Palomba, Lia

Abstract Background: Undetectable minimal residual disease (uMRD) at the end of first-line (1L) treatment (tx) with 12-cycles (C) of venetoclax (ven) + obinutuzumab (obin) is associated with prolonged survival for patients (pts) with chronic lymphocytic leukemia (CLL, Al Sawaf et al. Blood 2024). We hypothesized that MRD may be used to guide ven tx duration for CLL pts treated with 1L ven + obin. Methods In this ongoing phase II, multicenter investigator-initiated study, pts receive ven + obin for 1L tx of CLL/small lymphocytic lymphoma (NCT04447768). Eligible pts have a CIRS score of ≤ 6 and require 1L tx per iwCLL 2018 criteria. Pts receive 6 x 28-day C of obin and initiate ven on C1D22. Ven duration is dependent on peripheral blood (PB) MRD status measured by ClonoSeq next generation sequencing. At C7, pts undergo MRD testing. Pts uMRD6 (<10-6 sensitivity) at both C7 and C9 dc ven after 9C and enter treatment free observation (TFO). Pts with detectable MRD6 (dMRD6) at C7 undergo repeat testing at C12; if uMRD5 (<10-5) pts dc ven after 12C. Pts dMRD5 at C12 continue ven for an additional 12C (24C total) prior to TFO. The primary study endpoint is 36-month PFS; the unpromising rate is set at 82% and will be tested by a nonparametric survival estimate (Kaplan-Meier) along with Greenwood's formula. RNA sequencing (RNAseq) was performed pre-tx on patient bone marrow (or PB if inaspirable) samples. Unsupervised clustering using machine learning (ML) based on consensus nonnegative matrix factorization was applied to the most variable genes to identify patient clusters. Clusters were then biologically characterized by gene signature scoring using xCell algorithm and assessed for association with uMRD6 at C7 using a Fisher exact test. Results Baseline characteristics of the 100 pts who initiated tx include: median age 58 (range 34-81); 71% male, 90% White, 3% Black and 2% Asian, 5% unknown; 49% IGHV unmutated, 16% TP53 mutation, 8% del17p (previously reported, Roeker et al. ASH 2024). 3 pts stopped tx prior to C7. 51 pts were uMRD6 at C7 and C9 and completed 9C ven. 46 pts were dMRD6 at C7; 6 pts stopped tx outside of meeting protocol requirements and are included in intention-to-treat (IIT) analyses. 32 pts were uMRD5 at C12 and dc ven after 12C. 8 pts were dMRD5 at C12: 5 continued ven per protocol (3 completed 24C ven, 2 ongoing tx as of 15 May 2025 data cut-off), 2 stopped ven outside of protocol requirements (included in ITT analyses), and 1 pt withdrew consent. At a median follow-up of 35 months, the 36-month PFS rate is 90% (95% CI: 84%, 97%). 36-month OS is 94% (95% CI: 89%, 99%). Landmark PFS analyses from EOT were performed for pts who dc ven after 9C due to uMRD6 (24-month PFS 92%, 95% CI: 85, 100%, n=51) and pts who dc ven after 12C due to uMRD5 (24-month PFS 96%, 95% CI: 89%, 100%, n=32). For pts dc ven after 9C due to uMRD6 (n=51), PB MRD at 12C after EOT was: 59% uMRD6, 12% uMRD5, 4% uMRD4, 8% dMRD4 and 18% unknown. For pts dc ven after 12C due to uMRD5 status (n=32), PB MRD at 12C following EOT was: 9% uMRD6, 31% uMRD5, 9% uMRD4, 25% dMRD4 and 25% unknown. Of the 5 pts with PD, 3 pts have had Richter Transformation to diffuse large B-cell lymphoma (all uMRD6 at C7 / 9). Two pts with PD have not met iwCLL tx criteria and remain in TFO. Five pts have died (suicide, West Nile encephalitis, COVID-19, complications of glioblastoma and RT DLBCL). Five C12 dMRD5 pts who continued ven have reached C18, with only 1 of 5 converting to uMRD5 in PB. However, all 5 maintained uMRD4 (<10-4). Of 3 pts that completed 24C ven (2 ongoing tx), 1 pt had deepening of response to uMRD5 at C24, and 2 pts had rising MRD on ven (dMRD4 at C24). To investigate patient heterogeneity at baseline and its relationship to uMRD, we clustered patient RNAseq samples into two clusters using artificial intelligence/ML based unsupervised clustering. The clusters associated with uMRD6 at C7 (Fisher exact test p=0.038), and patients in the cluster with significantly higher immunosuppressive cells such as T-regulatory cells and M2 macrophages were less likely to be uMRD6 at C7. Conclusions At a median follow-up of 35 months, the estimated 36-month PFS rate is 90%. RNAseq transcriptomic analyses identified that patients with enriched immunosuppressive cells were less likely to be uMRD6 at C7. Additional follow-up is required to confirm the durability of this MRD-guided ven + obin tx strategy.

Background:Ibrutinib is approved in Europe and the US for the treatment of Waldenstrom macroglobulinemia (WM) with a median progression‐free survival (PFS) measured on several years. As PFS is commonly used for drug approval by regulatory entities, there is an unmet need of reliable surrogate markers for PFS that could help accelerating such process. This is of importance with novel BTK inhibitors currently in clinical trials.Aims:We hypothesized that the depth of response at 6 months can be predictive of PFS in patients with WM treated with the BTK inhibitor ibrutinib.Methods:We evaluated our hypothesis in two separate cohorts of WM patients treated with ibrutinib. The learning cohort was composed by participants of two prospective clinical trials at Dana‐Farber Cancer Institute (DFCI), Memorial Sloan Kettering Cancer Center and Stanford Cancer Center. The validation cohort was composed by consecutive WM patients treated with ibrutinib off clinical trial at DFCI and Mayo Clinic. Categorical responses at 6 months were assessed based on criteria from the 6thInternational Workshop for WM. PFS6 was defined as the time from the 6‐month response assessment until progression of disease or death from any cause. PFS6 curves were generated using the Kaplan‐Meier method and compared using the log‐rank test. Cox proportional hazard regression models were fitted for PFS6. Pvalues <0.05 were considered statistically significant.Results:The learning and validation cohorts were composed by 92 and 190 WM patients treated with ibrutinib, repsectively. There were no statistical differences between cohorts with regards to age, sex, serum IgM level, hemoglobin level, bone marrow involvement, prior treatment status, and MYD88 and CXCR4 mutational status (p>0.05 for all variables). The rates of partial response (PR) or better at 6 months in the learning and validation cohorts were 63% (54/86) and 72% (114/159), respectively (p = 0.15). The median PFS6 was not reached in the learning cohort and was 53 months (95% CI 44‐not reached) in the validation cohort. In the learning cohort, the median PFS6 for patients who attained a PR or better at 6 months was not reached, while for the patients who did not attained PR at 6 months was 48 months (95% CI 33‐not reached). The 3‐year PFS rate for patients who attained a PR or better at 6 months was 83% (95% CI 68–91%), while for patients who did not attained PR at 6 months was 58% (95% CI 33–76%) (Figure, left, log‐rank p = 0.02). Attaining PR or better at 6 months was associated with a hazard ratio (HR) or progressing or dying of 0.37 (95% CI 0.16–0.87; p = 0.02).In the validation cohort, the median PFS6 for patients who attained a PR or better at 6 months was 53 months (95% CI 44‐not reached), while for the patients who did not attained PR at 6 months was 32 months (95% CI 22‐not reached). The 3‐year PFS rate for patients who attained a PR or better at 6 months was 79% (95% CI 67–87%), while for patients who did not attained PR at 6 months was 50% (95% CI 26–70%) (Figure, right, log‐rank p = 0.04). Attaining PR or better at 6 months was associated with a hazard ratio (HR) or progressing or dying of 0.46 (95% CI 0.22–0.98; p = 0.04). Age, sex, serum IgM level, hemoglobin level, bone marrow involvement and prior treatment status were not prognostic of PFS6 in both cohorts.Summary/Conclusion:Attaining a PR or better at 6 months to ibrutinib is associated with longer median PFS and higher rates of 3‐year PFS in WM patients. Depth of response at 6 months could serve as a surrogate for PFS in clinical trials evaluating BTK inhibitors in WM patients.image