Valeant Pharmaceuticals International said on Monday it has withdrawn its sweetened takeover bid for ISTA Pharmaceuticals Inc , citing a lack of progress.

"We were not interested in participating in a lengthy evaluation process and we are disappointed that the ISTA team was not willing to fully explore our proposal by January 31," said Valeant Chief Executive Michael Pearson in a statement.

In December, California-based ISTA rejected the original $314 million bid from Valeant, calling it grossly inadequate. Earlier this month, Valeant raised its bid to $7.50 from $6.50 a share in cash, while indicating it could offer up to $8.50 a share, subject to due diligence.

Acquisition-hungry Canadian drugmaker Valeant said at the time that its offer would expire on Jan. 31.

Last year, Valeant agreed to acquire Australia's iNova Pharmaceuticals from private equity firms Archer Capital and Ironbridge for A$625 million. It also recently completed the C$88 million acquisition of Canadian cold and flu medicine maker Afexa Life Sciences.

"We continue to be disciplined on our M&A strategy and we are actively working on other opportunities that we believe can create value for our shareholders," said Pearson.