Security	Date	Code	Shares	Price	A/D	Owned after	D/I	Nature of ownership
Common Stock^F1,F4,F5	Oct 19, 2015	P	64,613	$2.9224	A	4,267,502	I	Through Deerfield Special Situations Fund, L.P.
Common Stock^F1,F4,F5	Oct 19, 2015	P	64,613	$2.9224	A	235,811	I	Through Deerfield Private Design Fund III, L.P.
Common Stock^F2,F4,F5	Oct 20, 2015	P	50,065	$2.9973	A	4,317,567	I	Through Deerfield Special Situations Fund, L.P.
Common Stock^F2,F4,F5	Oct 20, 2015	P	50,065	$2.9973	A	285,876	I	Through Deerfield Private Design Fund III, L.P.
Common Stock^F3,F4,F5	Oct 21, 2015	P	80,342	$3.0002	A	4,397,909	I	Through Deerfield Special Situations Fund, L.P.
Common Stock^F3,F4,F5	Oct 21, 2015	P	80,342	$3.0002	A	366,218	I	Through Deerfield Private Design Fund III, L.P.
Common Stock^F4,F5	holding	—	—		—	181,222	I	Through Deerfield Private Design Fund II, L.P.
Common Stock^F4,F5	holding	—	—		—	207,667	I	Through Deerfield Private Design International II, L.P.

Table II — derivative securities

No Table II lines on this filing.

Explanation of responses

F1The price reported in Column 4 is a weighted average price. The shares were purchased in multiple transactions at prices ranging from $2.73 to $3.04, inclusive. The reporting persons undertake to provide to the Issuer, and security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in footnotes (1), (2) and (3) of this Form 4.
F2The price reported in Column 4 is a weighted average price. The shares were purchased in multiple transactions at prices ranging from $2.96 to $3.00, inclusive.
F3The price reported in Column 4 is a weighted average price. The shares were purchased in multiple transactions at prices ranging from $2.95 to $3.09, inclusive.
F4This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt III, L.P. is the general partner of Deerfield Private Design Fund III, L.P. ("Fund III"). Deerfield Mgmt L.P. is the general partner of Deerfield Special Situations Fund, L.P., Deerfield Private Design Fund II, L.P. and Deerfield Private Design International II, L.P. (collectively with Fund III, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt III, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.
F5In accordance with Instruction 4 (b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

Remarks

Jonathan Isler, Attorney-in-Fact: Power of Attorney, which is hereby incorporated by reference to Exhibit 24 to a Form 3 with regard to Avalanche Biotechnologies, Inc. filed with the Securities and Exchange Commission on July 30, 2014 by Deerfield Mgmt III, L.P., Deerfield Mgmt, L.P., Deerfield Management Company, L.P., Deerfield Special Situations Fund, L.P., Deerfield Special Situations International Master Fund, L.P., Deerfield Private Design Fund III, L.P. and James E. Flynn