Stabilizing a Tubulysin Antibody-Drug Conjugate To Enable Activity Against Multidrug-Resistant Tumors

Area of Science:

• Oncology
• Medicinal Chemistry
• Pharmacology

Background:

• Tubulysins are potent anticancer agents targeting microtubules.
• Their high efficacy is limited by systemic toxicity, making antibody-drug conjugates (ADCs) a promising targeted therapy approach.
• Developing stable and active tubulysin-based ADCs is crucial for clinical application.

Purpose of the Study:

• To design and synthesize stable and bioreversible tubulysin-antibody conjugates (ADCs).
• To evaluate the *in vitro* and *in vivo* activity of these novel ADCs.
• To address metabolic liabilities observed with initial ADC designs.

Main Methods:

• Conjugation of tubulysins to antibodies using a peptide trigger and a quaternary ammonium salt linker.
• Assessment of *in vitro* cytotoxicity against cancer cell lines, including multidrug-resistant types.
• Evaluation of *in vivo* stability and efficacy in preclinical tumor models, with modifications to address metabolic degradation.

Main Results:

• Initial tubulysin ADCs demonstrated potent *in vitro* activity.
• Metabolism of an acetate ester in the drug was identified as a key *in vivo* liability, reducing efficacy.
• A modified ADC utilizing a propyl ether replacement exhibited enhanced stability and significant antitumor activity against resistant lymphoma models.

Conclusions:

• A novel strategy for creating stable tubulysin ADCs was successfully developed.
• Overcoming *in vivo* metabolic degradation is critical for the therapeutic potential of tubulysin-ADCs.
• The optimized tubulysin ADC demonstrates significant promise for treating multidrug-resistant cancers.