Zydelig (idelalisib)  is an approved treatment for three types of blood cancerchronic lymphocytic leukemia (CLL), follicular B-cell non-Hodgkin lymphoma (FL), and small lymphocytic lymphoma (SLL) — in people whose cancer has returned (relapsed) despite prior treatment. It was developed by Gilead Sciences.

In case of CLL, Zydelig is approved to be used together with Rituxan (rituximab) in patients who have relapsed.

Zydelig was granted accelerated approval to treat patients with FL and SLL whose cancer has relapsed or failed to respond to at least two other treatments. Continuation of this approval depends on its clinical benefits being validated in confirmatory trials.

How Zydelig works

Zydelig is an inhibitor of phosphoinositide 3-kinase (PI3K) delta, an enzyme that plays a role in the activation, proliferation, and survival of a type of immune cell known as B-cells.

PI3K delta is hyperactivated, or found in excessive levels, in many B-cell malignancies (leukemias and lymphomas), where it works on cellular pathways to promote B-cell proliferation and  survival.

By inhibiting PI3K delta, Zydelig aims to prevent the growth, proliferation, survival, and spread of cancerous B-cells in the body.

Zydelig in clinical trials

Zydelig was approved to treat CLL in combination with Rituxan based on the results of a Phase 3, randomized, multicenter, and placebo-controlled clinical trial (NCT01539512) that evaluated its safety and efficacy in 220 people with advanced CLL. Patients were randomly assigned to receive either Zydelig (150 mg twice daily) plus Rituxan, or placebo plus Rituxan. Data showed that Zydelig-treated patients lived for at least another 10.7 months without their cancer getting worse (progression-free survival), compared to about 5.5 months for those given placebo.

As an FL and SLL treatment, Zydelig’s accelerated approval was based on the results from a Phase 2 open-label, multicenter, and single-arm clinical trial (NCT01282424) that assessed its safety and efficacy in 123 patients with relapsed FL and SLL, who have had at least two prior treatments. Results showed that 54 percent of FL patients and 58 percent of SLL patients responded completely or partly to treatment, with no or little advance in their cancer  (objective response rate or ORR). The median duration of response was 12.5 months, and progression-free survival was a median of 11 months.

Ongoing trials

Zydelig is currently under study as a monotherapy or in combination with other treatment  in trials of FL patients (NCT02536300), FL and mantle cell lymphoma patients (NCT02603445), people with CLL or other B-cell non-Hodgkin lymphomas (NCT02332980), and CLL and SLL patients (NCT02639910). These trials are enrolling patients; information is available by clicking on their respective identification numbers.

Planned trials

Several trials, not yet open for recruitment, are being readied to study Zydelig. One such trial (NCT03133221) aims to test Zydelig in B-cell non-Hodgkin’s lymphoma as a maintenance therapy following a stem cell transplant. Another trial (NCT03349346will evaluate Zydelig in combination with four chemotherapy drugs in people with diffuse large B-cell lymphoma (DLBCL) or mediastinal B-cell lymphoma (MLBCL). Information is available by clicking on their respective identification numbers.

Other information

Zydelig can cause serious side effects, including liver toxicity, diarrhea, colon inflammation, lung inflammation, and intestinal perforation. Regular medical checkups are needed when using this medication. Common side effects include diarrhea, fever, fatigue, nausea, cough, pneumonia, abdominal pain, chills, and rash.


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