GRTS - Gritstone self-amplifying mRNA COVID vaccine shows promise in 2 early stage trials

Gritstone bio ( NASDAQ: GRTS ) on Tuesday said its self-amplifying mRNA (samRNA) COVID vaccine showed tolerability and immunogenicity in two phase 1 trials.

CORAL-CEPI :

The study includes 340 people and is evaluating T cell-enhanced omicron- and beta-spike constructs in people who are vaccine-naïve, convalescent and HIV+.

The data is from Part A of the study (n=120) where people received beta-spike plus T Cell Epitope candidate vaccines at 3 dose levels.

The company said 3 people developed transient grade 3 adverse events (AEs). All dose levels tested (3µg, 10µg and 30µg) were well tolerated.

Gritstone added that all dose levels were immunogenic in all groups.

Two doses of samRNA vaccine candidate in SARS-CoV-2-naïve people induced strong nAb against both beta and delta variants, according to the company.

In addition, One dose in COVID convalescent people boosted nAb titers.

The study is being run in South Africa with support from the Coalition for Epidemic Preparedness Innovations (CEPI).

CORAL-BOOST :

The phase 1 trial in the U.K. is evaluating a single dose of samRNA vaccine candidate (10µg or 30µg) as a booster in healthy volunteers >60 years old. The study previously focused on people who had received two prior doses of AstraZeneca's Vaxzervria but expanded in January 2022 to include two groups that previously received an mRNA primary series.

Gritstone said that in the 32 people, 3 developed transient grade 3adverse events (AEs). Both doses were well-tolerated, with transient mild to moderate AEs.

Broad neutralizing antibodies (nAb) and anti-Spike IgG responses, were elicited against the vaccine variant (D614G) and variants of concern (VoC) including beta, delta, omicron BA.1, and omicron BA.4/5, the company added.

Gritstone noted that persistence of nAb responses to 6 months was seen.

In addition, the vaccine showed a durable boost to pre-existing T cell responses to Spike antigens.

The company said the vaccine showed increased  and durable Spike-specific T cell responses 4 weeks and 6 months post-boost in people after primary series of AstraZeneca's vaccine.

The shot also demonstrated priming of T cell responses to the non-Spike viral epitopes, which are part of the vaccine cassette, with a single samRNA vaccine.

GRTS -0.88% to $2.24 premarket Oct. 25

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