The new drug idelalisib appears to offer hope for fighting slow-growing , or indolent, non-Hodgkin lymphomas (iNHLs). These lymphomas are difficult to treat, with most patients relapsing repeatedly and the disease becoming increasingly resistant to therapy over time.

The phase 2 study involved 125 patients aged 33 to 87 years with indolent non-Hodgkin lymphoma (iNHL) who had not responded to conventional treatments or had relapsed within six 6 months of therapy. The patients, who were from the Seattle, Washington, area, as well as around the United States and Europe, were given a twice-daily dose of idelalisib, a highly selective oral drug that inhibits phosphoinositide 3-kinase (PI3K) delta. P13K deltas are a family of enzymes seen in many types of B-cell malignancies.

Following treatment with idelalisib, tumor size shrunk by at least half in 57% of the patients and 6% had no measurable evidence of cancer. The study was published in the New England Journal of Medicine (2014; doi:10.1056/NEJMoa1314583), and it is the first publication of clinical trial data on idelalisib, which is made by Gilead Sciences Inc., based in Foster City, California. The U.S. Food and Drug Administration (FDA) accepted the drug for review in early January and also gave it a Breakthrough Therapy designation for treatment of relapsed chronic lymphocytic leukemia (CLL) based on the results of another clinical trial.

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“These are patients who had exhausted current standard therapies,” said Ajay Gopal, MD, a member of Fred Hutchinson Cancer Research Center’s Clinical Research Division in Seattle, Washington, and the study’s lead and corresponding author. “In terms of effective therapy available, there really wasn’t much left.”

iNHLIndolent non-Hodgkin lymphomas comprise about one-third of all cases of NHLlymphoma. About 20,000 people in the United States were diagnosed with iNHL in 2012, and approximately 7,000 died of the disease. The standard treatment for iNHL is a combination of rituximab, a drug that targets the protein CD20 found on B cells, and chemotherapy.

While Although conventional treatment can be initially effective, iNHLs relapse over time and can lead to life-threatening complications such as infections and marrow failure. And, unlike the toxic effects of chemotherapy, the most common side effects among patients in the trial were diarrhea and colitis, which occurred in a minority of participants and could usually be managed with dosage adjustments.

Dr. Gopal, who helped write the protocol for the trial and treated many of the patients involved, said that while whereas it does not appear that the drug is curative, it holds tremendous promise for helping to control the disease for long periods of time.

“I think there’s going to be a lot of interest in it,” he said.

Dr. Gopal said explained that, depending on the FDA review, idelalisib could be approved for clinical use later this year. Such drugs, he saidnoted, represent a highly targeted and less harmful approach to treating cancer.
“Chemotherapy is a very blunt instrument,” he said. “This is much more specific.”