Improved Access to Key Management Personnel

        Currently, only one of our executive officers lives in Edmonton, Alberta, and we have experienced substantial difficulty attracting key management and scientific talent over many years. Although we intend to maintain the operating and management activities currently taking place at our Edmonton, Alberta facilities, our board of directors believes that relocating our principal administrative and scientific functions to a market with a larger biotechnology work force will be in the best interests of our business and, therefore, in the best interests of our shareholders. Given that our principal decision-making and product development functions will be moved to the United States, our board of directors believes it also appropriate to migrate our corporate entity into the United States in order, among other reasons, to avoid additional administrative costs and complexities associated with operating a business in the United States through a foreign corporate entity.

Negative Factors Considered by the Board of Directors

        In addition to considering the anticipated benefits of the arrangement described above, our board of directors also considered the following possible negative factors associated with the arrangement:

•

The arrangement will be taxable to our shareholders resident in Canada to the extent that the fair market value of the shares of Oncothyreon stock received in the arrangement exceeds the adjusted cost base to the shareholders of their shares of Biomira being exchanged. See "Material Tax Consequences of the Arrangement—Residents of Canada" beginning on page 59.



•

Despite our board of directors' current beliefs, the arrangement may not expand our base of potential investors, improve our ability to obtain financing, or have a favorable impact on our valuation or enhance our ability to recruit additional talented employees.



•

We will incur substantial costs in connection with completing the arrangement, including, among other costs, fees and expenses of legal, tax and accounting advisors in both Canada and the United States, and the costs of holding a special meeting of shareholders to consider and approve the arrangement and the arrangement agreement.



•

Some of our shareholders may exercise their right of dissent, which would entitle them to receive, in lieu of shares of Oncothyreon, a cash payment equal to the fair market value of the shares of our common shares or, in the case of the University of Alberta, our 12,500 outstanding Class A preference shares. If holders of a substantial number of our shares were to exercise dissent rights, we would not likely proceed with the arrangement as we would be unable to make substantial cash payments to shareholders.



•

The effective reverse stock split being implemented in connection with the arrangement could have an adverse effect on trading volumes for our common stock after the arrangement.



•

Biomira Canco may not satisfy certain prescribed conditions that must be met to become a public corporation so as to qualify for an exception to the withholding obligation that Oncothyreon would otherwise have with respect to non-Canadian residents. If the prescribed conditions are not met and the Canadian federal tax authorities assess Oncothyreon for failure to withhold, the amount of the assessment could be as high as 25% of the fair market value of the Oncothyreon shares issued on the second amalgamation to non-Canadian residents. See "Material Tax Consequences of the Arrangement—Non-Residents of Canada" on page 61.

Consideration of the Arrangement by Our Board of Directors

        In making its unanimous determination to approve the arrangement and the arrangement agreement and to recommend that shareholders vote "FOR" the special resolution to approve the arrangement and the arrangement agreement, our board of directors determined that these negative

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factors were outweighed by the potential benefits of the arrangement to our business and our shareholders.

Opinion of Our Financial Advisor

        Our board of directors retained Janney Montgomery Scott LLC, or Janney, to act as its financial advisor in connection with its analysis and consideration of the arrangement and reincorporation of Biomira from Canada to the State of Delaware in the United States. On September 11, 2007, Janney delivered its verbal opinion to our board of directors to the effect that, as of such date, the arrangement was fair from a financial point of view to us, subject to the completion of due diligence. Janney subsequently delivered the fairness opinion, which concludes that as of that date, and subject to and based on the various assumptions made, procedures followed, matters considered and qualifications and limitations of the review set forth therein, the consideration under the arrangement is fair from a financial point of view to us.

         The complete text of the fairness opinion, which sets forth the assumptions made, matters considered and limitations on the review undertaken in connection with the opinion is attached to this proxy statement/prospectus as Annex G. The fairness opinion addresses only the fairness of the arrangement from a financial point of view and is not and should not be construed as a valuation of us or our assets or securities or a recommendation to any of our shareholders as to whether to vote in favor of the resolutions relating to the arrangement. Our shareholders are urged to, and should, read the fairness opinion in its entirety.

        In connection with rendering its opinion, Janney:

•

reviewed a draft of the plan of arrangement dated July 31, 2007;



•

reviewed a draft of this Form S-4 dated September 11, 2007;



•

reviewed and analyzed comparable peer public firms headquartered in the US and Canada with respect to market capitalization and trading volume; and



•

conducted discussions with senior management regarding the business and transactions contemplated by the plan of arrangement.

        In preparing its opinion, Janney assumed and relied upon the accuracy and completeness of the information publicly available and financial and other information used by it without assuming any responsibility for independent verification of such information. Janney further relied upon the assurances of management of Biomira that they are not aware of any facts or circumstances that would make such information inaccurate or misleading. With respect to the financial projections of Oncothyreon and Biomira, upon advice of Oncothyreon, Janney assumed that such projections had been reasonably prepared on a basis reflecting the best currently available estimates and judgments of the management of Oncothyreon as to the future financial performance of Oncothyreon and Biomira and that Oncothyreon and Biomira will perform substantially in accordance with such projections. Janney assumed that the final plan of arrangement will be substantially identical to the terms of the plan of arrangement reviewed by it. Janney neither made nor assumed any responsibility for making any independent valuation or appraisal of the assets or liabilities of either Biomira or Oncothyreon, including real estate assets, nor have we been furnished with any such appraisals. Janney did not conduct any future cash flow, discounted cash flow, sensitivity, taxation or other similar types of analyses typically performed in connection with the delivery of an opinion in the context of an acquisition, nor has it done any analysis of the financial terms of transactions comparable to the plan of arrangement. In addition, Janney did not evaluate the solvency of Biomira or Oncothyreon under any state or federal laws relating to bankruptcy, insolvency or similar matters. Janney also assumed that all governmental, regulatory or other consents and approvals that are required in connection with the arrangement will be obtained without any adverse effect on Biomira or Oncothyreon or on the

45

expected benefits of the arrangement in any way meaningful to its analysis. In addition, Janney assumed that the arrangement will be consummated in accordance with its terms without material modification, waiver or delay. Janney's opinion is based on financial, economic, market and other conditions as in effect on, and the information and draft proposed reorganization plan made available to it, as of the date hereof. Janney assumed that the tax, accounting and cost analyses conducted by Biomira and its advisors are complete and correct and Janney specifically reviewed whether similarly situated companies incorporated in the United States trade at a higher value and have higher trading volumes than peer companies incorporated in Canada. Based on these assumptions, Janney made its determination that the arrangement is fair, from a financial point of view, to Biomira's shareholders.

        The fairness opinion was rendered on the basis of securities markets, economic, financial and general business conditions prevailing as at the date thereof and the condition and prospects, financial and otherwise of us and our subsidiaries and affiliates as they were reflected in the information and as they were represented to Janney in discussions with our management. In its analyses and in connection with the preparation of its opinion, Janney made numerous assumptions with respect to industry performance, general business and economic conditions and other matters, many of which are beyond the control of Janney or any party involved in the arrangement.

        Financial Analyses.     At the September 11, 2007 meeting of the board of directors, and in connection with preparing its opinion for the board of directors, Janney made a presentation of certain financial analyses of the proposed arrangement.

        The following is a summary of the material analyses contained in the presentation that was delivered to the board of directors. Some of the summaries of financial analyses include information presented in tabular format. In order to understand fully the financial analyses performed by Janney, the table must be read together with the accompanying text of each summary. The table alone does not constitute a complete description of the financial analyses, including the methodologies and assumptions underlying the analyses, and if viewed in isolation could create a misleading or incomplete view of the financial analyses performed by Janney.

        The fact that any specific analysis has been referred to in the summary below and in this registration statement on Form S-4 is not meant to indicate that such analysis was given more weight by Janney than any other analysis in reaching its conclusion. Janney arrived at its ultimate opinion based on the results of all analyses undertaken by it and assessed as a whole and believes the totality of the factors considered and performed by Janney in connection with its opinion operated collectively to support its determinations as to the fairness of the arrangement from a financial point of view to the holders of shares of company common stock. Janney did not draw, in isolation, conclusions from or with regard to any one factor or method of analysis.

        The following summary is not a complete description of all of the analyses performed and factors considered by Janney in connection with its opinion, but rather is a summary of the material financial analyses performed and factors considered by Janney. The preparation of a fairness opinion is a complex process involving subjective judgments and is not necessarily susceptible to partial analysis.

        Company Trading Analysis.     Using publicly available information, Janney performed a trading analysis to analyze and compare the trading volume and valuation of selected companies on the life sciences sector that it deemed comparable to Biomira. In performing its trading analysis, Janney reviewed the trading history of selected companies headquartered in Canada versus selected companies headquartered in the United States by clinical phase of development. In particular, it reviewed each company's 52 week high and low trading price, market capitalization and enterprise value as well as each company's value in dollars with respect to its yearly trading volume. Based on this review, Janney determined that Biomira's current trading volume was in line with other Canadian headquartered

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companies with similar market capitalizations and that United States headquartered companies with similar market capitalizations trade at a higher volume. The public companies reviewed were:

        Based on this review, Janney determined that Biomira's current trading volume was in line with other Canadian headquartered companies with similar market capitalizations and that United States headquartered companies with similar market capitalizations trade at a higher volume.

        Valuation and Liquidity Analysis.     Using publicly available information, Janney performed valuation and liquidity analyses to analyze and compare the trading and valuation statistics of companies in the life sciences sector which are headquartered in Canada versus the United States. The review focused on isolating companies located in Canada and the United States and further separating each by the clinical trial phase in which each company currently operated. Janney further revised its analyses to reduce the data set to include only those companies with market capitalizations similar to the market capitalization

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of Biomira as well as looking only at oncology companies with lead products in phase 2 or phase 3 of development. Below is a summary of the broad peer group data:

        Miscellaneous.     Janney is acting as financial advisor to the board of directors in connection with the arrangement. Under the terms of its engagement, Biomira has agreed to pay Janney a customary fee for its financial advisory services. Biomira has also agreed to reimburse Janney for expenses reasonably incurred in performing its services, including reasonable fees and expenses of its legal counsel, and to indemnify Janney and certain related persons for various liabilities related to or arising out of its engagement, including liabilities arising under the federal securities laws. Neither Janney nor any of its affiliates is an insider, associate or affiliate of us. Janney acts as a trader and dealer, both as principal and agent, in major financial markets and, as such, may have had and may in the future have positions in the securities of Biomira or Oncothyreon or any of their associates or affiliates and, from time to time, may have executed or may execute transactions on behalf of such companies or clients for which it received or may receive compensation. In addition, as an investment dealer, Janney conducts research on securities and in the ordinary course of its business provides research reports and investment advice to its clients on investment matters, including with respect to us. Janney also acted as our financial advisor in our acquisition of ProlX and received a fee on the delivery of a fairness opinion to our board of directors and the consummation of the acquisition.

Shareholder Approval of the Arrangement

        In order for the arrangement to become effective, the arrangement resolution must be passed, with or without variation, by at least two-thirds of the eligible votes cast at the special meeting in respect of the arrangement resolution by our shareholders voting together as a single class.

        After careful consideration of the terms and conditions of the arrangement, our board of directors unanimously determined it advisable and in the best interests of us and our shareholders to proceed with the arrangement. Our board of directors unanimously recommends that you vote or give instruction to vote "FOR" the special resolution to approve of the arrangement and the arrangement agreement.

        If the arrangement resolution is not passed by an adequate two-thirds majority of the eligible votes at the special meeting, the arrangement will not be completed.

Court Approval and Completion of the Arrangement

        A plan of arrangement under the CBCA requires court approval. Prior to the mailing of this proxy statement/prospectus, we obtained the interim order from the Alberta Court of Queen's Bench, which we refer to as the court, authorizing the calling and holding of the special meeting and prescribing the conduct of the special meeting. The interim order is attached as Annex I to this proxy statement/prospectus. The interim order, among other things, provides for the calling and holding of the special meeting and resulted in the issuance of a notice of application for a final order. The interim order does not constitute approval of the arrangement or the contents of this proxy statement/prospectus by the court. As set forth in the interim order, the hearing in respect of the final order is scheduled to take

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place before the court on [    •    ], 2007, at [    •    ] a.m. (Mountain Time) at the Law Courts, 1A Sir Winston Churchill Square, Edmonton, Alberta, T5J 0R2, subject to the approval of the plan of arrangement by our shareholders eligible to vote at the special meeting. Any shareholder of Biomira may participate, be represented and present evidence or arguments at the hearing for the final order.

        The authority of the court is very broad under the CBCA. We have been advised by our counsel that the court may make any enquiry it considers appropriate and may make any order it considers appropriate with respect to the plan of arrangement. The court will consider, among other things, the fairness and reasonableness of the plan of arrangement to our shareholders. The court may approve the plan of arrangement either as proposed or as amended in any manner the court may direct, subject to compliance with such terms and conditions, if any, as the court thinks fit.

        Assuming that the final order is granted and the other conditions in respect of the arrangement, as set out in the arrangement agreement, are satisfied or waived, it is anticipated that articles of arrangement will be filed under the CBCA to give effect to the plan of arrangement, which is attached to the arrangement agreement as Schedule 1, and the various other documents necessary to complete the arrangement will be executed and delivered.

        It is currently anticipated that the effective date of the arrangement will be on or about [    •    ], 2008. We refer to this date as the effective date.

Dissent Rights

        If you are a registered holder of Biomira shares, you will have the right to dissent from the arrangement resolution under Section 190 of the CBCA, as modified by the interim order and the arrangement agreement. Section 190 of the CBCA is reprinted in its entirety and attached to this proxy statement/prospectus as Annex C. The following summary is qualified by the provisions of Section 190 of the CBCA, the interim order and the plan of arrangement.

        If the arrangement becomes effective and you properly dissent from the arrangement resolution in compliance with Section 190 of the CBCA, the interim order and the plan of arrangement, you will be entitled to be paid by Biomira the fair value of your Biomira common shares or your Biomira Class A preference shares, determined as of the effective date of the arrangement. If you want to dissent, you must dissent with respect to all your Biomira shares on behalf of any one beneficial owner and registered in your name. As a consequence, you may only exercise the right to dissent in respect of the Biomira shares that are registered in your name.

        In many cases, people beneficially own shares that are registered either:

•

in the name of an intermediary, such as a bank, trust company, securities dealer, broker, trustee or administrator of "registered retirement savings plans," "registered retirement income funds," "registered educational savings plans" and similar plans and their nominees, as these terms are defined under the ITA; or



•

in the name of a clearing agency in which the intermediary participates, such as The Canadian Depositary for Securities Limited or The Depository Trust Company.

        If you want to dissent and your Biomira shares are registered in someone else's name, you must contact your intermediary and either:

•

instruct your intermediary to exercise the dissent rights on your behalf (which, if the Biomira shares are registered in the name of a clearing agency, will require that the Biomira shares first be re-registered in your intermediary's name); or



•

instruct your intermediary to re-register the Biomira shares in your name, in which case you will have to exercise your dissent rights directly.

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         In other words, if your Biomira shares are registered in someone else's name, you will not be able to exercise your dissent rights directly unless the shares are re-registered in your name.

         In order for you to dissent, a written dissent notice to the arrangement resolution must be received by us, to the attention of the Secretary, at 2011 - 94 Street, Edmonton, Alberta, Canada T6N 1H1, no later than 5:00 p.m. (Mountain Time) on the business day immediately preceding the day of the special meeting (or any postponement or adjournment thereof). We refer to this notice as the dissent notice. If you do not strictly comply with this requirement, you could lose your right to dissent. It is important that registered shareholders strictly comply with this requirement, as it is different from the statutory dissent procedures of the CBCA that would permit a dissent notice to be provided at or prior to the special meeting.

        If you send a dissent notice, you still have the right to vote at the special meeting. However, under the CBCA if you send a dissent notice and then vote in favor of the arrangement resolution, you will no longer be considered a dissenting shareholder with respect to that class of Biomira shares voted in favor of the arrangement resolution. You must either vote against the arrangement resolution or abstain to dissent.

        The CBCA does not provide (and we will not assume) that a vote against the arrangement resolution or an abstention constitutes a dissent notice. Similarly, if you give someone a proxy to vote for the arrangement resolution and then revoke the proxy, your revocation does not constitute a dissent notice. However, if you want to dissent, you should revoke any proxy that instructs the proxy holder to vote for the arrangement resolution to prevent the proxy holder from voting your Biomira shares in favor of the arrangement resolution and causing you to forfeit your dissent rights. For instructions on revoking a proxy, see the section entitled "The Special Meeting—Revocation of Proxies." If you dissent, we will be required to notify you that the arrangement resolution has been adopted within 10 days after our shareholders adopt the resolution. We are not required to send you a notice if you vote for the arrangement resolution or withdraw your dissent notice.

        If you dissent, you must send us (at the address above) a written demand for payment within 20 days after you receive our notice that the arrangement resolution has been adopted. If you do not receive that notice, you must send a written demand for payment of the fair value of your shares within 20 days after you learn that the arrangement resolution has been adopted. Your demand for payment of the fair value of your shares must contain:

•

your name and address;



•

the number of our common shares or Class A preference shares, or both, for which you are dissenting; and



•

a demand for payment of the fair value of such shares.

        If you dissent, within 30 days of sending a demand for payment, you must send us (at the address above) the share certificates representing your dissenting shares. If you do not send in your share certificates, you forfeit your right to dissent. Our transfer agent will endorse on your share certificates a notice that you are a dissenting shareholder and will then send the share certificates back to you.

        After you send your demand for payment, you will no longer have any rights as a shareholder other than the right to be paid the fair value of your shares unless:

•

you withdraw your demand for payment before we make a written offer to pay;



•

we do not make you a timely written offer to pay and you withdraw your demand for payment; or



•

our board of directors revokes the arrangement resolution.

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        In all three cases described above, your rights as a shareholder will be reinstated, and in the first two cases, your shares will be subject to the arrangement if it has been completed. Upon completion of the arrangement, if you duly exercise your dissent rights and are ultimately determined to have the right to be paid the fair value of your shares, you will be deemed to have transferred such shares to us for cancellation, as of the effective date. If you exercise your dissent rights but are ultimately determined for any reason not to have the right to be paid the fair value of your shares, you will be deemed to have participated in the arrangement like any non-dissenting shareholder and you will receive one share of common stock in Oncothyreon for every six Biomira common shares held by you and one share of Class UA preferred stock in Oncothyreon for each Biomira Class A preference share held by you.

        If you properly dissent, within seven days after the later of the effective date of the arrangement and the date when we receive your demand for payment, we are required to send you an offer to pay for your Biomira shares. That offer must be in an amount that our board of directors considers, as the case may be, to be the fair value of the Biomira shares. We must also send you a statement with the offer to pay showing how the fair value was determined. Every offer to pay for a dissenting Biomira shareholder's shares must be on the same terms for Biomira shares of the same class. We must pay for your Biomira shares within 10 days after you accept the offer to pay, but our offer to pay you will lapse if your acceptance is not received within 30 days after we have made the offer to pay.

        If you do not accept the offer or if we fail to make you an offer to pay after you have sent your demand for payment, we may apply to the court to fix a fair value for the Biomira shares of all dissenting Biomira shareholders. If we decide to apply to the court to fix the fair value, we must do so within 50 days after the effective date of the arrangement or within any longer period that the court allows. If we fail to apply to the court, you may apply to the court for the same purpose within a further period of 20 days or within any longer period that the court allows. You are not required to give security for the costs of applying to the court.

        If we, you or another dissenting Biomira shareholder applies to the court, all dissenting Biomira shareholders whose Biomira shares have not been purchased by us will be joined as parties and will be bound by the court's decision. We will be required to notify each affected dissenting Biomira shareholder of the date, place and consequences of the application and of such shareholder's right to appear and be heard in person or by counsel. The court may determine whether any person is a dissenting Biomira shareholder who should be joined as a party, and the court will then fix a fair value for the Biomira shares of all dissenting Biomira shareholders. The court will render a final order against us in favor of each dissenting Biomira shareholder and for the amount of the fair value of the dissenting Biomira shareholder's Biomira shares. The court may, in its discretion, allow a reasonable rate of interest on the amount payable to each Biomira shareholder from the effective date of the arrangement until the date of payment.

         The foregoing is only a summary of the provisions of Section 190 of the CBCA, as modified by the interim order and the plan of arrangement, which provisions as so modified are technical and complex. It is suggested that anyone wishing to exercise dissent rights seek legal advice as failure to comply strictly with the provisions of the CBCA, as modified by the interim order and the plan of agreement, may prejudice such Biomira shareholder's dissent rights.

         The Canadian federal income tax consequences to a holder of Biomira shares who exercises dissent rights and who receives fair value for the holder's Biomira shares may be different from the consequences to a holder who participates in the arrangement. For more information see the section entitled "Material Tax Consequences of the Arrangement—Material Canadian Federal Income Tax Consequences of the Arrangement," on page 58.

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ARRANGEMENT AGREEMENT

General

        Pursuant to the arrangement agreement, Biomira Canco, Biomira Sub-1, Biomira, Oncothyreon and Biomira Sub-2, which are described in greater detail under the captions "The Arrangement" and "Arrangement Agreement," have agreed to complete the arrangement pursuant to which, among other things, Biomira will amalgamate with Biomira Sub-1 to form Biomira Edmonco, which we refer to as the first amalgamation. Immediately following the first amalgamation, Biomira Canco will amalgamate with Biomira Sub-2 to form Biomira Amalco, which we refer to as the second amalgamation. Following the second amalgamation, Biomira Amalco will be a wholly owned subsidiary of Oncothyreon, and Biomira Edmonco will be the wholly owned subsidiary of Biomira Amalco. The completion of the arrangement is conditioned upon, among other things, obtaining a final order from Alberta Court of Queen's Bench, which we refer to as the court, and the filing of the articles of arrangement with the director under the Canada Business Corporations Act, or CBCA. See "Conditions to the Effectiveness of the Arrangement" below.

         The following description of the arrangement is qualified in its entirety by reference to the full text of the arrangement agreement, a copy of which attached as Annex B to this proxy statement/prospectus, and the plan of arrangement, which forms Schedule 1 to the arrangement agreement. Each of these documents should be read carefully in its entirety.

        Pursuant to the plan of arrangement, the following would occur and be deemed to occur in the following chronological order without further act or formality:

        (a)   Biomira Sub-1 and Biomira would amalgamate to form Biomira Edmonco and would continue as one corporation under the CBCA in the manner set out in section 181 of the CBCA;

        (b)   all of the shareholders who owned shares of Biomira immediately before the first amalgamation would receive shares of the capital stock of Biomira Canco as set forth in (c) below;

        (c)   immediately upon the first amalgamation to form Biomira Edmonco as set forth in (a) above:

          (i)  each six issued and outstanding Biomira common shares held by a shareholder (other than shares held by a dissenting shareholder) would be exchanged for one Biomira Canco common share, having the effect of a 6 for 1 reverse split of Biomira's outstanding common shares, whereupon such Biomira common shares would be cancelled by Biomira (as continued in amalgamated form);

         (ii)  each of the 12,500 issued and outstanding Biomira Class A preference shares (other than shares held by a dissenting shareholder) would be exchanged for one preferred share of Biomira Canco, whereupon such Biomira preference share would be cancelled by Biomira (as continued in amalgamated form);

        (iii)  each issued and outstanding Biomira Sub-1 share held by Biomira Canco would be converted into one Biomira Edmonco common share;

        (iv)  each originally issued and outstanding Biomira Canco share immediately prior to the effective date would be cancelled by Biomira Canco; and

         (v)  immediately upon the first amalgamation, Biomira Edmonco would add to the stated capital account maintained in respect of the Biomira Edmonco common shares an aggregate amount equal to the paid-up capital for purposes of the Income Tax Act (Canada) of all of the shares (except any shares held by either of Biomira Sub-1 and Biomira in the other) of the capital of each of Biomira Sub-1 and Biomira immediately before the Effective Date, which amount shall be allocated to the stated capital account maintained for the Biomira Edmonco common shares;

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        (d)   Biomira Sub-2 and Biomira Canco would amalgamate to form Biomira Amalco and would continue as one corporation under the CBCA in the manner set out in section 181 of the CBCA;

        (e)   all of the shareholders who owned shares of the capital stock of Biomira Canco immediately before the second amalgamation, would receive shares of the capital stock of Oncothyreon as set forth in (f) below;

        (f)    immediately upon the second amalgamation to form Biomira Amalco as set forth in (d) above:

          (i)  each issued and outstanding Biomira Canco common share would be exchanged for one share of Oncothyreon common stock, whereupon such Biomira Canco common shares would be cancelled by Biomira Canco (as continued in amalgamated form);

         (ii)  each issued and outstanding Biomira Canco preferred share would be exchanged for one share of Class UA preferred stock of Oncothyreon, whereupon such Biomira Canco preferred shares would be cancelled by Biomira Canco (as continued in amalgamated form);

        (iii)  each issued and outstanding share of Biomira Sub-2 held by Oncothyreon immediately prior to the effective date would be converted into one common share of Biomira Amalco;

        (iv)  each originally issued and outstanding share of Oncothyreon stock immediately prior to the effective date would be cancelled by Oncothyreon; and

         (v)  immediately upon the second amalgamation, Biomira Amalco would add to the stated capital account maintained in respect of the Biomira Amalco common shares an aggregate amount equal to the paid-up capital for purposes of the Income Tax Act (Canada) of all of the shares (except any shares held by either of Biomira Sub-2 and Biomira Canco in the other) of the capital of each of Biomira Sub-2 and Biomira Canco immediately before the effective date, which amount would be allocated to the stated capital account maintained for the Biomira Amalco common shares;

        (g)   each option to purchase Biomira common shares would be exchanged for an option of Oncothyreon to purchase that number of shares of Oncothyreon common stock equal to the number of shares subject to such Biomira option divided by six. Such Oncothyreon option would provide for an exercise price per share of common stock equal to the exercise price per share of such Biomira option immediately prior to the effective date multiplied by six;

        (h)   each share or restricted share unit of Biomira would be exchanged for a restricted share or unit of Oncothyreon restricted common stock to purchase that number of shares of Oncothyreon common stock equal to the number of shares subject to such Biomira RSU divided by six. Such Oncothyreon RSU would provide for an exercise price per share equal to the exercise price per share of such Biomira RSU immediately prior to the effective date multiplied by six;

        (i)    each warrant for the purchase of Biomira common shares would be exchanged for a warrant of Oncothyreon to purchase that number of shares of Oncothyreon common stock equal to the number of shares subject to such Biomira warrant divided by six. Such Oncothyreon warrant would provide for an exercise price per share equal to the exercise price per share of such Biomira warrant immediately prior to the effective date multiplied by six;

Authority of the Board of Directors

        By passing the special resolution approving the arrangement, our shareholders eligible to vote at the special meeting will also be giving authority to our board of directors to use its best judgment to proceed with and cause Biomira to complete the arrangement in the event of any variation of, or

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amendments to, the arrangement agreement, without any requirement to seek or obtain any further approval of our shareholders.

Conditions to the Effectiveness of the Arrangement

        The arrangement agreement provides that the arrangement will be subject to the fulfillment of certain conditions, any of which are waivable by the parties to the arrangement agreement including the following:

        (a)   the interim order shall have been granted in form and substance satisfactory to us;

        (b)   the arrangement resolution shall have been approved by our shareholders;

        (c)   the rights of dissent in relation to the arrangement shall not have been exercised by holders of more than 1% of the issued and outstanding Biomira shares;

        (d)   the final order shall have been obtained in form and substance satisfactory to us;

        (e)   there shall not be in force any order or decree restraining or enjoining the arrangement from being completed or the other transactions contemplated by the arrangement agreement;

        (f)    the arrangement agreement shall not have been terminated as provided for therein;

        (g)   the shares of common stock shall have been conditionally approved for listing on the Toronto Stock Exchange and the NASDAQ Global Market, subject to the filing of required documentation;

        (h)   all other approvals, consents, waivers, permits, orders, exemptions, agreements and amendments and modifications to agreements, indentures or arrangements of third persons (other than government authorities), the failure of which to obtain or the non-expiration of which would, or could reasonably be expected, to have a material adverse effect or materially impede the completion of the arrangement, shall have been obtained or received on terms that are reasonably satisfactory to Biomira Canco, Biomira Sub-1, Biomira, Oncothyreon and Biomira Sub-2;

        (i)    the board of directors of each of Biomira Canco, Biomira Sub-1, Biomira, Oncothyreon and Biomira Sub-2 shall have taken all necessary corporate actions to permit the completion of the arrangement upon filing of articles of arrangement;

        (j)    all regulatory approvals shall have been obtained; and

        (k)   there shall not exist any prohibition at law against the completion of the arrangement.

        These conditions are for the mutual benefit of Biomira Canco, Biomira Sub-1, Biomira, Oncothyreon and Biomira Sub-2 and may be waived, in whole or in part, by mutual consent of each of them at any time. Waiver of any of these terms by Biomira does not require the approval of Biomira's shareholders. If any of the above conditions shall not have been complied with or waived by each of Biomira Canco, Biomira Sub-1, Biomira, Oncothyreon and Biomira Sub-2, as applicable, on or before the effective date or, if earlier, the date required for the performance thereof, then any one of them may terminate the arrangement agreement.

No Fractional Shares

        No fractional shares of common stock would be issued pursuant to the arrangement and any amount of fractional shares of common stock otherwise issuable would be paid in cash. The issue price for any fractional share of common stock shall be paid in Canadian dollars and based on the ten day weighted average trading price of the Biomira common shares listed on the Toronto Stock Exchange immediately prior to the effective date of the arrangement.

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Assumption of Stock Options, Restricted Share Units and Warrants

        As of the effective date, Oncothyreon would assume the obligations of Biomira under each of the Biomira Share Option Plan, the Biomira Restricted Share Unit Plan and outstanding warrants to acquire Biomira common shares all on the terms contained therein, subject to any amendments or modifications required to be made to such plans to give effect to the arrangement as set forth in the plan of arrangement.

Termination; Effect of Termination

        The arrangement may be terminated, and the arrangement may be abandoned, at any time, either before or after approval thereof by the Biomira shareholders, if any of the following occur: (1) the parties to the arrangement agreement mutually agree, or (2) certain conditions are not satisfied or waived as provided for in the arrangement agreement.

Exchange Procedures

        If the arrangement is completed, Biomira shareholders will receive a transmittal letter from the transfer agent in the arrangement instructing Biomira shareholders how to exchange their Biomira stock certificates for Oncothyreon stock certificates. Biomira shareholders should not send any stock certificates until they have received the transmittal letter. If there are any questions, Biomira shareholders may contact Oncothyreon's transfer agent at Computershare Investor Services Inc., Suite 600, 530 8th Avenue SW, Calgary, Alberta T2P 3S8, (403) 267-6800, or at 350 Indiana St., Suite 800, Golden, Colorado 80401, (214) 340-0757. Biomira shareholders should not contact Computershare Investor Services Inc. with questions about the exchange of certificates or the arrangement until after the arrangement has been completed.

        In the event of a transfer of ownership of Biomira shares that is not registered in the transfer records of Biomira, a certificate representing the proper number of Oncothyreon shares may be issued to the transferee if the certificate representing such Biomira shares is presented to the depositary, accompanied by all documents required to evidence and effect such transfer.

        Until surrendered, each certificate which immediately prior to the effective date represented Biomira shares will be deemed, at any time after the effective date, to represent only the right to receive upon such surrender the certificate representing Oncothyreon shares that the holder thereof has the right to receive in respect of the certificate pursuant to the plan of arrangement.

        No fractional share of common stock will be issued to former Biomira shareholders upon the surrender of Biomira common shares for exchange. Each Biomira shareholder otherwise entitled to receive a fractional interest in common stock will receive a cash payment.

        If any certificate that immediately prior to the effective date represented outstanding Biomira shares has been lost, stolen or destroyed, upon the making of an affidavit of that fact by the person claiming such certificate to be lost, stolen or destroyed, the depositary will cause to be issued in exchange for such lost, stolen or destroyed certificate, a certificate representing Oncothyreon shares deliverable in respect thereof in accordance with such holder's letter of transmittal, as determined in accordance with the arrangement. When authorizing such delivery in exchange for any lost, stolen or destroyed certificate, the person to whom a certificate representing Oncothyreon shares is to be issued must, as a condition precedent to the issuance thereof, give a bond satisfactory to the depositary in such amount as Biomira and the depositary may direct or otherwise indemnify Oncothyreon in a manner satisfactory to Oncothyreon and the depositary against any claim that may be made against Biomira and the depositary with respect to the certificate alleged to have been lost, stolen or destroyed.

        No dividends or other distributions declared or made after the effective date with respect to Oncothyreon shares with a record date after the effective date will be delivered to the holder of any

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unsurrendered certificate that immediately prior to the effective date represented outstanding Biomira shares that were exchanged pursuant to the arrangement, unless and until the holder of record of such certificate surrenders such certificate (together with a letter of transmittal which has been completed and signed in the manner required thereby in respect of such certificate) or complies with the required procedures in respect of lost, stolen or destroyed certificates. Subject to applicable law, at the time of such surrender of any such certificate or compliance with the required procedures in respect of lost, stolen or destroyed certificates, there will be paid to the holder of record of the certificate representing Oncothyreon shares, without interest, the amount of dividends or other distributions with a record date after the effective date but prior to surrender paid with respect to such Oncothyreon shares.

        Oncothyreon and the depositary are entitled to deduct and withhold from any dividend or distribution otherwise payable to any holder of Biomira shares or Oncothyreon shares such amounts as Oncothyreon or the depositary is required or permitted to deduct and withhold with respect to such payment under the ITA or any provision of provincial, state, local or foreign tax law. To the extent that amounts are so withheld, such withheld amounts will be treated for all purposes hereof as having been paid to the holder of the shares in respect of which such deduction and withholding was made, provided that such withheld amounts are actually remitted to the appropriate taxing authority.

        To the extent that a Biomira shareholder has not surrendered the certificates representing the Biomira shares held by such former Biomira shareholder on or before the date which is six years after the effective date, which we refer to as the final proscription date, then the Oncothyreon shares which such former Biomira shareholder was entitled to receive will be delivered to Oncothyreon by the depositary for cancellation and will be cancelled by Oncothyreon, and the interest of the former Biomira shareholder in such Oncothyreon shares will be terminated as of such final proscription date.

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MATERIAL TAX CONSEQUENCES OF THE ARRANGEMENT

Material United States Federal Income Tax Consequences of the Arrangement

        The following summary discusses the material United States federal income tax consequences of the arrangement, when taken together with the amalgamation of Biomira Amalco and Biomira Sub-3 to form Biomira ULC (the arrangement together with such amalgamation to form Biomira ULC are referred to as the "combined transactions"), assuming that the combined transactions are effected as described in this proxy statement/prospectus. This summary is based on the Internal Revenue Code of 1986, as amended, applicable U.S. Treasury regulations under the Internal Revenue Code, administrative rulings and judicial authority, all as of the date of this proxy statement. All of the foregoing authorities are subject to change, with or without retroactive effect, and any change could affect the continuing validity of this summary.

        This summary assumes that Biomira shareholders hold their shares as capital assets. The summary does not address the tax consequences that may be applicable to particular Biomira shareholders in light of their individual circumstances or to Biomira shareholders who are subject to special tax rules, such as shareholders that are not U.S. Holders (as described below), dealers in securities, shareholders who acquired Biomira common shares through the exercise of options or otherwise as compensation or through a qualified retirement plan, and Biomira shareholders who hold their Biomira common shares as part of a straddle, hedge or conversion transaction. In addition, this summary does not address the tax consequences of the combined transactions to holders of options or warrants to acquire capital stock of Biomira or the tax consequences of transactions effectuated prior or subsequent to, or concurrently with, the combined transactions, whether or not any such transactions are undertaken in connection with the combined transactions. This summary also does not address any consequences arising under the tax laws of any state, local or non-U.S. jurisdiction.

         In general, we refer to a "U.S. Holder" in this proxy statement/prospectus as any Biomira shareholder that is:

•

a citizen or resident of the United States;



•

a corporation created or organized in or under the laws of the United States or any political subdivision of the United States;



•

an estate, the income of which is includible in gross income for U.S. federal income tax purposes regardless of its source; or



•

a trust, if (a) a court within the United States is able to exercise primary supervision over the administration of the trust and one or more U.S. persons have the authority to control all substantial decisions of the trust or (b) it has a valid election in effect under applicable U.S. Treasury regulations to be treated as a United States person.

        Generally, an individual may be treated as a resident of the United States in any calendar year for U.S. federal income tax purposes by, among other ways, being present in the United States for at least 31 days in that calendar year and for an aggregate of at least 183 days during a three-year period ending in the current calendar year. For purposes of this calculation, such individual would count all of the days in which he or she was present in the current year, one-third of the days present in the immediately preceding year, and one-sixth of the days present in the second preceding year. Residents of the United States are taxed for U.S. federal income tax purposes as if they were citizens of the United States.

        BIOMIRA SHAREHOLDERS ARE URGED TO CONSULT THEIR OWN TAX ADVISORS REGARDING THE APPLICATION OF THE U.S. FEDERAL INCOME TAX LAWS TO THEIR PARTICULAR SITUATIONS AND THE CONSEQUENCES OF FEDERAL ESTATE OR GIFT TAX LAWS, NON-U.S. LAWS, STATE OR LOCAL LAWS AND TAX TREATIES.

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        The combined transactions are expected to qualify as a reorganization within the meaning of Section 368(a) of the Internal Revenue Code. Qualification of the combined transactions as a reorganization will result in the following material U.S. federal income tax consequences:

•

U.S. Holders will recognize no gain or loss upon the conversion of their Biomira common shares solely into Oncothyreon common stock in the arrangement.



•

U.S. Holders who receive cash in the arrangement in lieu of a fractional share of Oncothyreon common stock will recognize gain or loss equal to the difference between the cash received and such holder's basis in such fractional share interest. Such gain or loss should be capital gain or loss to the U.S. Holder, provided the fractional share interest is a capital asset in the hands of such holder.



•

The aggregate tax basis of Oncothyreon common stock received by a U.S. Holder in the arrangement (including the basis in any fractional share for which cash is received) will be the same as such holder's aggregate tax basis in Biomira common shares surrendered in the arrangement.



•

The holding period of Oncothyreon common stock received by a U.S. Holder in the arrangement will include the holding period of the Biomira common shares held by such U.S. Holder.



•

Neither Oncothyreon nor Biomira will recognize any gain or loss as a result of the combined transactions.

        Biomira will not request a ruling from the Internal Revenue Service or an opinion of counsel in connection with the arrangement or the combined transactions. A successful IRS challenge to the status of the combined transactions as a tax-free reorganization would result in U.S. Holders being treated as if they sold such stock in a taxable transaction. In such event, each U.S. Holder would recognize gain or loss with respect to the disposition of each of his or her Biomira common shares equal to the difference between the holder's basis in each such share and the fair market value, as of the date the arrangement becomes effective, each share of Oncothyreon common stock received in the arrangement. Such gain or loss would be treated as capital gain or capital loss for each such U.S. Holder. U.S. Holders' aggregate basis in the Oncothyreon common stock so received would equal its fair market value as of the date of the arrangement, and the U.S. Holders' holding period for such Oncothyreon common stock would begin the day after the arrangement.

         THE PRECEDING DISCUSSION IS INTENDED ONLY AS A SUMMARY OF CERTAIN FEDERAL INCOME TAX CONSEQUENCES OF THE ARRANGEMENT AND THE COMBINED TRANSACTIONS AND DOES NOT PURPORT TO BE A COMPLETE ANALYSIS OR DISCUSSION OF ALL POTENTIAL TAX EFFECTS RELEVANT THERETO. BIOMIRA SHAREHOLDERS ARE URGED TO CONSULT THEIR OWN TAX ADVISORS AS TO THE SPECIFIC TAX CONSEQUENCES TO THEM, INCLUDING TAX RETURN REPORTING REQUIREMENTS, THE APPLICABILITY AND EFFECT OF FEDERAL, STATE, LOCAL, NON-U.S. AND OTHER APPLICABLE TAX LAWS AND ANY PROPOSED TAX LAW CHANGES.

Material Canadian Federal Income Tax Consequences of the Arrangement

        The following is a summary of the principal Canadian federal income tax considerations generally applicable to Biomira shareholders in respect of the arrangement. This summary applies generally to Biomira shareholders who, at all relevant times, for the purposes of the Income Tax Act (Canada), which we refer to as the ITA, deal at arm's length with Biomira, are not affiliated with Biomira and hold their Biomira shares as capital property. A holder's Biomira shares are generally considered to be capital property provided that such holder is not a trader or dealer in securities, is not engaged in an adventure in the nature of trade with respect to the shares and does not hold the shares in the course

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of carrying on a business of buying and selling securities. This summary does not address income tax considerations applicable to directors, officers or other insiders of Biomira. This summary does not apply to any holder that is a "financial institution" (as defined in the ITA for the purposes of the mark-to-market rules contained in the ITA). This summary addresses the tax considerations applicable to Biomira only to the extent expressly set out herein.

        This summary is based on the current provisions of the ITA, the regulations under the ITA in force on the date hereof, all proposals to amend the ITA or the regulations publicly announced by or on behalf of the federal Minister of Finance (Canada), which we refer to as the proposed amendments, prior to the date hereof and counsel's understanding of the current published administrative practices of the Canada Revenue Agency, or the CRA. It has been assumed that the proposed amendments will be enacted as proposed and that there will be no other relevant change to the ITA or other applicable law or policy, whether by judicial, legislative or other governmental action, although no assurance can be given in this regard.

        This summary does not take into account or anticipate provincial, territorial or foreign tax considerations, which considerations may differ significantly from those discussed herein.

         This summary is not exhaustive of all Canadian federal income tax considerations and is of a general nature only. It is not intended to be, and should not be construed to be, legal or tax advice to any particular holder. The tax consequences to any particular holder will depend on a variety of factors, including the holder's own particular circumstances. Therefore, all holders should consult their own tax advisors with respect to their particular circumstances and the income tax consequences to them of the proposed transactions. An advance income tax ruling has not been obtained with respect to the transactions contemplated in this proxy statement/prospectus. The discussion below is qualified accordingly.

Residents of Canada

        The following portion of this summary is applicable to Biomira shareholders who, at all relevant times, for the purposes of the ITA and any applicable income tax treaty, are resident in Canada or are deemed to be resident in Canada. Certain Biomira shareholders who are resident in Canada and whose Biomira shares might not otherwise be considered capital property may, in some circumstances, make an irrevocable election in accordance with subsection 39(4) of the ITA to have their Biomira shares and all other Canadian securities (as defined in the ITA) owned by them in the taxation year in which the election is made, and in all subsequent taxation years, treated as capital property.

Triangular Amalgamation of Biomira and Biomira Sub-1 to form Biomira Edmonco

        Biomira shareholders (other than those who dissent) will realize neither a capital gain nor a capital loss on the amalgamation of Biomira and Biomira Sub-1 to form Biomira Edmonco, in the course of which the holders' shares of Biomira will be exchanged for shares of Biomira Canco. The cost to a holder of such Biomira Canco shares will be equal to the adjusted cost base to the holder of the Biomira shares that were exchanged for the Biomira Canco shares by virtue of the first amalgamation.

        Holders who intend to dissent should consult their own tax advisors with respect to the tax treatment of payments received as a result of the exercise of dissent rights, which are described in the section entitled "The Arrangement—Dissent Rights." On the understanding that it will be Biomira Edmonco, and not Biomira, which pays to a dissenting Biomira shareholder an amount equal to the fair value of the holder's Biomira shares, under the current published administrative practices of the CRA, the holder will be considered to have disposed of those shares for proceeds of disposition equal to the amount of the cash payment so received (other than the portion, if any, of such payment attributable to interest). Such a holder will realize a capital gain (or a capital loss) to the extent that

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such proceeds of disposition exceed (or are less than) the aggregate of the adjusted cost base to the holder of the holder's Biomira shares and any reasonable costs of disposition.

        One-half of any capital gain, which is called a taxable capital gain, realized by a holder will be included in the holder's income for the holder's taxation year in which the first amalgamation occurs. One-half of any capital loss, which is called an allowable capital loss, realized by a holder must be deducted by the holder against taxable capital gains in computing the holder's income for the year of disposition. Any excess of allowable capital losses over taxable capital gains of the holder for the year of disposition may be carried back up to three taxation years or forward indefinitely and deducted against net capital gains in those other years to the extent and in the circumstances stipulated in the ITA.

        Capital gains realized by an individual or a trust, other than certain specified trusts, may give rise to alternative minimum tax under the ITA. A holder which is throughout the relevant taxation year a Canadian-controlled private corporation (as defined in the ITA) may be liable to pay an additional refundable tax of 6 ² / 3 % on taxable capital gains.

        If a holder is a corporation, the amount of any capital loss arising on a disposition or deemed disposition of any share may be reduced by the amount of dividends received or deemed to have been received by it on such share to the extent and under the circumstances stipulated in the ITA. Similar rules may apply where a corporation is a member of a partnership or a beneficiary of a trust that owns shares, or where a partnership or trust of which a corporation is a member or a beneficiary is itself a member of another partnership or a beneficiary of another trust that owns shares. Dissenting shareholders to whom these rules may be relevant should consult their own tax advisors.

        A dissenting shareholder who receives interest as a result of the exercise of dissent rights will be required to include the full amount of that interest in computing the dissenting shareholder's income.

Triangular Amalgamation of Biomira Canco and Biomira Sub-2 to form Biomira Amalco

        The amalgamation of Biomira Canco and Biomira Sub-2 to form Biomira Amalco will not qualify for the tax-deferred or rollover treatment described above in the context of the first amalgamation. Accordingly, on the second amalgamation, holders of Biomira Canco shares will be treated as disposing of those shares for proceeds of disposition equal to the fair market value of the Oncothyreon shares received in exchange for their Biomira Canco shares. Each holder will realize a capital gain (or a capital loss) to the extent that those proceeds of disposition exceed (or are less than) the adjusted cost base to the holder of the Biomira Canco shares and any reasonable costs of disposition. The tax considerations applicable to a capital gain or capital loss referred to in this paragraph are similar to those discussed above.

        If the Oncothyreon shares are considered to be identical to the Biomira Canco shares, any capital loss realized by an individual holder on the second amalgamation will (unless, within 30 days after the second amalgamation, the holder disposes of the holder's Oncothyreon shares to a person who is not affiliated (as defined in the ITA) with the holder, and neither the holder nor an affiliated person reacquires those shares within that 30-day period) be a superficial loss, the deductible amount of which will be deemed to be zero. The amount of the undeductible superficial loss may generally be added to the adjusted cost base to the holder of the Oncothyreon shares received on the second amalgamation. If the Oncothyreon shares are considered to be identical to the Biomira Canco shares and if the holder is a corporation, trust or partnership, the deduction of any capital loss will be suspended until the Oncothyreon shares are disposed of to, and held for at least 30 days by, a person who is not affiliated (as defined in the ITA) with the holder.

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Dividends Received from Oncothyreon

        To the extent that dividends paid on Oncothyreon shares to a holder resident in Canada are subject to U.S. withholding tax, the holder may be entitled to a Canadian foreign tax credit in computing the tax payable under the ITA by the holder.

Non-Residents of Canada

        The following portion of this summary is applicable to Biomira shareholders who, for purposes of the ITA and any applicable income tax treaty, have not been and will not be resident or deemed to be resident in Canada at any time while they have held Biomira shares and who, at all relevant times, do not use or hold and are not deemed to use or hold their Biomira shares in carrying on a business in Canada. Special rules, which are not discussed in this summary, may apply to a non-resident that is an insurer carrying on an insurance business in Canada or elsewhere. The tax treatment of non-residents of Canada under the ITA and the following discussion can be affected by the provisions of an applicable income tax treaty. Non-resident holders should consult their own tax advisors with regard to the availability of relief under an applicable income tax treaty in their particular circumstances.

Triangular Amalgamation of Biomira and Biomira Sub-1 to Form Biomira Edmonco

        Non-resident shareholders of Biomira (other than dissenting shareholders) will realize neither a capital gain nor a capital loss by reason of their Biomira shares being exchanged for Biomira Canco shares on the amalgamation of Biomira and Biomira Sub-1 to form Biomira Edmonco. The cost of such Biomira Canco shares to a non-resident shareholder will be equal to the adjusted cost base to the shareholder of the Biomira shares which are exchanged for Biomira Canco shares by virtue of the first amalgamation.

        Non-resident dissenting shareholders are referred to the discussion above concerning residents of Canada for a general description of the tax considerations applicable on the exercise of their dissent rights. However, non-resident dissenting shareholders generally will not be subject to tax under the ITA in respect of any capital gain realized on a disposition of Biomira shares unless those shares constitute or are deemed to constitute taxable Canadian property of the holder for the purposes of the ITA and the gain is not exempt from tax under an applicable tax treaty.

        Generally, Biomira shares will not be taxable Canadian property of a non-resident dissenting shareholder at a particular time provided that those shares are listed on a prescribed stock exchange (which includes the Toronto Stock Exchange), and the holder, either alone or together with persons with whom the holder does not deal at arm's length, has not owned 25% or more of the issued shares of any class or series of capital stock of Biomira at any time during the 60-month period that ends at the particular time. Even if the Biomira shares constitute or are deemed to constitute taxable Canadian property of a non-resident dissenting shareholder and the disposition would give rise to a capital gain, an exemption from tax may be available under the terms of an applicable income tax treaty between Canada and the country of residence of the non-resident dissenting shareholder.

        Non-resident shareholders whose Biomira shares constitute taxable Canadian property and who exercise their dissent rights and dispose of those shares will be required to file an income tax return under the ITA.

        Interest paid by Biomira Edmonco to a non-resident dissenting shareholder will generally be subject to Canadian non-resident withholding tax at the rate of 25% on the gross amount of the interest. A tax exemption or withholding-tax rate reduction may be available under the terms of an applicable income tax treaty.

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Triangular Amalgamation of Biomira Canco and Biomira Sub-2 to form Biomira Amalco

        The amalgamation of Biomira Canco and Biomira Sub-2 to form Biomira Amalco will not qualify for tax-deferred or rollover treatment, with the result that a non-resident holder of Biomira Canco shares will be treated as disposing of those shares for proceeds of disposition equal to the fair market value of the Oncothyreon shares received in exchange for those Biomira Canco shares. Each non-resident holder will realize a capital gain (or a capital loss) to the extent that those proceeds of disposition exceed (or are less than) the adjusted cost base to the holder of the holder's Biomira Canco shares and any reasonable costs of disposition. However, a non-resident holder generally will not be subject to tax under the ITA in respect of any capital gain realized on a disposition of Biomira Canco shares unless those shares constitute or are deemed to constitute taxable Canadian property of the holder for the purposes of the ITA and the gain is not exempt from tax under an applicable tax treaty.

        Since the Biomira Canco shares will not be listed on a prescribed stock exchange, the Biomira Canco shares of a particular holder will be taxable Canadian property of the holder, unless Biomira Canco becomes a public corporation, as defined in the ITA, the Biomira Canco shares are deemed to be listed on a prescribed stock exchange and the holder, either alone or together with persons with whom the holder does not deal at arm's length, has not owned 25% or more of the issued shares of any class or series of the capital stock of Biomira Canco at any time before the second amalgamation. Biomira Canco intends to file an election in prescribed manner with the CRA, whereby Biomira Canco may become a public corporation, provided that Biomira Canco complies with certain prescribed conditions, as a result of which the Biomira Canco shares will likely be deemed to be listed on a prescribed stock exchange. However, even if Biomira Canco does not become a public corporation and even though a disposition by a non-resident holder of Biomira Canco shares may give rise to a capital gain, an exemption from tax may be available under the terms of an applicable income tax treaty between Canada and the country of residence of the non-resident holder.

        Even if a treaty exemption is available, unless Biomira Canco becomes a public corporation and the Biomira Canco shares are deemed to be listed on a prescribed stock exchange, non-resident holders of Biomira Canco shares will be required to apply to the CRA for a certificate under section 116 of the ITA in respect of the disposition of those shares. If Biomira Canco does not become a public corporation and if a certificate under section 116 of the ITA is not obtained by a particular non-resident holder, Oncothyreon will be required to withhold and liquidate sufficient Oncothyreon shares, which would otherwise be issued to that holder, to enable Oncothyreon to remit to the CRA 25% of the cost to Oncothyreon of the Biomira Canco shares acquired from that holder. As indicated above, Biomira Canco intends to file an election in prescribed manner with the CRA, whereby Biomira Canco may become a public corporation, provided that Biomira Canco complies with certain prescribed conditions, as a result of which the Biomira Canco shares will likely be deemed to be listed on a prescribed stock exchange. It is the understanding of Oncothyreon that Biomira Canco will comply with the prescribed conditions, such that Oncothyreon will not require non-resident holders of Biomira Canco shares to obtain certificates under section 116 of the ITA, nor will Oncothyreon withhold any portion of the Oncothyreon shares to be issued on the second amalgamation.

Biomira

Triangular Amalgamation of Biomira and Biomira Sub-1 to form Biomira Edmonco

        The amalgamation of Biomira and Biomira Sub-1 to form Biomira Edmonco will qualify for tax-deferred or rollover treatment under the ITA, with the result that Biomira will realize neither a gain nor a loss in respect of any of its property which becomes property of Biomira Edmonco by virtue of the first amalgamation. In addition, the various tax accounts, tax bases and other tax attributes and pools of Biomira (such as losses, tax credits and scientific research and experimental development

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expenditures) will generally be available to Biomira Edmonco. However, those losses, credits and expenditures will be usable by Biomira Edmonco only to the extent it has sufficient income.

Triangular Amalgamation of Biomira Canco and Biomira Sub-2 to form Biomira Amalco

        The second amalgamation will not qualify for the tax-deferred or rollover treatment available under the ITA in respect of the first amalgamation. However, since the applicable corporate law provides for Biomira Canco and Biomira Sub-2 to continue as one corporation, Biomira Canco and Biomira Sub-2 will not be considered to dispose of any property on the second amalgamation, with the result that neither Biomira Canco nor Biomira Sub-2 will realize a gain or a loss in respect of any of the property of Biomira Canco or Biomira Sub-2 that becomes property of Biomira Amalco by virtue of the second amalgamation. However, the various tax accounts and other tax attributes and pools of Biomira Canco and Biomira Sub-2 will not be available to Biomira Amalco. The losses, credits and expenditures of Biomira which will become available to Biomira Edmonco on the first amalgamation (see the preceding paragraph) will not be available to Biomira Amalco or Oncothyreon after the second amalgamation.

Amalgamation of Biomira Amalco and Biomira Sub-3 to form Biomira ULC

        The amalgamation of Biomira Amalco and Biomira Sub-3 to form Biomira ULC will qualify for tax-deferred or rollover treatment under the ITA, with the result that neither Biomira Amalco nor Biomira Sub-3 will realize a gain or a loss in respect of any of their respective properties which become property of Biomira ULC by virtue of this amalgamation. As well, the various tax accounts, tax bases and other tax attributes and pools of Biomira Amalco and Biomira Sub-3 will generally be available to Biomira ULC.

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