Exhibit 10.6

EXCHANGE AGREEMENT

THIS EXCHANGE AGREEMENT (this “ Agreement ”) is dated as of June 25, 2009, by and between Arrowhead Research Corporation, a Delaware corporation (the “ Corporation ”), and TEL Venture Capital, Inc. (the “ Holder ”). The Corporation and each Holder are referred to as a “ Party ” and collectively as the “ Parties ”.

W I T N E S S E T H :

WHEREAS, the Corporation and the Holder are shareholders of Unidym, Inc., a Delaware corporation (“ Unidym ”);

WHEREAS, the Holder desires to exchange shares of Series C Preferred Stock, $0.0001 par value per share and Series C-1 Preferred Stock, $0.0001 par value per share, of Unidym (each, a “ Unidym Share ” and, collectively, the “ Unidym Shares ”) in the amounts set forth on Exhibit A , attached hereto for common stock of the Corporation, $0.001 par value per share (each, an “ Arrowhead Share ” and, collectively the “ Arrowhead Shares ”);

WHEREAS, the Corporation desires to exchange (the “ Exchange ”) one newly issued and unregistered Arrowhead Share for each Unidym Share and the agreement of the Holder to certain restrictions on the transfer and sale of any Arrowhead Shares it receives pursuant to this Agreement (the Arrowhead Shares received in the Exchange, referred to in this Agreement as the “ Exchanged Shares ”); and

WHEREAS, in partial consideration for the Exchange and to the extent Holder retains any Unidym Shares after the Exchange (“Retained Unidym Shares”), the Corporation desires that the Holder waive certain rights associated with respect to the Unidym Shares and the Retained Unidym Shares;

WHEREAS, the Holder is willing to waive certain rights with respect to the Unidym Shares and confirm that it prepared to waive certain rights with respect to Retained Unidym Shares subject to certain terms and conditions; and

NOW, THEREFORE, for good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties hereto agree as follows:

1. Exchange .

(a) Exchange Ratio . The Corporation and the Holder hereby agree to exchange at the Closing the Unidym Shares in the amounts set forth on Exhibit A , attached hereto, for Arrowhead Shares in the following ratio: one Unidym Share for one Arrowhead Share (1:1).

(b) Exchange . To effect this exchange, the Holder will deliver to the Corporation the stock certificate or certificates representing the Unidym Shares together with duly executed stock powers related thereto and the Corporation will deliver to the Holder a stock certificate or certificates representing the Exchanged Shares.

2. The Closing .

(a) Closing Date . The closing of the transactions contemplated by this Agreement (the “ Closing ”) shall take place at the offices of Arrowhead Research Corporation at 10:00 a.m., Los Angeles time, on such date as agreed to by the parties on or after the date the conditions to closing set forth in this Agreement are satisfied (“ Closing Date ”), or at such other place, date or time as the parties may mutually agree in writing.

(b) Conditions to Closing of Holder . The obligation of the Holder to consummate the transactions on the Closing Date as contemplated by this Agreement shall be subject to the satisfaction or waiver on or prior to the Closing Date of the following conditions:

(i) the Corporation shall have performed and complied in all material respects with all obligations and agreements required to be performed and complied with by the Corporation hereunder on or prior to the Closing Date;

(ii) the representations and warranties of the Corporation contained in this Agreement shall be true and correct in all material respects as of the Closing Date as if made as of such date;

(iii) the Corporation shall have delivered to the Holder one or more stock certificates evidencing such Holder’s ownership of the Exchanged Shares to be delivered on the Closing Date duly executed by the Corporation;

(iv) the Corporation shall have delivered to the Transfer Agent the instructions and pre-authorizations described in Section 5(b) of this Agreement relating to the acceptance of the opinion of counsel satisfactory to the Corporation authorizing the removal of the legends from the Exchanged Shares after the expiration of the Prohibited Period (as defined herein); and

(v) the Corporation shall have received all third party consents and all authorizations, consents and approvals of any Governmental Authority necessary to consummate the transactions contemplated hereby .

(c) Conditions to Closing of Corporation . The obligation of the Corporation to consummate the transactions on the Closing Date shall be subject to the satisfaction or waiver on or prior to the Closing Date of the following conditions:

(i) The Holder shall have each performed and complied in all material respects with all obligations and agreements required to be performed and complied with by each Holder hereunder on or prior to the Closing Date;

(ii) Holder shall have delivered to Corporation evidence and supporting documents satisfactory to Corporation that the Holder has complied with or obtained all necessary consents under the terms and conditions of the Amended and Restated Right of first Refusal and Co-Sale Agreement, (the “ ROFR and Co-Sale Agreement ”) to exchange all the Unidym Shares free and clear of any Claims as required under this Agreement and with the requested assistance of the Corporation in obtaining such consents as set forth in Section 11(b) of this Agreement;

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(iii) the representations and warranties of the Holder contained in this Agreement shall be true and correct in all material respects as of the Closing Date as if made as of such date;

(iv) Holder shall have delivered to the Corporation a certificate or the certificates representing all the Unidym Shares owned by Holder to be exchanged on such date and related executed stock powers; and

(v) Holder shall have received all third party consents and all authorizations, consents and approvals of any Governmental Authority necessary to consummate the transactions contemplated hereby.

3. Representations and Warranties of the Corporation . The Corporation represents and warrants to Holder as follows:

(a) Corporate Status . The Corporation is a corporation incorporated, validly existing and in good standing under the laws of the State of Delaware with full right, power and authority to execute, deliver and perform this Agreement.

(b) Authorization/Enforceability . This Agreement has been duly authorized, executed and delivered by the Corporation and constitutes the valid and legally binding obligation of the Corporation, enforceable in accordance with its terms and conditions. The Corporation need not give any notice to, make any filing with, or obtain any authorization, consent, or approval of any Governmental Authority in order to consummate the transactions contemplated by this Agreement.

(c) Non-Contravention . Neither the execution and the delivery of this Agreement, nor the consummation of the transactions contemplated hereby, will (i) violate any constitution, statute, regulation, rule, injunction, judgment, order, decree, ruling, charge, or other restriction of any Governmental Authority to which the Corporation is subject, or (ii) conflict with, result in a breach of, constitute a default under, result in the acceleration of, create in any party the right to accelerate, terminate, modify, or cancel, or require any notice under the certificate of incorporation or bylaws of the Corporation, or any agreement, contract, lease, license, instrument, or other arrangement to which the Corporation is a party or by which it is bound or to which any of its assets is subject.

(d) Consents/Approvals . No consent, approval, authorization, order, registration or qualification of or with any Governmental Authority or other Person or entity is required for the issuance and sale of the Exchanged Shares by the Corporation to Holder or the consummation by the Corporation of the transactions contemplated by this Agreement.

(e) Exchanged Shares Authorization . The Exchanged Shares have been duly authorized and, when issued and delivered, will be duly and validly issued and fully paid and nonassessable. Upon consummation of the transactions contemplated hereby, good and valid title to the Exchanged Shares, free and clear of all Claims, will be transferred by the Corporation to Holder.

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(f) The Corporation has such knowledge and experience in financial and business matters so as to be capable of evaluating the merits and risk of an investment in and holding the Unidym Shares. The Corporation acknowledges that it has had access to all information concerning Unidym and it businesses, assets, liabilities, financial statements, and obligations which have been requested and has been provided the opportunity to ask questions of and receive answers from Unidym to fully and effectively