Efficacy of venetoclax monotherapy in patients with relapsed chronic lymphocytic leukaemia in the post-BCR inhibitor setting: a UK wide analysis.

Venetoclax is a BCL2 inhibitor with activity in relapsed/refractory (R/R) chronic lymphocytic leukaemia (CLL). We conducted a multi-centre retrospective analysis of 105 R/R CLL patients who received venetoclax pre-National Health Service commissioning. The median age was 67 years and median prior lines was 3 (range: 1-15). 48% had TP53 disruption. At ≥2 lines, 60% received a Bruton Tyrosine Kinase inhibitor (BTKi) and no prior phosphoinositide 3-kinase inhibitor (Pi3Ki), 25% received a Pi3Ki and no prior BTKi, and 10% received both. Patients discontinued B cell receptor inhibitor (BCRi) because of toxicity in 44% and progression in 54%. Tumour lysis syndrome risk was low, intermediate or high in 27%, 25%, and 48% respectively. Overall response was 88% (30% complete response [CR]). The overall response rate was 85% (CR 23%) in BTKi-exposed patients, 92% (CR 38%) in Pi3Ki-exposed patients and 80% (CR 20%) in both (P = 0·59). With a median follow-up of 15·6 months, 1-year progression-free survival was 65·0% and 1-year overall survival was 75·1%. Dose reduction or temporary interruption did not result in an inferior progression-free or discontinuation-free survival. Risk of progression or death after stopping a prior BCRi for progression was double compared to those stopping for other reasons (predominantly toxicity) (Hazard Ratio 2·01 P = 0·05). Venetoclax is active and well tolerated in R/R CLL post ≥1 BCRi. Reason(s) for stopping BCRi influences venetoclax outcomes.

Ibrutinib induces chromatin reorganisation of chronic lymphocytic leukaemia cells.

Chronic lymphocytic leukaemia (CLL) is the most common leukaemia in Western countries. It has recently been shown that the homogeneity of the chromatin landscape between CLL cells contrasts with the important observed genetic heterogeneity of the disease. To gain further insight into the consequences of disease evolution on the epigenome's plasticity, we monitored changes in chromatin structure occurring in vivo in CLL cells from patients receiving continuous Ibrutinib treatment. Ibrutinib, an oral inhibitor of the Bruton's tyrosine kinase (BTK) has proved to be remarkably efficient against treatment naïve (TN), heavily pre-treated and high-risk chronic lymphocytic leukaemia (CLL), with limited adverse events. We established that the chromatin landscape is significantly and globally affected in response to Ibrutinib. However, we observed that prior to treatment, CLL cells show qualitative and quantitative variations in chromatin structure correlated with both EZH2 protein level and cellular response to external stimuli. Then, under prolonged exposure to Ibrutinib, a loss of the two marks associated with lysine 27 (acetylation and trimethylation) was observed. Altogether, these data indicate that the epigenome of CLL cells from the peripheral blood change dynamically in response to stimuli and suggest that these cells might adapt to the Ibrutinib "hit" in a process leading toward a possible reduced sensitivity to treatment.