TRMS Trimeris (MM)

SUMMARY

This joint proxy statement/prospectus is being sent to Trimeris stockholders and Synageva stockholders. This summary highlights selected information from this joint proxy statement/prospectus. It may not contain all of the information that is important to you with respect to the Trimeris Merger Proposals, the Synageva Merger Proposal, or any other matter described in this joint proxy statement/prospectus. Trimeris and Synageva urge you to carefully read this joint proxy statement/prospectus, as well as the documents attached to, referred to or incorporated by reference in this joint proxy statement/prospectus, to fully understand the Merger. In particular, you should read the Merger Agreement, the form of Trimeris stockholder voting agreement, and the form of Synageva stockholder voting agreement, which are described elsewhere in this joint proxy statement/prospectus and attached as Annexes A, B and C, respectively. To understand the Merger fully, you should read carefully this entire document, including the business and financial information about Trimeris and Synageva, and the documents to which this joint proxy statement/prospectus refers, including the annexes attached hereto. See the section entitled “Where You Can Find Additional Information” beginning on page 249.

The Companies

Trimeris, Inc.

Trimeris is a biopharmaceutical company that pioneered the development of a class of antiviral drug treatments called fusion inhibitors. Fusion inhibitors prevent viral fusion, a complex process by which viruses attach to, penetrate and infect host cells. If a virus cannot enter a host cell, the virus cannot replicate. By inhibiting the fusion process of particular types of viruses, like HIV, Trimeris’ first and only commercial product, FUZEON (whose generic name is enfuvirtide, originally known as T-20), offers a novel mechanism of action to treat and potentially prevent the transmission of HIV. In late 2007, Trimeris shifted its corporate strategy to maximizing cash flows from FUZEON, advancing its only remaining drug candidate, TRI-1144, to a value-creating milestone if possible, and exploring strategic alternatives for Trimeris. As a result of this shift in strategic emphasis, Trimeris has not staffed a research and development function since late 2008. In addition, Trimeris currently has no manufacturing, sales, marketing, or distribution capability, and has only three employees.

Trimeris is headquartered in Durham, North Carolina and was incorporated in Delaware in 1993. Trimeris’ principal offices are located at 2530 Meridian Parkway, 2nd Floor, Durham, North Carolina 27713 and its telephone number is (919) 806-4682. Trimeris’ principal website is www.trimeris.com . Trimeris common stock is listed on the NASDAQ Global Market and trades under the symbol “TRMS”. Additional information about Trimeris and its subsidiary is included elsewhere in this joint proxy statement/prospectus. See the sections entitled “Trimeris’ Business”, “Trimeris’ Management’s Discussion and Analysis of Financial Condition and Results of Operations”, and Trimeris’ financial statements beginning on pages 153, 164, and F-1, respectively.

Synageva BioPharma Corp.

Synageva is a clinical stage biopharmaceutical company focused on the discovery, development, and commercialization of therapeutic products for patients with life-threatening rare diseases and unmet medical needs. Synageva has several protein therapeutics in development, including two enzyme replacement therapies for lysosomal storage disorders and two programs for life-threatening genetic conditions for which there are currently no approved treatments. Its lead program, SBC-102, is a recombinant human lysosomal acid lipase ( “LAL” ) currently under clinical investigation in the U.S. and EU for the treatment of patients with LAL Deficiency, which is a rare, devastating disease that causes significant morbidity and mortality. SBC-102 has been granted orphan designations ( “Orphan Drug Designations” ) by the U.S. Food and Drug Administration ( “FDA” ) and the European Medicines Agency (the “EMA” ). Orphan Drug Designation is a status granted by regulatory agencies for products intended to treat rare diseases and such status qualifies the sponsor of the product to receive certain benefits, including access to grant funding for clinical trials, tax credits, waivers of

certain fees, and a period of market exclusivity. Synageva has also been granted fast track designation ( “ Fast Track Designation” ) by the FDA. Fast track programs are designed to facilitate the development and expedite the review of new drugs that are intended to treat serious or life-threatening conditions and that demonstrate the potential to address unmet medical needs. In February 2011, Synageva initiated Phase I/II clinical trials for SBC-102 and in May 2011 began enrolling patients into its Phase I/II study to evaluate the safety and tolerability of SBC-102 in adult patients with liver dysfunction due to late onset LAL Deficiency and in children with growth failure due to early onset LAL Deficiency. Synageva has not yet received approval to market this product, and is not currently commercializing any other products.

Synageva is headquartered in Lexington, Massachusetts and was incorporated in Delaware in 1996. Synageva’s principal offices are located at 128 Spring Street, Suite 520, Lexington, Massachusetts 02421 and its telephone number is (781) 357-9900. Synageva’s principal website is www.synageva.com . Additional information about Synageva is included elsewhere in this joint proxy statement/prospectus. See the sections entitled “Synageva’s Business”, “Synageva’s Management’s Discussion and Analysis of Financial Condition and Results of Operations”, and Synageva’s financial statements beginning on pages 184, 202, and F-37, respectively.

Tesla Merger Sub, Inc.

Merger Sub is a wholly owned subsidiary of Trimeris and was incorporated in Delaware in June 2011, solely for the purpose of facilitating the Merger. Merger Sub has not carried on any activities to date, except for activities incidental to its formation and activities undertaken in connection with the transactions contemplated by the Merger Agreement.

The Merger

Trimeris and Synageva have entered into the Merger Agreement, which provides that, subject to the terms and conditions of the Merger Agreement and in accordance with the DGCL at the Effective Time, Merger Sub will merge with and into Synageva, with Synageva continuing as the surviving entity and as a wholly owned subsidiary of Trimeris. Each of the board of directors of Trimeris and Synageva has unanimously approved the Merger.

What Synageva Stockholders Will Receive in the Merger

Upon completion of the Merger, Synageva stockholders will have the right to receive, for each share of Synageva capital stock they hold, a number of shares of Trimeris common stock equal to the Exchange Ratio and, upon completion of the Merger, Synageva stockholders are expected to receive shares of Trimeris common stock representing an aggregate of approximately 75% of the outstanding shares of common stock of the combined company calculated on a fully diluted basis (without taking into account any shares of Trimeris common stock held by Synageva stockholders prior to the completion of the Merger). The Exchange Ratio will be determined immediately prior to the completion of the Merger by dividing (i) the product of (a) three times (b) the total number of outstanding shares of Trimeris common stock calculated on a fully diluted basis (in other words, inclusive of all shares of Trimeris common stock issuable upon conversion of any securities convertible into or exercisable or exchangeable for shares of Trimeris common stock) as of immediately prior to the completion of the Merger (but after giving effect to the reverse stock split described elsewhere in this joint proxy statement/prospectus), by (ii) the total number of outstanding shares of Synageva common stock calculated on a fully diluted basis (in other words, inclusive of all shares of Synageva capital stock issuable upon conversion of any securities convertible into or exercisable or exchangeable for shares of Synageva common stock) as of immediately prior to the completion of the Merger.

Since the Exchange Ratio is based on the number of shares of Trimeris common stock and Synageva capital stock outstanding, in each case calculated on a fully diluted basis immediately prior to the completion of the Merger, the exact Exchange Ratio will not be determined until that time. Accordingly, any changes in the number of shares of outstanding capital stock of either Trimeris or Synageva calculated on a fully diluted basis, as a

result of option grants, option expirations, or otherwise prior to the Effective Time, would result in a corresponding change to the Exchange Ratio. Additionally, no adjustments to the Exchange Ratio will be made based upon changes in the price of Trimeris common stock or the value of Synageva capital stock prior to the completion of the Merger. As a result, the aggregate market value of the shares of Trimeris common stock that Synageva stockholders will have the right to receive in connection with the Merger will not be known before the Merger is completed and will fluctuate as the price of Trimeris common stock fluctuates.

No fractional shares of Trimeris common stock will be issued to Synageva stockholders in connection with the Merger. Instead, Synageva stockholders will be entitled to receive cash in lieu of any fractional shares of Trimeris common stock that such stockholders would otherwise be entitled to receive in connection with the Merger.

For a more complete discussion of what Synageva stockholders will receive in connection with the Merger and the formula that will be used to calculate the Exchange Ratio, see the sections entitled “The Merger—What Synageva Stockholders Will Receive in the Merger” and “The Merger Agreement—Merger Consideration” beginning on pages 60 and 112, respectively.

Ownership of the Combined Company After the Completion of the Merger

Upon completion of the Merger and regardless of the exact Exchange Ratio (or any reverse stock split), Synageva stockholders are expected to receive shares of Trimeris common stock representing an aggregate of approximately 75% of the outstanding shares of common stock of the combined company calculated on a fully diluted basis. Trimeris stockholders will continue to own their existing shares of Trimeris common stock, which will not be affected by the Merger, and, unless they hold shares of Synageva capital stock, will not receive any additional shares of Trimeris common stock in connection with the Merger. As a result, such shares will represent an aggregate of approximately 25% of the outstanding shares of common stock of the combined company calculated on a fully diluted basis.

Treatment of Synageva Stock Options and Warrants

Upon completion of the Merger, all outstanding and unexercised options and warrants to purchase Synageva capital stock will be assumed by Trimeris and converted into options or warrants, as applicable, to purchase Trimeris common stock, in each case with the number of shares subject to and the exercise price applicable to such options and warrants being appropriately adjusted based on the Exchange Ratio. Such assumed and converted stock options and warrants will be subject to the same vesting and other terms and conditions applicable to the original Synageva stock options and warrants. As of September 21, 2011, the latest practicable date before the printing of this joint proxy statement/prospectus, there were outstanding options to purchase 3,435,273 shares of Synageva capital stock and outstanding warrants to purchase 75,094 shares of Synageva capital stock.

For a more complete discussion of the treatment of Synageva stock options and warrants, see the section entitled “The Merger—Treatment of Synageva Stock Options and Warrants” beginning on page 61.

Treatment of Trimeris Stock Options

Pursuant to the terms of Trimeris’ equity incentive plans, all outstanding options to acquire shares of Trimeris common stock will immediately vest and become exercisable in full upon completion of the Merger.

Board of Directors and Executive Officers of the Combined Company After the Completion of the Merger

Upon completion of the Merger, the combined company will have a nine member board of directors, comprised of Dr. Felix Baker, who is currently a member of both the Trimeris and Synageva boards of directors, Mr. Stephen Davis and Dr. Barry Quart, both of whom are currently members of the Trimeris board of directors, and Mr. Sanj Patel, Dr. Srini Akkaraju, Dr. Stephen Biggar, Dr. Mark Goldberg, Mr. Thomas Malley, and Ms. Robyn Samuels, each of whom are currently members of the Synageva board of directors.

The executive management team of the combined company is expected to be composed of current Synageva executives, including the following individuals:

Recommendations of the Trimeris Board of Directors and its Reasons for the Merger

The Trimeris board of directors, after considering the recommendation of the Trimeris Special Committee and the factors described in the section entitled “The Merger—Recommendations of the Trimeris Board of Directors and its Reasons for the Merger” beginning on page 76, has approved the Merger Agreement and the transactions contemplated thereby, including the Merger. The Trimeris board of directors has determined that the Merger Agreement and the transactions contemplated thereby, including the Merger, are advisable and fair to, and in the best interests of, Trimeris and its stockholders, and therefore recommends that the Trimeris stockholders vote “FOR” the Share Issuance Proposal, “FOR” the Reverse Stock Split Proposal, “FOR” the Authorized Shares Increase Proposal and “FOR” the Name Change Proposal, as contemplated by the Merger Agreement. The Trimeris Special Committee made its recommendation to the Trimeris board of directors after considering the factors described in this joint proxy statement/prospectus, consulting with its legal and financial advisors. For a more complete discussion of the recommendations of the Trimeris board of directors and its reasons for the Merger, see the section entitled “The Merger—Recommendations of the Trimeris Board of Directors and its Reasons for the Merger” beginning on page 76.

Recommendation of the Synageva Board of Directors and its Reasons for the Merger

The Synageva board of directors, after considering the recommendation of the Synageva Transaction Committee and the factors described in the section entitled “The Merger—Recommendation of the Synageva Board of Directors and its Reasons for the Merger” beginning on page 80, has approved the Merger Agreement and the transactions contemplated thereby, including the Merger. The Synageva board of directors has determined that the Merger Agreement and the transactions contemplated thereby, including the Merger, are advisable and fair to, and in the best interests of, Synageva and its stockholders, and therefore recommends that the Synageva stockholders vote “FOR” the Synageva Merger Proposal. In reaching these decisions, the Synageva board of directors considered the factors described in this joint proxy statement/prospectus. For a more complete discussion of the recommendations of the Synageva board of directors and its reasons for the Merger, see the section entitled “The Merger—Recommendation of the Synageva Board of Directors and its Reasons for the Merger” beginning on page 80.

Opinion of the Financial Advisor to the Special Committee of the Trimeris Board of Directors

The Trimeris Special Committee retained MTS Health Partners, L.P. ( “MTS Health Partners” ) to act as its financial advisor in connection with considering strategic alternatives for Trimeris. On June 11, 2011, MTS Securities, LLC, an affiliate of MTS Health Partners ( “MTS Securities” ), rendered its oral opinion to the Trimeris Special Committee, which opinion was subsequently confirmed in writing on June 12, 2011, that, as of the date of the written opinion and subject to the various assumptions made, procedures followed, matters considered, and qualifications and limitations set forth therein, the Exchange Ratio was fair, from a financial point of view, to the Trimeris stockholders (other than any affiliate of Trimeris, any holder of Synageva capital stock, or any of their respective affiliates). The full text of the written opinion of MTS Securities (the “MTS Opinion” ), which sets forth the assumptions made, procedures followed, matters considered, and qualifications and limitations on the review undertaken by MTS Securities in connection with such opinion, is attached as Annex D to this joint proxy statement/prospectus. Trimeris urges you to carefully read the MTS Opinion, together with the description thereof

elsewhere in this joint proxy statement/prospectus, in its entirety. MTS Securities provided the MTS Opinion for the information and assistance of the Trimeris Special Committee in connection with its consideration of the Merger. The MTS Opinion addressed solely the fairness, from a financial point of view, to the Trimeris stockholders (other than any affiliate of Trimeris, any holder of Synageva capital stock, or any of their respective affiliates) of the Exchange Ratio. The MTS Opinion is not a recommendation to any Trimeris stockholder or Synageva stockholder or any other person as to how such stockholder or other person should vote with respect to the Merger or take any other action in connection with the Merger or otherwise. For a more complete discussion of the MTS Opinion, see the section entitled “The Merger—Opinion of the Financial Advisor to the Special Committee of the Trimeris Board of Directors” beginning on page 87.

Interests of Directors and Executive Officers in the Merger

You should be aware that certain directors and executive officers of Trimeris and Synageva have interests in the Merger that are different from, or in addition to, the interests of the stockholders of Trimeris and Synageva generally.

Trimeris Directors and Executive Officers

Interests of the Trimeris directors and executive officers relate to (i) the continuing service of each of Dr. Felix Baker, Mr. Davis and Dr. Quart as directors of the combined company following the completion of the Merger, (ii) the fact that Dr. Felix Baker currently serves as a director of both Trimeris and Synageva, (iii) the ownership by Dr. Felix Baker and Mr. Julian Baker, together with their affiliated entities, of equity interests in both Trimeris and Synageva, which is expected to result in Dr. Felix Baker and Mr. Julian Baker, together with their affiliated entities, having beneficial ownership of approximately 36.3% of the outstanding shares of common stock of the combined company, (iv) severance benefits of approximately $852,534 and $473,918, respectively, to which Dr. Martin Mattingly, Trimeris’ Chief Executive Officer, and Mr. James Thomas, Trimeris’ Chief Financial Officer, will become entitled following the completion of the Merger, (v) the accelerated vesting of all Trimeris stock options held by the Trimeris executive officers and directors, exercisable for approximately 298,899 shares of Trimeris common stock with an aggregate acceleration value of approximately $51,050, upon completion of the Merger, (vi) the right to continued indemnification and insurance coverage for directors and executive officers of Trimeris following the completion of the Merger pursuant to the terms of the Merger Agreement, and (vii) the payment of a flat fee of $35,000 to each of Mr. Stephen Davis and Dr. Barry Quart, the members of the Trimeris Special Committee, and a monthly payment of $7,500 to each such member commencing on March 10, 2011, the date on which the Trimeris Special Committee was formed, and continuing through the completion of the Merger.

The Trimeris Special Committee and the Trimeris board of directors were aware of and considered these interests, among other matters, in evaluating and negotiating the Merger Agreement and in recommending that Trimeris stockholders approve the Trimeris Merger Proposals.

For a more complete discussion of the interests of the directors and executive officers of Trimeris in the Merger, see the section entitled “The Merger—Interests of Trimeris Directors and Executive Officers in the Merger” beginning on page 98.

Synageva Directors and Executive Officers

Interests of the Synageva directors and executive officers relate to (i) the fact that Dr. Felix Baker serves as a director of both Trimeris and Synageva, (ii) the appointment of Mr. Patel, Dr. Akkaraju, Dr. Biggar, Dr. Goldberg, Mr. Malley, and Ms. Robyn Samuels (each of whom is a current member of the Synageva board of directors) as directors of the combined company in connection with the completion of the Merger, (iii) the appointment of Mr. Patel, Mr. Boess, Dr. Quinn, and Mr. Grinstead (each of whom is a current officer of Synageva) as executive officers of the combined company in connection with the completion of the Merger, with

the aggregate amount of the salaries to be paid to such executive officers expected to equal approximately $1,313,490, (iv) the ownership by Dr. Felix Baker and his affiliated entities of equity interests in both Trimeris and Synageva, (v) the right to continued indemnification and insurance coverage for directors and executive officers of Synageva following the completion of the Merger pursuant to the terms of the Merger Agreement, and (vi) transaction bonus payments payable to Mr. Patel, Dr. Quinn, and Mr. Grinstead, in the aggregate amount of $144,070.

The following table sets forth information as of September 21, 2011, regarding the beneficial ownership of the combined company for each executive officer and director of Synageva following the completion of the Merger. Percentage of beneficial ownership is calculated in relation to 87,901,307 shares of common stock of the combined company outstanding upon completion of the Merger, assuming that the Exchange Ratio to be used in connection with the Merger is approximately 2.078 shares of Trimeris common stock for each share of Synageva capital stock (without giving effect to the proposed reverse stock split described elsewhere in this joint proxy statement/prospectus). Beneficial ownership is determined in accordance with the rules of the SEC, which generally attribute beneficial ownership of securities to persons who possess sole or shared voting or investment power with respect to those securities, and includes shares of Synageva capital stock, and if applicable, shares of Trimeris common stock, issuable pursuant to the exercise of stock options or other securities that are exercisable or convertible into shares of Synageva capital stock or Trimeris common stock, as applicable, within 60 days of September 21, 2011. The table also sets forth the total number of additional options that each executive officer and director of Synageva will have the right to acquire following the Merger, but which are not exerciseable within 60 days of September 21, 2011.

For a more complete discussion of the interests of the directors and executive officers of Synageva in the Merger, see the section entitled “The Merger—Interests of Synageva Directors and Executive Officers in the Merger” beginning on page 101.

Anticipated Accounting Treatment of the Merger

The Merger will be treated by Trimeris as a reverse merger under the acquisition method of accounting in accordance with U.S. generally accepted accounting principles ( “ GAAP ” ). For accounting purposes, Synageva is considered to be acquiring Trimeris in this transaction. For a more complete discussion of the anticipated accounting treatment of the Merger, see the section entitled “The Merger—Anticipated Accounting Treatment” beginning on page 103.

Material U.S. Federal Income Tax Consequences of the Merger

The Merger is intended to qualify as a “reorganization” within the meaning of Section 368(a) of the Code, and it is a condition to the completion of the Merger that Trimeris and Synageva each receive written opinions from their respective outside legal counsel regarding such qualification. Assuming the Merger qualifies as a “reorganization,” Synageva stockholders generally will not recognize gain or loss for U.S. federal income tax purposes upon the exchange of their shares of Synageva capital stock for shares of Trimeris common stock in connection with the Merger. However, if a Synageva stockholder receives cash in lieu of a fractional share of Trimeris common stock, then such stockholder generally will recognize gain or loss equal to the difference between such stockholder’s adjusted tax basis in the fractional share and the amount of cash received. Moreover, a Synageva stockholder who perfects appraisal rights and receives cash in exchange for such stockholder’s Synageva capital stock will recognize gain or loss measured by the difference between the amount of cash received and such stockholder’s adjusted tax basis in those shares. Trimeris stockholders generally will not recognize gain or loss for U.S. federal income tax purposes as a result of the Merger.

Tax matters are very complicated, and the tax consequences of the Merger to a particular Trimeris or Synageva stockholder will depend in part on such stockholder’s circumstances. Accordingly, Trimeris and Synageva urge you to consult your own tax advisor for a full understanding of the tax consequences of the Merger to you, including the applicability and effect of federal, state, local and foreign income and other tax laws. For a more complete discussion of the material U.S. federal income tax consequences of the Merger, see the section entitled “Material U.S. Federal Income Tax Consequences of the Merger” beginning on page 108.

Restrictions on Sales of Shares of Trimeris Common Stock Received By Synageva Stockholders in the Merger

Pursuant to the Merger Agreement, the shares of Trimeris common stock received by Synageva stockholders in the Merger may not be sold, transferred, or encumbered for a staggered 180-day period following the completion of the Merger, except in limited circumstances. The restrictions on the sale, transfer, or encumbrance with respect to such shares of Trimeris common stock lapse as to 25% of such shares on the 90th day following the completion of the Merger and as to an additional 25% of such shares each 30 days thereafter, until the 180th day following the completion of the Merger, at which time the restrictions lapse as to all such shares.

In addition to the restrictions on sale, transfer or encumbrance discussed in the preceding paragraph, shares of Trimeris common stock received by Synageva stockholders who become affiliates of Trimeris for purposes of Rule 144 under the Securities Act may be resold by them only in transactions permitted by Rule 144, or as otherwise permitted under the Securities Act.

For a more complete discussion of the restrictions on sales of shares of Trimeris common stock received by Synageva stockholders in the Merger, see the sections entitled “The Merger—Restrictions on Sales of Shares of Trimeris Common Stock Received by Synageva Stockholders in the Merger” and “The Merger Agreement—Transfer Restrictions” beginning on pages 104 and 114, respectively.

Appraisal Rights

Under the DGCL, Synageva stockholders are entitled to appraisal rights in connection with the Merger. Holders of Trimeris common stock are not entitled to appraisal rights in connection with the Merger. For additional information about appraisal rights, see the provisions of Section 262 of the DGCL, attached to this joint proxy statement/prospectus as Annex E, and the section entitled “The Merger—Appraisal Rights” beginning on page 104.

Regulatory Approvals

As of the date of this joint proxy statement/prospectus, neither Trimeris nor Synageva is required to make filings or to obtain approvals or clearances from any antitrust regulatory authorities in the U.S. or other countries to complete the Merger. In the U.S., Trimeris must comply with applicable federal and state securities laws and the rules and regulations of the NASDAQ Global Market in connection with the issuance of shares of Trimeris common stock and the resulting change in control of Trimeris and the filing of this joint proxy statement/prospectus with the SEC.

Conditions to the Completion of the Merger

Trimeris and Synageva expect to complete the Merger as soon as possible following the approval of the Trimeris Merger Proposals and Synageva Merger Proposal, at their respective special meetings. Completion of the Merger will only be possible, however, after all closing conditions contained in the Merger Agreement are satisfied or waived, including after Trimeris and Synageva receive stockholder approvals at their respective special meetings. It is possible, therefore, that factors outside of each company’s control could require them to complete the Merger at a later time or not complete it at all.

The obligations of Trimeris and Synageva to complete the Merger are each subject to the satisfaction of the following conditions, among others and subject, in some cases, to the exceptions or limitations contained in confidential disclosure schedules delivered to each party by the other:

In addition, the obligations of Trimeris and Synageva to complete the Merger are each subject to the satisfaction of the following conditions (which, in order to complete the Merger, may not be waived), subject to the exceptions or limitations contained in confidential disclosure schedules delivered to each party by the other:

For a more complete discussion of the conditions to the completion of the Merger, see the section entitled “The Merger Agreement—Conditions to the Completion of the Merger” beginning on page 124.

No Solicitation

In the Merger Agreement, each of Trimeris and Synageva has agreed that it will not directly or indirectly:

The Merger Agreement does not, however, prohibit either Trimeris or Synageva from considering an unsolicited written alternative acquisition proposal from a third party prior to obtaining the requisite stockholder approval of the Trimeris Merger Proposals or Synageva Merger Proposal, as applicable, if specified conditions are met. For a more complete discussion of the prohibition on solicitation of acquisition proposals from third parties, see the section entitled “The Merger Agreement—No Solicitation” beginning on page 121.

Termination of the Merger Agreement

Generally and except as specified below, the Merger Agreement may be terminated and the Merger may be abandoned at any time prior to the completion of the Merger, including after the required Trimeris stockholder approval and/or Synageva stockholder approval is obtained:

For a more complete discussion of termination of the Merger Agreement, see the section entitled “The Merger Agreement—Termination of the Merger Agreement” beginning on page 125.

Termination Fees and Expenses

All fees and expenses incurred in connection with the Merger Agreement will be paid by the party incurring such expenses.

If the Merger Agreement is terminated by either party because the other party’s stockholders, as applicable, have voted not to approve their respective merger proposals, the party whose stockholders failed to approve the applicable merger proposals shall be required to reimburse the other party’s reasonable expenses in relation to the Merger Agreement, up to $1.5 million. Additionally, a termination fee of $3 million may be payable by Trimeris to Synageva upon the termination of the Merger Agreement by Synageva under certain circumstances.

For a more complete discussion of termination fees and expenses, see the section entitled “The Merger Agreement—Termination Fees and Expenses” beginning on page 126.

Voting Agreements

In connection with the execution of the Merger Agreement, the directors, executive officers, and certain stockholders of each of Trimeris and Synageva entered into stockholder voting agreements, whereby each such director, executive officer, and stockholder has agreed to vote all of their respective shares of Trimeris common stock or Synageva capital stock, as applicable, in favor of the Trimeris Merger Proposals, in the case of Trimeris’ directors, executive officers, and certain stockholders, and in favor of the Synageva Merger Proposal, in the case of Synageva’s directors, executive officers, and certain stockholders. As of September 21, 2011, the latest practicable date before the printing of this joint proxy statement/prospectus, the shares of Trimeris common stock and Synageva capital stock beneficially owned by the applicable directors, executive officers, and stockholders and thus subject to the voting agreements constituted approximately 19.3% of the total outstanding voting power of Trimeris and approximately 88.3% of the total outstanding voting power of Synageva on that date, respectively.

For a more complete discussion of the voting agreements, see the section entitled “The Voting Agreements” beginning on page 127.

Voting by Trimeris and Synageva Directors and Executive Officers

As of September 21, 2011, the latest practicable date before the printing of this joint proxy statement/prospectus, directors and executive officers of each of (i) Trimeris beneficially owned and were entitled to vote 4,515,146 shares of Trimeris common stock, or approximately 19.3% of the total outstanding voting power of Trimeris and (ii) Synageva beneficially owned and were entitled to vote 22,961,853 shares of Synageva capital stock, representing approximately 71.0% of the total outstanding voting power of Synageva on that date.

Pursuant to the voting agreements described above that were entered into between Trimeris, Synageva and the directors, executive officers, and certain stockholders of Synageva, such directors, executive officers, and stockholders of Synageva will vote their respective shares of Synageva capital stock in favor of the Synageva Merger Proposal. Likewise, Synageva, and the directors, executive officers, and certain stockholders of Trimeris entered into voting agreements and such directors, executive officers, and stockholders of Trimeris will vote their respective shares of Trimeris common stock in favor of the Trimeris Merger Proposals. As a group, the directors, executive officers, and certain stockholders of each of Trimeris and Synageva subject to such voting agreements

collectively hold 15.8% of the total voting power of Trimeris and 87.9% of the total voting power of Synageva, respectively, outstanding as of September 21, 2011, the latest practicable date before the printing of this joint proxy statement/prospectus.

Rights of Synageva Stockholders Will Change as a Result of the Merger

Due to differences between the governing documents of Trimeris and Synageva, Synageva stockholders receiving Trimeris common stock in connection with the Merger will have different rights once they become Trimeris stockholders. The material differences are described in detail under the section entitled “Comparison of Rights of Trimeris Stockholders and Synageva Stockholders” beginning on page 241.

Risk Factors

The Merger, including the possibility that the Merger may not be completed, poses a number of risks to each company and its respective stockholders, including the following:

In addition, each of Trimeris, Synageva, and the combined company are subject to various risks associated with their businesses. The risks are discussed in greater detail in the section entitled “Risk Factors” beginning on page 34. Trimeris and Synageva both encourage you to read and consider all of these risks carefully.

Matters to Be Considered at the Trimeris Special Meeting and Synageva Special Meeting

Trimeris Special Meeting

Date, Time and Place . The Trimeris special meeting will be held on             , 2011 at         , local time, at the offices of Paul Hastings LLP, 4747 Executive Drive, 12th Floor, San Diego, California 92121.

Matters to be Considered at the Trimeris Special Meeting . At the Trimeris special meeting, and any adjournments or postponements thereof, Trimeris stockholders will be asked to:

Record Date . The Trimeris board of directors has fixed the close of business on September 21, 2011 as the record date for determining the Trimeris stockholders entitled to notice of and to vote at the Trimeris special meeting and any adjournment or postponement thereof.

Required Vote . Approval of the Share Issuance Proposal requires the affirmative vote of the holders of a majority of the shares of Trimeris common stock present and entitled to vote on the matter either in person or by proxy at the Trimeris special meeting. Approval of the Reverse Stock Split Proposal, the Authorized Shares Increase Proposal and the Name Change Proposal requires the affirmative vote of the holders of a majority of the shares of Trimeris common stock outstanding and entitled to vote on the matter either in person or by proxy at the Trimeris special meeting. Approval of the adjournment of the Trimeris special meeting, if necessary, to solicit additional proxies if there are not sufficient votes in favor of the Trimeris Merger Proposals requires the affirmative vote of the holders of a majority of the shares of Trimeris common stock present and entitled to vote on the matter either in person or by proxy at the Trimeris special meeting. As of the close of business on the record date for the Trimeris special meeting, there were 22,399,649 shares of Trimeris common stock outstanding.

For additional information about the Trimeris special meeting, see the section entitled “The Special Meeting of Trimeris Stockholders” beginning on page 135.

Synageva Special Meeting

Date, Time and Place . The Synageva special meeting will be held on             ,             , 2011 at         , local time, at the offices of Ropes & Gray LLP, Prudential Tower, 800 Boylston Street, Boston, Massachusetts 02199.

Matters to be Considered at the Synageva Special Meeting . At the Synageva special meeting, and any adjournments or postponements thereof, Synageva stockholders will be asked to:

Record Date . The Synageva board of directors has fixed the close of business on September 23, 2011 as the record date for determining the Synageva stockholders entitled to notice of and to vote at the Synageva special meeting and any adjournment or postponement thereof.

Required Vote . Approval of the Synageva Merger Proposal requires the affirmative vote of the holders of (i) a majority of voting power of the Synageva common stock and Synageva preferred stock, voting together as a single class, and (ii) at least 70% of the voting power of the Synageva preferred stock, voting together as a single class, in each case, outstanding as of the record date. The affirmative vote of the holders of a majority of the voting power of the Synageva common stock and Synageva preferred stock, voting together as a single class, present and entitled to vote either in person or by proxy at the Synageva special meeting is required for approval of the proposal to adjourn the meeting, if necessary, to solicit additional proxies if there are not sufficient votes in favor of the Synageva Merger Proposal. At the close of business on the record date, Synageva had outstanding (i) 524,153 shares of common stock entitled to an aggregate of 524,153 votes at the special meeting,

(ii) 245,637 shares of Series A-2 preferred stock entitled to an aggregate of 245,637 votes at the special meeting,

(iii) 4,168,674 shares of Series B-2 preferred stock entitled to an aggregate of 4,168,674 votes at the special meeting,

(iv) 3,583,040 shares of Series C-2 preferred stock entitled to an aggregate of 3,583,040 votes at the special meeting, and (v) 18,000,000 shares of Series D-2 preferred stock entitled to an aggregate of 22,999,987 votes at the special meeting.

For additional information about the Synageva special meeting, see the section entitled “The Special Meeting of Synageva Stockholders” beginning on page 149.

SELECTED HISTORICAL FINANCIAL DATA OF TRIMERIS

The following table sets forth Trimeris’ selected historical financial data as of the dates and for each of the periods indicated. The financial data for the years ended December 31, 2010, 2009, and 2008 and as of December 31, 2010 and 2009 is derived from Trimeris’ audited financial statements, which are included elsewhere in this joint proxy statement/prospectus. The financial data for the years ended December 31, 2007 and 2006 and as of December 31, 2008, 2007, and 2006 is derived from Trimeris’ audited historical financial statements, which are not included or incorporated by reference into this joint proxy statement/prospectus. The financial data for each six-month period ended and as of June 30, 2011 and 2010 is derived from Trimeris’ unaudited financial statements which are included elsewhere in this joint proxy statement/prospectus. In Trimeris’ opinion, such unaudited financial statements include all adjustments (consisting of normal recurring adjustments) necessary for a fair presentation of its financial position and results of operations for such periods. Interim results for the six months ended and as of June 30, 2011 are not necessarily indicative of, and are not projections for, the results to be expected for the fiscal year ending December 31, 2011.

You should read the selected historical financial data below together with “Trimeris’ Management’s Discussion and Analysis of Financial Condition and Results of Operations” and with the financial statements and notes thereto for the year ended December 31, 2010 and for the six months ended June 30, 2011, each of which are included elsewhere in this joint proxy statement/prospectus.