GlaxoSmithKline is expected to announce later today that it has acquired Human Genome Sciences, by offering $200 million more than its previously-rejected $2.60 billion hostile bid.

The proposed deal was first reported by Reuters which quoted unnamed sources as saying that GSK is likely to up its $13 per share bid by about a dollar to finally get hold of HGS. The news has come out on the day the US biotech's deadline for offers was reached (July 16) and it appears that no other companies were prepared to come up with any concrete bid.

Reuters reports that as the deadline approached, HGS shareholders had been pressing management to engage with GSK. One of the sources told the news agency that HGS did indeed make an approach.

They also claimed that a contingent value right, entitling the latter's shareholders to payments linked to the success of the late-stage cardiovascular treatment darapladib and albiglutide, currently in Phase III for type 2 diabetes, is unlikely to be part of the deal. Those two drugs have been jointly developed by GSK and HGS, as was the lupus drug Benlysta (belimumab).