FDA Approves GSK’s Shingles Vaccine with Agenus’ QS-21 Stimulon Adjuvant

Agenus Inc., an immuno-oncology company with a pipeline of immune checkpoint antibodies and cancer vaccines, announced that the US Food and Drug Administration (FDA) granted marketing authorization to GlaxoSmithKline’s (GSK) herpes zoster vaccine, SHINGRIX, containing Agenus’ proprietary immune adjuvant QS-21 Stimulon. SHINGRIX is indicated for prevention of herpes zoster (also known as shingles) in adults aged 50 years and older. The addition of QS-21 Stimulon helps improve the vaccine’s effectiveness by boosting immune response in older adults who often experience age-related decline in immunity.

Shingles is a major public health issue in the US, impacting as many as 1 in 3 older adults over the age of 50 years. Shingles is caused by a virus called varicella zoster, which is also known as the chicken pox virus. Nearly all older adults have the varicella zoster virus dormant in their nervous system waiting to reactivate with advancing age and weakened immune systems.

QS-21 Stimulon is an immune-potent adjuvant designed to boost the immune system by helping the body generate antibodies and T cells that guard against infection. The addition of QS-21 Stimulon to the SHINGRIX vaccine enhances the immune response in these older adults.

“We are delighted by the remarkable efficacy of SHINGRIX, containing our proprietary QS-21 Stimulon adjuvant and the public health benefit; this FDA approval marks a significant milestone for Agenus,” said Garo Armen, Ph.D., Chairman and CEO, Agenus. “The addition of QS-21 Stimulon enhances the immunogenicity of SHINGRIX and is beneficial in an older adult population who often experience a decline in immunity.  Beyond shingles, our QS-21 Stimulon is under investigation in numerous vaccines and is a critical component of our neoantigen vaccine formulation, which is currently advancing in a Phase 1 clinical trial in patients with cancer.”

The FDA approval of SHINGRIX was based on data pooled from two pivotal Phase III clinical trials in more than 37,000 people, which demonstrated an efficacy rate against shingles greater than 90% independent of age, as well as a sustained efficacy over the four-year follow-up period. SHINGRIX also reduced the overall incidence of postherpetic neuralgia (PHN), the most common and oftentimes debilitating chronic nerve pain associated with shingles. The benefit of SHINGRIX in the prevention of PHN can be attributed to the effect of the vaccine on the prevention of shingles. The most common side effects reported in clinical trials of SHINGRIX were pain, redness and swelling at the injection site, the majority of which were transient and mild to moderate in intensity, lasting less than three days.

The addition of QS-21 Stimulon is being studied to determine its potential to help a diverse range of vaccines work more effectively to treat or cure difficult-to-treat diseases, like cancer. QS-21 Stimulon is currently being used in combination with Agenus’ neoantigen vaccine, AutoSynVax™, now in a Phase 1 clinical trial in cancer.

QS-21 Stimulon is also currently being evaluated in numerous GSK vaccine development candidates for both therapeutic and prophylactic applications.