AMENDMENT NO. 4 TO EXCLUSIVE SUBLICENSE AGREEMENT

Exhibit 10.1

*Confidential Treatment has been

requested for the marked portions

of this exhibit pursuant to Rule

24b-2 of the Securities Exchange

Act of 1934, as amended.

AMENDMENT NO. 4 TO

EXCLUSIVE SUBLICENSE AGREEMENT

THIS AMENDMENT NO. 4 (the “ Amendment ”) dated as of May 8, 2009 to the Exclusive Sublicense Agreement by and between Alkermes, Inc., a Pennsylvania corporation with its principal offices at 88 Sidney Street, Cambridge, MA 02139 (“ Alkermes ”), and Targeted Genetics Corporation, a Washington corporation with its principal offices at 1100 Olive Way, Suite 100, Seattle, Washington 98101 (“ Targeted ”),

WITNESSETH:

WHEREAS, Alkermes and Targeted entered into an Exclusive Sublicense Agreement dated June 9, 1999, as previously amended on March 12, 2002, May 29, 2003 and March 9, 2007 (the “ Agreement ”); and

WHEREAS, Alkermes, on the one hand, and Children’s Hospital Research Foundation and Children’s Hospital Inc., on the other hand, have entered into various amendments to the License Agreement between these parties, dated as of April 10, 1996 (the “ AAV License Agreement ”), which is the license agreement underlying the Agreement; and

WHEREAS, in accordance with the terms and conditions hereinafter set forth, Alkermes and Targeted now wish to amend the Agreement to conform to the changes made to the AAV License Agreement pursuant to such amendments;

NOW, THEREFORE, in consideration of the foregoing premises and the mutual covenants and agreements set forth herein, the Parties agree as follows:

1. Definitions . Unless otherwise provide herein, all defined terms used in this Amendment shall have the same meanings as set forth in the Agreement. The Agreement shall be amended to add the following new definitions:

“1.18 “Customers” means research institutes, academic institutions, universities and other organizations of higher education, and/or hospitals that contract with Licensor for the manufacture of Licensed Products. In no event shall a Customer be (a) a for-profit entity or (b) a not-for-profit foundation, such as the [*] . A Customer must own or control rights in the product, or use thereof, that it desires Licensor to manufacture and supply using the rights Licensor retains under the AAV License Agreement, which ownership or control may be evidenced solely from a filing of a patent application regarding such Licensed Product or its use.

1.19 “Educational and Research Purposes” means education and/or research activities which includes clinical trials up to or consisting of Phase II Clinical Trials.

1.20 “Funders” means not-for-profit organizations, including not-for-profit foundations such as the [*] , and governmental entities such as the National Institutes of Health.

1.21 “Licensor” means Children’s Hospital Research Foundation and Children’s Hospital Inc.”

2. Section 2.2 . Section 2.2 of the Agreement shall be deleted in its entirety and replaced with a new Section 2.2 which shall read as follows:

“2.2 Reserved Rights .

(a) Alkermes reserves unto itself the personal, non-transferable right to make, have made, and use Licensed Product(s) and Licensed Material in the Fields of Use for internal research purposes only, and for no other purpose in the Fields of Use.

(b) Alkermes reserves for Licensor the non-exclusive right to use and have used the Licensed Patent Rights, Licensed Products and/or Licensed Processes, and associated information and technology of Licensor, (i) for research and/or educational purposes; and (ii) subject to Sections 2.2 (c) and (d), to manufacture products containing AAV vectors for use by Licensor and Customers for Educational and Research Purposes. The reservation of rights in this Section 2.2(b) does not permit, in any way, any entity except Licensor from using the Licensed Patent Rights, Licensed Products or Licensed Processes, and associated information and technology of Licensor, to manufacture Licensed Products.

(c) Customers may only receive funding for the manufacture by Licensor of Licensed Products under this Section 2.2 by either self-funding or receiving money from Funders. Licensed Products manufactured and supplied by Licensor pursuant to this Section 2.2 shall not, in whole or in part, be funded by, owned by, optioned or licensed for development and commercialization to a for-profit entity at the time the Licensed Product is so manufactured by Licensor or during the conduct of clinical trials utilizing such Licensed Product so manufactured. A not-for-profit organization, including Licensor, may receive funding from a Funder for the manufacture by Licensor of products pursuant to this Section 2.2; provided however , that such funding for the manufacture by Licensor by any one Funder shall not exceed [*] per year per Licensed Product manufactured and, in the event that the Customer receives funding from a Funder that is a not-for-profit foundation, the not-for-profit foundation must not own or have licensed any patent rights necessary or useful for the Licensed Products manufactured by Licensor, other than a non-exclusive license or option to any inventions made during the manufacture by Licensor of Licensed Products pursuant to Section 2.2 and funded by such not-for-profit foundation. In no instance shall Licensor receive any funding from [*] relating to the manufacture of Licensed Products consistent with this Section 2.2. Nothing herein shall limit Licensor’s or a Customer’s ability to receive funding from any source for any purpose, including Educational and Research Purposes, not related to the manufacture of a Licensed Product under this Section 2.2.

(d) Restrictions on Manufacturing . In no event shall Licensor manufacture and supply any Licensed Products pursuant to this Section 2.2 for Educational and Research Purposes on the following without the prior written consent of Alkermes, which consent shall be provided on behalf of Alkermes by its sublicensee Targeted: [*] . Alkermes shall be informed by Licensor of any such consent provided by Alkermes’ sublicensee, Targeted. Licensor will not grant the right to use Licensed Products manufactured and supplied to Customers by Licensor pursuant to this Section 2.2 by for-profit entities (excluding those conducting the clinical trials, e.g. hospitals, and the CROs administering them).”

3. Section 2.4 . The penultimate sentence of Section 2.4 of the Agreement shall be deleted in its entirety and replaced with a new penultimate sentence which shall read as follows:

“Targeted shall keep Alkermes apprised of all ongoing sublicensing negotiations and the general nature of same in a timely manner; Targeted shall also give Alkermes prompt notification of the identity and address of each Sublicensee with whom it concludes a Sublicense Agreement and shall supply Alkermes with a copy of each such Sublicense Agreement.”

4. Section 2.6 . Section 2.6 of the Agreement shall be deleted in its entirety and replaced with a new Section 2.6 which shall read as follows:

“2.6