Bavarian Nordic gets a vaccine booster

There is no approved vaccine for respiratory syncytial virus, but several companies are hoping to change this. Bavarian Nordic marked itself out as a contender today with promising data from a mid-stage study of its candidate, MVA-BN RSV.

The Danish group could soon go toe-to-toe with the likes of Pfizer, Glaxosmithkline and Johnson & Johnson, but speed is of the essence, and Bavarian will need a partner to be able to compete. With RSV cases rising as post-Covid lockdown restrictions ease, at least carrying out trials might be getting easier.

Challenge accepted

The company’s chief executive, Paul Chaplin, reckons the latest data should reignite partnering discussions, having sent Bavarian’s stock up 9% today. The results come from a phase 2 trial in which 61 healthy adults received either MVA-BN RSV or placebo, followed by an intranasal challenge with RSV 28 days later.

The study met its primary endpoint, showing a significant reduction in viral load, measured by PCR testing, with MVA-BN RSV versus placebo over 12 days.

Furthermore, MVA-BN RSV was found to be 79% effective in preventing moderately symptomatic RSV, with a case defined as two positive PCR tests plus at least one grade two RSV symptom. Only two cases of moderate disease were seen with Bavarian’s vaccine.

The project was less effective at preventing mildly symptomatic disease, or all cases including those that were asymptomatic, with efficacy of 76% and 52% respectively.

On a cross-trial basis the results look better than those seen with Johnson & Johnson’s candidate, Ad26.RSV.preF, which was 52% effective in preventing moderate disease in its phase 2 challenge trial.

However, MVA-BN RSV’s efficacy appears to fall short of that seen with Pfizer’s PF-06928316. The pharma giant recently said its contender was 100% effective in its phase 2 challenge trial, but did not give many details.

Mr Chaplin said during a conference call today that he assumed that the 100% figure quoted by Pfizer referred to prevention of moderately symptomatic RSV. He then questioned whether a difference of two cases between PF-06928316 and MVA-BN RSV was meaningful given the small study sizes involved.

MVA-BN RSV works differently versus the other late-stage candidates. While PF-06928316, Ad26.RSV.preF and Glaxosmithkline’s GSK3844766A are based on the prefusion form of RSV’s F protein, MVA-BN RSV incorporates five different RSV antigens including the F protein.

Bavarian says its candidate spurs a broad T-cell response, which could in turn help prevent severe disease.

Chasing

This needs to be proven, of course, and perhaps larger phase 3 trials will answer the question of which RSV vaccine is best. And here Bavarian is behind the pack. The company plans initially to develop MVA-BN RSV for elderly people, where Ad26.RSV.preF and GSK3844766A are already in pivotal trials. Meanwhile, PF-06928316 is set to enter a phase 3 study in adults this quarter.

Bavarian knows it needs to move fast, with Mr Chaplin saying: “It’s all about time to market.” The company had previously planned to run its pivotal study over two RSV seasons, but now looks likely to opt for a one-season trial in order to keep its rivals in sight.

Now all it needs to do is find a partner. The adult RSV vaccine market could be worth $7bn per year at peak, according to Leerink analysts, so interest could be high.