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OBJECTIVE Mavrilimumab, a human monoclonal antibody, targets granulocyte-macrophage colony-stimulating factor receptor α. We undertook to determine the long-term safety and efficacy of mavrilimumab in rheumatoid arthritis patients in 2 phase IIb studies (1071 and 1107) and in 1 open-label extension study (ClinicalTrials.gov identifier: NCT01712399). METHODS In study 1071, patients with an inadequate response to disease-modifying antirheumatic drugs (DMARDs) received mavrilimumab (30, 100, or 150 mg) or placebo every other week plus methotrexate. In study 1107, patients with an inadequate response to anti-tumor necrosis factor agents and/or DMARDs received 100 mg mavrilimumab every other week or 50 mg golimumab every 4 weeks plus methotrexate. Patients entering the open-label extension study received 100 mg mavrilimumab every other week plus methotrexate. Long-term safety and efficacy of mavrilimumab were assessed. RESULTS A total of 442 patients received mavrilimumab (14 of 245 patients from study 1071, 9 of 70 patients from study 1107, and 52 of 397 patients from the open-label extension study discontinued mavrilimumab treatment throughout the studies). The cumulative safety exposure was 899 patient-years; the median duration of mavrilimumab treatment was 2.5 years (range 0.1-3.3 years). The most common treatment-emergent adverse events (AEs) were nasopharyngitis (n = 69; 7.68 per 100 patient-years) and bronchitis (n = 51; 5.68 per 100 patient-years). At weeks 74 and 104, 3.5% and 6.2% of patients, respectively, demonstrated reduction in forced expiratory volume in 1 second, while 2.9% and 3.4% of patients, respectively, demonstrated reduction in forced vital capacity (>20% reduction from baseline to

Background RA is associated with pulmonary comorbidity and lung function decline over time, but longitudinal assessment of pulmonary abnormalities in the context of RA treatment needs further characterisation. Mavrilimumab, an investigational human monoclonal antibody, inhibits GM-CSF by binding to the GM-CSF receptor α subunit. Objectives To investigate the pulmonary safety of mavrilimumab because of the theoretical risk of inhibiting alveolar macrophage function and causing pulmonary alveolar proteinosis (PAP). Methods Pulmonary monitoring included standardised serial pulmonary function testing (spirometry and diffusing capacity of lung carbon monoxide [DLCO]), chest X-rays, assessments of dyspnoea and pulmonary adverse events (AEs) in two randomised, double-blind studies (NCT01706926; NCT01715896) where patients (pts) with moderate to severe RA received mavrilimumab 30, 100 or 150 mg every other week (eow), or placebo and mavrilimumab 100 mg eow or golimumab 50 mg every 4 weeks, respectively. Eligible pts transferred to the open-label extension study (NCT01712399) and received mavrilimumab 100 mg eow. All studies excluded pts with clinically significant uncontrolled pulmonary disease. An Independent Pulmonary Evaluation Committee (IPEC), blinded to treatment, adjudicated pulmonary AEs and lung function abnormalities. Results Mavrilimumab was received by 442 pts with cumulative safety data exposure of approximately 900 pt-yrs and a median (range) exposure time of 2.5 (0.1–3.3) yrs. Baseline (BL) characteristics are shown (Table). Mean dyspnoea (Table), forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC) and DLCO were mostly maintained within 5% of BL values for pts treated with mavrilimumab during the clinical programme. Clinically relevant decreases in predicted FEV1 and FVC (>20% from BL and Conclusions We believe this is the most comprehensive longitudinal study of pulmonary function in a clinical RA programme. The BL pulmonary function profile indicates that this is not a normal population from a pulmonary health perspective. Mavrilimumab was not associated with substantial decline in pulmonary function or PAP in pts treated up to 3.3 years; its acceptable safety profile advocates initiation of Phase III studies with mavrilimumab. Further studies are now required to fully characterise pulmonary function over time in RA. Acknowledgements Funded by MedImmune. Medical writing support: R Plant, QXV Comms, an Ashfield company, funded by MedImmune. ^Senior author. Disclosure of Interest G. Burmester Consultant for: MedImmune, M. Michaels Employee of: MedImmune, D. Close Employee of: MedImmune, A. Godwood Shareholder of: AstraZeneca, Employee of: MedImmune, K. Middleton Employee of: MedImmune (contracted employment at time of study), P. Miranda Grant/research support from: Amgen, Medimmune, Janssen, Pfizer, Celltrion, Abbott, Sanofi, Actelion, Merck & Co, Boehringer, BMS, Consultant for: Pfizer [Etanecept: Fee less than USD5000], J. Vencovský Consultant for: Pfizer, Elli Lilly, MSD, Novartis, Speakers bureau: Biogen, Pfizer, MSD, Abbvie, Novartis, Boehringer, UCB, BMS, J. Kremer Shareholder of: Corrona, Grant/research support from: Abbvie, Amgen, Genentech, Lilly, Pfizer, Consultant for: Abbvie, Amgen, BMS, Genentech, Lilly, Pfizer, Employee of: Corrona, I. McInnes Grant/research support from: MedImmune [The University of Glasgow is a charity registered in Scotland, charity number SC004401 Grant/research support: Research award to University of Glasgow], Consultant for: MedImmune, M. Albulescu Shareholder of: MedImmune, Employee of: MedImmune, M. Weinblatt Grant/research support from: BMS, UCB, Crescendo Bioscience. Amgen, dxterity, Consultant for: MedImmune, Astra Zeneca, Amgen, Abbvie, BMS, Crescendo bioscience, Lilly, Pfizer, UCB, Roche, novartis

Objective This 24‐week, phase IIb, double‐blind study was undertaken to evaluate the efficacy and safety of mavrilimumab (a monoclonal antibody to granulocyte–macrophage colony‐stimulating factor receptor α) and golimumab (a monoclonal antibody to tumor necrosis factor [anti‐TNF]) in patients with rheumatoid arthritis (RA) who have had an inadequate response to disease‐modifying antirheumatic drugs (DMARDs) (referred to as DMARD‐IR) and/or inadequate response to other anti‐TNF agents (referred to as anti‐TNF–IR). Methods Patients with active RA and a history of DMARD‐IR (≥1 failed regimen) or DMARD‐IR (≥1 failed regimen) and anti‐TNF–IR (1–2 failed regimens) were randomized 1:1 to receive either mavrilimumab 100 mg subcutaneously every other week or golimumab 50 mg subcutaneously every 4 weeks alternating with placebo every 4 weeks, administered concomitantly with methotrexate. The primary end points were the American College of Rheumatology 20% improvement (ACR20), 50% improvement, and 70% improvement response rates at week 24, percentage of patients achieving a Disease Activity Score in 28 joints using C‐reactive protein level (DAS28‐CRP) of 0.22 on the Health Assessment Questionnaire (HAQ) disability index (DI) at week 24, and safety/tolerability measures. This study was not powered to formally compare the 2 treatments. Results At week 24, differences in the ACR20, ACR50, and ACR70 response rates between the mavrilimumab treatment group (n = 70) and golimumab treatment group (n = 68) were as follows: in all patients, −3.5% (90% confidence interval [90% CI] −16.8, 9.8), −8.6% (90% CI −22.0, 4.8), and −9.8% (90% CI −21.1, 1.4), respectively; in the anti‐TNF–IR group, 11.1% (90% CI −7.8, 29.9), −8.7% (90% CI −28.1, 10.7), and −0.7% (90% CI −18.0, 16.7), respectively. Differences in the percentage of patients achieving a DAS28‐CRP of 0.22 improvement in the HAQ DI score at week 24 was similar between the treatment groups. Treatment‐emergent adverse events were reported in 51.4% of mavrilimumab‐treated patients and 42.6% of golimumab‐treated patients. No deaths were reported, and no specific safety signals were identified. Conclusion The findings of this study demonstrate the clinical efficacy of both treatments, mavrilimumab at a dosage of 100 mg every other week and golimumab at a dosage of 50 mg every 4 weeks, in patients with RA. Both regimens were well‐tolerated in patients who had shown an inadequate response to DMARDs and/or other anti‐TNF agents.

Background Mavrilimumab, a fully human monoclonal antibody, which targets granulocyte-macrophage colony-stimulating factor receptor-α, has demonstrated efficacy and an acceptable safety profile in prior 12- and 24-week studies.1,2 Objectives This analysis evaluated all long-term (LT) safety and efficacy, through 74 weeks of treatment, of mavrilimumab. Methods This open-label extension (OLE) study (NCT01712399) enrolled adult rheumatoid arthritis (RA) patients (pts) who had completed the EARTH EXPLORER 12 and 2 (NCT01715896) Phase IIb studies or were rescued as inadequate responders (from Week 12). Pts received subcutaneous mavrilimumab 100 mg every other week (eow), consistent with data from the Phase IIa study1. The primary objective was to assess the LT risk:benefit ratio of mavrilimumab via evaluation of i) Treatment emergent adverse events (TEAEs), TE serious AEs (TESAEs), and independently adjudicated pulmonary function tests (PFTs) ii) Exploratory LT efficacy endpoints (DAS28–CRP/ACR responses). AEs with onset date after start of mavrilimumab are presented. Change from baseline (BL) in modified Total Sharp Score (mTSS) was used to explore radiographic progression in EARTH EXPLORER 1 pts. Results At the 74 week (includes original study) cutoff, 391 pts had been enrolled in the OLE study. Of these, 329 (84.1%) continued on treatment, 62 (15.9%) discontinued (due to withdrawal of consent, 9 [2.3%]; adverse event, 7 [1.8%]; non study-related site closure, 20 [5.1%]; other, 24 [6.1%]; lost-to-follow-up, 1 [0.3%]; death [sudden cardiac arrest, preferred term cardiopulmonary failure], 1 [0.3%]), and 239 (61.1%) were assessed for efficacy at Week 74. Between the Phase IIb and OLE studies, 440 pts received mavrilimumab, with a safety exposure of 603 pt years (yr) and median duration of 1.6 yr. Most common TEAEs (n [/100 pt yr]) were nasopharyngitis (51 [8.45]), bronchitis (36 [5.97]) and hypertension (32 [5.30]); the serious infection rate was 1.82/100 pt yr. Pulmonary events/defined PFT changes occurred in a few pts and were generally transient with no signal identified (Table). Mavrilimumab demonstrated sustained efficacy (DAS28–CRP/ACR responses) (Table). After 74 weeks of treatment, 68% of pts showed no radiographic progression ( Conclusions Mavrilimumab continues to demonstrate a sustained efficacy and safety profile in pts with active RA, over the 74 week treatment duration reported. Although mavrilimumab 100 mg eow is suboptimal compared with 150 mg eow in DMARD-IR pts,2 efficacy results are comparable with those of previous studies.1,2 References Burmester G, et al. Ann Rheum Dis 2013;72:1445–1452 Burmester G, et al. Arthritis Rheum 2014;66:S1231 Acknowledgement Funded by MedImmune. Editorial assistance: K Alexander, QXV Comms, an Ashfield business, UK Joint senior authors: D. Close and M. Weinblatt Disclosure of Interest G. Burmester Consultant for: MedImmune, I. McInnes Grant/research support from: Research award to University of Glasgow, Consultant for: MedImmune, AstraZeneca, J. Kremer Shareholder of: Corrona, Grant/research support from: Abbvie, Amgen, Genentech, Lilly, Pfizer, Consultant for: Abbvie, Amgen, BMS, Genentech, Lilly, Pfizer, Employee of: Corrona, P. Miranda Grant/research support from: Clinical trials Amgen, Medimmune, Janssen, Pfizer, Celltrion, Abbott, Sanofi, Actelion, Merck & Co, Boehringer, BMS, Consultant for: Pfizer for Etanecept (fee less than USD5000), J. Vencovský Consultant for: Pfizer, Servier, Samsumg, Eli lilley, BMS, Novartis, A. Godwood Shareholder of: AstraZeneca, Employee of: MedImmune, M. Albulescu Employee of: MedImmune, D. Close, Employee of: MedImmune, M. Weinblatt, Grant/research support from: BMS, UCB, Crescendo Bioscience, Consultant for: MedImmune, AstraZeneca, Amgen, Abbvie, BMS, Crescendo Bioscience, Lilly, Pfizer, UCB, Roche

Background Mavrilimumab, a fully human monoclonal antibody targeting the granulocyte-macrophage colony-stimulating factor receptor-α, has demonstrated efficacy and safety in disease-modifying antirheumatic drug (DMARD)-inadequate responder (IR) patients (pts) with rheumatoid arthritis (RA). 1 Objectives Few head-to-head studies in tumor necrosis factor antagonist (aTNF)-IR assess alternative aTNFs vs. other agents; this Phase IIb exploratory study (NCT01715896) evaluates the efficacy and safety of mavrilimumab and golimumab in aTNF-IR and DMARD-IR pts. Methods This 24-week study enrolled pts with active RA (28-joint Disease Activity Score [DAS28]–C-reactive protein [CRP]/erythrocyte sedimentation rate ≥3.2); ≥4 swollen joints; inadequate response to ≥1 DMARDs and/or 1–2 aTNFs receiving concomitant methotrexate (MTX; 7.5–25.0 mg/week). Pts received subcutaneous mavrilimumab 100 mg every other week (eow), based on data from the Phase IIa study, 2 or golimumab 50 mg alternating with placebo eow. Key endpoints were ACR20/50/70 responses, DAS28–CRP 0.22 at Week 24 and safety/tolerability. Treatment estimates for mavrilimumab and golimumab are presented with standard errors. Results Pts were randomized to mavrilimumab or golimumab (1:1) (Table). Data for pts receiving mavrilimumab 100 mg eow and golimumab 50 mg at Week 24 are shown for the aTNF-IR, DMARD-IR and overall strata (Table). The most common treatment-emergent adverse events (TEAEs) for mavrilimumab 100 mg and golimumab 50 mg were nasopharyngitis (5.7%, 1.5%), headache (4.3%, 2.9%), upper respiratory tract infection (4.3%, 2.9%), viral upper respiratory tract infection (4.3%, 2.9%), and hepatic enzyme increase (4.3%, 2.9%), respectively. Related serious TEAEs were pneumocystis pneumonia (n=1) and lung disorder (n=1) [both in golimumab-treated pts]. No deaths were reported and no significant pulmonary safety signals were identified. Conclusions In this exploratory study, mavrilimumab 100 mg eow and golimumab 50 mg demonstrated efficacy and an acceptable safety profile in DMARD-IR and aTNF-IR pts. The study was not powered to demonstrate statistical significance between mavrilimumab and golimumab. As mavrilimumab 100 mg eow has previously been shown to be suboptimal compared with 150 mg eow in DMARD-IR pts (EARTH EXPLORER 1), 1 additional studies are needed to establish the benefit of a higher dose in pts with moderate to severe RA and inadequate response to aTNF agents. References Burmester G, et al. Arthritis Rheum. 2014;66:S1231 Burmester G, et al. Ann Rheum Dis. 2013;72:1445–1452 Acknowledgement Funded by MedImmune. Editorial assistance: K Alexander, QXV Comms, an Ashfield business, UK Joint senior authors: D. Close and G. Burmester Disclosure of Interest M. Weinblatt Grant/research support from: BMS, UCB, Crescendo Bioscience, Consultant for: MedImmune, Astra Zeneca, Amgen, Abbvie, BMS, Crescendo Bioscience, Lilly, Pfizer, UCB, Roche, I. McInnes Grant/research support from: Research award to University of Glasgow, Consultant for: MedImmune, Astra Zeneca, J. Kremer Shareholder of: Corrona, Grant/research support from: Abbvie, Amgen, Genentech, Lilly, Pfizer, Consultant for: Abbvie, Amgen, BMS, Genentech, Lilly, Pfizer, Employee of: Corrona, P. Miranda Grant/research support from: Clinical trials: Amgen, Medimmune, Janssen, Pfizer, Celltrion, Abbott, Sanofi, Actelion, Merck & Co, Boehringer, BMS, Consultant for: Pfizer for Etanecept (fee less than USD5000), J. Vencovský Consultant for: Pfizer, Servier, Samsumg, Eli lilley, BMS, Novartis, A. Godwood Shareholder of: AstraZeneca, Employee of: MedImmune, M. Albulescu Employee of: MedImmune, D. Close, Employee of: MedImmune, G. Burmester, Consultant for: MedImmune

Background Of patients with RA, ∼40% of do not achieve a minimal acceptable improvement (ACR20) despite modern biologic therapy.1,2,3 Granulocyte-macrophage colony-stimulating factor (GM–CSF) is implicated in RA pathogenesis via myeloid and granulocyte cell lineage activation. In a 12-week Phase IIa study, mavrilimumab, a first-in-class inhibitor of the GM–CSF receptor-α demonstrated a sustained effect via this novel therapeutic pathway in RA.4 Objectives To evaluate the efficacy and safety of mavrilimumab in patients with moderate to severe, adult-onset RA in a 24-week, Phase IIb study. Methods Patients (18–80 yrs; inadequate response to ≥1 DMARDs; DAS28–CRP ≥3.2; ≥4 SJC) receiving MTX were randomized to receive 1 of 3 SC mavrilimumab dosages (150, 100, 30 mg every other week [eow]) or placebo (PBO) plus MTX (7.5–25.0 mg/week). Co-primary endpoints were change in DAS28–CRP (Day 1 to Week 12) and ACR20 response rate (Week 24). Safety and tolerability were measured through assessment of AEs and pulmonary parameters. Results were analyzed using the modified ITT population. Results 326 patients from Europe, South America, and South Africa (mean [SD] age, 51.8 [11.1] yrs; female, 86.5%; mean [SD] DAS28–CRP, 5.8 [0.9]; RF+/anti-CCP+, 81.9%) received mavrilimumab 150, 100 or 30 mg eow or PBO (N=79, 85, 81 and 81, respectively). At Week 12, a statistically significant difference in DAS28–CRP change from baseline (p 90% of patients entered a long-term, open-label extension study. Conclusions This Phase IIb study demonstrated the potential benefit of inhibiting macrophage activity via the GM–CSF receptor-α pathway on RA disease activity. The study met both co-primary endpoints with a clear dosage response. Mavrilimumb was well-tolerated over the 24-week study period. References Weinblatt ME, et al. N Engl J Med 1999;340:253–9. Lipsky PE, et al. N Engl J Med 2000;343:1594–602. Weinblatt ME, et al. Arthritis Rheum 2003;48:35–45, Burmester GR, et al. Ann Rheum Dis 2013;72:1445–52. Acknowledgements Funded: MedImmune. Editorial assistance: N Panagiotaki, QXV Communications, UK †Joint senior authors. Disclosure of Interest G. Burmester Grant/research support from: AbbVie, Pfizer, UCB, Roche, Consultant for: AbbVie, BMS, Novartis, MedImmune, MSD, Pfizer, UCB, Roche, Speakers bureau: AbbVie, BMS, Novartis, MSD, Pfizer, UCB, Roche, I. McInnes Grant/research support from: MedImmune (Research award to University of Glasgow), Consultant for: MedImmune, AstraZeneca, J. Kremer Shareholder of: Corrona, Grant/research support from: AbbVie, Amgen, Genentech, Lilly, Pfizer, Consultant for: AbbVie, Amgen, Genentech, Lilly, Pfizer, BMS, Employee of: Corrona, P. Miranda Grant/research support from: MedImmune (to support protocol), M. Korkosz: None declared, J. Vencovsky: None declared, A. Rubbert-Roth Grant/research support from: Pfizer, Chugai, Consultant for: MSD, USB, Abbott, Pfizer, Roche, BMS, Chugai, Speakers bureau: Roche, Pfizer, UCB, E. Mysler Grant/research support from: Medimmune, Roche, BMS, Pfizer, M. Sleeman Shareholder of: AstraZeneca, Employee of: MedImmune, A. Godwood Shareholder of: AstraZeneca, Employee of: MedImmune, M. Albulescu Employee of: MedImmune, D. Close Shareholder of: AstraZeneca, Employee of: MedImmune, M. Weinblatt Grant/research support from: BMS, UCB, Crescendo Bioscience, Consultant for: MedImmune, AstraZeneca, Amgen, Abbvie, BMS, Crescendo Bioscience, Lilly, Pfizer, UCB, Roche

Background Macrophages are pivotal to the pathogenesis of rheumatoid arthritis (RA), and their inflammatory products drive many of the signs and symptoms of disease. Mavrilimumab inhibits macrophage activation and survival via blockade of granulocyte-macrophage colony-stimulating factor receptor-α (GM–CSFR-α) and has demonstrated sustained clinical benefit in patients with RA. 1 Objectives To examine time to onset of clinical response to mavrilimumab in the EARTH EXPLORER 1 study. Methods In a 24-week, Phase IIb study (NCT01706926), patients with adult-onset RA (18–80 years; Disease Activity Score 28 C-reactive protein [DAS28–CRP] >3.2; ≥4 swollen joints; inadequate response to ≥1 disease-modifying antirheumatic drugs [DMARDs]) receiving concomitant methotrexate were enrolled. Patients received mavrilimumab (150, 100, or 30 mg every other week [eow]) or placebo, administered subcutaneously with methotrexate (7.5–25.0 mg/week). Efficacy assessments included DAS28–CRP, American College of Rheumatology (ACR)20/50/70 responses, CRP, erythrocyte sedimentation rate (ESR), swollen joint count (SJC), tender joint count (TJC), and pain assessments. Results 326 patients with mean (SD) DAS28–CRP 5.8 (0.9) were randomized to mavrilimumab (150, 100, or 30 mg eow) or placebo (N=79, 85, 81, and 81, respectively). At Week 1 (first assessment), all mavrilimumab dosages demonstrated significant reductions from baseline in DAS28–CRP ( p p =0.003 to p Conclusions By targeting activated macrophages via inhibition of GM–CSFR-α, mavrilimumab substantially reduced patients9 RA disease activity early in their treatment, from first dose (Week 1) to final assessment for many patients, as evaluated by several clinical outcomes. References Burmester GR, et al. Ann Rheum Dis. 2013;72:1445–52. Acknowledgements Funded: MedImmune Ltd. Editorial assistance: N Panagiotaki, QXV Communications, UK Disclosure of Interest I. McInnes Grant/research support from: MedImmune (Research award to University of Glasgow), Consultant for: MedImmune, AstraZeneca, G. Burmester Grant/research support from: AbbVie, Pfizer, UCB, Roche, Consultant for: AbbVie, BMS, Novartis, MedImmune, MSD, Pfizer, UCB, Roche, Speakers bureau: AbbVie, BMS, Novartis, MSD, Pfizer, UCB, Roche, J. Kremer Shareholder of: Corrona, Grant/research support from: AbbVie, Amgen, Genentech, Lilly, Pfizer, Consultant for: AbbVie, Amgen, Genentech, Lilly, Pfizer, BMS, Employee of: Corrona, P. Miranda Grant/research support from: MedImmune (to support protocol), M. Korkosz: None declared, J. Vencovsky: None declared, A. Rubbert-Roth Grant/research support from: Pfizer, Chugai, Consultant for: MSD, UCB, Abbott, Pfizer, Roche, BMS, Chugai, Speakers bureau: Roche, Pfizer, UCB, E. Mysler Grant/research support from: MedImmune, Roche, BMS, Pfizer, D. Close Shareholder of: AstraZeneca, Employee of: MedImmune, M. Sleeman Shareholder of: AstraZeneca, Employee of: MedImmune, A. Godwood Shareholder of: AstraZeneca, Employee of: MedImmune, M. Albulescu Employee of: MedImmune, M. Weinblatt Grant/research support from: BMS, UCB, Crescendo Bioscience, Consultant for: MedImmune, AstraZeneca, Amgen, Abbvie, BMS, Crescendo bioscience, Lilly, Pfizer, UCB, Roche

Background Active RA significantly impairs patients9 health-related quality of life (HRQOL) and physical function. Granulocyte-macrophage colony-stimulating factor (GM–CSF) plays a key role in macrophage activation and RA pathogenesis, including inflammatory and arthritic pain development. A Phase IIa study in active RA demonstrated that mavrilimumab produced clinically meaningful improvements across a variety of PROs. 1 Objectives To assess mavrilimumab9s effects on HRQOL and physical function in RA patients in a 24-week Phase IIb study. Methods In an RCT (NCT01706926), we evaluated the efficacy and safety of 3 subcutaneous mavrilimumab dosages (150 mg, 100 mg, and, 30 mg every other week [eow]) vs. placebo over 24 weeks. Patients with adult-onset RA (18–80 years; DAS28–CRP ≥3.2; ≥4 swollen joints; inadequate response to ≥1 DMARDs) receiving concomitant methotrexate were enrolled. Co-primary endpoints were changes in DAS28–CRP score (Day 1 to Week 12) and ACR20 response (Week 24). PRO endpoints included changes from baseline and percentage responders in patient assessments of pain, HRQOL (SF-36 Mental Component Summary [MCS] and Physical Component Summary [PCS] scores), physical function (HAQ DI), and fatigue (FACIT-F). Patients could enter a long-term, open-label extension study at Week 12 (not reported). Results 326 patients (mean [SD] age, 51.8 [11.1] years; female, 86.5%) with a mean (SD) DAS28–CRP of 5.8 (0.9) were randomized to mavrilimumab 150, 100, or 30 mg eow, or placebo (N=79, 85, 81, and 81, respectively). Both co-primary endpoints (DAS28–CRP at Week 12; ACR20 at Week 24) were met at all mavrilimumab dosages. At Weeks 12 and 24, all mavrilimumab treatment groups exhibited improvements in pain, SF-36 PCS, SF-36 MCS, HAQ DI and FACIT-F vs. placebo, with >50% of patients receiving mavrilimumab 150 mg eow achieving a clinically meaningful response. At this dosage, significant improvements were demonstrated across all PRO endpoints ( p =0.019 to p p =0.007, Week 24; p =0.187). Statistically significant improvements in pain were demonstrated for mavrilimumab beginning at Week 1. Of patients receiving mavrilimumab 150, 100, and 30 mg eow with a pain response at Week 12, 66.7% (28/42), 69.2% (27/39), and 72.2% (26/36) maintained responses at Week 24. HAQ DI responses at Week 12 were maintained at Week 24 in 78.8% (41/52), 84.0% (42/50), and 75.0% (33/44) of patients (mavrilimumab 150, 100, and 30 mg eow, respectively). Conclusions Targeting activated macrophages through inhibition of the GM–CSFR-α pathway with mavrilimumab, especially at a dosage of 150 mg eow, substantially and rapidly reduced RA disease activity. In turn, patients receiving mavrilimumab achieved significant, clinically meaningful, and sustained improvements in PROs that reflected the patients9 pain, HRQOL, physical function, and fatigue. The majority of mavrilimumab patients with improvement in pain and physical function at Week 12 sustained these improvements through Week 24 References Burmester GR, et al. Ann Rheum Dis. 2013;72:1445–52. Acknowledgements Funded: MedImmune Ltd. Editorial assistance: N Panagiotaki, QXV Communications, UK Disclosure of Interest J. Kremer Shareholder of: Corrona, Grant/research support from: AbbVie, Amgen, Genentech, Lilly, Pfizer, Consultant for: AbbVie, Amgen, Genentech, Lilly, Pfizer, BMS, Employee of: Corrona, G. Burmester Grant/research support from: AbbVie, Pfizer, UCB, Roche, Consultant for: AbbVie, BMS, Novartis, MedImmune, MSD, Pfizer, UCB, Roche, Speakers bureau: AbbVie, BMS, Novartis, MSD, Pfizer, UCB, Roche, M. Weinblatt Grant/research support from: BMS, UCB, Crescendo Bioscience, Consultant for: MedImmune, AstraZeneca, Amgen, Abbvie, BMS, Crescendo bioscience, Lilly, Pfizer, UCB, Roche, A. Williams Shareholder of: AstraZeneca, Employee of: MedImmune, N. Karlsson Shareholder of: AstraZeneca, Employee of: AstraZeneca, A. Godwood Shareholder of: AstraZeneca, Employee of: MedImmune, M. Albulescu Employee of: MedImmune, D. Close Shareholder of: AstraZeneca, Employee of: MedImmune