ITRI-148: A Next-Generation AR Degrader Targeting Resistance at Its Core

A new experimental compound, ITRI-148, may represent a meaningful shift in how advanced prostate cancer is treated, particularly in patients who develop resistance to current androgen receptor (AR)-targeted therapies. Resistance to drugs like enzalutamide is frequently driven by AR splice variants such as AR-V7, which lack the ligand-binding domain (LBD) targeted by existing therapies, allowing cancer cells to bypass treatment entirely.

ITRI-148 takes a different approach. Instead of targeting the LBD, it binds to the androgen receptor’s N-terminal domain (NTD), a region shared by both full-length AR and its splice variants. Using a PROTAC (proteolysis-targeting chimera) mechanism, the drug recruits the E3 ligase cereblon (CRBN), marking AR proteins for degradation by the proteasome. This enables the selective removal of both canonical AR and resistant variants like AR-V7, rather than simply inhibiting their activity.

Preclinical data suggest that this strategy may overcome key resistance pathways. In enzalutamide-resistant prostate cancer cell models, ITRI-148 demonstrated stronger antiproliferative effects than both enzalutamide and the LBD-targeting degrader ARV-110. Notably, while prolonged enzalutamide exposure led to increased AR-V7 expression and a rebound in PSA signaling, ITRI-148 maintained sustained suppression of AR activity without triggering similar adaptive responses.

The compound also showed promising in vivo activity. Oral administration led to tumor regression in AR-driven xenograft models and inhibited growth in AR-V7–expressing tumors under hormone-intact conditions. These findings suggest potential utility across different stages of castration-resistant prostate cancer. Early toxicology data in animal models indicate favorable systemic exposure and tolerability, with no significant weight loss or hematologic toxicity observed at therapeutic doses.

One of the most striking aspects of this work is the identification of a druggable pocket within the AR N-terminal domain, a region long considered structurally disordered and difficult to target. If validated, this could open the door to an entirely new class of therapies aimed at degrading AR independently of the ligand-binding domain, addressing both splice variant–driven resistance and LBD mutations.

While these results are still preclinical and require confirmation in human trials, ITRI-148 introduces a compelling strategy: directly eliminating the androgen receptor in all its clinically relevant forms.

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