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The chemokine receptor CXCR4 is highly expressed and associated with poor prognosis in multiple malignancies. Upon engagement by its ligand, CXCL12, CXCR4 triggers intracellular signaling pathways that control trafficking of cells to tissues where the ligand is expressed, such as the bone marrow (BM). In hematologic cancers, CXCR4-driven homing of malignant cells to the BM protective niche is a key mechanism driving disease and therapy resistance. We developed a humanized CXCR4 immunoglobulin G1 (IgG1) antibody (Ab), PF-06747143, which binds to CXCR4 and inhibits CXCL12-mediated signaling pathways, as well as cell migration. In in vivo preclinical studies, PF-06747143 monotherapy rapidly and transiently mobilized cells from the BM into the peripheral blood. In addition, PF-06747143 effectively induced tumor cell death via its Fc constant region–mediated effector function. This Fc-mediated cell killing mechanism not only enhanced antitumor efficacy, but also played a role in reducing the duration of cell mobilization, when compared with an IgG4 version of the Ab, which does not have Fc-effector function. PF-06747143 treatment showed strong antitumor effect in multiple hematologic tumor models including non-Hodgkin lymphoma (NHL), acute myeloid leukemia (AML), and multiple myeloma (MM). Importantly, PF-06747143 synergized with standard-of-care agents in a chemoresistant AML patient-derived xenograft model and in an MM model. These findings suggest that PF-06747143 is a potential best-in-class anti-CXCR4 antagonist for the treatment of hematologic malignancies, including in the resistant setting. PF-06747143 is currently in phase 1 clinical trial evaluation (registered at www.clinicaltrials.gov as #NCT02954653).

The chemokine receptor CXCR4 is highly expressed and associated with poor prognosis in multiple malignancies. Upon engagement by its ligand, CXCL12, CXCR4 triggers intracellular signaling pathways that control trafficking of cells to tissues where the ligand is expressed, such as the bone marrow (BM). In hematologic cancers, CXCR4-driven homing of malignant cells to the BM protective niche is a key mechanism driving disease and therapy resistance. We developed a humanized CXCR4 immunoglobulin G1 (IgG1) antibody (Ab), PF-06747143, which binds to CXCR4 and inhibits CXCL12-mediated signaling pathways, as well as cell migration. In in vivo preclinical studies, PF-06747143 monotherapy rapidly and transiently mobilized cells from the BM into the peripheral blood. In addition, PF-06747143 effectively induced tumor cell death via its Fc constant region–mediated effector function. This Fc-mediated cell killing mechanism not only enhanced antitumor efficacy, but also played a role in reducing the duration of cell mobilization, when compared with an IgG4 version of the Ab, which does not have Fc-effector function. PF-06747143 treatment showed strong antitumor effect in multiple hematologic tumor models including non-Hodgkin lymphoma (NHL), acute myeloid leukemia (AML), and multiple myeloma (MM). Importantly, PF-06747143 synergized with standard-of-care agents in a chemoresistant AML patient-derived xenograft model and in an MM model. These findings suggest that PF-06747143 is a potential best-in-class anti-CXCR4 antagonist for the treatment of hematologic malignancies, including in the resistant setting. PF-06747143 is currently in phase 1 clinical trial evaluation (registered at www.clinicaltrials.govas #NCT02954653).

Pernasetti: Pfizer: Employment. Liu:Pfizer: Employment. Hallin:Pfizer: Employment. Gu:Pfizer: Employment. Ho:Pfizer: Employment. Zhang:Pfizer: Employment. Pascual:Pfizer: Employment. Simmons:Pfizer: Employment. Yan:Pfizer: Employment. Huser:Pfizer: Employment. Wang:Pfizer: Employment. Lam:Pfizer: Employment. Spilker:Pfizer: Employment. Blasi:Pfizer: Employment. Tran:Pfizer: Employment. Kudaravalli:Pfizer: Employment. Ma:Pfizer: Employment. Chin:Pfizer: Employment. Shelton:Pfizer: Employment. Smeal:Pfizer: Employment. Fantin:Pfizer: Employment.

CXCR4 is a chemokine receptor that belongs to the G-coupled protein receptor (GPCR) family. It is over-expressed in various cancers, including solid tumors and hematological malignancies, and correlates with poor prognosis. CXCR4 expressing cells actively respond to CXCL12 (SDF-1), a chemokine constitutively secreted by stromal cells in bone marrow. Activation of CXCR4 induces cell trafficking and homing to the marrow microenvironment, where CXCL12 retains these cells in close contact with marrow stromal cells that provide growth signals, promote self-renewal, and contribute to drug resistance, leading to poor prognosis and relapse. Here we describe the generation of a highly potent and selective anti-CXCR4 humanized IgG1 antagonist Ab (PF-06747143) that binds to human CXCR4 with high affinity and blocks SDF-1-induced Calcium flux and cAMP signaling. We have also characterized the ability of PF-06747143 to induce cell death through three different mechanisms: a) mobilization of cells from CXCL12-rich niches, making them more sensitive to chemotherapy b) direct cell-death through a mechanism dependent on the antibody’s bivalency; c) ADCC- and CDC-dependent cell death through the Fc-region in IgG1 backbone, when in the presence of effector cells or serum proteins. Weekly administration of PF-06747143 at 10 mg/kg, as a monotherapy, significantly improved survival, induced sustained regression and reduced bone marrow tumor burden in various patient population relevant murine disseminated tumor models of Acute Myeloid Leukemia (MV4-11, PDXs), Non Hodgkin Lymphoma (Raji and Ramos), Chronic Lymphocytic Leukemia (JVM-13) and Multiple Myeloma (OPM-2). The CXCR4 IgG1 antibody was also shown to be similar or more efficacious than approved standards of care agents currently employed for treatment of hematological malignancies. The safety and PK/PD profile of PF-06747143 were evaluated in a Non-Human Primate (NHP) exploratory toxicology study. Results from this study indicate that the CXCR4 IgG1 Ab was well tolerated in a two-week exploratory study at pharmacologically relevant doses. Upon treatment with PF-06747143, egression of white blood cells (WBC) from bone marrow (leukocytosis) was noted, which is consistent with target (CXCR4) modulation. Following the peak of leukocytosis between 1-6 hours post antibody administration, the number of circulating WBCs rapidly decreased back to baseline levels at 24 hrs. These results are likely explained by the direct cell killing through the effector function of this IgG1 CXCR4 antibody. Altogether, the promising preclinical efficacy and safety data support clinical evaluation of PF-06747143 in hematological malignacies.