Humanigen, Inc. (Nasdaq: HGEN) (“Humanigen”), a clinical stage biopharmaceutical company focused on preventing and treating an immune hyper-response called ‘cytokine storm’ with its lead drug candidate, lenzilumab™, today announced that the Company’s management team will participate in a fireside chat at the Roth Conference being held from March 15-17, 2021. An Advance Video Webinar will also be available starting on Monday, March 8, 2021, not March 5, 2021 as previously communicated.

Management will discuss its Phase 3 clinical trial of lenzilumab in patients hospitalized with COVID-19 including the timeline for the topline data release and the submission for Emergency Use Authorization (EUA) to the U.S. Food and Drug Administration, provide an update on the commercial preparation ahead of a potential EUA for lenzilumab and an overview of the Company’s other development programs.

Details for the upcoming webcasts are below:

Roth Conference

Advance Video Webinar viewable starting on Monday, March 8, 2021 Webcast Link: https://wsw.com/webcast/roth35/hgen/1811466

Live Fireside Chat with Roth Analyst Tony Butler Date: Tuesday, March 16, 2021 Time: 1:00 PM ET Time: https://wsw.com/webcast/roth35/hgen2/1882116

About Humanigen, Inc.

Humanigen, Inc. is developing its portfolio of clinical and pre-clinical therapies for the treatment of cancers and infectious diseases via its novel, cutting-edge GM-CSF neutralization and gene-knockout platforms. Humanigen believes that its GM-CSF neutralization and gene-editing platform technologies have the potential to reduce the inflammatory cascade associated with coronavirus infection. Humanigen’s immediate focus is to prevent or minimize the cytokine release syndrome that precedes severe lung dysfunction and ARDS in serious cases of SARS-CoV-2 infection. Humanigen is also focused on creating next-generation combinatory gene-edited CAR-T therapies using strategies to improve efficacy while employing GM-CSF gene knockout technologies to control toxicity. In addition, Humanigen is developing its own portfolio of proprietary first-in-class EphA3-CAR-T for various solid cancers and EMR1-CAR-T for various eosinophilic disorders. Humanigen is also exploring the effectiveness of its GM-CSF neutralization technologies (either through the use of lenzilumab as a monoclonal antibody or through GM-CSF gene knockout) in combination with other CAR-T, bispecific or natural killer (NK) T cell engaging immunotherapy treatments to break the efficacy/toxicity linkage, including to prevent and/or treat graft-versus-host disease (GvHD) in patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT). Additionally, Humanigen and Kite, a Gilead Company, are evaluating lenzilumab in combination with Yescarta® (axicabtagene ciloleucel) in patients with relapsed or refractory large B-cell lymphoma in a clinical collaboration. For more information, visit www.humanigen.com and follow Humanigen on LinkedIn, Twitter and Facebook.

Forward-Looking Statements

This release contains 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 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 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 and elsewhere in the Company's periodic and other filings with the Securities and Exchange Commission.

All forward-looking statements are expressly qualified in their entirety by this cautionary notice. You should not place undue reliance on any forward-looking statements, which speak only as of the date of this release. 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 or to reflect new information or the occurrence of unanticipated events, except as required by law.

Humanigen Media Grace Catlett RXMD gcatlett@rxmedyn.com 516-318-8563 Humanigen Investors Alan Lada Solebury Trout ALada@SoleburyTrout.com 617-221-8006