Citations

Abstract MAJIC is a phase II trial of Ruxolitinib (RUX) vs Best Available Therapy (BAT) in essential thrombocythemia (ET) patients with resistance/intolerance to Hydroxycarbamide (HC) per European LeukemiaNet (ELN) criteria. Primary outcome was rate of complete hematological response (CHR) within 1 year (ELN criteria); secondary outcomes included partial HR, safety, thrombosis, hemorrhage, progression free survival (including transformation), molecular response (MR), symptom & quality of life (QOL) assessment. We present new data concerning molecular, symptom & clinical responses. Patients were stratified by JAK2V617F status, patient-reported symptoms & QOL determined using EQ5D, MDASI & MPN Symptom Assessment Form (MPN10), & compared using linear mixed models of post-baseline scores through month 12 adjusting for baseline; response was defined as ≥50% reduction in MPN10 total symptom score (TSS). JAK2/CALR/MPL allele burdens were assessed at baseline & 4 monthly. 110 patients were eligible for the modified ITT analysis, 58 (52%) & 52 (48%) in RUX & BAT arms respectively, comprising 44 males, 66 females, mean age 64.2ys, & resistant (24.5%), intolerant (51.8%) or both (22.7%) to HC. CHR was achieved in 27 (46.6%) of RUX patients vs 23 (44.2%) BAT patients (χ2 test p= 0.81). PHR occurred in 26 (44.8%) & 27 (51.9%) of RUX & BAT treated respectively. Grade 3 or 4 anemia occurred in 19% & 0% for RUX arm vs 0% (both grades) for BAT arm, grade 3 or 4 thrombocytopenia in 5.2% & 1.7% of RUX vs 0% (both grades) of BAT patients respectively. Grade 3 or 4 infections occurred in 10.3% of RUX patients vs 3.6% BAT arm. 9 RUX treated patients had 10 thrombotic events & 1 RUX patient a hemorrhage; vs 5 thrombotic & 5 hemorrhagic events in BAT patients (adjusted following central review). Transformations to post-ET MF occurred in 8 RUX vs 3 BAT treated patients, 1 RUX patient developed AML. 2 non-treatment related deaths occurred in each arm. Mean MPN-10 TSS & individual symptoms of early satiety & itching during the first 12 months were all significantly lower for RUX vs BAT (all p<0.05). Patients who achieved CHR had significantly better TSS, fatigue, inactivity, concentration problems, & MDASI symptom interference (all p<0.05) at baseline vs those without; however, scores during treatment did not appear to differ between CHR & non CHR groups after adjusting for these baseline differences. Allele burden during study & MRs (per ELN-IWG criteria Barosi Blood 2013) are shown in Table 1. Assays for JAK2 V617F were performed independently in 3 centres using qPCR (Guy's), TSCA NGS (Oxford) & amplicon-based NGS (Salisbury) & revealed Mean (range): JAK2 (Guy's): 33.2 (0.1-94.6), N=52; JAK2 (Oxford): 38.0 (0.5-92.2), N=52; JAK2 (Sal): 38.3 (0-90.0), N=50 (limited to JAK2 positive only). With Interclass Correlation Coefficient as follows ICC (Guy's v Oxford): 0.92 (95% CI 0.86-0.95) ICC (Guy's v Sal): 0.92 (95% CI 0.86-0.95) ICC (Oxford v Sal): 0.997 (95% CI 0.994-0.998). Notably MRs (n=5) only occurred with RUX treatment. There was no pattern of MR or progression with C/PHR or transformation, but 1 patient who transformed to PET MF had a complete MR. In a separate analysis baseline symptoms & QOL were not associated with JAK2, CALR, nor MPL status. Within RUX, baseline symptoms & QOL did not predict MR; however, fatigue, early satiety & abdominal discomfort (all p<0.05, Table 1) were significantly lower among those with MR vs not during treatment with a descriptively higher symptom response rate (2/4 [50%] vs 9/30 [30%]). Three non pre-specified multivariate analyses were performed to assess baseline factors influencing CHR (modelled for: treatment received, HC resistance or intolerance, white cell count, platelets, Hb & JAK2/CALR status); occurrence of ≥ grade 3 anemia or thrombocytopenia (modelled for: Hb (≥ 100g/dl) JAK2/CALR status); & transformation to PET-MF (modelled for: treatment, Hb ≤100g/dl). Only baseline Hb ≤100g/dl was significant for grade 3+ anemia (OR [95% CI]=0.17 [0.04, 0.72]), & PET-MF only occurred in patients with baseline WBC <10x109/L. This updated analysis shows that HC resistant/intolerant ET is clinically & molecularly diverse. We confirm that these patients are at high risk of thrombosis & transformation as suggested in prior retrospective studies. Molecular responses were limited to RUX & for the first time we demonstrate such responses may correlate with symptom improvement but not always with progression events. Disclosures Harrison: Shire: Honoraria, Speakers Bureau; Gilead: Honoraria, Speakers Bureau; Incyte Corporation: Honoraria, Speakers Bureau; Baxaltra: Consultancy, Honoraria, Speakers Bureau; Novartis: Consultancy, Honoraria, Other: travel, accommodations, expenses, Research Funding, Speakers Bureau. Mead:Novartis: Honoraria, Research Funding, Speakers Bureau. Aliman:Novartis: Other: Institutional funding and grant for international conference. . Chen:Novartis: Other: Advisory Board. Coppell:Novartis: Other: Travel, accommodation and conference attendance. Knapper:ONO pharmaceuticals: Research Funding; Novartis: Honoraria, Other: Travel and expenses for international conferences. Ali:Novartis: Honoraria, Other: Conference sponsorship, advisory board meetings. Hamblin:Novartis: Other: Advisory Board. Dueck:Bayer: Honoraria. Cross:Novartis: Consultancy, Honoraria, Research Funding, Speakers Bureau. Mesa:Celgene: Research Funding; Promedior: Research Funding; CTI: Research Funding; Gilead: Research Funding; Incyte: Research Funding; Galena: Consultancy; Ariad: Consultancy; Novartis: Consultancy. McMullin:Novartis: Honoraria, Speakers Bureau.

Abstract Background: PAC is an oral kinase inhibitor with specificity for JAK2, FLT3, IRAK1, and CSF1R that has demonstrated significant and sustained spleen volume reduction (SVR) and symptom control vs BAT (excluding JAK2 inhibitors) in MF pts regardless of platelet count (PERSIST-1). The PERSIST-2 study was a randomized, controlled, open-label, phase 3 trial of PAC 200 mg BID and PAC 400 mg QD vs BAT (including JAK1/JAK2 inhibitor ruxolitinib [RUX]) in pts with 10 or 20 MF whose platelet counts were ≤100,000/µL, a recognized adverse prognostic variable. Prior JAK2 inhibitor use was allowed. Methods: Pts were randomized 1:1:1 to PAC BID, PAC QD, or BAT. The co-primary efficacy endpoints were the percentages of pts achieving ≥35% SVR (MRI or CT) and ≥50% reduction in total symptom score (TSS; MPN-SAF TSS 2.0), both from baseline to Week 24. The primary objective was to compare the efficacy of pooled PAC (BID+QD) to BAT and the secondary objectives were to compare PAC BID and PAC QD individually to BAT. PK samples were collected and analyzed for PAC. Safety analyses were based on all pts exposed to study treatment of any duration (safety population); efficacy analyses were based on ITT pts with a randomization date allowing Week 24 endpoint evaluations prior to the full clinical hold* (ITT efficacy population). Results: 311 pts were randomized (107 PAC BID, 104 PAC QD, 100 BAT), 308 received study drug, and 221 were included in the ITT efficacy population (74 PAC BID, 75 PAC QD, 72 BAT). Demographics and baseline disease characteristics were generally balanced among the treatment arms (Table) and analysis populations. A total of 32 (44%) BAT pts in the ITT efficacy population received RUX as treatment at some point on study. Population PK analyses showed that the steady-state plasma levels achieved with BID were higher than with QD, however the Cmax levels were lower. A significantly higher percentage of pts in the pooled PAC arm achieved SVR ≥35% (18% [27/149]) vs the BAT arm (3% [2/72]; p=0.001; Figure 1A). 25% of PAC pts (37/149) had ≥50% reduction in TSS vs 14% of BAT pts (p=0.079; Figure 1B). In secondary analyses vs BAT, PAC BID demonstrated significant improvement over BAT for both efficacy endpoints with 22% achieving SVR ≥35% (BAT=3%; p=0.001) and 32% achieving ≥50% reduction in TSS (BAT=14%; p=0.011). The PAC QD arm had a significant SVR ≥35% (15% v 3%, respectively; p=0.017), but a similar proportion with ≥50% reduction in TSS (17% v 14%, respectively; p=0.652). More PAC pts reduced their red blood cell transfusion dependence at Week 24 (defined as a ≥50% reduction in average transfusions/month for 3 months relative to baseline) with 19% (7/37) in the PAC QD arm, 22% (8/36) in PAC BID, and 9% (3/35) in BAT. There was no significant difference observed in OS across the treatment arms (Figure 2). Hazard ratios for OS (95% confidence intervals) were 0.68 (0.30, 1.53) for PAC BID v BAT, 1.18 (0.57, 2.44) for PAC QD v BAT, and 0.61 (0.27, 1.35) for PAC BID v QD. PAC BID maintained this survival advantage vs BAT across nearly all demographic and MF-associated risk factors. During the course of the study, 10 (9%), 15 (14%), and 15 (14%) died on PAC BID, PAC QD, and BAT, respectively. The most common treatment-emergent adverse events (AEs) associated with PAC were gastrointestinal (diarrhea, nausea, vomiting) and hematologic (anemia and thrombocytopenia), and were generally less frequent for BID vs QD administration. Grade 3/4 cardiac AEs occurred in 7%, 13% and 9% of PAC BID, PAC QD, and BAT pts, respectively, and grade 3/4 bleeding AEs occurred in 14%, 7%, and 7%, respectively. Grade 3/4 bleeding AEs were associated with grade 3/4 thrombocytopenia, which was also more common in the PAC BID group. Nine pts had cardiac failure (2% PAC QD, 4% PAC BID, 3% BAT) and 1 (1%, PAC QD) had intracranial hemorrhage.* Conclusions: The PERSIST-2 study is the only randomized, controlled trial to date in pts with MF and thrombocytopenia (platelets ≤100,000/µL), allowed prior JAK2 inhibitor treatment exposure (including RUX), and allowed RUX as BAT comparator. Irrespective of prior JAK2 inhibitor treatment, both PAC arms were more effective at SVR than BAT; however, PAC BID appeared more active than QD dosing and achieved significance versus BAT for both SVR and TSS. The most frequent AEs with PAC were gastrointestinal and hematologic toxicities. *PAC on full clinical hold by the FDA on 2/8/2016 based on concerns around excess deaths and cardiac and hemorrhagic events in PERSIST-1. Disclosures Mascarenhas: Incyte: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; CTI BioPharma: Research Funding; Janssen: Research Funding; Roche: Research Funding; Promedior: Research Funding. Talpaz:CTI BioPharma: Research Funding; Pfizer: Research Funding; Incyte Corporation: Research Funding; Ariad: Other: Expense reimbursement, travel accomodation expenses, Research Funding; Gilead: Other: Travel, Accommodations, Expenses, Research Funding; BMS - Canada: Consultancy. Gerds:CTI BioPharma: Research Funding; Astra-Zeneca: Research Funding; Roche: Research Funding; Incyte: Research Funding. Stein:Incyte Corporation: Consultancy. Gupta:Incyte Corporation: Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding. Drummond:CTI BioPharma: Honoraria; Celgene: Consultancy, Honoraria, Research Funding, Speakers Bureau; BMS: Consultancy, Honoraria; Gilead: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Other: Travel, Accommodations, Expenses, Research Funding, Speakers Bureau; Roche: Speakers Bureau. Granston:CTI BioPharma Corp.: Employment. Daly:CTI BioPharma Corp.: Employment. Dean:CTI BioPharma Corp.: Employment, Equity Ownership. Al-Fayoumi:CTI BioPharma Corp.: Employment, Equity Ownership. Callahan:CTI BioPharma: Employment. Singer:CTI BioPharma Corp.: Employment, Equity Ownership, Other: Leadership . Gotlib:Novartis: Other: Travel, Accommodations, Expenses; Steering Committee Chairman, Research Funding; Promedior: Research Funding; CTI BioPharma: Research Funding; Gilead: Research Funding; Incyte: Consultancy, Honoraria, Other: Travel, Accommodations, Expenses, Research Funding. Jamieson:GSK: Research Funding; Johnson & Johnson: Research Funding; CTI BioPharma: Research Funding. Harrison:Novartis: Consultancy, Honoraria, Other: Travel, Accommodations, Expenses, Research Funding, Speakers Bureau; CTI BioPharma: Consultancy, Honoraria, Speakers Bureau; Baxter: Consultancy, Honoraria; Shire: Speakers Bureau; Gilead: Speakers Bureau; Incyte: Speakers Bureau. Mesa:Novartis: Consultancy, Honoraria; Incyte: Research Funding; Gilead: Research Funding; CTI BioPharma: Research Funding; Celgene: Research Funding; Genetech: Research Funding; Promedior: Research Funding. Verstovsek:CTI BioPharma Corp: Research Funding.

Abstract Background:The Janus kinase (JAK) 1/JAK2 inhibitor ruxolitinib has been evaluated for patients with MF in the phase 3 COMFORT studies. In both trials, ruxolitinib prolonged OS, reduced splenomegaly, and improved MF-related symptoms and quality of life compared with controls. Here, we report the results of an exploratory pooled analysis of OS in the COMFORT studies at 5 years of follow-up. Methods: The double-blind COMFORT-I trial and the open-label COMFORT-II trial were randomized phase 3 studies that evaluated the safety and efficacy of ruxolitinib in patients with intermediate-2 (int-2) or high-risk primary MF (PMF), post-polycythemia vera MF (PPV-MF), or post-essential thrombocythemia MF (PET-MF). The comparator was placebo in COMFORT-I and best available therapy (BAT) in COMFORT-II. The ruxolitinib starting dose was 15 or 20 mg twice daily based on baseline platelet counts (100-200 and >200 × 109/L, respectively); dose modifications were permitted for safety and efficacy. Patients were allowed to cross over to ruxolitinib from the control arm for progressive splenomegaly, defined as a ≥25% increase in spleen volume from baseline (COMFORT-I) or study nadir (COMFORT-II), or select protocol-defined progression events; crossover was mandatory following treatment unblinding in COMFORT-I. OS was a secondary endpoint in both studies and was evaluated in an intent-to-treat (ITT) analysis using a Cox proportional hazard model that estimated the treatment effect stratified by clinical trial and International Prognostic Scoring System (IPSS) risk. The crossover-corrected treatment effect was estimated using a rank-preserving structural failure time (RPSFT) method. Results: Overall, 528 patients were randomized: 301 to ruxolitinib (COMFORT-I, n=155; COMFORT-II, n=146) and 227 to placebo (n=154) or BAT (n=73). All ongoing patients in the control arms crossed over to ruxolitinib by the 3-year follow-up. Patient populations were similar between the two trials and their details were previously published. In the combined ruxolitinib group, 162 patients (53.8%) had high-risk MF and 139 (46.2%) had int-2 risk MF based on IPSS criteria. At the 5-year ITT analysis, 128 patients (42.5%) died in the ruxolitinib group compared with 117 (51.5%) in the control group. The risk of death was reduced by 30% with ruxolitinib compared with control (median OS: ruxolitinib, 63.5 mo; control, 45.9 mo; HR, 0.70; 95% CI, 0.54-0.91; P=0.0065; Figure A). After correcting for crossover using RPSFT, OS advantage was more pronounced for patients originally randomized to ruxolitinib (median OS: ruxolitinib, 63.5 mo; control, 27 mo; HR, 0.35; 95% CI, 0.23-0.59; Figure B). An analysis of OS censoring patients at the time of crossover also demonstrated that ruxolitinib prolonged survival compared with control (median OS: ruxolitinib, 63.5 mo; control, 28.3 mo; HR, 0.53; 95% CI, 0.36−0.78; P=0.0013; Figure C). Among all patients treated with ruxolitinib, those with lower-risk disease had longer survival compared with those with high-risk disease (median OS: int-2, not reached [estimated, 102 mo]; high-risk, 50 mo; HR, 2.86; 95% CI, 1.95-4.20; P<0.0001; Figure D). In a subgroup analysis, OS favored ruxolitinib compared with placebo for patients with int-2 or high-risk MF (data not shown). At 5 years, median OS appeared to favor patients with int-2 (n=58) or high-risk (n=89) PMF who were originally randomized to ruxolitinib compared with historical (Cervantes et al; J Clin Oncol 30:2981-2987) controls (int-2 PMF, not reached [estimated, 70 mo] vs 48 mo; high-risk PMF, 34 vs 27 mo); OS was longer among patients with int-2 vs high-risk PMF (P=0.0003). Subgroup analyses showed that ruxolitinib provided an OS advantage regardless of age (>65 or ≤65 y), sex, disease type (PMF, PPV-MF, PET-MF), risk status (int-2 or high), JAK2V617F mutation status, baseline spleen volume (>10 or ≤10 cm), anemia, white blood cell count (>25 or ≤25 × 109L), or platelet count (>200 or ≤200 × 109/L). Conclusion: Long-term treatment with ruxolitinib up to 5 years prolonged survival in patients with MF compared with BAT or placebo. Corrections for patients who crossed over to ruxolitinib suggested that the separation between ruxolitinib and control OS curves was primarily caused by a delay in ruxolitinib treatment. The results suggest that earlier treatment with ruxolitinib may provide a greater survival advantage for patients with MF. Disclosures Gupta: Incyte Corporation: Consultancy, Research Funding; Novartis: Consultancy, Honoraria, Research Funding. Mesa:Incyte: Research Funding; Ariad: Consultancy; Novartis: Consultancy; Celgene: Research Funding; CTI: Research Funding; Promedior: Research Funding; Galena: Consultancy; Gilead: Research Funding. Vannucchi:Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Kiladjian:AOP Orphan: Research Funding; Novartis: Research Funding. Cervantes:AOP Orphan: Membership on an entity's Board of Directors or advisory committees; Baxalta: 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, Speakers Bureau. Sun:Incyte Corporation: Employment, Equity Ownership. Gao:Incyte Corporation: Employment, Equity Ownership. Dong:Novartis Pharmaceutical Corporation: Employment, Equity Ownership. Naim:Incyte Corporation: Employment, Equity Ownership. Gopalakrishna:Novartis Pharma AG: Employment, Equity Ownership. Harrison:Incyte Corporation: Honoraria, Speakers Bureau; Baxaltra: Consultancy, Honoraria, Speakers Bureau; Gilead: Honoraria, Speakers Bureau; CTI Biopharma: Consultancy, Honoraria, Speakers Bureau; Shire: Honoraria, Speakers Bureau; Novartis: Consultancy, Honoraria, Other: travel, accommodations, expenses, Research Funding, Speakers Bureau.

Abstract Background: Patients (pts) with refractory aggressive non-Hodgkin lymphoma (NHL) have poor outcomes with currently available therapies, with a complete response (CR) rate of 8%, a partial response (PR) rate of 18%, and median overall survival (OS) of 6.6 months (mo) as demonstrated in the 635 pt SCHOLAR-1 meta-analysis (Crump, ASCO 2016; abstract 7516). ZUMA-1 is the first multicenter trial of anti-CD19 chimeric antigen receptor (CAR) T cells in refractory, aggressive NHL (NCT02348216). The phase 1 portion of ZUMA-1 showed ongoing CRs at 12+ mos in 43% of pts (Locke, ESMO 2016; abstract 1048O). The pivotal phase 2 portion of ZUMA-1 comprises 2 cohorts based on tumor type: DLBCL (cohort 1) and primary mediastinal B-cell lymphoma or transformed follicular lymphoma (cohort 2). Here, we present results of a prespecified interim analysis from cohort 1. Methods: Pts received a target dose of 2 × 106 anti-CD19 CAR T cells/kg after a low-dose conditioning regimen of cyclophosphamide (500 mg/m2) and fludarabine (30 mg/m2) daily for 3 days. The primary endpoint is objective response rate (ORR) per 2007 IWG criteria. Key secondary endpoints include duration of response, frequency of adverse events (AEs), and levels of CAR T cells and serum cytokines. Key inclusion criteria include age ≥18 years, ECOG performance status (PS) 0-1, and refractory disease defined as progressive disease or stable disease as best response to last line of therapy, or disease progression ≤12 mos after autologous stem cell transplant (ASCT). Pts must have received a prior anti-CD20 antibody and an anthracycline-containing regimen. A prespecified interim analysis was to be conducted to determine early efficacy with a nominal alpha level of 0.017 in 50 treated pts in cohort 1 with a minimum follow-up of 3 mos. Results: In total, 111 pts from 22 institutions were enrolled and leukapheresed, and 101 pts received KTE-C19. As of August 24, 2016, 51 pts in cohort 1 were eligible for analysis. Median age was 58 years (range, 25-76), 73% were male, 71% had ECOG PS 1, 78% were refractory to ≥2 lines of therapy, 20% relapsed ≤12 mos of ASCT, and 61% were treated with ≥3 lines of prior therapy. KTE-C19 was successfully manufactured in 99% of pts enrolled. Average turnaround time from apheresis to receipt of KTE-C19 at the clinical site was 17.4 days. With an ORR of 76%, the study met the primary endpoint (P<0.0001; exact binomial test comparing observed ORR to a historical control assumption of 20%), with 47% CRs and 29% PRs. 92% of responses occurred within the 1st mo, and 39% of pts had ongoing responses (CR in 33%) at 3 mos. Responses were seen across key covariates, including refractory subgroup (refractory to chemotherapy=76%, relapse post ASCT=80%). Kaplan-Meier estimates of progression-free survival at 1 and 3 mos were 92% and 56%, respectively. The most common grade ≥3 treatment-emergent AEs were neutropenia (67%), anemia (39%), thrombocytopenia (29%), febrile neutropenia (27%), and encephalopathy (24%). Grade ≥3 cytokine release syndrome (CRS) and neurologic events occurred in 20% and 29% of pts, respectively. There was 1 grade 5 KTE-C19-related event of hemophagocytic lymphohistiocytosis. CAR T cells expanded within 14 days of KTE-C19 infusion, and peak expansion was associated with ongoing response at mo 3 (P=0.008). Pts who developed grade ≥3 neurological events had increased serum levels of IL-15 (P=0.0002), IL-6 (P=0.003); IL-10 (P=0.009) and IP-10 (P=0.0003). Cytokines/chemokines returned to baseline levels in most pts by day 28. Data from 93 pts with at least 1 mo of follow-up at the data cutoff will be presented. Conclusions: ZUMA-1 is the first reported multicenter trial of CAR T cell therapy in pts with refractory aggressive NHL. KTE-C19 induced a nearly 6-fold higher CR rate compared to historical outcomes in SCHOLAR-1. Efficacy strongly associated with peak CAR T levels. Central manufacturing, logistics, and AE management were successfully implemented across 22 sites, most with no prior CAR T therapy experience. Results from cohort 2 of ZUMA-1 are also presented (Abstract #998). KTE-C19 demonstrated significant clinical benefit in pts with no curative treatment options. Supported in part by funding from The Leukemia & Lymphoma Society Therapy Acceleration Program®. Drs Neelapu and Locke contributed equally to this study. Disclosures Neelapu: Kite Pharma: Membership on an entity's Board of Directors or advisory committees, Research Funding. Locke:Kite: Membership on an entity's Board of Directors or advisory committees. Miklos:pharmacyclics: Research Funding; Kite Pharma: Research Funding; Roche: Research Funding; Novartis: Research Funding. Jacobson:Kite: Membership on an entity's Board of Directors or advisory committees. Siddiqi:Pharmacyclics: Speakers Bureau; Janssen: Speakers Bureau; Seattle Genetics: Speakers Bureau. Lin:Mayo Clinic: Employment; Janssen: Research Funding. Timmerman:Bristol-Myers Squibb, Kite Pharma, Valor Biopharmaceuticals, Janssen: Research Funding; Seattle Genetics, Genmab, Celgene: Consultancy, Honoraria. Goy:COTA: Membership on an entity's Board of Directors or advisory committees; Janssen/Pharmacyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Research funding for clinical trials through institution, Speakers Bureau; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Research funding for clinical trials through institution; Acerta: Consultancy, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Genentech: Other: Research funding for clinical trials through institution. Smith:Abbvie: Research Funding; Celgene: Honoraria; Spectrum: Honoraria; Genentech: Honoraria. Deol:Jazz Pharmaceuticals: Consultancy. Avivi:Tel Aviv Sourasky Medical center: Consultancy, Other: consultancy to :BMS Roche. Westin:Genentech: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Spectrum: Membership on an entity's Board of Directors or advisory committees; ProNAi: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Chavez:Janssen: Speakers Bureau. Levy:Kite Pharma: Consultancy; Five Prime Therapeutics: Consultancy; Innate Pharma: Consultancy; Beigene: Consultancy; Corvus: Consultancy; Dynavax: Research Funding; Pharmacyclics: Research Funding. Reagan:Seattle Genetics: Research Funding. Bot:Kite Pharma: Employment, Equity Ownership. Rossi:Kite Pharma: Employment, Equity Ownership. Navale:Kite Pharma: Employment, Equity Ownership. Jiang:Kite Pharma: Employment, Equity Ownership. Aycock:Kite Pharma: Employment, Equity Ownership. Elias:Kite: Employment, Equity Ownership. Wiezorek:Kite Pharma: Employment, Equity Ownership. Go:Kite Pharma: Employment, Equity Ownership.

Abstract Introduction: AL amyloidosis is a very heterogeneous disease. Prognosis is a function of organ tropism, extent of organ damage, and ability of tissues to heal, the last of which relates both to hematologic response and intrinsic toxicity of the light chain. Using mass spectroscopy (MS) technology, we are able to distinguish immunoglobulin light chain variable gene family (IGVL) usage on clinical samples. The goal of this study was to evaluate if IGVL usage impacts patient outcomes in patients with light chain amyloidosis (AL). Methods: IGVL usage was determined by mass spectroscopy (MS) of amyloid in clinical tissue specimens of Mayo Clinic patients. Specimens were from fat pad (n=257), bone marrow (n=172), myocardium (n=113), gastrointestinal (n=58), kidney (n=20), lung (n=15), and nerve (n=5). For those cases for which the IGVL could not be identified--not otherwise specified (NOS)—but constant region could be identified as lambda or kappa, we assume that the amyloid consisted primarily of immunoglobulin light chain gene constant regions or variable genes with somatic mutations making them uninterpretable to our matching algorithms. The medical records from these 700 patients were abstracted for relevant clinical and laboratory data. Results: The baseline characteristics of patients are shown in table 1. Three hundred and thirty-two patients have died with a median follow-up of surviving patients of 38 months. The estimated median survival for the entire population is 59 months. Out of 700 patients, 214 (31%) achieved a CR or a VGPR, 432 (62%) were not evaluable (NE) for hematologic or organ response, and 54 (8%) achieved a PR or did not respond (NR). The distribution of IGVL cases is shown in table 2. Overall survival (OS) for the whole group was not different across different IGVLs on univariate analysis, but when corrected for hematologic response, outcomes differed significantly based on IGVL. Patients could be further assembled into two groups, based on risk for death on univariate analyses: an IGVL high risk, which included KV1, LV1, LV2, LV3, and LV6; and low risk, which included all other cases (Figure). In a multivariate model that included level of hematologic response (CR/VGPR versus PR/NR/NE) and IGVL, IGVL family was independently associated with overall survival (RR=1.5 (95% CI 1.2-1.9, p=0.008). The risk ratio for CR/VGPR was 0.28 (95% CI 0.20-0.38, p<0.0001). This effect persisted when either the Mayo 2006 or the 2012 staging system was included in the multivariate. Conclusion: IGVL usage appears to have prognostic significance in patients who have not achieved VGPR or better to initial chemotherapy. Table 1. Baseline characteristics of patients N= 700 Age 63 (32-94) Male, (%) 447 (64%) Biopsy site Solid organ/Soft tissue 271 (39%) Fat pad 257 (37%) Bone Marrow 172 (25%) Organ involvement Cardiac 432 (62%) Renal 346 (49%) Gastrointestinal 168 (24%) Liver 56 (8%) Nerve 107 (15%) Lung 42 (6%) Soft Tissue 92 (13%) Organs involved 1 321 (46%) 2 228 (33%) ≥3 151 (22%) Laboratory characteristics NTBNP, pg/ml 2547 (11.3-70000) Troponin, ng/ml 0.03 (0.001-0.84) dFLC, mg/dl 26 (0.04-2330) Cardiac Stage 1 59 (18%) 2 125 (38%) 3 144 (44%) Table 2. Variable region family distribution. Light Chain N=700 N (%) KV1 107 (15%) KV2 3 (0.4%) KV3 17 (2%) KV4 25 (4%) KV6 1 (0.1%) LV1 85 (12%) LV2 64 (9%) LV3 118 (17%) LV4 3 (0.4%) LV6 97 (14%) LV8 1 (0.1%) LV9 1 (0.1%) Kappa NOS1 34 (4%) Lambda NOS1 140 (19%) Heavy chain amyloidosis 4 (0.6%) 1 No IGVL family could be identified Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Abstract BACKGROUND: The introduction of novel agents and proteasome inhibitors, and advances in high dose therapy administration has made an impact on the survival outcomes for MM patients. However, HRMM still remains a therapeutic challenge with poor prognosis. Even with aggressive approaches such as the Total Therapy protocols, patients with poor genomic risk have a 2-year event-free survival of ~50% (Nair et al, Blood 2010). A randomized Phase I/II trial was designed to evaluate the efficacy of adding immunotherapy into the first line for HRMM patients, comparing lenalidomide, bortezomib and dexamethasone (RVD) with or without addition of elotuzumab (Elo), a humanized monoclonal antibody that binds to SLAMF7/CS1. We are reporting on the Phase I portion of the study. PATIENTS & METHODS: The objective of Phase I was to determine the maximum tolerated dose (MTD) of RVD-Elo. Both low/standard risk MM and HRMM patients were eligible. HRMM was defined by one or more of the following: (1) poor risk genomics by the Arkansas 70-gene model, (2) translocation (14;16), translocation (14;20) and/or deletion (17p) by florescent in-situ hybridization (FISH), (3) primary plasma cell leukemia and (4) serum LDH > 2 times normal levels. The treatment consisted of induction chemotherapy for 8 cycles with RVD-Elo (lenalidomide 25 mg orally days 1-14 of every 21-day cycle; bortezomib 1.3 mg/m2 subcutaneously days 1,4,8,11; dexamethasone 20 mg orally days 1,2,4,5,8,9,11,12; elotuzumab 10 mg/kg intravenously days 1,8,15 cycles 1-2 then days 1,11 cycles 3-8) followed by dose-attenuated RVD-Elo maintenance (lenalidomide 25 mg orally days 1-14; bortezomib 1.0 mg/m2 subcutaneously days 1,8,15; dexamethasone 12 mg orally days 1,8,15; elotuzumab 10 mg/kg intravenously days 1,15) until disease relapse, progression or intolerance. Adverse events (AE) were recorded as per the NCI CTCAEv4.0. RESULTS: Eight newly diagnosed MM patients were enrolled on the Phase I run-in study. Six patients (Figure 1) were evaluable for dose limiting toxicities (DLT) during Cycle 1 as per protocol. The median age of patients was 67 years (range: 56-79 years), with 67% ≥65 years, Hgb was less than 10 g/dL in 50%, creatinine was greater than 2 mg/dL in all patients. ISS stage distribution was 17% (I), 33% (II) and 50% (III). Deletion 13 was observed in 1 patient (17%). The most common AEs (all grades) were fatigue (100%), peripheral sensory neuropathy (83%), edema (83%), lymphopenia (66%) and leukopenia (50%). The most common Grade 3 AEs were peripheral sensory neuropathy (33%), one of which was a DLT, neutropenia (17%) and thrombocytopenia (17%). One Grade 4 lymphopenia was observed. All 6 patients have completed 8 cycles of RVD-Elo induction therapy and 5 patients have completed at least 4 cycles of RVD-Elo maintenance. Overall median days on therapy per cycle were 13 days during induction and 20 days per cycle during maintenance. Dose adjustments were made in 83% of patients for bortezomib, 83% for lenalidomide and 33% for dexamethasone. There were no dose reductions for elotuzumab, although three patients had 1 event each of dose delays/missed dosing attributable to AE/SAE from RVD. Efficacy data will be released at the time that the phase II study of RVD +/- Elo is mature. Discussion/Conclusion: The RVD-Elo is a safe well-tolerated regimen for newly diagnosed MM patients without major additive AE/SAE beyond what is already known about RVD. This is the first report of the only phase I experience combining the triple-drug regimen RVD with the monoclonal antibody Elotuzumab for newly diagnosed MM. Support: NCI grants CA32102, CA38926, CA180821, CA31946, CA21076, CA180799, CA21115, CA180820 and in part by Bristol-Myers Squibb Company Disclosures Usmani: Celgene Corporation: Consultancy, Honoraria, Research Funding; Millennium: Consultancy, Honoraria; Onyx: Consultancy, Honoraria, Research Funding; Sanofi: Consultancy; Array BioPharma: Research Funding; Janssen: Research Funding; Pharmacyclics: Research Funding. Off Label Use: Lenalidomide in newly diagnosed multiple myeloma patients. Ailawadhi:Millennium: Honoraria. Shah:Onyx Pharmaceuticals: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Millennium Pharmaceuticals: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Array: Consultancy, Research Funding. Rosenzweig:Celgene: Speakers Bureau. Durie:IRC J&J: Membership on an entity's Board of Directors or advisory committees; Celgene Corp: Expert Board Committee Other; IRC Onyx: Membership on an entity's Board of Directors or advisory committees; DMC Millennium: Membership on an entity's Board of Directors or advisory committees. Orlowski:Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees, Research Funding; Onyx Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding; Millennium: The Takeda Oncology Company: Membership on an entity's Board of Directors or advisory committees, Research Funding; Spectrum Pharmaceuticals: Research Funding; JW Pharmaceutical: Research Funding; Array BioPharma: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees; Janssen Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees.

Abstract Background: The association of clinical trial participation with outcomes in cancer patients is controversial, with some studies reporting better outcomes for trial participants while others do not. It is possible that the difference in outcomes is due to differences in baseline characteristics of participants and non-participants. The Blood and Marrow Transplant Clinical Trials Network (BMT CTN) 0201 trial was a large randomized, multi-center study comparing peripheral blood (PB) with bone marrow (BM) for hematopoietic cell transplantation (HCT) from HLA-matched or 1 allele mismatched unrelated donors (URD) in patients with acute leukemia, chronic myeloid leukemia and myelodysplastic syndromes. The trial reported no significant survival differences between PB and BM; there was decreased risk of graft failure but increased risk of chronic graft-versus-host disease (GVHD) with PB grafts (Anasetti et al NEJM 2012). Methods: We compared characteristics of BMT CTN 0201 study participants (n=494) with HCT recipients who did not participate on the trial (n=1384) but were potentially eligible by virtue of known characteristics. These patients received similar conditioning and GVHD prophylaxis as trial participants at 38 United States trial centers during the study time-period. Centers that had no eligible non-trial participants were excluded. Outcomes between patients on and off trial were compared using Cox proportional hazards regression models. Data were obtained from the Center for International Blood and Marrow Transplant Research (CIBMTR) that collects patient data on all trial and non-trial allogeneic HCT recipients through its registry function. Results: Approximately 29% [494/1878] of apparently eligible patients were randomized and analyzed as part of the trial. There were no significant differences between study participants and non-participants in age or sex distribution, disease types, HLA or sex matching, comorbidities, or interval from diagnosis to HCT. Higher proportions of non-participants were Hispanic, had a lower performance status and lower disease risk, and received myeloablative conditioning and antithymocyte globulin (ATG) or Campath than the study participants. PB was used more commonly as the graft source in the non-participants as compared to the study participants (65% vs. 50%, p<0.001). In multivariate models, overall mortality (HR 1.09, 95% CI 0.95-1.25, p=0.22), transplant-related mortality (HR 1.08, 95% CI 0.89-1.32, p=0.42) and risks of acute grade II-IV (HR 0.96, 95% CI 0.82-1.12, p=0.57) and chronic GVHD (HR 1.06, 95% CI 0.92-1.23, p=0.41) were comparable between study non-participants and participants. Non-participants were at higher risk for relapse than participants (HR 1.24, 95%CI 1.04-1.49, p=0.02) in the multivariate analysis adjusted for disease risk and other clinical variables. Center effect was examined and was not found to be significant (p=0.10). There was no significant interaction between graft source and trial participation (P=0.22) and the risk of mortality was comparable for BM (HR 0.99, 95% CI 0.80-1.22, p=0.90) and PB recipients (HR 1.17, 95% CI 0.97-1.41, p=0.09) whether on trial or off trial. (Figure) Conclusion: Approximately 29% of patients who appeared eligible and were treated with conditioning and GVHD prophylaxis regimens allowed on the trial were enrolled. Despite some differences in clinical characteristics, most of the outcomes of non-trial participants were comparable to trial participants, suggesting that there is no definitive evidence that the outcomes of patients in a clinical trial are superior to those of the non-participants treated in a similar fashion. The comparable outcomes also indicate that the results of this trial were not seriously affected by selection bias and are therefore representative of the larger population. Figure 1: Adjusted overall survival in BMT CTN 0201 trial participants and non-participants Figure 1:. Adjusted overall survival in BMT CTN 0201 trial participants and non-participants Figure 2 Figure 2. Disclosures No relevant conflicts of interest to declare.

Abstract Background: JAK2 inhibitors have been shown to improve symptoms and produce durable reductions in splenomegaly in patients with myelofibrosis (MF), and ruxolitinib has been shown to improve survival in MF patients (Cervantes et al., 2013; Verstovsek et al., 2013). Current prognostic models such as DIPSS plus (Gangat et al., 2011) predict survival in MF based on clinical, laboratory, and cytogenetic information, but their value in predicting clinical response or survival during treatment with JAK2 inhibitors remains unknown. We hypothesized that clinical features such as bone marrow fibrosis and splenomegaly may have independent effects on therapy response. Therefore, we conducted a retrospective analysis to create a new model to risk stratify patients with respect to their likelihood of responding to oral JAK2-inhibitor therapy. Methods: We studied a cohort of 203 patients with bone marrow biopsy-proven MF seen at University of Michigan, Stanford University, and Mayo Clinic in Scottsdale, AZ. These patients were all treated with ruxolitinib or an experimental JAK2 inhibitor. Our primary endpoint was defined as IWG-MRT criteria for splenic response by palpation (Tefferi et al., 2013). Response in patients with spleen size of less than 5 cm was defined as complete resolution of splenomegaly. Of the 203 patients studied, splenic response was evaluated after 3 months of therapy in 167 patients and after 6 months of therapy in 138 patients; 127 patients were in both groups. A logistic regression was performed to identify factors that would predict clinical response. Results: The following characteristics were significantly associated with spleen response at 3 and 6 months: initial spleen size, European consensus criteria grading of MF on bone marrow biopsy, initial DIPSS plus score, and initial WBC count. Cellularity on marrow biopsy was not significant. We enriched a baseline logistic model of initial dose of oral JAK2 therapy and DIPSS plus score with additional prognostic factors. We found the following clinical characteristics to be jointly associated with splenic response: normalized initial dose of oral JAK2 inhibitor, initial spleen size, DIPSS plus score, degree of fibrosis by European consensus criteria. Duration of disease from time of diagnosis to time of treatment initiation was not prognostic for splenic response. We used this model to calculate the probability of splenic response based on a risk score: Risk score = –1.18(Dose) + 0.09(Initial Spleen Size in cm) + 0.20(DIPSS-plus Points) +0.92 (if fibrosis is MF-3). The probability at 6 months can then be calculated from the risk score as follows: [1/(1+e(risk score-2.6))]. The figure demonstrates the prognostic gain of our model over a model based on DIPSS plus alone. Conclusion: With this observational study, we propose a predictive model which may serve as a clinical tool to identify which patients are most likely to benefit from JAK2 inhibitor-based therapies. Further validation in independent data sets will be required before this model can be more widely applied. Disclosures Mesa: Incyte Corporation, CTI, NPS Pharma, Inc., Gilead Science Inc., Celgene: Research Funding. Gotlib:Incyte: Consultancy, Honoraria, Research Funding, Travel Reimbursement Other; Gilead: Research Funding; Sanofi: Research Funding; Novartis: Research Funding, Travel Reimbursement, Travel Reimbursement Other. Talpaz:ARIAD Pharmaceuticals, Inc., BMS, Sanofi, Incyte, Pfizer: Research Funding.

Abstract Abstract 800 Background: Ruxolitinib (RUX), an oral JAK1/JAK2 inhibitor, reduced spleen volume (SV), improved myelofibrosis (MF)-associated symptoms and quality of life (QoL), and appeared to exhibit a survival advantage over placebo (PBO) in patients (pts) with MF regardless of JAK2V617F mutation status in the phase III COMFORT-I study. We describe long-term efficacy and safety of RUX from COMFORT-I, with 1 year of additional follow up beyond previously published data. Methods: Eligible pts (N=309) were randomized (1:1) to RUX or PBO. The primary analysis occurred when all pts completed 24 weeks (wks) and when half the pts completed 36 wks of treatment. All pts receiving PBO were eligible for crossover to RUX after the primary analysis; crossover before wk 24 was permitted if pts met protocol-defined criteria for worsening splenomegaly. The proportion of pts with ≥35% SV reduction at 24 wks (primary endpoint) and durability of SV response were assessed. Although symptom burden (measured daily using the modified MF Symptom Assessment Form v2.0) was only measured up to wk 24, QoL continued to be evaluated beyond wk 24 (every 24 wks) using the EORTC QoL Questionnaire-Core 30 (QLQ-C30). Overall survival (OS) was assessed according to original randomized treatment. Results: In this updated analysis, median follow-up of pts randomized to RUX was 102 wks. All pts receiving PBO completed crossover or discontinued within 3 months of the primary analysis. Of 134 pts randomized to RUX who remained on treatment after the primary data analysis, 100 continue on study. Mean SV reduction in pts randomized to RUX was 31.6% at wk 24 and has remained stable with additional follow up through wk 96 (Table). In pts who achieved a ≥35% SV reduction, response was durable, with a median response duration of 108 wks. RUX treatment was also associated with durable improvements in the Global Health Status/QoL (Table) and the 5 functional domains of the EORTC QLQ-C30. Twenty-seven (27) pts randomized to RUX and 41 pts randomized to PBO died, representing a continued OS benefit in favor of RUX (HR=0.58; 95% CI: 0.36, 0.95; P = 0.028; Fig 1) similar in magnitude to that previously reported. OS favored RUX across subgroups including starting dose as well as baseline risk status and hemoglobin (Hgb). Of 34 pts randomized to RUX who discontinued after the primary analysis, 4 discontinued for an adverse event (AE). In pts who continued on RUX, anemia and thrombocytopenia remained the most frequently reported AEs. New onset of grade 3 or 4 anemia and thrombocytopenia was reported in only 12 and 5 pts, respectively. One pt discontinued for anemia. Overall, among all pts randomized to RUX, Grade 3 and 4 anemia regardless of baseline Hgb was reported in 37.4% and 14.8% of pts, respectively. Similarly, Grade 3 and 4 thrombocytopenia was reported in 11.0% and 5.2% of pts, respectively. These rates were similar to those reported in the primary analysis. By wk 36, the proportion of pts receiving red blood cell transfusions decreased to the level seen with PBO and remained stable thereafter (Fig 2). Rates of nonhematologic AEs adjusted for increased follow-up duration remain similar to those seen at the time of the primary data analysis. No additional cases of acute myeloid leukemia (AML) in pts randomized to RUX were reported. Two pts originally randomized to PBO developed AML, 21 and 178 days after crossover to RUX. There continued to be no reports of a withdrawal syndrome after RUX discontinuation. Conclusions: RUX provides durable reductions in SV and improvements in QoL. Although all pts randomized to PBO crossed over to RUX shortly after the primary analysis, with 1 year of additional follow up, RUX continues to be associated with a survival advantage over PBO. RUX continues to be well tolerated; the AE profile with long-term treatment is consistent with that previously reported. The proportion of pts receiving transfusions decreased over time to rates similar to PBO, and there were no reports of a specific withdrawal syndrome or cytokine rebound phenomenon after RUX discontinuation. Disclosures: Verstovsek: Incyte Corporation: Research Funding. Mesa:Incyte: Research Funding; Lilly: Research Funding; Sanofi: Research Funding; NS Pharma: Research Funding; YM Bioscience: Research Funding. Gotlib:Incyte: Consultancy, travel to congress Other. Levy:Incyte: Employment, Equity Ownership. Gupta:Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Research Funding; YM Biosciences: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Sanofiå]Aventis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Catalano:Incyte: Consultancy. Deininger:Bristol-Myers Squibb: Consultancy, Research Funding; Novartis: Consultancy; Ariad: Consultancy. Miller:Novartis: Consultancy, Research Funding, Speakers Bureau, development of educational presentations Other; Incyte: development of educational presentations, development of educational presentations Other. Talpaz:Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; B.M.S.: Membership on an entity's Board of Directors or advisory committees, Research Funding; Ariad: Research Funding; Sanofi: Membership on an entity's Board of Directors or advisory committees, Research Funding; Teva: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees. Winton:Incyte: Consultancy, Honoraria. Arcasoy:Incyte: Research Funding. Lyons:Incyte: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; Novartis: Research Funding; Telik: Research Funding. Paquette:Incyte: Consultancy. Vaddi:Incyte: Employment, Equity Ownership. Erickson-Viitanen:Incyte: Employment, Equity Ownership. Sun:Incyte Corporation: Employment, Equity Ownership. Sandor:Incyte Corporation: Employment, Equity Ownership. Kantarjian:Incyte: grant support Other.

Abstract Abstract 755 Background: TG101348 is a potent, orally bioavailable, JAK2-selective small molecule inhibitor, that is currently being evaluated in a Phase I study for the treatment of myelofibrosis. Data from the dose escalation cohort (n=28; 30-800mg administered as a single daily dose) showed dose-linear plasma exposure, with mean elimination T1/2 at steady state ranging from 20 to 52 hours. The dose-limiting toxicity was asymptomatic grade 3 or 4 amylasemia/lipasemia that was reversible, and the maximum tolerated dose (MTD) was 680mg. The most frequent non-hematological toxicities were mild nausea, vomiting, and/or diarrhea that were easily controlled or resolved spontaneously. Grade 3/4 neutropenia and thrombocytopenia were observed in 14% and 25% of patients, respectively. TG101348 had activity in reducing spleen size, leukocyte count, and JAK2V617F (VF) allele burden. Here, we present updated results with a focus on data from the dose confirmation cohort who initiated treatment at a dose of 680mg/day. Results: Fifty nine patients (median age=66 years; range 43-86) have been treated – 28 in the dose escalation phase, and 31 in the dose confirmation phase. Overall, 44 patients had PMF, 12 post-PV MF, and 3 post-ET MF; 86% were VF-positive. Median palpable spleen size was 18cm and 22 patients were RBC transfusion-requiring at study enrollment. After a median follow-up of 12 weeks (range <1-76), 18 (31%) patients have discontinued treatment due to toxicity (n=7; thrombocytopenia=3, neutropenia=1), comorbidities (n=5), withdrawal of consent (n=4), or non-compliance/lack of response (1 each). The remaining 41 patients are currently at the following dose levels: 680mg (n=14), 520-600mg (n=16), 360-440mg (n=10), and 240mg (n=1). The cumulative drug exposure to date is 362 patient-months; exposure at or above MTD (≥680mg) is 154 patient-months. Forty patients (68%) started treatment at ≥680mg. Toxicity: TG101348 is well tolerated. Of the patients who started at ≥680mg, Gr3/4 neutropenia was observed in 15/0% and Gr3/4 thrombocytopenia in 20/10%. Twenty four (60%) patients did not require RBC transfusions at baseline (median Hgb=9.6g/dL; range 7.4-13.1); of these, 42% and 8% of patients developed Gr3 and Gr4 anemia, respectively. The majority of patients who started at ≥680mg developed mild nausea (1 Gr3), vomiting (1 Gr3), and/or diarrhea (3 Gr3) that were self-limited or easily controlled. Other non-hematological toxicities included Gr1/2 transaminitis (38%), Gr1/2 serum creatinine elevation (38%), and asymptomatic hyperlipasemia (33%). Efficacy: Thirty three patients who started at ≥680mg have completed at least 3 cycles of treatment; at 3 months, reduction in palpable spleen size (baseline median=18cms; range 6-32) was at least 50% in 22 (67%) patients; the spleen became non-palpable in 9 (27%) patients. All 21 patients with leukocytosis at baseline (WBC range 11 to 203 ×109/L) who started at ≥680mg have experienced a marked reduction in their WBC count (range 4 to 90); 70% had a normal WBC count at their last follow-up visit. Overall, 48 of the 51 VF-positive patients completed at least 1 cycle and were evaluable for response in VF allele burden; at last available follow-up, the median decrease in granulocyte mutant allele burden was 48%; 21 (44%) patients have had a ≥50% reduction, and in the group who started treatment at ≥680mg, 48% have had a ≥50% reduction. Of those evaluable, there was clinically significant benefit or resolution of constitutional symptoms, including early satiety, fatigue, cough, pruritus, and night sweats. Conclusions: TG101348 continues to be well tolerated in patients with myelofibrosis. Spleen and leukocyte responses are frequent, observed early, and produce substantial clinical benefit for patients. These responses are associated with significant decrease in VF allele burden and point to activity of TG101348 against the malignant clone in myelofibrosis. Disclosures: Pardanani: TargeGen: Research Funding; Cytopia: Research Funding. Off Label Use: Data from ongoing clinical trial will be presented. Gotlib:TargeGen: Research Funding. Jamieson:Merck: Research Funding; Pfizer: Research Funding; Wintherix: Consultancy; TargeGen: Research Funding; Celgene: Research Funding. Cortes:Targegen: Research Funding. Stone:Cephalon: ad hoc advisory board. Silverman:TargeGen: Consultancy. Shorr:TargeGen: Employment, Equity Ownership. Gilliland:Merck: Employment. Tefferi:TargeGen: Research Funding.