Cancer Stem Cell-targeted Antibody-drug Conjugates for Cancer Immunotherapy

Cancer stem cells (CSCs) participate in cancer initiation, metastasis, and therapy tolerance, presenting a formidable challenge in cancer treatment. Antibody-drug conjugates (ADCs) have been established as a potential strategy for selectively targeting and eradicating CSCs, thereby overcoming resistance mechanisms and preventing tumor recurrence. ADCs integrate a monoclonal antibody specific to CSC surface markers, such as CD44, CD133, EpCAM, and ALDH1, with a potent cytotoxic payload linked by a stable chemical linker. Upon antigen binding, ADCs undergo receptor-mediated internalization, leading to intracellular payload release and CSC apoptosis. Recent advances in ADC technology have enhanced selectivity and efficacy while minimizing off-target toxicity. Preclinical studies demonstrate that CSC-targeted ADCs, including CD133- and CD44-directed therapies, effectively deplete CSC populations in glioblastoma, breast, colorectal, and lung cancers. EpCAM-targeted ADCs have also shown efficacy in epithelial tumors with potential synergy in combination immunotherapies. Moreover, emerging approaches, such as bispecific antibodies and optimized linker chemistry, further refine CSC-targeted ADCs for clinical applications. Despite these advancements, challenges remain, including CSC heterogeneity, immune evasion, and limitations in biomarker specificity. Addressing these hurdles requires continued innovation in ADC engineering, novel payloads, and combinatory strategies with immune checkpoint inhibitors or CAR-T cell therapies. While clinical evaluations are still in the early phases, preliminary trials underscore the potential of CSC-targeted ADCs in revolutionizing precision oncology. This review explores the mechanisms, recent developments, and prospects of CSC-targeted ADCs, highlighting their transformative potential in cancer immunotherapy.