Castro, Januario E.

Abstract Background Patients (pts) with aggressive B-cell non-Hodgkin lymphoma (NHL) progressing after anti-CD19 chimeric antigen receptor T (CART) cell therapy have poor prognosis and may benefit from new therapy options through clinical trials. However, in a single center report, only 12% of such pts were treated in trials (Chow et al. Am J Hematol, 2019). Identifying the reasons for this low enrollment is needed to design future studies for this population. Here, we evaluated the eligibility criteria for recent landmark trials for relapsed/refractory aggressive B-cell NHL to learn what eligibility barriers are present. Methods Pts with aggressive B-cell NHL who received FDA-approved CART cell therapy at Mayo Clinic (Rochester, Arizona, Florida) since 2018 and progressed after CART cell therapy were identified. The potential eligibility for the following key trials was evaluated: a) polatuzumab + bendamustine + rituximab, b) tafasitamab + lenalidomide, c) selinexor and d) loncastuximab. The eligibility for each trial was retrospectively assessed at the time of disease progression after CART cell therapy based on hemoglobin (Hb), absolute neutrophils count (ANC), platelet count (Plt), renal and liver function tests, ECOG performance status (PS), and central nervous system (CNS) involvement. Results Seventy-five pts had disease progression to axicabtagene ciloleucel (N=73, 97%) or tisagenlecleucel (N=2, 3%) and are included in this analysis. Median time to progression after CART was 2.1 months (IQR: 1.0 - 3.1). Thirteen (17%) pts were treated in clinical trials after progression following CART cell therapy, while 46 (61%) were treated off trials, and 16 (22%) pts never received any treatment after progression. At a median follow-up of 13.6 months (IQR: 9.1 - 26.7) from CART progression, the median overall survival (mOS) from CART progression was 5.8 months (95% CI 3.5 - 10.1) and 53 (71%) pts died. Thirty-eight pts (51%) did not meet eligibility criteria for any of the 4 recent landmark trials. Hematologic impairment was the most common barrier to inclusion of these patients in clinical trials: Hb < 9 g/dL n=23 (31%) or Hb < 10 g/dL n=36 (48%), ANC < 1.0 x 10 9/L n=19 (25%) or ANC < 1.5 x 10 9/L n=32 (43%), and Plt < 75 x 10 9/L n=30 (40%) or Plt < 90 x 10 9/L n=34 (45%). Renal (n=11, 15%) or liver dysfunction (n=5, 7%), CNS involvement (n=8, 11%) and ECOG PS > 2 (n=3, 4%) were less common reasons leading to exclusion from trials. Post CART trial ineligible pts had significantly shorter time to progression (median 1.7 months, IQR: 1.0 - 2.6 vs. 3.0 months IQR: 1.9 - 3.4, p < 0.01) and inferior overall response to CART (45% vs 67%, p = 0.06) compared to pts who met trial eligibility post CART. Baseline Hb (median Hb 9.5 g/dL, IQR: 8.5 - 10.5 vs. 10.9 g/dL, IQR: 9.7 - 12.2, p < 0.01) and Plt (median Plt 106 x 10 9/L IQR: 54 - 165 vs. 201 x 10 9/L IQR: 141 - 243, p < 0.01) were also significantly lower in pts ineligible for trials post CART. There were no significant differences between pts eligible or ineligible for trials with regards to age (median 59 vs. 60 years), number of prior therapies (median 3 vs. 3), prior autologous stem cell transplant (41% vs. 37%), bridging therapy (65% vs. 63%), baseline ANC (median 4,1 vs. 3,0 x10 9/L), or high-grade (grade ≥ 2) cytokine release syndrome (19% vs. 21%) or neurotoxicity (32%, vs. 42%), respectively. Survival after CART progression was significantly shorter (mOS 2.5 months, 95% CI: 1.6 - 5.1) for the 38 pts ineligible for trials compared to pts eligible for trials (mOS 10.6 months, 95% CI: 8.9 - NA), (p < 0.01). In the 59 pts who received therapy post CART progression, the mOS of pts treated on (n = 13) or off (n = 46) trials was 13.8 months (95% CI: 9.2 - NA) vs. 6.6 months (4.9 - 10.7), respectively (p = 0.047). Conclusion Approximately half of the pts (51%) with aggressive B-cell NHL progressing after CART cell therapy would have be excluded from landmark clinical trials. The current hematologic exclusion criteria are a major barrier to enrollment in clinical trials, which would exclude many pts who have disease progression within 3 months of CART cell therapy (ie, primary refractory disease), in whom cytopenia as a toxicity from therapy is prevalent. Given the known delayed hematologic recovery after CART cell therapy and the unmet need of pts progressing to CART cell therapy, the hematologic exclusion criteria should be adjusted to increase trial participation of this population, especially of those with primary refractory disease. Figure 1 Figure 1. Disclosures Munoz: Gilead/Kite Pharma, Kyowa, Bayer, Pharmacyclics/Janssen, Seattle Genetics, Acrotech/Aurobindo, Beigene, Verastem, AstraZeneca, Celgene/BMS, Genentech/Roche.: Speakers Bureau; Janssen: Research Funding; Pharmacyclics/Abbvie, Bayer, Gilead/Kite Pharma, Pfizer, Janssen, Juno/Celgene, BMS, Kyowa, Alexion, Beigene, Fosunkite, Innovent, Seattle Genetics, Debiopharm, Karyopharm, Genmab, ADC Therapeutics, Epizyme, Beigene, Servier: Consultancy; Seattle Genetics: Research Funding; Millennium: Research Funding; Pharmacyclics: Research Funding; Genentech: Research Funding; Incyte: Research Funding; Portola: Research Funding; Merck: Research Funding; Celgene: Research Funding; Gilead/Kite Pharma: Research Funding; Bayer: Research Funding; Seattle Genetics: Honoraria; Physicians' Education Resource: Honoraria; Targeted Oncology: Honoraria; OncView: Honoraria; Kyowa: Honoraria. Murthy: CRISPR Therapeutics: Research Funding. Maurer: Morphosys: Membership on an entity's Board of Directors or advisory committees, Research Funding; Nanostring: Research Funding; Kite Pharma: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; Genentech: Research Funding; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees. Bennani: Purdue Pharma: Other: Advisory Board; Daichii Sankyo Inc: Other: Advisory Board; Kyowa Kirin: Other: Advisory Board; Vividion: Other: Advisory Board; Kymera: Other: Advisory Board; Verastem: Other: Advisory Board. Paludo: Karyopharm: Research Funding. Wang: Genentech: Research Funding; Incyte: Membership on an entity's Board of Directors or advisory committees, Research Funding; MorphoSys: Research Funding; TG Therapeutics: Membership on an entity's Board of Directors or advisory committees; Eli Lilly: Membership on an entity's Board of Directors or advisory committees; LOXO Oncology: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Research Funding; InnoCare: Research Funding. Ansell: Bristol Myers Squibb, ADC Therapeutics, Seattle Genetics, Regeneron, Affimed, AI Therapeutics, Pfizer, Trillium and Takeda: Research Funding. Witzig: Karyopharm Therapeutics, Celgene/BMS, Incyte, Epizyme: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene/BMS, Acerta Pharma, Kura Oncology, Acrotech Biopharma, Karyopharm Therapeutics: Research Funding. Nowakowski: Celgene, NanoString Technologies, MorphoSys: Research Funding; Celgene, MorphoSys, Genentech, Selvita, Debiopharm Group, Kite/Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees. Lin: Vineti: Consultancy; Takeda: Research Funding; Sorrento: Consultancy; Novartis: Consultancy; Juno: Consultancy; Legend: Consultancy; Janssen: Consultancy, Research Funding; Bluebird Bio: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Merck: Research Funding; Gamida Cell: Consultancy; Kite, a Gilead Company: Consultancy, Research Funding.

Objective/background: Despite the success of chimeric antigen receptor (CAR) T-cell therapy in patients with aggressive non-Hodgkin lymphoma (aNHL), some patients still fail treatment, and their prognosis is dismal. Methods: We performed a retrospective study of aNHL patients treated with axicabtagene ciloleucel (axi-cel) at two Mayo Clinic centers between 2018 and 2020. We evaluated predictive factors, toxicities, and responses to salvage regimens after CAR T-cell therapy. Results: Thirty-four patients received axi-cel with a median length of hospitalization of 14 days. Cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome of any grade occurred in 91% and 41% of patients, respectively. Furthermore, 71% of patients responded to therapy, with 53% achieving a complete response (CR). The CRS grade and absolute lymphocyte count at leukapheresis (ALC Leuk ) correlated with CR and overall survival (OS), respectively. After a median follow-up of 6.8 months (interquartile range [IQR] 4.6–14.9), 15 patients (44%) showed progressive disease (PD). Most patients (60%) progressed during the first 3 months and had persistent CD19 tumor expression. Elevated C-reactive protein at baseline increased the risk of PD, whereas elevated ferritin increased PD and mortality risk. Twelve patients received salvage therapy, but only three responded. Median OS of relapsed/refractory patients to axi-cel was 3 months (IQR 1.3–5.1). Conclusion: The grade of CRS and ALC Leuk correlated with better outcomes to axi-cel therapy. In addition, elevated inflammatory markers at baseline were associated with PD and shorter survival. Relapses after treatment frequently occur within months after axi-cel infusion; they confer a poor prognosis and create an urgent need for novel and effective treatment options in this patient population.

Abstract Usually used in emergency settings, bedside sonographic measurement of optic nerve sheath diameter can aid in diagnosing elevated intracranial pressure. We report a case of a 26-year-old male hospitalized for CAR T-cell therapy with Axicabtagene Ciloleucel for treatment of relapsed diffuse large B-cell lymphoma, who developed progressive symptoms of immune effector cell-associated neurotoxicity syndrome. Fundoscopic examination suggested the presence of blurred optic disc margins. Bedside ocular ultrasound revealed wide optic nerve sheath diameters and bulging optic discs bilaterally. The patient had a ventriculostomy placed for monitoring and received treatment with steroids and mannitol, as well as tocilizumab. After 7 days in the ICU, the patient recovered with no evidence of long-term neurological deficits.

Abstract Ibrutinib-based therapies are costly and require continuous administration. We hypothesized combining BTK inhibition with anti-CD20 monoclonal antibodies would yield deep remissions allowing discontinuation. We enrolled 32 therapy-naïve CLL patients to receive ibrutinib plus obinutuzumab, followed by single-agent ibrutinib. Patients could discontinue ibrutinib after 36 months with sustained complete response (CR). We evaluated treatment safety, efficacy, and outcomes after ibrutinib discontinuation. The overall response rate was 100%, 28% achieved a CR, and 12.5% achieved bone marrow undetectable minimal residual disease. At a three-year median follow-up, 91% remain in remission with 100% overall survival. Five patients in sustained CR stopped ibrutinib and have not progressed. Eight non-CR patients discontinued for other reasons, with only two progressing. The treatment was safe, with a lower IRR rate. All patients responded to treatment with longer time-to-progression after discontinuation of ibrutinib. Our data support the evaluation of ibrutinib discontinuation strategies in more extensive clinical trials.

e14516 Background: IEC are arguably the most promising therapy in oncology, and FDA approvals for CAR T cells are a testament to their real potential. This has led to a great growth of clinical trials (CT), making the evaluation of their associated data increasingly challenging. To facilitate this process, we performed a systematic review of ClinicalTrials.gov focused on IEC therapies in oncology. We performed an analysis of the CT data and forecast trends for 2025. Methods: CT registries were retrieved from ClinicalTrials.gov with a systematic search query. We included CT registered between 1993-2020, which used IEC-based therapies in oncology. Statistical analysis using descriptive and inferential methods allowed us to identify trends and establish forecasts. Results: We identified 938 registrations of IEC-CTs in oncology, and 51% of those were active. The most common IEC type was CAR T (51%), followed by NK (15%), TCR T (8%), TIL (8%), and CIK (3%). 69% of IEC-CTs were aimed at a specific target vs. 31% that lack that specificity. The number of annual CAR T-CTs continue to increase, and we forecast 320 registrations during 2025. Since 2018, the number of CTs using unmodified T cells and TIL has increased (largely due to metastatic melanoma studies). NK cells CTs represent 8% of all registrations, and by 2025 we anticipate that >150 NK-based CTs will be registered per year, a number similar to CAR T-CTs registered during 2020. IEC-CTs based on allogeneic sources represent 18% of all registrations and are expected to grow 2.5 fold in the next 5 years. In solid tumors, the most common IEC-CTs are based on Non-CAR studies, while in hem-malignancies 76% of CTs are CAR T. Only one solid tumor, CAR T-CT, has reached phase 2/3, while 7 CIK-CTs were used to target various organ tumors. Conclusions: IEC-CTs continue to grow exponentially and represent an active field of clinical research in oncology. Allogeneic and NK-CTs increase rapidly and are among the most promising IEC-CTs. A rising proportion of CTs in solid tumors are using CIK and TIL rather than CAR T-cells, which are more popular for treating hem-malignancies. This is a direct reflection of the challenges associated with CAR T infiltration and persistence in solid tumors. Our analyses indicate that annual IEC-CTs registrations will double by 2025. We anticipate the increase in cellular therapy options will demand an organized response, including adequate logistical planning and policy implementation in response to the landscape changes in clinical oncology during the upcoming years.[Table: see text]

7541 Background: FT516 is an investigational, NK cell cancer immunotherapy derived from a clonal master iPSC line. FT516 is engineered with a novel hnCD16 Fc receptor, demonstrated preclinically to maximize antibody-dependent cellular cytotoxicity (Zhu et al. Blood 2020). FT516 can be mass produced and made available off-the-shelf for broad pt access and multi-dose administration. Methods: This is a Phase I trial of FT516 combined with rituximab (R) in pts with R/R BCL. Treatment consists of 2 cycles, each with 3 days lympho-conditioning (fludarabine 30 mg/m 2 and cyclophosphamide 500 mg/m 2 ) and 1 dose of R followed by 3 weekly infusions of FT516 (planned doses 30-900 million/dose) with IL-2 (6 MIU after each FT516 dose). The primary objective is to identify the incidence of dose-limiting toxicity (DLT)/dose cohort and the recommended Phase II dose using a standard 3+3 design. Additional objectives include safety, tolerability, preliminary activity, pharmacokinetics, and immunogenicity. Results: Six pts (5 DLBCL, 1 FL, median age 65.5 y) have completed (5) or discontinued (1) study treatment after the DLT period (data cutoff 9 Dec 2020): 2 received 30 million cells/dose, 3 received 90 million cells/dose, and 1 received 300 million cells/dose. All pts received > 1 prior R-containing regimen, and median number of prior therapies was 3 (range 2-6), including CAR-T in 3 pts. FT516 was primarily administered in the outpatient setting. No FT516-related Grade ≥3 adverse events (AEs) or serious AEs, and no events of cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS), or graft-versus-host disease (GvHD) of any grade were reported. DLT (Grade 4 neutrophil count decreased, not recovered to baseline by D29) was reported in the first pt at 30 million cells/dose and R dosing of 375 mg/m 2 weekly x 4/cycle, resulting in modification of R dosing to once/cycle; no DLTs were observed with modified R dosing. Most common all grade AEs in ≥3 pts: fatigue (4 pts) and decreased appetite, nausea, neutrophil count decreased, and headache (3 pts each). Grade ≥3 AEs in ≥2 pts: neutrophil count decreased (3 pts) and febrile neutropenia and platelet count decreased (2 pts each); none considered related to FT516. Host anti-product B- or T-cell immunogenicity was not observed. Three of 4 pts treated at ≥90 million cells/dose achieved objective response (2 complete responses [CRs] and 1 partial response). Conclusions: Administration of up to 6 doses of FT516 cells, including up to 300 million cells/dose, appears to be safe and tolerable, without CRS, ICANS, or GvHD. Activity was observed, including CRs, in heavily pretreated pts. Dose escalation is ongoing. Updated clinical and translational data will be presented. Clinical trial information: NCT04023071.

Abstract ZUMA-3 is a phase 1/2 study evaluating KTE-X19, an autologous anti-CD19 chimeric antigen receptor (CAR) T-cell therapy, in adult relapsed/refractory (R/R) B-cell acute lymphoblastic leukemia (B-ALL). We report the phase 1 results. After fludarabine-cyclophosphamide lymphodepletion, patients received a single infusion of KTE-X19 at 2 × 106, 1 × 106, or 0.5 × 106 cells per kg. The rate of dose-limiting toxicities (DLTs) within 28 days after KTE-X19 infusion was the primary end point. KTE-X19 was manufactured for 54 enrolled patients and administered to 45 (median age, 46 years; range, 18-77 years). No DLTs occurred in the DLT-evaluable cohort. Grade ≥3 cytokine release syndrome (CRS) and neurologic events (NEs) occurred in 31% and 38% of patients, respectively. To optimize the risk-benefit ratio, revised adverse event (AE) management for CRS and NEs (earlier steroid use for NEs and tocilizumab only for CRS) was evaluated at 1 × 106 cells per kg KTE-X19. In the 9 patients treated under revised AE management, 33% had grade 3 CRS and 11% had grade 3 NEs, with no grade 4 or 5 NEs. The overall complete remission rate correlated with CAR T-cell expansion and was 83% in patients treated with 1 × 106 cells per kg and 69% in all patients. Minimal residual disease was undetectable in all responding patients. At a median follow-up of 22.1 months (range, 7.1-36.1 months), the median duration of remission was 17.6 months (95% confidence interval [CI], 5.8-17.6 months) in patients treated with 1 × 106 cells per kg and 14.5 months (95% CI, 5.8-18.1 months) in all patients. KTE-X19 treatment provided a high response rate and tolerable safety in adults with R/R B-ALL. Phase 2 is ongoing at 1 × 106 cells per kg with revised AE management. This trial is registered at www.clinicaltrials.gov as #NCT02614066.

AbstractIntroductionHypoalbuminemia is a known adverse prognostic factor in lymphomas. Yet, it is unknown if axicabtagene ciloleucel (axi‐cel) overcomes the adverse prognostic impact of hypoalbuminemia in relapsed/refractory large B‐cell lymphoma.MethodsWe conducted a retrospective analysis across three Mayo Clinic centers to assess the relationship of hypoalbuminemia (defined as a serum albumin (SA) levels ≤ 3.5 g/dL) on outcomes of patients treated with axi‐cel.ResultsThis analysis included 81 patients. Two patients had no available SA levels preceding axi‐cel infusion. Eighteen patients (22.8%) had hypoalbuminemia with a median SA of 3.3 g/dL. Patients with normal SA had a statistically higher ORR than those without hypoalbuminemia (P = .018). There was no difference in 1‐year PFS and OS between the group with hypoalbuminemia and the group with normal SA levels (48% vs 49%, P = .81) and (74% vs 73%, P = .97), respectively. There was no difference in the severity or median duration of cytokine release syndrome or neurotoxicity between the two groups.ConclusionNotwithstanding the limitations related to the relatively small sample size, axi‐cel therapy appears to overcome the adverse effect of hypoalbuminemia on OS and PFS. Large multicenter clinical studies are certainly needed to validate these findings.

Background: Autologous T cells engineered to express a chimeric antigen receptor (CAR) targeting the B-cell lineage antigen CD19 (CAR19) in patients with relapsed/refractory (r/r) aggressive B-cell lymphomas (BCL) and pre-B acute lymphoblastic leukemia (B-ALL) have resulted in transformative improvements in clinical outcomes. However, there remain significant limitations concerning autologous CAR19 T cell manufacturing, including dysfunctional starting material, lack of product consistency and purity following genetic engineering, manufacturing timelines that necessitate the administration of bridging therapy in patients with aggressive disease, and insufficient quantities of CAR19 T cells, especially in severely cytopenic patients, to allow for more than single-dose administration routinely. The ability to consistently administer more than a single dose of CAR19 T cells enables dosing schedules that may reduce the risk of potentially life-threatening toxicities such as cytokine release syndrome and neurotoxicity, while maintaining or improving the depth and durability of anti-tumor responses. FT819 is a first-of-kind, off-the-shelf CAR19 T cell product candidate derived from a clonal master engineered induced pluripotent stem cell (iPSC) line, which can be used as a renewable source for the mass production of off-the-shelf CAR T cells for broad patient access. FT819 is engineered with the following features designed to improve the safety and efficacy of CAR T cell therapy: a novel 1XX CAR signaling domain, which has been shown to extend T cell effector function without eliciting exhaustion; integration of the CAR transgene directly into the T cell receptor alpha constant (TRAC) locus, which has been shown to promote uniform CAR expression and enhanced T cell potency; and complete bi-allelic disruption of T cell receptor (TCR) expression for the prevention of graft-versus-host disease (GVHD). FT819 has demonstrated antigen-specific cytolytic activity in vitro against CD19-expressing leukemia and lymphoma cell lines comparable to that of donor-derived CAR T cells, and persists and maintains tumor clearance in the bone marrow in an in vivo disseminated xenograft model of lymphoblastic leukemia (Mandal et al. 2020). The properties of FT819 and its ability to improve outcomes of patients with B-cell malignancies warrants further clinical investigation. Study Design and Methods: This study is a multicenter, Phase I clinical trial of FT819 in patients with r/r B-cell malignancies, including BCL, chronic lymphocytic leukemia (CLL), and B-ALL. The primary objective of the trial is to determine the recommended Phase II dose of FT819. Key secondary objectives include evaluation of FT819 safety and tolerability, anti-tumor activity, and pharmacokinetics (PK). Exploratory objectives include characterization of FT819 pharmacodynamics as assessed by peripheral blood biomarkers, and by phenotypic and genetic characterization of the tumor microenvironment from paired pre- and post-treatment tumor biopsies. The dose-escalation part of the trial utilizes a 3+3 dose-escalation design to identify the maximum tolerated dose for BCL, CLL, and B-ALL. The dose-expansion part of the trial is designed to further characterize the safety, efficacy, and PK of FT819 in multiple indications. Up to a maximum of 300 patients will be enrolled. The trial will test up to four FT819 dose levels ranging from 30 to 900 million cells. Three FT819 dosing regimens each will be tested for BCL, CLL, and B-ALL: Regimen A, FT819 administered as a single dose; Regimen A1, FT819 administered as a single dose in combination with interleukin (IL)-2; and Regimen B, FT819 administered as fractionated doses on Days 1, 3, and 5. Lympho-conditioning will consist of three consecutive days of fludarabine and cyclophosphamide administered prior to the first dose of FT819. Key inclusion criteria include r/r disease after standard approved therapies, documented CD19 expression, and adequate organ function. Key exclusion criteria include ongoing immunosuppression such as systemic GVHD therapy, prior allograft organ transplant, active central nervous system involvement of disease, and known allergy to FT819 components. The trial is expected to begin patient recruitment in 2020. Disclosures Park: Novartis: Consultancy; Fate Therapeutics: Research Funding; Amgen: Consultancy, Research Funding; Genentech/Roche: Research Funding; Kite: Consultancy, Research Funding; Incyte: Consultancy, Research Funding; GSK: Consultancy; Autolus: Consultancy, Research Funding; Intellia: Consultancy; Minverva: Consultancy; Takeda: Consultancy, Research Funding; AstraZeneca: Consultancy; Servier: Consultancy, Research Funding; Allogene: Consultancy; Juno Therapeutics: Research Funding; Artiva: Membership on an entity's Board of Directors or advisory committees. Jain:Pfizer: Research Funding; ADC Therapeutics: Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Research Funding; Servier: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Research Funding; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Adaptive Biotechnologies: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; TG Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Aprea Therapeutics: Research Funding; BeiGene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Genentech: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Precision Bioscienes: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AstraZeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Fate Therapeutics: Research Funding; Verastem: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Cellectis: Research Funding; Pharmacyclics: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. McGuirk:Bellicum Pharmaceutical: Research Funding; Gamida Cell: Research Funding; Astellas: Research Funding; Pluristem Ltd: Research Funding; Novartis: Research Funding; Juno Therapeutics: Consultancy, Honoraria, Research Funding; Kite Pharmaceuticals: Consultancy, Honoraria, Research Funding, Speakers Bureau; Fresenius Biotech: Research Funding; Allo Vir: Consultancy, Honoraria, Research Funding. Diaz:Fate Therapeutics, Inc.: Current Employment. Valamehr:Fate Therapeutics, Inc: Current Employment, Current equity holder in publicly-traded company. Chu:Fate Therapeutics, Inc.: Current Employment, Current equity holder in publicly-traded company; Roche Holding AG: Current equity holder in publicly-traded company. Castro:Kite Pharma: Research Funding; Pharmacyclics: Research Funding; Fate Therapeutics: Research Funding. OffLabel Disclosure: Cyclophosphamide and fludarabine will be used as lympho-conditioning therapy prior to FT819 administration. IL-2 will be administered in order to promote the expansion and function of FT819 as a T-cell product.

Single oral targeted therapies have emerged as a standard of care in chronic lymphocytic leukemia (CLL). However, accessibility, side effects, and financial burden associated with long term administration limit their clinical use. Mainly, it is unclear in what clinical situation discontinuation of oral therapy can be recommended. The combination of type II anti-CD20 antibody obinutuzumab-Gazyva® with ibrutinib (GI) has shown a significant progression-free survival benefit in patients (pts) with CLL, including those with high-risk genomic aberrations. We conducted a phase 1b/2, single-arm, open-label trial to evaluate the safety and efficacy of GI as first-line treatment in 32 CLL pts. We report the outcome in pts that discontinued ibrutinib (either after 3 years of sustained complete response (CR) as stipulated in the clinical protocol, or due to other reasons). CLL pts enrolled in this protocol were ≥65 years old, or unfit/unwilling to receive chemotherapy. Pts received GI for six cycles, followed by daily single-agent ibrutinib. The protocol was designed to ensure that pts with a sustained CR after 36 months were allowed to discontinue ibrutinib. The median age was 66 years (IQR 59-73), and 6% of the evaluated pts had 17p deletion. All pts were able to complete the six planned cycles of obinutuzumab. The combination regimen was well-tolerated, and the most common adverse events (>5% CTCAE grade 3-4) were neutropenia, thrombocytopenia, and hyperglycemia. The rate and severity of infusion-related reactions (IRR) were much lower than expected (Grade≥ 3, 3%), and pts without IRR had lower serum levels of cytokines/chemokines CCL3 (P=0.0460), IFN-γ (P=0.0457), and TNF-α (P=0.0032) after infusion. The overall response rate was 100%, with nine pts (28%) achieving a CR, and four pts (12.5%) with undetectable minimal residual disease (uMRD) in the bone marrow, defined as <10-4 CLL cells on multicolor flow cytometry. At a median follow-up of 35.5 months (IQR 24.5-42.7) after starting treatment, 91% of the enrolled pts remain in remission with a 100% overall survival. Sixteen pts have completed a long-term follow-up of 36 months. Six pts showed CR, with three of them achieving uMRD in the bone marrow. Ten of these pts were in PR, and only one had disease progression and started treatment for symptomatic stage I disease with obinutuzumab plus venetoclax. In total, thirteen pts (41%) have stopped ibrutinib, with a median time on treatment prior to discontinuation of 35 months. Five (16%) of these pts had CRs and discontinued after 36 months. Eight additional pts (25%) had PRs and discontinued ibrutinib without being eligible: three pts discontinued prior to 36 months due to toxicities, and five pts discontinued after 36 months (3 due to side effects, and 2 due to financially driven decision). One patient eligible to discontinue ibrutinib, decided to remain on treatment despite sustained CR. After a median follow up time following ibrutinib discontinuation of 8 months (IQR 3.5-17), only two out of 13 pts have progressed (10 and 17 months after Ibrutinib discontinuation). None of the pts that stopped ibrutinib after achieving a CR have shown signs of disease progression. Of note, the pharmaceutical sponsor provided ibrutinib for the first 36 months, after which pts or their insurer became financially responsible. This particular scenario could bias the discontinuation pattern compared to a real world experience. It also provided us with a perspective about diverse factors affecting the treatment choices of pts. In summary, the obinutuzumab plus ibrutinib combination therapy was well-tolerated, with a much lower IRR rate. Efficacy compares favorably with historical controls with all pts responding to therapy, no deaths associated with treatment or disease progression, and a longer than expected time-to-progression after discontinuation of ibrutinib. The rate of ibrutinib discontinuation was higher than reported in the literature, most likely influenced by the protocol design and financial decisions driven by the switch from sponsor-provided ibrutinib to insurance or self-paid medication. Our observations regarding safety, efficacy and lack of disease progression after ibrutinib discontinuation are encouraging, and warrant confirmation in long-term prospective studies. Clinicaltrials.gov Identifier NCT02315768. Funding: Pharmacyclics LLC. Disclosures Choi: AbbVie: Consultancy, Speakers Bureau. Amaya-Chanaga:AbbVie: Ended employment in the past 24 months, Other: Research performed while employed as an investigator of this study at UCSD.. Kipps:Pharmacyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Castro:Kite Pharma: Research Funding; Pharmacyclics: Research Funding; Fate Therapeutics: Research Funding.