A New York investment firm disclosed a 10.3% stake in Amag Pharmaceuticals (AMAG)  and said it would consider proposing a number of changes at the Waltham, Mass., drugmaker.

An Aug. 15 Securities and Exchange Commission Form 13D shows that Caligan Partners holds nearly 3.5 million shares of Amag.

The stock was purchased from June 21 to Aug. 12 for a total $29.5 million, or an average $8.44 a share.

In the filing, Caligan called Amag "undervalued" and an "attractive investment opportunity."

Caligan said it would take actions including potentially proposing that the company undertake a "strategic review or sales process," including transactions in which Caligan might participate.

Other proposals to Amag might include changes to its operations, management, board, dividend policy and strategy, among other things, the filing says.

Caligan said it would contact management and the board about such subjects and communicate with other shareholders and third parties.

Amag said in an email that it "welcomes shareholder input and values constructive feedback. The company is committed to acting in the best interests of shareholders and maximizing long-term value creation. We remain confident in our business strategy and our robust pipeline of innovative medicines."

On its website Amag says it focuses on "complex but undertreated health conditions ... including anemia, pregnancy complications, women's sexual function and menopause-related issues." 

Prominent among its products is Vyleesi, which treats premenopausal women who have low sexual desire.

The stock traded in the regular Thursday session down 6.3% at $11.40 a share. It rose 1% after hours.

In the past 52 weeks, the stock has traded as low as $6.81 and as high as $25.20.

For the second quarter, Amag reported its loss widened to $3.57 a share from 58 cents in the year-earlier quarter. Revenue fell 47% to $78.1 million.