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Mutated KRAS promotes the activation of the MAPK pathway and the progression of colorectal cancer (CRC) cells. Aberrant activation of the PI3K pathway strongly attenuates the efficacy of MAPK suppression in KRAS‐mutated CRC. The development of a novel strategy targeting a dual pathway is therefore highly essential for the therapy of KRAS‐mutated CRC. In this study, a quadruple‐depleting system for the KRAS, MEK1, PIK3CA, and MTOR genes based on CRISPR/SaCas9 was developed. Adenovirus serotype 5 (ADV5) was integrated with two engineered proteins, an adaptor and a protector, to form ADV‐protein complex (APC) for systemic delivery of the CRISPR system. Quadruple‐editing could significantly inhibit the MAPK and PI3K pathways in CRC cells with oncogenic mutations of KRAS and PIK3CA or with KRAS mutation and compensated PI3K activation. Compared with MEK and PI3K/MTOR inhibitors, quadruple‐editing induced more significant survival inhibition on primary CRC cells with oncogenic mutations of KRAS and PIK3CA. The adaptor specifically targeting EpCAM and the hexon‐shielding protector could dramatically enhance ADV5 infection efficiency to CRC cells and significantly reduce off‐targeting tropisms to many organs except the colon. Moreover, quadruple‐editing intravenously delivered by APC significantly blocked the dual pathway and tumor growth of KRAS‐mutated CRC cells, without influencing normal tissues in cell‐ and patient‐derived xenograft models. Therefore, APC‐delivered quadruple‐editing of the MAPK and PI3K pathways shows a promising therapeutic potential for KRAS‐mutated CRC., Aberrant activation of the PI3K pathway interferes with the therapeutic efficacies of MAPK signaling inhibitors in KRAS‐mutated colorectal cancer (CRC). However, overlapping toxicities of small molecule inhibitors limit the treatment effects of combined therapy targeting the MAPK and PI3K pathways. Multiplex genome editing may provide a novel dual‐inhibition strategy for KRAS‐mutated CRC. A quadruple‐depleting system of KRAS, MEK1, PIK3CA, and MTOR based on CRISPR/SaCas9, which were packaged by ADV5 and integrated with two engineered proteins, an adaptor and a protector, to enhance infection efficiency and specificity to CRC cells, could effectively and specifically block tumor progression of KRAS‐mutated CRC models through systemic delivery without vital organ injury, providing a potential option for CRC therapy.