Vaxcyte has been granted breakthrough therapy designation from the US Food and Drug Administration (FDA) for its investigational 24-valent pneumococcal conjugate vaccine (PCV) candidate VAX-24 for the prevention of invasive pneumococcal disease (IPD) in adults.

The clinical-stage vaccine company has designed the vaccine candidate with the intention to improve upon the standard-of-care PCVs by covering the serotypes responsible for most of the pneumococcal diseases that are presently in circulation.

The breakthrough designation is backed by positive topline results from a phase 1/2 proof-of-concept study. The study assessed the safety, tolerability, and immunogenicity of VAX-24 in adults aged between 18 and 64 years.

In the phase 1/2 study, VAX-24 met the primary safety and tolerability objectives and showed a safety profile resembling that of Prevnar 20 (PCV20) for all the examined dosages.

The study also showed that the vaccine candidate, which the company plans to advance into a phase 3 programme, met or surpassed the regulatory immunogenicity standards for all 24 serotypes at the usual 2.2mcg dose.

For all 20 serotypes that are common with PCV20 at this dose, VAX-24 fulfilled the standard opsonophagocytic activity response non-inferiority criteria, of which 16 elicited stronger immune responses, Vaxcyte said.

Vaxcyte CEO and co-founder Grant Pickering said: “The FDA’s Breakthrough Therapy designation supports further acceleration of the VAX-24 development program in adults, while also providing validation of the potential of VAX-24 to deliver broader coverage and better immune responses relative to the standard of care.

“Our focus remains on advancing our VAX-24 clinical programs in both adults and infants and we anticipate announcing the topline data from the Phase 2 study in adults 65 and older in the second quarter of 2023.”