e14078 Background: EGFR is a validated target for anti-cancer drug development. Several anti-EGFR monoclonal antibodies (mAb) are used in clinics, but associated with a variety of toxicities. A new anti-EGFR mAb might offer better efficacy with less toxicities. Methods: we have developed a new humanized anti-EGFR mAb, HLX07, through engineering of Fab portion and improvement of glycosylation profile and tested in in vitro assays, in vivo xenograft animal models and primate pharmacokinetic (PK) and toxicokinetic (TK) studies. Results: HLX07 exerted potent antibody-dependent, cell-mediated cytotoxicity in vitro. It specifically binds to monkey and human but not rodent EGFR. HLX07 has better binding affinity to human EGFR, compared with cetuximab (KD 1.43x10-10 vs. 2.62x10-10). HLX07 completely inhibited the phosphorylation of EGFR in H292 cells at ≥0.1 nM, The IC50 of HLX07 for DiFi and H292 cells were 54.2 and 23.9 ng/mL, respectively, compared with 63.7 and 37.2 ng/mL by cetuximab, respectively. In vivo xenogenic studies also demonstrated that HLX07 significantly inhibited the growth of H292, A432 and WiDi cells in a dose-dependent manner. Xenogenic studies also showed that HLX07 used with gemcitabine and/or cisplatin was more active than either agent alone. HLX07 was more effective than cetuximab in inhibiting the growth of FaDu cells when used with local radiotherapy in vivo. Single-dose and 13-week repeat-dose GLP pharmacokinetic and toxicokinetic studies in cynomulgus monkeys up to 60 mg/kg/wk shows minimal-to-mild toxicities (see table). Conclusions: The detailed preclinical characterization indicates that HLX07 has better efficacy and less toxicity than cetuximab. A phase 1 first-in-human study is ongoing (NCT02648490). [Table: see text]