French healthcare company Sanofi S.A. (Euronext Paris:SAN) (Nasdaq:SNY) announced on Tuesday that it has entered into an agreement to acquire London-based biotechnology company Vicebio Ltd for an upfront payment of USD1.15bn, with up to USD450m in potential milestone payments.

Subject to regulatory approvals, the transaction is expected to close in the fourth quarter of 2025.

This acquisition adds VXB-241, a bivalent vaccine candidate targeting respiratory syncytial virus (RSV) and human metapneumovirus (hMPV), currently in an exploratory phase 1 study in older adults. It also includes VXB-251, a preclinical trivalent vaccine candidate targeting RSV, hMPV and parainfluenza virus Type 3 (PIV3).

Vicebio's 'Molecular Clamp' platform, which stabilises viral proteins in their native shape, enhances vaccine efficacy and enables faster development of fully liquid combination vaccines that can be stored at standard refrigeration temperatures.

The deal complements Sanofi's existing respiratory vaccine portfolio by adding a non-mRNA approach and expanding its capabilities in the prevention of lower respiratory tract infections. These infections -- caused by RSV, hMPV and PIV3 -- contribute to seasonal surges in illness among older adults and are a leading cause of pneumonia, frailty, hospitalisation and mortality.

Sanofi stated that the acquisition will not significantly impact its 2025 financial guidance.