Abstract DDT02-02: Preclinical development of LFA102, a highly potent and selective neutralizing antibody against the prolactin receptor

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL The prolactin receptor (PRLR) is a class I cytokine receptor frequently expressed in breast and prostate cancer. The polypeptide hormone prolactin (PRL) has been demonstrated to induce PRLR signaling through the Jak/Stat, PI3-kinase/AKT and MAPK pathways, leading to cell proliferation and survival. Breast- and prostate-specific overexpression of PRL in transgenic mice leads to a higher incidence of mammary and prostate tumors, respectively. In addition, the PRLR locus is the site of frequent viral integrations in MMTV-derived mammary tumors. Elevated serum PRL levels in humans have been correlated with an increased risk for breast cancer, and an analysis of more than 3000 breast tumor specimens indicates that PRLR is expressed with high prevalence (60-70% of tumors) across all breast cancer subtypes. In prostate cancer specimens, the presence of prolactin and phosphorylated Stat5 have been reported to be associated with high-grade tumors and poor clinical outcomes, suggesting a role of the PRL/PRLR signaling pathway in the pathology of this disease as well. All of these lines of evidence support the hypothesis that targeting the PRL/PRLR axis may be a new approach for addressing unmet medical need in these tumor types. LFA102 is a Human Engineered™ anti-PRLR antibody of the IgG1 isotype that neutralizes the function of PRLR through a nonligand competitive binding interaction. LFA102 blocks PRL-induced signaling and proliferation in T47D and MCF7 human breast cancer cells in vitro, and abolishes PRL-induced phospho-Stat5 signaling in T47D xenograft tumors in vivo. This antibody also cross-reacts with and neutralizes rat PRLR and is capable of potently regressing PRL-dependent Nb2-C11 pre-T cell lymphoma tumors in vivo. In vitro studies have shown that LFA102 can mediate antibody-dependent cellular cytotoxicity (ADCC) and inhibit the PRL-dependent release of the proangiogenic factor VEGF from breast cancer cells. Thus, there are multiple potential mechanisms through which LFA102 could show antitumor activity in vivo. Preclinical toxicological studies of LFA102 indicate that this therapeutic is well tolerated and exhibits a normal pharmacokinetic profile in relevant animal species. The safety and pharmacokinetics of LFA102 in humans are currently being evaluated in a phase I healthy volunteer trial. A phase 1b trial in breast and prostate cancer is planned to evaluate the efficacy of this antibody in patient populations predicted to have the highest probability of benefiting from an anti-PRLR therapeutic. This presentation will provide a summary of the preclinical data supporting the clinical development of LFA102. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr DDT02-02. doi:10.1158/1538-7445.AM2011-DDT02-02