Humanigen Announces Peer-Reviewed Publication in Thorax Supporting Early Treatment of Hospitalized COVID-19 Patients with Lenzilumab Guided by C-Reactive Protein

• A sub-analysis of the Phase 3 LIVE-AIR study of lenzilumab showed a strong correlation between C-reactive protein (CRP) and outcomes with lenzilumab treatment with the greatest clinical benefit experienced by patients with baseline CRP<150 mg/L
• In these patients, likelihood of survival without mechanical ventilation (SWOV) was achieved in 90% of LIVE-AIR patients treated with lenzilumab plus standard of care compared to 79% treated with placebo plus standard of care, which was highly statistically significant (HR 2.54, p=0.0009)
• Lenzilumab-treated patients had a 62% relative reduction in the risk of progression to invasive mechanical ventilation or death (OR=0.38; p=0.0053)

Humanigen, Inc. (Nasdaq: HGEN) (“Humanigen”), a late-stage clinical biopharmaceutical company focused on preventing and treating an immune hyper-response called ‘cytokine storm,’ today announced a peer-reviewed publication in Thorax, one of the world’s leading respiratory medicine journals and the official journal of the British Thoracic Society, describing the role of CRP in identifying patients that derive the greatest benefit of lenzilumab. Participants in the LIVE-AIR study with baseline CRP <150 mg/L treated with lenzilumab demonstrated a 62% reduction in the relative risk of invasive mechanical ventilation and death compared to placebo.¹

“A growing body of scientific evidence links CRP levels and response to certain immunomodulatory therapies, suggesting an important role of CRP as a biomarker to guide treatment of COVID-19,” said Dale Chappell, M.D., Chief Scientific Officer, Humanigen. “These data demonstrate the importance of selecting the right treatment for the right patient at the right time which can be guided by the widely available biomarker CRP. These data are important because they demonstrate the utility of early neutralization of GM-CSF, an upstream driver of the cytokine storm cascade which can prevent downstream production of IL-6, IL-1, and markers of systemic inflammation including CRP, resulting in better patient outcomes.”

Lenzilumab improved clinical outcomes in hospitalized non-mechanically ventilated hypoxic COVID-19 patients.² The greatest benefit was observed in those with a CRP level below 150 mg/L in the LIVE-AIR study. In this sub-analysis, lenzilumab improved the likelihood of SWOV compared with placebo (HR: 2.54; p=0.0009), demonstrated reduced odds (OR 0.38; p=0.0053) and a 62% reduction in the relative risk of progressing to mechanical ventilation or death in lenzilumab-treated patients, there were more ventilator-free days (p=0.0045), fewer ICU days (p=0.0458), and improved time-to-recovery (p=0.0219).¹

“We believe data from our LIVE-AIR study provides a compelling argument for utilizing CRP as a biomarker to identify hospitalized patients for whom lenzilumab may provide the greatest benefit and we look forward to results of the NIH’s ACTIV-5/BET-B study of lenzilumab, which is designed to confirm this approach,” stated Dr. Cameron Durrant, Chairman and CEO, Humanigen. “Following consultation with the FDA, Humanigen expects that if the ACTIV-5/BET-B study is positive, which has its primary analysis focused on patients with CRP <150mg/L, it would be sufficient to support an Emergency Use Authorization submission to FDA.”

Lenzilumab is an investigational product and is not approved or authorized in any country.

About Lenzilumab

Lenzilumab is a proprietary Humaneered® first-in-class monoclonal antibody that has been proven to neutralize GM-CSF, a cytokine of critical importance in the hyperinflammatory cascade, sometimes referred to as cytokine release syndrome, or cytokine storm, associated with COVID-19 and other indications. Lenzilumab binds to and neutralizes GM-CSF, potentially improving outcomes for patients hospitalized with COVID-19. Humanigen believes that GM-CSF neutralization with lenzilumab also has the potential to reduce the hyper-inflammatory cascade known as cytokine release syndrome common to chimeric antigen receptor T-cell (CAR-T) therapy and acute Graft versus Host Disease (aGvHD).

In CAR-T, lenzilumab successfully achieved the pre-specified primary endpoint at the recommended dose in a Phase 1b study with Yescarta® in which the overall response rate was 100% and no patient experienced severe cytokine release syndrome or severe neurotoxicity. Based on these results, Humanigen plans to test lenzilumab in a randomized, multicenter, potentially registrational, Phase 3 study (“SHIELD”) to evaluate its efficacy and safety when combined with Yescarta and Tecartus® CAR-T therapies in non-Hodgkin lymphoma. Lenzilumab will also be tested to assess its ability to prevent and/or treat aGvHD in patients undergoing allogeneic hematopoietic stem cell transplantation.

A study of lenzilumab is also underway for patients with chronic myelomonocytic leukemia (CMML) exhibiting RAS pathway mutations. This study builds on evidence from a Phase 1 study, conducted by Humanigen, that showed RAS mutations are associated with hyper-proliferative features, which may be sensitive to GM-CSF neutralization.

About Humanigen

Humanigen, Inc. (Nasdaq: HGEN) (“Humanigen”), is a late-stage clinical 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 the potential clinical benefits of lenzilumab, statements pertaining to the sufficiency of results from ACTIV-5/BET-B to support an amended EUA submission; statements regarding the SHIELD, aGvHD, and CMML studies, and other statements regarding improving the safety and efficacy of CAR-T and 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 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. Temesgen, Z. et al. (2022). C-reactive protein, a biomarker for early lenzilumab treatment of COVID-19, improves efficacy: a sub-analysis of the randomized phase 3 ‘LIVE-AIR’ trial. Thorax. http://dx.doi.org/10.1136/thoraxjnl-2022-218744
2. Temesgen, Z. et al. (2021). Lenzilumab in hospitalised patients with COVID-19 pneumonia (LIVE-AIR): a phase 3, randomised, placebo-controlled trial. The Lancet Respiratory Medicine. https://doi.org/10.1016/S2213-2600(21)00494-X

Humaneered® is a trademark of Humanigen, Inc.

Yescarta® and Tecartus® are trademarks of Gilead Sciences, Inc., or its related companies.

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