Acceleron Announces Luspatercept Phase 3 MEDALIST and BELIEVE Presentations Selected for “Best of ASH” by the American Society of Hematology

CAMBRIDGE, Mass.–(BUSINESS WIRE)–Acceleron Pharma Inc. (Nasdaq:XLRN) today announced that the
presentations of the MEDALIST and BELIEVE Phase 3 trial results of
luspatercept in patients with lower-risk myelodysplastic syndromes (MDS)
and beta-thalassemia associated anemias, respectively, were selected for
“Best of ASH” by the American Society of Hematology at its 60th
Annual Meeting Exposition in San Diego. Luspatercept is an
investigational therapy that is part of a global collaboration between
Acceleron and Celgene.

The Society describes its “Best of ASH” selections, chosen from among
the thousands of meeting abstracts, as “the biggest breakthroughs from
the meeting’s scientific presentations.”

“Having both the MEDALIST and BELIEVE trials included in the Best of ASH
session at the close of the annual meeting is extraordinarily
gratifying,” said Habib Dable, President and Chief Executive Officer of
Acceleron. “Throughout its development, luspatercept has demonstrated
promising results in patients with these two distinct diseases
associated with anemia. Yesterday’s event is a clear indication that the
global hematology community recognizes the potential clinical impact of

The full titles of the trials highlighted during the Best of ASH session
are as follows:

‘MEDALIST’ trial presentation

Title: The MEDALIST Trial: Results of a Phase 3, Randomized,
Double-Blind, Placebo-Controlled Study of Luspatercept to Treat Anemia
in Patients with Very Low-, Low-, or Intermediate-Risk Myelodysplastic
Syndromes (MDS) with Ring Sideroblasts (RS) who Require Red Blood Cell
(RBC) Transfusions
(Plenary Scientific Session, Abstract #1)

‘BELIEVE’ trial presentation

Title: The BELIEVE Trial: Results of a Phase 3, Randomized,
Double-Blind, Placebo-Controlled, Study of Luspatercept in Adults Who
Require Regular Red Blood Cell (RBC) Transfusions Due to β-Thalassemia

Luspatercept is an investigational therapy that is not approved for any
use in any country. Celgene and Acceleron are planning regulatory
application submissions of luspatercept in the United
States and Europe in the first half of 2019.

About Luspatercept

Luspatercept is a first-in-class erythroid maturation agent (EMA) that
is believed to regulate late-stage red blood cell maturation. Acceleron
and Celgene are jointly developing luspatercept as part of a global
collaboration. In addition to the Phase 3 MEDALIST and BELIEVE studies
reported at ASH, luspatercept is being evaluated in multiple other
clinical trials. The Phase 3 COMMANDS trial was recently initiated in
first-line, lower-risk, MDS patient population. The BEYOND Phase 2 trial
in non-transfusion-dependent beta-thalassemia and a Phase 2 trial in
myelofibrosis are ongoing. For more information, please visit

About MDS

Patients with lower-risk MDS suffer from insufficient production of red
blood cells, resulting in chronic anemia that can lead to debilitating
fatigue, diminished quality of life and increased mortality. Many
patients with lower-risk MDS-related chronic anemia require frequent red
blood cell transfusions.

About Beta-Thalassemia

Beta-thalassemia is caused by a genetic defect in the production of
hemoglobin, a protein that carries oxygen to red blood cells throughout
the body. Patients suffer from severe, chronic anemia and often
experience fatigue, organ enlargement, and bone complications. Patients
require lifelong therapy that includes frequent red blood cell
transfusions and treatment of the consequent iron overload.

About Acceleron

Acceleron is a Cambridge-based, clinical-stage biopharmaceutical company
dedicated to the discovery, development, and commercialization of
therapeutics to treat serious and rare diseases. The Company’s
leadership in the understanding of TGF-beta biology and protein
engineering generates innovative compounds that engage the body’s
ability to regulate cellular growth and repair.

Acceleron focuses its research and development efforts in hematologic,
neuromuscular, and pulmonary diseases. In hematology, the Company and
its global collaboration partner, Celgene, are developing luspatercept
for the treatment of chronic anemia in myelodysplastic syndromes,
beta-thalassemia, and myelofibrosis. Acceleron is also advancing its
neuromuscular franchise with two distinct Myostatin+ agents, ACE-083 and
ACE-2494, and a Phase 2 pulmonary program with sotatercept in pulmonary
arterial hypertension.

For more information, please visit
Follow Acceleron on Social Media: @AcceleronPharma and

Forward-Looking Statements

This press release contains forward-looking statements about Acceleron’s
strategy, future plans and prospects, including statements regarding the
development of Acceleron’s compounds, the timeline for clinical
development and regulatory approval of Acceleron’s compounds and the
expected timing for reporting of data from ongoing clinical trials. 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 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 the
development of Acceleron’s compounds will take longer and/or cost more
than planned, that Acceleron or its collaboration partner, Celgene, will
be unable to successfully complete the clinical development of
Acceleron’s compounds, that the Company or Celgene may be delayed in
initiating, enrolling or completing any clinical trials, and that
Acceleron’s compounds will not receive regulatory approval or become
commercially successful products. 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.