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Drug deep dive: Enzalutamide
How Does Enzalutamide — Actually Work?
Enzalutamide stops prostate cancer cells from using testosterone as fuel. It does this by blocking the androgen receptor — the molecular switch cancer cells need to grow — at multiple points in the signalling pathway.
Medically reviewed by Dr. Bharati Devi Gorantla, Medical Oncologist, MBBS · MD · DM (Adyar, Chennai) · ECMO · MRCP SCE (UK) · Last reviewed August 2026
- Blocks at three steps — It works further along the signalling pathway than older hormone therapies, not just at one point.
- Not the same as ADT — It does not lower testosterone in the blood. It blocks the receptor that uses testosterone.
- Oral tablet, once daily — Taken by mouth at home, not given as an injection or infusion at the clinic.
- Usually combined with ADT — Most patients take it alongside hormone injections that also lower testosterone levels.
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Enzalutamide blocks testosterone and other androgens from activating the androgen receptor — the switch that drives prostate cancer cell growth. It works at three steps along that pathway, not just one. This makes it more thorough at shutting down androgen signalling than older hormone therapies.
How does enzalutamide stop prostate cancer from growing?
Prostate cancer cells carry a protein called the androgen receptor. Testosterone and related hormones attach to it like a key in a lock, which signals the cancer cell to grow and divide.
Enzalutamide works at three points along this chain. It stops testosterone attaching to the receptor. It then stops the activated receptor from moving into the cell nucleus. And it stops the receptor from binding to DNA once inside. This multi-step action is why it is classed as an androgen receptor signalling inhibitor, not simply an anti-androgen.
Older hormone therapies worked mainly by reducing testosterone in the blood. Enzalutamide targets the receptor itself — which matters because castration-resistant prostate cancer cells can sometimes activate their androgen receptors even when testosterone is very low, or produce small amounts of androgens on their own.
What do the terms on your prescription and clinic letters mean?
- Androgen receptor (AR)
- A protein inside prostate cancer cells that acts as an on-switch. When testosterone or a similar hormone attaches to it, the cell receives a signal to grow.
- Androgens
- A family of hormones that includes testosterone. Most prostate cancers are driven by androgens, at least early in the disease.
- Androgen receptor signalling inhibitor (ARSI)
- The drug class enzalutamide belongs to. It blocks the receptor and the steps that follow activation, not just the hormone that triggers it.
- Androgen deprivation therapy (ADT)
- Injections or implants — such as LHRH agonists — that lower testosterone levels in the blood. Often prescribed alongside enzalutamide but works by a different mechanism.
- Castration-resistant prostate cancer (CRPC)
- Prostate cancer that continues to grow despite very low testosterone levels — usually because the androgen receptor itself has become overactive or structurally altered.
- PSA (prostate-specific antigen)
- A protein produced by prostate cells and measured in a blood test. Your oncologist uses PSA trends to judge how well treatment is working.
How is enzalutamide different from standard hormone injections?
Standard hormone therapy — LHRH agonists such as leuprolide, or antagonists such as degarelix — signals the body to produce far less testosterone. It reduces the fuel available to cancer cells.
Enzalutamide targets the other end of the same pathway: the receptor that uses that fuel. Even when testosterone levels are very low, castration-resistant cancer cells can sometimes keep the androgen receptor active. Enzalutamide is designed to block the receptor before that can happen.
In most patients, enzalutamide is prescribed alongside ADT rather than instead of it. NCCN and ASCO guidelines support this combination for the relevant stages of prostate cancer, because the two treatments act at different points in the same pathway.
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What should you know before starting enzalutamide?
- Enzalutamide is a tablet taken once daily at home — you do not come to the clinic for infusions.
- Most patients take it alongside ongoing ADT injections, not instead of them.
- PSA is checked regularly by blood test to track whether treatment is working.
- Tell your oncologist and pharmacist every medicine, supplement and herbal remedy you take — enzalutamide interacts with several common drugs.
- Do not stop taking it without telling your treating team, even if you feel well.
- Fatigue and hot flushes are common. Let your team know if either becomes difficult to manage.
What do patients commonly ask after being prescribed enzalutamide?
Will enzalutamide lower my testosterone level?
No, not directly. Enzalutamide blocks the androgen receptor — the lock — rather than reducing testosterone itself. If you are also on ADT injections, those are what lower your testosterone levels. The two work together: ADT reduces the amount of testosterone circulating, and enzalutamide blocks whatever the receptor might still pick up. Some patients find it helpful to think of ADT as turning down the fuel supply, and enzalutamide as blocking the engine from using what remains.
How will I know if enzalutamide is working?
The main measure is your PSA level, checked with blood tests at regular intervals. A falling or stable PSA generally indicates the treatment is controlling cancer growth. Imaging — CT or bone scans, or sometimes PET-CT coordinated through partner imaging centres — may be used at key decision points. The question to ask your oncologist is what PSA trend they are expecting and at what point they would consider a change. Not every patient sees the same pattern or timeline.
Why is enzalutamide prescribed for castration-resistant cancer specifically?
When prostate cancer grows despite very low testosterone levels, it has usually found a way to keep using the androgen receptor — through changes such as receptor amplification or mutation. Standard ADT lowers testosterone but cannot address the receptor itself. Enzalutamide was developed specifically to block the receptor more completely in this situation. NCCN and ASCO guidelines include it as a standard option for both metastatic and non-metastatic castration-resistant prostate cancer.
Can prostate cancer stop responding to enzalutamide?
Yes, in a proportion of patients, the cancer eventually finds ways to work around the receptor block — through further mutations in the androgen receptor, or by switching to growth signals that do not depend on androgens at all. When PSA begins rising again or imaging shows progression, your oncologist will review the situation and discuss next steps. We do not yet fully understand all the mechanisms that drive resistance, and research is ongoing. Progression on one agent does not mean there are no further options.
How does enzalutamide compare to abiraterone?
They address the same pathway but at different points. Abiraterone targets an enzyme called CYP17A1, which prostate cancer cells need to produce androgens — including the small amounts that castration-resistant cells can make themselves. Enzalutamide acts downstream: it blocks the receptor those androgens would bind to. In practice, oncologists choose between them or sequence them based on your cancer's characteristics, your other medical conditions, and which side effects you are better placed to manage. Your oncologist will advise what applies to your situation.
Did you know?
For decades, castration-resistant prostate cancer was thought to have become independent of androgens entirely. Research established that the androgen receptor remains active and often continues to drive growth even when testosterone in the blood is near undetectable — a finding that changed how the disease is understood and how drugs like enzalutamide came to be developed.
Blocking the receptor directly, rather than only lowering testosterone, became a central goal in prostate cancer drug development because of that shift.
Source: ASCO and NCCN guidelines on castration-resistant prostate cancer; mechanistic findings summarised in ESMO clinical practice guidelines for prostate cancer
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Common questions
Frequently asked questions
Is enzalutamide a chemotherapy drug?
No. Enzalutamide is a hormone therapy — specifically an androgen receptor signalling inhibitor. It works by blocking the androgen receptor rather than attacking dividing cells the way chemotherapy does. Hair loss and bone marrow suppression are not typical effects. The side effects most people notice are fatigue, hot flushes, and sometimes dizziness. That said, it is a prescription cancer medicine and should always be taken exactly as directed by your oncologist.
What stage of prostate cancer is enzalutamide used for?
Enzalutamide is used across several stages. NCCN and ASCO guidelines include it for metastatic castration-sensitive prostate cancer, non-metastatic castration-resistant prostate cancer, and metastatic castration-resistant prostate cancer. Which setting applies to you depends on whether the cancer has spread and whether it is still responding to standard hormone therapy. Your oncologist will explain which category your diagnosis falls into and what that means for how the drug is used.
Does enzalutamide interact with other medicines?
Yes, and this matters. Enzalutamide affects how the liver processes many other drugs, and some medicines affect how enzalutamide itself behaves. Before you start, your oncologist or pharmacist should review every medicine and supplement you take — including herbal remedies and over-the-counter products. If another doctor prescribes you something new during treatment, tell them you are on enzalutamide so they can check for interactions before dispensing.
Can enzalutamide cause seizures?
Seizures are a rare but recognised risk listed in enzalutamide's prescribing information. The risk is higher in people with a prior history of seizures or conditions that lower the seizure threshold. Your oncologist will ask about your history before prescribing it. If you have ever had a seizure, brain surgery, or stroke, or take medicines that affect seizure threshold, raise this explicitly. Most patients without these risk factors complete treatment without any seizure episode — but your family should know it is listed so they can report any unusual episode immediately.
How long will I need to take enzalutamide?
There is no fixed duration that applies to everyone. Enzalutamide is taken continuously — not in cycles — for as long as it is working and tolerable. Your oncologist will monitor PSA and arrange imaging at agreed intervals. Treatment continues until there is evidence the cancer is no longer responding, or a side effect makes it unsafe to continue. At that point, your team will discuss what the next step is.
Is enzalutamide treatment available at CION?
Enzalutamide is an oral tablet taken at home, so it does not require a clinic visit for administration. At CION, prescribing and monitoring of enzalutamide is managed by your treating oncologist across centres in Telangana and Andhra Pradesh. Monitoring blood tests and PSA checks are done at the centre. Imaging such as PET-CT is coordinated through partner imaging centres. Your team will explain the monitoring schedule and who to contact if you have concerns between appointments.