Psioxis Therapeutics LTD.

PsiOxus Therapeutics Announces First-in-Human Dosing of their Second Gene Therapy Cancer Treatment

March 13, 2019 – OXFORD, UK – PsiOxus Therapeutics, Ltd. (PsiOxus), the gene therapy for cancer company, today announced that it has started dosing NG-350A, an antibody based cancer gene therapy, to cancer patients. The Phase 1 FORTITUDE study is being conducted at multiple cancer centers in the United States and will assess the safety, tolerability and preliminary antitumor activity of NG-350A in subjects with solid tumors.

“Our approach is to systemically deliver a gene therapy vector to turn tumor cells into drug
factories,” stated Dr Brian Champion, the Chief Scientific Officer of PsiOxus. “The patient’s own
tumor cells are used to produce the therapeutic antibody directly in the tumor micro-environment
to treat their cancer.” The monoclonal antibody delivered by NG-350A is a CD40 agonist, a
potentially powerful activator of a patient’s immuno-inflammatory response. When delivered
systemically, CD40 agonists have produced adverse events that may limit their use. NG-350A
directs the production of the antibody locally within the tumor and PsiOxus is developing this
agent to improve the potential for a tolerable and effective treatment. John Beadle, M.D., Chief
Executive Officer of PsiOxus stated “PsiOxus is delighted to have our second cancer gene therapy
in clinical development. We look forward to generating clinical data on this exciting new product
to treat and benefit cancer patients.”

FORTITUDE is an open-label, dose expansion, multicenter, Phase 1 study expected to enroll up
to 125 patients across multiple clinical study sites in the United States. Phase 1a of the study will
assess the safety, tolerability and dose of NG-350A and will enroll patients at study sites in the
United States, led by Dr Aung Naing of the MD Anderson Cancer Center. Phase 1b of the study
will evaluate NG-350A in expansion cohorts in subjects with specific metastatic or advanced
tumors. The ClinicalTrials.gov identifier for the NG-350A study is: NCT03852511. A link to the
ClinicalTrials.gov listing for the study can be found here.

PsiOxus’ proprietary T-SIGn platform uses the enadenotucirev oncolytic virus as a vector to
deliver combinations of therapeutic transgenes to carcinomas to fight cancer. All T-SIGn products
are administered intravenously and are designed to selectively infect and replicate only in tumor
cells. NG-348, the first T-SIGn virus to enter clinical trials, is licensed to Bristol-Myers Squibb.

About PsiOxus Therapeutics

PsiOxus aims to be the world’s leading cancer gene therapy company, delivering medicines of
value to patients with cancer. Our work is product and platform based with a focus on discovering
and developing gene-based immuno-oncology therapies for the treatment of solid tumors. The TSIGn
gene therapy platform is based on the company’s oncolytic virus, enadenotucirev, which has
properties that allow systemic IV delivery and payload capacity to deliver genes as a viral vector.
While delivered systemically, PsiOxus’ T-SIGn gene therapy products act locally within the tumor
micro-environment, replicating only in tumor cells. T-SIGn gene therapy products are “armed”
through the addition of genes that cause the tumor to express combinations of biologics including
antibodies, cytokines, immunomodulatory proteins, or nucleotides (RNA). In effect, the T-SIGn
viruses turn the tumor cells into “drug factories” to express combination gene therapy. The result
is a revolutionary way to deliver biological anticancer therapeutics that act locally within the tumor
microenvironment for the treatment of cancer.

PsiOxus’ first gene therapy program, NG-348, is partnered with Bristol-Myers Squibb and is in
clinical development. In addition to NG-350A, PsiOxus has multiple additional gene therapy
programs in research and pre-clinical development. Clinical trials are also ongoing with the
unarmed enadenotucirev oncolytic virus in solid tumors and in combination trials with a
checkpoint inhibitor and with a chemotherapeutic.

Contacts
PsiOxus Therapeutics Ltd.
John Beadle, +44 1235 42 98 40, PublicRelations@psioxus.com