(Adds details from Caligan's filing, background on Amag)
Sept 20 (Reuters) - Camber Capital Management on Friday unveiled a stake of about 13% in Amag Pharmaceuticals Inc and said it intends to discuss the drugmaker's board composition with shareholders, weeks after an activist investor called for a board shake-up.
Caligan Partners, which owns 10.3% stake in the company, earlier this month sought shareholders' consent on its call for removal of four directors from Amag's board.
The drugmaker in June won U.S. approval for its therapy to restore sexual desire in premenopausal women, yet two months later lowered its full-year revenue expectations, hurt by dismal sales in its women's health segment.
On Friday, Camber reported a 12.9% stake in Amag as of Sept. 20 and said the company's shares were undervalued, but added that it currently did not have a proposal for the drugmaker. (bit.ly/2kHF19L)
Camber said it may further engage in discussions with Amag's management aimed at enhancing shareholder value, including discussions about potential deals and other strategic alternatives.
Amag said in an emailed statement that it valued constructive discussions with its shareholders.
It has in the past said Caligan's actions are not in the best interest of the company and its shareholders.
Camber did not respond to Reuters request for additional details.
In Caligan's September filing, the shareholder said it believed Amag could be worth more than $30 per share, which is more than double the company's current share prices.
Caligan had said Amag should conduct a review of its alternatives, including separating its women's health products from its treatments for other disorders.
Amag last traded above $30 per share in early January 2017 and its shares were as high as $77.73 at their peak in 2015.
The company's shares were up 10% at $13.27 on Friday.
Reporting by Manas Mishra and Anuron Kumar Mitra in Bengaluru; Editing by Shinjini Ganguli