Panoply™ Human FSHR Over-expressing Stable Cell Line

Despite advances in ovarian cancer (OC) treatment, recurrent OC remains a disease with a poor prognosis. Due to the close interplay between OC cells and the tumor microenvironment (TME), developing strategies that target tumor cells and act on TME components is crucial. A major hurdle in the development of OC therapies is identifying targets that are exclusively expressed on the tumor surface to avoid off-target interactions. The follicle-stimulating hormone receptor (FSHR) is selectively expressed in ovarian granulosa cells and is expressed in 50%–70% of serous OC. Here, researchers used an in vivo-expressed FSHR construct to generate mAbs targeting the external domain of FSHR. Using high-throughput flow cytometry, they identified multiple clones and screened for D2AP11, a potent FSHR surface-targeting mAb. D2AP11 recognized important OC cell lines derived from tumors harboring diverse mutations, including BRCA1/2, as well as cell lines resistant to multiple therapies. The researchers used D2AP11 to develop a bispecific T cell engager. In vitro, addition of PBMCs and T cells to D2AP11-TCE resulted in specific and potent killing of diverse genetically and immune-evasive OC cell lines with EC50 values in the ng/ml range and reduced tumor burden in an OC-challenged mouse model. These studies demonstrate the potential utility of FSHR-targeted biologics for OC and other FSHR-positive cancers.

Bispecific T cell engagers (TCEs) represent a recent major advancement in monoclonal antibody technology. Given the initial levels of ADCC (antibody-dependent cellular cytotoxicity) demonstrated by the D2AP11 anti-FSHR antibody, researchers sought to enhance its potential. They designed a TCE-targeted FSHR antibody (D2AP11-TCE). They genetically optimized and fused the scFv of this FSHR monoclonal antibody to a developed scFv encoding an optimized sequence for anti-CD3 (engineered from UCHT1) (Figure 1A and B). D2AP11-TCE was efficiently expressed in vitro after DNA transfection in Expi293F cells (Figure 1C). This bispecific antibody exhibited no nonspecific binding to K562 cells, which do not express FSHR (Figure 1D), while retaining binding to FSHR-overexpressing K562 cells (Figure 1E). Its binding to FSHR was further confirmed in CAOV3 (Figure 1F) and FSHR-expressing CAOV3 cells (Figure 1G). CD3 binding of the D2AP11-TCE bispecific was confirmed using primary human T cells (Figure 1H).

Figure 1. Generation, expression, and antitumor activity of D2AP11-TCE. (Bordoloi D, et al., 2022)