Lilly has announced plans to acquire ImClone for $6.5 billion.

The move follows months of bickering between ImClone and Bristol-Myers Squibb (BMS) regarding the appraisal value, the potential of ImClone’s pipeline and, in early September, the emergence of a secret bidder.

BMS, which owns 16.6% of ImClone, had initially offered to buy the remainder of ImClone for $60 a share, valuing the company at $4.5 billion. That bid was rejected, and BMS returned to the table with a $4.7 billion dollar offer, upping the share price to $62. Imclone rejected that bid as well, citing a mystery bidder prepared to offer $70 a share, pending due diligence.

Lilly turned out to be the mystery bidder, and successfully entered into a definitive merger with ImClone on October 6. Erbitux, ImClone’s billion dollar cancer treatment, will continue to be co-marketed by ImClone and BMS in the US.

“We think very highly of ImClone’s groundbreaking work in oncology, particularly its success with Erbitux…and its ability to advance promising biotech molecules in its pipeline,” said John Lechleiter, president and CEO of Lilly, in a statement.