Humanigen, Inc. (Nasdaq: HGEN), 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 it has submitted all the planned modules as well as a risk management plan and pediatric investigation plan for the lenzilumab Conditional Marketing Authorization (CMA) in hospitalized COVID-19 patients to the UK’s Medicines and Healthcare Products Regulatory Agency (MHRA). MHRA has previously accepted the application for expedited COVID-19 rolling review.

“We are pleased with the engagement with MHRA and are committed to continue to work with the agency as necessary to enable MHRA to review our application. As the United Kingdom’s Health Secretary recently stated, the UK is leading the world in identifying and rolling out life-saving medicines, particularly for COVID-19,”¹ said Cameron Durrant, CEO of Humanigen. “A UK study funded by the Medical Research Council demonstrated benefits of GM-CSF neutralization in hospitalized COVID-19 patients and we believe results of our LIVE-AIR Phase 3 trial of lenzilumab provide further evidence for the benefits of this approach. Thus, we are seeking Conditional Marketing Authorization with a view to bringing lenzilumab to patients in the UK. We note in the UK there have been more than 20,000 new hospitalizations in the month of September and as of September 27^th there were 7,007 people currently hospitalized for COVID-19.”^2,3

About the LIVE-AIR, Phase 3 Study of Lenzilumab

This study was a randomized, double-blind, placebo-controlled, multi-center Phase 3 trial for the treatment and prevention of serious and potentially fatal outcomes in patients hospitalized with COVID-19 pneumonia. The LIVE-AIR study enrolled 520 patients in 29 sites in the US and Brazil who were at least 18 years of age; experienced blood oxygen saturation (SpO2) of less than or equal to 94%; or required low-flow supplemental oxygen, or high-flow oxygen support, or non-invasive positive pressure ventilation; and were hospitalized but did not require invasive mechanical ventilation (IMV). Following enrollment, subjects were randomized to receive three infusions of either lenzilumab or placebo, with each infusion separated by eight hours over a 24-hour period. The primary objective was to assess whether lenzilumab, in addition to other treatments, which included dexamethasone (or other steroids) and/or remdesivir, could alleviate the immune-mediated ‘cytokine storm’ and improve survival without ventilation, or ‘SWOV’ (sometimes referred to as ‘ventilator-free survival’). SWOV is a composite endpoint of time to death and time to IMV, which is a robust measure that is less prone to favor a treatment with discordant effects on survival or days free of ventilation. SWOV is an important clinical endpoint that measures not only mortality, but the morbidity associated with mechanical ventilation.

The LIVE-AIR study achieved its primary endpoint of SWOV measured through day 28 following treatment (HR: 1.54; 95%CI: 1.02-2.32, p=0.0403). The Kaplan-Meier estimate for IMV and/or death was 15.6% (95%CI: 11.5-20.9) in the lenzilumab arm versus 22.1% (95%CI: 17.4-27.9) in the placebo arm. Approximately 94% of patients received dexamethasone (or other steroids), 72% received remdesivir, and 69% received both. In this study, lenzilumab appeared to be safe and well-tolerated, there were no serious adverse events (SAEs) attributed to lenzilumab and no suspected unexpected serious adverse reactions (SUSARS) reported for lenzilumab. No SAEs have been attributed to lenzilumab in four completed studies across multiple indications. Results of LIVE-AIR have been submitted for publication in a peer-reviewed journal.

Lenzilumab has not been authorized or approved for use in any indication by any regulatory agency.

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 submission to MHRA; the potential use of lenzilumab as a therapy for the treatment of patients hospitalized with COVID-19 pneumonia; and our other 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 or to reflect new information or the occurrence of unanticipated events, except as required by law.

Reference

1. UK Government - Department of Health and Social Care. (September 17, 2021). “Thousands of patients to benefit from life-saving COVID-19 treatment”. Retrieved September 30, 2021, from https://www.gov.uk/government/news/thousands-of-patients-to-benefit-from-life-saving-covid-19-treatment.
2. Fisher, B. A., Veenith, T., Slade, D., et al investigators, on behalf of C. A. T. A. L. Y. S. T. (June 9, 2021). Namilumab or infliximab compared to standard of care in hospitalised patients with covid-19 (catalyst): A phase 2 randomised adaptive trial. medRxiv. Retrieved September 30, 2021, from https://www.medrxiv.org/content/10.1101/2021.06.02.21258204v1.
3. Hannah Ritchie, Edouard Mathieu, et. Al. (2020) - "Coronavirus Pandemic (COVID-19)". Published online at OurWorldInData.org. United Kingdom Weekly and Current Hospitalizations Retrieved September 30, 2021 from: https://ourworldindata.org/coronavirus.

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