Targeted nanoparticle delivery of irinotecan enhances tumor response to PD-L1 blockade in colorectal cancer

Colorectal cancer (CRC) remains a leading cause of cancer mortality, with limited therapeutic options in advanced stages. CD44v6, a splice variant overexpressed in CRC, promotes tumor progression and immune evasion, representing a relevant target for selective drug delivery. In this work, irinotecan-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles functionalized with CD44v6 ligands (Iri@NP-v6) were developed to improve irinotecan delivery and therapeutic responses in CRC. Iri@NP-v6 showed controlled physicochemical properties, high drug loading, and sustained release. In vitro, targeted NPs achieved selective uptake and enhanced cytotoxicity in CD44v6⁺ CRC cell lines. In immune-stromal co-culture spheroids, Iri@NP-v6 combined with anti-PD-L1 reduced viability, promoted Th1-associated cytokines, and limited tumor-supportive MCP-1 production. While NP monotherapy induced mixed inflammatory signals, PD-L1 blockade redirected this response toward a Th1-dominated profile. In immunocompetent mice with MC38 tumors, combination therapy significantly reduced tumor burden and increased CD4⁺ and CD8⁺ T cell infiltration without systemic toxicity. Importantly, free irinotecan triggered broad systemic inflammation, whereas NP-based delivery limited systemic cytokine release while maintaining intratumoral immune activation. These findings demonstrate that CD44v6-targeted irinotecan NPs in combination with PD-L1 blockade, reshape the CRC immune microenvironment while reducing systemic inflammation, supporting their potential as a tumor-selective chemo-immunotherapy platform.