The UK FLAIR trial demonstrated for the first time that a time-limited regimen (ibrutinib-venetoclax), guided by MRD to a median duration of 27 months, achieved superior progression-free and overall survival compared to continuous ibrutinib therapy in frontline CLL.
An MD Anderson study showed that delaying the addition of obinutuzumab to an acalabrutinib-venetoclax regimen achieved similar deep remission rates (uMRD) as upfront administration. This sequencing strategy significantly reduced severe neutropenia (52% vs 12%) and infections, making the potent combination safer.
In the AMPLIFY trial, the acalabrutinib-venetoclax (AV) arm showed superior overall survival. This was heavily influenced by the COVID-19 pandemic, as regimens containing the anti-CD20 antibody obinutuzumab (AVO and chemo) had significantly more fatal COVID cases, making the antibody a liability during that period.
The CLL17 trial revealed a counterintuitive finding: unfit patients had worse outcomes on continuous ibrutinib, likely due to toxicity-related discontinuations. The logistically harder venetoclax-obinutuzumab fixed-duration regimen produced equal efficacy in both fit and unfit patients, making it a better choice for the less fit.
The FLAIR trial's MRD-guided protocol, while effective, created a paradox. Lower-risk, IGHV-mutated patients, who typically do well on shorter treatments, took longer to achieve undetectable MRD. This resulted in them receiving a longer duration of therapy than their higher-risk counterparts, representing likely overtreatment.
The zanubrutinib-venetoclax arm of the SEQUOIA trial, while technically 'MRD-guided', had such strict criteria for stopping treatment (e.g., two bone marrow biopsies) that very few patients qualified. This design flaw meant most patients effectively received continuous zanubrutinib after the initial combination phase.