Acceleron Initiates Phase 2 Study of ACE-536 to Treat Anemia in Patients with Myelodysplastic Syndromes

  Acceleron Initiates Phase 2 Study of ACE-536 to Treat Anemia in Patients
  with Myelodysplastic Syndromes

   Acceleron earns $10 million milestone payment from collaboration partner
                             Celgene Corporation

Business Wire

CAMBRIDGE, Mass. -- January 29, 2013

Acceleron Pharma, Inc., a biopharmaceutical company developing protein
therapeutics for cancer and orphan diseases, today announced the initiation of
a phase 2 study of its investigational protein therapeutic, ACE-536, to treat
anemia in patients with myelodysplastic syndromes (MDS). MDS are a group of
hematologic malignancies of the bone marrow that result in low levels of one
or more types of blood cells resulting most commonly in severe and chronic
anemia (low levels of red blood cells). Acceleron is developing ACE-536 in a
global collaboration with Celgene Corporation (NASDAQ: CELG). Acceleron earned
a $10 million milestone for initiating this phase 2 study and is still
eligible to receive development, regulatory and commercial milestones of up to
$200 million for the ACE-536 program.

“The anemia experienced by patients with MDS is clinically challenging because
it is often unresponsive to administration of erythropoietin and many patients
ultimately require red blood cell transfusions,” said Professor Uwe
Platzbecker, M.D., Director outpatient department of Hematology/Oncology at
Universitatsklinikum Carl Gustav Carus in Dresden, Germany and coordinating
principal investigator of the ACE-536 “PACE-MDS” phase 2 study. “We are
excited to explore ACE-536 as a potential new treatment for MDS patients in
this phase 2 study”.

“ACE-536 has the potential to make a significant impact on the treatment of
anemia in MDS,” said Matthew Sherman, M.D., Chief Medical Officer of
Acceleron. “Unlike erythropoietin, ACE-536 may target the specific defect in
the erythropoietic maturation process in MDS patients and we are optimistic
that it could become an important new therapeutic option for this underserved
patient population.”

About the Phase 2 Clinical Trial

The phase 2 clinical trial is designed to evaluate the safety, tolerability
and efficacy of ACE-536 in patients with low-risk or intermediate-1 risk MDS.
Efficacy measures include increases in hemoglobin levels, reduction of red
blood cell transfusion burden, and other hematologic parameters, as well as
biomarkers of iron and bone metabolism. For additional information on this
clinical trial, please visit clinicaltrials.gov, identifier NCT01749514.

About Myelodysplastic Syndromes

Myelodysplastic syndromes (MDS) are a heterogeneous group of hematologic
malignancies of the bone marrow commonly leading to severe and chronic anemia
due to ineffective erythropoiesis (red blood cell formation). The National
Cancer Institute estimates that more than 10,000 people are diagnosed with MDS
in the United States each year. Patients with MDS have a hypercellular bone
marrow with various dysplastic changes of the cells that are also seen in
peripheral blood, resulting in cytopenias (low blood cell counts) and an
increased risk of progression to acute myeloid leukemia (AML). Nearly all MDS
patients suffer from anemia. The anemia in MDS is due to ineffective
erythropoiesis, which is characterized by high endogenous levels of
erythropoietin driving an abundance of early stage red blood cell precursors
and an inability of these precursor cells to properly differentiate into
healthy, functional red blood cells. Many patients are therefore unresponsive
to the administration of erythropoietin to correct the resulting anemia and
instead require red blood cell transfusions, which can increase the risk of
infection and iron-overload related toxicities.

About ACE-536

ACE-536 is a modified type II activin receptor fusion protein that acts as a
ligand trap for members in the TGF-beta superfamily involved in late stages of
erythropoiesis. ACE-536 promotes late-stage erythrocyte precursor cell
differentiation, distinct from erythropoietin which acts during early,
proliferative stages of erythropoiesis. This mechanism of action to increase
red blood cells has the potential to treat patients with anemia in diseases
such as myelodysplastic syndromes (MDS) and beta-thalassemia that are
inadequately managed with current therapy. In a phase 1 clinical study of
healthy volunteers, ACE-536 produced a dose-dependent increase in red blood
cells and hemoglobin levels. Acceleron and Celgene are jointly developing
ACE-536 for diseases such as beta-thalassemia and myelodysplastic syndromes
(MDS).

About Acceleron

Acceleron is a privately-held biopharmaceutical company committed to discover,
develop, manufacture and commercialize novel protein therapeutics for orphan
diseases and cancer. Acceleron’s scientific approach takes advantage of its
unique insight to discover first-in-class therapies based on the TGF-β protein
superfamily. Acceleron utilizes proven biotherapeutic technologies and
capitalizes on the company’s internal GMP manufacturing capability to advance
its therapeutic programs rapidly and efficiently. The investors in Acceleron
include Advanced Technology Ventures, Alkermes, Avalon Ventures, Bessemer
Ventures, Celgene, Flagship Ventures, MPM BioEquities, OrbiMed Advisors,
Polaris Ventures, QVT Financial, Sutter Hill Ventures and Venrock. For further
information on Acceleron, please visit www.acceleronpharma.com.

Contact:

Acceleron Pharma
Steven Ertel, 617-649-9234
Chief Business Officer
or
Maureen L. Suda (Media)
Suda Communications LLC
585-387-9248