AMENDMENT NUMBER ONE TO SECOND AMENDED AND RESTATED RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT

Exhibit 4.7

AMENDMENT NUMBER ONE TO

SECOND AMENDED AND RESTATED

RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT

THIS AMENDMENT NUMBER ONE TO SECOND AMENDED AND RESTATED RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT (the “Amendment”) is made and effective as of July 9, 2012, by and among AKEBIA THERAPEUTICS, INC., a Delaware corporation (the “Company”), and those Investors executing and delivering a counterpart signature page hereto. Capitalized terms not defined herein have the meanings given them in that certain Second Amended and Restated Right of First Refusal and Co-Sale Agreement, dated as of April 6, 2011, by and among the Company, the Investors and the Major Holders (as amended, the “Agreement”).

WHEREAS, the Company and the Investors desire to amend the Agreement to modify the definition of Preferred Stock and add a definition for the Series X Preferred Stock of the Company; and

WHEREAS, the Investors hold more than the Appropriate Percentage of the shares of Common Stock required to amend the Agreement pursuant to the provisions of Section 6.8 of the Agreement;

NOW, THEREFORE, in consideration of the foregoing recitals and the mutual promises hereinafter set forth and set forth in the Agreement, the parties hereby agree as follows:

1. Amendment.

(a) The definition of “Preferred Stock” shall be deleted in its entirety and replaced with the following: “‘Preferred Stock’ means all shares of Series A Preferred Stock, Series B Preferred Stock, and Series X Preferred Stock.”

(b) A new definition of “Series X Preferred Stock” shall be added to the Agreement and shall read as follows: ‘”Series X Preferred Stock’ shall mean shares of the Series X Preferred Stock of the Company, par value $0.00001 per share.”

2. Miscellaneous Amendments. The Agreement is amended hereby so that any reference therein to the Agreement shall be deemed to be a reference to the Agreement as amended by this Amendment.

3. Continuance of Agreement. Except as specifically amended by this Amendment, the Agreement shall remain in full force and effect.

4. Governing Law. The laws of the State of Delaware govern all matters arising out of or relating to this Amendment, including, without limitation, its interpretation, construction, performance, and enforcement, without giving effect to such state’s conflicts of law principles or rules of construction concerning the drafter hereof.

6. Counterparts. This Amendment may be executed in two or more counterparts, including by facsimile or PDF signature, each of which shall be deemed an original, but all of which together shall constitute one and the same instrument.

[Signature Page Follows]

2

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the date first written above.

SIGNATURE PAGE TO AMENDMENT NUMBER ONE TO SECOND AMENDED AND RESTATED RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the date first written above.

SIGNATURE PAGE TO AMENDMENT NUMBER ONE TO SECOND AMENDED AND RESTATED RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the date first written above.

SIGNATURE PAGE TO AMENDMENT NUMBER ONE TO SECOND AMENDED AND RESTATED RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the date first written above.

SIGNATURE PAGE TO AMENDMENT NUMBER ONE TO SECOND AMENDED AND RESTATED RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the date first written above.

SIGNATURE PAGE TO AMENDMENT NUMBER ONE TO SECOND AMENDED AND RESTATED RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the date first written above.

SIGNATURE PAGE TO AMENDMENT NUMBER ONE TO SECOND AMENDED AND RESTATED RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the date first written above.

SIGNATURE PAGE TO AMENDMENT NUMBER ONE TO SECOND AMENDED AND RESTATED RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the date first written above.

SIGNATURE PAGE TO AMENDMENT NUMBER ONE TO SECOND AMENDED AND RESTATED RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the date first written above.

SIGNATURE PAGE TO AMENDMENT NUMBER ONE TO SECOND AMENDED AND RESTATED RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the date first written above.

SIGNATURE PAGE TO AMENDMENT NUMBER ONE TO SECOND AMENDED AND RESTATED RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the date first written above.

SIGNATURE PAGE TO AMENDMENT NUMBER ONE TO SECOND AMENDED AND RESTATED RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the date first written above.

SIGNATURE PAGE TO AMENDMENT NUMBER ONE TO SECOND AMENDED AND RESTATED RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the date first written above.

SIGNATURE PAGE TO AMENDMENT NUMBER ONE TO SECOND AMENDED AND RESTATED RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the date first written above.

SIGNATURE PAGE TO AMENDMENT NUMBER ONE TO SECOND AMENDED AND RESTATED RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the date first written above.

SIGNATURE PAGE TO AMENDMENT NUMBER ONE TO SECOND AMENDED AND RESTATED RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the date first written above.

SIGNATURE PAGE TO AMENDMENT NUMBER ONE TO SECOND AMENDED AND RESTATED RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the date first written above.

SIGNATURE PAGE TO AMENDMENT NUMBER ONE TO SECOND AMENDED AND RESTATED RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the date first written above.

SIGNATURE PAGE TO AMENDMENT NUMBER ONE TO SECOND AMENDED AND RESTATED RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the date first written above.

SIGNATURE PAGE TO AMENDMENT NUMBER ONE TO SECOND AMENDED AND RESTATED RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the date first written above.

SIGNATURE PAGE TO AMENDMENT NUMBER ONE TO SECOND AMENDED AND RESTATED RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the date first written above.

SIGNATURE PAGE TO AMENDMENT NUMBER ONE TO SECOND AMENDED AND RESTATED RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the date first written above.

SIGNATURE PAGE TO AMENDMENT NUMBER ONE TO SECOND AMENDED AND RESTATED RIGHT OF FIRST REFUSAL AND CO-SALE AGREEMENT