Exhibit 4.2

ONCOTHYREON INC.

PIGGYBACK REGISTRATION RIGHTS AGREEMENT

This Piggyback Registration Rights Agreement (this “Agreement”) is made and entered into as of August 8, 2014 by and between Oncothyreon Inc., a Delaware corporation (the “Company”) and each of Jay Venkatesan and Mitchell H. Gold (collectively, the “Founders”).

R E C I T A L S

A. In connection with that certain Agreement and Plan of Reorganization dated as of August 8, 2014, by and among the Company, AB Acquisition (DE) Corp., a Delaware corporation and wholly-owned subsidiary of Acquiror, Alpine Biosciences, Inc., a Delaware corporation and Jay Venkatesan as Stockholders’ Agent (the “Merger Agreement”), the Company has agreed to issue to the Founders certain shares of Common Stock (the “Founders Shares”).

B. Pursuant to Section 4.6 of the Merger Agreement, the Company has agreed to grant the Founders certain “piggyback” registration rights for the Founders Shares acquired by each of the Founders as more fully described below.

C. The Founders Shares will also be subject to certain lock-up restriction (i.e., lock-up agreements) for a period of 180 days following the Closing (as defined in the Merger Agreement) (the “Lock-Up Period”).

NOW, THEREFORE, in consideration of the foregoing recitals and the mutual promises hereinafter set forth, the parties hereto hereby agree as follows:

1 Definitions.

(a) Common Stock. The term “Common Stock” means the Common Stock of the Company and any other common equity securities issued by the Company, and any other shares of stock issued or issuable with respect thereto (whether by way of a stock dividend or stock split or in exchange for or upon conversion of such shares or otherwise in connection with a combination of shares, recapitalization, merger, consolidation or other corporate reorganization).

(b) Exchange Act. The term “Exchange Act” means the Securities Exchange Act of 1934, as amended, or any similar successor federal statute, and the rules and regulations of the Commission thereunder, all as the same shall be in effect at the time.

(c) Registration. The terms “register,” “registered” and “registration” refer to a registration effected by preparing and filing a registration statement in compliance with the Securities Act of 1933, as amended (the “Securities Act”), and the declaration or ordering of effectiveness of such registration statement.

(d) Registrable Securities. The term “Registrable Securities” means (i) the Founders Shares, in each case that are now owned or may hereafter be acquired by Holder or any of Holder’s permitted successors and assigns; (ii) any shares of Common Stock issued as a dividend or other distribution with respect to, or in exchange for or in replacement of, all such Founders Shares described in clause (i) of this subsection (d); excluding in all cases, however, any Registrable Securities sold by a person in a transaction in which rights under this Agreement are not assigned in accordance with this Agreement or any Registrable Securities sold to the public or sold pursuant to Rule 144 promulgated under the Securities Act.

(e) Holder. The term “Holder” means any person (i) owning of record Registrable Securities that have not been sold to the public or pursuant to Rule 144 promulgated under the Securities Act and (ii) if such person is not a Founder, then who is an assignee of record of such Registrable Securities to whom rights under this Agreement have been duly assigned in accordance with this Agreement.

(f) SEC. The term “SEC” or “Commission” means the U.S. Securities and Exchange Commission.

2. Piggyback Registrations. At any time after the Lock-Up Period, the Company will notify all Holders in writing at least twenty (20) days prior to filing any registration statement under the Securities Act for purposes of effecting a public offering of securities of the Company (including, but not limited to, registration statements relating to secondary offerings of securities of the Company, but excluding registration statements relating to any employee benefit plan or a corporate reorganization) and will afford each such Holder an opportunity to include in such registration statement all or any part of the Registrable Securities then held by such Holder. Each Holder desiring to include in any such registration statement all or any part of the Registrable Securities held by such Holder will, within fifteen (15) days after receipt of the above-described notice from the Company, so notify the Company in writing, and in such notice will inform the Company of the number of Registrable Securities such Holder wishes to include in such registration statement. If a Holder decides not to include all of its Registrable Securities in any registration statement thereafter filed by the Company, such Holder will nevertheless continue to have the right to include any Registrable Securities in any subsequent registration statement or registration statements as may be filed by the Company with respect to offerings of its securities, all upon the terms and conditions set forth herein.

(a) Underwriting. If a registration statement under which the Company gives notice under this Section 2 is for an underwritten offering, then the Company will so advise the Holders. In such event, the right of any such Holder to be included in a registration pursuant to this Section 2 will be conditioned upon such Holder’s participation in such underwriting and the inclusion of such Holder’s Registrable Securities in the underwriting to the extent provided herein. All Holders proposing to distribute their Registrable Securities through such underwriting will enter into an underwriting agreement in customary form with the managing underwriter or underwriter(s) selected for such underwriting. Notwithstanding any other provision of this Agreement, if the Company or managing underwriter determines that marketing or other factors require a limitation of the number of shares to be underwritten, then the Company may exclude shares (including all or any portion of the Registrable Securities) from the registration and the underwriting. If any Holder disapproves of the terms of any such underwriting, such Holder may elect to withdraw therefrom by written notice to the Company and the underwriter, delivered at least twenty (20) days prior to the effective date of the registration statement. Any Registrable Securities excluded or withdrawn from such underwriting will be excluded and withdrawn from the registration.

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(b) Expenses. All expenses incurred in connection with a registration pursuant to this Section 2 (excluding underwriters’ and brokers’ discounts and commissions), including, without limitation all federal and “blue sky” registration and qualification fees, printers’ and accounting fees, fees and disbursements of counsel for the Company (but excluding counsel for the Holders), will be borne by the Company.

3. Obligations of the Company. Whenever required to effect the registration of any Registrable Securities under this Agreement, the Company will, as efficiently as reasonably possible:

(a) Prepare and file with the SEC a registration statement with respect to such Registrable Securities and use its reasonable, diligent efforts to cause such registration statement to become and remain effective until completion of the proposed offering.

(b) Prepare and file with the SEC such amendments and supplements to such registration statement and the prospectus used in connection with such registration statement as may be necessary to comply with the provisions of the Securities Act with respect to the disposition of all securities covered by such registration statement.

(c) Furnish to the Holders such number of copies of a prospectus, including a preliminary prospectus, in conformity with the requirements of the Securities Act, and such other documents as they may reasonably request in order to facilitate the disposition of the Registrable Securities owned by them that are included in such registration.

(d) Use reasonable, diligent efforts to register and qualify the securities covered by such registration statement under such other securities or Blue Sky laws of such jurisdictions as will be reasonably requested by the Holders, provided that the Company will not be required in connection therewith or as a condition thereto to qualify to do business or to file a general consent to service of process in any such states or jurisdictions.

(e) In the event of any underwritten public offering, enter into and perform its obligations under an underwriting agreement, in usual and customary form, with the managing underwriter(s) of such offering. Each Holder participating in such underwriting will also enter into and perform its obligations under such an agreement.

(f) Notify each Holder of Registrable Securities covered by such registration statement at any time when a prospectus relating thereto is required to be delivered under the Securities Act of the happening of any event as a result of which the prospectus included in such registration statement, as then in effect, includes an untrue statement of a material fact or omits to state a material fact required to be stated therein or necessary to make the statements therein not misleading in the light of the circumstances then existing.

(g) Furnish, at the request of any Holder requesting registration of Registrable Securities, on the date that such Registrable Securities are delivered to the underwriters for sale, if such securities are being sold through underwriters, or, if such securities are not being sold through underwriters, on the date that the registration statement with respect to such securities becomes effective, (i) an opinion, dated as of such date, of the counsel representing the Company

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for the purposes of such registration, in form and substance as is customarily given to underwriters in an underwritten public offering, addressed to the underwriters, if any, and (ii) a “comfort” letter dated as of such date, from the independent certified public accountants of the Company, in form and substance as is customarily given by independent certified public accountants to underwriters in an underwritten public offering, addressed to the underwriters, if any.

(h) Cause the securities covered by such registration statement to be listed on the securities exchange or quoted on the quotation system on which the Common Stock is then listed or quoted.

4. Obligations of the Holders.

(a) Furnish Information. It will be a condition precedent to the obligations of the Company to take any action pursuant to Section 2 hereof that the selling Holders will furnish to the Company such information regarding themselves, the Registrable Securities held by them, and the intended method of disposition of such securities as will be required to timely effect the registration of their Registrable Securities.

(b) Underwriting Agreement. In the event of any underwritten public offering, each Holder will enter into, and perform its obligations under, an underwriting agreement, in usual and customary form, with the managing underwriter(s) of such offering.

5. Delay of Registration. No Holder will have any right to obtain or seek an injunction restraining or otherwise delaying any such registration as the result of any controversy that might arise with respect to the interpretation or implementation of this Agreement.

6. Indemnification. In the event any Registrable Securities are included in a registration statement under Section 2 hereof:

(a) By the Company. To the extent permitted by law, the Company will indemnify and hold harmless each Holder, the partners, members, officers and directors of each Holder, any underwriter (as defined in the Securities Act) for such Holder and each person, if any, who controls such Holder or underwriter within the meaning of the Securities Act or the Exchange Act, against any losses, claims, damages, or liabilities (joint or several) to which they may become subject under the Securities Act, the Exchange Act or other federal or state law, insofar as such losses, claims, damages, or liabilities (or actions in respect thereof) arise out of or are based upon any of the following statements, omissions or violations (collectively a “Violation”):

(i) any untrue statement or alleged untrue statement of a material fact contained in such registration statement, including any preliminary prospectus or final prospectus contained therein or any amendments or supplements thereto;

(ii) the omission or alleged omission to state therein a material fact required to be stated therein, or necessary to make the statements therein not misleading, or

(iii) any violation or alleged violation by the Company of the Securities Act, the Exchange Act, any federal or state securities law or any rule or regulation promulgated under the Securities Act, the Exchange Act or any federal or state securities law in connection with the offering covered by such registration statement;

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and the Company will reimburse each such Holder, partner, member, officer or director, underwriter or controlling person for any legal or other expenses reasonably incurred by them, as incurred, in connection with investigating or defending any such loss, claim, damage, liability or action; provided however, that the indemnity agreement contained in this Section 6 will not apply to amounts paid in settlement of any such loss, claim, damage, liability or action if such settlement is effected without the consent of the Company (which consent will not be unreasonably withheld), nor will the Company be liable in any such case for any such loss, claim, damage, liability or action to the extent that it arises out of or is based upon a Violation that occurs in reliance upon and in conformity with written information furnished expressly for use in connection with such registration by such Holder, partner, member, officer, director, underwriter or controlling person of such Holder.

(b) By Selling Holders. To the extent permitted by law, each selling Holder will indemnify and hold harmless the Company, each of its directors, each of its officers who have signed the registration statement, each person, if any, who controls the Company within the meaning of the Securities Act, any underwriter and any other Holder selling securities under such registration statement or any of such other Holder’s partners, directors or officers or any person who controls such Holder within the meaning of the Securities Act or the Exchange Act, against any losses, claims, damages or liabilities (joint or several) to which the Company or any such director, officer, controlling person, underwriter or other such Holder, partner or director, officer or controlling person of such other Holder may become subject under the Securities Act, the Exchange Act or other federal or state law, insofar as such losses, claims, damages or liabilities (or actions in respect thereto) arise out of or are based upon any Violation, in each case to the extent (and only to the extent) that such Violation occurs in reliance upon and in conformity with written information furnished by such Holder expressly for use in connection with such registration; and each such Holder will reimburse any legal or other expenses reasonably incurred by the Company or any such director, officer, controlling person, underwriter or other Holder, partner, officer, director or controlling person of such other Holder in connection with investigating or defending any such loss, claim, damage, liability or action; provided, however, that the indemnity agreement contained in this Section 6 will not apply to amounts paid in settlement of any such loss, claim, damage, liability or action if such settlement is effected without the consent of the Holder, which consent will not be unreasonably withheld; and provided further, that the total amounts payable in indemnity by a Holder under this Section 6 in respect of any Violation will not exceed the net proceeds received by such Holder in the registered offering out of which such Violation arises.

(c) Notice. Promptly after receipt by an indemnified party under this Section 6 of notice of the commencement of any action (including any governmental action), such indemnified party will, if a claim in respect thereof is to be made against any indemnifying party under this Section 6, deliver to the indemnifying party a written notice of the commencement thereof and the indemnifying party will have the right to participate in, and, to the extent the indemnifying party so desires, jointly with any other indemnifying party similarly noticed, to assume the defense thereof with counsel mutually satisfactory to the parties; provided, however, that an indemnified party will have the right to retain its own counsel, with the fees and expenses to be paid by the indemnifying party, if representation of such indemnified party by the counsel retained by the indemnifying party would be inappropriate due to actual or potential conflict of

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interests between such indemnified party and any other party represented by such counsel in such proceeding. The failure to deliver written notice to the indemnifying party within a reasonable time of the commencement of any such action, if prejudicial to its ability to defend such action, will relieve such indemnifying party of any liability to the indemnified party under this Section 6, but the omission so to deliver written notice to the indemnifying party will not relieve it of any liability that it may have to any indemnified party otherwise than under this Section 6.

(d) Defect Eliminated in Final Prospectus. The foregoing indemnity agreements of the Company and Holders are subject to the condition that, insofar as they relate to any Violation made in a preliminary prospectus but eliminated or remedied in the amended prospectus on file with the SEC at the time the registration statement in question becomes effective or the amended prospectus filed with the SEC pursuant to SEC Rule 424(b) (the “Final Prospectus), such indemnity agreement will not inure to the benefit of any indemnified party if a copy of the Final Prospectus was furnished to such indemnified party and was not furnished to the person asserting the loss, liability, claim or damage at or prior to the time such action is required by the Securities Act, where such indemnified party had a legal obligation to deliver or cause to be delivered the Final Prospectus.

(e) Contribution. In order to provide for just and equitable contribution to joint liability under the Securities Act in any case in which either (i) any Holder exercising rights under this Agreement, or any controlling person of any such Holder, makes a claim for indemnification pursuant to this Section 6 but it is judicially determined (by the entry of a final judgment or decree by a court of competent jurisdiction and the expiration of time to appeal or the denial of the last right of appeal) that such indemnification may not be enforced in such case notwithstanding the fact that this Section 6 provides for indemnification in such case, or (ii) contribution under the Securities Act may be required on the part of any such selling Holder or any such controlling person in circumstances for which indemnification is provided under this Section 6; then, and in each such case, the Company and such Holder will contribute to the aggregate losses, claims, damages or liabilities to which they may be subject (after contribution from others) in such proportion so that such Holder is responsible for the portion represented by the percentage that the public offering price of its Registrable Securities offered by and sold under the registration statement bears to the public offering price of all securities offered by and sold under such registration statement, and the Company and other selling Holders are responsible for the remaining portion; provided, however, that, in any such case, (A) no such Holder will be required to contribute any amount in excess of the public offering price of all such Registrable Securities offered and sold by such Holder pursuant to such registration statement; and (B) no person or entity guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of the Securities Act) will be entitled to contribution from any person or entity who was not guilty of such fraudulent misrepresentation.

(f) Survival. The obligations of the Company and Holders under this Section 6 will survive the completion of any offering of Registrable Securities in a registration statement, and otherwise.

7. Termination of the Company’s Obligations. The Company will have no obligations pursuant to Section 2 with respect to any Registrable Securities proposed to be sold by a Holder in a registration pursuant to Section 2 hereof if, in the opinion of counsel to the Company, all such Registrable Securities proposed to be sold by a Holder may be sold in a three-month period without registration under the Securities Act pursuant to Rule 144 under the Securities Act and such Holder holds less than one percent (1%) of the outstanding shares of the Company’s capital stock.

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8. Assignment. Notwithstanding anything herein to the contrary, the rights of a Holder under this Agreement may be assigned only if the Company has given prior written consent thereto; provided, that any such assignee shall receive such assigned rights subject to all the terms and conditions of this Agreement, including without limitation the provisions of this Section 8.

9. Miscellaneous.

(a) Termination of this Agreement. This Agreement may be terminated voluntarily by written agreement of (1) the Company and (2) the Founders. Such termination will be binding upon all Holders of Registrable Securities.

(b) Notices. Unless otherwise provided, any notice required or permitted under this Agreement will be given in writing and will be deemed effectively given upon personal delivery to the party to be notified, or three (3) days after deposit with the United States Post Office, by registered or certified mail, postage prepaid, or by deposit with a nationally recognized courier service such as FedEx, or by facsimile with confirmed receipt and addressed to the party to be notified at the address indicated for the Company and the Founders on the signature page hereof, or at such other address as any party may designate by giving at least ten (10) days advance written notice to all other parties, pursuant to this Section 9(b).

(c) Entire Agreement. This Agreement constitutes the entire agreement and understanding of the parties with respect to the subject matter hereof and supersedes any and all prior negotiations, correspondence, agreements, understandings duties or obligations between the parties with respect to the subject matter hereof.

(d) Amendment and Waiver. Any provision of this Agreement may be amended and the observance thereof may be waived (either generally or in a particular instance and either retroactively or prospectively) only with the written consent of (1) the Company and (2) the Founders. Any amendment or waiver effected in accordance with this Section 9(d) will be binding upon each Holder, each permitted successor or assignee of any Holder, and the Company.

(e) Governing Law. This Agreement will be governed by and construed under the internal laws of the State of Delaware as applied to agreements among Delaware residents entered into and to be performed entirely within Delaware, without reference to principles of conflict of laws or choice of laws.

(f) Severability. If any provision of this Agreement is held to be unenforceable under applicable law, such provision will be excluded from this Agreement and the balance of the Agreement will be interpreted as if such provision were so excluded and will be enforceable in accordance with its terms.

(g) Third Parties. Nothing in this Agreement, express or implied, is intended to confer upon any person, other than the parties hereto and their successors and assigns, any rights or remedies under or by reason of this Agreement.

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(h) Successors And Assigns. The terms and conditions of this Agreement will inure to the benefit of and be binding upon the respective successors and assigns of the parties.

(i) Headings. The headings and captions used in this Agreement are used for convenience only and are not to be considered in construing or interpreting this Agreement. All references in this Agreement to sections, paragraphs, exhibits and schedules will, unless otherwise provided, refer to sections and paragraphs hereof and exhibits and schedules attached hereto, all of which exhibits and schedules are incorporated herein by this reference.

(j) Counterparts. This Agreement may be executed in two or more counterparts, each of which will be deemed an original, but all of which together will constitute one and the same instrument.

(k) Costs And Attorneys’ Fees. In the event that any action, suit or other proceeding is instituted concerning or arising out of this Agreement or any transaction contemplated hereunder, the prevailing party will recover all of such party’s costs and reasonable attorneys’ fees incurred in each such action, suit or other proceeding, including any and all appeals or petitions therefrom.

(l) Further Assurances. From and after the date of this Agreement, upon the request of the Founders or the Company, the Company and the Founders will execute and deliver such instruments, documents or other writings as may be reasonably necessary or desirable to confirm and carry out and to effectuate fully the intent and purposes of this Agreement.

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IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of the date and year first above written.

COMPANY

FOUNDERS

[SIGNATURE PAGE TO ONCOTHYREON INC. PIGGYBACK REGISTRATION RIGHTS AGREEMENT]