(Reuters) -German biotech firm BioNTech has agreed to acquire domestic peer CureVac for about $1.25 billion worth of BioNTech shares, it said on Thursday, to boost its work on new mRNA-based cancer treatments. Under the deal, which pairs two former rivals in the race to develop COVID-19 vaccines, CureVac shareholders stand to receive a premium of 55% over the three-month average share price, and leave them with a stake of about 4%-6% in BioNTech, the suitor said. CureVac's Frankfurt-listed shares surged 27% to a five-month high, valuing the company at 1.04 billion euros ($1.2 billion), while BioNTech shares were down 2% by 1237 GMT.