SC 13D/A

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C.  20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 1)*

RELYPSA, INC.

(Name of Issuer)

COMMON STOCK

(Title of Class of Securities)

759531106

(CUSIP Number)

OrbiMed Advisors LLC

OrbiMed Capital GP IV LLC

Samuel D. Isaly

601 Lexington Avenue, 54th Floor

New York, NY 10022

Telephone:  (212) 739-6400

(Name, Address and Telephone Number of Person

Authorized to Receive Notices and Communications)

April 16, 2014

(Date of Event Which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of § 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box o.

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits.  See § 240.13d-7(b) for other parties to whom copies are to be sent.

*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).

SCHEDULE 13D

CUSIP No. 759531106 Page 2 of 11 Pages

1	NAME OF REPORTING PERSONS OrbiMed Advisors LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions) (a) o (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS (See Instructions) N/A
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e)			o
6	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		7	SOLE VOTING POWER 0
		8	SHARED VOTING POWER 9,941,551
		9	SOLE DISPOSITIVE POWER 0
		10	SHARED DISPOSITIVE POWER 9,941,551
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 9,941,551
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (See Instructions)			o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 29.37%*
14	TYPE OF REPORTING PERSON (See Instructions) IA

_____________________________

*This percentage is calculated based upon 33,844,979 shares of the Issuer’s Common Stock (defined below) outstanding, as set forth in the Issuer’s prospectus filed with the Securities and Exchange Commission (the “SEC”) on April 11, 2014, taking into account the underwriter’s exercise of the over-allotment option.

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SCHEDULE 13D

CUSIP No. 759531106 Page 3 of 11 Pages

1	NAME OF REPORTING PERSONS OrbiMed Capital GP IV LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions) (a) o (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS (See Instructions) N/A
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e)			o
6	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		7	SOLE VOTING POWER 0
		8	SHARED VOTING POWER 9,941,551
		9	SOLE DISPOSITIVE POWER 0
		10	SHARED DISPOSITIVE POWER 9,941,551
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 9,941,551
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (See Instructions)			o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 29.37%*
14	TYPE OF REPORTING PERSON (See Instructions) OO

_________________________

*This percentage is calculated based upon 33,844,979 shares of the Issuer’s Common Stock outstanding, as set forth in the Issuer’s prospectus filed with the SEC on April 11, 2014, taking into account the underwriter’s exercise of the over-allotment option.

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SCHEDULE 13D

CUSIP No. 759531106 Page 4 of 11 Pages

1	NAME OF REPORTING PERSONS Samuel D. Isaly
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions) (a) o (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS (See Instructions) N/A
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e)			o
6	CITIZENSHIP OR PLACE OF ORGANIZATION United States
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		7	SOLE VOTING POWER 0
		8	SHARED VOTING POWER 9,941,551
		9	SOLE DISPOSITIVE POWER 0
		10	SHARED DISPOSITIVE POWER 9,941,551
11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 9,941,551
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (See Instructions)			o
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 29.37%*
14	TYPE OF REPORTING PERSON (See Instructions) IN

____________________________

*This percentage is calculated based upon 33,844,979 shares of the Issuer’s Common Stock outstanding, as set forth in the Issuer’s prospectus filed with the SEC on April 11, 2014, taking into account the underwriter’s exercise of the over-allotment option.

                          

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Item 1. Security and Issuer

This Schedule 13D (the “Statement”) relates to the common stock of Relypsa, Inc. (the “Common Stock”), a corporation organized under the laws of the state of Delaware (the “Issuer”), with its principal executive offices located at 700 Saginaw Drive, Redwood, California 94063.  The Common Stock is listed on the NASDAQ National Market under the ticker symbol “RLYP.”  Information given in response to each item shall be deemed incorporated by reference in all other items, as applicable.

On April 16, 2014, the Issuer announced the closing of an underwritten public offering of 4,130,611 shares of Common Stock (“Shares”) at $24.50 per Share, which included the purchase by the underwriters of 538,775 Shares pursuant to their option to purchase additional Shares at the public offering price (the “Share Issuance”).  As a result of the Share Issuance, the Issuer’s total number of outstanding Shares increased to 33,844,979 (the “Outstanding Share Increase”).  The Reporting Persons did not participate in, or acquire or dispose of any Shares in the Shares Issuance.  As a result of the Share Issuance (and more specifically, the Outstanding Share Increase), the percentage of outstanding Shares that the Reporting Persons may be deemed to be the beneficial owner of was reduced by more than one percent of the Issuer’s Shares outstanding after completion of the Share Issuance.

Item 2. Identity and Background

(a)               This Statement is being filed by OrbiMed Advisors LLC (“Advisors”), a limited liability company organized under the laws of Delaware, OrbiMed Capital GP IV LLC (“GP IV”), a limited liability company organized under the laws of Delaware, and Samuel D. Isaly (“Isaly”), an individual (collectively, the “Reporting Persons”).

(b) – (c)      Advisors, a registered investment adviser under the Investment Advisers Act of 1940, as amended, is the sole managing member of GP IV, which is the sole general partner of OrbiMed Private Investments IV, LP (“OPI IV”), which holds Shares, as more particularly described in Item 3 below.  Advisors has its principal offices at 601 Lexington Avenue, 54th Floor, New York, New York 10022.

GP IV has its principal offices at 601 Lexington Avenue, 54th Floor, New York, New York 10022.  Isaly, a natural person, owns a controlling interest in Advisors.

The directors and executive officers of Advisors and GP IV are set forth on Schedules I and II, attached hereto.  Schedules I and II set forth the following information with respect to each such person:

(i)                name;

(ii)               business address;

(iii)              present principal occupation or employment and the name, principal business and address of any corporation or other organization in which such employment is conducted;

(iv)              citizenship.

(d) – (e)      During the last five years, neither the Reporting Persons nor any Person named in Schedule I or II have been (i) convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors) or (ii) a party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

(f)                Isaly is a citizen of the United States.

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Item 3. Source and Amount of Funds or Other Consideration

Not applicable.  As described more fully in Item 1 above, the event giving rise to the obligation of the Reporting Persons to file this Amendment did not involve any transactions effected by one or more Reporting Persons with respect to the Shares.

Item 4. Purpose of Transaction

Not applicable.  As described more fully in Item 1 above, the events giving rise to the obligation of the Reporting Persons to file this Statement did not involve any transactions effected by one or more Reporting Persons with respect to the Shares.

The Reporting Persons from time to time intend to review their investment in the Issuer on the basis of various factors, including the Issuer’s business, financial condition, results of operations and prospects, general economic and industry conditions, the securities markets in general and those for the Issuer’s Shares in particular, as well as other developments and other investment opportunities.  Based upon such review, the Reporting Persons will take such actions in the future as the Reporting Persons may deem appropriate in light of the circumstances existing from time to time.  If the Reporting Persons believe that further investment in the Issuer is attractive, whether because of the market price of Shares or otherwise, they may acquire Shares or other securities of the Issuer either in the open market or in privately negotiated transactions.  Similarly, depending on market and other factors, the Reporting Persons may determine to dispose of some or all of the Shares currently owned by the Reporting Persons or otherwise acquired by the Reporting Persons either in the open market or in privately negotiated transactions.

Except as set forth in this Statement, the Reporting Persons have not formulated any plans or proposals which relate to or would result in:  (a) the acquisition by any person of additional securities of the Issuer or the disposition of securities of the Issuer, (b) an extraordinary corporate transaction, such as a merger, reorganization or liquidation, involving the Issuer or any of its subsidiaries, (c) a sale or transfer of a material amount of the assets of the Issuer or any of its subsidiaries, (d) any change in the present Board of Directors or management of the Issuer, including any plans or proposals to change the number or term of directors or to fill any existing vacancies on the board, (e) any material change in the Issuer’s capitalization or dividend policy of the Issuer, (f) any other material change in the Issuer’s business or corporate structure, (g) any change in the Issuer’s charter or bylaws or other instrument corresponding thereto or other action which may impede the acquisition of control of the Issuer by any person, (h) causing a class of the Issuer’s securities to be deregistered or delisted from a national securities exchange or to cease to be authorized to be quoted in an inter-dealer quotation system of a registered national securities association, (i) a class of equity securities of the Issuer becoming eligible for termination of registration pursuant to Section 12(g)(4) of the Act or (j) any action similar to any of those enumerated above.

Item 5. Interest in Securities of the Issuer

(a)-(b)         As of the date of this filing, Advisors, GP IV and Isaly may be deemed, for purposes of Rule 13d-3 of the Act, directly or indirectly, including by reason of their mutual affiliation, to be the beneficial owners of the Shares described in Item 3 above.  Based upon information contained in the most recent available filing by the Issuer with the SEC, such Shares constitute approximately 29.37% of the issued and outstanding Shares.  Advisors, pursuant to its authority as the sole managing member of GP IV, the sole general partner of OPI IV, may be deemed to indirectly beneficially own the Shares held by OPI IV.  GP IV, pursuant to its authority as the general partner of OPI IV, may be deemed to indirectly beneficially own the Shares held by OPI IV.  Isaly, pursuant to his authority as the managing member of Advisors and owner of a controlling interest in Advisors, pursuant to its limited liability company agreement, may also be deemed to indirectly beneficially own the Shares attributable to Advisors.  As a result, Isaly, Advisors and GP IV share the power to direct the vote and to direct the disposition of the Shares described in Item 3 above.

(c)               Except as disclosed in Item 3, the Reporting Persons have not effected any transactions in the Shares during the past sixty (60) days.

(d)               Not applicable.

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(e)               Not applicable.

Item 6. Contracts, Arrangements, Understandings or Relationship with Respect to Securities of the Issuer

In addition to the relationships between the Reporting Persons described in Items 2, 3 and 5 above, GP IV is the sole general partner of OPI IV, pursuant to the terms of the limited partnership agreement of OPI IV.  Advisors is the sole managing member of GP IV, pursuant to the terms of the limited liability company agreement of GP IV.  Pursuant to these agreements and relationships, Advisors and GP IV have discretionary investment management authority with respect to the assets of OPI IV.  Such authority includes the power of GP IV to vote and otherwise dispose of securities purchased by OPI IV.  The number of outstanding Shares attributable to OPI IV is 9,941,551 Shares.  Advisors may be considered to hold indirectly 9,941,551 Shares, and GP IV may be considered to hold indirectly 9,941,551 Shares.

Jonathan Silverstein (“Silverstein”), a member of Advisors, has been a member of the Board of Directors of the Issuer since August 2010, and, accordingly, the Reporting Persons may have the ability to affect and influence control of the Issuer.  On July 24, 2013, Silverstein was the recipient of a grant of options to purchase 10,140 Shares.  From time to time, Silverstein may receive additional stock options or other awards of equity-based compensation pursuant to the Issuer’s compensation arrangements for non-employee directors.  Pursuant to an agreement with the Reporting Persons, Silverstein is obligated to transfer any Shares issued under any such stock options or other awards to the Reporting Persons, which will distribute such Shares to OPI IV.

In connection with a purchase of Shares in the Issuer’s initial public offering, OPI IV entered into a lock-up agreement with Morgan Stanley & Co. LLC, Merrill Lynch, Pierce, Fenner & Smith Incorporated and Cowen and Company, LLC (the “Lock-Up Agreement”).  In addition, OPI IV and certain other stockholders of the Issuer are parties to a second amended and restated investor rights agreement with the Issuer (the “Investor Rights Agreement”).  Summaries of the Lock-Up Agreement and the Investor Rights Agreement are set forth at Item 6 of the original Statement.

Other than as described in this Schedule 13D, to the best of the Reporting Persons’ knowledge, there are no other contracts, arrangements, understandings or relationships (legal or otherwise) among the persons named in Item 2 and between such persons and any person with respect to any securities of the Issuer.

Item 7. Materials to Be Filed as Exhibits

Exhibit	Description
1.	Joint Filing Agreement among OrbiMed Advisors LLC, OrbiMed Capital GP IV LLC and Samuel D. Isaly

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SIGNATURE

After reasonable inquiry and to the best of each of the undersigned’s knowledge and belief, each of the undersigned certifies that the information set forth in this statement is true, complete and correct.

Dated:  April 17, 2014

OrbiMed Advisors LLC a Delaware Limited Liability Company
By:	/s/ Samuel D. Isaly
	Name:	Samuel D. Isaly
	Title:	Managing Member

OrbiMed Capital GP IV LLC a Delaware Limited Liability Company
By:	OrbiMed Advisors LLC A Delaware Limited Liability Company and its Managing Member
By:	/s/ Samuel D. Isaly
	Name:	Samuel D. Isaly
	Title:	Managing Member

By:	/s/ Samuel D. Isaly
	Name:	Samuel D. Isaly

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Schedule I

The name and present principal occupation of each of the executive officers and directors of OrbiMed Advisors LLC are set forth below.  Unless otherwise noted, each of these persons are United States citizens and have as their business address 601 Lexington Avenue, 54th Floor, New York, NY 10022.

Name	Position with Reporting Person	Principal Occupation
Samuel D. Isaly	Managing Member	Managing Member OrbiMed Advisors LLC
Carl L. Gordon	Member	Member OrbiMed Advisors LLC
Sven H. Borho German and Swedish Citizen	Member	Member OrbiMed Advisors LLC
Jonathan T. Silverstein	Member	Member OrbiMed Advisors LLC
W. Carter Neild	Member	Member OrbiMed Advisors LLC
Geoffrey C. Hsu	Member	Member OrbiMed Advisors LLC
Evan D.  Sotiriou	Chief Financial Officer	Chief Financial Officer OrbiMed Advisors LLC

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Schedule II

The business and operations of OrbiMed Capital GP IV LLC are managed by the executive officers and directors of its managing member, OrbiMed Advisors LLC, set forth on Schedule I attached hereto.

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EXHIBIT INDEX

Exhibit	Description
1.	Joint Filing Agreement among OrbiMed Advisors LLC, OrbiMed Capital GP IV LLC and Samuel D. Isaly

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EX-99.1

EXHIBIT 1

JOINT FILING AGREEMENT

The undersigned hereby agree that the Statement on this Schedule 13D, dated April 17, 2014 (the “Schedule 13D”), with respect to the Common Stock of Relypsa, Inc. is filed on behalf of each of us pursuant to and in accordance with the provisions of Rule 13d-1(k) under the Securities and Exchange Act of 1934, as amended, and that this Agreement shall be included as an Exhibit to this Schedule 13D.  Each of the undersigned agrees to be responsible for the timely filing of the Schedule 13D, and for the completeness and accuracy of the information concerning itself contained therein.  This Agreement may be executed in any number of counterparts, all of which taken together shall constitute one and the same instrument.

IN WITNESS WHEREOF, the undersigned have executed this Agreement as of the 17th day of April, 2014.

OrbiMed Advisors LLC a Delaware Limited Liability Company
By:	/s/ Samuel D. Isaly
	Name:	Samuel D. Isaly
	Title:	Managing Member

OrbiMed Capital GP IV LLC a Delaware Limited Liability Company
By:	OrbiMed Advisors LLC A Delaware Limited Liability Company and its Managing Member
By:	/s/ Samuel D. Isaly
	Name:	Samuel D. Isaly
	Title:	Managing Member

Samuel D. Isaly
By:	/s/ Samuel D. Isaly
	Samuel D. Isaly