What is Zydelig used for and how does it work?

In the United States, Zydelig is approved to treat relapsed chronic lymphocytic leukemia (CLL) in combination with rituximab, where rituximab is appropriate to use taking into account other health conditions a person may have.

In other countries, such as the European Union, United Kingdom, Canada, Australia, New Zealand, and Switzerland, Zydelig is also approved to treat relapsed follicular B-cell non-Hodgkin lymphoma (FL). Zydelig initially also received accelerated approval to treat FL and relapsed small lymphocytic lymphoma (SLL) in the U.S. in 2014 but this approval was contingent upon further research which has been unable to be undertaken and so approval for these two indications (FL and SLL) in the U.S. was voluntarily withdrawn by the company, Gilead Sciences, Inc., in 2022.

Zydelig cannot be used for first-line treatment of any patient with cancer, including CLL, SLL, FL, or indolent non-Hodgkin lymphomas; it is only approved for relapsed CLL in the United States. It should also not be used if bendamustine is being given with rituximab.

How does Zydelig work?

Zydelig works by blocking the effects of an enzyme called PI3K-delta which enables the growth, migration, and survival of white blood cells but is overactive in blood cancers. By blocking the effects of this enzyme, Zydelig causes the cancer cells to die which delays or stops the progression of the cancer.