Sec Form 4 Filing - BAKER BROS. ADVISORS LP @ Mirati Therapeutics, Inc. - 2015-09-16

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person BAKER BROS. ADVISORS LP 2. Issuer Name and Ticker or Trading Symbol Mirati Therapeutics, Inc. [ MRTX] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 667 MADISON AVENUE, 21ST FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 09/16/2015 (Street) NEW YORK, NYUS 10065 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 40,308 I See Footnote ( 1 ) ( 5 ) Common Stock 09/16/2015 P 10,780 A $ 45 170,714 I See Footnote ( 2 ) ( 3 ) ( 5 ) Common Stock 09/16/2015 P 139,220 A $ 45 2,744,052 I See Footnote ( 2 ) ( 4 ) ( 5 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Common Stock Warrants (right to buy) $ 6.74 09/16/2015 J( 6 ) 274 04/04/2011 04/04/2016 Common Stock 274 $ 0 0 I See Footnote ( 5 ) ( 6 ) Common Stock Warrants (right to buy) $ 6.74 09/16/2015 J( 6 ) 137 ( 7 ) 04/04/2011 04/04/2016 Common Stock 137 $ 0 137 D Common Stock Warrants (right to buy) $ 6.74 09/16/2015 J( 6 ) 137 ( 8 ) 04/04/2011 04/04/2016 Common Stock 137 $ 0 137 D Common Stock Warrants (right to buy) $ 6.74 04/04/2011 04/04/2016 Common Stock 310,003 310,003 I See Footnote ( 5 ) ( 9 ) Common Stock Warrants (right to buy) $ 6.74 04/04/2011 04/04/2016 Common Stock 3,479 3,479 I See Footnote ( 5 ) ( 10 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other BAKER BROS. ADVISORS LP 667 MADISON AVENUE, 21ST FLOOR NEW YORK, NYUS 10065 X BAKER FELIX 667 MADISON AVENUE, 21ST FLOOR NEW YORK, NYUS 10065 X BAKER JULIAN 667 MADISON AVENUE, 21ST FLOOR NEW YORK, NYUS 10065 X Baker Bros. Advisors (GP) LLC 667 MADISION AVENUE 21ST FLOOR NEW YORK, NYUS 10065 X Signatures By: Baker Bros. Advisors LP Name: Scott L. Lessing Title: President /s/ Scott L. Lessing 09/16/2015 Signature of Reporting Person Date /s/ Felix J. Baker 09/16/2015 Signature of Reporting Person Date /s/ Julian C. Baker 09/16/2015 Signature of Reporting Person Date BY: Name: Scott L. Lessing Title: President /s/ Scott L. Lessing 09/16/2015 Signature of Reporting Person Date Baker Bros. Advisors LP, Mgmt. Co. and Inv. Adviser to BAKER BROTHERS LIFE SCIENCES, L.P., pursuant to authority granted by Baker Brothers Life Sciences Capital, L.P., GP to Baker 09/16/2015 Signature of Reporting Person Date Baker Bros. Advisors LP, Mgmt. Co. and Inv. Adviser to 667, L.P., pursuant to authority granted by Baker Biotech Capital, L.P., GP to 667, L.P. Title President /s/ Scott L. Lessing 09/16/2015 Signature of Reporting Person Date Baker Bros. Advisors LP, Mgmt. Co. and Inv. Adviser to Baker Bros. Investments II, L.P., pursuant to authority granted by Baker Bros. Capital, L.P., GP to Baker Bros. Investments II, L.P. Title President /s/ Scott L. Lessing 09/16/2015 Signature of Reporting Person Date

Explanation of Responses:

( 1 )As a result of their ownership interest in 14159 Capital (GP), LLC, Julian C. Baker and Felix J. Baker may be deemed to have an indirect pecuniary interest in 40,308 shares of Common Stock of Mirati Therapeutics, Inc. (the "Issuer") directly held by 14159, L.P. ("14159"), a limited partnership of which the sole general partner is 14159 Capital, L.P., a limited partnership of which the sole general partner is 14159 Capital (GP), LLC, due to 14159 Capital, L.P.'s right to receive an allocation of a portion of the profits from 14159. ( 2 )On September 16, 2015, 667, L.P.("667") and Baker Brothers Life Sciences, L.P. ("Life Sciences") purchased 10,780 and 139,220 shares of the Common Stock of the Issuer, respectively, pursuant to an underwritten public offering. ( 3 )After giving effect to the transaction reported herein, and as a result of their ownership interest in Baker Biotech Capital (GP), LLC, Julian C. Baker and Felix J. Baker may be deemed to have an indirect pecuniary interest in the Issuer's shares of Common Stock reported in column 5 of Table I directly held by 667, a limited partnership of which the sole general partner is Baker Biotech Capital, L.P., a limited partnership of which the sole general partner is Baker Biotech Capital (GP), LLC, due to Baker Biotech Capital, L.P.'s right to receive an allocation of a portion of the profits from 667. ( 4 )After giving effect to the transaction reported herein, and as a result of their ownership interest in Baker Brothers Life Sciences Capital (GP), LLC, Julian C. Baker and Felix J. Baker may be deemed to have an indirect pecuniary interest in the Issuer's shares of Common Stock reported in column 5 of Table I directly held by Life Sciences, a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital, L.P., a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital (GP), LLC, due to Baker Brothers Life Sciences Capital, L.P.'s right to receive an allocation of a portion of the profits from Life Sciences. ( 5 )Baker Bros. Advisors LP (the "Adviser") serves as the Investment Adviser to 14159, Life Sciences, and Baker Bros. Investments II, L.P. (collectively, the "Funds"). In connection with the services provided by the Adviser, the Adviser receives an asset-based management fee that does not confer any pecuniary interest in the securities held by the Funds. Baker Bros. Advisors (GP) LLC (the "Adviser GP") is the Adviser's sole general partner. Julian C. Baker and Felix J. Baker are principals of the Adviser GP. The Adviser has complete and unlimited discretion and authority with respect to the investment and voting power of the securities held by the Funds. The general partners of the Funds relinquished to the Adviser all discretion and authority with respect to the investment and voting power of the securities held by the Funds. Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held directly by the Funds except to the extent of their pecuniary interest therein, and this report shall not be deemed an admission that any of Julian C. Baker, Felix J. Baker, the Adviser GP or the Adviser is a beneficial owner of such securities for purposes of Section 16 or any other purpose. ( 6 )Represents 137 warrants to purchase Common Stock of the Issuer distributed by Baker Bros. Investments II, L.P. to each of Julian C. Baker and Felix J. Baker as part of an in-kind pro rata distribution in accordance with the pecuniary interest of Felix J. Baker and Julian C. Baker in Baker Bros. Investments II, L.P. for no consideration. ( 7 )Reflects warrants to purchase Common Stock of the Issuer held by Felix J. Baker received in the in-kind pro rata distribution without consideration reported above. Such distribution did not result in a change in pecuniary interest. ( 8 )Reflects warrants to purchase Common Stock of the Issuer held by Julian C. Baker received in the in-kind pro rata distribution without consideration reported above. Such distribution did not result in a change in pecuniary interest. ( 9 )As a result of their ownership interest in Baker Brothers Life Sciences Capital (GP), LLC, Felix J. Baker and Julian C. Baker may be deemed to have an indirect pecuniary interest in 310,003 warrants to purchase Common Stock of the Issuer beneficially owned by Life Sciences, a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital, L.P., a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital (GP), LLC, due to Baker Brothers Life Sciences Capital, L.P.'s right to receive an allocation of a portion of the profits from Life Sciences. ( 10 )As a result of their ownership interest in 14159 Capital (GP), LLC, Felix J. Baker and Julian C. Baker may be deemed to have an indirect pecuniary interest in 3,479 warrants to purchase Common Stock of the Issuer beneficially owned by 14159, a limited partnership of which the sole general partner is 14159 Capital, L.P., a limited partnership of which the sole general partner is 14159 Capital (GP), LLC, due to 14159 Capital, L.P.'s right to receive an allocation of a portion of the profits from 14159.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

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