Abstract Background & Goals: Epidermal growth factor receptor (EGFR), an oncogenic receptor tyrosine kinase, is a major therapeutic target in several types of cancers. Several EGFR inhibitors are used to treat EGFR-positive colorectal cancer (CRC). Unfortunately, primary and acquired resistance to the inhibitors is very common. Current approaches to combating the resistance include combining EGFR inhibitors with agent(s) that targets compensatory signaling molecules (HER2, HER3, IGF1R, MET, KRAS, BRAF and PIK3CA). However, responses to such combination treatments are modest, if any. Overcoming drug resistance remains a major unmet medical need in EGFR-positive CRC. Results: Here, we show the main reason for CRC resistance to EGFR inhibitors and a therapeutic strategy that overcomes it. The sensitivity of CRC cells to EGFR inhibitors correlates with EGFR downregulation. PEPDG278D, a recombinant human protein that induces the degradation of both EGFR and HER2, strongly inhibits oncogenic signaling and growth of CRC in vitro and in vivo (subcutaneous tumors, orthotopic tumors, and patient-derived xenografts), regardless of activating mutations of KRAS, BRAF and PIK3CA. siRNA knockdown of EGFR or HER2 also inhibits CRC cells resistant to EGFR inhibitors. PEPDG278D indirectly suppresses HER3, IGF1R and MET by disrupting their heterodimerization with EGFR or HER2. While excessive tumor-generated EGFR ligands may block target engagement by PEPDG278D, inhibiting ligand shedding by aderbasib enables PEPDG278D to exert strong antitumor activity, and fluorouracil further enhances tumor inhibition. Collectively, our study shows that CRC resistance to EGFR inhibitors result primarily from their inability to eliminate their target and a PEPDG278D-centered combination treatment overcomes the resistance. Conclusions & Therapeutic Relevance: The therapeutic activity of PEPDG278D highlights that EGFR and HER2 remain indispensable to the survival of CRC cells resistant to EGFR inhibitors. The strong therapeutic activity of PEPDG278D-centered combination treatment in preclinical models of CRC, which carry clinically relevant gene mutations that confer resistance to current EGFR inhibitors, provides the scientific premise for potential evaluation of this recombinant human protein in patients with drug-resistant CRC. Citation Format: Lu Yang, Arup Bhattacharya, Yun Li, Sandra Sexton, Xiang Ling, Fengzhi Li, Yuesheng Zhang. Depleting EGFR and HER2 overcomes resistance to EGFR inhibitors in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2612.