Larsen, Jeremy T.

TPS8057 Background: Multiple myeloma (MM) is the second most prevalent blood cancer, representing approximately 1% of all cancers. Although overall survival has improved in recent years due to new approved agents, the vast majority of MM patients (pts) ultimately stop responding to treatment. Moreover, about a quarter of MM pts characterized as “high risk” experience limited benefit from existing treatments. Seminal genomic sequencing research efforts, such as the MMRF CoMMpass study, have highlighted that a large number of MM cases harbor potentially actionable oncogenic molecular alterations and published reports on small numbers of cases suggest that Precision Medicine (PM) interventions clinically targeting such actionable drivers may benefit MM pts. These results suggest that PM approaches in MM are possible and should be further studied clinically. To that end, we have launched MyDRUG, a master protocol aimed at developing new myeloma regimens based on individual pt’s genomics. Methods: This study is a Phase I-II, multicenter master protocol in functional high risk MM patients (i.e patients having progressed from baseline treatment within 18 months without maintenance or 3 years on maintenance) with 1-3 prior lines of therapy. Patients are screened for actionable genomic alterations on the CLIA-grade MI-ONCOSEQ platform. Patients with actionable alterations are assigned to the appropriate targeted agent used in combination with a backbone regimen ixazomib, pomalidomide and dexamethasone (IPd), whereas patients without such alterations go on an immune arm (see Table). Inclusion criteria include measurable disease (as measured by M-protein and FLC) and acceptable hematologic and metabolic functions. A maximum of 12 evaluable pts will be accrued onto the phase I portion of each arm and an additional 21 evaluable phase II pts will be accrued onto each arm for a total of 27 evaluable pts at the MTD combination dose. The primary objective of the study is to evaluate ORR per IMWG consensus criteria. Secondary objectives are to assess adverse events (AEs), progression-free survival, and overall survival (OS). Experimental correlative aims include assessing molecular or clonal response, molecular and immune signatures of resistance/response, MRD. Clinical trial information: NCT03732703. [Table: see text]

8006 Background: IBER is a novel cereblon E3 ligase modulator (CELMoD) with enhanced tumoricidal and immunostimulatory activities. Preclinically, IBER overcomes immunomodulatory drug (IMiD) resistance and has synergy with daratumumab (DARA), bortezomib (BORT), and DEX. Methods: A phase 1b/2a multicenter, open-label, dose-escalation study evaluated the maximum tolerated dose (MTD), recommended phase 2 dose (RP2D), safety, and preliminary efficacy of IBER. Eligible pts had RRMM and must have received ≥ 2 prior regimens including lenalidomide (LEN) and/or pomalidomide (POM), and a proteasome inhibitor (PI). All pts had progressed on or within 60 days of last MM therapy. Escalating doses of IBER were given on days 1–21, in combination with DEX 40 mg (20 mg in pts age > 75 years) on days 1, 8, 15, and 22, of each 28-day cycle. Dose escalation was reviewed by a dose escalation committee. Results: As of Jan 2019,58 pts received IBER + DEX. Median age was 64.5 years (range 33–79), and median number of prior regimens was 5 (2–12). Prior therapies included autologous stem cell transplant (79%), LEN (100%), POM (69%), PIs (100%), and DARA (66%). IBER dose ranged from 0.3 to 1.2 mg; MTD/RP2D was not reached. Median duration of therapy was 12+ weeks (range 4–109). Grade 3–4 adverse events (AEs) were reported in 41 (72%) pts and were not related to dose. Grade 3–4 neutropenia, thrombocytopenia, neuropathy, and fatigue occurred in 26%, 11%, 2%, and 0% pts, respectively. Three pts discontinued treatment due to AEs. Clinical activity occurred early and was observed across all dose levels (Table); 20 of 51 pts remain on treatment (2–27+ cycles). Conclusions: IBER + DEX showed favorable efficacy and safety in heavily pretreated pts with RRMM who failed multiple prior therapies. This study is ongoing, including combinations of IBER with DARA or BORT. Clinical trial information: NCT02773030. [Table: see text]

Introduction: Despite advances in treatment strategy, multiple myeloma (MM) remains a challenging, incurable disease as patients (pts) often relapse. Here we describe preclinical data of a novel cereblon (CRBN) E3 ligase modulatory compound (CELMoD), iberdomide (IBER; CC-220), as well as clinical and translational data from a current phase 1/2 clinical trial (NCT02773030). These data support a differentiated profile for IBER from immunomodulatory agents (IMiD agents), and development of IBER as a foundation of combination therapy for the treatment of relapsed/refractory MM (RRMM). Methods: Preclinical analyses were performed on pomalidomide (POM)-sensitive and acquired-resistant MM cell lines and peripheral blood mononuclear cells from healthy volunteers. Eligible pts enrolled on the clinical trial had RRMM and had received ≥ 2 prior regimens, containing at least an IMiD agent and proteasome inhibitor (PI), and had experienced disease progression within 60 days of last MM therapy. Escalating doses of IBER were given on Days 1-21, in combination with dexamethasone (DEX; 40 mg; 20 mg in pts aged > 75 years) on Days 1, 8, 15, and 22, of each 28-day cycle. Immunohistochemistry (IHC) data on CRBN, Ikaros, Aiolos, and ZFP91 expression was obtained from pt bone marrow specimens at screening and at Cycle 2, Day 15. Immune profiling was evaluated by flow cytometry of peripheral blood at Cycle 1, Day 1 and Cycle 2, Day 15. Primary objectives were to evaluate maximum tolerated dose (MTD), recommended phase 2 dose (RP2D), safety, and preliminary efficacy. Results: Preclinically, IBER exhibited potent tumoricidal anti-MM and immunostimulatory activity. IBER was more potent than lenalidomide (LEN) or POM in overcoming the immunosuppressive activity of bortezomib (BORT), inducing a more than twofold increase in T cell proliferation in the presence of BORT. IBER also enhanced the antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity of daratumumab (DARA), leading to deeper responses than combinations with LEN or POM. Further differentiating from both LEN and POM, IBER showed activity alone and in combination with BORT or DARA in POM-resistant MM cell lines. As of June 28, 2019, 69 pts with RRMM had received IBER + DEX. Median age was 65 years (range 33-80), and median number of prior regimens was 5 (range 2-12). Prior therapies included autologous stem cell transplantation (80%), LEN (100%), POM (70%), PIs (100%), DARA (71%) and anti-BCMA (6%), including CAR T cells. Clinical activity was observed across all dose levels with an overall response rate (ORR) of 29%, clinical benefit rate of 45%, and disease control rate of 80%. ORR was 30%, 28% and 29% in IMiD agent-refractory, DARA-refractory and Quad-class (IMiD agents/PIs/steroids/CD-38 antibodies)-refractory pts, respectively. IBER + DEX showed a favorable safety profile, with grade 3-4 neutropenia, infections, and thrombocytopenia, occurring in 29%, 25%, and 12% of pts, respectively. To date, IBER doses range from 0.3 to 1.3 mg and the MTD/RP2D has not yet been reached. Pharmacodynamic immunophenotyping changes were dose-dependent. Treatment with IBER (at doses > 0.75mg) + DEX doubled the percentage of proliferating T cells and NK cells (P < 0.001 for each) and increased activated and effector memory CD8+ and CD4+ T cells by > 50% (P < 0.01 for each subset). Pharmacodynamic changes in pt bone marrow by quantitative IHC scoring showed significant degradation of substrates (Ikaros, P = 0.006; Aiolos, P < 0.001; ZFP91, P < 0.001) and downregulation of c-myc (P = 0.027), including in pts refractory to POM and with low CRBN expression. Conclusions: IBER + DEX has shown notable clinical activity and favorable tolerability in heavily pretreated pts with RRMM, including pts refractory to prior IMiD therapy. Preclinical and translational data suggest a differentiated profile of IBER from IMiD agents in regard to activity in POM-resistant models, potency in combination with BORT and DARA, and by inducing changes in CD4+ T cells that were not observed in pts treated with POM from prior studies. Taken together, these data support a differentiated profile for IBER from IMiD agents, and the clinical development of IBER as a foundation of combination therapy for the treatment of RRMM. This study is ongoing, and includes cohorts evaluating the combinations of IBER + DEX with DARA, BORT, and carfilzomib. Updated results will be presented at the meeting. Disclosures Lonial: Karyopharm: Consultancy; GSK: Consultancy; Takeda: Consultancy, Research Funding; Celgene Corporation: Consultancy, Research Funding; Amgen: Consultancy; Genentech: Consultancy; Janssen: Consultancy, Research Funding; BMS: Consultancy. Amatangelo:Celgene Corporation: Employment, Equity Ownership. Popat:Celgene Corporation: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel, accommodations, expenses; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; GSK: Consultancy, Honoraria; Takeda: Honoraria, Other: travel, accommodations, expenses; Janssen: Honoraria, Other: travel support to meetings. Minnema:Gilead: Honoraria; Celgene Corporation: Honoraria, Research Funding; Amgen: Honoraria; Servier: Honoraria; Jansen Cilag: Honoraria. Zonder:Alnylam: Consultancy, Membership on an entity's Board of Directors or advisory committees; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Oncopeptides: Consultancy, Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Intellia: Consultancy, Membership on an entity's Board of Directors or advisory committees; Caelum: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene Corporation: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Larsen:Janssen Oncology: 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. Oriol Rocafiguera:Celgene Corporation: Consultancy, Speakers Bureau; Janssen: Consultancy; Amgen: Consultancy, Speakers Bureau. Rodriguez Otero:Celgene Corporation: Consultancy, Honoraria, Speakers Bureau; Janssen: Consultancy, Honoraria; Takeda: Consultancy; BMS: Honoraria; Kite Pharma: Consultancy. Badros:Celgene Corporation: Consultancy; Amgen: Consultancy. Siegel:Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Bristol-Myers Squibb Company: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Jagannath:Bristol-Myers Squibb: Consultancy; Janssen Pharmaceuticals: Consultancy; Karyopharm Therapeutics: Consultancy; AbbVie: Consultancy; Merck & Co.: Consultancy; Celgene Corporation: Consultancy. Bringhen:Bristol-Myers Squibb: Honoraria; Celgene Corporation: 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; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy. Gironella:Amgen: Honoraria; Janssen: Honoraria; Celgene Corporation: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Kaiser:Takeda, Janssen, Celgene, Amgen: Honoraria, Other: Travel Expenses; Abbvie, Celgene, Takeda, Janssen, Amgen, Abbvie, Karyopharm: Consultancy; Celgene, Janssen: Research Funding. Cook:Janssen, Takeda, Sanofi, Karyopharm, Celgene: Consultancy, Honoraria, Speakers Bureau; Amgen, Bristol-Myers Squib, GlycoMimetics, Seattle Genetics, Sanofi: Honoraria; Celgene, Janssen-Cilag, Takeda: Honoraria, Research Funding. Gamberi:Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sanofi: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria; Celgene Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees. Sonneveld:SkylineDx: Research Funding; Takeda: Honoraria, Research Funding; Karyopharm: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; BMS: Honoraria; Amgen: Honoraria, Research Funding. Nguyen:Celgene Corporation: Employment, Equity Ownership. Chen:Celgene Corporation: Employment, Equity Ownership. Homan:Celgene Corporation: Employment. Bjorklund:Celgene Corporation: Employment, Equity Ownership. Wang:Celgene Corporation: Employment, Equity Ownership. Pierceall:Celgene Corporation: Employment, Equity Ownership. Bensmaine:Celgene Corporation: Employment, Equity Ownership. Thakurta:Celgene: Employment, Equity Ownership. Peluso:Celgene Corporation: Employment. Van De Donk:Janssen Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding; Servier: Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: 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; Roche: Membership on an entity's Board of Directors or advisory committees; AMGEN: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bayer: Membership on an entity's Board of Directors or advisory committees.

Background: Combinations of alkylating agents with proteasome inhibitors have demonstrated efficacy in newly diagnosed and relapsed multiple myeloma (MM), with melphalan or cyclophosphamide combinations being some of the commonly used regimens for initial treatment of MM. Ixazomib (Ixa) is an oral proteasome inhibitor that is approved for use in combination with lenalidomide for patients with relapsed MM. We examined if Ixa can be effectively combined with cyclophosphamide (Ctx) in order to develop a less expensive, all oral regimen for patients with relapsed MM. Patients and Methods: Patients with relapsed MM, who were proteasome inhibitor naïve OR have received less than 6 cycles of therapy with bortezomib and had a better than PR with no progression at the time of discontinuation, were enrolled. The primary objective was to determine overall response rate (ORR). Treatment consisted of Ixa 4mg PO days 1, 8, 15; Ctx 300 mg/m2 PO days 1, 8, 15, 22 and dexamethasone (Dex) 40 mg PO weekly in a 28-day cycle. Overall, 37 patients were accrued; data on 33 eligible patients were available for analysis as of July 18, 2019. Results: The median age was 71 (48-89), 61% were male and the median duration from diagnosis was 46 months (mos). Median number of prior lines of therapy was 4 (range 1-5), 76%, 42% and 67% respectively had a prior IMiD, proteasome inhibitor or stem cell transplant, respectively. At data cutoff, 22 (67%) had progressed, 4 (12%) had died and the median follow up of those alive was 21.3 mos. Fourteen patients are still receiving treatment, with median of 8.5 cycles. Most common reason for treatment discontinuation was disease progression (10 pts; 53%). The ORR was 60% including 6% CR and 24% VGPR. The median event free survival was 11.3 mos (95%CI: 9.0 - 26.8). Overall, 401 cycles have been administered across the study, with dose modifications/ hold required for Ixa, Ctx, and Dex in 9 (27%), 14 (42%), and 22 (67%) patients respectively, the most common reason being hematologic toxicity. A grade 3 or higher adverse event at least possibly attributed to the study drugs was seen in 77% of patients, hematologic in 67% and non-hematologic in 30%. (Table 1) The most commonly observed hematologic toxicities included thrombocytopenia, neutropenia, lymphopenia and anemia; for non-hematologic was nausea, diarrhea, peripheral neuropathy toxicity and fatigue. Conclusions: The combination of Ixa, Ctx and Dex (ICd) offers a convenient, all oral regimen for treatment of relapsed disease not refractory to proteasome inhibitors. The regimen has good efficacy in this group f heavily pretreated patients, with an acceptable toxicity profile. Disclosures Lacy: Celgene: Research Funding. Gertz:Ionis: Honoraria; Spectrum: Honoraria, Research Funding; Janssen: Honoraria; Celgene: Honoraria; Prothena: Honoraria; Alnylam: Honoraria. Ailawadhi:Takeda: Consultancy; Janssen: Consultancy, Research Funding; Cellectar: Research Funding; Pharmacyclics: Research Funding; Amgen: Consultancy, Research Funding; Celgene: Consultancy. Bergsagel:Janssen Pharmaceuticals: Consultancy; Celgene: Consultancy; Ionis Pharmaceuticals: Consultancy. Fonseca:AbbVie, Amgen, Bayer, Celgene, Kite, Janssen, Juno, Merck, Pharmacylics, Sanofi, Takeda: Other: Consultant/Advisor; Prognosticatin of MM based on Genetic Categorization by FISH: Patents & Royalties; Adaptive Biotechnologies: Other: Scientific Advisory Board. Dingli:alexion: Consultancy; Janssen: Consultancy; Millenium: Consultancy; Rigel: Consultancy; Karyopharm: Research Funding. Kapoor:Amgen: Research Funding; Takeda: Honoraria, Research Funding; Glaxo Smith Kline: Research Funding; Sanofi: Consultancy, Research Funding; Celgene: Honoraria; Cellectar: Consultancy; Janssen: Research Funding. Chanan-Khan:AbbVie: Research Funding; Pharmacyclics: Research Funding; Xencor: Research Funding; Merck: Research Funding; Jansen: Research Funding; Mayo Clinic: Employment; Ascentage: Research Funding; Millennium: Research Funding. Larsen:Janssen Oncology: 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. Russell:Imanis: Equity Ownership. Stewart:Roche: Consultancy; Seattle Genetics: Consultancy; Takeda: Consultancy; Ionis: Consultancy; Janssen: Consultancy, Research Funding; Oncopeptides: Consultancy; Ono: Consultancy; Amgen: Consultancy, Research Funding; Bristol Myers-Squibb: Consultancy; Celgene: Consultancy, Research Funding. Kumar:Celgene: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; Takeda: Research Funding.

Abstract Introduction - IMIDs are critical in the treatment of multiple myeloma (MM). Unfortunately, many patients become resistant and this is a major challenge in MM therapy. IMID resistance can be caused by CRBN mutations (rarely) and by upregulation of specific antioxidative mechanisms. We hypothesized that measuring baseline antioxidative capacity might be a useful predictor of IMID sensitivity in the clinic. Methods - To develop a quantitative assay for determining cellular antioxidative capacity of MM cells we measured total cellular oxidized flavin adenine dinucleotide (FAD) after treatment with H2O2. FAD has auto-fluorescent properties that can be measured via flow cytometry. Cells with high antioxidative capacity generate more FAD, and cells with low anti-oxidative capacity generate less FAD. MM cells with an increase in FAD after H2O2 were considered IMID resistant and those with no change in FAD were considered IMID sensitive (Figure 1). Clinical IMID resistance/sensitivity was defined clinically during blinded retrospective review, with disease progression based on the IMWG criteria. After blinded review of clinical outcomes, the patient flow cytometry results were disclosed to evaluate the predictive value of the flow cytometry assay for detection of IMID resistance. Results - Of 40 patients who underwent testing, 26 were IMID resistant via flow and were considered as being clinical resistant 17 (65%). Conversely, 14 patients were IMID sensitive via flow and 12 (86%) were considered to be clinical sensitive. There was a significant correlation between clinical assessment and flow cytometry in determination of IMID resistance patterns (Table 1). The sensitivity and specificity of our assay was 89% and 57% with a positive and negative predictive value of 65% and 86% respectively. A limitation of our clinical assessment was that 16 patients (38%) were treated with combination therapy; IMIDs plus a proteasome inhibitor or a monoclonal antibody. Of the 11 patients with discordant results by flow and clinical outcome, 7 (64%) were not on therapy at the time of testing and 6 (55%) had flow testing on the bone marrow sample performed on day 100 following an autologous transplant. Two (7%) of the 29 patients with correlative results were off all therapy at the time of testing, 1 with testing on the day 100 marrow sample after transplant. Conclusions - This early testing of our assay shows promising results predicting clinical sensitivity via our flow based assay. The testing demonstrates a high sensitivity and negative predictive value, with less ability to assess for resistance. However, there were limitations to this study. The majority of patients with discordant results were off IMID therapy at the time of flow cytometry and many of these were assessed on transplant day 100 marrow samples. Depth of measureable residual disease was not readily available on all marrow samples tested. It is probable that flow testing for IMID resistance is inaccurate in patients with deeper responses to therapy, especially those who are minimum residual disease (MRD) negative. Additionally, several patients were on combination IMID, proteasome inhibitor, and monoclonal antibody. It is possible that clinical IMID resistance was not detected due to the anti-MM activity of the additional therapies. Additional larger scale prospective studies are needed to validate these findings as this method of testing could potentially provide providers with powerful information allowing them to personalize therapy for their patients. Disclosures Fonseca: Mayo Clinic: Employment; Amgen: Consultancy.

Abstract Background : Ibrutinib, a Bruton's tyrosine kinase (BTK) inhibitor was approved for the treatment of Waldenstrom Macroglobulinemia (WM) in January, 2015 based on the results of a clinical trial of 63 previously-treated patients with WM. Data on outcomes with ibrutinib outside of clinical trials are limited. Methods : Medical records of patients with WM seen consecutively between 02/01/2015 and 06/01/2018 at Mayo Clinic, MN, FL and AZ were reviewed and those treated with ibrutinib at any point during their disease were included. Refractoriness to prior therapy was defined as disease progression on therapy or within 2 months of stopping treatment. The response rates were assessed by WM VI International Workshop Criteria. Adverse events were graded using National Cancer Institute Common Toxicity Criteria for Adverse Events (AEs) v4.03. All time-to-event analyses were performed from the time of initiation of ibrutinib. Results : Eighty patients [previously treated, n=67 (84%), treatment-naïve, n=13 (16%)] received ibrutinib for active WM. Median follow-up was 18 months (95% CI: 12-19) and the median overall survival (OS) was not reached (NR) (95% CI: 27-NR) for the entire cohort at the date of last follow-up. The median age was 67 years (range: 50-88) and the median ECOG performance score was 1 (range: 0-3) at the time of ibrutinib initiation. Median lines of therapies prior to ibrutinib for the previously-treated patients was 2 (range: 1-9) and 35 patients (44%) had received ≥3 prior lines of therapy. Of the 80 patients, 52 patients (43 previously treated, 9 treatment-naïve) had data for response assessment. The baseline characteristics and laboratory parameters at initiation of ibrutinib are outlined in Table 1a and prior therapies are mentioned in Table 1b. Overall response rate (ORR) was 90% (100% in patients with ibrutinib as primary therapy and 88% in salvage therapy setting); major-response rate (MRR) was 77%. Median time to first and best response was 2.1 months (95% CI: 1.5-3.5) and 5.4 months (95% CI: 3.5-13), respectively. Other clinically relevant endpoints and AEs related to ibrutinib therapy are outlined in Table 2 and 3, respectively. The median time-to-next therapy was 33 months (95% CI: 28-NR). At last follow-up, 25 (32%) patients had discontinued ibrutinib therapy. The reasons for discontinuation was progression (n=8), elevated liver enzymes (n=4), cognitive changes (n=1), inability to achieve better than MR (n=1), atrial fibrillation (n=3), consolidation with autologous stem cell transplantation after PR with ibrutinib (n=1), transition to hospice care due to progressive head and neck cancer (n=1), infection in lower extremity (n=1), transformation to DLBCL (n=1), blistering rash which resolved after ibrutinib discontinuation (n=1), obscure GI bleed that resolved after ibrutinib discontinuation (n=1), fatigue (n=1) and for unclear reasons recorded as treatment intolerance (n=1). Following discontinuation of ibrutinib, 21 patients received salvage therapy. Of these, data regarding the response to salvage therapy was available in 9 (43%) patients (VGPR=2, PR=3, SD=3 and progressive disease=1); median PFS from the salvage therapy following ibrutinib discontinuation was 18 months (95% CI: 2-25). Of the 4 patients who were not treated following ibrutinib discontinuation; 1 elected hospice care due to concurrent head and neck cancer progression, and the other 3 patients elected to be monitored off therapy (one had achieved SD and two had PR from ibrutinib). Fourteen patients were evaluable for IgM rebound following ibrutinib discontinuation. Of those, 5 (36%) had sudden increase in IgM level [median: 158% from the IgM level after ibrutinib discontinuation (range: 22%-1368%)] within a median of 2 months (range: 1-3 months) and 1 patient required plasmapheresis for symptomatic hyperviscosity. Four of 5 patients received salvage therapy between 0-15 months. At last follow-up, 11 patients (14%) had died of whom 3 were on ibrutinib at the time of death [CNS involvement, (n=1), causes unrelated to WM, (n=2)]. Conclusions : Ibrutinib is an effective agent in WM patients with MYD88L265Pmutation. Our data regarding outcomes in non-trial setting appear comparable to the results observed in the pivotal clinical trial. Hematologists should be aware of unique ibrutinib associated toxicities and clinically relevant IgM rebound phenomenon following abrupt discontinuation of ibrutinib. Disclosures Ailawadhi: Celgene: Consultancy; Janssen: Consultancy; Takeda: Consultancy; Pharmacyclics: Research Funding; Amgen: Consultancy. Gertz:janssen: Consultancy; Prothena: Honoraria; Medscape: Consultancy; Teva: Consultancy; celgene: Consultancy; annexon: Consultancy; Alnylam: Honoraria; Physicians Education Resource: Consultancy; spectrum: Consultancy, Honoraria; Apellis: Consultancy; Amgen: Consultancy; Abbvie: Consultancy; Ionis: Honoraria; Research to Practice: Consultancy. Kumar:Novartis: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Research Funding; AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; KITE: 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; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Oncopeptides: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees; KITE: Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Membership on an entity's Board of Directors or advisory committees, Research Funding. Lacy:Celgene: Research Funding. Dispenzieri:Celgene, Takeda, Prothena, Jannsen, Pfizer, Alnylam, GSK: Research Funding. Witzig:Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Dingli:Millennium Takeda: Research Funding; Alexion Pharmaceuticals, Inc.: Other: Participates in the International PNH Registry (for Mayo Clinic, Rochester) for Alexion Pharmaceuticals, Inc.; Alexion Pharmaceuticals, Inc.: Other: Participates in the International PNH Registry (for Mayo Clinic, Rochester) for Alexion Pharmaceuticals, Inc.; Millennium Takeda: Research Funding. Kapoor:Celgene: Research Funding; Takeda: Research Funding.

Abstract Abstract 3948 Background: Smoldering multiple myeloma (SMM) is an asymptomatic precursor disease of multiple myeloma, and is defined by excess bone marrow plasma cells and monoclonal protein without evidence of end-organ damage (hypercalcemia, renal insufficiency, anemia, or bone lesions [CRAB]). The identification of SMM patients with more aggressive underlying disease remains a challenge. We hypothesize that SMM is a clinical entity comprised of both premalignant, high-risk MGUS and early multiple myeloma in transition to malignant disease, which may be differentiated with the use of the serum FLC (FLC) ratio. Methods: This was a retrospective analysis of 586 patients with newly diagnosed SMM from 1970–2010 with available stored serum samples around the time of diagnosis to be utilized for quantification of FLC ratios. SMM was defined by the International Myeloma Working Group 2003 definition; serum M-protein ≥ 3 g/dL and/or ≥ 10% bone marrow plasma cells with no evidence of CRAB features. The immunoglobulin FLC assay (Binding Site, U.K.) was used for testing. The FLC ratio was calculated as κ/λ (reference range 0.26–1.65). The involved/uninvolved FLC ratio was recorded to simplify the reporting of data. Receiver Operating Characteristics (ROC) curves were created to assess the ability of the FLC ratio to discriminate patients who progressed to symptomatic multiple myeloma (MM) in the first 2 years or at any point during follow-up versus patients without evidence of progression. Patients with less than 24 months follow-up without progression were censored. The optimal diagnostic cut-point for FLC involved/uninvolved ratio to identify patients with progressive disease from the ROC curve was >88.6 (equivalent to <0.011 or >88.6). For ease of clinical application, the optimal value for involved/uninvolved FLC ratio was rounded to >100. Time to progression (TTP) from date of the initial FLC to active MM was calculated using Kaplan-Meier analysis and compared to patients with a high (>100) and low (<100) involved/uninvolved FLC ratio at time of SMM diagnosis. TTP within 24 months of the initial FLC was also calculated. Results: During the study period, 54% of patients progressed to active MM. On ROC analysis, a cut-point of >100 corresponded to a sensitivity of 25% (95% CI, 20.5–30.4) and specificity of 99.3% (97.3–99.9), with positive likelihood (+LR) ratio of 33.9 (38.1–41.0), negative likelihood ratio (−LR) of 0.75 (0.2–3.0), positive predictive value (PPV) of 97.6 (91.5–99.7) and negative predictive value of 53.0 (48.5–57.4). Using the ROC to assess progression to MM within 24 months (Figure 1), sensitivity was 29.6% (23.5–36.4), specificity 94.5% (91.7–96.5), +LR 5.36 (4.3–6.6), -LR 0.75 (0.5–1.1), PPV 85.8 (77.7–91.8), and NPV 54.3 (49.8–58.9). Median TTP to active MM in the FLC >100 group was 15 months (9–17) versus 52 months (44–60) in the FLC <100 group (p <.0001) [Figure 2]. In the FLC ratio >100 group, progression at 1 year was 47%, 76% at 2 years, and 90% at 3 years. Only 25% of the FLC <100 patients had progressed at 2 years. The most common progression event was bone disease (42%), followed by anemia (26%), renal impairment (23%), and hypercalcemia (5%). Conclusion: Elevation of the FLC ratio >100 (or <0.01) is highly specific for the future development of active MM, with 76% of these patients developing end-organ damage requiring therapy within 2 years. Risk of transformation to MM in the FLC <100 group was similar to previously reported rates of 10% per year for the first 5 years. Development of an FLC ratio >100 is associated with increasing disease burden and in this study behaved in a malignant fashion rather than a precursor state. The FLC is a simple and useful predictor of progression to MM in SMM, and patients with FLC ratios of <0.01 or >100 within the first 2 years of SMM diagnosis should be monitored especially closely. Future studies are needed to determine optimum cutoffs for FLC ratio to where a change in definition of MM could be considered. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 4048 Background: The plasma cell labeling index (PCLI) is measured as the percentage of bone marrow plasma cells (PC) in the S phase of the cell cycle and provides an estimate of the proliferative capacity of malignant PC in multiple myeloma (MM). The International Myeloma Working Group (IMWG) uniform response criteria measure the monoclonal (M) protein and serum free light chain (FLC) assay to evaluate clinical response. An elevated PCLI is an established adverse prognostic risk factor for survival, however it is unknown if the PCLI response to therapy offers further prognostic value. Methods: Data from 176 newly diagnosed MM patients from 1985 to 2005 were collected from the Mayo Clinic dysproteinemia database. Inclusion criteria for the study required a minimum initial PCLI of 0.5% and a subsequent PCLI 4 months after initiation of therapy. Baseline and subsequent serum M-protein, progression date, and overall survival were recorded. Clinical responses were assessed by the IMWG uniform response criteria. The association of PCLI response and treatment response (CR, VGPR, or PR) was assessed univariately. Overall survival based on PCLI response, M-spike reduction, and treatment response by IMWG criteria was estimated using the Kaplan-Meier method. Results: The median overall survival (OS) was 47 months (range: 4 – 165). Ninety-four patients (53%) demonstrated a ≥60% reduction in PCLI after initial therapy (responders) and this conferred a significant OS advantage of 51 months vs. 34 months (P<0.01; Figure 1) compared to those who achieved <60% PCLI reduction (non-responders) after initial therapy. The median PCLI percent difference following 4 months of therapy was -67% (+/− 137%; range: -100 to 953%). When patients were stratified into high (PCLI of ≥3%), intermediate (PCLI ≥1%) and low (PCLI <1%) risk groups, OS was significantly improved in the high and intermediate PCLI groups if they achieved ≥60% reduction in PCLI after initial therapy, 31 vs. 7 months (P<0.0022; Figure 2) and 63 vs. 25 months (P<0.0005; Figure 3), respectively. As observed in prior studies, patients with PCLI of ≥3% at diagnosis had shorter overall survival (17 months) when compared to patients with an initial PCLI of <1% (61 months; P < 0.0001). Of the 94 responders, 39% (n=37) did not achieve a response to therapy as measured by M-protein. Thirteen patients (14%) had no measurable serum M-protein at baseline. Conversely, 35% (n=31) of patients that responded by M-protein criteria did not achieve a PCLI response. In patients who achieved CR/PR after 4 months of therapy, the median PCLI reduction was 83.7% vs. 22.5% (P <0.0004) compared to patients with stable disease (not meeting criteria for CR or PR) or progressive disease (as specified by IMWG response criteria). This reflects a significant reduction in disease burden and as expected, median OS was better in the CR/PR group (53 vs. 31 months, P <0.0016). Conclusion: Our study demonstrates that the degree of PCLI reduction after therapy is important in predicting overall survival and response to therapy. This is an important finding in the current setting of effective MM treatment options, whereby patients who do not achieve an adequate response as defined as ≥60% reduction in PCLI in our study, may require change in therapy. Our data confirm that reduction of M-protein is an important surrogate endpoint, as patients who achieved PR and CR lived significantly longer. A significant portion of individuals 39% had a measurable response by PCLI that was not detected by M-protein. Further studies are needed to evaluate the predictive value of the addition a criterion that looks at reduction in proliferative rate as measured by PCLI or other methods such as flow cytometry. Disclosures: Greipp: Mayo Clinic: Patents & Royalties.

Hypoalbuminemia has been reported as common in patients with symptomatic Waldenström macroglobulinemia (WM), but it is not typically mentioned as a manifestation of the disease in review articles or articles discussing indications for treatment. We present the case of a patient with WM for whom symptomatic hypoalbuminemia was the primary reason for initiating treatment. Except in rare cases of WM with renal or gastrointestinal involvement, hypoalbuminemia is thought to be due to the effects of elevated levels of inflammation-associated cytokines, and it has been associated with greater likelihood of progression of asymptomatic to symptomatic disease, greater disease severity, and poorer prognosis. Hypoalbuminemia in WM may become symptomatic, and it may be a reason to initiate treatment if symptoms affect quality of life.

Background:IBER is a novel cereblon E3 ligase modulator (CELMoD) with enhanced tumoricidal and immunostimulatory activities. Preclinically, IBER overcomes immunomodulatory drug (IMiD) resistance and has synergy with daratumumab (DARA), bortezomib (BORT), and dexamethasone (DEX).Aims:This phase 1b/2a multicenter, open‐label, dose‐escalation study (NCT02773030) was conducted to evaluate the maximum tolerated dose (MTD), recommended phase 2 dose (RP2D), safety and preliminary efficacy of IBER in combination with DEX, in patients with relapsed/refractory multiple myeloma (RRMM).Methods:Eligible patients had RRMM and must have received ≥2 prior regimens including lenalidomide (LEN) and/or pomalidomide (POM), and a proteasome inhibitor (PI). All patients had progressed on or within 60 days of last MM therapy. Escalating doses of IBER were given on days 1–21, in combination with DEX 40 mg (20 mg in patients aged >75 years) on days 1, 8, 15, and 22, of each 28‐day cycle. Dose escalation was reviewed by a dose escalation committee.Results:As of January 2019, 58 patients had received IBER + DEX. Median age was 64.5 years (range 33–79), and median number of prior regimens was 5 (2–12). Prior therapies included autologous stem cell transplantation (79%), LEN (100%), POM (69%), PIs (100%), and DARA (66%). IBER dose ranged from 0.3 to 1.2 mg; MTD/RP2D was not reached. Median duration of therapy was 12+ weeks (range 4–109). Grade 3–4 adverse events (AEs) were reported in 41 (72%) patients and were not related to dose. Grade 3–4 neutropenia, thrombocytopenia, neuropathy, and fatigue occurred in 26%, 11%, 2%, and 0% patients, respectively. Three patients discontinued treatment due to AEs. Clinical activity occurred early and was observed across all dose levels (Table 1); 20 of 51 patients remain on treatment (2–27+ cycles).Summary/Conclusion:IBER + DEX showed favorable efficacy and safety in heavily pretreated patients with RRMM who failed multiple prior therapies. This study is ongoing, including combinations of IBER with DARA or BORT.image