Document:

EX-4.1

 Exhibit 4.1 

CASCADIAN THERAPEUTICS, INC. 

CERTIFICATE OF DESIGNATION OF PREFERENCES, 

RIGHTS AND LIMITATIONS 

OF 
 SERIES D CONVERTIBLE
PREFERRED STOCK 
 PURSUANT TO SECTION 151 OF THE 

DELAWARE GENERAL CORPORATION LAW 

CASCADIAN THERAPEUTICS, INC., a Delaware corporation (the “Corporation”), in accordance with the provisions of
Section 103 of the Delaware General Corporation Law (the “DGCL”) does hereby certify that, in accordance with Sections 141(c) and 151 of the DGCL, the following resolution was duly adopted by the Board of Directors of
the Corporation by a duly authorized committee thereof on June 23, 2016: 
 RESOLVED, pursuant to authority expressly set forth in
the Amended and Restated Certificate of Incorporation of the Corporation, as amended (the “Certificate of Incorporation”), the issuance of a series of Preferred Stock designated as the Series D Convertible Preferred Stock,
par value $0.0001 per share, of the Corporation is hereby authorized and the designation, number of shares, powers, preferences, rights, qualifications, limitations and restrictions thereof (in addition to any provisions set forth in the Certificate
of Incorporation that are applicable to the Preferred Stock of all classes and series) are hereby fixed, and the Certificate of Designation of Preferences, Rights and Limitations of Series D Convertible Preferred Stock is hereby approved as follows:

 SERIES D CONVERTIBLE PREFERRED STOCK 

Section 1. Definitions. For the purposes hereof, the following terms shall have the following meanings: 

“Affiliate” means any person or entity that, directly or indirectly through one or more intermediaries, controls or is
controlled by or is under common control with a person or entity, as such terms are used in and construed under Rule 144 under the Securities Act. With respect to a Holder, any investment fund or managed account that is managed on a discretionary
basis by the same investment manager as such Holder will be deemed to be an Affiliate of such Holder. 
 “Alternate
Consideration” shall have the meaning set forth in Section 7(b). 
 “Beneficial Ownership
Limitation” shall have the meaning set forth in Section 6(c). 
 “Business Day” means any day
except Saturday, Sunday, any day which shall be a federal legal holiday in the United States or any day on which banking institutions in the State of New York are authorized or required by law or other governmental action to close. 

“Buy-In” shall have the meaning set forth in Section 6(d)(iii). 

“Closing Sale Price” means, for any security as of any date, the last closing trade price for such security prior to
4:00 p.m., New York City time, on the principal securities exchange or trading market where such security is listed or traded, as reported by Bloomberg, L.P. (or an equivalent, reliable reporting service mutually acceptable to and hereafter
designated by Holders of a majority of the then-outstanding Series D Preferred Stock and the Corporation), or if the foregoing do not apply, the last trade price of such security in the over-the-counter market on the electronic bulletin board for
such security as reported by Bloomberg, L.P., or, if no last trade price is reported for such security by Bloomberg, L.P., the average of the bid prices of any market makers for such security as reported on the OTC Pink Market by OTC Markets Group,
Inc. If the Closing Sale Price cannot be calculated for a security on a particular date on any of the foregoing bases, the Closing Sale Price of such security on such date shall be the fair market value as determined in good faith by the Board of
Directors of the Corporation. 

  
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 “Commission” means the Securities and Exchange Commission. 

“Common Stock” means the Corporation’s common stock, par value $0.0001 per share, and stock of any other class of
securities into which such securities may hereafter be reclassified or changed into. 
 “Common Stock Equivalents”
means any securities of the Corporation or the subsidiaries which would entitle the holder thereof to acquire at any time Common Stock, including, without limitation, any debt, preferred stock, rights, options, warrants or other instrument that is
at any time convertible into or exchangeable for, or otherwise entitles the holder thereof to receive, Common Stock. 

“Conversion Date” shall have the meaning set forth in Section 6(a). 

“Conversion Price” shall mean $0.80, as adjusted pursuant to paragraph 7 hereof. 

“Conversion Ratio” shall have the meaning set forth in Section 6(b). 

“Conversion Shares” means, collectively, the shares of Common Stock issuable upon conversion of the shares of Series D
Preferred Stock in accordance with the terms hereof. 
 “Daily Failure Amount” means the product of (x) .005
multiplied by (y) the Closing Sale Price of the Common Stock on the applicable Share Delivery Date. 
 “DGCL”
shall mean the Delaware General Corporation Law. 
 “Distributions” shall have the meaning set forth in
Section 5(a). 
 “DTC” shall have the meaning set forth in Section 6(a). 

“DWAC Delivery” shall have the meaning set forth in Section 6(a). 

“Exchange Act” means the Securities Exchange Act of 1934, as amended, and the rules and regulations promulgated
thereunder. 
 “Fundamental Transaction” shall have the meaning set forth in Section 7(b). 

“Holder” means any holder of Series D Preferred Stock. 

“Issuance Date” June 28, 2016. 

“Junior Securities” shall have the meaning set forth in Section 5(a). 

“Notice of Conversion” shall have the meaning set forth in Section 6(a). 

“Parity Securities” shall have the meaning set forth in Section 5(a). 

“Person” means any individual or corporation, partnership, trust, incorporated or unincorporated association, joint
venture, limited liability company, joint stock company, government (or an agency or subdivision thereof) or other entity of any kind. 

“Securities Act” means the Securities Act of 1933, as amended, and the rules and regulations promulgated thereunder.

 “Senior Securities” shall have the meaning set forth in Section 5(a). 

“Series D Preferred Stock” shall have the meaning set forth in Section 2(a). 

  
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 “Series D Preferred Stock Register” shall have the meaning set forth in
Section 2(b). 
 “Share Delivery Date” shall have the meaning set forth in Section 6(d)(i). 

“Stated Value” shall mean $800.00. 

“Trading Day” means a day on which the Common Stock is traded for any period on the principal securities exchange or
if the Common Stock is not traded on a principal securities exchange, on a day that the Common Stock is traded on another securities market on which the Common Stock is then being traded. 

Section 2. Designation, Amount and Par Value; Assignment. 

a) The series of preferred stock designated by this Certificate of Designation shall be designated as the Corporation’s Series D
Convertible Preferred Stock (the “Series D Preferred Stock”) and the number of shares so designated shall be 17,250. Each share of Series D Preferred Stock shall have a par value of $0.0001 per share. The Series D Preferred
Stock may be issued in certificated form or in book-entry form. To the extent that any shares of Series D Preferred Stock are issued in book-entry form, references herein to “certificates” shall instead refer to the book-entry notation
relating to such shares. 
 b) The Corporation shall register shares of the Series D Preferred Stock, upon records to be maintained by the
Corporation for that purpose (the “Series D Preferred Stock Register”), in the name of the Holders thereof from time to time. The Corporation may deem and treat the registered Holder of shares of Series D Preferred Stock as
the absolute owner thereof for the purpose of any conversion thereof and for all other purposes. The Corporation shall register the transfer of any shares of Series D Preferred Stock in the Series D Preferred Stock Register, upon surrender of the
certificates evidencing such shares to be transferred, duly endorsed by the Holder thereof, to the Corporation at its address specified herein. Upon any such registration or transfer, a new certificate evidencing the shares of Series D Preferred
Stock so transferred shall be issued to the transferee and a new certificate evidencing the remaining portion of the shares not so transferred, if any, shall be issued to the transferring Holder, in each case, within three Business Days. The
provisions of this Certificate of Designation are intended to be for the benefit of all Holders from time to time and shall be enforceable by any such Holder. 

Section 3. Dividends. Holders shall not be entitled to receive any dividends in respect of the Series D Preferred Stock,
unless and until specifically declared by the Board of Directors of the Corporation to be payable to the Holders of the Series D Preferred Stock. 

Section 4. Voting Rights Amendments. Except as otherwise provided herein or as otherwise required by the DGCL, the
Series D Preferred Stock shall have no voting rights. However, as long as any shares of Series D Preferred Stock are outstanding, the Corporation shall not, without the affirmative vote of the Holders of a majority of the then outstanding
shares of the Series D Preferred Stock, (a) alter or change adversely the powers, preferences or rights given to the Series D Preferred Stock or alter or amend this Certificate of Designation, amend or repeal any provision of, or add any
provision to, the Certificate of Incorporation or bylaws of the Corporation, or file any articles of amendment, certificate of designation, preferences, limitations and relative rights of any series of preferred stock, if such action would adversely
alter or change the preferences, rights, privileges or powers of, or restrictions provided for the benefit of the Series D Preferred Stock, regardless of whether any of the foregoing actions shall be by means of amendment to the Certificate of
Incorporation or by merger, consolidation or otherwise, (b) issue further shares of Series D Preferred Stock or increase or decrease (other than by conversion) the number of authorized shares of Series D Preferred Stock or (c) enter
into any agreement with respect to any of the foregoing. 
 Section 5. Rank; Liquidation. 

a) The Series D Preferred Stock shall rank (i) senior to all of the Common Stock; (ii) senior to any class or series of capital
stock of the Corporation hereafter created specifically ranking by its terms junior to any Series D Preferred Stock (“Junior Securities”); (iii) on parity with all shares of the Corporation’s Series A Convertible
Preferred Stock; (iv) on parity with all shares of the Corporation’s Series B Convertible Preferred Stock; (v) on parity with all shares of the Corporation’s Series C Convertible Preferred Stock; (vi) on parity with any
class or 

  
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series of capital stock of the Corporation hereafter created specifically ranking by its terms on parity with the Series D Preferred Stock (together with the Corporation’s Series A
Convertible Preferred Stock, Series B Convertible Preferred Stock and Series C Convertible Preferred Stock, the “Parity Securities”); (vii) junior to Class UA Preferred Stock, no par value; and (viii) junior to any
class or series of capital stock of the Corporation hereafter created specifically ranking by its terms senior to any Series D Preferred Stock (“Senior Securities”), in each case, as to distributions of assets upon
liquidation, dissolution or winding up of the Corporation, whether voluntarily or involuntarily (all such distributions being referred to collectively as “Distributions”). 

b) Subject to the prior and superior rights of the holders of Class UA Preferred Stock and any other Senior Securities of the Corporation,
upon liquidation, dissolution or winding up of the Corporation, whether voluntary or involuntary, each holder of shares of Series D Preferred Stock shall be entitled to receive, in preference to any distributions of any of the assets or surplus
funds of the Corporation to the holders of the Common Stock and Junior Securities and pari passu with any distribution to the holders of Parity Securities, an amount equal to $0.0001 per share of Series D Preferred Stock, plus an additional amount
equal to any dividends declared but unpaid on such shares, before any payments shall be made or any assets distributed to holders of any class of Common Stock or Junior Securities. If, upon any such liquidation, dissolution or winding up of the
Corporation, the assets of the Corporation shall be insufficient to pay the holders of shares of the Series D Preferred Stock the amount required under the preceding sentence, then all remaining assets of the Corporation shall be distributed ratably
to holders of the shares of the Series D Preferred Stock and Parity Securities. 
 Section 6. Conversion. 

a) Conversions at Option of Holder. Each share of Series D Preferred Stock shall be convertible, at any time and from time to time from
and after the Issuance Date, at the option of the Holder thereof, into a number of shares of Common Stock equal to the Conversion Ratio. Holders shall effect conversions by providing the Corporation with the form of conversion notice attached hereto
as Annex A (a “Notice of Conversion”), duly completed and executed. Other than a conversion following a Fundamental Transaction or following a notice provided for under Section 7(d)(ii) hereof, the Notice
of Conversion must specify at least a number of shares of Series D Preferred Stock to be converted equal to the lesser of (x) 100 shares (such number subject to appropriate adjustment following the occurrence of an event specified in
Section 7(a) hereof) and (y) the number of shares of Series D Preferred Stock then held by the Holder. Provided the Corporation’s transfer agent is participating in the Depository Trust Company (“DTC”) Fast
Automated Securities Transfer program, the Notice of Conversion may specify, at the Holder’s election, whether the applicable Conversion Shares shall be credited to the account of the Holder’s prime broker with DTC through its Deposit
Withdrawal Agent Commission system (a “DWAC Delivery”). The “Conversion Date”, or the date on which a conversion shall be deemed effective, shall be defined as the Trading Day that the Notice of
Conversion, completed and executed, is sent by facsimile to, and received during regular business hours by, the Corporation; provided that the original certificate(s) (if applicable) representing such shares of Series D Preferred Stock being
converted, duly endorsed, and the accompanying Notice of Conversion, are received by the Corporation within two (2) Trading Days thereafter. In all other cases, the Conversion Date shall be defined as the Trading Day on which the original share
certificate(s) (if applicable) of Series D Preferred Stock being converted, duly endorsed, and the accompanying Notice of Conversion, are received by the Corporation. The calculations set forth in the Notice of Conversion shall control in the
absence of manifest or mathematical error. 
 b) Conversion Ratio. The “Conversion Ratio” for each share of
Series D Preferred Stock shall be equal to the Stated Value divided by the Conversion Price. 
 c) Beneficial Ownership Limitation.
Notwithstanding anything herein to the contrary, the Corporation shall not effect any conversion of the Series D Preferred Stock, and a Holder shall not have the right to convert any portion of the Series D Preferred Stock, to the extent that, after
giving effect to an attempted conversion set forth on an applicable Notice of Conversion, such Holder (together with such Holder’s Affiliates, and any other Person whose beneficial ownership of Common Stock would be aggregated with the
Holder’s for purposes of Section 13(d) or Section 16 of the Exchange Act and the applicable regulations of the Commission, including any “group” of which the Holder is a member (the foregoing, “Attribution
Parties”)) would beneficially own a number of shares of Common Stock in excess of the Beneficial Ownership Limitation (as defined below). For purposes of the foregoing sentence, the number

  
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of shares of Common Stock beneficially owned by such Holder and its Attribution Parties shall include the number of shares of Common Stock issuable upon conversion of the Series D Preferred Stock
subject to the Notice of Conversion with respect to which such determination is being made, but shall exclude the number of shares of Common Stock which are issuable upon (A) conversion of the remaining, unconverted Series D Preferred Stock
beneficially owned by such Holder or any of its Attribution Parties, and (B) exercise or conversion of the unexercised or unconverted portion of any other securities of the Corporation (including any warrants) beneficially owned by such Holder
or any of its Attribution Parties that are subject to a limitation on conversion or exercise similar to the limitation contained herein. For purposes of this Section 6(c), beneficial ownership shall be calculated in accordance with
Section 13(d) of the Exchange Act and the applicable regulations of the Commission. In addition, for purposes hereof, “group” has the meaning set forth in Section 13(d) of the Exchange Act and the applicable regulations of the
Commission. For purposes of this Section 6(c), in determining the number of outstanding shares of Common Stock, a Holder may rely on the number of outstanding shares of Common Stock as stated in the most recent of the following: (A) the
Corporation’s most recent periodic or annual filing with the Commission, as the case may be, (B) a more recent public announcement by the Corporation that is filed with the Commission, or (C) a more recent notice by the Corporation or
the Corporation’s transfer agent to the Holder setting forth the number of shares of Common Stock then outstanding. Upon the written request of a Holder (which may be by email), the Corporation shall, within three (3) Trading Days thereof,
confirm in writing to such Holder (which may be via email) the number of shares of Common Stock then outstanding. In any case, the number of outstanding shares of Common Stock shall be determined after giving effect to any actual conversion or
exercise of securities of the Corporation, including shares of Series D Preferred Stock, by such Holder or its Attribution Parties since the date as of which such number of outstanding shares of Common Stock was last publicly reported or confirmed
to the Holder. The “Beneficial Ownership Limitation” shall be 19.99% of the number of shares of the Common Stock outstanding immediately after giving effect to the issuance of shares of Common Stock pursuant to such Notice of
Conversion (to the extent permitted pursuant to this Section 6(c)); provided, however, that by written notice to the Corporation, which will not be effective until the 61st day after such notice is delivered to the Corporation, the Holder may
waive or amend the provisions of this Section 6(c) to change the Beneficial Ownership Limitation to any other number less than or equal to 19.99%, and the provisions of this Section 6(c) shall continue to apply. The Corporation shall be
entitled to rely on representations made to it by the Holder in any Notice of Conversion regarding its Beneficial Ownership Limitation. 

d) Mechanics of Conversion  

i. Delivery of Certificate or Electronic Issuance Upon Conversion. Not later than three Trading Days after the applicable Conversion
Date, or if the Holder requests the issuance of physical certificate(s), two (2) Trading Days after receipt by the Corporation of the original certificate(s) representing such shares of Series D Preferred Stock being converted, duly endorsed,
and the accompanying Notice of Conversion (the “Share Delivery Date”), the Corporation shall (a) deliver, or cause to be delivered, to the converting Holder a physical certificate or certificates representing the number
of Conversion Shares being acquired upon the conversion of shares of Series D Preferred Stock or (b) in the case of a DWAC Delivery, electronically transfer such Conversion Shares by crediting the account of the Holder’s prime broker with
DTC through its DWAC system. If in the case of any Notice of Conversion such certificate or certificates are not delivered to or as directed by or, in the case of a DWAC Delivery, such shares are not electronically delivered to or as directed by,
the applicable Holder by the Share Delivery Date, the applicable Holder shall be entitled to elect to rescind such Conversion Notice by written notice to the Corporation at any time on or before its receipt of such certificate or certificates for
Conversion Shares or electronic receipt of such shares, as applicable, in which event the Corporation shall promptly return to such Holder any original Series D Preferred Stock certificate delivered to the Corporation and such Holder shall promptly
return to the Corporation any Common Stock certificates or otherwise direct the return of any shares of Common Stock delivered to the Holder through the DWAC system, representing the shares of Series D Preferred Stock unsuccessfully tendered for
conversion to the Corporation. 
 ii. Obligation Absolute. Subject to Section 6(c) hereof and subject to Holder’s right to
rescind a Conversion Notice pursuant to Section 6(d)(i) above, the Corporation’s obligation to issue and deliver the Conversion Shares upon conversion of Series D Preferred Stock in accordance with the terms hereof are absolute and
unconditional, irrespective of any action or inaction by a Holder to enforce the same, any waiver or consent with respect to any provision hereof, the recovery of any judgment against any Person or any action to enforce the same, or any setoff,
counterclaim, recoupment, limitation or termination, or any breach or alleged breach by such Holder or any other 

  
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Person of any obligation to the Corporation or any violation or alleged violation of law by such Holder or any other Person, and irrespective of any other circumstance which might otherwise limit
such obligation of the Corporation to such Holder in connection with the issuance of such Conversion Shares. Subject to Section 6(c) hereof and subject to Holder’s right to rescind a Conversion Notice pursuant to Section 6(d)(i)
above, in the event a Holder shall elect to convert any or all of its Series D Preferred Stock, the Corporation may not refuse conversion based on any claim that such Holder or anyone associated or affiliated with such Holder has been engaged in any
violation of law, agreement or for any other reason, unless an injunction from a court, on notice to Holder, restraining and/or enjoining conversion of all or part of the Series D Preferred Stock of such Holder shall have been sought and obtained by
the Corporation, and the Corporation posts a surety bond for the benefit of such Holder in the amount of 150% of the value of the Conversion Shares into which would be converted the Series D Preferred Stock which is subject to such injunction, which
bond shall remain in effect until the completion of arbitration/litigation of the underlying dispute and the proceeds of which shall be payable to such Holder to the extent it obtains judgment. In the absence of such injunction, the Corporation
shall, subject to Section 6(c) hereof and subject to Holder’s right to rescind a Conversion Notice pursuant to Section 6(d)(i) above, issue Conversion Shares upon a properly noticed conversion. If the Corporation fails to deliver to a
Holder such certificate or certificates, or electronically deliver (or cause its transfer agent to electronically deliver) such shares in the case of a DWAC Delivery, pursuant to Section 6(d)(i) on or prior to the fifth (5th) Trading Day
after the Share Delivery Date applicable to such conversion (other than a failure caused by incorrect or incomplete information provided by Holder to the Corporation), then, unless the Holder has rescinded the applicable Conversion Notice pursuant
to Section 6(d)(i) above, the Corporation shall pay (as liquidated damages and not as a penalty) to such Holder an amount payable, at the Corporation’s option, either (a) in cash or (b) to the extent that it would not cause the
Holder or its Attribution Parties to exceed the Beneficial Ownership Limitation, in shares of Common Stock that are valued for these purposes at the Closing Sale Price on the date of such calculation, in each case equal to the product of
(x) the number of Conversion Shares required to have been issued by the Corporation on such Share Delivery Date, (y) an amount equal to the Daily Failure Amount and (z) the number of Trading Days actually lapsed after such fifth
(5th) Trading Day after the Share Delivery Date during which such certificates have not been delivered, or, in the case of a DWAC Delivery, such shares have not been electronically delivered; provided, however, the Holder shall only receive up
to such amount of shares of Common Stock such that Holder and its Attribution Parties and any other persons or entities whose beneficial ownership of Common Stock would be aggregated with the Holder’s for purposes of Section 13(d) of the
Exchange Act (including shares held by any “group” of which the Holder is a member, but excluding shares beneficially owned by virtue of the ownership of securities or rights to acquire securities that have limitations on the right to
convert, exercise or purchase similar to the limitation set forth herein) shall not collectively beneficially own greater than the Beneficial Ownership Limitation. Nothing herein shall limit a Holder’s right to pursue actual damages for the
Corporation’s failure to deliver Conversion Shares within the period specified herein and such Holder shall have the right to pursue all remedies available to it hereunder, at law or in equity including, without limitation, a decree of specific
performance and/or injunctive relief; provided that Holder shall not receive duplicate damages for the Corporation’s failure to deliver Conversion Shares within the period specified herein. The exercise of any such rights shall not prohibit a
Holder from seeking to enforce damages pursuant to any other Section hereof or under applicable law. 
 iii. Compensation for Buy-In on
Failure to Timely Deliver Certificates Upon Conversion. If the Corporation fails to deliver to a Holder the applicable certificate or certificates or to effect a DWAC Delivery, as applicable, by the Share Delivery Date pursuant to
Section 6(d)(i) (other than a failure caused by incorrect or incomplete information provided by Holder to the Corporation), and if after such Share Delivery Date such Holder is required by its brokerage firm to purchase (in an open market
transaction or otherwise), or the Holder’s brokerage firm otherwise purchases, shares of Common Stock to deliver in satisfaction of a sale by such Holder of the Conversion Shares which such Holder was entitled to receive upon the conversion
relating to such Share Delivery Date (a “Buy-In”), then the Corporation shall (A) pay in cash to such Holder (in addition to any other remedies available to or elected by such Holder) the amount by which (x) such
Holder’s total purchase price (including any brokerage commissions) for the shares of Common Stock so purchased exceeds (y) the product of (1) the aggregate number of shares of Common Stock that such Holder was entitled to receive
from the conversion at issue multiplied by (2) the actual sale price at which the sell order giving rise to such purchase obligation was executed (including any brokerage commissions) and (B) at the option of such Holder, either reissue
(if surrendered) the shares of Series D Preferred Stock equal to the number of shares of Series D Preferred Stock submitted for conversion or deliver to such Holder the number of shares of Common Stock that would have been issued if the Corporation
had timely complied with its delivery requirements under Section 6(d)(i). For example, if a Holder purchases shares of 

  
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Common Stock having a total purchase price of $11,000 to cover a Buy-In with respect to an attempted conversion of shares of Series D Preferred Stock with respect to which the actual sale
price (including any brokerage commissions) giving rise to such purchase obligation was a total of $10,000 under clause (A) of the immediately preceding sentence, the Corporation shall be required to pay such Holder $1,000. The Holder shall
provide the Corporation written notice, within three (3) Trading Days after the occurrence of a Buy-In, indicating the amounts payable to such Holder in respect of such Buy-In together with applicable confirmations and other evidence reasonably
requested by the Corporation. Nothing herein shall limit a Holder’s right to pursue any other remedies available to it hereunder, at law or in equity including, without limitation, a decree of specific performance and/or injunctive relief with
respect to the Corporation’s failure to timely deliver certificates representing shares of Common Stock upon conversion of the shares of Series D Preferred Stock as required pursuant to the terms hereof; provided, however, that the Holder shall
not be entitled to both (i) require the reissuance of the shares of Series D Preferred Stock submitted for conversion for which such conversion was not timely honored and (ii) receive the number of shares of Common Stock that would have
been issued if the Corporation had timely complied with its delivery requirements under Section 6(d)(i). 
 iv. Reservation of
Shares Issuable Upon Conversion. The Corporation covenants that it will at all times reserve and keep available out of its authorized and unissued shares of Common Stock for the sole purpose of issuance upon conversion of the Series D Preferred
Stock, free from preemptive rights or any other actual contingent purchase rights of Persons other than the Holders of the Series D Preferred Stock, not less than such aggregate number of shares of the Common Stock as shall be issuable (taking into
account the adjustments of Section 7) upon the conversion of all outstanding shares of Series D Preferred Stock. The Corporation covenants that all shares of Common Stock that shall be so issuable shall, upon issue, be duly authorized, validly
issued, fully paid and nonassessable. 
 v. Fractional Shares. No fractional shares or scrip representing fractional shares of Common
Stock shall be issued upon the conversion of the Series D Preferred Stock. As to any fraction of a share which a Holder would otherwise be entitled to receive upon such conversion, the Corporation shall pay a cash adjustment in respect of such final
fraction in an amount equal to such fraction multiplied by the Conversion Price. 
 vi. Transfer Taxes. The issuance of certificates
for shares of the Common Stock upon conversion of the Series D Preferred Stock shall be made without charge to any Holder for any documentary stamp or similar taxes that may be payable in respect of the issue or delivery of such certificates,
provided that the Corporation shall not be required to pay any tax that may be payable in respect of any transfer involved in the issuance and delivery of any such certificate upon conversion in a name other than that of the registered Holder(s) of
such shares of Series D Preferred Stock and the Corporation shall not be required to issue or deliver such certificates unless or until the Person or Persons requesting the issuance thereof shall have paid to the Corporation the amount of such tax
or shall have established to the satisfaction of the Corporation that such tax has been paid. 
 e) Status as Stockholder. Upon each
Conversion Date, (i) the shares of Series D Preferred Stock being converted shall be deemed converted into shares of Common Stock and (ii) the Holder’s rights as a holder of such converted shares of Series D Preferred Stock shall
cease and terminate, excepting only the right to receive certificates for such shares of Common Stock and to any remedies provided herein or otherwise available at law or in equity to such Holder because of a failure by the Corporation to comply
with the terms of this Certificate of Designation. In all cases, the holder shall retain all of its rights and remedies for the Corporation’s failure to convert Series D Preferred Stock. 

Section 7. Certain Adjustments. 

a) Stock Dividends and Stock Splits. If the Corporation, at any time while this Series D Preferred Stock is outstanding: (A) pays
a stock dividend or otherwise makes a distribution or distributions payable in shares of Common Stock (which, for avoidance of doubt, shall not include any shares of Common Stock issued by the Corporation upon conversion of this Series D Preferred
Stock) with respect to the then outstanding shares of Common Stock; (B) subdivides outstanding shares of Common Stock into a larger number of shares; or (C) combines (including by way of a reverse stock split) outstanding shares of Common
Stock into a smaller number of shares, then the Conversion Price shall be multiplied by a fraction of which the numerator shall be the number of shares of Common Stock (excluding any treasury shares of the Corporation) outstanding immediately before
such 

  
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event and of which the denominator shall be the number of shares of Common Stock outstanding immediately after such event (excluding any treasury shares of the Corporation). Any adjustment made
pursuant to this Section 7(a) shall become effective immediately after the record date for the determination of stockholders entitled to receive such dividend or distribution and shall become effective immediately after the effective date in
the case of a subdivision or combination. 
 b) Fundamental Transaction. If, at any time while this Series D Preferred Stock is
outstanding, (A) the Corporation effects any merger or consolidation of the Corporation with or into another Person or any stock sale to, or other business combination (including, without limitation, a reorganization, recapitalization,
spin-off, share exchange or scheme of arrangement) with or into another Person (other than such a transaction in which the Corporation is the surviving or continuing entity and its Common Stock is not exchanged for or converted into other
securities, cash or property), (B) the Corporation effects any sale of all or substantially all of its assets in one transaction or a series of related transactions, (C) any tender offer or exchange offer (whether by the Corporation or
another Person) is completed pursuant to which more than 50% of the Common Stock not held by the Corporation or such Person is exchanged for or converted into other securities, cash or property, or (D) the Corporation effects any
reclassification of the Common Stock or any compulsory share exchange pursuant (other than as a result of a dividend, subdivision or combination covered by Section 7(a) above) to which the Common Stock is effectively converted into or exchanged
for other securities, cash or property (in any such case, a “Fundamental Transaction”), then, upon any subsequent conversion of this Series D Preferred Stock the Holders shall have the right to receive, in lieu of the right
to receive Conversion Shares, for each Conversion Share that would have been issuable upon such conversion immediately prior to the occurrence of such Fundamental Transaction, the same kind and amount of securities, cash or property as it would have
been entitled to receive upon the occurrence of such Fundamental Transaction if it had been, immediately prior to such Fundamental Transaction, the holder of one share of Common Stock (the “Alternate Consideration”). For
purposes of any such subsequent conversion, the determination of the Conversion Ratio shall be appropriately adjusted to apply to such Alternate Consideration based on the amount of Alternate Consideration issuable in respect of one share of Common
Stock in such Fundamental Transaction, and the Corporation shall adjust the Conversion Ratio in a reasonable manner reflecting the relative value of any different components of the Alternate Consideration. If holders of Common Stock are given any
choice as to the securities, cash or property to be received in a Fundamental Transaction, then the Holders shall be given the same choice as to the Alternate Consideration it receives upon any conversion of this Series D Preferred Stock following
such Fundamental Transaction. To the extent necessary to effectuate the foregoing provisions, any successor to the Corporation or surviving entity in such Fundamental Transaction shall file a new Certificate of Designation with the same terms and
conditions and issue to the Holders new preferred stock consistent with the foregoing provisions and evidencing the Holders’ right to convert such preferred stock into Alternate Consideration. The terms of any agreement to which the Corporation
is a party and pursuant to which a Fundamental Transaction is effected shall include terms requiring any such successor or surviving entity to comply with the provisions of this Section 7(b) and insuring that this Series D Preferred Stock (or
any such replacement security) will be similarly adjusted upon any subsequent transaction analogous to a Fundamental Transaction. The Corporation shall cause to be delivered to each Holder, at its last address as it shall appear upon the stock books
of the Corporation, written notice of any Fundamental Transaction at least 20 calendar days prior to the date on which such Fundamental Transaction is expected to become effective or close. 

c) Calculations. All calculations under this Section 7 shall be made to the nearest cent or the nearest 1/100th of a share, as the
case may be. For purposes of this Section 7, the number of shares of Common Stock deemed to be issued and outstanding as of a given date shall be the sum of the number of shares of Common Stock (excluding any treasury shares of the Corporation)
issued and outstanding. 
 d) Notice to the Holders. 

i. Adjustment to Conversion Price. Whenever the Conversion Price is adjusted pursuant to any provision of this Section 7, the
Corporation shall promptly deliver to each Holder a notice setting forth the Conversion Ratio after such adjustment and setting forth a brief statement of the facts requiring such adjustment. 

ii. Other Notices. If (A) the Corporation shall declare a dividend (or any other distribution in whatever form) on the Common
Stock, (B) the Corporation shall declare a special nonrecurring cash dividend on or a redemption of the Common Stock, (C) the Corporation shall authorize the granting to all holders of the Common Stock of rights or

  
 A-8 

 
warrants to subscribe for or purchase any shares of capital stock of any class or of any rights, (D) the approval of any stockholders of the Corporation shall be required in connection with
any reclassification of the Common Stock, any consolidation or merger to which the Corporation is a party, any sale or transfer of all or substantially all of the assets of the Corporation, or any compulsory share exchange whereby the Common Stock
is converted into other securities, cash or property, or (E) the Corporation shall authorize the voluntary or involuntary dissolution, liquidation or winding up of the affairs of the Corporation, then, in each case, the Corporation shall cause
to be filed at each office or agency maintained for the purpose of conversion of this Series D Preferred Stock, and shall cause to be delivered to each Holder at its last address as it shall appear upon the stock books of the Corporation, at least
20 calendar days prior to the applicable record or effective date hereinafter specified, a notice stating (x) the date on which a record is to be taken for the purpose of such dividend, distribution, redemption, rights or warrants, or if a
record is not to be taken, the date as of which the holders of the Common Stock of record to be entitled to such dividend, distributions, redemption, rights or warrants are to be determined or (y) the date on which such reclassification,
consolidation, merger, sale, transfer or share exchange is expected to become effective or close, and the date as of which it is expected that holders of the Common Stock of record shall be entitled to exchange their shares of the Common Stock for
securities, cash or other property deliverable upon such reclassification, consolidation, merger, sale, transfer or share exchange, provided that the failure to deliver such notice or any defect therein or in the delivery thereof shall not affect
the validity of the corporate action required to be specified in such notice. 
 Section 8. Miscellaneous. 

a) Notices. Any and all notices or other communications or deliveries to be provided by the Holders hereunder including, without
limitation, any Notice of Conversion, shall be in writing and delivered personally, by facsimile, or sent by a nationally recognized overnight courier service, addressed to the Corporation, at 2601 Fourth Avenue, Suite 500, Seattle, Washington
98121, facsimile number (206) 801-2101, or such other facsimile number or address as the Corporation may specify for such purposes by notice to the Holders delivered in accordance with this Section. Any and all notices or other communications
or deliveries to be provided by the Corporation hereunder shall be in writing and delivered personally, by facsimile, or sent by a nationally recognized overnight courier service addressed to each Holder at the facsimile number or address of such
Holder appearing on the books of the Corporation, or if no such facsimile number or address appears on the books of the Corporation, at the principal place of business of such Holder. Any notice or other communication or deliveries hereunder shall
be deemed given and effective on the earliest of (i) the date of transmission, if such notice or communication is delivered via facsimile at the facsimile number specified in this Section prior to 5:30 p.m. (New York City time) on any date,
(ii) the date immediately following the date of transmission, if such notice or communication is delivered via facsimile at the facsimile number specified in this Section between 5:30 p.m. and 11:59 p.m. (New York City time) on any date,
(iii) the second Business Day following the date of mailing, if sent by nationally recognized overnight courier service, or (iv) upon actual receipt by the party to whom such notice is required to be given. 

b) Lost or Mutilated Series D Preferred Stock Certificate. If a Holder’s Series D Preferred Stock certificate shall be mutilated,
lost, stolen or destroyed, the Corporation shall execute and deliver, in exchange and substitution for and upon cancellation of a mutilated certificate, or in lieu of or in substitution for a lost, stolen or destroyed certificate, a new certificate
for the shares of Series D Preferred Stock so mutilated, lost, stolen or destroyed, but only upon receipt of evidence of such loss, theft or destruction of such certificate, and of the ownership thereof, reasonably satisfactory to the
Corporation and, in each case, customary and reasonable indemnity, if requested. Applicants for a new certificate under such circumstances shall also comply with such other reasonable regulations and procedures and pay such other reasonable
third-party costs as the Corporation may prescribe. 
 c) Waiver. Any waiver by the Corporation or a Holder of a breach of any
provision of this Certificate of Designation shall not operate as or be construed to be a waiver of any other breach of such provision or of any breach of any other provision of this Certificate of Designation or a waiver by any other Holders. The
failure of the Corporation or a Holder to insist upon strict adherence to any term of this Certificate of Designation on one or more occasions shall not be considered a waiver or deprive that party (or any other Holder) of the right thereafter to
insist upon strict adherence to that term or any other term of this Certificate of Designation. Any waiver by the Corporation or a Holder must be in writing. Notwithstanding any provision in this Certificate of Designation to the contrary, any
provision contained herein and any right of the Holders of Series D Preferred Stock granted hereunder may be waived as to all shares of Series D Preferred Stock (and the Holders thereof) upon the written consent of the

  
 A-9 

 
Holders of not less than a majority of the shares of Series D Preferred Stock then outstanding, unless a higher percentage is required by the DGCL, in which case the written consent of the
Holders of not less than such higher percentage shall be required. 
 d) Severability. If any provision of this Certificate of
Designation is invalid, illegal or unenforceable, the balance of this Certificate of Designation shall remain in effect, and if any provision is inapplicable to any Person or circumstance, it shall nevertheless remain applicable to all other Persons
and circumstances. If it shall be found that any interest or other amount deemed interest due hereunder violates the applicable law governing usury, the applicable rate of interest due hereunder shall automatically be lowered to equal the maximum
rate of interest permitted under applicable law. 
 e) Next Business Day. Whenever any payment or other obligation hereunder shall be
due on a day other than a Business Day, such payment shall be made on the next succeeding Business Day. 
 f) Headings. The headings
contained herein are for convenience only, do not constitute a part of this Certificate of Designation and shall not be deemed to limit or affect any of the provisions hereof. 

g) Status of Converted Series D Preferred Stock. If any shares of Series D Preferred Stock shall be converted or reacquired by the
Corporation, such shares shall resume the status of authorized but unissued shares of preferred stock and shall no longer be designated as Series D Preferred Stock. 

******************** 

  
 A-10 

 IN WITNESS WHEREOF, the undersigned has executed this Certificate of Designation this
    th day of June 2016. 
  

	
	  

	Scott Myers, Chief Executive Officer

 SIGNATURE PAGE TO 

CERTIFICATE OF DESIGNATION OF PREFERENCES, 

RIGHTS AND LIMITATIONS OF 

SERIES D PREFERRED STOCK 

 ANNEX A 

NOTICE OF CONVERSION 
 (TO BE
EXECUTED BY THE REGISTERED HOLDER IN ORDER TO CONVERT SHARES OF SERIES D PREFERRED STOCK) 
 The undersigned Holder hereby irrevocably elects to convert the
number of shares of Series D Preferred Stock indicated below, represented by stock certificate No(s).         (the “Preferred Stock Certificates”), into shares of common stock, par
value $0.0001 per share (the “Common Stock”), of Cascadian Therapeutics, Inc., a Delaware corporation (the “Corporation”), as of the date written below. If securities are to be issued in the name of a
person other than the undersigned, the undersigned will pay all transfer taxes payable with respect thereto. Capitalized terms utilized but not defined herein shall have the meaning ascribed to such terms in that certain Certificate of Designation
of Preferences, Rights and Limitations of Series D Convertible Preferred Stock (the “Certificate of Designation”) filed by the Corporation with the Secretary of State of the State of Delaware on June
[    ], 2016. 
 As of the date hereof, the number of shares of Common Stock beneficially owned by the undersigned Holder (together with
such Holder’s Affiliates, and any other Person whose beneficial ownership of Common Stock would be aggregated with the Holder’s for purposes of Section 13(d) or Section 16 of the Exchange Act and the applicable regulations of the
Commission, including any “group” of which the Holder is a member (the foregoing, “Attribution Parties”)), including the number of shares of Common Stock issuable upon conversion of the Series D Preferred Stock
subject to this Notice of Conversion, but excluding the number of shares of Common Stock which are issuable upon (A) conversion of the remaining, unconverted Series D Preferred Stock beneficially owned by such Holder or any of its Attribution
Parties, and (B) exercise or conversion of the unexercised or unconverted portion of any other securities of the Corporation (including any warrants) beneficially owned by such Holder or any of its Attribution Parties that are subject to a
limitation on conversion or exercise similar to the limitation contained in Section 6(c) of the Certificate of Designation, is     %. For purposes hereof, beneficial ownership shall be calculated in accordance with
Section 13(d) of the Exchange Act and the applicable regulations of the Commission. In addition, for purposes hereof, “group” has the meaning set forth in Section 13(d) of the Exchange Act and the applicable regulations of the
Commission. 
 Conversion calculations: 
  

			
	Date to Effect Conversion:	 	  

 

			
	Number of shares of Series D Preferred Stock owned prior to Conversion:	 	  

 

			
	Number of shares of Series D Preferred Stock to be Converted:	 	  

 

			
	Number of shares of Common Stock to be Issued:	 	  

 

			
	Address for delivery of physical certificates:	 	  

 

			
	or	 	
		
	for DWAC Delivery:	 	  

 

			
	DWAC Instructions:	 	  

 

			
	 Broker no:
	 	  

		
	 Account no:
	 	  

 
					
	HOLDER
		
	By:	 	  

			
		 	Name:	 	  

			
		 	Title:	 	  

			
		 	Date:	 	  

  
 13EX-10.1

 Exhibit 10.1 

SUBSCRIPTION AGREEMENT 
 Cascadian
Therapeutics, Inc. 
 2601 Fourth Avenue, Suite 500 
 Seattle,
Washington 98121 
 Ladies and Gentlemen: 
 The undersigned
(the “Investor”) hereby confirms and agrees with you as follows: 
  

	1.	This Subscription Agreement (this “Agreement”) is made as of the date set forth below between Cascadian Therapeutics Inc., a Delaware corporation (the “Company”) and the Investor.

  

	2.	The Company has authorized the sale and issuance of up to 17,250 shares (the “Shares”) of the Company’s Series D Convertible Preferred Stock, $0.0001 par value per share (the “Preferred
Stock”), for a purchase price of $800.00 per Share. The offering and sale of the Shares (the “Offering”) is being made pursuant to (a) an effective Registration Statement on Form S-3, initially filed on
December 30, 2014 (No. 333-201317) by the Company with the Securities and Exchange Commission (the “Commission”) and any registration statement relating to the Offering and filed pursuant to Rule 462(b) under the Rules and
Regulations (collectively, the “Registration Statement”), which contains the base prospectus dated January 7, 2015 (the “Base Prospectus”), (b) if applicable, certain “free writing prospectus”
(as that term is defined in Rule 405 under the Securities Act of 1933, as amended), that have or will be filed with the Commission and delivered to the Investor on or prior to the date hereof, (c) if applicable, a preliminary prospectus
supplement to the Base Prospectus (together with the Base Prospectus, the “Statutory Prospectus”), and (d) a final prospectus supplement, dated June 23, 2016 (the “Prospectus Supplement” and together with
the Base Prospectus, the “Prospectus”) containing certain supplemental information regarding the Shares and terms of the Offering that will be filed with the Commission and delivered to the Investor (or made available to the
Investor by the filing by the Company of an electronic version thereof with the Commission) along with the Company’s counterpart to this Agreement. The Investor hereby consents to the receipt of the Company’s Prospectus in portable
document format, or PDF, via electronic e-mail. 

  

	3.	As of the Closing (as defined below) and subject to the terms and conditions hereof, the Company and the Investor agree that the Investor will purchase from the Company and the Company will issue and sell to the
Investor such number of Shares as is set forth on the signature page hereto. Certificates representing the Shares purchased by the Investor will not be issued to the Investor; instead, such Shares will be credited to the Investor using customary
procedures for book-entry transfer through the facilities of The Depository Trust Company. The Investor acknowledges that the Offering is not a firm commitment underwriting and that there is no minimum offering amount. This Offering will not clear
directly through the Placement Agent (as defined below) acting in such capacity. Consequently, the Investor must instruct their individual broker how to settle the transaction. 

 

	4.	The completion of the purchase and sale of the Shares shall occur on the third day following the date hereof on which The NASDAQ Global Market is open for trading, or such other time not later than 10 business days
after such date as shall be agreed upon by the Company and the Investor (the “Closing”). At the Closing, (a) the Company shall cause its transfer agent to release to the Investor the number of Shares being purchased by the
Investor and (b) the aggregate purchase price for the Shares being purchased by the Investor will be delivered by or on behalf of the Investor to the Company. Settlement for the Shares shall occur via Deposit/Withdrawal At Custodian. The
provisions set forth in Exhibit A hereto shall be incorporated herein by reference as if set forth fully herein. 

  

	5.	The Company has entered into a Placement Agency Agreement (the “Placement Agreement”), dated June 23, 2016 with Cowen and Company, LLC and Trout Capital LLC (the “Placement
Agents”), which will act as the Company’s placement agent with respect to the Offering and receive a fee in connection with the sale of the Shares. The Placement Agreement contains certain representations and warranties of the Company.
The Company acknowledges and agrees that the Investor may rely on the representations and warranties made by it to the Placement Agents in Section 2 of the Placement Agreement to the same extent as if such representations and warranties had
been incorporated in full herein and made directly to the Investor, which shall be third party beneficiary thereof. 

	6.	The Company hereby makes the following representations, warranties and covenants to the Investor: 

(a) The Company has the requisite corporate power and authority to enter into and to consummate the transactions contemplated
by this Agreement and otherwise to carry out its obligations hereunder. The execution and delivery of this Agreement by the Company and the consummation by it of the transactions contemplated hereunder have been duly authorized by all necessary
action on the part of the Company. This Agreement has been duly executed by the Company and, when delivered in accordance with the terms hereof, will constitute the valid and binding obligation of the Company enforceable against the Company in
accordance with its terms, except as may be limited by any bankruptcy, insolvency, reorganization, moratorium, fraudulent conveyance or other similar laws affecting the enforcement of creditors’ rights generally or by general principles of
equity. 
 (b) The Company shall (i) before 9:30 A.M., New York City time, on June 23, 2016, issue a press release,
disclosing all material aspects of the transactions contemplated hereby, (ii) on June 23, 2016, file with the Commission a Current Report on Form 8-K, disclosing the material terms and conditions of the transactions contemplated hereby and
(ii) make such other filings and notices in the manner and time required by the Commission with respect to the transactions contemplated hereby. 

(c) The Company shall not sell, offer for sale or solicit offers to buy any security (as defined in Section 2 of the
Securities Act) in a transaction that would be (i) integrated with the offer or sale of the Shares for purposes of the rules and regulations of The NASDAQ Global Market and (ii) would require approval of the Company’s stockholders
prior to the closing of such other transaction, unless such stockholder approval is obtained before the closing of such other transaction. 

(d) If the Company applies to have the Common Stock traded on any trading market other than The NASDAQ Global Market, it will
then include in such application all of the Shares, and will take such other action as is reasonably necessary to cause all of the Common Stock to be listed or quoted on such other trading market as promptly as possible. 

 

	7.	The obligations of the Company and the Investor to complete the transactions contemplated by this Agreement shall be subject to the following: 

(a) The Company’s obligation to issue and sell the Shares to the Investor shall be subject to: (i) the receipt by the
Company of the purchase price for the Shares being purchased hereunder as set forth on the signature page hereto and (ii) the accuracy of the representations and warranties made by the Investor and the fulfillment of those undertakings of the
Investor to be fulfilled prior to the Closing Date. 
 (b) The Investor’s obligation to purchase the Shares shall be
subject to the accuracy of the representations and warranties made by the Company and the fulfillment of those undertakings of the Company to be fulfilled prior to the Closing Date, including without limitation, those contained in the Placement
Agreement, and to the condition that the Placement Agents shall not have: (i) terminated the Placement Agreement pursuant to the terms thereof or (ii) determined that the conditions to closing in the Placement Agreement have not been
satisfied. The Investor’s obligations are expressly not conditioned on the purchase by any or all of the other Investors of the Shares that they have agreed to purchase from the Company. 

 

	8.	The Investor hereby makes the following representations, warranties and covenants to the Company: 

(a) The Investor represents that it has received or had full access to the Statutory Prospectus as well as the Company’s
periodic reports and other information incorporated by reference therein, prior to or in connection with its receipt of this Agreement. 

(b) The Investor has the requisite power and authority to enter into this Agreement and to consummate the transactions
contemplated hereby. The execution and delivery of this Agreement by the Investor and the consummation by it of the transactions contemplated hereunder have been duly authorized by all necessary action on the part of the Investor. This Agreement has
been executed by the Investor and, when delivered in accordance with the terms hereof, will constitute a valid and binding obligation of the Investor enforceable against the Investor in accordance with its terms. 

(c) The Investor understands that nothing in this Agreement or any other materials presented to the Investor in connection with
the purchase and sale of the Shares constitutes legal, tax or investment advice. The Investor has consulted such legal, tax and investment advisors as it, in its sole discretion, has deemed necessary or appropriate in connection with its purchase of
Shares. 

  
 2 

 (d) The making, execution and performance of this Agreement by the Investor and
the consummation of the transactions contemplated herein will not conflict with or result in a breach or violation of any of the terms and provisions of, or constitute a default under, (i) the charter, bylaws or other organizational documents
of such Investor, as applicable, or (ii) any law, order, rule, regulation, writ, injunction, judgment or decree of any court, administrative agency, regulatory body, government or governmental agency or body, domestic or foreign, having
jurisdiction over such Investor or its properties, except for any conflict, breach, violation or default which is not reasonably likely to have a material adverse effect on such Investor’s performance of its obligations hereunder or the
consummation of the transactions contemplated hereby. 
 (e) Neither the Investor nor any Person acting on behalf of, or
pursuant to any understanding with or based upon any information received from, the Investor has, directly or indirectly, engaged in any Short Sales involving the Company’s securities since the date that is the tenth (10th) trading day prior to the date of this Agreement. “Short Sales” include, without limitation, all “short sales” as defined in Rule 200 promulgated under Regulation SHO under
the Securities Exchange Act of 1934, as amended (the “Exchange Act”), whether or not against the box, and all types of direct and indirect stock pledges, forward sale contracts, options, puts, calls, short sales, swaps, “put
equivalent positions” (as defined in Rule 16a- 1(h) under the Exchange Act) and similar arrangements (including on a total return basis), and sales and other transactions through non-U.S. broker dealers or foreign regulated brokers. The
Investor covenants that neither it, nor any Person acting on behalf of, or pursuant to any understanding with or based upon any information received from, the Investor will engage in any transactions in the securities of the Company (including Short
Sales) prior to the time that the transactions contemplated by this Agreement are publicly disclosed. Notwithstanding the foregoing, in the case of an Investor and/or its affiliates that is, individually or collectively, a multi-managed investment
bank or vehicle whereby separate portfolio managers manage separate portions of such Investor’s or affiliates assets and the portfolio managers have no direct knowledge of the investment decisions made by the portfolio managers managing other
portions of such Investor’s or affiliates assets, the representation set forth above shall only apply with respect to the portion of assets managed by the portfolio managers that have knowledge about the financing transaction contemplated by
this Agreement. 
 (f) The Investor represents that, except as set forth below and except as set forth in any Information
Statement filed under Section 13D of the Securities Exchange Act of 1934, (i) it has had no position, office or other material relationship within the past three years with the Company or persons known to it to be affiliates of the
Company, (ii) it is not a member of the Financial Industry Regulatory Authority, Inc. (“FINRA”) or an Associated Person (as such term is defined under FINRA’s NASD Membership and Registration Rules Section 1011) as of
the date hereof and (iii) neither it nor any group of investors (as identified in a public filing made with the Commission) of which it is a member, acquired or obtained the right to acquire 20% or more of the Common Stock (or securities
convertible or exercisable for Common Stock) or voting power of the Company on a post-transaction basis. 
 (g) If the
Investor is a retirement plan or is investing on behalf of a retirement plan, the Investor acknowledges that an investment in the Shares poses additional risks, including the inability to use losses generated by an investment in the Shares to offset
taxable income. 
 (h) The Investor acknowledges that no action had been or will be taken in any jurisdiction outside the
United States by the Company that would permit an offering of the Shares, or possession or distribution of offering materials in connection with the issue of the Shares, in any jurisdiction outside the United States where action for that purpose is
required. Each Investor outside the United States will comply with all applicable laws and regulations in each foreign jurisdiction in which it purchases, offers, sells or delivers Shares or has in its possession or distributes any offering
material, in all cases at its own expense. 
 (i) The Investor acknowledges that the Company and others will rely upon the
truth and accuracy of the foregoing representations, acknowledgements and agreements and agrees that if any of the representations, warranties and acknowledgements deemed to have been made by it by its purchase of the Shares is no longer accurate,
the Investor shall promptly notify the Company. If the Investor is acquiring Shares as a fiduciary or agent for one or more investor accounts, it represents that is has sole investment discretion with respect to each such account and it has full
power to make the foregoing representations, warranties, acknowledgements and agreements on behalf of such account. 
  

	9.	 No offer by the Investor to buy Shares will be accepted and no part of the aggregate purchase price will be
delivered to the Company until the Investor has received the Statutory Prospectus and the Company has accepted such offer by countersigning a copy of this Subscription, and any such offer may be withdrawn or

  
 3 

	 	
revoked, without obligation or commitment of any kind, at any time prior to the Company (or the Placement Agents on behalf of the Company) sending (orally, in writing or by electronic mail)
notice of its acceptance of such offer. This subscription will constitute only an indication of interest, involving no obligation or commitment of any kind, until the Statutory Prospectus has been delivered or made available to the Investor and this
subscription is accepted and countersigned by or on behalf of the Company. 

  

	10.	Notwithstanding any investigation made by any party to this Agreement, all covenants, agreements, representations and warranties made by the Company and the Investor herein will survive the execution of this Agreement,
the delivery to the Investor of the Shares being purchased and the payment therefor. The Placement Agents shall be a third party beneficiary with respect to representations, warranties and agreements of the Investor herein. 

 

	11.	At the Closing, the Investor agrees to pay, or reimburse the Company if paid, for reasonable and documented legal and accounting expenses incurred by the Company and directly related to the Offering, not to exceed
$15,000 in the aggregate. 

  

	12.	This Agreement may not be modified or amended except pursuant to an instrument in writing signed by the Company and the Investor. 

  

	13.	The headings of the various sections of this Agreement have been inserted for convenience of reference only and shall not be deemed to be part of this Agreement. 

 

	14.	In case any provision contained in this Agreement should be invalid, illegal or unenforceable in any respect, the validity, legality and enforceability of the remaining provisions contained herein will not in any way be
affected or impaired thereby. 

  

	15.	This Agreement will be governed by, and construed in accordance with, the internal laws of the State of New York, without giving effect to the principles of conflicts of law that would require the application of the
laws of any other jurisdiction. 

  

	16.	This Agreement may be executed in counterparts, each of which will constitute an original, but all of which, when taken together, will constitute but one instrument, and will become effective when counterparts have been
signed by each party hereto and delivered to the other party. 

  

	17.	The Investor acknowledges and agrees that such Investor’s receipt of the Company’s counterpart to this Agreement shall constitute written confirmation of the Company’s agreement to sell Shares to such
Investor. No federal or state agency or authority has made any finding or determination as to the accuracy or adequacy of the Registration Statement or as to the fairness of the terms of the Offering nor any recommendation or endorsement of the
Shares. Any representation to the contrary is a criminal offense. In making an investment decision, Investors must rely on their own examination of the Company and the terms of the Offering, including the merits and risks involved.

  
 4 

 Number of Shares:
                 
 Purchase Price Per Share: $
         
 Aggregate Purchase Price: $          

Please confirm that the foregoing correctly sets forth the agreement between us by signing in the space provided below for that purpose. 

Dated as of: June     , 2016 
  

			
	  

	INVESTOR
	By:	 	  

			
	Print Name: 	 	  

			
	Title: 	 	  

 Name in which Shares are to be registered: 

Mailing Address: 
 Taxpayer Identification Number: 

Agreed and Accepted this      day of             , 2016: 

 

					
	CASCADIAN THERAPEUTICS, INC.
		
	By:	 	  

		 	Title:	 	 Scott Myers, Chief Executive Officer

 Sales of the Shares purchased hereunder were made pursuant to a registration statement or in a transaction in which a final
prospectus would have been required to have been delivered in the absence of Rule 172 promulgated under the Securities Act. 

  
 5 

 EXHIBIT A 

TO BE COMPLETED BY INVESTOR 

DWAC SETTLEMENT 
 Delivery by electronic
book-entry at The Depository Trust Company (“DTC”), registered in the Investor’s name and address as set forth on the signature page of the Agreement to which this Exhibit A is attached, and released by Computershare
Trust Company, N.A., the Company’s transfer agent (the “Transfer Agent”), to the Investor at the Closing. 
  

			
	Name of DTC Participant (broker-dealer at which the account or accounts to be credited with the Shares are maintained):	 	  

		
	DTC Participant Number:	 	  

		
	Name of Account at DTC Participant being credited with the Shares:	 	  

		
	Account Number at DTC Participant being credited with the Shares:	 	  

 NO LATER THAN ONE (1) BUSINESS DAY AFTER THE EXECUTION OF THE AGREEMENT TO WHICH THIS EXHIBIT A IS ATTACHED BY
THE INVESTOR AND THE COMPANY, THE INVESTOR SHALL:  
  

	 	(I)	DIRECT THE BROKER-DEALER AT WHICH THE ACCOUNT OR ACCOUNTS TO BE CREDITED WITH THE SHARES ARE MAINTAINED TO SET UP A DEPOSIT/WITHDRAWAL AT CUSTODIAN (“DWAC”) ON THE CLOSING DATE INSTRUCTING THE TRANSFER
AGENT TO CREDIT SUCH ACCOUNT OR ACCOUNTS WITH THE SHARES, AND 

  

	 	(II)	REMIT BY WIRE TRANSFER THE AMOUNT OF FUNDS EQUAL TO THE AGGREGATE PURCHASE PRICE FOR THE SHARES BEING PURCHASED BY THE INVESTOR TO THE FOLLOWING ACCOUNT: 

  
 6

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