November 6, 2023
SymBio Pharmaceuticals Limited
Fuminori Yoshida
Representative Director
President and Chief Executive Officer(Securities Code: 4582)

SymBio To Present Positive Data from Ongoing Phase 2a Study of IV Brincidofovir
in Adenovirus Infection in Oral Presentation
at the 65th American Society of Hematology (ASH) Annual Meeting•

Adenovirus viremia clearance from plasma was demonstrated in 100% of patients treated withintravenous brincidofovir at 0.4 mg/kg* twice weekly.
In 90% of those patients, viral clearance was achieved in within 4 weeks of treatment.

•No serious treatment-related adverse events (TRAEs) including gastrointestinal and hepatic•

toxicities were observed, and all TRAEs were reversible and resolved after the completion ofthe treatment.
TOKYO, Japan, November 6, 2023 -- SymBio Pharmaceuticals Limited (Headquarters: Tokyo, “SymBio”
or the “Company”) today announced that preliminary data from Phase 2a study of intravenous
brincidofovir (IV BCV) in immunocompromised patients with adenovirus (AdV) infection has been
accepted as an oral presentation at the 65th American Society of Hematology (ASH) Annual Meetingand Exposition, December 9-12, 2023, in San Diego, California. The presenter is Michael Grimley, MD,
Medical Director, Division of Bone Marrow Transplantation and Immune Deficiency, Cincinnati
Children's Hospital Medical Center, Cincinnati, Ohio.
Brincidofovir (BCV) is broad spectrum antiviral agent that has demonstrated the greatest in vitro
potency and broad-spectrum activity against opportunistic double-stranded DNA viruses, including
adenoviruses. Oral BCV has been approved by the FDA as a countermeasure against smallpox withevidence of gastrointestinal toxicity. The intravenous preparation devoid of this toxicity to date is being
developed by SymBio company for multiple indications. AdV infections occurs in approximately 30% of
pediatric recipients of hematopoietic cell transplant (HCT) and 6% of adult HCT recipients.
Disseminated AdV disease is associated with high mortality, especially when it is associated withpneumonia.
In a dose ascending Phase 2a study, a total of 27 immunocompromise patients with AdV viremia,
including recipients of allogeneic hematopoietic cell transplant, were treated in 3 cohorts with IV BCV twiceweekly. Treatment with IV BCV at 0.4 mg/kg* demonstrated potent antiviral activity with AdV viremia
clearance in 100% of 10 patients treated. Among 90% of those patients, AdV viremia clearance wasachieved within 4 weeks of treatment. IV BCV was highly effective in AdV viremia clearance in a dose-1

dependent manner. Among all 27 patients treated with IV BCV twice weekly across all cohorts, TRAEs
were observed in 7 patients and serious TRAEs including gastrointestinal and hepatic toxicities
described with the oral BCV formulation were not observed. All TRAEs were reversible and resolved after
the completion of the treatment. Adverse event-related discontinuations were observed in 6 of 27
patients across cohorts, including one of 10 patients treated with 0.4 mg/kg IV BCV.
In view of promising results and in the absence of any other approved treatments for AdV infection,
results support the need for further exploration and additional clinical trials of IV BCV as a treatment
for AdV infections.
“We are excited to share the preliminary data from our Phase 2a study of brincidofovir for the treatmentof adenovirus infections, which continue to support the transformational potential of brincidofovir.
Based on preliminary data from this study, SymBio will consider a phase 3 study to support theregistration of brincidofovir in a highly unmet medical need. We are very pleased with the enthusiasm
we are seeing from leading transplant centers around the world” said Fuminori Yoshida, President andCEO.
“We are pleased to have the opportunity to present this encouraging interim data from this ongoingtrial as we work to bring a much needed treatment to these patients with limited treatment options,”
Says Nkechi Azie MD, the global CMO. “We are proud of our continued clinical progress as we remaincommitted to bringing this innovative, broad spectrum potent antiviral to market as a potential option
for patients with difficult to treat life threatening viral infections.
Details of the presentation at ASH are as follows:
https://ash.confex.com/ash/2023/webprogram/Paper179901.html
Title: Preliminary Results of a Phase 2a Clinical Trial to Evaluate Safety, Tolerability and Antiviral
Activity of Intravenous Brincidofovir in Immunocompromised Patients with Adenovirus Infection(Abstract #112)
Session Name: 721. Allogeneic Transplantation: Conditioning Regimens, Engraftment and Acute
Toxicities: Improving Outcomes by Reducing Transplant-Related Complications
Session Date: Saturday, December 9, 2023
Session Time: 9:30 AM - 11:00 AM
Presentation Time: 10:15 AM
Room: San Diego Convention Center, Room 11*: or 20 mg for patients weighing ≥50 kg2

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(Note)About the anti-viral drug Brincidofovir
Brincidofovir (BCV) has a new mechanism of action as a lipid conjugate of cidofovir (CDV). CDV is anantiviral drug already approved and marketed in the United States and the European Union, but
unapproved in Japan. BCV is expected to be an effective treatment against a wide spectrum of dsDNAvirus infections (cytomegalovirus, adenovirus, Epstein-Barr virus, herpes virus, BK virus,
papillomavirus and smallpox virus including monkeypox, etc.), with superior features such as highactivity antiviral effect in comparison with CDV and other antiviral drugs.
Due to the breakthrough nature of the BCV molecule, in which a specific length of lipid chain is attachedto the CDV, BCV is converted into a molecule that acts directly within the cell, thereby dramaticallyincreasing the efficiency of cellular uptake and showing a high antiviral activity.
In September 2019, SymBio entered into a license agreement with Chimerix for the exclusive worldwide
rights to develop, market, and manufacture BCV for all diseases except orthopoxviruses (such assmallpox and monkeypox).
The tablets and oral suspension (oral formulation) were approved on June 4, 2021, for the treatment ofsmallpox in adults and pediatric patients, including neonates.
In addition to its high antiviral activity, BCV is also expected to have anti-tumor effects. We are
currently conducting collaborative studies with the National Cancer Centre Singapore, the Universityof California, San Francisco, and other institutions to confirm its anti-cancer activity and to identify
synergistic effects when combined with its antiviral activity.
Clinical trials and important R&D collaborations with prominent research institutions include:- Initiated a Phase II clinical trial in patients with adenovirus infection after hematopoietic stem celltransplantation (March 2021) and received Fast Track designation from the FDA (April 2021). Proof ofConcept (POC) of antiviral efficacy established based on data up to cohort 3 (May 2023).
- Initiated a non-clinical trial at the University of California, San Francisco Neurosurgery Brain Tumor
Center to evaluate the anti-tumor effect of BCV on refractory brain tumors (September 2021).
- In recent years, large numbers of studies have demonstrated that EBV is a risk factor for MS. SymBio
entered into CRADA with the NINDS in March 2023 to establish a new antiviral treatment method forMS, and has been conducting collaborative research to develop a clinical trial.
- CRADA with the National Institute of Allergy and Infectious Diseases (NIAID), affiliated with theNIH, to evaluate the efficacy of BCV for EB virus-associated lymphoproliferative diseases (April 2023).
- Research on the involvement of infection by reactivation of latent viruses in various neurologicalseverity diseases of the brain, including Alzheimer's disease, has been ongoing for the past several years,
and a simple three-dimensional mimicry of human neural stem cell cultures and brain tissue
established by Tufts University in the United States, the A Sponsored Research Agreement was signed(December 2022) to examine the effect of BCV on HSV infection using a herpes simplex virus (HSV)

4infection/reactivation model established by Tufts University in the U.S., which uses human neural stem
cells cultured to mimic brain tissue in three dimensions.
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., called SymBio Pharma USA,Inc. (Headquarters: Durham, North Carolina, representative: Stephane Berthier). The Company’s
underlying corporate mission is to “deliver hope to patients in need” as it aspires to be a leading global
specialty biopharmaceutical company dedicated to addressing underserved medical needs.

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