Merrimack Pharmaceuticals, which postponed its IPO in February, announced new terms on Monday. The Cambridge, MA-based company now plans to raise $100 million (down from $150 million) by offering 14.3 million shares at a price of $7.00. At the $7 price, Merrimack Pharmaceuticals will command a market value of $647 million (down from $853 million). Merrimack Pharmaceuticals, which uses its Network Biology system to discover and develop cancer treatments, plans to list on the NASDAQ under the symbol MACK. J.P. Morgan is the bookrunner on the deal.