Peter Hillmen, MBChb, PhD, FRCP, FRCPath from St. James’ University Hospital, Leeds, UK discusses the use of idelalisib and duvelisib in chronic lymphocytic leukemia (CLL) in light of the adverse events observed with idelalisib. He also talks about what this means for PI3 kinase inhibitors in general. The question according to Prof. Hillmen, is whether the adverse events observed with idelalisib are a drug effect or class of drug effect. With idelalisib there is data from the randomized trials and the ones that are ongoing. Prof. Hillmen mentions how the toxicity is immune toxicity, either immune suppression or autoimmunity, and that it is worse for patients earlier on in the disease. Furthermore, Prof. Hillmen also mentions how patients receiving frontline therapy with a more active immune system have a problem. With duvelisib, a PI3K-delta and gamma inhibitor, the same outcome may or may not be observed, but data is yet to be collected. He also notes that there are a few other similar drugs that may have similar, but lighter problems. Prof. Hillmen describes that there was an acceptance amongst hematologists when the news about idelalisib became known, that the drug had a level of toxicity, but that it could be dealt with. Prof. Hillmen finishes off by stating that in his view, there is a role for PI3 kinase inhibitors but its finding it that will be the challenge. Recorded at the European Hematology Association (EHA) 2016 Annual Congress in Copenhagen, Denmark.