Humanigen, Inc. (Nasdaq: HGEN) (“Humanigen”), a clinical-stage biopharmaceutical company focused on preventing and treating an immune hyper-response called ‘cytokine storm,’ announced that management will present and participate at multiple virtual investor conferences in October 2021. Details of the conferences are as follows:

Guggenheim 2nd Annual Vaccines and Infectious Diseases Conference

Dale Chappell, MD, Chief Scientific Officer, will participate in a fireside chat at 9:00am EDT on October 5, 2021. A livestream will be available and a webcast link to a recording of the event will be posted to the “Events and Presentations” section of Humanigen’s investor relations website after the event.

Webcast: https://kvgo.com/guggenheim/humanigen-inc-oct-2021

The webcast will be archived for up to one year under the Investor Relations section of the company’s website at www.ir.humanigen.com

Sachs Associates 8th Annual HealthTech Investment Forum

Cameron Durrant, Chairman & CEO participated in a panel to discuss “Advances in Covid Therapeutics”, which was pre-recorded and will be available to participants in the forum starting at 5:20am EDT on October 6, 2021. Sachs and Associates plans to share a video of the panel via its social media networks 1-2 weeks after the event. For more information, please access the event agenda at https://sachsevent.com/event/8th-htif/agenda.

LD Micro Main Event XIV (Virtual and In-person)

Humanigen will participate in this combination virtual and in-person event on October 12, 2021. Cameron Durrant, Chairman & CEO will provide a corporate update, which was pre-recorded and will become available at 11:30am EDT on October 12. A corresponding presentation will also be made at the same time in-person at the conference. Registration is required to view the webcast.

Webcast: https://me21.mysequire.com/

Cytokines 2021 – 9^th Annual Meeting of the International Cytokine & Interferon Society

The International Cytokine & Interferon Society (ICIS), is the world’s largest multidisciplinary organization advancing both fundamental and clinical research specific to the role of cytokines in health and disease. Humanigen will present data from its LIVE-AIR Phase 3 study during the Exhibitor Breaking News Session virtual meeting platform, which will take place from 1:15-2:45pm Central European Time (CET) on October 17, 2021. Humanigen will also have a virtual medical information booth at the meeting and is sponsoring a session, entitled “Targeting Cytokines in COVID-19”, through an unrestricted educational grant. The session will be moderated by Cameron Durrant, Chairmen and CEO of Humanigen, along with Christopher Hunter, the Mindy Halikman Heyer Distinguished Professor of Pathobiology at the School of Veterinary Medicine of the University of Pennsylvania who will become President ICIS following the October Cytokines 2021 meeting. The session is scheduled to take place from 11:45am-12:45pm CET on October 19th. For more information please review the Cytokine 2021 website: https://cardiff.cytokinesociety.org/

About Humanigen

Humanigen, Inc. (Nasdaq: HGEN) (“Humanigen”), is a clinical-stage biopharmaceutical company focused on preventing and treating an immune hyper-response called ‘cytokine storm’. Lenzilumab is a first-in class antibody that binds to and neutralizes granulocyte-macrophage colony-stimulating factor (GM-CSF). Results from preclinical models indicate GM-CSF is an upstream regulator of many inflammatory cytokines and chemokines involved in the cytokine storm. Early in the COVID-19 pandemic, investigation showed high levels of GM-CSF secreting T cells were associated with disease severity and intensive care unit admission. Humanigen’s Phase 3 LIVE-AIR study suggests early intervention with lenzilumab may prevent consequences of a full-blown cytokine storm in hospitalized patients with COVID-19. Humanigen is developing lenzilumab as a treatment for cytokine storm associated with COVID-19 and CD19-targeted CAR-T cell therapies and is also exploring the effectiveness of lenzilumab in other inflammatory conditions such as acute Graft versus Host Disease in patients undergoing allogeneic hematopoietic stem cell transplantation, eosinophilic asthma, and rheumatoid arthritis. For more information, visit www.humanigen.com and follow Humanigen on LinkedIn, Twitter, and Facebook.

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, including, without limitation, statements regarding our plans relating to lenzilumab.

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 to grow our business; 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; 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 presentation to reflect events or circumstances after the date hereof, to reflect new information or the occurrence of unanticipated events, 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.

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