Doxorubicin immunoconjugates containing bivalent, lysosomally-cleavable dipeptide linkages

Area of Science:

• Bioconjugation Chemistry
• Cancer Therapeutics
• Antibody-Drug Conjugates

Background:

• Monoclonal antibody BR96 targets tumor-associated antigens.
• Doxorubicin (DOX) is a potent chemotherapy drug.
• Developing targeted drug delivery systems is crucial for cancer treatment.

Purpose of the Study:

• To synthesize and characterize bivalent doxorubicin-dipeptide conjugates with the BR96 antibody.
• To evaluate the in vitro efficacy of these immunoconjugates in killing tumor cells.
• To assess the drug loading and stability of the resulting conjugates.

Main Methods:

• Preparation of bivalent doxorubicin-dipeptides (16a-c).
• Conjugation of dipeptides to the BR96 monoclonal antibody.
• Lysosomal protease cleavage assay.
• In vitro tumor cell killing assays (IC50 determination).
• Size exclusion chromatography for conjugate analysis.

Main Results:

• Conjugate 18b demonstrated antigen-specific in vitro tumor cell killing with an IC50 of 0.2 microM.
• The conjugate was equipotent to free doxorubicin (DOX).
• A near doubling of drug molecules per antibody (MAb) was achieved.
• Size exclusion chromatography revealed 18b formed a noncovalent dimer immediately upon conjugation.

Conclusions:

• Bivalent doxorubicin-dipeptide conjugates with BR96 are effective in targeted tumor cell killing.
• The immunoconjugate approach enhances drug potency and delivery.
• This strategy holds promise for developing novel antibody-drug conjugates for cancer therapy.