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Enzalutamide – Uses, Dosage, Side Effects, Interaction

Mechanism of Action

Enzalutamide is a competitive androgen receptor inhibitor that affects multiple stages of the signaling pathway. It is able to inhibit androgen binding to its receptor, androgen receptor nuclear translocation, and subsequent interaction with DNA. As a result, the proliferation of prostate cancer cells decreases which ultimately leads to apoptosis and decreased tumor volume.

Enzalutamide is an androgen receptor (AR) inhibitor for the treatment of castration-resistant prostate cancer (CRPC), both metastatic and non-metastatic.[rx] It is a second-generation antiandrogen agent that the FDA approved on August 31, 2012.[rx,rx] Although androgen deprivation therapy (ADT) is the first-line treatment of prostate cancer and remission can be achieved, arising resistance is inevitable, becoming castration-resistant prostate cancer.[rx] Until recently, docetaxel is the only treatment available for metastatic CRPC; however, AR inhibitors have been developed for more targeted therapy, although first-generation AR inhibitors like bicalutamide did not substantially increase the survival rate.[rx] Second-generation such as enzalutamide is more efficacious due to a higher affinity to AR and no partial agonist activity compared to bicalutamide.[rx,rx]

Enzalutamide is a second-generation antiandrogen that blocks the activity of androgen and androgen receptor (AR) in prostate cancer. AR activity and prostate cancer progression are closely related due to the normal physiology of prostate cells, providing the rationale for androgen deprivation therapy (ADT).[rx] However, resistance will eventually arise after the commencement of ADT in 2-3 years due to the accumulation of mutations, including constitutively active mutation, AR overexpression, and changes in AR splicing variants.[rx,rx] Enzalutamide was therefore designed to exploit these mutations.[rx] In vitro experiments in human prostate cancer cell line VCaP showed that enzalutamide can suppress cell growth and induce apoptosis while other antiandrogens like bicalutamide did not.[rx]

Clinical trials on prostate cancer patients indicated that enzalutamide can lead to a decrease in serum PSA for at least 12 weeks, although this response can be short-lived and thus result in enzalutamide resistance.[rx,rx] Patients receiving enzalutamide also had a 37% decrease in the risk of death compared to placebo.[rx]

Indications

  • Enzalutamide is indicated for the treatment of patients with metastatic castration-resistant prostate cancer who have previously received docetaxel.
  • Xtandi is indicated for the treatment of adult men with metastatic hormone-sensitive prostate cancer (mHSPC) in combination with androgen deprivation therapy the treatment of adult men with high-risk non-metastatic castration-resistant prostate cancer (CRPC) the treatment of adult men with metastatic CRPC who are asymptomatic or mildly symptomatic after failure of androgen deprivation therapy in whom chemotherapy is not yet clinically indicated the treatment of adult men with metastatic CRPC whose disease has progressed on or after docetaxel therapy.
  • Enzalutamide is a nonsteroidal antiandrogen used to treat metastatic castration-resistant prostate cancer.
  • It is indicated for use in conjunction with castration in the treatment of metastatic castration-resistant prostate cancer (mCRPC),[rx] nonmetastatic castration-resistant prostate cancer,[rx] and metastatic castration-sensitive prostate cancer (mCSPC).[rx] It is taken by mouth.[rx]
  • Castration-Resistant Prostate Cancer
  • Metastatic Castration Sensitive Prostate Cancer

Use in Cancer

Enzalutamide is approved to treat:

Enzalutamide is also being studied in the treatment of other types of cancer.

Contraindications

  • a low seizure threshold
  • brain injury
  • a low supply of oxygen-rich blood to the heart
  • a transient ischemic attack, a type of stroke that lasts only a few minutes
  • seizures
  • pregnancy
  • a patient who is producing milk and breastfeeding
  • a type of brain disorder called posterior reversible encephalopathy syndrome
  • history of stroke

Dosage

Strengths: 40 mg; 80 mg

Prostate Cancer

  • 160 mg (four 40 mg capsules) orally once a day
  • This drug can be taken with or without food.
  • Swallow the capsules whole. Do not chew, dissolve, or open the capsules.
  • Patients receiving this drug should also receive a gonadotropin-releasing hormone (GnRH) analog concurrently or should have had bilateral orchiectomy.
  • Metastatic and non-metastatic castration-resistant prostate cancer

Dose Adjustments

Grade 3 or more toxicity or intolerable side effect:

  • Withhold dosing for one week or until symptoms improve to Grade 2 or less, then resume at the usual dose or reduce the dose to 120 mg or 80 mg once daily if necessary.

Strong CYP450 2C8 inhibitors:

  • Avoid concomitant use. If concomitant use is necessary, reduce the dose to 80 mg once daily and return to the prior dose if the strong CYP450 2C8 inhibitor is discontinued.

Strong CYP450 3A4 inducers:

  • The concomitant use of strong CYP450 3A4 inducers should be avoided if possible. If coadministration is necessary, increase the dose to 160 to 240 mg once daily. If the strong CYP450 3A4 is discontinued, the dose should be returned to the dose used prior to the initiation of the strong CYP450 3A4 inducer.

Administration advice:

  • Take it with or without food.
  • Swallow capsules whole with water. Do not chew, dissolve, or open the capsules.

Side Effects

The Most Common

  • asthenia/fatigue,
  • back pain,
  • diarrhea,
  • arthralgia,
  • hot flush,
  • peripheral edema,
  • musculoskeletal pain,
  • headache,
  • upper respiratory infection,
  • muscular weakness,
  • dizziness, insomnia,
  • lower respiratory infection,
  • spinal cord compression and cauda equina syndrome,
  • hematuria, paresthesia, anxiety, and hypertension.

More Common

  • weakness
  • tiredness
  • joint pain
  • muscle weakness or stiffness
  • weight loss
  • loss of appetite
  • headache
  • dizziness
  • burning, numbness, or tingling in the arms, hands, or feet
  • decreased sense of touch or ability to feel sensation
  • hot flashes
  • difficulty falling asleep or staying asleep
  • anxiety
  • difficulty remembering, thinking, or paying attention
  • diarrhea
  • constipation
  • itching
  • dry skin
  • nosebleeds
  • frequent urination
  • taste changes
  • seizures
  • headache; confusion; or vision changes
  • swelling of the face, tongue, lips, throat, arms, legs, hands, or feet
  • fever, cough, sore throat, or other signs of infection
  • chest pain
  • shortness of breath
  • pain in the back, muscles, and/or legs
  • numbness or tingling in the buttocks or legs
  • difficulty controlling urination or bowel movements
  • difficulty breathing
  • falling
  • broken bones or fractures
  • hallucinating (seeing things or hearing voices that do not exist)
  • breast enlargement in men
  • pink or red urine

Rare

  • cough with mucus
  • difficulty with breathing
  • dizziness
  • fever
  • loss of bladder or bowel control
  • nervousness
  • painful or difficult urination
  • pounding in the ears
  • slow or fast heartbeat
  • sore throat
  • tingling of the hands or feet
  • unable to move the legs
  • unusual weight gain or loss
  • Anxiety
  • confusion or excitement
  • depression
  • fainting
  • falling
  • lightheadedness
  • loss of memory
  • memory or attention span problems
  • nightmares or vivid dreams
  • rapid, shallow breathing
  • Headache
  • hives, itching, skin rash
  • hoarseness
  • irritation
  • joint pain, stiffness, or swelling
  • redness of the skin
  • swelling of the eyelids, face, lips, hands, or feet
  • tightness in the chest
  • trouble breathing or swallowing
  • unusual drowsiness, tiredness, weakness, or feeling of sluggishness

Drug Interaction

Pregnancy and Lactation

AU TGA pregnancy category: X
US FDA pregnancy category: Not assigned.

Pregnancy

There are no data on pregnant women; however, in animal studies giving this drug during organogenesis caused adverse developmental effects at doses lower than the equivalent maximum recommended human dose (MRHD). This drug is not indicated for use in females. This drug should not be handled by women who are or may become pregnant. Male patients with female partners of reproductive potential should use effective contraception during therapy and for 3 months after the last dose. This drug may impair fertility in males of reproductive potential.

Lactation

  • This drug is not indicated for use in female patients.
  • Excreted into human milk: Unknown
  • Excreted into animal milk: Yes
  • This drug is not indicated for use in females.
  • The effects on the nursing infant are unknown.

What special precautions should I follow?

Before taking enzalutamide,

  • tell your doctor and pharmacist if you are allergic to enzalutamide, any other medications, or any of the ingredients in enzalutamide tablets or capsules. Ask your pharmacist or check the manufacturer’s information for the patient for a list of the ingredients.
  • tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, and nutritional supplements you are taking or plan to take. Be sure to mention any of the following: anticoagulants (‘blood thinners) such as warfarin (Coumadin, Jantoven), carbamazepine (Carbatrol, Equetro, Tegretol, others), clopidogrel (Plavix), cyclosporine (Gengraf, Neoral, Sandimmune), dihydroergotamine (D.H.E. 45, Migranal), ergotamine (in Migergot, in Cafergot), fentanyl (Actiq, Duragesic, Fentora, Subsys, others), gemfibrozil (Lopid), itraconazole (Onmel, Sporanox), omeprazole (Prilosec), midazolam, phenobarbital, phenytoin (Dilantin, Phenytek), pimozide (Orap), quinidine (in Nuedexta), rifabutin (Mycobutin, in Talicia), rifampin (Rimactane, in Rifamate, in Rifater), rifapentine (Priftin), sirolimus (Rapamune), and tacrolimus (Prograf). Your doctor may need to change the doses of your medications or monitor you carefully for side effects. Many other medications may also interact with enzalutamide, so be sure to tell your doctor about all the medications you are taking, even those that do not appear on this list.
  • tell your doctor what herbal products you are taking, especially St. John’s wort.
  • tell your doctor if you have or have ever had seizures, a brain injury, a brain tumor, a brain arteriovenous malformation (an abnormal connection between arteries and veins in the brain that forms before birth and may cause bleeding in the brain), broken bones, osteoporosis (a condition in which the bones become thin and weak and break easily), diabetes, high cholesterol levels, high blood pressure, heart disease, or have had a stroke or ministroke.
  • you should know that enzalutamide is only for use in men. Women should not take this medication, especially if they are or may become pregnant or are breastfeeding. Women, especially those who are or who may become pregnant should not touch enzalutamide capsules. If taken by pregnant women, enzalutamide may harm the fetus. If a pregnant woman takes enzalutamide, she should call her doctor immediately.
  • you should know that this medication may decrease fertility in men. However, you should not assume that your female partner cannot become pregnant. If your partner is pregnant, you must use a condom whenever you have sex during your treatment with enzalutamide and for 3 months after your final dose. If your partner is not pregnant but could become pregnant, you must use effective birth control whenever you have sex during your treatment and for 3 months after your final dose.
  • if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking enzalutamide.
  • you should know that enzalutamide may cause seizures. Do not drive a car or operate machinery until you know how this medication affects you.

References

  1. https://www.accessdata.fda.gov/drugsatfda_docs/label/2012/203415lbl.pdf
  2. https://clinicaltrials.gov/ct2/show/NCT03927391
  3. https://pubchem.ncbi.nlm.nih.gov/compound/Enzalutamide
  4. https://pubchem.ncbi.nlm.nih.gov/compound/Enzalutamide-D3
  5. https://medlineplus.gov/druginfo/meds/a612033.html
  6. https://en.wikipedia.org/wiki/Enzalutamide
  7. https://go.drugbank.com/drugs/DB08899
  8. https://www.drugs.com/enzalutamide.html
  9. https://www.mayoclinic.org/drugs-supplements/enzalutamide-oral-route/side-effects/drg-20075790?p=1
  10. https://www.webmd.com/drugs/2/drug-162321/enzalutamide-oral/details/list-contraindications
  11. Guide to Pharmacology Target Classification
  12. ChemIDplus Chemical Information Classification
  13. CompTox Chemicals Dashboard Chemical Lists
  14. NCI Thesaurus Tree
  15. NORMAN Suspect List Exchange Classification
  16. PubChem
  17. Therapeutic category of drugs in Japan
    Anatomical Therapeutic Chemical (ATC) classification
    Target-based classification of drugs
  18. NCBI

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