PERSEID THERAPEUTICS LLC VOTING AGREEMENT

Exhibit 2.1.7

PERSEID THERAPEUTICS LLC

VOTING AGREEMENT

September 18, 2009

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PERSEID THERAPEUTICS LLC

VOTING AGREEMENT

This Voting Agreement (this “ Agreement ”) is made as of September 18, 2009 by and among Perseid Therapeutics LLC, a Delaware limited liability company (the “ Company ”), Maxygen, Inc., a Delaware corporation (“ Maxygen ”), and Astellas Bio Inc., a Delaware corporation (“ Bio ”) (each of Bio and Maxygen an “ Investor ,” and collectively the “ Investors ”), and the persons and entities listed on Exhibit A, as amended from time to time (each a “ Common Unitholder ,” and collectively the “ Common Unitholders ”). The Investors and the Common Unitholders are also referred to herein collectively as the “ Voting Parties .” All capitalized terms used and not defined herein shall have such meanings as set forth in the Master Joint Venture Agreement by and among Maxygen, Astellas Pharma Inc., and Bio dated as of June 30, 2009 (the “ Joint Venture Agreement ”).

RECITALS

The Company proposes to sell Series A Preferred Units and Series B Preferred Units (together, “ Preferred Units ”) to the Investors pursuant to the Series A and Series B Preferred Unit Purchase Agreement (the “ Purchase Agreement ”) of even date herewith (the “ Financing ”). The Company’s common units (the “ Common Units ”) together with the Preferred Units are referred to as the “ Units .”

The Company’s LLC Agreement provides that (i) the board of managers of the Company shall consist of five members; and (ii) the holders of the Company’s Preferred Units shall be entitled to elect five managers (the “ Preferred Managers ”) so long as at least 6,000,000 Preferred Units (as adjusted for units dividends, units splits, combinations of units, reorganizations, recapitalizations, reclassifications or other similar events) remain outstanding.

As a condition to the Financing, the Voting Parties have agreed to enter into this Agreement.

The parties therefore agree as follows:

SECTION 1

VOTING

1.1 General . During the term of this Agreement, the Voting Parties each agree to vote all Units having voting rights under the LLC Agreement (“ Voting Company Units ”) now or hereafter owned by them, whether beneficially or otherwise, or as to which they have voting power in accordance with the provisions of this Agreement.

SECTION 2

ELECTION OF MANAGERS

2.1 Voting . During the term of this Agreement and so long as at least 6,000,000 Preferred Units (as adjusted for units dividends, units splits, combinations of units, reorganizations, recapitalizations, reclassifications or other similar events) remain outstanding, each Voting Party agrees to vote all Units in such manner as may be necessary to elect (and maintain in office) as members of the Company’s board of managers the following individuals:

(a) the four Majority Preferred Designees (as defined below) as four of the Preferred Managers; and

(b) the Minority Preferred Designee (as defined below) as one of the Preferred Managers.

2.2 Designation of Managers . The Preferred Managers (each a “ Designee ”) shall be selected as follows:

(a) The four “ Majority Preferred Designees ” shall be chosen by Maxygen; provided that , during such time as Bio holds more than fifty percent 50% of the outstanding Units (assuming conversion of all outstanding Preferred Units) (the “ Outstanding Equity ”) then the four Majority Preferred Designees shall be chosen by Bio.

(b) The one “ Minority Preferred Designee ” shall be chosen by Bio; provided that , during such time as Bio is entitled to choose the Majority Preferred Designees pursuant to Section 2.2(a) above, then, the one Minority Preferred Designee shall be chosen by Maxygen.

(c) Notwithstanding the foregoing, at any such time that neither Maxygen nor Bio holds greater than 50% of the Outstanding Equity, the number of Designees to be chosen by each of Maxygen and Bio shall be determined on a ratable basis, based on the number of Units of Outstanding Equity held by each such Investor, with any Designees not chosen by either Maxygen or Bio to be chosen by a majority vote of all the Outstanding Equity. For example, if Maxygen holds 45% of the Outstanding Equity and Bio holds 40% of the Outstanding Equity, then each of Maxygen and Bio shall be entitled to choose two Designees and the remaining Designee shall be chosen by a majority vote of all the Outstanding Equity.

2.3 Current Designees . For the purpose of this Agreement, the initial managers of the Company shall be the following Designees:

(a) the Majority Preferred Designees shall be Grant Yonehiro, Isaac Stein, Jim Sulat and Gordon Ringold; and

(b) the Minority Preferred Designee shall be Naoki Okamura.

2.4 Changes in Designees . From time to time during the term of this Agreement, Voting Parties who hold sufficient Units to select a Designee pursuant to this Agreement may, in their sole discretion:

(a) notify the Company in writing of an intention to remove from the Company’s board of managers any incumbent Designee who occupies a board seat for which such Voting Parties are entitled to designate the Designee; or

(b) notify the Company in writing of an intention to select a new Designee for election to a board seat for which such Voting Parties are entitled to designate the Designee (whether to replace a prior Designee or to fill a vacancy in such board seat).

In the event of such an initiation of a removal or selection of a Designee under this section, the Company shall take such reasonable actions as are necessary to facilitate such removals or elections, including, without limitatio