UPDATE 1-FDA panel to focus on safety of Novartis gene therapy drug

(Updates with details of FDA report)

July 10 (Reuters) - The U.S. Food and Drug Administration will ask a panel of advisors to focus on the safety of Novartis AG's experimental gene therapy drug when it meets to review the product on Wednesday.

The keenly anticipated preliminary review of the leukemia treatment, posted on the FDA's website on Monday, comes two days ahead of the advisory panel meeting, which will discuss the drug and vote on whether the benefits exceed the risks.

If approved, the drug would be first gene therapy to be approved in the United States. The FDA is not obliged to follow the recommendations of its advisors but typically does so. The panel's decision could have significant implications not only for Novartis but for companies making similar drugs, including Kite Pharma Inc. Juno Therapeutics Inc and bluebird bio Inc.

All four are developing drugs based on a new technology known as CAR-T, or chimeric antigen receptor T-cell therapy, which harnesses the body's own immune cells to recognize and attack malignant cells.

Novartis is applying for approval in the first instance to treat B-cell acute lymphoblastic leukemia (ALL), the most common type of childhood cancer in the United States.

A clinical trial showed that 83 percent of patients who had relapsed or failed chemotherapy achieved complete or partial remission three months post infusion. Patients with ALL who fail chemotherapy typically have only a 16 to 30 percent chance of survival.

The FDA said it is not asking the panel to focus on whether the drug works, as it successfully met the main goal of the clinical trial. The panel will be asked only to focus on the short-term and long-term safety risks.

About half the patients experienced a serious complication known as cytokine release syndrome (CRS) which occurs when the body's immune system goes into overdrive. Doctors were able to manage the condition and it caused no patient deaths.

The FDA also raised concerns that the drug may cause secondary malignancies to occur and said long-term safety monitoring may be needed to address this concern.

(Reporting by Toni Clarke in Washington; Editing by Nick Zieminski)