CLINICAL TRIALS PROFILE FOR IDELALISIB

All Clinical Trials for Idelalisib

Trial ID	Title	Status	Sponsor	Phase	Start Date	Summary
NCT00836914 ↗	Study to Investigate Effects of CAL-101 in Subjects With Allergic Rhinitis Exposed to Allergen in an Environmental Chamber	Completed	Gilead Sciences	Phase 1	2009-02-01	The purpose of this study is to determine the safety and effect of CAL-101 in subjects with allergic rhinitis.
NCT01088048 ↗	Study to Investigate Idelalisib in Combination With Chemotherapeutic Agents, Immunomodulatory Agents and Anti-CD20 Monoclonal Antibody (mAb) in Participants With Relapsed or Refractory Indolent B-cell Non-Hodgkin's Lymphoma, Mantle Cell Lymphoma or	Completed	Gilead Sciences	Phase 1	2010-03-25	The primary objective of the study is to evaluate the safety of idelalisib in combination with an anti-CD20 monoclonal antibody (mAb), a chemotherapeutic agent, a mammalian target of rapamycin (mTOR) inhibitor, a protease inhibitor, an antiangiogenic agent, and/or an immunomodulatory agent in participants with relapsed or refractory indolent B-cell non-Hodgkin lymphoma (NHL), mantle cell lymphoma (MCL), or chronic lymphocytic leukemia (CLL).
NCT01090414 ↗	An Extension Study for Subjects Who Are Deriving Benefit With Idelalisib (GS-1101; CAL-101) Following Completion of a Prior Idelalisib Study	Terminated	Gilead Sciences	Phase 1/Phase 2	2010-03-22	This is a long-term safety extension study of idelalisib (GS-1101; CAL-101) in patients with hematologic malignancies who complete other idelalisib studies. It provides the opportunity for patients to continue treatment as long as the patient is deriving clinical benefit. Patients will be followed according to the standard of care as appropriate for their type of cancer. The dose of idelalisib will generally be the same as the dose that was administered at the end of the prior study, but may be titrated up to improve clinical response or down for toxicity. Patients will be withdrawn from the study if they develop progressive disease, unacceptable toxicity related to idelalisib, or if they no longer derive clinical benefit in the opinion of the investigator.
NCT01203930 ↗	A Study of Idelalisib and Rituximab in Elderly Patients With Untreated CLL or SLL	Terminated	Gilead Sciences	Phase 2	2010-10-01	This study is to evaluate the safety and clinical activity of idelalisib alone and in combination with rituximab in patients with CLL or SLL. This Phase 2 study will be the first time that idelalisib is administered to previously untreated patients with hematologic malignancies. Idelalisib has demonstrated clinical activity as a single agent in relapsed or refractory CLL and SLL with acceptable toxicity, which supports its evaluation in previously untreated patients. The study population is limited to patients over 65 years of age because younger patients are generally appropriate for standard immunochemotherapy regimens that are highly active. Since the mechanism of action of idelalisib is distinct from rituximab, it is hypothesized that the combination will be more active than either agent alone. This study will establish initial safety and clinical activity of idelalisib in combination with rituximab in patients with CLL or SLL. Cohort 2 of this study will establish safety and clinical activity of idelalisib alone in subjects with untreated CLL or SLL.
NCT01282424 ↗	Efficacy and Safety Study of Idelalisib in Participants With Indolent B-Cell Non-Hodgkin Lymphomas	Completed	Gilead Sciences	Phase 2	2011-03-18	The primary objective will be to assess the overall response rate and to evaluate the efficacy and safety of idelalisib (IDELA; GS-1101) in participants with previously treated indolent Non-Hodgkin Lymphoma (iNHL) that is refractory both to rituximab and to alkylating-agent-containing chemotherapy. Eligible participants will initiate oral therapy with idelalisib at a starting dose of 150 mg taken twice per day. Treatment with idelalisib can continue in compliant participants as long as the study is still ongoing and the participants appear to be benefiting from treatment with acceptable safety.
NCT01306643 ↗	Safety and Efficacy Study of Idelalisib (GS-1101, CAL-101) in Patients With Previously Treated Low-grade Lymphoma	Completed	Gilead Sciences	Phase 1/Phase 2	2011-02-01	The primary objectives of this study is to evaluate the safety and efficacy of idelalisib (GS-1101, CAL-101) in participants with previously treated indolent non-Hodgkin lymphoma (iNHL). Eligible patients will initiate oral therapy with idelalisib at a starting dose of 150 mg twice per day. Treatment with idelalisib can continue in compliant participants for up to twelve 28-day cycles of idelalisib. Participants who appear to be benefiting from treatment at the completion of 12 cycles of treatment with idelalisib may be eligible for participation in a long-term safety extension study of idelalisib.
NCT01393106 ↗	Safety and Efficacy of Idelalisib in Relapsed or Refractory Hodgkin Lymphoma	Completed	Gilead Sciences	Phase 2	2011-09-01	This study will evaluate the efficacy and safety of idelalisib in participants with relapsed of refractory Hodgkin Lymphoma (HL). The primary objective will be to assess the overall response rate. Eligible participants will initiate oral therapy with idelalisib at a starting dose of 150 mg twice daily. Treatment with idelalisib will continue until tumor progression or unacceptable toxicity.

Clinical Trial Conditions for Idelalisib

Condition Name

Condition Name for Idelalisib
Intervention	Trials
Chronic Lymphocytic Leukemia	22
Small Lymphocytic Lymphoma	10
Follicular Lymphoma	9
Marginal Zone Lymphoma	4

Condition MeSH

Condition MeSH for Idelalisib
Intervention	Trials
Leukemia, Lymphocytic, Chronic, B-Cell	38
Leukemia, Lymphoid	33
Leukemia	30
Lymphoma	29

Clinical Trial Locations for Idelalisib

Trials by Country

Trials by Country for Idelalisib
Location	Trials
United States	381
Australia	45
France	44
Japan	36
United Kingdom	35

Trials by US State

Trials by US State for Idelalisib
Location	Trials
New York	30
California	28
Texas	23
Ohio	19
Washington	19

Clinical Trial Progress for Idelalisib

Clinical Trial Phase

Clinical Trial Phase for Idelalisib
Clinical Trial Phase	Trials
PHASE4	1
PHASE3	3
Phase 4	1

Clinical Trial Status

Clinical Trial Status for Idelalisib
Clinical Trial Phase	Trials
Terminated	21
Completed	15
Active, not recruiting	14

Clinical Trial Sponsors for Idelalisib

Sponsor Name

Sponsor Name for Idelalisib
Sponsor	Trials
Gilead Sciences	39
National Cancer Institute (NCI)	7
OHSU Knight Cancer Institute	3

Sponsor Type

Sponsor Type for Idelalisib
Sponsor	Trials
Industry	60
Other	36
NIH	7

Idelalisib (Zydelig): Clinical Trials Update, Market Analysis, and Projection

Last updated: April 26, 2026

What is idelalisib and where is it positioned?

Idelalisib is an oral, small-molecule inhibitor of PI3K-delta (PI3Kδ). It was developed for B-cell malignancies and indolent lymphomas, with initial approvals focused on chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL) and follicular lymphoma (FL).

Current label footprint (US)

• Zydelig (idelalisib) has an FDA history that includes accelerated and subsequent label narrowing tied to safety findings (notably hepatotoxicity, pneumonitis, and infections).
• Use restrictions have limited patient eligibility and sequencing across indications over time. (FDA label history and safety communications.) [1]

What does the clinical trials pipeline look like right now?

A full, current “active trial” snapshot requires live registry querying. Under the constraint to avoid incomplete or speculative listings, the actionable update is limited to what is determinable from stable, citable sources: idelalisib’s clinical development has moved from broad first-line ambition to constrained use, with most incremental work shifting to PI3Kδ-class competitors and combination strategies. The practical read for R&D and investment is that idelalisib is not a growth driver for new indications; it is a legacy asset with diminishing trial activity relative to newer PI3Kδ inhibitors and alternate targeted pathways.

Clinical reality: trial activity has concentrated into safety and sequencing-era evidence

Across the PI3Kδ class, the industry shift is visible in:

• Post-marketing safety-driven label constraints for idelalisib.
• Higher preference for agents with improved therapeutic index or dosing regimens.

This is consistent with FDA communications regarding safety risks for idelalisib and the label restrictions that followed. [1]

What are the key safety and benefit-risk factors shaping commercialization?

Idelalisib’s market trajectory is tightly linked to safety risk management and prescribing restrictions.

Core safety signals that drove label tightening

FDA safety-related content includes risks of:

• Hepatotoxicity
• Pneumonitis
• Severe infections
• Diarrhea/colitis and other immune-mediated adverse events
  These safety issues appear in FDA labeling and FDA communications that led to restricted use. [1]

Commercial consequence

• Prescribers manage risk through careful selection, monitoring, dose interruption, and combination sequencing where appropriate.
• Competitors with lower discontinuation rates or more favorable safety profiles have taken share, particularly in newer treatment lines.

Which markets matter and how does geography affect demand?

For a legacy oncology small molecule like idelalisib, geography drives demand through:

• Reimbursement intensity
• Local guideline adoption
• Formulary access after label restrictions
• Availability of alternatives in-line

Where idelalisib retains access, demand stays tied to:

• Patient segments still aligned with label criteria.
• Physician comfort with monitoring and combination therapy protocols.

Market analysis: supply-side competition and pricing pressure

Idelalisib faces sustained competitive pressure from:

• New PI3Kδ inhibitors with more favorable benefit-risk profiles.
• Alternative targeted therapies and chemoimmunotherapy regimens with better tolerability or deeper evidence in earlier lines.

Competitive set (business-relevant)

• PI3Kδ class competitors: agents with constrained toxicity profiles and updated guideline positioning.
• BTK inhibitors, BCL2 inhibitors, and CD20-based regimens: these have absorbed many patient pathways in CLL/SLL and follicular lymphoma over time.

The net effect is that idelalisib demand typically moves from “broad use” to “narrower label-aligned cohorts.”

What do current fundamentals imply for revenue and utilization?

Under the constraints of avoiding unsupported numeric revenue forecasts, the projection focuses on utilization dynamics, not precise dollar values.

Utilization drivers

1. Label restrictions reduce eligible populations (safety-driven).
2. Oral oncology competition increases switch rates (better tolerance, guideline preference).
3. Long-term use trends depend on persistence: PI3Kδ adverse events affect discontinuation and treatment completion.

Utilization headwinds

• Ongoing substitution to newer targeted regimens reduces incident prescriptions for idelalisib.
• Remaining demand concentrates in smaller cohorts that can tolerate therapy and comply with monitoring.

Projection: scenario-based direction for 2025-2030

Because a numeric forecast would require live commercial datasets, the projection is directional and tied to structural drivers: label constraints, competitive substitution, and class evolution.

Base-case trajectory (directional)

• 2025-2026: Declining utilization as prescribers consolidate on newer options; idelalisib persists in limited, label-aligned use.
• 2027-2030: Further slow decline or plateau at a low level, driven by remaining guideline pathways and patient tolerance selectivity.

Upside scenario (directional)

• Stable or slower decline if:
  • Guideline or payer policies preserve access in specific subgroups.
  • Safety protocols improve real-world persistence. This is constrained by the safety legacy and expanding alternative options.

Downside scenario (directional)

• Faster erosion if:
  • Further payer restrictions tighten.
  • Competing PI3Kδ and non-PI3K pathways continue to expand in earlier lines.

Key implications for investors and R&D

If you are underwriting idelalisib as a commercial asset

• Model it as a declining, high-friction legacy product where margins depend on:
  • Contracted pricing and formulary access
  • Patient persistence after adverse-event management
  • Conversion away from PI3Kδ to other targeted regimens

If you are assessing idelalisib as a development reference

• The major value is platform learnings in PI3Kδ inhibition:
  • Benefit-risk management
  • Combination sequencing
  • Safety monitoring protocols that shape newer assets

Key Takeaways

• Idelalisib’s market position is constrained by FDA-driven safety risk management and label narrowing, shaping prescribing behavior and access. [1]
• Clinical development momentum has shifted toward the modern PI3Kδ competitive landscape and alternative targeted regimens, leaving idelalisib as a legacy, label-aligned therapy rather than a new-growth entrant.
• The 2025-2030 outlook is directional decline or plateau driven by competitive substitution, payer/formulary friction, and class evolution, with limited room for utilization growth under existing safety and eligibility constraints.

FAQs

1. Is idelalisib still approved for oncology indications in the US?
   Yes, but usage is constrained by label conditions and safety-driven restrictions reflecting risks such as hepatotoxicity and pneumonitis. [1]

2. What safety issues most affect idelalisib prescribing?
   Hepatotoxicity, pneumonitis, and severe infections are central to FDA safety communications and label restrictions. [1]

3. What is the primary commercialization headwind for idelalisib?
   Patient eligibility and persistence are limited by safety risk management and competition from newer targeted therapies with improved tolerability and broader guideline uptake.

4. Where does demand typically concentrate for a legacy PI3Kδ inhibitor?
   In smaller cohorts aligned to label criteria, where clinicians can implement monitoring and manage adverse events.

5. Does idelalisib represent a viable growth platform today?
   As a standalone product, idelalisib is mainly a legacy asset; class evolution and safety precedent have shifted growth to newer PI3Kδ and non-PI3K regimens.

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References

[1] U.S. Food and Drug Administration (FDA). Zydelig (idelalisib) prescribing information and safety communications. FDA label and drug safety-related content. (Accessed via FDA drug label resources).