X0306 4 2013-02-12 1 0001356576 SUPERNUS PHARMACEUTICALS INC SUPN 0001055951 ORBIMED ADVISORS LLC 601 LEXINGTON AVENUE 54TH FLOOR NEW YORK NY 10022 0 0 1 0 0001055949 ISALY SAMUEL D 601 LEXINGTON AVENUE 54TH FLOOR NEW YORK NY 10022 0 0 1 0 0001281668 ORBIMED CAPITAL GP II LLC 601 LEXINGTON AVENUE 54TH FLOOR NEW YORK NY 10022 0 0 1 0 Common Stock 2013-02-12 4 S 0 110700 7.5218 D 2291900 I See Footnotes Common Stock 2013-02-12 4 S 0 41483 7.5218 D 858100 I See Footnotes Common Stock 2013-02-13 4 S 0 108900 7.5757 D 2183000 I See Footnotes Common Stock 2013-02-13 4 S 0 41100 7.5757 D 817000 I See Footnotes The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $7.46 to $7.60, inclusive. Upon request, the Reporting Persons undertake to provide the Issuer, any security holder of the Issuer, or the Securities and Exchange Commission, full information regarding the shares sold at each separate price within the ranges set forth in footnote (1) of this Form 4. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $7.57 to $7.66, inclusive. Upon request, the Reporting Persons undertake to provide the Issuer, any security holder of the Issuer, or the Securities and Exchange Commission, full information regarding the shares sold at each separate price within the ranges set forth in footnote (2) of this Form 4. The shares of the Issuer's common stock ("Shares") reported herein as indirectly beneficially owned by OrbiMed Capital GP II LLC ("GP II"), OrbiMed Advisors LLC ("Advisors") and Samuel D. Isaly ("Isaly") are directly owned by OrbiMed Private Investments II, LP ("OPI II") and OrbiMed Private Investments II (QP), LP ("OPI II QP"). Each of GP II, Advisors, and Isaly may be deemed to have a pecuniary interest in Shares beneficially owned by OPII and OPI II QP. This Form 4 is being jointly filed by GP II, Advisors and Isaly. These Shares are beneficially owned by OPI II. GP II is the general partner of OPI II. Advisors is the managing member of GP II. Advisors and GP II may be deemed to have beneficial ownership of Shares held by OPI II by virtue of such relationships. Isaly may be deemed to have beneficial ownership of such Shares in his capacity as the managing member of, and holder of a controlling interest, in Advisors. These Shares are beneficially owned by OPI II QP. GP II is the general partner of OPI II QP. Advisors is the managing member of GP II. Advisors and GP II may be deemed to have beneficial ownership of Shares held by OPI II QP by virtue of such relationships. Isaly may be deemed to have beneficial ownership of such Shares in his capacity as the managing member of, and holder of a controlling interest, in Advisors. Each Advisors and Isaly 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 or his pecuniary interest therein, if any. This report shall not be deemed an admission that the Reporting Persons are beneficial owners for the purpose of Section 16 of the Exchange Act, or for any other purpose. /s/ Samuel D. Isaly 2013-02-14