Eric Chevalier

The novel CXCR4 antagonist POL5551 mobilizes hematopoietic stem and progenitor cells with greater efficiency than Plerixafor

Mobilized blood has supplanted bone marrow (BM) as the primary source of hematopoietic stem cells for autologous and allogeneic stem cell transplantation. Pharmacologically enforced egress of hematopoietic stem cells from BM, or mobilization, has been achieved by directly or indirectly targeting the CXCL12/CXCR4 axis. Shortcomings of the standard mobilizing agent, granulocyte colony-stimulating factor (G-CSF), administered alone or in combination with the only approved CXCR4 antagonist, Plerixafor, continue to fuel the quest for new mobilizing agents. Using Protein Epitope Mimetics technology, a novel peptidic CXCR4 antagonist, POL5551, was developed. In vitro data presented herein indicate high affinity to and specificity for CXCR4. POL5551 exhibited rapid mobilization kinetics and unprecedented efficiency in C57BL/6 mice, exceeding that of Plerixafor and at higher doses also of G-CSF. POL5551-mobilized stem cells demonstrated adequate transplantation properties. In contrast to G-CSF, POL5551 did not induce major morphological changes in the BM of mice. Moreover, we provide evidence of direct POL5551 binding to hematopoietic stem and progenitor cells (HSPCs) in vivo, strengthening the hypothesis that CXCR4 antagonists mediate mobilization by direct targeting of HSPCs. In summary, POL5551 is a potent mobilizing agent for HSPCs in mice with promising therapeutic potential if these data can be corroborated in humans.

The CXCR4 antagonist POL5551 is equally effective as sirolimus in reducing neointima formation without impairing re-endothelialisation

Impaired endothelial recovery after the implantation of drug-eluting stents is a major concern because of the increased risk for late stent thrombosis. The disruption of the chemokine axis CXCL12/CXCR4 inhibits neointima formation by blocking the recruitment of smooth muscle progenitor cells. To directly compare a CXCR4-targeting treatment strategy with drugs that are currently used for stent coating, we studied the effects of the CXCR4 antagonist POL5551 and the drug sirolimus on neointima formation. Apolipoprotein E-deficient mice were treated with POL5551 or sirolimus continuously for 28 days after a carotid wire injury. POL5551 inhibited neointima formation by 63% (for a dosage of 2 mg/kg/day) and by 70% (for a dosage of 20 mg/kg/day). In comparison, sirolimus reduced the neointimal area by 69%. In contrast to treatment with POL5551 during the first three days after injury, injection of POL5551 (20 mg/kg) once per day for 28 days diminished neointimal hyperplasia by 53%. An analysis of the cellular composition of the neointima showed a reduction in the relative smooth muscle cell (SMC) and macrophage content in mice that had been treated with a high dose of POL5551. In contrast, the diminished SMC content after sirolimus treatment was associated with a neointimal enrichment of macrophages. Furthermore, endothelial recovery was impaired by sirolimus, but not by POL5551. Therefore, the inhibition of CXCR4 by POL5551 is equally effective in preventing neointima formation as sirolimus, but POL5551 might be more beneficial because treatment with it results in a more stable lesion phenotype and because it does not impair re-endothelialisation.

CXCR4 Protein Epitope Mimetic Antagonist POL5551 Disrupts Metastasis and Enhances Chemotherapy Effect in Triple-Negative Breast Cancer

The SDF-1 receptor CXCR4 has been associated with early metastasis and poorer prognosis in breast cancers, especially the most aggressive triple-negative subtype. In line with previous reports, we found that tumoral CXCR4 expression in patients with locally advanced breast cancer was associated with increased metastases and rapid tumor progression. Moreover, high CXCR4 expression identified a group of bone marrow–disseminated tumor cells (DTC)-negative patients at high risk for metastasis and death. The protein epitope mimetic (PEM) POL5551, a novel CXCR4 antagonist, inhibited binding of SDF-1 to CXCR4, had no direct effects on tumor cell viability, but reduced migration of breast cancer cells in vitro. In two orthotopic models of triple-negative breast cancer, POL5551 had little inhibitory effect on primary tumor growth, but significantly reduced distant metastasis. When combined with eribulin, a chemotherapeutic microtubule inhibitor, POL5551 additively reduced metastasis and prolonged survival in mice after resection of the primary tumor compared with single-agent eribulin. Hypothesizing that POL5551 may mobilize tumor cells from their microenvironment and sensitize them to chemotherapy, we used a “chemotherapy framing” dosing strategy. When administered shortly before and after eribulin treatment, three doses of POL5551 with eribulin reduced bone and liver tumor burden more effectively than chemotherapy alone. These data suggest that sequenced administration of CXCR4 antagonists with cytotoxic chemotherapy synergize to reduce distant metastases. Mol Cancer Ther; 14(11); 2473–85. ©2015 AACR.

Abstract 1114: Combination of a novel CXCR4 antagonist with chemotherapy reduces breast cancer bone metastatic tumor burden

Background: Bone is the most common site of metastasis for patients with breast cancer. Tumor cells migrate to and reside in the protective bone marrow microenvironment niche through adhesive interaction between tumor CXCR4 and stromal CXCL12 (SDF1). CXCL12 is produced by activated osteoblasts, bone marrow and lung stromal cells, and endothelial cells. Nearly 60% of breast cancers express CXCR4 and this is associated with decreased survival. We hypothesized that a Protein Epitope Mimetic (PEM) POL5551, a novel CXCR4 antagonist, will limit the extent of tumor metastasis by disrupting stromal-mediated protection from cytotoxic chemotherapy and in turn may prolong survival. Approach: In vitro, POL5551 had no direct cytotoxic activity and did not reduce proliferation of CXCR4+ MDA-MB-231 or 4T1 osteolytic breast cancer cell lines. However, in an in vitro scratch-wound assay POL5551 inhibited migration of MDA-MB-231 cells. In a Gaussia luciferase (GLuc) complementation model in MDA-MB-231 cells, the interaction of CXCL12 with CXCR4, but not CXCR7, was blocked by low nanomolar concentrations of POL5551. At 20 mg/kg administered from day 10 post inoculation, POL5551 displayed no single agent activity on primary tumor xenografts, and in combination with eribulin there was no synergistic effect on primary tumor xenografts. However, continuation of treatment with POL5551 after surgical tumor removal decreased tumor metastasis and prolonged survival to 58 days compared to control at 45 days and eribulin alone at 51 days. Also, POL5551 showed effects on immune infiltration to the primary tumor. To test the hypothesis that CXCR4 antagonism disrupts the protective bone marrow niche in which tumor cells reside and sensitizes them to cytotoxic chemotherapy, we employed a “framing dosing strategy”. In a second model of metastasis produced by intracardiac injection of MDA-MB-231 cells, POL5551 (20 mg/kg, s.c.) was administered to mice with bone metastases 4 hours before and 4 & 18 hours after eribulin chemotherapy (0.2 mg/kg, i.v.). While bone is the predominant site of metastasis with these cell lines, lung and liver metastasis also occurs. POL5551 in combination with eribulin decreased bone tumor burden more than eribulin alone (reduction in leg bone & liver tumor burden, versus control respectively: eribulin alone 58% & 75%, n.s.; POL5551+eribulin: 89% & 86%, P Conclusion: These preclinical data support a synergism of CXCR4 antagonism during chemotherapy for the treatment of metastatic breast cancer. These and additional data support initiation of a Phase I clinical trial to evaluate a related PEM CXCR4 antagonist in combination with eribulin chemotherapy in patients with metastatic breast cancer who have failed at least 2 lines of therapy. Note: This abstract was not presented at the meeting. Citation Format: Jingyu Xiang, Michelle A. Hurchla, Kathryn Luker, Garry Douglas, Barbara Romagnoli, Eric Chevalier, Michael Bauer, Johann Zimmermann, Klaus Dembowsky, Gary Luker, Katherine N. Weilbaecher. Combination of a novel CXCR4 antagonist with chemotherapy reduces breast cancer bone metastatic tumor burden. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1114. doi:10.1158/1538-7445.AM2014-1114

Abstract A20: A novel CXCR4 antagonist interferes with antivascular endothelial growth factor therapy-induced glioma dissemination

Background: Resistance to antiangiogenic therapy (AT) in patients with glioblastoma (GBM) treated with bevacizumab (BEV) is characterized by local recurrence and distant dissemination of gliomas associated with remodeling of tumor vessels and pronounced hypoxia known to promote glioma cell invasion. Expression of the chemokine receptor CXCR4 and its ligand stromal cell-derived factor-1α (SDF-1α) is enhanced in invading tumor cells (CXCR4) and neurons and blood vessels (SDF-1α) in GBM and associated with tumor hypoxia, proliferation, invasion and angiogenesis. Using Protein Epitope Mimetics (PEM) technology (Robinson JA et al., 2008), Polyphor Ltd. has developed selective, highly potent CXCR4 antagonists (De Marco SJ et al., 2006) (U.S. Patent no. 8,716,242), such as POL5551. To address the problem of resistance to AT, we sought to determine whether combined therapy (CTx) with POL5551 and the murine equivalent of BEV (antibody B20-4.1.1) could inhibit the invasion and associated pathologic characteristics of gliomas in vivo. Methods: Adult C57BL/6 mice implanted orthotopically with syngeneic CT-2A or GL261 glioma cells were randomized on day 14 into 4 groups: 1) control, 2) POL5551 (5 mg/kg s.c.), 3) anti-murine vascular endothelial growth factor (VEGF) monoclonal antibody B20-4.1.1 (5 mg/kg i.p.; Genentech Inc.) (Bagri A et al., 2010) and 4) combined POL5551 and B20-4.1.1 (CTx). On day 28, brain tissues were processed, sections analyzed for tumor volume and invasiveness (Sottoriva A et al., 2010) (HE May 27-30, 2015; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2015;75(23 Suppl):Abstract nr A20.