Idelalisib

ZYDELIG

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Pronunciation: eye-del-a-LIS-ib (zye-DEL-ig)

Idelalisib ballicule: receptor binding, kinetics and half-life diagram — Mechanism of action: Idelalisib ballicule

What it isPI3K-delta inhibitor; relapsed CLL with rituximab. The follicular lymphoma and SLL approvals were withdrawn in 2022.

Why this oneTargets a signaling node specific to B cells.

What limits itSevere autoimmune toxicity — colitis, pneumonitis, hepatitis — which limited its use. A strong CYP3A4 inhibitor.

Idelalisib molecular structure (skeletal formula) — Molecular structure: Idelalisib

Idelalisib prescription history

Animated chart of estimated U.S. prescriptions per year, Oral anticancer meds (1953–2026). Idelalisib enters in 2014 (estimated).

FDA-approved for

relapsed CLL, with rituximab (2014)
relapsed follicular lymphoma and SLL (US approval withdrawn 2022) (2014)

Classes and tags

Clinical profile

Therapeutic safety burden3 / 4

Overdose danger2 / 4

Weight-gain liability0 / 4

Sedation liability0 / 4

QT / Torsades0 / 4

Direct muscarinic antagonism0 / 4

Embryofetal risk3 / 4

Legacy pregnancy categoryD

Defining liabilityMyelosuppression and agent-specific hepatic, cardiac, pulmonary, neurologic or reproductive toxicity require oncology monitoring.

FDA label

Read the full label on DailyMed ↗

BOXED WARNING Fatal/serious hepatotoxicity, severe diarrhea/colitis, pneumonitis, infections, and intestinal perforation.

FDA dosing	Population	Start	Target	Max
Relapsed CLL (with rituximab), when rituximab alone would be appropriate due to other co-morbidities	Adults	150 mg BID	150 mg BID	150 mg BID (reduce to 100 mg BID for toxicity)

Renal Undefined

Hepatic No adjustment for ALT/AST/bilirubin > ULN; limited data with baseline AST/ALT >2.5×ULN or bilirubin >1.5×ULN — monitor

Instructions

Swallow tablets whole; with or without food
If dose missed <6 h, take ASAP; if >6 h, skip that dose
Provide PJP prophylaxis; monitor for CMV
Reduce to 100 mg BID when resuming after interruption for toxicity

Available strengths

tab 100, 150 mg

Contraindications

History of toxic epidermal necrolysis with any drug

Cautions

Hepatotoxicity
Severe diarrhea/colitis
Pneumonitis
Serious infections (incl PJP, CMV)
Intestinal perforation
Severe cutaneous reactions (SJS/TEN/DRESS)
Serious hypersensitivity/anaphylaxis
Neutropenia
Embryo-fetal toxicity

Adverse reactions

Diarrhea
Pneumonia
Pyrexia
Fatigue
Rash
Cough
Nausea
Neutropenia and ALT/AST elevations

Pregnancy May cause fetal harm; use effective contraception during and 1 month after

Lactation Do not breastfeed during and for 1 month after last dose

Cost

Idelalisib (ZYDELIG)

Strength		#/mo	generic $/mo	CostPlus
100 mg	tab	60 BID		not offered
150 mg	tab	60 BID		not offered

NADAC is a voluntary CMS survey of what retail community pharmacies pay for the drugs they stock. Idelalisib is dispensed outside retail pharmacies, so it rarely appears on surveyed invoices.

Generic entry2026

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Self-check

Which PI3K isoform does idelalisib inhibit?
Delta.
How does idelalisib affect CYP3A4?
Strong inhibition.