Tam, Constantine S.

Abstract Hairy cell leukemia (HCL) and HCL variant (HCLv) are distinct, rare, and chronic splenic B-cell lymphomas/leukemias that partially overlap in clinicopathologic presentation but differ in genetic basis, prognosis, and management. HCL is caused by the BRAF-V600E kinase–activating mutation in >95% of the patients, usually has excellent responses to chemotherapy with purine analogues, and is also amenable to BRAF inhibitor–based targeted treatments. In contrast, HCLv lacks BRAFV600E mutation, requires combined therapy with purine analogues in addition to rituximab, and generally shows less durable responses. Here, an international team of hematologists, experts on these rare diseases, was convened by the Hairy Cell Leukemia Foundation to update the previous guidelines (published in 2017) by providing a summary of current methods to diagnose and manage patients with HCL and HCLv as well as a prospective on newer targeted therapies to further improve outcomes.

Abstract Introduction Bruton tyrosine kinase inhibitors (BTKis) have changed the treatment algorithm for patients with high-risk relapsed/refractory (R/R) chronic lymphocytic leukemia (CLL). Efficacy was demonstrated for zanubrutinib and ibrutinib in high-risk R/R CLL patients in the ALPINE (NCT03734016) trial, for ibrutinib and acalabrutinib in the ELEVATE-RR (NCT02477696) trial, and for acalabrutinib in the ASCEND (NCT00135226) trial. While there is limited head-to-head comparative trial data of all covalent BTKis in the treatment of high-risk R/R CLL, a previously published network meta-analysis (NMA) used data from the ALPINE, ELEVATE-RR, and ASCEND trials, and reported that zanubrutinib demonstrated significantly improved relative efficacy compared to ibrutinib and acalabrutinib in high-risk R/R CLL (Shadman 2025). Within this NMA, high-risk R/R CLL populations were defined based on the prespecified definitions within each trial, including patients with del(17p) and/or TP53 mutations in the ALPINE and ASCEND trials, and del(17p)/del(11q) in the ELEVATE-RR trial. This study aimed to compare zanubrutinib versus ibrutinib and acalabrutinib in high-risk R/R CLL by calculating the number needed to treat (NNT) to avoid one progression or death. Methods A model was developed to evaluate the NNT among high-risk R/R CLL patients to avoid a progression or death. Progression free survival (PFS) data for zanubrutinib in high-risk patients were extracted from the ALPINE trial. PFS values for ibrutinib and acalabrutinib were derived from the previously published NMA study. PFS for ibrutinib and acalabrutinib were calculated by applying PFS hazard ratio from the NMA results to the zanubrutinib PFS value for the high-risk population in the ALPINE trial. 24-month PFS (72.6% for zanubrutinib, 52.0% for ibrutinib, and 55.9% for acalabrutinib) were used for the base case analysis of the model. Sensitivity analyses were conducted to examine the impact of alternative PFS inputs for ibrutinib, derived directly from the high-risk populations in ALPINE trial (unadjusted). Results The base case results from the NNT model indicate that for the treatment of patients with high-risk R/R CLL over 24-months, every five patients treated with zanubrutinib instead of ibrutinib results in the avoidance of one disease progression or death and every six patients treated with zanubrutinib instead of acalabrutinib results in the avoidance of one disease progression or death. Applying the model result to a hypothetical scenario of 100 patients with high-risk R/R CLL treated with zanubrutinib versus ibrutinib for two years finds approximately 20 patients will avoid disease progression events or deaths. Treating the same population with zanubrutinib versus acalabrutinib for two years will result in the avoidance of 17 disease progression events or death. Sensitivity analysis showed consistent NNT results.Conclusions The NNT analysis suggests that among high-risk R/R CLL patients, zanubrutinib is associated with more favorable clinical outcomes compared to ibrutinib and acalabrutinib. Over 24 months, zanubrutinib demonstrated a NNT of five to prevent one disease progression or death compared to ibrutinib, and an NNT of six compared to acalabrutinib, in high-risk R/R CLL patients. Study findings should be interpreted based on modeling assumptions and potential patient population differences across trials.

Abstract Introduction: The first-generation BCL2 inhibitor,venetoclax, is an effective treatment for CLL/SLL, but its usage may be limited by toxicity. Sonrotoclax, a next-generation BCL2 inhibitor, is a more selective and pharmacologically potent inhibitor of BCL2 than venetoclax, with a shorter half-life and no drug accumulation. BGB-11417-101 (NCT04277637) is an ongoing, phase 1/1b, dose-escalation/expansion study in patients with B-cell malignancies. Presented here are preliminary data for sonrotoclax + obinutuzumab in patients with treatment-naive (TN) CLL/SLL in BGB-11417-101. Methods: Obinutuzumab is administered intravenously at 100 mg on day (D) 1, 900 mg on D2, 1,000 mg on D8 and D15 of cycle (C) 1, and then 1,000 mg on D1 of C2-6 of each 28-day cycle. Beginning on C2D1, sonrotoclax is administered orally once daily with ramp-up to the target doses, 160 or 320 mg. Patients can continue treatment until progressive disease (PD), unacceptable toxicity, or undetectable minimal residual disease (uMRD4; <1 CLL cell per 10,000 leukocytes [<0.01%]) in peripheral blood (PB) by next-generation sequencing (NGS; ClonoSEQ) after 15 treatment cycles. Study endpoints include safety per NCI-CTCAE v5.0, overall response rate (ORR) per iwCLL guidelines, and MRD status in PB per modified ERIC flow cytometry (FC) assay or NGS, depending on the timepoint. Tumor lysis syndrome (TLS) is assessed per Howard (2011) criteria. Results: As of May 16, 2025, 55 patients with TN CLL/SLL were enrolled (160 mg, n=20; 320 mg, n=35), and 21 patients (all 320 mg) have discontinued sonrotoclax + obinutuzumab (due to uMRD4 per NGS as protocol-mandated [n=17], PI decision uMRD4 per FC [n=2], and PD [n=2]). Four patients discontinued obinutuzumab only per PI decision (160 mg, n=1), thrombocytopenia (320 mg, n=2), and prostate cancer prior to starting sonrotoclax (160 mg, n=1). For all patients, the median age was 62 y, 65% were male, and 89% were White. At baseline, 14% of patients (8/55) had high tumor burden and 58% (31/53) had unmutated IGHV. Median study follow-up was 8.9 months (range, 0.4-25.4 months) for all patients; 6.4 months (range, 0.4-9.0 months) for 160 mg; and 16.0 months (range, 2.9-25.4 months) for 320 mg. Maximum tolerated dose was not reached. The most common any-grade treatment-emergent AEs (TEAEs) were thrombocytopenia (56%), infusion-related reaction (56%), and neutropenia (49%). Neutropenia was the most common grade ≥3 TEAE (38%). No deaths due to TEAEs occurred, and no TEAEs led to sonrotoclax discontinuation. Two cases of laboratory TLS occurred after C1D1 of obinutuzumab prior to starting sonrotoclax; no clinical or laboratory TLS occurred during sonrotoclax ramp up. No meaningful safety differences were observed among sonrotoclax dose cohorts. In 37 efficacy-evaluable patients (160 mg, n=7; 320 mg, n=30), the ORR was 89%; for the 320-mg cohort, ORR was 93% (28/30). Complete response (CR) rates (CR + CR with incomplete marrow recovery [CRi]) were 46% (all patients) and 43% (320 mg). For 23 patients in the 320 mg cohort who reached the C15 MRD assessment, the best C15 uMRD4 rate per FC was 87% (20/23; 2 not evaluable; 1 missing); per NGS, the uMRD4 rate at C15 was 78% (18/23; 5 missing). All patients with an available C15 MRD assessment achieved uMRD4 and remain in remission as of the data cutoff date. The median time from reaching sonrotoclax target dose to uMRD4 was 2.3 months (range, 1.4-5.6 months) in the 320-mg cohort. Three patients experienced PFS events: 1 died from an indeterminate cause (160 mg, discontinued treatment after C1D9 of obinutuzumab) and 2 had PD (320 mg; both Richter's transformation at C6 and C2). Conclusions: Sonrotoclax + obinutuzumab was generally well tolerated in patients with TN CLL/SLL, with no sonrotoclax discontinuations or deaths due to TEAEs. No laboratory or clinical TLS events occurred during sonrotoclax ramp-up. Encouraging antitumor activity was observed with sonrotoclax 320 mg. High rates of blood uMRD4 occurred early and deepened over time. All patients with an available C15 MRD assessment by NGS or FC achieved uMRD4 and remain in remission. A registrational phase 3 study (CELESTIAL-RRCLL, BGB-11417-303) assessing this combination with sonrotoclax 320 mg is currently recruiting.

Abstract Introduction: BGB-16673 is an orally available protein degrader that blocks BTK signaling by tagging BTK for degradation through the cell's proteasome pathway, leading to tumor regression. CaDAnCe-101 (BGB-16673-101; NCT05006716) is an ongoing open-label, phase 1/2 study evaluating BGB-16673 monotherapy in patients with B-cell malignancies. Here, updated safety and efficacy results of BGB-16673 are presented in patients with WM in the phase 1 portion of the study. Methods Eligible patients had confirmed relapsed/refractory (R/R) WM (≥2 prior therapies), an ECOG performance status of 0-2 (0-1 in the EU), and previous treatment with an anti-CD20 antibody and, in the US, Japan, and EU, a covalent BTK inhibitor. BGB-16673 was dosed once daily orally. The primary objectives of this phase 1 study were to evaluate safety and tolerability (NCI-CTCAE v5.0) and establish the maximum tolerated dose and recommended dose for expansion. A secondary objective was to evaluate the overall response rate (ORR; modified IWWM-6 consensus criteria), with the first assessment after 4 weeks of treatment. Results As of May 23, 2025, 42 patients with WM were enrolled and treated (100 mg, n=15; 200 mg, n=14; 350 mg, n=13). Median age was 72.0 years (range, 46-81 years), and the median number of prior therapies was 3 (range, 2-11), including prior covalent BTK inhibitors (n=42 [100%]), BCL2 inhibitors (n=10 [23.8%]), noncovalent BTK inhibitors (n=7 [16.7%]), anti-CD20 monoclonal antibodies (n=42 [100%]), and chemotherapy (n=39 [92.9%]). In total, 33.3% of patients (12/36) had WM with BTK mutations, 85.7% (36/42) with MYD88 mutations, 51.3% (20/39) with CXCR4 mutations, 52.8% (19/36) with TP53 mutations, and 5.6% (2/36) with PLCG2 mutations. Median follow-up was 8.8 months (range, 0.8-31.0 months). Overall, 97.6% of patients experienced treatment-emergent adverse events (TEAEs) of any grade (grade ≥3, 59.5%; serious TEAEs, 35.7%). The most common (≥20% incidence) TEAEs (any grade; grade ≥3) were neutropenia (38.1%; grade ≥3, 33.3%, most common grade ≥3 TEAE), diarrhea (26.2%; no grade ≥3), contusion/bruising (26.2%; no grade ≥3), and thrombocytopenia (21.4%; grade ≥3, 7.1%). No atrial fibrillation was observed. Grade 3 febrile neutropenia and major hemorrhage (grade 3 hematemesis caused by concurrent gastritis/duodenitis unrelated to treatment) occurred in 1 patient (2.4%) each. Seven patients (16.7%) had a grade ≥3 infection, including 2 patients with fungal infections. Three patients (7.1%) had TEAEs that led to treatment discontinuation (anemia, cerebral aspergillosis, pericardial effusion/pleural effusion; n=1 each), and 2 patients (4.8%) had a TEAE that led to dose reduction. Two patients (4.8%) died due to TEAEs (septic shock in the context of progressive disease [PD] and cerebral aspergillosis; n=1 each). All 42 patients were response-evaluable and the ORR (minor response [MR] or better) was 83.3% (n=35), the major response rate (partial response [PR] or better) was 64.3% (n=27), and the very good partial response (VGPR) rate was 26.2% (n=11). Median time to first overall response was 1.0 months (range, 0.9-3.8 months) and to best overall response was 1.9 months (range, 0.9-7.4 months). Responses deepened over time: of 9 patients with stable disease at first disease assessment, 3 transitioned to MR and 2 to PR; of 20 patients with initial MR, 10 transitioned to PR and 2 to VGPR; and of 13 patients with initial PR, 7 transitioned to VGPR. Thirty patients (71.4%) remain on treatment. Two deaths were due to PD. Responses were seen in patients previously treated with a covalent BTK inhibitor (35/42 [83.3%]) and a noncovalent BTK inhibitor (7/7 [100%]) and in patients who discontinued a prior BTK inhibitor due to PD (28/35 [80%]). Responses were independent of mutations in BTK (with, 12/12; without, 17/24), MYD88 (with, 30/36; without, 5/6), CXCR4 (with, 18/20; without, 14/19), TP53 (with, 16/19; without, 13/17), and PLCG2 (with, 1/2; without, 28/34). The 9-month duration of response rate was 84.1% (95% CI, 63.1%-93.7%). Conclusions Data from this ongoing phase 1 study demonstrate that the novel BTK degrader BGB-16673 was well tolerated and continued to show substantial antitumor activity in patients with heavily pretreated BTK inhibitor–exposed R/R WM, including those with BTK, MYD88, CXCR4, and TP53 mutations. Enrollment is ongoing in the phase 2 portion of the study.

Abstract Background: Despite the efficacy of covalent Bruton tyrosine kinase inhibitors (cBTKi) in R/R MCL, patients (pts) ultimately discontinue treatment due to intolerance or development of resistance and disease relapse. Pirtobrutinib is a highly selective, non-covalent BTKi that inhibits BTK with low nM potency throughout the daily dosing interval. Pirtobrutinib was safe and effective in the phase 1/2 BRUIN study in pts with R/R B-cell malignancies, including those previously treated with a BTKi. Pirtobrutinib is approved in the EU for adults with R/R MCL after prior treatment with a BTKi (EMA Conditional Approval, Oct 2023), and in the USA for adults with R/R MCL after ≥ 2 lines of systemic therapy, including a BTKi (FDA Accelerated Approval, Jan 2023).Here, we report the final results from the phase 1/2 BRUIN study (NCT03740529), with a follow-up period of up to 5 yrs, focusing on the efficacy and safety of pirtobrutinib in all R/R MCL pts. Methods: Pts with R/R MCL who received ≥1 prior lines of therapy (including BTKi) were eligible for treatment with pirtobrutinib monotherapy. Key endpoints included overall response rate (ORR), duration of response (DOR) and progression-free survival (PFS), all assessed by independent review committee (IRC) per Lugano 2014 criteria (presented here) and investigator, overall survival (OS), and safety. Pts were included across the range of doses evaluated in dose escalation and expansion (25-300 mg/day). A data cutoff on 27 January 2025 was utilized, with a median study follow-up of 17.5 months (range, 0.5-69.6). Results: Among the 166 pts with R/R MCL, 153 (92%) received the pirtobrutinib approved dose of 200 mg/day, 152 (92%) had received prior cBTKi, of which 128 (84.2%) discontinued any prior cBTKi due to progressive disease (PD), and 15 (9.9%) due to toxicity. The cBTKi-pre-treated pts had a median age of 70 yrs (range, 46-88), 52% had intermediate-risk and 28.3% had high-risk sMIPI scores. The median number of prior lines of therapy was 3 (range 1-9), with most pts having received a prior anti-CD20 antibody (96.7%) and chemotherapy (90.1%). Additional prior therapies included hematopoietic stem cell transplantation (21.7%; 19.7% auto and 4.6% allo), BCL-2 inhibitor (15.8%), CAR-T cell therapy (8.6%). As of the data cutoff, 11 (7.2%) pts who received a prior cBTKi and 6 (42.9%) cBTKi naïve pts remained on treatment. The cBTKi pre-treated pts had an ORR of 49.3% (95% CI, 41.1-57.6), including 15.8% complete responses (CR) (n=24) and 33.6% partial responses (PR) (n=51). The 75 responding pretreated pts had a median DOR of 21.6 months (95% CI, 9.2-27.2) at a median follow-up of 24 months. The ORR among 128 pts who had discontinued any prior cBTKi due to PD and 15 pts who discontinued due to toxicity was 43.0% and 93.3%, respectively. The median PFS and OS for cBTKi pre-treated pts were 5.6 months (95% CI, 5.3-9.2) and 23.9 months (95% CI, 17.3-51.5), respectively. Fourteen pts (9.2%) were censored for PFS due to subsequent anticancer therapy without documented PD, including 8 pts who received CAR-T. The cBTKi naïve pts (n=14) had an ORR of 85.7% (95% CI, 57.2-98.2), including 50.0% CR (n=7) and 35.7% PR (n=5). The 12 responding naïve pts had a median DOR of 42.7 months (95% CI, 25.8-NE) at a median follow-up of 43 months. The median PFS and OS in the cBTKi naïve pts were 44.6 months (95% CI, 16.7-NE) and not reached (95% CI, 33.5-NE), respectively. Among all R/R MCL pts (n=166), the most frequent treatment-emergent adverse events (TEAE), regardless of attribution, were fatigue (31.9%), diarrhea (22.9%), anemia (18.1%), and dyspnea (18.1%). The most common Grade ≥3 TEAE was neutropenia/neutrophil count decreased (13.3%), and the rate of Grade ≥3 infections was 21.1%. Grade ≥3 hemorrhage/hematoma (2.4%) and all-grade atrial fibrillation/flutter (3.6%) were infrequent. In total, 13 (7.8%) pts had a fatal TEAE, with 4 (2.4%) classified as infections. Overall, 8 pts (4.8%) had treatment-related AE leading to dose reductions, and 6 (3.6%) had treatment-related AE leading to pirtobrutinib discontinuation. Conclusion: Pirtobrutinib continues to demonstrate efficacy in pts with heavily pre-treated R/R MCL including both those who previously received a cBTKi and those who were BTKi-naïve. The safety profile of pirtobrutinib remained favorable with a low-rate of dose reductions/discontinuations due to drug-related toxicity. No new safety signals were identified after up to 5 yrs of follow-up.

Abstract Richter transformation (RT) is defined as an aggressive lymphoma emerging in patients with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL). Despite novel therapeutics developed in CLL, RT is associated with poor outcomes. In light of recent progress regarding the diagnostic procedures and therapeutic concepts of RT, an international group of experts, under the coordination of the European Research Initiative on CLL, has developed consensus recommendations for clinical procedures and future research on this disease. Patients with RT typically present with a rapid clinical decline, worsening B-symptoms, elevated lactate dehydrogenase, and/or rapidly enlarging lymphadenopathy. Workup should include a positron emission tomography–computed tomography scan for patients with suspected RT. An excisional biopsy should be taken from an accessible lesion, preferably with the highest fluorodeoxyglucose avidity, and analyzed for the presence of aggressive lymphoma. The molecular relationship to the original CLL clone(s) should be defined. Because no effective standard treatment for RT exists, patients should be treated in a clinical trial. Response of both RT and CLL should be assessed at an early time point, and survival end points should be prioritized in trial design. We hope that these recommendations can help to harmonize clinical and translational research and improve outcomes for patients with RT.