CDX Effective as Conditioning Therapeutic in vivo

Hemogenyx Pharmaceuticals plc

("Hemogenyx" or the "Company")

CDX Antibody is Effective as Conditioning Therapeutic in vivo

Hemogenyx Pharmaceuticals plc (LSE: HEMO) announces further progress with its original core development: the use of a CDX bi-specific antibody ("CDX antibody") product candidate as a conditioning therapy for bone marrow transplants. The Company has obtained the first data results from in vivo testing of its CDX antibody developed in collaboration with a global pharmaceutical company under the partnership previously announced by the Company on 14 May 2018.

The first data results demonstrate that the CDX antibody is capable of eliminating human hematopoietic stem cells/hematopoietic progenitors ("HSC"/"HP" aka blood stem cells) in vivo. The Company verified the efficacy of CDX as a conditioning therapeutic using its proprietary advanced hematopoietic chimeric ("AHC") mice (humanised mice).

The CDX antibody was shown to target blood stem cells that express the protein FLT3. The CDX antibody binds to the FLT3 protein that is located on the surface of unwanted (target) cells and also binds to the CD3 protein on the surface of T-cells, and ultimately redirects T-cells to kill the target cells.

The mechanism of elimination of acute myeloid leukemia ("AML") and acute lymphoblastic leukemia ("ALL") cells (announced on June 5, 2019 and May 30, 2019 respectively) and HSC/HP that is necessary to condition a patient for bone marrow transplantation is essentially the same. The Company is greatly encouraged by the positive results received from in vivo and in vitro testing. These results together potentially significantly expand the use of CDX and make the Company's leading product candidate more appealing for co-development in a potential partnership.

Background on conditioning for bone marrow ("BM")/ HSC transplantations

Conditioning (preparation) of a patient for a BM/HSC transplant is a critical element of the procedure, serving two main purposes:

1. It provides adequate immunosuppression of the patient and clears sufficient niche space in the bone marrow for the transplanted HSC/HP (blood stem cells). This allows the transplanted cells to engraft in the recipient.

2. It also often helps to eradicate the source of the malignancy such as AML or ALL, two forms of blood cancer, and potentially in the future other blood/immune diseases.

Conditioning of patients has traditionally been achieved by administering high-dose chemotherapy with or without radiation. All conditioning regimens that are currently in use are toxic and have severe side effects that can be life threatening due to their off-target activity.

There were more than 20,000 BM/HSC transplants performed in the US in 2017 and more than twice as many in Europe. Non-malignant conditions such as multiple sclerosis, systemic sclerosis, systemic lupus erythematosus, and Type I diabetes (severe autoimmune diseases), among others, may also be treated and potentially cured using BM/HSC transplants. Based on current clinical protocols used for the treatment of malignant blood diseases and the number of people diagnosed with severe autoimmune conditions, the Directors believe that a large number of additional transplantations could have been performed in the US and Europe if conditioning regimens were significantly less harmful and dangerous for patients. Hence, the development of safe and efficient conditioning therapeutics could potentially greatly expand the market for BM/HSC transplantation.

Vladislav Sandler, Chief Executive Officer, commented, "This new data demonstrates our continuing progress in developing potential uses for our CDX antibody. Our new data demonstrates the efficacy of the CDX antibody as a conditioning therapeutic when tested in vivo in our own proprietary advanced humanised mouse model which closely replicates the human immune system. We are much encouraged by this new data, and we will endeavor to keep shareholders informed of further progress as it occurs."

Market Abuse Regulation (MAR) Disclosure

Certain information contained in this announcement would have been deemed inside information for the purposes of Article 7 of Regulation (EU) No 596/2014 until the release of this announcement.

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About Hemogenyx Pharmaceuticals plc

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

Hemogenyx is a pre-clinical stage biopharmaceutical group developing new medicines and treatments to bring the curative power of bone marrow transplantation to a greater number of patients suffering from otherwise incurable life-threatening diseases. Hemogenyx is developing two distinct and complementary products, as well as a platform technology that it uses as an engine 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. Hemogenyx'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.