French healthcare company Sanofi S.A. (Euronext Paris:SAN) (Nasdaq:SNY) confirmed on Thursday that it has completed its acquisition of UK biotechnology company Vicebio Ltd, adding an early-stage combination vaccine candidate for respiratory syncytial virus (RSV) and human metapneumovirus (HMPV) to its pipeline.

This addition strengthens Sanofi's position in respiratory vaccines by introducing a non-mRNA option and expanding its design and development capabilities through Vicebio's Molecular Clamp technology. The technology stabilises viral proteins in their native form, supporting faster development of fully liquid combination vaccines that can be stored at standard refrigeration temperatures and offered in prefilled syringes to improve efficiency across healthcare settings.

Vicebio's portfolio includes VXB-241, a bivalent RSV and HMPV vaccine candidate in an exploratory phase 1 study in older adults, and VXB-251, a preclinical trivalent candidate targeting RSV, HMPV and parainfluenza virus Type 3.

Under the agreement announced in July 2025, Sanofi agreed to acquire all of Vicebio's share capital for USD1.15bn upfront, plus potential milestone payments of up to USD450m.

The acquisition was not expected to materially affect Sanofi's financial guidance for 2025.