Rivera, Candido E.

Abstract Momelotinib (MMB) is a JAK1/2 and ACVR1 inhibitor with demonstrated clinical activity in all 3 hallmarks of myelofibrosis (MF): anemia, constitutional symptoms, and splenomegaly. In this phase 2 open-label translational biology study (NCT02515630) of 41 transfusion-dependent patients with MF, we explored mechanisms underlying the favorable activity of MMB on MF-associated iron-restricted anemia, including its impact on serum hepcidin levels, and markers of iron storage and availability, erythropoiesis, and inflammation. A transfusion-independent response (TI-R), defined as red blood cell transfusion independence (TI) ≥12 weeks at any time on study, occurred in 17 patients (41%; 95% confidence interval [CI], 26%-58%), including 14 patients (34%; 95% CI, 20%-51%) who achieved TI-R by week 24. In addition, 78% of TI nonresponse (TI-NR) patients achieved a ≥50% decrease in transfusion requirement for ≥8 weeks. Adverse events (AEs) were consistent with previous studies of MMB in MF, with cough, diarrhea, and nausea as the most common. Twenty-one patients experienced grade ≥3 AEs, most commonly anemia and neutropenia. Consistent with preclinical data, daily MMB treatment led to an acute and persistent decrease in blood hepcidin associated with increased iron availability and markers of erythropoiesis. Baseline characteristics associated with TI-R were lower inflammation and hepcidin as well as increased markers of erythropoiesis and bone marrow function. Overall, the study demonstrates that MMB treatment decreases hepcidin in conjunction with improving iron metabolism and erythropoiesis, suggesting a mechanistic explanation for the reduced transfusion dependency observed in transfusion-dependent MF patients treated with MMB, thereby addressing the key unmet medical need in the MF population.

Abstract Background: Previous studies have proposed combination of various factors that predict poor mobilization after GCSF stimulation. However, there is no single clinical or laboratory test that reliably correlates with bone marrow reserve and PBPC mobilization. Peripheral blood CD34+ cell count (pCD34) reliably correlates with PBPC mobilization and yield but only after GCSF administration. Methods: We have prospectively followed 36 autologous PBPC transplant candidates, from the time of initial evaluation to transplant, to evaluate factors the correlate with bone marrow reserve and autologous PBPC mobilization. Results: The patients median age was 63 (range 26 – 76). 21 of the 36 patients were diagnosed with dysproteinemia, primarily multiple myeloma, 10 patients had non-Hodgkin’s lymphoma while the remaining 5 had other form of hematological malignancies. Our evaluation shows baseline platelet count prior to growth factor administration significantly correlate with total CD34+ cell yield (spearman: r = 0.64, p <0.001, Figure 1). In addition, daily platelet count during PBPC harvest correlate with CD34+ cell yield for the day (spearman: r = 0.6, p <0.001). Using multiple linear regression model (F = 19.1, p <0.001, R2 = 0.64), we have determined patients’ age (p = 0.03) and type of disease (p <0.001), in addition to platelet count (p<0.001), significantly correlate with total CD34+ cell yield. Further analysis showed low baseline platelet count predicts poor PBPC mobilization. Using Receiver Operating Curve (ROC), we have determined that platelet count of 174,000/ul was the best cut-off for collecting at least 2 million/Kg CD34+ cells with sensitivity of 81% and specificity of 78% and estimated correct classification of 81%. Even though pCD34 counts were slightly more sensitive and were better at identifying poor mobilizers in our cohort (best cut-off 10/ul, sensitivity 96%, specificity 67%, correct classification 89%), their clinical utility were diminished since the values were only known after GCSF administration. Conclusion: Baseline platelet count is a sensitive predictor of bone marrow reserve and can be used prior to growth factor administration to predict poor mobilization. Figure 1: Correlation of baseline platelet count and total CD34+ cell yield Figure 1:. Correlation of baseline platelet count and total CD34+ cell yield

Abstract Background: Myelofibrosis (MF) shortens survival but also compromises quality of life from disease associated splenomegaly and constitutional symptoms (fatigue, weight loss, night sweats, and bone pain). No current validated instrument of patient reported outcomes (PRO) captures the spectrum of MF associated symptoms. In an era of rapid development and testing of therapeutic agents which may impact the natural history and symptoms associated with MF (such as JAK2 inhibitors) a uniform and validated instrument for capturing the presence, severity (and potentially improvement) of MF symptoms is needed. We sought to develop and validate such an instrument, the myelofibrosis symptom assessment form (MFSAF). Methods: Based upon the results in our MF QOL survey (Cancer2007;109(1):68–76), we developed the MFSAF to assess fatigue (via the brief fatigue inventory (BFI-Cancer1999;85:1186)), additional symptoms were independently assessed for presence and severity on a scale from 0 (absent) to 10 (worst possible) for splenomegaly associated symptoms (early satiety, pain, inactivity, cough) night sweats, itching, bone pain, fever, unintentional weight loss as well as an estimate of overall quality of life. Additionally, patients provided feedback on the quality and nature of the MFSAF, and also completed for comparison validated instruments including the Memorial Symptom Assessment Scale (MSAS), the Insomnia Severity Index (ISI), and the Brief Pain Index. Physician input was included including their assessment of patient’s fatigue, spleen symptoms, and quality of life (blinded to patient’s responses) as well as clinical history, lab and exam findings. Results: MFSAF Results 34 MPD patients were enrolled (24 MF, 10 in the comparison group (4 polycythemia vera (PV), 6 essential thrombocythemia (ET)). the MFSAF was rated by patients as easy to understand (median score 1, range 0–6), and “addressed most of my symptoms” (median score 1, range 0–6) both on a scale of 0 (as good as possible to 10 as bad as possible). When asked if a symptom was not addressed (open ended response) no single symptom was named more than once. As we have previously reported fatigue was common with BFI scores (median 3.6 (0–10) for MF and 2.5 (range 0.2–3.8) for the ET/PV group (increasing BFI score associated with worsening fatigue) worse than median score of published “healthy” controls 2.2. Additional MF associated symptoms were captured well by the MFSAF with splenic, constitutional symptoms, and QOL (median 3 (range 0–7) MF, median 2 (0–3) ET/PV) documented easily and worse than ET/PV controls. Physicians estimation of QOL was excellent (median 3 (0–8) for MF, median 2 (0–4) for ET/PV). MFSAF Comparison to other Instruments: The MSAS demonstrated more adverse values for MF (than ET/PV) in the PSYCH (psychologic stress; mean-1.27 (STD DEV 0.80), PHYS (physical symptoms; mean 0.90 (STD DEV 0.53)), GDI (Global Distress Index mean-1.29 (STD DEV 0.77)) and a total MSAS symptom score (mean 0.85 (std dev (0.49)) comparable with advanced renal disease (PSYCH 0.99, PHYS 0.99, GDI 1.27, and MSAS of 0.81; J of Pall Med2007;10(6):1266), as well as advanced lung disease, AIDS, and various advanced malignancies. Individual, previously validated MSAS questions were all highly correlated (all p<0.01) with MFSAF (in italic) counterparts including lack of energy (fatigue), cough (same), pain (both abdominal pain and bone pain), sweats (night sweats), itching (same), and weight loss (same). Further validation of pain measurements in the MFSAF came from comparison to the BPI where both individually the presence, and intensity of pain (both abdominal and bone) were highly correlated (all p<0.01). Insomnia, not yet included in the MFSAF, was present in 68% and 63% of patients (MSAS and ISI, respectively). Additionally, problems with sexual interest, or activity, was noted in 35% of patients to the MSAS. Conclusions: Currently available instruments of PRO and symptoms are lengthy, and individually incomplete for assessing the presence and severity of the diverse nature of symptoms associated with MF. The proposed MFSAF, was comprehensive and well understood by patients and the results for the individual symptoms assessed were highly correlated with previously validated instruments for other conditions as well as with physicians perceptions of fatigue and QOL. The MFSAF, with the addition of questions regarding insomnia and sexuality, should be utilized in all trials of therapeutic agents in MF patients in which symptomatic improvements are an endpoint.

Abstract Melphalan (M), Prednisone (P) and Lenalidomide (R) are active in the treatment of multiple myeloma (MM). We evaluated the toxicity and efficacy of MPR in a phase I/II trial. Results of phase I part were previously reported (Blood2006, 108(11) abst 3558). M 5 mg/m2 on days (d) 1–4, 60 mg/m2 d 1–4 and R 10 mg d 1–21 of a 28 day cycle was determined as MTD for the phase II study. Methods: Patients with previously untreated MM who were not candidates for stem cell transplantation, age ≥18 yr, ECOG PS 0–3, evaluable or measurable disease, ANC >1500, platelets > 100,000 and creatinine ≤ 3.0 mg/dL were eligible. All patients received aspirin 325 mg/d as DVT prophylaxis. Routine antibacterial prophylaxis was not used. G/GM-CSF was used at the discretion of the treating physician for neutropenia. Response rate (RR), confirmed on two consecutive determinations was the primary end-point. The study had 90% power to detect a RR of at least 45%. Results: Twenty-six patients were accrued between July ’06 and Feb ’08. The median age was 74 y (64 – 87y), 17 (65%) were men. Six, 13, 6, 1 (23%, 50%, 23%, and 4%) patients had ECOG PS 0, 1, 2, and 3, respectively. Three (12%), 11 (42%) and 10 (38%) patients were ISS stage 1, 2 and 3. A total of 106 cycles were administered; median 4.5 (1–13). Seventy-seven % patients experienced at least 1 grade 3 or 4 toxicity. Neutropenia (42%/8%) and thrombocytopenia (20%/8%) were the most common grade 3/4 adverse events followed by anemia (16%/0%), fatigue (8%/4%), rash (11%/0%), and hyperglycemia (4%/0%). There were 20 treatment delays in 9 patients, and 18 dose reductions (9 in R, 11 in M and 1 P) occurred in 7 patients, most commonly because of neutropenia or thrombocytopenia. Eleven patients (42%) required G-CSF treatment. Eleven patients are currently receiving treatment; 15 have gone off study (4 completed per protocol, 3 refused, 3 adverse effects, 3 unrelated illnesses, 2 other). Median follow up of survivors is 8 m (0 – 22m). Eighteen (69 %; 95%CI 48–86) patients had a PR or better according to International Myeloma Working Group Uniform Response criteria; 3 (12 %) CR, 5 (19 %) VGPR and 10 (38%) PR. Median number of cycles before achieving a response was 2 (1 – 11). Median Progression Free and Overall Survival is 16.7m (95% CI 11.2–23.0), and 23 m (95% CI: 22 – 23), respectively. Conclusions: MPR combination is feasible with a manageable toxicity profile and has significant activity in the treatment of patients with MM who are not candidates for stem cell transplant, with an overall response rate of 69%, and a CR plus VGPR rate of 31%. Grade 3 or 4 neutropenia and thrombocytopenia was the most common toxicity, seen in up to 50% of patients in this cohort of predominantly elderly patients. Dose reduction in R and/or M was required in 27% patients. No patient developed neuropathy or thromboembolic complications.

AbstractObjectiveTo determine the presence of racial/ethnic differences in patients with anemia and serum folate deficiency.MethodsWe performed a retrospective analysis of data from patient samples collected from January 2010 to October 2018. Reference laboratory ranges were determined by Mayo Clinic Reference Laboratories. Race and ethnicity were classified according to National Institutes of Health categories.ResultsThe analysis comprised 197 974 samples. Hemoglobin, hematocrit, and SF results were available for 173 337, 173 056, and 129 760 samples, respectively. Of the samples, 46 505 (26.8%) showed anemia, with a higher prevalence among American Indian/Alaskan Natives (AI/AN) 42.9% and African Americans (AA) 47.2% (P < .001). SF deficiency was present in 897 (0.7%), with a higher prevalence among AI/AN (9, [1.4%]) and AA (78, [1.2%]) and a lower prevalence in non‐Hispanic whites (NHW) (758, [0.7%]), Hispanics (40, [0.6%]), and Asians (8, [0.3%]). In multivariable analysis, the prevalence of anemia was higher in all non‐NHW racial/ethnic groups: AA (OR, 3.67, [95%CI: 3.47‐3.88, P < .001]), AI/AN (OR, 3.25, [95%CI: 2.71‐3.90, P < .001]), Asians (OR, 1.62, [95%CI: 1.47‐1.77, P < .001]), and Hispanics (OR, 1.41, [95%CI: 1.32‐1.50, P < .001]). SF deficiency was more common in AA (OR, 1.48, [95%CI: 1.17‐1.88, P.001]) and less common in Asians (OR, 0.35, [95%CI: 0.17‐0.70, P = .003]), compared with NHW.ConclusionsWe showed significant racial/ethnic differences in anemia and SF deficiency. Differences were observed especially among NHW, AA, and Asians. We believe that these differences may be explained by social determinants of health. More research is needed regarding the causes of these differences and their clinical implications at a population level.

Abstract Introduction Immune thrombocytopenia (ITP) is an acquired disorder characterized by immune-mediated platelet destruction along with decreased platelet production. Adults with ITP are treated initially with glucocorticoids, intravenous immunoglobulin, and/or anti-D, but as many as 80% of patients (pts) will eventually relapse and become steroid-refractory. There is no universally agreed upon 2nd line therapy for ITP and consensus guidelines recommend either rituximab (R) or splenectomy (S) as acceptable, potentially curative options. Long-term responses to 2nd line S have been reported around 60%, and around 25% for R. It is unknown whether long-term outcome in the 3rd line setting is influenced by sequence of therapy. We evaluated the impact of sequence of 2nd and 3rdline therapy with R and/or S. Methods We identified all pts with ITP treated from 1990 through 2015 at the three Mayo Clinic (Arizona, Florida, and Minnesota) sites that were treated with R and/or S. Patients were excluded who were <18 years of age at the time of second-line treatment. Those with secondary ITP that received specific treatment for an infectious, autoimmune, or malignant condition causing thrombocytopenia were excluded. Patients with Evan's syndrome were included if the treatment was for thrombocytopenia, and not primarily for hemolytic anemia. For this analysis, secondary ITP was defined as ITP associated with hematologic malignancy. Hematologic malignancies did not require specific therapy at the time of treatment for ITP. Patients with uncontrolled infections or uncontrolled autoimmune disorders were excluded from analysis. We collected data from medical records regarding demographics, medical history, treatment history, response to treatment, and relapse. Medical history was captured for all concurrent diagnoses that could be considered associated with ITP including infectious and autoimmune conditions. Primary end-points were freedom from relapse after 2nd and 3rd line treatment with R or S. We used Kaplan-Meier method to estimate freedom from relapse after 2nd and 3rd line treatments. We also evaluated response to treatment, as defined by a platelet count >30,000/mm3 according to consensus guidelines. We performed three separate analyses for the entire cohort, primary ITP, and secondary ITP (separating out those with a concurrent diagnosis of malignancy). Results We identified 222 patients with a diagnosis of ITP, of which 191 had primary and 31 had secondary ITP. Treatment characteristics were similar in all groups except that pts treated initially with S were younger at diagnosis than pts treated with R (49 vs 60 years, P=0.003) and at time of 2ndline treatment (51.5 vs 61 years, P=0.018). For the overall cohort, patients treated with S as second-line therapy were more likely to achieve CR (86.6% vs 44%, P<0.0001), and had a significantly higher freedom from relapse at 5y (53.57% v. 14.96%, P<0.0001). Patients treated with S followed by R (S to R) had a trend towards higher 2y freedom from relapse than those treated with R followed by S (R to S) (69.48% v. 58.43%, P=0.3264). These data remained similar when primary ITP and secondary ITP were separated (data not shown). Conclusions These data support that S provides superior FFR at 5 years compared to R as second line treatment and suggests that, when needed, splenectomy followed by rituximab as opposed to rituximab followed by splenectomy might have a slight advantage. Disclosures No relevant conflicts of interest to declare.

Background: Chimeric antigen receptor T-cell (CAR-T) therapy has revolutionized the treatment of relapsed/refractory B-cell lymphoid malignancies. Axicabtagene ciloleucel (axi-cel), an anti-CD19 CAR-T not only targets the malignant B-cell, but can potentially also target and eliminate normal B-cells. This can interfere with the normal B-cell repertoire, compromising host humoral immunity such as decreased titers of common vaccines (DTaP, MMR). To assess if this was a clinically significant problem, we evaluated all recipients of axi-cel at our center between 6/2018 through 7/2019. Patients and methods: For patients who received commercial axi-cel, humoral immunity was evaluated both quantitatively [absolute lymphocyte count (ALC)] as well as qualitatively by serology titers [IgG antibodies (Abs)] for diphtheria, tetanus, pertussis, measles, mumps, and rubella, and total Immunoglobulin G (IgG) levels. Data was collected within 30 days prior to CAR-T infusion, then at day +30 and between days +60 and +100 after CAR-T infusion. Results: We identified 10 patients (males = 5, 50%), with a median age of 49.9 years (range 30-65) who received commercial axi-cel during the study period. Patient characteristics and indications for CAR-T therapy are shown in Table 1; the cohort represented a heavily pre-treated aggressive B-cell lymphoma patient population. Baseline information on antibody (Ab) titers was available in 8 patients. At baseline, all patients had positive tetanus IgG Abs (≥0.01 IU/mL), 7 had positive diphtheria IgG Abs (≥0.01 IU/mL), 6 had positive measles IgG Abs (≥ 1.1 AI), 5 had positive rubella IgG Abs (≥ 1.0 AI), 3 had positive mumps IgG Abs (≥ 1.1 AI). None of the patients had a positive pertussis IgG Abs (≥100 IU/mL). At follow-up, all patients with positive Ab at baseline maintained titers in the positive range at day +30 and between days +60 and +100 (Figure 1). None of the patients demonstrated a clinically meaningful decrease in Abs titers, despite a drop in ALC and IgG levels (table 2). Conclusions: Albeit a small sample size, IgG Ab titers for diphtheria, tetanus, measles, mumps, and rubella did not appear to be affected by axi-cel at a short interval follow-up after infusion (up to day +100). We plan to extend this analysis in a larger cohort with a longer-term prospective follow-up to validate our findings, especially in light of dropping absolute lymphocyte counts and IgG levels. Disclosures Ailawadhi: Celgene: Consultancy; Amgen: Consultancy, Research Funding; Cellectar: Research Funding; Janssen: Consultancy, Research Funding; Takeda: Consultancy; Pharmacyclics: Research Funding. Foran:Agios: Honoraria, Research Funding. Tun:Celgene: Research Funding; Curis: Research Funding; TG Therapeutics: Research Funding; Mundi-pharma: Research Funding; DTRM Biopharma: Research Funding; BMS: Research Funding. Chanan-Khan:Pharmacyclics: Research Funding; Merck: Research Funding; Jansen: Research Funding; Mayo Clinic: Employment; Ascentage: Research Funding; Millennium: Research Funding; AbbVie: Research Funding; Xencor: Research Funding. Kharfan-Dabaja:Daiichi Sankyo: Consultancy; Pharmacyclics: Consultancy.

Abstract BACKGROUND: Glanzmann's thrombasthenia (GT) is an inherited platelet disorder (IPD) that leads to clinically significant bleeding. Platelets from patients with GT can show qualitative or quantitative defects of platelet membrane glycoprotein (GP) IIb/IIIa complex. Most GT are caused by autosomal recessive genetic defects in ITGA2B and ITGB3 (genes for GPIIb and GPIIIa, respectively) with rare cases showing an autosomal dominant pattern. Accurate diagnosis of GT requires a constellation of both phenotypic and genetic studies. Here we report a unique case of autosomal dominant GT resulted from thorough phenotypic and genetic studies. PATIENTS AND METHODS: A 19 year-old woman was recently evaluated for life-long history of easy bruising and severe menorrhagia that was only partially responsive to medroxyprogesterone. She has severe thrombocytopenia first recognized shortly after birth with a platelet count around 20x109/L. Platelet size was normal. She was presumed to have immune-mediated thrombocytopenia (ITP) since early infancy, but lacking responsiveness to the conventional treatments of ITP including immunomodulation, splenectomy and thrombopoietin receptor agonists. Family history was negative for a bleeding diathesis. Both von Willebrand factor antigen and activity were within normal range. Bone marrow aspirate and biopsy with associated chromosome studies were all normal. Platelet surface glycoprotein assessment by flow cytometry using antibodies to GP IIb, IIIa, Ia, Ib-a, VI, IX, and whole exome sequencing (WES) utilizing a predefined list of 53 clinically significant genes* related to genetically IPDs were performed. Due to thrombocytopenia platelet aggregation studies could not be performed. METHODS/RESULTS: Platelet surface expression of GPIIb (CD41) and GPIIIa (CD61) were markedly decreased suggestive of a variant of GT (Figure). WES performed with Illumina HiSeq 2500 sequencing system by using Agilent SureSelelct CRE kit V1 to capture and target the exonic regions showed presence of a heterozygous mutation in ITGB3 gene (c2213T>G; p.Leu738Arg). By in silico prediction modeling, this mutation is likely to be pathogenic and results in the substitution of hydrophobic leucine with hydrophilic arginine in the transmembrane domain of the β3 subunit of alpha IIb/beta 3 integrin (αIIbβ3), the platelet receptor that binds to fibrinogen. Interestingly, GPVI is also decreased which may be associated with GPIIb and GPIIIa deficiency or due to accelerated shedding since no GPVI mutation was identified. CONCLUSION: We describe a patient with GT associated with a novel heterozygous autosomal dominant mutation in ITGB3 gene with substitution of leucine with arginine (c2213T>G; p.Leu738Arg). This deletion caused a low expression of αIIbβ3 integrin on her platelets surface and severe thrombocytopenia. This case underscores the importance of an integrated phenotyping and genotyping approach to render a definitive diagnosis of an IPD. *Platelet exome gene list: ABCG5, ABCG8, ACBD5, ACTN1, ANKRD26, ANO6, AP3B1, BLOC1S3, BLOC1S6, CYCS, DTNBP1, ETV6, FLI1, FLNA, GATA1, GFI1B, GP1BA, GP1BB, GP6, GP9, HOXA11, HPS1, HPS3, HPS4, HPS5, HPS6, ITGA2B, ITGB3, LYST, MASTL, MPL, MYH9, NBEAL2, ORAI1, PSRX1, P2RY12, PLA2G4A, PRKACG, RASGRP2, RBM8A, RUNX1, STIM1, STX11, STXBP2, TBXA2R, TBXAS1, THPO, TUBB1, UNC13D, VIPAS39, VPS33B, VPS45, WAS Figure Figure. Disclosures No relevant conflicts of interest to declare.

Abstract Introduction: Patients develop anemia as a result of myelofibrosis (MF) or its treatment, including Janus kinase (JAK) inhibitors. However, momelotinib (MMB), a JAK1/2 and Activin A receptor type I (ACVR1) inhibitor with demonstrated clinical activity in MF, improved anemia in prior clinical trials. JAK1/2 and ACVR1 respond to inflammation and iron stores to control iron availability through hepcidin, the key regulator of the entry of iron into circulation. Like other inflammatory diseases, MF is characterized by high hepcidin. MMB inhibited ACVR1 to modulate hepcidin and ameliorate anemia in a rodent model (Asshoff, Blood 2017). The impact of MMB was investigated on blood hepcidin, along with markers of iron storage and availability, erythropoiesis, and inflammation to explore mechanisms of the favorable effects of MMB on MF-associated anemia. Methods: In a phase 2 open-label study, MMB 200 mg once daily was given for 24 weeks to transfusion-dependent (TD; ≥4 units red blood cells [RBC] transfusion in the 8 weeks prior to first dose of MMB) patients with primary or post-ET/PV MF (age ≥18 yrs, required MF therapy, CrCl ≥ 60 mL/min, platelets ≥50 K, and absence of Gr ≥2 peripheral neuropathy, baseline palpable spleen was not required, patients with prior splenectomy were excluded). Patients were evaluated for MMB efficacy and safety. Total symptom score (TSS) was based on a modified Myeloproliferative Neoplasm Symptom Assessment Form. Transfusion-independent response/non-response (TI-R/NR) was defined as RBC transfusion-independence ≥12 weeks at any time on study. Serial blood samples were analyzed for a panel of biomarkers and liver iron content (LIC) was measured by MRI. Blood hepcidin was evaluated at every study visit in the morning (8-10am) pre-dose and 6 hours post-dose using a mass spectrometry assay and, prior to first dose, the normal daily increase of blood hepcidin was observed in half the population. Results: 41 patients (mean age 70, 63% male, 88% white) received MMB. By week 24, 14 (34.1%, 90% CI: 22.0-48.1%) patients had a TI-R and 39.0% had no RBC transfusion for ≥8 weeks at any time (90% CI: 26.2-53.1%). Six patients (15.8%, 90% CI: 7.1-28.8%) had a ≥50% reduction from baseline to week 24 in TSS and 5 patients (12.2%, 90% CI: 4.9-23.9%) had a ≥35% reduction in spleen volume; in those patients with week 24 data, the TSS and splenic response rates were 28.6% and 19.2% respectively. TSS and spleen volume assessments were not available for 17 (44.5%) and 15 (36.6%) patients, respectively, and these patients were considered non-responders. Adverse events were consistent with previous studies of MMB in MF, with cough, diarrhea, nausea, and fatigue as the most common. AEs ≥Gr 3 were experienced by 21 patients, most commonly anemia and neutropenia. At every study visit, median blood hepcidin decreased 6 hours after dosing with MMB (Fig. 1). Daily inhibition of hepcidin did not lead to an increase in serum iron for the entire population. However, serum iron, transferrin, hemoglobin, reticulocytes, and hematocrit increased at week 2 in patients with TI-R. Following this peak, serum iron decreased while hemoglobin, hematocrit and platelet count increased through week 24. At baseline, TI-R was associated with lower hepcidin, LIC, serum iron, reduced inflammation (C-reactive protein and ferritin), and higher hematocrit, erythrocytes, reticulocytes, platelets, and hemoglobin than TI-NR (Fig. 2). In multivariable analysis, TI-R was strongly associated with baseline hemoglobin ≥8g/dL (p=0.036) and lower morning hepcidin (p=0.013), weakly associated with younger age (p=0.070) and lower DIPSS score (p=0.075), but not with gender, type of MF (primary vs post-ET/PV), spleen volume, TSS, or JAK2V617F mutation. Conclusion: Safety findings and rate of TI-R were similar to TD MF patients in other MMB trials. Consistent with preclinical data, daily MMB treatment led to a transient decrease in blood hepcidin. In patients with TI-R, hepcidin suppression was associated with increased iron availability and markers of erythropoiesis. At baseline, TI-R associated with reduced inflammation, lower hepcidin, and increased markers of erythropoiesis and bone marrow function. Overall, the study suggests that transient modulation of hepcidin by MMB is sufficient to boost erythropoiesis in those transfusion-independent MF patients with lower baseline inflammation and greater erythropoietic potential. Disclosures Oh: Takeda: Research Funding; Janssen: Research Funding; CTI Biopharma: Research Funding; Gilead: Research Funding; Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Gerds:Celgene: Consultancy; Apexx Oncology: Consultancy; CTI Biopharma: Consultancy; Incyte: Consultancy. Gupta:Novartis: Consultancy, Honoraria, Research Funding; Incyte: Research Funding. Verstovsek:Italfarmaco: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Incyte: Consultancy; Celgene: Membership on an entity's Board of Directors or advisory committees. Mesa:Novartis: Consultancy; Celgene: Research Funding; NS Pharma: Research Funding; Genentech: Research Funding; Incyte Corporation: Research Funding; Promedior: Research Funding; Pfizer: Research Funding; CTI Biopharma: Research Funding; Gilead: Research Funding; UT Health San Antonio - Mays Cancer Center: Employment. Miller:Gilead Sciences, Inc.: Consultancy, Research Funding; Incyte: Consultancy, Honoraria, Research Funding, Speakers Bureau; Novartis: Honoraria, Research Funding, Speakers Bureau. Heaney:Decipheral: Research Funding; Novartis: Research Funding; Blueprint: Research Funding; Incyte: Research Funding; Roche: Consultancy, Research Funding. O'Connell:Incyte: Research Funding. Arcasoy:Gilead Sciences, Inc.: Research Funding; Incyte: Research Funding; CTI BioPharma: Research Funding; Samus Therapeutics: Research Funding. Zhang:Gilead Sciences, Inc.: Employment. Kawashima:Gilead Sciences, Inc.: Employment, Equity Ownership. Ganz:Intrinsic LifeScience: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Silarus Pharma: Consultancy, Equity Ownership; Keryx Pharma: Consultancy, Research Funding; Akebia: Consultancy, Research Funding; Vifor: Consultancy; Gilead: Consultancy; Ablynx: Consultancy; La Jolla Pharma: Consultancy, Patents & Royalties: Patent licensed to La Jolla Pharma by UCLA. Baker Brachmann:Gilead Sciences, Inc.: Employment, Equity Ownership.