Outcome of Patients Receiving Venetoclax for Chronic Lymphocytic Leukemia (CLL) in Real-Life Clinical Practice: Results of the French ATU Program on Behalf of the Filo Group

Introduction.The BCL-2 inhibitor venetoclax has demonstrated high efficiency in relapsed/refractory (R/R) CLL patients with an overall response rate (ORR) of 79%, regardless of the TP53gene status. Venetoclax has then been EMEA-approved for CLL patients with TP53disruption who are unsuitable for or have failed a BCR inhibitor (BCRi) and those without TP53 inactivation who have failed both immunochemotherapy and a BCRi. Whether this agent provides a well-balanced safety/efficacy profile and a prolonged survival in real-world practice remains to be investigated.

Methods. An early access program (ATU) of venetoclax was available in France between July 22^thand December 4^th, 2016 for R/R CLL patients as per EMEA label. We retrospectively analyzed the outcome of patients included in this program who had received at least one day of venetoclax. Data quality was ensured using on-site data verification and computerized discrepancy errors.

Results. Data concerning both clinical features andoutcome were available for 72 of the 93 patients for whom venetoclax was requested in this program. Among them, only 63 patients received at least one day of venetoclax for progressive CLL or Richter syndrome (RS) and were included in the present analysis. Median age was 69 years (range, 25-89) and sex ratioM/F was 47/16. A total of 56 patients received venetoclax for CLL and 7 for RS. Patients had previously received a median of 4 prior therapeutic lines (range, 0-7) including FCR in 43 (68%) of them, BTK inhibitor (BTKi) in 46 (73%) and PI3Kδ inhibitor (PI3Kδi) in 21 (33%); 5 had prior autologous stem cell transplantation (SCT) and 4 allogeneic SCT. At time of treatment with venetoclax, 32 (76%) patients carried TP53disruption (data available for 42 patients) and 19 (61%) had complex karyotype (CK) defined as ≥ 3 abnormalities (data available for 31 patients). IGHV mutational status was available for 26 patients. Treatment was administered as per label recommandations with a 5-week ramp up phase until the target dosage of 400 mg per day.

Median follow-up was 17 months. Median time on therapy was 11.9 months (range, 0.1-24.6). Among adverse events of interest, tumor lysis syndrome (TLS) was observed in 19% of case, most of them being biological TLS and 3% were clinical TLS, and 15 (24%) patients developed infections requiring hospitalization. Autoimmune cytopenia was seen in 9.5% of patients. Four (7%) patients developed RS while on venetoclax for progressive CLL. To date, a total of 30% of patients remains on therapy. Three patients proceeded to allo-SCT after venetoclax therapy.

Among the 7 patients who received venetoclax for RS, 2 had an objective response that lasted 7 and 14 months. However, median overall survival (OS) was only 1.1 months (95% CI, 0.7-1.5).

Regarding the CLL cohort, ORR was 73%. It did not significantly differ according to the TP53status (90% with TP53disruption vs 69%, P= 0.189). Conversely, CK was associated with a lower ORR (92% vs 56%, P= 0.024). No impact of the type of prior BCRi (BTKi vs PI3Kδ inhibitor) was noted. 2-year progression-free survival (PFS) was 62% without significant impact of the TP53status (59% in case of TP53disruption vs 68% if wt-TP53,P= 0.587). Patients with CK had 2-year PFS of 44% compared to 78% for those without CK (P= 0.182). 2-year overall survival (OS) was 65% for the whole cohort and significantly better for responding patients than for non responders (76% vs 31%, P< 0.001). TP53disruption was associated with 2-year OS of 65% vs 90% (P= 0.176). Patients with CK had 53% of 2-year OS vs 62% for the remaining cohort (P= 0.236). There was no difference for the type of prior therapies (BTKi, PI3Kδ inhibitor or prior SCT) or IGHV mutational status. Patients who stopped venetoclax therapy had a very poor outcome with a median OS of 5 months.

Conclusions.Our real-life study shows response rates and survival data that are in line with those observed in pioneer venetoclax clinical trials. CK should be evaluated as a predictive factor for response to venetoclax.