On December 6, 2021 Gritstone bio, Inc. (Nasdaq: GRTS), a clinical-stage biotechnology company developing next generation cancer and infectious disease immunotherapies, and CEPI, the Coalition for Epidemic Preparedness Innovations, reported the expansion of their agreement in order to support the development of a self-amplifying mRNA (SAM) vaccine designed to tackle the Omicron COVID-19 variant (Press release, Gritstone Oncology, DEC 6, 2021, View Source [SID1234596537]). CEPI will provide up to $5 million in additional funding to conduct a Phase 1 clinical trial of Gritstone’s Omicron vaccine candidate in South Africa, where a CEPI-funded clinical trial of Gritstone’s Beta variant COVID-19 vaccine is due to begin shortly. The SARS-CoV-2 T cell epitopes (TCEs) administered within Gritstone’s SAM COVID-19 vaccines are minimally impacted by mutations found within the Omicron variant, reinforcing the platform’s potential to address both Omicron and future variants of concern.
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CEPI is already funding up to $20.6 million to support preclinical studies, manufacturing process optimization, and a Phase 1 trial of Gritstone’s Beta variant vaccine candidate (containing beta-Spike plus additional TCEs), which will be initiated by South Africa’s University of the Witwatersrand in the coming weeks. The funding announced today will expand the Phase 1 trial to include additional arms to evaluate an Omicron-specific version of the vaccine (which contains omicron-Spike plus TCEs). Gritstone has commenced manufacturing its SAM vaccine to specifically target the Omicron variant, and the Omicron arms of the Phase 1 trial are expected to begin in Q2 2022, subject to regulatory approval.
The recently described Omicron variant, first identified in South Africa on November 9, 2021, was designated a variant of concern by the World Health Organization (WHO) on November 26, 2021. Early evidence suggests that Omicron carries an increased risk of re-infection, and sequence analysis has revealed many mutations in Spike, which may reduce clinical effectiveness of existing vaccines and/or therapeutic antibodies.
Enabling equitable access
CEPI is committed to global equitable access to COVID-19 vaccines so, through this agreement, CEPI and Gritstone have agreed that this Omicron vaccine candidate will be made available to the COVAX Facility for procurement and allocation, if it is proven to be safe and effective. The COVAX Facility aims to deliver equitable access to COVID-19 vaccines for all countries, at all levels of development, that wish to participate.
Dr Richard Hatchett, CEO of CEPI, said: "While key questions are yet to be answered about Omicron, its transmissibility, and its potential ability to evade our current vaccines, the stakes are too high to delay developing Omicron-specific vaccine candidates. Given the uncertainties, we must accelerate crucial R&D so vaccines are available to tackle Omicron as soon as possible – just in case we need them. There is no time to lose, so I’m pleased that within 10 days of Omicron being declared a Variant of Concern by the WHO, CEPI is expanding its partnership with Gritstone to support a new Omicron vaccine candidate which can be made globally accessibly through COVAX."
"Our vaccine platforms are built on the premise that a best-in-class vaccine against a virus will drive strong neutralizing antibodies directed to surface antigens such as Spike, and strong cytotoxic T cell responses against other conserved viral antigens to eliminate virally infected cells. This broad immune response would, in principle, provide superior protection against a virus that is mutating its surface protein. Omicron is an example of a novel SARS-CoV-2 variant that may escape clinical protection conferred by vaccines that only afford narrow, Spike-specific immunity," said Andrew Allen, M.D., Ph.D., co-founder, president and chief executive officer of Gritstone. "Our SAM technology provides an innovative platform likely capable of delivering on the attractive concept of broad, durable immunity. We are thrilled to be quickly expanding our relationship with CEPI in our shared goal of finding new vaccine solutions to battle this deadly virus on a global scale and help prevent current and perhaps future COVID outbreaks."
Self-amplifying mRNA vaccines
As with the mRNA-based COVID-19 vaccines that are now in global use, self-amplifying mRNA vaccines use the body’s own machinery to make antigenic protein itself rather than injecting the antigen directly into the body.
However, in self-amplifying mRNA vaccines, viral RNA is adapted in a way that allows only the genetic sequence for a specific antigen to be expressed, while keeping the part of the RNA that allows it to produce multiple copies of itself—the self-amplification machinery.
The benefit of this approach is that the dose of RNA can be reduced while maintaining the potency of the vaccine. Gritstone’s vaccine candidate may also elicit T-cell immune responses against non-Spike gene fragments, which are slower to mutate than the genes associated with the SARS-CoV-2 Spike protein and could potentially provide broad protection against other SARS-CoV-2 strains.