June 3, 2013
SymBio Pharmaceuticals Limited
Fuminori Yoshida
Representative Director
President and Chief Executive Officer

Onconova Presents Phase 2 Data for Oral rigosertib
at 2013 American Society of Clinical Oncology Annual Meeting- Oral rigosertib (ON 01910.Na) in Transfusion-Dependent Lower Risk MDS -TOKYO, Japan, June 3, 2013 -- SymBio Pharmaceuticals Limited (Headquarters: Tokyo, “SymBio”)
announces that Onconova Therapeutics, Inc. (Headquarters: Newtown, PA and Pennington, NJ,“Onconova”) presented favorable data from its US Phase 2 ONTARGET trial in transfusion-dependent
lower risk myelodysplastic syndrome (MDS) patients treated with oral rigosertib (ON 01910.Na) at the2013 American Society of Clinical Oncology (ASCO) Annual Meeting (ASCO Abstract #7031) in Chicago,IL on June 1, 2013. This Phase 2 study follows the positive findings of a Phase I dose escalation study inMDS patients treated with orally-administered rigosertib. SymBio signed a license agreement withOnconova in July, 2011, for the exclusive right to develop and commercialize both the intravenous andoral forms of rigosertib in Japan and Korea.

Azra Raza, MD, Director, MDS Center, Columbia University Medical Center, New York, NY presented
interim results in 43 patients enrolled in the ONTARGET study. ONTARGET is a randomized, two-arm
study of oral rigosertib (560 mg bid) administered either intermittently (two out of three weeks) orcontinuously. Transfusion-dependent patients must have received at least four units of red blood cells(RBC) transfusions over eight weeks before randomization and can receive transfusions and erythrocyte
stimulating agents (ESAs) while on study.

In the ONTARGET study, 13 of the 26 (50%) evaluable patients in the intermittent dosing arm and 2 of
the 8 (25%) evaluable patients in the continuous dosing arm achieved transfusion independence,defined as no RBC transfusions for at least eight consecutive weeks. Onset of transfusion independence
ranged from 1 -24 weeks following the initiation of rigosertib dosing, and the duration of transfusion
independence ranged from eight to greater than 48 weeks. None of the responders had a del5q
karyotype. Transfusion independence was durable and two patients continue to benefit from therapy
more than nine months after starting rigosertib. Eleven of the 13 transfusion-independent patients in theintermittent dosing arm received one or more injections of ESAs during the time of oral rigosertib
administration, and the patterns of hemoglobin responses observed in a few patients suggest a possiblesynergy between oral rigosertib and ESAs.

Evaluation of safety indicated that oral rigosertib was generally well tolerated with the most frequently
observed side effects being urologic in nature. In the continuous dosing arm of the study, grade 2+
urinary side effects were observed in five of the first nine patients. Accordingly, the protocol wasamended to allow all patients to be treated with intermittent dosing. The most frequent urinary adverse
events in the intermittent dosing arm were grade 2+ urinary urgency/frequency (38% of patients), grade2+ dysuria (15%), and hematuria (15%). Other grade 2+ adverse events included intermittent
neutropenia (1 grade 3/1 grade 4). Median onset of Gr2+ urinary Adverse Events in the intermittent
dosing arm was 28 weeks compared with 12 weeks in the continuous dosing arm. Median duration oftreatment in the intermittent dosing arm has not yet been reached (greater than 48 weeks compared with
24 weeks in the continuous dosing arm). Renal function was unaffected and gastrointestinal adverse
events were infrequently observed.

Rigosertib is being developed in both oral and intravenous forms. Onconova is conducting late-stage
clinical trials with rigosertib in the U.S., Europe and India for the treatment of MDS and solid tumors.
Onconova recently announced reaching the enrollment goal in its randomized, controlled ONTIME
Phase 3 trial for intravenous rigosertib in adult patients with myelodysplastic syndromes whose diseasehas failed azacitidine or decitabine therapy. Rigosertib is also being evaluated in a Phase 3 trial forfirst-line treatment in combination with gemcitabine for patients with metastatic pancreatic cancer who
had not previously received any chemotherapy.
In Japan, two Phase 1 trials are underway by SymBio Pharmaceuticals, Onconova’s licensee for Japan
Korea, in relapsed or refractory high-risk MDS patients using the IV formulation of the drug (SyB L-1101),and in frontline low-risk MDS patients using the oral formulation of rigosertib (SyB C-1101). SymBio isstriving to ensure that this much-needed drug is made available to MDS patients in Japan as soon aspossible.

[Please see the following for further information on MDS, rigosertib, and Onconova ][Contact]
Tomoyuki Watanabe
Director, Head of Finance & Accounting, and Corporate Planning Group
Tel: +081(0)3 5472 1125

Note to Editors

About Myelodysplastic Syndrome (MDS)MDS represents a group of diverse myeloid (bone marrow) stem cell disorders that gradually affect theability of bone marrow to produce normal red blood cells, white blood cells, and platelets. Blood stem
cells fail to mature into healthy blood cells, and the immature blood cells, called blasts, do not function
normally and either die in the bone marrow or enter the blood. A higher percent of blasts is linked to ahigher likelihood of developing leukemia and poorer overall prognosis. The risk of MDS increases withage and the disease commonly affects the elderly.
About rigosertib
Rigosertib is an inhibitor of two important cellular signaling pathways, phosphoinositide 3-kinase, or PI3K,
and polo-like kinase, or PLK, both of which are frequently activated in cancer cells. Rigosertib is being
developed in both oral and intravenous forms as a treatment for hematological diseases and solidtumors. Onconova recently announced reaching the enrollment goal in its randomized, controlled
ONTIME Phase 3 Trial for intravenous rigosertib in adult patients with myelodysplastic syndromes
whose disease has failed azacitidine or decitabine therapy. Rigosertib is also being evaluated in a Phase
3 trial for first-line treatment in combination with gemcitabine for patients with metastatic pancreaticcancer who had not previously received any chemotherapy. The oral form of rigosertib is currently being
studied in Phase 2 trials in patients with transfusion-dependent lower risk myelodysplastic syndromes
and in patients with head and neck cancer. Rigosertib has been granted orphan drug status for MDS inboth the United States and Europe, as well as orphan drug status for pancreatic cancer in the UnitedStates. Rigosertib is being developed in partnership with Baxter International (commercialization rightsin Europe) and SymBio Pharmaceuticals (Japan and Korea). Onconova has retained all other territories
for commercialization.

About Onconova Therapeutics, Inc.
Onconova Therapeutics is a clinical-stage biopharmaceutical company focused on discovering anddeveloping novel products to treat cancer. Onconova's clinical and pre-clinical stage drug development
candidates are derived from its extensive proprietary chemical library and are designed to work against
specific cellular pathways that promote cancer while causing minimal damage to normal cells. In addition
to rigosertib, the Company’s most advanced product candidate, two other candidates are in clinical trials,and several candidates are in pre-clinical stages. For more information, please visit
http://www.onconova.com.

About SymBio Pharmaceuticals Limited
SymBio Pharmaceuticals Limited, based in Tokyo, Japan, was established in March, 2005 by Fuminori
Yoshida, who previously served concurrently as Corporate VP of Amgen Inc. and founding President ofAmgen Japan.

The company’s underlying corporate mission is to “deliver hope to patients in need” asit aspires to be a leading specialty pharma in Asia Pacific dedicated to addressing underserved medical
needs in the areas of oncology, hematology and autoimmune.

The company’s lead drug candidate,bendamustine hydrochloride, has been successfully developed and launched in Japan forrefractory/relapsed indolent non-Hodgkin’s lymphoma (NHL) and mantle cell lymphoma. SymBio isalso actively developing bendamustine in frontline indolent NHL, refractory/relapsed aggressive NHL
and multiple myeloma in Japan.

The product has been launched in Hong Kong, Singapore and Korea,

with market approval recently granted in Taiwan. For additional information, please visit our homepage
at http://www.symbiopharma.com.