Letter Agreement dated September 19, 2014, by and among the Company, Oxford Finance LLC and Silicon Valley Bank

1.

Collateral Agent and Lenders hereby waive Borrower’s failure to comply with Section 6.10 of the Agreement, strictly for the Waiver Period, and hereby waive any Event of Default that such failure may constitute under the Agreement.

2.

The waiver set forth in Section 1 above is effective for the purposes set forth herein and shall be limited precisely as written and shall not be deemed to (a) be a consent to any amendment, waiver or modification of any other term or condition of any Loan Document, or (b) otherwise prejudice any right or remedy which Collateral Agent or Lenders may now have or may have in the future under or in connection with any Loan Document.

3.

This Waiver Letter shall be construed in connection with and as part of the Loan Documents and all terms, conditions, representations, warranties, covenants and agreements set forth in the Loan Documents, except as herein waived, are hereby ratified and confirmed and shall remain in full force and effect.

4.

To induce Collateral Agent and Lenders to enter into this Waiver Letter, Borrower hereby represents and warrants to Collateral Agent and Lenders as follows:

a.

Immediately after giving effect to this Waiver Letter, (a) the representations and warranties contained in the Loan Documents are true, accurate and complete in all material respects as of the date hereof (except to the extent such representations and warranties relate to an earlier date, in which case they are true and correct as of such date), and (b) no Event of Default has occurred and is continuing;

b.

Borrower has the power and due authority to execute and deliver this Waiver Letter and to perform its obligations under the Loan Agreement, as waived by this Waiver Letter;

c.

The organizational documents of Borrower delivered to Collateral Agent on the Effective Date remain true, accurate and complete and have not been amended, supplemented or restated except  for the Certificate of Incorporation which was amended and restated to reflect the increase in the authorized shares of the Company (and a copy of which, as amended and restated, has been provided to Collateral Agent and Lenders), and are and continue to be in full force and effect;

d.

The execution and delivery by Borrower of this Waiver Letter and the performance by Borrower of its obligations under the Loan Agreement, as waived hereby, do not and will not contravene (i) any law or regulation binding on or affecting Borrower, (ii) any contractual restriction with a Person binding on Borrower, (iii) any order, judgment or decree of any court or other governmental or public body or authority, or subdivision thereof, binding on Borrower, or (iv) the organizational documents of Borrower;

e.

The execution and delivery by Borrower of this Waiver Letter and the performance by Borrower of its obligations under the Loan Agreement, as waived by this Waiver Letter, do not require any order, consent, approval, license, authorization or validation of, or filing, recording or registration with, or exemption by any governmental or public body or authority, or subdivision thereof, binding on Borrower, except as already has been obtained or made; and

f.

This Waiver Letter has been duly executed and delivered by Borrower and is the binding obligation of Borrower, enforceable against Borrower in accordance with its terms, except as such enforceability may be limited by bankruptcy, insolvency, reorganization, liquidation, moratorium or other similar laws of general application and equitable principles relating to or affecting creditors’ rights.

5.

To induce Collateral Agent and Lenders to enter into this Waiver Letter, on October 6, 2014, Borrower shall terminate each of the outstanding Warrants (“Old Warrants”) issued pursuant to the Agreement and simultaneously issue in lieu thereof new Warrants (“New Warrants”) to the holders of the Old Warrants.  Unless otherwise agreed to by each party in its sole discretion, each New Warrant shall be in such form and substance as is identical to the corresponding Old Warrant (in lieu of which it is being issued) other than the date of the issuance of such New Warrant and the warrant exercise price (referred to as “Warrant Price” in the Old Warrants) for such New Warrant.  The warrant exercise price (referred to as “Warrant Price” in the Old Warrants) for such New Warrant shall be equal to the lower of (i) the closing purchase price per share of Borrower’s common stock, par value $0.001per share (the “Common Stock”) on the NASDAQ stock market for September 30, 2014, or (ii) the average closing price per share of the Common Stock on the NASDAQ stock market for October 1, 2 and 3, 2014.

6.

Except as expressly set forth herein, the Loan Agreement and the other Loan Documents shall continue in full force and effect without alteration or amendment.  This Waiver Letter and the Loan Documents represent the entire agreement about this subject matter and supersede prior negotiations or agreements.

7.

This Waiver Letter shall be deemed effective as of the date hereof upon the due execution and delivery to Collateral Agent of this Waiver Letter by each party hereto, but shall be subject to the Borrower’s representations and warranties made herein being true and accurate and the fulfilment of Borrower’s obligations hereunder including without limitation, the (a) Borrower’s payment of all Lenders’ Expenses incurred through the date hereof, which may be debited from any of Borrower’s accounts with Lenders and (b) Borrower’s fulfilment of its obligations set forth in Section 5 above.

8.

This Waiver Letter may be executed in any number of counterparts, each of which shall be deemed an original, and all of which, taken together, shall constitute one and the same instrument.

9.

This Waiver Letter and the rights and obligations of the parties hereto shall be governed by and construed in accordance with the laws of the State of California.