{\rtf1\deflang1033\deflangfe1033\margl720\margr720\margt360\margb360{\stylesheet{\fs20\lang1033\snext0 Normal;} {\s1\sb240\keepn{\*\pn \pnlvl1\pndec\pnprev1\pnstart1\pnsp144}\b\f0\fs30\lang1033 \sbasedon0\snext0 heading 1;} {\s2\sb200\keepn{\*\pn \pnlvl2\pndec\pnprev1\pnstart1\pnsp144{\pntxtb.}}\b\f0\fs26\lang1033 \sbasedon0\snext0 heading 2;} {\s3\sb180\keepn{\*\pn \pnlvl3\pndec\pnprev1\pnstart1\pnsp144{\pntxtb.}}\b\f0\fs22\lang1033 \sbasedon0\snext0 heading 3;} {\s4\sb160\keepn{\*\pn \pnlvl4\pnucltr\pnprev1\pnstart1\pnsp144{\pntxtb.}}\b\f0\fs22\lang1033 \sbasedon0\snext0 heading 4;} {\s5\sb140\keepn{\*\pn \pnlvl5\pncltr\pnprev1\pnstart1\pnsp144}\b\f0\fs20\lang1033 \sbasedon0\snext0 heading 5;} {\s6\tqc\lang1033\sbasedon0\snext6 footer;} {\*\cs16 \additive\super\sbasedon10 footnote reference;} {\*\cs18 \additive\sbasedon10 page number;}} {\fonttbl{\f0\fnil Times New Roman;}{\f1\fnil Courier New}{\f2005\fnil Courier New;}{\f2010\fnil Wingdings;}{\f2020\fnil Webdings;}{\f2\fnil Arial;}{\f3\fnil Arial;}{\f4\fnil LucidaHandwriting;}{\f5\fnil Symbol;}{\f6\fnil Symbol;}{\f7\fnil Ferdsch;}{\f30\fnil Myriad Cn Semibold;}{\f31\fnil Myriad Roman;}{\f50\fnil Courier New;}{\f51\fnil Times New Roman;}{\f52\fnil Arial;}{\f53\fnil Symbol;}{\f54\fnil Wingdings;}{\f55\fnil Wingdings 2;}{\f56\fnil Wingdings 3;}{\f57\fnil Webdings;}{\f58\fnil Arial Narrow;}{\f59\fnil Arial Unicode MS;}{\f60\fnil Cyberbit;}{\f61\fnil Morningstar 1U Light;}{\f62\fnil Calibri;}} {\colortbl;\red0\green0\blue0;\red127\green0\blue0;\red0\green0\blue255;\red127\green127\blue127;\red0\green51\blue153;\red255\green204\blue0;\red255\green255\blue255;\red246\green244\blue236;\red0\green0\blue0;\red153\green153\blue153;} {\*\bkmkstart filing_1}{\*\bkmkend filing_1}{\*\bkmkstart doc_1_1}{\*\bkmkend doc_1_1}\par\pard\plain\cf1\f51\fs20\qr Filed by Akebia Therapeutics, Inc. \par\pard\plain\fs16\pard\plain\cf1\f51\fs20\qr Pursuant to Rule 425 under the Securities Act of 1933 \par\pard\plain\fs16\pard\plain\cf1\f51\fs20\qr Commission File No.: 001-36352 \par\pard\plain\fs16 \par\pard\plain\fs16\pard\plain\cf1\f51\fs20\qr Subject Company: Keryx Biopharmacuticals, Inc. \par\pard\plain\fs16\pard\plain\cf1\f51\fs20\qr Commission File No.: 000-30929 \par\pard\plain\fs16\pard\plain\cf1\f51\fs20\qr Date: June 28, 2018\par\pard\plain\cf1\f51\fs24\ql \~ \par\pard\plain {\trowd\clvertalc\cellx5508\clvertalb\cellx5723\clvertalc\cellx10800\trrh66 \pard\plain\intbl\f0\fs16\ql \~\cell\pard\plain\intbl\f0\fs16\ql \~\cell\pard\plain\intbl\f0\fs16\ql \~\cell{ {\trowd\clvertalc\cellx5508\clvertalb\cellx5723\clvertalc\cellx10800\trrh66\row}}} {\trowd\cellx5508\clvertalb\cellx5723\cellx10800\trrh248 \pard\plain\intbl\f0\fs16\ql \~\cell\pard\plain\intbl\cf1\f51\fs20\ql \~\~\cell\pard\plain\intbl\f0\fs16\ql \~\cell{ {\trowd\cellx5508\clvertalb\cellx5723\cellx10800\trrh248\row}}}\pard\plain\cf1\f51\fs16\ql \~\par\pard\plain\cf1\f51\fs20\b\ql Vendor Letter from Akebia\par\pard\plain\cf1\f51\fs20\ql The following is a copy of a letter sent by Akebia Therapeutics, Inc. to its vendors.\par\pard\plain\brdrb\brdrs\sa44\cf1\f51\fs20\ql \~\par\pard\plain\sb264\cf1\f51\fs20\ql Dear [Vendor / INSERT]\par\pard\plain\sb264\cf1\f51\fs20\ql This morning, we made the announcement that Akebia Therapeutics, Inc. (Akebia) and Keryx Biopharmaceuticals, Inc. (Keryx)\plain\cf1\f51\fs20\ql are planning to combine to create a fully integrated biopharmaceutical company focused on the development and\plain\cf1\f51\fs20\ql commercialization of therapeutics for patients with kidney disease.\par\pard\plain\sb264\cf1\f51\fs20\ql The combined company will have an expanded and complementary nephrology portfolio with the potential to deliver an all-oral\plain\cf1\f51\fs20\ql treatment approach for patients with anemia due to chronic kidney disease. We believe the combined organization will become a\plain\cf1\f51\fs20\ql partner of choice for the renal community and for companies developing renal products.\par\pard\plain\sb264\cf1\f51\fs20\ql We expect to complete the transaction by the end of 2018, following the satisfaction of customary closing conditions, including\plain\cf1\f51\fs20\ql approval by the shareholders of both companies. Until then, Akebia and Keryx will continue to be separate, independent\plain\cf1\f51\fs20\ql companies, and we will operate as usual. During this time, your contacts at our company will remain the same.\par\pard\plain\sb264\cf1\f51\fs20\ql If you have any questions about what this announcement means for you, please feel free to reach out directly to your usual\plain\cf1\f51\fs20\ql Akebia contacts.\par\pard\plain\sb264\cf1\f51\fs20\ql We look forward to embarking on this exciting new chapter in our mission to make a difference in the lives of patients. Thank\plain\cf1\f51\fs20\ql you for your ongoing efforts and commitment to our business.\par\pard\plain\sb264\cf1\f51\fs20\ql Yours truly,\par\pard\plain\sb264\cf1\f51\fs20\ql [Akebia Contact]\par\pard\plain\sb528\cf1\f51\fs20\b\qc Important Information\par\pard\plain\sb132\cf1\f51\fs20\b\i\ql About Akebia\par\pard\plain\sb132\cf1\f51\fs20\ql Akebia Therapeutics, Inc. is a biopharmaceutical company headquartered in Cambridge, Massachusetts, focused on delivering\plain\cf1\f51\fs20\ql innovative therapies to patients with kidney disease through hypoxia-inducible factor biology. For more information, please visit\plain\cf1\f51\fs20\ql our website at www.akebia.com, which does not form a part of this release.\par\pard\plain\sb396\cf1\f51\fs20\b\i\ql About Keryx\par\pard\plain\sb132\cf1\f51\fs20\ql Keryx Biopharmaceuticals, Inc., headquartered in Boston, Massachusetts, is focused on the development and commercialization of\plain\cf1\f51\fs20\ql innovative medicines that provide unique and meaningful advantages to people with kidney disease. The Keryx team consists of\plain\cf1\f51\fs20\ql approximately 200 committed people working with passion to advance the care of people with this complex disease. This\plain\cf1\f51\fs20\ql dedication has resulted in two FDA-approved indications for Keryx\u8217?s first medicine, Auryxia (ferric citrate) tablets. For\plain\cf1\f51\fs20\ql more information about Keryx, please visit \plain\cf1\f51\fs20\ul\ql www.keryx.com\plain\cf1\f51\fs20\ql . \page\par\pard\plain\f0\fs4\par\pard\plain\f0\fs2\brdrt\brdrs\brdrw15\brdrcf2\brdrsp0\par\pard\plain\f0\fs4\par \par\pard\plain {\trowd\clvertalc\cellx5508\clvertalb\cellx5723\clvertalc\cellx10800\trrh66 \pard\plain\intbl\f0\fs16\ql \~\cell\pard\plain\intbl\f0\fs16\ql \~\cell\pard\plain\intbl\f0\fs16\ql \~\cell{ {\trowd\clvertalc\cellx5508\clvertalb\cellx5723\clvertalc\cellx10800\trrh66\row}}} {\trowd\cellx5508\clvertalb\cellx5723\cellx10800\trrh248 \pard\plain\intbl\f0\fs16\ql \~\cell\pard\plain\intbl\cf1\f51\fs20\ql \~\~\cell\pard\plain\intbl\f0\fs16\ql \~\cell{ {\trowd\cellx5508\clvertalb\cellx5723\cellx10800\trrh248\row}}}\pard\plain\cf1\f51\fs16\ql \~\par\pard\plain\cf1\f51\fs20\b\i\ql Additional Information and Where to Find It\par\pard\plain\sb132\cf1\f51\fs20\ql In connection with the proposed merger, Akebia and Keryx plan to file with the SEC and mail or otherwise provide to their\plain\cf1\f51\fs20\ql respective stockholders a joint proxy statement/prospectus regarding the proposed transaction. BEFORE MAKING ANY\plain\cf1\f51\fs20\ql VOTING DECISION, AKEBIA\u8217?S AND KERYX\u8217?S RESPECTIVE STOCKHOLDERS ARE URGED TO READ\plain\cf1\f51\fs20\ql THE JOINT PROXY STATEMENT/PROSPECTUS IN ITS ENTIRETY WHEN IT BECOMES AVAILABLE AND ANY\plain\cf1\f51\fs20\ql OTHER DOCUMENTS FILED BY EACH OF AKEBIA AND KERYX WITH THE SEC IN CONNECTION WITH THE\plain\cf1\f51\fs20\ql PROPOSED MERGER OR INCORPORATED BY REFERENCE THEREIN BECAUSE THEY WILL CONTAIN IMPORTANT\plain\cf1\f51\fs20\ql INFORMATION ABOUT THE PROPOSED TRANSACTION AND THE PARTIES TO THE PROPOSED TRANSACTION.\plain\cf1\f51\fs20\ql Investors and stockholders will be able to obtain a free copy of the joint proxy statement/prospectus and other documents\plain\cf1\f51\fs20\ql containing important information about Akebia and Keryx, once such documents are filed with the SEC, through the website\plain\cf1\f51\fs20\ql maintained by the SEC at www.sec.gov. Akebia and Keryx make available free of charge at www.akebia.com and\plain\cf1\f51\fs20\ql www.keryx.com, respectively (in the \u8220?Investors\u8221? section), copies of materials they file with, or furnish to, the SEC.\par\pard\plain\sb396\cf1\f51\fs20\b\i\ql Participants in the Solicitation\par\pard\plain\sb132\cf1\f51\fs20\ql This document does not constitute a solicitation of proxy, an offer to purchase or a solicitation of an offer to sell any securities.\plain\cf1\f51\fs20\ql Akebia, Keryx and their respective directors, executive officers and certain employees and other persons may be deemed to be\plain\cf1\f51\fs20\ql participants in the solicitation of proxies from the stockholders of Akebia and Keryx in connection with the proposed merger.\plain\cf1\f51\fs20\ql Security holders may obtain information regarding the names, affiliations and interests of Akebia\u8217?s directors and officers in\plain\cf1\f51\fs20\ql Akebia\u8217?s Annual Report on Form 10-K for the fiscal year ended December\~31, 2017, which was filed with the SEC on\plain\cf1\f51\fs20\ql March\~12, 2018 and its definitive proxy statement for the 2018 annual meeting of stockholders, which was filed with the SEC on\plain\cf1\f51\fs20\ql April\~30, 2018. Security holders may obtain information regarding the names, affiliations and interests of Keryx\u8217?s directors\plain\cf1\f51\fs20\ql and officers in Keryx\u8217?s Annual Report on Form 10-K for the fiscal year ended December\~31, 2017, which was filed with\plain\cf1\f51\fs20\ql the SEC on February\~21, 2018, and the Amendment No.\~1 on Form 10-K/A, which was filed with the SEC on April\~30, 2018,\plain\cf1\f51\fs20\ql and its definitive proxy statement for the 2018 annual meeting of stockholders, which was filed with the SEC on May\~31, 2018.\plain\cf1\f51\fs20\ql To the extent the holdings of Akebia securities by Akebia\u8217?s directors and executive officers or the holdings of Keryx\plain\cf1\f51\fs20\ql securities by Keryx\u8217?s directors and executive officers have changed since the amounts set forth in Akebia\u8217?s or\plain\cf1\f51\fs20\ql Keryx\u8217?s respective proxy statement for its 2018 annual meeting of stockholders, such changes have been or will be\plain\cf1\f51\fs20\ql reflected on Statements of Change in Ownership on Form 4 filed with the SEC. Additional information regarding the interests of\plain\cf1\f51\fs20\ql such individuals in the proposed merger will be included in the joint proxy statement/prospectus relating to the proposed merger\plain\cf1\f51\fs20\ql when it is filed with the SEC. These documents (when available) may be obtained free of charge from the SEC\u8217?s website\plain\cf1\f51\fs20\ql at www.sec.gov, Akebia\u8217?s website at www.akebia.com and Keryx\u8217?s website at \plain\cf1\f51\fs20\ul\ql www.keryx.com\plain\cf1\f51\fs20\ql .\par\pard\plain\sb396\cf1\f51\fs20\b\i\ql Forward-Looking Statements\par\pard\plain\sb132\cf1\f51\fs20\ql These materials contain forward-looking statements within the meaning of the federal securities law. Such statements are based\plain\cf1\f51\fs20\ql upon current plans, estimates and expectations that are subject to various risks and uncertainties. The inclusion of\plain\cf1\f51\fs20\ql forward-looking statements should not be regarded as a representation that such plans, estimates and expectations will be\plain\cf1\f51\fs20\ql achieved. Words such as \u8220?anticipate,\u8221? \u8220?expect,\u8221? \u8220?project,\u8221? \u8220?intend,\u8221?\plain\cf1\f51\fs20\ql \u8220?believe,\u8221? \u8220?may,\u8221? \u8220?will,\u8221? \u8220?should,\u8221? \u8220?plan,\u8221?\plain\cf1\f51\fs20\ql \u8220?could,\u8221? \u8220?target,\u8221? \u8220?contemplate,\u8221? \u8220?estimate,\u8221? \u8220?predict,\u8221?\plain\cf1\f51\fs20\ql \u8220?potential\u8221? and words and terms of similar substance used in connection with any discussion of future plans, actions\plain\cf1\f51\fs20\ql or events identify forward-looking statements. All statements, other than historical facts, including statements regarding the\plain\cf1\f51\fs20\ql expected timing of the closing of the merger; the ability of the parties to complete the merger considering the various closing\plain\cf1\f51\fs20\ql conditions; the expected benefits of the merger, such as efficiencies, cost savings, tax benefits, enhanced revenues and cash flow,\plain\cf1\f51\fs20\ql growth potential, market profile and financial strength; the competitive ability and position of the combined company; and any\plain\cf1\f51\fs20\ql assumptions underlying any of the foregoing, are forward-looking statements. Important factors that could cause actual results to\plain\cf1\f51\fs20\ql differ materially from Akebia\u8217?s and Keryx\u8217?s plans, \page\par\pard\plain\f0\fs4\par\pard\plain\f0\fs2\brdrt\brdrs\brdrw15\brdrcf2\brdrsp0\par\pard\plain\f0\fs4\par \par\pard\plain {\trowd\clvertalc\cellx5508\clvertalb\cellx5723\clvertalc\cellx10800\trrh66 \pard\plain\intbl\f0\fs16\ql \~\cell\pard\plain\intbl\f0\fs16\ql \~\cell\pard\plain\intbl\f0\fs16\ql \~\cell{ {\trowd\clvertalc\cellx5508\clvertalb\cellx5723\clvertalc\cellx10800\trrh66\row}}} {\trowd\cellx5508\clvertalb\cellx5723\cellx10800\trrh248 \pard\plain\intbl\f0\fs16\ql \~\cell\pard\plain\intbl\cf1\f51\fs20\ql \~\~\cell\pard\plain\intbl\f0\fs16\ql \~\cell{ {\trowd\cellx5508\clvertalb\cellx5723\cellx10800\trrh248\row}}}\pard\plain\cf1\f51\fs16\ql \~\par\pard\plain\cf1\f51\fs20\ql estimates or expectations could include, but are not limited to: (i)\~Akebia or Keryx may be unable to obtain stockholder approval\plain\cf1\f51\fs20\ql as required for the merger; (ii)\~conditions to the closing of the merger may not be satisfied; (iii)\~the merger may involve\plain\cf1\f51\fs20\ql unexpected costs, liabilities or delays; (iv)\~the effect of the announcement of the merger on the ability of Akebia or Keryx to\plain\cf1\f51\fs20\ql retain and hire key personnel and maintain relationships with customers, suppliers and others with whom Akebia or Keryx does\plain\cf1\f51\fs20\ql business, or on Akebia\u8217?s or Keryx\u8217?s operating results and business generally; (v)\~Akebia\u8217?s or Keryx\u8217?s\plain\cf1\f51\fs20\ql respective businesses may suffer as a result of uncertainty surrounding the merger and disruption of management\u8217?s\plain\cf1\f51\fs20\ql attention due to the merger; (vi)\~the outcome of any legal proceedings related to the merger; (vii)\~Akebia or Keryx may be\plain\cf1\f51\fs20\ql adversely affected by other economic, business, and/or competitive factors; (viii)\~the occurrence of any event, change or other\plain\cf1\f51\fs20\ql circumstances that could give rise to the termination of the merger agreement; (ix)\~risks that the merger disrupts current plans and\plain\cf1\f51\fs20\ql operations and the potential difficulties in employee retention as a result of the merger; (x)\~the risk that Akebia or Keryx may be\plain\cf1\f51\fs20\ql unable to obtain governmental and regulatory approvals required for the transaction, or that required governmental and regulatory\plain\cf1\f51\fs20\ql approvals may delay the transaction or result in the imposition of conditions that could reduce the anticipated benefits from the\plain\cf1\f51\fs20\ql proposed transaction or cause the parties to abandon the proposed transaction; (xi)\~risks that the anticipated benefits of the merger\plain\cf1\f51\fs20\ql or other commercial opportunities may otherwise not be fully realized or may take longer to realize than expected; (xii)\~the\plain\cf1\f51\fs20\ql impact of legislative, regulatory, competitive and technological changes; (xiii)\~expectations for future clinical trials, the timing and\plain\cf1\f51\fs20\ql potential outcomes of clinical studies and interactions with regulatory authorities; and (xiv)\~other risks to the consummation of the\plain\cf1\f51\fs20\ql merger, including the risk that the merger will not be consummated within the expected time period or at all. Additional factors\plain\cf1\f51\fs20\ql that may affect the future results of Akebia and Keryx are set forth in their respective filings with the SEC, including each of\plain\cf1\f51\fs20\ql Akebia\u8217?s and Keryx\u8217?s most recently filed Annual Report on Form 10-K, subsequent Quarterly Reports on Form\plain\cf1\f51\fs20\ql 10-Q, Current Reports on Form 8-K and other filings with the SEC, which are available on the SEC\u8217?s website at\plain\cf1\f51\fs20\ql www.sec.gov. See in particular Item 1A of Akebia\u8217?s Quarterly Report on Form 10-Q for the quarter ended March\~31,\plain\cf1\f51\fs20\ql 2018 under the heading \u8220?Risk Factors\u8221? and Item 1A of Keryx\u8217?s Quarterly Report on Form 10-Q for the\plain\cf1\f51\fs20\ql quarter ended March\~31, 2018 under the heading \u8220?Risk Factors.\u8221? The risks and uncertainties described above and in\plain\cf1\f51\fs20\ql Akebia\u8217?s most recent Quarterly Report on Form 10-Q and Keryx\u8217?s most recent Quarterly Report on Form 10-Q\plain\cf1\f51\fs20\ql are not exclusive and further information concerning Akebia and Keryx and their respective businesses, including factors that\plain\cf1\f51\fs20\ql potentially could materially affect their respective businesses, financial condition or operating results, may emerge from time to\plain\cf1\f51\fs20\ql time. Readers are urged to consider these factors carefully in evaluating these forward-looking statements, and not to place undue\plain\cf1\f51\fs20\ql reliance on any forward-looking statements. Readers should also carefully review the risk factors described in other documents\plain\cf1\f51\fs20\ql that Akebia and Keryx file from time to time with the SEC. The forward-looking statements in these materials speak only as of\plain\cf1\f51\fs20\ql the date of these materials. Except as required by law, Akebia and Keryx assume no obligation to update or revise these\plain\cf1\f51\fs20\ql forward-looking statements for any reason, even if new information becomes available in the future.}