Highly Cytotoxic Cryptophycin Derivatives with Modification in Unit D for Conjugation

Area of Science:

• Medicinal Chemistry
• Natural Product Synthesis
• Cancer Therapeutics

Background:

• Cytotoxic payloads are crucial for antibody-drug conjugates in targeted cancer therapy.
• Cryptophycins are highly cytotoxic cyclodepsipeptides, but functionalization for conjugation is challenging.
• Modification of unit D (leucic acid) was identified as a potential site for conjugation handles.

Purpose of the Study:

• To develop a scalable synthetic route for conjugable cryptophycins.
• To synthesize novel cryptophycin analogues with diverse functional groups for conjugation.
• To evaluate the cytotoxicity and efficacy of new analogues, particularly against multidrug-resistant cancer cells.

Main Methods:

• Development of a versatile and efficient synthetic route for modified cryptophycins.
• Synthesis of a library of cryptophycin analogues with various conjugation handles (amino, hydroxy, carboxy, sulfur-containing groups).
• Cytotoxicity assays, including evaluation against multidrug-resistant cell lines.
• X-ray crystallography of tubulin-bound cryptophycin and quantitative structure-activity relationship (QSAR) analysis.

Main Results:

• Successful synthesis of novel, conjugable cryptophycin analogues with modifications in unit D.
• Several derivatives demonstrated extremely high cytotoxicity (low picomolar range).
• Lipophilic modifications, such as alkylated amino groups, enhanced potency and efficacy against multidrug-resistant tumors.
• Established structure-activity relationships and confirmed the suitability of unit D modifications.

Conclusions:

• The developed synthetic strategy enables the creation of highly potent, conjugable cryptophycins.
• Modified cryptophycins show promise as payloads for targeted cancer therapies, including against resistant cancers.
• Unit D modifications are well-tolerated and crucial for developing effective drug conjugates.