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Introduction: DARA is a human IgGκ monoclonal antibody targeting CD38 and is approved for intravenous (IV) infusion across lines of therapy for MM. In phase 3 clinical studies, DARA IV plus Rd for RRMM (POLLUX) and DARA IV plus VMP for transplant-ineligible (TIE) NDMM (ALCYONE) led to deep and durable responses and reduced the risk of disease progression or death by ≥56% (Kaufman J, Blood 2019. 134[Suppl 1]:1866; Mateos M, Lancet 2020). In the phase 1b MMY1001 study of DARA IV plus carfilzomib/dexamethasone (Kd) in RRMM, DARA IV plus Kd was well tolerated and demonstrated deep responses, regardless of prior lenalidomide treatment (Chari A, Blood 2019.134[Suppl 1]:1876). In the phase 3 CANDOR study, DARA IV plus Kd reduced the risk of disease progression or death by 37% in pts with RRMM (Dimopoulos M, Lancet 2020). A formulation of DARA for subcutaneous administration (DARA SC) was developed (1,800 mg DARA co-formulated with recombinant human hyaluronidase PH20 [rHuPH20]; ENHANZE® drug delivery technology, Halozyme, Inc.). Advantages of DARA SC include reduced administration time (3-5 minutes) and lower rates of infusion-related reactions (IRRs). The phase 2 PLEIADES study is evaluating the safety and efficacy of DARA SC combined with SoC for MM, including D-Kd for RRMM, D-Rd for RRMM, and D-VMP for TIE NDMM. In the primary analysis of the D-Rd and D-VMP cohorts in PLEIADES, D-Rd and D-VMP demonstrated clinical activity and safety comparable to corresponding DARA IV regimens, with low rates of IRRs, leading to approval in the United States (Chari A, Clin Lymphoma Myeloma Leuk 2019.19[10]:e16-e17). Here, we present the primary analysis of the D-Kd cohort and updated data for the D-Rd and D-VMP cohorts of PLEIADES. Methods: RRMM pts with 1 prior line of therapy (including 2 consecutive cycles of lenalidomide therapy) received 28-day cycles of Kd (K: 20 mg/m2 IV Cycle 1 Day 1, escalated to 70 mg/m2 on Cycle 1 Days 8 and 15, then 70 mg/m2 on Days 1, 8 and 15 of each cycle thereafter; d: 40 mg IV or PO QW) with DARA SC (QW for Cycles 1-2, Q2W for Cycles 3-6, and Q4W for Cycles 7+). RRMM pts with ≥1 prior line received 28-day cycles of Rd (R: 25 mg PO Days 1-21; d: 40 mg IV or PO QW for each cycle) with DARA SC (QW for Cycles 1-2, Q2W for Cycles 3-6, and Q4W for Cycles 7+). TIE NDMM pts received 9, 6-week cycles of VMP (V: 1.3 mg/m2 SC twice weekly in Cycle 1 and QW in Cycles 2-9; M [9 mg/m2] and P [60 mg/m2] PO on Days 1-4 of Cycles 1-9) with DARA SC (QW for Cycle 1, Q3W for Cycles 2-9, and Q4W for Cycles 10+ in 28-day cycles). All pts were treated until disease progression/unacceptable toxicity. Overall response rate (ORR) was the primary endpoint for each cohort. Additional outcomes were VGPR or better rate, CR or better rate, duration of response, minimal residual disease (MRD)-negativity rate, DARA serum concentrations, and safety. Results: At the time of the clinical cutoff for the D-Kd cohort, 66 pts were treated and the median duration of follow-up was 8.7 months. The ORR for D-Kd was 84.8% (90% CI, 75.7-91.5; Table) and response rates were consistent with DARA IV plus Kd in CANDOR (Dimopoulos M, Lancet 2020). For the updated analysis of the D-Rd cohort (n=65), median follow-up was 23.1 months, and the ORR was 93.8% (90% CI, 86.5-97.9; Table). Response rates for D-Rd were consistent with DARA IV plus Rd in POLLUX (Kaufman J, Blood 2019. 134[Suppl 1]:1866). For the updated analysis of the D-VMP cohort (n=67), median follow-up was 22.6 months. The ORR for D-VMP was 89.6% (90% CI, 81.3-95.0; Table), and response rates were consistent with DARA IV plus VMP in ALCYONE (Mateos M, Lancet 2020). The median duration of DARA SC administration was 5 minutes for all D-Kd injections. The safety profile of D-Kd was consistent with DARA IV as combination therapy with SoC regimens. The rates of IRRs and injection-site reactions were comparable to those observed with DARA SC monotherapy in the COLUMBA study (Mateos M, Lancet Haematol 2020). Additional data will be presented including MRD-negativity rates for all cohorts and updated safety data for the D-Rd and D-VMP cohorts. Conclusions: The primary analysis of the D-Kd cohort demonstrated comparable clinical activity and safety to DARA IV plus Kd. With extended follow-up in the D-Rd and D-VMP cohorts, clinical activity was comparable to corresponding DARA IV-containing regimens (DARA IV plus Rd [POLLUX]; DARA IV plus VMP [ALCYONE]). A low incidence of IRRs and a short duration of administration were reported in the D-Kd cohort in PLEIADES. Table 1 Disclosures Moreau: Celgene/Bristol-Myers Squibb: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Takeda: Honoraria; Abbvie: Consultancy, Honoraria; Novartis: Honoraria. Chari:Janssen, Celgene, Novartis, Amgen, Pharmacyclics, Seattle Genetics, Millennium/Takeda: Research Funding; Janssen, Celgene, Novartis, Amgen, Bristol-Myers Squibb, Karyopharm, Sanofi, Genzyme, Seattle Genetics, Oncopeptides, Millennium/Takeda, Antengene, Glaxo Smith Kline, Secura Bio: Consultancy. Haenel:Amgen, Novartis, Roche, Celgene, Takeda, Bayer: Honoraria. Oriol:Janssen: Consultancy; Amgen: Consultancy, Speakers Bureau; Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; GlaxoSmithKline: Membership on an entity's Board of Directors or advisory committees; Sanofi: Membership on an entity's Board of Directors or advisory committees. Rodriguez-Otero:Abbvie: Consultancy, Honoraria; Oncopeptides: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Celgene/Bristol-Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); GlaxoSmithKline: Consultancy, Current Employment, Current equity holder in publicly-traded company, Honoraria; Medscape: Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); Sanofi: Consultancy, Honoraria; Kite: Consultancy, Honoraria. McCarthy:Janssen: Honoraria; Abbvie: Membership on an entity's Board of Directors or advisory committees. Suzuki:Bristol-Myers Squibb, Celgene and Amgen: Research Funding; Takeda, Amgen, Janssen and Celgene: Consultancy; Takeda, Celgene, ONO, Amgen, Novartis, Sanofi, Bristol-Myers Squibb, AbbVie and Janssen: Honoraria. Sureda Balari:BMS: Speakers Bureau; Janssen: Consultancy, Honoraria; Incyte: Consultancy; Celgene: Consultancy, Honoraria; Gilead/Kite: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria; Merck Sharpe and Dohme: Consultancy, Honoraria, Speakers Bureau; Celgene/Bristol-Myers Squibb: Consultancy, Honoraria; Takeda: Consultancy, Honoraria, Speakers Bureau; Roche: Honoraria. Hulin:Celgene/Bristol-Myers Squibb, Janssen, GlaxoSmithKline, and Takeda: Honoraria. Magen:AbbVie: Research Funding; Merck Sharpe and Dohme: Research Funding; Janssen: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Ono: Honoraria, Research Funding; Takeda: Honoraria, Research Funding; Daiichi Sankyo: Honoraria, Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding; Sano: Honoraria, Research Funding; Chugai: Research Funding; Kyowa Kirin: Research Funding. Iida:Bristol-Myers Squibb: Honoraria, Research Funding; Daiichi Sankyo: Honoraria, Research Funding; Takeda: Honoraria, Research Funding; Ono: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Merck Sharpe Dohme: Research Funding; AbbVie: Research Funding; Kyowa Kirin: Research Funding; Chugai: Research Funding; Sanofi: Honoraria, Research Funding. Maisnar:Janssen, Amgen, Takeda, Celgene/Bristol-Myers Squibb, Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Karlin:Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, personal fees; Celgene/Bristol-Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support; GlaxoSmithKline: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, personal fees; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, personal fees; Sanofi: Honoraria; Celgene: Other: Personal fees. Touzeau:Takeda: Consultancy, Honoraria, Other: Travel, Accommodations, Expenses; GlaxoSmithKline: Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Other: Travel, Accommodations, Expenses; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi: Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Other: Travel, Accommodations, Expenses; Abbvie: Consultancy, Honoraria, Other: Travel, Accommodations, Expenses, Research Funding. Yang:Janssen: Current Employment. Kosh:Janssen: Current Employment. Delioukina:Maria Delioukina: Current Employment. Heuck:Christoph Heuck: Current Employment, Current equity holder in publicly-traded company. Goldschmidt:GlaxoSmithKline (GSK): Honoraria; Merck Sharp and Dohme (MSD): Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Grants and/or provision of Investigational Medicinal Product:, Research Funding; University Hospital Heidelberg, Internal Medicine V and National Center for Tumor Diseases (NCT), Heidelberg, Germany: Current Employment; Mundipharma GmbH: Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Grants and/or provision of Investigational Medicinal Product:, Research Funding; Novartis: Honoraria, Research Funding; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding; Incyte: Research Funding; Adaptive Biotechnology: Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Grants and/or provision of Investigational Medicinal Product, Research Funding; Johns Hopkins University: Other: Grants and/or provision of Investigational Medicinal Product; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Grants and/or provision of Investigational Medicinal Product:, Research Funding; Chugai: Honoraria, Other: Grants and/or provision of Investigational Medicinal Product:, Research Funding; Dietmar-Hopp-Foundation: Other: Grants and/or provision of Investigational Medicinal Product:; Molecular Partners: Research Funding. OffLabel Disclosure: This abstract includes discussion of a combination therapy with subcutaneous daratumumab plus carfilzomib and dexamethasone, which is currently under investigation in clinical trials, but has not yet been approved. Subcutaneous daratumumab is approved as monotherapy and in combination with other standard-of-care regimens for the treatment of multiple myeloma.

Bruton tyrosine kinase (BTK) inhibition is an effective treatment approach for patients with Waldenström macroglobulinemia (WM). The phase 3 ASPEN study compared the efficacy and safety of ibrutinib, a first-generation BTK inhibitor, with zanubrutinib, a novel highly selective BTK inhibitor, in patients with WM. Patients with MYD88L265P disease were randomly assigned 1:1 to treatment with ibrutinib or zanubrutinib. The primary end point was the proportion of patients achieving a complete response (CR) or a very good partial response (VGPR) by independent review. Key secondary end points included major response rate (MRR), progression-free survival (PFS), duration of response (DOR), disease burden, and safety. A total of 201 patients were randomized, and 199 received ≥1 dose of study treatment. No patient achieved a CR. Twenty-nine (28%) zanubrutinib patients and 19 (19%) ibrutinib patients achieved a VGPR, a nonstatistically significant difference (P = .09). MRRs were 77% and 78%, respectively. Median DOR and PFS were not reached; 84% and 85% of ibrutinib and zanubrutinib patients were progression free at 18 months. Atrial fibrillation, contusion, diarrhea, peripheral edema, hemorrhage, muscle spasms, and pneumonia, as well as adverse events leading to treatment discontinuation, were less common among zanubrutinib recipients. Incidence of neutropenia was higher with zanubrutinib, although grade ≥3 infection rates were similar in both arms (1.2 and 1.1 events per 100 person-months). These results demonstrate that zanubrutinib and ibrutinib are highly effective in the treatment of WM, but zanubrutinib treatment was associated with a trend toward better response quality and less toxicity, particularly cardiovascular toxicity.

Introduction: Waldenström's Macroglobulinaemia (WM) is a rare indolent B-cell lymphoma characterised by lymphoplasmacytic infiltrate with an IgM paraproteinaemia. Approximately 400 patients (pts) are diagnosed annually in the United Kingdom (UK). National and regional registries provide important insights on the epidemiology and clinical features of this distinct uncommon disorder. Previous authors from the United States have reported significant differences in age at diagnosis and overall survival (OS) in WM between ethnic groups from Surveillance, Epidemiology and End Results data [1]. We aimed to determine baseline demographics, symptoms and survival outcomes across different ethnic groups in the UK. Methods: We retrospectively reviewed data from the WMUK Rory Morrison Registry, collating descriptive data of WM as well as non-IgM Lymphoplasmacytic lymphoma (LPL) cases from 20 centres across the UK, diagnosed between June 1978 and May 2021. Research ethics approval was obtained. Results: 732 pts with documented ethnicity were included here. Ethnicity was categorised in accordance with the UK National Census. Those other than the White cohort (662/732; 90%) were collectively termed 'Ethnic Minorities' (EM) (70/732; 9%): 39/70 (56%) Asian (13 Indian, 6 Chinese, 4 Pakistani, 16 other); 19/70 (27%) Mixed (1 White & Black African, 1 White & Asian, 1 Arab, 16 other); 12/70 (17%) Black (6 Caribbean, 3 African, 3 other). Baseline characteristics are displayed in table 1. EM presented at a significantly younger age compared to White cohort (60 vs 64 years, p=0.01) and had a significantly lower paraprotein at diagnosis (11 vs 18g/L, p=0.05). MYD88 L265P mutation tested in 250 pts (34%): positive in the majority 218/250 (87%) and notably less common in EM (p=0.09), most significantly in the Asian cohort compared to White (67% v 88%, p=0.01). The EM cohort had a smaller proportion of WM diagnoses compared to White cohort (77% vs 93%, p=0.02) with the Asian cohort accounting for the highest proportion of non-IgM LPL (15% vs 4%, p=0.002). Bone marrow trephine infiltration at diagnosis was lower in the EM cohort compared to the White cohort, although not statistically significant (25% vs 37%, respectively; p=0.10). IPSSWM scores were similar throughout. Approximately half of both the White & EM cohorts were asymptomatic at diagnosis. The most common presenting symptoms in EM were anaemia-related (10/34; 29%), B symptoms (6/34; 18%) and fatigue (4/34; 12%). 6/18 (33%) of Asians presented with cryoglobulinaemia, amyloid, nephropathy or acquired von Willebrand's Disease. Of EM, 51/70 (73%) had treatment, 35/51 (69%) within the first year from diagnosis with time to treatment 2 months (range 0-364). Time to next therapy was 14 months. Median lines of therapy were 2 (range 1-8). The most common indication for first line therapy was lymphoma-related (16/39; 41%) followed by paraprotein-related (peripheral neuropathy, hyperviscosity and autoimmune) (13/39; 33%). First line therapies included Bendamustine-Rituximab (BR; 8/49; 16%), Dexamethasone Rituximab Cyclophosphamide (DRC; 7/49; 14%) and R-CHOP (5/49; 10%) with smaller proportions receiving Rituximab monotherapy, Cladribine + Rituximab or Fludarabine + Cyclophosphamide + Rituximab (FCR) (3/49 (6.1% each). Two of 41 (5%) of EM had first treatment as a part of a clinical trial, compared to 16/156 (10%) of the White cohort (p=0.28). Response to first line therapy was similar between the White & EM cohorts (Table 1). For EM, at a median follow up of 7 years, 17 died (1/17; 6% disease related). Median OS was not reached (Figure 1). Estimated 5-year and 10- year OS was 91% (95% CI 96-80%) and 75% (95% CI 85-60%), respectively. Conclusions: This first report on ethnic disparities in WM and non-IgM LPL in the UK identified key differences in presentation of disease. Ethnic minorities present at a younger age, with a lower paraprotein. The Asian cohort had a greater proportion of non-IgM LPL cases and fewer MYD88 mutated cases. A small proportion of Ethnic Minorities have treatment on a clinical trial which may warrant further attention. Further analysis including associations with socioeconomic status, deprivation indices and comorbidities are ongoing. Ailawadhi, Sikander et al. "Outcome disparities among ethnic subgroups of Waldenström's macroglobulinemia: a population-based study." Oncology vol. 86,5-6 (2014): 253-62. doi:10.1159/000360992 Disclosures McCarthy: Janssen: Honoraria; Astra zenica pharmaceuticals: Honoraria; Amgen: Honoraria. Pratt: Amgen: Consultancy; Binding Site: Consultancy; BMS/Celgene: Consultancy; Gilead: Consultancy; Janssen: Consultancy; Takeda: Consultancy. El-Sharkawi: AbbVie: Honoraria, Other: Travel Support, Ad boards; AstraZeneca: Honoraria, Other: Ad boards; Janssen: Honoraria, Other: Ad boards; Roche: Honoraria; Takeda: Honoraria; Novartis: Other: Travel Support; ASTEX: Other: Ad boards; Beigene: Other: Ad boards; Kyowa Kirin: Other: Ad boards. Linton: Genmab: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Aptitude Health: Honoraria; Hartley Taylor: Honoraria; Celgene: Research Funding; BeiGene: Research Funding; University of Manchester: Current Employment. Gatto: Roche: Consultancy. D'Sa: Janssen Cilag: Honoraria, Research Funding; BeiGene: Honoraria, Research Funding; Sanofi: Honoraria.

Background IgM paraprotein-associated peripheral neuropathies (PN) are a heterogenous group of disorders seen in patients with IgM MGUS and Waldenström's Macroglobulinaemia (WM). Anti-myelin associated glycoprotein (MAG) antibodies are causally identified in ~50% of such cases, but other neuropathies with other IgM-targets are described, along with AL amyloidosis and cryoglobulinaemic vasculitis amongst others. Presence of neuropathy alone is typically not an indication for treatment, but progressive disability is. Due to their relative rarity and heterogeneity, the true prevalence and optimal management of these neuropathies is currently unclear. Methods The Rory Morrison WMUK Registry, a national IgM-related disorders database incorporating 18 centres, was searched for all patients with PN and retrospective data clinical data extracted. Research ethics approval was obtained. Results IgM-related PN was identified 153 patients, of whom 99 (64.7%) had underlying WM and 54 (35.3%) had IgM MGUS. Anti-MAG neuropathy was present in 83 (54.6%) patients, anti-ganglioside in 3 (2%), AL amyloid in 7 (4.3%), cryoglobulinemia in 6 (3.7%), one (0.6%) case of CANOMAD syndrome, and a non-MAG IgM-neuropathy in 53 (34.5%%). PN was present at diagnosis in 143 (93.5%) whereas 10 (6.5%) were diagnosed during the course of their disease. Median age at diagnosis was 64 years (30-92) and 101/153 (66%) were male. Table 1 details results at diagnosis. κ-light chain was present in 80.3%, λ in 11.8% and 7.9% had multiple M-protein bands expressing both light chains. MYD88L265P was identified in 44/55 tested patients (80%) and in 23/30 (76.7%) cases of anti-MAG. In those with an IgM-related disorder, 13/20 (65%) had MYD88L265P, higher than in other IgM MGUS patients (7/14, 50%). CXCR4MUT were found in 3/22 (13.6%). Median bone marrow infiltration on trephine was 13% (range 0-85%), but 10 patients had no evidence of disease, 5 had disease on flow cytometry only, 2 an isolated finding of MYD88L265P and 1 isolated CXCR4MUT on PCR. IgM-related PN was seen in 99/719 (13.8%) of all registry patients with WM. At diagnosis, the bone marrow burden, M-protein and B2M were all significantly lower (p Therapy had been required in 81 (53.3%) patients, including at time of diagnosis in 23 (15%). Median time from diagnosis to treatment was long, at 6.7 years (95% CI 3.2-9.1 years). PN was the sole treatment indication in 64/81 (79%) cases. Time to treatment commencement did not appear to be affected by M-protein quantity or marrow burden, but patients with WM were more likely to have received treatment for their PN (59/108, 54.6%). Frontline treatment incorporated rituximab (R) in 66/81 (81.5%) patients, including R-monotherapy in 30, DRC 20, R-CHOP/R-CVP eight and BR in seven. A major biochemical response was seen in 19/34 (55.9%) patients. Clinical response was seen in 34 of 45 evaluable cases (75.6%), with improvement in 13 (28.9%) and stabilisation in 21 (46.7%). Clinical response or stabilisation was significantly more likely with R-containing therapy (82.1% vs 33.3%, p 0.04), non-amyloid related PN (82% vs 0%, p = 0.01) and attainment of ≥ partial response. All patients (n=12) with normal BMAT or isolated MYD88L265P responded to R-containing frontline therapy, another positive prognostic factor (p = 0.08). Progression of PN occurred after an initiation period of clinical response in 7/34 (20.5%), necessitating re-treatment at a median of 4.3 years after frontline therapy. Median time to 2nd line therapy was 6.7 years, longer than for other WM treatment indications (p = 0.04). Conclusions IgM-related PN is a cause of morbidity for a significant proportion of patients with WM, with a prevalence of 13.7%. However, a third of cases occur in those with IgM MGUS and even very small clonal populations seem capable of causing disease but appear responsive to rituximab therapy. Patients typically have comparatively low systemic disease burden and low rates of CXCR4MUT, perhaps representing a more indolent phenotype or a product of earlier diagnosis. PN is frequently the sole indication for treatment, reflecting this. Clinical improvement or stabilisation was seen in 75% of treated patients, and attainment of ≥50% reduction in IgM (PR) and treatment with rituximab is associated with a more favourable outcome, whereas AL amyloid neuropathy appears to be more treatment resistant. Disclosures Lindsay: Amgen: Other: Travel Expenses; Takeda: Honoraria, Other: Travel Expenses; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel Expenses. Carr:Lupin: Honoraria; CSL: Honoraria; Grifols: Other: Travel support. McCarthy:Janssen: Honoraria; Abbvie: Membership on an entity's Board of Directors or advisory committees. El-Sharkawi:Roche: Other: Conference fees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Pratt:Binding Site Ltd: Other: Personal fees; Amgen: Other: Personal fees; Janssen: Other: Personal fees; Celgene: Other: Personal fees; Takeda: Other: Personal fees; Gilead: Other: Personal fees; Sanofi-Genzyme: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Beigene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Karyopharm: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. D'Sa:Janssen: Honoraria, Research Funding; Sanofi: Honoraria; BeiGene: Honoraria, Research Funding.

Introduction: CNS relapse of DLBCL is associated with poor prognosis. Estimated incidence varies between 1.9 and 8.4%1. The CNS-International prognostic index (IPI)2 help risk stratify and estimate the 2-year risk of CNS relapse in DLBCL patients treated with R-CHOP chemotherapy. CNS prophylaxis is indicated in patients with a high risk of CNS relapse (a score of ≥4 equated to a 10.2% risk). High-risk DLBCL patients outside the CNS-IPI system include double/triple-hit (MYC/BCL-2/BCL-6 translocations) lymphoma, HIV lymphoma, testicular lymphoma, primary cutaneous lymphoma-leg type, stage IE breast lymphoma3. IT methotrexate or cytarabine administered during the course of systemic chemotherapy has been the most widely employed method of CNS prophylaxis but there is paucity of data validating its efficacy. Aim: The primary aim of the study was to evaluate the CNS relapse rates in DLBCL patients who received CNS prophylaxis. Patients and Methods: This was a single-centre retrospective observational study conducted in a district general hospital. Data was extracted from the regional (Dorset Cancer Network) DLBCL database and laboratory reports for CSF analysis at the time of the first intrathecal chemotherapy. Medical records of patients with DLBCL who received CNS prophylaxis were evaluated for the following patient-related and disease-related demographics: age at diagnosis, gender, stage, systemic treatment, CNS prophylaxis, treatment response, remission duration, systemic relapse rates, CNS relapse rates and survival. CNS-IPI scores were retrospectively calculated and additional indications evaluated for patients who received CNS prophylaxis. Results: Between 2013 and 2018, 178 patients were diagnosed with DLBCL. All patients were treated with RCHOP chemo-immunotherapy. CNS prophylaxis was administered in 47 (26%) patients. Median age was 69 years (range 20-86 years) and 62% were males. All 47 patients (100%) received IT methotrexate as CNS prophylaxis, with 43 (91%) receiving all of the planned 4 doses of IT methotrexate 12.5 mg each. A CNS-IPI score of ³4 was present in 31 (66%) patients, and a score of 2-3 in 9 (19%) patients. Additional risk factors identified included testicular lymphoma in 3 patients, breast lymphoma in 2 patients and oropharyngeal lymphoma in 2 patients. Ten (21%) patients received their treatment at the outset with courses 1-4 of R-CHOP. Of the 47 patients who received CNS prophylaxis, 5 (10%) relapsed; all had isolated CNS lymphoma at relapse. Median time to CNS relapse was 25 months (range 12-36 months) from initial diagnosis of DLBCL. Median survival after CNS relapse was 5 months (range 2-9 months). Of the remaining 141 patients, 2 patients relapsed with isolated CNS lymphoma. Conclusion: Although the overall incidence was low (4%), CNS relapse was observed in 10% of high-risk patients all of whom received CNS prophylaxis with IT methotrexate. The efficacy of CNS prophylaxis with IT chemotherapy remains unproven. There is no randomised study to show that IT prophylaxis alone is effective. Current British guidelines recommend high-dose intravenous methotrexate over IT methotrexate if patient's physiological fitness and renal function are acceptable4. The median age in our cohort was 69 years which makes it challenging to deliver dose-intensive systemic therapy concurrently with intravenous high-dose methotrexate. The role of CNS prophylaxis in high-risk patients including its efficacy and safety in older patients need further evaluation in prospective randomised studies. References Eyre T et al.Efficacy of central nervous system prophylaxis with stand-alone intrathecal chemotherapy in diffuse large B-cell lymphoma patients treated with anthracycline-based chemotherapy in the rituximab era: a systematic review. Hematologica. 2019;105(7):1914-1924.Norbert Schmitz et al.CNS International prognostic Index: A risk model for CNS relapse in patients with diffuse large B-cell lymphoma treated with R-CHOPJ Clin Oncol 2016; 34:3150-3156.Andrew D Zelenetz et al.National Comprehensive Cancer Network (NCCN) Guidelines: B-Cell Lymphomas.Version 2.2020.Pamela McKay et al.The prevention of central nervous system relapse in diffuse large B-cell lymphoma: a British Society for Haematology good practice paper. Onlinelibrary.wiley.com. 2020. Available from: https://onlinelibrary.wiley.com/doi/epdf/10.1111/bjh.16866 Disclosures Hall: Janssen:Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: sponsored for educational meetings;Karyopharm:Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: sponsored for educational meetings;Takeda:Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: sponsored for educational meetings;Celgene:Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: sponsored for educational meetings.Killick:Celgene:Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Support for attending educational meetings;Jazz Pharmaceuticals:Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Support for attending educational meetings;Novartis:Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Support for attending educational meetings;Gilead:Honoraria, Other: Support for attending education meetings.McCarthy:Janssen:Honoraria;Abbvie:Membership on an entity's Board of Directors or advisory committees.Walewska:AbbVie:Other: sponsored for educational meetings, Speakers Bureau;Janssen:Other: sponsored for educational meetings, Speakers Bureau;Gilead:Speakers Bureau;Astra Zeneca:Membership on an entity's Board of Directors or advisory committees.Chacko:Astellas:Honoraria;Daiichi-Sankyo:Honoraria;Novartis:Honoraria, Other: Travel Grants;Gilead:Other: Travel grants;Jazz Pharmaceuticals:Other: Travel grants;Celgene:Other: Travel grants.

BACKGROUND Bendamustine and Rituximab (BR) therapy is recommended in international consensus guidelines for treatment of Waldenström Macroglobulinaemia (WM) in both frontline and relapsed settings. The optimal dose and schedule of Bendamustine is not well established. Dose options include 90mg/m2 or 70mg/m2 on days 1&2 of each of 6 cycles (total Bendamustine dose of 1080mg/m2 and 840mg/m2, respectively) +/- reduction from 6 to 4 cycles. AIMS Determine response rates (IWWM criteria), PFS and toxicity following BR in frontline and relapsed settings Determine the impact of depth of response and Bendamustine dose on PFS METHODS A multicentre, retrospective cohort analysis was undertaken of consecutive WM patients treated with BR in the frontline or relapsed settings. Data were collected from 17 sites across 4 countries, including UK centres participating in the Rory Morrison Registry. RESULTS Data from Sep 2010 to May 2020 were collected for 250 patients. Frontline (n=139, 55.6%) and relapsed (n=111, 44.4%) cohorts were matched in terms of sex, age at commencement of BR, ECOG score, and baseline parameters including: haemoglobin, platelet count, bone marrow infiltration, and presence of adenopathy, splenomegaly and extranodal disease. At a median follow up of 37 months, disease progression had occurred in 25 frontline patients (18.0%) and 48 relapsed patients (43.2%; p Major responses (≥PR) differed significantly between frontline and relapsed cohorts (91.4% vs 73.9%, respectively; p Best response significantly impacted on PFS and OS. Two-year predicted PFS rates for those achieving CR/VGPR vs PR were 96% vs 82%, respectively (p=0.002, Fig. 1A). Median OS was 83 months after achieving CR/VGPR, 65 months after achieving PR/MR and 28 months after achieving SD/PD (p Relapsed patients had received 1 (n=53, 47.7%), 2 (n=28, 25.2%) or ≥3 (n=30, 27.0%) prior therapies. PFS was significantly longer in the frontline cohort compared with recipients of ≥2 prior lines of treatment, but not between cohorts treated frontline vs after 1 prior therapy line (Fig. 1B). Rates of toxicity-related treatment truncation were significantly lower in the frontline setting (17.3% vs 35.1%; p Frontline patients received higher total Bendamustine doses than relapsed patients (median total dose 1080mg/m2 vs 720mg/m2; p Age did not significantly affect tolerated dose in the frontline cohort, with similar median total Bendamustine doses in the CONCLUSION Outcomes for WM patients following BR are excellent. Frontline patients tolerate higher doses of Bendamustine, and achieve deeper responses and longer PFS than relapsed patients. In both settings, attaining CR/VGPR results in superior PFS and OS. Our data clearly delineate the Bendamustine doses required to achieve optimum PFS. At frontline, 6 cycles of 90mg/m2 on days 1&2 is superior to lower doses with respect to response and PFS. In the relapsed cohort, maximum response and PFS benefit are seen with 4 cycles of 90mg/m2 on days 1&2; a starting dose of 70mg/m2 on days 1&2 is also sufficient provided 5-6 cycles are administered. Disclosures Menne: Kyowa Kirin: Other: Travel expenses; AstraZeneca: Research Funding; Pfizer: Honoraria, Other; Atara: Honoraria; Novartis: Honoraria, Research Funding; Kite/Gilead: Honoraria, Other: Travel expenses; Celgene: Honoraria, Other: Travel expenses; Daiichi Sankyo: Honoraria; Amgen: Honoraria, Other: Travel expenses; Janssen: Honoraria, Research Funding; Takeda: Honoraria; Bayer: Other: Travel expenses; Roche: Honoraria. Talaulikar:Janssen: 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; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Research Funding. Pratt:Binding Site Ltd: Other: Personal fees; Amgen: Other: Personal fees; Janssen: Other: Personal fees; Celgene: Other: Personal fees; Takeda: Other: Personal fees; Gilead: Other: Personal fees; Sanofi-Genzyme: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Beigene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Karyopharm: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Manos:Bristol-Myers Squibb: Other: Conference sponsorship. Gavriatopoulou:Genesis Pharma: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Karyopharm: Consultancy, Honoraria. Minnema:Kite, a Gilead Company: Speakers Bureau; Celgene: Other: travel support, Research Funding; Servier: Consultancy; Amgen: Consultancy. El-Sharkawi:Roche: Other: Conference fees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Kersten:Kite, a Gilead Company: Consultancy, Honoraria, Other: travel support; Novartis: Consultancy, Honoraria, Other: travel support; Miltenyi: Consultancy, Honoraria, Other: travel support; Roche: Research Funding; Takeda: Research Funding; Celgene: Research Funding. McCarthy:Abbvie: Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria. Bishton:Janssen: Consultancy; Takeda: Other: Travel/accommodations/expenses, Research Funding; Roche: Other: Travel/accommodations/expenses, Research Funding; Gilead: Other: Travel/accomodations/expenses, Research Funding; AbbVie: Research Funding. Follows:Roche: Consultancy, Other: Paid lecturing; Karyopharm: Consultancy, Other: Paid lecturing; Janssen: Consultancy, Other: Paid lecturing; Abbvie: Consultancy, Other: Paid lecturing; Bristol Myers Squibb: Consultancy, Other: Paid lecturing; Astrazeneca: Consultancy, Other: Paid lecturing. Wechalekar:Janssen, Takeda, Caelum, Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees. D'Sa:BeiGene: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Sanofi: Honoraria.

Introduction Waldenström's macroglobulinaemia (WM), an indolent IgM-secreting non-Hodgkin's B-cell lymphoplasmacytic lymphoma, has a reported average age of diagnosis of 65-70 years. and it is often regarded as a disease of the elderly. However, a significant proportion of patients are diagnosed at a younger age and data about this cohort is relatively limited, partly because of the low disease incidence. We seek to further elucidate the characteristics and impact of the disease in the younger patient cohort. Methods The WMUK Rory Morrison Registry (RMR) was searched for all patients younger than 60 years on day of diagnosis. Demographics, disease characteristics, treatment information and survival status were collected retrospectively. Results of patient reported outcome measures (PROMs) were collated. Results 269 patients from 16 UK centres were identified, with years of diagnosis between 1978 and 2018. Analysis focused on 235 patients who fulfilled diagnostic criteria for WM. Patient characteristics are shown in table 1. M:F ratio was 1.61:1 of which 158 patients were Caucasian, 17 Asian, 5 Black, 3 mixed and 6 of other ethnicity, 56 unrecorded. Bone marrow results were available in 156 patients from time of diagnosis, with a median infiltration of 40%. MYD88 L265P was found in 61/74 patients (82.4%) and CXCR4 mutation in 14/39 patients (35.9%). Median Hb was 114/L (range 33-170), platelet count 250x109/L (range 24-689), IgM 19 (range 0-65) and B2-microglobulin 2.7mcg/mL (range 0.5-56.3). The baseline IPSSWM scores were available for 115 patients. 9 patients were anti-MAG antibody positive and 11 had cryoglobulins. Treatment was received by 164 patients (69.8%). The median time from diagnosis to treatment was 2.5 months, range 0-312 months; 69 patients had one line, 32 two lines, 31 three lines, 12 four lines, and 20 five or more lines.14% received R-CHOP as first line therapy, 12.2% DRC,12.2% R-Bendamustine, 7.3% Rituximab monotherapy, 6.7% R-CVP and 6.7% chlorambucil. However, since 2010 DRC and R-Bendamustine were the most frequent. Following first line treatment, 14.7% achieved CR, 55.3% PR or VGPR, 11.9% MR and 14% had SD or PD. At some point in their disease course, high-grade transformation (HGT) was noted in 2 patients and CNS involvement in 10. 30 patients had undergone autologous and six patients allogenic transplantation. Complete, up to date survival information was available for 188 patients, of who 40 patients were deceased (median time from diagnosis 116 months, range 14-451 months). Unfortunately, cause of death was available for only 8 patients at time of analysis, including disease-related in 4, sepsis in 2, HGT in 1 and subdural haemorrhage in 1. One-, 5- and 10-year overall survival (OS) rates were 99.5%, 90% and 81.1%. There was a significant difference in OS according to IPSSWM risk (log rank, P Of 164 patients asked about their level of disease understanding on a scale of 0-10, the median rating was 0 (average rating 1.85). Only eight patients rated it as 10. Functional information was available for 62 patients, of who 42 (67.7%) had impairment in their ability to go for a walk outside, eight patients (12.9%) required assistance with self-care and one patient (1.6%) was fully dependent on others for personal care. 32 patients (51.6%) needed to spend some or most of their day in a bed or chair. 29 patients (47.8%) had suffered significant financial difficulties because of their diagnosis. Of 59 patients who responded about psychological wellbeing, 36 patients (61%) described feeling depressed. One patient described feeling 'very' depressed, 8 patients 'moderately' depressed and 27 patients 'slightly' depressed. Conclusion A significant proportion of patients with WM are diagnosed under the age of 60 years, and despite its limitations, this retrospective analysis of a large cohort of younger patients illustrates the evolving treatment landscape in the UK. To be expected, WM significant impacts on quality of life and psychological and financial wellbeing in a cohort who would expect to be in work. Encouragingly, OS rates are generally good, although a high IPSSWM risk carries a markedly lower 5-year OS rate also in the younger cohort. A more detailed analysis is underway to explore these issues further. Disclosures McCarthy: Janssen: Honoraria, Other: Educational grant to attend meetings . Pratt:Binding Site, Amgen, Takeda, Janssen, Gilead: Consultancy, Honoraria, Other: Travel support. D'Sa:Janssen: Honoraria, Research Funding.

Background Waldenström's macroglobulinaemia (WM) is a rare non-Hodgkin B cell lymphoma. Given its rarity, information about both patient demographics and disease characteristics are limited. Treatment is indicated for symptomatic patients and treatment regimens have evolved significantly in recent years. The Rory Morrison Registry (RMR) has comprehensive patient data available for analysis. We seek to draw conclusions about UK patient demographics and disease characteristics, and evaluate how treatment practices have evolved. Methods The RMR was searched for all patients with a diagnosis of WM. Patient demographics, disease characteristic, pathology results, treatment information and survival status retrieved. Kaplan Meier and log rank analysis was performed. Results 671 patients were identified from 19 different UK centres. Median age at diagnosis was 64 years (range 27-92, figure 1). Year of diagnosis ranged from 1978 to 2019, with 7 patients diagnosed Median haemoglobin at diagnosis was 112g/L (range 33-170), platelet count 242 (3-806), B2M 3 (range 0.2-56.3) and M-protein 17g/L (range 0-110.5). Median bone marrow infiltration was 40% (range 0-100%), with 35% lymphocytes and 5% plasma cell. MYD88 L265P mutations were detected in 160/190 patients (84.2%). CXCR4 mutations, for which testing is not widely available, were detected in 20/76 patients (26.3%). Peripheral neuropathy was seen in 74 patients, with 28 anti-MAG antibody positive. Other manifestations at diagnosis included cryoglobulinaemia (26), amyloidosis (12) and Schnitzler's syndrome (7). 2/317 patients were HIV positive, 4/341 HCV antibody positive, 27/334 HBSAb positive, and 12/327 HBCAb positive. IPSSWM score at diagnosis was available for 352 patients, with a low score in 122 (34.7%), intermediate score in 103 (29.3%), and high score in 123 (45%). 440 patients (65.6%) had received treatment, with a median time from diagnosis to treatment of two months (range 0-312). Indications for first line treatment initiation were: 35% paraprotein-related, 30% lymphoma-related , 2.1% B-symptoms, and a combination of indications for the remainder. Hyperviscosity was the treatment indication in 24.8% of patients, fatigue in 21.6% and peripheral neuropathy in 9.8%. At treatment commencement, 47% of patients had a haemoglobin of Lines of therapy received was one in 43.6%, two in 24.1%, three in 4.8%, four in 6.6% and ≥5 in 10.9%. In the past decade, 27.8% received DRC, 16.4% R-Bendamustine, 8.9% rituximab monotherapy, 7.7% R-CHOP and the rest varying combinations. 2.2% had received Bortezomib-containing therapy. Before 2010, chlorambucil (21.8%), R-CHOP (10.9%) and FC (9.3%) were the most frequently used first line treatments. BTK-inhibitors have become the most commonly used second line therapy, representing 23% of second line therapy after 2010, reflecting the availability of Ibrutinib on the Cancer Drugs Fund from 2017 and the availability of BTKi trials since 2015. 88 patients had received a BTKi at some point. 118 patients had deceased. Only 30 patients had a cause of death available; this included 7 patients who died from WM itself, 6 from pneumonia, 5 from sepsis (2 were neutropaenic), 3 from HGT, 2 from haemorrhage, 2 from thrombotic events, and 1 from CNS relapse. 5- and 10-year OS rates from diagnosis were 90.5% and 79.4%, with a significant difference in OS rates according to IPSSWM risk at diagnosis (p Conclusions The median age at diagnosis was 64 years, with a third of patients diagnosed under the age of 60. Although diverse, the most frequent indications for treatment in this cohort are hyperviscosity, fatigue and peripheral neuropathy. OS rates are high and correlate with IPSSWM risk, but a majority of patients had received multiple lines of therapy reflecting the chronically relapsing nature of WM. Treatment practices are clearly evolving, with increasing first line use of DRC and R-Bendamustine, as well as BTK inhibitors for relapsed disease. Disclosures McCarthy: Janssen: Honoraria, Other: Educational grant to attend meetings . Pratt:Binding Site, Amgen, Takeda, Janssen, Gilead: Consultancy, Honoraria, Other: Travel support. D'Sa:Janssen: Honoraria, Research Funding.

Introduction : Daratumumab (DARA) 16 mg/kg intravenous (IV) is approved as monotherapy for relapsed or refractory multiple myeloma (RRMM) and in combination with standard-of-care regimens for transplant-ineligible newly diagnosed multiple myeloma (NDMM). A subcutaneous (SC) co-formulation of DARA (DARA SC; 1,800 mg) with recombinant human hyaluronidase PH20 (rHuPH20; ENHANZE® drug delivery technology, Halozyme, Inc.) is under investigation in a number of ongoing studies. In the phase 3 COLUMBA study, DARA SC was shown to be noninferior to DARA IV, demonstrating similar efficacy and pharmacokinetics (PK), with a significantly decreased rate of infusion-related reactions (IRRs) and reduced administration time (median, 5 minutes; Mateos MV, et al. J Clin Oncol. 2019). This phase 2, open-label, multicenter study (PLEIADES) assessed the efficacy and safety of DARA SC combined with bortezomib, lenalidomide, and dexamethasone (D-VRd) and bortezomib, melphalan, and prednisone (D-VMP) in patients with NDMM, and combined with lenalidomide and dexamethasone (D-Rd) in patients with RRMM. The primary analysis of PLEIADES is to be presented at an upcoming meeting; here, we report updated results with longer follow-up. Methods: Transplant-ineligible NDMM patients received DARA SC (QW for Cycle 1 and Q3W for Cycles 2-9 in 42-day cycles, and Q4W for Cycles 10+ in 28-day cycles until disease progression) in combination with VMP for 9 cycles (V 1.3 mg/m2 SC on Days 1, 4, 8, 11, 22, 25, 29, and 32 for Cycle 1 and Days 1, 8, 22, and 29 for Cycles 2-9; M 9 mg/m2 orally [PO] Days 1-4 for Cycles 1-9; P 60 mg/m2 PO Days 2-4 for Cycles 1-9) and dexamethasone (20 mg PO QW for Cycle 1, Days 1 and 22 for Cycles 2-9, and Day 1 for Cycles 10+). RRMM patients with ≥1 prior line of therapy received DARA SC (QW for Cycles 1-2, Q2W for Cycles 3-6, Q4W for Cycles 7+ until disease progression in 28-day cycles) in combination with Rd (R 25 mg PO Days 1-21 and d 40 mg IV or PO QW for each cycle until disease progression). Transplant-eligible NDMM patients received 4 cycles of DARA SC (QW for Cycles 1-3, Day 1 for Cycle 4 in 21-day cycles) in combination with VRd induction therapy for 4 cycles (V 1.3 mg/m2 SC Days 1, 4, 8, and 11 for each cycle; R 25 mg PO Days 1-14 for each cycle; d 20 mg IV or PO Days 1, 2, 8, 9, 15, and 16 for each cycle); subsequent therapy/autologous stem cell transplant were performed off study. Primary efficacy endpoints were overall response rate (ORR) for D-VMP and D-Rd and rate of very good partial response (VGPR) or better for D-VRd. Secondary endpoints included rate of VGPR or better for the D-VMP and D-Rd treatment cohorts and ORR for the D-VRd cohort. Secondary endpoints included rate of complete response or better, duration of response, minimal residual disease (MRD)-negativity rate, and DARA serum concentrations. Safety data included rates of treatment-emergent adverse events and IRRs. Results: 199 patients were enrolled (D-VMP, n = 67; D-Rd, n = 65; D-VRd, n = 67). At the clinical cutoff date (8 July 2019), median duration of follow up was 11.0 months for D-VMP, 11.2 months for D-Rd, and 7.1 months for D-VRd. ORR for D-VMP was 89.6% (90% confidence interval [CI], 81.3 - 95.0) and for D-Rd was 93.8% (90% CI, 86.5 - 97.9). Rate of VGPR or better for D-VRd was 70.1% (90% CI, 59.6 - 79.3). Response rates were comparable to published ORRs from the ALCYONE (Mateos MV, et al. N Engl J Med. 2018) and POLLUX (Dimopoulos MA, et al. N Engl J Med. 2016) studies of DARA IV plus VMP and Rd, respectively. The median duration of DARA SC administration was 5 minutes in all cohorts for the first, second, and all subsequent injections. The safety profiles in all cohorts were consistent with DARA IV in combination with various backbone standard-of-care regimens. Rates of IRRs and injection site reactions were consistent with those observed with DARA SC monotherapy in the COLUMBA study. The PK of DARA SC and each regimen was consistent with historical data and immunogenicity of DARA and rHuPH20 were comparable to previous reports. Updated efficacy data based on longer follow-up, including MRD-negativity rate, and updated safety data will be presented at the meeting. Conclusions: With longer follow-up, DARA SC in combination with standard-of-care regimens demonstrated comparable clinical activity and safety to corresponding DARA IV regimens, with considerably lower IRR rates and substantially shorter durations of administration. Disclosures Chari: Janssen, Celgene, Novartis Pharmaceuticals, Amgen, Bristol Myers Squibb, Pharmacyclics, Karyopharm, Sanofi, Seattle Genetics, OncoPeptides, Millenium/Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. San-Miguel:Amgen, Bristol-Myers Squibb, Celgene, Janssen, MSD, Novartis, Roche, Sanofi, and Takeda: Consultancy, Honoraria. McCarthy:Janssen: Honoraria, Other: Educational grant to attend meetings . Suzuki:Celgene: Honoraria; Janssen: Honoraria; Ono: Research Funding; BMS: Honoraria, Research Funding; Takeda: Honoraria. Hungria:Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees; BMS: Consultancy, Honoraria, Speakers Bureau; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS: Consultancy, Honoraria, Speakers Bureau; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Sureda:Sanofi: Honoraria; BMS: Honoraria; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria; Roche: Honoraria; Takeda: Consultancy, Honoraria, Speakers Bureau; Gilead: Honoraria; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel Support; Amgen: Membership on an entity's Board of Directors or advisory committees. Perrot:jannsen: Honoraria, Membership on an entity's Board of Directors or advisory committees; takeda: Honoraria; Amgen: Honoraria; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi: Honoraria. Hulin:Janssen, AbbVie, Celgene, Amgen: Honoraria; celgene: Consultancy, Honoraria. Iida:Daichi Sankyo: Honoraria, Research Funding; Takeda: Honoraria, Research Funding; Chugai: Research Funding; Kyowa Kirin: Research Funding; Abbvie: Research Funding; MSD: Research Funding; Sanofi: Research Funding; Teijin Pharma: Research Funding; Astellas: Research Funding; Gilead: Research Funding; Celgene: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding; Novartis: Honoraria, Research Funding. Maisnar:Janssen, Amgen, Celgene, Takeda, BMS: Consultancy, Honoraria. Karlin:Takeda: 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, Other: Travel Support; Celgene: 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, Other: Travel Support. Parasrampuria:Janssen: Employment, Equity Ownership. Masterson:Janssen: Employment, Equity Ownership. Kosh:Janssen: Employment, Equity Ownership. Yang:Janssen: Employment, Equity Ownership. Delioukina:Janssen: Employment, Equity Ownership. Qi:Janssen: Employment. Carson:Janssen: Employment, Equity Ownership. OffLabel Disclosure: This abstract includes data from a phase 2 clinical trial of a subcutaneous formulation of daratumumab in combination with standard-or-care regimens. Subcutaneous daratumumab is currently under investigation in several clinical trials, but has not yet been approved. However, the intravenous formulation of daratumumab is approved as monotherapy and in combination with standard-of-care regimens for the treatment of multiple myeloma.

Background: Ibrutinib has transformed the clinical approach to relapsed mantle cell lymphoma (MCL) with those receiving ibrutinib at first relapse obtaining the greatest benefit encouraging use earlier in the treatment algorithm (Rule et al, 2019). However, the general applicability of clinical trial findings is not established and concerns regarding ibrutinib tolerability persist, especially in non-trial populations enriched for frailer patients with multiple co-morbidities. In the United Kingdom, ibrutinib is funded as standard of care at first relapse. This study has analysed the clinical effectiveness and tolerability of this approach in a non-clinical trial real world population. Method: 23 centres across the United Kingdom contributed data from consecutive patients treated with ibrutinib for MCL at first relapse. Patients received standard dose 560 mg OD, unless documented, and commenced treatment between August 2014 and April 2019. Response to therapy was defined as per Lugano classification (Cheson et al, 2014), although CR assessment by bone marrow biopsy was not always undertaken. Data was collected on baseline characteristics, including response to prior therapy, and MIPI at time of relapse. The study primary outcome was PFS. Predictors of progression were determined using univariate Cox regression. Results: 169 patients were included in the study. Median age at start of ibrutinib was 72 years (range 33 to 97) and 122 (72.2%) were male. At diagnosis 13.5% had blastoid histology; 59.3% Ki67 ≥30%; 32.0% received cytarabine based induction and 27.8% HSCT consolidation; 11.2% received low intensity frontline therapy (i.e. not fit for R-CHOP) due to frailty. Median PFS following frontline therapy was 21.4 months (95% CI 14.6 to 28.3) and 52.1% progressed within 2 years. At start of ibrutinib 52.2% were MIPI high risk; 23.9% were ECOG 2 or higher and 2.4% had CNS involvement. Overall response rate (ORR) to ibrutinib was 71.6% with 30.4% achieving CR/CRu. Estimated median PFS from start of ibrutinib was 16.5 months (95% CI 11.5 to 21.5) and estimated OS 23.9 months (95% CI 13.0 to 34.8), with median follow up 26 months. Median PFS for patients with early relapse to frontline therapy (progression of disease 1 were also negative predictors of PFS (see table 1 for univariate analysis). 10 patients (5.9%) received attenuated dose from start of therapy due to frailty and 20 patients (11.8%) underwent dose reductions while on therapy due to drug toxicity. Of 109 patients to discontinue ibrutinib 72 (66.1%) were due to progressive disease, 15 for consolidation alloHSCT (13.8%), 13 due to medical co-morbidities and unrelated death (11.9%), and 9 due to drug toxicity (8.3%), including 1 bleed. Only 5.3% of all patients stopped therapy due to drug toxicity. Patients ≥80 yrs were more likely to stop therapy early for reasons other than progressive disease or alloHSCT (OR 2.92, p=0.02), but frailer patients who received low intensity frontline therapy also showed a trend for more durable response with second-line ibrutinib (PFS 10.0 months versus 4.0 months, p=0.36) justifying use in this patient group. Conclusion: This study population is enriched for several recognised adverse prognostic markers, including older age and poor performance status, which is likely to explain differences in PFS relative to clinical trial data. Despite these features response rates were similar, and it is notable that 46.7% of evaluable pts achieved longer PFS with ibrutinib than preceding front-line therapy. It is reassuring that the proportion of patients stopping ibrutinib due to toxicity was similar to trial data and bleeding events that required alterations to therapy were rare (3 cases, 1.8%). Although ibrutinib represents a significant breakthrough with clear benefit to most patients the results also highlight that outcome for many remains poor. 40% of patients progressed within 1 year of starting ibrutinib and median OS post ibrutinib was only 3.6 months. 35.2% of patients died within 1 month of documented relapse suggesting many, predominantly older patients, were not fit for further therapy. Of the 53 pts surviving beyond 1 month median OS was 7.5 months and 21.9% lived beyond 1 year. Improved treatment strategies in the post-ibrutinib setting remains a priority. Disclosures Rule: Pharmacyclics: Consultancy, Honoraria; Gilead: Consultancy, Honoraria; Sunesis: Consultancy, Honoraria; TG Therapeutics: Consultancy, Honoraria; Napp: Consultancy; Roche: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Astra-Zeneca: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; Kite: Consultancy. Eyre:Gilead: Consultancy, Honoraria, Other: commercial research support; Abbvie: Honoraria; Janssen: Honoraria; Roche: Honoraria. Furtado:Abbvie: Honoraria. Shah:ABBVIE: Consultancy. Campbell:Novartis: Consultancy, Other: Educational support; Takeda: Consultancy, Other: Educational support; Bristol Myers-Squibb: Other: Educational support; Roche: Other: Educational support; Celgene: Other: Educational support. McCarthy:Janssen: Honoraria, Other: Educational grant to attend meetings . Lambert:Takeda Pharmaceuticals: Other: Funding to attend a scientific conference in 2018. McKay:Epizyme: Consultancy, Honoraria. Osborne:Roche: Consultancy, Honoraria, Other: Travel, Speakers Bureau; Gilead: Consultancy; MSD: Consultancy; Takeda: Consultancy, Honoraria, Other: Travel, Speakers Bureau; Novartis: Other: Travel; Pfizer: Honoraria, Speakers Bureau; Servier: Consultancy. Bishton:Takeda: Other: Travel support, Research Funding; AbbVie: Research Funding; Celltrion: Membership on an entity's Board of Directors or advisory committees, Other: travel support; Janssen: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; Roche: Other: Travel support, Research Funding. Crosbie:Janssen: Honoraria.

In chronic lymphocytic leukemia (CLL), analysis of immunoglobulin heavy chain variable regions for somatic hypermutation identifies 2 prognostic subsets, mutated and unmutated. Investigators have postulated that unmutated and mutated CLL arises from malignant transformation of pre– and post–germinal center (GC) B cells, respectively. Alternatively, unmutated cases may arise from B cells stimulated by T-cell–independent antigens or from GC B cells with inactive somatic hypermutation. Activation-induced cytidine deaminase (AID), a protein essential for somatic hypermutation, is expressed by GC B cells in which this process occurs. We investigated AID mRNA expression in 20 CLL cases. In 8 cases we detected high expression of wild-type AID mRNA and 2 splice variants; in 12 cases and 5 normal peripheral blood B-cell samples we detected no expression using standard conditions. Of 8 CLL cases that highly expressed AID, 7 were unmutated, suggesting that this subset may arise from GC-experienced B cells with inactive somatic hypermutation, and may predict prognosis.

Background: Chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL) occurs primarily in older patients (pts) who often have increased comorbidities and cannot tolerate aggressive treatments, which leads to poorer outcomes (Balducci, Cancer Control 2015; Thurmes, Leuk Lymphoma 2008). Alkylating agents, such as chlorambucil (clb), have been commonly used to treat these pts (Eichhorst, Blood 2009). Ibrutinib (ibr), a first-in-class, once-daily, inhibitor of Bruton's tyrosine kinase, is indicated by the US FDA for the treatment of pts with CLL/SLL and allows for treatment without chemotherapy. RESONATE-2 (PCYC-1115) is a randomized phase 3 trial designed to compare the efficacy and safety of ibr vs clb in pts with treatment-naïve (TN) CLL/SLL (Tedeschi, ASH 2015). Primary results, as assessed by an independent review committee (IRC), demonstrated with a median follow-up of 18.4 mo that ibr significantly reduced the risk of progression or death by 84% (P Methods: Eligible pts with TN CLL/SLL aged ≥65 y were randomized 1:1 to receive 420 mg ibr daily until progression or 0.5 mg/kg clb (max 0.8 mg/kg) on days 1 and 15 of a 28-d cycle for up to 12 cycles. Pts with del17p were excluded. Pts were stratified by ECOG status and Rai stage. The primary endpoint was PFS per iwCLL 2008 criteria, with 2012 clarification for treatment related lymphocytosis. Secondary endpoints included OS, ORR, rate of hematologic improvement, and safety; longer term follow-up safety data focused on ibr. Pts in the 1115 study with progressive disease (PD) were enrolled in the PCYC-1116 extension study. At 1115 study closure, all pts in 1115 rolled over to 1116. Pts on the clb arm with PD could cross-over to ibr or investigator's choice. Results: Median age of the 269 pts was 73 y (70% ≥70 y). Baseline characteristics were balanced between arms; 45% had advanced Rai stage, 20% had del11q, and 69% had comorbidities at baseline, including CIRS score >6, reduced creatinine clearance, or ECOG performance status of 2. With a median follow-up of 28.6 mo, prolongation of PFS for ibr vs clb was sustained (89% vs 34% at 24-mo; HR, 0.121; 95% CI 0.074-0.198; P Conclusions: With a median time on study of 28.6 mo, ibr continued to have substantial efficacy, with 88% reduction in risk of progression or death. Furthermore, the quality of responses has improved over time, with 18% of CLL/SLL pts achieving a CR/CRi with single agent ibr. Treatment limiting AEs decreased in frequency with longer follow-up, with 79% of this elderly pt population continues daily ibr. Lastly, even with a high rate of cross-over in the clb arm, OS remains significantly improved for pts randomized to ibr. Disclosures Barr: AbbVie: Consultancy; Pharmacyclics, LLC, an AbbVie Company: Consultancy, Research Funding. Robak:AbbVie: Consultancy, Honoraria, Research Funding; Pharmacyclics, LLC, an AbbVie Company: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding. Owen:Gilead: Honoraria, Research Funding; Janssen: Honoraria; Lundbeck: Honoraria; Roche: Consultancy, Honoraria, Research Funding; AbbVie: Honoraria; Celgene: Honoraria; Pharmacyclics, LLC, an AbbVie Company: Research Funding. Bairey:Janssen: Consultancy. Bartlett:Gilead: Consultancy. Burger:Janssen: Consultancy, Other: Travel, Accommodations, Expenses; Portola: Consultancy; Pharmacyclics, LLC, an AbbVie Company: Research Funding; Gilead: Research Funding; Roche: Other: Travel, Accommodations, Expenses. Hillmen:Pharmacyclics: Research Funding; Janssen: Honoraria, Research Funding; Roche: Honoraria, Research Funding; Gilead: Honoraria, Research Funding; Abbvie: Research Funding. Coutre:AbbVie: Research Funding; Pharmacylics, LLC, an AbbVie Company: Consultancy, Research Funding; Janssen: Consultancy. Devereux:Roche: Consultancy, Other: Travel, Accommodations, Expenses ; Gilead: Consultancy, Other: Travel, Accommodations, Expenses, Speakers Bureau; GSK: Consultancy; Janssen: Consultancy, Other: Travel, Accommodations, Expenses, Speakers Bureau. McCarthy:Roche: Consultancy, Other: Travel, Accomodations, Expenses; Chugai: Other: Travel, Accomodations, Expenses; Celgene: Other: Travel, Accomodations, Expenses. Simpson:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees. Offner:Novartis: Consultancy; GSK: Consultancy. Zhou:AbbVie: Equity Ownership; Pharmacyclics, LLC, an AbbVie Company: Employment. Styles:AbbVie: Equity Ownership; Pharmacyclics, LLC, an AbbVie Company: Employment. James:Pharmacyclics, LLC, an AbbVie Company: Employment; AbbVie: Equity Ownership. Kipps:Roche: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy, Honoraria, Research Funding; Pharmacyclics, LLC, an AbbVie Company: Consultancy, Honoraria; Gilead: Consultancy, Honoraria, Speakers Bureau. Ghia:Janssen: Consultancy; Pharmacyclics, LLC, an AbbVie Company: Consultancy; Roche: Consultancy, Research Funding; GSK: Research Funding; AbbVie: Consultancy; Adaptive: Consultancy; Gilead: Consultancy, Research Funding, Speakers Bureau.

Introduction: Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) primarily affects older patients (pts) who often have medical comorbidities along with disease-related immunosuppression and myelosuppression. Although alkylating agents such as chlorambucil (clb) have been commonly used in these pts, novel therapies are needed. Ibrutinib (ibr) is a first-in-class, oral, covalent inhibitor of Bruton's tyrosine kinase FDA-approved for pts with CLL who received ≥1 prior therapy and for del17p CLL (including first-line). Ibr showed high activity in treatment-naïve pts age ≥65 years, with an overall response rate (ORR) of 84% (complete response [CR] in 23%) and 30-month progression-free survival (PFS) of 96% (Byrd et al. Blood 2015). We conducted a randomized, open-label phase 3 trial to evaluate efficacy and safety of single-agent ibr vs clb in treatment-naïve older pts with CLL/SLL. Methods: Pts aged ≥65 years with treatment-naïve CLL/SLL were randomized 1:1 to receive 420 mg ibr daily until progression or clb 0.5 mg/kg (up to maximum of 0.8 mg/kg) on days 1 and 15 of a 28-day cycle for up to 12 cycles. Pts with del17p were excluded. Primary endpoint was independent review committee (IRC)-assessed PFS per iwCLL 2008 criteria, with 2012 clarification for treatment-related lymphocytosis. Secondary endpoints included overall survival (OS), ORR, event-free survival (EFS), rate of hematologic improvement, and safety. Pts with IRC-confirmed progression could transfer to an extension study where next-line therapy (including ibr) could be initiated if they had an iwCLL indication for treatment. Results: Among 269 pts enrolled, median age was 73 years (70% ≥70 years). Baseline characteristics were balanced between arms; 45% had advanced Rai stage, 20% had del11q, and 69% had comorbidities at baseline including CIRS score >6, reduced creatinine clearance, or ECOG status of 2. For pts treated with clb, 40% completed 12 cycles of therapy (mean dose 0.6 mg/kg). At a median follow-up of 18.4 months (mos), ibr significantly prolonged IRC-assessed PFS vs clb (median not reached [NR] vs 18.9 mos; HR 0.16, 95% CI 0.09-0.28, P Conclusions: Treatment with single-agent ibr was superior to clb in terms of PFS, OS, ORR, EFS and hematologic improvement in treatment-naïve older CLL/SLL patients, with an 84% reduction in risk of death, and an acceptable safety profile. Disclosures Off Label Use: ibrutinib in first-line CLL (including non-del17p CLL). Barr:Gilead: Consultancy; Abbvie: Consultancy; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding. Robak:Janssen: Consultancy, Research Funding; MorphoSys AG: Consultancy, Honoraria, Research Funding. Owen:Janssen: Honoraria; Lundbeck: Honoraria; Gilead: Honoraria; Roche: Honoraria. Ghia:Adaptive: Consultancy; Pharmacyclics: Consultancy; Gilead: Consultancy, Research Funding, Speakers Bureau; GSK: Research Funding; AbbVie: Consultancy; Janssen: Consultancy; Roche: Consultancy, Research Funding; Acerta Pharma BV: Research Funding. Hillmen:Janssen: Consultancy, Honoraria, Research Funding; AbbVie: Honoraria, Research Funding; Roche Pharmaceuticals: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Celgene: Research Funding; Pharmacyclics LLC, an AbbVie Company: Honoraria, Research Funding; Gilead: Honoraria, Research Funding. Bartlett:Novartis: Research Funding; Millennium: Research Funding; Pharmacyclics: Research Funding; Gilead: Consultancy, Research Funding; Genentech: Research Funding; MERC: Research Funding; Insight: Research Funding; Colgene: Research Funding; Medimmune: Research Funding; Seattle Genetics: Consultancy, Research Funding; Janssen: Research Funding; Pfizer: Research Funding; Kite: Research Funding; Dynavax: Research Funding; Idera: Research Funding; Portola: Research Funding; Bristol Meyers Squibb: Research Funding; Infinity: Research Funding; LAM Theapeutics: Research Funding. Coutre:Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics LLC, an AbbVie Company: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Research Funding. Quach:Celgene Corp, ONYX, Janssen, Takeda, Novartis, BMS: Honoraria, Research Funding. Janssens:Mundipharma: Speakers Bureau; Roche: Consultancy, Speakers Bureau; Janssen: Consultancy. O'Dwyer:Celgene: Honoraria, Research Funding. Hellmann:BMS: Consultancy, Other: funding of travel, accomodations or expenses, Speakers Bureau; Novartis: Consultancy, Other: funding of travel, accomodations or expenses, Research Funding, Speakers Bureau. Schuh:Acerta Pharma BV: Research Funding. Siddiqi:Seattle Genetics: Speakers Bureau; Pharmacyclics/Jannsen: Speakers Bureau; Kite pharma: Other: attended advisory board meeting. Tam:AbbVie: Honoraria; Roche: Honoraria; Janssen: Consultancy, Honoraria, Research Funding. Keating:Glaxo-Smith-Kline Inc.: Other: Advisory board; Celgene Corp.: Consultancy. Suri:Pharmacyclics LLC, an AbbVie Company: Employment. Zhou:Pharmacyclics LLC, an AbbVie Company: Employment. Clow:Pharmacyclics LLC, an AbbVie Company: Employment. Styles:Pharmacyclics LLC, an AbbVie Company: Employment. James:Pharmacyclics LLC, an AbbVie Company: Employment. Kipps:Pharmacyclics Abbvie Celgene Genentech Astra Zeneca Gilead Sciences: Other: Advisor; Pharmacyclics Abbvie Celgene Genentech Astra Zeneca Gilead Sciences: Other: Advisor. Burger:Pharmacyclics LLC, an AbbVie Company: Research Funding.

Most patients with follicular lymphoma (FL) have somatically mutated V genes with intraclonal variation, consistent with location in the germinal center site. Using our own and published sequences, we have investigated the frequency of potential N-glycosylation sites introduced into functional VH genes as a consequence of somatic mutation. FL cells were compared with normal memory B cells or plasma cells matched for similar levels of mutation. Strikingly, novel sites were detected in 55 of 70 (79%) patients with FL, compared to 7 of 75 (9%) in the normal B-cell population (P

Background The JAK2 V617F mutation is present in almost 95% of patients with Polycythemia Vera (PV). Prior to the discovery of this mutation, red cell mass and plasma volume measurement to establish the presence of true erythrocytosis was required first, before the diagnosis could be confirmed using other criteria. The revised WHO criteria no longer mandate this. Besides, access to this test is restricted in our region, due to non-availability of radio-isotopes. We previously showed the utility of early JAK2 mutation screening when used with history, physical examination, oxygen saturation, complete blood count, blood film examination, splenomegaly, serum erythropoietin, phlebotomy trial, bone marrow biopsy and, when available, red cell mass studies. Patients Between 2002 and 2006 we screened 231 consecutive patients referred to our institution with raised hemoglobin and hematocrit for JAK2 mutation. PV was diagnosed in 27 patients. Polycythemia of unknown cause (idiopathic) was identified in 40 patients after excluding patients with transient polycythemia and secondary polycythemia due to hypoxia, sleep apnoea, excessive smoking, alcohol abuse, renal disease, androgens or inherited causes. All PV patients were assessed at 3-6 monthly intervals from diagnosis until death or to present day. All idiopathic polycythemia patients were assessed at 6-12 monthly intervals until discharge, death or to present day. Patients with idiopathic polycythemia were discharged from follow-up when their hematocrit returned to normal range without any interventions for at least 12 months. All patients received thromboprophylaxis with aspirin or vitamin K antagonists as appropriate unless contra-indicated. Results Of 27 PV patients, 15 were males and 13 females. The median age at diagnosis was 69 years (range 21-88 years). Leucocytosis was present at diagnosis in 14 and thrombocytosis in 15 patients. Patients were treated with phlebotomy to a target hematocrit Conclusion Disease progression occurred in 11% (3/27) and thrombosis in 33% (9/27) of patients with PV. Idiopathic polycythemia was associated with thrombosis in 37% (15/40) of patients. Our findings indicate that thrombosis occurs with equal or higher frequency in idiopathic group when compared to PV group. These patients require a stricter target hematocrit control to Disclosures: Chacko: Amgen : Membership on an entity’s Board of Directors or advisory committees; GSK: Membership on an entity’s Board of Directors or advisory committees. Killick:Celgene: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Speakers Bureau; Novartis: Honoraria, Membership on an entity’s Board of Directors or advisory committees.

Abstract 60 Background: The length of remission in patients with chronic lymphocytic leukemia (CLL) is dependent on the level of minimal residual disease (MRD) at the end of therapy, regardless of the therapy received. The conversion of remissions from MRD positive to negative should prolong remissions and survival. Several small studies have used alemtuzumab as consolidation therapy following conventional chemotherapy but with concerns over toxicity; primarily due to immune suppression and infections. The dose and timing (i.e. interval between prior chemotherapy and alemtuzumab) seem to be critical. Trial Design: The Phase II NCRN CLL207 Trial assessed alemtuzumab consolidation post-chemotherapy. Between 6 and 24 months from completing treatment (1 to 3 prior therapies) blood was screened for MRD using multi-parameter flow cytometry with a sensitivity of less than a single CLL cell in 10,000 leucocytes (0.01%). The marrow of MRD positive patients was assessed to quantify the CLL before treatment with alemtuzumab at a dose of 30mg given subcutaneously 3 times a week for 6 weeks, at which time the marrow was repeated. MRD negative patients and non-responders stopped therapy; MRD positive patients with at least one log reduction in MRD continued therapy for a further 6 weeks. All patients received prophylaxis with co-trimoxazole and aciclovir as well as weekly cytomegalovirus (CMV) monitoring by PCR. It was pre-determined that at least 14 of up to 54 (26%) patients would need to be converted from MRD positivity to negativity to justify further studies of this treatment strategy. Results: 47 patients received alemtuzumab in NCRN CLL207 with median age of 58 yrs (40-77) and 35 (74.5%) males. There was a median of 2 prior therapies (range 1 to 4) with 46 pts receiving fludarabine combinations as the latest therapy and 9 receiving rituximab-containing combinations. There were a total of 21 SAE's in 17 (36.2%) pts with 2 (4.3%) treatment related deaths (EBV-LPD and a parainfluenza infection). Alemtuzumab was stopped in 6 patients before week 6 mainly due to toxicity, 32 patients received 6–8 weeks of treatment and 9 patients received a 12-week course. G-CSF was given when the neutrophil count fell below 1 × 10^9/l and 14 (30%) patients required G-CSF during alemtuzumab with an additional 13 (28%) receiving G-CSF after completion of alemtuzumab. Positive CMV PCRs were detected in 21 (45%) patients, all of whom were successfully treated with pre-emptive antiviral therapy. Prior to alemtuzumab 24 patients were in complete remission (CR) and 23 were in partial remission (PR). Three months after alemtuzumab 13/23 (56%) PR converted to CR. 39/47 (83%) patients had MRD negative marrows at the end of alemtuzumab, 7 (15%) remained MRD positive and 1 (2%) was not evaluable. Blood MRD assessment 6 months after completing alemtuzumab showed that 15/31 (48%) MRD negative patients became MRD positive, although all except 2 had low CLL levels (below 0.1×10^9/l) at this time-point. Therefore overall 16/39 (41%) patients were MRD negative 6 months after completing alemtuzumab and of these 8/9 (89%) remained MRD negative in the blood at 12 months. Therefore MRD negativity in the blood at 6 months seems to better predict for persistent MRD negativity than the marrow at the end of therapy and appears to be the most appropriate assessment for the outcome of consolidation. Patients who are MRD negative at this time-point usually have durable remissions. 6 of the 9 patients receiving 12 weeks of alemtuzumab were MRD negative at the end of treatment but only 1 (11%) remained MRD negative in the blood at 6 months. In contrast 33/38 patients receiving up to 8 weeks of alemtuzumab were MRD negative at the end of treatment and 15 (39%) remained MRD negative at 6 months suggesting that the patients who benefit most from alemtuzumab consolidation are those who are MRD negative at 6 weeks. Conclusion: Alemtuzumab consolidation results in the eradication of detectable MRD in 83% of patients and 41% remain MRD negative 6 months later. Consolidation with alemtuzumab is associated with mainly infective toxicities, which are largely manageable with prophylaxis and close monitoring. These results justify the continued investigation of this approach in CLL within a clinical trial setting and with appropriate monitoring of patients. To this end we are now commencing a randomized Phase III trial of consolidation with alemtuzumab compared to observation (the CLARET study). Disclosures: Pocock: F.Hoffmann-La Roche Ltd: Honoraria, Membership on an entity's Board of Directors or advisory committees. Rawstron:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; BD Bioscience: Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties; Genzyme: Honoraria. Dearden:Roche Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees; Genzyme: Honoraria, Membership on an entity's Board of Directors or advisory committees. Hillmen:Genzyme: Honoraria, Research Funding, Speakers Bureau; Roche Pharmaceuticals: Honoraria, Research Funding, Speakers Bureau; Glaxo Smith Kline: Honoraria, Research Funding.