U.S. Approval and Issuance of CDX Antibody Patent

2 June 2021

Hemogenyx Pharmaceuticals plc

("Hemogenyx Pharmaceuticals" or the "Company")

U.S. Approval and Issuance of CDX Antibody Patent

Hemogenyx Pharmaceuticals plc (LSE: HEMO), the biopharmaceutical group developing new therapies and treatments for blood diseases, is pleased to announce that a patent application entitled METHOD OF ELIMINATING HEMATOPOIETIC STEM CELLS/HEMATOPOIETIC PROGENITORS (HSC/HP) IN A PATIENT USING BI-SPECIFIC ANTIBODIES has been approved and issued by the United States Patent and Trademark Office. The patent was issued as Patent Number US 11,021,536 B2 (https://tinyurl.com/yspjv89w).

This patent covers a method of use of a bi-specific antibody ("CDX"), one of the Company's original and lead product candidates, for conditioning bone marrow/hematopoietic stem cell ("BM/HSC") transplantation. It also covers a composition of matter (a subset of sequences) of monoclonal antibodies against target proteins existing on the surface of hematopoietic stem cells/hematopoietic progenitors ("HSC/HP"), and/or a number of leukemias such as acute myeloid leukemia ("AML") as well as a protein that exists on the surface of immune cells (T cells).

The method described in the patent (the "Method") was invented by Dr Vladislav Sandler, CEO and Co-founder of Hemogenyx Pharmaceuticals, working alone, and was then further developed and refined together with the Company's team of scientists in its laboratory facilities in New York City. The patent provides a method for preparing or conditioning of BM/HSC transplantation in lieu of the traditional conditioning protocol involving chemotherapy, which is highly toxic. The Method provides a recombinant single chain bi-specific antibody that binds to both human FMS-like tyrosine kinase 3 (FLT3) on the surface of "unwanted cells" and human CD3 on the surface of T cells, and the administering of a therapeutic amount of a pharmaceutical composition comprising the bi-specific antibody to the patient.

If fully and successfully developed, the Method would obviate the need for highly toxic conditioning protocols, including chemotherapy, in patients who require BM/HSC transplantation, and would result in the development of a superior pharmaceutical for the treatment of blood cancers, for which survival rates are currently very poor.

The bi-specific antibody described in the issued patent was developed by the Company and the patent application for it first filed in 2016. That filing, together with data showing its efficacy in humanised mice with respect to BM/HSC transplantation conditioning, formed the basis of the Company's collaboration with a leading global pharmaceutical company ("GlobalCo") to develop CDX further (https://hemogenyx.com/investors/announcements/announcement/2018/
Hemogenyx-Pharma-Plc---Development-Agreement/).

Dr Vladislav Sandler, CEO & Co-Founder of Hemogenyx, commented: "The issue of this patent is significant for the Company because it protects the Company's IP in one of its lead product candidates, while further solidifying its leading position in the field of the development of groundbreaking therapies for the treatment of blood cancers and BM/HSC transplantation conditioning. The Company continues to progress the laboratory and commercial development of the CDX antibody, and is focused on bringing it to clinical trials."

About AML

AML, the most common type of acute leukemia in adults, has poor survival rates (a five-year survival rate of less than 30% in adults) and is currently treated using chemotherapy, rather than the potentially more benign and effective form of therapy being developed by Hemogenyx Pharmaceuticals. The successful development of the new therapy for AML would have a major impact on treatment and survival rates for the disease.

Further information about the development of the Company's bi-specific antibody technology can be found on Hemogenyx Pharmaceuticals' web site: https://hemogenyx.com/technology/cdx-antibodies.

Market Abuse Regulation (MAR) Disclosure

The information contained within this announcement is deemed to constitute inside information as stipulated under the Market Abuse Regulation ("MAR") (EU) No. 596/2014, as incorporated into UK law by the European Union (Withdrawal) Act 2018. Upon the publication of this announcement, this inside information is now considered to be in the public domain.

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About Hemogenyx Pharmaceuticals plc

Hemogenyx Pharmaceuticals is a publicly traded company (LSE: HEMO) headquartered in London, with its US operating subsidiaries, Hemogenyx Pharmaceuticals LLC and Immugenyx LLC, located in New York City at its state-of-the-art research facility.

The Company is a pre-clinical stage biopharmaceutical group developing new medicines and treatments to treat blood and autoimmune disease and to bring the curative power of bone marrow transplantation to a greater number of patients suffering from otherwise incurable life-threatening diseases. Hemogenyx Pharmaceuticals is developing several distinct and complementary product candidates, as well as platform technologies that it uses as engines for novel product development.

For more than 50 years, bone marrow transplantation has been used to save the lives of patients suffering from blood diseases. The risks of toxicity and death that are associated with bone marrow transplantation, however, have meant that the procedure is restricted to use only as a last resort. The Company's technology has the potential to enable many more patients suffering from devastating blood diseases such as leukemia and lymphoma, as well as severe autoimmune diseases such as multiple sclerosis, aplastic anemia and systemic lupus erythematosus (Lupus), to benefit from bone marrow transplantation.