GSK’s older adult RSV vaccine candidate, containing Agenus’ QS-21 STIMULON™, shows 94.1% reduction in severe RSV disease and overall vaccine efficacy of 82.6% in pivotal trial

• Data show overall vaccine efficacy of 82.6% against RSV-lower respiratory tract disease (LRTD) in adults aged 60 years and above, with consistent high vaccine efficacy observed in severe disease (94.1%), adults aged 70-79 years (93.8%) and those with underlying comorbidities (94.6%)
• Regulatory filings anticipated in the second half of 2022; if approved, GSK’s RSV older adult vaccine candidate would be one of three approved vaccines containing Agenus’ proprietary QS-21 STIMULON

LEXINGTON, Mass., Oct. 13, 2022 (GLOBE NEWSWIRE) — Agenus Inc. (NASDAQ: AGEN), an immuno-oncology company with an extensive pipeline of therapies and adjuvants designed to activate the immune response to cancer and infections, today shared that GSK has disclosed positive pivotal phase III trial results for its respiratory syncytial virus (RSV) vaccine candidate for adults aged 60 years and above and plans to present full data at ID Week on October 20^th. The vaccine candidate was highly efficacious, demonstrating overall vaccine efficacy of 82.6% (96.95% CI, 57.9–94.1) against RSV lower respiratory tract disease (RSV-LRTD), meeting the trial’s primary endpoint.

Consistent high vaccine efficacy was also observed across a range of pre-specified secondary endpoints, highlighting the impact the vaccine could have on the populations most at risk of the severe adverse outcomes of RSV. Efficacy against severe RSV-LRTD, defined as LRTD with at least two lower respiratory signs or assessed as severe by the investigator and confirmed by the external adjudication committee, was 94.1% (95% CI, 62.4–99.9), while efficacy against RSV-LRTD in participants with pre-existing comorbidities and adults aged 70-79 years was 94.6% (95% CI, 65.9–99.9) and 93.8% (95% CI, 60.2-99.9), respectively.

Vaccine efficacy against LRTD was consistent across both RSV-A and RSV-B subtypes, consistent with the robust neutralizing antibody response generated against both subtypes.  The vaccine was well tolerated with a favorable safety profile.

“These are exceptional results, particularly for high-risk populations such as older adults and those with pre-existing co-morbidities. The effectiveness and durability of vaccines containing QS-21 STIMULON has been demonstrated in Shingrix, with best-in-class protection exceeding 9 years,” said Dr. Garo H. Armen, Chief Executive Officer of Agenus Inc. “Our subsidiary, SaponiQx, is developing a proprietary plant cell culture manufacturing process designed to enable broader use of QS-21 STIMULON through a sustainable, eco-friendly production method scalable to address pandemic and other vaccine needs.”

QS-21 STIMULON is a key component of GSK’s AS01 adjuvant derived from saponin extracts. It is approved for use in both GSK’s shingles vaccine, Shingrix¹, and malaria vaccine, Mosquirix,¹ which have generated significant immune responses and a favorable safety profile. Vaccine adjuvants may play an important role in vaccine supply in the future, as they can improve antigen stability and increase immunogenicity in populations with lower levels of natural immunity.

Agenus’ subsidiary, SaponiQx, was formed in 2021 to pursue scalable, sustainable, and cost-effective production of adjuvants, including saponins. The company expects to be able to supply its first GMP material by the end of 2022. Once SaponiQx’s plant cell culture process is fully scaled, Agenus’ wholly-owned manufacturing campus is designed to support the capacity for broad use across disease settings, as well as scalability to address future pandemic threats.

About Agenus

Agenus is a clinical-stage immuno-oncology company focused on the discovery and development of therapies that engage the body’s immune system to fight cancer and infections. The Company’s vision is to expand the patient populations benefiting from cancer immunotherapy by pursuing combination approaches that leverage a broad repertoire of antibody therapeutics, adoptive cell therapies (through its subsidiary MiNK Therapeutics), and adjuvants (through its subsidiary SaponiQx). The Company is equipped with a suite of antibody discovery platforms and a state-of-the-art GMP manufacturing facility with the capacity to support clinical programs. Agenus is headquartered in Lexington, MA. For more information, please visit www.agenusbio.com and our Twitter handle @agenus_bio. Information that may be important to investors will be routinely posted on our website and Twitter.

Statement Regarding Forward-Looking Statements

This press release contains forward-looking statements that are made pursuant to the safe harbor provisions of the federal securities laws, including statements regarding QS-21 STIMULON adjuvant, alone and formulated in GSK vaccines Shingrix and Mosquirix and GSK RSV older adult vaccine candidate for instance, statements regarding vaccine efficacy, safety, mechanism of action and durability; clinical development and regulatory plans and timelines; current and future manufacturing capabilities, including our ability to scale-up manufacturing and to manufacture in a consistent, sustainable, eco-friendly, and cost effective manner; the ability of QS-21 STIMULON adjuvant to be used in effective and safe vaccines for the prevention and/or treatment of infectious disease; and any other statements containing the words “may,” “believes,” “expects,” “is designed to,” “estimates,” “will,” “establish,” “validated,” “best in class,” and similar expressions are intended to identify forward-looking statements. These forward-looking statements are subject to risks and uncertainties that could cause actual results to differ materially. These risks and uncertainties include, among others, the factors described under the Risk Factors section of our most recent Quarterly Report on Form 10-Q or Annual Report on Form 10-K filed with the Securities and Exchange Commission. Agenus cautions investors not to place considerable reliance on the forward-looking statements contained in this release. These statements speak only as of the date of this press release, and Agenus undertakes no obligation to update or revise the statements, other than to the extent required by law. All forward-looking statements are expressly qualified in their entirety by this cautionary statement.

For further information, please contact

Agenus Inc.

Ethan Lovell

Chief External Affairs & Communications Officer

339.927.1763

ethan.lovell@agenusbio.com

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1} Shingrix and Mosquirix trade marks are owned by or licensed to the GSK group of companies. QS-21 STIMULON trade mark is owned by Agenus, Inc.