VOTING AGREEMENT THIS VOTING AGREEMENT (this Agreement ) is made and entered into as of

VOTING AGREEMENT (this Agreement ) is made and entered into as of June 28, 2018, by and between Akebia Therapeutics, Inc., a Delaware corporation ( Akebia ), and the undersigned stockholder (the

Stockholder ) of Keryx Biopharmaceuticals, Inc., a Delaware corporation ( Keryx ).

WHEREAS, Keryx, Akebia and Alpha Therapeutics Merger Sub, Inc., a Delaware corporation ( Merger Sub ) have entered

into an Agreement and Plan of Merger of even date herewith (the Merger Agreement );

WHEREAS, pursuant to the Merger

Agreement, Merger Sub will be merged with and into Keryx, the separate corporate existence of Merger Sub will thereupon cease and Keryx will continue as the surviving corporation and a wholly owned Subsidiary of Akebia (the

WHEREAS, pursuant to the Merger, all outstanding shares of capital stock of Keryx will be converted into the

right to receive the consideration set forth in the Merger Agreement.

WHEREAS, as of the date hereof, the Stockholder or its affiliates

is the beneficial owner (as defined in Rule 13d-3 under the Securities Exchange Act of 1934, as amended from time to time (the Exchange Act )) of that number of shares of the outstanding

capital stock of Keryx, and the holder of Zero Coupon Convertible Senior Notes due 2021 (the Notes ) convertible into that number of shares of capital stock of Keryx, in each case, as set forth on the signature page of this

WHEREAS, as a condition and inducement to the willingness of Keryx and Akebia to enter into the Merger Agreement, the

Stockholder (in the Stockholder s capacity as such) has agreed to enter into this Agreement.

NOW, THEREFORE, intending to be legally

bound, the parties hereto agree as follows:

1. Certain Definitions. All capitalized terms that are used but

not defined herein shall have the respective meanings ascribed to them in the Merger Agreement. For all purposes of and under this Agreement, the following terms shall have the following respective meanings:

(a) Acquisition Proposal shall mean an Acquisition Proposal (as defined in the Merger Agreement) in

(b) Expiration Date shall mean the earlier to occur of (i) such date

and time as the Merger Agreement shall have been validly terminated pursuant to Article 7 thereof, (ii) such date and time as the Merger shall be consummated in accordance with the terms and provisions of the Merger Agreement, (iii) a

Superior Proposal or (iv) in the event that the Keryx Board or any committee thereof (A) makes a Keryx Adverse Recommendation Change, (B) does not include the Keryx Recommendation in the Joint Proxy Statement or (C) publicly

proposes or allows Keryx to publicly propose to take either of the actions set forth in clause (A) or (B) of this Section 1(b)(iii).

(c) Shares shall mean (i) all shares of capital

stock of Keryx (including Keryx Shares) beneficially owned by the Stockholder or its affiliates as of the date hereof other than unissued Keryx Shares issuable upon conversion of the Notes, and (ii) all additional shares of capital stock of

Keryx (including Keryx Shares) which the Stockholder or its affiliates acquires beneficial ownership of during the period from the date of this Agreement through the Expiration Date (including by way of exercise of any convertible or derivative

security, stock dividend or distribution, split-up, recapitalization, combination, exchange of shares and the like, but excluding all unissued Keryx Shares issuable upon conversion of the Notes).

(d) Transfer A Person shall be deemed to have effected a Transfer of a Share if

such Person directly or indirectly (i) sells, pledges, encumbers, hypothecates, assigns, grants an option with respect to (or otherwise enters into a hedging arrangement with respect to), transfers, tenders or disposes (by merger, by

testamentary disposition, by operation of law or otherwise) of such Share or any interest in or right to such Share, (ii) deposits any Share into a voting trust or enters into a voting agreement or arrangement or grants any proxy or power of

attorney with respect thereto that is inconsistent with this Agreement, or (iii) agrees or commits (whether or not in writing) to take any of the actions referred to in the foregoing clause (i) or (ii).

2. Transfer Restrictions. The Stockholder agrees that from the date hereof until the Expiration Date, the

Stockholder shall not Transfer (or cause, permit or commit to the Transfer of) any of the Shares, or enter into any agreement relating thereto, except (i) transferring Shares to Affiliates, provided that, as a condition to such

Transfer, the recipient agrees to be bound by this Agreement, (ii) transferring Shares to any custodian or nominee for the purpose of holding such Shares for the account of the Stockholder or its Affiliates or (iii) with

Akebia s prior written consent and in Akebia s sole discretion (such exceptions set forth in sections (i), (ii) and (iii), referred to as Permitted Transfers ). Any Transfer (other than a Permitted Transfer), or purported

Transfer (other than a Permitted Transfer), of Shares in breach or violation of this Agreement shall be void and of no force or effect.

3. Agreement to Vote Shares.

(a) From the date hereof until the earlier of (x) the receipt of Keryx Shareholder Approval and (y) the

Expiration Date, at every meeting of the stockholders of Keryx, and at every adjournment or postponement thereof, and on every action or approval by written consent of the stockholders of Keryx, the Stockholder (in the Stockholder s capacity as

such) agrees to, unconditionally and irrevocably, vote, or to cause the holder of record on any applicable record date to vote, all Shares that are then-owned by the Stockholder and entitled to vote or act by

(i) in favor of the adoption of the Merger Agreement, and in favor of any other matters

presented or proposed as to approval of the Merger or any part or aspect thereof or any other transactions contemplated by the Merger Agreement;

(ii) against approval of any proposal made in opposition to, in competition with, or inconsistent with, the Merger

Agreement or the Merger or any other transactions contemplated by the Merger Agreement;

(iii) against any of the following actions (other than those actions that

relate to the Merger and any other transactions contemplated by the Merger Agreement): (A) any merger, consolidation, business combination, sale of assets, reorganization or recapitalization of or involving Keryx or any Keryx Subsidiaries,

(B) any sale, lease or transfer of all or substantially all of the assets of Keryx or any Keryx Subsidiaries, (C) any reorganization, recapitalization, dissolution, liquidation or winding up of Keryx or any Keryx Subsidiaries, (D) any

material change in the capitalization of Keryx or any Keryx Subsidiaries, or the corporate structure of Keryx or any Keryx Subsidiaries, (E) any Acquisition Proposal or (F) any other action that is intended to, or would reasonably be

expected to materially, impede, interfere with, delay, postpone, discourage or adversely affect the Merger or any other transactions contemplated by the Merger Agreement;

(iv) against any action, proposal, transaction or agreement that would reasonably be expected to result in a breach in

any respect of any covenant, representation or warranty or any other obligation or agreement of Akebia contained in the Merger Agreement, or of the Stockholder contained in this Agreement; and

(v) in favor of any other matter necessary or appropriate to the consummation of the transactions contemplated by the

Merger Agreement, including the Merger.

The Stockholder shall retain at all times the right to vote its Shares in its sole discretion and without any

other limitation on any matters other than those set forth in clauses (i) through (v), above, that are at any time or from time to time presented for consideration to the Company s stockholders generally.

(b) The Stockholder shall not enter into any agreement or understanding with any Person to vote or give instructions in

any manner inconsistent with the terms of this Section 3.

(a) From the date hereof until the Expiration Date, the Stockholder shall not, and shall instruct its

Representatives not to, directly or indirectly, (i) initiate, seek or solicit, or knowingly encourage or facilitate (including by way of furnishing non-public information) or take any other action that is

reasonably expected to promote, directly or indirectly, any inquiries or the making or submission of any proposal that constitutes, or would reasonably be expected to lead to, an Acquisition Proposal with respect to Keryx, (ii) participate or

engage in discussions or negotiations with, or disclose any non-public information or data relating to, Keryx or any of its Subsidiaries to any Person that has made or could reasonably be expected to make an

Acquisition Proposal with respect to Keryx or (iii) enter into any agreement with a party other than Akebia, Keryx or their Affiliates, including any letter of intent, memorandum of understanding, agreement in principle, merger agreement,

acquisition agreement or other similar agreement, with respect to an Acquisition Proposal with respect to Keryx. The Stockholder shall, and shall instruct its Representatives to, (x) cause to be terminated any solicitation, encouragement,

discussion or negotiation with or involving any Person (other than Akebia and its Affiliates) conducted heretofore with respect to an Acquisition Proposal, or which could reasonably be expected to lead to an Acquisition Proposal, and, in connection

immediately discontinue access by any Person (other than Akebia and its Affiliates) to any data room (virtual or otherwise) established for such purpose and (y) request the return or

destruction of all confidential and non-public information provided to third parties (other than the Stockholder s Representatives) since January 1, 2017, relating to an Acquisition Proposal, within

two (2) Business Days from the date hereof.

(b) In addition to the obligations set forth in

Section 4(a), the Stockholder shall, subject to applicable law, rule or regulation (including that of a national securities exchange or self-regulatory organization), (i) as promptly as practicable after receipt thereof,

and in any event within 24 hours, advise Akebia in writing of any request for information or any Acquisition Proposal with respect to Keryx, and the terms and conditions of such request, Acquisition Proposal, inquiry, discussions or negotiations,

and (ii) provide to Akebia copies of any written materials received by the Stockholder in connection with any of the foregoing and the identity of the Person or group making any such request, Acquisition Proposal or inquiry or with whom any

discussions are taking place.

5. Directors and Officers. Notwithstanding any provision of this Agreement to

the contrary, nothing in this Agreement shall limit or restrict a Stockholder, or a designee of the Stockholder, who is a director or officer of Keryx from acting in such capacity or fulfilling the obligations of such office, including by voting, in

his capacity as a director of Keryx, in the Stockholder s, or its designee s, sole discretion on any matter (it being understood that this Agreement shall apply to the Stockholder solely in the Stockholder s capacity as a stockholder

of Keryx). In this regard, the Stockholder shall not be deemed to make any agreement or understanding in this Agreement in Stockholder s capacity as a director or officer of Keryx.

6. Update of Beneficial Ownership Information. Promptly following the written request of Akebia, the Stockholder

shall send to Akebia a notice in the form of Exhibit A hereto, setting forth the number of Shares beneficially owned by such Stockholder or its affiliates as of the record date of the Keryx Stockholders Meeting.

7. Representations and Warranties of the Stockholder. The Stockholder hereby represents and warrants to Akebia

(a) Power; Organization; Binding Agreement. The Stockholder has full power and authority (or

capacity, in the case of Stockholders that are natural persons) to execute and deliver this Agreement, to perform the Stockholder s obligations hereunder and to consummate the transactions contemplated hereby. In the case of Stockholders that

are not natural persons, such Stockholder is duly organized, validly existing and in good standing under the laws of its jurisdiction of formation (except to the extent the good standing concept is not applicable in any relevant

jurisdiction). This Agreement has been duly executed and delivered by the Stockholder, and, assuming this Agreement constitutes a valid and binding obligation of Akebia, constitutes a valid and binding obligation of the Stockholder, enforceable

against the Stockholder in accordance with its terms, except that such enforceability may be limited by applicable bankruptcy, insolvency, reorganization, moratorium and other similar laws affecting or relating to creditors rights generally

and is subject to general principles of equity (regardless of whether such enforceability is considered in a proceeding in equity or at law).

(b) No Conflicts. None of the execution and delivery by the

Stockholder of this Agreement, the performance by the Stockholder of its obligations hereunder or the consummation by the Stockholder of the transactions contemplated hereby will (i) result in a violation or breach of any agreement to which the

Stockholder is a party or by which the Stockholder may be bound, including any voting agreement or voting trust, (ii) violate any Law or order applicable to the Stockholder or (iii) violate the constituent or organizational document of

such Stockholder, in the case of Stockholders that are not natural persons, except, in each case, as would not prevent or materially delay such Stockholder from performing such Stockholder s obligations under this Agreement.

(c) Ownership of Shares. The Stockholder, together with its Affiliates, (i) is the sole beneficial owner of

the shares of capital stock of Keryx set forth on the signature page of this Agreement, all of which are free and clear of any Lien (except any Lien arising under securities laws or arising hereunder), (ii) is the beneficial owner of the Notes

convertible into the number of Keryx Shares set forth on the signature page of this Agreement, all of which Keryx Shares issuable upon the conversion of such Notes are free and clear of any Lien (except any Lien arising under securities laws or

arising hereunder) and (iv) except as set forth on the signature page to this Agreement, does not own, beneficially or otherwise, any voting securities of Keryx other than as set forth on the signature page of this Agreement.

(d) Voting Power. The Stockholder, or its Affiliate, The Baupost Group, L.L.C., have sole voting power, sole

power of disposition, sole power to issue instructions with respect to the matters set forth herein, and sole power to agree to all of the matters set forth in this Agreement, in each case with respect to all of the Shares, with no limitations,

qualifications or restrictions on such rights, subject to applicable federal securities laws and arising under the terms of this Agreement.

(e) No Finder s Fees. No broker, investment banker, financial advisor, finder, agent or other Person is

entitled to any broker s, finder s, financial adviser s or other similar fee or commission in connection with this Agreement based upon arrangements made by or on behalf of the Stockholder in his or her capacity as such.

(f) Reliance by Akebia. The Stockholder understands and acknowledges that Akebia is entering into the Merger

Agreement in reliance upon the Stockholder s execution and delivery of this Agreement.

Actions. Stockholder agrees that Stockholder will not in Stockholder s capacity as a Stockholder of Keryx bring, commence, institute, maintain, prosecute or voluntarily aid any Action, which (i) challenges the validity of or seeks to