Shionogi's COVID-19 vaccine matches Pfizer's Comirnaty in booster trial

Shionogi’s COVID-19 vaccine candidate has held its own against Pfizer’s Comirnaty in a study of the effect of booster shots on antibody levels, offering the company encouragement as it barrels toward a filing for approval of S-268019 in Japan.

The clinical trial randomized 206 adults to receive a shot of S-268019 or Comirnaty six months or more after they completed a primary two-dose series with the Pfizer-BioNTech vaccine. Shionogi designed the clinical trial to compare the immunogenicity of its recombinant protein-based vaccine to that of Pfizer’s market-leading mRNA shot.

S-268019 passed the test. Shionogi found its vaccine was noninferior to Comirnaty against the primary endpoint, which looked at neutralizing antibody titers 29 days after the administration of the booster shot. 

The safety and tolerability data presented by Shionogi are free from red flags. Fever, headache, fatigue, muscle aches and injection site pain were the most frequent treatment-related adverse events, as they have been in studies of other COVID-19 vaccines. Most solicited local and systemic events were mild, and the incidence of solicited events was lower in the S-268019 cohort.

The data drop is a small step on the path to pivotal readouts. Shionogi is running four other phase 2/3 or phase 3 clinical trials, including a study that is aiming to enroll 50,000 subjects to assess whether giving S-268019 to unvaccinated people protects them from symptomatic COVID-19. The other, smaller trials are comparing S-268019 to AstraZeneca’s Vaxzevria and as a booster to Moderna’s Spikevax.

Shionogi only started the 50,000-subject phase 3 late last year but it is already gearing up for approval, opening talks with Japan’s Pharmaceuticals and Medical Devices Agency about a filing last month.