Sec Form 4 Filing - MAVERICK CAPITAL LTD @ CASTLIGHT HEALTH, INC. - 2018-06-20

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 MAVERICK CAPITAL LTD 2. Issuer Name and Ticker or Trading Symbol CASTLIGHT HEALTH, INC. [ CSLT] 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) 300 CRESCENT COURT, 18TH FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 06/20/2018 (Street) DALLAS, TX75201 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 Class B common stock 06/20/2018 A 32,183 ( 1 ) A $ 0 1,771,350 I ( 2 ) See footnote ( 3 )

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

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other MAVERICK CAPITAL LTD 300 CRESCENT COURT 18TH FLOOR DALLAS, TX75201 X MAVERICK CAPITAL MANAGEMENT LLC 300 CRESCENT COURT 18TH FLOOR DALLAS, TX75201 X AINSLIE LEE S III 767 FIFTH AVENUE 11TH FLOOR NEW YORK, NY10153 X Warford Andrew Held 300 CRESCENT COURT, 18TH FLOOR DALLAS, TX75201 X Signatures /s/ Trevor Wiessmann, Attorney-in-Fact 06/22/2018 Signature of Reporting Person Date /s/ Trevor Wiessmann, Attorney-in-Fact 06/22/2018 Signature of Reporting Person Date /s/ Trevor Wiessmann, Attorney-in-Fact 06/22/2018 Signature of Reporting Person Date /s/ Trevor Wiessmann, Attorney-in-Fact 06/22/2018 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Represents an award of restricted stock units ("RSUs") to David B. Singer. The RSUs will vest in four equal quarterly installments during the first year following the date of grant. Each RSU represents a contingent right to receive one share of the Issuer's Class B common stock upon settlement for no consideration. ( 2 )Of the shares of Class B Common Stock ("Shares") reported, 32,183 represent RSUs held by Mr. Singer and 77,125 represent Shares which prior to conversion, were held by Mr. Singer as RSUs, in each case, for the benefit of entities managed by Maverick Capital, Ltd. ("Maverick Capital"). Mr. Singer is an employee of an affiliate of Maverick Capital. ( 3 )Maverick Capital is a registered investment adviser under the Investment Advisers Act of 1940, as amended, and acts as the investment manager for each of the portfolio funds for which Mr. Singer holds the RSUs. Maverick Capital Management, LLC ("Maverick Management") is the general partner of Maverick Capital. Lee S. Ainslie III is the manager of Maverick Management. Andrew H. Warford serves as the Chairman of the Stock Committee of Maverick Capital. Each reporting owner disclaims beneficial ownership of the reported securities except to the extent of its pecuniary interest therein.

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

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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