Fludarabine, cyclophosphamide, and rituximab as first-line treatment in patients with chronic lymphocytic leukemia: A long-term analysis of the German CLL Study Group (GCLLSG) registry.

Long-term data of chronic lymphocytic leukemia (CLL) patients with favorable risk who were treated with fludarabine, cyclophosphamide, and rituximab (FCR) within clinical trials show good efficacy. We here report long-term data collected within the GCLLSG registry. Altogether, 417 CLL patients who received first-line treatment with FCR were analyzed, of which 293 (70.3%) were treated outside of clinical trials. The median observation time from first-line was 95.8 (interquartile range 58.7-126.8) months. Focusing on data of 194 (46.5%) patients who received FCR first-line treatment after 2013 (start of data collection within GCLLSG registry), responses were documented in 85% of the patients, non-responses in 15%, and for 3.6% the assessment was missing. Median event-free survival (EFS, time until disease progression, subsequent treatment, or death) was 60.2 months with a 5-year EFS-rate of 50.6%. Patients with higher-risk disease, characterized by unmutated IGHV (N = 78), had a median EFS of 45.4 months with a 5-year EFS rate of 36.3%, while the median EFS was 77.5 months with a 5-year EFS rate of 60.3% in patients with mutated IGHV (N = 40). Median overall survival was not reached with a 5-year survival rate of 92.7%. In summary, first-line FCR was associated with long EFS, especially in patients exhibiting a mutated IGHV status.

Acalabrutinib, venetoclax and obinutuzumab in relapsed CLL: Final efficacy and ctDNA analysis of the CLL2-BAAG trial.

The phase 2 CLL2-BAAG trial tested the measurable residual disease (MRD)-guided triple combination of acalabrutinib, venetoclax and obinutuzumab after an optional bendamustine debulking in 45 patients with relapsed/refractory CLL (one patient was excluded from the analysis due to a violation of exclusion criteria). MRD was measured by flow cytometry (FCM, undetectable MRD <10-4) in peripheral blood (PB) and circulating tumor DNA (ctDNA) by digital droplet PCR (ddPCR) of variable-diversity-joining (VDJ) rearrangements and CLL-related mutations in plasma. MRD recurrence was defined as detectable ctDNA and/or MRD ≥10-4 after achieving both uMRD/undetectable ctDNA. The median number of previous treatments was 1 (range 1-4), 18 patients (40%) had received a BTK inhibitor (BTKi) and/or venetoclax prior to inclusion, 14/44 (31.8%) had TP53 aberrations, 34 (75.6%) had unmutated IGHV. With a median observation time of 36.3 months and all patients off treatment for a median of 21.9 months, uMRD <10-4 in PB was achieved in 42/45 patients (93.3%) at any time point, including 17/18 (94.4%) previously exposed to venetoclax/BTKi and 13/14 (92.9%) with TP53 aberrations. The estimated three-year progression-free and overall survival rates were 85.0% and 93.8%. Overall 585 paired FCM/ctDNA samples were analyzed and 18 MRD recurrences (5 with and 13 without clinical progression) occurred after the end of treatment. Twelve were first detected by ctDNA, three by FCM and three synchronously. Patients with earlier detection by ctDNA appeared to have genetically higher risk disease. In conclusion, time-limited MRD-guided acalabrutinib, venetoclax and obinutuzumab achieved deep remissions in almost all patients with relapsed/refractory CLL. The addition of ctDNA-based analyses to FCM MRD assessment seems to improve early detection of relapses. ClinicalTrials.gov Identifier: NCT03787264.

Chronic Lymphocytic Leukemia: Time-Limited Therapy in the First-Line Setting and Role of Minimal Residual Disease.

PURPOSE OF REVIEW: In this review, we provide an overview of different time-limited combination therapies of chronic lymphocytic leukemia (CLL) and summarize the data of pivotal clinical studies. Furthermore, we discuss the relevance of MRD in clinical trials and summarize the challenges that arise in routine clinical care. Finally, we provide an outlook on studies and datasets needed to optimize the use of time-limited treatment strategies and MRD assessments in modern CLL management. RECENT FINDINGS: In recent years, first-line treatment of CLL has undergone a considerable transformation, with targeted substances having largely replaced chemoimmunotherapy (CIT) as a time-limited strategy in the frontline setting. BTK inhibitors were the first class of targeted agents introduced in CLL, which achieved longer progression-free survival (PFS) and in some cases also overall survival (OS) than CIT. However, this required an indefinite drug intake until disease progression, while CIT is generally administered over the course of few months. In contrast to BTK inhibitors, BCL2 inhibitors, another class of targeted agents, can achieve high rates of undetectable minimal residual disease (uMRD) levels and induce deep molecular remissions with the potential to stop treatment while maintaining remissions. Combinations of BCL2 inhibitors with CD20 antibodies or with BTK inhibitors have been explored to establish time-limited treatment strategies with targeted agents. In this context, one of the strongest predictors of long-term outcomes is MRD status at the end of treatment, which has been shown to correlate closely with PFS and OS in most cases.

Tislelizumab plus zanubrutinib for Richter transformation: the phase 2 RT1 trial.

In patients with chronic lymphocytic leukemia, Richter transformation (RT) reflects the development of an aggressive lymphoma that is associated with poor response to chemotherapy and short survival. We initiated an international, investigator-initiated, prospective, open-label phase 2 study in which patients with RT received a combination of the PD-1 inhibitor tislelizumab plus the BTK inhibitor zanubrutinib for 12 cycles. Patients responding to treatment underwent maintenance treatment with both agents. The primary end point was overall response rate after six cycles. Of 59 enrolled patients, 48 patients received at least two cycles of treatment and comprised the analysis population according to the study protocol. The median observation time was 13.9 months, the median age was 67 (range 45-82) years. Ten patients (20.8%) had received previous RT-directed therapy. In total, 28 out of 48 patients responded to induction therapy with an overall response rate of 58.3% (95% confidence interval (CI) 43.2-72.4), including 9 (18.8%) complete reponse and 19 (39.6%) partial response, meeting the study's primary end point by rejecting the predefined null hypothesis of 40% (P = 0.008). Secondary end points included duration of response, progression-free survival and overall survival. The median duration of response was not reached, the median progression-free survival was 10.0 months (95% CI 3.8-16.3). Median overall survival was not reached with a 12-month overall survival rate of 74.7% (95% CI 58.4-91.0). The most common adverse events were infections (18.0%), gastrointestinal disorders (13.0%) and hematological toxicities (11.4%). These data suggest that combined checkpoint and BTK inhibition by tislelizumab plus zanubrutinib is an effective and well-tolerated treatment strategy for patients with RT. ClinicalTrials.gov Identifier: NCT04271956 .