SEC Filing - Acadia Pharmaceuticals Inc.

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SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 ________________ Schedule 13G/A ________________ INFORMATION TO BE INCLUDED IN STATEMENTS PURSUANT TO RULES 13d-1(b),(c) AND (d) AND AMENDMENTS THERETO FILED PURSUANT TO 13d-2 UNDER THE SECURITIES EXCHANGE ACT OF 1934* (Amendment No. 1) Acadia Pharmaceuticals Inc. (Name of Issuer) Common Stock, $0.0001 par value (Title of Class of Securities) 004225108 (CUSIP Number) December 31, 2014 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pursuant to which this Schedule is filed: [ ] Rule 13d-1(b) [X] Rule 13d-1(c) [ ] Rule 13d-1(d) ___________ * The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page. The information required in the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

Schedule 13G/A PAGE 2 of 17 CUSIP No. 004225108 _____________________________________________________________________________ (1) NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON Viking Global Investors LP _____________________________________________________________________________ (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) [ ] (b) [x] _____________________________________________________________________________ (3) SEC USE ONLY _____________________________________________________________________________ (4) CITIZENSHIP OR PLACE OF ORGANIZATION Delaware _____________________________________________________________________________ NUMBER OF (5) SOLE VOTING POWER 0 SHARES ______________________________________________________________ BENEFICIALLY (6) SHARED VOTING POWER 2,956,266 OWNED BY ______________________________________________________________ EACH (7) SOLE DISPOSITIVE POWER 0 REPORTING ______________________________________________________________ PERSON WITH (8) SHARED DISPOSITIVE POWER 2,956,266 _____________________________________________________________________________ (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,956,266 _____________________________________________________________________________ (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES [ ] _____________________________________________________________________________ (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 3.0% _____________________________________________________________________________ (12) TYPE OF REPORTING PERSON PN _____________________________________________________________________________

Schedule 13G/A PAGE 3 of 17 CUSIP No. 004225108 _____________________________________________________________________________ (1) NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON Viking Global Performance LLC _____________________________________________________________________________ (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) [ ] (b) [x] _____________________________________________________________________________ (3) SEC USE ONLY _____________________________________________________________________________ (4) CITIZENSHIP OR PLACE OF ORGANIZATION Delaware _____________________________________________________________________________ NUMBER OF (5) SOLE VOTING POWER 0 SHARES ______________________________________________________________ BENEFICIALLY (6) SHARED VOTING POWER 2,096,660 OWNED BY ______________________________________________________________ EACH (7) SOLE DISPOSITIVE POWER 0 REPORTING ______________________________________________________________ PERSON WITH (8) SHARED DISPOSITIVE POWER 2,096,660 _____________________________________________________________________________ (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,096,660 _____________________________________________________________________________ (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES [ ] _____________________________________________________________________________ (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 2.1% _____________________________________________________________________________ (12) TYPE OF REPORTING PERSON OO _____________________________________________________________________________

Schedule 13G/A PAGE 4 of 17 CUSIP No. 004225108 _____________________________________________________________________________ (1) NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON Viking Global Equities LP _____________________________________________________________________________ (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) [ ] (b) [x] _____________________________________________________________________________ (3) SEC USE ONLY _____________________________________________________________________________ (4) CITIZENSHIP OR PLACE OF ORGANIZATION Delaware _____________________________________________________________________________ NUMBER OF (5) SOLE VOTING POWER 0 SHARES ______________________________________________________________ BENEFICIALLY (6) SHARED VOTING POWER 714,963 OWNED BY ______________________________________________________________ EACH (7) SOLE DISPOSITIVE POWER 0 REPORTING ______________________________________________________________ PERSON WITH (8) SHARED DISPOSITIVE POWER 714,963 _____________________________________________________________________________ (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 714,963 _____________________________________________________________________________ (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES [ ] _____________________________________________________________________________ (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 0.7% _____________________________________________________________________________ (12) TYPE OF REPORTING PERSON PN _____________________________________________________________________________

Schedule 13G/A PAGE 5 of 17 CUSIP No. 004225108 _____________________________________________________________________________ (1) NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON Viking Global Equities II LP _____________________________________________________________________________ (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) [ ] (b) [x] _____________________________________________________________________________ (3) SEC USE ONLY _____________________________________________________________________________ (4) CITIZENSHIP OR PLACE OF ORGANIZATION Delaware _____________________________________________________________________________ NUMBER OF (5) SOLE VOTING POWER 0 SHARES ______________________________________________________________ BENEFICIALLY (6) SHARED VOTING POWER 41,936 OWNED BY ______________________________________________________________ EACH (7) SOLE DISPOSITIVE POWER 0 REPORTING ______________________________________________________________ PERSON WITH (8) SHARED DISPOSITIVE POWER 41,936 _____________________________________________________________________________ (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 41,936 _____________________________________________________________________________ (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES [ ] _____________________________________________________________________________ (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 0.0% _____________________________________________________________________________ (12) TYPE OF REPORTING PERSON PN _____________________________________________________________________________

Schedule 13G/A PAGE 6 of 17 CUSIP No. 004225108 _____________________________________________________________________________ (1) NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON VGE III Portfolio Ltd. _____________________________________________________________________________ (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) [ ] (b) [x] _____________________________________________________________________________ (3) SEC USE ONLY _____________________________________________________________________________ (4) CITIZENSHIP OR PLACE OF ORGANIZATION Cayman Islands _____________________________________________________________________________ NUMBER OF (5) SOLE VOTING POWER 0 SHARES ______________________________________________________________ BENEFICIALLY (6) SHARED VOTING POWER 1,339,761 OWNED BY ______________________________________________________________ EACH (7) SOLE DISPOSITIVE POWER 0 REPORTING ______________________________________________________________ PERSON WITH (8) SHARED DISPOSITIVE POWER 1,339,761 _____________________________________________________________________________ (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 1,339,761 _____________________________________________________________________________ (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES [ ] _____________________________________________________________________________ (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 1.3% _____________________________________________________________________________ (12) TYPE OF REPORTING PERSON CO _____________________________________________________________________________

Schedule 13G/A PAGE 7 of 17 CUSIP No. 004225108 _____________________________________________________________________________ (1) NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON Viking Long Fund GP LLC _____________________________________________________________________________ (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) [ ] (b) [x] _____________________________________________________________________________ (3) SEC USE ONLY _____________________________________________________________________________ (4) CITIZENSHIP OR PLACE OF ORGANIZATION Delaware _____________________________________________________________________________ NUMBER OF (5) SOLE VOTING POWER 0 SHARES ______________________________________________________________ BENEFICIALLY (6) SHARED VOTING POWER 859,606 OWNED BY ______________________________________________________________ EACH (7) SOLE DISPOSITIVE POWER 0 REPORTING ______________________________________________________________ PERSON WITH (8) SHARED DISPOSITIVE POWER 859,606 _____________________________________________________________________________ (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 859,606 _____________________________________________________________________________ (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES [ ] _____________________________________________________________________________ (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 0.9% _____________________________________________________________________________ (12) TYPE OF REPORTING PERSON OO _____________________________________________________________________________

Schedule 13G/A PAGE 8 of 17 CUSIP No. 004225108 _____________________________________________________________________________ (1) NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON Viking Long Fund Master Ltd. _____________________________________________________________________________ (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) [ ] (b) [x] _____________________________________________________________________________ (3) SEC USE ONLY _____________________________________________________________________________ (4) CITIZENSHIP OR PLACE OF ORGANIZATION Cayman Islands _____________________________________________________________________________ NUMBER OF (5) SOLE VOTING POWER 0 SHARES ______________________________________________________________ BENEFICIALLY (6) SHARED VOTING POWER 859,606 OWNED BY ______________________________________________________________ EACH (7) SOLE DISPOSITIVE POWER 0 REPORTING ______________________________________________________________ PERSON WITH (8) SHARED DISPOSITIVE POWER 859,606 _____________________________________________________________________________ (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 859,606 _____________________________________________________________________________ (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES [ ] _____________________________________________________________________________ (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 0.9% _____________________________________________________________________________ (12) TYPE OF REPORTING PERSON CO _____________________________________________________________________________

Schedule 13G/A PAGE 9 of 17 CUSIP No. 004225108 _____________________________________________________________________________ (1) NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON O. Andreas Halvorsen _____________________________________________________________________________ (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) [ ] (b) [x] _____________________________________________________________________________ (3) SEC USE ONLY _____________________________________________________________________________ (4) CITIZENSHIP OR PLACE OF ORGANIZATION Norway _____________________________________________________________________________ NUMBER OF (5) SOLE VOTING POWER 0 SHARES ______________________________________________________________ BENEFICIALLY (6) SHARED VOTING POWER 2,956,266 OWNED BY ______________________________________________________________ EACH (7) SOLE DISPOSITIVE POWER 0 REPORTING ______________________________________________________________ PERSON WITH (8) SHARED DISPOSITIVE POWER 2,956,266 _____________________________________________________________________________ (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,956,266 _____________________________________________________________________________ (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES [ ] _____________________________________________________________________________ (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 3.0% _____________________________________________________________________________ (12) TYPE OF REPORTING PERSON IN _____________________________________________________________________________

Schedule 13G/A PAGE 10 of 17 CUSIP No. 004225108 _____________________________________________________________________________ (1) NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON David C. Ott _____________________________________________________________________________ (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) [ ] (b) [x] _____________________________________________________________________________ (3) SEC USE ONLY _____________________________________________________________________________ (4) CITIZENSHIP OR PLACE OF ORGANIZATION United States _____________________________________________________________________________ NUMBER OF (5) SOLE VOTING POWER 0 SHARES ______________________________________________________________ BENEFICIALLY (6) SHARED VOTING POWER 2,956,266 OWNED BY ______________________________________________________________ EACH (7) SOLE DISPOSITIVE POWER 0 REPORTING ______________________________________________________________ PERSON WITH (8) SHARED DISPOSITIVE POWER 2,956,266 _____________________________________________________________________________ (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,956,266 _____________________________________________________________________________ (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES [ ] _____________________________________________________________________________ (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 3.0% _____________________________________________________________________________ (12) TYPE OF REPORTING PERSON IN _____________________________________________________________________________

Schedule 13G/A PAGE 11 of 17 CUSIP No. 004225108 _____________________________________________________________________________ (1) NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON Thomas W. Purcell, Jr. _____________________________________________________________________________ (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) [ ] (b) [x] _____________________________________________________________________________ (3) SEC USE ONLY _____________________________________________________________________________ (4) CITIZENSHIP OR PLACE OF ORGANIZATION United States _____________________________________________________________________________ NUMBER OF (5) SOLE VOTING POWER 0 SHARES ______________________________________________________________ BENEFICIALLY (6) SHARED VOTING POWER 2,956,266 OWNED BY ______________________________________________________________ EACH (7) SOLE DISPOSITIVE POWER 0 REPORTING ______________________________________________________________ PERSON WITH (8) SHARED DISPOSITIVE POWER 2,956,266 _____________________________________________________________________________ (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,956,266 _____________________________________________________________________________ (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES [ ] _____________________________________________________________________________ (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 3.0% _____________________________________________________________________________ (12) TYPE OF REPORTING PERSON IN _____________________________________________________________________________

Schedule 13G/A PAGE 12 of 17 CUSIP No. 004225108 _____________________________________________________________________________ (1) NAME OF REPORTING PERSON S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON Daniel S. Sundheim _____________________________________________________________________________ (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) [ ] (b) [x] _____________________________________________________________________________ (3) SEC USE ONLY _____________________________________________________________________________ (4) CITIZENSHIP OR PLACE OF ORGANIZATION United States _____________________________________________________________________________ NUMBER OF (5) SOLE VOTING POWER 0 SHARES ______________________________________________________________ BENEFICIALLY (6) SHARED VOTING POWER 2,956,266 OWNED BY ______________________________________________________________ EACH (7) SOLE DISPOSITIVE POWER 0 REPORTING ______________________________________________________________ PERSON WITH (8) SHARED DISPOSITIVE POWER 2,956,266 _____________________________________________________________________________ (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,956,266 _____________________________________________________________________________ (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES [ ] _____________________________________________________________________________ (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 3.0% _____________________________________________________________________________ (12) TYPE OF REPORTING PERSON IN _____________________________________________________________________________

Schedule 13G/A PAGE 13 of 17 CUSIP No. 004225108 ITEM 1(a). NAME OF ISSUER: Acadia Pharmaceuticals Inc. ITEM 1(b). ADDRESS OF ISSUER'S PRINCIPAL EXECUTIVE OFFICES: 11085 Torreyana Road, Suite 100 San Diego, California 92121 ITEM 2(a). NAME OF PERSON FILING: Viking Global Performance LLC ("VGP"), Viking Global Investors LP ("VGI"), Viking Global Equities LP ("VGE"), Viking Global Equities II LP ("VGEII"), VGE III Portfolio Ltd. ("VGEIII"), Viking Long Fund GP LLC ("VLFGP"), Viking Long Fund Master Ltd. ("VLFM"), O. Andreas Halvorsen, David C. Ott, Thomas W. Purcell, Jr. and Daniel S. Sundheim (collectively, the "Reporting Persons") ITEM 2(b). ADDRESS OF PRINCIPAL OFFICE OR, IF NONE, RESIDENCE: The business address of each of the Reporting Persons is 55 Railroad Avenue, Greenwich, Connecticut 06830. ITEM 2(c). CITIZENSHIP: VGE, VGEII and VGI are Delaware limited partnerships, VGEIII and VLFM are Cayman Islands exempted companies, and VGP and VLFGP are both Delaware limited liability companies. O. Andreas Halvorsen is a citizen of Norway. David C. Ott, Thomas W. Purcell, Jr. and Daniel S. Sundheim are citizens of the United States. ITEM 2(d). TITLE OF CLASS OF SECURITIES: Common Stock, $0.0001 par value ("Common Stock") ITEM 2(e). CUSIP NUMBER: 004225108 ITEM 3. IF THIS STATEMENT IS FILED PURSUANT TO 13d-1(b) OR 13d-2(b) OR (c), CHECK WHETHER THE PERSON FILING IS A: (a) [ ] Broker or dealer registered under Section 15 of the Act (b) [ ] Bank as defined in Section 3(a)(6) of the Act (c) [ ] Insurance Company as defined in Section 3(a)(19) of the Act (d) [ ] Investment Company registered under Section 8 of the Investment Company Act of 1940 (e) [ ] Investment Adviser registered under Section 203 of the Investment Advisers Act of 1940: see Rule 13d- 1(b)(1)(ii)(E) (f) [ ] Employee Benefit Plan, Pension Fund which is subject to the provisions of the Employee Retirement Income Security Act of 1974 or Endowment Fund; see Rule 13d- 1(b)(1)(ii)(F)

Schedule 13G/A PAGE 14 of 17 CUSIP No. 004225108 (g) [ ] Parent Holding Company, in accordance with Rule 13d- 1(b)(ii)(G) (h) [ ] Savings Associations as defined in Section 3(b) of the Federal Deposit Insurance Act (i) [ ] Church Plan that is excluded from the definition of an investment company under Section 3(c)(14) of the Investment Company Act of 1940 (j) [ ] A non-U.S. institution in accordance with Rule 240.13d-1(b)(1)(ii)(J) (k) [ ] Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K). If filing as a non-U.S. institution in accordance with Rule 240.13d-1(b)(1)(ii)(J), please specify the type of institution: ITEM 4. OWNERSHIP. A. VGI (a) Amount beneficially owned: 2,956,266 (b) Percent of class: 3.0% The percentages used herein and in this Item 4 are calculated based upon the Company's Form 10-Q for the quarterly period ended September 30, 2014 filed on November 10, 2014, which states that as of October 31, 2014 there were 99,770,300 shares of Common Stock outstanding. (c) Number of shares as to which such person has: (i) sole power to vote or to direct the vote 0 (ii) shared power to vote or to direct the vote 2,956,266 (iii) sole power to dispose or to direct the disposition of 0 (iv) shared power to dispose or to direct the disposition of 2,956,266 VGI provides managerial services to VGE, VGEII,VGEIII and VLFM. VGI has the authority to dispose of and vote the shares of Common Stock. Based on Rule 13d-3 of the Securities Exchange Act of 1934, as amended (the "Act"), VGI may be deemed to beneficially own the shares of Common Stock directly held by VGE, VGEII, VGEIII and VLFM. VGI does not directly own any shares of Common Stock.

Schedule 13G/A PAGE 15 of 17 CUSIP No. 004225108 B. VGP (a) Amount beneficially owned: 2,096,660 (b) Percent of class: 2.1% (c) Number of shares as to which such person has: (i) sole power to vote or to direct the vote 0 (ii) shared power to vote or to direct the vote 2,096,660 (iii) sole power to dispose or to direct the disposition of 0 (iv) shared power to dispose or to direct the disposition of 2,096,660 VGP, as the general partner of VGE and VGEII, has the authority to dispose of and vote the shares of Common Stock directly owned by VGE and VGEII. VGP serves as investment manager to VGEIII and has the authority to dispose of and vote the shares of Common Stock directly owned by VGEIII. VGP does not directly own any shares of Common Stock. Based on Rule 13d-3 of the Act, VGP may be deemed to beneficially own the shares of Common Stock directly held by VGE, VGEII and VGEIII. C. VLFGP (a) Amount beneficially owned: 859,606 (b) Percent of class: 0.9% (c) Number of shares as to which such person has: (i) sole power to vote or to direct the vote 0 (ii) shared power to vote or to direct the vote 859,606 (iii) sole power to dispose or to direct the disposition of 0 (iv) shared power to dispose or to direct the disposition of 859,606 VLFGP serves as the investment manager of VLFM and has the authority to dispose of and vote the shares of Common Stock directly owned by VLFM. VLFGP does not directly own any shares of Common Stock. Based on Rule 13d-3 of the Act, VLFGP may be deemed to beneficially own the shares of Common Stock directly held by VLFM. D. VGE (a) Amount beneficially owned: 714,963 (b) Percent of class: 0.7% (c) Number of shares as to which such person has: (i) sole power to vote or to direct the vote 0 (ii) shared power to vote or to direct the vote 714,963 (iii) sole power to dispose or to direct the disposition of 0 (iv) shared power to dispose or to direct the disposition of 714,963 VGE has the authority to dispose of and vote the shares of Common Stock directly owned by it, which power may be exercised by its general partner, VGP, and by VGI, an affiliate of VGP, which provides managerial services to VGE. E. VGEII (a) Amount beneficially owned: 41,936 (b) Percent of class: 0.0% (c) Number of shares as to which such person has: (i) sole power to vote or to direct the vote 0 (ii) shared power to vote or to direct the vote 41,936 (iii) sole power to dispose or to direct the disposition of 0 (iv) shared power to dispose or to direct the disposition of 41,936 VGEII has the authority to dispose of and vote the shares of Common Stock directly owned by it, which power may be exercised by its general partner, VGP, and by VGI, an affiliate of VGP, which provides managerial services to VGEII. F. VGEIII (a) Amount beneficially owned: 1,339,761 (b) Percent of class: 1.3% (c) Number of shares as to which such person has: (i) sole power to vote or to direct the vote 0 (ii) shared power to vote or to direct the vote 1,339,761 (iii) sole power to dispose or to direct the disposition of 0 (iv) shared power to dispose or to direct the disposition of 1,339,761 VGEIII has the authority to dispose of and vote the shares of Common Stock directly owned by it, which power may be exercised by its investment manager, VGP, and by VGI, an affiliate of VGP, which provides managerial services to VGEIII. Viking Global Equities III Ltd. (a Cayman Islands exempted company) invests substantially all of its assets through VGEIII. G. VLFM (a) Amount beneficially owned: 859,606 (b) Percent of class: 0.9% (c) Number of shares as to which such person has: (i) sole power to vote or to direct the vote 0 (ii) shared power to vote or to direct the vote 859,606 (iii) sole power to dispose or to direct the disposition of 0 (iv) shared power to dispose or to direct the disposition of 859,606 VLFM has the authority to dispose of and vote the shares of Common Stock directly owned by it, which power may be exercised by its investment manager, VLFGP, and by VGI, an affiliate of VLFGP, which provides managerial services to VLFM. Viking Long Fund LP (a Delaware limited partnership) and Viking Long Fund III Ltd. (a Cayman Islands exempted company), through its investment in Viking Long Fund Intermediate LP (a Cayman Islands limited partnership), invest substantially all of their assets through VLFM.

Schedule 13G/A PAGE 16 of 17 CUSIP No. 004225108 H. O. Andreas Halvorsen, David C. Ott, Thomas W. Purcell, Jr. and Daniel S. Sundheim (a) Amount beneficially owned: 2,956,266 (b) Percent of class: 3.0% (c) Number of shares as to which such person has: (i) sole power to vote or to direct the vote 0 (ii) shared power to vote or to direct the vote 2,956,266 (iii) sole power to dispose or to direct the disposition of 0 (iv) shared power to dispose or to direct the disposition of 2,956,266 Messrs. Halvorsen, Ott, Purcell and Sundheim, as Executive Committee Members of VGI, VGP and VLFGP, have shared authority to dispose of and vote the shares of Common Stock beneficially owned by VGI, VGP and VLFGP. None of Messrs. Halvorsen, Ott, Purcell and Sundheim directly owns any shares of Common Stock. Based on Rule 13d-3 of the Act, each may be deemed to beneficially own the shares of Common Stock directly held by VGE, VGE II, VGEIII and VLFM. ITEM 5. OWNERSHIP OF FIVE PERCENT OR LESS OF A CLASS. If this statement is being filed to report the fact that as of the date hereof the Reporting Persons has ceased to be the beneficial owner of more than five percent of the class of securities, check the following.[X] ITEM 6. OWNERSHIP OF MORE THAN FIVE PERCENT ON BEHALF OF ANOTHER PERSON. Not applicable. ITEM 7. IDENTIFICATION AND CLASSIFICATION OF THE SUBSIDIARY WHICH ACQUIRED THE SECURITY BEING REPORTED ON BY THE PARENT HOLDING COMPANY. Not applicable. ITEM 8. IDENTIFICATION AND CLASSIFICATION OF MEMBERS OF THE GROUP. Not applicable. ITEM 9. NOTICE OF DISSOLUTION OF GROUP. Not applicable. ITEM 10. CERTIFICATION. (if filing pursuant to Rule 13d-1(c)) By signing below each Reporting Person certifies that, to the best of its knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and not held in connection with or as a participant in any transaction having that purpose or effect.

Schedule 13G/A PAGE 17 of 17 CUSIP No. 004225108 SIGNATURES After reasonable inquiry and to the best of our knowledge and belief, the undersigned certify that the information set forth in this statement is true, complete and correct. DATED: February 17, 2015 /s/ O. ANDREAS HALVORSEN By: O. Andreas Halvorsen - individually and as an Executive Committee Member of VIKING GLOBAL PERFORMANCE LLC, on behalf of itself and VIKING GLOBAL EQUITIES LP, VIKING GLOBAL EQUITIES II LP,VGE III PORTFOLIO LTD. and as an Executive Committee Member of Viking Global Partners LLC, on behalf of VIKING GLOBAL INVESTORS LP, and as an Executive Committee Member of VIKING LONG FUND GP LLC on behalf of itself and VIKING LONG FUND MASTER LTD. /s/ DAVID C. OTT By: David C. Ott - individually and as an Executive Committee Member of VIKING GLOBAL PERFORMANCE LLC, on behalf of itself and VIKING GLOBAL EQUITIES LP, VIKING GLOBAL EQUITIES II LP,VGE III PORTFOLIO LTD. and as an Executive Committee Member of Viking Global Partners LLC, on behalf of VIKING GLOBAL INVESTORS LP, and as an Executive Committee Member of VIKING LONG FUND GP LLC on behalf of itself and VIKING LONG FUND MASTER LTD. /s/ THOMAS W. PURCELL, JR. By: Thomas W. Purcell, Jr. - individually and as an Executive Committee Member of VIKING GLOBAL PERFORMANCE LLC, on behalf of itself and VIKING GLOBAL EQUITIES LP, VIKING GLOBAL EQUITIES II LP,VGE III PORTFOLIO LTD. and as an Executive Committee Member of Viking Global Partners LLC, on behalf of VIKING GLOBAL INVESTORS LP, and as an Executive Committee Member of VIKING LONG FUND GP LLC on behalf of itself and VIKING LONG FUND MASTER LTD. /s/ DANIEL S. SUNDHEIM By: Daniel S. Sundheim - individually and as an Executive Committee Member of VIKING GLOBAL PERFORMANCE LLC, on behalf of itself and VIKING GLOBAL EQUITIES LP, VIKING GLOBAL EQUITIES II LP,VGE III PORTFOLIO LTD. and as an Executive Committee Member of Viking Global Partners LLC, on behalf of VIKING GLOBAL INVESTORS LP, and as an Executive Committee Member of VIKING LONG FUND GP LLC on behalf of itself and VIKING LONG FUND MASTER LTD.