Additional Clinical Sites Expected to Enroll CMML Patients in Australia

Short Hills, New Jersey and Adelaide, South Australia--(Newsfile Corp. - September 12, 2022) - Humanigen, Inc. (Nasdaq: HGEN), Humanigen Australia Pty Ltd, ("Humanigen") and the South Australian Health and Medical Research Institute ("SAHMRI") today announced an expansion of the ongoing development Precision Approach to Chronic Myelomonocytic Leukemia ("PREACH-M") study of lenzilumab in chronic myelomonocytic leukemia ("CMML"), a rare blood cancer, in patients with NRAS, KRAS, and CBL genetic mutations. The PREACH-M study will expand from the first two sites at the Royal Adelaide Hospital in Adelaide, Southern Australia and Austin Health-Austin Hospital in Heidelberg, Victoria to add up to 6 additional sites; one in Queensland, one in Western Australia, two sites in New South Wales, a site in Tasmania, and options being explored for an additional site in New Zealand.

The primary investigator for PREACH-M, Associate Professor Daniel Thomas, leader of the Myeloid Metabolism Laboratory at SAHMRI and Associate Professor of Medicine at the University of Adelaide stated, "CMML is difficult to diagnose and to treat. SAHMRI and the Precision Cancer Medicine group are pleased to be able to expand the number of centres to reach more patients in need of new treatment options. Previous studies have shown that lenzilumab has been extremely well tolerated. The overarching goal of the clinical trial is to investigate the possibility of lenzilumab improving response rates in CMML according to updated uniform response criteria for myelodysplasia / myeloproliferative disorder overlap syndromes such as CMML".

"Expansion of the PREACH-M study is a critical next step in our realignment strategy. Associate Professor Thomas is a world expert in CMML and program leader for Blood Cancers at SAHMRI. SAHMRI is a leader in precision medicine that assists patients in finding the proper treatment for their cancer," commented Cameron Durrant, Chairman and CEO of Humanigen. "Lenzilumab was discovered in Australia, so it is only fitting that we leverage the wealth of local knowledge that exists for lenzilumab as we continue clinical development. Expanding the number of sites may accelerate enrollment. We anticipate seeing preliminary results from this study in the first half of 2023."

About CMML

The current standard of care for CMML are hypomethylating agents such azacitidine and decitabine, which historically have a partial and complete response rates in the 7-18% range, according to the International Working Group Criteria.^1,2,3

The incidence of CMML in the US, UK, and Australia is about 1,700 patients annually.⁴ As a rare disease, lenzilumab may qualify for certain regulatory and commercial advantages that may accelerate development and approval. Humanigen and the Principal Investigator are assessing regulatory pathways that may enable early results to support a regulatory submission and potential approval by the Therapeutic Goods Administration in Australia, which could be expanded through Project Orbis (https://www.fda.gov/about-fda/oncology-center-excellence/project-orbis) to the United States and the United Kingdom.

There have been no new therapeutic agents for patients with high-risk CMML in 30 years⁵ and independent publications have demonstrated the key role of GM-CSF and RAS pathway mutations in this and other cancers, including juvenile myelomonocytic leukemia ("JMML"), myelodysplastic syndromes, myeloproliferative neoplasms, and acute myeloid leukemia.^6,7,8

A clinical protocol is also being developed for JMML with NRAS, KRAS, PTPN11 and/or NF1 genetic mutations.

About Humanigen

Humanigen, Inc. (Nasdaq: HGEN) ("Humanigen"), is a clinical-stage biopharmaceutical company focused on developing lenzilumab, a first-in-class antibody that binds to and neutralizes granulocyte-macrophage colony-stimulating factor. Humanigen is developing lenzilumab as a treatment for chronic myelomonocytic leukemia and acute graft versus host disease. Humanigen is also exploring use of lenzilumab to prevent toxicities associated with CAR-T therapy through investigator-initiated trials. Humanigen is also developing an antibody drug conjugate (ADC) utilizing its EphA-3 targeted monoclonal antibody ifabotuzumab ("ifab") for solid tumors. For more information, visit www.humanigen.com.

About PREACH-M Trial

The Precision Approach to Chronic Myelomonocytic Leukemia ("PREACH-M") clinical trial is sponsored by the South Australian Health and Medical Research Institute ("SAHMRI") and funded by a Medical Research Future Fund grant from the National Health and Medical Research Council of the Australian government to the University of Adelaide. Humanigen is providing lenzilumab for use in the study through its Australian subsidiary, Humanigen Australia Pty Ltd. The trial is open to newly diagnosed CMML patients who haven't had any treatment yet but are beginning to have symptoms - low blood counts or high fevers or large spleen or high white cell count and who generally feel unwell. Until now, these patients have been limited to having blood transfusions and supportive care. Anyone who is interested in learning more about the study, or additional information can visit the Australian New Zealand Clinical Trials Registry (www.anzctr.org.au).

About SAHMRI

SAHMRI is South Australia's flagship independent not-for-profit health and medical research institute. The Precision Cancer Medicine Theme is committed to understanding the factors that determine patient-specific responses to disease or therapeutic intervention, enabling us to better predict patient outcomes, to stratify patients to the best treatment options and to develop more personalised, targeted interventions.

Forward-Looking Statements

All statements other than statements of historical facts contained in this press release are forward-looking statements. Forward-looking statements reflect management's current knowledge, assumptions, judgment, and expectations regarding future performance or events. Although management believes that the expectations reflected in such statements are reasonable, they give no assurance that such expectations will prove to be correct, and you should be aware that actual events or results may differ materially from those contained in the forward- looking statements. Words such as "will," "expect," "intend," "plan," "potential," "possible," "goals," "accelerate," "continue," and similar expressions identify forward-looking statements.

Forward-looking statements are subject to a number of risks and uncertainties including, but not limited to, the risks inherent in our lack of profitability and need for additional capital; our dependence on partners to further the development of our product candidates; the uncertainties inherent in the development, attainment of the requisite regulatory authorizations and approvals and launch of any new pharmaceutical product; the outcome of pending or future litigation or arbitration; and the various risks and uncertainties described in the "Risk Factors" sections of our latest annual and quarterly reports and other filings with the SEC.

All forward-looking statements are expressly qualified in their entirety by this cautionary notice. You should not rely upon any forward-looking statements as predictions of future events. We undertake no obligation to revise or update any forward-looking statements made in this press release to reflect events or circumstances after the date hereof, to reflect new information or the occurrence of unanticipated events, or to update the reasons why actual results could differ materially from those anticipated in the forward-looking statements, in each case, except as required by law.

References

1. Costa, R., et. al. (2010, December 23). Activity of azacitidine in chronic myelomonocytic leukemia. Cancer, 117(12), 2690-2696. https://doi.org/10.1002/cncr.25759. https://doi.org/10.1002/ajh.26455
2. South Australian Registry data, South Australian Health and Medical Research Institute, April 14, 2021
3. Pleyer, L., et. al. (2014, April). Azacitidine in CMML: Matched-pair analyses of daily-life patients reveal modest effects on clinical course and survival. Leukemia Research, 38(4), 475-483. https://doi.org/10.1016/j.leukres.2014.01.006
4. Incidence extrapolated by applying American Cancer Society incidence rate of four per one million people to the population of U.S., UK, and Australia. https://www.cancer.org/cancer/chronic-myelomonocytic-leukemia/about/key-statistics.html
5. Aim of first-ever CMML study - to improve survival. Leukaemia Foundation. (2021, October 11). Retrieved July 21, 2022, from https://www.leukaemia.org.au/stories/aim-of-first-ever-cmml-study-to-improve-survival/
6. Gupta, A. et al. (2021, February 28). Juvenile myelomonocytic leukemia-A comprehensive review and recent advances in management. American Journal of Blood Research, 11(1), 1-21. Retrieved July 21, 2022, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8010610/pdf/ajbr0011-0001.pdf
7. Padron, E., et al. (2013, June 20). GM-CSF-dependent PSTAT5 sensitivity is a feature with therapeutic potential in chronic myelomonocytic leukemia. Blood, 121(25), 5068-5077. https://doi.org/10.1182/blood-2012-10-460170
8. Emanuel, P. D., et al. (1991, March 1). Selective hypersensitivity to granulocyte-macrophage colony-stimulating factor by juvenile chronic myeloid leukemia hematopoietic progenitors. Blood, 77(5), 925-929. https://doi.org/10.1182/blood.v77.5.925.925

Humanigen Investor Relations
Tim Morris
COO & CFO
tmorris@humanigen.com
650-400-6874

Source: Humanigen, Inc.

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