Gilead scores early PhIII success for idelalisib in chronic lymphocytic leukemia

Norbert Bischofberger, the R&D chief at Gilead

Just weeks after sending in an application to the FDA seeking approval to start marketing its PI3k-delta inhibitor idelalisib for non-Hodgkin's lymphoma, Gilead ($GILD) says it has wrapped a Phase III study of the drug early because of the extremely promising progression-free survival data that had been gathered for previously treated chronic lymphocytic leukemia, one of the most common blood cancers.

Already looking at a likely near-term approval for the hepatitis C drug sofosbuvir, Gilead's success with this cancer drug--obtained from Calistoga in a $600 million deal--signaled another big step forward for a drug with blockbuster potential. Gilead, which built its reputation and revenue on HIV therapies, says it will start a conversation with the FDA now to map out plans for a regulatory submission on CLL.

Shares of Gilead are up about 6% Thursday.

"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 Norbert Bischofberger, the R&D chief at Gilead. "This is the first Phase III 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. We extend thanks to the investigative sites and to the other research collaborators participating in this study, as well as to the patients who volunteered, and we look forward to sharing these data with the hematology community."

The data from this PhIII will be presented at a future scientific conference. But Gilead has already unveiled some impressive Phase II results for indolent non-Hodgkin's lymphoma. Back in June the biotech reported interim results reflecting a 53.6% response rate among patients, with a median duration close to a full year. The PFS rate was 11.4 months with lymph nodes shrinking in 89% of patients.

Gilead's drug is designed to block overactive PI3K (phosphoinositide 3-kinase) delta signaling, inhibiting a major driver of cancer growth in B-cell leukemias and lymphomas. Gilead faces major league competition in CLL. Johnson & Johnson's ($JNJ) ibrutinib--partnered with Pharmacyclics ($PCYC)--and GA101 at Roche ($RHHBY) are both targeted at the blood cancer, with "breakthrough therapy" designations from the FDA. Infinity's IPI-145, ($INFI) a PI3K delta and gamma inhibitor, has also been mentioned alongside idelalisib, though it recently came under a shadow on safety concerns. 

"This was a modest upside surprise to us in both timing and result, and positions idelalisib to compete directly in CLL against JNJ/PCYC's ibrutinib as soon as ~6 months after ibrutinib's CLL approval," notes ISI's Mark Schoenebaum. "Note that JNJ/PCYC filed in the US in July 2013 for (what we believe is) ibrutinib monotherapy in relapsed/refractory del17p CLL patients, so the majority of direct competition may be off-label and dependent on use directed by NCCN guidelines."

- here's the press release

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