Response to Subsequent Novel Therapies and Time to Second Progression-Free Survival Event in the MURANO Trial in Patients with Relapsed/Refractory Chronic Lymphocytic Leukemia Previously Treated with Fixed-Dose Venetoclax Plus Rituximab

Background: The randomized Phase III MURANO trial (NCT02005471) assessed fixed-duration treatment with venetoclax (Ven) plus rituximab (R) in patients (pts) with relapsed/refractory (R/R) chronic lymphocytic leukemia (CLL). Despite improved clinical outcomes (progression-free survival [PFS], overall survival [OS] and time-to-next-treatment [TTNT], as well as minimal residual disease conversion and progressive disease [PD] association [Seymour et al. Blood 2022]) for pts randomized to VenR compared with bendamustine-R (BR), most pts will ultimately require subsequent therapies. However, the efficacy of subsequent treatment after relapse remains largely unexplored. This study was conducted prior to the widespread availability of other targeted therapies, so pts were not previously exposed to targeted therapies prior to MURANO treatment allocation. Here we report response rates to follow-up therapy with Ven-based regimens, or Bruton tyrosine kinase inhibitor (BTKi) therapy, as well as time to the second PFS events from the final analysis of the MURANO trial.

Methods: Overall, 389 pts were randomized to VenR (2 years of Ven, with R for the first 6 months) or 6 months of BR. Pts in either arm with PD were followed for disease response to any subsequent anti-CLL therapeutic regimens, PFS and OS. A sub-study, introduced in 2018, allowed pts who developed PD following treatment with VenR or BR to receive the MURANO VenR regimen. Pts who initiated new anti-CLL therapy without a response assessment reported by the investigator, were considered unevaluable.

Results : At the final clinical cutoff date of August 3, 2022, all pts had ceased study-specified treatment and the median follow-up of the main study was 85.7 (range: 0-99.2) months. PFS and OS benefits were maintained at the 7-year follow-up (Kater et al. EHA 2023).

Overall, 73/194 (37.6%) pts in the VenR arm had not received a next-line therapy at the final cutoff, and 26 pts had died without subsequent therapy. Median TTNT or death with VenR was 63.0 months vs 24.0 months with BR (hazard ratio: 0.30). Following PD, 95/194 (49.0%) pts randomized to VenR and 131/195 (67.2%) pts randomized to BR had received subsequent anti-CLL therapy; the median (range) time off therapy in these pts was 28.3 months (-0.1-68.6) and 17.9 months (0.7-82.4), respectively. Of the 95 VenR pts receiving subsequent anti-CLL therapy, 30 (32.3%) received BTKi therapy (ibrutinib [n=25], acalabrutinib [n=4] and zanubrutinib [n=1]), with 18 ongoing at the time of the final cutoff; 47 (51.6%) received Ven-based therapy, with 12 ongoing at the time of the final cutoff; and 16 (17.2%) received chemoimmunotherapy (CIT). Two pts received a non-CLL therapy for another malignancy so were excluded from the subsequent analysis. Of the 131 BR pts receiving subsequent therapy, 79 (60.3%) received BTKi therapy (ibrutinib [n=69], acalabrutinib [n=6] and zanubrutinib [n=4]), with 20 ongoing at the time of the final cutoff; 17 (13.0%) received Ven-based therapy, with 3 ongoing at the time of the final cutoff; 24 (18.3%) received CIT; and 11 (8.4%) received other novel agents. Median time from randomization to second PFS event was 85.9 months (95% confidence interval [CI]: 81.8-88.2) in pts randomized to VenR and 48.4 months (95% CI: 44.5-56.6) in pts randomized to BR; p<0.0001 ( Figure).

Best overall response (BOR; defined as complete remission [CR], CR with incomplete count recovery, partial remission [PR] and nodular PR) rates to first subsequent anti-CLL therapy for pts with evaluable responses were 75/93 (80.6%) for VenR and 85/107 (79.4%) for BR. Among evaluable pts previously treated with VenR and BR, the BOR rate to subsequent BTKi therapy was 19/22 (86.4%) and 51/65 (78.5%), respectively, while BOR rate to subsequent Ven-based therapies was 32/42 (76.2%) and 15/17 (88.2%), respectively.

Conclusions: Final data from MURANO demonstrate that, despite the majority of BR pts receiving novel therapies after relapse on MURANO, there was a significantly prolonged time to second PFS event observed in favor of the VenR arm. Pts who had relapsed and received retreatment or crossed over to Ven-based regimens or subsequent BTKi therapy also demonstrated high response rates. These results indicate that early intervention with fixed-duration VenR in R/R CLL is an effective approach and does not compromise subsequent therapy response.