This Amendment No. 4 to Schedule 13D is being filed jointly on behalf of the following persons (collectively, the “ Reporting Persons ”): (i) Francisco Partners IV, L.P., a Cayman Islands exempted limited partnership (“ FP I V ”), (ii) Francisco Partners IV-A, L.P., a Cayman Islands exempted limited partnership (“ FP IV-A ”), (iii) Francisco Partners GP IV, L.P., a Cayman Islands exempted limited partnership (“ FP GP IV ”), and (iv) Francisco Partners GP IV Management Limited, a Cayman Islands exempted company (“ FP GP Management ” and collectively with FP IV, FP IV-A, FP GP IV and their affiliates, “ Francisco Partners ”), to supplement and amend the Schedule 13D filed on behalf of the Reporting Persons on May 9, 2016, as amended on June 14, 2016, August 15, 2016 and August 26, 2016. Each item below amends and supplements the information disclosed under the corresponding item of Schedule 13D. Capitalized terms defined in the Schedule 13D are used herein with their defined meaning.

The response set forth in Item 3 of the Schedule 13D is hereby amended and supplemented by the following:

In a series of transactions on September 9, 2016, the Reporting Persons acquired 53,173 shares of Common Stock for approximately $86,713 in investment capital, excluding brokerage commissions and fees, at prices per share ranging from $1.63 to $1.65, inclusive, for a weighted average price per share of $1.6308. In a series of transactions on September 12, 2016, the Reporting Persons acquired 600 shares of Common Stock for approximately $990 in investment capital, excluding brokerage commissions and fees, at a price per share of $1.65. In a series of transactions on September 13, 2016, the Reporting Persons acquired 18,370 shares of Common Stock for approximately $31,064 in investment capital, excluding brokerage commissions and fees, at prices per share ranging from $1.65 to $1.70, inclusive, for a weighted average price per share of $1.691. The Reporting Persons undertake to provide upon request by the Commission staff, the Issuer, or a security holder of the Issuer full information regarding the number of shares purchased or sold at each separate price. The source of funds for this consideration was the available capital of Francisco Partners, which may, at any given time, include borrowings under a working capital line of credit with First Republic Bank or capital contributions from investors in the Francisco Partners funds, each in the ordinary course of business.

The response set forth in Item 5 of the Schedule 13D is hereby amended and supplemented by the following:

Based on the information set forth in the Company’s Registration Statement on Form S-3, filed with the Securities and Exchange Commission on August 30, 2016, there were 22,344,064 shares of the Common Stock issued and outstanding as of August 26, 2016.

FP IV directly owns 2,414,050 shares of Common Stock and 33,306 shares of Preferred Stock, convertible at any time at FP IV’s option into 7,492,369 shares of Common Stock. FP IV-A directly owns 1,209,972 shares of Common Stock and 16,694 shares of Preferred Stock, convertible at any time at FP IV-A’s option into 3,755,408 shares of Common Stock.

As a result, (i) FP IV beneficially owns 9,906,419 shares of Common Stock, or 29.5% of the Common Stock deemed issued and outstanding as of the Filing Date, (ii) FP IV-A beneficially owns 4,965,380 shares of Common Stock, or 14.8% of the Common Stock deemed issued and outstanding as of the Filing Date, (iii) FP GP IV beneficially owns 14,871,799 shares of Common Stock, or 44.3% of the Common Stock deemed issued and outstanding as of the Filing Date, and (iv) FP GP Management owns 14,871,799 shares of Common Stock, or 44.3% of the Common Stock deemed issued and outstanding as of the Filing Date.

SIGNATURES

After reasonable inquiry and to the best of my knowledge and belief, the undersigned certifies that the information set forth in this statement is true, complete and correct.

Dated: September 13, 2016