Humanigen Data Presented at the 2019 National Comprehensive Cancer Network (NCCN) Annual Conference Demonstrates Potential to Improve the Efficacy of CAR-T Therapy

• Enhanced anti-tumor activity, improved overall survival, and improved durability of response with a reduced rate of relapse observed with GM-CSF neutralization
• Lenzilumab (an anti-GM-CSF monoclonal antibody) used in combination with CAR-T therapy prevents cytokine release syndrome, significantly reduces neuroinflammation and results in an exponential increase in CAR-T cell expansion
• GM-CSF neutralization with lenzilumab is a next generation strategy to improve efficacy, safety and durability of CAR-T therapy

BURLINGAME, Calif., March 21, 2019 (GLOBE NEWSWIRE) -- Humanigen, Inc., (OTCQB: HGEN) (“Humanigen”) a biopharmaceutical company focused on the development of its proprietary Humaneered® monoclonal antibodies focused on chimeric antigen receptor T (CAR-T) cell therapy optimization and immuno-oncology, announced that on Thursday, March 21st, data from the study entitled “GM-CSF Blockade during Chimeric Antigen Receptor T-cell (CART) Therapy Reduces Cytokine Release Syndrome and Neurotoxicity and may Enhance CART Effector Function” were presented at the 2019 NCCN Annual Conference: Improving the Quality, Effectiveness, & Efficiency of Cancer Care^™ in Orlando, Florida in the oral plenary session focused on new immunotherapy strategies for improving outcomes. The study was conducted using lenzilumab, the company’s proprietary Humaneered® anti-GM-CSF monoclonal antibody, and was recently featured on the front cover of the February 14, 2019 edition of ‘blood’®, the official journal of the American Society of Hematology, available online at .

The study was designed to closely replicate the findings seen in CAR-T clinical trials and utilized human acute lymphoblastic leukemia (ALL), human CD19 targeted CAR-T (CART19), and human peripheral blood mononuclear cells (PBMCs) and conducted in mice.

The prophylactic administration of lenzilumab in combination with CART19 therapy resulted in an exponential increase in CART19 cell proliferation, enhanced anti-tumor activity, and a significant improvement in leukemic disease control sustained over time for at least 35 days post CART19 infusion compared to CART19 plus control. In addition, improved overall survival was observed with GM-CSF neutralization. This suggests that GM-CSF neutralization may play a role in reducing relapse and increasing durable complete response after CART19 therapy. This is a significant finding, given that more than 50% of adult lymphoma patients who initially respond to CART19 therapy subsequently relapse within the first year of follow-up.

Moreover, the prophylactic administration of lenzilumab prevented the onset of Cytokine Release Syndrome (CRS) and resulted in a 75% reduction in Neuroinflammation (NI) by quantitative MRI.

Despite the dramatic initial overall response rates observed, the commercialization of CAR-T therapies has been limited by significant relapse rates and a tight linkage between efficacy and toxicity which limits strategies aimed at improving long term complete response. “This study identifies GM-CSF as a key trigger in the inflammatory cascade resulting in CRS and NI and demonstrates the ability to break the efficacy toxicity linkage by targeting the key cytokine in the inflammatory cascade,” stated Dr. Cameron Durrant, CEO of Humanigen. “These results suggest that GM-CSF neutralization would improve the efficacy and toxicity profile of current CAR-T therapies and opens the possibility for other combinations with agents that might further improve efficacy but would too toxic if used in the absence of GM-CSF neutralization.” Multi-center phase Ib/II clinical trials of lenzilumab in combination with CART19 therapies are expected to be initiated in the coming months.

About Humanigen, Inc.

Humanigen, Inc. is developing its portfolio of Humaneered® monoclonal antibodies to address cutting-edge CAR-T optimization and the need for new oncology drugs that provide safer, better, and more effective cancer therapies. Derived from the company’s Humaneered® platform, lenzilumab, ifabotuzumab, and HGEN005 are monoclonal antibodies with first-in-class mechanisms. Lenzilumab, which neutralizes human GM-CSF, is in development as a potential biologic therapy to make CAR-T therapy safer and more effective, as well as a potential treatment for hematologic cancers. Ifabotuzumab, which targets the Eph type-A receptor 3 (EphA3), is being explored as a potential treatment for glioblastoma multiforme (GBM) and a range of solid tumors, both as an optimized naked antibody and as part of an antibody-drug conjugate, as well as a backbone for a novel CAR-T construct, and a bispecific antibody platform. HGEN005 which selectively targets the eosinophil receptor EMR1 is being explored as a potential treatment for a range of eosinophilic diseases including eosinophilic leukemia both as an optizimized naked antibody and as the backbone for a novel CAR-T construct. For more information, visit .

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, including, without limitation, statements regarding our expectations for future development of lenzilumab to help CAR-T therapy reach its full potential. Forward-looking statements are subject to a number of risks and uncertainties including, but not limited to, the risks inherent in Black Horse Capital and its affiliates owning more than 50% of our outstanding common stock, including their ability to control the company; our lack of profitability and need for additional capital to operate our business as a going concern; the uncertainties inherent in the development 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.

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