You are given a text that consists of multiple sentences. Your task is to perform abstractive summarization on this text. Use your understanding of the content to express the main ideas and crucial details in a shorter, coherent, and natural sounding text.

CAMBRIDGE, Mass.--(BUSINESS WIRE)--Acceleron Pharma Inc. (Nasdaq:XLRN), a biopharmaceutical company dedicated to the discovery, development, and commercialization of TGF-beta superfamily therapeutics to treat serious and rare diseases, today reported financial results for the first quarter ended March 31, 2021. Acceleron made significant operational progress during the first quarter, said Habib Dable, President and Chief Executive Officer of Acceleron. With the STELLAR Phase 3 trial already enrolling patients, we expect to initiate multiple mid- and late-stage clinical trials across our pipeline in pulmonary disease throughout 2021. We were thrilled to have data from the PULSAR Phase 2 trial of sotatercept in PAH recently featured in the New England Journal of Medicine. These data along with the results from our ongoing and planned Phase 3 trials will support our vision of establishing sotatercept as a backbone therapy for patients with all stages of PAH. We are looking forward to hosting a research and development day in late June to primarily discuss Acceleron's plans and vision in rare pulmonary diseases with sotatercept in pulmonary hypertension and ACE-1334 in systemic sclerosis-associated interstitial lung disease, or SSc-ILD. Added Mr. Dable: In our hematology program, Acceleron and our partner, Bristol-Myers Squibb Company (Bristol Myers Squibb), are leveraging the key learnings from the early success of the commercial launch of REBLOZYL in the United States. We continue to transition from the initial bolus patient group earlier in the launch to underlying new patient demand. Bristol Myers Squibb expects launches in multiple additional countries across the globe this year as REBLOZYL receives reimbursement. Most importantly, assuming success in current and future potential indications associated with anemia, we continue to estimate that peak annual sales of REBLOZYL will surpass $4 billion. Program Highlights Pulmonary Sotatercept: Pulmonary Arterial Hypertension (PAH) Sotatercept is an investigational reverse-remodeling agent designed to be a selective ligand trap for members of the TGF-beta superfamily to rebalance BMPR2 signaling, which is a key molecular driver of PAH. ACE-1334: Systemic Sclerosis-associated Interstitial Lung Disease (SSc-ILD) ACE-1334 is an Acceleron-discovered, TGF-beta superfamily-based ligand trap designed to bind and inhibit TGF-beta 1 and 3 ligands but not TGF-beta 2. ACE-1334 has shown robust anti-fibrotic activity in multiple preclinical models of fibrosis. Hematology REBLOZYL (luspatercept-aamt): REBLOZYL is the first and only approved erythroid maturation agent designed to promote late-stage red blood cell (RBC) production. REBLOZYL is part of the global collaboration between Acceleron and Bristol Myers Squibb. Corporate Highlights Financial Results Non-GAAP Financial Measures Acceleron supplements its results of operations prepared in accordance with U.S. generally accepted accounting principles, or GAAP, with certain non-GAAP financial measures, including non-GAAP R&D expense, non-GAAP SG&A expense, adjusted net loss and adjusted net loss per share, that exclude stock-based compensation expense and depreciation and amortization expense. These results should not be viewed as a substitute for the Companys GAAP results and are provided as a complement to results provided in accordance with GAAP. Management believes these non-GAAP financial measures provide investors with additional insight into underlying trends of the Company's ongoing business, and are important in comparing current results with prior period results. Investors are cautioned that there are material limitations associated with the use of non-GAAP financial measures. In addition, other companies may report similarly titled non-GAAP measures, but calculate them differently, which reduces their usefulness as a comparative measure. In the reconciliation tables below, Acceleron presents these non-GAAP financial measures reconciled to their comparable GAAP financial measures. Conference Call and Webcast The Company will host a webcast and conference call to discuss its first quarter 2021 financial results on May 6, 2021, at 5:00 p.m. EDT. The webcast will be accessible under "Events & Presentations" in the Investors & Media page of the Companys website at www.acceleronpharma.com. To participate in the conference call, please dial 833-494-1483 (domestic) or 236-714-2620 (international) and reference code #5559908. An archived version of the webcast will be available for replay on the Company's website for approximately one year. About Acceleron Acceleron is a biopharmaceutical company dedicated to the discovery, development, and commercialization of therapeutics to treat serious and rare diseases. Accelerons leadership in the understanding of TGF-beta superfamily biology and protein engineering generates innovative compounds that engage the body's ability to regulate cellular growth and repair. Acceleron focuses its research, development, and commercialization efforts in pulmonary and hematologic diseases. In pulmonary, Acceleron is developing sotatercept for the treatment of pulmonary arterial hypertension (PAH), having reported positive topline results of the PULSAR Phase 2 trial. The Company is currently planning multiple Phase 3 trials with the potential to support its long-term vision of establishing sotatercept as a backbone therapy for patients with PAH at all stages of the disease. Acceleron is also investigating the potential of its early-stage pulmonary candidate, ACE-1334, which it plans to advance into a Phase 1b/Phase 2 trial in systemic sclerosis-associated interstitial lung disease (SSc-ILD) this year. In hematology, REBLOZYL (luspatercept-aamt) is the first and only erythroid maturation agent approved in the United States, Europe, and Canada for the treatment of anemia in certain blood disorders. REBLOZYL is part of a global collaboration partnership with Bristol Myers Squibb. The Companies co-promote REBLOZYL in the United States and are also developing luspatercept for the treatment of anemia in patient populations of myelodysplastic syndromes, beta-thalassemia, and myelofibrosis. For more information, please visit www.acceleronpharma.com. Follow Acceleron on Social Media: @AcceleronPharma and LinkedIn. ACCELERON PHARMA INC. CONDENSED CONSOLIDATED BALANCE SHEET (Amounts in thousands) (unaudited) March 31, 2021 December 31, 2020 Cash and cash equivalents $ 455,513 $ 670,952 Short and long-term investments 339,929 186,536 Operating lease - right of use asset, net 20,415 21,988 Other assets 59,936 52,861 Total assets $ 875,793 $ 932,337 Operating lease liability - right of use, short-term and long-term $ 22,425 $ 24,077 Other liabilities 42,537 53,153 Total liabilities 64,962 77,230 Total stockholders equity 810,831 855,107 Total liabilities and stockholders equity $ 875,793 $ 932,337 ACCELERON PHARMA INC. CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Amounts in thousands except per share data) (unaudited) Three Months Ended March 31, 2021 2020 Revenue: Collaboration revenue $ 24,758 $ 4,344 Costs and expenses: Research and development 57,299 37,663 Selling, general and administrative 31,062 18,253 Total costs and expenses 88,361 55,916 Loss from operations (63,603) (51,572) Other, income net 137 648 Loss before income taxes (63,466) (50,924) Income tax provision (5) (15) Net loss $ (63,471) $ (50,939) Net loss per share- basic and diluted $ (1.05) $ (0.95) Weighted-average number of common shares used in computing net loss per share- basic and diluted 60,579 53,361 ACCELERON PHARMA INC. RECONCILIATION OF GAAP TO NON-GAAP COSTS and EXPENSES (Amounts in thousands) (unaudited) Three Months Ended March 31, 2021 2020 GAAP research and development $ 57,299 $ 37,663 Less adjustments: Stock-based compensation 8,158 3,141 Depreciation and amortization 936 932 Non-GAAP research and development $ 48,205 $ 33,590 GAAP selling, general and administrative $ 31,062 $ 18,253 Less adjustments: Stock-based compensation 7,468 3,538 Depreciation and amortization 91 63 Non-GAAP selling, general and administrative $ 23,503 $ 14,652 ACCELERON PHARMA INC. RECONCILIATION OF GAAP TO ADJUSTED NON-GAAP NET LOSS AND NET LOSS PER SHARE (Amounts in thousands except per share data) (unaudited) Three Months Ended March 31, 2021 2020 GAAP net loss $ (63,471) $ (50,939) Adjustments: Stock-based compensation 15,626 6,679 Depreciation and amortization 1,026 996 Adjusted net loss (non-GAAP) $ (46,819) $ (43,264) GAAP net loss per share- basic and diluted $ (1.05) $ (0.95) Adjustments: Stock-based compensation 0.26 0.13 Depreciation and amortization 0.02 0.02 Adjusted net loss per share (non-GAAP) $ (0.77) $ (0.80) Weighted-average number of common shares used in computing net loss per share 60,579 53,361 Cautionary Note on Forward-Looking Statements This press release contains forward-looking statements about the Company's strategy, future plans and prospects, including statements regarding the development and commercialization of the Company's compounds, the timeline for clinical development and regulatory approval of the Company's compounds, the expected timing for reporting of data from ongoing clinical trials, the Company's future cash position and the potential of REBLOZYL (luspatercept-aamt) as a therapeutic drug. The words "anticipate," "believe," "could," "estimate," "expect," "goal," "intend," "may," "plan," "potential," "project," "should," "target," "will," "would," and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Actual results could differ materially from those included in the forward-looking statements due to various factors, risks and uncertainties, including, but not limited to, that preclinical testing of the Company's compounds and data from clinical trials may not be predictive of the results or success of other clinical trials, that regulatory approval of the Companys compounds in one indication or country may not be predictive of approval in another indication or country, that the development of the Companys compounds may take longer and/or cost more than planned or accelerate faster than currently expected, that the Company or its collaboration partner, Bristol Myers Squibb Company (BMS), may be unable to successfully complete the clinical development of the Companys compounds, that the Company or BMS may be delayed in initiating, enrolling or completing any clinical trials, and that the Companys compounds may not receive regulatory approval or become commercially successful products. These and other risks and uncertainties are identified under the heading Risk Factors included in the Companys most recent Annual Report on Form 10-K and other filings that the Company has made and may make with the SEC in the future. The forward-looking statements contained in this press release are based on management's current views, plans, estimates, assumptions, and projections with respect to future events, and the Company does not undertake and specifically disclaims any obligation to update any forward-looking statements.

Answer: Acceleron Reports First Quarter 2021 Financial Results - PULSAR Phase 2 trial results published in New England Journal of Medicine - - Updates from the PULSAR and SPECTRA Phase 2 trials of sotatercept in patients with pulmonary arterial hypertension (PAH) to be presented at the American Thoracic Society (ATS) 2021 International Conference on May 19, 2021 - - Acceleron recognized approximately $22.4 million in royalty revenue for Q1 2021 from approximately $112 million in net sales of REBLOZYL (luspatercept-aamt) - - REBLOZYL, the first and only erythroid maturation agent, was approved by Health Canada for the treatment of transfusion-dependent anemia in adults with myelodysplastic syndromes (MDS) -