing a 5-day period of monotherapy in which they receive daily doses of BL-8040, followed by 21-day cycles in which patients receive one dose of pembrolizumab and 3 doses/week of BL-8040 until disease progression or discontinuation. To date, 32 patients have been enrolled. Methods: On Day 1 and Day 5, blood samples were taken at pre- and post-dosing, to evaluate peripheral immune cell subset frequency by flow cytometry. In addition, core biopsies were taken from liver metastases, where possible, to assess immune cell infiltration into tumors and the tumor microenvironment (TME). Results: Here we present interim PD biomarker data from the BL-8040 monotherapy portion of the trial. Flow cytometry shows that BL-8040 monotherapy caused an approximately two-fold reduction in frequency of peripheral T regulatory cells, but had no effect on the frequency of T cells, NKT cells or cell populations that contain B cells (CD3- CD56-). Additionally, BL-8040 remained bound to CXCR4 on peripheral immune cells throughout the period of monotherapy. Analysis of available biopsies (N = 7) shows an up to 15-fold increase in the CD3+ population, and up to two-fold increase of CD8+ cells, in the tumor periphery and TME of 43% (3/7) of the patients after five days of BL-8040 monotherapy compared to baseline. Conclusions: In summary, the PD biomarker results in humans support the proposed mechanism of action for BL-8040 that was based on preclinical mouse models. Analysis of tumor biopsies is ongoing, with an emphasis on investigating the effects of BL-8040 on tumor-resident immune cells and the TME. Clinical trial information: NCT02826486.

Evaluation of pharmacodynamic (PD) biomarkers in patients with metastatic pancreatic cancer treated with BL-8040, a novel CXCR4 antagonist

276

Background: BL-8040 is a novel CXCR4 antagonist being developed for multiple oncology indications. Preclinical studies demonstrated that BL-8040 increases the number of immune cells in peripheral blood and promotes CD8+ T cell infiltration into orthotropic pancreatic mouse tumors, reducing tumor load. BL-8040 is being evaluated in a Phase 2a, multicenter, open label trial in patients with metastatic pancreatic cancer (the COMBAT study). Patients are undergoing a 5-day period of monotherapy in which they receive daily doses of BL-8040, followed by 21-day cycles in which patients receive one dose of pembrolizumab and 3 doses/week of BL-8040 until disease progression or discontinuation. To date, 32 patients have been enrolled. Methods: On Day 1 and Day 5, blood samples were taken at pre- and post-dosing, to evaluate peripheral immune cell subset frequency by flow cytometry. In addition, core biopsies were taken from liver metastases, where possible, to assess immune cell infiltration into tumors and the tumor microenvironment (TME). Results: Here we present interim PD biomarker data from the BL-8040 monotherapy portion of the trial. Flow cytometry shows that BL-8040 monotherapy caused an approximately two-fold reduction in frequency of peripheral T regulatory cells, but had no effect on the frequency of T cells, NKT cells or cell populations that contain B cells (CD3- CD56-). Additionally, BL-8040 remained bound to CXCR4 on peripheral immune cells throughout the period of monotherapy. Analysis of available biopsies (N = 7) shows an up to 15-fold increase in the CD3+ population, and up to two-fold increase of CD8+ cells, in the tumor periphery and TME of 43% (3/7) of the patients after five days of BL-8040 monotherapy compared to baseline. Conclusions: In summary, the PD biomarker results in humans support the proposed mechanism of action for BL-8040 that was based on preclinical mouse models. Analysis of tumor biopsies is ongoing, with an emphasis on investigating the effects of BL-8040 on tumor-resident immune cells and the TME. Clinical trial information: NCT02826486.

A pilot study to assess the efficacy, safety, and pharmacodynamic effects of pembrolizumab and BL-8040 in patients with metastatic pancreatic cancer

TPS533

Background: Checkpoint inhibitors such as pembrolizumab are active against a variety of tumor types; however, pancreatic cancer patients generally do not see improvements in their disease from single agent treatment. Blocking CXCR4 may potentiate the activity of checkpoint inhibitors by (1) increasing mobilization of lymphocytes from bone marrow, (2) blocking production of SDF-1, in turn allowing better penetration of immune cells into the tumor, (3) reducing the entry of suppressor T cells into tumor, and (4) upregulating CCL20 in the tumor microenvironment, which may help attract dendritic cells into the tumor. We have launched a study combining BL8040, a CXCR4 antagonist, with pembrolizumab in order to determine the efficacy of this combination. Methods: Major inclusion criteria require patients with pancreatic adenocarcinoma whose tumors have progressed through at least one line of therapy. There must be sufficient disease to allow for pre- and post-treatment biopsy as well as measurement of response by RECIST criteria. Patients must be age 18 or older and ECOG 0-1. Liver function, renal, and hematologic criteria are fairly rigorous. Major exclusion criteria include patients with viral infections or those who require supraphysiologic steroid use. Treatment includes a two week cycle of single agent BL-8040 given on days 1-5 and 8-12. Cycles 2 and beyond include treatment on day 1 with pembrolizumab, 200 mg flat dose, plus BL-8040 given SQ on days 1,4,8, and 11 of a two week cycle. The primary endpoint is response rate; other major clinical objectives include progression free and overall survival. Scientific correlates include assessments of immune cell infiltrates into tumor via histology and immunoflourescence, histological assessment of stromal components, and gene expression signatures. Blood is likewise being collected for serum cytokine analysis, circulating free DNA analysis, circulating tumor cells, and exosome analysis. Clinical trial information: NCT02907099.