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Abstract Background: Fc receptor-homolog 5 (FcRH5) is a type I membrane protein that is expressed exclusively in the B-cell lineage, and at a higher level on myeloma cells than on normal B cells. Cevostamab is a FcRH5xCD3 bispecific antibody (BsAb) that facilitates T cell-directed killing of myeloma cells. Initial data from the dose-escalation phase of the ongoing Phase I study (NCT03275103) of cevostamab monotherapy in patients (pts) with heavily pre-treated RRMM demonstrated promising activity and manageable safety, along with near ubiquitous FcRH5 expression on myeloma cells (Cohen et al. ASH 2020; Sumiyoshi et al. EHA 2021). We present updated safety and efficacy data from a larger cohort of pts, including results comparing Cycle (C) 1 single step-up (SS) and double step-up (DS) dosing for the mitigation of cytokine release syndrome (CRS). Methods: Participants have RRMM for which no established therapy is available or appropriate. Cevostamab (intravenous infusion) is administered in 21-day cycles. In the SS cohorts, the step dose (0.05-3.6mg) is given on C1 Day (D) 1 and the target dose (0.15-198mg) on C1D8. In the DS cohorts, the step doses are given on C1D1 (0.3-1.2mg) and C1D8 (3.6mg), and the target dose (60-160mg) on C1D15. In both regimens, the target dose is given on D1 of subsequent cycles. Cevostamab is continued for a total of 17 cycles, unless progressive disease or unacceptable toxicity occurs. CRS is reported using ASTCT criteria (Lee et al. Biol Blood Marrow Transplant 2019). Results: At data cut-off (18 May 2021), 160 pts had been enrolled (median age: 64 years, range: 33-82 years; male: 58.1%); 21.3% of pts had extramedullary disease. Median number of prior lines of therapy was 6 (range: 2-18). Most pts (85.0%) were triple-class refractory (PI, IMiD, anti-CD38 antibody). 28 pts (17.5%) had received ≥1 prior CAR-T, 13 pts (8.1%) ≥1 prior BsAb, 27 pts (16.9%) ≥1 prior antibody-drug conjugate (ADC), and 54 pts (33.8%) ≥1 prior anti-BCMA targeting agent. Median follow-up in exposed pts was 6.1 months. Almost all had ≥1 adverse event (Table). The most common was CRS (128/160 pts [80.0%]; Grade [Gr] 1: 42.5%; Gr 2: 36.3%; Gr 3: 1.3%). Immune effector cell-associated neurotoxicity syndrome (ICANS) associated with CRS was observed in 21 pts (13.1%) and in 34/211 (16.1%) CRS events (Gr 1: 8.5%; Gr 2: 6.2%; Gr 3: 1.4%). Most CRS events occurred in C1 (87.2%), arose within 24 hours of cevostamab administration (70.5%), and resolved within 48 hours of onset (83.4%). In the pts with CRS, tocilizumab was used for CRS management in 43.8% and steroids in 25.8% (both agents: 18.0%). In SS dose-escalation (68 pts), 3.6mg was chosen as the most effective C1D1 SS dose for limiting CRS in C1, with no target dose-dependent increase in the rate or severity of CRS observed after the C1D8 administration. Likewise, in DS dose-escalation (30 pts), 0.3/3.6mg was identified as the preferred C1D1/C1D8 DS dose for limiting CRS in C1. Notably, the overall rate of CRS was lower in the pts who received the 0.3/3.6mg/target DS regimen than in those who received the 3.6mg/target SS regimen (77.3% [34/44] vs 88.2% [75/85], respectively). The rate of ICANS associated with CRS was also lower in the 0.3/3.6mg/target DS cohort than in the 3.6mg/target SS cohort (4.5% [2/44] vs 21.2% [18/85], respectively). At data cut-off, 158/160 pts were efficacy evaluable. In dose-escalation, responses were observed at the 20-198mg target dose levels, and data suggested a target dose-dependent increase in clinical efficacy. Median time to response was 29 days (range: 20-179 days). Two dose-expansion cohorts were opened: ORR was higher at the 160mg dose level (54.5%, 24/44 pts) than at the 90mg dose level (36.7%, 22/60). At target dose levels >90mg, ORRs in pts with prior exposure to CAR-Ts, BsAbs, ADCs, and anti-BCMA targeting agents were 44.4% (4/9 pts), 33.3% (3/9), 50.0% (7/14), and 36.4% (8/22) respectively. Median follow-up among all responders (n=61) was 8.1 months; estimated median duration of response was 15.6 months (95% CI: 6.4, 21.6). Conclusions: Cevostamab monotherapy continues to show clinically meaningful activity in a large cohort of pts with heavily pre-treated RRMM, with a target dose-dependent increase in ORR, but no increase in CRS rate. Responses appear durable, and are observed in pts with prior exposure to CAR-Ts, BsAbs, and ADCs. Compared with SS dosing, DS dosing at the 0.3/3.6mg level appears to be associated with a trend for an improved C1 safety profile. Figure 1 Figure 1. Disclosures Trudel: Amgen: Honoraria, Research Funding; GlaxoSmithKline: Consultancy, Honoraria, Research Funding; Roche: Consultancy; Genentech: Research Funding; Pfizer: Honoraria, Research Funding; BMS/Celgene: Consultancy, Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Sanofi: Honoraria. Cohen: BMS/Celgene: Consultancy; GlaxoSmithKline: Consultancy, Research Funding; Oncopeptides: Consultancy; Novartis: Research Funding; Genentech/Roche: Consultancy; AstraZeneca: Consultancy; Janssen: Consultancy; Takeda: Consultancy. Krishnan: MAGENTA: Consultancy; BMS: Consultancy, Current equity holder in publicly-traded company, Speakers Bureau; JANSSEN: Consultancy, Research Funding; City of Hope Cancer Center: Current Employment; REGENERON: Consultancy; SANOFI: Consultancy; GSK: Consultancy; Amgen: Speakers Bureau. Fonseca: Kite: Consultancy; Juno: Consultancy; Merck: Consultancy; Sanofi: Consultancy; Pharmacyclics: Consultancy; Novartis: Consultancy; OncoTracker: Consultancy, Membership on an entity's Board of Directors or advisory committees; Aduro: Consultancy; Caris Life Sciences: Membership on an entity's Board of Directors or advisory committees; Patent: Prognosticaton of myeloma via FISH: Patents & Royalties; AbbVie: Consultancy; GSK: Consultancy; Scientific Advisory Board: Adaptive Biotechnologies: Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy; Amgen: Consultancy; Mayo Clinic in Arizona: Current Employment; Celgene: Consultancy; BMS: Consultancy; Takeda: Consultancy; Janssen: Consultancy. Spencer: Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees. Berdeja: Bluebird bio, BMS, Celgene, CRISPR Therapeutics, Janssen, Kite Pharma, Legend Biotech, SecuraBio, Takeda: Consultancy; Abbvie, Acetylon, Amgen: Research Funding; EMD Sorono, Genentech: Research Funding; Celularity, CRISPR Therapeutics: Research Funding; GSK, Ichnos Sciences, Incyte: Research Funding; Lilly, Novartis: Research Funding; Poseida, Sanofi, Teva: Research Funding. Lesokhin: Serametrix, Inc: Patents & Royalties; Behringer Ingelheim: Honoraria; Genetech: Research Funding; Iteos: Consultancy; Janssen: Honoraria, Research Funding; pfizer: Consultancy, Research Funding; bristol myers squibb: Research Funding; Trillium Therapeutics: Consultancy. Forsberg: University of Colorado: Current Employment; Karyopharm, Sanofi, Genentech: Research Funding. Costa: Karyopharm: Consultancy, Honoraria; BMS: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria, Speakers Bureau; Amgen: Consultancy, Honoraria, Research Funding, Speakers Bureau. Rodriguez-Otero: Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene-BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; GSK: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees; Kite: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria; Regeneron: Honoraria; Clínica Universidad de Navarra: Current Employment. Kaedbey: Takeda, Sanofi: Honoraria; Celgene/BMS, Janssen: Honoraria; Royal Victoria Hospital Lakeshore Hospital: Ended employment in the past 24 months; Jewish General Hospital - McGill University: Current Employment. Richter: Janssen, Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Adaptive biotechnologies: Speakers Bureau; BMS, Karyopharm, Antengene: Membership on an entity's Board of Directors or advisory committees; Tisch Cancer Institute: Icahn School of Medicine at Mount Sinai: Current Employment. Mateos: Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene - Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Regeneron: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sea-Gen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Oncopeptides: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Honoraria; Bluebird bio: Honoraria; GSK: Honoraria; Oncopeptides: Honoraria. Thomas: Pharmacyclics: Membership on an entity's Board of Directors or advisory committees; Genentech: Research Funding; Acerta Pharma: Research Funding; X4 Pharma: Research Funding; Ascentage Pharma: Research Funding; BeiGene: Membership on an entity's Board of Directors or advisory committees; BMS: Research Funding. Wong: Genentech: Current Employment; CTMX, UBX, BMRN: Current equity holder in publicly-traded company. Li: Genentech/Roche: Current Employment, Current equity holder in publicly-traded company. Choeurng: Genentech: Current Employment, Current equity holder in publicly-traded company. Vaze: Roche/Genentech: Current Employment, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company. Samineni: Genentech: Current Employment, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company. Sumiyoshi: Genentech: Current Employment, Current equity holder in publicly-traded company, Divested equity in a private or publicly-traded company in the past 24 months. Cooper: Genentech: Current Employment; Roche: Current holder of individual stocks in a privately-held company. Harrison: Haemalogix: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Roche/Genentech: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen Cilag: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene/ Juno/ BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; GSK: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Eusa: Consultancy, Honoraria, Speakers Bureau; Terumo BCT: Consultancy, Honoraria. OffLabel Disclosure: Cevostamab is a FcRH5xCD3 bispecific antibody that facilitates T cell-directed killing of myeloma cells. Cevostamab is an investigational agent.

Abstract Introduction: Plasmablastic lymphoma (PBL) is an aggressive B-cell lymphoma that predominantly occurs in patients with HIV or other causes of immunodeficiency. Frequent infection by the Epstein-Barr virus (EBV) and MYC translocations have been described as major features contributing to the pathogenesis of PBL. Prior studies examining the genetic landscape of PBL have largely relied on targeted capture-based sequencing approaches. As such, the molecular features of PBL remain to be fully explored. Here, we provide a comprehensive description of the genomic landscape of PBL using whole-genome and whole-exome sequencing to identify commonly perturbed pathways. Method: Archival diagnostic fresh frozen and formalin fixed paraffin embedded tissue biopsies from 58 PBL tumours were accrued from Lymphoma/Leukemia Molecular Profiling Project (LLMPP) sites, including 15 tumours from Ramis-Zaldivar et al., Haematolgica 2021. MYC rearrangements were identified by break-apart fluorescent in situ hybridization (FISH) and rearrangement partner was determined in a subset of tumours from capture or genome sequencing data using structural variant callers Manta, GRIDSS, and Delly. High confidence somatic mutations (SNVs/Indels) were identified in data from whole-genome (n=5) or whole-exome (n=53) sequencing through an ensemble voting approach utilizing four variant callers (Strelka2, Lofreq, Mutect2, SAGE). Mutation frequencies in known lymphoma-related genes were compared to activated B-cell (ABC)-DLBCL (Schmitz et al., NEJM 2018), as the closest tumour entity in terms of putative cell-of-origin differentiation stage, to identify differences in genetic aberrations. Candidate somatic copy number alterations (CNAs) were identified from exome and genome sequencing data, using CopywriteR and ControlFREEC, respectively, and high-confidence CNAs were determined using GISTIC2.0. Results: Within the study cohort, 81% of patients were male with a median age of 59 years (range 11-88). HIV and EBV statuses were available for 47% of patients and 95% of tumours, respectively, with 49% (13/27) of the patients being HIV+ and 69% (38/55) of tumours being EBV+. MYC rearrangement was observed in 60% (35/58) of PBLs, with IGH as the partner gene in 88% (21/24) of tumours. The most frequently mutated genes were STAT3 (38%), TP53 (22%), NRAS (21%), and TET2 (16%), consistent with previous studies, however novel mutations were seen in DUSP2 (21%), KLHL6 (16%), and BHLHE41 (16%). Recurrent CNAs included amplifications in 1q, whole gains of 7, 8q24, 11p12 and deletions affecting 4p16, 5p15, 10q11.22. While the mutational landscapes were similar between samples with and without a MYC translocation, the MYC-translocated PBLs showed more frequent amplification of 1q32.1. When stratifying by EBV status, STAT3 and SOCS1 mutations were more frequent in EBV-positive tumours, whereas TP53, TET2, KRAS, and MMRN2 mutations were associated with EBV-negativity. In comparison to ABC-DLBCL, PBLs were significantly enriched in STAT3 and NRAS mutations, and lacked common mutations affecting the NF-κB pathway (eg. MYD88, CD79B, and NFKBIZ 3' UTR mutations). Mutations in genes that are frequently mutated in ABC-DLBCLs, such as those associated with plasma cell differentiation (eg. PRDM1) or a memory B-cell fate (eg. TBL1XR1), were also not mutated in PBLs. Finally, genetic alterations associated with immune evasion, such as deletion of MHC I and II and mutations in B2M, CIITA, and CD58, were rarely observed. Conclusion: These data present a comprehensive overview of the genomic landscape of PBLs in a large cohort. We show frequent mutations involving the JAK-STAT and MAPK pathways, wherein the genetic landscape can be differentially characterized by EBV status and MYC rearrangement status. We show that PBLs are genetically distinct from ABC-DLBCLs, with absence of mutations in genes affecting the NF-κB pathway, immune evasion, and driving a memory B-cell fate. Disclosures Slack: Seagen: Consultancy, Honoraria. Raess: Scopio Labs: Research Funding. Holte: Gilead: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; Nordic: Membership on an entity's Board of Directors or advisory committees; Nanovector: Membership on an entity's Board of Directors or advisory committees, Other: lectures honorarias; Novartis: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees. Savage: Servier: Consultancy, Honoraria; Roche: Research Funding; BMS: Consultancy, Honoraria, Other: Institutional clinical trial funding; Astra-Zeneca: Consultancy, Honoraria; Merck: Consultancy, Honoraria, Other: Institutional clinical trial funding; AbbVie: Consultancy, Honoraria; Seattle Genetics: Consultancy, Honoraria; Takeda: Other: Institutional clinical trial funding; Beigene: Other: Institutional clinical trial funding; Genentech: Research Funding. Steidl: Seattle Genetics: Consultancy; Curis Inc.: Consultancy; Bayer: Consultancy; Epizyme: Research Funding; Trillium Therapeutics: Research Funding; AbbVie: Consultancy; Bristol-Myers Squibb: Research Funding. Rimsza: NanoString Technologies: Other: Fee-for-service contract. Morin: Foundation for Burkitt Lymphoma Research: Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy; Epizyme: Patents & Royalties. Scott: Abbvie: Consultancy; AstraZeneca: Consultancy; Rich/Genentech: Research Funding; BC Cancer: Patents & Royalties: Patent describing assigning DLBCL COO by gene expression profiling--licensed to NanoString Technologies. Patent describing measuring the proliferation signature in MCL using gene expression profiling. ; Incyte: Consultancy; Janssen: Consultancy, Research Funding; Celgene: Consultancy; NanoString Technologies: Patents & Royalties: Patent describing measuring the proliferation signature in MCL using gene expression profiling..

Abstract Introduction: Light chain (AL) amyloidosis is a plasma cell disease characterized by the deposition of insoluble amyloid fibrils into organs leading to organ dysfunction and death. The analysis at 6 and 12 months of the ANDROMEDA study (NCT03201965) showed that the addition of subcutaneous (SC) daratumumab to the standard of care combination of bortezomib, cyclophosphamide, and dexamethasone (VCd) was superior to VCd alone, with higher rates of hematologic complete response (CR) and an acceptable safety profile. Based on these findings daratumumab with VCd (D-VCd) was approved for newly diagnosed AL amyloidosis in January 2021 in the US and June 2021 in the EU. Here, we present data from the analysis at 18 months of the ANDROMEDA study. Methods: ANDROMEDA is a randomized, open-label, active-controlled phase 3 study including patients with newly diagnosed AL amyloidosis with measurable hematologic disease, ≥1 involved organ, cardiac stage I-IIIA, estimated glomerular filtration rate ≥20 mL/min, and absence of symptomatic multiple myeloma. Patients were randomized (1:1) to D-VCd or VCd for 6 28-day cycles. Bortezomib (1.3 mg/m 2), cyclophosphamide (300 mg/m 2 up to 500 mg per week), and dexamethasone (20-40 mg) were administered weekly. SC daratumumab (1800 mg co-formulated with recombinant human hyaluronidase PH20 in 15 mL) was administered once weekly in cycles 1 and 2 and every 2 weeks in cycles 3 to 6. Patients in the D-VCd arm received only SC daratumumab after cycle 6, every 4 weeks (up to a total of 24 cycles from first dose). The primary endpoint was overall (ie, at any time) hematologic CR rate, defined here as normalization of free light chain (FLC) levels and ratio (FLCr) and negative serum and urine immunofixation, confirmed at a subsequent visit; normalization of uninvolved FLC level and FLCr were not required if involved FLC was lower than the upper limit of normal. Secondary endpoints included major organ deterioration progression-free survival (PFS), organ response rate, time to hematologic response, overall survival (OS), and safety. Results: A total of 388 patients were randomized to receive D-VCd (N=195) or VCd alone (N=193). At the May 2021 clinical cutoff, the median duration of treatment for D-VCd and VCd arms was 21.3 and 5.3 months, respectively. In the D-VCd arm, 149 patients (77.2%) received daratumumab monotherapy after completing 6 cycles of D-VCd; of those, 17 (11.4%) were still receiving treatment. The rates of deep hematological responses favored the D-VCd treatment arm (Table). At a median follow-up of 25.8 months, the rate of hematologic CR was significantly higher in the D-VCd arm vs the VCd arm (59.5% vs 19.2%; odds ratio [95% confidence interval (CI)], 6.03 [3.80-9.58]; P<0.0001). Similarly, more patients achieved a very good partial response or better (≥VGPR) (D-VCd vs VCd, 79.0% vs 50.3%; odds ratio [95% CI], 3.74 [2.39-5.86]; P<0.0001). Among patients who responded, the median time from randomization to ≥VGPR was shorter in the D-VCd arm (0.56 months) vs the VCd arm (0.82 months). Comparable to the cardiac response analysis at 6 months (D-VCd vs VCd, 42% vs 22%), greater cardiac response rates were achieved with D-VCd compared with VCd at 18 months (53% vs 24%). Similarly, renal response rates remained superior with D-VCd vs VCd alone at 18 months (58% vs 26% compared with 6 months [54% vs 27%]). A total of 79 deaths occurred (D-VCd, N=34; VCd, N=45). In the D-VCd arm, only 1 additional grade 3/4 treatment-emergent adverse event occurred over 18 months vs 12 months (119 [61.7%] vs 118 [61.1%] patients) and no additional infusion-related reactions were reported. OS will be analyzed and major organ deterioration PFS will be updated after approximately 200 events have occurred. Conclusions: These results demonstrate the sustained clinical benefits of D-VCd vs VCd in terms of hematologic and organ responses with longer follow-up, although it should be noted that many patients in the D-VCd arm received daratumumab monotherapy following 6 cycles of D-VCd, while patients in the VCd group stopped study treatment. Nevertheless, the study continues to support the use of D-VCd over VCd alone in patients with newly diagnosed AL amyloidosis. Following its recent approval, D-VCd represents a new SOC for patients with AL amyloidosis. Figure 1 Figure 1. Disclosures Comenzo: Prothena Biosciences: Consultancy, Research Funding; Takeda: Research Funding; Unum: Membership on an entity's Board of Directors or advisory committees, Research Funding; Karyopharm: Research Funding; Caelum: Consultancy, Research Funding; Sanofi-Aventis: Membership on an entity's Board of Directors or advisory committees; Janssen: Patents & Royalties: WO2016187546A1, Research Funding. Palladini: Pfizer: Honoraria; Siemens: Honoraria; Janssen Global Services: Honoraria, Other: advisory board fees. Kastritis: Pfizer: Consultancy, Honoraria, Research Funding; Takeda: Honoraria; Amgen: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Genesis Pharma: Honoraria. Minnema: Janssen: Consultancy; BMS: Consultancy; Kite/Gilead: Consultancy; Celgene: Other: Travel expenses; Alnylam: Consultancy; Cilag: Consultancy. Wechalekar: Amgen: Research Funding; Janssen: Consultancy; Takeda: Honoraria; Celgene: Honoraria; Caelum Biosciences: Other: Clinical Trial Funding; Alexion, AstraZeneca Rare Disease: Consultancy. Jaccard: Pfizer: Honoraria; Abbvie: Honoraria; Janssen: Membership on an entity's Board of Directors or advisory committees. Dispenzieri: Janssen: Consultancy, Research Funding; Sorrento Therapeutics: Consultancy; Oncopeptides: Consultancy; Alnylam: Research Funding; Pfizer: Research Funding; Takeda: Research Funding. Lee: Karyopharm: Consultancy; Celgene: Consultancy; Takeda Pharmaceuticals: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; GlaxoSmithKline: Consultancy, Research Funding; Sanofi: Consultancy; Genentech: Consultancy; Legend Biotech: Consultancy; Janssen: Consultancy, Research Funding; Oncopetides: Consultancy; Bristol Myers Squibb: Consultancy; Regeneron: Research Funding. Sanchorawala: Oncopeptide: Research Funding; Karyopharm: Research Funding; Sorrento: Research Funding; Pfizer: Honoraria; Proclara: Membership on an entity's Board of Directors or advisory committees; Regeneron: Membership on an entity's Board of Directors or advisory committees; Caelum: Membership on an entity's Board of Directors or advisory committees, Research Funding; Abbvie: Membership on an entity's Board of Directors or advisory committees; Prothena: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Research Funding; Celgene: Research Funding. Gibbs: AbbVie: Consultancy; Janssen, Celgene, Amgen, Takeda, BMS and Pfizer: Consultancy, Honoraria. Mollee: Janssen, Pfizer: Research Funding; Amgen, BMS, Janssen, Caelum, EUSA, Pfizer, SkylineDx, Takeda: Membership on an entity's Board of Directors or advisory committees, Other: No personal fees received. Venner: BMS: Honoraria; Amgen: Research Funding; Celgene: Research Funding; Amgen: Honoraria; Takeda: Honoraria; Janssen: Honoraria; Sanofi: Honoraria; Pfizer: Honoraria. Schönland: Janssen: Honoraria, Other: Travel grants, Research Funding; Pfizer: Honoraria; Takeda: Honoraria, Other: Travel grants; Prothena: Honoraria, Other: Travel grants; Sanofi: Research Funding. Suzuki: Abie: Honoraria; Sanofi: Honoraria; Novartis: Honoraria; ONO: Honoraria; Takeda: Consultancy, Honoraria; Amgen: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding; Janssen: Consultancy, Honoraria. Kim: BMS: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding. Cibeira: Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Akcea: Honoraria, Membership on an entity's Board of Directors or advisory committees. Beksac: Oncopeptides: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sanofi: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Amgen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Libby: Genentech: Research Funding; BMS: Research Funding; GSK: Research Funding; Janssen: Consultancy, Research Funding. Valent: Caelum Biosciences: Other: Clinical Trial Funding; Celgene Corporation: Speakers Bureau; Takeda Pharmaceuticals: Speakers Bureau; Amgen: Speakers Bureau. Hungria: Amgen, BMS, Celgene, Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Support for attending meetings/travel ; Abbvie: Honoraria; Sanofi: Honoraria, Other: Support for attending meetings/travel ; Takeda: Honoraria. Wong: Amgen: Consultancy; Genentech: Research Funding; Fortis: Research Funding; Janssen: Research Funding; GloxoSmithKlein: Research Funding; Dren Biosciences: Consultancy; Caelum: Research Funding; BMS: Research Funding; Sanofi: Membership on an entity's Board of Directors or advisory committees. Rosenzweig: Janssen: Consultancy, Speakers Bureau; Bristol Myers Squibb: Speakers Bureau; Akcea: Speakers Bureau; Takeda: Speakers Bureau; Onocopeptides: Speakers Bureau. Bumma: Amgen, Sanofi: Speakers Bureau; Janssen, Oncopeptides, Sanofi: Consultancy. Tran: Janssen: Current Employment, Current equity holder in publicly-traded company. Qin: Janssen: Current Employment. Khaled: Jazz: Honoraria; Astellas: Honoraria; Alexion: Honoraria, Speakers Bureau; Omeros: Honoraria; Janssen: Current Employment. Vermeulen: Janssen: Current Employment, Current equity holder in publicly-traded company.

Abstract Introduction: Cytokine release syndrome (CRS) is a common toxicity associated with chimeric antigen receptor (CAR) T-cell therapies. Corticosteroids and steroid-sparing therapies such as tocilizumab, an interleukin-6 receptor antagonist, and anakinra, an interleukin-1 receptor antagonist, have been used to reduce the incidence and severity of these toxicities. Preclinical and clinical case studies of anakinra, administered subcutaneously or intravenously at various doses, have shown promising results in the management of CRS and systemic inflammatory responses resembling hemophagocytic lymphohistiocytosis (HLH)/macrophage activation syndrome (MAS). In CARTITUDE-1, CRS occurred in 95% of heavily pretreated patients with relapsed/refractory multiple myeloma (RRMM) receiving ciltacabtagene autoleucel (cilta-cel), a CAR T-cell therapy with 2 B-cell maturation antigen-targeting single-domain antibodies (Berdeja et al. Lancet 2021). Per protocol, tocilizumab was required to manage CRS with option to give steroids and/or anakinra per investigator discretion. Here, we report the institutional experiences of anakinra use in the management of CRS in patients who have received cilta-cel as part of the CARTITUDE-1 study. Methods: Eligible patients had MM and received ≥3 prior therapies or were refractory to a proteasome inhibitor (PI) and immunomodulatory drug (IMiD), and had received a PI, IMiD, and anti-CD38 antibody (Berdeja et al. Lancet 2021). After apheresis, bridging therapy was permitted. Patients received a single cilta-cel infusion (target dose: 0.75×10 6 CAR+ viable T cells/kg; range 0.5-1.0×10 6) 5-7 days after lymphodepletion (300 mg/m 2 cyclophosphamide, 30 mg/m 2 fludarabine daily for 3 days). Lee et al (Blood 2014) grading criteria for CRS were mapped to the ASTCT criteria for CRS. Post-hoc analysis of data revealed use of anakinra at some sites in patients who failed to respond to the initial management of CRS with tocilizumab +/- dexamethasone or in clinical settings where rise of ferritin and/or liver function tests were indicative for continued HLH/MAS-like manifestations (Kennedy et al. ASH 2020). Results: Of 97 patients in CARTITUDE-1, CRS occurred in 92 (95%) patients; 4% were grade 3/4. The median time to onset was 7 days (range 1-12) and median duration was 4 days (range 1-14). Supportive measures to treat CRS were administered to 91% of patients, most commonly tocilizumab (69%; 4 patients received ≥3 doses), corticosteroids (22%), and anakinra (18 patients, 19%). CRS resolved in 99% of patients. Anakinra was administered after initial tocilizumab and within the first 48 hours (range 0-6 days) of CRS onset for the majority of patients as part of effective management of CRS. Anakinra was administered at a dose of 100-200 mg every 8-12 hours over a median of 2.5 days (range 1-15 days). CRS uniformly resolved following anakinra use in CARTITUDE-1, apart from one patient who died from sepsis (grade 5 outcome) due to HLH/MAS considered related to treatment (Table). Conclusions: CRS events in cilta-cel-treated patients in CARTITUDE-1 were common, generally low-grade, and successfully managed with standard tocilizumab +/- dexamethasone. The use of anakinra should be considered in patients with persistent CRS/inflammatory symptoms despite tocilizumab use, and in particular in patients with HLH/MAS-like symptoms/phenotype occurring following CRS or in the absence of prior CRS. Figure 1 Figure 1. Disclosures Wong: Amgen: Consultancy; Genentech: Research Funding; Fortis: Research Funding; Janssen: Research Funding; GloxoSmithKlein: Research Funding; Dren Biosciences: Consultancy; Caelum: Research Funding; BMS: Research Funding; Sanofi: Membership on an entity's Board of Directors or advisory committees. Richard: Karyopharm, Janssen: Honoraria. Lin: Juno: Consultancy; Legend: Consultancy; Merck: Research Funding; Bluebird Bio: Consultancy, Research Funding; Sorrento: Consultancy; Janssen: Consultancy, Research Funding; Kite, a Gilead Company: Consultancy, Research Funding; Novartis: Consultancy; Celgene: Consultancy, Research Funding; Takeda: Research Funding; Gamida Cell: Consultancy; Vineti: Consultancy. Madduri: Janssen: Current Employment. Jackson: Janssen: Current Employment; Memorial Sloan Kettering Cancer Center: Consultancy. Zudaire: Janssen: Current Employment. Romanov: Janssen: Current Employment. Trigg: Janssen: Current Employment. Vogel: Janssen Global Services, LLC: Current Employment, 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. Garrett: Legend Biotech USA: Current Employment. Nesheiwat: Legend Biotech USA: Current Employment. Martin: Oncopeptides: Consultancy; Sanofi: Research Funding; Janssen: Research Funding; GlaxoSmithKline: Consultancy; Amgen: Research Funding. Jagannath: Bristol Myers Squibb: Consultancy; Legend Biotech: Consultancy; Karyopharm Therapeutics: Consultancy; Janssen Pharmaceuticals: Consultancy; Takeda: Consultancy; Sanofi: Consultancy. OffLabel Disclosure: At the time of abstract submission, cilta-cel is being investigated for the treatment of multiple myeloma but is not yet approved

Abstract EEG source imaging is becoming widely used for the evaluation of medically refractory focal epilepsy. The validity of EEG source imaging has been established in several studies comparing source imaging to the surgical resection cavity and subsequent seizure freedom. We present a cohort of 87 patients and compare EEG source imaging of both ictal and interictal scalp EEG to the seizure onset zone on intracranial EEG. Concordance of EEG source imaging with intracranial EEG was determined on a sublobar level and was quantified by measuring the distance between the source imaging result and the centroid of the active seizure onset zone electrodes. The EEG source imaging results of a subgroup of 26 patients with high density 76-channel EEG were compared with the localization of three experienced epileptologists. Of 87 patients, 95% had at least one analysis concordant with intracranial EEG and 74% had complete concordance. There was a higher rate of complete concordance in temporal lobe epilepsy compared to extratemporal (89.3 and 62.8%, respectively, P = 0.015). Of the total 282 analyses performed on this cohort, higher concordance was also seen in temporal discharges (95%) compared to extratemporal (77%) (P = 0.0012), but no difference was seen comparing high-density EEG with standard (32-channel) EEG. Subgroup analysis of ictal waveforms showed greater concordance for ictal spiking, compared with rhythmic activity, paroxysmal fast activity, or obscured onset. Median distances from the dipole and maximum distributed source to a centroid of seizure onset zone electrodes were 30.0 and 32.5 mm, respectively, and the median distances from dipole and maximum distributed source to nearest seizure onset zone electrode were 22.8 and 21.7, respectively. There were significantly shorter distances in ictal spiking. There were shorter distances in patients with Engel Class 1 outcome from surgical resection compared to patients with worse outcomes. For the subgroup of 26 high-density EEG patients, EEG source localization had a significantly higher concordance (92% versus 65%), sensitivity (57% versus 35%) and positive predictive value (60% versus 36%) compared with epileptologist localization. Our study demonstrates good concordance between ictal and interictal source imaging and intracranial EEG. Temporal lobe discharges have higher concordance rates than extratemporal discharges. Importantly, this study shows that source imaging has greater agreement with intracranial EEG than visual review alone, supporting its role in surgical planning.

AbstractObjectiveDrug‐resistant epilepsy (DRE) occurs at higher rates in children <3 years old. Epilepsy surgery is effective, but rarely utilized in young children despite developmental benefits of early seizure freedom. The present study aims to identify unique patient characteristics and evaluation strategies in children <3 years old who undergo epilepsy surgery evaluation as a means to assess contributors and potential solutions to health care disparities in this group.MethodsThe Pediatric Epilepsy Research Consortium Epilepsy Surgery Database, a multicentered, cross‐sectional collaboration of 21 US pediatric epilepsy centers, collects prospective data on children <18 years of age referred for epilepsy surgery evaluation. We compared patient characteristics, diagnostic utilization, and surgical treatment between children <3 years old and those older undergoing initial presurgical evaluation. We evaluated patient characteristics leading to delayed referral (>1 year) after DRE diagnosis in the very young.ResultsThe cohort included 437 children, of whom 71 (16%) were <3 years of age at referral. Children evaluated before the age of 3 years more commonly had abnormal neurological examinations (p = .002) and daily seizures (p = .001). At least one ancillary test was used in 44% of evaluations. Fifty‐nine percent were seizure‐free following surgery (n = 34), with 35% undergoing limited focal resections. Children with delayed referrals more often had focal aware (p < .001) seizures and recommendation for palliative surgeries (p < .001).SignificanceThere are relatively few studies of epilepsy surgery in the very young. Surgery is effective, but may be disproportionally offered to those with severe presentations. Relatively low utilization of ancillary testing may contribute to reduced surgical therapy for those without evident lesions on magnetic resonance imaging. Despite this, a sizeable portion of patients have favorable outcome after focal epilepsy surgery resections.

Introduction Considerable observational evidence suggests that cancer online support groups reduce feelings of isolation, depression and anxiety, enhance coping and self-management, and lead to better informed patients. Other studies indicate that cancer online support groups can increase distress. Yet no studies theorise the complex, context-dependent mechanisms by which cancer online support groups generate their—sometimes contrasting—outcomes. Methods and analysis Guided by an integrated knowledge translation approach and the strategy for patient-oriented research, we will conduct a realist review of cancer online support groups in partnership with stakeholders. We will follow Pawson’s five steps and existing quality standards to develop a program theory that explains how cancer online support groups work, for whom and in what circumstances. The specific research questions will be: what positive and negative outcomes have been reported on cancer online support groups? What are the mechanisms that are associated with these outcomes, in which contexts and for whom? Through a rigorous review of relevant scientific and grey literature, as well as ongoing dialogue with stakeholders, a program theory will be developed to explain who benefits from cancer online support groups and who does not, what benefits they derive (or do not), and the factors that affect these outcomes. Ethics and dissemination The use of secondary data for this review precludes the need for ethical approval. Dissemination will be informed by the knowledge-to-action framework and will consist of tailored knowledge products that are conceived of collaboratively with stakeholders. These will include peer-reviewed publications on how cancer online support groups can be optimised and best practice recommendations to maximise the benefits experienced by people with cancer. These traditional scientific outputs, along with their respective evidence summaries, will be amplified through strategic social media events hosted and promoted by knowledge users. PROSPERO registration number CRD42021250046.