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Background: Autologous stem cell transplantation is an effective treatment modality for patients with multiple myeloma. While most of the patients relapse after ASCT with a median time to progression of 2 years, there is a significant heterogeneity in the duration of response. It has been hypothesized that the effect of high dose alkylator therapy used for conditioning may have a dual effect on the myeloma cells as well as marrow microenvironment. It is also known that hematopoiesis, especially thrombopoiesis, depends to some extent on signals form the marrow microenvironment. We examined if there was any relationship between delayed platelet engraftment and outcome after ASCT. Methods: We examined the outcomes in a group of patients undergoing ASCT for myeloma at our institution to compare the response duration to platelet engraftment kinetics. We studied 687 patients undergoing ASCT with melphalan conditioning followed by peripheral blood stem cell transplant. Results: Among the 687 patients undergoing ASCT, 200 pts (29%) achieved a platelet count of 50,000 by day 21 (early group) and the rest achieved this level after 21 days or never engrafted (late group). The median time to progression (TTP) among the late group was 24.8 months (95% CI; 19.6, 30 months) vs. 16.8 months (95% CI; 15.1, 18.6 months) for the late group (p < 0.001) (Figure). Patients in the late engraftment group were more likely to achieve a complete response compared to the early group; 39% vs. 30%, p = 0.02. In a multivariate analysis examining factors predicting for longer time to progression after ASCT, delayed platelet engraftment was independent of transplant within 12 months of diagnosis, CR with ASCT, absence of cytogenetic abnormalities, B2M < 3.5 mg/L and a plasma cell labeling index < 1% at the time of ASCT (Table). Conclusions: In this study, we have demonstrated for the first time a relationship between delayed platelet engraftment after ASCT and the duration of response following ASCT. This intriguing finding raises several hypotheses. It is possible that the delayed platelet engraftment is a marker of marrow microenvironment dysfunction secondary to high dose therapy, given the role of marrow microenvironment on thrombopoiesis. It is possible that this is a surrogate marker for the biological effectiveness of the melphalan dose, which can affect the other cells in the marrow microenvironment as well. It is likely a reflection of the marrow microenvironment dependence on the myeloma cells for its survival. These findings should be confirmed in other larger patient groups. Predictors of progression Variable Hazard Ratio P Platelet Engraftment > 21 days 0.80 (0.60, 0.96) 0.02 Late transplant (>12 months from diagnosis) 1.6 (1.3, 2.0) <0.01 Plasma cell labeling index > 1% 1.9 (1.5, 2.4) <0.01 Complete response 0.41 (0.33, 0.51) <0.01 Abnormal Cytogenetics 1.8 (1.4, 2.3) <0.01 B2M > 3.5 1.2 (0.96, 1.5) 0.12 Figure Figure

Abstract Background: Pomalidomide is an immunomodulatory agent (IMiD®) that has been approved for treatment of relapsed and refractory multiple myeloma (MM). Combinations of IMiDs and proteasome inhibitors offer the potential for deeper and more durable responses due to enhanced efficacy. Preliminary results of a phase 1 study of twice weekly bortezomib with pomalidomide have been reported with promising results (Richardson, ASH 2012). This phase I/II trial was designed to evaluate the maximum tolerated doses (MTD) as well as safety and efficacy of the combination of pomalidomide, once weekly bortezomib and dexamethasone (PVD) in patients with relapsed, lenalidomide refractory, MM. Patients and methods: We included patients with relapsed MM who had 1-4 prior lines of therapy and were resistant or refractory to lenalidomide. In the phase I portion of the trial, dose level 1 consisted of pomalidomide 4 mg days 1-21 PO, bortezomib 1.0mg/m2 days 1,8,15, and 22 IV or SQ and dexamethasone 40 mg days 1,8,15, and 22 PO, given every 28 days. Bortezomib was increased to 1.3mg/m2 for dose level 2 and and was adopted for the phase 2 portion. The primary aim of the phase I cohort was to determine the MTD of the combination, and for the phase II cohort was to evaluate the confirmed response rate (PR, VGPR, or CR) in relapsed refractory MM. Response was assessed by the IMWG criteria and toxicity was graded using the CTCAE v4.0. Results: 50 patients were accrued between March 2012 and July 2014 (dose level (DL)1: 3, DL 2: 6, Phase II: 41). We describe results in 47 patients treated at MTD and phase II. Median age was 66, 51% were female and median time from diagnosis to study was 46 months (15-142). Twenty five percent had mSMART defined high-risk status. Median number of prior regimens was 3. All patients had prior lenalidomide, 68% had stem cell transplant, 17% received thalidomide, 56% had alkylators and 57% had bortezomib. With median follow up of 9 months, 72% remain progression free, 96% are alive and 66% remain on treatment. The most common AEs at least possibly attributable to the combination were anemia, fatigue, leukopenia and thrombocytopenia; however, the majority of these were grade 1-2. Grade ≥3 AEs (regardless of attribution) that occurred in at least 3 patients included neutropenia (29), leukopenia (15), lung infection (6), lymphopenia (8) dyspnea (3) and syncope (3). DVT/PE occurred in one patient. Among the 42 patients who were evaluable, confirmed responses (PR, VGPR, or CR) were seen in 34 (81%) including sCR (3), CR (5), VGPR (8), PR (18). Confirmed responses were seen in 9 of 11( 82%) high risk patients. Median progression free survival was 17.7 months (95%CI: 9.5-NA). Conclusions: PVD is a highly effective combination in patients refractory to lenalidomide with confirmed responses in over 80%. Weekly administration of bortezomib enhanced the tolerability and convenience of this regimen. Toxicities are manageable, mostly consisting of mild cytopenias with no significant neuropathy or DVT. PVD is a highly attractive option in patients with relapsed and refractory MM. Disclosures Lacy: Celgene: Research Funding. Lust:Senesco: PI Other. Fonseca:Medtronic, Otsuka, Celgene, Genzyme, BMS, Lilly, Onyx, Binding Site, Millennium, AMGEN: Consultancy, patent for the prognostication of MM based on genetic categorization of the disease. He also has sponsored research from Cylene and Onyx Other, Research Funding. Stewart:Celgene: Consultancy; Novartis: Consultancy; Array BioPharma: Consultancy; BMS: Consultancy; Millenium: Research Funding. Reeder:Millennium, Celgene, Novartis: Research Funding. Mikhael:Onyx: Research Funding; Celgene: Research Funding; Sanofi: Research Funding; Novartis: Research Funding.

Abstract Cold agglutinin disease (CAD) is an autoimmune hemolytic anemia characterized by the presence of autoantibodies (cold agglutinins) that bind to red blood cells (RBC) at low temperatures. Cold agglutinin binding to RBCs results in antibody-mediated classical complement activation with deposition of complement C4 and C3 fragments onto the RBC surface. Complement-opsonized RBCs are removed from the circulation by macrophage-driven phagocytosis in the liver or spleen and via intravascular hemolysis following assembly of the terminal lytic complex (C5b - C9), together resulting in clinical anemia. C1q is the initiating molecule for cold agglutinin-mediated complement activation on the surface of human RBCs. We hypothesized that directly blocking C1q recruitment onto cold agglutinin-sensitized RBCs will prevent complement activation and opsonization and reduce hemolysis. To this end, we have developed a humanized monoclonal antibody (ANX005) that binds with high-affinity (~10 pM) to C1q and blocks classical complement activation & hemolysis in an in vitro sheep RBC assay. We evaluated the impact of ANX005 on hemolysis and complement deposition on human RBCs that were pre-sensitized with sera from CAD subjects. ANX005 showed a dose-dependent reduction in hemolysis using both individual and pooled CAD sera as the source of cold agglutinin. We further demonstrated that C1q blockade led to a robust reduction in C4 and C3 fragment deposition onto human RBCs. These results demonstrate that C1q inhibition is an effective way to impede C4 and C3 activation and downstream assembly of the lytic complex in sera from CAD patients, and support the clinical development of ANX005 in CAD and other antibody-mediated diseases. Disclosures Gertz: Prothena Therapeutics: Research Funding; Sandoz Inc: Honoraria; NCI Frederick: Honoraria; Celgene: Honoraria; Med Learning Group: Honoraria, Speakers Bureau; Research to Practice: Honoraria, Speakers Bureau; Alnylam Pharmaceuticals: Research Funding; Novartis: Research Funding; Ionis: Research Funding; Annexon Biosciences: Research Funding; GSK: Honoraria. Qiu:Annexon Biosciences: Employment, Equity Ownership. Kendall:Annexon Biosciences: Employment, Equity Ownership. Saltarelli:Mallinckrodt: Equity Ownership; Abbvie: Equity Ownership; Annexon Biosciences: Employment, Equity Ownership, Patents & Royalties. Yednock:Annexon, Inc: Employment, Equity Ownership. Sankaranarayanan:Annexon Biosciences: Employment, Equity Ownership.

Abstract Background Conflicting results have emerged, especially with respect to the impact on overall survival (OS), from trials evaluating lenalidomide maintenance (LM) therapy after induction therapy alone or post-autologous stem cell transplant (ASCT) in multiple myeloma (MM). We performed a systematic review and meta-analysis of existing outcome data from LM trials to evaluate role of lenalidomide as maintenance strategy in MM. Patients and methods A comprehensive search of electronic databases and abstracts through June 2013 was performed to identify randomized controlled trials (RCTs) that compared LM vs. placebo/no maintenance. Single arm studies were excluded. Pooled hazard ratio (HR) or odds ratio (OR) estimates with 95% confidence intervals (CIs) were calculated using the random-effects model for clinical endpoints of progression free survival (PFS), OS, response rate (RR) and adverse events (AEs), including second primary malignancies (SPMs). Analyses were performed using Comprehensive Meta-Analysis Software Version 2. We assessed between-study heterogeneity with the Cochran Q test and quantified its extent with the I2 statistic. Results Overall, five RCTs, with data extractable from four phase III trials (3 publications and 1 abstract) were identified (n= 1935). All studies were RCTs with an adequate randomization. MRC MM XI study was excluded from analyses as survival data are not available. Two placebo controlled trials (IFM 05-02, CALGB 100104) addressed the role of LM post-ASCT, one placebo-controlled trial (MM-015) studied LM therapy in the non-transplant setting and the remaining trial (RV-MM-PI209) had a 2 X 2 design comprising of both ASCT and non-transplant randomized arms followed by a second randomization of LM versus no maintenance. There was no heterogeneity for estimate of PFS results (Cochran Q, p=0.68; I2=0%), but considerable heterogeneity for estimate of OS (Cochran Q, p=0.09; I2= 55%), among the studies. There was significant prolongation of both PFS (HR 0.49, 95% CI, 0.41–0.58, p<0.001) and OS (HR 0.77, 95% CI, 0.62–0.95, p=0.013) with LM vs. placebo/no maintenance (Figure 1). Best response during maintenance was reported only in 2 studies and odds of responding (very good partial response or better) were not significantly different with LM (OR 1.28, p=0.3). Grade 3-4 AEs data were available from 3 trials for calculation of pooled OR with LM compared with placebo. We observed a nearly two-fold increase in the risk of SPMs with LM (OR 1.99; 95% CI, 1.31–3.04; p=0.001). Patients on LM were more likely to have grade 3-4 AEs than placebo: neutropenia (OR 4.9, p<0.001), thrombocytopenia (OR 2.7, p<0.001), fatigue (OR 2.3, p=0.01) and venous thromboembolism (OR 3.2, p=0.02). Odds of discontinuing treatment were also significantly higher in patients on lenalidomide (OR 2.9, p<0.001). Conclusions Meta-analysis of RCTs demonstrates significant improvement in PFS and modest improvement in OS with LM. There is an increased risk of grade 3-4 adverse effects, including SPMs with LM. Substantial heterogeneity for estimate of OS among protocols is a limitation of this analysis. Lack of uniform access to lenalidomide upon disease progression in the placebo/no maintenance arms of the constituent studies should be taken into account while interpreting aggregate effect estimates for OS in this meta-analysis. OS: Cochran Q p=0.09, I2=55%, substantial heterogeneity PFS: Cochran Q p=0.68, I2=0%, minimal heterogeneity Disclosures: Off Label Use: Lenalidomide for maintenance therapy in multiple myeloma. Kumar:Merck: Consultancy, Honoraria; Celgene: Consultancy, Research Funding; Millennium: The Takeda Oncology Company: Research Funding; Novartis: Research Funding; Genzyme: Research Funding. Dispenzieri:Celgene, Millenium, Jansenn, Pfizer: Research Funding. Bergsagel:Onyx: Consultancy. Lacy:Celgene Corporation: Research Funding.

Abstract Background: Proliferation rate of plasma cells (PC) is a powerful tool in evaluating all types of monoclonal gammopathies, predicting for progression as well as survival in all phases of the disease. A flow cytometry (FC)-based method to delineate the cell cycle of clonotypic PCs and determine the proportion in S-phase was developed. This method replaces a labor-intensive slide based methodology, but the prognostic power of this FC approach has not been clearly elucidated. Methods: A total of 1061 patients who had bone marrow (BM) FC PC proliferation analysis at Mayo Clinic, Rochester from May 2012 to December 2013 were studied. These included MGUS/ SMM (n=134), newly diagnosed (NMM; n=88), plateau in response (>=PR; n=544), and stable disease (n=38), and relapsed disease (RMM; n=257). PC proliferation was measured by 8-color FC using antibodies to CD19, CD38, CD138, CD45, and cytoplasmic kappa and lambda Ig light chains, and DAPI DNA staining. The DNA content of the abnormal, clonotypic PCs was specifically analyzed and the %S-phase was determined by measuring the proportion of cells between G0/G1 and G2/M. All studies collected 5x105 events on BD FACSCanto II instruments and analysis was performed with BD FACSDiva software. The CV of the DAPI staining of G0/G1 lymphocytes as an internal control population was always less than 3.5. Patients with fewer than 300 PCs for assessment of %SP were designated as 0%. Results: The median follow up from testing for the entire cohort was 13 months (95% CI; 12.7, 13.3); 156 (15%) had died. The proportion of patients with adequate numbers of plasma cells available for %SP estimation and the median (IQR) %SP for the different groups are as shown in table. As expected, patients with MGUS/SMM and those in a response state had slightly lower proportions of patients with sufficient PCs to estimate %SP. The clinical features and outcomes were further analyzed using two cutoffs, %SP ≥1 and ≥2, in the different patient groups. Among most of the disease groups, especially the newly diagnosed MM and relapsed disease, %SP was prognostic for OS using both cutoffs (Table). Among the NMM in univariate analysis, %SP ≥2, B2microglobulin >5.5, age >70 and creatinine > 2 mg/dl were all significant, but only B2microglobulin >5.5 retained significance in multivariable analysis. Among the RMM, in univariate analysis, %SP ≥2, B2microglobulin >5.5, HR FISH (t4; 14, t14;16, t14;20 & del17p) and LDH >221 were all significant, but only %SP ≥2 was significant in multivariable analysis. Conclusion: The %S-phase of clonal PCs determined by FC is of prognostic value in patients with MM, in all disease phases. This is particularly relevant among patients with relapsed disease, where it is independent of some of the other known poor prognostic factors such as high risk FISH. This is in sharp contrast with recent studies that have shown no prognostic value for slide based labeling index in patients treated with novel agents. Abstract 2053. Table MGUS/SMM NMM >=PR SD Relapse N 134 88 544 38 257 N (%) with PCs measurable for proliferation 103 (77%) 84 (96%) 245 (45%) 31 (82%) 210 (82%) %SP (IQR) 0.3(0.1-0.7) 0.8 (0.4- 1.5) 0(0- 0.9) 0.8(0.3-1.3) 1.2(0.4- 2.7) OS (%SP >1 vs. rest) NS NR for either(P<0.01) NR for either (P<0.001) NR for either(P=0.02) 19 vs. NR(P<0.001) OS (%SP >2 vs. rest) NS NR for either (P=0.03) 20 vs. NR(P<0.001) NR for either(P=NS) 16 vs. NR(P<0.001) Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Abstract There are a number of rare monoclonal gammopathies that do not have a characteristic laboratory, imaging, or pathologic study. Recognition requires keeping the specific syndrome in mind. This article reviews 6 rare syndromes associated with monoclonal proteins and gives specific “pearls” so a clinician can be certain not to overlook these important disorders that easily can be misdiagnosed as MGUS, Waldenstrom, and multiple myeloma.

Abstract Introduction: Primary systemic amyloidosis occurs when a clonal plasma cell population secretes light chains (or light chain fragments) that deposit in tissues as amyloid and cause organ failure and ultimately patient death. Primary systemic amyloidosis generally results from non-proliferative small populations of plasma cells. While it is known that IgG, IgA and light chain producing plasma cells can secrete amyloid in association with myeloma, fewer medical professionals recognize that IgM-secreting lymphoplasmacytic cells can produce amyloid proteins. When monoclonal IgM secreting marrow lymphocytes are present, amyloidosis can result with or without overt Waldenstrom Macroglobulinemia. Patients and Methods: All patients seen at the Mayo Clinic between January 1968 and August 2000 with both a serum IgM monoclonal protein and biopsy-proven amyloidosis were analyzed. The Mayo Clinic Dysproteinemia Database recognized 128 patients (42 female, 86 male) with a median age of 65 years. Results: Seventy-two percent (n=92) of the patients have died with a median survival of 1.72 years following biopsy proven amyloidosis (figure 1). Median serum IgM monoclonal spike was 1.38 g/dL. In addition, serum IgM kappa to lambda light chain ratios (1:3) were found to be reversed in patients with IgM gammopathy when amyloid was present (compared to the reverse ratio (3:1) in patients with Waldenstrom macroglobulinemia in the absence of amyloidosis). Subcutaneous fat, rectum and bone marrow revealed amyloid in 72%, 69% and 70%, respectively, providing non-invasive techniques for amyloidosis diagnosis without the risks of bleeding associated with renal or hepatic percutaneous biopsy. Variables not shown to affect survival included the following: age, gender, serum M spike, urine protein, alkaline phosphatase, creatinine, light chain isotype, ejection fraction, and percent marrow plasma cells. The presence of amyloid cardiomyopathy (defined as a cardiac interventricular septal thickness greater than 12 mm.) was the only variable to adversely affect survival. Of the patients with echocardiographic evidence of cardiomyopathy, the median survival was 10.8 months. In contrast, the patients without echocardiographic evidence of cardiomyopathy at diagnosis had a median survival of 39 months (figure 2). Conclusion: Amyloidosis is underappreciated and should be considered in the differential diagnosis of all patients presenting with IgM gammopathy. Patients found to have amyloidosis in this setting should be tested for amyloid cardiomyopathy, as its presence predicts poor outcome. Lambda light chain in serum IgM samples should increase the index of suspicion for the presence of amyloid since IgM lambda is present in only 25% of IgM MGUS or Macroglobulinemia patients but is seen in 75% of IgM amyloidosis patients. Figure Figure

Abstract Background: Previous studies have demonstrated inferior overall survival (OS) among patients with AL amyloidosis who have bone marrow plasmacytosis (BMPC) >10%. It is well recognized that AL patients who achieve the deepest hematologic responses have superior organ response and OS rate. Methods: We designed a study to determine if BMPC% affects CR rate post ASCT and whether pre-transplant induction therapy improves response rate and OS among patients with a higher baseline BMPC burden. Results: Among 415 AL patients who underwent ASCT at Mayo Clinic, Rochester within 12 months of diagnosis, 116 (28%) had BMPC>10% at diagnosis. The median age was 57.2 years. The median follow up for surviving patients was 67.3 months. There was no statistically significant difference in age, gender, time from diagnosis to transplant, or use of attenuated conditioning regimen between groups with high (>10%) and low (≤ 10%) bone marrow involvement. The high BMPC group tended to receive more induction chemotherapy before ASCT, and presented with greater value of albumin, beta-2 microglobulin and difference in serum free light chain (dFLC). A higher CR rate was observed in low BMPC group (44.6% versus 26.7%, p=0.0013). In patients with high BMPC, a higher CR rate (33.9% versus 17.7%, p<0.05) was seen in those who received pre-ASCT induction therapy compared with no induction therapy. Among 3 groups of patients who had: no pre-ASCT therapy; steroid only as induction; and induction chemotherapy, the 5-year OS rates were 50.5%, 40% & 67.5%, respectively, p<0.03. Conclusions: Lower bone marrow burden at diagnosis yielded a deeper response following ASCT. Compared to no therapy, patients who were treated with steroid only pre-ASCT had an inferior OS, but other induction regimens appeared to improve survival. These data would support the concept that using induction therapy prior to ASCT conditioning among patients with higher tumor burden may be of value. Figure 1. In BMPC > 10% at diagnosis, OS comparison between induction therapies pre-ASCT Figure 1. In BMPC > 10% at diagnosis, OS comparison between induction therapies pre-ASCT Figure 2. Figure 2. Figure 3. Figure 3. Disclosures Kumar: Celgene: Research Funding; Celgene, Millenium, Sanofi, Skyline, BMS, Onyx, Noxxon,: Other: Consultant, no compensation,; Sanofi: Research Funding; AbbVie: Research Funding; Millenium/Takeda: Research Funding; Onyx: Research Funding; Skyline, Noxxon: Honoraria; Janssen: Research Funding. Gertz:Celgene: Honoraria; millenium: Consultancy, Honoraria; Onyx: Honoraria; Novartis: Honoraria; Smith Kline: Honoraria.

Abstract Background: While B-cell receptor (BCR) signaling is essential for the development, of normal B cells, its aberrant hyper-activation results in neoplastic transformation of B-lymphocytes. Recent investigations using small molecule inhibitors validate the BCR pathway as a valuable target. Bruton’s tyrosine kinase (BTK) is one of the components of a signaling hub that transduces signals from the BCR into the cell for its activation and has been shown to be a therapeutic target. Ibrutinib (PCI-32765), an irreversible BTK inhibitor has shown clinical efficacy in CLL, mantle cell lymphoma (MCL) and Waldenströms macroglobulinemia (WM). Ibrutinib binds to cysteine-481 of the BTK protein and blocks its phosphorylation, resulting in termination of BCR-mediated activation of cells with a concomitant induction of death. Despite the clinical success of ibrutinib, a high percentage of patients achieve only partial response and eventually acquire resistance to the drug, resulting in aggressive relapse of the disease. A mutation of Cys481-Ser in BTK (ibrutinib-BTK binding site) has been reported to be one of the reasons for the development of ibrutinib resistance (IR). To understand the mechanisms resulting in acquisition of IR, we developed preclinical models of IR in WM and MCL. Materials: Ibrutinib was obtained from Pharmacyclics, CA. Validated human WM models (BCWM.1, RPCI-WM1 and MWCL.1 cell lines) and human MCL models (Jeko-1 and Maver cell lines) were used for the study. Results: BTK was constitutively phosphorylated at Y223 and Y551 in all the cell lines tested and this was inhibited by ibrutinib in a dose dependent manner. Phosphorylation of other kinases in the cascade such as SYK (Y323 and Y525/526) and PLCg2 (Y759 and Y1217) were also inhibited while AKT phosphorylation at both Ser473 and Thr308 was consistently increased in presence of ibrutinib. Treatment with ibrutinib induced cell cycle arrest in the G1 phase by 24h followed by apoptosis. Cell growth assays (MTS assay) showed that BCWM.1 was the most sensitive cell line followed by MWCL-1, RPCI-WM1, Maver and Jeko-1. Exposure of WM and MCL cells for prolonged periods of time with progressively increasing concentrations of ibrutinib resulted in outgrowth of clones (IR WM and MCL cell lines) that were resistant to apoptosis with a slow growth rate as compared to wild type parental cells. IR cells attained 2 – 20 fold resistance to ibrutinib as compared to the respective parental lines as determined by MTS assay. Sequence analysis of the BTK gene in all the cell lines revealed no mutation in IR cells at Cys481 suggesting that in an acquired IR state, resistance to ibrutinib can be developed independent of BTK Cys481 mutation. Interestingly, we found p-BTK levels to be markedly reduced in IR cells. Ibrutinib reversal experiments suggested that while a continuous presence of ibrutinib is needed for inhibition of BTK phosphorylation, a stable IR state could be maintained (for >1 month) in the absence of ibrutinib. This suggested the cells reliance on a parallel survival pathway, independent of BTK phosphorylation. Focused mRNA (Nanostring nCounter assay) and immunoblot analysis revealed significant changes in the expression profiles of several cellular elements. These included transcription factors such as PU.1, IRF4, BLIMP1, BCL-6 b-catenin as well as the phosphorylated ERK1/2, STAT1 and 3 suggesting a reprogramming of critical cellular networks, which IR tumor cells might be utilizing to overcome ibrutinib-induced cytotoxicity. Importantly, we observed that IR cells retained high levels of p-AKT and showed an increase in expression of BCL2 family members, as well as BCL-2 itself. Treatment of IR cells with ibrutinib +/- MK2206 (AKT inhibitor), or ABT-199 (BCL-2 inhibitor), synergistically induced cytotoxicity in IR cells, suggesting the importance of these parallel survival pathways (AKT/BCL2) in maintaining an IR state. Conclusion: Here we demonstrate that in the absence of BTK Cys481 mutation, an IR state is associated with reprogramming of transcriptional networks countering ibrutinib-induced toxicity by activation of AKT and BCL-2. Our current data exposes multiple vulnerabilities within IR cells, which can be therapeutically exploited to potentially delay onset of IR, by targeting alternative oncogenic mechanisms that are activated in presence of sustained BTK inhibition. Disclosures No relevant conflicts of interest to declare.

Abstract Background: Cryoglobulinemia(CG) is a relatively uncommon disorder which has been recognized as a syndrome for nearly forty years. The further classification into types I, II, and III was established thirty years ago, with Type II consisting of a monoclonal immunoglobulin possessing activity towards a polyclonal component. In the interim, many disease associations have been described and various therapies tried, but clinical trials remain rare, and the natural history, causes, and pathways of CG require further investigation. Methods: We examined the records of all patients seen at the Mayo Clinic, Rochester, with Type II CG between 3/2/1994 and 11/27/2000 using a prospectively held dysproteinemia database. Results: Of 66 total patients 30 were male(45%) and 36 were female(55%) with mean ages of 52.7±11.0 and 60.9±12.6, respectively. 63 patients were Caucasian, with one each of African, Hispanic, and other. 34 patients(52%) presented with purpura, 16 with edema(24%), 12 with neuropathy(18%), 12 with fatigue, 10 with arthralgia(15%), 8 with weight loss(12%), 5 with livido reticularis(8%), 4 with leg ulcers(6%), and 2 with infarcted extremities(2%). Of our patients, 13 had Type II CG (20%) unassociated with infection or lymphoma. 38 patients(58%) had hepatitis C(HCV), of whom 12 underwent genotyping with 10 having genotype 1a or 1b and 2 having genotype 2a or 2b. No patients had isolated Hepatitis B(HBV) though 8 HCV patients were coinfected with HBV. One patient each had CMV and EBV. 7 patients(10%) had Sjogren’s disease, and 1 had scleroderma. 11 patients (17%) had a lymphoproliferative disorder (LPD), and 5 more went on to develop LPD. Of these, 7 patients had a B-cell LPD, 4 had a MALT lymphoma, 4 had a non specific LPD, one had a lymphoplasmacytic lymphoma, and one had Gaucher’s thrombocytopenia. Significant renal disease developed in 23 patients(35%), with 12 being membranoproliferative glomerulonephritis (18%) and 3 being mesangioproliferative glomerulonephritis. Pertinent laboratory finding included a mean cryocrit of 7.6%±12.5, a positive rheumatoid factor in 36 out of 36, and hypocomplementemia in 33 of 41(80%). Liver function testing was reflective of the patient’s hepatitis status. Serum electrophoresis in 48 patients revealed the following patterns: 22 were normal(46%), 15 had a γ peak(31%), 5 polyclonal patterns(10%), 5 hypogammaglobulinemia, and one a β-γ peak. Of 32 samples where a monoclonal antibody was isolated 29 were IgM (91%), and 3 IgG (9%). The light chains were 88% κ, with 12% λ. Treatment was generally guided by the comorbidities, and many (30%) required no specific treatment for Type II CG. In the 38 HCV patients, 17 received interferon with or without ribavirin and 18 were deemed not to need treatment, while 2 received steroids alone and 1 was lost to follow up. In 28 patients without HCV 20 received steroids(71%), while 5 received other treatments and 3 were untreated. Of 46 patients who received any treatment, 27 (59%) achieved no response or had disease progression and required a change in therapy. To date, 8 patients have died, with none of deaths specifically attributable to complications of cryoglobulinemia. Conclusion: Type II CG is a non fatal disease most frequently associated with HCV. Optimal disease specific treatment is as yet undefined, and is generally directed at the underlying comorbidity when possible. Not all cases require treatment and many can be followed symptomatically.