Roy, Vivek

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: BT062 (Biotest AG Dreieich, Germany) is an antibody-drug conjugate (ADC), comprising the anti-CD138 chimerized MAb (nBT062) and the maytansinoid DM4 as a cytotoxic agent. It is designed to bind to CD138 on cancer cells, and then release DM4 after internalization to cause cell death. CD138 (Syndecan-1) is highly overexpressed on various solid tumors and in hematological malignancies, and represents one of the most specific target antigens for identification of multiple myeloma (MM) cells. BT062 was investigated as a single agent and found to have an acceptable tolerability profile and evidence of activity in patients with heavily pretreated relapsed and/or refractory MM (1). Preclinical studies showed enhanced anti-MM activity when BT062 was combined with lenalidomide and dexamethasone (Len/Dex). Based on these data, a Phase I/IIa study in MM was initiated to evaluate the safety and efficacy of BT062 in combination with Len/Dex. Objectives: To determine the dose-limiting toxicities (DLTs), the maximum tolerated dose (MTD), the recommended phase II dose (RPTD), pharmacokinetics (PK), and anti-MM activity of increasing doses of BT062 (days 1, 8, and 15, every 4 weeks) used in combination with Len (25 mg, daily on days 1-21) and low dose Dex (40 mg on days 1, 8, 15, and 22) in patients with relapsed and/or refractory MM. Methods: This is a prospective, open label, multicenter Phase I/IIa study. The Phase I part includes dose escalation, and the Phase IIa the expansion of the RPTD cohort. Patients aged ≥18 years with relapsed and/or refractory MM who have failed at least one prior therapy were eligible to participate. Prior treatment with Len and/or Dex was allowed. Patients with clinical response (or no evidence of progressive disease) and without unacceptable toxicities were eligible for additional treatment cycles. Patients were enrolled in cohorts of at least 3 at each dose level; DLT in the first cycle triggered cohort expansion. Toxicities were assessed by CTCAE v4 and clinical response was assessed according to International Myeloma Working Group criteria. Results: The maximum administered dose (MAD) was 120 mg/m². Two of six patients treated at this dose had a DLT: mucosal inflammation (CTC grade 3) and anemia (CTC grade 3). The MTD was defined as 100 mg/m² and selected as RPTD. Additional patients are being treated at this RPTD to further evaluate safety and efficacy. Enrollment into the study is ongoing. As of July 2014, a total of 45 patients had received BT062 at dose levels of 80 mg/m² (N=3), 100 mg/m² (N=36) or 120 mg/m² (N=6). Fifteen patients discontinued study treatment: 5 for disease progression, 7 for adverse events, 1 died (not treatment related) and 2 for withdrawal of consent. The other 30 patients remain on treatment. The median treatment duration was 123 days (range 1–597). The median number of prior therapies was 3 (range 1–11). 68% of patients had prior exposure to both Len and bortezomib, 73% of patients had prior Len exposure, and 30% were Len-refractory. According to preliminary data from this ongoing study, about 89% of reported Adverse Events (AEs) were CTC grade 1 or 2. The most common reported AEs were diarrhea, fatigue, nausea, and hypokalemia. Amongst the 36 patients across all dose levels currently evaluable for efficacy, the overall response rate (ORR) is 78%; including 1 stringent complete response, 2 complete responses, 10 very good partial responses, and 15 partial responses. Two patients achieved a minor response and 6 patients disease stabilization, resulting in a clinical benefit in 100% of the evaluable patients. The ORR was 83% among the 30 evaluable patients receiving the RPTD. Interestingly, the ORR was 70% among the 23 patients with prior exposure to Len and bortezomib, and among 10 patients refractory to prior treatment with Len. Conclusion: Preliminary data from this ongoing study indicate that BT062 is well tolerated in combination with Len/Dex at dose levels that induce responses in patients with relapsed and/or refractory multiple myeloma, including patients with prior exposure to both Len and bortezomib and patients refractory to prior treatment with Len. Updated results on safety and efficacy will be presented. References Heffner et al, BT062, an Antibody-Drug Conjugate Directed Against CD138, Given Weekly for 3 Weeks in Each 4 Week Cycle: Safety and Further Evidence of Clinical Activity. Blood. 2012; 120: Abstract 4042. Disclosures Kelly: Celgene: Speakers Bureau. Heffner:Amgen: Honoraria, Research Funding; Biotest: Research Funding; Dana Farber CI: Research Funding; Genentech: Research Funding; Gilead: Research Funding; Idera: Research Funding; Janssen: Research Funding; Pfizer: Research Funding; Pharmacyclics: Honoraria, Research Funding; Onyx: Research Funding; Spectrum: Research Funding; Talon Therapeutics: Research Funding. Somlo:Millennium: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees. Siegel:Celgene: Honoraria, Speakers Bureau; Onyx: Honoraria, Speakers Bureau; Millennium: Honoraria, Speakers Bureau. Munshi:Celgene: Consultancy; Onyx: Consultancy; Janssen: Consultancy; Sanofi-Aventis: Consultancy; Ocopep: Consultancy, Equity Ownership, Patents & Royalties. Jagannath:Celgene: Consultancy; Millennium: Consultancy; Sanofi: Consultancy. Lonial:Millennium: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Onyx: Consultancy, Research Funding. Ailawadhi:Millennium: Consultancy, Honoraria. Barmaki-Rad:Biotest AG: Employment. Chavan:Biotest Pharmaceuticals: Employment. Patel:Biotest Pharmaceuticals: Employment. Wartenberg-Demand:Biotest AG: Employment. Haeder:Biotest AG: Employment. Anderson:Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Millennium: Consultancy, Membership on an entity's Board of Directors or advisory committees; Onyx: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sanofi Aventis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Oncopep: Equity Ownership; Acetylon: Equity Ownership.

Abstract Background: The proteasome is an established and druggable target for the treatment of plasma cell-related malignancies including Waldenstrom macroglobulinemia (WM). WM cells as a consequence of high immunoglobulin production and increased B-cell receptor (BCR) mediated proliferation upregulate proteasome activity. Additionally, microenvironmental influence mediated through BCR signaling directly influences Bcl-2 and its BH3 family members, supporting tumor cell survival. Indeed, WM patients derive significant clinical benefit from proteasome-inhibitor (PI) based therapy with agents such as bortezomib and carfilzomib. However, resistance to PI develops over time and for these patients the optimal choice and sequence of therapy has yet to be determined. Using our WM models of PI-resistance we interrogated molecular events within the BCR and Bcl-2 pathways to determine therapeutic potential of targeting these crucial pathway in PI-resistance. Materials & Methods: WM cell lines (BCWM.1 and MWCL-1) and carfilzomib-resistant (CR) subclones (BCWM.1/CR and MWCL-1/CR) were used in experiments. Gene-expression and long-noncoding (LNC) RNA analysis was performed (Arraystar) and validated by real-time PCR. Bortezomib, carfilzomib, ABT199 and ibrutinib were purchased from Sellekchem. Results: To determine the functional impact of BCR and Bcl-2 signaling in PI-resistance, as well as therapeutic sensitivity of PI-resistant cells to their inhibitors (ibrutinib, ABT-199, respectively), we established and characterized WM cell lines resistant to carfilzomib. BCWM.1/CR cells showed approximately 20-fold resistance to carfilzomib (IC50 = 92.75nM) and MWCL-1/CR cells approximately 10-fold resistance (Fig. 1A). Both CR clones also displayed some cross-resistance to bortezomib. Gene expression and LNC-RNA profiling demonstrated several changes between carfilzomib-resistant vs. sensitive WM cells. Analysis of proteasome-related mRNA revealed downregulation of PSMB5, PSMB1, PSMB2 and PSMB8. Similarly, profiling of BCR-associated genes demonstrated decreased expression of several components, including BTK and SPI1. This observation functionally manifested as reduced sensitivity to the BTK-inhibitor ibrutinib, wherein CR cells displayed 1.5 - 2 fold growth resistance to ibrutinib on 72hr MTS assay. Next we examined the expression of Bcl-2 family members in CR cells. Intriguingly, we observed that Bcl-2 and Mcl-1 were significantly downregulated but XIAP (inhibitor of apoptosis) was significantly increased in CR cells vs. wildtype WM cells- both at transcriptional and translational levels. This suggested that upon acquisition of CR, a transcriptional shift towards XIAP occurs to accommodate sustained therapeutic stress from carfilzomib and maintain steady antiapoptotic composure. To test if the PI-resistant cells have moved away from their survival dependence on Bcl-2, we treated CR cells to increasing concentrations of the Bcl-2-specific inhibitor, ABT199, and as anticipated, CR cells displayed reduced apoptosis in presence of ABT199 compared to wildtype WM cells (32% annexin-V staining vs. 50%, respectively) (Fig. 1B). Conclusions: Our study sheds insight into the differential drivers of PI-resistance particularly towards carfilzomib, in WM cells. We demonstrate that acquisition of CR is associated with downregulation of Bcl-2 and Mcl-1, which is countered by upregulation of XIAP- an event that renders CR cells resistant to ABT199 (as it targets only Bcl-2). Likewise, downregulation of BCR-related components in CR cells was associated with reduced sensitivity towards ibrutinib. These observations suggest that acquisition of resistance to PI such as carfilzomib can impact future treatment with agents such as ibrutinib or ABT199. Our preclinical models provide rationale or early sequencing of ibrutinib or ABT199 in therapeutic planning of WM patients prior to induction of PI resistance. Figure 1. Figure 1. Disclosures No relevant conflicts of interest to declare.

Abstract Abstract 201 Background: Pomalidomide at doses of 2 or 4 mg/d has demonstrated excellent activity in patients with relapsed multiple myeloma (MM). Between November 2007 and March 2012, we opened 6 sequential phase 2 trials and treated 345 patients with relapsed MM with pomalidomide at differing doses with weekly dexamethasone (Pom/dex). Results of 164 of these patients have been previously published. Here we describe long term follow up of these patients as well as results of an additional 181 patients with relapsed MM treated with the Pom/dex regimen. Methods: The six cohorts consisted of: Cohort 1 (N=60): relapsed MM with 1–3 prior regimens, 2 mg dose; Cohort 2 (N=34): lenalidomide (LEN) refractory, 2 mg dose; Cohort 3 (N=35): BZ)/LEN refractory, 2 mg dose; Cohort 4 (N=35): BZ/LEN refractory, 4 mg dose; Cohort 5 (N=60) LEN refractory, 1–3 prior regimens, 4 mg dose; and Cohort 6 (N=120) LEN refractory, 4 mg dose. Pomalidomide was given orally 2 mg daily or 4mg daily on days 1–28(cohorts 1–5) or 1–21 (cohort 6) of a 28-day cycle with oral dexamethasone given 40 mg daily on days 1, 8, 15 and 22. Response was assessed by the International Myeloma Working Group Uniform Response criteria. All patients received aspirin 325 mg daily for deep venous thrombosis (VTE) prophylaxis or full dose anticoagulation. Results: A total of 345 patients were enrolled across all 6 cohorts. One patient was ineligible and excluded from analysis. The median age was 64 years (32–88). The median time since diagnosis was 53 months. The median number of prior therapies was 3 (1–14). 147 (44%) had high-risk molecular markers by mSMART criteria. Prior therapies consisted of thalidomide 52%, lenalidomide 87%, bortezomib 75%, autologous stem cell transplant 70% and allogeneic transplant 3%. The median follow-up is 10.4 months (5.4–34 months). Sixty-seven percent are alive and 32% remain progression free. 46 patients are continuing to receive treatment. The most common toxicities (grade 3 or higher) were neutropenia (31%), anemia (16%), thrombocytopenia (12%), pneumonia (8%) and fatigue (8%). VTE was seen in 10 patients (3%). Outcomes are shown in Table 1. Across all 6 cohorts confirmed responses of partial response (PR) or better were seen in 34%. The response rate in all patients with mSMART high risk status was 30.6%. Responses and duration of response (DOR) in those with high risk molecular markers include: 17p– 19 of 56 (34%) DOR 8.2 months; t(4;14) 6 of 24 (25%) and DOR 4.8 months; t(14;16) 7 of 11(64%) and DOR 9.5 months; deletion 13 by cytogenetics 13 of 37 (35%) with DOR 8.2 months. In a multivariate analysis, only LDH > ULN, number of prior regimens, and prior BZ therapy were predictive of a shorter TTP and factors associated with a poor OS following initiation of pomalidomide therapy included B2M > 5.5, LDH > ULN,number of prior regimens, and prior BZ therapy. Conclusions: Pom/dex is active and well tolerated even in heavily pretreated patients and those with high risk molecular markers. Remissions are durable. Response rates and toxicity are similar between the 2 mg and 4 mg doses. Disclosures: Lacy: Celgene: Research Funding. Stewart:Celgene: Consultancy, Honoraria. Reeder:Celgene: Mayo Clinic receives funding from Celgene to support clinical trials Other, Research Funding.

Abstract Abstract 76 Background: We measured proliferation in MM cells transfected with 13,984 small interfering RNAs in the absence/presence of increasing concentrations of bortezomib (BTZ) and identified 37 non lethal genes as reproducible BTZ sensitizers. The strongest hit was CDK5 a gene expressed at high levels in MM and neural tissues with relatively low expression in other organs suggesting a large therapeutic window. The small molecule CDK5 inhibitor Dinaciclib is a novel, potent, small molecule inhibitor of cyclin dependent kinases (CDK). It selectively inhibits CDK1, CDK 2, CDK 5 and CDK9 with 50% inhibitory concentrations (IC50) in the low nanomolar concentration. Based on these data, we undertook the current trial to evaluate the maximally tolerated dose of Dinaciclib in this patient population as well as assess the efficacy of single agent Dinaciclib in relapsed MM. Patients and Methods: Patients with relapsed MM and measurable disease were enrolled on this phase 1/2 trial provided they had not more than 4 prior lines of therapy for MM, had adequate performance status and organ and hematological function. Patients receiving strong inhibitors/inducers of CYP3A4 were not allowed unless the drugs could be discontinued. The primary objectives were to (i) to determine the MTD of dinaciclib in subjects with relapsed MM (phase 1) and (ii) to evaluate the confirmed response rate with dinaciclib in patients with relapsed MM (phase 2). Dinaciclib was administered on day 1 of a 21-day cycle at doses of 30–50 mg/m2. Dose escalation was done using a 3+3 design and MTD was defined as one dose level below that resulted in >=2 DLTs among 6 patients. Results: Overall, twenty-nine patients were accrued to this study (19 phase I, 10 phase II) from July 2009 to December 2011. Two patients were replaced for study violations and are not included in analysis. The Phase II analysis included the 6 patients treated at the Phase I dose level 50mg/m2 as well as the first 9 patients accrued to the Phase II portion (15 evaluable patients). The median age of the 27 evaluable patients was 66 (range, 49–81); 52% were male. The median duration from diagnosis was 42 months (range, 7–207 months); median number of prior therapies was 4 (range, 1–5). Overall, 11 (41%) patients were considered high-risk by FISH and 56% were ISS stage III at study entry. Patients have received a median of 2 cycles (range: 1–12) and all patients have discontinued treatment for disease progression (18), alternative Treatment (2), adverse Event (4), or other reasons (3). One dose limiting toxicity was seen over all dose levels. One patient at 40 mg/m2 experienced grade 3 constipation possibly related to treatment. The dose level of 50 mg/m2 was determined to be the MTD for the Phase II portion. The overall confirmed response rate was 3 of 27 (11%); including two patients at 40 mg/m2 dose (1 VGPR, 1 PR) and one patient at 50 mg/m2 dose (1 VGPR) with a PR or better. In addition, two patients at 50 mg/mg2 dose have achieved an MR; translating to an overall response rate of 18.5% (5 of 27). Figure 1 shows a waterfall plot of the M protein responses among patients with a measurable M spike. Overall, 21 patients had disease progression and 14 patients have died. Median follow-up for patients still alive is 11.8 months (range: 6.5–19.3). Leukopenia and thrombocytopenia were the most common hematological AEs, and gastrointestinal symptoms, alopecia, and fatigue, were the most common non-hematological AEs seen in the study. Conclusions: The current study demonstrates potential single agent anti-myeloma activity of dinaciclib in a relapsed MM patient population with 2 patients achieving a deep response (VGPR) and many patients obtaining some degree of M protein stabilization or decrease. Ongoing studies are examining dinaciclib in combination with proteasome inhibitors, exploring both weekly and every three-week dosing schedules. Disclosures: Zonder: Millennium Pharmaceuticals, Inc: Consultancy, Research Funding; Celgene: Research Funding.

Abstract Background: Outcomes in multiple myeloma (MM) have significantly improved, leading to higher prevalence of this disease. Increasing efforts have been made by various agencies to educate patients (pts), manage quality of life (QoL) and survivorship. A global impact of these efforts including pt awareness, disease knowledge and participation in their care, as well as the physical and emotional impact of MM and its treatments (Rx) has not been assessed. We undertook an international, pt-reported survey to investigate these factors and understand any underlying disparities. Methods: A 61-question patient-reported questionnaire (MM-Q), addressing global aspects of MM pts care (components in Figure 1) was used. MM-Q was administered in collaboration with the International Myeloma Foundation (IMF). To limit responses by MM pt only, “SmartPatient” MM community members and IMF Support Group Leader list were invited to complete the survey. Some of the questions were mandatory, and those with missing responses were withdrawn from the final analysis of that pts MM-Q. Categorical and continuous variables were compared among groups using the Chi-square and Kruskal-Wallis tests, respectively using SAS software (v9.3) with a two-sided significance level of 0.05. Results: Survey responses are available from 894/1240 (72%) individuals thus far. Average survey completion time was 16 minutes. Data from 746 MM-Q was included in this analysis with 466 (62.5%) complete responses. Pts from United States (US) represented 85.7% of the responders (majority from New York State). Ethnicity (n=590) was reported as non-Latino by 97%, race (n=580) was reported as White by 95%, family history of MM was reported by 19 pts and 81 reported prior history of a primary malignancy (most common, 37% non-melanoma skin cancer). Living situation questions (n=538) revealed majority were in a household of 2 (62%), were unemployed/on public assistance (53.5%), travelled alone to medical appointments (74%), with travel times varying from <30 min (55%) to >1 hr (17%). Majority (83%) had no prior knowledge of MM, 63% were patient support group members, and 92% did MM-related research on internet. With respect to MM Rx (n=524), 70% had been on Rx within 3 months and 12% reported non-compliance. Prior Rx included thalidomide (30%), lenalidomide (66%), pomalidomide (11.5%), bortezomib (63.5%), carfilzomib (11%), steroids (100%), and clinical trial participation in 25% pts. Side effects from Rx/QoL in prior 3 months (n=403) are summarized in figure 2. Pts satisfaction with Rx/treating staff (n=378) revealed majority felt their Rx to be effective (92%), right for them (87%) and side effects were as expected (84%). In general, pts acknowledged positive attributes of the Rx staff (worked towards same goal; 91%, participated in decisions; 81%, honesty 89%, confidence; 92%), and their doctor's explanations regarding Rx (benefits; 84%, side effects; 74%, test results; 83%), with the exception of emotional effects of Rx (48%). 94% pts rated their care as good/excellent and 95% were willing to participate in a follow-up survey. Stratification of statistically significant responses by geographical categories, age and time since diagnosis are shown in table 1 and analysis by occupation and educational status is ongoing. Conclusions: We conducted a large patient-reported survey to understand the current state of awareness among MM pts and a global impact of the diagnosis and its Rx on them. We showed that majority of pts who accessed the survey responded (72%), which may be a product of literacy, education and access to technology. Majority of the pts were White and non-Latino, highlighting the possible role of access and awareness in ethnic minorities. We report the large prevalence of psychophysical burden of MM and its Rx in MM pts. In general, MM pts had a high rate of satisfaction related to the Rx and their healthcare providers, but the frequency of discussion regarding emotional effects of Rx between doctors and pts was conspicuously low (48%) and the more recently diagnosed pts were less likely to be satisfied with their treating staff. We also demonstrated significant behavioral pattern differences in geographical, age and time-since-diagnosis subgroups, some of which may be sociocultural, while others may be a result of more patient awareness and understanding of the disease. This knowledge will be very helpful in devising MM survivorship strategies. Disclosures No relevant conflicts of interest to declare.

Abstract Abstract 1184 Lenalidomide, a second generation immunomodulatory derivative of thalidomide, has demonstrated significant clinical benefit in myelodysplastic syndrome, multiple myeloma and B-cell malignancies. Its side effects include myelosuppression, particularly neutropenia, and impaired filgrastim induced stem cell mobilization in patients with myeloma. The precise mechanism of action of lenalidomide on hematopoietic and bone marrow microenvironment remains largely unknown. In this study, we investigated the effect of lenalidomide on survival, lineage commitment and differentiation of normal purified CD34+ hematopoietic stem cells. Mobilized peripheral blood progenitor cells (PBPCs) were obtained from a normal allogeneic stem cell donor with an informed consent, and were subjected to positive selection with the EasySep magnetic cell selection system to purify CD34+ cells (purity of 95%). Unsorted and CD34- accessory cells were used as controls. To assess the direct cytotoxic and proliferative effect of lenalidomide on purified CD34+ cells, lenalidomide (Celgene, NJ) was dissolved in DMSO and was diluted in culture medium to final concentration of 0.1, 1, 10, or 100 μM. Purified CD34+, CD34- and unsorted cells were plated in triplicates at a density of 2×104/mL in serum-free StemSpan® medium supplemented with growth factors and cytokines. 24 hours after plating the cells, lenalidomide or 0.1% DMSO as control was added. 72 hours following treatment, cells were counted with Beckman coulter counter and phenotypically analyzed using Accuri C6 flow-cytometer. The percentage of viable cells was determined using 7AAD staining. While no difference in viability was noted in the treated vs. untreated purified CD34+ cells, the viability of CD34- cells and unsorted cells was reduced to 30% and 40% respectively by lenalidomide. Contrary to our assumption, lenalidomide, in a dose dependant manner, induced proliferation of purified CD34+ cells. Maximal increase in proliferation was observed between 1mM and 10mM concentrations. The rate of growth plateaued beyond the 10mM concentration and 100mM concentration appeared to have no additional effect. At the peak of growth (10mM), the cell count nearly tripled. (Fig. 1) Lenalidomide appeared to be cytotoxic to CD34- and unsorted cells in a dose dependant manner. At 100mM concentration, the CD34- cell proliferation dropped by 4 fold and the unsorted cells by 7 fold. To examine the effect of lenalidomide on the clonogenic potential of purified CD34+ cells, 2,000 cells were seeded onto MethoCult® media (Stem cell technologies) supplemented with growth factors and cytokines. Cells were cultured in the presence of lenalidomide (0.1, 1, 10 and 100 μM) or 0.1 % DMSO as control. BFU-E, CFU-GM and CFU-mix were scored on day 14 with the use of an inverted microscope and standard morphological criteria. Significance of difference between groups was determined by student's t test for paired samples. Lenalidomide induced a significant increase in clonogenic activity of CD34+ cells (148 ± 27 colonies per 103 CD34+ cells, p = 0.01), most evident at the dose of 10 μM with enhanced formation of BFU-E (102 ± 23/ per 103 CD34+ cells, p = 0.01) but demonstrated no significant impact on CFU-GM (36 ± 14 per 103 CD34+ cells, p = 0.83) compared to control. (Fig. 2) This study demonstrates that lenalidomide has pronounced effects on both CD34+ and CD34- components of mobilized PBPCs. It enhances the proliferative and clonogenic potentials of CD34+ cells with lineage commitment towards erythroid differentiation. It also has cytotoxic activity towards CD34- cells. It is likely that neutropenia and impaired mobilization of stem cells in patients treated with lenalidomide is mediated via its impact on CD34- accessory cells in the bone marrow microenvironment. Further studies exploring the impact of lenalidomide on normal bone marrow stromal cells, T and NK cell mediated signaling are needed. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 194 Background: Immunomodulatory drugs (IMiDs) are key components of treatment for hematologic malignancies, especially multiple myeloma (MM). Recently, we demonstrated that CRBN expression is the major mediator of IMiD action operating at least in part via interferon regulatory factor 4 (IRF4), however the clinical significance of this finding remains unclear. Methods: To better understand clinical impact, we retrospectively reviewed 148 MM patients whose tumor cells were tested for CRBN expression by Gene Expression Profiling (GEP) prior to treatment with an IMiD containing therapy. Results: GEP studies show no significant differences in CRBN expression between MGUS, smoldering MM (SMM), untreated symptomatic MM and normal plasma cells. However, differences were observed between MM cell lines of varying drug sensitivity to IMiDs and between other B-cell Neoplasia (eg low grade lymphoma has higher levels). Within the genetic subtypes of MM, levels were significantly higher for hyperdiploid patients (median 1.26) as opposed to significantly lower levels for TC class D2 (median 0.76) and average for the 4p16 (median 0.97). We next screened the University of Arkansas Medical School (UAMS) GEP database of MM patients treated with combination therapies and did not find significant correlation between CRBN expression and survival in this multi-agent regimen. We then focused on patients that received only single agent IMiD therapy with low dose dexamethasone. Review of the twelve lowest expressing patients demonstrated a lack of response to IMiDs in any patient. Finally we analyzed 53 relapsed or relapsed/refractory patients treated homogeneously in a study with pomalidomide 2–4mg daily and weekly dexamethasone 40mg. CRBN levels were assessed prior to therapy initiation. Response rates varied significantly based on gene expression level. The percentage of patients that demonstrated at least a partial response was 0% for CRBN <0.81, 19% for CRBN expression of 0.81–0.90, and 33% for CBN expression >0.9. Significant differences in PFS (3.0 months vs. 8.9 months, p = 0.0006) and in OS (9.1 months vs. 27.2 months, p = 0.01) were observed when the lowest quartile of CRBN expression was compared to the top three quartiles. Values used for the cut offs are as follows: (25%: 0.889687; 50%: 1.026542, 75%: 1.211133). While this study demonstrates a positive correlation between CRBN expression and response to pomalidomide and dexamethasone, an important caveat with respect to PFS and OS is that CRBN mRNA level is primarily a reflection of the number of copies of CRBN. Since focal deletions are uncommon, this mostly reflects chromosome 3p copy number. Since trisomy 3 is common in hyperdiploid, good prognosis disease, CRBN not only is required for IMiD function but higher levels also serve as a surrogate for low risk disease. Optimal gene expression cut offs for survival were determined using the Contal and O'Quigley method. The optimal cut point for PFS was 1.18443 and for OS was 1.17816. Conclusion: In summary, this study demonstrates, for the first time, a clinical correlation between CRBN expression and response to IMiD and dexamethasone therapy. CRBN expression is also predictive of survival outcomes and when quantified prior to therapy could potentially be utilized as a predictive biomarker for response to an IMiD based treatment. Disclosures: Stewart: Celgene: Consultancy, Honoraria.

Cutaneous involvement by precursor T-cell lymphoblastic leukemia/lymphoma (T-ALL/LBL) is rare, and almost all cases are seen in association with bone marrow, blood, and/or lymph node involvement. Presentation with isolated skin involvement is very rare. Literature review revealed only one case report of primary cutaneous T-cell LBL. We discuss here another patient diagnosed with primary cutaneous T-cell LBL at our institute. This patient was initially misdiagnosed as having peripheral T-cell lymphoma NOS. Cytogenetic analysis showed the CDKN2A deletion (−9p21×2) in addition to three intact copies of ABL1 (+9q34). Although she failed multiple lines of intensive chemotherapy, her disease remained confined to the skin. We believe that this presentation of T-LBL is underreported, and many patients are likely misdiagnosed as having high-grade cutaneous T-cell lymphomas. With this case and literature review, we would like to highlight the importance of keeping lymphoblastic lymphoma on the differential diagnosis of cutaneous T-cell lymphoma-like lesions to avoid delay in diagnosis and inappropriate treatment of this aggressive disease.