Cu2+-coordinated NLG919: A drug delivery nanoplatform to activate antitumor immunity via inducing immunogenic cell death and inhibiting indoleamine 2,3-dioxygenase-1

Led by Dr. Shi-Ying Li (The Fifth Affiliated Hospital, Guangzhou Medical University), this study addresses a critical challenge in cancer therapy: the inability of single-agent chemotherapies to elicit durable antitumor immunity due to the immunosuppressive tumor microenvironment (ITM). The team’s solution—a metal-coordinated nanoplatform—combines two key functions: triggering ICD to activate immune responses and inhibiting IDO1 to reverse immune suppression.

Traditional nanocarrier-based drug delivery systems often suffer from complex fabrication, low drug loading, and carrier-related toxicity. In contrast, CuN is formed via self-assembly of Cu²⁺ and NLG919 through Cu-N coordination bonds (confirmed by X-ray photoelectron spectroscopy, XPS). This simplified, carrier-free design enables high-efficiency encapsulation of diverse chemotherapeutic agents, regardless of their physicochemical properties. For example, cinnamic acid, mitoxantrone, docetaxel, β-lapachone, tazemetostat, and mocetinostat were all successfully loaded into CuN, with encapsulation rates ranging from 16.1% to 81.6%. The resulting nanomedicines (e.g., Lap@CuN) exhibit uniform spherical morphology (mean diameter ~180 nm), good aqueous stability, and pH/glutathione (GSH)-responsive drug release—critical for targeted drug delivery to the acidic, GSH-rich tumor microenvironment.

To validate therapeutic efficacy, the team focused on Lap@CuN. β-lapachone, a chemotherapeutic agent activated by NAD(P)H quinone dehydrogenase 1 (NQO1, overexpressed in many cancers), generates excessive reactive oxygen species (ROS) to kill tumor cells and trigger ICD. In vitro experiments with 4T1 breast cancer cells showed that Lap@CuN significantly enhanced cellular uptake of drugs, increased ROS production, and induced robust ICD—evidenced by elevated exposure of calreticulin (CRT) and release of high mobility group box 1 (HMGB1), two key ICD biomarkers. Lap@CuN also exhibited superior cytotoxicity (cell viability <40% at equivalent doses) and selectivity for tumor cells (lower toxicity to normal 3T3 cells) compared to free drugs or unassembled drug mixtures.

In vivo studies using 4T1 tumor-bearing mice further confirmed Lap@CuN’s therapeutic potential. Fluorescence imaging showed that Lap@CuN accumulated more efficiently in tumor tissues than free drugs, due to passive targeting (enhanced permeability and retention, EPR effect). Treatment with Lap@CuN resulted in the smallest primary tumor volume (282 mm³ vs. 564 mm³ in the PBS group) and lightest tumor weight, with no significant body weight loss in mice—indicating low systemic toxicity. Immunofluorescence staining of tumor tissues revealed the strongest ROS production, CRT exposure, and HMGB1 release in the Lap@CuN group, confirming in vivo ICD induction.

A key advantage of Lap@CuN is its ability to reverse the ITM via IDO1 inhibition. NLG919, a second-generation IDO1 inhibitor, blocks the conversion of tryptophan (Trp) to kynurenine (Kyn)—a metabolic pathway that suppresses effector T cell function and promotes regulatory T (Treg) cells. The team found that Lap@CuN significantly reduced the Kyn/Trp ratio in mouse blood (24.4 vs. 31.9 in the PBS group), increased the infiltration of cytotoxic CD3⁺CD8⁺ T cells in tumors (22.4% vs. 10.4% in the unassembled drug group), and decreased the proportion of immunosuppressive CD3⁺CD4⁺FOXP3⁺ Treg cells. This immune reprogramming led to an abscopal effect: Lap@CuN not only inhibited primary tumor growth but also suppressed lung and liver metastasis, as shown by reduced metastatic nodules in H&E-stained organ sections.

When compared to Doxil (a clinically approved nanomedicine), Lap@CuN demonstrated superior safety and efficacy. Doxil at 5 mg/kg caused moderate tumor inhibition but severe body weight loss, while Lap@CuN achieved smaller tumor volumes (215.6 mm³ vs. 243.1 mm³ for Doxil 5 mg/kg) without adverse effects on liver or kidney function (as confirmed by blood chemistry tests for ALT, AST, BUN, and UA).

“This metal-coordinated nanoplatform addresses key limitations of traditional drug delivery systems,” says Dr. Shi-Ying Li. “By combining ICD induction and IDO1 inhibition in a single carrier-free system, we provide a versatile tool for optimizing chemotherapeutic combinations and activating durable antitumor immunity.” Dr. Lin-Ping Zhao adds, “Our findings open new avenues for developing carrier-free nanomedicines, especially for treating metastatic tumors where systemic immune activation is critical.”

While the study focuses on breast cancer (4T1 model), the versatility of CuN suggests potential applications for other cancer types. Future work will explore long-term in vivo stability of CuN, optimize dosing regimens, and test combinations with other immunomodulators to further enhance therapeutic efficacy.

See the article:

Cu²⁺-Coordinated NLG919: A Drug Delivery Nanoplatform to Activate Antitumor Immunity via Inducing Immunogenic Cell Death and Inhibiting Indoleamine 2,3-Dioxygenase-1

https://doi.org/10.1002/mba2.70024