Valeant Pharmaceuticals has raised the cash portion of its takeover offer for Botox-maker Allergan for the second time this week in the hopes of kicking off negotiations between the two companies.

Valeant and Allergan’s largest shareholder, Pershing Square Capital, said in a joint announcement Friday afternoon that they have increased the cash component of their offer for Allergan by more than 23%, to $72 per share from the $58.30 they offered on Wednesday. The offer from Valeant and Pershing Square, which also still includes 0.83 Valeant shares for each share of Allergan stock, is contingent on Allergan agreeing to enter into negotiations.

The latest offer for Allergan values the company at roughly $53 billion and comes just two days after Valeant CEO J. Michael Pearson told CNBC his company would be “persistent” but “patient” with regard to its pursuit of Allergan.

“We believe our revised offer provides enormous value to both Valeant and Allergan shareholders,” Pearson said in the announcement. “We strongly believe that applying Valeant’s operating philosophy, strategy, and financial discipline to a broader set of durable assets will continue to create substantial returns for shareholders over the short, intermediate, and long term. We are very committed to getting this deal done, and are now modifying our offer with the assistance of Pershing Square to increase the economics for all Allergan shareholders.”

Pershing Square founder and activist hedge fund manager William Ackman said he has agreed to swap out his entire 9.6% Allergan share for Valeant stock.