On May 30, 2019, the Company entered into a clinical collaboration agreement with Kite, providing in part for conduct of a multi-center Phase 1b study of lenzilumab with Kite’s Yescarta in patients with relapsed or refractory B-cell lymphoma, including DLBCL. On April 19, 2021, the Company announced positive preliminary data from this study. As a result of this positive preliminary data and the conclusion of the Phase 1b portion of the study, the Company elected to terminate the clinical collaboration agreement with Kite. Enrollment in the Phase 1b portion of the study is closed and the study itself shall be closed by the fourth quarter of 2021. The effective date of termination of the clinical collaboration with Kite shall be December 31, 2021. Until the Phase 1b portion of the study is terminated and the last subject transitioned onto the Kite long term follow up protocol, Humanigen and Kite will cooperate to ensure the orderly wind down of study activities. The Company is preparing to initiate a Company-sponsored Phase 3 study with commercially available CD19 CAR-T therapies in non-Hodgkin lymphoma in 2022 and has scheduled a meeting with FDA in December 2021 to discuss the study protocol. The Company currently plans to enroll approximately 250 patients in the study.

License and Collaboration Agreements	9 Months Ended
Sep. 30, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
License and Collaboration Agreements	9. License and Collaboration Agreements Kite Agreement On May 30, 2019, the Company entered into a clinical collaboration agreement with Kite, providing in part for conduct of a multi-center Phase 1b study of lenzilumab with Kite’s Yescarta in patients with relapsed or refractory B-cell lymphoma, including DLBCL. On April 19, 2021, the Company announced positive preliminary data from this study. As a result of this positive preliminary data and the conclusion of the Phase 1b portion of the study, the Company elected to terminate the clinical collaboration agreement with Kite. Enrollment in the Phase 1b portion of the study is closed and the study itself shall be closed by the fourth quarter of 2021. The effective date of termination of the clinical collaboration with Kite shall be December 31, 2021. Until the Phase 1b portion of the study is terminated and the last subject transitioned onto the Kite long term follow up protocol, Humanigen and Kite will cooperate to ensure the orderly wind down of study activities. The Company is preparing to initiate a Company-sponsored Phase 3 study with commercially available CD19 CAR-T therapies in non-Hodgkin lymphoma in 2022 and has scheduled a meeting with FDA in December 2021 to discuss the study protocol. The Company currently plans to enroll approximately 250 patients in the study. Mayo Agreement On June 19, 2019, the Company entered into an exclusive worldwide license agreement (the “Mayo Agreement”) with the Mayo Foundation for Medical Education and Research (“Mayo”) for certain technologies used to create CAR-T cells lacking GM-CSF expression through various gene-editing tools including CRISPR-Cas9 (“GM-CSF^KO CAR-T”). The license covers various patent applications and know-how developed by Mayo in collaboration with the Company. These licensed technologies complement and broaden the Company’s position in the GM-CSF neutralization space and expand the Company’s discovery platform aimed at improving CAR-T to include gene-edited CAR-T cells. Pursuant to the Mayo Agreement, the Company paid $0.2 million to Mayo in June 2020, which payment was accrued as Research and development expense in June 2019. The Mayo Agreement also requires the payment of milestones and royalties upon the achievement of certain regulatory and commercialization milestones. Zurich Agreement On July 19, 2019, the Company entered into an exclusive worldwide license agreement (the “Zurich Agreement”) with the University of Zurich (“UZH”) for technology used to prevent or treat GvHD through GM-CSF neutralization. The Zurich Agreement covers various patent applications filed by UZH which complement and broaden the Company’s position in the application of GM-CSF and expands the Company’s development platform to include improving allogeneic Hematopoietic Stem Cell Transplantation (“HSCT”). The Zurich Agreement also requires the payment of annual maintenance fees and milestones and royalties upon the achievement of certain regulatory and commercialization milestones. 15 Table of Contents Clinical Trial Agreement with the National Institute of Allergy and Infectious Diseases On July 24, 2020, the Company entered into a clinical trial agreement (the “ACTIV-5 Clinical Trial Agreement”) with the National Institute of Allergy and Infectious Diseases (“NIAID”), part of NIH, which is part of the U.S. Government Department of Health and Human Services, as represented by the Division of Microbiology and Infectious Diseases. Pursuant to the ACTIV-5 Clinical Trial Agreement, lenzilumab is being evaluated in the NIAID-sponsored ACTIV-5/BET-B in hospitalized patients with COVID-19. See Note 1 above for further information regarding ACTIV-5/BET-B. Pursuant to the ACTIV-5 Clinical Trial Agreement, NIAID will serve as sponsor and will be responsible for funding, supervising and overseeing ACTIV-5/BET-B. The Company will be responsible for providing lenzilumab to NIAID without charge and in quantities to ensure a sufficient supply of lenzilumab. The ACTIV-5 Clinical Trial Agreement imposes additional obligations on the Company that are reasonable and customary for clinical trial agreements of this nature, including in respect of compliance with data privacy laws and potential indemnification obligations. The Company will have access to data from ACTIV-5/BET-B once concluded. CRADA On November 5, 2020, the Company and the Department of Defense (“DoD”) Joint Program Executive Office for Chemical, Biological, Radiological and Nuclear Defense (“JPEO-CBRND” or “JPEO”) entered into a Cooperative Research and Development Agreement (“CRADA”) in collaboration with the Biomedical Advanced Research and Development Authority (“BARDA”), part of the Office of the Assistant Secretary for Preparedness and Response (“ASPR”) at the U.S. Department of Health and Human Services (“HHS”), in support of Operation Warp Speed (“OWS”), to assist in the development of lenzilumab, in connection with a potential EUA for COVID-19. On January 22, 2021, the Company announced an expansion of the CRADA that it had previously entered into with JPEO on November 5, 2020, was subsequently co-signed by BARDA and is set to expire on January 21, 2022. This provides the Company with access to manufacturing capacity reserved by BARDA for fill-finish product to accelerate the drug product manufacturing of lenzilumab. Pursuant to the CRADA, the Company has been provided access to a full-scale, integrated team of OWS manufacturing, and regulatory subject matter experts, leading decision makers and statistical support in its efforts to apply for EUA for lenzilumab as a potential treatment for COVID-19.

On June 19, 2019, the Company entered into an exclusive worldwide license agreement (the “Mayo Agreement”) with the Mayo Foundation for Medical Education and Research (“Mayo”) for certain technologies used to create CAR-T cells lacking GM-CSF expression through various gene-editing tools including CRISPR-Cas9 (“GM-CSF^KO CAR-T”). The license covers various patent applications and know-how developed by Mayo in collaboration with the Company. These licensed technologies complement and broaden the Company’s position in the GM-CSF neutralization space and expand the Company’s discovery platform aimed at improving CAR-T to include gene-edited CAR-T cells.

Pursuant to the Mayo Agreement, the Company paid $0.2 million to Mayo in June 2020, which payment was accrued as Research and development expense in June 2019. The Mayo Agreement also requires the payment of milestones and royalties upon the achievement of certain regulatory and commercialization milestones.

On July 19, 2019, the Company entered into an exclusive worldwide license agreement (the “Zurich Agreement”) with the University of Zurich (“UZH”) for technology used to prevent or treat GvHD through GM-CSF neutralization. The Zurich Agreement covers various patent applications filed by UZH which complement and broaden the Company’s position in the application of GM-CSF and expands the Company’s development platform to include improving allogeneic Hematopoietic Stem Cell Transplantation (“HSCT”).

The Zurich Agreement also requires the payment of annual maintenance fees and milestones and royalties upon the achievement of certain regulatory and commercialization milestones.

Table of Contents

Clinical Trial Agreement with the National Institute of Allergy and Infectious Diseases

On July 24, 2020, the Company entered into a clinical trial agreement (the “ACTIV-5 Clinical Trial Agreement”) with the National Institute of Allergy and Infectious Diseases (“NIAID”), part of NIH, which is part of the U.S. Government Department of Health and Human Services, as represented by the Division of Microbiology and Infectious Diseases. Pursuant to the ACTIV-5 Clinical Trial Agreement, lenzilumab is being evaluated in the NIAID-sponsored ACTIV-5/BET-B in hospitalized patients with COVID-19. See Note 1 above for further information regarding ACTIV-5/BET-B.

Pursuant to the ACTIV-5 Clinical Trial Agreement, NIAID will serve as sponsor and will be responsible for funding, supervising and overseeing ACTIV-5/BET-B. The Company will be responsible for providing lenzilumab to NIAID without charge and in quantities to ensure a sufficient supply of lenzilumab. The ACTIV-5 Clinical Trial Agreement imposes additional obligations on the Company that are reasonable and customary for clinical trial agreements of this nature, including in respect of compliance with data privacy laws and potential indemnification obligations. The Company will have access to data from ACTIV-5/BET-B once concluded.

CRADA

On November 5, 2020, the Company and the Department of Defense (“DoD”) Joint Program Executive Office for Chemical, Biological, Radiological and Nuclear Defense (“JPEO-CBRND” or “JPEO”) entered into a Cooperative Research and Development Agreement (“CRADA”) in collaboration with the Biomedical Advanced Research and Development Authority (“BARDA”), part of the Office of the Assistant Secretary for Preparedness and Response (“ASPR”) at the U.S. Department of Health and Human Services (“HHS”), in support of Operation Warp Speed (“OWS”), to assist in the development of lenzilumab, in connection with a potential EUA for COVID-19.

On January 22, 2021, the Company announced an expansion of the CRADA that it had previously entered into with JPEO on November 5, 2020, was subsequently co-signed by BARDA and is set to expire on January 21, 2022. This provides the Company with access to manufacturing capacity reserved by BARDA for fill-finish product to accelerate the drug product manufacturing of lenzilumab.

Pursuant to the CRADA, the Company has been provided access to a full-scale, integrated team of OWS manufacturing, and regulatory subject matter experts, leading decision makers and statistical support in its efforts to apply for EUA for lenzilumab as a potential treatment for COVID-19.