Androgen receptor (AR)

Overview

The androgen receptor (AR; Wikidata Q416601) is a member of the nuclear receptor superfamily of ligand-activated transcription factors, encoded by the AR gene on chromosome Xq11–12. It is built from an N-terminal domain carrying most of its transcriptional activity and a polymorphic polyglutamine tract, a central zinc-finger DNA-binding domain, and a C-terminal ligand-binding domain — a modular arrangement that matters clinically, since nearly every AR-directed drug engages one domain and can be escaped by altering another. Upon binding cognate androgens such as testosterone and its more potent metabolite dihydrotestosterone (DHT), AR undergoes a conformational change, dissociates from cytoplasmic chaperone complexes, and translocates to the nucleus, where it binds androgen response elements (AREs) in target gene promoters and enhancers to drive transcriptional programs governing cell proliferation, survival, and differentiation. Loss-of-function mutations cause androgen insensitivity syndrome, and expansion of the polyglutamine tract causes spinal and bulbar muscular atrophy, so both too little AR activity and an aberrant receptor produce distinct disease. Beyond its classical role in male sexual development and the prostate, AR exerts context-dependent effects in hair follicles, the central nervous system, immune cells, and a variety of epithelial Cancers.

AR is best recognized as the central oncogenic driver in prostate cancer, where sustained androgen signaling fuels tumor growth even under systemic androgen deprivation; prostate cancer that progresses despite castrate androgen levels or androgen-deprivation therapy is termed castration-resistant prostate cancer (CRPC). CRPC does not proceed by abandoning the receptor but by restoring its signal: AR amplification and overexpression that respond to residual ligand, gain-of-function mutations that let antagonists or adrenal steroids act as agonists, intratumoral androgen synthesis, constitutively active splice variants — notably AR-V7, which lacks the ligand-binding domain altogether and so is indifferent to drugs that target it — and cistrome reprogramming that redirects AR to non-canonical transcriptional networks.

Therapy follows the same logic in reverse, attacking ligand supply and receptor function at separate points: gonadal suppression, abiraterone blocking the CYP17A1 step of androgen synthesis including within the tumor, and receptor antagonists such as enzalutamide that prevent nuclear translocation and DNA binding. Because escape routes converge on restoring AR output, degraders that remove the protein and agents directed at the N-terminal domain are being pursued to defeat variants no ligand-binding-site drug can reach. Prolonged suppression also selects for tumors that stop depending on AR entirely, emerging as neuroendocrine prostate cancer. Emerging evidence implicates AR in tumor immunology, metabolic regulation, and conditions such as androgenetic alopecia (AGA), broadening therapeutic interest well beyond prostate cancer.

Recent Publications Summary

Recent publications have extensively investigated androgen receptor as a therapeutic target across multiple cancer types and non-malignant conditions. In prostate cancer, novel degradation strategies have advanced beyond traditional antagonism. BMS-986365 was identified as a dual-function compound that both selectively degrades wild-type and clinically relevant mutant ARs while antagonizing residual AR activity, resulting in robust inhibition of AR-driven pathways and prostate cancer cell growth 42430428Jul. Similarly, bavdegalutamide (ARV-110), a PROTAC-based AR degrader, was evaluated in combination with abiraterone in metastatic prostate cancer patients experiencing PSA progression 42227954Jun. Beyond traditional ligand-binding domain inhibitors, AR's N-terminal transactivation domain (TAD) emerged as a druggable target; AR-TAD inhibitors demonstrated differential selectivity and potency through disruption of AR and co-regulator interactions in resistant prostate cancer models 42045150Apr. Additionally, S-94, a novel antagonist with marked selectivity for the T878A-mutant AR, showed 50-fold greater potency against mutant versus wild-type AR and antagonized other clinically relevant T878A-associated AR mutations 42030710Apr.

Mechanistic studies revealed that AR pathway inhibitors selectively induce BCL-2 expression across diverse castration-resistant prostate cancer subtypes, identifying BCL-2 as a shared vulnerability; a Phase Ib trial combining enzalutamide with the BCL-2 inhibitor venetoclax demonstrated reduced circulating tumor cells in responding patients 42067541May. Resistance mechanisms involve complex lineage plasticity; the eIF4E cap-binding domain was identified as a critical regulator of lineage plasticity, with inhibition reprogramming castration-resistant tumors toward a luminal state and restoring sensitivity to AR pathway inhibitors 41984598Apr. Neuroendocrine transformation represents another escape mechanism; HOXD11 was identified as a driver of neuroendocrine prostate cancer progression that suppresses AR signaling through activation of NMDAR subunits, with pharmacological NMDAR inhibition via memantine showing preclinical efficacy and a preliminary clinical response 42126948May. Cell-free DNA profiling revealed divergent resistance trajectories, with rapid progressors harboring non-AR alterations indicative of intrinsic resistance, whereas delayed progressors showed progressive AR amplifications and structural rearrangements 41996129Apr. OGDHL, an alternative metabolic enzyme, regulates neuroendocrine marker expression and modulates treatment-induced lineage plasticity in aggressive prostate cancer 41591383Jan.

In breast cancer, AR emerged as a potential biomarker with prognostic significance. AR expression was significantly associated with hormone receptor positivity and lower tumor grade; however, AR expression was not predictive of pathological complete response to neoadjuvant chemotherapy and showed prognostic but not predictive value for survival outcomes 42376794Jun. In a Caucasus population cohort, moderate-to-strong AR expression patterns were evaluated in stage II-III breast cancer patients undergoing neoadjuvant chemotherapy 42601757Aug. Conversely, selective AR modulation emerged as a therapeutic strategy; EP0062, a selective AR modulator, displayed comparable antitumor efficacy to selective ER degraders in estrogen receptor-positive metastatic breast cancer models, with sensitivity enriched in GATA3-mutant tumors and enhanced efficacy when combined with palbociclib 42310300Jun.

For androgenetic alopecia, dual soft drug design strategies advanced topical AR antagonist development. A second-generation compound (39) achieved potent AR antagonism (IC50 = 20.6 ± 2.3 nM) and favorable pharmacokinetic profiles, demonstrating comparable efficacy to pyrilutamide in hair-growth models with accelerated response kinetics (14-day versus 21-day onset) while maintaining safety 42418259Jul. Complementing pharmacological approaches, spermine-derived ionizable lipid nanoparticles were developed for siRNA delivery targeting AR; intradermal administration in androgenetic alopecia model mice effectively suppressed aberrant AR protein expression and promoted hair follicle recovery 42003109Apr.

Beyond traditional malignancies, AR inhibition demonstrated immunomodulatory potential. In hepatocellular carcinoma, AR inhibition induced immunogenic cell death through transcriptional repression of valosin-containing protein (VCP), promoted dendritic cell maturation, and enhanced CD8+ T-cell infiltration; combination with anti-PD-1 therapy and oncolytic virus augmented therapeutic efficacy 42364832Jun. In head and neck squamous cell carcinoma, AR signaling drove CD8+ T-cell dysfunction through early growth response 4; androgen deprivation therapy suppressed tumor growth and improved intratumoral CD8+ T-cell function, with combination treatment with immune checkpoint inhibitors showing enhanced antitumor efficacy 41661680Feb. Finally, darolutamide treatment was observed to induce transient PSMA upregulation (the "PSMA flare phenomenon") in castration-resistant prostate cancer, potentially enhancing sensitivity and accuracy of PSMA-based molecular imaging and disease staging 42315278Jun.

What Changes, What Holds

1. Dual-function AR degraders and N-terminal domain inhibitors achieve clinical efficacy in resistant prostate cancer
REINFORCES BMS-986365 and ARV-110 now demonstrate robust activity against wild-type and mutant AR in clinical trials 42430428Jul42227954Jun, confirming the Overview's identification of N-terminal domain agents and degraders as strategies being pursued to overcome ligand-binding-domain resistance. AR-TAD inhibitors disrupting co-regulator interaction add specificity within this class 42045150Apr, sharpening rather than displacing established expectations that the N-terminal domain is druggable.

2. Molecular drivers of lineage plasticity and neuroendocrine transformation reveal targetable vulnerabilities in resistant prostate cancer
NEW DIRECTION Specific mechanisms now explain neuroendocrine emergence that the Overview mentions as an escape after prolonged suppression but without mechanistic detail. eIF4E and HOXD11 regulate lineage plasticity 42126948May41984598Apr, OGDHL modulates treatment-induced plasticity 41591383Jan, while BCL-2 emerges as a shared vulnerability in resistant lines 42067541May, enabling combination therapies (enzalutamide + venetoclax) now tested clinically. Identifying these druggable targets represents advancement beyond the baseline's acknowledgment of resistance mechanisms.

3. AR shows prognostic but not predictive value as a biomarker in breast cancer and emerges as a therapeutic target via selective modulation
NEW DIRECTION breast cancer presents a new setting where AR expression correlates with prognostic factors yet fails to predict chemotherapy response 42376794Jun—distinct from prostate's well-established AR dependence. Selective AR modulators like EP0062 display antitumor efficacy comparable to ER degraders in ER+ disease, particularly in GATA3-mutant tumors 42310300Jun, establishing AR as a separate therapeutic axis that the Overview does not address.

4. Topical AR antagonists and lipid nanoparticle-based siRNA delivery demonstrate efficacy in androgenetic alopecia
REINFORCES Compound 39 and spermine-derived ionizable lipid nanoparticles exemplify therapeutic advances in AGA that the Overview identifies as an emerging area of AR-directed interest. Topical antagonists achieve accelerated hair-growth kinetics versus established agents 42418259Jul, while intradermal siRNA delivery suppresses AR protein in mouse models 42003109Apr. Both advances validate the therapeutic potential the baseline predicted without prescribing specific mechanisms.

5. AR inhibition activates immunogenic pathways in non-prostate malignancies and induces PSMA upregulation in CRPC
NEW DIRECTION AR inhibition in hepatocellular carcinoma and head and neck cancer now reveals immune mechanisms absent from the Overview's brief reference to emerging evidence in tumor immunology. VCP repression, dendritic cell maturation, and CD8+ infiltration occur in HCC 42364832Jun; in head and neck cancer, androgen deprivation restores CD8+ function suppressed by AR-driven early growth response 4 41661680Feb. Darolutamide-induced PSMA flare—transient upregulation enhancing imaging sensitivity 42315278Jun—is a pharmacological phenomenon not previously described.

Overview update candidates: Specific drivers of lineage plasticity and neuroendocrine transformation (BCL-2, HOXD11, eIF4E; OGDHL); AR as prognostic biomarker and therapeutic target in breast cancer; immune mechanisms of AR inhibition in non-prostate malignancies (HCC; head and neck); PSMA flare phenomenon; siRNA-based AR therapies.