Kileza (Fulvestrant)

Kileza (fulvestrant) is used in the management of hormone‑driven breast cancer pathways.

• Estrogen receptor‑positive metastatic breast cancer: provides tumor growth inhibition after progression on prior endocrine therapy.
• Hormone receptor‑positive advanced breast cancer: offers an alternative SERD option for patients with disease progression.
• Postmenopausal women with ER‑positive disease: delivers targeted estrogen receptor degradation to control tumor spread.

• Fulvestrant binds competitively to the estrogen receptor (ER) with high affinity, inducing a conformational change that targets the receptor for proteasomal degradation. By reducing cellular ER levels, it blocks estrogen‑mediated transcriptional activity, thereby inhibiting proliferation of ER‑dependent tumor cells.

Common Side Effects

• Injection site pain: mild to moderate discomfort at the intramuscular injection site.
• Hot flashes: transient episodes of warmth and sweating.
• Nausea: occasional upset stomach or vomiting.
• Fatigue: feeling of tiredness or reduced energy.
• Arthralgia: joint pain or stiffness.
• Headache: mild to moderate head discomfort.

Serious or Rare Side Effects

• Hepatic toxicity: elevated liver enzymes or hepatitis.
• Pulmonary embolism: sudden shortness of breath, chest pain, or coughing up blood.
• Severe allergic reaction: rash, swelling, or anaphylaxis requiring immediate medical attention.
• Tumor progression: rapid disease worsening despite therapy.
• Hyperglycemia: significant rise in blood glucose levels.

Before initiating therapy, clinicians should assess patient-specific risk factors and monitor relevant parameters.

• Liver function monitoring: check ALT/AST levels regularly.
• Thromboembolic risk assessment: evaluate history of clotting disorders.
• Hypersensitivity evaluation: screen for prior allergic reactions to fulvestrant or excipients.
• Osteoporosis caution: use with care in patients with severe bone loss.
• Pregnancy and lactation: avoid use; safety unknown in pregnant or breastfeeding women.
• Store at 2-8°C: keep refrigerated, protect from light, do not freeze or shake.

Fulvestrant may interact with other medicines that affect its metabolism or therapeutic effect.

Major Interactions (Avoid)

• Strong CYP3A4 inducers (e.g., rifampin, carbamazepine): may markedly reduce fulvestrant exposure.
• Concurrent estrogen therapy: can antagonize fulvestrant’s anti‑estrogen activity.
• Co‑administration with other SERDs: may lead to overlapping toxicity.

Moderate Interactions (Monitor Closely)

• CYP3A4 inhibitors (e.g., ketoconazole, itraconazole): may increase fulvestrant plasma levels.
• Anticoagulants (e.g., warfarin): may alter INR and bleeding risk.
• Herbal supplements such as St. John’s wort: could affect drug metabolism and efficacy.