PARIS - Sanofi is dropping plans for its own mRNA-based COVID-19 vaccine because of the dominant role of the BioNTech-Pfizer alliance as well as Moderna in the fight against the pandemic, the company said on Tuesday.

The move highlights the challenges of competing in particular with pioneer BioNTech, which rose from obscurity through its alliance with pharma major Pfizer last year. The pair have delivered close to 1.5 billion doses so far, making them the western world's largest COVID-19 vaccine maker.

French healthcare group Sanofi will instead focus on efforts with British partner GlaxoSmithKline to bring another COVID-19 vaccine candidate to market based on the more conventional protein-based approach, where mass trials are ongoing.

The decision to drop clinical development of the mRNA shot, acquired as part of its takeover of Translate Bio, came despite positive Phase I/II study interim results announced on Tuesday where participants' blood readings showed a strong immune reaction.

But Sanofi said the read-out encouraged it only to pursue the technology as a potential vaccine against influenza and other diseases, giving up on the area of COVID-19 because of the strong market presence of the two approved mRNA shots.

"These results will clearly help inform the path forward for our mRNA development programs," said Jean-Francois Toussaint, global head of research and development at Sanofi Pasteur.

The company said it started testing an mRNA shot against seasonal influenza in humans in June and will launch follow-on clinical studies next year.

German biotech firm CureVac earlier this month also acknowledged rivals' dominance when it cancelled some of the contract manufacturing deals for its experimental mRNA COVID-19 vaccine with two prospective partners.

CureVac's product is under review by the European Union's drugs regulator with an uncertain outcome after disappointing trial results.

The mRNA vaccines trick the human body into producing proteins known as antigens that are found on the surface of the coronavirus that causes COVID-19. That primes the immune system to quell future infections.

Under the more traditional protein-based vaccine approach that Sanofi will now focus on, the antigen is bioengineered in labs and combined with an efficacy booster known as adjuvant, provided by GSK.

Sanofi executive Thomas Triomphe told journalists in a briefing that the EU and Britain had ordered 75 million doses of this vaccine, banking on future regulatory approval.

(Reporting by Ludwig Burger, Sarah White and Sudip Kar-Gupta, editing by Louise Heavens and David Evans) ((; +49 30 220133634; Reuters Messaging: