| Size | Price | Stock | Qty |
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| 1mg |
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| 5mg | |||
| Other Sizes |
| Targets |
OSu-PEG4-VC-PAB-MMAE does not directly target a biological receptor; rather, the OSu ester reacts chemically with primary amine groups (lysine ε-amines) on antibodies under mild basic conditions (pH 8.0-8.5) to form stable amide bonds. After conjugation, the resulting ADC targets specific cell-surface antigens (e.g., HER2, CD30, Trop-2) on cancer cells. Upon internalization and lysosomal trafficking, the valine-citrulline linker is cleaved by cathepsin B, releasing the active MMAE payload. MMAE then binds to tubulin, inhibiting microtubule polymerization, causing G2/M cell cycle arrest and apoptosis. The PEG4 spacer enhances solubility and reduces ADC aggregation.
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| ln Vitro |
In vitro, the activity of OSu-PEG4-VC-PAB-MMAE is assessed after conjugation to a targeting antibody. The resulting ADC is tested against antigen-positive and antigen-negative cancer cell lines. For a HER2-targeting ADC, SK-BR-3 (HER2+) cells show potent cytotoxicity with IC50 values in the sub-nanomolar to low nanomolar range, while antigen-negative cells (e.g., MDA-MB-231) are unaffected (IC50 >100 nM). The ADC induces G2/M arrest and apoptosis as measured by flow cytometry, Annexin V/PI staining, and caspase-3/7 activation. The unconjugated linker-payload is not tested directly on cells because it is a reactive intermediate. Free MMAE controls show potent cytotoxicity (IC50 0.1-1 nM) across cell lines. ADC-mediated cytotoxicity is time- and concentration-dependent, with maximal effect after 72-120 hours.
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| ln Vivo |
In vivo, ADCs prepared using OSu-PEG4-VC-PAB-MMAE demonstrate potent antitumor activity in xenograft models. In a HER2-positive NCI-N87 gastric cancer xenograft model, a single intravenous dose of the ADC (1-3 mg/kg) induces significant tumor growth inhibition and often complete regression. The efficacy is antigen-dependent; a non-targeting isotype control ADC shows no effect. The released MMAE is retained in tumor cells, minimizing systemic toxicity. Body weight loss is minimal at therapeutic doses. In mouse models, the ADC exhibits a half-life of 5-10 days, and the valine-citrulline linker remains stable in circulation. The compound is used only as part of an ADC; free linker-payload is never administered systemically.
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| Enzyme Assay |
A non-cellular protocol for using OSu-PEG4-VC-PAB-MMAE involves its conjugation to an antibody. The antibody (5-10 mg/mL) is buffer-exchanged into conjugation buffer (PBS pH 8.0-8.5 or 0.1 M sodium bicarbonate pH 8.5). The compound is dissolved in DMSO to 10 mM and added to the antibody at 3-10 molar equivalents (final DMSO <10%). The reaction proceeds for 1-4 hours at room temperature with gentle stirring. Unreacted compound is removed by dialysis or size-exclusion chromatography (e.g., Zeba spin column). The resulting ADC is characterized by UV-Vis (protein concentration), HIC-HPLC or LC-MS for drug-to-antibody ratio (DAR, typically 2-4), SEC-HPLC for aggregation (<5%), and LAL assay for endotoxin (<1 EU/mg). Conjugation efficiency is confirmed by reduction of free lysine residues. The ADC is stored at 4degC or -80degC with stabilizers.
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| Cell Assay |
An in vitro cellular protocol for evaluating an ADC made with OSu-PEG4-VC-PAB-MMAE uses antigen-positive and antigen-negative cells. SK-BR-3 (HER2+) cells are seeded in 96-well plates at 5×103 cells/well in DMEM with 10% FBS. After overnight attachment, serial dilutions of the ADC (0.001-100 nM, prepared in culture medium) are added, and cells are incubated for 96 hours. Antigen-negative MDA-MB-231 cells serve as negative control. Cell viability is measured by CellTiter-Glo luminescent assay. The IC50 is calculated from dose-response curves. For mechanism studies, cells are treated with 10 nM ADC for 24-48 hours, then harvested for propidium iodide cell cycle analysis (G2/M arrest), Annexin V/PI apoptosis detection, and Western blot for cleaved PARP and tubulin. Internalization is confirmed by fluorescently labeled ADC using confocal microscopy.
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| Animal Protocol |
An in vivo animal protocol for evaluating an ADC from OSu-PEG4-VC-PAB-MMAE uses a NCI-N87 xenograft model. Female BALB/c nu/nu mice (6-8 weeks) receive subcutaneous injections of 5×10⁶ NCI-N87 cells in 0.1 mL PBS/Matrigel (1:1). When tumors reach 150-200 mm3 (≈14 days), mice are randomized (n=8/group). The ADC is formulated in PBS and administered intravenously (tail vein) as a single dose at 0.3, 1, or 3 mg/kg. Control groups: vehicle (PBS), unconjugated antibody, and isotype ADC. Tumor volume (length×width2/2) and body weight are measured twice weekly. At study end (day 28-35), tumors are excised for histology (H&E, Ki67 IHC, TUNEL). Efficacy endpoints: tumor growth inhibition (TGI, %), complete regressions, and progression-free survival. MMAE concentrations in plasma and tumor are measured by LC-MS/MS at 1, 24, 48, 96 h post-dose.
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| ADME/Pharmacokinetics |
OSu-PEG4-VC-PAB-MMAE is a reactive intermediate, not a therapeutic agent; its pharmacokinetics are defined only after conjugation to an antibody. The ADC exhibits typical antibody-like PK: long terminal half-life (t½ of 5-10 days in mice), low volume of distribution (≈50-100 mL/kg), and clearance via proteolytic degradation. The valine-citrulline linker is stable in plasma (<5% release of MMAE over 7 days). After lysosomal cleavage, MMAE is rapidly distributed to tubulin, metabolized by CYP3A4, and excreted in bile. The OSu group is hydrolyzed and does not circulate. Free OSu-PEG4-VC-PAB-MMAE is never administered in vivo; it would react with plasma proteins, causing severe toxicity. No PK data exist for the unconjugated compound.
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| Toxicity/Toxicokinetics |
OSu-PEG4-VC-PAB-MMAE is highly toxic and must be handled with extreme care. It is a potent tubulin inhibitor (MMAE payload) and a reactive electrophile (OSu ester). Use double nitrile gloves, chemical-resistant lab coat, safety goggles, and face shield inside a certified fume hood. Avoid skin contact, inhalation, and ingestion. The compound is moisture- and light-sensitive; store under nitrogen at -80degC in a sealed container. Thawed solutions must be used immediately and not refrozen. Spills: decontaminate with 5% sodium hypochlorite solution followed by ethanol. There are no human safety data; animal studies with free linker-payload have not been performed due to extreme toxicity. After conjugation to an antibody, the ADC shows dose-limiting toxicity (neutropenia, thrombocytopenia) at high doses, typical of MMAE-based ADCs. This compound is for research use only, not for human therapeutic or diagnostic use.
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| References | |
| Additional Infomation |
OSu-PEG4-VC-PAB-MMAE is a next-generation linker-payload for ADC development. Its features include: (1) OSu ester for facile, random lysine conjugation to antibodies; (2) hydrophilic PEG4 spacer to improve solubility and reduce aggregation; (3) valine-citrulline dipeptide that is stable in circulation but cleaved by cathepsin B in lysosomes; (4) PAB self-immolative spacer for efficient MMAE release; (5) MMAE, a potent anti-tubulin agent. The resulting ADCs achieve high DAR (2-4) and exhibit potent, antigen-dependent antitumor activity in preclinical models. As of 2026, OSu-PEG4-VC-PAB-MMAE is a research-grade chemical and is not an FDA-approved drug. It is used solely for laboratory research to develop novel ADCs for targeted cancer therapy. The compound should be stored at -80degC, desiccated, and protected from light.
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| Molecular Formula |
C74H117N11O21
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|---|---|
| Molecular Weight |
1496.78190112114
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| Exact Mass |
1495.842
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| CAS # |
2762518-86-3
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| PubChem CID |
163297181
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| Appearance |
White to off-white solid powder
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| LogP |
2.9
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| Hydrogen Bond Donor Count |
8
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| Hydrogen Bond Acceptor Count |
21
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| Rotatable Bond Count |
50
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| Heavy Atom Count |
106
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| Complexity |
2770
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| Defined Atom Stereocenter Count |
12
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| SMILES |
O(C)[C@H]([C@H](C(N[C@H](C)[C@H](C1C=CC=CC=1)O)=O)C)[C@@H]1CCCN1C(C[C@H]([C@H]([C@@H](C)CC)N(C)C([C@H](C(C)C)NC([C@H](C(C)C)N(C(=O)OCC1C=CC(=CC=1)NC([C@H](CCCNC(N)=O)NC([C@H](C(C)C)NC(CCOCCOCCOCCOCCC(=O)ON1C(CCC1=O)=O)=O)=O)=O)C)=O)=O)OC)=O
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| InChi Key |
BPGOFDCJYPGDRK-KUVCCIEHSA-N
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| InChi Code |
InChI=1S/C74H117N11O21/c1-15-48(8)65(56(99-13)43-60(89)84-34-20-24-55(84)67(100-14)49(9)68(92)77-50(10)66(91)52-21-17-16-18-22-52)82(11)72(96)63(46(4)5)81-71(95)64(47(6)7)83(12)74(98)105-44-51-25-27-53(28-26-51)78-69(93)54(23-19-33-76-73(75)97)79-70(94)62(45(2)3)80-57(86)31-35-101-37-39-103-41-42-104-40-38-102-36-32-61(90)106-85-58(87)29-30-59(85)88/h16-18,21-22,25-28,45-50,54-56,62-67,91H,15,19-20,23-24,29-44H2,1-14H3,(H,77,92)(H,78,93)(H,79,94)(H,80,86)(H,81,95)(H3,75,76,97)/t48-,49+,50+,54-,55-,56+,62-,63-,64-,65-,66+,67+/m0/s1
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| Chemical Name |
(2,5-dioxopyrrolidin-1-yl) 3-[2-[2-[2-[3-[[(2S)-1-[[(2S)-5-(carbamoylamino)-1-[4-[[[(2S)-1-[[(2S)-1-[[(3R,4S,5S)-1-[(2S)-2-[(1R,2R)-3-[[(1S,2R)-1-hydroxy-1-phenylpropan-2-yl]amino]-1-methoxy-2-methyl-3-oxopropyl]pyrrolidin-1-yl]-3-methoxy-5-methyl-1-oxoheptan-4-yl]-methylamino]-3-methyl-1-oxobutan-2-yl]amino]-3-methyl-1-oxobutan-2-yl]-methylcarbamoyl]oxymethyl]anilino]-1-oxopentan-2-yl]amino]-3-methyl-1-oxobutan-2-yl]amino]-3-oxopropoxy]ethoxy]ethoxy]ethoxy]propanoate
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| HS Tariff Code |
2934.99.9001
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| Storage |
Powder -20°C 3 years 4°C 2 years In solvent -80°C 6 months -20°C 1 month Note: (1). This product requires protection from light (avoid light exposure) during transportation and storage. (2). Please store this product in a sealed and protected environment (e.g. under nitrogen), avoid exposure to moisture. |
| Shipping Condition |
Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)
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| Solubility (In Vitro) |
DMSO: 80 mg/mL (53.45 mM)
H2O: 1.67 mg/mL (1.12 mM) |
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| Solubility (In Vivo) |
Solubility in Formulation 1: 2 mg/mL (1.34 mM) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution; with sonication.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL. Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution. Solubility in Formulation 2: ≥ 2 mg/mL (1.34 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution. For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly. Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution. View More
Solubility in Formulation 3: ≥ 2 mg/mL (1.34 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution. |
| Preparing Stock Solutions | 1 mg | 5 mg | 10 mg | |
| 1 mM | 0.6681 mL | 3.3405 mL | 6.6810 mL | |
| 5 mM | 0.1336 mL | 0.6681 mL | 1.3362 mL | |
| 10 mM | 0.0668 mL | 0.3341 mL | 0.6681 mL |
*Note: Please select an appropriate solvent for the preparation of stock solution based on your experiment needs. For most products, DMSO can be used for preparing stock solutions (e.g. 5 mM, 10 mM, or 20 mM concentration); some products with high aqueous solubility may be dissolved in water directly. Solubility information is available at the above Solubility Data section. Once the stock solution is prepared, aliquot it to routine usage volumes and store at -20°C or -80°C. Avoid repeated freeze and thaw cycles.
Calculation results
Working concentration： mg/mL；
Method for preparing DMSO stock solution： mg drug pre-dissolved in μL DMSO (stock solution concentration mg/mL). Please contact us first if the concentration exceeds the DMSO solubility of the batch of drug.
Method for preparing in vivo formulation:：Take μL DMSO stock solution, next add μL PEG300, mix and clarify, next addμL Tween 80, mix and clarify, next add μL ddH2O，mix and clarify.
(1) Please be sure that the solution is clear before the addition of next solvent. Dissolution methods like vortex, ultrasound or warming and heat may be used to aid dissolving.
(2) Be sure to add the solvent(s) in order.
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