Document:

Form of Debt Securities

 EXHIBIT 4.3 
 [If the Holder of this Security is a depository, such as The Depository Trust Company (“DTC”) or a nominee of DTC, this Security is a Global Security and insert the following two legends: 
 THIS SECURITY IS A GLOBAL SECURITY WITHIN THE MEANING OF THE INDENTURE HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME OF A DEPOSITORY (AS DEFINED
IN THE INDENTURE) OR A NOMINEE THEREOF. THIS GLOBAL SECURITY IS EXCHANGEABLE FOR SECURITIES REGISTERED IN THE NAME OF A PERSON OTHER THAN THE DEPOSITORY OR ITS NOMINEE ONLY IN THE LIMITED CIRCUMSTANCES DESCRIBED IN THE INDENTURE AND, UNLESS AND
UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR SECURITIES IN DEFINITIVE FORM, THIS GLOBAL SECURITY MAY NOT BE TRANSFERRED EXCEPT AS A WHOLE BY THE DEPOSITORY TO A NOMINEE OF THE DEPOSITORY, OR BY A NOMINEE OF THE DEPOSITORY TO THE DEPOSITORY OR
ANOTHER NOMINEE OF THE DEPOSITORY, OR BY THE DEPOSITORY OR ANY SUCH NOMINEE TO A SUCCESSOR DEPOSITORY OR A NOMINEE OF SUCH SUCCESSOR DEPOSITORY. 
 UNLESS THE SECURITY IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF [THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION (“DTC”),] TO THE COMPANY (AS DEFINED BELOW) OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT,
AND ANY SECURITY ISSUED IS REGISTERED IN THE NAME OF [CEDE & CO. OR IN] SUCH [OTHER] NAME AS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF [THE DEPOSITORY] [DTC] (AND ANY PAYMENT IS MADE TO [CEDE & CO. OR TO] SUCH [OTHER] ENTITY AS
IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF [THE DEPOSITORY] [DTC]), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER HEREOF[, CEDE & CO.,] HAS AN INTEREST
HEREIN.] 
 [Insert any applicable legend(s) required by the Internal Revenue Code] 
 NO.     $             
 ZYMOGENETICS, INC. 
 [Designation of
Series] 
 ZYMOGENETICS, INC., a Washington corporation (hereinafter called the “Company”, which term includes any successor
corporation under the Indenture referred to below), for value received, hereby promises to pay to             , or registered assigns, the principal sum of
             Dollars ($            ) on
            ,              [If the Security is to bear interest prior to Maturity, insert — , and to
pay interest thereon from              or from the most recent Interest Payment Date to which interest has been paid or duly provided for, semiannually on
             and              in each year, commencing
            , [If the Security is to bear interest at a fixed rate, insert — at the rate of     % per annum] [If the Security is to bear
interest at an adjustable rate, insert — at a rate per annum computed or determined in accordance with the provisions below], until the principal hereof is paid or made available for payment [If applicable, insert –, and (to the
extent 

 
that the payment of such interest shall be legally enforceable) at the rate of     % per annum on any overdue principal and
premium and on any overdue installment of interest from the dates such amounts are due until they are paid or made available for payment and such interest shall be payable on demand]. [If applicable, insert — Interest on this Security
shall be computed on the basis of a 360-day year of twelve 30-day months. If any Interest Payment Date or the maturity date falls on a day that is not a Business Day, the required payment shall be made on the next Business Day as if it were made on
the date such payment was due and no interest shall accrue on the amount so payable for the period from and after such Interest Payment Date or the maturity date, as the case may be, to such next Business Day.] The interest so payable and punctually
paid or duly provided for on any Interest Payment Date will, as provided in such Indenture, be paid to the Person in whose name this Security (or one or more Predecessor Securities) is registered at the close of business on the regular record date
for such interest, which shall be              or              (whether or not a Business Day), as the case may be,
next preceding such Interest Payment Date. Any such interest which is payable but not punctually paid or duly provided for on any Interest Payment Date shall forthwith cease to be payable to the registered Holder hereof on the relevant regular
record date by virtue or having been such holder, and may be paid to the Person in whose name this Security (or one or more Predecessor Securities) is registered at the close of business on a subsequent special record date (which shall be at least
10 days before the payment date) for the payment of such defaulted interest to be fixed by the Company, notice whereof shall be given to the Holders of Securities of this series not less than 10 days prior to such Special Record Date, or
may be paid at any time in any other lawful manner not inconsistent with the requirements of any securities exchange on which the Securities may be listed, and upon such notice as may be required by such exchange, all as more fully provided in such
Indenture. 
 [If the Security is not to bear interest prior to Maturity, insert — The principal of this Security shall not bear
interest except in the case of a default in payment of principal upon acceleration or redemption or at the Stated Maturity and in such case the overdue principal of this Security shall bear interest at the rate of     %
per annum (to the extent that the payment of such interest shall be legally enforceable), which shall accrue from the date of such default in payment to the date payment of such principal has been made or duly provided for. Interest on any overdue
principal shall be payable on demand. Any such interest on any overdue principal that is not so paid on demand shall bear interest at the rate of     % per annum (to the extent that the payment of such interest shall be
legally enforceable), which shall accrue from the date of such demand for payment to the date payment of such interest has been made or duly provided for, and such interest shall also be payable on demand.] 
 Payment of the principal of and [If applicable, insert — any such] interest on this Security will be made at the office or agency of the
Company maintained for that purpose in The Borough of Manhattan, The City of New York, in such coin or currency of the United States of America as at the time of payment is legal tender for payment of public and private debts [If applicable,
insert — ; provided, however, that, at the option of the Company, interest may be paid by check mailed to the address of the Person entitled thereto as such address shall appear in the Security Register;] [If applicable, insert
— provided, further, that payment to [DTC or] any [successor] depository may be made by wire transfer to the account designated by [DTC or] such [successor] depository in writing]. 
 This Security is one of a duly authorized issue of securities of the Company (herein called the “Securities”), issued and to be issued in one
or more series under an Indenture, dated as of                     , 20     (herein called, together with all
indentures supplemental thereto, the “Indenture”), between the Company and             , as Trustee (herein called the “Trustee”, which term includes any
successor trustee under the Indenture), to which Indenture and all indentures 

  

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supplemental thereto reference is hereby made for a statement of the respective rights, limitations of rights, duties and immunities thereunder of the
Company, the Trustee and the Holders of the Securities, and of the terms upon which the Securities are, and are to be, authenticated and delivered. This Security is one of the series designated on the face hereof [, initially limited (subject to
exceptions provided in the Indenture) to the aggregate principal amount of $            ]. 
 [If applicable, insert — The indebtedness evidenced by the Securities is, to the extent provided in the Indenture, subordinate and subject in right of payment to the prior payment in full of all
indebtedness and obligations of the Company as are defined in the Indenture as “Senior Indebtedness,” and this Security is issued subject to the provisions of the Indenture with respect thereto, and each Holder of this Security, by
accepting the same, agrees to and shall be bound by such provisions. Each Holder of this Security, by accepting the same, agrees that each holder of Senior Indebtedness, whether created or acquired before or after the issuance of this Security,
shall be deemed conclusively to have relied on such subordination provisions in acquiring and continuing to hold, or in continuing to hold, such Senior Indebtedness.] 
 [If the Security is not an Original Issue Discount Security, insert — If an Event of Default with respect to the Securities shall occur and be continuing, the principal of the Securities may be declared
due and payable in the manner and with the effect provided in the Indenture.] 
 [If the Security is an Original Issue Discount Security,
insert — If an Event of Default with respect to Securities of this series shall occur and be continuing, an amount of principal of the Securities of this series may be declared due and payable in the manner and with the effect provided in
the Indenture. Such amount shall be equal to [insert formula for determining the amount]. Upon payment (i) of the amount of principal so declared due and payable and (ii) of interest on any overdue principal, premium and interest
(in each case to the extent that the payment of such interest shall be legally enforceable), all of the Company’s obligations in respect of the payment of the principal of and premium and interest, if any, on the Securities of this series shall
terminate.] 
 [If applicable, insert — The Securities may not be redeemed prior to the Stated Maturity.] 
 [If applicable, insert — The Securities are not subject to any sinking fund.] 
 [If applicable, insert — The Securities are subject to redemption [(l) [If applicable, insert — on
             in any year commencing with the year              and ending with the year
             through operation of the sinking fund for this series at a Redemption Price equal to 100% of the principal amount, and (2)] [If applicable, insert — at
any time [on or after             ], as a whole or in part, at the election of the Company, at the following Redemption Prices (expressed as percentages of the principal amount): if
redeemed on or before             ,     % and if redeemed during the 12-month period beginning
             of the years indicated at the Redemption Prices indicated below: 
  

			
	 Year
	  	Redemption Price

 and thereafter at a Redemption Price equal to     % of the principal amount, together
in the case of any such redemption [If applicable, insert — (whether through operation of the sinking fund or otherwise)] with accrued interest to the Redemption Date; provided, however, that installments of 

  

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interest on this Security whose Stated Maturity is on or prior to such Redemption Date will be payable to the Holder of this Security, or one or more
Predecessor Securities, of record at the close of business on the relevant Record Dates referred to on the face hereof, all as provided in the Indenture.] 
 [If applicable, insert — The Securities are subject to redemption (1) on              in any year commencing with the year
             and ending with the year              through operation of the sinking fund for this series at the
Redemption Prices for redemption through operation of the sinking fund (expressed as percentages of the principal amount) set forth in the table below, and (2) at any time [on or after
            ], as a whole or in part, at the election of the Company, at the Redemption Prices for redemption otherwise than through operation of the sinking fund (expressed as
percentages of the principal amount) set forth in the table below: if redeemed during the 12-month period beginning              of the years indicated below: 
  

					
	 Year
	  	Redemption Price
for Redemption
through Operation
of the Sinking Fund	  	Redemption Price for
Redemption
Otherwise than
through Operation
of the Sinking Fund

 and thereafter at a Redemption Price equal to     % of the principal amount, together
in the case of any such redemption (whether through operation of the sinking fund or otherwise) with accrued interest to the Redemption Date; provided, however, that installments of interest on this Security whose Stated Maturity is on or prior to
such Redemption Date will be payable to the Holder of this Security, or one or more Predecessor Securities, of record at the close of business on the relevant Record Dates referred to on the face hereof, all as provided in the Indenture.]

 [If applicable, insert — Notwithstanding the foregoing, the Company may not, prior to
            , redeem any Securities as contemplated by [Clause (2) of] the preceding paragraph as a part of, or in anticipation of, any refunding operation by the application,
directly or indirectly, of moneys borrowed having an interest cost to the Company (calculated in accordance with generally accepted financial practice) of less than     % per annum.] 
 [If applicable, insert — The sinking fund for the Securities provides for the redemption on
             in each year, beginning with the year              and ending with the year
            , of [not less than] $            [(“mandatory sinking fund”) and not more than
$            ] aggregate principal amount of the Securities of this series. [The Securities acquired or redeemed by the Company otherwise than through [mandatory] sinking fund
payments may be credited against subsequent [mandatory] sinking fund payments otherwise required to be made in the [describe order].]] 
 [If applicable, insert — Notice of redemption will be given by mail to Holders of Securities, not less than 30 nor more than 60 days prior to the Redemption Date, all as provided in the Indenture.] 
  

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 [If applicable, insert — In the event of redemption of this Security in part only, a new
Security or Securities for the unredeemed portion hereof shall be issued in the name of the Holder hereof upon the cancellation hereof.] 
 The Indenture contains provisions permitting, with certain exceptions as therein provided, the amendment thereof and the modification of the rights and obligations of the Company and the rights of the Holders of the Securities of each
series issued under the Indenture at any time by the Company and the Trustee with the written consent of the Holders of not less than a majority in aggregate principal amount of the Securities at the time Outstanding of each series affected thereby.
The Indenture also contains provisions permitting the Holders of specified percentages in aggregate principal amount of the Securities of any series at the time Outstanding, on behalf of the Holders of all Securities of such series, to waive
compliance by the Company with certain provisions of the Indenture and certain past defaults under the Indenture and their consequences. Any such consent or waiver by the Holder of this Security shall be conclusive and binding upon such Holder and
upon all future Holders of this Securities and of any Securities issued upon the registration of transfer hereof or in exchange herefor or in lieu hereof, whether or not notation of such consent or waiver is made upon this Security. 
 No reference herein to the Indenture and no provision of this Security or of the Indenture shall alter or impair the obligation of the Company, which is
absolute and unconditional, to pay the principal of and interest on this Security, at the times, place and rate, and in the coin or currency, herein and in the Indenture prescribed. 
 As provided in the Indenture and subject to certain limitations set forth therein and in this Security, the transfer of this Security may be registered
on the Security Register upon surrender of this Security for registration of transfer at the office or agency of the Company maintained for that purpose in any place where the principal of and interest on this Security are payable, duly endorsed by,
or accompanied by a written instrument of transfer in form satisfactory to the Company and the Security Registrar duly executed by, the Holder hereof or by his attorney duly authorized in writing, and thereupon one or more new Securities of this
series and of like tenor, of authorized denominations and for the same aggregate principal amount, will be issued to the designated transferee or transferees. 
 [If applicable, insert — The Securities are issuable only in registered form [without coupons] in the denominations of $             and
any integral multiple thereof.] As provided in the Indenture and subject to certain limitations set forth in the Indenture, and in this Security, the Securities are exchangeable for a like aggregate principal amount of Securities of this series in
different authorized denominations, as requested by the Holders surrendering the same. 
 No service charge shall be made for any such
registration of transfer or exchange, but the Company may require payment of a sum sufficient to cover any tax or other governmental charge payable in connection therewith, other than in certain cases provided in the Indenture. 
  

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 Prior to due presentment of this Security for registration of transfer, the Company, the Trustee and any
agent of the Company or the Trustee may treat the Person in whose name this Security is registered as the owner hereof for all purposes, whether or not this Security be overdue, and neither the Company, the Trustee nor any such agent shall be
affected by notice to the contrary. 
 [If applicable, insert — The Indenture contains provisions whereby (i) the Company
may be discharged from its obligations with respect to the Securities (subject to certain exceptions) or (ii) the Company may be released from its obligations under specified covenants and agreements in the Indenture, in each case if the
Company irrevocably deposits with the Trustee money or Government Obligations, or a combination thereof, in an amount sufficient, without consideration of any reinvestment, to pay and discharge the entire indebtedness on all Securities of this
series, and satisfies certain other conditions, all as more fully provided in the Indenture.] 
 This Security shall be governed by and
construed in accordance with the laws of the State of New York applicable to agreements made or instruments entered into and, in each case, performed in said State. 
 All terms used in this Security without definition that are defined in the Indenture shall have the meanings assigned to them in the Indenture. 
 [Remainder of Page Intentionally Left Blank] 
  

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 Unless the Certificate of Authentication hereon has been executed by or on behalf of the Trustee under
the Indenture by the manual signature of one of its authorized officers, this Security shall not be entitled to any benefits under the Indenture or be valid or obligatory for any purpose. 
 IN WITNESS WHEREOF, the Company has caused this instrument to be duly executed under its corporate seal. 
  

									
	 [SEAL]
	 		 	ZYMOGENETICS, INC.
				
		 		 	By:	 	 
		 		 		 		 	Name:
		 		 		 		 	Title:
			
	 Attest:
	 		 	
				
		 		 	By:	 	 
		 		 		 		 	Name:
		 		 		 		 	Title:

 CERTIFICATE OF AUTHENTICATION 
 This is one of the Securities of the series designated therein referred to in the within-mentioned Indenture. 
  

											
		 		 	_______________________________________________________,
		 		 	as Trustee
				
	Dated:                     	 		 	By:	 	 
		 		 		 		 	Name:	 	
		 		 		 		 	Title:	 	Authorized OfficerForm of Convertible Debt Securities

 EXHIBIT 4.4 
 [If the Holder of this Security is a depository, such as The Depository Trust Company (“DTC”) or a nominee of DTC, this Security is a Global Security and insert the following two legends: 

THIS SECURITY IS A GLOBAL SECURITY WITHIN THE MEANING OF THE INDENTURE HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME OF A DEPOSITORY (AS
DEFINED IN THE INDENTURE) OR A NOMINEE THEREOF. THIS GLOBAL SECURITY IS EXCHANGEABLE FOR SECURITIES REGISTERED IN THE NAME OF A PERSON OTHER THAN THE DEPOSITORY OR ITS NOMINEE ONLY IN THE LIMITED CIRCUMSTANCES DESCRIBED IN THE INDENTURE AND, UNLESS
AND UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR SECURITIES IN DEFINITIVE FORM, THIS GLOBAL SECURITY MAY NOT BE TRANSFERRED EXCEPT AS A WHOLE BY THE DEPOSITORY TO A NOMINEE OF THE DEPOSITORY, OR BY A NOMINEE OF THE DEPOSITORY TO THE DEPOSITORY OR
ANOTHER NOMINEE OF THE DEPOSITORY, OR BY THE DEPOSITORY OR ANY SUCH NOMINEE TO A SUCCESSOR DEPOSITORY OR A NOMINEE OF SUCH SUCCESSOR DEPOSITORY. 
 UNLESS THE SECURITY IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF [THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION (“DTC”),] TO THE COMPANY (AS DEFINED BELOW) OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT,
AND ANY SECURITY ISSUED IS REGISTERED IN THE NAME OF [CEDE & CO. OR IN] SUCH [OTHER] NAME AS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF [THE DEPOSITORY] [DTC] (AND ANY PAYMENT IS MADE TO [CEDE & CO. OR TO] SUCH [OTHER] ENTITY AS
IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF [THE DEPOSITORY] [DTC]), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER HEREOF[, CEDE & CO.,] HAS AN INTEREST
HEREIN.] 
 [Insert any applicable legend(s) required by the Internal Revenue Code] 
  

			
	NO.         	  	$             

 ZYMOGENETICS, INC. 
 [Designation of Series] 
 ZYMOGENETICS, INC., a Washington corporation (hereinafter
called the “Company”, which term includes any successor corporation under the Indenture referred to below), for value received, hereby promises to pay to
            , or registered assigns, the principal sum of              Dollars
($            ) on             ,
             [If the Security is to bear interest prior to Maturity, insert — , and to pay interest thereon from
             or from the most recent Interest Payment Date to which interest has been paid or duly provided for, semiannually on
             and              in each year, commencing
            , [If the Security is to bear interest at a fixed rate, insert — at the rate of     % per annum] [If the Security is to bear
interest at an adjustable rate, insert — at a rate per annum computed or determined in accordance with the provisions below], until 

 
the principal hereof is paid or made available for payment [If applicable, insert —, and (to the extent that the payment of such interest shall
be legally enforceable) at the rate of             % per annum on any overdue principal and premium and on any overdue installment of interest from the dates such amounts are due
until they are paid or made available for payment and such interest shall be payable on demand]. [If applicable, insert — Interest on this Security shall be computed on the basis of a 360-day year of twelve 30-day months. If any Interest
Payment Date or the maturity date falls on a day that is not a Business Day, the required payment shall be made on the next Business Day as if it were made on the date such payment was due and no interest shall accrue on the amount so payable for
the period from and after such Interest Payment Date or the maturity date, as the case may be, to such next Business Day.] The interest so payable and punctually paid or duly provided for on any Interest Payment Date will, as provided in such
Indenture, be paid to the Person in whose name this Security (or one or more Predecessor Securities) is registered at the close of business on the regular record date for such interest, which shall be
             or              (whether or not a Business Day), as the case may be, next preceding such Interest
Payment Date. Any such interest which is payable but not punctually paid or duly provided for on any Interest Payment Date shall forthwith cease to be payable to the registered Holder hereof on the relevant regular record date by virtue or having
been such holder, and may be paid to the Person in whose name this Security (or one or more Predecessor Securities) is registered at the close of business on a subsequent special record date (which shall be at least 10 days before the payment date)
for the payment of such defaulted interest to be fixed by the Company, notice whereof shall be given to the Holders of Securities of this series not less than 10 days prior to such Special Record Date, or may be paid at any time in any other lawful
manner not inconsistent with the requirements of any securities exchange on which the Securities may be listed, and upon such notice as may be required by such exchange, all as more fully provided in such Indenture. 
 [If the Security is not to bear interest prior to Maturity, insert — The principal of this Security shall not bear interest except in the
case of a default in payment of principal upon acceleration or redemption or at the Stated Maturity and in such case the overdue principal of this Security shall bear interest at the rate of     % per annum (to the extent
that the payment of such interest shall be legally enforceable), which shall accrue from the date of such default in payment to the date payment of such principal has been made or duly provided for. Interest on any overdue principal shall be payable
on demand. Any such interest on any overdue principal that is not so paid on demand shall bear interest at the rate of     % per annum (to the extent that the payment of such interest shall be legally enforceable), which
shall accrue from the date of such demand for payment to the date payment of such interest has been made or duly provided for, and such interest shall also be payable on demand.] 
 Payment of the principal of and [If applicable, insert — any such] interest on this Security will be made at the office or agency of the
Company maintained for that purpose in The Borough of Manhattan, The City of New York, in such coin or currency of the United States of America as at the time of payment is legal tender for payment of public and private debts [If applicable,
insert — ; provided, however, that, at the option of the Company, interest may be paid by check mailed to the address of the Person entitled thereto as such address shall appear in the Security Register;] [If applicable, insert
— provided, further, that payment to [DTC or] any [successor] depository may be made by wire transfer to the account designated by [DTC or] such [successor] depository in writing]. 
 This Security is one of a duly authorized issue of securities of the Company (herein called the “Securities”), issued and to be issued in one
or more series under an Indenture, dated as of             , 20     (herein called, together with all indentures supplemental thereto, the
“Indenture”), 

  

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between the Company and             , as Trustee (herein called the “Trustee”,
which term includes any successor trustee under the Indenture), to which Indenture and all indentures supplemental thereto reference is hereby made for a statement of the respective rights, limitations of rights, duties and immunities thereunder of
the Company, the Trustee and the Holders of the Securities, and of the terms upon which the Securities are, and are to be, authenticated and delivered. This Security is one of the series designated on the face hereof [, initially limited (subject to
exceptions provided in the Indenture) to the aggregate principal amount of $            ]. 
 Subject to and upon compliance with the provisions of the Indenture, the Holder of this Security is entitled, at his option, at any time on or before the close of business on
            ,             , or in case this Security or a portion hereof is called for redemption, then in respect
of this Security or such portion hereof until and including, but (unless the Company defaults in making the payment due upon redemption) not after, the close of business on the Business Day immediately preceding the Redemption Date, to convert this
Security (or any portion of the principal amount hereof which is $1,000 or an integral multiple thereof or in the case of Bearer Securities $5,000 or an integral multiple of $5,000), at the principal amount hereof, or of such portion, into fully
paid and non-assessable shares (calculated as to each conversion to the nearest 1/100 of a share) of Common Stock of the Company at a conversion price equal to $            
aggregate principal amount of Securities for each share of Common Stock (or at the current adjusted conversion price if an adjustment has been made as provided in the Indenture) by surrender of this Security, duly endorsed or assigned to the Company
or in blank, to the Company at its office or agency in             , accompanied by written notice to the Company that the Holder hereof elects to convert this Security, or if less
than the entire principal amount hereof is to be converted, the portion hereof to be converted (in the case of Bearer Securities, any Bearer Security surrendered for conversion must be accompanied by all Coupons maturing subsequent to the date of
surrender of such Bearer Security for conversion or the amount of any such missing Coupons will be deducted from the amount due on such Security used to determine the amount of shares of Common Stock such Bearer Security may be converted into), and,
in case such surrender shall be made during the period from the close of business on any Regular Record Date next preceding any Interest Payment Date to the opening of business on such Interest Payment Date (unless this Security or the portion
thereof being converted has been called for redemption on a Redemption Date such that the conversion right of this Security would terminate between such Regular Record Date and the close of business on such Interest Payment Date), also accompanied
by payment in funds reasonably acceptable to the Company of an amount equal to the interest payable on such Interest Payment Date on the principal amount of this Security then being converted (with similar provision to be made for Bearer
Securities). In case surrender of this Security for conversion shall be made during the period from the close of business on any Regular Record Date next preceding any Interest Payment Date to the opening of business on such Interest Payment Date
and if this Security or portion hereof has been called for redemption on a Redemption Date with the consequence that the conversion right of this Security would terminate between such Regular Record Date and the close of business on such Interest
Payment Date, then the Holder of this Security will be entitled to receive the interest accruing hereon from the Interest Payment Date next preceding the date of such conversion to such succeeding Interest Payment Date and shall not be required to
pay such interest upon surrender of this Security for conversion. Subject to the aforesaid requirement for payment and, in the case of a conversion after the Regular Record Date next preceding any Interest Payment Date and on or before such Interest
Payment Date, to the right of the Holder of this Security (or any Predecessor Security) of record at such Regular Record Date to receive an installment of interest (with certain exceptions provided in the Indenture), no payment or adjustment is to
be made on conversion for interest accrued hereon or for dividends on the Common Stock issued on conversion. No fractions of shares or scrip representing fractions of 

  

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shares will be issued on conversion, but instead of any fractional interest the Company shall pay a cash adjustment as provided in the Indenture. The
conversion price is subject to adjustment as provided in the Indenture. In addition, the Indenture provides that in case of certain consolidations or mergers to which the Company is a party or the transfer of substantially all of the assets of the
Company, the Indenture shall be amended, without the consent of any Holders of Securities, so that this Security, if then outstanding, will be convertible thereafter, during the period this Security shall be convertible as specified above, only into
the kind and amount of securities, cash and other property receivable upon the consolidation, merger or transfer or conveyance by a holder of the number of shares of Common Stock into which this Security might have been converted immediately prior
to such consolidation, merger or transfer or conveyance (assuming such holder of Common Stock failed to exercise any rights of election and received per share the kind and amount received per share by a plurality of nonelecting shares). 

[If applicable, insert — The indebtedness evidenced by the Securities is, to the extent provided in the Indenture, subordinate and subject
in right of payment to the prior payment in full of all indebtedness and obligations of the Company as are defined in the Indenture as “Senior Indebtedness,” and this Security is issued subject to the provisions of the Indenture with
respect thereto, and each Holder of this Security, by accepting the same, agrees to and shall be bound by such provisions. Each Holder of this Security, by accepting the same, agrees that each holder of Senior Indebtedness, whether created or
acquired before or after the issuance of this Security, shall be deemed conclusively to have relied on such subordination provisions in acquiring and continuing to hold, or in continuing to hold, such Senior Indebtedness.] 
 [If the Security is not an Original Issue Discount Security, insert — If an Event of Default with respect to the Securities shall occur and
be continuing, the principal of the Securities may be declared due and payable in the manner and with the effect provided in the Indenture.] 
 [If the Security is an Original Issue Discount Security, insert — If an Event of Default with respect to Securities of this series shall occur and be continuing, an amount of principal of the Securities of this series may be
declared due and payable in the manner and with the effect provided in the Indenture. Such amount shall be equal to [insert formula for determining the amount]. Upon payment (i) of the amount of principal so declared due and payable and
(ii) of interest on any overdue principal, premium and interest (in each case to the extent that the payment of such interest shall be legally enforceable), all of the Company’s obligations in respect of the payment of the principal of and
premium and interest, if any, on the Securities of this series shall terminate.] 
 [If applicable, insert — The Securities may
not be redeemed prior to the Stated Maturity.] 
 [If applicable, insert — The Securities are not subject to any sinking fund.]

 [If applicable, insert — The Securities are subject to redemption [(l) [If applicable, insert — on
             in any year commencing with the year              and ending with the year
             through operation of the sinking fund for this series at a Redemption Price equal to 100% of the principal amount, and (2)] [If applicable, insert — at any
time [on or after             ], as a whole or in part, at the election of the Company, at the following Redemption Prices (expressed as percentages of the principal amount): if
redeemed on or before             ,     % and if redeemed during the 12-month period beginning
             of the years indicated at the Redemption Prices indicated below: 
  

			
	 Year
	  	Redemption Price

  

 -4- 

 and thereafter at a Redemption Price equal to     % of the principal amount, together in the
case of any such redemption [If applicable, insert — (whether through operation of the sinking fund or otherwise)] with accrued interest to the Redemption Date; provided, however, that installments of interest on this Security whose
Stated Maturity is on or prior to such Redemption Date will be payable to the Holder of this Security, or one or more Predecessor Securities, of record at the close of business on the relevant Record Dates referred to on the face hereof, all as
provided in the Indenture.] 
 [If applicable, insert — The Securities are subject to redemption (1) on
             in any year commencing with the year              and ending with the year
             through operation of the sinking fund for this series at the Redemption Prices for redemption through operation of the sinking fund (expressed as percentages of the
principal amount) set forth in the table below, and (2) at any time [on or after             ], as a whole or in part, at the election of the Company, at the Redemption Prices
for redemption otherwise than through operation of the sinking fund (expressed as percentages of the principal amount) set forth in the table below: if redeemed during the 12-month period beginning
             of the years indicated below: 
  

					
	 Year
	  	Redemption Price
for Redemption
through Operation
of the Sinking Fund	  	Redemption Price for
Redemption
Otherwise than
through Operation
of the Sinking Fund

 and thereafter at a Redemption Price equal to     % of the principal amount, together
in the case of any such redemption (whether through operation of the sinking fund or otherwise) with accrued interest to the Redemption Date; provided, however, that installments of interest on this Security whose Stated Maturity is on or prior to
such Redemption Date will be payable to the Holder of this Security, or one or more Predecessor Securities, of record at the close of business on the relevant Record Dates referred to on the face hereof, all as provided in the Indenture.]

 [If applicable, insert — Notwithstanding the foregoing, the Company may not, prior to
            , redeem any Securities as contemplated by [Clause (2) of] the preceding paragraph as a part of, or in anticipation of, any refunding operation by the application,
directly or indirectly, of moneys borrowed having an interest cost to the Company (calculated in accordance with generally accepted financial practice) of less than     % per annum.] 
 [If applicable, insert — The sinking fund for the Securities provides for the redemption on
             in each year, beginning with the year              and ending with the year
            , of [not less than] $            [(“mandatory sinking fund”) and not more than
$            ] aggregate principal amount of the Securities of this series. [The Securities acquired or redeemed by the Company otherwise than through [mandatory] sinking fund
payments may be credited against subsequent [mandatory] sinking fund payments otherwise required to be made in the [describe order].]] 
  

 -5- 

 [If applicable, insert — Notice of redemption will be given by mail to Holders of Securities,
not less than 30 nor more than 60 days prior to the Redemption Date, all as provided in the Indenture.] 
 In the event of [If applicable,
insert — redemption or] conversion of this Security in part only, a new Security or Securities for the [If applicable, insert — unredeemed or] unconverted portion hereof shall be issued in the name of the Holder hereof upon the
cancellation hereof. 
 The Indenture contains provisions permitting, with certain exceptions as therein provided, the amendment thereof and
the modification of the rights and obligations of the Company and the rights of the Holders of the Securities of each series issued under the Indenture at any time by the Company and the Trustee with the written consent of the Holders of not less
than a majority in aggregate principal amount of the Securities at the time Outstanding of each series affected thereby. The Indenture also contains provisions permitting the Holders of specified percentages in aggregate principal amount of the
Securities of any series at the time Outstanding, on behalf of the Holders of all Securities of such series, to waive compliance by the Company with certain provisions of the Indenture and certain past defaults under the Indenture and their
consequences. Any such consent or waiver by the Holder of this Security shall be conclusive and binding upon such Holder and upon all future Holders of this Securities and of any Securities issued upon the registration of transfer hereof or in
exchange herefor or in lieu hereof, whether or not notation of such consent or waiver is made upon this Security. 
 No reference herein to
the Indenture and no provision of this Security or of the Indenture shall alter or impair the obligation of the Company, which is absolute and unconditional, to pay the principal of and interest on this Security, at the times, place and rate, and in
the coin or currency, herein or to convert this Security, and in the Indenture prescribed. 
 As provided in the Indenture and subject to
certain limitations set forth therein and in this Security, the transfer of this Security may be registered on the Security Register upon surrender of this Security for registration of transfer at the office or agency of the Company maintained for
that purpose in any place where the principal of and interest on this Security are payable, duly endorsed by, or accompanied by a written instrument of transfer in form satisfactory to the Company and the Security Registrar duly executed by, the
Holder hereof or by his attorney duly authorized in writing, and thereupon one or more new Securities of this series and of like tenor, of authorized denominations and for the same aggregate principal amount, will be issued to the designated
transferee or transferees. 
 [If applicable, insert — The Securities are issuable only in registered form [without coupons] in
the denominations of $             or any integral multiple thereof.] As provided in the Indenture and subject to certain limitations set forth in the Indenture, and in this
Security, the Securities are exchangeable for a like aggregate principal amount of Securities of this series in different authorized denominations, as requested by the Holders surrendering the same.] 
 No service charge shall be made for any such registration of transfer or exchange, but the Company may require payment of a sum sufficient to cover any
tax or other governmental charge payable in connection therewith, other than in certain cases provided in the Indenture. 
  

 -6- 

 Prior to due presentment of this Security for registration of transfer, the Company, the Trustee and any
agent of the Company or the Trustee may treat the Person in whose name this Security is registered as the owner hereof for all purposes, whether or not this Security be overdue, and neither the Company, the Trustee nor any such agent shall be
affected by notice to the contrary. 
 [If applicable, insert — The Indenture contains provisions whereby (i) the Company
may be discharged from its obligations with respect to the Securities (subject to certain exceptions) or (ii) the Company may be released from its obligations under specified covenants and agreements in the Indenture, in each case if the
Company irrevocably deposits with the Trustee money or Government Obligations, or a combination thereof, in an amount sufficient, without consideration of any reinvestment, to pay and discharge the entire indebtedness on all Securities of this
series, and satisfies certain other conditions, all as more fully provided in the Indenture.] 
 This Security shall be governed by and
construed in accordance with the laws of the State of New York applicable to agreements made or instruments entered into, and in each case, performed in said State. 
 All terms used in this Security without definition that are defined in the Indenture shall have the meanings assigned to them in the Indenture. 
 [Remainder of Page Intentionally Left Blank] 
  

 -7- 

 Unless the Certificate of Authentication hereon has been executed by or on behalf of the Trustee under
the Indenture by the manual signature of one of its authorized officers, this Security shall not be entitled to any benefits under the Indenture or be valid or obligatory for any purpose. 
 IN WITNESS WHEREOF, the Company has caused this instrument to be duly executed under its corporate seal. 
  

									
	 [SEAL]
	 		 	ZYMOGENETICS, INC.
					
		 		 		 	By:	 	 
		 		 		 		 	Name:
		 		 		 		 	Title:

  

									
	 Attest:
	 		 	
					
		 		 		 	By:	 	 
		 		 		 		 	Name:
		 		 		 		 	Title:

 CERTIFICATE OF AUTHENTICATION 
 This is one of the Securities of the series designated therein referred to in the within-mentioned Indenture. 
  

									
		 		 	__________________________________________________,
		 		 	as Trustee
					
	Dated:	 	 	 		 	By:	 	 
		 		 		 		 	Name:
		 		 		 		 	Title: Authorized Officer

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