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FDA Approves Zydelig (Idelalisib) for Three Types of Blood Cancer

Phosphoinositide kinase inhibitor treats leukemia and lymphoma

The FDA has given the nod to Zydelig (idelalisib, Gilead Sciences) for the treatment of patients with three types of blood cancer.

The drug was granted traditional approval to treat patients whose chronic lymphocytic leukemia (CLL) has relapsed. Used in combination with rituximab (Rituxan, Genentech), idelalisib is to be used in patients for whom rituximab alone would not be considered appropriate therapy because of co-morbidities. Idelalisib is the fifth new drug with a “breakthrough therapy” designation to be approved by the FDA and the third drug with this designation approved to treat CLL.

The FDA has also granted accelerated approval to idelalisib for the treatment of patients with relapsed follicular B-cell non-Hodgkin lymphoma (FL) or relapsed small lymphocytic lymphoma (SLL), another type of non-Hodgkin lymphoma. Idelalisib is intended to be used in patients who have received at least two prior systemic therapies.

The FDA approved obinutuzumab (Gazyva, Genentech) in November 2013; ibrutinib (Imbruvica, Pharmacyclics) in February 2014; and a new use for ofatumumab (Arzerra, GlaxoSmithKline) in April 2014 to treat CLL. Both obinutuzumab and ofatumumab also received a “breakthrough therapy” designation for this indication. Like these two drugs, idelalisib was granted “orphan drug” status because it is intended to treat a rare disease.

The safety and effectiveness of idelalisib in treating relapsed CLL were established in a clinical trial involving 220 subjects who were randomly assigned to receive idelalisib and rituximab or placebo and rituximab. The trial was stopped for efficacy after the first pre-specified interim analysis point, which showed that subjects treated with idelalisib and rituximab had the possibility of living at least 10.7 months without disease progression (i.e., progression-free survival) compared with approximately 5.5 months for subjects treated with placebo and rituximab. Results from a second interim analysis continued to show a statistically significant improvement for idelalisib and rituximab compared with placebo and rituximab.

The safety and effectiveness of idelalisib for the treatment of relapsed FL and relapsed SLL were established in a clinical trial involving 123 subjects with indolent non-Hodgkin lymphomas. All of the subjects were treated with idelalisib and were evaluated for the complete or partial disappearance of their cancer after treatment (i.e., the objective response rate [ORR]). The results showed that 54% of the subjects with relapsed FL and 58% of those with SLL experienced ORR.

The labeling for idelalisib includes a boxed warning alerting patients and health care professionals about the potential for fatal and serious toxicities, including liver toxicity, diarrhea, colitis, pneumonitis, and intestinal perforation.

Common side effects of treatment with idelalisib include diarrhea, pyrexia, fatigue, nausea, cough, pneumonia, abdominal pain, chills, and rash. Common laboratory abnormalities include neutropenia, hypertriglyceridemia, hyperglycemia, and elevated liver enzyme levels.

Idelalisib is an oral inhibitor of phosphoinositide 3-kinase (PI3K) delta, a protein that plays a role in the activation, proliferation, and viability of B cells — a critical component of the immune system. PI3K delta signaling is active in many B-cell leukemias and lymphomas, and by inhibiting the PI3K delta protein, idelalisib blocks several cellular signaling pathways that drive B-cell viability.

Sources: FDA; July 23, 2014; and Gilead Sciences; July 23, 2014.

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