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Herein, we present the final report of a single-center, prospective phase II study evaluating ibrutinib 420 mg once daily in 30 treatment-naive patients with Waldenstrom macroglobulinemia (WM). The present study is registered with ClinicalTrials.Gov (NCT02604511). With a median follow-up of 50 months, the overall, major, and VGPR response rates were 100%, 87%, and 30%. The VGPR rate was numerically but not significantly lower in patients with than without CXCR4 mutations (14% vs. 44%; p = 0.09). The median time to a minor response was 0.9 months, and to a major response was 1.9 months, though were longer in those with mutated CXCR4 at 1.7 months (p = 0.07) and 7.3 months (p = 0.01). Six patients had disease progression. The median progression-free survival (PFS) was not reached, and the 4-year PFS rate was 76%. There was also a non-significant lower 4-year PFS rate in patients with than without CXCR4 mutations (59% vs. 92%; p = 0.06). The most common treatment-related adverse events were fatigue, upper respiratory infection, and hematoma. Atrial fibrillation occurred in 20% of patients. Ibrutinib monotherapy induced durable responses in treatment-naive patients with WM. CXCR4 mutations impacted VGPR attainment, time to major response, and 4-year PFS rate., (© 2021. The Author(s).)

Purpose: BCL2 is overexpressed and confers prosurvival signaling in malignant lymphoplasmacytic cells in Waldenström macroglobulinemia (WM). Venetoclax is a potent BCL2 antagonist and triggers in vitro apoptosis of WM cells. The activity of venetoclax in WM remains to be clarified., Patients and Methods: We performed a multicenter, prospective phase II study of venetoclax in patients with previously treated WM (NCT02677324). Venetoclax was dose-escalated from 200 mg to a maximum dose of 800 mg daily for up to 2 years., Results: Thirty-two patients were evaluable, including 16 previously exposed to Bruton tyrosine kinase inhibitors (BTKis). All patients were MYD88 L265P -mutated, and 17 carried CXCR4 mutations. The median time to minor and major responses was 1.9 and 5.1 months, respectively. Previous exposure to BTKis was associated with a longer time to response (4.5 v 1.4 months; P < .001). The overall, major, and very good partial response rates were 84%, 81%, and 19%, respectively. The major response rate was lower in those with refractory versus relapsed disease (50% v 95%; P = .007). The median follow-up time was 33 months, and the median progression-free survival was 30 months. CXCR4 mutations did not affect treatment response or progression-free survival. The only recurring grade ≥ 3 treatment-related adverse event was neutropenia (n = 14; 45%), including one episode of febrile neutropenia. Laboratory tumor lysis without clinical sequelae occurred in one patient. No deaths have occurred., Conclusion: Venetoclax is safe and highly active in patients with previously treated WM, including those who previously received BTKis. CXCR4 mutation status did not affect treatment response., Competing Interests: Jorge J. CastilloConsulting or Advisory Role: Janssen, Roche/Genentech, Beigene, AbbVie/PharmacyclicsResearch Funding: Pharmacyclics (Inst), AbbVie (Inst), Janssen (Inst), BeiGene (Inst), TG Therapeutics (Inst) John N. AllanHonoraria: AstraZeneca, AbbVie, Pharmacyclics/Janssen, BeiGeneConsulting or Advisory Role: AbbVie/Genentech, Pharmacyclics, Ascentage Pharma, BeiGene, Janssen Oncology, Epizyme, AstraZeneca, TG Therapeutics, ADC TherapeuticsResearch Funding: Genentech, Janssen, Celgene, TG Therapeutics Tanya SiddiqiConsulting or Advisory Role: Juno Therapeutics, AstraZeneca, BeiGene, Celgene, Pharmacyclics, Bristol Myers Squibb/CelgeneSpeakers' Bureau: Pharmacyclics/Janssen, AstraZeneca, BeiGene, Bristol Myers Squibb/CelgeneResearch Funding: Juno Therapeutics (Inst), Kite, a Gilead company (Inst), Acerta Pharma (Inst), TG Therapeutics (Inst), BeiGene (Inst), Pharmacyclics (Inst), Celgene (Inst), Oncternal Therapeutics (Inst), Bristol-Myers Squibb/Sanofi (Inst) Ranjana H. AdvaniConsulting or Advisory Role: Genentech/Roche, Seattle Genetics, Takeda, Portola Pharmaceuticals, Celgene, Sanofi, Kura Oncology, Merck, Karyopharm Therapeutics, ADC Therapeutics, Daiichi Sankyo, Bristol Myers Squibb/Celgene, Epizyme, IncyteResearch Funding: Millennium (Inst), Seattle Genetics (Inst), Genentech/Roche (Inst), Pharmacyclics (Inst), Janssen (Inst), Merck (Inst), Kura Oncology (Inst), Forty Seven (Inst), Cyteir (Inst) Catherine A. FlynnConsulting or Advisory Role: Pharmacyclics, Karyopharm Therapeutics Shayna SarosiekResearch Funding: Acrotech Biopharma (Inst) Andrew R. BranaganConsulting or Advisory Role: Pharmacyclics/Janssen, Genzyme, Adaptive Biotechnologies, BeiGene, Karyopharm Therapeutics, CSL Behring Xia LiuEmployment: Merck (I) Guang YangEmployment: AbbVie (I), Blueprint MedicinesStock and Other Ownership Interests: Blueprint MedicinesHonoraria: Janssen Matthew S. DavidsHonoraria: Research to PracticeConsulting or Advisory Role: Genentech, Janssen, Pharmacyclics, TG Therapeutics, AbbVie, AstraZeneca, Celgene, MEI Pharma, Adaptive Biotechnologies, Verastem, Ascentage Pharma, BeiGene, Lilly, Novartis, Takeda, Bristol Myers SquibbResearch Funding: Genentech (Inst), TG Therapeutics (Inst), Pharmacyclics (Inst), Surface Oncology (Inst), MEI Pharma (Inst), Verastem (Inst), Ascentage Pharma (Inst), AstraZeneca (Inst), Novartis (Inst)Travel, Accommodations, Expenses: TG Therapeutics, Janssen, AbbVie, BeiGene, Genentech Richard R. FurmanHonoraria: Janssen, AstraZeneca, Pharmacyclics, Janssen Biotech, Genentech/Roche, Loxo, TG Therapeutics, Verastem, Acerta Pharma, AstraZeneca, Beigene, Incyte, OncoTracker, AbbVie, MorphoSys, SanofiResearch Funding: Acerta Pharma, TG TherapeuticsExpert Testimony: AbbVie, Janssen OncologyTravel, Accommodations, Expenses: TG Therapeutics, Janssen OncologyOther Relationship: Incyte, Janssen Biotech Steven P. TreonHonoraria: Abbvie/Pharmacyclics, Janssen Oncology, BeiGeneConsulting or Advisory Role: Janssen, Pharmacyclics, Beigene, X4 Pharmaceuticals, Bristol Myers SquibbResearch Funding: Pharmacyclics, Bristol Myers Squibb (Inst), X4 Pharmaceuticals (Inst), Lilly (Inst), Beigene (Inst), AbbVie (Inst)Patents, Royalties, Other Intellectual Property: My institution holds patents related to use of MYD88 and CXCR4 testing for which a predetermined financial distribution to the laboratory and individuals is provided. I have not received any income to this date related to these patents (Inst)Travel, Accommodations, Expenses: Janssen OncologyOther Relationship: Janssen, Pharmacyclics, BeigeneNo other potential conflicts of interest were reported.

MYD88 and CXCR4 mutations are common in Waldenström macroglobulinemia (WM). Mutated CXCR4 (CXCR4Mut) impacts BTK-inhibitor response. We conducted a phase 1 trial of the CXCR4-antagonist ulocuplumab with ibrutinib in this first-ever study to target CXCR4Mut in WM. Ibrutinib was initiated at 420 mg/d with cycle 1 and continued until intolerance or progression; ulocuplumab was given cycles 1 to 6, with a 3 + 3 dose-escalation design. Each cycle was 4 weeks. Thirteen symptomatic patients, of whom 9 were treatment-naive patients were enrolled. Twelve were evaluable for response. At best response, their median serum immunoglobulin M declined from 5574 to 1114 mg/dL; bone marrow disease decreased from 65% to 10%, and hemoglobin increased from 10.1 to 14.2 g/dL (P < .001). The major and VGPR response rates were 100% and 33%, respectively, with VGPRs observed at lower ulocuplumab dose cohorts. Median times to minor and major responses were 0.9 and 1.2 months, respectively. With a median follow-up of 22.4 months, the estimated 2-year progression-free survival was 90%. The most frequent recurring grade ≥2 adverse events included reversible thrombocytopenia, rash, and skin infections. Ulocuplumab dose-escalation did not impact adverse events. The study demonstrates the feasibility of combining a CXCR4-antagonist with ibrutinib and provides support for the development of CXCR4-antagonists for CXCR4Mut WM. This trial was registered at www.clinicaltrials.gov as #NCT03225716., (© 2021 by The American Society of Hematology.)

Ibrutinib is associated with durable responses in patients with Waldenström macroglobulinaemia (WM). We hypothesized that response depth is predictive of progression-free survival (PFS) in WM patients treated with ibrutinib. Using landmark analyses, we evaluated response depth in two cohorts of WM patients treated with ibrutinib monotherapy. The learning cohort was composed of 93 participants from two clinical trials, and the validation cohort of 190 consecutive patients treated off clinical trial. Rates of partial response (PR) or better at six months in learning and validation cohorts were 64% and 71% respectively (P = 0·29). In the learning cohort, three-year PFS rates for patients who attained PR or better at six months versus not were 81% and 57% respectively (P = 0·009). In the validation cohort, three-year PFS rates for patients who attained PR or better at six months versus not were 83% and 54% respectively (P = 0·008). In multivariate analyses, attaining PR or better at six months was associated with superior PFS in the learning [hazard ratio (HR) 0·38; P = 0·01] and validation cohorts (HR 0·18; P = 0·004). Attaining PR at six months on ibrutinib emerges as an intermediate outcome of interest and should be validated as surrogate for PFS in clinical trials evaluating Bruton tyrosine kinase inhibitors in WM., (© 2020 British Society for Haematology and John Wiley & Sons Ltd.)

Proteasome inhibition is a standard of care for the primary treatment of patients with Waldenström macroglobulinemia (WM). We present the long-term follow-up of a prospective, phase II clinical trial that evaluated the combination of ixazomib, dexamethasone, and rituximab (IDR) in 26 treatment-naive patients with WM. IDR was administered as 6 monthly induction cycles followed by 6 every-2-month maintenance cycles. The MYD88 L265P mutation was detected in all patients, and CXCR4 mutations were detected in 15 patients (58%). The median time to response (TTR) and time to major response (TTMR) were 2 and 6 months, respectively. Patients with and without CXCR4 mutations had median TTR of 3 months and 1 month, respectively (P = .003), and median TTMR of 10 months and 3 months, respectively (P = .31). The overall, major, and very good partial response (VGPR) rates were 96%, 77%, and 19%, respectively. The rate of VGPR in patients with and without CXCR4 mutations were 7% and 36%, respectively (P = .06). The median progression-free survival (PFS) was 40 months, the median duration of response (DOR) was 38 months, and the median time to next treatment (TTNT) was 40 months. PFS, DOR, and TTNT were not affected by CXCR4 mutational status. The safety profile was excellent with no grade 4 adverse events or deaths to date. IDR provides a safe and effective frontline treatment option for symptomatic patients with WM. This study was registered at www.clinicaltrials.gov as #NCT02400437., (© 2020 by The American Society of Hematology.)

Ibrutinib is highly active in Waldenström macroglobulinaemia (WM) patients, but disease progression can occur due to acquired mutations in BTK, the target of ibrutinib, or PLCG2, the protein downstream of BTK. However, not all resistant patients harbour these alterations. We have performed a whole-exome sequencing study to identify alternative molecular mechanisms that can drive ibrutinib resistance. Our findings include deletions on chromosomes 6q, including homozygous deletions, and 8p, which encompass key regulators of BTK, MYD88/NF-κB, and apoptotic signalling. Moreover, we have identified recurring mutations in ubiquitin ligases, innate immune signalling, and TLR/MYD88 pathway regulators in ibrutinib-resistant WM patients., (© 2020 British Society for Haematology and John Wiley & Sons Ltd.)

Cases of non-IgM lymphoplasmacytic lymphoma (LPL) are rare. We performed a case-control study comparing features and outcomes of 31 non-IgM LPL cases and 93 Waldenström macroglobulinemia (WM) controls matched by age, sex, and year of diagnosis. Odds of MYD88 mutations were lower (odds ratio (OR) 0.22, p  = .05), and median time to treatment was shorter in cases than in controls (4 vs. 32 months; p  < .001). Odds of extramedullary disease were higher (OR 4.20, p  = .01), while odds of neuropathy (OR 0.22, p  = .25), and hyperviscosity (OR 0.26, p  = .26) were lower in cases than in controls. Odds of using chemoimmunotherapy were higher (OR 2.62, p  = .11) while odds of using proteasome inhibitors (OR 0.35, p  = .15) and BTK inhibitors (OR 0.17, p  = .21) were lower in cases than in controls. There were no differences in response and overall survival (OS) between cases and controls. Despite clinicopathological differences, response, and survival outcomes are similar between non-IgM LPL cases and WM controls.

Rituximab-containing regimens are commonly used for frontline therapy in patients with symptomatic Waldenström macroglobulinemia (WM). We had observed that a portion of WM patients experienced deepening of response months to years after therapy completion. We carried a retrospective study aimed at describing this phenomenon. We gathered baseline data, and responses at end of induction, end of maintenance and best response. Deepening of response was defined as ≥25% decrease in serum IgM achieved at a later time from therapy completion. Of 178 patients included, 116 (65%) received maintenance therapy and 62 (35%) were observed. In patients who received maintenance, 44 (38%) had ≥25% decrease in serum IgM level after the end of maintenance with a median time from end of maintenance to lowest IgM level of 1.6 years (range 0.1-7.9 years). In patients who were observed, 19 (31%) had ≥25% decrease in serum IgM level after the end of induction with a median time from end of induction to lowest IgM level of 1.6 years (range 0.2-5.1 years). Baseline hemoglobin <11.5 g/dL, bone marrow involvement ≥50%, CXCR4 mutations and serum IgM ≥4000 mg/dL were associated with lower odds of deepening of response after therapy completion. Deepening of response was associated with better progression-free survival (PFS; HR 0.46, 95% CI 0.26-0.80; P = .006) and better survival after frontline treatment initiation (SAFTI; HR 0.21, 95% CI 0.06-0.73; P = .01). In conclusion, deepening of response occurs in one third of WM patients after completing rituximab-containing regimens and was associated with better PFS and SAFTI., (© 2019 Wiley Periodicals, Inc.)

Ibrutinib is associated with response rate of 90% and median progression-free survival (PFS) in excess of 5 years in Waldenström macroglobulinaemia (WM) patients. CXCR4 mutations are detected in 30-40% of patients with WM and associate with lower rates of response and shorter PFS to ibrutinib therapy. Both frameshift (CXCR4 FS ) and nonsense (CXCR4 NS ) CXCR4 mutations have been described. The impact of these mutations on outcomes to ibrutinib have not been evaluated in WM patients. We studied consecutive patients with a diagnosis of WM, on ibrutinib therapy, for the presence of CXCR4 FS and CXCR4 NS mutations and evaluated the differences in response and PFS between groups. Of 180 patients, 68 patients (38%) had CXCR4 mutations; 49 (27%) had CXCR4 NS and 19 (11%) had CXCR4 FS mutations. In multivariate models, patients with CXCR4 NS had lower odds of major response (Odds ratio 0·25, 95% confidence interval [CI] 0·12-0·53; P < 0·001) and worse PFS (Hazard ratio 4·02, 95% CI 1·95-8·26; P < 0·001) than patients without CXCR4 mutations. CXCR4 FS was not associated with worse major response or PFS rates than patients without CXCR4 mutations. Our results suggest different response and PFS rates to ibrutinib for WM patients with CXCR4 NS and CXCR4 FS , and advocate in favour of CXCR4 mutational testing as well as CXCR4-directed therapy., (© 2019 British Society for Haematology and John Wiley & Sons Ltd.)

Little is known about TP53 mutations in Waldenström Macroglobulinaemia (WM). We evaluated 265 WM patients for TP53 mutations by next-generation sequencing, and validated the findings by Sanger sequencing. TP53 mutations were identified and validated in 6 (2·6%) patients that impacted the DNA-binding domain. All six were MYD88- and CXCR4-mutated. Ibrutinib showed activity in patients carrying all three mutations. With a median follow-up of 18 months, 2 (33%) with biallelic TP53 inactivation died of progressive disease. TP53 mutations are rare in WM, and associate with MYD88 and CXCR4 mutations. WM patients with TP53 mutations show response to ibrutinib., (© 2018 British Society for Haematology and John Wiley & Sons Ltd.)

Activating MYD88 mutations are present in 95% of Waldenström macroglobulinemia (WM) patients, and trigger NF-κB through BTK and IRAK. The BTK inhibitor ibrutinib is active in MYD88- mutated (MYD88 MUT ) WM patients, but shows lower activity in MYD88 wild-type ( MYD88 WT ) disease. MYD88 WT patients also show shorter overall survival, and increased risk of disease transformation in some series. The genomic basis for these findings remains to be clarified. We performed whole exome and transcriptome sequencing of sorted tumor samples from 18 MYD88 WT patients and compared findings with WM patients with MYD88 MUT disease. We identified somatic mutations predicted to activate NF-κB ( TBL1XR1 , PTPN13, MALT1 , BCL10 , NFKB2 , NFKBIB , NFKBIZ, and UDRL1F ), impart epigenomic dysregulation ( KMT2D , KMT2C, and KDM6A) , or impair DNA damage repair ( TP53 , ATM , and TRRAP ). Predicted NF-κB activating mutations were downstream of BTK and IRAK, and many overlapped with somatic mutations found in diffuse large B-cell lymphoma. A distinctive transcriptional profile in MYD88 WT WM was identified, although most differentially expressed genes overlapped with MYD88 MUT WM consistent with the many clinical and morphological characteristics that are shared by these WM subgroups. Overall survival was adversely affected by mutations in DNA damage response in MYD88 WT WM patients. The findings depict genomic and transcriptional events associated with MYD88 WT WM and provide mechanistic insights for disease transformation, decreased ibrutinib activity, and novel drug approaches for this population., (© 2018 by The American Society of Hematology.)