Mal-Propionyl-PEG6-Gly-Gly-Phe-Gly-PAB(m-PEG4)-Exatecan m-peg4-pab 354 SMILES OCCOCC(=O)NC1=C2CN(C3CCC(=O)NC3=O)C(=O)C2=CC=C1 Purity (HPLC)

354 SMILES OCCOCC(=O)NC1=C2CN(C3CCC(=O)NC3=O)C(=O)C2=CC=C1 Purity (HPLC) >= 95% Shipping Conditions Room temperature Storage Conditions Refrigerated Shelf Life 12 months after the date of delivery Regulatory Statement For Research Use Only

49 SMILES [H][C@]12CS[C@@H](CCCCC(=O)NCCOCCOCCC(O)=O)[C@@]1([H])NC(=O)N2 Purity (HPLC) >= 95% Shipping Conditions Room temperature Storage Conditions Refrigerated Shelf Life 12 months after the date of delivery Regulatory Statement For Research Use Only

546 SMILES OCCOCCOCCOCCOCCOCC#CC1=C2C(=O)N(C3CCC(=O)NC3=O)C(=O)C2=CC=C1 Purity (HPLC) >= 95% Shipping Conditions Room temperature Storage Conditions Refrigerated Shelf Life 12 months after the date of delivery Regulatory Statement For Research Use Only

eLife 2020

Mal-Propionyl-PEG6-Gly-Gly-Phe-Gly-PAB(m-PEG4)-Exatecan m-peg4-pab 354 SMILES OCCOCC(=O)NC1=C2CN(C3CCC(=O)NC3=O)C(=O)C2=CC=C1 Purity (HPLC)SOLU KNEX cleavable linker features a Gly Gly Phe Gly (GGFG) peptide. The conventional maleimidocaproyl (MC) unit is replaced by Mal Propionyl PEG6 moiety to enhance aqueous solubility. The Mal Propionyl group may also improve retro Michael addition stability during antibody conjugation. m PEG4 is attached to the commonly used self immolative para aminobenzyl (PAB) moiety to increase aqueous solubility. The payload is Exatecan, a highly potent