Gilead Stops Pivotal Trial Early as New Leukemia Drug Demonstrates Strong Efficacy

Gilead Sciences Inc. (GILD) said after Wednesday’s closing bell that it is stopping a phase 3 trial of its leukemia drug because an independent data monitoring committee deemed it clear that the drug is working effectively.  Shares of Gilead jumped 3 percent in extended trading following the news.

The trial, called Study 116, was evaluating idelalisib in previously-treated chronic lymphocytic leukemia (CLL) patients that are not eligible for chemotherapy.  The monitoring committee made its recommendation based upon a predefined protocol showing “highly statistically significant efficacy” for the primary endpoint of progression-free survival in patients receiving a cocktail of idelalisib and rituximab compared to rituximab by itself.

“Given the significant unmet medical need in CLL, particularly in this population of patients who are not fit for chemotherapy, we are pleased that idelalisib has shown a clinically meaningful benefit for patients,” said Dr. Norbert W. Bischofberger, Gilead’s Executive Vice President, Research and Development and Chief Scientific Officer. “This is the first Phase 3 study to report positive results for a new class of targeted therapies that inhibit B-cell receptor signaling as a major component of their mechanism of action, an important area of focus in the development of chemotherapy-free regimens in CLL and other B-cell malignancies.”

Rituximab (brand name Rituxan) was developed by IDEC Pharmaceuticals and become the first monoclonal antibody therapy for cancer with its FDA approval in 1997.  IDEC merged with Biogen, creating Biogen Idec Inc. (BIIB) in 2003.

On a similar note, idelalisib is part of a new class of oral drugs that selectively inhibit phosphoinositide 3-kinase (PI3K) delta, a protein known to promote tumor growth in specific blood cancers.  Gilead is developing the drug as a stand-alone therapy and in combination with other approved drugs.  Other late-stage trials are ongoing for patients with chronic lymphocytic leukemia and indolent non-Hodgkins lymphoma, or iNHL.

The 220-patient Study 116 trial treated patients with disease progression within two years of completing a different type of therapy.  Patients were split into two groups, receiving either infusions of rituximab and oral doses of idelalisib over 24 weeks or rituximab and a placebo at the same regimen.

Patients that demonstrated disease progression were eligible to move on to another Gilead clinical trial (Study 117) for addition idelalisib therapy.

Gilead said that it has informed the U.S. Food and Drug Administration of the plan to end the study and will contact the regulatory agency about requisite filings seeking to advance the drug towards commercialization.  In September, Gilead filed a New Drug Application with the FDA looking for approval of idelalisib for the treatment of iNHL.

Shares of GILD closed the regular session Wednesday at $58.90, down 0.8 percent on the day, but have reversed course in extended trading to $60.80.  So far in 2013, shares of Gilead have appreciated by about 60 percent.