Billionaire investor Bill Ackman's Pershing Square Capital Management said on Tuesday it would buy 10 million newly issued shares of Howard Hughes Holdings for $900 million as it revised its proposal to the real estate developer.

The deal would give hedge-fund manager Bill Ackman’s firm a 48% stake in the company known for master-planned community developments.

Howard Hughes Holdings (HHH) shares retreated 8% in Wednesday late morning trading, wiping out Tuesday's 6.8% gain, after confirming a revised takeover proposal from billionaire investor Bill Ackman's Pershing Square Capital Management.