FDA Approves PI3K Inhibitor, Idelalisib for Treatment of Relapsed CLL, Follicular Lymphoma and SLL

It is the fifth new drug with breakthrough therapy designation to be approved by the FDA

The USA Food and Drug Administration (FDA) announced on 23 July 2014 that has approved idelalisib (Zydelig), PI3K inhibitor, for treatment of patients with relapsed chronic lymphocytic leukemia (CLL), follicular lymphoma and small lymphocytic lymphoma (SLL).

Idelalisib is being granted approval for treatment of patients with relapsed CLL. Used in combination with rituximab (Rituxan), idelalisib is to be used in patients for whom rituximab alone would be considered appropriate therapy due to co-morbidities. Idelalisib is the fifth new drug with breakthrough therapy designation to be approved by the FDA and the third drug with this designation approved to treat CLL.

The FDA is also granting idelalisib accelerated approval to treat patients with relapsed follicular B-cell non-Hodgkin lymphoma and relapsed SLL, another type of non-Hodgkin lymphoma. Idelalisib is intended to be used in patients who have received at least two prior systemic therapies.

Other recently approved drugs by FDA for CLL

“In less than a year, we have seen considerable progress in the availability of treatments for chronic lymphocytic leukemia,” said Dr Richard Pazdur, who is director of the Office of Hematology and Oncology Products in the FDA’s Center for Drug Evaluation and Research. “Zydelig’s approval to treat CLL reflects the promise of the breakthrough therapy designation program and represents the FDA’s commitment to working cooperatively with companies to expedite a drug’s development, review and approval.”

The FDA approved obinutuzumab (Gazyva) in November 2013, ibrutinib (Imbruvica) in February 2014 and a new use for ofatumumab (Arzerra) in April 2014 to treat CLL. Both obinutuzumab and ofatumumab also received breakthrough therapy designation for this indication.

Like the other two drugs, idelalisib was also granted orphan product designation, because it is intended to treat a rare disease.

Approval based on trial results

Idelalisib’s safety and effectiveness to treat relapsed CLL were established in a clinical trial of 220 participants who were randomly assigned to receive idelalisib and rituximab or placebo and rituximab. The trial was stopped for efficacy following the first pre-specified interim analysis point, which showed in participants treated with idelalisib and rituximab longer progression-free survival, 10.7 months compared to 5.5 months in participants treated with placebo and rituximab. Results from a second interim analysis continued to show a statistically significant improvement for idelalisib and rituximab over placebo and rituximab.

Idelalisib’s safety and effectiveness to treat relapsed follicular lymphoma and relapsed SLL were established in a clinical trial with 123 participants with indolent non-Hodgkin lymphomas. All participants were treated with idelalisib and were evaluated for complete or partial response (objective response rate - ORR). Results showed 54% of participants with relapsed follicular lymphoma and 58% of participants with SLL experienced ORR.

The FDA is approving idelalisib to treat follicular lymphoma and SLL under the agency’s accelerated approval programme, which allows approval of a drug to treat a serious or life-threatening disease based on clinical data showing the drug has an effect on a surrogate endpoint reasonably likely to predict clinical benefit to patients. This programme provides earlier patient access to promising new drugs while the company conducts confirmatory clinical trials.

Safety

Idelalisib carries a Boxed Warning alerting patients and health care professionals of fatal and serious toxicities including liver toxicity, diarrhea and colitis, pneumonitis and intestinal perforation. Idelalisib is also being approved with a Risk Evaluation and Mitigation Strategy comprised of a communication plan to ensure healthcare providers who are likely to prescribe idelalisib are fully informed about these risks.

Common side effects include diarrhea, pyrexia, fatigue, nausea, cough, pneumonia, abdominal pain, chills and rash. Common laboratory abnormalities include neutropaenia, hypertriglyceridemia, hyperglycemia and elevated levels of liver enzymes.

Zydelig is marketed by Gilead Sciences. Rituxan and Gazyva are marketed by Genentech, a member of the Roche Group. Imbruvica is co-marketed by Pharmacyclics and Janssen Biotech, Inc. Arzerra is marketed by GlaxoSmithKline.