[FORM OF FACE OF NOTE] [INCLUDEFOLLOWING LEGEND IF A GLOBAL NOTE]

Exhibit 10.5

[FORM OF FACE OF NOTE]

[INCLUDE FOLLOWING LEGEND IF A GLOBAL NOTE]

[UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION (“DTC”), TO THE COMPANY OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE, OR PAYMENT, AND ANY CERTIFICATE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR IN SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT HEREUNDER IS MADE TO CEDE & CO. OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF 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.

THIS NOTE IS A GLOBAL NOTE WITHIN THE MEANING OF THE INDENTURE HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME OF A DEPOSITARY OR A NOMINEE OF A DEPOSITARY OR A SUCCESSOR DEPOSITARY. THIS NOTE IS NOT EXCHANGEABLE FOR NOTES REGISTERED IN THE NAME OF A PERSON OTHER THAN THE DEPOSITARY OR ITS NOMINEE EXCEPT IN THE LIMITED CIRCUMSTANCES DESCRIBED IN THE INDENTURE, AND NO TRANSFER OF THIS NOTE (OTHER THAN A TRANSFER OF THIS NOTE AS A WHOLE BY THE DEPOSITARY TO A NOMINEE OF THE DEPOSITARY OR BY A NOMINEE OF THE DEPOSITARY TO THE DEPOSITARY OR ANOTHER NOMINEE OF THE DEPOSITARY) MAY BE REGISTERED EXCEPT IN THE LIMITED CIRCUMSTANCES DESCRIBED IN THE INDENTURE.]

[INCLUDE FOLLOWING LEGEND IF A RESTRICTED SECURITY]

[THIS SECURITY AND THE COMMON STOCK, IF ANY, ISSUABLE UPON CONVERSION OF THIS SECURITY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), AND MAY NOT BE OFFERED, SOLD, PLEDGED OR OTHERWISE TRANSFERRED EXCEPT IN ACCORDANCE WITH THE FOLLOWING SENTENCE. BY ITS ACQUISITION HEREOF OR OF A BENEFICIAL INTEREST HEREIN, THE ACQUIRER:

(1) REPRESENTS THAT IT AND ANY ACCOUNT FOR WHICH IT IS ACTING IS A “QUALIFIED INSTITUTIONAL BUYER” (WITHIN THE MEANING OF RULE 144A UNDER THE SECURITIES ACT) AND THAT IT EXERCISES SOLE INVESTMENT DISCRETION WITH RESPECT TO EACH SUCH ACCOUNT, AND

(2) AGREES FOR THE BENEFIT OF OREXIGEN THERAPEUTICS, INC. (THE “COMPANY”) THAT IT WILL NOT OFFER, SELL, PLEDGE OR

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OTHERWISE TRANSFER THIS SECURITY OR ANY BENEFICIAL INTEREST HEREIN EXCEPT:

(A) TO THE COMPANY OR ANY SUBSIDIARY THEREOF; OR

(B) PURSUANT TO A REGISTRATION STATEMENT WHICH HAS BECOME EFFECTIVE UNDER THE SECURITIES ACT; OR

(C) TO A QUALIFIED INSTITUTIONAL BUYER IN COMPLIANCE WITH RULE 144A UNDER THE SECURITIES ACT; OR

(D) PURSUANT TO AN EXEMPTION FROM REGISTRATION PROVIDED BY RULE 144 UNDER THE SECURITIES ACT OR ANY OTHER AVAILABLE EXEMPTION FROM THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT.

PRIOR TO THE REGISTRATION OF ANY TRANSFER IN ACCORDANCE WITH CLAUSE (2)(D) ABOVE, THE COMPANY AND THE TRUSTEE RESERVE THE RIGHT TO REQUIRE THE DELIVERY OF SUCH LEGAL OPINIONS, CERTIFICATIONS OR OTHER EVIDENCE AS MAY REASONABLY BE REQUIRED BY THE COMPANY IN ORDER TO DETERMINE THAT THE PROPOSED TRANSFER IS BEING MADE IN COMPLIANCE WITH THE SECURITIES ACT AND APPLICABLE STATE SECURITIES LAWS. NO REPRESENTATION IS MADE AS TO THE AVAILABILITY OF ANY EXEMPTION FROM THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT.]

THE FOLLOWING INFORMATION IS SUPPLIED SOLELY FOR U.S. FEDERAL INCOME TAX PURPOSES. THIS NOTE WAS ISSUED WITH ORIGINAL ISSUE DISCOUNT (“OID”) WITHIN THE MEANING OF SECTION 1273 OF THE INTERNAL REVENUE CODE OF 1986, AS AMENDED (THE “CODE”), AND THIS LEGEND IS REQUIRED BY SECTION 1275(c) OF THE CODE.

Holders may obtain information regarding the amount of any OID, the issue price, the issue date and the yield to maturity relating to the Notes by contacting: Orexigen Therapeutics, Inc., 3344 N. Torrey Pines Ct., Suite 200, La Jolla, California, 92037, Attention: General Counsel, Fax: (858) 875-8650.

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OREXIGEN THERAPEUTICS, INC.

0% Convertible Senior Secured Note due 2020

CUSIP No. [            ]

OREXIGEN THERAPEUTICS, INC., a corporation duly organized and validly existing under the laws of the State of Delaware (the “Company,” which term includes any successor corporation or other entity under the Indenture referred to on the reverse hereof), for value received hereby promises to pay to [CEDE & CO.]² [        ]³, or registered assigns, the principal sum [as set forth in the “Schedule of Exchanges of Notes” attached hereto]⁴ [of $[        ]]⁵, which amount, taken together with the principal amounts of all other outstanding Notes, shall not, unless permitted by the Indenture, exceed $165,000,000 in aggregate at any time, in accordance with the rules and procedures of the Depositary, on July 1, 2020, and interest thereon as set forth below.

This Note shall not bear interest unless the Stockholder Approval is not obtained prior to the Stockholder Approval Deadline, in which case the Notes held by a Qualifying Holder shall bear interest from the Stockholder Approval Deadline at the rate of 8% per annum, or from the most recent date to which interest had been paid or provided for to, but excluding, the next scheduled Interest Payment Date, if applicable, until July 1, 2020 or until the principal and any unpaid and accrued interest are paid or duly provided for or until Stockholder Approval is obtained. Interest is payable semi-annually in arrears on each July 1 and January 1, commencing on January 1, 2017, to Holders of record at the close of business on the preceding June 15 and December 15 (whether or not such day is a Business Day), respectively. Additional Interest will be payable as set forth in Section 4.06(d) and Section 6.03 of the within-mentioned Indenture, and any reference to interest on, or in respect of, any Note therein shall be deemed to include Additional Interest if, in such context, Additional Interest is, was or would be payable pursuant to any of such Section 4.06(d) or Section 6.03, and any express mention of the payment of Additional Interest in any provision therein shall not be construed as excluding Additional Interest in those provisions thereof where such express mention is not made.

Any Defaulted Amounts shall accrue interest per annum at the rate borne by the Notes plus one percent (of if the Notes bear no interest, at the rate of one percent), subject to the enforceability thereof under applicable law, from, and including, the relevant payment date to, but excluding, the date on which such Defaulted Amounts shall have been paid by the Company, at its election, in accordance with Section 2.03(c) of the Indenture.

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The Company shall pay the principal of and interest, if applicable, on this Note, if and so long as such Note is a Global Note, in immediately available funds to the Depositary or its nominee, as the case may be, as the registered Holder of such Note. As provided in and subject to the provisions of the Indenture, the Company shall pay the principal of any Notes (other than Notes that are Global Notes) (i) at the office or agency designated by the Company for that purpose or, at the Company’s option, by check mailed to the Holder’s address as it appears in the Note Register or (ii) under certain circumstances, by wire transfer in immediately available funds to the Holder’s account within the United States. The Company has initially designated the Trustee as its Paying Agent, Conversion Agent, Custodian and Note Registrar in respect of the Notes and its agency in the Borough of Manhattan, The City of New York, as a place where Notes may be presented for payment or for registration of transfer and exchange.

Reference is made to the further provisions of this Note set forth on the reverse hereof, including, without limitation, provisions giving the Holder of this Note the right to convert this Note into shares of Common Stock on the terms and subject to the limitations set forth in the Indenture. Such further provisions shall for all purposes have the same effect as though fully set forth at this place.

This Note will be secured by the Collateral. Reference is made to the Indenture and the Collateral Documents for terms relating to such security, including the release, termination and discharge thereof. The Company shall not be required to make any notation on this Note to reflect any grant of such security or any such release, termination or discharge.

The Company’s obligations under this Note and all other Obligations are fully and unconditionally guaranteed, jointly and severally, by the Guarantors from time to time party to the Indenture.

This Note, and any claim, controversy or dispute arising under or related to this Note, shall be construed in accordance with and governed by the laws of the State of New York.

In the case of any conflict between this Note and the Indenture, the provisions of the Indenture shall control and govern.

This Note shall not be valid or become obligatory for any purpose until the certificate of authentication hereon shall have been signed manually by the Trustee or a duly authorized authenticating agent under the Indenture.

[Remainder of page intentionally left blank]

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IN WITNESS WHEREOF, the Company has caused this Note to be duly executed.

Dated:

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[FORM OF REVERSE OF NOTE]

OREXIGEN THERAPEUTICS, INC.

0% Convertible Senior Secured Note due 2020

This Note is one of a duly authorized issue of Notes of the Company, designated as its 0% Convertible Senior Secured Notes due 2020 (the “Notes”), initially limited to the aggregate principal amount of $165,000,000 all issued or to be issued under and pursuant to an Indenture dated as of March [●], 2016 (the “Indenture”), between the Company and U.S. Bank National Association, as the trustee (in such capacity, the “Trustee”) and the collateral agent, to which Indenture and all indentures supplemental thereto reference is hereby made for a description of the rights, limitations of rights, obligations, duties and immunities thereunder of the Trustee, the Company and the Holders of the Notes. Capitalized terms used in this Note and not defined in this Note shall have the respective meanings set forth in the Indenture.

In case certain Events of Default shall have occurred and be continuing, the principal of, and interest on, all Notes may be declared, by either the Trustee or Holders of at least 25% in aggregate principal amount of Notes then outstanding, and upon said declaration shall become, due and payable, in the manner, with the effect and subject to the conditions and certain exceptions set forth in the Indenture.

Subject to the terms and conditions of the Indenture, the Company will make payment in respect of the principal amount of any Note on the Maturity Date (i) to the Holder who surrenders a Note at the office or agency designated by the Company for that purpose to collect such payment in respect of the Note or, at the Company’s option, by check mailed to such Holder at its address as it appears on the Note Register or (ii) under certain circumstances, by wire transfer in immediately available funds to the Holder’s account within the United States. The Company will make all payments in respect of the Fundamental Change Repurchase Price on the Fundamental Change Repurchase Date in accordance with Section 2.03 of the Indenture. The Company will pay cash amounts in money of the United States that at the time of payment is legal tender for payment of public and private debts.

The Indenture contains provisions permitting the Company and the Trustee in certain circumstances, without the consent of the Holders of the Notes, and in certain other circumstances, with the consent of the Holders of not less than a majority in aggregate principal amount of the Notes at the time outstanding, evidenced as in the Indenture provided, to execute supplemental indentures modifying the terms of the Indenture and the Notes as described therein. It is also provided in the Indenture that, subject to certain exceptions, the Holders of a majority in aggregate principal amount of the Notes at the time outstanding may on behalf of the Holders of all of the Notes waive any past Default or Event of Default under the Indenture and its consequences.

No reference herein to the Indenture and no provision of this Note or of the Indenture shall alter or impair the obligation of the Company, which is absolute and unconditional, to pay

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or deliver, as the case may be, the principal (including the Fundamental Change Repurchase Price, if applicable) of, accrued and unpaid interest, if any, on, and the cash or shares of Common Stock, as applicable, due upon conversion of, this Note at the place, at the respective times, at the rate and in the lawful money or shares of Common Stock, as the case may be, herein prescribed.

The Notes are issuable in registered form without coupons in denominations of $1,000 principal amount and integral multiples thereof. At the office or agency of the Company referred to on the face hereof, and in the manner and subject to the limitations provided in the Indenture, Notes may be exchanged for a like aggregate principal amount of Notes of other authorized denominations, without payment of any service charge but, if required by the Company or Trustee, with payment of a sum sufficient to cover any transfer or similar tax that may be imposed in connection therewith as a result of the name of the Holder of the new Notes issued upon such exchange of Notes being different from the name of the Holder of the old Notes surrendered for such exchange.

No sinking fund is provided for the Notes. The Notes are redeemable, as a whole or in part, at any time prior to the Maturity Date at the option of the Company with the consent of the holders of at least seventy percent (70%) of the aggregate principal amount of the Notes then outstanding. The Redemption Price for any such Optional Redemption is equal to 100% of the principal amount of the Notes to be redeemed, together with accrued and unpaid interest, if any, to, but excluding, the Redemption Date.

Upon the occurrence of a Fundamental Change, the Holder has the right, at such Holder’s option, to require the Company to repurchase for cash all of such Holder’s Notes or any portion thereof (in principal amounts of $1,000 or integral multiples thereof) on the Fundamental Change Repurchase Date at a price equal to the Fundamental Change Repurchase Price.

Subject to the provisions of the Indenture, the Holder hereof has the right, at its option, prior to the close of business on the second Scheduled Trading Day immediately preceding the Maturity Date, to convert any Notes or portion thereof that is $1,000 or an integral multiple thereof, into shares of Common Stock at the Conversion Rate specified in the Indenture, as adjusted from time to time as provided in the Indenture.

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ABBREVIATIONS

The following abbreviations, when used in the inscription of the face of this Note, shall be construed as though they were written out in full according to applicable laws or regulations:

TEN COM = as tenants in common

UNIF GIFT MIN ACT = Uniform Gifts to Minors Act

CUST = Custodian

TEN ENT = as tenants by the entireties

JT TEN = joint tenants with right of survivorship and not as tenants in common

Additional abbreviations may also be used though not in the above list.

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SCHEDULE A⁶

SCHEDULE OF TRANSFERS AND EXCHANGES OF NOTES

OREXIGEN THERAPEUTICS, INC.

0% Convertible Senior Secured Notes due 2020

The initial principal amount of this Global Note is          DOLLARS ($[        ]). The following increases or decreases in this Global Note have been made:

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ATTACHMENT 1

[FORM OF NOTICE OF CONVERSION]

OREXIGEN THERAPEUTICS, INC.

0% Convertible Senior Secured Notes due 2020

60 Livingston Avenue

St. Paul, MN 55107

The undersigned registered owner of this Note hereby exercises the option to convert this Note, or the portion hereof (that is $1,000 principal amount or an integral multiple thereof) below designated, into shares of Common Stock or cash, as applicable, in accordance with the terms of the Indenture referred to in this Note, and directs that any shares of Common Stock issuable and deliverable upon such conversion, together with any cash for any fractional share, or cash, as applicable, and any Notes representing any unconverted principal amount hereof, be issued and delivered to the registered Holder hereof unless a different name has been indicated below. If any shares of Common Stock or any portion of this Note not converted are to be issued in the name of a Person other than the undersigned, the undersigned will pay all documentary, stamp or similar issue or transfer taxes, if any in accordance with Section 14.02(f) and Section 14.02(g) of the Indenture. Any amount required to be paid to the undersigned on account of interest accompanies this Note. Capitalized terms used herein but not defined shall have the meanings ascribed to such terms in the Indenture.

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ATTACHMENT 2

[FORM OF FUNDAMENTAL CHANGE REPURCHASE NOTICE]

OREXIGEN THERAPEUTICS, INC.

0% Convertible Senior Secured Notes due 2020

60 Livingston Avenue

St. Paul, MN 55107

The undersigned registered owner of this Note hereby acknowledges receipt of a notice from Orexigen Therapeutics, Inc. (the “Company”) as to the occurrence of a Fundamental Change with respect to the Company and specifying the Fundamental Change Repurchase Date and requests and instructs the Company to pay to the registered Holder hereof in accordance with Section 15.02 of the Indenture referred to in this Note (1) the entire principal amount of this Note, or the portion thereof (that is $1,000 principal amount or an integral multiple thereof) below designated, and (2) if such Fundamental Change Repurchase Date does not fall during the period after a Regular Record Date and on or prior to the corresponding Interest Payment Date, accrued and unpaid interest, if any, thereon to, but excluding, such Fundamental Change Repurchase Date. Capitalized terms used herein but not defined shall have the meanings ascribed to such terms in the Indenture.

In the case of Physical Notes, the certificate numbers of the Notes to be repurchased are as set forth below:

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ATTACHMENT 3

[FORM OF ASSIGNMENT AND TRANSFER]

For value received                      hereby sell(s), assign(s) and transfer(s) unto                      (Please insert social security or Taxpayer Identification Number of assignee) the within Note, and hereby irrevocably constitutes and appoints                      attorney to transfer the said Note on the books of the Company, with full power of substitution in the premises.

In connection with any transfer of the within Note, as defined in the Indenture governing such Note, the undersigned confirms that such Note is being transferred:

¨ To Orexigen Therapeutics, Inc. or a subsidiary thereof; or

¨ Pursuant to a registration statement that has become or been declared effective under the Securities Act of 1933, as amended; or

¨ Pursuant to and in compliance with Rule 144A under the Securities Act of 1933, as amended; or

¨ Pursuant to and in compliance with Rule 144 under the Securities Act of 1933, as amended, or any other available exemption from the registration requirements of the Securities Act of 1933, as amended.

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NOTICE: The signature on the assignment must correspond with the name as written upon the face of the Note in every particular without alteration or enlargement or any change whatever.

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