GlaxoSmithKline is betting on a new vaccine technology based on chimpanzee viruses by acquiring Swiss-based Okairos for €250 million ($321 million) - the latest bolt-on biotech buy by a big drugmaker.

Britain's largest pharmaceuticals group said on Wednesday that the privately owned company's know-how was expected to play an important role in GSK's development of vaccines to both prevent and treat diseases.

Okairos was spun out from Merck & Co in 2007 and has laboratories in Rome and Naples, with headquarters in Basel.

It specialises in making vaccines that target the immune system's CD8 T-cells - an approach that could yield preventative vaccines against several intractable infectious diseases, including hepatitis C, and also help fight cancer.

It does this by delivering genetic material using deactivated chimpanzee-derived adenoviruses that produce a very strong response against target diseases.

Adenoviruses, which cause the common cold, have long been studied as a useful delivery vehicle for genetic material - but they are so common that many people already have antibodies against them.

Chimp viruses, which are not so easily detected by the body's immune system, have an advantage since they can operate for longer and therefore elicit a powerful T-cell response.

The Okairos technology has already been tested in clinical studies involving more than 700 subjects, including mid-stage Phase II programmes in hepatitis C and malaria.

A hepatitis C shot could be particularly promising commercially, since there is currently no vaccine and treating the condition with drugs has become a multibillion-dollar business.

Okairos also has early stage products for diseases such as respiratory syncytial virus (RSV), tuberculosis, ebola and HIV.

New generation of vaccines

The real attraction lies less in individual products than in the company's technology platform, which GSK hopes to exploit within its own vaccine development programmes.

As such, the deal represents a long-term investment in a promising new scientific area, rather than one that will yield immediate financial rewards.

Christophe Weber, GSK's head of vaccines, said the acquisition of Okairos was "expected to contribute to the development efforts for an exciting new generation of vaccines".

GSK's Chief Executive Andrew Witty said earlier this year he had a "very low appetite" for acquisitions but, like many rivals in the industry, his company is constantly looking for bolt-on transactions to boost its pharmaceuticals, vaccines and consumer healthcare operations.

Last November, for example, GSK agreed to spend $1 billion to raise the stakes it holds in Indian and Nigerian consumer healthcare subsidiaries.

Smaller British rival AstraZeneca has a more urgent need for acquisitions, given its thin pipeline of new medicines to replace those losing patent protection. It agreed on Tuesday to pay up to $443 million for Omthera Pharmaceuticals, a U.S.-based specialist in fish oil-derived medicine.

Okairos's venture capital investors include BioMedInvest, the Boehringer Ingelheim Venture Fund, LSP, Novartis Venture Funds and Versant Ventures.