Security	Date	Code	Shares	Price	A/D	Owned after	D/I	Nature of ownership
Common Stock^F1,F2	holding	—	—		—	4,481,788	I	Through Deerfield Partners, L.P.
Common Stock^F1,F2	holding	—	—		—	1,411,628	I	Through Deerfield Special Situations Fund, L.P.

Table II — derivative securities

Security	Conv. / exercise price	Date	Code	Shares	A/D	Exercisable	Expires	Underlying	Underlying shares	Owned after	D/I
Cash-Settled Total Return Swap^F3,F1,F2	$7.00	Jan 11, 2019	J	1	A	—	Jan 19, 2022	Common Stock	1,851	1	I
Cash-Settled Total Return Swap^F4,F1,F2,F5	$6.969	Jan 14, 2019	J	1	A	—	Jan 19, 2022	Common Stock	61,789	1	I
Cash-Settled Total Return Swap^F6,F1,F2,F7	$6.931	Jan 15, 2019	J	1	A	—	Jan 19, 2022	Common Stock	48,254	1	I

Explanation of responses

F1This 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, L.P. is the general partner of Deerfield Partners, L.P. ("Deerfield Partners") and Deerfield Special Situations Fund, L.P. (collectively with Deerfield Partners, 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, L.P. and Deerfield Management Company, L.P.
F2In 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.
F3On January 11, 2019, Deerfield Partners entered into a cash-settled total return swap agreement with an unaffiliated third party financial institution, which provides Deerfield Partners with economic exposure to an aggregate of 1,851 notional shares. The swap agreement provides Deerfield Partners with economic results that are comparable to the economic results of ownership of, based on the applicable reference price, but does not provide Deerfield Partners with the power to vote or direct the voting of, or dispose of or direct the disposition of, the shares of common stock that are the subject of such swap agreement.
F4On January 14, 2019, Deerfield Partners entered into a cash-settled total return swap agreement with an unaffiliated third party financial institution, which provides Deerfield Partners with economic exposure to an aggregate of 61,789 notional shares. The swap agreement provides Deerfield Partners with economic results that are comparable to the economic results of ownership of, based on the applicable reference prices, but does not provide Deerfield Partners with the power to vote or direct the voting of, or dispose of or direct the disposition of, the shares of common stock that are the subject of such swap agreement.
F5The price reported in Column 2 represents a weighted average reference price associated with the swap agreement. The reference prices applicable to the 61,789 notional shares subject to the swap agreement reported herein range from $6.85 to $7.00, inclusive. The reporting persons undertake to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of notional shares subject to each separate reference price within the ranges set forth in footnotes (5) and (7) of this Form 4.
F6On January 15, 2019, Deerfield Partners entered into a cash-settled total return swap agreement with an unaffiliated third party financial institution, which provides Deerfield Partners with economic exposure to an aggregate of 48,254 notional shares. The swap agreement provides Deerfield Partners with economic results that are comparable to the economic results of ownership of, based on the applicable reference prices, but does not provide Deerfield Partners with the power to vote or direct the voting of, or dispose of or direct the disposition of, the shares of common stock that are the subject of such swap agreement.
F7The price reported in Column 2 represents a weighted average reference price associated with the swap agreement. The reference prices applicable to the 48,254 notional shares subject to the swap agreement reported herein range from $6.79 to $7.00, inclusive.

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 Proteon Therapeutics, Inc. filed with the Securities and Exchange Commission on August 4, 2017 by Deerfield Special Situations Fund, L.P., Deerfield Partners, L.P., Deerfield International Master Fund, L.P., Deerfield Private Design Fund III, L.P., Deerfield Private Design Fund IV, L.P., Deerfield Mgmt, L.P., Deerfield Mgmt III, L.P., Deerfield Mgmt IV, L.P., Deerfield Management Company, L.P., and James E. Flynn. See footnote (1)