13G Filing: Billionaire David Shaw’s D. E. Shaw & Co. and AMAG Pharmaceuticals Inc. (AMAG)

SECURITIES AND EXCHANGE COMMISSION

 

Washington, D.C. 20549

 

SCHEDULE 13G

 

Under the Securities Exchange Act of 1934

 

AMAG Pharmaceuticals, Inc.

(Name of Issuer)

Common Stock, par value $0.01

(Title of Class of Securities)

 

00163U106

(CUSIP Number)

 

January 4, 2016

(Date of Event Which Requires Filing of this
Statement)

Check the following box to designate the rule pursuant to which
the Schedule is filed:

¨

Rule 13d-1(b)

x

Rule 13d-1(c)

¨

Rule 13d-1(d)

*The remainder of this cover page shall be filled out for a reporting
person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing
information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall
not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or
otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however,
see the Notes).