Moderna’s flu vaccine trial delayed by case numbers

Moderna’s aspiration to become a player in the seasonal influenza vaccine market has hit a hurdle – likely a delay rather than anything more serious – but its stock has still come under pressure.

Shares in the company dipped around 3% today after the revelation that one of a pair of phase 3 studies of its quadrivalent flu vaccine mRNA-1010 had not seen enough cases of flu at the time of an interim analysis to allow the study to be stopped early.

While the Northern Hemisphere P302 trial can still continue to follow-up patients in the hope that enough flu cases will accrue to allow a comparison with the active control – GSK’s licensed flu jab, Fluarix Tetra – investors were clearly spooked by the revelation, which was made during a Moderna pipeline update today.

Some of that nervousness could stem from the antibody data from the P301 trial in the Southern Hemisphere, released in February, which painted a slightly mixed picture for the shot, matching the control on just two of the four flu strains tested, and causing more side effects.

mRNA-1010 seemed to be slightly more effective against two influenza A serotypes, but did not meet the non-inferiority threshold against two influenza B strains. On antibody titres, the P302 study seems more positive, with the vaccine showing levels that were “consistent with superiority” for the A strains and “consistent with non-inferiority” for the B.

Moderna said it has developed an update to mRNA-1010 that is expected to have improved immunogenicity against B strains and will start a confirmatory phase 3 trial this month.

It’s worth noting, however, that A strains account for most flu-related disease in older people, who are most vulnerable to complications from infection, so greater efficacy against A compared to current shots could be a big selling point.

It has no fewer than five flu vaccines in clinical development, including pentavalent and hexavalent candidates that increase the breadth of protection against common flu strains and versions that are targeted at less variable targets in the neuraminidase antigen, which could move the needle towards provision of a ‘universal’ vaccine.

The decline in Moderna’s share price came despite a number of other positive pipeline developments at the biotech, including the start of phase 3 testing for a new-generation COVID-19 vaccine, the anticipated filing of a respiratory syncytial virus (RSV) vaccine this quarter, and a new jab targeting Lyme disease – its first vaccines against a bacterial disease.