ORBIMED ADVISORS LLC bought ETRA

Footnotes

Reflects shares of the Issuer's Common Stock purchased in the Issuer's initial public offering.; These securities are held directly by OrbiMed Private Investments VII, LP ("OPI VII"). OrbiMed Capital GP VII LLC ("GP VII") is the general partner of OPI VII. OrbiMed Advisors LLC ("OrbiMed Advisors") is the managing member of GP VII. By virtue of such relationships, GP VII and OrbiMed Advisors may be deemed to have voting power and investment power over the securities held by OPI VII and as a result, may be deemed to have beneficial ownership over such securities. OrbiMed Advisors exercises voting and investment power through a management committee comprised of Carl L. Gordon, W. Carter Neild, and Geoffrey C. Hsu, each of whom disclaims beneficial ownership of the shares held by OPI VII.; This report on Form 4 is jointly filed by OrbiMed Advisors, GP VII and Genesis GP. Each of the Reporting Persons disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of its pecuniary interest therein, if any. The Reporting Persons have designated Carl L. Gordon, a member of OrbiMed Advisors, to serve on the Issuer's board of directors. This report shall not be deemed an admission that any of such entity or person is a beneficial owner of such securities for purposes of Section 16 of the Exchange Act, or for any other purpose.