Novel daunorubicin‐carrier peptide conjugates derived from human calcitonin segments

Abstract

Severe and often therapy-limiting side effects are a major obstacle in cancer chemotherapy. New delivery concepts reducing systemic side effects are needed in order to optimize anticancer therapies. Several approaches have been followed, most of them concentrating on macromolecular carriers like liposomes, monoclonal antibodies, serum proteins or polyethylene glycol. We present here a novel type of anthracycline conjugate, using a small carrier peptide derived from the peptide hormone human calcitonin (hCT). The carrier peptide hCT(9-32) has so far been shown to be capable of transporting fluorophores or proteins across cellular membranes. Two different carrier peptide-daunorubicin conjugates were prepared, one with an acid-stable amide bond, the second with an acid-labile hydrazone bond. In vitro studies with daunorubicin linked to the carrier peptide via an acid-labile hydrazone bond demonstrated comparable cytotoxicity to daunorubicin in various daunorubicin sensitive cell lines (neuroblastoma cell lines SK-N-MC and SMS-KAN; HEK 293 T cells). In addition, fluorescence microscopy provided further insight into the mechanism of uptake of the carrier peptide hCT(9-32), indicating that endosomal compartments with reduced pH are involved in the intracellular release of daunorubicin.

Cell-penetrating peptides: tools for intracellular delivery of therapeutics

“…Hence the 9-32 fragment was investigated with respect to its ability to behave as a carrier peptide [20]. The 9-32 fragment of hCT, called hCT(9-32) has been used for transfer of green flurescent protein (GFP) through cellular membranes via a covalent carrier-cargo linkage [104] and also for the delivery of daunorubicine into several cell lines [105]. More recently, another derivative of hCT has been developed in which an NLS has been branched on a lysine side chain.…”

New daunomycin–oligoarginine conjugates: Synthesis, characterization, and effect on human leukemia and human hepatoma cells

“…The first conjugations of anthracyclines on this site were performed in the 1970s by using glutaraldehyde and periodate oxidation or m-maleimidobenzoyl-N-hydroxysuccinimide ester linkage as reported by Baurain et al 2 The maleimide linkers are frequently applied not only with the amino group. [8][9][10] Amide bond formation can also be utilized assuming that this bond could be hydrolyzed by lysosomal 2,3,11 or organ-specific enzymes. 12 In other cases, acidlabile linkers were introduced between the anthracycline and carrier so the drug could be released under acidic circumstances (e.g., the inside of lysosomes).…”

Peptide‐mediated targeted drug delivery

“…Then, nucleophilic attack of the double bond of the maleimide group by the thiol of the Cys1 residue on hCT(9-32) peptide produced the desired conjugate. 30 A similar approach was used for conjugation of DOX to Vectocell peptides (i.e., CVKRGLKLRHVRPRVTRMDV and SRRARRSPRHLGSGC) by amide bond formation with the carboxylic acid group of maleimidobutyric acid. 31 Amide linkage was also used for conjugation of a b hairpin peptide (RWQYVpGKFTVQ) with an a 4 b 1 integrin recognition peptide sequence LDV at the N-terminus and 7-amino-4carbamoylmethylcoumarin (a fluorescent probe for enzymatic hydrolysis) at the C-terminus.…”

“…The activated carboxylic acid is then reacted with an amine group of the counterpart (i.e., drug or peptide) in the presence of a strong base (i.e., diisopropylethylamine or triethylamine) in different solvents, including dimethylformamide or dimethylsulfoxide to give the desired conjugate. DOX has been conjugated to different peptides, including cIBR [cyclo (1,12 30 and Vectocell peptides using an amide bond. 31 For conjugation to cIBR peptide, the DOX was modified to DOX-hemisuccinate by reacting the amino group of DOX with succinic anhydride to generate free carboxylic acid ( Fig.…”