GalNAc

Li Q, et al. RSC Advances, 2024, 14(25), 17461-17466.

N-Acetylgalactosamine (GalNAc)-conjugated small interfering RNA (siRNA) has emerged as a promising strategy for targeted gene therapy, particularly for liver-specific delivery. This approach leverages the strong interaction between GalNAc ligands and the asialoglycoprotein receptor (ASGPR), enabling efficient cellular uptake in hepatocytes. Recent advancements in GalNAc-based conjugates have significantly improved the efficacy of RNA-based therapies, including antisense oligonucleotides (ASOs) and siRNAs, which are crucial for treating “undruggable” diseases such as rare and metabolic disorders.
This study presents a novel class of GalNAc conjugates featuring a diamine-scaffold structure, which was synthesized and evaluated for its siRNA delivery capabilities. These new conjugates, TG1 and TG2, were incorporated at the 5'- and 3'-ends of the siRNA sequence, respectively. The biological evaluation demonstrated that TG1 exhibited comparable delivery efficiency to the NAG37 GalNAc ligand, a phase II clinical candidate targeting ANGPTL3. Furthermore, TG2-modified siRNA demonstrated superior silencing activity when compared to the standard L96-modified siRNA, which targets transthyretin (TTR), showcasing the potential of diamine-scaffolded GalNAc conjugates in enhancing gene silencing.
GalNAc conjugates, particularly those using trivalent or tetravalent ligands, have already shown clinical promise in liver-targeted siRNA delivery, exemplified by inclisiran (ALN-PCSsc), which reduces LDL cholesterol by inhibiting PCSK9. The continued development of new GalNAc ligands, such as those described in this study, offers a significant opportunity for improving the therapeutic outcomes of siRNA-based treatments, with implications for a wide range of genetic and metabolic diseases.

Wu T, et al. Nano Today, 2024, 56, 102288.

Fusobacterium nucleatum (Fn)-induced chemoresistance is a significant challenge in the treatment of colorectal cancer (CRC). Conventional antimicrobial approaches face the risk of bacterial resistance and gut microbiome disruption, necessitating alternative strategies. A promising non-antimicrobial approach involves disrupting Fn adhesion to CRC cells, a critical step in Fn-mediated chemoresistance. This study introduces a GalNAc-derived nanoplatform (OGPA/P-C) designed to specifically target Fn adhesion to CRC cells and enhance chemotherapy efficacy.
The nanoplatform is synthesized by conjugating GalNAc-modified oligopolyethyleneimine (OEI) with oxaliplatin (OxPt) and azobenzene (AZO), and incorporating polyethylene glycol-β-cyclodextrin (PEG-CD) via host-guest interactions. The resulting OGPA/P-C nanocarrier demonstrates selective accumulation in CRC tumors, avoiding GalNAc-mediated liver targeting. Upon reaching the tumor site, the PEG-armed nanoplatform is activated by CRC-associated azo-reductase, exposing GalNAc residues that competitively inhibit Fn binding to CRC cells via the Fn lectin Fap2.
The nanoplatform not only disrupts the critical host-pathogen interaction but also overcomes chemotherapy resistance by suppressing autophagy activation, thereby sensitizing CRC cells to OxPt treatment. In both in vitro and in vivo models, OGPA/P-C exhibited remarkable anticancer effects, providing an effective strategy to combat Fn-associated chemoresistance. This non-lethal antiadhesion strategy holds great promise for improving chemotherapeutic outcomes in solid tumors burdened by Fn, offering a novel approach for enhancing the treatment of CRC and potentially other microbiota-associated cancers.

Hua Y, et al. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2024, 694, 134098.

The asialoglycoprotein receptor (ASGPR), predominantly expressed on hepatocyte membranes, is a key target for the diagnosis and monitoring of liver-related diseases. This study presents the synthesis and biological evaluation of a novel 68Ga-labeled GalNAc derivative, 68Ga-NOTA-GalNAc, developed as a positron emission tomography (PET) imaging probe specifically targeting ASGPR. The primary aim was to assess its potential in visualizing liver dysfunction associated with ASGPR expression, including conditions like liver fibrosis, nonalcoholic fatty liver disease (NAFLD), and hepatocellular carcinoma (HCC).
68Ga-NOTA-GalNAc was synthesized with high radiochemical purity (>99%) and demonstrated excellent biocompatibility and specificity for ASGPR, with a moderate binding affinity (KD = 6.82 μM). PET imaging of various animal models revealed distinct liver uptake profiles, with significantly lower accumulation in the livers of mice with liver fibrosis and NAFLD compared to normal controls (P < 0.0001). Notably, the probe also successfully differentiated hepatoma lesions in HepG2 xenograft models, correlating with ASGPR expression verified through immunohistochemistry.
The results underscore the potential of 68Ga-NOTA-GalNAc as a non-invasive and sensitive imaging agent for ASGPR-targeted liver dysfunction. Its high specificity for ASGPR and ability to clearly differentiate pathological liver conditions, including early-stage liver fibrosis and hepatoma, position this PET probe as a promising tool for early diagnosis and monitoring of liver diseases.

Li Q, et al. Molecular Therapy, 2024, 32(3), 637-645.

Atherosclerotic cardiovascular diseases (ASCVDs) remain a global health challenge, despite advances in lipid-lowering therapies like PCSK9 inhibitors. Small interfering RNA (siRNA) therapies, particularly those conjugated with N-acetylgalactosamine (GalNAc), have emerged as a promising class of precision medicines for targeting dyslipidemia, a primary driver of ASCVDs. GalNAc conjugation significantly enhances the liver-specific delivery of oligonucleotides, improving both efficacy and safety while minimizing systemic toxicity.
Inclisiran, a GalNAc-conjugated siRNA targeting PCSK9, is a prime example of this approach. By leveraging the natural liver-targeting properties of GalNAc, inclisiran has demonstrated durable reductions in LDL cholesterol (LDL-C) levels with a convenient dosing schedule of once every six months. This breakthrough has the potential to help millions of patients with primary hypercholesterolemia and mixed dyslipidemia. However, the focus is now expanding to other lipid-related risk factors, such as lipoprotein (a) [Lp(a)] and triglycerides (TG), which are also implicated in ASCVD progression.
Incorporating GalNAc into the design of siRNAs targeting ANGPTL3, a regulator of TG and LDL-C metabolism, has shown promise in preclinical and clinical studies, reducing both LDL-C and TG levels. Furthermore, novel oligonucleotide-based agents targeting Lp(a) have exhibited a significant reduction in Lp(a) levels, further contributing to the lipid-lowering therapeutic landscape.
The development of optimized GalNAc conjugation strategies is crucial for enhancing oligonucleotide delivery to hepatocytes, which, in turn, maximizes therapeutic outcomes. Innovations in GalNAc design, such as the use of monomeric GalNAc conjugates, are driving cost-effective solutions for new lipid-lowering therapies, with the potential to revolutionize the treatment of ASCVD and related disorders.