Amended Statement of Ownership (sc 13g/a)

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

SCHEDULE 13G/A

Amendment No. 4

Under the Securities Exchange Act of 1934

NxStage Medical, Inc.

(Name of Issuer)

Common Stock

(Title of Class of Securities)

69404D108

(CUSIP Number)

December 31, 2016

(Date of Event Which Requires Filing of this Statement)

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

☐	Rule 13d-1(b)
☒	Rule 13d-1(c)
☐	Rule 13d-1(d)

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 (the “ 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).

1	NAME OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) Larry N. Feinberg
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions) (a) ☐ (b) ☐
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION United States
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH:		5	SOLE VOTING POWER 125,000
		6	SHARED VOTING POWER 2,596,636
		7	SOLE DISPOSITIVE POWER 125,000
		8	SHARED DISPOSITIVE POWER 2,596,636
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,721,626
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (See Instructions) ☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 4.20%*
12	TYPE OF REPORTING PERSON (See Instructions) IN

* Calculated based on a total of 64,756,107 shares of common stock outstanding as of October 31, 2016, as reported by the Issuer in its Quarterly Report on Form 10-Q filed with the Securities Exchange Commission (the “ SEC ”) on November 3, 2016 (the “ Quarterly Report ”).

1	NAME OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) Oracle Partners, L.P.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions) (a) ☐ (b) ☐
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION United States
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH:		5	SOLE VOTING POWER 0
		6	SHARED VOTING POWER 1,703,992
		7	SOLE DISPOSITIVE POWER 0
		8	SHARED DISPOSITIVE POWER 1,703,992
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 1,703,992
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (See Instructions) ☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 2.63%*
12	TYPE OF REPORTING PERSON (See Instructions) PN

* Calculated based on a total of 64,756,107 shares of common stock outstanding as of November 3, 2016, as reported by the Issuer in the Quarterly Report.

1	NAME OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) Oracle Institutional Partners, L.P.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions) (a) ☐ (b) ☐
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH:		5	SOLE VOTING POWER 0
		6	SHARED VOTING POWER 322,035
		7	SOLE DISPOSITIVE POWER 0
		8	SHARED DISPOSITIVE POWER 322,035
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 322,035
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (See Instructions) ☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 0.50%*
12	TYPE OF REPORTING PERSON (See Instructions) PN

* Calculated based on a total of 64,756,107 shares of common stock outstanding as of November 3, 2016, as reported by the Issuer in the Quarterly Report.

1	NAME OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) Oracle Ten Fund Master, LP
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions) (a) ☐ (b) ☐
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH:		5	SOLE VOTING POWER 0
		6	SHARED VOTING POWER 500,103
		7	SOLE DISPOSITIVE POWER 0
		8	SHARED DISPOSITIVE POWER 500,103
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 500,103
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (See Instructions) ☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 0.77%*
12	TYPE OF REPORTING PERSON (See Instructions) PN

* Calculated based on a total of 64,756,107 shares of common stock outstanding as of November 3, 2016, as reported by the Issuer in the Quarterly Report.

1	NAME OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) Oracle Investment Management Employees Retirement Fund
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions) (a) ☐ (b) ☐
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION Connecticut
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH:		5	SOLE VOTING POWER 0
		6	SHARED VOTING POWER 58,906
		7	SOLE DISPOSITIVE POWER 0
		8	SHARED DISPOSITIVE POWER 58,906
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 58,906
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (See Instructions) ☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 0.09%*
12	TYPE OF REPORTING PERSON (See Instructions) OO

* Calculated based on a total of 64,756,107 shares of common stock outstanding as of November 3, 2016, as reported by the Issuer in the Quarterly Report.

1	NAME OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) The Feinberg Family Foundation
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions) (a) ☐ (b) ☐
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION Connecticut
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH:		5	SOLE VOTING POWER 0
		6	SHARED VOTING POWER 11,600
		7	SOLE DISPOSITIVE POWER 0
		8	SHARED DISPOSITIVE POWER 11,600
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 11,600
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (See Instructions) ☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 0.02%*
12	TYPE OF REPORTING PERSON (See Instructions) OO

* Calculated based on a total of 64,756,107 shares of common stock outstanding as of November 3, 2016, as reported by the Issuer in the Quarterly Report.

1	NAME OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) Oracle Associates, LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions) (a) ☐ (b) ☐
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION Connecticut
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH:		5	SOLE VOTING POWER 0
		6	SHARED VOTING POWER 2,526,130
		7	SOLE DISPOSITIVE POWER 0
		8	SHARED DISPOSITIVE POWER 2,526,130
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,526,130
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (See Instructions) ☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 3.90%*
12	TYPE OF REPORTING PERSON (See Instructions) PN

* Calculated based on a total of 64,756,107 shares of common stock outstanding as of November 3, 2016, as reported by the Issuer in the Quarterly Report.

1	NAME OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) Oracle Investment Management, Inc.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions) (a) ☐ (b) ☐
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION United States
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH:		5	SOLE VOTING POWER 0
		6	SHARED VOTING POWER 559,009
		7	SOLE DISPOSITIVE POWER 0
		8	SHARED DISPOSITIVE POWER 559,009
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 559,009
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (See Instructions) ☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 0.86%*
12	TYPE OF REPORTING PERSON (See Instructions) CO

* Calculated based on a total of 64,756,107 shares of common stock outstanding as of November 3, 2016, as reported by the Issuer in the Quarterly Report.

This Amendment No. 4 to Schedule 13G (this “ Amendment No. 4 ”) is being filed with respect to the Common Stock, par value $.001 (“ Common Stock ”) NxStage Medical, Inc., a Delaware corporation (the “ Issuer ”), to amend the Schedule 13G filed on December 30, 2013, as previously amended by Amendment No. 1, filed on February 7, 2014, Amendment No. 2, filed on January 30, 2015 and Amendment No. 3, filed on February 3, 2016 (as so amended, the “ Schedule 13G” ), in accordance with the annual amendment requirements. This Amendment No. 4 is being filed on behalf of Oracle Partners, LP, a Delaware limited partnership (“ Oracle Partners ”), Oracle Ten Fund Master, LP, a Cayman Islands exempted company (“ Oracle Ten Fund ”), Oracle Institutional Partners, LP, a Delaware limited partnership (“ Institutional Partners ” and, collectively with Oracle Partners and Oracle Ten Fund, the “ Oracle Entities ”), Oracle Investment Management, Inc. Employees’ Retirement Plan, an employee benefit plan organized in Connecticut (the “ Retirement Plan ”), Oracle Associates, LLC, a Delaware limited liability company and the general partner of Oracle Partners, Oracle Ten Fund and Institutional Partners (“ Oracle Associates ”), Oracle Investment Management, Inc., a Delaware corporation and the investment manager to Oracle Ten Fund and the Retirement Plan (the “ Investment Manager ”), The Feinberg Family Foundation, a foundation organized in Connecticut (the “ Foundation ”), and Larry N. Feinberg, the managing member of Oracle Associates, the sole shareholder, director and president of the Investment Manager and the trustee of the Foundation (each of the foregoing, a “ Reporting Person ” and collectively, the “ Reporting Persons ”). Capitalized terms used but not defined herein have the meaning ascribed thereto in the Schedule 13G.

Item 4. Ownership:

Item 4 of the Schedule 13G is hereby amended and restated as follows:

A. Larry N. Feinberg

(a) Amount beneficially owned: 2,721,626

(b) Percent of class: 4.20%

(i) Sole power to vote or direct the vote: 125,000

(ii) Shared power to vote or direct the vote: 2,596,636

(iii) Sole power to dispose or direct the disposition: 125,000

(iv) Shared power to dispose or direct the disposition: 2,596,636

B. Oracle Partners

(a) Amount beneficially owned: 1,703,992

(b) Percent of class: 2.63%

(i) Sole power to vote or direct the vote: 0

(ii) Shared power to vote or direct the vote: 1,703,992

(iii) Sole power to dispose or direct the disposition: 0

(iv) Shared power to dispose or direct the disposition: 1,703,992

C. Institutional Partners

(a) Amount beneficially owned: 322,035

(b) Percent of class: 0.50%

(i) Sole power to vote or direct the vote: 0

(ii) Shared power to vote or direct the vote: 322,035

(iii) Sole power to dispose or direct the disposition: 0

(iv) Shared power to dispose or direct the disposition: 322,035

D. Oracle Ten Fund

(a) Amount beneficially owned: 500,103

(b) Percent of class: 0.77%

(i) Sole power to vote or direct the vote: 0

(ii) Shared power to vote or direct the vote: 500,103

(iii) Sole power to dispose or direct the disposition: 0

(iv) Shared power to dispose or direct the disposition: 500,103

E. Retirement Plan

(a) Amount beneficially owned: 58,906

(b) Percent of class: 0.09%

(i) Sole power to vote or direct the vote: 0

(ii) Shared power to vote or direct the vote: 58,906

(iii) Sole power to dispose or direct the disposition: 0

(iv) Shared power to dispose or direct the disposition: 58,906

F. Foundation

(a) Amount beneficially owned: 11,600

(b) Percent of class: 0.02%

(i) Sole power to vote or direct the vote: 0

(ii) Shared power to vote or direct the vote: 11,600

(iii) Sole power to dispose or direct the disposition: 0

(iv) Shared power to dispose or direct the disposition: 11,600

G. Oracle Associates

(a) Amount beneficially owned: 2,526,130

(b) Percent of class: 3.90%

(i) Sole power to vote or direct the vote: 0

(ii) Shared power to vote or direct the vote: 2,526,130

(iii) Sole power to dispose or direct the disposition: 0

(iv) Shared power to dispose or direct the disposition: 2,526,130

H. Investment Manager

(a) Amount beneficially owned: 559,009

(b) Percent of class: 0.86%

(i) Sole power to vote or direct the vote: 0

(ii) Shared power to vote or direct the vote: 559,009

(iii) Sole power to dispose or direct the disposition: 0

(iv) Shared power to dispose or direct the disposition: 559,009

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

If this statement is being filed to report the fact that as of the date hereof the Reporting Person has ceased to be the beneficial owner of more than 5 percent of the class of securities, check the following [x].

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 3, 2017

	ORACLE PARTNERS, L.P.
	By: ORACLE ASSOCIATES, LLC, its general partner
	By: /s/ Larry N. Feinberg Larry N. Feinberg, Managing Member

	ORACLE TEN FUND PARTNERS, LP
	By: ORACLE ASSOCIATES, LLC, its general partner
	By: /s/ Larry N. Feinberg Larry N. Feinberg, Managing Member

	ORACLE INSTITUTIONAL PARTNERS, LP
	By: ORACLE ASSOCIATES, LLC, its general partner
	By: /s/ Larry N. Feinberg Larry N. Feinberg, Managing Member
	ORACLE INVESTMENT MANAGEMENT, INC. EMPLOYEES’ RETIREMENT PLAN
	By: /s/ Larry N. Feinberg Larry N. Feinberg , Trustee

	THE FEINBERG FAMILY FOUNDATION By: /s/ Larry N. Feinberg Larry N. Feinberg, Trustee

	ORACLE INVESTMENT MANAGEMENT, INC. By: /s/ Larry N. Feinberg Larry N. Feinberg, President

	ORACLE ASSOCIATES, LLC By: /s/ Larry N. Feinberg Larry N. Feinberg, Manager Member

	/s/ Larry N. Feinberg Larry N. Feinberg, individually