Stung by Prostvac failure, Bavarian Nordic kicks off booster study for RSV shot

When a key drug disappoints, it’s only natural for biopharma companies to steer their attention to other assets. That’s exactly what Bavarian Nordic is doing with its RSV vaccine after cancer hopeful Prostvac failed as a monotherapy in prostate cancer.  

The Danish company is focusing on its MVA-BN RSV vaccine, targeting a market worth up to $6 billion. It has started a phase 2 extension study to help determine whether a single shot can last over multiple seasons or only remains effective for one season, like a flu shot, according to a release.

Bavarian Nordic is treading very carefully with its RSV candidate. Interim phase 2 data showed the shot maintains immunogenicity through six months, or about one RSV season, and investigators are following some subjects for another six months for longer-term evaluation.

On top of that work is the new extension study, where investigators will re-enroll 86 of the total 421 subjects, giving them a single shot of either a low or high dose of the vaccine to see whether the follow-up shot boosts the effects of the original dose. The goal is to determine whether MVA-BN RSV should be administered annually.

RELATED: After Prostvac flop, Bavarian Nordic showcases 6-month RSV data

After data from the booster study come out in the first half of 2018 and before a phase 3 trial, BN plans to start a human challenge study to guide future development. The company touts its RSV vaccine as superior to others in development because it encodes five different RSV targets—compared to the single F-protein target in Novavax’s version. The BN shot is also able to induce responses from both T-cells and antibodies, according to the biotech.

After Prosvac's recent trial failure, the company's hopes for that vaccine now live in its potential in combination with immuno-oncology drugs, now in testing in a Bristol-Myers Squibb collaboration.

In an interview with FiercePharma, Bavarian Nordic spokesperson Seth Lewis said that in hindsight, they might have designed the trial differently, especially as other cancer vaccines failed to deliver in late-stage monotherapy tests afterward. CEO Paul Chaplin, as well as some experts, still express a firm belief that combination therapy is the path forward.

RELATED: Despite notable failures, cancer vaccines are poised for a leap onto the market: expert

Details from the terminated Prostvac phase 3 study are yet to be shared, and the company is looking to put more emphasis on what Lewis called its “highly diversified pipeline" that includes the smallpox vaccine Imvamune, a Janssen-partnered Ebola shot, and other programs.

But these assets are either almost out of the clinic—Imvamune is already marketed in Canada and the EU, and there’s little doubt about its freeze-dried version currently in phase 2—or still in early phases. The RSV vaccine, on the other hand, is in midstage testing.

As the company revealed in its third-quarter results, the Prostvac flop didn’t affect its 2017 topline forecasts of about 1.3 billion Danish kroner ($206 million), because the company's revenues this year mostly derive from an upfront payment from BMS and expected government contracts for Imvamune.

But with Prostvac milestone payments mostly finished, near-term attention naturally shifted to MVA-BN RSV. RSV features quite a large potential market of $6 billion and there are no approved vaccines to protect against the infection.

Novavax previously had a late-stage vaccine trial failure that crushed its share price.