# Idelalisib

Source: https://onco.cc/drugs/idelalisib/  
OnCo record `idelalisib` (Treatment). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Idelalisib was the first PI3K inhibitor for blood cancers; it is effective in CLL with rituximab but so toxic (colitis, hepatitis, pneumonitis, infections) that the class has largely been abandoned.

## Summary

Approved 2014 (CLL with rituximab; FL and SLL accelerated). Trials in earlier lines were halted in 2016 over fatal infections and toxicity; the FL/SLL indications were withdrawn in 2022. Remains an option in relapsed CLL after BTK and BCL2 inhibitors. Its history shaped FDA scepticism of PI3K inhibitors (2022 ODAC).

## Fields

- Kind: Treatment
- Status: approved
- Last checked: 2026-09-08
- Tags: gap-fill
- Brand: Zydelig
- Modality: Small-molecule PI3Kδ inhibitor
- Mechanism: Selective inhibition of the delta isoform of PI3K, blocking B-cell receptor-driven survival signalling in malignant B cells.
- Approvals: US 2014: Relapsed CLL with rituximab; relapsed FL and SLL (accelerated, withdrawn 2022); EU 2014: CLL, FL

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Idelalisib
- Label (DailyMed): https://dailymed.nlm.nih.gov/dailymed/search.cfm?labeltype=all&query=idelalisib

## Connected records

- cancers: [Chronic lymphocytic leukaemia](https://onco.cc/cancers/cll/), [Follicular lymphoma](https://onco.cc/cancers/follicular-lymphoma/), [Relapsed or refractory chronic lymphocytic leukaemia](https://onco.cc/cancers/cll-relapsed/)
- technologies: [Small-molecule kinase inhibitors](https://onco.cc/technologies/kinase-inhibitors/)
- targets: [PI3K delta (PIK3CD)](https://onco.cc/targets/pik3cd/), [PIK3CA / PI3K-alpha](https://onco.cc/targets/pik3ca/)
- companies: [Gilead Sciences (incl. Kite)](https://onco.cc/companies/gilead/)
- pathways: [PI3K / AKT / mTOR](https://onco.cc/pathways/pi3k-akt-mtor/)
- trials: [A Study of Acalabrutinib vs Investigator's Choice of Idelalisib Plus Rituximab or Bendamustine Plus Rituximab in R/R CLL](https://onco.cc/trials/nct02970318/), [A Study of Tacabrutideg (BGB-16673) Compared to Investigator's Choice in Participants With Chronic Lymphocytic Leukemia or Small Lymphocytic Lymphoma Previously Exposed to Both Bruton Tyrosine Kinase (BTK) and B-cell Leukemia/Lymphoma 2 Protein (BCL2) Inhibitors](https://onco.cc/trials/nct06846671/), [Study to Investigate Outcome of Individualized Treatment in Patients With Metastatic Colorectal Cancer](https://onco.cc/trials/nct05725200/)
- terms: [Indication withdrawal](https://onco.cc/terms/approval-withdrawal/), [Infection prophylaxis in lymphoma: PJP, herpes, fungal risk and vaccination](https://onco.cc/terms/lymphoma-tx-pjp-and-infection-prophylaxis/)

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