FIRST AMENDMENT OF LETTER OF AGREEMENT REGARDING PURCHASE OF PARTNERSHIP INTEREST This FIRST AMENDMENT OF LETTER OF AGREEMENT REGARDING PURCHASE OF PARTNERSHIP INTEREST effective September 3, 2013 by and between William H. Gates ("Gates") and Dr. Boris Nikolic ("Dr. Nikolic") is made on and dated as of October 6, 2015 ("Amendment"). WHEREAS, Gates and Dr. Nikolic entered into a certain Letter of Agreement Regarding Purchase of Partnership Interests effective September 3, 2013 (the "Letter Agreement"); and WHEREAS, while serving as a member of the Board of Directors of Foundation Medicine, Inc. ("FMI"), lock-ups and other restrictions on transfer with respect to the securities of FMI which were imposed on members of FMI's Board of Directors have substantially limited Dr. Nikolic's ability during the first two years of the Payment Period (as defined in the Letter Agreement) to exercise his rights under the Letter Agreement to deliver to Gates Investment Entity Payment Demands (as defined in the Letter Agreement) with respect to the securities of FMI; and WHEREAS, Dr. Nikolic is no longer a member of FMI's Board of Directors, and Gates and Dr. Nikolic agree that in order to effectuate the original intention of the transactions contemplated under the Letter Agreement, the opportunity to deliver Investment Entity Payment Demands freely and without restriction, which was effectively lost while Dr. Nikolic served on FMI's Board of Directors during the first two years of the Payment Period, should be restored by amending the Letter Agreement to extend the expiration date of the Payment Period from September 3, 2016 until September 3, 2018; and WHEREAS, pursuant to paragraph 2 of the section of the Letter Agreement encaptioned "Miscellaneous", the Letter Agreement may not be amended other than in writing signed by Gates and Dr. Nikolic; NOW, THEREFORE, in consideration of the foregoing premises, and pursuant to paragraph 2 of the section of the Lette