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Programmed cell death-1 (PD-1)/programmed death ligand-1 blockade may potentially augment graft-vs-tumor effects following allogeneic hematopoietic cell transplantation (alloHCT), but retrospective studies of anti–PD-1 therapy reported substantial toxicity from graft-versus-host-disease (GVHD). Here, we report the results of a prospective clinical trial of PD-1 blockade for relapsed hematologic malignancies (HMs) after alloHCT (NCT01822509). The primary objective in this phase 1 multicenter, investigator-initiated study was to determine maximum tolerated dose and safety. Secondary objectives were to assess efficacy and immunologic activity. Patients with relapsed HMs following alloHCT were eligible. Nivolumab was administered every 2 weeks until progression or unacceptable toxicity, starting with a 1-mg/kg cohort, with planned deescalation based on toxicity to a 0.5-mg/kg cohort. Twenty-eight patients were treated (n = 19 myeloid, n = 9 lymphoid). Median age was 57 years (range 27-76), and median time from alloHCT to enrollment was 21 months (range 5.6-108.5). Two of 6 patients treated at 1 mg/kg experienced dose-limiting toxicity (DLT) from immune-related adverse events (irAEs). Twenty-two patients were treated at 0.5 mg/kg, and 4 DLTs occurred, including 2 irAEs and 2 with fatal GVHD. The overall response rate in efficacy-evaluable patients was 32% (8/25). With a median follow-up of 11 months, the 1-year progression-free survival and overall survival were 23% and 56%, respectively. In this first prospective clinical trial of an anti–PD-1 antibody for post–alloHCT relapse, GVHD and irAEs occurred, requiring dose deescalation, with only modest antitumor activity. Further studies of anti–PD-1 therapy post–alloHCT may require specific toxicity mitigation strategies. This trial was registered at www.clinicaltrials.gov as #NCT 01822509.

Summary Background Patients with relapsed or refractory high-risk chronic lymphocytic leukaemia or mantle cell lymphoma often do not derive durable benefit from ibrutinib monotherapy. We hypothesised that dual B-cell receptor pathway blockade would be tolerable and efficacious. We investigated a next-generation phosphoinositide-3-kinase-δ inhibitor (PI3K-δi), umbralisib, plus a Bruton tyrosine kinase inhibitor (BTKi), ibrutinib, in relapsed or refractory chronic lymphocytic leukaemia and mantle cell lymphoma. Methods We did an investigator-initiated, multicentre, phase 1–1b study of patients from five sites in the USA (academic and community sites). Patients were 18 years and older with relapsed or refractory chronic lymphocytic leukaemia or mantle cell lymphoma, with an Eastern Cooperative Oncology Group performance status of 2 or less, and were given umbralisib orally once daily (400 mg, 600 mg, or 800 mg) and ibrutinib orally once daily (420 mg for chronic lymphocytic leukaemia or 560 mg for mantle cell lymphoma) until disease progression or unacceptable toxicity. The phase 1 dose-escalation cohorts for each histology escalated independently in a standard 3 × 3 design. The primary endpoints were intention-to-treat assessment of maximum-tolerated dose, safety, and dose-limiting toxicities. This trial is ongoing and is registered with ClinicalTrials.gov , number NCT02268851 . Findings Between Dec 5, 2014, and March 7, 2018, we enrolled 44 patients, of which 42 were given at least one dose of study drug (chronic lymphocytic leukaemia, n=21; mantle cell lymphoma, n=21). Patients had a median age of 68 years (range 48–85) and had a median of two (IQR 1–3) previous therapies. No dose-limiting toxicities were observed and the maximum-tolerated dose of umbralisib was not reached. The recommended phase 2 dose of umbralisib when given in combination with ibrutinib was 800 mg once daily. The most frequent adverse events included diarrhoea (22 [52%] patients, 10% of whom had grade 3), infection (21 [50%], 17% grade 3–4), and transaminitis (ten [24%], 2% grade 3). Serious adverse events occurred in 12 (29%) patients and included lipase elevation, atrial fibrillation, hypophosphataemia, adrenal insufficiency, transaminitis, and infections. Interpretation Umbralisib plus ibrutinib is well tolerated and active in relapsed or refractory chronic lymphocytic leukaemia and mantle cell lymphoma, with a recommended phase 2 dose of umbralisib 800 mg once daily. To the best of our knowledge, these are the first clinical data on a BTKi and PI3K-δi doublet in B-cell malignancies, and the results suggest that this approach is feasible and worthy of further study. Funding TG Therapeutics, Leukemia and Lymphoma Society Therapy Accelerator Program.

BACKGROUND: Patients (pts) with relapsed hematologic malignancies (HM) after alloHCT are a unique population, given the potential to harness a dormant graft-vs.-tumor effect therapeutically. We previously reported that CTLA-4 blockade with ipilimumab was feasible and active in this population (Davids et al., N Eng J Med, 2016). In retrospective studies, anti-PD1 antibodies were active in pts with relapsed lymphoid malignancies after alloHCT, though with substantial toxcity due to GVHD (Herbaux et al. and Haverkos et al., Blood, 2017). Here, we report on the first prospective clinical trial of PD1 blockade in pts with relapsed HM after alloHCT. METHODS: The primary objectives in this ph I/Ib, multicenter, investigator-initiated, CTEP-sponsored study (CTEP 9204) were to determine MTD and evaluate safety of nivolumab (nivo). Secondary objectives were to assess efficacy and immunologic correlates. Pts with any HM with relapse or persistent disease after alloHCT were eligible. Nivo was initially given to a 1 mg/kg cohort, with planned escalation to a 3 mg/kg cohort or de-escalation to a 0.5 mg/kg cohort depending on toxicities. Nivo was dosed q2 wks until progression or unacceptable toxicity, and disease-specific response evaluations were q4 cycles. RESULTS: A total of 28 pts with relapsed HM after alloHCT were treated. Median age was 57 (range 27-76), and pts had the following HM: AML (n=11), MDS (n=7), Hodgkin lymphoma (HL, n=5), non-Hodgkin lymphoma (NHL, n=3), MPD and CLL (n=1 each). Median number of prior therapies was 2 (range 1-9), and 18/28 (64%) had progressed after at least 1 prior therapy for relapse post alloHCT. The median time from alloHCT to study enrollment was 21 mo. (range 5.7-174 mo.). Six pts were treated initially with nivo 1 mg/kg. Two immune-related adverse events (irAEs) resulted in DLTs, including one pt with sepsis and fatal ARDS, and one pt with new anti-phospholipid antibodies and a fatal thrombotic cerebral vascular accident. Other irAEs included gr3 pneumonitis and transaminitis (n=1 each). One pt had cGVHD (NIH mild). Response was observed in 3/6 pts, including 1 CR (PMBCL) and 2 PR (HL and CMML). Due to the toxicities at 1 mg/kg, a cohort of 8 pts was then treated with nivo 0.5 mg/kg, which was generally well-tolerated, with no DLTs. A phase Ib expansion cohort then accrued 14 more pts at 0.5 mg/kg. Accrual was terminated after 14 pts were treated due to meeting the protocol-defined stopping rule of ≥4 DLTs in the first 15 pts in this cohort. These DLTs included 2 cases of grade III acute GVHD (liver and gut) as well as gr3 elevated bilirubin (n=1) and gr3 transaminitis (n=1) which did not recover to ≤gr1 within 4 wks. The 2 pts with liver dysfunction without histological evidence of GVHD eventually improved, but both pts with GVHD died due to complications from GVHD. Other toxicities included gr4 lipase elevation, gr3 rash, gr3 transaminitis, gr3 orthostatic hypotension, and gr2 seizure in a pt with a known seizure disorder (n=1 each). In the 22 pts treated at nivo 0.5 mg/kg, 10 pts (45%) had new onset or worsening of GVHD, including 1 with aGVHD only, 7 with cGVHD only (3 of whom had baseline cGVHD), and 2 with both acute and cGVHD. Shorter time from alloHCT was significantly associated with higher risk of developing GVHD (p=0.019). The overall response rate in the 19 evaluable pts treated at nivo 0.5 mg/kg was 16%, including 1 pt with HL with CR and 1 pt each with HL and AML achieving PR. Nine pts had stable disease for at least 1 response evaluation, and 7 pts had progressive disease as best response. Studywide, the overall response rate was 24% (6/25), the median number of cycles received was 3 (range 1-25), and 12/28 (43%) had at least 1 dose delay due to toxicity. With a median follow-up of 3.9 mo. (range 1.4-20.9 mo.), the 6 mo. PFS and OS were 39% and 61%, respectively. CONCLUSIONS: In this first prospective clinical trial of an anti-PD1 antibody for relapsed HM post-alloHCT, severe GVHD and irAEs occurred, even at the lower dose of nivo 0.5 mg/kg, leading to early closure due to toxicity. Modest anti-tumor activity was observed mainly in lymphoid malignancies known already to be responsive to anti-PD1 therapy, which may justify further exploration of anti-PD1 therapy in those populations in trials with strategies to mitigate toxicity; however, given the more favorable safety and efficacy profile of anti-CTLA-4 therapy in other HM, our future studies focus on combining ipilimumab with novel partners to improve outcomes. Disclosures Davids: Celgene: Consultancy; MEI Pharma: Consultancy, Research Funding; Verastem: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astra-Zeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche/Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Consultancy; BMS: Research Funding; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees; AbbVie, Inc: Consultancy, Membership on an entity's Board of Directors or advisory committees; Surface Oncology: Research Funding. Costello:Celgene: Consultancy; Takeda: Consultancy; Poseida Therapeutics, Inc.: Research Funding. Herrera:Seattle Genetics: Research Funding; Pharmacyclics: Consultancy, Research Funding; Merck, Inc.: Consultancy, Research Funding; KiTE Pharma: Consultancy, Research Funding; Immune Design: Research Funding; AstraZeneca: Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; Gilead Sciences: Research Funding. Locke:Novartis Pharmaceuticals: Other: Scientific Advisor; Cellular BioMedicine Group Inc.: Consultancy; Kite Pharma: Other: Scientific Advisor. Chen:Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees; Magenta Therapeutics: Consultancy; REGiMMUNE: Consultancy; Takeda Pharmaceuticals: Consultancy. Nikiforow:Kite Pharma: Consultancy. Ho:Jazz Pharmaceuticals: Consultancy. Wu:Neon Therapeutics: Equity Ownership. Soiffer:Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees.

Introduction: Patients (pts) with newly diagnosed multiple myeloma (MM) are commonly treated with the standard of care combination of lenalidomide (Len), bortezomib (Bz), and dexamethasone (Dex), also known as RVD. A recent randomized phase 3 study found that the addition of Bz to Len and Dex significantly increased median overall and progression free survival as well as response rate (Durie et al. Lancet 2017). Mild to moderate peripheral neuropathy (PN) is commonly reported with Bz use, although lower rates of PN have been reported with subcutaneous (SC) administration of single agent Bz compared with IV Bz (Moreau et al. Lancet Oncol 2011). Here we present preliminary results of a multi-center, open-label, single arm phase II trial of Len, SC Bz, and Dex in pts with newly diagnosed MM. Maintenance was risk-stratified, with high risk patients (defined as those with high risk cytogenetics (del17p, t(4:14), t(14;16)) or ISS stage II or III) receiving Bz in addition to Len. Primary endpoints included 1) overall response rate (ORR) after 4 induction cycles, 2) best response to induction therapy, and 3) rate and severity of PN during induction therapy. Methods: Patients enrolled in this study were newly diagnosed with active MM as defined by the revised IMWG criteria (Rajkumar et al. Lancet Oncol 2014). Protocol specified induction treatment consisted of 21-day cycles with Len 25 mg on days 1-14, SQ Bz 1.3 mg/m2 days 1, 4, 8, and 11, and Dex 20 mg on days 1, 2, 4, 5, 8, 9, 11, and 12. Stem cell mobilization followed induction cycle 4 and patients subsequently proceeded to either high dose melphalan and autologous stem cell transplant (ASCT) or 4 additional cycles of induction therapy based on patient preference with provider input. Following ASCT or completion of the 8th induction cycle pts proceeded to risk-stratified maintenance therapy. Maintenance consisted of 28-day cycles of therapy with Len on days 1-21 for all patients, while those pts defined as high-risk also received SC bortezomib Bz on days 1 and 15. Patients remained on maintenance therapy until progression, unacceptable toxicity, or withdrawal from protocol-directed treatment. Response was based on the IMWG uniform criteria (Rajkumar et al. Lancet Oncol 2011) and toxicities were graded based on the NCI-CTCAE V4. Correlative samples of blood and bone marrow for genomics and proteomics were collected from baseline and then throughout the study, and are currently being analyzed. Results: Forty-five pts were enrolled across 8 US sites between December 2015 and June 2017. Median age at enrollment was 61 years (range: 43 to 79) and 60% of the patients were male, 40% female. FISH cytogenetics found del 17p in 8% of pts tested, t(14;16) in 9%, and t(4;14) in 14%. At baseline, 60% of pts were ISS II/III. High risk pts comprised 62% of the study population overall. 80% of pts (36/45) collected stem cells and 31% of pts (14/45) continued to ASCT. The median number of CD34+ stem cells collected was 9.67 x 10^6. The median number of induction cycles completed was 8 (1 to 8 cycles) and 43 of 45 pts were evaluable for the primary endpoint of response after 4 induction cycles, with preliminary results indicating an ORR of 91% (39/43). Three pts did not reach the end of cycle 4 and 1 patient had stable disease. ORR at any point up to the beginning of maintenance was 98% (42/43). Any grade PN was reported by 80% of patients, including 38% with grade 1 and 36% with grade 2 PN. There were two cases of Grade 3 PN and one case of Grade 4 PN. Among the three patients with Grade ≥ 3 PN, symptoms improved to Grade ≤ 2 with dose reduction, modification of treatment schedule, or discontinuation of Bz. Importantly, given the higher than expected rate of all and high-grade PN, hydration with IV normal saline 500-1000 ccs prior to Bz administration as part of supportive care in selected patients was instituted and a comprehensive evaluation of the impact of this intervention on PN is in process. Conclusions: The combination of RVD with SC Bz is a highly effective treatment regimen for patients with newly diagnosed MM, including high risk pts. However, rates of all- and high-grade PN were greater than expected despite the use of SC Bz. Prompt dose reduction and/or change in schedule of Bz administration to weekly administration is recommended, with careful attention to supportive care in order to further improve tolerability. Disclosures Rosenblatt: Bristol-Myers Squibb: Research Funding; Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Merck: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding. Matous:Celgene: Consultancy, Honoraria, Speakers Bureau. Farber:Charles M. Farber, MD, PhD, LLC-Medical legal consulting: Consultancy; Gilead: Honoraria; Genentech: Honoraria, Research Funding, Speakers Bureau; Pharmacyclics: Research Funding; ummit Medical Group-MD Anderson Cancer Center: Employment; BeiGene: Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Honoraria, Speakers Bureau; Acerta: Research Funding. Ghobrial:Celgene: Consultancy; BMS: Consultancy; Takeda: Consultancy; Janssen: Consultancy. Richardson:Karyopharm: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Oncopeptides: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Research Funding; Amgen: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding.

Background This study aimed to determine the benefit of early therapeutic intervention with the combination of elotuzumab, Lenalidomide, and Dexamethasone in patients with high-risk smoldering multiple myeloma (SMM). ClinicalTrials.gov Identifier: NCT02279394. Aims The overarching objective of this trial is to determine progression free survival to symptomatic multiple myeloma (MM). Furthermore, the study examined whether genomic studies can help in determining patients who would benefit the most from this early therapeutic intervention. Methods Patients enrolled in this study met eligibility for high-risk SMM based on the newly defined criteria proposed by Rajkumar et al, Blood 2014. Patients were administered weekly elotuzumab (10 mg/kg) on days 1, 8, 15, and 22 for the first two 28-day cycles while receiving lenalidomide on days 1-21. For cycles 3-8, patients were administered elotuzumab infusions on days 1, 8, and 15. dexamethasone (40mg) was given on days 1, 8 and 15 to 40 of the 50 enrolled patients. After 8 cycles or best response, patients were given the option to mobilize with either cyclophosphamide or plerixafor and collect stem cells for future transplant. Patients were then allowed to continue on maintenance therapy where they were administered elotuzumab (20 mg/kg) on day 1, in combination with lenalidomide days 1-21 of a 28-day cycle. Bone marrow (BM) samples of 32 patients were obtained before starting therapy for baseline assessment and whole exome sequencing (WES) of plasma cells. Results In total, 50 patients were enrolled on this study from January 2015 and completed accrual in December 2016, with the participation of eight sites. The median age of enrolled patients was 62 years (range, 29-79) with 18 males (36%) and 32 females (64%). Interphase fluorescence in situ hybridization (iFISH) detected high-risk cytogenetics (defined by the presence of 17p deletion, t(4;14), and 1q gain) in 20 patients. The median time to response was 2.8 months (range, 1.8-4.6). The most common toxicities were fatigue (92%), followed by diarrhea (72%), and hyperglycemia (62%). The most common grade 3 or more adverse events were hypophosphatemia (34%), neutropenia (26%), and lymphocyte count decreased (22%). Three patients (6%) had grade 4 hypophosphatemia during treatment. Additionally, grade 4 cholecystitis, cataract, lymphocyte count increase, hyperglycemia, neutropenia, and thrombocytopenia occurred in one patient (2%). Diabetic Ketoacidosis and sepsis led to death in a patient (2%). Stem cell collection was successful in all mobilized patients to date. As of this abstract date, the overall response rate is 84% (41/49). There were 3 complete responses (6%), 18 very good partial responses (37%), 20 partial responses (41%), 5 minimal responses (10%), 3 stable disease (6%), and 2 unevaluable patients. All the study participants except for three have finished treatment and are currently under follow up. None of the patients showed progression to overt MM to date. We continue to collect data for progression free survival. WES was performed on 32 samples at the time of initiation of therapy. Recurrent mutations in the MAPK pathway (KRAS, NRAS) and tumor suppressor gene, TP53, were detected in 40% of the cases (16% and 24%, respectively), while mutations in the NF-KB and plasma cell differentiation pathways were present in 13% of patients. Somatic copy number alterations (SCNAs) were called based on WES: 1q duplication, 13q, 17p, and 1p deletions were identified in 25, 31, 12, and 7% of cases, respectively. Interestingly, in 6 patients, high-risk SCNAs (1q gain and 17p deletion) were not reported in iFISH but were detected by WES. The analysis of these 32 samples showed that patients who are harboring mutations in the DNA repair pathway genes, had modest response to treatment. Finally, we are analyzing the transcriptomic profile of CD138 negative cells, which represent the BM microenvironment cells (immune and stromal cells) to characterize the BM microenvironment at baseline and end of treatment, and thus, elucidate the role of these cells in the differential response to therapy. Conclusion The combination of elotuzumab, lenalidomide, and dexamethasone is well tolerated and demonstrates a high response rate with no progression to overt MM to date. Correlation with genomic studies can help define patients who benefit the most from this early therapeutic intervention. Disclosures Ghobrial: Takeda: Consultancy; Janssen: Consultancy; BMS: Consultancy; Celgene: Consultancy. Bustoros:Dava Oncology: Honoraria. Badros:GSK: Research Funding; Celgene: Consultancy, Research Funding; Karyopharm: Research Funding. Matous:Celgene: Consultancy, Honoraria, Speakers Bureau. Rosenblatt:Merck: Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Research Funding; Celgene: Research Funding; Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees. Jakubowiak:Karyopharm: Consultancy, Honoraria; SkylineDx: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Bristol-Myers Squibb: Consultancy, Honoraria; Adaptive Biotechnologies: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria. Usmani:Abbvie, Amgen, Celgene, Genmab, Merck, MundiPharma, Janssen, Seattle Genetics: Consultancy; Amgen, BMS, Celgene, Janssen, Merck, Pharmacyclics,Sanofi, Seattle Genetics, Takeda: Research Funding. Zonder:Celgene: Consultancy, Honoraria; Pharmacyclics: Other: DSMC; Janssen: Honoraria; Takeda: Honoraria; Alnylam: Honoraria; Coelum: Honoraria; BMS: Research Funding. Munshi:OncoPep: Other: Board of director. Anderson:Gilead: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Consultancy; C4 Therapeutics: Equity Ownership, Other: Scientific founder; OncoPep: Equity Ownership, Other: Scientific founder; Millennium Takeda: Consultancy; Celgene: Consultancy. Richardson:Amgen: Membership on an entity's Board of Directors or advisory committees; Oncopeptides: Membership on an entity's Board of Directors or advisory committees; BMS: Research Funding; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding.

Background This study aimed to determine the benefit of early therapeutic intervention with the combination of elotuzumab, Lenalidomide, and Dexamethasone in patients with high-risk smoldering multiple myeloma (SMM). ClinicalTrials.gov Identifier: NCT02279394. Aims The overarching objective of this trial is to determine progression free survival to symptomatic multiple myeloma (MM). Furthermore, the study examined whether genomic studies can help in determining patients who would benefit the most from this early therapeutic intervention. Methods Patients enrolled in this study met eligibility for high-risk SMM based on the newly defined criteria proposed by Rajkumar et al, Blood 2014. Patients were administered weekly elotuzumab (10 mg/kg) on days 1, 8, 15, and 22 for the first two 28-day cycles while receiving lenalidomide on days 1-21. For cycles 3-8, patients were administered elotuzumab infusions on days 1, 8, and 15. dexamethasone (40mg) was given on days 1, 8 and 15 to 40 of the 50 enrolled patients. After 8 cycles or best response, patients were given the option to mobilize with either cyclophosphamide or plerixafor and collect stem cells for future transplant. Patients were then allowed to continue on maintenance therapy where they were administered elotuzumab (20 mg/kg) on day 1, in combination with lenalidomide days 1-21 of a 28-day cycle. Bone marrow (BM) samples of 32 patients were obtained before starting therapy for baseline assessment and whole exome sequencing (WES) of plasma cells. Results In total, 50 patients were enrolled on this study from January 2015 and completed accrual in December 2016, with the participation of eight sites. The median age of enrolled patients was 62 years (range, 29-79) with 18 males (36%) and 32 females (64%). Interphase fluorescence in situ hybridization (iFISH) detected high-risk cytogenetics (defined by the presence of 17p deletion, t(4;14), and 1q gain) in 20 patients. The median time to response was 2.8 months (range, 1.8-4.6). The most common toxicities were fatigue (92%), followed by diarrhea (72%), and hyperglycemia (62%). The most common grade 3 or more adverse events were hypophosphatemia (34%), neutropenia (26%), and lymphocyte count decreased (22%). Three patients (6%) had grade 4 hypophosphatemia during treatment. Additionally, grade 4 cholecystitis, cataract, lymphocyte count increase, hyperglycemia, neutropenia, and thrombocytopenia occurred in one patient (2%). Diabetic Ketoacidosis and sepsis led to death in a patient (2%). Stem cell collection was successful in all mobilized patients to date. As of this abstract date, the overall response rate is 84% (41/49). There were 3 complete responses (6%), 18 very good partial responses (37%), 20 partial responses (41%), 5 minimal responses (10%), 3 stable disease (6%), and 2 unevaluable patients. All the study participants except for three have finished treatment and are currently under follow up. None of the patients showed progression to overt MM to date. We continue to collect data for progression free survival. WES was performed on 32 samples at the time of initiation of therapy. Recurrent mutations in the MAPK pathway (KRAS, NRAS) and tumor suppressor gene, TP53, were detected in 40% of the cases (16% and 24%, respectively), while mutations in the NF-KB and plasma cell differentiation pathways were present in 13% of patients. Somatic copy number alterations (SCNAs) were called based on WES: 1q duplication, 13q, 17p, and 1p deletions were identified in 25, 31, 12, and 7% of cases, respectively. Interestingly, in 6 patients, high-risk SCNAs (1q gain and 17p deletion) were not reported in iFISH but were detected by WES. The analysis of these 32 samples showed that patients who are harboring mutations in the DNA repair pathway genes, had modest response to treatment. Finally, we are analyzing the transcriptomic profile of CD138 negative cells, which represent the BM microenvironment cells (immune and stromal cells) to characterize the BM microenvironment at baseline and end of treatment, and thus, elucidate the role of these cells in the differential response to therapy. Conclusion The combination of elotuzumab, lenalidomide, and dexamethasone is well tolerated and demonstrates a high response rate with no progression to overt MM to date. Correlation with genomic studies can help define patients who benefit the most from this early therapeutic intervention. Disclosures Ghobrial:Takeda: Consultancy; Janssen: Consultancy; BMS: Consultancy; Celgene: Consultancy. Bustoros:Dava Oncology: Honoraria. Badros:GSK: Research Funding; Celgene: Consultancy, Research Funding; Karyopharm: Research Funding. Matous:Celgene: Consultancy, Honoraria, Speakers Bureau. Rosenblatt:Merck: Membership on an entity9s Board of Directors or advisory committees; Bristol-Myers Squibb: Research Funding; Celgene: Research Funding; Bristol-Myers Squibb: Membership on an entity9s Board of Directors or advisory committees. Jakubowiak:Karyopharm: Consultancy, Honoraria; SkylineDx: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Bristol-Myers Squibb: Consultancy, Honoraria; Adaptive Biotechnologies: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria. Usmani:Abbvie, Amgen, Celgene, Genmab, Merck, MundiPharma, Janssen, Seattle Genetics: Consultancy; Amgen, BMS, Celgene, Janssen, Merck, Pharmacyclics,Sanofi, Seattle Genetics, Takeda: Research Funding. Zonder:Celgene: Consultancy, Honoraria; Pharmacyclics: Other: DSMC; Janssen: Honoraria; Takeda: Honoraria; Alnylam: Honoraria; Coelum: Honoraria; BMS: Research Funding. Munshi:OncoPep: Other: Board of director. Anderson:Gilead: Membership on an entity9s Board of Directors or advisory committees; Bristol Myers Squibb: Consultancy; C4 Therapeutics: Equity Ownership, Other: Scientific founder; OncoPep: Equity Ownership, Other: Scientific founder; Millennium Takeda: Consultancy; Celgene: Consultancy. Richardson:Amgen: Membership on an entity9s Board of Directors or advisory committees; Oncopeptides: Membership on an entity9s Board of Directors or advisory committees; BMS: Research Funding; Karyopharm: Membership on an entity9s Board of Directors or advisory committees; Janssen: Membership on an entity9s Board of Directors or advisory committees; Jazz Pharmaceuticals: Membership on an entity9s Board of Directors or advisory committees, Research Funding; Takeda: Membership on an entity9s Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity9s Board of Directors or advisory committees, Research Funding.