Ajinomoto Bio-Pharma Services and Humanigen Expand Manufacturing Agreement to Support Fill Finish for Investigational COVID-19 Therapeutic, Lenzilumab, Nearing Completion of Phase 3 Study

January 27, 2021 – San Diego, CA and Burlingame, CA – Ajinomoto Bio-Pharma Services (“Aji BioPharma”), a leading provider of biopharmaceutical contract development and manufacturing services,
and 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 the companies will be expanding their manufacturing
agreement for the fill finish supply of lenzilumab, which is one of the few Phase 3 treatment options in
development for patients hospitalized with COVID-19.

Aji Bio-Pharma will assume a key role in simplifying the supply chain efforts for Humanigen by providing
drug product aseptic fill finish services at its San Diego facility to support continued clinical trial efforts
through potential commercialization. Humanigen is actively enrolling patients in a Phase 3 study in the
U.S. and Brazil and preparing for a potential COVID-19 Emergency Use Authorization (EUA) for

“We are very pleased to be working with Aji Bio-Pharma for the fill finish production of lenzilumab,” said
Cameron Durrant, MD, MBA, Chief Executive Officer of Humanigen. “This partnership allows us to utilize
Aji Bio-Pharma’s high quality drug product aseptic fill finish services to provide a timely supply of
lenzilumab as we near the end of our clinical phase 3 study and prepare for EUA application submission.”
“We are excited to continue to support Humanigen’s efforts to provide this potential therapeutic in the
fight against COVID-19,” said Kristin DeFife, Ph.D., Sr. VP of Operations & Site Head at Ajinomoto BioPharma Services. “Through this collaboration, we are able to leverage our drug product experience,
infrastructure and strong regulatory track record to assist in the efforts that may ultimately help patients
struggling with this devastating disease.”

About Ajinomoto Bio-Pharma Services
Ajinomoto Bio-Pharma Services is a fully integrated contract development and manufacturing
organization with sites in Belgium, United States, Japan, and India, providing comprehensive
development, cGMP manufacturing, and aseptic fill finish services for small and large molecule APIs
and intermediates. Ajinomoto Bio-Pharma Services offers a broad range of innovative platforms and
capabilities for pre-clinical and pilot programs to commercial quantities, including Corynex® protein
expression technology, oligonucleotide synthesis, antibody drug conjugations (ADC), high potency
APIs (HPAPI), biocatalysis, continuous flow manufacturing, and more. Ajinomoto Bio-Pharma
Services is dedicated to providing a high level of quality and service to meet our client’s needs. Learn
more: www.AjiBio-Pharma.com

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
neutralizing 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.


Humanigen Forward-Looking Statements
This press release contains forward-looking statements. Forward-looking statements reflect
management’s current knowledge, assumptions, judgment and expectations regarding future
performance or events. Although Humanigen 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 use of lenzilumab to treat patients hospitalized with COVID19, Humanigen’s expectations regarding the timeline to file for and obtain EUA, statements regarding
Humanigen’s ability to attain necessary manufacturing support from contract development and
manufacturing organizations, the potential for an expanded manufacturing services relationship with AjiBioPharma, and statements regarding Humanigen’s beliefs relating to any of the other technologies in
Humanigen’s current pipeline. These forward-looking statements are subject to a number of risks and
uncertainties including, but not limited to, the risks inherent in Humanigen’s lack of profitability and need
for additional capital to grow Humanigen’s business; Humanigen’s dependence on partners to further
the development of Humanigen’s product candidates; the uncertainties inherent in the development,
attainment of the requisite regulatory approvals or authorization for emergency or broader patient use
for the product candidate 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 Humanigen’s periodic and other filings with the Securities and Exchange Commission.