1. Represents a cross-trade of common stock of the Issuer among certain private funds managed by Redmile Group, LLC ("Redmile" and such private funds, the "Redmile Funds"). The reported transactions occurred simultaneously at no profit to the Reporting Persons and resulted in no change in the aggregate beneficial ownership of the Reporting Persons.

2. The common stock of the Issuer reported herein are directly owned by the Redmile Funds, none of which individually is a 10% owner, and may be deemed beneficially owned by Redmile as investment manager of the Redmile Funds. The reported securities may also be deemed beneficially owned by Jeremy Green as the principal of Redmile. Each of Redmile and Mr. Green (collectively, the "Reporting Persons") disclaims beneficial ownership of the reported securities except to the extent of their pecuniary interest therein. This report shall not be deemed an admission that such Reporting Persons are a beneficial owner of such securities for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, or for any other purpose.

3. Mr. Robert Faulkner, a member of the board of directors of the Issuer and a managing director of Redmile, was elected to the board of the Issuer as a representative of Redmile. As a result, the Reporting Persons are directors by deputization for purposes of Section 16 of the Securities Exchange Act of 1934, as amended.