Not Construed Against Drafter. The language of this Agreement shall not be interpreted in favor of or against any Party as the drafter of this Agreement.

Representations and Warranties of Each Party. Each of Merck and Licensee hereby represents, warrants and covenants to the other Party hereto as follows:

Documents Mutually Drafted. ​ and ​ agree that this Agreement each other Program Document prepared in connection with the Transactions set forth herein have been mutually drafted and negotiated by each party, and consequently such documents shall not be construed against either party as the drafter thereof.

This Agreement is the product of arm’s-length negotiations between the parties. Each of the parties agrees that neither party will claim that any ambiguity in this Agreement shall be construed against the other party or against the drafter of this Agreement.

Each U.S. Lender shall deliver to the ​ and the ​ on or before the date on which it becomes a party to this Agreement two properly completed and duly signed originals of IRS Form W-9 certifying that such Lender is exempt from U.S. federal backup withholding.

Each U.K. Lender which becomes a Party after the Closing Date (a “New U.K. Lender”) shall indicate in the relevant Assignment and Assumption or other agreement executed pursuant to the terms of this Agreement which it executes on becoming a Party as a U.K. Lender, and for the benefit of the Administrative Agent and without liability to any U.K. Borrower, which of the following categories it falls in: # not a U.K. Qualifying Lender; # a U.K. Qualifying Lender (other than a U.K. Treaty Lender); or # a U.K. Treaty Lender, and if the New U.K. Lender fails to indicate its status in accordance with this [Section 3.01(i)(ix)] then such New U.K. Lender shall be treated for the purposes of this Agreement (including by each U.K. Borrower) as if it is not a U.K. Qualifying Lender until such time as it notifies the Administrative Agent which category applies (and the Administrative Agent, upon receipt of such notification, shall inform the relevant U.K. Borrower). For the avoidance of doubt, an Assignment and Assumption or any other such agreement pursuant to any Person becomes a Party shall not be invalidated by any failure of a Lender to comply with this [Section 3.01(i)(ix)].

Each U.K. Borrower hereby irrevocably and unconditionally jointly and severally guarantees to the Administrative Agent and the U.K. Lenders the full and punctual payment when due (whether at stated maturity, by required pre-payment, by acceleration or otherwise) of all of the Obligations of the other U.K. Borrower hereunder and under the other Loan Documents in consideration of the financial accommodations to be provided by the Lenders, the Agents and the L/C Issuers under this Agreement, for the mutual benefit, directly and indirectly, of each U.K. Borrower and in consideration of the undertakings of the other U.K. Borrower to accept joint and several liability for the Obligations. Each U.K. Borrower agrees that this is an absolute, unconditional and continuing guaranty of the full and punctual payment of all of the Obligations of the other U.K. Borrower hereunder and under the other Loan Documents and not of their collectability only and is in no way conditioned upon any requirement that the Administrative Agent or any U.K. Lender first attempt to collect any of such Obligations from such U.K. Borrower or resort to any collateral security or other means of obtaining payment. Each U.K. Borrower, jointly and severally, hereby irrevocably and unconditionally accepts, not merely as a surety but also as a co-debtor, joint and several liability with the other U.K. Borrower with respect to the payment and performance of all of the Obligations (including, without limitation, any Obligations arising under this [Section 10.10(a)]), it being the intention of the parties hereto that all of the Obligations of the U.K. Borrowers shall be the joint and several Obligations of each U.K. Borrower without preferences or distinction among them. Each U.K. Borrower hereby waives all defenses relating to the joint and several liability described above, including, without limitation, all suretyship defenses.

Each U.K. Revolving Borrowing, each conversion of U.K. Revolving Loans from Eurodollar Rate Loans to Domestic Base Rate Loans, each conversion of U.K. Revolving Loans from Domestic Base Rate Loans to Eurodollar Rate Loans, and each continuation of Eurodollar Rate Loans or Alternative Currency Term Rate Loans shall be made upon the applicable U.K. Borrower’s irrevocable notice to the Administrative Agent, which may be given by telephone or a U.K. Loan Notice; provided, that, any telephonic notice must be confirmed immediately by delivery to the Administrative Agent of a U.K. Loan Notice. Each U.K. Loan Notice must be received by the Administrative Agent not later than # ​ (London time) # three (3) Business Days prior to the requested date of any U.K. Revolving Borrowing of, conversion to, or continuation of Eurodollar Rate Loans, or any conversion of Eurodollar Rate Loans to Domestic Base Rate Loans, and # three (3) Business Days prior to the requested date of any U.K. Revolving Borrowing of Alternative Currency Loans, or any continuation of Alternative Currency Term Rate Loans, and # ​ (Eastern time) on the requested date of any U.K. Revolving Borrowing of Domestic Base Rate Loans; provided, that, if the applicable U.K. Borrower wishes to request U.K. Revolving Loans that are Eurodollar Rate Loans or Alternative Currency Term Rate Loans having an Interest Period other than one (1), three (3), or six (6) months in duration as provided in the definition of “Interest Period,” the applicable notice must be received by the Administrative Agent not later than ​ (London time) four (4) Business Days prior to the requested date of such U.K. Revolving Borrowing, conversion or continuation of Eurodollar Rate Loans or Alternative Currency Term Rate Loans, whereupon the Administrative Agent shall give prompt notice to the U.K. Lenders of such request and determine whether the requested Interest Period is acceptable to all of them. Not later than ​ (London time), three (3) Business Days prior to the requested date of such U.K. Revolving Borrowing, conversion or continuation of Eurodollar Rate Loans or Alternative Currency Term Rate Loans, the Administrative Agent shall notify the applicable U.K. Borrower (which notice may be by telephone) whether or not the requested Interest Period has been consented to by all the U.K. Lenders. Except as provided in [Section 2.04(c)(iii)(A)], Each U.K. Revolving Borrowing or continuation of Eurodollar Rate Loans, and each U.K. Revolving Borrowing, conversion or continuation of Alternative Currency Loans shall be in a minimum principal amount of ​ if denominated in Dollars, ​ if denominated in Sterling, or ​ if denominated in Euro or a whole multiple of ​ if denominated in Dollars, ​ if denominated in Sterling, or ​ if denominated in Euro in excess thereof. Each U.K. Revolving Borrowing of or conversion to Domestic Base Rate Loans shall be in a minimum principal amount of ​ or a whole multiple of ​ in excess thereof. Each U.K. Loan Notice shall specify # whether the applicable U.K. Borrower is requesting a U.K. Revolving Borrowing, a conversion of U.K. Revolving Loans from Eurodollar Rate Loans to Domestic Base Rate Loans, a conversion of U.K. Revolving Loans from Domestic Base Rate Loans to Eurodollar Rate Loans, a continuation of Eurodollar Rate Loans, or a continuation of Alternative Currency Term Rate Loans, # the requested date of such U.K. Revolving Borrowing or continuation, as the case may be (which shall be a Business Day), # the currency and principal amount of the U.K. Revolving Loans to be borrowed or continued, # the Type of U.K. Revolving Loans to be borrowed, # if applicable, the duration of the Interest Period with respect thereto, and # the applicable U.K. Borrower. If the applicable U.K. Borrower fails to specify a currency in a U.K. Loan Notice requesting a U.K. Revolving Borrowing, then the Revolving Loans so requested shall be made in Sterling. If the applicable U.K. Borrower fails to timely request a continuation of Eurodollar Rate Loans or Alternative Currency Term Rate Loans, as applicable, such U.K. Revolving Loans shall be continued as Eurodollar Rate Loans or Alternative Currency Term Rate Loans, as applicable in their original currency with an Interest Period of one (1) month. If the applicable U.K. Borrower requests a U.K. Revolving Borrowing of, or continuation of, Eurodollar Rate Loans or Alternative Currency Term Rate Loans in any such U.K. Loan Notice, but fails to specify an Interest Period, it will be deemed to have specified an Interest Period of one (1) month. Except as otherwise provided in this Agreement, no U.K. Revolving Loan may be converted into or continued as a U.K. Revolving Loan denominated in a different currency, but instead must be repaid in the original currency of such U.K. Revolving Loan and reborrowed in the other currency.

The agreement of Lenders to make any Advance requested to be made on any date (including the initial Advance), is subject to the satisfaction of the following conditions precedent as of the date such Advance is made:

Each of the U.S. Loan Parties is validly existing and in good standing under the laws of its jurisdiction of incorporation.

Each of the U.S. Loan Parties has the corporate power and authority to execute, deliver and perform its obligations under the Loan Documents to which it is a party.

Each of [Section 11.06] (Successors and Assigns), [Section 11.10] (Counterparts; Integration; Effectiveness), [Section 11.12] (Severability), [Section 11.14] (Governing Law; Jurisdiction; Etc.) and [Section 11.15] (Waiver of right to Trial by Jury) of the Credit Agreement hereby are incorporated herein by reference, mutatis mutandis.

Conditions to Each Purchase. As a condition precedent to any purchase of a Participation Interest by ​ from ​ hereunder, in addition to all other requirements set forth herein, ​ shall deliver to ​ all of the following, each being duly executed, endorsed, notarized where applicable and delivered and in form and content satisfactory to ​ in its sole and absolute discretion:

Deliveries of Each Purchaser. At each Closing (except as otherwise indicated), each Purchaser shall deliver or cause to be delivered to the Partnership:

By Each Selling Holder. Each Selling Holder severally and not jointly (other than the BlackRock Purchaser which obligations will be joint and several) agrees to indemnify and hold harmless the Partnership, the General Partner and their respective directors, officers, employees and agents and each Person, who, directly or indirectly, controls the Partnership within the meaning of the Securities Act or of the Exchange Act to the same extent as the foregoing indemnity from the Partnership to the Selling Holders, but only with respect to information regarding such Selling Holders furnished in writing by or on behalf of such Selling Holder expressly for inclusion in a Registration Statement or any other registration statement contemplated by this Agreement, any preliminary prospectus, prospectus supplement or final prospectus contained therein, or any amendment or supplement thereto or any free writing prospectus relating thereto;

Each of [Schedule 10.1] (Permitted Existing Liens) and [Schedule 10.2] (Permitted Existing Investments) is amended and restated in the form attached to this letter agreement as [Schedules 10.1] and 10.2, respectively.

Taxes, Indebtedness, etc

Consultation with Independent Counsel. The Parties hereto have each consulted with and been counseled by their own legal counsel and tax advisors, and are entering into this Agreement voluntarily and with full understanding of the meaning and legal effects of each provision contained in this Agreement. Snell and Wilmer L.L.P. has acted as legal counsel to ​ and has not acted as legal counsel to any other Party. The Parties hereto and their respective legal counsel have been involved in the negotiation and drafting of this Agreement. In the event of any dispute regarding the interpretation of any provision of this Agreement, the Parties agree that this Agreement and the provisions hereof shall not be construed against any one Party as the drafter of this Agreement.