Acceleron to Host Conference Call and Webcast to Review Clinical Trial Updates, Preclinical Presentations on Sotatercept in Pulmonary Arterial Hypertension (PAH) Presented at the American Thoracic Society (ATS) 2021 International Conference

Rhea-AI Summary

Acceleron Pharma (Nasdaq:XLRN) will hold a conference call on May 19, 2021, at 10:30 a.m. EDT to discuss updates from the PULSAR and SPECTRA Phase 2 trials of sotatercept for pulmonary arterial hypertension (PAH). Notable results from PULSAR include achieving primary endpoints related to pulmonary vascular resistance and exercise capacity. Sotatercept has received Breakthrough Therapy designation from the FDA. The ongoing SPECTRA trial will further investigate its efficacy. The company's future Phase 3 studies aim to establish sotatercept as a primary treatment for PAH.

Positive

• PULSAR Phase 2 trial successfully met primary and key secondary endpoints.
• Sotatercept received Breakthrough Therapy designation from the FDA.
• Ongoing SPECTRA Phase 2 exploratory trial to assess further efficacy.
• Phase 3 development plan announced, including the registrational STELLAR trial currently enrolling patients.

Negative

• None.

Acceleron Pharma Inc. (Nasdaq:XLRN), a leading biopharmaceutical company in the discovery, development, and commercialization of TGF-beta superfamily therapeutics to treat serious and rare diseases, today announced it will host a conference call and webcast on Wednesday, May 19, 2021 at 10:30 a.m. EDT to review updates from the PULSAR and SPECTRA Phase 2 clinical trials of sotatercept in patients with pulmonary arterial hypertension (PAH). Data from the PULSAR and SPECTRA trials will have been presented during clinical presentations at the American Thoracic Society 2021 International Conference (ATS 2021) earlier that day.

Guest Presenter:

• Aaron Waxman¹, M.D., Ph.D., Director of the Pulmonary Vascular Disease Program at Brigham and Women’s Hospital; Associate Professor of Medicine at Harvard Medical School

The webcast will be accessible under "Events & Presentations" in the Investors & Media page of the Company’s 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 #6565123.

An archived version of the webcast will be available for replay on the Company’s website for approximately one year.

1 Dr. Waxman is the principal investigator of the SPECTRA trial and a paid consultant to Acceleron.

About Sotatercept

Sotatercept is an investigational reverse-remodeling agent designed to be a selective ligand trap for members of the TGF-beta superfamily to rebalance signaling in the BMP pathway, which is a key molecular driver of PAH. In preclinical studies, sotatercept was shown to reverse the vascular remodeling that is a hallmark of PAH. The PULSAR Phase 2 trial evaluating sotatercept in combination with approved PAH-specific medicines in patients with PAH achieved its primary endpoint of improvement in pulmonary vascular resistance and its key secondary endpoint of improvement in 6-minute walk distance. Sotatercept was generally well tolerated in the trial. Adverse events observed in the study were generally consistent with previously published data on sotatercept in other diseases. Following the PULSAR results, sotatercept was granted Breakthrough Therapy designation from the FDA and Priority Medicines designation from the EMA in PAH. Sotatercept is also being evaluated in the SPECTRA Phase 2 exploratory trial.

The Company recently presented details of its Phase 3 development plan, including the design for the registrational STELLAR trial, which is currently enrolling patients with PAH. Acceleron is planning two additional Phase 3 studies in patients with PAH: the HYPERION trial in newly diagnosed patients and the ZENITH trial assessing intervention in patients diagnosed with World Health Organization (WHO) functional class IV disease.

Sotatercept is an investigational therapy that is not approved for any use in any country. Sotatercept is part of a licensing agreement with Bristol Myers Squibb.

About PAH

PAH is a rare and chronic, rapidly progressing disorder characterized by the constriction of small pulmonary arteries and elevated blood pressure in the pulmonary circulation. PAH results in significant strain on the heart, often leading to limited physical activity, heart failure, and reduced life expectancy. The 5-year survival rate for patients with PAH is approximately 57%. Available therapies generally act by promoting the dilation of pulmonary vessels without addressing the underlying cause of the disease. As a result, PAH often progresses rapidly for many patients despite standard of care treatment. A growing body of research has implicated imbalances in BMP and TGF-beta signaling as a primary driver of PAH in familial, idiopathic, and acquired forms of the disease.

About Acceleron

Acceleron is a biopharmaceutical company dedicated to the discovery, development, and commercialization of therapeutics to treat serious and rare diseases. Acceleron’s 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.

Forward-Looking Statements

This press release contains forward-looking statements about Acceleron’s strategy, future plans and prospects, including statements regarding the development of sotatercept in PAH, the timeline for clinical development and regulatory approval of sotatercept in PAH, the expected timing for reporting of data from ongoing clinical trials, and the potential of Acceleron’s compounds as therapeutic drugs. The words "anticipate," "believe," "could," "estimate," "expect," "goal," "intend," "may," "plan," “possible,” "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 Acceleron’s compounds and data from clinical trials may not be predictive of the results or success of ongoing or later clinical trials, that regulatory approval of Acceleron’s compounds in one indication or country may not be predictive of approval in another indication or country, that the development of Acceleron’s compounds will take longer and/or cost more than planned, that Acceleron will be unable to successfully complete the clinical development of Acceleron’s compounds, that Acceleron may be delayed in initiating, enrolling or completing any clinical trials, that Acceleron’s compounds will not receive regulatory approval or become commercially successful products, and that Breakthrough Therapy or PRIME designation may not expedite the development or review of sotatercept. These and other risks and uncertainties are identified under the heading “Risk Factors” included in Acceleron’s most recent Annual Report on Form 10-K and other filings that Acceleron 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 Acceleron does not undertake and specifically disclaims any obligation to update any forward-looking statements.

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FAQ

What are the results from Acceleron Pharma's PULSAR trial for sotatercept?

The PULSAR Phase 2 trial achieved its primary endpoint of improved pulmonary vascular resistance and key secondary endpoint of enhanced 6-minute walk distance.

What is the significance of the Breakthrough Therapy designation for sotatercept?

The Breakthrough Therapy designation from the FDA expedites the drug's development and review, potentially improving patient access.

When is the conference call to discuss sotatercept updates?

The conference call will be held on May 19, 2021, at 10:30 a.m. EDT.

What is the SPECTRA trial studying?

The SPECTRA Phase 2 trial is exploring the efficacy of sotatercept in patients with pulmonary arterial hypertension.

What are the future plans for sotatercept?

Acceleron plans multiple Phase 3 trials to further develop sotatercept as a treatment for pulmonary arterial hypertension.