Abstract: Introduction: The GEM-CESAR trial is a potentially curative strategy for high-risk smoldering multiple myeloma (HRsMM) patients in which the primary endpoint is the assessment of bone marrow minimal residual disease negativity by next generation flow (NGF). However, alternative methods of tumor burden evaluation in serum, like Quantitative Immunoprecipitation Mass Spectrometry (QIP-MS), a polyclonal antibody-based technology to identify intact immunoglobulins, have been also evaluated. Patients and Methods: Ninety HRsMM patients included in the GEM-CESAR trial received six 4-weeks cycles of carfilzomib, lenalidomide and dexamethasone followed by high dose melphalan and ASCT and 2 further cycles of consolidation with the same regimen. All patients received maintenance with lenalidomide up to 2 years. SPEP and IFE were performed using standard procedures and MRD was analyzed by flow cytometry following EuroFlow recommendations. QIP-MS assessment has been previously described (1) and allowed us the characterization of the isotype of each Ig trough immunoprecipitation with paramagnetic beads as well as the measurement of the molecular mass of each Ig for each specific patient, with enough precision and accuracy to establish clonality. Standard response assignment was carried out as per the IMWG guidelines. Results: First, we confirmed the higher sensitivity of QIP-MS to identify the presence of a serum M-spike as compared to conventional protein immunofixation electrophoresis methods. Amongst patients in CR, QIP-MS identified the M-spike in 18/30 (60%) post-induction, 18/47(38%) post-ASCT and 25/58(43%) post-consolidation. Interestingly, similar results were obtained with MRD-NGF post-induction [17/30(57%)] and post-ASCT [15/47(32%)] although the positive rate post-consolidation [15/58(26%)] was higher with QIP-MS. Then, we analyzed the overall concordance between the results obtained with QIP-MS and MRD-NGF at the three timepoints of disease evaluation, finding an overall concordance of 81% post-induction (n=76), 70% post-transplant (n=76) and 68% post-consolidation (n=77). Thus, when compared to the results of MRD-NGF, QIP-MS demonstrated sensitivities of 100%, 79% and 77% post-induction, post-ASCT and post-consolidation, and negative predictive values (NPV) of 100%, 79% and 82% at each respective time-point. (P & lt; 0,0001; P = 0,0004; P = =,0012) Evaluation of discrepant cases showed 14 out of 22 MRD-NGF-negative patients post-induction for whom QIP-MS identified a M-spike; in some cases (i.e. IgG MM isotype) this may be related to a longer immunoglobulin half-life. There were no cases with detectable disease by NGF but QIP-MS negative. By contrast, post-ASCT, QIP-MS was negative in seven MRD-positive patients, two of whom became MRD-NGF-negative after consolidation; at last follow-up, none of them have progressed. On the other hand, sixteen patients with negative MRD-NGF after ASCT had a detectable M-spike by mass spectrometry. Of note, the M-spike became undetectable after consolidation in six out of these 16 patients. Post-consolidation, there were 7 patients in which MRD-NGF was positive but QIP-MS negative: MRD evaluation during maintenance is pending but none of them have so far progressed. By contrast, there were 18 patients with the M-spike detectable by QIP-MS but MRD-NGF negative: follow-up of these patients will address their outcome but, the only patient that has progressed so far had MRD-NGF negative post-induction, becoming positive post-transplant and consolidation, but the M-spike was detectable by QIP-MS throughout. Conclusions: M-spike monitoring by QIP-MS shows a moderate concordance with the MRD assessment by NGF in this group of HRsMM homogeneously treated. Longer follow-up will allow us to unravel the outcome of discordant cases and to define the specificity of QIP-MS and its complementary value to NGF. North S, Barnidge D, Brusseau S, Patel R, Haselton M, Du Chateau B, et al. QIP-MS: A specific, sensitive, accurate, and quantitative alternative to electrophoresis that can identify endogenous m-proteins and distinguish them from therapeutic monoclonal antibodies in patients being treated for multiple myeloma. Clinica Chimica Acta 2019;493:S433. Disclosures Puig: Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Research Funding; The Binding Site: Honoraria; Takeda, Amgen: Consultancy, Honoraria. Mateos:Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive: Honoraria; GSK: Membership on an entity's Board of Directors or advisory committees; Pharmamar: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Janssen: 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; EDO: Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees. Paiva:Amgen, Bristol-Myers Squibb, Celgene, Janssen, Merck, Novartis, Roche, and Sanofi; unrestricted grants from Celgene, EngMab, Sanofi, and Takeda; and consultancy for Celgene, Janssen, and Sanofi: Consultancy, Honoraria, Research Funding, Speakers Bureau. Rodriguez Otero:Takeda: Consultancy; Kite Pharma: Consultancy; BMS: Honoraria; Celgene Corporation: Consultancy, Honoraria, Speakers Bureau; Janssen: Consultancy, Honoraria. Oriol:Celgene, Amgen, Takeda, Jansse: Consultancy, Speakers Bureau. Rios:Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees. Alegre:Celgene, Amgen, Janssen, Takeda: Membership on an entity's Board of Directors or advisory committees. de la Rubia:AbbVie: Consultancy; Janssen: Consultancy; Amgen: Consultancy; Celgene: Consultancy; Takeda: Consultancy. De Arriba:Amgen: Consultancy, Honoraria; Takeda: Honoraria; Janssen: Consultancy, Honoraria; Celgene: Consultancy, Honoraria. Ocio:Mundipharma: Research Funding; Pharmamar: Consultancy; Amgen: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria; AbbVie: Consultancy; Takeda: Consultancy, Honoraria; Array Pharmaceuticals: Research Funding; Sanofi: Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Seattle Genetics: Consultancy; Novartis: Consultancy, Honoraria; BMS: Honoraria. Bladé:Janssen, Celgene, Amgen, Takeda: Membership on an entity's Board of Directors or advisory committees; Irctures: Honoraria. Lahuerta:Takeda, Amgen, Celgene and Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees.

Abstract: Introduction:SMM is an asymptomatic and heterogeneous plasma cell disorder. The Spanish Myeloma Group demonstrated that patients at high risk of progression benefit from early treatment with Rd. In addition, our preliminary results of the curative approach (GEM-CESAR) showed encouraging results (Mateos ASH 2017). Aim: The primary end-point was to evaluate the Minimal Residual Disease negative (MRD-ve) rate by next generation flow (NGF) after induction and ASCT and the sustained MRD-ve rate at 3 and 5 yrs after ASCT as secondary end-points. Our aim was to increase the MRD -ve rate from 34% (reported in NDMM patients after VTD and ASCT) to 50%. As all patients have completed induction and ASCT, we report the results of the primary end point, efficacy and safety after induction and ASCT. Methods: In this phase II single arm trial, 90 SMM patients at high-risk of progression ( 〉 50% at 2 yrs), younger than 70 yrs and transplant candidates were included. The high risk was defined by the presence of both ≥PC 10% and MC ≥3g/dL (Mayo criteria) or ifonly one criterion was present, patients must have a proportionof aberrant PCs within the total PCsBM compartment by immunophenotypingof 95% plus immunoparesis (Spanish criteria). Asymptomatic MM patients with any of the three biomarkers recently included into the definition of active MM were allowed to be included. Induction therapy consisted on six 4-weeks cycles of KRd in which K was given at dose of 36 mg/m2twice per week plus R at dose of 25 mg on days 1-21 and dexamethasone at dose of 40 mg weekly. Melphalan at dose of 200 mg/m2followed by ASCT was given as intensification therapy and three months later, patients received two KRd consolidation cycles followed by maintenance with R at dose of 10 mg on days 1-21 plus dex at dose of 20 mg weekly for up to 2 yrs Results: Between June 2015 and June 2017, the 90 SMM patients at high risk of progression were recruited. Twenty-eight pts (32%) shared at least one of the new biomarkers predicting imminent risk of progression to MM. The primary end point of the trial was met, since 55% of the patients who completed induction and ASCT achieved MRD -ve by NGF (sensitivity 3 x 10-6). Upon analyzing the results after induction, 88 patients completed the 6 induction cycles and were evaluable for response (two patients early discontinued): the ORR was 98% including 41% of ≥CR (32% sCR and 9% CR) and 41% of VGPR rate. Two patients were mobilization failures and one patient rejected ASCT. Two additional patients experienced biological progression before ASCT and went off the study. Eighty-three patients, therefore, proceeded to HDT-ASCT and were evaluable at day +100: the ORR was 100% including ≥CR in 63% of the patients (51% sCR and 12% CR) and VGPR rate in 23%. The MRD-ve rate increased from 31% after induction to 55% with the ASCT. No differences in outcome have been observed according neither to the definition of high risk (Mayo or Spanish model) nor ultra high risk SMM. Concerning toxicity, during induction, G3-4 neutropenia and thrombocytopenia were reported in 5 (6%) and 10 pts (11%), respectively. G3-4 infections were the most frequent non-hematological AE observed in 16 pts (18%), followed by skin rash in 8 pts (9%). One patient reported G1 atrial fibrillation and another cardiac failure secondary to respiratory infection. Three patients reported hypertension (G2 in two and G3 in one). Thirteen patients required lenalidomide dose reduction whilst carfilzomib was not reduced in any patient. In four patients, dexamethasone was reduced. In all but two of the pts, PBSC collection was successful with a median of 4.10 x 106/Kg CD34 cells collected. All patients engrafted. Consolidation and maintenance phases are ongoing. After a median follow-up of 17 months (5-36), 94% of patients remain alive and free of progression and 97% of them alive. Three patients experienced biological progression and discontinued the study: one of them was refractory to the rescue therapies and died and the other two are receiving rescue therapies. One additional patient died early during induction due to a massive ischemic stroke unrelated to the treatment. Conclusions: Although longer follow-up is required, this "curative strategy for high risk SMM" continues being encouraging with an acceptable toxicity profile. The study has met its primary endpoint. The depth of response improved over the treatment: 63% of patients who completed induction and ASCT achieved ≥CR with a MRD-ve rate of 55%. Disclosures Mateos: Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; 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; GSK: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; GSK: Consultancy, Membership on an entity's Board of Directors or advisory committees. Rodriguez Otero:Takeda: Consultancy; Celgene: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria; Bristol Myers Squibb: Research Funding; Clínica Universidad de Navarra: Employment. Ocio:AbbVie: Consultancy; Pharmamar: Consultancy; Seattle Genetics: Consultancy; Janssen: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; BMS: Consultancy; Takeda: Consultancy, Honoraria; Sanofi: Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Mundipharma: Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Array Pharmaceuticals: Research Funding. Oriol:Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Rios:Amgen, Celgene, Janssen, and Takeda: Consultancy. Rosinol:Janssen, Celgene, Amgen, Takeda: Honoraria. Alegre:Takeda: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees. Puig:Janssen: Consultancy, Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Takeda: Consultancy, Honoraria. De La Rubia:Ablynx: Consultancy, Other: Member of Advisory Board. García Mateo:Binding Site: Research Funding; Amgen: Honoraria; Celgene: Honoraria. Bladé:Janssen: Honoraria. Lahuerta:Celgene: 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; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees. San-Miguel:Novartis: Honoraria; Janssen: Honoraria; BMS: Honoraria; Amgen: Honoraria; Celgene: Honoraria; Sanofi: Honoraria; Roche: Honoraria.

Abstract: Introduction: SMM is an asymptomatic plasma cell disorder with heterogeneous clinical behavior. Both the Spanish Myeloma and ECOG Groups have demonstrated that patients (pts) at high risk of progression to active MM have prolonged time-to progression upon receiving early treatment with R-based regimens. Our next step was to perform a phase 2, single arm trial, focusing on the same population, but aiming at abrogating the risk of progression through the achievement of sustained minimal residual disease negativity (MRD-ve) at 3 and 5 years after HDT-ASCT. Patients and methods: Ninety SMM pts at high-risk of progression ( & gt;50% at 2 yrs), younger than 70 years and transplant candidates were included. The high risk was defined by the presence of both ≥PC 10% and MC ≥3g/dL (Mayo criteria) or ifonly one criterion was present, pts should have & gt;95%of aberrant PCs within the total PCsBM compartment by immunophenotyping plus immunoparesis (Spanish criteria). Induction therapy consisted of six 4-weeks cycles of KRd in which K was given at dose of 36 mg/m 2 twice per week plus R at dose of 25 mg on days 1-21 and dexamethasone at dose of 40 mg weekly. Melphalan at dose of 200 mg/m 2 followed by ASCT was given as intensification therapy followed by two KRd consolidation cycles and maintenance with R at dose of 10 mg plus dexamethasone at dose of 20 mg weekly for up to 2 yrs. The primary end-point was to evaluate the MRD-ve rate by next generation flow (NGF) after ASCT and MRD-ve rate maintained at 3 and 5 years after ASCT. Results: Between June 2015 and June 2017, 90 high-risk SMM pts were recruited and 70 pts (78%) have completed the treatment protocol. The reasons for early discontinuations were: IC withdrawal (4 pts), adverse events (8 pts) or biological progression (BP), either biochemical or because of MRD conversion from negative to positive (1 pt during induction and 7 pts during maintenance). Thirty-one pts (34%) shared at least one of the biomarkers considered as myeloma defining events that currently reclassify SMM into active MM. In the intent-to-treat (ITT) pts' population, after induction, the ≥CR rate was 41% and increased to 65% after HDT-ASCT and 72% after consolidation. During maintenance therapy, 7 pts experienced biological progression (2 pts conversion from MRD-ve into +ve and 5 pts biochemical progression) and the ≥CR rate at the end of treatment was 63.3%. In the ITT population, MRD-ve rates at 10 -5 were observed in 40% of pts after induction, 63% after HDT-ASCT, 68% after consolidation and 52% after maintenance therapy. Among MRD-ve patients after maintenance therapy that had MRD assessed one year after, 67% showed sustained MRD-ve. After a median f/u of 55 months (range: 6.2-71), only three patients progressed to symptomatic disease and the three had at baseline anyone of the biomarkers defining myeloma-defining events. At 5 years, 94% of pts remain alive and progression-free and 95% of pts alive (Figure 1). Overall, twenty-six pts (29%) have experienced biological progression (19 of them were conversion of MRD-ve into +ve), 8 of them during treatment phase (1 during induction and 7 during maintenance) and 16 pts during the follow-up period. The only factors predicting biological progression was failure to achieve MRD-ve at the end of treatment and unsustained MRD-ve at 1 year after finalizing maintenance. Concerning toxicity, during induction, G3-4 neutropenia and thrombocytopenia were reported in 5 (6%) and 10 pts (11%), respectively. G3-4 infections were reported in 16 pts (18%), followed by skin rash in 8 pts (9%). One patient reported G1 atrial fibrillation and another cardiac failure secondary to respiratory infection. Three pts reported hypertension (G2 in two and G3 in one). In all but two of the pts, PBSC collection was successful with a median of 4.10 x 10 6/Kg CD34 cells collected. All pts engrafted but one patient developed late graft failure. During consolidation, 2 pts developed G3-4 neutropenia, 3 pts G3-4 infections and 1 pt skin rash. Seven pts had to discontinue maintenance therapy due to: G3-4 hematological toxicity (4 pts), SPM (2pts) and cardiac arrest (1pt). One additional patient withdrew the IC. Conclusions: These results suggest that early treatment with intention to abrogate risk of progression in transplant candidate high risk SMM patients is associated with a 94% PFS at 55 months and a sustained MRD negative rate at 1 year post treatment of 67%. Figure 1 Figure 1. Disclosures Mateos: Sea-Gen: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Honoraria; Regeneron: 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; Roche: 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; Adaptive Biotechnologies: 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; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bluebird bio: Honoraria; Celgene - Bristol Myers Squibb: 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; GSK: Honoraria; Oncopeptides: Honoraria. Rodríguez-Otero: Celgene-BMS, Janssen, Amgen, Sanofi, GSK, Oncopeptides: Honoraria, Membership on an entity's Board of Directors or advisory committees; Regeneron: Honoraria. Gonzalez-Calle: BMS, Janssen, Amgen: Honoraria. Oriol: Celgene: Consultancy, Speakers Bureau; Takeda: Consultancy, Speakers Bureau; Janssen: Consultancy; Amgen: Consultancy, Speakers Bureau. Rosinol: Janssen, Celgene, Amgen and Takeda: Honoraria. de la Rubia: Takeda: Consultancy; Amgen, Bristol Myers Squibb,: Honoraria, Speakers Bureau; GSK: Consultancy; Celgene, Takeda, Janssen, Sanofi: Honoraria; Ablynx/Sanofi: Consultancy; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel Accommodations; Celgene: Consultancy; AbbVie: Consultancy; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES; Sanofi: Membership on an entity's Board of Directors or advisory committees. De Arriba: Amgen: Consultancy, Honoraria; Glaxo Smith Kline: Consultancy, Honoraria; BMS-Celgene: Consultancy, Honoraria, Speakers Bureau; Janssen: Consultancy, Honoraria, Speakers Bureau. Ocio: MSD: Honoraria; Sanofi: Consultancy, Honoraria; Karyopharm: Consultancy; Takeda: Consultancy, Honoraria, Speakers Bureau; Janssen: Consultancy, Honoraria, Speakers Bureau; Bristol-Myers Squibb/Celgene: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Oncopeptides: Consultancy, Honoraria; Pfizer: Consultancy; Secura-Bio: Consultancy. Paiva: Bristol-Myers Squibb-Celgene, Janssen, and Sanofi: Consultancy; Adaptive, Amgen, Bristol-Myers Squibb-Celgene, Janssen, Kite Pharma, Sanofi and Takeda: Honoraria; Celgene, EngMab, Roche, Sanofi, Takeda: Research Funding. Puig: Celgene, Janssen, Amgen, Takeda: Research Funding; Celgene: Speakers Bureau; Amgen, Celgene, Janssen, Takeda: Consultancy; Amgen, Celgene, Janssen, Takeda and The Binding Site: Honoraria. Cedena: Janssen, Celgene and Abbvie: Honoraria. Lahuerta: Celgene: Other: Travel accomodations and expenses; Celgene, Takeda, Amgen, Janssen and Sanofi: Consultancy. San-Miguel: AbbVie, Amgen, Bristol-Myers Squibb, Celgene, GlaxoSmithKline, Janssen, Karyopharm, Merck Sharpe & Dohme, Novartis, Regeneron, Roche, Sanofi, SecuraBio, Takeda: Consultancy, Other: Advisory board.

Abstract: Introduction: The GEM-CESAR trial is a potentially curative strategy for high-risk smoldering multiple myeloma (HRsMM) patients (pts) in which the primary endpoint is the achievement of bone marrow minimal residual disease (MRD) negativity. However, other methods of disease evaluation in serum such as heavy+light chain (HLC) assessment, with a potential complementary value to the IMWG response criteria, have also been tested. Aim: To evaluate the performance of HLC assay in HRsMM pts at diagnosis and after consolidation, comparing the results with standard serological methods and Next Generation Flow (NGF) for the assessment of bone marrow MRD. Patients and Methods: Ninety HRsMM pts included in the GEM-CESAR trial received six 4-weeks cycles of carfilzomib, lenalidomide and dexamethasone followed by high dose melphalan and 2 further cycles of consolidation with the same regimen. All pts received maintenance treatment with lenalidomide for up to 2 years. SPEP and IFE were performed using standard procedures. Serum IgGk, IgGl, IgAk and IgAl HLC concentrations were measured using Hevylite (The Binding Site Group Ltd, Birmingham, UK) on a SPA PLUS turbidimeter. HLC concentrations and ratios were considered abnormal if they were outside the 95% reference ranges provided by the manufacturer. MRD was analyzed by flow cytometry following EuroFlow recommendations (sensitivity, 2x10-6). Standard response assignment was carried out as per the IMWG guidelines. Hevylite responses were assigned and HLC-pair suppression was defined as in Michalet et al (Leukemia 2018). Results: Out of 90 HRsMM pts, 75 had monoclonal intact immunoglobulin and samples available at diagnosis (50 IgG and 25 IgA). HLC ratio was abnormal in 98% of IgG pts and in 100% of IgA pts. Response assessment by Hevylite and standard IMWG criteria were available in 62 pts post-consolidation (Table 1). A good agreement was found between the two methods (kappa quadratic weighting = 0,6327 (0,4016 - 0,8638)). Among 46 pts with assigned CR as per the IMWG response criteria, there were 3 and 8 pts in PR and VGPR according to the Hevylite method, respectively. In 62 cases, paired Hevylite and MRD assessment data were available. Concordant results were found in 72.5% of cases (45/62; HLC+/NGF+ in 15 and HLC-/NGF- in 30 cases) while in the remaining 27.4% of cases results were discordant (17/62; HLC-/NGF+ in 6 and HLC+/NGF- in 11 cases). Post-consolidation, 24, 25.8 and 42.3% of the 62 samples were positive by SPEP, NGF and Hevylite, respectively. HLC-pair suppression was identified in 13/62 pts; 10 had severe HLC-pair suppression at the end of consolidation. After a median follow-up of 32 months (8-128), 93% of pts remain alive and progression-free. Three patients that have already progressed had their responses assessed post-consolidation. The first pt was assigned VGPR by the standard IMWG criteria and PR by Hevylite and was MRD positive by NGF; the second pt was assigned CR by IMWG criteria and Hevylite but had severe HLC-pair immunosuppression and was MRD positive by NGF; the third pt was in CR by IMWG and HLC criteria and was MRD positive by MFC. Conclusions: Moderate agreement was found between response assessment by Hevylite and the standard IMWG methods as well as between Hevylite and MRD assessment by NGF. Most discordances were a result of Hevylite detecting disease in samples negative by the standard methods, but longer follow-up is needed to ascertain its clinical value. HLC assessment could have anticipated the progression noted in 2 (out of 3) patients. Disclosures Puig: Takeda, Amgen: Consultancy, Honoraria; The Binding Site: Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Paiva:Amgen, Bristol-Myers Squibb, Celgene, Janssen, Merck, Novartis, Roche and Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene, Janssen, Sanofi and Takeda: Consultancy. Rodriguez Otero:Kite Pharma: Consultancy; Celgene Corporation: Consultancy, Honoraria, Speakers Bureau; BMS: Honoraria; Janssen: Consultancy, Honoraria; Takeda: Consultancy. Oriol:Celgene, Amgen, Takeda, Jansse: Consultancy, Speakers Bureau. Rios:Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees. Alegre:Celgene, Amgen, Janssen, Takeda: Membership on an entity's Board of Directors or advisory committees. de la Rubia:Amgen: Consultancy; Janssen: Consultancy; Celgene: Consultancy; Takeda: Consultancy; AbbVie: Consultancy. De Arriba:Celgene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Takeda: Honoraria. Ocio:Celgene: Consultancy, Honoraria, Research Funding; Sanofi: Research Funding; BMS: Honoraria; Novartis: Consultancy, Honoraria; Array Pharmaceuticals: Research Funding; Pharmamar: Consultancy; Seattle Genetics: Consultancy; Mundipharma: Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria; AbbVie: Consultancy; Janssen: Consultancy, Honoraria. Bladé:Janssen, Celgene, Amgen, Takeda: Membership on an entity's Board of Directors or advisory committees; Irctures: Honoraria. Mateos:Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pharmamar: Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; GSK: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; EDO: Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive: Honoraria; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees.

Abstract: Peter Paschka and Hartmut Döhner contributed equally. Background. SARS-CoV-2 infection (COVID-19) has had a great impact worldwide and its mortality has been reported to be higher in patients with haematological malignancies. However, description of its effects and outcomes among recipient of hematopoietic stem cell transplantation (HSCT) is scarce. Objectives. To describe the characteristics, treatment and outcome of COVID-19 in recipients of HSCT reported to the Madrid registry of COVID-19 ("HEMATO-MADRID COVID-19 registry"). Results. Data of 842 patients from 23 hospitals with haematological malignancies and COVID-19 infection were reported in the Madrid registry between March and June 2020. Among those, 87 (10.3%) patients were HSCT recipients: 58 auto-HSCT and 29 allo-HSCT (7 of them from matched related donor (MRD), 12 matched unrelated donor (MUD) and 10 haplo-HSCT). Characteristics of the population are described in Table 1. Median age at COVID-19 infection was 61 years (IQR, 53-67) and 35 patients (40%) were female. Recipients of auto-HSCT with COVID-19 were older and showed a trend towards a higher incidence of arterial hypertension (28% vs 10%, p=0.067) without statistical differences in other comorbidities; active disease requiring treatment at COVID-19 diagnosis was more frequent in auto-HSCT recipients (65% vs. 21%, p & lt;0.001). Median time from transplant to COVID19 infection was shorter in allo-HSCT patients (32 vs. 19 months, p=0.043). Nearly 40% of allo-recipients had active GVHD at COVID-19 debut, including pulmonary GVHD. A total of 63 (72%) patients required hospital admission and 13 patients (15%) received intensive care support. Allo-recipients showed a trend towards a higher need of hospital admission (79% vs. 68%, p=0.081). Most patients received anti-viral treatment with either hydroxichloroquine (47 patients, 54%), lopinavir/ritonavir (34 patients, 39%), remdesivir (5, 4%) and/or other treatments including azythromicin or interferon. 23 patients (26%) received anticytokine treatment with tocilizumab (15, 17%) and/or anakinra (8, 9%) and 27 patients (31%) received steroids. The overall response rate to treatment and supportive care was 80% in both groups. After a median follow-up of 50 days after the infection debut, overall-survival at day 50 was 84% for auto and 82% for allo-HSCT recipients (p=0.915). However, global mortality rate among the complete observation period was significantly higher in allo-recipients (24% vs. 17%, p & lt;0.001). Conclusion. In our multicentric experience in a high COVID-19 impacted area, the median time of COVID-19 infection presentation was relatively late in transplanted patients, however shorter in allo-transplanted patients. COVID-19 related mortality was high in HSCT recipients, significantly higher in allo-transplanted patients. Factors associated to this higher mortality should be further investigated to promptly identify high-risk patients since the pandemic is still highly active worldwide. Disclosures Kwon: Gilead: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Jazz: Consultancy, Honoraria. Duarte:Incyte Corporation: Other: Has received speaker and advisor fees. Hernandez-Rivas:Rovi: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees; Celgene/BMS: Membership on an entity's Board of Directors or advisory committees. Jimenez Yuste:NovoNordisk: Consultancy, Honoraria, Research Funding; Roche: Consultancy, Honoraria; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; Grifols: Honoraria, Research Funding; Bayer: Honoraria; Sobi: Consultancy, Honoraria, Research Funding; CSL: Honoraria; Octapharma: Honoraria.

Abstract: Despite improvement in the treatment of advanced classical Hodgkin lymphoma, approximately 30% of patients relapse or die as result of the disease. Current predictive systems, determined by clinical and analytical parameters, fail to identify these high-risk patients accurately. We took a multistep approach to design a quantitative reverse-transcription polymerase chain reaction assay to be applied to routine formalin-fixed paraffin-embedded samples, integrating genes expressed by the tumor cells and their microenvironment. The significance of 30 genes chosen on the basis of previously published data was evaluated in 282 samples (divided into estimation and validation sets) to build a molecular risk score to predict failure. Adequate reverse-transcription polymerase chain reaction profiles were obtained from 262 of 282 cases (92.9%). Best predictor genes were integrated into an 11-gene model, including 4 functional pathways (cell cycle, apoptosis, macrophage activation, and interferon regulatory factor 4) able to identify low- and high-risk patients with different rates of 5-year failure-free survival: 74% versus 44.1% in the estimation set (P & lt; .001) and 67.5% versus 45.0% in the validation set (P = .022). This model can be combined with stage IV into a final predictive model able to identify a group of patients with very bad outcome (5-year failure-free survival probability, 25.2%).

Abstract: Introduction In the first weeks of the Covid-19 pandemic when healthcare systems in many areas were overstretched, we documented that hospital mortality in multiple myeloma (MM) patients infected by Sars-Cov-2 was 50% higher than in age matched Covid-19 patients without cancer. In the following months, the pressure on healthcare systems in Spain continued although it did not reach the extreme levels of the first weeks of the pandemic. In this study, we proposed to determine if the severity of Covid-19 outcomes in MM patients has changed over the first year of the pandemic. Patients and methods The Spanish MM Collaborative Group (Pethema-GEM) conducted a survey at national level on plasma cell disorder patients infected by SARS-Cov-2 between March 2020 and February 2021. Sixty-six (69%) out of 96 contacted healthcare centers, from all 17 regions in Spain, reported 502 patients. Data on Covid-19 acute and post-acute phase outcomes (hospitalization, oxygen requirements, severity of symptoms and mortality) were reported first in May 2020 (Martinez-Lopez et al, BCJ 2021) and updated in February 2021. In this study, we compared outcome occurrence between two study periods: P1, a period of extreme stress for the healthcare system in Spain, from March to mid-June 2020; and a second period, P2, up to mid-February 2021 with a sustained but lower burden on the national health care system. Results Among the 451 patients with plasma cell disorders and a Sars-Cov-2 infection documented with an rRT-PCR positive test, 377 (84%) were MM patients, 15 SMM (3%), 40 MGUS (9%) and 19 amyloidosis (4%). The number of MM weekly reported cases was 57% (95%CI, 48-65) lower in P2 (188 cases in 35 weeks) compared to P1 (189 cases in 15 weeks), p & lt;0.001. The mean (SD) age and the proportion of men did not differ between P1 and P2, respectively 69.8 (10.9) vs 68.6 (11.0) years, p=0.6, and 53.3% vs 59.6%, p=0.2. MM patients with active or progressive disease at time of Covid-19 diagnosis were 24% in P1 and 34% in P2, p=0.05; patients on active treatment were more frequent in P1, 89%, than in P2, 79%, p=0.01. MM treatment was withheld in 78% and 82% of patients, p=0.4. Covid-19 treatment changed over time: MM inpatients received more remdesivir and corticoids in the second period (3% vs 31% p & lt;0.001, and 49% vs 73%, p & lt;0.001, respectively). In P1, 90% of the reported MM patients were hospitalized compared to 71% in P2, p & lt;0.001. Thirty-one and 41% of patients did not require oxygen support during P1 and P2, respectively; non-invasive ventilation in 19% and 14%, and mechanical ventilation in 7% and 8%, p=0.12. Overall, acute clinical Covid-19 severity was reduced from P1 to P2: 75% to 51%, p & lt;0.001: moderate/severe pneumonia was reduced from 68% to 36%, p & lt;0.001 but severe distress syndrome increased from 7% to 15%, p=0.03. However, mortality in all reported patients was 30.7% in P1 vs 26.1% in P2, p=0.3; and no differences in mortality were observed in hospitalized patients, 32.2% in P1 and 35.3% in P2, p=0.6. We performed a multivariable adjustment with the predictors identified in our previous study (BCJ 2021) and confirmed that inpatient mortality was similar in both study periods, odds ratio (OR) 0.99 (95%CI 0.59-1.66). Independently of the study period, an increased mortality was observed in men (OR 1.81, 1.08-3.05), patients over 65 (OR 2.40, 1.33-4.36), and patients with active or progressive disease (OR 2.12, 1.24-3.62). The severity of Covid-19 clinical outcomes -besides mortality, was associated with increased age but not with active or progressive disease. Conclusions Although COVID-19 clinical severity has decreased over the first year of the pandemic in multiple myeloma patients, mortality remains high with no change between the initial weeks of the pandemic and the following months. Prevention and vaccination strategies should be strengthened in this vulnerable population, particularly in patients with active or progressive disease at time of Covid-19 diagnosis. Disclosures Martínez-López: Janssen, BMS, Novartis, Incyte, Roche, GSK, Pfizer: Consultancy; Roche, Novartis, Incyte, Astellas, BMS: Research Funding. Mateos: Oncopeptides: 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; Amgen: 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; 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; AbbVie: Honoraria; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees; 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; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bluebird bio: Honoraria; GSK: Honoraria; Oncopeptides: Honoraria. López-Muñoz: Amgen: Consultancy. Sureda: GSK: Consultancy, Honoraria, Speakers Bureau; Sanofi: 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; Roche: Other: Support for attending meetings and/or travel; Mundipharma: Consultancy; Bluebird: Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Kite, a Gilead Company: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; MSD: Consultancy, Honoraria, Speakers Bureau; BMS/Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Support for attending meetings and/or travel, Speakers Bureau; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Support for attending meetings and/or travel, Research Funding, Speakers Bureau. Rosinol: Janssen, Celgene, Amgen and Takeda: Honoraria. Lahuerta: Celgene, Takeda, Amgen, Janssen and Sanofi: Consultancy; Celgene: Other: Travel accomodations and expenses. San-Miguel: AbbVie, Amgen, Bristol-Myers Squibb, Celgene, GlaxoSmithKline, Janssen, Karyopharm, Merck Sharpe & Dohme, Novartis, Regeneron, Roche, Sanofi, SecuraBio, Takeda: Consultancy, Other: Advisory board.

Abstract: Abstract 3660 Poster Board III-596 Introduction Despite the major advances in the treatment of classical Hodgkin Lymphoma (cHL) patients, around 30% to 40% of cases in advanced stages may relapse or die as result of the disease. Current predictive systems, based on clinical and analytical parameters, fail to identify accurately this significant fraction of patients with short failure-free survival (FFS). Transcriptional analysis has identified genes and pathways associated with clinical failure, but the biological relevance and clinical applicability of these data await further development. Robust molecular techniques for the identification of biological processes associated with treatment response are necessary for developing new predictive tools. Patients and Methods We used a multistep approach to design a quantitative RT-PCR-based assay to be applied to routine formalin-fixed, paraffin-embedded samples (FFPEs), integrating genes known to be expressed either by the tumor cells and their reactive microenvironment, and related with clinical response to adriamycin-based chemotherapy. First, analysis of 29 patient samples allowed the identification of gene expression signatures related to treatment response and outcome and the design of an initial RT-PCR assay tested in 52 patient samples. This initial model included 60 genes from pathways related to cHL outcome that had been previously identified using Gene Set Enrichment Analysis (GSEA). Second, we selected the best candidate genes from the initial assay based on amplification efficiency, biological significance and treatment response correlation to set up a novel assay of 30 genes that was applied to a large series of 282 samples that were randomly split and assigned to either estimation (194) or validation series (88). The results of this assay were used to design an algorithm, based on the expression levels of the best predictive genes grouped in pathways, and a molecular risk score was calculated for each tumor sample. Results Adequate RT-PCR profiles were obtained in 264 of 282 (93,6%) cases. Normalized expression levels (DCt) of individual genes vary considerably among samples. The strongest predictor genes were selected and included in a multivariate 10-gene model integrating four gene expression pathway signatures, termed CellCycle, Apoptosis, NF-KB and Monocyte, which are able to predict treatment response with an overall accuracy of 68.5% and 73.4% in the estimation and validation sets, respectively. Patients were stratified by their molecular risk score and predicted probabilities identified two distinct risk groups associated with clinical outcome in the estimation (5-year FFS probabilities 75.6% vs. 45.9%, log rank statistic p≈0.000) and validation sets (5-year FFS probabilities 71.4% vs. 43.5%, log rank statistic p 〈 0.004). Moreover, this biological model is independent of and complementary to the conventional International Prognostic Score using multivariate Cox proportional hazards analysis. Conclusions We have developed a molecular risk algorithm that includes genes expressed by tumoral cells and their reactive microenvironment. This makes it possible to classify advanced cHL patients with different risk of treatment failure using a method that could be applied to routinely prepared tumor blocks. These results could pave the way for more individualized and risk-adapted treatment strategies of cHL patients, enabling subsets of patients to be identified who might benefit from alternative approaches Disclosures: No relevant conflicts of interest to declare.

Abstract: C-type lectin-like receptor 2 (CLEC-2) is an essential platelet-activating receptor in hemostasis and thrombosis that is activated by the snake venom rhodocytin. We present here a differential proteomic analysis of basal and rhodocytin-activated platelets with the aim of providing novel clues on CLEC-2 signaling regulation. Proteome analysis was based on 2D-DIGE, phosphotyrosine immunoprecipitations followed by 1D SDS-PAGE and mass spectrometry. Protein-protein interactions were studied by coimmunoprecipitations and a systems biology approach. Overall, we identified 132 proteins differentially regulated after CLEC-2 platelet activation, including most of the major players reported so far in the signaling cascade. In addition, we identified various proteins not previously known to participate in CLEC-2 signaling, such as the adapters Dok-2 and ADAP, tyrosine kinase Fer, and tyrosine phosphatase SHIP-1. We also report an increased association between Dok-2 and SHIP-1 in rhodocytin-stimulated platelets, which might negatively regulate CLEC-2 signaling. Moreover, we also present a comparative analysis of proteomic data for CLEC-2 and glycoprotein VI signaling. We think that our data provide thrombosis-relevant information on CLEC-2 signaling regulation, contributing to a better understanding of this important signaling cascade.

Abstract: Clonal evolution in acute myeloid leukemia (AML) originates long before diagnosis and is a dynamic process that may affect survival. However, it remains uninvestigated during routine diagnostic workups. We hypothesized that the mutational status of bone marrow dysplastic cells and leukemic blasts, analyzed at the onset of AML using integrated multidimensional flow cytometry (MFC) immunophenotyping and fluorescence-activated cell sorting (FACS) with next-generation sequencing (NGS), could reconstruct leukemogenesis. Dysplastic cells were detected by MFC in 285 of 348 (82%) newly diagnosed patients with AML. Presence of dysplasia according to MFC and World Health Organization criteria had no prognostic value in older adults. NGS of dysplastic cells and blasts isolated at diagnosis identified 3 evolutionary patterns: stable (n = 12 of 21), branching (n = 4 of 21), and clonal evolution (n = 5 of 21). In patients achieving complete response (CR), integrated MFC and FACS with NGS showed persistent measurable residual disease (MRD) in phenotypically normal cell types, as well as the acquisition of genetic traits associated with treatment resistance. Furthermore, whole-exome sequencing of dysplastic and leukemic cells at diagnosis and of MRD uncovered different clonal involvement in dysplastic myelo-erythropoiesis, leukemic transformation, and chemoresistance. Altogether, we showed that it is possible to reconstruct leukemogenesis in ∼80% of patients with newly diagnosed AML, using techniques other than single-cell multiomics.