Celgene Corporation and Acceleron Pharma Announce U.S. FDA Accepts Luspatercept Biologics License Application in Myelodysplastic Syndromes and Beta-Thalassemia

U.S. Food and Drug Administration grants priority review for
beta-thalassemia indication and sets target action date of December 4,
2019

U.S. Food and Drug Administration sets target action date of April 4,
2020 for myelodysplastic syndromes indication

Luspatercept EU Marketing Authorization Application also validated

SUMMIT, N.J. & CAMBRIDGE, Mass.–(BUSINESS WIRE)–$CELG–Celgene Corporation (NASDAQ: CELG) and Acceleron Pharma Inc. (NASDAQ:
XLRN) today announced that the U.S. Food and Drug Administration (FDA)
has accepted Celgene’s Biologics License Application (BLA) for
luspatercept, an investigational erythroid maturation agent, for the
treatment of adult patients with very low to intermediate-risk
myelodysplastic syndromes (MDS)-associated anemia who have ring
sideroblasts and require red blood cell (RBC) transfusions, and for the
treatment of adult patients with beta-thalassemia-associated anemia who
require RBC transfusions. The FDA has granted Priority Review to this
BLA for the evaluation of the beta-thalassemia indication and set a
Prescription Drug User Fee Act (PDUFA), or target action, date of
December 4, 2019. The FDA has also set a PDUFA date of April 4, 2020 for
the evaluation of the MDS indication.

“The acceptance of the luspatercept filings and granting of the U.S.
priority review for beta-thalassemia represent another important step in
delivering this novel therapy to patients in need,” said Jay Backstrom,
M.D., Chief Medical Officer for Celgene. “We believe that luspatercept
can play a critical role in treating the anemia associated with these
serious blood diseases, and with these milestones achieved we look
forward to working closely with the agency to move this therapy toward
approval.”

The safety and efficacy results provided in the application are from the
pivotal phase 3 studies MEDALIST and BELIEVE, which evaluated the
ability of luspatercept to effectively treat the anemia associated with
MDS and beta-thalassemia, respectively. MEDALIST and BELIEVE were both
presented at the 2018 American Society of Hematology annual meeting,
where MEDALIST was included in the plenary session.

The companies also announced that Celgene’s Marketing Authorization
Application in the EU has been successfully validated and the review is
now underway.

“The ongoing U.S. and European regulatory reviews of the luspatercept
filings in MDS and beta-thalassemia strongly support our primary goal,
which has always been to bring a potentially transformative new
treatment to these patients with unmet clinical need as quickly as
possible,” said Habib Dable, President and Chief Executive Officer of
Acceleron. “At the same time, we continue to explore the ability of
luspatercept to address anemia in additional settings, including
patients with treatment-naïve MDS, non-transfusion-dependent
beta-thalassemia, and myelofibrosis.”

Luspatercept is an investigational therapy that is not approved for any
use in any country.

About Luspatercept

Luspatercept is a first-in-class erythroid maturation agent (EMA) that
regulates late-stage red blood cell maturation. Acceleron
and Celgene are jointly developing luspatercept as part of a global
collaboration. A phase 3 trial (COMMANDS) in ESA-naïve, lower-risk MDS
patients, 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 www.clinicaltrials.gov.

About MEDALIST

MEDALIST is a phase 3, randomized, double blind, placebo-controlled,
multi-center study evaluating the safety and efficacy of luspatercept in
adults with very low-, low-, or intermediate-risk myelodysplastic
syndromes (MDS). All patients were RBC transfusion dependent and were
either refractory or intolerant to prior erythropoiesis-stimulating
agent (ESA) therapy or were ESA naïve with endogenous serum
erythropoietin ≥ 200 U/L and had no prior treatment with disease
modifying agents. The median age of the patients enrolled in the trial
was 71 years in the luspatercept treatment group and 72 years in the
placebo group. Median transfusion burden in both treatment arms was 5
RBC units/8 weeks. 229 patients were randomized to receive either
luspatercept 1.0 mg/kg (153 patients) or placebo (76 patients) by
subcutaneous injection once every 21 days. The study was conducted at 65
sites in 11 countries.

About BELIEVE

BELIEVE is a phase 3, randomized, double blind, placebo-controlled
multicenter study comparing luspatercept + best supportive care (BSC)
versus placebo + BSC in adults with beta-thalassemia patients who
require regular RBC transfusions. The median age of the patients was 30
years in both treatment arms. 336 patients were randomized to receive
either luspatercept 1.0 mg/kg (224 patients) or placebo (112 patients)
by subcutaneous injection every 21 days for up to 48 weeks. Crossover to
the luspatercept treatment groups was allowed after unblinding based on
the recommendation of an independent Data Safety Monitoring Committee;
patients treated with luspatercept will be followed for up to 3 years.
The study was conducted at 65 sites in 15 countries.

About Celgene

Celgene Corporation, headquartered in Summit, New Jersey, is an
integrated global biopharmaceutical company engaged primarily in the
discovery, development and commercialization of innovative therapies for
the treatment of cancer and inflammatory diseases through
next-generation solutions in protein homeostasis, immuno-oncology,
epigenetics, immunology and neuro-inflammation. For more information,
please visit www.celgene.com.

Follow Celgene on Social Media: Twitter,
Pinterest,
LinkedIn,
Facebook
and YouTube.

About Acceleron

Acceleron is a 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 superfamily 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 program with ACE-083, a locally-acting Myostatin+ agent in
Phase 2 development in facioscapulohumeral muscular dystrophy and
Charcot-Marie-Tooth disease and is conducting 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 within the
meaning of The Private Securities Litigation Reform Act of 1995. Such
forward-looking statements include those regarding the potential
benefits of, and plans relating to the collaboration between Acceleron
and Celgene; the potential of luspatercept as a therapeutic drug; and
the benefit of each company’s strategic plans and focus. The words
“anticipate,” “believe,” “estimate,” “expect,” “intend,” “may,” “plan,”
“predict,” “project,” “will,” “would,” “could,” “potential,” “possible,”
“hope” and similar expressions are intended to identify forward-looking
statements, although not all forward-looking statements contain these
identifying words. Such statements are subject to numerous important
factors, risks and uncertainties that may cause actual events or results
to differ materially from current expectations and beliefs. For example,
there can be no guarantee that luspatercept will be successfully
developed or complete necessary clinical phases. Forward-looking
statements in this press release could also be affected by risks and
uncertainties relating to a number of other important factors,
including: results of clinical trials, including subsequent analysis of
existing data and new data received from ongoing and future studies; the
content and timing of decisions made by the U.S. FDA and other
regulatory authorities, investigational review boards at clinical trial
sites and publication review bodies; the ability to obtain and maintain
requisite regulatory approvals and to enroll patients in planned
clinical trials; the ability to obtain, maintain and enforce patent and
other intellectual property protection for luspatercept; the ability to
maintain key collaborations; and general economic and market conditions.
These and other risks are described in greater detail under the caption
“Risk Factors” included in each company’s public filings with
the Securities and Exchange Commission and with respect to Celgene
includes risk factors related to the proposed transaction between
Bristol-Myers Squibb and Celgene, such as, but not limited to, the risks
that: management’s time and attention is diverted on transaction related
issues; disruption from the transaction makes it more difficult to
maintain business, contractual and operational relationships; and
Bristol-Myers Squibb, Celgene or the combined company is unable to
retain key personnel. Any forward-looking statements contained in this
press release speak only as of the date hereof, and neither company has
any obligation to update any forward-looking statements, whether as a
result of new information, future events or otherwise, except as may be
required by law.

Hyperlinks are provided as a convenience and for informational
purposes only. Neither Celgene nor Acceleron bears responsibility for
the security or content of external websites or websites outside of
their respective control.

Contacts

Celgene Corporation
Investors:
+1-908-673-9628
[email protected]
or
Media:
+1-908-673-2275
[email protected]

Acceleron
Pharma Inc.
Investors:
Todd James, IRC, (617) 649-9393
Vice
President, Investor Relations and Corporate Communications
or
Media:
Matt
Fearer, (617) 301-9557
Director, Corporate Communications