Surprising finding in upfront use of idelalisib monotherapy

They found that grade 3 or higher transaminitis (52%) and any grade pneumonitis (13%) were higher in their trial than in the 3 other trials.

Colitis/diarrhea was about the same in 2 of the 3 other trials. But in the paper by O’Brien et al, 42% of patients experienced grade 3 or greater colitis/diarrhea.

The lower rate of colitis in the present trial may be due to the shorter follow-up, Dr Lampson said, as colitis is a late adverse event.

The O’Brien trial was also an upfront study, so patients had no prior therapies. The investigators observed that toxicities appeared to be more common in less heavily pretreated patients.

“As the median number of prior therapies decreases,” Dr Lampson said, “the frequency of adverse events increases.”

He noted that, in the O’Brien trial, idelalisib was started simultaneously with the other drugs, perhaps accounting for its somewhat lower rate (21%) of grade 3 or higher transaminitis.

Additionally, the patient population in the O’Brien trial was older than the population in the current trial, which could account for the higher rate of transaminitis, as younger age is a risk factor.

Decrease in regulatory T cells

Investigators noted a decrease in regulatory T cells while patients were on therapy. Eleven of 15 patients (73%) with matched samples had a significant (P<0.05) decrease in the percentage of T cells over time.

This, they say, could provide a possible explanation for the development of early hepatotoxicity.

The trial is investigator-initiated and funded by Gilead Sciences.

*Data in the presentation differs from the abstract.