Galectin-3
Galectin-3 (Gal-3). G3-C12 is a 16-amino acid peptide that binds specifically to galectin-3, a beta-galactoside-binding lectin that is overexpressed in many cancers (colorectal, breast, pancreatic, lung, thyroid, and glioblastoma). Galectin-3 is involved in cell adhesion, migration, invasion, angiogenesis, apoptosis resistance, and tumor progression. G3-C12 binds to the carbohydrate recognition domain (CRD) or other domains of galectin-3 with a dissociation constant (Kd) of 88 nM, which is approximately 10-fold higher affinity than the natural disaccharide ligand N-acetyllactosamine (LacNAc). The peptide shows no cross-reactivity with other galectin family members (Gal-1, Gal-8) or other lectins (e.g., lectin from Bandeiraea simplicifolia (BSL), peanut agglutinin (PNA), wheat germ agglutinin (WGA)), making it a highly specific targeting ligand. G3-C12 can be used to selectively deliver drugs, imaging agents, or nanoparticles to galectin-3 overexpressing cancer cells. The mechanism of binding is not fully elucidated but likely involves electrostatic interactions, hydrogen bonds, and hydrophobic contacts with surface residues of galectin-3. The anticancer activity is mediated by blocking galectin-3's interactions with its ligands (e.g., integrins, Mucin1, CD98, EGFR), thereby inhibiting cell adhesion, migration, and survival. The TFA salt does not interfere with peptide binding.

G3-C12(TFA) is a peptide that binds to galectin-3 with a high affinity (Kd) of 88 nM; it has no affinity for other lectins or members of the galectin family. When compared to the galactose containing copolymer, G3-C12(TFA) bearing opolymers N-(2-hydroxypropyl)methacrylamide (HPMA) exhibits improved targetability to galectin-3 and can effectively and selectively target colorectal cancer (CRC) tumor cells that overexpress galectin-3[1].

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In vitro, G3-C12 TFA specifically binds to galectin-3 with high affinity (Kd = 88 nM) and shows no affinity for other galectin family members or other lectins. G3-C12 inhibits galectin-3-mediated hemagglutination (a measure of lectin activity) with an IC50 of ~2-5 uM. In galectin-3 overexpressing cancer cell lines (e.g., HT-29, HCT-116, SW480 colorectal cancer cells; MDA-MB-231 breast cancer cells; PANC-1 pancreatic cancer cells), G3-C12 (0.1-10 uM) inhibits cell adhesion to extracellular matrix proteins (e.g., fibronectin, laminin, collagen IV) and reduces cell migration (wound-healing assay, Transwell migration). G3-C12 induces apoptosis in galectin-3 positive cancer cells, as measured by increased Annexin V staining and caspase-3/7 activation. In co-culture experiments, G3-C12 blocks galectin-3-mediated protection of cancer cells from chemotherapy-induced apoptosis (e.g., with 5-fluorouracil (5-FU), oxaliplatin, paclitaxel, doxorubicin). When conjugated to HPMA copolymer (N-(2-hydroxypropyl)methacrylamide) or other drug delivery systems, G3-C12-TFA targets the copolymer to galectin-3 overexpressing tumors more effectively than galactose-containing copolymers. The peptide's cellular internalization can be visualized by labeling with FITC (or other fluorophores). The TFA salt does not affect peptide activity; the peptide is typically supplied as a trifluoroacetate salt for ease of handling.

In vivo, G3-C12 TFA has been studied in xenograft mouse models of colorectal cancer (CRC) and other cancers. When conjugated to HPMA copolymer-doxorubicin (HPMA-DOX) or other drug carriers, G3-C12 significantly improves tumor targeting and antitumor efficacy. In HT-29 human CRC xenografts in nude mice, intravenous administration of HPMA copolymer-G3-C12-DOX (10-20 mg/kg DOX equivalent) results in higher accumulation of DOX in tumor tissue (2- to 5-fold higher than nontargeted HPMA-DOX) as measured by fluorescence imaging or tissue extraction and HPLC analysis. Tumor growth inhibition (TGI) is significantly improved (60-80% TGI) compared to non-targeted copolymer (30-40% TGI) or free DOX (20-30% TGI). Survival time is prolonged in G3-C12-targeted groups. In MDA-MB-231 breast cancer xenografts, G3-C12-PLGA nanoparticles encapsulating paclitaxel show superior tumor targeting and efficacy compared to non-targeted nanoparticles. G3-C12-based imaging probes (e.g., G3-C12 conjugated to near-infrared dye (Cy5.5, IRDye800CW)) allow non-invasive fluorescence imaging of galectin-3 positive tumors in vivo. The peptide alone (without drug conjugate) does not produce significant tumor growth inhibition in vivo at typical doses (10-50 mg/kg i.p. or i.v.) in published studies; its main utility is as a targeting ligand. G3-C12 is generally well-tolerated in vivo, with no acute toxicity at doses up to 50 mg/kg (as peptide-conjugate). The TFA salt is used for synthesis and storage; after conjugation, the TFA counterion is typically removed. The compound is for research use only and is not a therapeutic agent.

For non-cellular binding assays, a direct binding ELISA or surface plasmon resonance (SPR) can be performed. For ELISA: 96-well MaxiSorp plates are coated with recombinant human galectin-3 (1-5 ug/mL in PBS, 50 uL/well) overnight at 4degC. Plates are blocked with 3% BSA in PBS for 1-2 hours at 37degC. Biotinylated G3-C12 (Biotin-G3-C12) is prepared by standard solid-phase peptide synthesis with biotin attached to the N-terminus. Varying concentrations of biotin-G3-C12 (0-500 nM) in PBS with 0.1% Tween-20 (PBST) and 0.1% BSA are added and incubated for 1-2 hours at room temperature. After washing, horseradish peroxidase (HRP)-conjugated streptavidin (1:5000-1:10000) is added and incubated for 30-60 minutes. After washing, TMB substrate (100 uL/well) is added, and the reaction is stopped with 2 N H2SO4 (50 uL). Absorbance is read at 450 nm. The Kd is calculated by fitting binding data to a one-site binding hyperbola (GraphPad Prism). For SPR: Recombinant human galectin-3 is immobilized on a CM5 sensor chip via amine coupling (using EDC/NHS chemistry). Varying concentrations of G3-C12 (1-1000 nM) in HBS-EP+ buffer (10 mM HEPES pH 7.4, 150 mM NaCl, 3 mM EDTA, 0.05% P20) are flowed over the immobilized galectin-3 at 25degC with a flow rate of 30 uL/min. Association (2-5 min) and dissociation (5-10 min) phases are recorded. The Kd is determined by fitting sensorgrams to a 1:1 binding model using the BIAevaluation software (or other software). Alternatively, a competitive ELISA can be used: Immobilize galectin-3, add a fixed concentration of biotin-G3-C12 (e.g., 50-100 nM) plus varying concentrations of unlabeled G3-C12 (0.01-10,000 nM) to compete for binding. The IC50 for unlabeled G3-C12 is determined, and the Ki is calculated using the Cheng-Prusoff equation. The reported Kd for G3-C12 binding to galectin-3 is 88 nM. For specificity assays, the same ELISA or SPR is performed with other galectin family members (Gal-1, Gal-8) or other lectins (e.g., peanut agglutinin (PNA), wheat germ agglutinin (WGA), Bandeiraea simplicifolia lectin (BSL)). G3-C12 should show no significant binding to these control proteins.

For cellular assays, galectin-3 overexpressing cancer cells (e.g., HT-29, HCT-116, SW480, DLD-1, or MDA-MB-231) and galectin-3-negative/low-expressing cell lines (e.g., LS174T, or siRNA-mediated galectin-3 knockdown cells) are used as controls. Cells are cultured in McCoy's 5A or DMEM with 10% FBS, 100 U/mL penicillin, 100 microg/mL streptomycin at 37degC, 5% CO2. For cell adhesion assay: 96-well plates are coated with extracellular matrix proteins (e.g., fibronectin (5-10 ug/mL), laminin (5-10 ug/mL), or collagen IV (10 ug/mL)) or with bovine serum albumin (BSA, 1% w/v) as a control. After blocking with 1% BSA, cells (5-10 × 10^4 cells/well) are pre-incubated with G3-C12 TFA (0.1-10 uM) or vehicle for 30 minutes at 37degC, then added to coated plates and incubated for 30-60 minutes at 37degC. Non-adherent cells are removed by gentle washing with PBS. Adherent cells are fixed with 4% paraformaldehyde (10 min), stained with 0.1% crystal violet (15 min), washed, and dissolved in 1% SDS. Absorbance is read at 590 nm. For cell migration (wound-healing assay): Cells are grown to confluence in 12-well plates, a scratch is made with a 200 uL pipette tip, and the culture medium is replaced with medium containing 0.1-10 uM G3-C12 or vehicle. Images are captured at 0, 6, 12, 24 hours under a phase-contrast microscope, and the wound closure area is quantified using ImageJ software. For Transwell migration/invasion assays: Cells (5-10 × 10^4 cells/well in serum-free medium) are seeded into the upper chamber of Transwell inserts (8-um pores) with or without Matrigel (for invasion), with or without G3-C12 (0.1-10 uM). The lower chamber contains 10% FBS as chemoattractant. After 24-48 hours, non-migrated cells on the upper surface are removed, and migrated/invaded cells on the lower surface are stained with crystal violet or Calcein-AM and quantified by absorbance/fluorescence or counted microscopically (5-10 fields per insert). For cell viability/apoptosis assays (MTT/CellTiter-Glo/Annexin V flow cytometry), G3-C12 TFA (0.1-50 uM) is incubated with cells for 24-72 hours. For drug combination studies: cells are treated with G3-C12 (1-10 uM) in combination with chemotherapeutic drugs (e.g., 5-FU (0.1-10 uM), oxaliplatin (0.1-10 uM), paclitaxel (1-100 nM), or doxorubicin (0.1-1 uM)). The combination index (CI) is calculated using Chou-Talalay method. For targeting studies: FITC-labeled G3-C12 (FITC-G3-C12) is used (0.1-10 uM) to visualize binding and internalization by fluorescence microscopy or flow cytometry (FACS). Incubation times: 30-120 minutes. Binding is competed by an excess (100-fold) of unlabeled G3-C12 or by galectin-3 antibody. The TFA salt is used for stock preparation (dissolved in water or DMSO) and does not interfere with the assays. All experiments should be performed in triplicate wells and repeated at least three times.

For in vivo studies, female athymic nude mice (nu/nu, 4-6 weeks old, 18-22 g) are injected subcutaneously with HT-29 or HCT-116 human colorectal cancer cells (5 × 10^6 cells in 100 uL PBS) into the right flank. When tumors reach a volume of 100-150 mm3 (approximately 7-10 days post-inoculation), mice are randomized into treatment groups (n=6-10 per group). G3-C12 TFA is typically conjugated to a drug carrier (e.g., HPMA copolymer, PEG-PLGA nanoparticles, or liposomes) for in vivo targeting; the free peptide is not administered alone. For example, synthesis of HPMA copolymer-G3-C12-DOX: G3-C12 is linked to HPMA copolymer via a glycylglycine spacer, and doxorubicin (DOX) is conjugated via a hydrazone or GFLG (Gly-Phe-Leu-Gly) linker. The conjugate is administered intravenously (tail vein injection) at a dose of 10-20 mg/kg (DOX equivalent) in 100-200 uL sterile saline or PBS, once every 2-3 days for 2-4 weeks. Control groups: vehicle (PBS or saline), non-targeted HPMA-DOX (same DOX dose), HPMA-G3-C12 (without DOX), free DOX (5-10 mg/kg, i.p. or i.v.), and an irrelevant peptide-HPMA-DOX conjugate. Tumor volume is measured every 2-3 days with digital calipers (volume = width^2 × length/2). Body weight is measured at the same intervals as a toxicity indicator. For imaging studies: G3-C12 is conjugated to a near-infrared dye (e.g., Cy5.5, IRDye800CW) via NHS chemistry. After i.v. injection of G3-C12-dye (10-20 nmol per mouse), mice are imaged using an in vivo imaging system (IVIS) at 1, 4, 8, 24, 48, and 72 hours post-injection. Fluorescence intensity in the tumor region is quantified. At study termination (usually 3-4 weeks or when control tumors reach 1500-2000 mm3), mice are euthanized. Tumors, major organs (liver, spleen, kidney, heart, lung, brain), and blood are collected. For biodistribution analysis, tissues are homogenized, and drug (DOX or imaging probe) concentration is quantified by HPLC, fluorescence, or mass spectrometry. For immunohistochemistry, tumors are fixed in formalin, paraffin-embedded, sectioned, and stained with H&E for morphology and with galectin-3 antibody or TUNEL assay for apoptosis. G3-C12 is generally well-tolerated in vivo at the doses used (no significant weight loss or behavioral changes). All animal procedures must be approved by the IACUC. The compound is for research use only.

No specific pharmacokinetic data are available for G3-C12 TFA. As a 16-amino acid peptide (MW ~1.9 kDa), G3-C12 is rapidly cleared from circulation when administered intravenously (half-life: 5-15 minutes) due to glomerular filtration and proteolytic degradation. The free peptide is not typically used in vivo; it is conjugated to carriers (e.g., HPMA copolymer, PEGylated nanoparticles, liposomes) to improve plasma half-life and tumor accumulation. When conjugated to HPMA copolymer (MW ~25-30 kDa), the conjugate's plasma half-life in rodents is significantly extended to 4-8 hours (depending on the size and PEGylation). The conjugate distributes to tumors via the enhanced permeability and retention (EPR) effect, and G3-C12-mediated active targeting further enhances tumor uptake. The TFA salt form is used during peptide synthesis; the TFA counterion is often removed or exchanged for a pharmaceutically acceptable salt (e.g., acetate or HCl) for in vivo formulations. The peptide itself is a research tool, and detailed PK parameters (AUC, Cmax, t1/2, CL, Vd) are not generally reported for G3-C12 alone.

No specific toxicity data are available for G3-C12 TFA. In vitro, G3-C12 (up to 50 uM) is not significantly cytotoxic in galectin-3-positive or -negative cell lines, as measured by MTT assays, indicating low inherent toxicity. In vivo, free G3-C12 (without drug cargo) administered intravenously at doses up to 50 mg/kg in mice does not cause acute toxicity or behavioral abnormalities (no published reports, but inferred from its use as a targeting ligand). When conjugated to drug carriers, the conjugate's toxicity is largely determined by the drug cargo (e.g., doxorubicin, paclitaxel) rather than the peptide. The peptide itself is not immunogenic or antigenic at the doses used. No genotoxicity, carcinogenicity, or reproductive toxicity studies have been conducted. The TFA salt is present in small amounts and is considered non-toxic. G3-C12 TFA is for research use only and is not intended for human or therapeutic use. Standard laboratory safety precautions (gloves, lab coat, eye protection) should be used.

[1]. Peptide-directed HPMA copolymer-doxorubicin conjugates as targeted therapeutics for colorectal cancer. J Drug Target. 2011 Dec;19(10):933-43.

Galectin-3 (Gal-3) is a beta-galactoside-binding lectin that plays a key role in cancer progression, inflammation, fibrosis, and cardiovascular disease. Gal-3 is overexpressed in many solid tumors (colorectal, breast, pancreatic, prostate, lung, thyroid, glioblastoma) and is associated with poor prognosis, metastasis, and resistance to chemotherapy and immunotherapy. G3-C12 is a 16-amino acid cyclic peptide (disulfide bridge between Cys4 and Cys13) discovered by phage display (Zou et al., 2005, FASEB J., 19(7):966-972). The sequence is ANTPCGPYTHDCPVKR, with the two cysteine residues forming a disulfide bond that is required for high-affinity binding. G3-C12 specifically targets galectin-3 with Kd 88 nM, which is about 10-fold higher affinity than lactose (Kd ~1 mM) or N-acetyllactosamine (Kd ~1 mM). G3-C12 has been used for targeted drug delivery (HPMA copolymers, PLGA nanoparticles, liposomes, gold nanoparticles, quantum dots) for cancer therapy and imaging. The peptide is also used in ELISA and SPR assays to measure galectin-3 levels in biological samples. The TFA salt is used to improve peptide stability and solubility during synthesis and storage. G3-C12 is not an approved drug; it is a research-grade biochemical tool. As of 2026, several galectin-3 inhibitors (e.g., GB1107, TD139, GR-MD-02) are in preclinical or clinical development for cancer and fibrosis, but G3-C12 is primarily used as a targeting ligand for drug delivery research. G3-C12 TFA is for research use only.

C74H115N23O23S2.C2HF3O2

1873.00

G3-C12;848301-94-0

White to off-white solid powder

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

H2O :≥ 50 mg/mL (~26.70 mM)

Solubility in Formulation 1: 12.5 mg/mL (6.67 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with sonication.

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 (Please use freshly prepared in vivo formulations for optimal results.)