Academic literature on the topic 'ACE-011'

Abstract Abstract 749 Background: Anemia is frequently observed in multiple myeloma (MM) patients and can result from cumulative marrow suppression by chemotherapy, invasion of bone marrow by tumor cells, renal insufficiency and other causes. The vast majority of therapies approved or in development for anemia target the erythropoietin (EPO) pathway. However, recent studies suggest that the use of recombinant EPO and its derivatives may be associated with an increased risk of mortality by stimulating tumor progression and/or the occurrence of thromboembolic events. The TGF-β superfamily of proteins has been reported to play a major role in red blood cell (RBC) development, but utilizes a fundamentally different pathway from EPO. ACE-011 is a novel, fully human, fusion protein derived from the activin receptor type IIA (ActRIIA) that binds to and prevents signaling of certain members of the TGF-β superfamily through the ActRIIA receptor. In animal studies, administration of ACE-011 has been shown to increase hemoglobin and RBC levels, promote bone formation, and inhibit breast cancer and MM tumor growth. We previously reported significant increases of hemoglobin, RBC levels, and bone mineral density observed in healthy volunteers who received ACE-011 (ASH, 2008). Here, we report the preliminary results of a randomized, double-blind, placebo-controlled study of ACE-011 in MM patients receiving a regimen of melphalan, prednisolone, and thalidomide (MPT). Methods: Patients with stage II/III multiple myeloma and evidence of osteolytic bone disease were eligible to be enrolled in this study, and randomized to receive either up to 4 monthly subcutaneous (SC) doses of ACE-011 at 0.1, 0.3 and 0.5 mg/kg (n=8 each) or placebo (n=6). All patients received a standardized regimen of MPT. Patients could not have received ESAs ≤ 21 days prior to initiation or during the course of study; bisphosphonate (BP) use was allowed only as a continuation of established therapy at stable doses (≥ 2 months). Results: A total of 30 patients were enrolled. The median age was 61.5 years (ranging from 41 to 79 years). Twenty-eight patients had at least one prior MM therapy (range 1-7 prior therapies), and 13 were on stable BPs. A total of 20 patients skipped at least one dose of ACE-011 or placebo based on dose modification rules. Two patients discontinued study drug prematurely: 1 withdrew consent and 1 due to an adverse event. An SAE of sudden death, cause unknown and considered “probably”-related to MPT or “possibly”-related to ACE-011, occurred 18 days after the last dose of ACE-011 (0.1 mg/kg). Dose-dependent increases in hemoglobin were observed after the first dose of ACE-011. After the first dose, the mean maximum Hb increase was 1.3 g/dL (±1.1) in the 0.5 mg/kg cohort compared to 0.68 g/dL (±0.29) in the placebo group. On day 29 of the study, 75% patients had an increase in Hb of ≥1 g/dL in the 0.5 mg/kg cohort compared to 33% in placebo group. A hemoglobin response defined as an increase of at least 1.5 g/dL increase for consecutive 28 days during study was achieved by 10 (45%) ACE-011 treated patients and 1 (17%) patient on placebo. ACE-011 substantially increased BSAP and slightly decreased S-CTX levels among BP-naïve patients. After the first dose of ACE-011, 6 patients (20%) were reported to have ≥10 mm reduction in pain, as measured by the Visual Analog Scale (VAS), which was sustained during the study. A greater trend to improvement in osteolytic lesions by skeletal X-rays was seen in ACE-011-treated patients. Of 22 evaluable patients treated with ACE-011, 7 patients (32%) achieved a CR or VGPR. Conclusions: ACE-011 is well-tolerated and has significant hematologic activity in MM patients receiving myelosuppressive chemotherapy. ACE-011 treatment also demonstrated clinically significant increases in biomarkers of bone formation, improvement in skeletal metastases, decreases in bone pain, and anti-tumor activity. The unique pharmacology of ACE-011 enables it to address multiple complications of MM, and presents a novel target to treat the underlying disease as well. These findings also demonstrate that ACE-011 has potential as a novel therapy for chemotherapy-induced anemia and may be an effective alternative to EPO-based treatments. To further explore the potential of this novel agent, a phase 2 study investigating ACE-011 in metastatic breast cancer patients with chemotherapy-induced anemia is currently underway. This study was supported in part by a grant from the Multiple Myeloma Research Foundation. Disclosures: Abdulkadyrov: Acceleron: Research Funding. Salogub:Acceleron: Research Funding. Khuazheva:Acceleron: Research Funding. Woolf:Acceleron: Employment, Equity Ownership. Haltom:Acceleron: Employment, Equity Ownership. Borgstein:Acceleron: Employment, Equity Ownership. Knight:Celgene: Employment, Equity Ownership. Renshaw:Celgene: Employment, Equity Ownership. Yang:Acceleron: Employment, Equity Ownership. Sherman:Acceleron: Employment, Equity Ownership.

Abstract ACE-011 is a soluble fusion protein consisting of the extracellular domain of activin receptor IIA linked to the Fc portion of human IgG1 and is a potent activin antagonist. ACE-011 is currently in clinical development for the treatment of bone loss in a variety of disease indications. In addition to its effect on bone forming cells, activin is also known as erythroid differentiation factor (EDF) and has been reported to have proerythrocytic effects and induced terminal differentiation of red blood cells (RBC). In preclinical studies, ACE-011 administration to mice and cynomolgus monkeys is associated with increases in erythropoiesis. A randomized, double-blind, placebo-controlled, multiple-dose, dose-escalation study was conducted in healthy postmenopausal women to evaluate the safety, tolerability and pharmacodynamics of ACE-011 in 4 cohorts of 10 subjects (8 active: 2 placebo). Subjects were to receive 4 monthly doses of ACE-011 at 0.1, 0.3, 1.0 and 2.0 mg/kg or placebo by subcutaneous (SC) route of administration and followed up for 3 months. Safety evaluations were conducted on each cohort prior to dose escalation. A total of 31 subjects received at least one dose of ACE-011 or placebo; 9 subjects in cohort 1 (0.1 mg/kg) received all 4 doses, 10 subjects in cohort 2 (0.3 mg/kg) received 3 doses and 9 subjects in cohort 3 (1 mg/kg) received 2 doses of either ACE-011 or placebo. A dose and time dependent increase in hemoglobin values was observed in all treatment groups; these elevations were statistically significant in the 0.3 and 1.0 mg/kg cohorts. A maximum tolerated dose level was determined to be 1 mg/kg after one subject experienced progressive and persistent hypertension that was attributed to a rapid and significant rise in hemoglobin levels approximately 1 week following her second dose of ACE-011. Increases in hemoglobin and hematocrit represent the dose limiting pharmacodynamic effects of ACE-011, and further dose escalation to the 2 mg/kg dose was suspended. These effects were seen in the red cell lineage; no significant effects on white blood cells or platelets were observed. JAK2 kinase activity was measured in 3 subjects with elevated hemoglobin levels after ACE-011 treatment and was negative. Preliminary analysis of the data, 29 days after the administration of the first dose, is shown below. Δ Hemoglobin (g/dL) from baseline Placebo (n=7) 0.1 mg/kg (n=8) 0.3 mg/kg (n=8) 1 mg/kg (n=8) * p<0.05, ** p<0.01 compared to placebo Day 8 Mean (SD) 0.171 (0.399) 0.675 (0.403) 0.85 (0.563)* 1.213 (0.506)** Median 0.3 0.65 0.75 1.25 Min, Max −0.3, 0.7 0.20, 1.2 0.2, 1.6 0.4, 2.0 Day 15 Mean (SD) −0.35 (0.695) 0.425 (0.413) 0.438 (0.912)* 1.75 (0.685)** Median −0.55 0.6 0.3 1.5 Min, Max −1.1, 0.8 −0.3, 0.9 −0.6, 2.4 0.9, 3.1 Day 29 Mean (SD) 0.34 (0.207) 0.613 (0.323) 1.212 (0.909) * 2.675 (0.997)** Median 0.4 0.7 1.15 2.45 Min, Max 0, 0.5 −0.1, 1.0 0.1, 2.8 1.7, 4.4 In one of the subjects with a history of chronic anemia, as a result of iron deficiency, the hemoglobin level increased by almost 2 g/dL from a baseline value of 8.4 g/dL following the first SC dose of 1 mg/kg ACE-011, and reached a level of 11 g/dL within 3 weeks after the second dose of ACE-011. ACE-011 was generally well tolerated, except for the case described above with uncontrolled hypertension at the 1 mg/kg dose level. The majority of the non-hematological treatment-emergent adverse events were mild in severity and not related to study drug. A dose-dependent decrease in serum FSH levels, a biological marker of activin inhibition, was also observed in postmenopausal subjects following treatment with ACE-011. These data indicate that ACE-011 is associated with increases in hemoglobin and hematocrit levels in both healthy volunteers as well as in a subject with iron deficiency anemia and may be a potential novel agent for the treatment of patients with impaired erythropoiesis.

Background Anemia is common in patients (pts) with myeloproliferative neoplasm (MPN)-associated myelofibrosis (MF). Furthermore, anemia is an on-target effect of therapeutic Janus kinase 2 (JAK2) inhibition, and may be the most frequent cause of ruxolitinib (rux) discontinuation (d/c) in clinical practice (Kuykendall, Ann Hematol 2018). Current therapies for anemia of MF (erythropoietin and analogs, danazol, IMiDs®) are unsatisfactory. Sotatercept (ACE-011) is a first-in-class, activin receptor type IIA ligand trap that may improve anemia by sequestering stromal transforming growth factor beta superfamily ligands that suppress terminal erythropoiesis (Iancu-Rubin, Exp Hematol 2013). Methods This is a phase 2, investigator-initiated, open-label, single institution study of sotatercept, administered subcutaneously every 3 weeks, in 2 cohorts of anemic pts (Hgb &lt;10 g/dl on every determination for 12 weeks (wks) or transfusion-dependent (TD) per IWG-MRT criteria (Tefferi, Blood 2013)) with MF: as a single agent, and in combination with a stable dose of rux. Pts on rux must have been on rux for ≥6 months with a stable dose for ≥8 weeks, and receive sotatercept at a dose of 0.75 mg/kg. Monotherapy pts receive either 0.75 or 1 mg/kg of sotatercept. In both cohorts, anemia response is defined as achievement of transfusion independence (TI) in TD pts, and an increase in Hgb level from baseline of ≥1.5 g/dl sustained for ≥12 wks in non-TD pts (Gale, Leuk Res 2011). Pts must have received ≥5 cycles of sotatercept to be response-evaluable. Results A total of 53 pts have been treated; one pt received only 0.3 mg/kg of sotatercept and is not considered further. Thirty one pts received sotatercept alone and 21 in combination with rux. Baseline characteristics appear in Table 1, panel A. Sixteen TD and 15 non-TD pts received sotatercept alone for a median of 5 (1-67) cycles. Thirteen pts received 0.75 mg/kg and 18, 1 mg/kg. Seven of 24 (29%) evaluable pts responded. Of these, 4 were anemia responses; 3 TD pts achieved TI. Five responses occurred at the 0.75 mg/kg dose, and 2 at the 1 mg/kg dose. Median time to response (TTR) was 21 (1-22) days and median duration of response (DOR) 13 (3.9-56.4) months. Seven pts (22.6%) received &lt;5 cycles and were not response-evaluable: 2 proceeded to stem cell transplant (SCT), 2 had logistical (travel) issues, and 1 each d/ced sotatercept because of hypertension (HTN), unrelated medical problems and pt decision. Three pts continue on study. Reasons for d/c included no response (11), progressive MF (6), SCT (3), travel logistics (3), patient decision (2), hypertension (1), unrelated medical complications (1) and transformation to AML (1). The combination cohort comprised 15 non-TD pts and 6 TD pts. The median number of cycles was 8 (2-43). Five of 17 (29%) evaluable pts in the combination cohort responded, all non-TD pts. Median TTR was 14 (7-147) days and median DOR 34.6 (3.1-47.9) months. Four pts (19%) received &lt;5 cycles and were not response-evaluable, 1 each due to MF progression, loss of insurance, SCT and pt decision. Five pts remain on study. Reasons for d/c included no response (6), SCT (4), progressive MF (2), travel logistics (2), loss of insurance (1) and pt decision (1). Several non-response-evaluable pts in both cohorts achieved ≥1.5 g/dl increments in Hgb from baseline that were not sustained for ≥12 wks because of early d/c of sotatercept. An additional pt in the combination cohort required a rux dose increase, leading to failure to sustain a ≥1.5 g/dl Hgb improvement. Across both cohorts, several responding pts required multiple protocol-specified drug holidays because of Hgb levels ≥11.5 g/dl, with resumption of sotatercept once Hgb was &lt;11 g/dl. Sotatercept was well-tolerated (Table 1, panel B). Grade 3 adverse events possibly related to sotatercept were HTN (n=7), limb (bone/muscle/joint) pain (n=3) and headache (1). Conclusions Sotatercept is safe and effective against anemia of MPN-associated MF, both in non-TD and TD pts, with a response rate of 29% both when used alone and in conjunction with a stable dose of rux. A total of 60 pts are planned to be treated on this trial (NCT01712308). Disclosures Bose: Blueprint Medicines Corporation: Honoraria, Research Funding; NS Pharma: Research Funding; Constellation Pharmaceuticals: Research Funding; Astellas Pharmaceuticals: Research Funding; Pfizer, Inc.: Research Funding; Incyte Corporation: Consultancy, Honoraria, Research Funding, Speakers Bureau; Celgene Corporation: Honoraria, Research Funding; CTI BioPharma: Honoraria, Research Funding; Promedior, Inc.: Research Funding; Kartos Therapeutics: Honoraria, Research Funding. Pemmaraju:Samus Therapeutics: Research Funding; AbbVie: Honoraria, Research Funding; MustangBio: Honoraria; SagerStrong Foundation: Other: Grant Support; Roche Diagnostics: Honoraria; Pacylex Pharmaceuticals: Consultancy; Plexxikon: Research Funding; Daiichi Sankyo: Research Funding; Stemline Therapeutics: Honoraria, Research Funding; Celgene: Honoraria; Incyte Corporation: Honoraria; Cellectis: Research Funding; Blueprint Medicines: Honoraria; Affymetrix: Other: Grant Support, Research Funding; Novartis: Honoraria, Research Funding; LFB Biotechnologies: Honoraria; DAVA Oncology: Honoraria. Daver:Fate Therapeutics: Research Funding; Bristol-Myers Squibb: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Karyopharm: Research Funding; Servier: Research Funding; Genentech: Research Funding; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novimmune: Research Funding; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Trovagene: Research Funding; Daiichi Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; KITE: Consultancy, Membership on an entity's Board of Directors or advisory committees; Agios: Consultancy, Membership on an entity's Board of Directors or advisory committees; ImmunoGen: Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Jazz: Consultancy, Membership on an entity's Board of Directors or advisory committees; Trillium: Consultancy, Membership on an entity's Board of Directors or advisory committees; Syndax: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees. Jabbour:BMS: Other: Advisory role, Research Funding; Amgen: Other: Advisory role, Research Funding; Pfizer: Other: Advisory role, Research Funding; AbbVie: Other: Advisory role, Research Funding; Takeda: Other: Advisory role, Research Funding; Adaptive Biotechnologies: Other: Advisory role, Research Funding; Genentech: Other: Advisory role, Research Funding. Kadia:Astellas: Research Funding; Pulmotec: Research Funding; Incyte: Research Funding; Ascentage: Research Funding; JAZZ: Honoraria, Research Funding; Cyclacel: Research Funding; Amgen: Research Funding; Celgene: Research Funding; Cellenkos: Research Funding; Genentech: Honoraria, Research Funding; BMS: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Novartis: Honoraria; Abbvie: Honoraria, Research Funding; Astra Zeneca: Research Funding. Andreeff:Daiichi-Sankyo; Jazz Pharmaceuticals; Celgene; Amgen; AstraZeneca; 6 Dimensions Capital: Consultancy; Amgen: Research Funding; Daiichi-Sankyo; Breast Cancer Research Foundation; CPRIT; NIH/NCI; Amgen; AstraZeneca: Research Funding; Centre for Drug Research & Development; Cancer UK; NCI-CTEP; German Research Council; Leukemia Lymphoma Foundation (LLS); NCI-RDCRN (Rare Disease Clin Network); CLL Founcdation; BioLineRx; SentiBio; Aptose Biosciences, Inc: Membership on an entity's Board of Directors or advisory committees. Cortes:Bristol-Myers Squibb: Research Funding; Pfizer: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; Sun Pharma: Research Funding; BioPath Holdings: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Telios: Research Funding; Astellas: Research Funding; Amphivena Therapeutics: Research Funding; Arog: Research Funding; BiolineRx: Consultancy, Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Jazz Pharmaceuticals: Consultancy, Research Funding; Merus: Research Funding; Immunogen: Research Funding; Novartis: Consultancy, Research Funding. Jain:BMS: Research Funding; Pharmacyclics: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Verastem: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Adaptive Biotechnologies: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Cellectis: Research Funding; TG Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Aprea Therapeutics: Research Funding; Precision Bioscienes: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Servier: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Fate Therapeutics: Research Funding; AstraZeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Incyte: Research Funding; BeiGene: Honoraria, Membership on an entity's Board of Directors or advisory committees; ADC Therapeutics: Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Genentech: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Research Funding. Borthakur:Nkarta Therapeutics: Consultancy; Treadwell Therapeutics: Consultancy; PTC Therapeutics: Research Funding; Jannsen: Research Funding; Abbvie: Research Funding; Novartis: Research Funding; Incyte: Research Funding; Polaris: Research Funding; Xbiotech USA: Research Funding; Oncoceutics: Research Funding; Curio Science LLC: Consultancy; FTC Therapeutics: Consultancy; Argenx: Consultancy; PTC Therapeutics: Consultancy; BioLine Rx: Consultancy; BioTherix: Consultancy; Cyclacel: Research Funding; GSK: Research Funding; BioLine Rx: Research Funding; BMS: Research Funding; AstraZeneca: Research Funding. Alvarado:Sun Pharma: Research Funding; Astex Pharmaceuticals: Research Funding; MEI Pharma: Research Funding; Daiichi-Sankyo: Research Funding; Tolero Pharmaceuticals: Research Funding; FibroGen: Research Funding; Jazz Pharmaceuticals: Research Funding; BerGenBio ASA: Research Funding. Huynh-Lu:Incyte Corporation: Speakers Bureau. Nguyen-Cao:Incyte Corporation: Speakers Bureau. Garcia-Manero:Acceleron Pharmaceuticals: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding; Jazz Pharmaceuticals: Consultancy; Novartis: Research Funding; Onconova: Research Funding; Helsinn Therapeutics: Consultancy, Honoraria, Research Funding; Merck: Research Funding; AbbVie: Honoraria, Research Funding; H3 Biomedicine: Research Funding; Astex Pharmaceuticals: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amphivena Therapeutics: Research Funding. Kantarjian:Oxford Biomedical: Honoraria; Actinium: Honoraria, Membership on an entity's Board of Directors or advisory committees; Delta Fly: Honoraria; Janssen: Honoraria; Ascentage: Research Funding; BioAscend: Honoraria; Amgen: Honoraria, Research Funding; Aptitute Health: Honoraria; Immunogen: Research Funding; Jazz: Research Funding; Novartis: Honoraria, Research Funding; Sanofi: Research Funding; Pfizer: Honoraria, Research Funding; Daiichi-Sankyo: Honoraria, Research Funding; BMS: Research Funding; Adaptive biotechnologies: Honoraria; Abbvie: Honoraria, Research Funding. Verstovsek:Sierra Oncology: Consultancy, Research Funding; Gilead: Research Funding; Celgene: Consultancy, Research Funding; CTI Biopharma Corp: Research Funding; Roche: Research Funding; NS Pharma: Research Funding; Promedior: Research Funding; Novartis: Consultancy, Research Funding; AstraZeneca: Research Funding; ItalPharma: Research Funding; Protagonist Therapeutics: Research Funding; PharmaEssentia: Research Funding; Incyte Corporation: Consultancy, Research Funding; Blueprint Medicines Corp: Research Funding; Genentech: Research Funding.

Abstract Background The hemoglobin (Hb) response to the activin receptor type IIA ligand trap ACE-011 (Sotatercept) in non-transfusion-dependent thalassemia (NTDT), and the transfusion requirement response in TDT are described, but the mechanisms of action, clinical predictors and markers of response, are unclear. In principle, ACE-011 may act on early and/or late erythroblasts to decrease ineffective erythropoiesis (IE), both in healthy subjects and in thalassemia. As erythropoiesis intimately links to iron metabolism, changes in markers of iron metabolism relative to those of erythropoiesis may inform the mechanisms and developmental stage at which ACE-011 acts. Methods Markers of IE and iron metabolism in 46 thalassemia patients (30 NTDT, 16 TDT) were taken before and during a median follow up of 722.5 days, (IQR 830.5, range 152-1427) of escalating doses of ACE-011 (3-weekly 0.1 to 1.0 mg/kg s.c. injections), depending on the protocol, as part of the approved study (Cappellini, et al. 2018 under review). Markers of erythropoiesis included Hb, Reticulocytes (Ret), soluble transferrin receptor 1 (sTfR), growth differentiation factor 11 and 15 (GDF11, GDF15), erythroferrone (ERFE). Markers of iron metabolism included plasma hepcidin, serum ferritin (SF), transferrin saturation (TSAT), and non-transferrin-bound iron (NTBI). Data were analyzed using longitudinal multilevel model for change (LMMC) on STATA (Version 14) as generalized linear mixed model with random and fixed effects to account for repeated measures and highly complex temporal data structure. Final LMMCs were built to explain the change in Hb from baseline and the behavior of key biomarkers. Independent variables were entered into the models based on the study design (predictors from design) and theoretical background (predictors of interest and control variables). P value <0.05 was considered statistically significant. Results Predictors of response. In NTDT, Hb response associated positively with dose and duration of exposure (both at p<0.0001), and negatively with baseline EPO (p=0.002), GDF15 (p<0.0001) or TSAT. In TDT, accounting for transfusion effect, baseline GDF15 and EPO positively predicted Hb response while ERFE was a negative predictor (all at p<0.0001). Biomarker changes with time In NTDT, significant changes with time on study were increases in Hb, sTfR, ERFE and Ret and decreases in hepcidin, bilirubin, and NTBI. GDF15 showed no change. In TDT, GDF15, sTfR and ERFE increased, whereas hepcidin decreased. The Hb change was insignificant in TDT (as expected per protocol) and was dose-independent, however the mean 41% reduction in transfusion iron load rate (ILR) was dose dependent, implying an equivalent net production of Hb in TDT (Table 1). Other significant relationships Absolute hepcidin level in NTDT and TDT was negatively predicted by ERFE (p<0.0001): the first longitudinal demonstration of this association in thalassemia patients. GDF11, the target for ACE-011 that was shown previously to negatively regulate erythroid differentiation (Dussiot et al, Nat Med 2014), fell significantly on study (preliminary data). Significant reduction in indirect bilirubin in NTDT, implying reduced hemolysis, suggests improved quality of produced erythrocytes. Interpretation and conclusions NTDT patients allow a cleaner interpretation of biomarker changes as these are confounded in TDT by increased bone marrow stress from less transfusion. In NTDT, sTfR and ERFE (total erythropoiesis) increase on study while GDF15 (IE) and EPO do not. Thus Hb gain may result from increased effectiveness of late stage erythropoiesis (sTfR+ and ERFE+) possibly from decreased apoptosis and more rapid maturation (Carrancio et al, BJH 2014) in this compartment. We speculate that increased survival of those erythroid progenitor cells expressing TfR (and hence sTfR) and ERFE (hence increased ERFE) also explains the observed hepcidin reduction. Despite exposure to lower hepcidin, there is no iron loading: NTBI falls against stable SF in NTDT, consistent with shunting of iron into the sink of effective erythropoiesis. The reduction in GDF11 in vivo, not previously reported for ACE-011, is also consistent with increased apoptosis of the early progenitor pool and with improved erythroblast differentiation relative to proliferation as suggested in murine β-thalassemia treated with ACE-011 (Dussiot, et al. Nat Med 2014). Disclosures Garbowski: Vifor: Consultancy. Hermine:Erythec: Research Funding; AB Science: Consultancy, Equity Ownership, Honoraria, Research Funding; Celgene Corporation: Research Funding; Hybrigenics: Research Funding; Novartis: Research Funding. Cappellini:Sanofi/Genzyme: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria; Vifor: Membership on an entity's Board of Directors or advisory committees; Celgene Corporation: Membership on an entity's Board of Directors or advisory committees. Origa:Bluebird Bio: Consultancy; Novartis: Honoraria; Cerus Corporation: Research Funding; Apopharma: Honoraria. Forni:Celgene: Research Funding; Novartis: Other: travel expenses, Research Funding; Shire: Research Funding; Roche: Consultancy; Apopharma: Other: DSM Board. Voskaridou:Acceleron: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene Corp: Membership on an entity's Board of Directors or advisory committees, Research Funding. Galactéros:Addmedica: Other: grant; Novartis: Other: grant. Taher:Novartis: Consultancy, Honoraria, Research Funding; La Jolla Pharmaceutical: Research Funding; Protagonist Therapeutics: Consultancy; Celgene Corp.: Research Funding; Ionis Pharmaceuticals: Consultancy. Ribeil:bluebird bio: Consultancy; Vitalaire: Other: grant; Addmedica: Other: grant; Cydan: Consultancy; Novartis: Consultancy. Laadem:Celgene: Employment, Equity Ownership. Miteva:Celgene Corporation: Employment, Other: grants. Zou:Celgene Corporation: Employment, Equity Ownership. Zinger:Celgene Corporation: Employment. Schwickart:Celgene Corporation: Employment, Equity Ownership. Sung:Celgene Corporation: Employment, Equity Ownership. Porter:Novartis: Consultancy; Cerus: Honoraria; Agios: Honoraria.

Abstract Introduction: Anemia is common in MPN-associated myelofibrosis (MF), and current therapies (e.g., erythropoiesis stimulating agents, androgens, danazol, immune modulatory drugs and corticosteroids) are unsatisfactory. Furthermore, anemia is not improved and initially worsened by ruxolitinib, an important MF therapy. New drugs with novel mechanisms of action are needed. Sotatercept is a first-in-class activin receptor type IIA (ActRIIA) ligand trap consisting of the extracellular domain of ActIIRA linked to the human IgG1 Fc domain. Sotatercept binds to and sequesters ligands of the transforming growth factor beta (TGF-ß) superfamily, thus relieving their blockade of terminal erythroid differentiation. Pre-clinically, sotatercept corrects ineffective erythropoiesis in ß-thalassemia (Dussiot, M. et al. Nat Med 2014) and its murine ortholog RAP-011 improves erythropoiesis in Diamond Blackfan anemia (Ear, J. et al. Blood 2015). Clinical trials in persons with lower risk myelodysplastic syndromes (Komrokji, R. et al. ASH 2014) and chemotherapy-induced anemia (Raftopoulos, H. et al. Support Care Cancer 2016) have shown promising results. Methods: This is an ongoing phase-2 study of sotatercept, 0.75 or 1 mg/kg subcutaneously every 3 weeks (1 cycle), in subjects with MF, whether primary (PMF) or post-polycythemia vera/essential thrombocythemia (post-PV/ET MF). Subjects must be RBC-transfusion-dependent (Gale, R.P. et al. Leuk Res 2011), have hemoglobin <10 g/dL on every determination during the 84 days preceding study entry without RBC transfusions, or have hemoglobin <10 g/dL despite intermittent RBC transfusions without fulfilling the criteria for transfusion dependence. Primary endpoints include anemia response and safety. Secondary endpoints include time to and duration of anemia response. Anemia response is a composite of RBC-transfusion-independence and hemoglobin response (increase of ≥1.5 g/dL from baseline on every determination consecutively over ≥84 days without RBC transfusions). Subjects must have received ≥5 cycles of sotatercept to be evaluable for response. Results: 18 subjects are enrolled to date. 1 subject received 6 cycles at a sub-therapeutic dose of 0.3 mg/kg and was not considered for efficacy evaluation, but was evaluable for safety. Of the remaining 17 subjects, 11 received 0.75 mg/kg and 6, 1 mg/kg. Median age was 67 years (range, 47-84 years); 10 were male and 7 female. 14 had PMF and 3, post-ET MF. 12 subjects had JAK2 V617F, 1 had MPLW515L and 2 had CALR exon 9 mutations. 1 subject was triple negative and 1 subject had no JAK2 or MPL mutation but was not tested for CALR mutations. All 17 subjects had intermediate-2 or high risk disease by the Dynamic International Prognostic Scoring System. Table 1 summarizes baseline variables for these 17 subjects. Median number of cycles of sotatercept received is 5 (range, 1-13). 14 of the 17 subjects received ≥5 cycles and were evaluable for response. The 3 other subjects received 1, 2 and 2 cycles and discontinued due to unrelated medical problems, hypertension and stem cell transplant (SCT), respectively. 5 of 14 (36%) evaluable subjects have responded; 4 of whom continue on study in ongoing response. All responders are female and all female subjects evaluable for response responded. Responses occurred across phenotypic driver mutation categories and in both transfusion-dependent (n=3) and -independent (n=2) subjects. 40% and 25% of evaluable patients responded in the 0.75 mg/kg and 1 mg/kg dose cohorts, respectively. Most adverse events (AEs) were grades 1 or 2. The only AEs possibly attributable to sotatercept include grade 3 hypertension leading to discontinuation, and grade 1 myalgia, bone pain, pain in extremity and injection site reaction. 5 subjects remain on study. 12 have discontinued because of no response (5), SCT (2), unrelated medical problems (1), hypertension (1), disease progression (1), transformation to AML (1) and withdrawal of consent (1). Conclusion: Sotatercept improves anemia and RBC-transfusion-dependence in persons with MF and is well-tolerated. Enrollment to the trial is ongoing; updated results will be presented. A separate cohort of subjects receiving ruxolitinib has been added and will also be discussed. Based on the preponderance of responses at the 0.75 mg/kg dose, this dose has been selected for the combination cohort. Disclosures Daver: Incyte: Consultancy, Other: Advisory board, Research Funding. Jabbour:ARIAD: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Novartis: Research Funding; BMS: Consultancy.

Abstract Diamond Blackfan Anemia (DBA) is a bone marrow failure disorder characterized by low red blood cell count but normal levels of platelets and white blood cells. Ribosomal mutations in RPS19, RPS26, RPL5, and RPL11 have been identified in approximately 50% of all DBA cases. Corticosteriod therapy and bone marrow transplantion are the most common treatment options for DBA patients. However, corticosteroids have severe side effects and bone marrow transplantation is risky; thus, novel therapeutics for DBA are needed. Sotatercept (ACE-011), an activin receptor IIA ligand trap which rapidly increased hemoglobin and hematocrit in both pharmacologic models and in healthy volunteers, is currently being evaluated in diseases of ineffective erythropoiesis such as ß-thalassemia and MDS. Non-clinical studies in mice have demonstrated that RAP-011, a murine ortholog of sotatercept, stimulates RBC parameters in mice through stimulating expansion of late-stage erythroblasts through a mechanism distinct from EPO. Here, we evaluated the effect of RAP-011 in zebrafish models of ribosome insufficiency in RPS19 and RPL11 that recapitulate the anemic phenotype seen in DBA patients. Treatment with RAP-011 treatment dramatically restored hemoglobin levels compromised by ribosome stress. Furthermore, the beneficial effect of RAP-011 is synergistic with corticosteriod treatment. In zebrafish embryos, RAP-011 likely stimulates erythropoietic activity by altering the microenvironment of erythroid cells, reducing p21 levels through a p53-independent manner. These findings uncover a novel signaling pathway in the pathogenesis of DBA and support the potential use of Sotatercept for the treatment of DBA patients with ribosomal disorders. Our studies also demonstrate, for the first time, that protein drugs can be effectively evaluated in zebrafish human disease models, which offer a unique opportunity to identify the targets and study their mechanisms of action. Disclosures: Sung: Celgene Corp.: Employment. Daniel:Celgene: Employment. Chopra:Celgene: Employment, Equity Ownership. Lin:Celgene: Research Funding.

Abstract Abstract 4075 The introduction of novel treatment strategies targeting tumor cells within their microenvironment have resulted in prolonged survival for Multiple Myeloma (MM) patients. Lenalidomide belongs to this category of agents working via tumoricidal, anti-osteoclast and immunomodulatory activities. However, lenalidomide lacks bone anabolic effects. We have recently reported that activin A mediates osteoblast inhibition in MM and neutralizing activin A via a soluble receptor, RAP-011 (murinized form of ACE-011) (Acceleron Pharma, Cambridge, MA), restores bone architecture and reduces tumor burden in vivo. We therefore hypothesized that the combination with RAP-011 may potentiate lenalidomide effects and vice versa as they act via complementary mechanisms. Our previous data demonstrates that 50% of MM patients have increased bone marrow (BM) levels of activin A that correlate with osteolytic burden. Here, we observed that 2 and 10 μ M lenalidomide (Selleck Chemicals, Houston, TX) upregulated activin A in 3 out 6 bone marrow stromal cell (BMSC) samples by 1.9 and 2.8 fold (average ± st.dev. 1052 ± 190 and 1667 ± 732 pg/ml respectively, compared to 734 ± 553 in control, p=0.2). There was no time-dependent upregulation of activin A. Of note, no augmentation of activin A was noted in BMSC which already expressed high baseline levels of the cytokine (average ± st.dev 3638 ± 3755 pg/ml in control vs 3074 ± 2997 after lenalidomide 10 μ M). Previous data suggest that high concentrations of activin A induce growth arrest and apoptosis in myeloma and breast cancer cells and may therefore mediate lenalidomide cytotoxicity. To ensure that inhibition of activin would not antagonize lenalidomide anti-tumor effects, we investigated whether activin A inhibition affected the cytotoxic and anti-proliferative effects of lenalidomide on MM cells alone and in co-culture with BMSC. As previously demonstrated, RAP-011 did not exert any direct anti-tumor effects. Lenalidomide 10 μ M induced between 20 and 40% of apoptosis in several myeloma cell lines, such as MM1.S, LR5, DOX40 and RPMI, independent of activin A inhibition. Similarly, lenalidomide almost completely reversed the proliferative advantage conferred by BMSC to tumor cells. Combining lenalidomide and RAP-011 was not antagonistic to the inhibition of the proliferative advantage conferred by BMSC to myeloma cells, suggesting that lenalidomide's direct anti-tumor activity is not mediated through activin A. Finally we assessed OB differentiation in the presence of both RAP-011 and lenalidomide. We have previously reported that activin A inhibitory effects on OB differentiation are reversed by RAP-011 treatment. Here, we noted diminished alkaline phosphatase (ALP, a marker of osteoblast activity) expression during osteoblastogenesis in the presence of increasing concentrations of lenalidomide (17% ± 3 decrease by 2 μ M and 26% ± 11 by 10 μ M compared to control, p=0.01 and 0.06 respectively). In contrast, combination with RAP-011 restored the osteogenic potential by increasing ALP expression close to control levels in healthy donor-derived BMSC and above control levels in MM-derived BMSC. These preliminary data suggest that lenalidomide results in upregulation of activin A expression in MM BMSCs which have low baseline levels. Combining lenalidomide with RAP-011 results in restored osteogenesis presumably by inhibiting activin signaling. Importantly, we observed no antagonistic effect of RAP-011 on lenalidomide's anti-tumor activity, confirming that activin A does not mediate the anti-tumor activity of lenalidomide. Ongoing in vivo studies using a murine model of myeloma will confirm the efficacy of this promising combination. Our results provide a preclinical rationale for combining lenalidomide with ACE-011 to target myeloma by manipulating the microenvironmental compartment, specifically the bone compartment. Disclosures: Seehra: Acceleron Pharma: Employment. Scadden:Fate Therapeutics: Consultancy, Equity Ownership, Patents & Royalties. Raje:Celgene, Novartis: Consultancy; Astrazeneca, Acetylon: Research Funding; Celgene, Amgen: Membership on an entity's Board of Directors or advisory committees.

Congenital Dyserythropoietic Anemias (CDAs) are subtypes of bone marrow failure syndromes, hallmarked by ineffective erythropoiesis. The most common form is CDA type II (CDAII), showing moderate/severe anemia, relative reticulocytopenia, jaundice, splenomegaly, and iron overload. It is inherited as an autosomal recessive disorder due to loss-of-function mutations in the SEC23B gene. Molecular pathogenesis of CDA II still has to be investigated because the described animal models did not recapitulate the clinical features observed in humans. To date, treatments for CDAII patients consist of supportive therapy, such as erythrocyte transfusions, or bone marrow transplantation or splenectomy in transfusion-dependent cases. Recently, members of TGF-β superfamily have been studied as potential regulators of erythropoiesis, especially the growth differentiation factor 11 (GDF11). Through the binding of specific receptors, GDF11 leads to an inhibited late-stage erythropoiesis. Indeed, two GDF11 inhibitors, ACE-011 and ACE-536, have been associated with an improvement of hematologic parameters. Studies with the mouse counterpart of ACE-011, RAP-011, on a mouse model of β-thalassemia showed increased differentiation of erythroid cells, improvement of the anemic condition and reduced iron overload in treated mice. The first aim of our study was the establishment of a cellular model of CDA II, that could reproduce the main defects of the disease, such as the lack of the erythroid differentiation due to the low or absent expression of SEC23B gene. For this aim, we selected the K562 cell line and, through short-hairpin RNA-based strategy, we obtained two different clones of K562 showing a stable silencing of SEC23B. Then, we decided to assess the effects of RAP-011 on this CDA II model, by investigating the pathway involved in the GDF11 signaling. This treatment simulated the ligand trap function played by RAP-011 towards GDF11. The administration of RAP-011 resulted in a reduction of SMAD2 phosphorylation induced by GDF11 and, moreover, in an increase of different erythroid differentiation markers.

Background: Problematic marijuana use is highly prevalent globally, particularly in young adults, with marijuana use disorder affecting 5.8%, or 2.0 million, of young adults (ages 18 – 25) in the United States alone (SAMHSA, 2020). Previous research has reported a significant association between Adverse Childhood Experiences (ACEs) and later marijuana use (Scheidell et al., 2018). Though existing research reports an association between exposure to ACEs and marijuana use outcomes, the underlying mechanisms that could explain these associations are unclear. In previous research, general drug use coping motives have been shown to significantly mediate the relationship between childhood emotional, physical, and sexual abuse and later drug use problems (Hogarth et al., 2019). Other research has suggested that the factors like distress tolerance, typically negatively associated with childhood trauma (Robinson et al., 2021) and maladaptive coping strategies (Zvolensky et al., 2010), can also play a role in specifically predicting future problematic marijuana use (Buckner et al., 2018). Objective: The present study aimed to probe this relationship by exploring the associations between ACEs, distress tolerance, marijuana use coping motives, and negative marijuana-related consequences. Specifically, we hypothesized that greater experiences of ACEs would relate to more negative marijuana-related consequences via lower distress tolerance and higher coping motives. Method: Participants were 752 marijuana-using (i.e., used marijuana in the past month) U.S. college students (66.0% female) who completed an online survey including measures of basic marijuana use patterns, marijuana use consequences (Brief Marijuana Consequences Questionnaire (MACQ); Simons et al., 2012), marijuana use motivations (Marijuana Motives Questionnaire (MMQ); Simons et al., 1998), ACEs (Adverse Childhood Experiences International Questionnaire (ACE-IQ); WHO, 2018), and distress tolerance (Distress Tolerance Scale, Simons et al., 2005). To address study aims, path analysis was performed within the whole sample to test the serial unique associations between ACEs → distress tolerance → using marijuana to cope → negative marijuana-related consequences. Results: Within our analytic sample, we found that only marijuana coping motives uniquely indirectly influenced the relationship between ACEs and negative marijuana-related consequences (indirect β = .079, 99% CIs = .042, .121). Distress tolerance did not significantly uniquely indirectly influence the relationship between ACEs and negative marijuana-related consequences. However, a significant double-mediation effect was found illustrating that a higher endorsement of ACEs was associated with lower distress tolerance, which in turn was associated with higher using marijuana to cope motives, which in turn was associated with more negative marijuana-related consequences (indirect β = .011, 99% CIs = .002, .026). Conclusions: These findings provide support for the relevance of distress tolerance and coping motives as potential factors in linking ACEs to problematic marijuana use among college students. Our preliminary findings encourage further exploration of these associations in longitudinal or experimental studies. Further these results lend support to the therapeutic targeting of distress tolerance and using marijuana to cope to mitigate harms stemming from ACEs and its impact on problematic marijuana use.