August 17, 2021
SymBio Pharmaceuticals Limited
Fuminori Yoshida
Representative Director
President and Chief Executive Officer(Securities Code: 4582)

SymBio Announces First Patient Dosed inPhase 2 Clinical Trial of anti-viral drug Brincidofovir IV
TOKYO, Japan, August 17, 2021 -- SymBio Pharmaceuticals Limited (Headquarters: Tokyo,"SymBio") today announced First Patient Dosed in its Phase 2 clinical trial of an intravenous
formulation of the anti-viral drug brincidofovir ("BCV IV") for treatment of pediatric adenovirus(“AdV”) infections. BCV IV was administered to the first patient on August 16, 2021 (Pacific Daylight
Time in USA).
The multinational Phase 2 study will evaluate the safety, tolerability, and efficacy of BCV IV inchildren with disseminated AdV infection and AdV infection in immunocompromised patients1, anarea with high unmet medical need as there currently exists no effective treatment and determine theappropriate dosage and administration for the next clinical trial. BCV IV was administered to thefirst patient in USA.
Statement from Mr. Fuminori Yoshida, President and Chief Executive Officer of SymBio: “Pediatric
AdV infection in immunocompromised conditions such as those occurring after hematopoietic stem
cell transplantation and organ transplantation is an underserved therapeutic area with urgent needfor a new treatment as there is currently no effective treatment. The achievement of the first patient
enrolled in our multinational study is an important first step in SymBio’s transformation into a globalbusiness."
Given BCV's broad antiviral activity in vitro against various dsDNA viruses2, BCV IV is expected todemonstrate efficacy in the treatment and prevention of infections caused by viral reactivations
following hematopoietic stem cell transplantation and organ transplantation. The Company isprioritizing development for disseminated AdV infection in pediatric patients, an infection which canbe fatal and for which there is high medical need worldwide due to lack of effective treatment. Basedon the efficacy and safety findings obtained in this study, the Company will pursue the possibility of
expanding the target indications of BCV IV to viral infections occurring after not only hematopoietic
stem cell transplantation but also kidney or other organ transplantation, aiming to maximize thebenefits to patients and the business value of BCV IV.
The Company does not expect the information presented herein to have any material impact on its
financial outlook for the fiscal year ending December 2021.

1

[Contact]
Investor Relations
Tel: +81 (0)3 5472 1125
(Note 1) Hematopoietic stem cell transplantation and infection
Hematopoietic stem cell transplantation is a treatment for certain hematologic cancers, such as
leukemia and malignant lymphoma, which cannot be treated by anti-cancer drug treatment orradiation therapy alone. Prior to hematopoietic stem cell transplantation, high doses of chemotherapy
and total body irradiation are used to target cancer cells and at the same time weaken the patient's
own immune system in order to reduce the risk of rejection of new stem cells from the donor. Next,
hematopoietic stem cell transplantation is performed by infusion. It takes about 2 to 4 weeks fortransplanted hematopoietic stem cells to produce blood in the patient's bone marrow. During the long
period of immune-system recovery after transplantation, the patient is susceptible to a variety ofinfections. An effective prophylaxis against viral infections could potentially reduce infections, leading
to better prognosis. Various infections after hematopoietic stem cell transplantation are areas forwhich no effective therapy has been established, and healthcare providers have long-sought aneffective and safe treatment.
(Note 2) Double-stranded DNA (dsDNA) viruses
Double-stranded DNA (dsDNA) viruses includes Herpesviridae (e.g., CMV, HHV-6), adenoviridae(AdVs), polyomaviridae (e.g., BK virus and JC virus), papillomaviridae (HPVs), and poxviridae.
About anti-viral drug Brincidofovir
SyB V-1901 (Generic Name: Brincidofovir, BCV) is a lipid conjugate of cidofovir (CDV). CDV is anantiviral drug already approved and marketed in the United States and the European Union, butunapproved in Japan. As BCV exhibits not only higher anti-viral activity, but also a superior safety
profile in comparison with CDV, BCV is expected to be an effective treatment against a wide
spectrum of infectious diseases caused by DNA viruses, including herpes viruses (including CMV),
adenovirus, BK virus, papilloma virus, and smallpox virus. Moreover, BCV is an easy-to-use andnovel highly active antimultiviral agent with reduced risk of nephrotoxicity, which is a serious side
effect of CDV.
SymBio entered into an exclusive global license agreement with Chimerix Inc. (Headquarters:Durham, NC, "Chimerix") for brincidofovir (BCV) on September 30, 2019. Under the terms of theagreement, Chimerix grants SymBio exclusive worldwide rights to develop, manufacture, andcommercialize BCV in all human indications, excluding the prevention and treatment oforthopoxvirus infections (which includes smallpox and monkeypox).

2

SymBio aims to further globalize business, establish an integrated system for the supply of highquality pharmaceutical products, and grow as a specialty pharmaceutical company through theexclusive global license for BCV. To develop global operations, the Company is considering
partnerships that will utilize regional characteristics of the target diseases, and striving to maximize
the business value of the products and to deliver to patients who need our products as soon aspossible. The Company aims to serve the patients not only in Japan but also in Europe and the U.S.
market where the market size for organ transplantation is large, and Asia, including the Chinesemarket.For further information, please see the SymBio’s press release dated October 1, 2019,https://www.symbiopharma.com/news/20191001.pdf
Innovativeness of Brincidofovir (BCV)Brincidofovir (BCV) is a lipid conjugate of cidofovir (CDV) with hexadecyloxypropyl (HDP), showing arapid incorporation to the plasma membrane with efficient cellular uptake due to the lipid conjugate.
Once inside target cells, the lipid chain is cleaved by action of intracellular phospholipases releasing
CDV, which is then converted to the active form, CDV diphosphate. As a result of enhanced uptake ofCDV diphosphate into the cells, the antiviral activity of BCV is dramatically improved compared withCDV. Furthermore, BCV can greatly reduce the risk of nephrotoxicity associated with CDV because
HDP conjugation greatly reduces plasma exposure to CDV and accumulation of CDV in renal tubularepithelial cells through the transporter (OAT-1).

3About Chimerix
Chimerix is a development-stage biopharmaceutical company dedicated to accelerating theadvancement of innovative medicines that make a meaningful impact in the lives of patients livingwith cancer and other serious diseases. In June 2021, the U. S. Food and Drug Administration
granted approval of TEMBEXA® for the treatment of smallpox as a medical countermeasure.
Chimerix has two other advanced clinical-stage development programs, ONC201 and dociparstat
sodium (DSTAT). ONC201 is currently in a registrational clinical program for recurrent H3 K27Mmutant glioma and blinded independent central review is expected later in 2021. DSTAT is indevelopment as a potential first-line therapy in acute myeloid leukemia. For further information,please visit the Chimerix website, www.chimerix.com.
About SymBio Pharmaceuticals Limited
SymBio Pharmaceuticals Limited was established in March, 2005 by Fuminori Yoshida who
previously served concurrently as Corporate VP of Amgen Inc. and founding President of Amgen
Japan. In May, 2016 the Company incorporated its wholly-owned subsidiary in the U.S., calledSymBio Pharma USA, Inc. (Headquarters: Menlo Park, California, President: Mr. Fuminori Yoshida).
The Company’s underlying corporate mission is to “deliver hope to patients in need” as it aspires to bea leading global specialty biopharmaceutical company dedicated to addressing underserved medical
needs.

4