UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT
TO RULE 13d-1(b), (c), AND (d) AND AMENDMENTS THERETO FILED
PURSUANT TO RULE 13d-2(b)

(AMENDMENT NO. 11)*

AMAG Pharmaceuticals, Inc.
(Name of Issuer)

Common Stock
(Title of Class of Securities)

00163U106
(CUSIP Number)

December 31, 2019
(Date of Event which Requires Filing of this Statement)

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

       [ X ] Rule 13d-1(b)
       [     ] 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 disclosures 
provided in a prior cover page.

The information required on 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).


CUSIP No. 00163U106
 
13G
 
Page 2 of 10 Pages

1.
NAMES OF REPORTING PERSONS OR
I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

Patrick Lee, MD
 
2.
CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
(see instructions)

(a) [    ]
(b) [ x ]
3.
SEC USE ONLY
 
 
4.
CITIZENSHIP OR PLACE OF ORGANIZATION
USA
 

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH
5.
SOLE VOTING POWER

 691

6.
SHARED VOTING POWER

3,044,374

7.
SOLE DISPOSITIVE POWER

 691

8.
SHARED DISPOSITIVE POWER

 3,044,374

9.
AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

 3,045,065
 
10.
CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES
(see instructions) [  ]
 
 
11.
PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

 8.98%
 
12.
TYPE OF REPORTING PERSON (see instructions)

 IN, HC
 
 





CUSIP No. 00163U106
 
13G
 
Page 3 of 10 Pages

1.
NAMES OF REPORTING PERSONS OR
I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

Anthony Joonkyoo Yun, MD
 
2.
CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
(see instructions)

(a) [    ]
(b) [ x ]
3.
SEC USE ONLY
 
 
4.
CITIZENSHIP OR PLACE OF ORGANIZATION
 USA
 

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH
5.
SOLE VOTING POWER

 0

6.
SHARED VOTING POWER

3,044,374

7.
SOLE DISPOSITIVE POWER

 0

8.
SHARED DISPOSITIVE POWER

 3,044,374

9.
AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

3,044,374
 
10.
CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES
(see instructions) [  ]
 
 
11.
PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

8.98%
 
12.
TYPE OF REPORTING PERSON (see instructions)

 IN, HC
 
 







CUSIP No. 00163U106
 
13G
 
Page 4 of 10 Pages

1.
NAMES OF REPORTING PERSONS OR
I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

Palo Alto Investors LP
 
2.
CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
(see instructions)

(a) [    ]
(b) [ x ]
3.
SEC USE ONLY
 
 
4.
CITIZENSHIP OR PLACE OF ORGANIZATION
California
 

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH
5.
SOLE VOTING POWER

 0

6.
SHARED VOTING POWER

3,044,374

7.
SOLE DISPOSITIVE POWER

 0

8.
SHARED DISPOSITIVE POWER

 3,044,374

9.
AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

 3,044,374
 
10.
CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES
(see instructions) [  ]
 
 
11.
PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

8.98%
 
12.
TYPE OF REPORTING PERSON (see instructions)

 OO, IA
 
 





CUSIP No. 00163U106
 
13G
 
Page 5 of 10 Pages

1.
NAMES OF REPORTING PERSONS OR
I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

PAI LLC
 
2.
CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
(see instructions)

(a) [    ]
(b) [ x ]
3.
SEC USE ONLY
 
 
4.
CITIZENSHIP OR PLACE OF ORGANIZATION
California
 

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH
5.
SOLE VOTING POWER

 0

6.
SHARED VOTING POWER

3,044,374

7.
SOLE DISPOSITIVE POWER

 0

8.
SHARED DISPOSITIVE POWER

 3,044,374

9.
AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

 3,044,374
 
10.
CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES
(see instructions) [  ]
 
 
11.
PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

8.98%
 
12.
TYPE OF REPORTING PERSON (see instructions)

 OO, IA
 
 





CUSIP No. 00163U106
 
13G
 
Page 6 of 10 Pages

1.
NAMES OF REPORTING PERSONS OR
I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

Palo Alto Healthcare Master Fund II, L.P.
 
2.
CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
(see instructions)

(a) [    ]
(b) [ x ]
3.
SEC USE ONLY
 
 
4.
CITIZENSHIP OR PLACE OF ORGANIZATION
Cayman Islands
 

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH
5.
SOLE VOTING POWER

 0

6.
SHARED VOTING POWER

1,863,117

7.
SOLE DISPOSITIVE POWER

 0

8.
SHARED DISPOSITIVE POWER

 1,863,117

9.
AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

 1,863,117
 
10.
CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES
(see instructions) [  ]
 
 
11.
PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

 5.49%
 
12.
TYPE OF REPORTING PERSON (see instructions)

 PN
 
 









CUSIP No. 00163U106
 
13G
 
Page 7 of 10 Pages

Item 1.

(a)
Name of Issuer

AMAG Pharmaceuticals, Inc.
 


 
(b)
Address of Issuers Principal Executive Offices

1100 Winter Street, Waltham, MA 02451

Item 2.

(a)
Name of Person Filing

Palo Alto Investors LP (PAI) 
PAI LLC (PAI GP)
Patrick Lee, MD
Anthony Joonkyoo Yun, MD
Palo Alto Healthcare Master Fund II, L.P. ("Healthcare Master II")
(collectively, the "Filers").
 


 
(b)
The address of the principal place of 
the Filers except for Healthcare Master
 II is located at: 

470 University Avenue, Palo Alto, CA 94301

The principal business office of Healthcare Master II is located at:

Cayman Corporate Centre, 27 Hospital Road
George Town, Grand Cayman KY1-9008
Cayman Islands
 


 
(c)
 For citizenship of Filers, see Item 4 of the cover sheet for each Filer.

 


 
(d)
Title of Class of Securities

Common Stock
 


 
(e)
CUSIP Number

00163U106

Item 3. If this statement is filed pursuant 
to 240.13d-1(b) or 240.13d-2(b) or 
(c), check whether the person filing is a:

 
(a)
[  ]
Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o).
 



 
(b)
[  ]
Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c).
 



 
(c)
[  ]
Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c).


 



 
(d)
[  ]
Investment company registered under section 8 of 
the Investment Company Act of 1940 (15 U.S.C. 80a-8).

 
(e)
[x]
An investment adviser in accordance with 
240.13d-1(b)(1)(ii)(E); (as to PAI)

CUSIP No. 00163U106
 
13G
 
Page 8 of 10 Pages





 



 
(f)
[  ]
An employee benefit plan or endowment fund in 
accordance with 240.13d-1(b)(1)(ii)(F);
 



 
(g)
[x] 
A parent holding company or control person in accordance with 
240.13d-1(b)(1)(ii)(G); (as to Dr. Lee and Dr. Yun)
 



 
(h)
[  ]
A savings associations as defined in Section 3(b) of the Federal
 Deposit Insurance Act (12 U.S.C. 1813);
 



 
(i)
[  ]
A church plan that is excluded from the definition of an
 investment company under section 3(c)(14) of the 
Investment Company Act of 1940 (15 U.S.C. 80a-3);
 



 
(j)
[  ]
Group, in accordance with 240.13d-1(b)(1)(ii)(J).

Item 4. Ownership.

See Items 5-9 and 11 of the cover page for each Filer. 

Item 5. Ownership of Five Percent or Less of a Class.

N/A

Item 6. Ownership of More than Five Percent on Behalf of Another Person.

PAI is a registered investment adviser and investment adviser of 
investment limited partnerships, and is the investment adviser
 to other investment funds. PAI GP is the general partner 
of investment limited partnerships. PAIs clients have 
the right to receive or the power to direct the receipt of 
dividends from, or the proceeds from the sale of, the Stock.
 No individual client outside of Healthcare Master
 II separately holds more than five percent of 
the outstanding Stock.
   
   
Item 7. Identification and Classification of the Subsidiary Which 
Acquired the Security Being Reported on By the Parent
 Holding Company.

N/A
   
Item 8. Identification and Classification of Members of the Group.

Dr. Lee and Dr. Yun co-manage PAI. The Filers are filing this 
Schedule 13G jointly, 
but not as members of a group, and each of them 
expressly disclaims membership in a group. 
Each Filer disclaims beneficial ownership of the
 Stock except to the extent of that Filers 
pecuniary interest therein.

Schedule 13G on behalf of Healthcare Master
 II should not be construed as an admission
 that any of them is, and each disclaims 
that it is, a beneficial owner, as defined 
in Rule 13d-3 under the Securities Exchange 
Act of 1934, of any of the Stock covered 
by this Schedule 13G.

Item 9. Notice of Dissolution of Group.

N/A


CUSIP No. 00163U106
 
13G
 
Page 9 of 10 Pages
   
Item 10. Certification.

By signing below I certify that, to the best of 
my knowledge and belief, the securities referred 
to above were not acquired and are not held 
for the purpose of or with the effect of 
changing or influencing the control of 
the issuer of the securities and were
 not acquired and are not held in 
connection with or as a participant 
in any transaction having that 
purpose or effect.

Exhibits.

Exhibit A Joint Filing Agreement.


SIGNATURE


After reasonable inquiry and to the best of my knowledge
 and belief,
 I certify that the information set forth in 
this statement is true, complete and correct.

Dated: February 14, 2020


PALO ALTO HEALTHCARE MASTER FUND II, L.P.

By: PAI LLC, General Partner


PALO ALTO INVESTORS LP

By: /s/ Angela Nguyen-Dinh, Chief Compliance Officer

PAI LLC

By: /s/ Patrick Lee, MD


/s/ Patrick Lee, MD




/s/ Anthony Joonkyoo Yun, MD



CUSIP No. 00163U106
 
13G
 
Page 10 of 10 Pages

EXHIBIT A
AGREEMENT REGARDING JOINT FILING
OF STATEMENT ON SCHEDULE 13D OR 13G

The undersigned agree to file jointly with the Securities 
and Exchange Commission (the "SEC") any and all 
statements on Schedule 13D or Schedule 13G 
(and any amendments or supplements thereto)
required under section 13(d) of the Securities 
Exchange Act of 1934, as amended, in connection 
with purchases and sales by the undersigned of the
 securities of any issuer until such time as the
undersigned file with the SEC a statement 
terminating this Agreement Regarding Joint Filing 
of Statement on Schedule 13D or 13G. For that purpose,
 the undersigned hereby constitute and appoint Palo Alto
 Investors, LP, a California limited partnership, as 
their true and lawful agent and attorney-in-fact, with 
full power and authority for and on behalf of the 
undersigned to prepare or cause to be prepared, sign, file with 
the SEC and furnish to any other person all certificates,
instruments, agreements and documents necessary to 
comply with section 13(d) and section 16(a) of the 
Securities Exchange Act of 1934, as amended, in 
connection with said purchases and sales, and to do 
and perform every act necessary and proper to be done 
incident to the exercise of the foregoing power, as fully 
as the undersigned might or could do if personally present, 
until such time as the undersigned file with the SEC 
a statement terminating this Agreement Regarding 
Joint Filing of Statement on Schedule 13D or 13G.

Dated: February 14, 2020

PALO ALTO HEALTHCARE MASTER FUND II, L.P.

By: PAI LLC, General Partner

PALO ALTO INVESTORS LP

By: /s/ Angela Nguyen-Dinh, Chief Compliance Officer

PAI LLC

By: /s/ Patrick Lee, MD


/s/ Patrick Lee, MD

/s/ Anthony Joonkyoo Yun, MD