Acceleron Receives FDA Orphan Drug Designation for ACE-083 in Facioscapulohumeral Muscular Dystrophy

CAMBRIDGE, Mass.–(BUSINESS WIRE)–Acceleron Pharma Inc. (NASDAQ:XLRN), a leading biopharmaceutical company
in the discovery and development of TGF-beta therapeutics to treat
serious and rare diseases, today announced that the United States Food
and Drug Administration (FDA) has granted orphan drug designation for
ACE-083, the Company’s locally acting “Myostatin+” muscle agent, for the
treatment of patients with facioscapulohumeral muscular dystrophy (FSHD).

“We are pleased to receive orphan drug designation for ACE-083, which
has shown the potential to address an area of high unmet medical need,”
said Robert K. Zeldin, M.D., Chief Medical Officer of Acceleron. “We
believe that ACE-083 could become an important new treatment for
patients with FSHD whose muscle weakness negatively affects their
functional abilities. We presented positive preliminary data from Part 1
of our Phase 2 trial in patients with FSHD earlier this year and look
forward to sharing Part 2 results later next year.”

Orphan designation is granted by the FDA Office of Orphan Products
Development to advance the evaluation and development of safe and
effective therapies for the treatment of rare diseases or conditions
affecting fewer than 200,000 people in the U.S. Under the Orphan Drug
Act, the FDA may provide grant funding toward clinical trial costs, tax
advantages, FDA user-fee benefits, and seven years of market exclusivity
in the United States following marketing approval by the FDA. The
granting of an orphan designation request does not alter the standard
regulatory requirements and process for obtaining marketing approval.
For more information about orphan designation, please visit the FDA
website at www.fda.gov.

In May of 2018, FDA granted ACE-083 Fast Track designation for FSHD,
which could facilitate its development and potentially expedite its
review. ACE-083 is currently being evaluated in two Phase 2 trials: one
in FSHD and one in Charcot-Marie-Tooth (CMT) disease. The final Part 1
results from both Phase 2 trials are expected in the second of half of
2018. Preliminary results from Part 2 of the trial in patients with FSHD
are expected in the second half of 2019.

About ACE-083

ACE-083 is a locally-acting therapeutic candidate, based on the
naturally-occurring protein follistatin, which utilizes the “Myostatin+”
approach to inhibit multiple TGF-beta ligands. It is designed to have a
concentrated effect along targeted muscles to maximize growth and
strength selectively in the muscles into which the drug is administered.
Acceleron is developing ACE-083 for disorders such as
Charcot-Marie-Tooth (CMT) disease and facioscapulohumeral muscular
dystrophy (FSHD), in which improved muscle strength in target muscles
may provide a clinical benefit and enhance quality of life. For more
information, please visit www.clinicaltrials.gov.

About Facioscapulohumeral Muscular Dystrophy (FSHD)

FSHD is a rare genetic muscle disorder affecting approximately 20,000
people in the United States for which there are currently no approved
treatments. The primary clinical presentation of FSHD is debilitating
skeletal muscle weakness and loss. The symptoms of FSHD develop in a
descending pattern, beginning with the face and upper body and
progressing to the lower body in a “muscle by muscle” fashion. The
disease is typically diagnosed by a characteristic pattern of muscle
weakness and other clinical symptoms, as well as through genetic testing.

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 www.acceleronpharma.com.
Follow Acceleron on social media: @AcceleronPharma and
LinkedIn.

Forward-Looking Statements

This press release contains forward-looking statements about the
Company’s strategy, future plans and prospects, including statements
regarding the development of the Company’s compounds, the timeline for
clinical development and regulatory approval of the Company’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 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 ongoing or later clinical
trials, that the results of any clinical trial may not be predictive of
the results or success of other clinical trials of the same product
candidate, that the development of the Company’s compounds will take
longer and/or cost more than planned, that the Company will be unable to
successfully complete the clinical development of the Company’s
compounds, that the Company may be delayed in initiating, enrolling or
completing any clinical trials, and that the Company’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 the Company’s 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.

Contacts

Acceleron Pharma Inc.
Todd James, IRC, 617-649-9393
Vice
President, Investor Relations and Corporate Communications
or
Candice
Ellis, 617-649-9226
Manager, Investor Relations and Corporate
Communications
or
Media:
Matt Fearer, 617-301-9557
Director,
Corporate Communications