Idelalisib: Oral PI3Kδ Inhibitor for Relapsed/Refractory Hematologic Malignancies

Overview​

Idelalisib is a highly selective oral PI3Kδ inhibitor that blocks the PI3K/Akt signaling pathway, inducing apoptosis in malignant B-cells. It is used for the treatment of relapsed/refractory hematologic malignancies, including chronic lymphocytic leukemia (CLL) with high-risk features such as 17p deletion, double-refractory follicular lymphoma (FL), and small lymphocytic lymphoma (SLL). The U.S. Food and Drug Administration (FDA) granted accelerated approval for idelalisib in lymphoma based on response rates; confirmatory trials are ongoing.

Indications​

• In combination with rituximab for relapsed CLL in patients for whom rituximab alone would be considered appropriate therapy due to comorbidities.

• For relapsed follicular B-cell non-Hodgkin lymphoma (FL) in patients who have received at least two prior systemic therapies.

• For relapsed small lymphocytic lymphoma (SLL) in patients who have received at least two prior systemic therapies.

Dosage and Administration​

The recommended adult dose is 150 mg taken orally twice daily, continued until disease progression or unacceptable toxicity. It may be taken with or without food. Tablets must be swallowed whole; do not crush, chew, or split.

Missed Dose: If a dose is missed by less than 6 hours, take it as soon as possible. If missed by more than 6 hours, skip the missed dose and resume the regular schedule. Do not double the dose.

Warnings and Precautions​

Idelalisib can cause severe, sometimes fatal hepatic, pulmonary, and intestinal toxicities. Contact your doctor immediately if you experience: upper abdominal pain, easy bruising/bleeding, dark urine, yellowing of skin/eyes, cough, wheezing, shortness of breath, fever, chills, worsening abdominal pain, or vomiting.

Life-threatening diarrhea may occur. If bowel movements increase by ≥6 per day above baseline, notify your healthcare provider right away. Idelalisib may also cause intestinal perforation. Seek immediate medical attention for watery/bloody stools, black tarry stools, or coughing up blood.

Before Taking Idelalisib​

• Do not use if you have had a severe skin allergic reaction to any drug.

• Inform your doctor if you have a history of liver disease, lung disease, or intestinal perforation.

• Reproductive safety: Idelalisib can harm a fetus. Female patients must avoid pregnancy during treatment and for at least 1 month after the last dose; male patients with partners of childbearing potential should use effective contraception during treatment and for at least 3 months after the last dose. Notify the doctor immediately if pregnancy occurs.

• Breastfeeding: Discontinue breastfeeding during treatment and for at least 1 month after the last dose.

• Pediatric use: Safety and efficacy in patients <18 years have not been established.

Adverse Reactions​

Emergency Allergic/Severe Skin Reactions: Signs of allergy (urticaria, difficulty breathing, swelling of face/throat) or severe cutaneous reactions (fever, sore throat, burning eyes, skin pain, red/purple rash with blistering/peeling) require immediate emergency care. Systemic drug reactions (rash, fever, lymphadenopathy, myalgia, severe fatigue, abnormal bleeding/bruising, jaundice) also warrant prompt evaluation.

Common Side Effects: Nausea, abdominal pain, diarrhea; fever, cough, pulmonary symptoms; decreased white blood cell count; elevated liver enzymes; rash; fatigue.

If severe adverse reactions occur (severe diarrhea, hepatotoxicity, pneumonitis, colitis, neutropenia), treatment may be interrupted or permanently discontinued.

Storage​

Store in original container at room temperature, away from moisture and heat.

Summary​

Idelalisib provides an important oral targeted option for patients with relapsed/refractory CLL, FL, and SLL. However, vigilant monitoring for hepatic, pulmonary, and gastrointestinal toxicities is essential. Use must be supervised by an experienced oncologist; patients should not adjust or stop treatment without medical advice.