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PURPOSE Idecabtagene vicleucel (ide-cel) is an autologous B-cell maturation antigen–directed chimeric antigen receptor T-cell therapy approved for relapsed/refractory multiple myeloma (RRMM) on the basis of the phase II pivotal KarMMa trial, which demonstrated best overall and ≥ complete response rates of 73% and 33%, respectively. We report clinical outcomes with standard-of-care (SOC) ide-cel under the commercial Food and Drug Administration label. METHODS Data were retrospectively collected from patients with RRMM who underwent leukapheresis as of February 28, 2022, at 11 US institutions with intent to receive SOC ide-cel. Toxicities were graded per American Society for Transplantation and Cellular Therapy guidelines and managed according to each institution's policies. Responses were graded on the basis of the International Myeloma Working Group response criteria. RESULTS One hundred fifty-nine of 196 leukapheresed patients received ide-cel by data cutoff. One hundred twenty (75%) infused patients would have been ineligible for participation in the KarMMa clinical trial because of comorbidities at the time of leukapheresis. Any grade and grade ≥ 3 cytokine release syndrome and neurotoxicity occurred in 82/3% and 18/6%, respectively. Best overall and ≥ complete response rates were 84% and 42%, respectively. At a median follow-up of 6.1 months from chimeric antigen receptor T infusion, the median progression-free survival was 8.5 months (95% CI, 6.5 to not reached) and the median overall survival was 12.5 months (95% CI, 11.3 to not reached). Patients with previous exposure to B-cell maturation antigen–targeted therapy, high-risk cytogenetics, Eastern Cooperative Oncology Group performance status ≥ 2 at lymphodepletion, and younger age had inferior progression-free survival on multivariable analysis. CONCLUSION The safety and efficacy of ide-cel in patients with RRMM in the SOC setting were comparable with those in the phase II pivotal KarMMa trial despite most patients (75%) not meeting trial eligibility criteria.

Secondary hemophagocytic lymphohistiocytosis (HLH) is a life-threatening immune dysregulation disorder. Use of chimeric antigen receptor T-cell therapy (CAR-T) is associated with cytokine release syndrome (CRS), Immune Effector Cell Associated Neurotoxicity Syndrome (ICANS) and secondary HLH. However, application of HLH scoring systems (H-score, HLH-2004 criteria) are not validated in this setting. We analyzed the utility of applying the H-score and the HLH-2004 criteria to identify patients with possible HLH post-CAR-T for Relapsed/Refractory Diffuse Large B-cell Lymphoma. Only two of four patients with post CAR-T HLH met five or more of the diagnostic criteria for HLH by HLH 2004 criteria. In contrast all four post CAR-T HLH patients had a high H-score (169); however, an additional ten patients that did not have HLH also had a high H-score. Thus, in this patient population, both scoring systems were demonstrated to have low prognostic significance in differentiating between high grade CRS and HLH.

Background CD19-directed chimeric antigen receptor (CAR) T-cell therapy (CAR-T) has emerged as effective for relapsed/refractory large B-cell lymphoma (R/R LBCL). The neurologic toxicity seen with CAR-T, referred to as immune effector cell–associated neurotoxicity syndrome (ICANS), is poorly understood. To better elucidate the clinical characteristics, treatment outcomes, and correlative biomarkers of ICANS, we review here a single-center analysis of ICANS after CAR T-cell therapy in R/R LBCL. Methods Patients (n = 45) with R/R LBCL treated with axicabtagene ciloleucel (axi-cel) were identified. Data regarding treatment course, clinical outcomes, and correlative studies were collected. Patients were monitored and graded for ICANS via CARTOX-10 scoring and Common Terminology Criteria for Adverse Events (CTCAE) v4.03 criteria, respectively. Results Twenty-five (56%) patients developed ICANS, 18 (72%) of whom had severe (CTCAE grades 3–4) ICANS. Median time to development of ICANS was 5 days (range, 3–11). Elevated pre-infusion (day 0 [D0]) fibrinogen (517 vs 403 mg/dL, upper limit of normal [ULN] 438 mg/dL, P = 0.01) and D0 lactate dehydrogenase (618 vs 506 units/L, ULN 618 units/L, P = 0.04) were associated with ICANS. A larger drop in fibrinogen was associated with ICANS (393 vs 200, P < 0.01). Development of ICANS of any grade had no effect on complete remission (CR), progression-free survival (PFS), or overall survival (OS). Duration and total dose of steroid treatment administered for ICANS did not influence CR, PFS, or OS. Conclusions ICANS after CAR-T with axi-cel for R/R LBCL was seen in about half of patients, the majority of which were high grade. Contrary to previous reports, neither development of ICANS nor its treatment were associated with inferior CR, PFS, or OS. The novel finding of high D0 fibrinogen level can identify patients at higher risk for ICANS.

As we have just stepped into a new decade of hopes, the mountain of knowledge learned from multiple myeloma (MM) remains unmatched among cancers. In the last decade alone, this rapid-sequence learning curve has led to regulatory approvals of eight drugs with mechanisms of actions representing five different areas of cell biology some of which made to the frontline setting, sparking debates about how to best sequence them in the treatment continuum of induction, consolidation, and maintenance and gained momentum with the realization of the implications of an effective upfront therapeutic approach with potential impact on survival.This review was written with an intent to introduce the reader to the current treatment approach of a newly diagnosed myeloma patient and acquaint with promising targets and mechanistic strategies. Medline and clinicaltrials.gov databases (2000-2020) and relevant meetings (ASH, ASCO, EHA, ESMO, IMW) reports were queried and guidelines (IMWG) were reviewed to distill to expert opinion in an inundating field.Future holds promise with new targets on the horizon. It is likely that the new age of myeloma will belong to quadruplets with the addition of acellular or cellular biologics to first-generation novel agents, leading to new paradigms.

Background/aimsChimeric antigen receptor T-cell (CAR T) therapy has been shown to improve the remission rate and survival for patients with refractory haematological malignancies. The aim of this study is to describe ocular adverse effects associated with CAR T therapy in patients with haematological malignancies.MethodsThis is a retrospective, single-institution, case series. Patients aged 18 years or older who received standard of care CAR T therapy for relapsed/refractory large B-cell lymphoma with a documented ophthalmic evaluation were included. The primary outcome was clinician ophthalmic examination findings.ResultsA total of 66 patients received CAR T-cell therapy from February 2018 to October 2019 with 11 receiving an ophthalmic examination. Eleven patients (n=22 eyes) who received CAR T-cell therapy were included in review. The median time from CAR T-cell infusion date to ocular examination was 57.5 days. The median patient age at the time of examination was 60.5 years. Ten patients had subjective symptoms prompting ophthalmic examination. Two patients reported floaters and photopsias. One patient had worsening ocular graft-versus-host disease. Two patients were identified with possible reactivation of viral infections, including herpes zoster ophthalmicus and regressing acute retinal necrosis.ConclusionsThe increasing use of CAR T therapy for malignancies underscores the importance of ophthalmologists and oncologists understanding the potential toxicities associated with its use, particularly ocular toxicities and when to refer for an ophthalmic examination.

Patient: Female, 60-year-old Final Diagnosis: Amyloid light-chain amyloidosis • hepatic amyloidosis Symptoms: Abdominal pain • anemia • emesis Medication: — Clinical Procedure: Bone marrow biopsy • exploratory laparotomy • hepatectomy • stem cell transplant Specialty: Hematology • Oncology Objective: Unusual clinical course Background: Immunoglobulin light chain (AL) amyloidosis is a plasma cell disorder in which excess light chain deposits in tissues, resulting in organ dysfunction and damage. Typically, AL amyloidosis presents as a systemic disease affecting multiple organs, and most patients have elevated serum free light chains. However, the presentation of AL amyloidosis is highly variable. The purpose of this case report is to raise awareness of the atypical presentations of AL amyloidosis in order to facilitate more rapid diagnosis, which has the potential to prevent additional organ damage when appropriate therapy is provided. Case Report: We describe a case of AL amyloidosis with amyloid deposition confined to the liver and bone marrow and lack of significant serum light chain elevation. The patient initially presented with a spontaneous hepatic hematoma, and was ultimately found to have hepatic AL amyloidosis, with monoclonal plasma cells in the bone marrow and monoclonal protein on serum protein electrophoresis. Our patient responded to treatment with cyclophosphamide-bortezomib-dexamethasone, the anti-CD38 antibody daratumumab, and autologous stem cell transplant, resulting in hematological and organ response. Conclusions: AL amyloidosis can present with end-organ damage confined to isolated organs, and it can present without the expected elevation in serum light chains. Such patients can benefit from appropriate treatment, including traditional chemotherapy, daratumumab, and stem cell transplant. As effective treatments for AL amyloidosis are now available, prompt diagnosis has the potential to limit end-organ damage and potentially improve patient outcomes.

Outcomes and life expectancy for patients with multiple myeloma (MM) have improved substantially over the last two decades with advancements in therapy, including autologous stem cell transplantati...

8042 Background: Ide-cel, a BCMA directed CAR T-cell therapy, was FDA approved 3/26/2021 for the treatment of RRMM after 4 prior lines of therapy. We evaluated the real-world outcomes of patients treated with standard of care ide-cel under the commercial FDA label. Methods: Ten US academic centers contributed data to this effort independent of the manufacturer. As of 1/10/2022, 138 patients were leukapheresed with overall manufacturing failure in 6 (4%). 108 patients were infused ≥ 30 days prior to data-cut off and constitute the study population for this retrospective analysis. Results: Table describes the study population compared to the pivotal KarMMa-1 trial (Munshi et al, NEJM 2021). Patients in our study were less likely to have ECOG PS of 0/1 (77%) and more likely to be penta-refractory (41%). 67% of patients would not have met eligibility criteria for KarMMa. Common reasons for ineligibility (> 1 reason in 22% patients) were co-morbidities (28%), cytopenias (22%), prior therapy with alloSCT/CAR-T/other BCMA therapy (19%), CNS myeloma/non-measurable disease/plasma cell leukemia (13%), and fitness (12%). 81% of patients received bridging therapy. Toxicity was comparable to that seen in KarMMa-1. Cytokine release syndrome (CRS) was seen in 82% (> grade 3: 4%) and immune effector cell-associated neurotoxicity syndrome (ICANS) in 15% (> grade 3: 5%) of patients, respectively. Tocilizumab and steroids were used in 72% and 25% of patients, respectively. Infections were seen in 34% of patients. Day 30 response was evaluable in 104 patients. Response rates were: ≥ partial response, 83%; ≥ very good partial response, 64%; and ≥ complete response (CR), 34%. 11% of patients have died by data cut-off, 7 due to disease progression and 5 due to other causes (1 grade 5 CRS, 1 hemophagocytic lymphohistiocytosis, 1 progressive neurological weakness, 2 COVID-19). Conclusions: This multicenter retrospective study delineates the real-world outcomes of ide-cel CAR T-cell therapy for RRMM. Despite more patients being penta-refractory and less fit compared to the pivotal KarMMa trial, safety and 30-day responses in the real-world setting (overall response rate: 83%, CR: 34%) are comparable to the clinical trial population. Follow-up is ongoing and updated data will be presented. [Table: see text]

Context The belamaf US EAP (NCT03763370) provided medicine access to patients unable to participate in a clinical trial prior to regulatory agency approval. Objective To obtain insight from the belamaf EAP on patient types potentially eligible for belamaf treatment in a real-world setting. Methods The EAP included patients with RRMM who received ≥3 prior lines of therapy and were refractory to proteasome inhibitors, immunomodulatory agents, and anti-CD38 monoclonal antibody. Patients received belamaf 2.5 mg/kg Q3W. Safety was closely monitored, and dose delays/reductions were permitted to manage adverse events. Treating physicians re-evaluated eligibility to continue belamaf at each treatment cycle; patients could withdraw at any time. The EAP closed following US FDA approval of belamaf. We report baseline characteristics from included patients. Results In this preliminary analysis (as of 3 Feb 2021), 263 patients were screened; 235 were treated with ≥1 dose of belamaf and were included in this analysis. The most common reasons for withdrawal were lack of continued clinical benefit (n=37) and death (n=21); 23 patients continued therapy beyond closure of the program. Of 235 treated patients, 137 (58.3%) were male. Median age was 66 years, with 106 patients (45.1%) aged 75 years. Two hundred eighteen patients had further medical history available; 61 (26.0%) had prior treatment-related toxicities, 10 (4.3%) had active renal disease, and 5 (2.1%) had undergone allogeneic stem cell transplant. Two hundred twenty-one patients had ocular baseline characteristics reported; these included prior glaucoma diagnosis (single-eye, n=16 [6.8%]), prior cataract diagnosis (single, n=124 [52.8%]), history of cataract surgery (single, n=66 [28.1%]), and prior dry eye diagnosis (n=46 [19.6%]). The most common prior anticancer therapies included bortezomib, lenalidomide, pomalidomide, and carfilzomib. Data cleaning is ongoing for this study. Conclusions This EAP provides insights from a real-world population of US belamaf-treated patients, which, in addition to data from the pivotal DREAMM-2 study, may help practitioners identify patients potentially eligible for belamaf treatment. Funding GlaxoSmithKline (213304). Drug linker technology licensed from Seagen Inc.; monoclonal antibody produced using POTELLIGENT Technology licensed from BioWa.

Most human cancers, including myeloma, are preceded by a precursor state. There is an unmet need for in vivo models to study the interaction of human preneoplastic cells in the bone marrow microenvironment with non-malignant cells. Here, we genetically humanized mice to permit the growth of primary human preneoplastic and malignant plasma cells together with non-malignant cells in vivo. Growth was largely restricted to the bone marrow, mirroring the pattern in patients with myeloma. Xenografts captured the genomic complexity of parental tumors and revealed additional somatic changes. Moreover, xenografts from patients with preneoplastic gammopathy showed progressive growth, suggesting that the clinical stability of these lesions may in part be due to growth controls extrinsic to tumor cells. These data demonstrate a new approach to investigate the entire spectrum of human plasma cell neoplasia and illustrate the utility of humanized models for understanding the functional diversity of human tumors.

Introduction Relapse and graft failure continue to be 2 major problems after allogeneic HSCT. DLI and/or SCB are capable of inducing complete remission in relapsed disease. However, DLI and SCB are associated with significant risks such as graft versus host disease (GVHD) or aplasia. There is a paucity of information regarding DLI/SCB safety, efficacy and toxicity. A better understanding of the risks and benefits of DLI/SCB after HSCT is an important unmet need. Objectives Our objectives are to provide descriptive characteristics of patients receiving DLI or SCB and information regarding the provided cell therapy (CD3+ and/or CD34+ cell dose). We also aim to evaluate relapses, donor chimerism, graft failure, GVHD, DFS and OS after cellular therapy. Methods Retrospective chart review was completed on all patients who received either DLI or SCB at University of Maryland from 2005-2018. Data were analyzed using SPSS v.25.0, SAS v9.4, and R-software v3.5.1. Continuous variables were summarized as median (range), and categorical variables were presented using frequencies (%). Qualitative and quantitative differences between groups were analyzed by the chi-square and the Fisher's exact test for categorical and the Mann Whitney test for continuous variables. The Kaplan-Meier method was used to estimate the OS and GVHD-free survival with the corresponding 95% confidence interval (CI); the log-rank test was used to compare the survival probabilities for different patients' groups. Results A total of 65 patients underwent either DLI or SCB from 2005-2018. Of these, 38 received DLI, and 27 received SCB. Relapsed disease was the most common indication in 78.9% and 61.5% of DLI and SCB, respectively. The average CD3+/kg dose was 5.6 × 10^6 for DLI and 9 × 10^7 for SCB. Average CD34+/kg dose was 3.8 × 10^6 for SCB patients. One-year OS rate was 54.2% for DLI and 37.5% for SCB. Two-year OS rate of OS was 50.3% for DLI and 26.8% for SCB. Remission rates from relapsed disease were 43.4% for DLI and 31.3% for SCB. One-year GVHD-free survival following cell therapy was 51.2% for DLI and 34.4% for SCB. This dropped to 35.3% for DLI and 24.6% for SCB at two years. The differences seen in OS and GVHD between the 2 cohorts were not statistically significant. Conclusion Our overall survival data is favorable compared to recently published data. However, this comes at the expense of GVHD with long-term rates of GVHD-free survival measuring 25-35%. The use of unmanipulated cryopreserved SCB for relapse disease is underreported in the literature. We observed comparable long-term survival and GVHD in both cohorts. Cellular therapy with DLI or SCB remains a viable treatment modality with reasonable long-term outcomes for relapsed/refractory hematologic malignancies after allogeneic HSCT.

Introduction Treatment options for relapsed/refractory (R/R) diffuse large B-cell lymphoma (DLBCL) post-chimeric antigen receptor therapy (CAR-T) are limited. Here, we report the successful treatment of R/R DLBCL with programmed cell death 1 (PD1) inhibition post-allogeneic CAR-T. Case Report A previously healthy 26-year-old Caucasian man developed B-symptoms and cervical lymphadenopathy. Biopsy revealed DLBCL, activated B-cell subtype, double expressor and Ki-67 >80%. PET/CT scan revealed disease above and below the diaphragm. He achieved a partial response (PR) after R-CHOP, progressive disease (PD) after R-ICE, stable disease (SD) after R-ESHAP, and PD one month after autologous CD19-targeted CAR-T with CTL019 (CD3ζ/4-1BB). He then received R-lenalidomide (len) with radiation (24 Gy) to his mediastinal mass achieving a PR, followed by a myeloablative (Cy/TBI-12 Gy) allogeneic stem cell transplant (aSCT) from his 10/10 HLAmatched brother. He achieved 100% donor chimerism 30 days post-aSCT (D+30). Despite persistent full donor chimerism, D+60 PET/CT showed PD with confirmed relapse upon biopsy. Immunosuppression was discontinued, and ibrutinib with len was started, followed by donor lymphocyte infusion (DLI) which led to a mixed response. He then continued on ibrutinib with weekly temsirolimus and received a second DLI achieving a PR, with PD shortly thereafter. He next proceeded to allogeneic CAR-T with axicabtagene-ciloleucel (CD3ζ/CD28), complicated by grade 1 cytokine release syndrome without neurotoxicity. Three weeks post-CAR-T, he developed diplopia due to a cranial nerve palsy. Brain MRI showed new pontine T2 changes. Cerebrospinal fluid (CSF) was negative for lymphoma and infection, but notable for T-cell predominance. One month postCAR-T, PET/CT showed a complete metabolic response (CMR). Repeat brain MRI was unchanged. Two months later, he developed dizziness and intractable nausea, and repeat brain MRI showed a new lesion in the inferior cerebellar vermis, with resolution of previous pontine change. Evaluation of the CSF and peripheral blood revealed no CAR T-cell persistence, and PET/CT confirmed disease relapse in the cerebellum and mediastinum. Patient then received focal radiation (24 Gy) to his cerebellar lesion along with pembrolizumab 200 mg IV every 3 weeks, after which his neurologic symptoms resolved. MRI one day after radiation showed near-complete resolution of enhancing vermis lesion. After 3 cycles of pembrolizumab, PET/CT showed a CMR, with no active disease on brain MRI. Three months into PD1-inhibition therapy, his disease remains in CMR, without GVHD nor treatment-related toxicities. Conclusion This case illustrates the efficacy of allogeneic CAR-T after failure of autologous CAR-T and aSCT. Furthermore, PD1 inhibition can be used safely after allogeneic CAR-T, underscoring the need for prospective clinical studies.

7560 Background: Axicabtagene Ciloleucel (Axi-cel), an anti-CD19 CART cell therapy, achieved 58% complete response (CR) rate, in patients with relapsed refractory (r/r) LBCL on the ZUMA-1 study (Neelapu, NEJM 2017). Early response assessment (PET-CT) at day 30 is a common clinical practice. Patients with partial response (PR) at day 30 pose a therapeutic dilemma. ZUMA-1 analysis showed 1/3rd PR patients would convert to a CR. No biomarkers exist to predict eventual response. We report comprehensive PET-CT biomarker analysis on patients with PR at day 30 treated with Axi-cel for r/r LBCL. Methods: Ten patients with PR based on PET-CT imaging at day 30 were retrospectively assessed. Day 30 PET-CT was compared to baseline and a day 90 PET-CT. Global burden of disease of each patient at every time-point were quantified using Total Tumor Glycolysis (TTG) methodology as the imaging biomarker. Using adaptive-thresholding method, each lesion on FDG PET image was segmented and the following parameters were quantified: metabolic-volume (MV), SUVmax, SUVpeak, Partial-Volume-Corrected SUVmean and five other imaging biomarkers. To evaluate the effect of baseline and early imaging biomarkers to predict the subsequent burden of disease multiple regression analysis was performed (STATA 15). Results: Day 90 PET-CT assessment revealed, 4 patients had progressive disease (PD), 4 had CR, and 2 had PR. TTG of patients with PD at day 90 was 900 vs. 29 in patients with non-PD (CR, PR). The Global-SUVmean of the patients with PD at day 90 was 725 vs. 86 in patient with non-PD. Regression analysis showed early-TTG as a significant predictor of subsequent-TTG (beta-coefficient = 1.26 (0.39-2.13); P-value = 0.02; adjusted-R-squared = 0.97), while the baseline-TTG didn’t have any effect on subsequent-TTG (P-value = 0.3). Additionally, the regression analysis didn’t show any significant predictive value in SUVmean and SUVmax of baseline and day 30 scans to predict subsequent burden of disease (TTG or Global-SUVmean) with P-values > 0.8. Conclusions: Early post-axi-cel TTG, rather than baseline, can predict subsequent response to treatment. None of the SUV indices, commonly used in daily practice, were predictive of eventual response.

Major clinical response to nivolumab in relapsed/refractory Hodgkin lymphoma after allogeneic stem cell transplantation

Multiple myeloma is the second most common hematologic malignancy. The treatment of this disease has changed considerably over the last two decades with the introduction to the clinical practice of novel agents such as proteasome inhibitors and immunomodulatory drugs. Basic research efforts towards better understanding of normal and missing immune surveillence in myeloma have led to development of new strategies and therapies that require the engagement of the immune system. Many of these treatments are under clinical development and have already started providing encouraging results. We, for the second time in the last two decades, are about to witness another shift of the paradigm in the management of this ailment. This review will summarize the major approaches in myeloma immunotherapies.

Background: The role of metabolism in outcomes of cancer patients is under investigation. A higher body mass index (BMI) substantially increases the risk of cancer and impacts the treatment. High BMI is also associated with increased risk of MM (Euro J Cancer 2011). However no data is available in the effect of BMI on myeloma survival after autologous stem cell transplantation (ASCT) Methods: We retrospectively reviewed patient charts who had ASCT between Jan 2010 - November 2011. Patients were selected if they have adequate data, two lines of induction treatment prior to transplantation. Most of the patients received maintenance treatment. IRB granted exemption for anonymous data collection. We collected demographic data, cytogenetic risk, response with induction and after transplant, progression free and overall survival. BMI was estimated at the time of ASCT. Results: A total of 223 post ASCT myeloma patients met inclusion criteria. Median age of the cohort was 58 years, 48.8% were African-American, 51% Caucasian, 1% Asian, and 0.5% Hispanic. Median BMI was 29.7 and 30 in female and males respectively. Median BMI was 29.4 in Caucasians and 29.6 in African-American cohorts. 24% of patients had high risk cytogenetics. 72% of patients experienced very good partial response (VGPR) or better post-transplant. On multivariate analysis, PFS and OS showed no association at any of the four BMI levels (p=0.573), age, gender, race, or depth of response. High risk cytogenetics was associated with PFS (p= 0.022). There was no association with high risk cytogenetic features at any BMI level, age, gender, race (p=0.245). For patients with BMI > 40, PFS differed significantly when compared to patients with normal BMI: 37 months versus 50, p=0.52. Unadjusted hazard ratio (HR) 2.10 (95% CI: 0.62-7.18) with respect to patients with normal BMI. Subgroup multivariate analysis with patients with morbid obesity did not show any association with depth of response (partial response or VGPR or better) or high-risk cytogenetic features. Conclusion: BMI as a surrogate marker does not significantly impact long term survival outcomes in patients with multiple myeloma in the post-transplant setting and thus should not factor in transplant decision-making. Patients with morbid obesity appear to have a trend towards shortened progression free survival and may warrant further investigation. Figure. Figure. Disclosures Badros: Karyopharm: Research Funding; Celgene: Consultancy, Research Funding; GSK: Research Funding.

BACKGROUND Galactomannan is an Aspergillus-specific polysaccharide released during aspergillosis and is detected by the quantitative serum galactomannan index (GMI) test. Preclinical and preliminary clinical reports have suggested a good correlation between GMI and aspergillosis outcome. METHODS We reviewed the literature to assess the strength of correlation between GMI and aspergillosis outcome using the kappa correlation coefficient. We included 27 studies that enrolled patients with hematological cancer and proven or probable aspergillosis and that used sequential GMI testing. We examined the 3 following outcomes: survival (survival vs. death), global outcome (survival vs. death [including autopsy findings]), and autopsy outcome (autopsy findings only). RESULTS Overall, 257 patients fulfilled criteria for proven or probable aspergillosis and were eligible for outcome evaluation. Correlation between GMI (within

In preclinical studies, pomalidomide mediated both direct antitumor effects and immune activation by binding cereblon. However, the impact of drug-induced immune activation and cereblon/ikaros in antitumor effects of pomalidomide in vivo is unknown. Here we evaluated the clinical and pharmacodynamic effects of continuous or intermittent dosing strategies of pomalidomide/dexamethasone in lenalidomide-refractory myeloma in a randomized trial. Intermittent dosing led to greater tumor reduction at the cost of more frequent adverse events. Both cohorts experienced similar event-free and overall survival. Both regimens led to a distinct pattern but similar degree of mid-cycle immune activation, manifested as increased expression of cytokines and lytic genes in T and natural killer (NK) cells. Pomalidomide induced poly-functional T-cell activation, with increased proportion of coinhibitory receptor BTLA(+) T cells and Tim-3(+) NK cells. Baseline levels of ikaros and aiolos protein in tumor cells did not correlate with response or survival. Pomalidomide led to rapid decline in Ikaros in T and NK cells in vivo, and therapy-induced activation of CD8(+) T cells correlated with clinical response. These data demonstrate that pomalidomide leads to strong and rapid immunomodulatory effects involving both innate and adaptive immunity, even in heavily pretreated multiple myeloma, which correlates with clinical antitumor effects. This trial was registered at www.clinicaltrials.gov as #NCT01319422.

BACKGROUND: Immunotherapy in MM is emerging as an effective modality in therapy of MM with the approval of several monoclonal antibodies and encouraging results for vaccines and T cell therapy. Programmed death 1 (PD-1) receptor and its ligand (PD-L1) is one mechanism of immune evasion by MM to suppress T cell function. In this trial, we hypothesized that pembrolizumab, a PD-1-blocking antibody, would enhance immune modulatory properties of pomalidomide in RRMM pts. METHODS: In this single center, phase II study, 48 patients with RRMM received 28-day cycles of pembrolizumab (at a dose of 200 mg IV) every 2 weeks (in a run in phase, first 6 patients received 200 mg IV every 4 weeks) plus pomalidomide (4 mg daily x 21 days) and dexamethasone 40 mg weekly. Study objectives were measurements of safety & efficacy and correlation of the CD3/PD-1 on T cells and PD-L1 on plasma cells with response. RESULTS: The median age was 64 years (range: 35-82); 38% were black and 65% were men, Patients had a median of 3 lines of prior therapy (range: 2-6); All patients had received both IMids and Proteosome inhibitors; 70% had prior auto-SCT. 80% were double refractory to both IMids (lenalidomide) and Proteosome inhibitors [bortezomib (n=18) or carfilzomib (n=20)] and an additional 20% were refractory to lenalidomide. The median time from MM diagnosis to study entry was 4 years (range: 1-25). Most common cytogenetic abnormalities were 1q+ (60%), hyperdiploidy (15%) and high-risk FISH [del 17p, t(4:14) and/or t(14:16)] in 38%. Six patients had soft tissue extramedullary plasmacytomas. There were no infusion-related reactions. Hematologic toxicities (≥ grade 3) were anemia (21%), neutropenia (40%), lymphopenia (15%) and thrombocytopenia (8%). Non-hematologic events Grade ≥3 were fatigue (15%), hyperglycemia (25%), upper respiratory tract infections (21%), rash (10%); and most frequent grade ≥2 were dyspnea (54%), dizziness (44%), increased creatinine 38%, edema (35%), rash (30%), constipation 30%) and arrhythmias (19%). Events of clinical significance, autoimmune mediated, included interstitial pneumonitis (13%), hypothyroidism (10%), transaminitis(6%), adrenal insufficiency (4%) and vitiligo (2%). Nine pts had pomalidomide dose reductions due to rash, neutropenia, palpitations and fatigue; one pt reduced pembrolizumab for pneumonitis. At a median follow up of 10 months (range: 2-18): 25 pts continue on the study and 23 pts discontinued therapy due to disease progression (n= 15), side effects (n=7) and protocol violation (n=1). Five pts died while on study due to progressive disease (n=3), sepsis (n=1, sAE), and one from a cardiac event. Three additional pts died off therapy. On intent to treat analysis; the overall response rate (ORR) with ≥ Partial response were observed in of 27 of 48 pts (56%) including: sCR (n=4, 8%), nCR (n=3, 6%), VGPR (n=6, 13%), PR (n=14, 29%). Additionally, 7 pts (15%) had minimal response, 9 (19%) had stable disease, 2 progressed and 3 were not evaluable for response. Of 38 double refractory pts ORR was 55% including, sCR (n=2, 5%), nCR (n=2, 5%), VGPR (n=4, 10%) and PR (n=13, 27%). Of 18 high-risk pts ORR was 33% including VGPR (n=2, 11%) and PR (n=4, 22%). Median duration of response for responding pts was 8.8 months and for pts ≥ VGPR, DOR was 10.7 months. Correlation of PD-1 and PD-L1 expression and response will be presented. CONCLUSION: Pembrolizumab, pomalidomide and dexamethasone shows promising durable therapeutic activity and an acceptable safety profile in RRMM pts. ClinicalTrials.gov number, NCT02289222 Disclosures No relevant conflicts of interest to declare.

BACKGROUND: SOX2 is an embryonic developmental transcription factor, which is important in the development of the respiratory tract. SOX2 overexpression is associated with aggressive disease in several tumor types. However, SOX2 overexpression and gene amplification associates with favorable outcome in lung squamous cell carcinomas (SCC) and dissimilar results have been reported in lung adenocarcinomas (ADC). The aim of the present study was to evaluate SOX2 expression in NSCLC and determine the relationship with clinico-pathological variables and outcome. METHODS: SOX2 protein levels were measured in tissue microarrays (TMAs) containing FFPE samples from two independent lung cancer cohorts (n = 340 & 307) using automated quantitative immunofluorescence (QIF). Assay validation was performed using FFPE preparations of cell lines with known SOX2 expression. Associations of SOX2 levels with main clinico-pathological characteristics and with overall survival were studied using uni-and multivariate analysis. RESULTS: SOX2 levels were higher in patients with SCC than in ADC in both cohorts (p value

Background: P is used in combination with G-CSF to improve the mobilization of peripheral blood hematopoietic stem cells in poor mobilizers. Limited data are available in regard to effects of P on post-transplant outcomes in comparison with non-P chemomobilized patients. Methods: In this retrospective study, we compare the engraftment and the outcomes of 34 patients mobilized with P + G-CSF or just-in-time rescue P in combination with chemotherapy and G-CSF to 143 patients (control group) mobilized with G-CSF with or without chemotherapy in lymphoma and myeloma patients who underwent ASCT between February 2012 and April 2014 at the University of Maryland Greenebaum Cancer Center. Post-transplantation outcomes including infections, hematologic recovery, relapse, progression and survival were recorded. Results: The median number of collected of CD34+ cells/Kg was 5.9 x 10(6) in the P group and 12.3 x 10(6) in the control group (p=0.0002). Median time to neutrophil engraftment (>0.5 × 10(9) /L) was comparable between the 2 groups: 12 days for the P group and 11 for the control group (p=0.28). There was a trend toward a shorter time to platelet engraftment (>20 × 10(9) /L) in the control (12 days) compared to the P group (14 days) (p=0.056). Progression-free survival at 1 year after (ASCT) was 88.2% in the P group and 81.8% in the control group. There was no difference in the overall survival of both groups (p=0.62) Conclusions: Short and long-term engraftment and outcomes after ASCT seem to be comparable in lymphoma and myeloma patients receiving plerixafor compared to chemomobilized patients without plerixafor. This observation support the use of plerixafor + G-CSF or just-in-time rescue P in patients who mobilize poorly without P. Figure 1. Figure 1. Disclosures No relevant conflicts of interest to declare.

BACKGROUND: Several recent studies have linked the interactions of programmed death 1 (PD-1) receptor and its ligand (PD-L1) to immunologic control of MM. Expression of PD-L1 on myeloma cells and the abundance of PD-1 on various bone marrow microenvironment components contribute to tumor-mediated immune suppression. We hypothesized that pembrolizumab, a PD-1-blocking antibody, will activate myeloma specific cytotoxic T cells that can be enhanced by pomalidomide in RRMM patients to induce clinical responses. METHODS: In this ongoing single arm, phase II study, 24 patients with RRMM received 28-day cycles of pembrolizumab (at a dose of 200 mg IV) every 2 weeks (in a run off phase, first 6 patients received 200 mg IV every 4 weeks) plus pomalidomide (4 mg daily x 21 days) and dexamethasone 40 mg weekly. Study objectives were measurements of safety and efficacy and assessment of the PD-1 and PD-L1 protein expression in bone marrow samples. RESULTS: The median age was 65 years (range: 41-75); 35% were African American and 71% were men. Of the 24 patients, 75% had prior autologous transplantation and 96% were refractory to last therapy. All patients had received both IMids and Proteosome inhibitors; 75% were double refractory to both IMids and Proteosome inhibitors and additional 21% were refractory to lenalidomide alone. Patients had received a median of 3 lines of prior therapy (range: 1-6). The median time from MM diagnosis to study entry was 4 years (range: 1.2-15). All patients had abnormal cytogenetics: most common were 1q+ (72%) and high-risk FISH (40%) [del 17p, t(4:14) and/or t(14:16)]. There were no infusion-related reactions. Hematologic toxicities (≥ grade 3) were neutropenia (29%), lymphopenia (17%) and thrombocytopenia (8%). Non-hematologic adverse events included (Grade ≤2; ≥3): fatigue (n=12; 1), constipation (n=10; 0), dyspnea (n=9; 2), itching (n=6; 0), muscle spasms (n=6; 0), infection (n=4; 3), hyperglycemia (n=5; 0), edema (n= 4; 0), fever (n=3; 0), palpitation (n=2; 1), rash (n=3; 1) and hypotension (n=3; 0). Events of clinical significance, autoimmune mediated, included hypothyroidism (n=2), transaminitis (n=2), and pneumonitis (n=1). Four patients had pomalidomide dose reductions due to rash, neutropenia, palpitations and fatigue. Two patients died; one after cycle 1 (progressive disease) and one during cycle 2 (sepsis). Objective responses (modified IMWG criteria) were observed in 11 of 22 evaluable patients (50%) including: near complete response (n=3), very good partial response (n=2), partial response (n=6); additionally, 3 patients had minimal response, 6 had stable disease and 2 progressed. At a median follow up of 16 weeks; 17 of 22 patients continued on the study. Reasons for discontinuation included disease progression (n= 4) and protocol violation (n=1). Analysis of pretreatment and post-treatment tumor specimens for PD-1 and PD-L1 is in progress. CONCLUSIONS: Pembrolizumab in combination with pomalidomide and dexamethasone has promising therapeutic activity and an acceptable safety profile in heavily treated RRMM patients. ClinicalTrials.gov number, NCT02289222. Disclosures Off Label Use: Pembrolizumab.

Background: The incidence of MM is 2 to 3 fold higher in blacks than in whites; they present at a younger age and have better overall survival. The biological bases for these disparities remain unclear. Outcome of MM is linked to cytogenetic and molecular changes, both primary (hyperdiploidy and heavy chain (IgH) translocations) and secondary (rearrangements of MYC, activating mutations of NRAS, KRAS or BRAF, and deletions of 17p). Methods: Cytogenomic alterations in consecutive MM patients were assessed using integration of metaphase chromosome analysis by GTG-banding and interphase fluorescence in situ hybridization (iFISH) in CD138-positive cells isolated from fresh BM samples using a protocol of magnetic-activated cell sorting. Changes evaluated included monosomy 13/del(13q), monosomy 17/del(17p), gain of 1q21, and rearrangements of the IGH gene including t(4;14), t(11;14) and t(14;16). Results: Samples from 218 consecutive MM patients were analyzed (Table 1). 108 were from black and 110 were from white patients. Median age for blacks was 59 years (range: 36 - 82) and for whites, 63 years (range: 39 - 83) (p=0.008). Fewer black men than whites were observed (46.3% versus 64.6%, p=0.007). Overall, blacks had fewer abnormal karyotypes compared to whites (18.1% versus 31.8%; p=0.02). Black patients had a lower frequency of non-hyperdiploid karyotypes (8.5% versus 20.6%; p=0.01) and had a trend toward lower frequencies of rearrangements of IGH (30.8% versus 43.5%; p=0.055) than white patients. Most notably, they had significantly lower frequencies of monosomy 17/del(17p) (5.6% versus 18.5%; p=0.003) and monosomy 13/del(13q) (28.9% versus 46.3%; p=0.008). After stratification by age (Figure 1), younger patients showed significantly higher frequencies of the monosomy 17/del(17p) abnormality (p=0.001) and the t(4;14) (p=0.04) than older patients, with the difference more significant in white patients. The associations among molecular cytogenetic abnormalities (Figure 2) showed a different association pattern for black and white patients. White patients with t(11;14) were more likely to have monosomy 13/del(13q) (p=0.003) and gain of 1q21 (p=0.02), while this association was not observed in black patients. Conclusion: Black MM patients had significantly different cytogenetic profiles detected by iFISH on CD-138 selected malignant cells, compared to whites. Black MM patients had a more favorable profile, including lower frequencies of non-hyperdiploid karyotype and of IGH rearrangements. This study supports a biological basis for previously described outcome disparities between black and white patients with MM. Further studies will focus on identifying specific molecular targets and their impact on therapy and on overall outcome. Table 1. Demographics and cytogenetic abnormalities of the MM patients Demographics Black White P-value# Total, n 108 110 Gender, n (%) =0.007* Male 50 (46.30%) 71 (64.55%) Female 58 (53.70%) 39 (35.45%) Age (median) 59 63 =0.008* Chromosome (karyotype) =0.022* Normal 86 (81.90%) 73 (68.22%) Abnormal 19 (18.10%) 34 (31.78%) Hyperdiploidy 8 (7.6%) 8 (7.4%) Non-hyperdiploidy 9 (8.5%) 22 (20.6%) =0.013* 11;14 translocation 2 (1.9%) 4 (3.7%) FISH abnormality -13/del(13q) 31 (28.97%) 50 (46.30%) =0.008* Gain of 1q21 35 (32.71%) 47 (43.52%) =0.103 -17/del(17p) 6 (5.61%) 20 (18.52%) =0.003* IGH rearrangements 33 (30.84%) 47 (43.52%) =0.055^ t(4;14) 7 (6.54%) 13 (12.38%) =0.146 t(11;14) 15 (20.55%) 15 (19.48%) =0.870 t(14;16) 2 (3.85%) 6 (10.71%) =0.175 others 16 (14.95%) 15 (13.89%) =0.824 *means statistical significant (p-value < 0.05), where ^ means marginal significant (0.05 < p-value < 0.10). #p-values come from the Cochran-Mantel-Haenszel tests for categorical variables, and t tests for continuous variables. Associations among eight molecular cytogenetic abnormalities. Each solid black line indicates one abnormality is statistically significantly associated with another abnormality. Figure 1. Distributions of cytogenetic abnormalities by age and race Figure 1. Distributions of cytogenetic abnormalities by age and race Figure 2. Relationship of various cytogenetic abnormalities in the MM patients Figure 2. Relationship of various cytogenetic abnormalities in the MM patients Disclosures No relevant conflicts of interest to declare.

Multiple myeloma (MM) is characterized by progressive growth of transformed plasma cells (PC) in the bone marrow. In nearly all cases, MM is preceded by clinically asymptomatic precursor states termed as monoclonal gammopathy of undetermined significance (MGUS) and asymptomatic MM (AMM). Almost all prior attempts to study the growth of transformed PCs in vivo have been restricted to patients with clinical MM, and there is an unmet need for in vivo models to understand the biology of precursor states. Major obstacles to xenotransplantation of human cells in immune-deficient mice include murine innate immune rejection, as well as presence of species-restricted non-cross reactive growth factors/cytokines. In order to help overcome these obstacles, we utilized humanized mice in which human versions of 5 genes important for innate immune cell development and hematopoiesis were knocked into their respective murine loci. These mice termed MIS(KI)TRG for human M-CSF, IL-3, GM-CSF, Thrombopoietin and SIRPα knock-in on a Rag2-/-IL-2Rγ-/- background, exhibited superior multi-lineage engraftment of human hematopoietic stem cells including innate immune cells. Interleukin-6 (IL-6) is well established as a critical growth factor for human MM cells and lacks species cross-reactivity. Therefore, we knocked-in human IL-6 to MIS(KI)TRG mice to generate MIS(KI)TRG6 mice that were utilized for these studies. MIS(KI)TRG6 mice were transplanted intra-femoral with bone marrow mononuclear cells isolated from patients with plasma cell disorders (n=27). Growth of tumor cells was monitored by flow cytometry and by ELISA detection of tumor-derived clonal human Ig. We observed successful engraftment of tumor cells following transplantation of purified CD138+ cells as well as CD3-depleted CD138- mononuclear cells or simply CD3-depleted bulk bone marrow mononuclear cells in >80% of experiments. Importantly, the engrafted myeloma cells were primarily restricted to the transplanted bone confirming the niche requirement of these cells. Growth of tumor cells in the contralateral bone was typically observed when samples from patients with more aggressive disease were transplanted. Growth of tumor cells in the spleen was only observed in the setting of patients with circulating phase tumors, such as those with plasma cell leukemia. In contrast to tumor cells, non-malignant cells such as human T, NK or myeloid cells readily migrated to the periphery and were detected in the spleen by flow cytometry. Together these data indicate that the capacity to grow independent of the marrow niche is a late event in the pathogenesis of MM. Importantly, in addition to clinical MM, this model also allowed for the first time, efficient growth of asymptomatic precursor states (MGUS/AMM) in 5 of 5 patients engrafted. Interestingly, tumor cells from MGUS/AMM mediate progressive growth in vivo, indicating that the clonal stability observed in these patients is likely mediated by features extrinsic to the plasma cell clone. Detailed analysis of phenotypic features of engrafted plasma cells by single cell mass cytometry revealed phenotypic similarities between freshly isolated tumor cells and those growing in mice. In summary, our studies demonstrate that humanized MIS(KI)TRG6 mice are an excellent host for in vivo growth of the entire spectrum of human plasma cell tumors, including for the first time, pre-neoplastic states. Our studies provide evidence that clonal stability in MGUS/AMM is likely in part due to growth controls extrinsic to the tumor cells. The capacity to metastasize from bone to bone and eventually to extra-medullary sites is acquired later during evolution of tumors. The ability to faithfully reproduce homing and growth patterns of primary tumor cells will allow detailed evaluation of plasma cell tumors in their natural microenvironment. Disclosures No relevant conflicts of interest to declare.

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA In preclinical and mostly in vitro studies, pomalidomide (Pom) has been shown to mediate direct anti-proliferative effects on tumor cells, as well as immune-modulatory effects on T cells, NK cells and monocytes. Cereblon (CRBN), a direct cellular target for Pom has been involved in the anti-proliferative effects in tumor cells via selective degradation of Ikaros (IKZF1) and Aiolos (IKZF3). Depletion of IKZF1/IKZF3 has also been implicated in Len-mediated amplification of anti-CD3-induced IL2 production in human T cells in culture. However the impact of pomalidomide on tumor proliferation and immune activation in vivo is unknown. Here we have evaluated the clinical and pharmacodynamic effects of continuous or intermittent dosing strategies of pomalidomide/dexamethasone in lenalidomide-refractory myeloma in a randomized trial. 39 eligible patients with relapsed myeloma were randomized to therapy with Pom/Dexamethazone (following Pom alone for cycle 1), utilizing either continuous Pom dosing (2 mg-28/28 days, cohort 1, n = 19) or an intermittent dosing schedule (4 mg-21/28 days, cohort 2, n = 20). Dexamethazone was administered at 40 mg weekly at cycle 2 and beyond. Intermittent dosing strategy, despite having frequent adverse events, led to greater tumor reduction. Both cohorts experienced similar event-free and overall survival. Both regimens led to a distinct pattern but similar degree of mid-cycle immune activation as manifest by increased expression of cytokines and lytic genes in T and NK cells. Pomalidomide induced polyfunctional T cell activation, with increased proportion of co-inhibitory receptor BTLA+ T cells and Tim-3+ NK cells. Baseline levels of cereblon, ikaros and aiolos protein in tumor cells using validated IHC assay on marrow biopsies, did not correlate with response or survival. Pomalidomide treatment led to a rapid decline in Ikaros in T and NK cells in vivo as measured by intranuclear flow staining, and therapy-induced activation of CD8+ T cells correlated with clinical response. These data demonstrate that pomalidomide leads to strong and rapid immunomodulatory effects involving both innate and adaptive immunity, even in heavily pre-treated MM, which correlate with clinical anti-tumor effects. Clinicaltrials.gov-[NCT01319422][1]. Citation Format: Rituparna Das, Kartik Sehgal, Lin Zhang, Rakesh Verma, Yanhong Deng, Mehmet Kocoglu, Juan Vasquez, Srini Koduru, Yan Ren, Maria Wang, Suzana Couto, Mike Breider, Donna Hansel, Stuart Seropian, Dennis Cooper, Anjan Thakurta, Xiaopan Yao, Kavita M. Dhodapkar, Madhav V. Dhodapkar. Comparison of pomalidomide dosing strategies in lenalidomide-refractory myeloma: Impact on clinical outcome, immune activation and cereblon targets. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1354. doi:10.1158/1538-7445.AM2015-1354 [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT01319422&atom=%2Fcanres%2F75%2F15_Supplement%2F1354.atom

Current therapy of myeloma including combination with IMID(R) immunomodulatory agent such as pomalidomide (POM) leads to high rates of clinical responses in patients with advanced multiple myeloma without translating to cures. Therefore, there is a need to better characterize the nature of residual disease after anti-myeloma therapy. POM has shown clinically promising efficacy in relapsed myeloma but nearly all patients eventually progress. In order to better understand the nature of residual disease, we compared baseline CD138+ myeloma tumor cells from 3 patients with those remaining after completing 2 cycles of therapy with POM (2-4 mg/day) and dexamethasone (40 mg/week). CD138+ plasma cells were isolated from the bone marrow before and after POM therapy and analyzed with gene expression profiling (GEP), and whole exome sequencing (WES). Principal component analysis (PCA) on the GEP data (pre vs. post POM treatment) revealed that in contrast to baseline samples, the ones with residual disease were clustered together, and this was further confirmed with unsupervised hierarchical clustering. Analysis of differentially expressed genes revealed nearly 600 differentially modulated genes, including some involved in the immune system regulation, inflammatory pathways and stem cells. Gene set enrichment analysis (GSEA) identified enrichment of distinct gene-sets/pathways including- transcriptional targets regulated by core embryonal stem (ES) cell factors SOX2 and NANOG. Analysis of genes in the core ES signature (Nat Genet. 2008; 40: 499) revealed that nearly 80% of these ES genes were enriched in the residual disease after treatment with POM. Whole exome sequencing has emerged as a powerful tool to dissect the genomic complexity in cancer. Genomic DNA from bone marrow derived CD138+ tumor cells before and after POM therapy was captured on the NimbleGen 2.1M human exome array and subjected to 74 base paired-end reads on the Illumina HiSeq instrument as described previously (Proc Natl Acad Sci U S A. 2009; 106:19096). Sequence reads were mapped to the reference genome (hg19) using the ELAND program. Reads outside the targeted sequences were discarded and statistics on coverage were collected from the remaining reads using perl scripts. ELAND was also used for indel detection. For matched normal/germline and CD138+ tumor pairs, somatic mutations were called by comparing reference and non-reference reads from the matched pair by Fisher’s exact test with tumor-specific thresholds determined from approximation of the null distribution. WES analysis of baseline (pre therapy) samples identified a median of 36 protein altering coding mutations per sample. Importantly, the degree of mutational load was very comparable between baseline and residual disease (post therapy), and nearly 80% of the mutations detected in the residual disease were also observed at baseline. These data suggest that residual disease following therapy in myeloma is characterized by high level of genomic complexity similar to that observed at baseline. However in spite of the genetic heterogeneity and complexity at baseline, the residual CD138+ plasma cells converge to a distinct signature enriched in a transcriptional program associated with embryonal stem cell genes known to be targets of SOX2 and NANOG. Drug resistant/residual CD138+ tumor cells in myeloma therefore show transcriptional profiles previously implicated in cancer stem cells. Targeting stemness-associated genes may be essential to effectively treat residual disease in myeloma. Disclosures: No relevant conflicts of interest to declare.

Pomalidomide (POM) is a novel IMiD(r) immunomodulatory agent with clinical activity in relapsed / resistant myeloma (RRMM) refractory to both lenalidomide and bortezomib. In prior phase II studies, the clinical activity of POM has been demonstrated using both continuous and intermittent dosing schedules. However the optimal dosing regimen for POM remains to be clarified and prospective data comparing these dosing schedules is limited. Herein we report the results of a randomized phase II clinical trial comparing the two POM dosing schedules. The primary objective was to compare clinical response to therapy (greater than or equal to partial response (PR) according to International Myeloma Working Group (IMWG) criteria). Patients (n=39) with RRMM documented to be refractory to lenalidomide were randomized to therapy with POM 2 mg/day for 28/28 days (Arm A, n=19) or POM 4 mg/day for 21/28 days (Arm B, n=20) of a 28 day cycle. All patients (pts) received POM alone at 2 or 4 mg for cycle 1, followed by the addition of dexamethasone at 40 mg weekly in subsequent cycles in both arms. Aspirin was utilized for thromboprophylaxis in both arms. Toxicity consisted primarily of myelosuppression which was manageable and similar in both cohorts. The incidence of serious adverse events (SAEs) was 36% in arm A and 55% in arm B. Grade 3 or 4 neutropenia (common toxicity criteria v4.0) was the most common toxicity and was observed in 42% and 45% of patients in arm A and arm B respectively. There was no treatment-emergent grade 3 or 4 neuropathy observed in either arm. Only one patient (in arm B) experienced grade 3 / 4 thromboembolic complication. Overall, objective response to therapy (greater than or equal to PR by IMWG criteria) was observed in 21% (4/19 patients) in arm A and 45% (9/20 patients) in arm B (p=0.18). There were no complete remissions in either cohort. Patients in arm B did have greater maximal reduction in measurable disease compared to arm A (percent maximal reduction mean (+ SD) 54% (+ 34%) in arm B versus 28% (+ 35%) in arm A, p=0.02). However both cohorts had comparable event-free survival (EFS) and overall survival (OS). The mean EFS in arm A and arm B was 4.4 months (95% confidence intervals (CI) 2.21 months, 7.67 months) and 5.1 months (95% CI 3.4 months, 9.2 months) respectively (p=0.56). Similarly the median OS in the arm A (17.7 months, 95% CI 10.02, not reached) was similar to that in arm B (17.7 months, 95% CI 9.98, not reached)(p=0.73). These data demonstrate in the context of a prospective randomized controlled clinical trial that both continuous (28/28) and intermittent (21/28) dosing regimens of POM with dexamethasone have remarkable clinical activity in this heavily pretreated MM population. These data provide further support towards the choice of POM at 4 mg/day for 21/28 days for phase III testing. The finding that intermittent dosing at 4 mg/day led to greater maximal cytoreduction of measurable disease compared to continuous dosing at 2 mg/day, without any differences in survival suggests that understanding the biology of residual disease will be essential to further improving outcome in these patients. Disclosures: No relevant conflicts of interest to declare.

Pomalidomide (POM) is a novel IMiD® immunomodulatory agent with clinical activity in several settings including in relapsed / resistant myeloma (RRMM). Several preclinical studies have documented the immunologic effects of IMiD® immunomodulatory drugs. IMiD® now form the backbone of several emerging combination therapies in hematologic malignancies. In prior studies, the clinical activity of POM in relapsed myeloma has been demonstrated using both continuous and intermittent dosing regimens with and without steroids. However the impact of the specific POM dosing regimen and the effect of concurrent steroids (as commonly utilized in most combination regimens) on POM-induced immune activation in vivo is unknown. In order to evaluate these issues more directly, we analyzed samples from patients enrolled in a randomized phase II clinical trial comparing two POM dosing schedules. Comparison of drug-induced immune activation between the two dosing schedules was one of the pre-specified endpoints in this study. Patients (n=39) with RRMM documented to be refractory to lenalidomide were randomized to therapy with POM 2 mg/day for 28/28 days (Arm A, n=19) or POM 4 mg/day for 21/28 days (Arm B, n=20) of a 28 day cycle. All patients (pts) received POM alone for cycle 1, followed by the addition of dexamethasone (DEX) at 40 mg weekly in subsequent cycles in both arms. In recent studies, we have shown that immune effects of lenalidomide are manifest early, within a week of initiation of therapy (Richter et al, Blood 121:423, 2013). Therefore each patient was analyzed 1 week after initiation of POM alone at 2 or 4 mg (cycle 1) or POM + DEX (cycle 2). POM therapy led to an increase in T cells at day 7 after initiation of therapy (mean percent increase compared to baseline 47%, p Disclosures: No relevant conflicts of interest to declare.

Abstract 325 Multiple Myeloma (MM) is a human hematopoietic malignancy of the B cell lineage with 5 year survival of only 40%. Most MM patients succumb to progressive disease and therefore novel therapies are urgently needed. MM is characterized by growth of malignant plasma cells in the bone marrow microenvironment (ME) leading to bone erosion and fracture. Interactions between tumor and host ME play a critical role in the biology of MM and are a target of most new therapies against this tumor. The dependence of human MM on ME is further illustrated by the preferential requirement for growth of primary MM cells in implanted human fetal bone, but not the murine bone in immune-deficient mice in the scid-hu model. This model is however suboptimal for preclinical testing of novel therapies and there is a major unmet need for development of newer models to study MM and the interactions between human MM and its microenvironment. Some of the barriers to growth and xenotransplantation of human cells in immune-deficient Rag2−/−Il2rg−/− mice include macrophage-mediated innate immune rejection, as well as non-cross reactive growth factors. In order to overcome these limitations, Rag2−/−Il2rg−/− mice were genetically engineered to express human versions of the macrophage receptor signal regulatory protein-alpha (SIRPa), as well as several non-cross-reactive growth factors. The combination of these growth factors leads to synergistic enhancement of growth of transplanted human cells in these mice. In order to facilitate the potential ability of these mice to serve as hosts for human MM, these mice were further modified to express a human growth factor that is a critical MM-related cytokine and that is also non-cross reactive between humans and mice. INA-6 is a human IL6 dependent MM cell line that is unable to grow in standard immunodeficient mice such as NOD/scid/Il2rg−/−, but instead grows only in the implanted fetal bone in the scid-hu model. Injection of genetically humanized mice with INA6 cells led to facile growth of MM cells in the bone, leading to lytic bone disease. Next we tested whether primary tumor cells from MM patients could grow in these genetically engineered mice. Bone marrow mononuclear cells were separated into CD138+ and T cell depleted-CD138- fractions. Injection of either fraction led to growth of MM cells in these mice. These data therefore indicate that the prior inability to reliably grow primary MM cells in mice outside of the scid-hu model was primarily related to the non-cross-reactive cytokines and innate immune barriers mediated by the CD47-SIRPa axis. These data demonstrate that the genetic humanization of immune-deficient mice to modify the bone marrow niche to express non-cross reactive growth factors leads to facile growth of primary human MM cells in vivo. These mice can therefore serve as a valuable tool to test new patient-specific therapies depending on the genetic makeup of the tumor. Further advancement of this model to include growth of autologous immune cells would lead to humanized immune-competent models much needed for patient-specific preclinical testing of novel targets. Similar approaches can also be extended to develop in vivo models for other hematologic malignancies as well. Disclosures: Dhodapkar: Celgene: Research Funding; KHK: Research Funding.