(C) Antitumor activity of IMGN853 was compared to controls, PBS CTRL, ADC isotype, and M9345A in uterine serous cancer xenograft tumor models of BIO(K)1 (FR=2+)

(C) Antitumor activity of IMGN853 was compared to controls, PBS CTRL, ADC isotype, and M9345A in uterine serous cancer xenograft tumor models of BIO(K)1 (FR=2+). tumor cell lines. In contrast, tumor cell lines with low FR showed no difference when exposed to IMGN853 versus control. IMGN853 induced bystander killing of FR = 0 tumor cells. In an endometrioid xenograft model (END(K)265), harboring 2+ FR, IMGN853 treatment showed complete resolution of tumors (p 0.001). Treatment with IMGN853 in USC PDX model (BIO(K)1), expressing 2+ FR, induced 2-fold increase in median survival (p 0.001). IMGN853 shows impressive anti-tumor activity PRT-060318 in biologically aggressive FR 2+ uterine cancers. This preclinical data suggests that patients with chemotherapy resistant/recurrent endometrial cancer overexpressing FR may benefit from this treatment. receptors (15,16) and is currently Food and Drugs Administration (FDA) and European Medical Agency (EMA) approved for the treatment of HER2-positive metastatic breast cancer patients who previously were treated with trastuzumab and a taxane chemotherapy. A more recently developed ADC, IMGN853 (Immunogen, Waltham, MA), is composed of a humanized antibody (M9346A) with high affinity to folic acid receptor alpha (FR) attached via a cleavable disulfide-containing hydrophilic linker (sulfo-SPDB), to the maytansinoid DM4, a potent microtubule toxin (17,18) IMGN853 binds with selectivity to tumor cells expressing FR and is internalized by receptor mediated endocytosis. Importantly, once intracellular, IMGN853 is degraded by acidic lysosomes allowing DM4 to inhibit microtubules, resulting in cell-cycle arrest and apoptosis. IMGN853 can also induce bystander cytotoxic activity. This action is considered to be particularly important for the activity of the ADC against tumors with heterogeneous expression of FR (ie, negative or low FR expressing malignant cells intermixed with FR highly expressing tumor cells) (18). FR is a glycosylphosphatidylinositol-anchored high-affinity folate receptor that localizes to the apical surface of epithelia and shows a restricted distribution pattern in normal tissues, with expression limited to a variety of polarized epithelia, such as Mouse monoclonal to IL-2 those found in the choroid plexus, kidney, uterus, ovary, lung, and placenta (19C21). Unlike normal tissues, FR may localize to the basolateral side in many tumors, and accordingly, epithelial ovarian cancer (EOC) and endometrial cancer have recently been identified as a target for anti-folic acid receptor agents. PRT-060318 Several reports have indicated an increased expression of FR in a large number of patients with EOC (19C21), and uterine cancer (22C24) and consistent with this view, the activity of IMGN853 is currently being tested in Phase II/III clinical trials with promising activity reported in platinum-resistant ovarian cancer patients (25C27). The objective of this study was to evaluate the expression of FR in biologically aggressive endometrial cancers and to examine the preclinical anti-tumor activity PRT-060318 of IMGN853 against primary endometrioid and USC cell lines with differential FR expression. We demonstrate for the first time that IMGN853 is highly active, both as well as against poorly differentiated, biologically aggressive endometrial tumors which cause the PRT-060318 overwhelming majority of endometrial cancer deaths. Clinical studies with IMGN853 in patients harboring FR overexpressing endometrial tumors resistant to chemotherapy are warranted. MATERIALS AND METHODS Establishment of endometrioid and serous uterine cancer cell lines Approval for this study was obtained through the Institutional Review Board (IRB). All patients signed consent before tissue collection per institutional guidelines. Nine primary endometrial endometrioid and 11 primary uterine serous cell lines were established from fresh tumor biopsy samples as described previously (28C31). In brief, tumors were processed by mechanical disruption in an enzymatic solution of 0.14% collagenase type I (Sigma) and 0.01% DNase (Sigma) in RPMI 1640. The resulting solution was incubated for PRT-060318 45 minutes at room temperature while stirring. The samples were then washed with RPMI 1640/10% FBS and plated in Petri dishes using RPMI 1640, 10% FBS, 1% penicillin with streptomycin and 1% amphotericin. The cell lines were kept in an incubator at 37 degrees Celsius with.