Enzalutamide is an oral medication used in the treatment of prostate cancer. Marketed as Xtandi, it functions as a nonsteroidal antiandrogen. This medication primarily manages prostate cancer that has progressed despite other hormone therapies.
How Enzalutamide Works
Prostate cancer growth is often fueled by male hormones, known as androgens, such as testosterone and dihydrotestosterone (DHT). These androgens bind to specific proteins called androgen receptors (ARs) within prostate cancer cells. This binding activates the receptors, sending signals that promote cancer cell growth and multiplication.
Enzalutamide targets and inhibits the androgen receptor signaling pathway at multiple steps. It acts as a competitive inhibitor, binding to the androgen receptor with higher affinity than natural androgens, preventing their activation. This effectively deprives cancer cells of necessary growth signals.
Beyond blocking androgen binding, enzalutamide also impedes the androgen receptor’s movement into the cell’s nucleus, where it interacts with DNA. It further interferes with the receptor’s ability to bind to DNA and recruit co-activator proteins for gene transcription. By disrupting these processes, enzalutamide suppresses androgen receptor signaling, leading to decreased cancer cell growth and promoting cell death.
When Enzalutamide is Prescribed
Enzalutamide is approved for several specific types of prostate cancer. It is commonly prescribed for metastatic castration-resistant prostate cancer (mCRPC), where the cancer has spread and continues to grow despite low testosterone levels from other hormone therapies.
The medication is also indicated for non-metastatic castration-resistant prostate cancer (nmCRPC) in individuals with high-risk features, such as a rapidly rising prostate-specific antigen (PSA) level. Here, the cancer is resistant to hormone therapy but has not yet visibly spread. Enzalutamide has been shown to improve metastasis-free survival in this patient group.
Enzalutamide can also be used for metastatic hormone-sensitive prostate cancer (mHSPC), where the cancer has spread but still responds to treatments that lower testosterone. In these contexts, enzalutamide is used with androgen deprivation therapy (ADT). This combined approach aims to prolong survival and delay disease progression.
Managing Treatment and Side Effects
Enzalutamide is administered as an oral capsule, taken once daily. The recommended dosage is 160 mg, which can be taken with or without food. Patients should swallow capsules whole, avoiding chewing, dissolving, or opening them. If a dose is missed, it should be taken as soon as possible on the same day, but patients should not double the dose.
Common side effects include fatigue, hot flashes, high blood pressure, and musculoskeletal pain, such as back or joint pain. Other reported side effects include diarrhea, headache, dizziness, and decreased appetite. These effects are temporary and may improve as the body adjusts to the medication.
Less common but serious side effects can occur, requiring prompt medical attention. These include seizures, which may present with confusion, loss of consciousness, or rapid eye movements. Posterior reversible encephalopathy syndrome (PRES, a rare neurological condition) is characterized by symptoms like headache, confusion, seizures, and vision changes due to brain swelling.
Patients taking enzalutamide should have regular monitoring by their healthcare provider. This includes periodic blood pressure checks, especially during the first few months of treatment, and blood tests to monitor overall health. It is important to discuss any new or worsening side effects with a doctor for proper management and dose adjustments if necessary.