Patients with Waldenström macroglobulinemia (WM) lacking activating mutations in the MYD88 gene (MYD88WT) have demonstrated relatively poor outcomes to ibrutinib monotherapy, with no major responses reported in a phase 2 pivotal study. Zanubrutinib is a novel, selective Bruton tyrosine kinase (BTK) inhibitor designed to maximize BTK occupancy and minimize off-target activity. The ASPEN study consisted of a randomized comparison of zanubrutinib and ibrutinib efficacy and safety in patients with WM who have the MYD88 mutation, as well as a separate cohort of patients without MYD88 mutation (MYD88WT) or with unknown mutational status who received zanubrutinib. Results from the latter single-arm cohort are reported herein. Efficacy endpoints included overall, major and complete (CR) or very good partial response (VGPR) rates, progression-free survival (PFS), duration of response (DOR), and overall survival (OS). Twenty-eight patients (23 relapsed/refractory; 5 treatment-naïve) were enrolled, including 26 with centrally confirmed MYD88WT disease and 2 with unknown MYD88 mutational status. At a median follow-up of 17.9 months, 7 of 26 MYD88WT patients (27%) had achieved a VGPR and 50% a major response (partial response or better); there were no CRs. At 18 months, the estimated PFS and OS rates were 68% and 88%, respectively, while the median DOR had not been reached. Two patients discontinued zanubrutinib due to adverse events. Treatment-emergent hypertension, atrial fibrillation, and major hemorrhages were reported in 3, 1 and 2 patients (including 1 concurrent with enoxaparin therapy), respectively. Results of this substudy demonstrate that zanubrutinib monotherapy can induce high quality responses in patients with MYD88WT WM. This trial is registered on www.clinicaltrials.gov as NCT #03053440.

7521 Background: ASPEN is a randomized, open-label, phase 3 study comparing ZANU, a potent and selective Bruton tyrosine kinase inhibitor (BTKi), with the first-generation BTKi IBR in patients with WM. We present data with a median follow-up of 43 months. Methods: Patients with MYD88 mutations were assigned to cohort 1 and randomized 1:1 to receive ZANU 160 mg twice daily or IBR 420 mg once daily. Randomization was stratified by CXCR4 mutational status and lines of prior therapy (0 vs 1-3 vs > 3). Patients without MYD88 mutations were assigned to cohort 2 and received ZANU 160 mg twice daily. The primary endpoint was proportion of patients achieving complete response or very good partial response (CR+VGPR). Results: A total of 201 patients (ZANU arm, n = 102; IBR arm, n = 99) were enrolled in cohort 1 and 28 patients were enrolled in cohort 2. A larger proportion of patients in the ZANU arm of cohort 1 vs IBR had CXCR4 mutations by next-generation sequencing (32% vs 20%, or 33 of 98 vs 20 of 92 with data available) and were aged > 75 years (33% vs 22%). Median duration of treatment was 42 months (ZANU) and 41 months (IBR), with 67% and 58% remaining on treatment, respectively. The CR+VGPR rate by investigator was 36% with ZANU vs 22% with IBR ( p= 0.02) in cohort 1, and 31% in cohort 2. One patient achieved CR (cohort 2). In patients with wild type or mutant CXCR4 from cohort 1, CR+VGPR rates with ZANU vs IBR were 45% vs 28% ( p= 0.04) and 21% vs 5% ( p= 0.15) , respectively. Median progression-free survival and overall survival were not yet reached. Rates of atrial fibrillation, diarrhea, hypertension, localized infection, hemorrhage, muscle spasms, pneumonia, and adverse events leading to discontinuation or death were lower with ZANU vs IBR (Table). Exposure-adjusted incidence rates of atrial fibrillation/flutter and hypertension were lower with ZANU vs IBR (0.2 vs 0.8 and 0.5 vs 1.0 persons per 100 person-months, respectively; p< 0.05). Rate of neutropenia was higher and rate of grade ≥3 infection was lower with ZANU vs IBR. Safety outcomes of ZANU were similar between cohorts 1 and 2. Conclusions: ASPEN is the largest phase 3 trial with head-to-head BTKi comparison in WM. At a median follow-up of 43 months, ZANU was associated with higher CR+VGPR rate and demonstrated clinically meaningful advantages in long-term safety and tolerability vs IBR. Clinical trial information: NCT03053440. [Table: see text]

Parsaclisib, a potent, highly selective, next-generation PI3Kd inhibitor, was evaluated as monotherapy in CITADEL-202 (NCT02998476), an open-label, multicenter, phase 2 study in patients with relapsed or refractory diffuse large B-cell lymphoma. Patients enrolled into 2 groups (A, Bruton tyrosine kinase [BTK] inhibitor naïve, n ¼ 55; B, BTK inhibitor experienced, n ¼ 5) received oral parsaclisib 20 mg once daily for 8 weeks, then 20 mg once weekly while deriving benefit. The futility boundary was crossed at the interim analysis of Group A, resulting in a negative study. Parsaclisib monotherapy demonstrated an objective response rate (ORR) of 25.5% (8 complete metabolic responses/6 partial metabolic responses) and a median duration of response of 6.2 months. ORR in Group B was 20.0% (1 complete metabolic response). Parsaclisib monotherapy demonstrated manageable toxicities with no new safety signals reported. Further evaluation of parsaclisib in combination with standard therapies and active investigational agents is underway.

8007 Background: Bruton tyrosine kinase (BTK) inhibition is an emerging standard of care for WM. ASPEN is a randomized phase 3 study comparing zanubrutinib (ZANU), a potent and selective BTK inhibitor, versus ibrutinib (IBR), a first generation BTK inhibitor, in WM patients. Methods: Patients with WM and MYD88 mutation were randomly assigned 1:1 to receive ZANU (160 mg twice daily) or IBR (420 mg once daily). Patients without MYD88 mutations were assigned to a separate cohort, received ZANU, and are reported separately. Randomization was stratified by CXCR4 mutational status and the number of lines of prior therapy (0 vs 1-3 vs >3). The primary end point was the proportion of patients achieving a complete response or very good partial response (CR+VGPR). Sample size was calculated to provide 81% power to detect a difference in CR+VGPR rate of 35% vs 15% in the subset of patients with relapsed or refractory (R/R) WM. Primary analysis was planned to occur at ~12 months after last patient enrolled. Results: In total, 201 patients were randomized from Jan 2017 to Jul 2018. The treatment groups were well balanced for important baseline factors, except in the ZANU arm there were more elderly patients (aged >75 years, 33.3% vs 22.2%) and more anemia (hemoglobin ≤110 g/L, 65.7% vs 53.5%). At a median follow-up of 19.4 months, the rate of CR+VGPR was 28.4% vs 19.2% with ZANU vs IBR, respectively (2-sided P=0.09). Rates of atrial fibrillation, contusion, diarrhea, edema peripheral, hemorrhage, muscle spasms, pneumonia, and adverse events (AEs) leading to discontinuation or death were lower with ZANU. The rate of neutropenia was higher with ZANU (Table); however, grade ≥ 3 infection rates were similar (17.8% vs 19.4%). Conclusions: ASPEN is the largest phase 3 trial of BTK inhibitors in WM and the first head-to-head comparison of BTK inhibitors in any disease. Although not statistically significant, ZANU was associated with a higher CR+VGPR response rate, and demonstrated clinically meaningful advantages in safety and tolerability compared to IBR. Clinical trial information: NCT03053440 . [Table: see text]

Introduction R-mini-CHOP is an established standard of care in elderly patients with DLBCL, with a 2yr OS of 59% and PFS of 47% (Peyrade et al, Lancet Oncol 2011). The addition of ibrutinib to full dose R-CHOP in younger pts with DLBCL has efficacy, but significant toxicity limits the ability to complete therapy in pts ≥60 yrs (Younes et al, JCO 2019). We previously demonstrated the deliverability of ibrutinib with R-mini-CHOP in 80 pts ≥75yrs with DLBCL with a median average relative total dose of 97%; 77% of pts received 6 cycles of R-mini-CHOP despite SAEs in 62% (Verner et al, Haematol Oncol 2019). Here we present the primary efficacy endpoint and key secondary and exploratory endpoints. Methods This was a prospective, multicenter, single-arm, phase 2 study of patients aged ≥75yrs with newly diagnosed DLBCL. Pts received six 21-day cycles of ibrutinib 560mg/d and R-mini-CHOP (Rituximab 375mg/m 2, cyclophosphamide 400mg/m 2, doxorubicin 25mg/m 2, vincristine 1mg on day 1 & prednisone 40mg/m 2 or 100mg/d x 5) followed by an additional two 21-day cycles of rituximab + ibrutinib (or high dose methotrexate for CNS prophylaxis). The efficacy primary endpoint was 2yr OS. Sample size calculations were made using a one-sample two-sided approach to detect a 15% improvement on the fixed reference OS (59%) and PFS (47%) rates (Peyrade et al, Lancet Oncol 2011). Results Eighty pts were recruited from Nov 2015 to Dec 2018. One died prior to receiving treatment and is not included in the analysis. Median age was 82yrs (75-95); 51% female, 81% stage III/IV and 63% IPI 3-5: 47% had a CIRS-G score of ≥6 (range 0-17). On centralized immunohistochemistry (IHC), 57% (45/79) were non-Germinal Centre B cell-like (GCB) subtype; 43% (34/79) were GCB. At a data cut-off of 6June 21, median follow-up was 29.5 months (m) (0.2 to 66.3). Two-year OS was 68% (95% CI 55-77%), not differing significantly from the null hypothesis of 59% (p=0.10), (Figure 1A). Median OS was not reached (NR) (95% CI 34m to NR), and was longer in those with lower IPI (IPI 1-3: NR, IPI 4: 35m, IPI 5: 19m). Two-year PFS was 60% (95% CI 47-70%), significantly different from the reference 47% (p&lt;0.03), (Figure 1B). Median PFS was NR (95% CI 20m to NR). Two-year DFS was 85% (95% CI 60-95%), median NR (95% CI 32m to NR). COO had no impact on either 2yr OS [median GCB NR (95% CI 29m to NR), median non-GCB NR (95% CI 24m to NR) p=0.99] or 2yr PFS [median GCB 39m (95% CI 17m to NR), median non-GCB NR (95% CI 19m to NR) p=0.97]. Cause of death in 28/79 pts (35%) was: 16 progressive lymphoma, 5 infection, 2 respiratory failure, 2 other malignancy, 1 cardiac arrest, 1 intra-abdominal hemorrhage, 1 gastric hemorrhage. At least one adverse event (AE) occurred in 99% pts (78/79): 30% (24/79) grade 1-2, 64% (49/79) grade 3-4, and 6% (5/79) grade 5. Most common grade ≥3 AEs were lung infection (13%), other infections (11%), anemia (11%), febrile neutropenia (9%), thrombocytopenia (9%), and atrial fibrillation (8%). Serious AEs occurred in 67%: most commonly lung infection (11%), atrial fibrillation (9%), fever (9%), and other infection (9%). 12/14 pts with atrial fibrillation/flutter were new onset. Ibrutinib was temporarily ceased in 62% of patients, and permanently ceased in 25%, mostly due to adverse events. As previously reported, the overall response rate on an intention to treat basis was 57/80 (71%) (Verner et al, ASH 2019). Response rates did not differ by cell of origin (COO) (ORR: non-GCB 76%, GCB 68% p=0.44). When recorded, pt's EORTC-QLQ-C30 global health status significantly improved between screening [n=78; mean (SD) 58(25)], end of treatment [n=57; 63(23)] and 18mo post-treatment [n=29; 74(19)] p=0.007. Significant reductions in fatigue, nausea and vomiting, pain, insomnia, appetite loss, constipation and diarrhea were also observed in respondents. There was no impact of CIRS-G score on disease response rate or risk of death. Conclusion The addition of ibrutinib to R-mini-CHOP was deliverable and improved 2-yr PFS compared to R-mini-CHOP alone. However, while there was a trend towards improvement in 2-yr OS, a target 15% increase was not achieved in this small sample size. Despite considerable and not unexpected toxicity in this elderly cohort, the QOL and functional improvements in survivors are also promising. These data support further study of the addition of ibrutinib to R-mini-CHOP in elderly patients with DLBCL. Figure 1 Figure 1. Disclosures Verner: Janssen-Cilag Pty Ltd: Research Funding. Hawkes: Merck KgA: Research Funding; Bristol Myers Squib/Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Specialised Therapeutics: Consultancy; Antigene: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Janssen: Speakers Bureau; Gilead: Membership on an entity's Board of Directors or advisory committees; Regeneron: Speakers Bureau; Merck Sharpe Dohme: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees, Other: Travel and accommodation expenses, Research Funding, Speakers Bureau; Astra Zeneca: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Lee: Roche: Honoraria; BeiGene: Membership on an entity's Board of Directors or advisory committees. Cheah: BMS: Consultancy, Research Funding; Abbvie: Research Funding; Janssen: Consultancy, Honoraria; MSD: Consultancy, Honoraria; Gilead: Consultancy, Honoraria; Ascentage Pharma: Consultancy, Honoraria; AstraZeneca: Consultancy, Honoraria; Lilly: Consultancy, Honoraria; TG therapeutics: Consultancy, Honoraria; Beigene: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Roche: Consultancy, Honoraria, Other: travel, Research Funding. Purtill: Novartis: Honoraria; Gilead: Honoraria; BMS Celgene: Honoraria. Enjeti: Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Speakers Bureau; AbbVie: Honoraria; Sanofi: Honoraria; Astra Zeneca: Honoraria. Curnow: Bayer: Consultancy, Research Funding; Pfizer/BMS: Consultancy, Honoraria; Mylan: Consultancy; Norgine: Consultancy, Honoraria. Butcher: WriteSource: Current Employment, Other: Medical writing for Pharma companies. Not pertinent to this abstract for which author is study Statisticiam. Trotman: JANSSEN: Research Funding; TAKEDA: Research Funding; BMS: Research Funding; PCYC: Research Funding; roche: Research Funding; beigene: Research Funding. OffLabel Disclosure: Ibrutinib is not approved for use in DLBCL