Safety and Activity of the First-in-Class Sym004 Anti-EGFR Antibody Mixture in Patients with Refractory Colorectal Cancer

Abstract Tumor growth in the context of EGFR inhibitor resistance may remain EGFR-dependent and is mediated by mechanisms including compensatory ligand upregulation and de novo gene alterations. Sym004 is a two-antibody mixture targeting nonoverlapping EGFR epitopes. In preclinical models, Sym004 causes significant EGFR internalization and degradation, which translates into superior growth inhibition in the presence of ligands. In this phase I trial, we observed grade 3 skin toxicity and hypomagnesemia as mechanism-based dose-limiting events during dose escalation. In dose-expansion cohorts of 9 and 12 mg/kg of Sym004 weekly, patients with metastatic colorectal cancer and acquired EGFR inhi…

Abstract 3363: Pharmacodynamic (PD) assessment of drug activity in tumor tissue from patients (pts) enrolled in a Phase I study of MEHD7945A (MEHD), a first-in-class HER3/EGFR dual action antibody, in pts with locally advanced or metastatic epithelial tumors.

Abstract Background Members of the human epidermal growth factor receptor (HER) family of oncogenes are often co-expressed and heterodimerized, suggesting that simultaneous blockade of multiple HER family receptors may be more effective than targeting single receptors. MEHD is a dual-action human IgG1 antibody that can bivalently bind to HER3 and EGFR and block ligand binding to either. FDG-PET imaging is a recognized method of assessing PD modulation with EGFR inhibitors in the clinic. HER3 and EGFR signaling via the MAPK and PI3K pathways can be monitored in tissue by examining phosphorylation of downstream markers. Methods A Phase 1, multicenter, open-label study was conducted to evaluat…

Proof-of-concept study of Sym004, an anti-EGFR monoclonal antibody (mAb) mixture, in patients (pts) with anti-EGFR mab-refractory KRAS wild-type (wt) metastatic colorectal cancer (mCRC).

3551 Background: KRAS wt mCRC pts progressing on chemotherapy and anti-EGFR mAbs have limited treatment options. Sym004 is a first-in-class drug mixture of two mAbs targeting non-overlapping epitopes on the EGFR, causing its internalization and degradation. With this unique mechanism of action, Sym004 overcomes acquired resistance to anti-EGFR mAbs in preclinical studies. Methods: Open-label, multicenter trial assessing safety (primary endpoint) and efficacy of 2 dose levels of Sym004 in KRAS wt mCRC pts with prior clinical benefit to anti-EGFR mAbs and subsequent progression during or within 6 months after treatment cessation. Sym004 was administered until disease progression or unaccepta…

Phase 1 study of biweekly (Q2W) anti-EGFR monoclonal antibody (mAb) mixture Sym004 in patients (pts) with metastatic colorectal cancer (mCRC) resistant to previous anti-EGFR treatment.

3551 Background: Preclinical models suggest that WT KRAS mCRC may retain EGFR dependency despite resistance developed to anti-EGFR mAb treatment (eg, cetuximab or panitumumab). Sym004 is the first-...

Safety and Pharmacokinetics/Pharmacodynamics of the First-in-Class Dual Action HER3/EGFR Antibody MEHD7945A in Locally Advanced or Metastatic Epithelial Tumors.

Abstract Purpose: The novel dual-action humanized IgG1 antibody MEHD7945A targeting HER3 and EGFR inhibits ligand-dependent HER dimer signaling. This phase I study evaluated the safety, pharmacokinetics, pharmacodynamics, and antitumor activity of MEHD7945A. Experimental Design: Patients with locally advanced or metastatic epithelial tumors received escalating doses of MEHD7945A (1–30 mg/kg) every 2 weeks (q2w) until disease progression or intolerable toxicity. An expansion cohort was enrolled at the recommended phase II dose (14 mg/kg, q2w). Plasma samples, tumor biopsies, FDG-PET were obtained for assessment of pharmacokinetics, and pharmacodynamic modulation downstream of EGFR and HER3. …

Abstract CT-08: A Phase 1 study of MEHD7945A (MEHD), a first-in-class EGFR/HER3 dual action antibody, in patients (pts) with locally advanced or metastatic epithelial tumors

Abstract Background Dysregulated human epidermal growth factor receptor tyrosine kinase (HER RTK) signaling is an important driver of tumor growth, metastasis, and survival. Extensive HER RTK co-expression and heterodimerization suggest that simultaneous blockade of multiple RTKs may be more effective than targeting individual RTKs, and may help prevent or delay development of resistance mechanisms. MEHD is a novel dual-action human IgG1 antibody. Each antigen-binding fragment blocks ligand binding to both EGFR and HER3, which is meant to inhibit the activity of the major ligand-dependent HER dimers in cancer. MEHD also elicits antibody-dependent cell-mediated cytotoxicity, and has single-a…

Human pharmacokinetic (PK) characterization of the novel dual-action anti-HER3/EGFR antibody MEHD7945A (MEHD) in patients with refractory/recurrent epithelial tumors.

2567 Background: MEHD is a novel dual-action human IgG1 antibody that blocks ligand binding to HER3 and EGFR, and elicits antibody-dependent cell-mediated cytotoxicity (ADCC). MEHD demonstrates single-agent activity in a broad panel of tumor models, including models resistant to anti-HER3 or anti-EGFR treatment alone. The objective of this analysis was to characterize the PK of MEHD associated with body weight (BW)-based dosing used in a phase I study in patients with epithelial tumors and to evaluate the potential for using fixed dosing in future studies. Methods: Preliminary non-compartmental and population PK analyses were performed using patient data from the dose-escalation stage [1, …

A phase I study of MEHD7945A (MEHD), a first-in-class HER3/EGFR dual-action antibody, in patients (pts) with refractory/recurrent epithelial tumors: Expansion cohorts.

2568 Background: Dysregulated human epidermal growth factor receptor tyrosine kinase (HER RTK) signaling is an important driver of tumor growth, metastasis, and survival. Extensive co-expression and heterodimerization suggest that simultaneous blockade of multiple HER RTKs may be more effective than blockade of a single RTK. MEHD is a novel dual-action human IgG1 antibody. Each antigen-binding fragment blocks ligand binding to HER3 or EGFR, and intended to inhibit signaling from all major ligand-dependent HER dimers. MEHD has single-agent activity in multiple tumor models including models resistant to anti-HER3 or anti-EGFR. Methods: This Phase I study evaluated safety, tolerability, pharm…

Heterogeneity of driver genes and therapeutic implications in colorectal cancer.