ImmunoPET of Ovarian and Pancreatic Cancer with AR9.6, a Novel MUC16-Targeted Therapeutic Antibody.

PURPOSE: Advances in our understanding of the contribution of aberrant glycosylation to the pro-oncogenic signaling and metastasis of tumor cells have reinvigorated the development of mucin-targeted therapies. Here, we validate the tumor-targeting ability of a novel monoclonal antibody (mAb), AR9.6, that binds MUC16 and abrogates downstream oncogenic signaling to confer a therapeutic response. EXPERIMENTAL DESIGN: The in vitro and ex vivo validation of the binding of AR9.6 to MUC16 was achieved via flow cytometry, radioligand binding assay (RBA), and immunohistochemistry (IHC). The in vivo MUC16 targeting of AR9.6 was validated by creating a 89Zr-labeled radioimmunoconjugate of the mAb and utilizing immunoPET and ex vivo biodistribution studies in xenograft models of human ovarian and pancreatic cancer. RESULTS: Flow cytometry, RBA, and IHC revealed that AR9.6 binds to ovarian and pancreatic cancer cells in an MUC16-dependent manner. The in vivo radiopharmacologic profile of 89Zr-labeled AR9.6 in mice bearing ovarian and pancreatic cancer xenografts confirmed the MUC16-dependent tumor targeting by the radioimmunoconjugate. Radioactivity uptake was also observed in the distant lymph nodes (LNs) of mice bearing xenografts with high levels of MUC16 expression (i.e., OVCAR3 and Capan-2). IHC analyses of these PET-positive LNs highlighted the presence of shed antigen as well as necrotic, phagocytized, and actively infiltrating neoplastic cells. The humanization of AR9.6 did not compromise its ability to target MUC16-expressing tumors. CONCLUSIONS: The unique therapeutic mechanism of AR9.6 combined with its excellent in vivo tumor targeting makes it a highly promising theranostic agent. huAR9.6 is poised for clinical translation to impact the management of metastatic ovarian and pancreatic cancers.

Correction to: Translational immune correlates of indirect antibody immunization in a randomized phase II study using scheduled combination therapy with carboplatin/paclitaxel plus oregovomab in ovarian cancer patients.

The original version of this article unfortunately contained a mistake.

Translational immune correlates of indirect antibody immunization in a randomized phase II study using scheduled combination therapy with carboplatin/paclitaxel plus oregovomab in ovarian cancer patients.

The standard-of-care (SOC) first-line therapy for ovarian cancer (OC) patients is plagued with high relapse rates. Several studies indicated the immune system's prominent role changing the disease course in OC patients. Chemo-immunotherapy regimens, currently being explored, include oregovomab, which is a monoclonal antibody specific for the OC associated antigen carbohydrate/cancer antigen 125 (CA125) that yielded promising results when administered together with SOC in a previous study. The QPT-ORE-002 multi-site phase II randomized study demonstrated that in patients with advanced OC, oregovomab combined with first-line SOC improved overall and progression-free survival, compared to SOC alone. The study included an Italian cohort in which we demonstrated that adding oregovomab to SOC resulted in increased patient numbers with amplified CA125-specific CD8+T lymphocytes/ml peripheral blood counts, which might explain the improved therapeutic effect of SOC + oregovomab over SOC alone. Predictive for oregovomab efficacy was a less suppressive immune environment at baseline as indicated by low numbers of circulating myeloid-derived suppressor cells, subset type 4, and a low neutrophil-and-monocyte to lymphocyte ratio.

Sonodynamic and photodynamic mechanisms of action of the novel hypocrellin sonosensitizer, SL017: mitochondrial cell death is attenuated by 11, 12-epoxyeicosatrienoic acid.

Development of sonosensitizers for sonodynamic therapy (SDT) which selectively target abnormal cells can limit undesired side effects in chemotherapeutic applications. Hypocrellin-B (HB) derivatives are low molecular weight compounds which belong to the perylenequinone family of photosensitizing and sonosensitizing compounds. In this study, we investigate the cytotoxic mechanisms of a novel HB-derived photo- and sonosensitizer, SL017. Human fibroblast WI-38 cells were treated with SL017 (0 µM, 0.1 µM or 10 µM) and subjected to photodynamic therapy (PDT) or SDT. Studies demonstrate that maximal uptake of SL017 occurs within 30 min, with a mitochondrial subcellular localization. Activation of SL017 by either visible light or ultrasound resulted in significant increases in reactive oxygen species (ROS) production as measured by CM-H2-DCFDA (5-(and-6)-chloromethyl-2'7'-dichlorodihydrofluorescein diacetate acetyl ester). Co-administration of the antioxidant, ascorbic acid, attenuated ROS production. Low concentrations of SL017 (100 nM) induced a rapid (<90 s) loss of mitochondrial membrane potential (ΔΨm). Epoxyeicosatrienoic acids (EETs), cytochrome P450-derived metabolites of arachidonic acid (AA) involved in maintaining homeostasis and protection against cell injury, were able to attenuate loss of ΔΨm, however ascorbic acid was not. SL017 treatment resulted in increased mitochondrial fragmentation which followed loss of ΔΨm. Our studies demonstrate that SL017 targets mitochondria, triggering collapse of mitochondrial membrane potential, generates ROS and subsequently results in mitochondrial fragmentation.