291 Phase Ib study of selicrelumab (CD40 agonist) in combination with atezolizumab (anti-PD-L1) in patients with advanced solid tumors

Background

Selicrelumab is a human IgG2 agonistic anti-CD40 monoclonal antibody. Binding of the antibody to CD40 expressed on antigen-presenting cells results in T- cell priming and T-cell dependent anti-tumor activity. In response to T-cell activation, tumor cells express programmed-death ligand 1 (PD-L1) that can suppress effector T-cells. Atezolizumab interrupts this feedback loop by blocking PD-L1, thereby supporting the combination with selicrelumab.

Methods

This phase Ib open-label, multicenter, dose escalation (DE)/expansion clinical study (NCT02304393) investigated safety, pharmacokinetic (PK), pharmacodynamics (PD) and efficacy of selicrelumab in combination with atezolizumab in unselected patients with advanced/metastatic solid tumors, not amenable to standard therapy. In DE cohorts, a single dose of selicrelumab was given, either by intravenous (IV) infusion at a 16 mg fixed dose or subcutaneously (SC) at a range from 1 to 64 mg/dose. In dose-expansion cohorts (small bowel and colorectal cancer, head and neck squamous cell carcinoma [HNSCC] and non-small cell lung carcinoma), patients received multiple doses of selicrelumab SC at a dose of 16 mg. In all treatment cohorts, patients received atezolizumab at a fixed dose of 1200 mg IV Q3W.

Results

In this study, 140 patients were treated. This included 95 patients in DE cohorts (6 patients in the IV cohort, 89 patients in the SC cohorts) and 45 patients in dose-expansion cohorts. In the IV cohort, infusion related reaction was the most frequent treatment-related adverse event (TRAE; 50%), while Grade ≥ 3 TRAE occurred in 1 patient (16.7%). In this cohort one dose-limiting toxicity (DLT) was reported (Grade 3 pancytopenia). In the SC cohorts, the most frequent TRAE was injection site reaction (ISR; 92%). Four DLTs were reported in four patients: three Grade 3 ISR and one Grade 3 transaminase increase. Grade ≥ 3 TRAE were reported in 22 patients (16.4%). Anti-tumor activity was observed across cohorts receiving SC selicrelumab (dose range 1 to 36 mg). Eight of 80 evaluable patients in DE cohorts experienced objective responses (9% ORR). In the dose-expansion HNSCC cohort, three of 16 evaluable patients responded (15.8% ORR). There were no objective responses in the IV cohort. Treatment with selicrelumab resulted in significant peripheral B-cell depletion and activation and CD8+ T cell proliferation.

Conclusions

Treatment with selicrelumab in combination with atezolizumab was well tolerated in patients with advanced solid tumors. Signals of clinical and PD activity were observed. However, efficacy of the combination in this unselected population was limited, when compared to monotherapy efficacy of atezolizumab.

Trial Registration

NCT02304393

Ethics Approval

This study was approved by the local IRB at each participating study site.

Abstract OT1-08-06: International, phase 3 trial: Balixafortide (a CXCR4 antagonist) + eribulin versus eribulin alone in patients with HER2 negative, locally recurrent or metastatic breast cancer (FORTRESS) international, phase 3 trial: Balixafortide (a CXCR4 antagonist) + eribulin versus eribulin alone in patients with HER2 negative, locally recurrent or metastatic breast cancer (FORTRESS)

Background: Balixafortide (B) is a potent CXCR4 antagonist. High CXCR4 levels correlate with aggressive metastatic phenotypes and poor prognosis in breast cancer (BC).

Encouraging safety and efficacy data were published from the Phase 1 trial investigating B + eribulin (E) in patients with HER2 negative metastatic BC1,2. The objective response rate (ORR), median progression free survival (PFS), median overall survival (OS), and 12, 18 and 24 month OS estimate in patients who received B + E as 2nd line or later therapy were respectively: 37.5%, 6.2 months, 18 months, 75%, 50%, and 33.3% for the Expanded Cohort (EC); 29.6%, 4.5 months, 16.8 months, 62%, 42.4%, and 25% for the Overall Efficacy Population. These OS data were observed regardless of line of study medication received and were numerically higher for patients who received study medication as 2nd line or later therapy.

Inter-trial comparisons suggest that these survival rates, especially for EC, are higher than those reported for E monotherapy in similar populations.

The following trial was designed and open to enrolment.

Trial design: International, multicenter, open-label, randomized, parallel, 2 arm, Phase 3

Eligibility criteria:

Age ≥18 years

Histologically confirmed BC

Metastatic BC (stage IV disease by AJCC criteria) or unresectable locoregionally recurrent BC

HER2 negative

Any estrogen or progesterone receptor (ER/PgR) status

Previously received 1−4 chemotherapeutic regimens for locally recurrent or metastatic BC.

Unless contra-indicated, prior therapy included an anthracycline and a taxane in either the adjuvant or metastatic setting.

ER+ and/or PgR+ patients treated with at least 1 line of endocrine therapy and unsuitable for further endocrine therapy.

At least 14 days from completion of previous cytotoxic chemotherapy, biological therapy, or other investigational agent

Refractory to most recent chemotherapy (progression on ≤6 months of therapy)

ECOG performance status 0−2

Life expectancy ≥3 months

If CNS involvement, metastases must have been treated and stable for at least 4 weeks after completion of radiation therapy and/or surgery

Patients with no concurrent malignancy or malignancy 2 years prior to randomization except for adequately treated basal and squamous cell carcinoma, non-melanomatous skin cancer or curatively resected cervical cancer.

Aims: to investigate the comparative efficacy and safety of B + E versus E monotherapy in terms of: PFS in the Overall Study Population and in the 3rd Line or Later Therapy Study PopulationOSTumor responseSafety and tolerabilityQuality of lifeExploring the association between comparative efficacy and ER or PgR status, CXCR4 expression levels, circulating and tumor tissue biomarkersExploring immune response using iRECISTEvaluating pharmacokinetics of balixafortide and its metabolites.

Statistical Methods: To provide efficacy and safety data in:

Overall Study Population for regulatory submissions in the EU and jurisdictions in which the 2nd line + E label applies.

3rd line or Later Therapy Study Population for regulatory submissions in the US and jurisdictions in which the 3rd line + E label applies.

The critical efficacy endpoints for both study populations are PFS and OS and additionally ORR for the 3rd line + Population. Alpha allocation and recycling will ensure control of the overall Type I error rate for the 2 study populations separately.

Accrual: approx. 400 patients

Contact information:

Frank Weber MD

Tel +41 61 567 1600

1. Pernas S et al. Lancet Oncol. 2018; 19: 812−24

2. Kaufman PA et al. J Clin Oncol. 2019; 37(Suppl 2606)

Citation Format: Peter Kaufmann MD, Javier Cortes MD, PhD, Miguel Martin, MD, PhD, Ingrid Mayer MD, Linda Vahdat, MD, Sonia Pernas MD, PhD, Peter Schmid MD, PhD, Heather McArthur MD, Rebecca Dent MD, Hope Rugo MD, Carlos Barrios MD, Debra Barker MD, Barbara Romagnoli PhD and Alexandra Bobirca MD. International, phase 3 trial: Balixafortide (a CXCR4 antagonist) + eribulin versus eribulin alone in patients with HER2 negative, locally recurrent or metastatic breast cancer (FORTRESS) international, phase 3 trial: Balixafortide (a CXCR4 antagonist) + eribulin versus eribulin alone in patients with HER2 negative, locally recurrent or metastatic breast cancer (FORTRESS) [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr OT1-08-06.

Abstract 3965: Circulating levels of IFN gammaand neutrophil counts in breast cancer patients who received balixafortide and eribulin combination therapy

Background: Balixafortide (B) is a highly selective antagonist of the chemokine receptor CXCR4. Clinical proof-of-concept in combination with eribulin (E) was achieved in a recent Phase 1 single arm dose-escalation trial in patients with metastatic HER2-negative breast cancer (NCT01837095). Safety and tolerability of B in combination with E was similar to that of B or E monotherapy.

Anti-cancer effects of CXCR4 antagonists include sensitization of tumor cells to chemotherapy, suppression of metastatic spread, inhibition of angiogenesis, and activation of immune cells.

Methods: Plasma samples from patients who received initial E monotherapy (1.4 mg/m2, run-in cycle) or combination of B and E (escalating doses of B intravenous up to 5.5 mg/kg plus E 1.4 mg/m2 in 21 days cycles) were immediately processed and stored at -80°C. Circulating levels of IFN-γ, an important marker of anti-tumor immune response, were determined by a high-sensitive S-Plex assay (Meso Scale Diagnostics). Absolute neutrophil counts (ANC) were measured by automated hematology instruments.

Results: E monotherapy did not increase IFN-γ levels in the first 8 hours post dosing, but led to an increase after 24 hours. Combination with B modulated IFN-γ levels and led to a sustained ANC increase 5 days post dosing. The increase pre vs post treatment can be up to 100-fold and receded prior to the next treatment cycle. Conclusions: E treatment led to a strong, transient increase of plasma IFN-γ levels in breast cancer patients modulated by B. The ANC increase by B may balance possible neutropenic actions of E.

Citation Format: Johann Zimmermann, Garry Douglas, Barbara Romagnoli, Debra Barker, Daniel Obrecht. Circulating levels of IFN gammaand neutrophil counts in breast cancer patients who received balixafortide and eribulin combination therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3965.

Balixafortide (a CXCR4 antagonist) + eribulin in HER2-negative metastatic breast cancer (MBC): Survival outcomes of the phase I trial

2606

Background: Balixafortide (B) is a potent antagonist of the chemokine receptor CXCR4. Preclinical evidence suggests that disrupting CXCR4 dependent pathways prevents development of breast cancer metastases, enhances the cytotoxic effect of chemotherapy and immunotherapy, and counteracts tumor cell evasion of the immune system. Encouraging safety and efficacy data were published recently from the ongoing Phase 1 trial investigating B + eribulin (E) in patients with HER2 negative MBC (Pernas S. et al. Lancet Oncol. 2018; 19: 812−24). The objective response rate, median progression free survival and median overall survival (OS) for the expanded cohort (EC) and the overall efficacy population (OEP) were 37.5% and 29.6%, 6.2 months and 4.5 months, and 18 months and 16.8 months, respectively. Here we report the 18 and 24 months landmark OS data from this trial. Methods: This trial enrolled 56 patients with HER2-negative, CXCR4-positive MBC, previously treated with 1−3 chemotherapy regimens for MBC. A 3+3 dose escalation design was used, followed by an EC. All cohorts received E on days 2 and 9, and B on days 1−3 and 8−10 of 21 day cycles. The association between various baseline biomarkers and treatment outcomes including OS is currently being investigated in a multivariate analysis (MVA). Results: Landmark survival data for the trial are shown in the table. Clinical trial information: NCT01837095. Conclusions: Landmark 18 months and 24 months OS data are consistent with the positive trend of all efficacy read-outs observed in this study and safety information is consistent with what was previously reported. Although inter-trial comparisons should be interpreted with caution, these survival rates, especially for the EC, are higher than those reported for eribulin monotherapy in similar MBC populations. These promising results suggest that B + E could potentially provide a new treatment option in heavily pre-treated patients with HER2 negative MBC and this is currently being investigated in a pivotal, randomized trial.[Table: see text]

Abstract PD1-02: Withdrawn

This abstract was withdrawn by the authors.

Citation Format: Cortes J, Martin M, Pernas S, Gomez Pardo P, Lopez-Tarruella S, Gil-Martin M, Manso L, Ciruelos E, Perez-Fidalgo JA, Hernando C, Ademuyiwa FO, Weilbaecher K, Mayer I, Pluard TJ, Martinez Garcia M, Vahdat L, Wach A, Barker D, Romagnoli B, Kaufman PA. Withdrawn [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD1-02.

Multifaceted C-X-C Chemokine Receptor 4 (CXCR4) Inhibition Interferes with Anti-Vascular Endothelial Growth Factor Therapy-Induced Glioma Dissemination

Resistance to antiangiogenic therapy in glioblastoma (GBM) patients may involve hypoxia-induced expression of C-X-C motif chemokine receptor 4 (CXCR4) on invading tumor cells, macrophage/microglial cells (MGCs), and glioma stem cells (GSCs). We determined whether antagonizing CXCR4 with POL5551 disrupts anti-vascular endothelial growth factor (VEGF) therapy-induced glioma growth and dissemination. Mice bearing orthotopic CT-2A or GL261 gliomas received POL5551 and/or anti-VEGF antibody B20-4.1.1. Brain tissue was analyzed for tumor volume, invasiveness, hypoxia, vascular density, proliferation, apoptosis, GSCs, and MGCs. Glioma cells were evaluated for CXCR4 expression and polymorphism and POL5551's effects on CXCR4 ligand binding, cell viability, and migration. No CXCR4 mutations were identified. POL5551 inhibited CXCR4 binding to its ligand, stromal cell-derived factor-1α, and reduced hypoxia- and stromal cell-derived factor-1α-mediated migration dose-dependently but minimally affected cell viability. In vivo, B20-4.1.1 increased hypoxic foci and invasiveness, as seen in GBM patients receiving anti-VEGF therapy. Combination of POL5551 and B20-4.1.1 reduced both glioma invasiveness by 16% to 39% and vascular density compared to B20-4.1.1 alone in both glioma models. Reduced populations of GSCs and MGCs were also seen in CT-2A tumors. POL5551 concentrations, evaluated by mass spectrometry, were higher in tumors than in neighboring brain tissues, likely accounting for the results. Inhibition of CXCR4-regulated tumoral, stem cell, and immune mechanisms by adjunctive CXCR4 antagonists may help overcome antiangiogenic therapy resistance, benefiting GBM patients.

Phase I study of the combination of balixafortide (CXCR4 inhibitor) and eribulin in HER2-negative metastatic breast cancer (MBC) patients (pts)

2555

Background: Balixafortide (POL6326) is a cyclic peptide and a potent, selective antagonist of the chemokine receptor CXCR4. Evidence suggests that CXCR4 inhibition interferes with the tumor-protective microenvironment and sensitizes tumor cells to chemotherapy. The combination of balixafortide (B) and eribulin (E) was safe with early signs of efficacy in the dose escalation part of this study. Methods: The expanded cohort of thisopen label phase I study was designed to assess the anti-tumor activity, safety and pharmacokinetics of the addition of the recommended phase 2 dose (RP2D) of B to E in pts with MBC and with any CXCR4 expression level at the tumor site. Patients received E (1.4 mg/m2) on days 2 and 9, flanked by B (5.5 mg/kg) on days 1-3, and 8-10 of 21-day cycles. Results: 24 pts with relapsed MBC (median age 59 [33-82]) were enrolled in the expanded cohort. Median number of prior chemotherapies for MBC was 2 (range 1-3). 20/24 (83%) pts were ER and/or PR positive; 3/24 (13%) pts had TNBC. Objective response rate (ORR) was 33%. 8/24 (33%) pts achieved a partial response and 4/24 (17%) pts had meaningful (≥ 6 months) stable disease for a Clinical Benefit Ratio of 50%. Median duration of treatment was 15.3 weeks (range 5-40) with 11 pts still on treatment. The most common Gr 3-4 adverse events were neutropenia (9/24, 38%) and leucopenia (3/24, 13%); 2 pts had febrile neutropenia and 1 patient died from sepsis. 15/24 (63%) pts experienced histamine-like infusion reactions related to B that were manageable with anti-histamines. Conclusions: The therapeutic activity of this treatment regimen appears promising with an ORR of 33% in patients with advanced MBC. B (5.5 mg/kg) can be combined safely with E (1.4 mg/m2) and the safety profile resembles E monotherapy as previously reported. This is the first study of the treatment combination of E with B in relapsed MBC pts. Further confirmatory studies are being considered. Clinical trial information: NCT01837095.

Mobilization of hematopoietic stem cells with the novel CXCR4 antagonist POL6326 (balixafortide) in healthy volunteers-results of a dose escalation trial

BACKGROUND

Certain disadvantages of the standard hematopoietic stem and progenitor cell (HSPC) mobilizing agent G-CSF fuel the quest for alternatives. We herein report results of a Phase I dose escalation trial comparing mobilization with a peptidic CXCR4 antagonist POL6326 (balixafortide) vs. G-CSF.

METHODS

Healthy male volunteer donors with a documented average mobilization response to G-CSF received, following ≥6 weeks wash-out, a 1-2 h infusion of 500-2500 µg/kg of balixafortide. Safety, tolerability, pharmacokinetics and pharmacodynamics were assessed.

RESULTS

Balixafortide was well tolerated and rated favorably over G-CSF by subjects. At all doses tested balixafortide mobilized HSPC. In the dose range between 1500 and 2500 µg/kg mobilization was similar, reaching 38.2 ± 2.8 CD34 + cells/µL (mean ± SEM). Balixafortide caused mixed leukocytosis in the mid-20 K/µL range. B-lymphocytosis was more pronounced, whereas neutrophilia and monocytosis were markedly less accentuated with balixafortide compared to G-CSF. At the 24 h time point, leukocytes had largely normalized.

CONCLUSIONS

Balixafortide is safe, well tolerated, and induces efficient mobilization of HSPCs in healthy male volunteers. Based on experience with current apheresis technology, the observed mobilization at doses ≥1500 µg/kg of balixafortide is predicted to yield in a single apheresis a standard dose of 4× 10E6 CD34+ cells/kg from most individuals donating for an approximately weight-matched recipient. Exploration of alternative dosing regimens may provide even higher mobilization responses. Trial Registration European Medicines Agency (EudraCT-Nr. 2011-003316-23) and clinicaltrials.gov (NCT01841476).

POL5551, a novel and potent CXCR4 antagonist, enhances sensitivity to chemotherapy in pediatric ALL

The importance of the cell surface receptor CXCR4 and the chemokine stromal cell-derived factor-1 (SDF-1/CXCL12) is well-established in normal and malignant hematopoiesis. The Protein Epitope Mimetic POL5551 is a novel and potent antagonist of CXCR4. POL5551 efficiently mobilizes hematopoietic stem and progenitor cells, but its effects in acute lymphoblastic leukemia (ALL) have not been reported. Here, we demonstrate that POL5551 is a potent antagonist of CXCR4 in pre-B and T cell ALL cell lines and pediatric ALL primary samples. POL5551 has activity at nanomolar concentrations in decreasing CXCR4 antibody binding, blocking SDF-1α-mediated phosphorylation of ERK1/2, inhibiting SDF-1α-induced chemotaxis, and reversing stromal-mediated protection from chemotherapy. POL5551 is significantly more effective at inhibiting CXCR4 antibody binding than the FDA-approved CXCR4 inhibitor plerixafor in ALL cell lines and primary samples. We also show that treatment with POL5551 in vitro and cytarabine +/− POL5551 in vivo modulates surface expression of adhesion molecules, findings that may guide the optimal clinical use of POL5551. Finally, we demonstrate that POL5551 increases sensitivity to cytarabine in a xenograft model of a high-risk pediatric ALL, infant MLL-rearranged (MLL-R) ALL. Therefore, disruption of the CXCR4/SDF-1 axis with POL5551 may improve outcomes in children with high-risk ALL.

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) (H&E), hypoxia (Hypoxyprobe), proliferation (pHH3, phosphohistone H3), vascular density (CD105), apoptosis (cleaved caspase 3) and microglial (IBA1, ionized calcium binding adaptor molecule 1) and stem (nestin) cellular fractions and the results analyzed by analysis of variance (ANOVA). The tissue concentrations of POL5551 were measured by mass spectrometry.

Results: Following B20-4.1.1, both glioma models recapitulated the increased invasive phenotype seen in human GBM associated with increased tumor hypoxia and reduced cellular proliferation and vascular density. Following POL5551 alone, tumor proliferation was slightly diminished. Nestin immunopositivity in CT-2A glioma was markedly reduced following POL5551, and to an intermediate level with CTx, consistent with a previous report (Barone A et al., 2014). In both models, CTx reduced tumor invasiveness (by up to 39.3% compared with B20-4.1.1 alone) and vascular density together with increased apoptosis. In CT-2A glioma, CTx also diminished IBA1 immunopositivity. The concentration of POL5551 was higher in GL261 glioma (45.8 nM) than in brain adjacent to tumor (23.7 nM) or normal brain (11.1 nM) and sufficient to account for its biological effects given the high binding affinity (0.5 nM) of POL5551 for CXCR4. In preliminary work, POL5551 reduced the rate of migration of GL261 glioma cells in vitro.

Conclusions: Following anti-VEGF antibody treatment, both murine glioma models recapitulated the increased invasive phenotype seen in human GBM associated with a more hypoxic tumor microenvironment. In both tumor models, CTx with POL5551 and B20-4.1.1 may be beneficial in overcoming AT-induced glioma dissemination. Importantly, POL5551 crossed the blood-brain barrier and accumulated to biologically active levels in glioma tissue. Our results suggest the potential clinical utility of PEM CXCR4 antagonists as adjunct therapy for patients with GBM.

Citation Format: Jean-Pierre Gagner, Yasmeen Sarfraz, Fawaz M. Alotaibi, Valerio Ortenzi, Awab T. Tayyib, Luis A. Chiriboga, Garry J. Douglas, Eric Chevalier, Barbara Romagnoli, Gerald Tuffin, Klaus Dembowsky, David Zagzag. A novel CXCR4 antagonist interferes with antivascular endothelial growth factor therapy-induced glioma dissemination. [abstract]. In: Proceedings of the AACR Special Conference: Advances in Brain Cancer Research; May 27-30, 2015; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2015;75(23 Suppl):Abstract nr A20.

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.

Combined VEGF and CXCR4 antagonism targets the GBM stem cell population and synergistically improves survival in an intracranial mouse model of glioblastoma

Glioblastoma recurrence involves the persistence of a subpopulation of cells with enhanced tumor-initiating capacity (TIC) that reside within the perivascular space, or niche (PVN). Anti-angiogenic therapies may prevent the formation of new PVN but have not prevented recurrence in clinical trials, suggesting they cannot abrogate TIC activity. We hypothesized that combining anti-angiogenic therapy with blockade of PVN function would have superior anti-tumor activity. We tested this hypothesis in an established intracranial xenograft model of GBM using a monoclonal antibody specific for murine and human VEGF (mcr84) and a Protein Epitope Mimetic (PEM) CXCR4 antagonist, POL5551. When doses of POL5551 were increased to overcome an mcr84-induced improvement in vascular barrier function, combinatorial therapy significantly inhibited intracranial tumor growth and improved survival. Anti-tumor activity was associated with significant changes in tumor cell proliferation and apoptosis, and a reduction in the numbers of perivascular cells expressing the TIC marker nestin. A direct effect on TICs was demonstrated for POL5551, but not mcr84, in three primary patient-derived GBM isolates. These findings indicate that targeting the structure and function of the PVN has superior anti-tumor effect and provide a strong rationale for clinical evaluation of POL5551 and Avastin in patients with GBM.

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<0.05; n=4-5 mice per group).

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

CXCR7-dependent angiogenic mononuclear cell trafficking regulates tumor progression in multiple myeloma

The CXCR4/stromal cell-derived factor-1 (SDF-1) axis is essential for cell trafficking and has been shown to regulate tumor progression and metastasis in many tumors including multiple myeloma (MM). A second chemokine receptor for SDF-1, CXCR7 was discovered recently and found on activated endothelial cells. We examined the role of CXCR7 in angiogenic mononuclear cells (AMCs) trafficking in MM. Our data demonstrate that AMCs are circulating in patients with MM and in vivo studies show that they specifically home to areas of MM tumor growth. CXCR7 expression is important for regulating trafficking and homing of AMCs into areas of MM tumor growth and neoangiogenesis. We demonstrate that the CXCR7 inhibitor, POL6926, abrogated trafficking of AMCs to areas of MM tumor progression leading to a significant inhibition of tumor progression. These effects were through regulation of endothelial cells and not through a direct tumor effect, indicating that targeting a bone marrow microenvironmental cell can lead to a delay in MM tumor progression. In conclusion, our studies demonstrate that CXCR7 may play an important role in the regulation of tumor progression in MM through an indirect effect on the recruitment of AMCs to areas of MM tumor growth in the bone marrow niche.

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.

Simultaneous determination of deoxynivalenol, zearalenone, T-2 and HT-2 toxins in breakfast cereals and baby food by high-performance liquid chromatography and tandem mass spectrometry

In this study, the simultaneous determination of deoxynivalenol (DON), zearalenone (ZEA), T-2 and HT-2 toxins in foodstuff was investigated. A new kind of multi-mycotoxin immunoaffinity columns (IACs) available on the market (DZT MS-PREP(®)) was tested. A sensitive, selective and accurate method by high-performance liquid chromatography and tandem mass spectrometry was developed, with electrospray ionization mass spectrometer operating in multiple reaction monitoring (MRM) mode, with negative-positive-negative ion switching. The method was used for the analysis of samples marked in Italy, in the frame of official monitoring plans. The advantages of combining IACs and LC-MS/MS technique are as follows: efficient removal of matrix interferences, simple chromatographic outline, high selectivity, low detection limits (DLs) and separation of a wide range of molecules with different physico-chemical properties in a single run. The method was studied on two different matrices, breakfast cereal and baby food, at contamination levels close to Regulation limits (EC) 1126/2007. The recoveries obtained (60-100%) fulfil the performance criteria required by Regulation (EC) 401/2006. The DL is 60 µg/kg for DON and 10 µg/kg for ZEA, T-2 and HT-2. Linearity range of the calibration curves is suitable for adult and baby food.

Anti-HIV activity and resistance profile of the CXC chemokine receptor 4 antagonist POL3026

We have studied the mechanism of action of Arg(*)-Arg-Nal(2)-Cys(1x)-Tyr-Gln-Lys-(d-Pro)-Pro-Tyr-Arg-Cit-Cys(1x)-Arg-Gly-(d-Pro)(*) (POL3026), a novel specific beta-hairpin mimetic CXC chemokine receptor (CXCR)4 antagonist. POL3026 specifically blocked the binding of anti-CXCR4 monoclonal antibody 12G5 and the intracellular Ca(2+) signal induced by CXC chemokine ligand 12. POL3026 consistently blocked the replication of human immunodeficiency virus (HIV), including a wide panel of X4 and dualtropic strains and subtypes in several culture models, with 50% effective concentrations (EC(50)) at the subnanomolar range, making POL3026 the most potent CXCR4 antagonist described to date. However, 1-[[4-(1,4,8,11-tetrazacyclotetradec-1-ylmethyl)phenyl]methyl]-1,4,8,11-tetrazacyclotetradecane (AMD3100)-resistant and stromal cell-derived factor-1alpha-resistant HIV-1 strains were cross-resistant to POL3026. Time of addition experiments and a multiparametric evaluation of HIV envelope function in the presence of test compounds confirmed the activity of POL3026 at an early step of virus replication: interaction with the coreceptor. Generation of HIV-1 resistance to POL3026 led to the selection of viruses 12- and 25-fold less sensitive and with mutations in gp120, including the V3 loop region. However, POL3026 prevented the emergence of CXCR4-using variants from an R5 HIV-1 strain that may occur in the presence of anti-HIV agents targeting CC chemokine receptor 5.

Discovery of novel, highly potent and selective beta-hairpin mimetic CXCR4 inhibitors with excellent anti-HIV activity and pharmacokinetic profiles

Novel highly potent CXCR4 inhibitors with good pharmacokinetic properties were designed and optimized starting from the naturally occurring beta-hairpin peptide polyphemusin II. The design involved incorporating important residues from polyphemusin II into a macrocyclic template-bound beta-hairpin mimetic. Using a parallel synthesis approach, the potency and ADME properties of the mimetics were optimized in iterative cycles, resulting in the CXCR4 inhibitors POL2438 and POL3026. The inhibitory potencies of these compounds were confirmed in a series of HIV-1 invasion assays in vitro. POL3026 showed excellent plasma stability, high selectivity for CXCR4, favorable pharmacokinetic properties in the dog, and thus has the potential to become a therapeutic compound for application in the treatment of HIV infections (as an entry inhibitor), cancer (for angiogenesis suppression and inhibition of metastasis), inflammation, and in stem cell transplant therapy.

Evaluation of by disubstituted acridone derivatives as telomerase inhibitors: the importance of G-quadruplex binding

The synthesis and evaluation of a group of 2,6-, 2,7- and 3,6-bis-aminoalkylamido acridones are reported, which show a similar level of activity against telomerase in vitro compared to their acridine counterparts. Computer modelling and calculations of relative binding energies suggest an equivalent binding mode to human intramolecular G-quadruplex DNA, but with significantly reduced affinity, as a result of the limited delocalisation of the acridone chromophore compared to the acridine system. Thermal melting studies on acridone and acridine quadruplex complexes using a FRET approach support these predictions. Long-term cell proliferation studies at sub-cytotoxic doses with two representative acridones using the SKOV3 cell line, show that neither compound produces growth arrest, in contrast with the effects produced by the tri-substituted acridine compound BRACO-19. It is concluded that telomerase inhibitory activity is a necessary though by itself insufficient property in order for cellular growth arrest to occur at sub-toxic concentrations, and that tight quadruplex binding is also required.

Structure-based design of selective and potent G quadruplex-mediated telomerase inhibitors

The telomerase enzyme is a potential therapeutic target in many human cancers. A series of potent inhibitors has been designed by computer modeling, which exploit the unique structural features of quadruplex DNA. These 3,6,9-trisubstituted acridine inhibitors are predicted to interact selectively with the human DNA quadruplex structure, as a means of specifically inhibiting the action of human telomerase in extending the length of single-stranded telomeric DNA. The anilino substituent at the 9-position of the acridine chromophore is predicted to lie in a third groove of the quadruplex. Calculated relative binding energies predict enhanced selectivity compared with earlier 3,6-disubstituted compounds, as a result of this substituent. The ranking order of energies is in accord with equilibrium binding constants for quadruplex measured by surface plasmon resonance techniques, which also show reduced duplex binding compared with the disubstituted compounds. The 3,6,9-trisubstututed acridines have potent in vitro inhibitory activity against human telomerase, with EC(50) values of up to 60 nM.