Targeting a Tumor-Specific Epitope on Podocalyxin Increases Survival in Human Tumor Preclinical Models

Abstract

Podocalyxin (Podxl) is a CD34-related cell surface sialomucin that is normally highly expressed by adult vascular endothelia and kidney podocytes where it plays a key role in blocking adhesion. Importantly, it is also frequently upregulated on a wide array of human tumors and its expression often correlates with poor prognosis. We previously showed that, in xenograft studies, Podxl plays a key role in metastatic disease by making tumor initiating cells more mobile and invasive. Recently, we developed a novel antibody, PODO447, which shows exquisite specificity for a tumor-restricted glycoform of Podxl but does not react with Podxl expressed by normal adult tissue. Here we utilized an array of glycosylation defective cell lines to further define the PODO447 reactive epitope and reveal it as an O-linked core 1 glycan presented in the context of the Podxl peptide backbone. Further, we show that when coupled to monomethyl auristatin E (MMAE) toxic payload, PODO447 functions as a highly specific and effective antibody drug conjugate (ADC) in killing ovarian, pancreatic, glioblastoma and leukemia cell lines in vitro. Finally, we demonstrate PODO447-ADCs are highly effective in targeting human pancreatic and ovarian tumors in xenografted NSG and Nude mouse models. These data reveal PODO447-ADCs as exquisitely tumor-specific and highly efficacious immunotherapeutic reagents for the targeting of human tumors. Thus, PODO447 exhibits the appropriate characteristics for further development as a targeted clinical immunotherapy.

A Cancer-Specific Monoclonal Antibody against Podocalyxin Exerted Antitumor Activities in Pancreatic Cancer Xenografts

“…Using an array of glycosylation defective cell lines, the epitope of PODO447 was revealed to be an O -linked core 1 glycan presented in the context of the PODXL peptide backbone [ 39 ]. Furthermore, PODO447 coupled with monomethyl auristatin E (MMAE) showed efficacy in targeting human pancreatic and ovarian tumor xenografts in mouse models [ 40 ].…”

A tumor-restricted glycoform of podocalyxin is a highly selective marker of immunologically cold high-grade serous ovarian carcinoma

“…Since the core protein of PODXL is aberrantly expressed by many human tumors and its expression is consistently linked to poor prognosis (reviewed in (4,8,14,17,18)), this PODO447 epitope serves as an excellent candidate for the development of targeted cancer immunotherapies. Indeed, we recently documented the effectiveness of a PODO447-directed ADC against human xenografted tumors as proof-of-principle to further support this concept (16). Intriguingly, in the case of high-grade serous ovarian carcinoma (HGSOC), we previously found that roughly 65% of these tumors express the PODO447 epitope (15).…”

“…Intriguingly, dysregulation of glycosylation pathways are known to frequently occur during cancer development and this can lead to the generation of tumor-associated carbohydrate antigens (TACA) which represent a potential array of tumorspecific neo-epitopes (13,14). Taking advantage of this peculiarity of neoplastic cells, we recently developed a novel monoclonal antibody (mAb), named PODO447, that targets a glycopeptide epitope of PODXL expressed on cancer cells, but is absent on normal, PODXL-expressing podocytes and vascular endothelia (15,16). This glycoepitope comprises a peptide sequence within the mucin domain of PODXL together with a core 1 disaccharide (Galb1-3GalNAc-a-1-O-Thr/Ser), also called the "T-antigen" (16).…”

“…Taking advantage of this peculiarity of neoplastic cells, we recently developed a novel monoclonal antibody (mAb), named PODO447, that targets a glycopeptide epitope of PODXL expressed on cancer cells, but is absent on normal, PODXL-expressing podocytes and vascular endothelia (15,16). This glycoepitope comprises a peptide sequence within the mucin domain of PODXL together with a core 1 disaccharide (Galb1-3GalNAc-a-1-O-Thr/Ser), also called the "T-antigen" (16). Since the core protein of PODXL is aberrantly expressed by many human tumors and its expression is consistently linked to poor prognosis (reviewed in (4,8,14,17,18)), this PODO447 epitope serves as an excellent candidate for the development of targeted cancer immunotherapies.…”

Spatial regulation of the glycocalyx component podocalyxin is a switch for prometastatic function

“…PODXL expression alone modestly stratifies outcome in some cancers but becomes a potent predictor of poor outcome when comparing cortical to intracellular levels of PODXL ( 11 , 23 – 28 ). Moreover, tumor-restricted glycosylation patterns have allowed the development of tumor cell–selective therapeutic anti-PODXL antibodies ( 29 ). This emphasizes that mucins such as PODXL require contextual modulation to form part of the tumor-associated, prometastatic bulky glycocalyx.…”