A Prodrug Strategy to Conditionally Trap Therapeutic Payloads for Improved Tumor Retention

Area of Science:

• Biotechnology
• Drug Delivery
• Molecular Biology

Background:

• Extracellular proteolysis is utilized for targeted drug activation in diseases like cancer.
• A key limitation is drug diffusion away from the target site after activation, reducing efficacy.
• Developing strategies to retain activated drugs at the disease site is crucial for enhanced therapeutic outcomes.

Purpose of the Study:

• To develop a drug delivery platform that couples proteolytic activation with membrane tethering for improved drug retention.
• To engineer restricted interaction peptides (RIPs) that activate and localize therapeutic cargos near the site of proteolysis.
• To demonstrate the efficacy of RIPs in delivering diverse therapeutic cargos, including cytotoxins and radioisotopes, for enhanced disease treatment.

Main Methods:

• Developed restricted interaction peptides (RIPs) that activate membrane-interacting peptides upon encountering elevated proteolytic activity.
• Engineered a specific RIP, "FRIP," for cleavage by fibroblast activation protein (FAP), which is upregulated in solid tumors.
• Incorporated efficient substrate sequences into FRIPs and validated cargo delivery and retention using cell-based assays, imaging studies, and in vivo antitumor efficacy assessments.

Main Results:

• RIPs successfully activated and localized therapeutic cargos, including cytotoxins (MMAE) and radioisotopes (Cu-67), near the site of proteolysis.
• FRIPs demonstrated FAP-dependent inhibition of cancer cell proliferation when delivering MMAE.
• In vivo imaging confirmed targeted tumor uptake with minimal distribution to normal tissues, and potent antitumor effects were observed with FRIP-delivered MMAE or Cu-67.

Conclusions:

• Coupling proteolytic activation with membrane tethering is an effective strategy to enhance drug retention within diseased tissues.
• The RIP platform offers a versatile approach for delivering various therapeutic cargos, improving localized drug efficacy.
• FRIPs show significant potential as a targeted therapeutic delivery system for FAP-expressing tumors, warranting further clinical investigation.