The destabilization of endothelial nitric-oxide synthase (eNOS) mRNA in hypoxic endothelial cells may be important in the etiology of vascular diseases, such as pulmonary hypertension. Recently, an overlapping antisense transcript to eNOS/NOS3 was implicated in the post-transcriptional regulation of eNOS. We demonstrate here that expression of sONE, also known as eNOS antisense (NOS3AS) or autophagy 9-like 2 (APG9L2), is robustly induced by hypoxia or functional deficiency of von Hippel-Lindau protein. sONE is also up-regulated in the aortas of hypoxic rats. In hypoxic endothelial cells, sONE expression negatively correlates with eNOS expression. Blocking the hypoxic induction of sONE by RNA interference attenuates the fall in both eNOS RNA and protein. We provide evidence that the induction of sONE primarily involves transcript stabilization rather than increased transcriptional activity and is von Hippel-Lindau-but not hypoxia-inducible factor 2␣-dependent. We also demonstrate that sONE transcripts are enriched in the nucleus of normoxic cells and that hypoxia promotes an increase in the level of cytoplasmic and polyribosome-associated, sONE mRNA. The finding that eNOS expression can be regulated by an overlapping cis-antisense transcript in a stimulus-dependent fashion provides evidence that sense/antisense interactions may play a previously unappreciated role in vascular disease pathogenesis.

Neutropenia is a major dose-limiting toxicity associated with lenalidomide in relapsed/refractory multiple myeloma (MM). The optimal dosing schedule of granulocyte colony-stimulating factor (G-CSF) is unclear. We developed an intermittent G-CSF schedule (4-6 doses per cycle) initiated upon onset of grade 3-4 neutropenia. Of 216 patients with relapsed/refractory MM treated at our center with lenalidomide/dexamethasone on an Expanded Access Program, there was a high incidence of grade 3-4 neutropenia (61%) and grade 3-4 infections (37%). Despite intermittent G-CSF use in 117 patients, recurrent grade 3-4 neutropenia was common (59%), and dose reductions were required in 40% of G-CSF recipients, most due to thrombocytopenia. G-CSF recipients had a longer duration on therapy and achieved a higher rate and depth of response. Intermittent G-CSF may be an effective approach for lenalidomide dose-preservation, which may lead to improved outcomes, although it does not prevent infections or thrombocytopenia-related dose limitations.

5034 Introduction Lenalidomide is approved in relapsed/refractory (rel/ref) MM based on 2 large phase III trials (Dimopoulos NEJM 2007; Weber NEJM 2007). In these trials, grade 3–4 neutropenia was common (29-41%) and was a main cause for lenalidomide (len) dose reductions despite mandated use of daily GCSF as first-step neutropenia management. Optimal management for len-induced neutropenia is unclear. At our institution, 216 patients (pts) with rel/ref MM were treated on the MM016, an Expanded Access Program (EAP), using len and dexamethasone (dex) at the same dose/schedule as that of the randomized trials. Due to limited access, GCSF was not mandated for grade 3–4 neutropenia, though we developed an intermittent schedule of GCSF (300ug SC 2–3 doses/week for weeks 3 and 4 of each 28 day cycle), typically continued into subsequent cycles to prevent recurrence. We aimed to avoid len dose reduction to maximize efficacy. In this retrospective analysis, our neutropenia management approach is evaluated, focusing upon recurrent neutropenia, infections, len dose-intensity, response, survival outcomes. Methods From 2005–2008, 216 rel/ref MM pts were treated on the EAP at our center. Similar to the phase III studies, len was initiated at 25mg OD × 21days with dex 40mg days 1–4, 9–12, 17–20 every 28 day cycle. Recurrent neutropenia and infectious complications were reviewed. Comparison of baseline variables and neutropenia/survival was performed between pts receiving GCSF (group 1) and those not (group 2). OS and PFS were estimated by Kaplan-Meier curves and log rank test. Results Neutropenia and G-CSF use: Of 216 pts treated with len, 117 pts (54.2%) received GCSF for grade 3–4 neutropenia (group 1); 99 pts (45.8%) did not (group 2). For group 1, the first episode of grade 3–4 neutropenia occurred early (median cycle 2, range 1–20) with GCSF started at median cycle 3 (range 1–19). Although most pts continued GCSF prophylactically into subsequent cycles, almost half (58 pts; 49.6%) recurred with ≥1 episode of grade 3–4 neutropenia, 18 pts (15.4%) ≥3 episodes. Despite GCSF use, pts in group 1 had more grade 3–4 infections (47.0% vs. 25.5%, p=0.002) and hospitalization due to infection (40.2% vs. 25.3%, p=0.021). In addition, len dose reductions were frequent in group 1 (40.2% vs 16.2%; p<0.001). As a surrogate for dose-intensity, the proportion of cycles at full-dose without delay was lower in group 1 (0.67 vs. 0.96, p<0.001). However, group 1 pts received more lines of prior therapy than group 2 (median 3 vs. 2, p=0.021), had lower baseline platelets (<100/uL in 41.0% vs. 23.2%, p=0.006) and neutrophils (<2.0 bil/L in 41.0% vs. 20.2%, p<0.001). All other baseline characteristics were similar between groups. Responses and survival: Pts receiving GCSF remained on len for longer (median duration 10.3 vs 3.7 mos; p=0.01), with primary causes for len discontinuation in both groups due to disease progression (65.2%) and toxicity (15.2%). Increased responses (66.7% vs. 45.5%, p=0.002) and improved quality of response (CR/VGPR 25.6% vs. 14.1%, p=0.03) were seen in the GCSF group. G-CSF use was associated with significantly longer PFS (9.1 vs. 4.0 mos, p=0.048), though the OS between groups was not statistically different (20.9 vs. 13.7 mos; p=0.28). On multivariate analysis, G-CSF support was associated with decreased risk of death (HR 0.46, 95% CI 0.31–0.67, p<0.0001). Conclusions: 1. Not unexpectedly, pts requiring GCSF were predisposed to len-induced neutropenia due to impaired marrow reserve from heavy pretreatment. Contrary to our predictions, our intermittent dosing schedule of GCSF did not significantly reduce rates of subsequent neutropenia, severe infections, or lenalidomide dose reduction. More intensive GCSF schedules than that used at our institution may be required. 2. However, GCSF use is associated with longer duration on len therapy, likely leading to observed improvements in responses, quality of response, and PFS. This suggests that those pts with compromised marrow reserve benefit from dose reductions and striving for full dose-intensity is not necessary. 3. Alternatively, given that GCSF is an independent predictor for prolonged PFS, one may hypothesize that GCSF has effects unrelated to its putative role in reducing neutropenia and may perhaps be related to its anti-inflammatory and immunomodulatory effects. Further studies evaluating the mechanisms and interactions of GCSF with len may provide insights. Disclosures: Reece: Celgene: Honoraria, Research Funding. Trudel:Celgene: Honoraria. Kukreti:Celgene: Honoraria. Chen:Celgene Corporation: Consultancy, Honoraria, Research Funding.

1866 Poster Board I-891 Introduction: Lenalidomide is currently approved for use in relapsed/refractory MM based on two large phase III trials accruing >700 patients (pts)(Dimopoulos et al, 2007; Weber et al, 2007). Subsequently, an Extended Access Program (EAP) supplied lenalidomide to an additional 1438 pts, providing confirmatory safety data (Chen et al, 2009). In this EAP protocol, lenalidomide was initiated in combination with dexamethasone at the same dose/schedule as that of the randomized trials. For all pts on the EAP, the median duration on therapy was short at 15.4 weeks (range 0.1–49.1), as most pts stopped protocol due to commercial availability of lenalidomide in the US. At our Canadian site, due to delays in lenalidomide availability, we maintained pts on the EAP until progressive disease (PD) or excessive toxicity. Of 122 MM pts on the EAP at our institution, 44(36%) received prolonged lenalidomide (≥12 cycles). We hypothesized that prolonged lenalidomide would be associated with improved progression-free survival (PFS) and aimed to identify disease/treatment variables that affect duration on therapy. Methods: From Sept 2005-Dec 2008, 122 relapsed/refractory MM pts treated on the EAP protocol at Princess Margaret Hospital were reviewed; 44(36%) of whom received ≥12 cycles of lenalidomide (Group 1), 78(64%) of who received <12 cycles (Group 2). Patient eligibility was identical to the pivotal phase III studies. Lenalidomide was initiated at 25mg PO daily for 21days with dexamethasone 40mg PO days 1–4, 9–12, 17–20 every 28day cycle. Comparison of variables (demographics, baseline disease characteristics, treatment details, responses, survival) between the 2 groups was performed. Results: Survival: As expected, both PFS and overall survival (OS) were prolonged for Group 1 versus Group 2: median PFS 21.8 vs 2.9 mos (p<0.0001); median OS > 42.5 vs 8.0 mos (p<0.0001). Causes of death were similar between groups: disease progression (PD)(87%), toxicity(11.5%)(p=0.17). Demographics and disease characteristics: Median age (122 pts) was 62 yrs (range 54–67); 58% male; MM subtypes: IgG 58%, IgA 20%, light chain only 19%. Most pts had received prior transplant (81%) and thalidomide (70%), without difference between the 2 groups. Comparison of baseline labs between Groups 1 and 2 identified significant differences in hemoglobin (median 110 vs 104g/L, p=0.002), platelet count (median 196 vs 126/uL, p=0.0005), LDH (median 165 vs 234 U/L, p<0.0001), respectively. Treatment and toxicity: The median number of lenalidomide cycles received were 18(12–40) for Group 1; 4(1–10) for Group 2. Although the number of pts requiring dose reductions was similar between groups (32% Group 1, 25% Group 2, p=0.5), Group 1 pts did not require dose reductions until significantly later (median cycle 8.5 vs 2.5, p<0.0001). Cytopenias were the major cause of dose reductions in all pts (67.6%), most due to thrombocytopenia. The higher baseline platelet counts in Group 1 may reflect greater marrow reserve, delaying the onset of drug-related thrombocytopenia. Thrombocytopenia did not, however, lead to differences in increased drug discontinuation between groups: PD (70% vs 74%), toxicity (14% vs17%)(p=0.4). Responses: More pts who were able to stay on lenalidomide longer (Group 1) vs those who discontinued early (Group 2) achieved a response to therapy (95% vs 55%, p<0.0001). In addition, more pts in Group 1 were able to stay on therapy longer to achieve a VGPR/CR (43% vs 9.5%, p<0.0001). Time to best response was accordingly prolonged in Group 1 vs Group 2 (5.7 cycles vs 1.8 cycles, p<0.0001). Conclusions: 1) Relapsed/refractory MM pts receiving lenalidomide therapy for longer than 12 cycles have improved PFS and OS over those with shorter exposures. 2) Longer duration on therapy may be necessary to achieve optimal rates of both overall response and quality of response. 3) Lower baseline platelet counts and dose-reductions for thrombocytopenia during therapy were more common in pts who discontinued therapy early and may contribute to earlier disease progression. 4) Approaches to allow prolongation of lenalidomide exposure in MM by minimizing early dose reductions for thrombocytopenia should be further evaluated. Such approaches may include lowered-dose lenalidomide combinations taking care to use platelet-sparing agents or supportive care with thrombopoeitin agonists. Disclosures: Reece: Celgene: Honoraria, Research Funding. Trudel:Celgene: Honoraria, Research Funding. Kukreti:Celgene: Honoraria. Chen:Celgene: Honoraria, Research Funding.