Enzalutamide

證據等級: L5

預測適應症: 10 個

Enzalutamide: From Prostate Cancer to Male Reproductive Organ Cancer

One-Sentence Summary

Enzalutamide (Xtandi®) is a second-generation androgen receptor (AR) antagonist, originally approved internationally for the treatment of prostate cancer across multiple disease stages — from metastatic castration-sensitive prostate cancer (mCSPC) through metastatic castration-resistant prostate cancer (mCRPC). The TxGNN model predicts with high confidence that it is effective for Male Reproductive Organ Cancer, supported by over 50 clinical trials and 20 publications. The most critical finding for Singapore is that Enzalutamide currently holds zero HSA registrations, making this a market access gap rather than an evidence gap.

Quick Overview

Item	Content
Original Indication	Prostate cancer (mCRPC / nmCRPC / mCSPC) — approved by FDA (2012–2019) and EMA
Predicted New Indication	Male Reproductive Organ Cancer
TxGNN Prediction Score	99.51%
Evidence Level	L1
Singapore Market Status	✗ Not marketed
Number of Registrations	0
Recommended Decision	Proceed with Guardrails

Why is This Prediction Reasonable?

Enzalutamide is a potent non-steroidal androgen receptor antagonist that directly targets the AR ligand-binding domain with approximately 5–8 fold higher binding affinity than first-generation anti-androgens such as bicalutamide. It simultaneously blocks three critical steps in androgen signalling: testosterone/DHT binding to AR, AR nuclear translocation, and AR–DNA/co-activator interactions. The net result is comprehensive suppression of androgen-driven gene transcription — the central driver of prostate tumour growth. Note: detailed MOA data was not available in this Evidence Pack; the above description is drawn from established clinical literature.

Male reproductive organ cancers, of which prostate adenocarcinoma is the dominant histotype, are paradigmatically dependent on AR signalling. Even in castration-resistant disease, AR remains the primary oncogenic driver through mechanisms such as AR gene amplification, ligand-binding domain mutations, and splice variants (e.g., AR-V7). This direct mechanistic alignment explains why Enzalutamide achieves clinical benefit across the full disease spectrum. The TxGNN model's 99.51% prediction confidence for male reproductive organ cancer essentially confirms the drug's established mechanism rather than proposing a novel indication.

The evidence base is exceptional. Landmark Phase 3 RCTs — AFFIRM (post-docetaxel mCRPC), PREVAIL (chemotherapy-naïve mCRPC), PROSPER (nmCRPC), ARCHES (mCSPC), and ENZAMET (mCSPC) — have each demonstrated statistically significant overall survival or metastasis-free survival benefits. It is worth noting that TxGNN's top five ranked predictions (ranks 1–4: genetic susceptibility loci, rare benign prostatic stromal tumours, Brenner tumour) all carry L5 evidence and "Hold" recommendations, reflecting knowledge-graph topological noise rather than true repurposing signals. The actionable signal sits squarely at ranks 6 and 9, where robust L1 evidence supports a Proceed with Guardrails decision.

Clinical Trial Evidence

Trial Number	Phase	Status	Enrollment	Key Findings
NCT01949337	Phase 3	Unknown	1,311	Randomized Phase III comparing Enzalutamide monotherapy vs. Enzalutamide + Abiraterone + Prednisone in castration-resistant metastatic prostate cancer — core high-level evidence for Enzalutamide efficacy
NCT04821622	Phase 3	Active, not recruiting	599	TALAPRO-3: Talazoparib + Enzalutamide vs. Placebo + Enzalutamide in DDR gene-mutated mCSPC — evaluates PARP inhibitor + ARSI combination in a genomically selected population
NCT05968599	N/A (RWE)	Completed	2,731	Large real-world comparison of Enzalutamide vs. Abiraterone in chemotherapy-naïve mCRPC (Flatiron EHR database); n=2,731 strengthens external validity of Phase 3 trial findings
NCT04179864	Phase 1b/2	Terminated	102	CELLO-1: Tazemetostat (EZH2 inhibitor) + Enzalutamide in mCRPC — exploratory epigenetic + AR dual-blockade strategy; terminated early, termination rationale unconfirmed
NCT04557449	Phase 1/2a	Active, not recruiting	362	PF-07220060 (CDK4/6 inhibitor) as single agent and in combination with Enzalutamide in advanced solid tumours including mCRPC — ongoing combination safety/efficacy study
NCT02588001	N/A	Completed	60	Japanese real-world study of Enzalutamide in nmCRPC over 5 years — provides East Asian safety and efficacy data directly relevant to Singapore clinical context
NCT05914116	Phase 1/2a	Recruiting	862	DB-1311/BNT324 (novel ADC) + Enzalutamide in advanced/metastatic solid tumours — first-in-human study expanding combination evidence in mCRPC
NCT07230106	Phase 2	Recruiting	218	HS-20093 or SHR2554 + Novel Hormonal Agents (including Enzalutamide) in metastatic prostate cancer — assessing PK, tolerability and efficacy of novel combination
NCT04033328	Phase 1b	Terminated	41	ORIC-101 (glucocorticoid receptor antagonist) + Enzalutamide in mCRPC progressing on Enzalutamide — explores glucocorticoid-mediated resistance reversal; terminated early, limited data
NCT03674814	Phase 1	Active, not recruiting	35	Relacorilant (glucocorticoid receptor antagonist) + Enzalutamide in mCRPC — mechanistic study addressing GR-mediated AR bypass resistance

Literature Evidence

PMID	Year	Type	Journal	Key Findings
28655021	2017	Review	JAMA	Comprehensive review of prostate cancer diagnosis and treatment; Enzalutamide positioned as a key second-generation AR inhibitor for advanced disease management
32534790	2020	Review	Trends in Cancer	Rapidly evolving treatment landscape: summarises Phase 3 evidence for Enzalutamide, Abiraterone, Apalutamide, Darolutamide, Docetaxel and Radium-223; discusses optimal drug sequencing
31614208	2020	Review	J Steroid Biochem Mol Biol	Intracrinology of androgen biosynthesis in prostate cancer; explains mechanistic basis for sustained AR signalling in CRPC and why AR-targeted therapies including Enzalutamide retain efficacy
36842160	2023	Review	The Prostate	3βHSD1 as a precision medicine target; 3βHSD1 activity increases after long-term Enzalutamide treatment, mediating resistance — identifies actionable co-treatment strategy
37844613	2023	Basic Science	Nature	Inhibition of myeloid chemotaxis reverses therapy resistance in a subset of prostate cancer patients; demonstrates tumour microenvironment as a combination target alongside AR inhibition
34489465	2021	Basic Science	Nature Communications	Single-cell ATAC + RNA sequencing identifies pre-existing resistant cell subpopulations before Enzalutamide treatment — major insight into primary resistance mechanisms and combination therapy rationale
34752846	2022	Basic Science	Cancer Letters	Enzalutamide-induced PTH1R-mediated TGFBR2 degradation in osteoblasts confers bone microenvironment-dependent resistance in ~50% of bone-metastatic PCa — supports need for combination strategies
33542074	2021	Basic Science	Clin Cancer Res	BCL-2 and IKKB dependencies emerge during acquired Enzalutamide resistance — identifies BCL-2 inhibition as a potential co-treatment to delay or overcome resistance
33483372	2021	Basic Science	Cancer Research	Ferroptosis inducers (FINs) show therapeutic potential in advanced prostate cancer models; mediators SLC7A11, SLC3A2, GPX expressed in treatment-resistant disease — potential synergy with Enzalutamide
32355025	2020	Basic Science	Science	Single-cell RNA sequencing reveals a rare Sca1+/Psca+ luminal stem-like prostate cell population surviving androgen deprivation — explains incomplete tumour elimination by AR inhibition and underpins combination strategy research

Singapore Market Information

Enzalutamide is currently not registered with Singapore's Health Sciences Authority (HSA). There are no product licences on record, and the drug is not commercially available through standard channels in Singapore.

For reference, Enzalutamide (Xtandi®, Astellas/Pfizer) holds the following international approvals:

Market	Indication	Year Approved
US FDA	mCRPC (post-docetaxel)	2012
US FDA	nmCRPC	2018
US FDA	mCSPC	2019
EMA	mCRPC, nmCRPC, mCSPC	2013–2020
Japan PMDA	mCRPC, nmCRPC, mCSPC	2014–2020

A formal HSA registration application, potentially supported by a collaborative registration pathway leveraging existing FDA or EMA data packages, would be the most direct route to Singapore market access.

Cytotoxicity

Enzalutamide is an antineoplastic agent used for the treatment of prostate cancer. It is classified as a targeted hormone therapy, not as a conventional cytotoxic chemotherapy drug.

Item	Content
Cytotoxicity Classification	Targeted therapy — Second-generation androgen receptor antagonist (non-steroidal; not cytotoxic)
Myelosuppression Risk	Low — Enzalutamide does not directly suppress bone marrow; clinically significant cytopenias are uncommon
Emetogenicity Classification	Low — nausea and vomiting rates in clinical trials were comparable to placebo
Monitoring Items	Liver function (ALT/AST), blood pressure, baseline seizure risk assessment, cognitive function and falls risk in elderly patients, PSA response
Handling Protection	Standard oncology medication precautions apply; not classified as a vesicant or highly hazardous cytotoxic requiring specialised chemotherapy-suite preparation

Safety Considerations

Safety data was not available in this Evidence Pack for local HSA/TFDA package insert warnings and contraindications.

Based on internationally recognised clinical trial data and regulatory labelling:

Seizure risk: A known class effect; approximately 0.5% incidence in Phase 3 trials. Exercise caution or avoid in patients with a history of seizure disorder, prior brain injury, or concurrent use of seizure-threshold-lowering medications.
Drug-drug interactions: Enzalutamide is a potent inducer of CYP3A4, CYP2C8, CYP2C9, and CYP2C19. Co-administered medications metabolised by these enzymes (including anticoagulants, opioids, and many cardiovascular drugs) may require dose adjustment or substitution.

Please refer to the FDA/EMA prescribing information and the future HSA-approved package insert for complete safety information.

Conclusion and Next Steps

Decision: Proceed with Guardrails

Rationale: Enzalutamide carries one of the most robust oncology evidence profiles available — multiple completed Phase 3 RCTs confirming overall survival benefit across the full prostate cancer disease spectrum. The sole barrier to use in Singapore is the absence of HSA registration, not a lack of clinical evidence.

To proceed, the following is needed:

Initiate HSA regulatory submission for Enzalutamide (Xtandi®), leveraging existing FDA/EMA approval dossiers via Singapore's collaborative registration pathway where applicable
Obtain the complete local or reference-country package insert to formally document contraindications, boxed warnings, and drug interaction profile for HSA review
Clarify reimbursability under Singapore's cancer drug list, MediShield Life, and/or Medisave framework
Review CYP induction-mediated drug interaction risks in the intended patient population, particularly given common co-medications (anticoagulants, analgesics)
Leverage existing East Asian safety data (Japanese nmCRPC study NCT02588001; n=60) as a pharmacovigilance reference while awaiting Singapore-specific post-marketing data
Establish institutional seizure risk screening and monitoring protocols prior to formulary listing
Disclaimer

This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.