Designed ankyrin repeat proteins for detecting prostate-specific antigen expression in vivo

Area of Science:

• Molecular Biology
• Biotechnology
• Oncology

Background:

• Late-stage prostate cancer often develops resistance to chemotherapy, becoming hormone-refractory and non-curative.
• Non-invasive tools are needed to monitor drug efficacy and detect resistance in prostate cancer patients.
• Prostate-specific antigen (PSA) is a key biomarker for clinical monitoring of prostate cancer.

Purpose of the Study:

• To develop novel Designed Ankyrin Repeat Proteins (DARPins) with high affinity for prostate-specific antigen (PSA).
• To create radiolabeled DARPins for potential non-invasive imaging of prostate cancer.
• To assess the efficacy of these agents in monitoring treatment response and detecting drug resistance.

Main Methods:

• Selection of PSA-binding DARPins using ribosome display and in vitro screening.
• Site-specific functionalization of DARPins with NODAGA chelator for radiolabeling with Gallium-68 (⁶⁸Ga).
• In vitro stability assays, binding assays, and in vivo biodistribution studies in prostate cancer xenograft models.

Main Results:

• Four lead DARPin candidates demonstrated nanomolar affinity for PSA.
• [⁶⁸Ga]GaNODAGA-DARPins exhibited high stability and retained specificity for PSA after radiolabeling.
• Three of the four radiolabeled DARPins showed specific tumor uptake in vivo, with DARPin-6 demonstrating significant tumor targeting.

Conclusions:

• The developed ⁶⁸Ga-labeled DARPins are promising as specific imaging agents for prostate cancer.
• These agents have the potential for non-invasive monitoring of treatment efficacy, particularly for androgen receptor (AR)-targeted therapies.
• Further development could lead to improved management strategies for patients with advanced prostate cancer.