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Chronic lymphocytic leukemia (CLL), the most common leukemia worldwide, is associated with increased COVID-19 mortality. Previous studies suggest only a proportion of vaccinated CLL patients develop SARS-CoV-2 spike antibodies. Whether the elicited antibodies are functional and/or accompanied by functional T-cell responses is unknown. This prospective cohort study (NCT05007860) included patients with CLL who received SARS-CoV-2 and PCV13 vaccines (not concurrently). The primary cohort included adults with CLL off therapy. Co-primary outcomes were serologic response to SARS-CoV-2 (receptor binding domain [RBD]-immunoassay) and PCV13 vaccines (23-serotype IgG assay). Characterization of SARS-CoV-2 antibodies and their functional activity and assessment of functional T-cell responses were performed. Sixty percent (18/30) of patients demonstrated serologic responses to SARS-CoV-2 vaccination, appearing more frequent among treatment-naïve patients (72%). Among treatment-naïve patients, an absolute lymphocyte count ≤24,000/uL was associated with serologic response (94% vs 14%, p<0.001). On interferon gamma release assays, 80% (16/20) of patients had functional spike-specific T-cell responses, including 78% (7/9) with a negative RBD-immunoassay, a group enriched for prior B-cell depleting therapies. A bead-based multiplex immunoassay identified antibodies against wildtype and variant SARS-CoV-2 (alpha, beta, gamma, and delta) in all tested patients, and confirmed Fc-receptor binding and effector functions of these antibodies. Of 11 patients with negative RBD-immunoassay post-vaccination, 6 (55%) responded to an additional mRNA-based vaccine dose. The PCV13 serologic response rate was 29% (8/28). Our data demonstrate that SARS-CoV-2 vaccination induces functional T-cell and antibody responses in CLL patients and provides the framework for investigating the molecular mechanisms and clinical benefit of these responses. This trial is registered at www.clinicaltrials.gov as NCT05007860.

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Background: Venetoclax (Ven; BH3 mimetic) and Obinutuzumab (O; CD20 antibody) is an approved, fixed-duration regimen (one year) that induces undetectable minimum residual disease (uMRD) and durable remissions in treatment naïve patients (pts) with chronic lymphocytic leukemia (CLL; Fischer NEJM 2019). In the CLARITY trial of venetoclax-ibrutinib (BTK inhibitor; BTKi) in relapsed or refractory CLL, peripheral blood (PB) MRD response kinetics predicted bone marrow (BM) uMRD and were associated with progression-free survival (Rawstron EHA 2020). We explored MRD as a biomarker to direct treatment duration in an investigator-initiated phase 2 trial of Zanubrutinib (BTKi) and O-Ven (BOVen). We hypothesize that early MRD kinetics will identify a defined cohort of pts with delayed BM MRD clearance, and early recurrent detectable MRD after discontinuation of treatment in pts attaining uMRD. Methods: In this multicenter, phase 2 trial (NCT03824483), eligible pts had previously untreated CLL requiring treatment (iwCLL), ECOG PS ≤2, absolute neutrophil count (ANC) ≥1,000/ul, platelets (PLT) ≥75,000/ul (ANC ≥0/ul, PLT ≥20,000/ul if due to CLL). Informed consent was obtained from all pts. BOVen was administered in 28-day (D) cycles (C): Zanubrutinib 160 mg by mouth (PO) twice daily starting D1; Obinutuzumab 1000 mg IV D1 (split D1-2 if lymphocyte count ≥25,000/ul or lymph node ≥5cm), D8, D15 of C1, and D1 of C2-8; Venetoclax ramp up initiated C3D1 (target 400 mg PO daily). MRD was evaluated by flow cytometry (MRD-FC) and immunosequencing (MRD-IS; Adaptive ClonoSEQ) with uMRD defined as ≤10 -4 for flow and ≤10 -5 for IS. Treatment consisted of 8-24 cycles with duration determined by prespecified MRD criteria. Beginning on C7D1 then every 2 cycles, pts with PB uMRD-FC had BM within 14 days. If BM uMRD, PB MRD was repeated after two additional cycles. Pts with confirmed uMRD-FC in PB and BM discontinued therapy and entered posttreatment surveillance. Response was assessed per iwCLL. Adverse events (AE) were assessed per CTCAE v5. MRD-IS failure free survival (FFS) was calculated from end-of-treatment (EOT) to the date of detectable MRD-IS (≥10 -5) using the Kaplan-Meier method. Results: The study accrued 39 pts (03/19-10/19): median age 59 years (23-73), 3:1 male predominance, 28/39 (72%) IGHV unmutated, 5/39 (12.8%) del(17p)/TP53M. All pts were evaluable for toxicity with 37 evaluable for efficacy. At a median follow up of 26+ months (mo; 4.5-30.5+), 95% (35/37) pts achieved uMRD-FC in PB, among whom 33 (94%) also achieved uMRD-IS. BM uMRD-FC was seen in 89% (33/37) at a median time of 8 mo (6-16), all of whom met prespecified MRD criteria and discontinued therapy after a median of 10 mo (8-18). Three pts discontinued therapy with persistent detectable BM MRD after 24 cycles. The most common AEs were neutropenia (51%), thrombocytopenia (44%), diarrhea (44%), infusion related reaction (41%) and bruising (41%). The most common grade ≥3 AE was neutropenia (15%). No laboratory or clinical TLS occurred (Howard definition). A ≥400-fold reduction in PB MRD-IS after 4 cycles (ΔMRD400) was selected using the Youden Index and was highly predictive of attaining BM uMRD in ≤8mo (sensitivity 88% [21/24], specificity 100% [11/11], PPV 100% [21/21], NPV 79% [11/14]. As a result, the median duration of therapy was shorter among patients who achieved ΔMRD400 (8 vs 13 mo). Of 33 pts who met prespecified uMRD criteria and stopped therapy, 31 (94%) remain uMRD-FC following a median 15 mo (0-20) from EOT, and 2 pts had recurrent MRD (1 with PD recaptured PB uMRD with retreatment). Of 33 pts who discontinued therapy after achieving the prespecified MRD endpoint, MRD-IS was evaluated every 3 months in 31 pts for a median of 12 mo (range, 3-18) from EOT. MRD-IS FFS was longer in pts who achieved ΔMRD400 (log rank p<0.001; Figure) despite shorter treatment duration. We did not observe differences in posttreatment MRD kinetics based on IGHV status or high-risk genetics. Conclusion: BOVen achieved frequent, durable uMRD. All pts completed therapy (median 10 mo treatment), including 89% (33/37) who met the prespecified PB/BM uMRD endpoint. With a median posttreatment follow-up of 15 mo, 31 (94%) remain uMRD-FC. ΔMRD400 identified a cohort of pts (40%) with delayed BM MRD clearance and earlier MRD recurrence, despite longer treatment duration. ΔMRD400 warrants further study as a predictive biomarker for treatment duration. Figure 1 Figure 1. Disclosures Soumerai: Seattle Genetics: Consultancy; AstraZeneca: Consultancy; BeiGene: Consultancy, Research Funding; BMS: Consultancy; Adaptive Biotechnologies: Consultancy, Research Funding; AbbVie: Consultancy; TG Therapeutics: Consultancy, Research Funding; BostonGene: Research Funding; GlaxoSmithKline: Research Funding. Mato: Janssen: Consultancy, Research Funding; LOXO: Consultancy, Research Funding; Johnson and Johnson: Consultancy, Research Funding; Acerta/AstraZeneca: Consultancy, Research Funding; DTRM BioPharma: Consultancy, Research Funding; Genmab: Research Funding; AstraZeneca: Consultancy; MSKCC: Current Employment; Genentech: Consultancy, Research Funding; Sunesis: Consultancy, Research Funding; Nurix: Research Funding; AbbVie: Consultancy, Research Funding; Adaptive Biotechnologies: Consultancy, Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; TG Therapeutics: Consultancy, Other: DSMB, Research Funding; BeiGene: Consultancy, Research Funding. Dogan: Seattle Genetics: Consultancy; Peer View: Honoraria; Takeda: Consultancy, Research Funding; Roche: Consultancy, Research Funding; Physicians' Education Resource: Honoraria; EUSA Pharma: Consultancy. Joffe: Epizyme: Consultancy; AstraZeneca: Consultancy. Hochberg: Leuko: Consultancy; Intervention Insights: Consultancy. Abramson: Bluebird Bio: Consultancy; Morphosys: Consultancy; Bristol-Myers Squibb Company: Consultancy, Research Funding; Kymera: Consultancy; BeiGene: Consultancy; Novartis: Consultancy; C4 Therapeutics: Consultancy; Genmab: Consultancy; EMD Serono: Consultancy; Kite Pharma: Consultancy; Incyte Corporation: Consultancy; Astra-Zeneca: Consultancy; Allogene Therapeutics: Consultancy; Seagen Inc.: Research Funding; AbbVie: Consultancy; Karyopharm: Consultancy; Genentech: Consultancy. Batlevi: TouchIME: Honoraria; BMS: Current holder of individual stocks in a privately-held company; Medscape: Honoraria; GLG Pharma: Consultancy; Dava Oncology: Honoraria; Kite Pharma: Consultancy; Juno/Celgene: Consultancy; ADC Therapeutics: Consultancy; Life Sciences: Consultancy; Moderna: Current holder of individual stocks in a privately-held company; Regeneron: Current holder of individual stocks in a privately-held company; Viatris: Current holder of individual stocks in a privately-held company; Pfizer: Current holder of individual stocks in a privately-held company; Karyopharm: Consultancy; TG Therapeutics: Consultancy; Memorial Sloan Kettering Cancer Center: Current Employment; Seattle Genetics: Consultancy; Bayer: Research Funding; Xynomic: Research Funding; Roche/Genentech: Research Funding; Novartis: Research Funding; Epizyme: Research Funding; Janssen: Research Funding; Autolus: Research Funding. Matasar: Rocket Medical: Consultancy, Research Funding; Merck Sharp & Dohme: Current holder of individual stocks in a privately-held company; Juno Therapeutics: Consultancy; Merck: Consultancy; Genentech, Inc.: Consultancy, Honoraria, Research Funding; Bayer: Consultancy, Honoraria, Research Funding; IGM Biosciences: Research Funding; GlaxoSmithKline: Honoraria, Research Funding; F. Hoffmann-La Roche Ltd: Consultancy, Honoraria, Research Funding; Memorial Sloan Kettering Cancer Center: Current Employment; Teva: Consultancy; TG Therapeutics: Consultancy, Honoraria; Pharmacyclics: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Takeda: Consultancy, Honoraria; Seattle Genetics: Consultancy, Honoraria, Research Funding; ImmunoVaccine Technologies: Consultancy, Honoraria, Research Funding; Daiichi Sankyo: Consultancy. Noy: Rafael Parhma: Research Funding; Morphosys: Consultancy; Targeted Oncology: Consultancy; Medscape: Consultancy; Pharmacyclics: Consultancy, Research Funding; Janssen: Consultancy, Honoraria; Epizyme: Consultancy. Palomba: Ceramedix: Honoraria; Seres: Honoraria, Other: Stock, Patents & Royalties, Research Funding; Notch: Honoraria, Other: Stock; Novartis: Consultancy; Kite: Consultancy; PCYC: Consultancy; BeiGene: Consultancy; Lygenesis: Honoraria; Nektar: Honoraria; Juno: Patents & Royalties; Wolters Kluwer: Patents & Royalties; Rheos: Honoraria; Magenta: Honoraria; Pluto: Honoraria; WindMIL: Honoraria; Priothera: Honoraria. Kumar: Abbvie Pharmaceuticals: Research Funding; Pharmacyclics: Research Funding; Kite Pharmaceuticals: Other: advisory board , Research Funding; Celgene: Honoraria, Other: advisory board, Research Funding; Astra Zeneca: Honoraria, Other: Advisory Board, Research Funding; Adaptive Biotechnologies, Celgene, Abbvie Pharmaceticals, Pharmacyclics, Seattle Genetics: Research Funding; Seattle Genetics: Research Funding. Roeker: AbbVie, AstraZeneca, Janssen, LOXO, Pharmacyclics, TG Therapeutics, Vaniam Group, Verastem: Consultancy; Pfizer: Consultancy, Research Funding; Pharmacyclics: Consultancy; TG Therapeutics: Consultancy; Loxo Oncology: Consultancy; Abbot Laboratories: Current equity holder in publicly-traded company. Thompson: VJHemOnc: Honoraria; MJH Life Sciences: Honoraria; Curio Science: Honoraria. Roshal: Physicians' Education Resource: Other: Provision of services; Auron Therapeutics: Other: Ownership / Equity interests; Provision of services; Celgene: Other: Provision of services. Huang: BeiGene: Current Employment, Current equity holder in publicly-traded company, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company, Divested equity in a private or publicly-traded company in the past 24 months, Other: Travel, Accommodations, Expenses; Protara Therapeutics: Current holder of individual stocks in a privately-held company, Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company). Biondo: Roche: Current holder of individual stocks in a privately-held company; Genentech, Inc.: Current Employment. Wu: Genentech, Inc.: Current Employment; Roche/GNE: Current equity holder in publicly-traded company, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company. Jacob: Adaptive Biotechnologies: Current Employment. Abdel-Wahab: H3B Biomedicine: Consultancy, Research Funding; Foundation Medicine Inc: Consultancy; Merck: Consultancy; Prelude Therapeutics: Consultancy; LOXO Oncology: Consultancy, Research Funding; Lilly: Consultancy; AIChemy: Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees; Envisagenics Inc.: Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees. Zelenetz: Novartis: Honoraria; Genentech/Roche: Honoraria, Research Funding; BMS/Celgene/JUNO: Honoraria, Other; AstraZeneca: Honoraria; MethylGene: Research Funding; Pharmacyclics: Honoraria; Amgen: Honoraria; MEI Pharma: Honoraria, Research Funding; Gilead: Honoraria, Research Funding; Verastem: Honoraria; Beigene: Honoraria, Other, Research Funding; Abbvie: Honoraria, Research Funding; SecuraBio: Honoraria; Janssen: Honoraria; Gilead: Honoraria; MorphoSys: Honoraria; NCCN: Other; LFR: Other. OffLabel Disclosure: Zanubrutinib is administered off-label in combination with venetoclax and obinutuzumab for patients with CLL/SLL.

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