Statement of Changes in Beneficial Ownership (4)

FORM 4 [ X ] 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 OF SECURITIES	OMB APPROVAL OMB Number: 3235-0287 Estimated average burden hours per response... 0.5
	Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

1. Name and Address of Reporting Person ^* Christianson Gary	2. Issuer Name and Ticker or Trading Symbol Cascadian Therapeutics, Inc. [ CASC ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __ X __ Officer (give title below) _____ Other (specify below) Chief Operating Officer
(Last) (First) (Middle) C/O CASCADIAN THERAPEUTICS, INC., 3101 WESTERN AVE., SUITE 600	3. Date of Earliest Transaction (MM/DD/YYYY) 3/9/2018
(Street) SEATTLE, WA 98121 (City) (State) (Zip)	4. If Amendment, Date Original Filed (MM/DD/YYYY)	6. Individual or Joint/Group Filing (Check Applicable Line) _ X _ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security (Instr. 3)	2. Trans. Date	2A. Deemed Execution Date, if any	3. Trans. 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)
1.Title of Security (Instr. 3)	2. Trans. Date	2A. Deemed Execution Date, if any	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Stock	3/9/2018		U		6515	D	⁽¹⁾	0	D

*Table II - Derivative Securities Beneficially Owned ( e.g.* , puts, calls, warrants, options, convertible securities)**
1. Title of Derivate Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Trans. Date	3A. Deemed Execution Date, if any	4. Trans. 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		7. Title and Amount of Securities Underlying Derivative Security (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)
1. Title of Derivate Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Trans. Date	3A. Deemed Execution Date, if any	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)			11. Nature of Indirect Beneficial Ownership (Instr. 4)
Stock Option (Right to buy)	$19.92	3/9/2018		D			8334	⁽²⁾	12/1/2018	Common Stock	8334	⁽³⁾	0	D
Stock Option (Right to buy)	$41.52	3/9/2018		D			8334	⁽⁴⁾	12/1/2019	Common Stock	8334	⁽³⁾	0	D
Stock Option (Right to buy)	$28.44	3/9/2018		D			8334	⁽⁵⁾	12/12/2020	Common Stock	8334	⁽³⁾	0	D
Stock Option (Right to buy)	$10.44	3/9/2018		D			25000	⁽⁶⁾	12/12/2021	Common Stock	25000	⁽³⁾	0	D
Stock Option (Right to buy)	$10.56	3/9/2018		D			16667	⁽⁷⁾	12/16/2022	Common Stock	16667	⁽³⁾	0	D
Stock Option (Right to buy)	$21.06	3/9/2018		D			41667	⁽⁸⁾	9/24/2023	Common Stock	41667	⁽³⁾	0	D
Stock Option (Right to buy)	$6.90	3/9/2018		D			41667	⁽⁹⁾	5/17/2024	Common Stock	41667	⁽¹⁰⁾	0	D
Stock Option (Right to buy)	$4.64	3/9/2018		D			51200	⁽¹¹⁾	1/11/2027	Common Stock	51200	⁽¹²⁾	0	D
Stock Option (Right to buy)	$3.99	3/9/2018		D			68000	⁽¹³⁾	9/18/2027	Common Stock	68000	⁽¹⁴⁾	0	D
Restricted Stock Units	⁽¹⁵⁾	3/9/2018		D			11300	⁽¹⁶⁾	⁽¹⁷⁾	Common Stock	11300	⁽¹⁵⁾	0	D
Restricted Stock Units	⁽¹⁸⁾	3/9/2018		D			15000	⁽¹⁹⁾	⁽¹⁷⁾	Common Stock	15000	⁽¹⁸⁾	0	D
Restricted Stock Units	⁽²⁰⁾	3/9/2018		D			164500	⁽²¹⁾	⁽¹⁷⁾	Common Stock	164500	⁽²⁰⁾	0	D

Explanation of Responses:
(1)	Shares of Common Stock tendered in the tender offer launched by Valley Acquisition Sub, Inc. on February 8, 2018 pursuant to that certain Agreement and Plan of Merger, dated January 30, 2018, among Seattle Genetics, Inc., Valley Acquisition Sub, Inc., and Cascadian Therapeutics, Inc. (the "Merger Agreement"), to acquire all of the outstanding shares of common stock of Cascadian Therapeutics, Inc., par value $0.0001 per share, at a purchase price of $10.00 per share ("Offer Price"), net to the seller in cash, without interest and less any required withholding taxes.
(2)	25% of the shares subject to the option vest on the first anniversary of the grant date of December 1, 2010, and the remainder vest monthly thereafter for 36 months.
(3)	Pursuant to the Merger Agreement, the option was cancelled and terminated without payment because the exercise price exceeded the Offer Price.
(4)	25% of the shares subject to the option vest on the first anniversary of the grant date of December 1, 2011, and the remainder vest monthly thereafter for 36 months.
(5)	25% of the shares subject to the option vest on the first anniversary of the grant date of December 12, 2012, and the remainder vest monthly thereafter for 36 months.
(6)	25% of the shares subject to the option vest on the first anniversary of the grant date of December 12, 2013, and the remainder vest monthly thereafter for 36 months.
(7)	25% of the shares subject to the option vest on the first anniversary of the grant date of December 16, 2014, and the remainder vest monthly thereafter for 36 months.
(8)	25% of the shares subject to the option vest on the first anniversary of the grant date of September 24, 2015, and the remainder vest monthly thereafter for 36 months.
(9)	25% of the shares subject to the option vest on the first anniversary of the grant date of May 17, 2016, and the remainder vest monthly thereafter for 36 months.
(10)	Pursuant to the Merger Agreement, the option was cancelled in exchange for a cash payment of $129,167.70, which represents the product of (a) the difference between $10.00 and the exercise price of the option per share, multiplied by (b) the number of shares subject to the option.
(11)	25% of the shares subject to the option vest on the first anniversary of the grant date of January 11, 2017, and the remainder vest monthly thereafter for 36 months.
(12)	Pursuant to the Merger Agreement, the option was cancelled in exchange for a cash payment of $274,432.00, which represents the product of (a) the difference between $10.00 and the exercise price of the option per share, multiplied by (b) the number of shares subject to the option.
(13)	25% of the shares subject to the option vest on the first anniversary of the grant date of September 18, 2017, and the remainder vest monthly thereafter for 36 months.
(14)	Pursuant to the Merger Agreement, the option was cancelled in exchange for a cash payment of $408,680.00, which represents the product of (a) the difference between $10.00 and the exercise price of the option per share, multiplied by (b) the number of shares subject to the option.
(15)	Pursuant to the Merger Agreement, the restricted stock units were cancelled in exchange for a cash payment of $113,000.00, which is the product of the total number of shares subject to such restricted stock unit grant multiplied by the Offer Price.
(16)	The restricted stock units were granted on January 11, 2017 and 25% of the shares vest on each anniversary of the grant date for four years.
(17)	The restricted stock units expire upon the earlier of the settlement of the units and the unitholder's termination of service.
(18)	Pursuant to the Merger Agreement, the restricted stock units were cancelled in exchange for a cash payment of $150,000.00, which is the product of the total number of shares subject to such restricted stock unit grant multiplied by the Offer Price.
(19)	The restricted stock units were granted on September 18, 2017 and 25% of the shares vest on each anniversary of the grant date for four years.
(20)	Pursuant to the Merger Agreement, the restricted stock units were cancelled in exchange for a cash payment of $1,645,000.00, which is the product of the total number of shares subject to such restricted stock unit grant multiplied by the Offer Price.
(21)	The restricted stock units were granted on January 31, 2018 and 25% of the shares vest on each anniversary of the grant date for four years.

Reporting Owners
Reporting Owner Name / Address	Relationships
Reporting Owner Name / Address	Director	10% Owner	Officer	Other
Christianson Gary C/O CASCADIAN THERAPEUTICS, INC. 3101 WESTERN AVE., SUITE 600 SEATTLE, WA 98121			Chief Operating Officer

Signatures
/s/ Julia M. Eastland (Attorney-in-Fact)		3/13/2018
^** Signature of Reporting Person		Date

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).
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