The CXC chemokine receptor 4 (CXCR4) is over-expressed in lung and breast tumors, leading to increased metastasis, poor prognosis and survival rates. Considering the limited treatment options for triple negative breast (TNBC) and non-small cell lung (NSCLC) cancers, CXCR4-based therapy, guided by targeted imaging, will provide a more effective and optimal therapeutic strategy. Here, a humanized anti-CXCR4 antibody (mAb) and its 89Zr-labeled counterpart ([89Zr]mAb) were evaluated for therapeutic efficacy and CXCR4-specific tumor accumulation by positron emission tomography (PET) imaging with the aim to establish a correlation between imaging and therapy in NSCLC and TNBC xenografts in mice.

The specificity of the [89Zr]mAb was evaluated in vitro using the NSCLC (CXCR4high H1155, CXCR4low A549) and TNBC (CXCR4high DU4775, CXCR4med MDA-MB-231) cancer cell lines. These cell lines were also used to establish subcutaneous and orthotopic breast and lung cancer xenografts in immunocompromised mice. The firefly luciferase-expressing MDA-MB-231 breast cancer cell line (231-Luc) was used to generate a spontaneous metastatic mouse model. PET imaging and ex vivo biodistribution studies were performed to evaluate [89Zr]mAb uptake in tumors and metastases. CXCR4 expression was confirmed by immunohistochemistry. For therapy, mice harboring lung and breast tumors were randomized (150mm3) and treated with vehicle (saline), control IgG4 mAb or targeted mAb (10mg/kg every third day, 5x, n = 7/group,). Weight of mice and tumor growth were monitored throughout the study.

In vitro binding studies demonstrated CXCR4-specific radiotracer uptake and correlated with CXCR4 expression as determined by flow cytometry. PET imaging and biodistribution studies in subcutaneous lung cancer xenografts showed a%ID/g of 32.9 ± 6.2 in H1155 and 6.8 ± 0.9 in A549 tumors, 24 h p.i. Preferential H1155 tumor uptake was observed over 120 h with a consistent H1155/A549 ratio of 4.5-5. Similar results were observed in orthotopic lung and breast tumors. PET imaging of 231-Luc xenografted mice demonstrated a [89Zr]mAb uptake [percentage injected dose (%ID)/cc] of 15.7 ± 1.9 and 16.1 ± 2.9 in primary tumors and lymph node metastases, respectively, at 24 h post-injection (p.i.). Therapeutic doses significantly reduced tumor growth in CXCR4high H1155, but not in CXCR4low A549 xenografts. A similar but less pronounced effect was observed in TNBC xenografts that have comparatively lower CXCR4 expression.

[89Zr]mAb-PET demonstrated CXCR4 uptake in primary tumors and metastases in experimental models of NSCLC and TNBC that correlated with therapeutic efficacy of the non-labeled mAb. [89Zr]mAb is a promising and translatable candidate for imaging of CXCR4 expression in various CXCR4 over-expressing cancers, which, in conjunction with the non-labeled antibody, can be utilized for therapeutic intervention and monitoring.

Citation Format: Babak Behnam Azad, Samit Chatterjee, Ala Lisok, Mrudula Pullambhatla, Wojciech G. Lesniak, Zaver M. Bhujwalla, Martin Pomper, Sridhar Nimmagadda. Assessment of a humanized CXCR4 monoclonal antibody for therapeutic monitoring and intervention in experimental NSCLC and TNBC mouse models. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4557. doi:10.1158/1538-7445.AM2015-4557