Biogen (APLS) closes Apellis buyout at $41 per share plus CVRs and delists stock

Rhea-AI Filing Summary

Apellis Pharmaceuticals has completed its acquisition by Biogen through a tender offer and follow‑on merger, giving stockholders $41.00 in cash per share plus one contingent value right (CVR) worth up to an additional $4.00 in cash upon future milestones. The tender offer closed with 105,687,831 shares validly tendered, representing about 82.4% of outstanding shares, satisfying the minimum condition for closing.

After the merger, Apellis became a wholly owned Biogen subsidiary and its common stock will be delisted from Nasdaq, with SEC registration and reporting to be terminated. All Apellis equity awards were converted into cash and CVRs or into contingent rights tied to continued service. Holders of Apellis’ 3.500% Convertible Senior Notes due 2026 can either require cash repurchase at approximately $1,008.46 per $1,000 principal on June 30, 2026, or convert during the make‑whole period to receive $1,080.77 in cash plus 26.3411 CVRs per $1,000 principal. The aggregate cash paid for shares in the offer and merger is about $5.3 billion, excluding fees and any CVR payments.

Positive

• Apellis stockholders receive liquidity at a defined premium value via $41.00 per share in cash plus up to $4.00 per share in contingent value rights, with approximately $5.3 billion in aggregate consideration paid in the offer and merger, excluding fees and any future CVR milestone payments.

Negative

• None.

Insights

M&A and capital structure analyst

Biogen’s cash-and-CVR takeover closes; Apellis equity cashed out, notes re-priced.

The transaction crystallizes value for Apellis stockholders at $41.00 per share in cash plus up to $4.00 per share via non-transferable CVRs tied to commercial milestones. With approximately 82.4% of shares tendered, the merger closed via a short-form process and Apellis is now wholly owned by Biogen.

For former equity holders, this effectively ends standalone upside in favor of fixed cash plus milestone exposure through CVRs. Noteholders gain meaningful optionality: they may elect cash repurchase at about $1,008.46 per $1,000 principal, or convert during the make-whole period for roughly $1,080.77 plus 26.3411 CVRs per $1,000. This structure offers an economic uplift relative to par, balanced against CVR milestone uncertainty.

The company is being delisted and intends to deregister its shares, eliminating future public reporting. Outstanding equity awards have been converted into cash and CVR-linked rights, which aligns employee economics with Biogen’s integration and product performance under the CVR agreement. Overall, this is a thesis-ending event for public Apellis investors and a capital-structure transition for noteholders.

8-K Event Classification

11 items: 1.01, 1.02, 2.01, 3.01, 3.03, 5.01, 5.02, 5.03, 7.01, 8.01, 9.01

11 items

Item 1.01 Entry into a Material Definitive Agreement Business

The company signed a significant contract such as a merger agreement, credit facility, or major partnership.

Item 1.02 Termination of a Material Definitive Agreement Business

A significant contract was terminated, which may affect business operations or revenue.

Item 2.01 Completion of Acquisition or Disposition of Assets Financial

The company completed a significant acquisition or sale of business assets.

Item 3.01 Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing Securities

The company received a delisting notice or transferred its listing to a different exchange.

Item 3.03 Material Modification to Rights of Security Holders Securities

A change was made that materially affects the rights of existing shareholders (e.g., dividend rights, voting rights).

Item 5.01 Changes in Control of Registrant Governance

A change in control of the company occurred, such as through a merger, takeover, or management buyout.

Item 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers Governance

Key personnel changes including departures, elections, or appointments of directors and executive officers.

Item 5.03 Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year Governance

The company amended its charter documents, bylaws, or changed its fiscal year.

Item 7.01 Regulation FD Disclosure Disclosure

Material non-public information disclosed under Regulation Fair Disclosure, often investor presentations or guidance.

Item 8.01 Other Events Other

Voluntary disclosure of events the company deems important to shareholders but not covered by other items.

Item 9.01 Financial Statements and Exhibits Exhibits

Financial statements, pro forma financial information, and exhibit attachments filed with this report.

Key Figures

Offer cash price per share: $41.00 per share Maximum CVR potential per share: up to $4.00 per share Shares tendered: 105,687,831 shares +5 more

8 metrics

Offer cash price per share $41.00 per share Tender offer consideration excluding CVR component

Maximum CVR potential per share up to $4.00 per share Aggregate milestone-based CVR payments

Shares tendered 105,687,831 shares Validly tendered, about 82.4% of outstanding before expiration

Aggregate offer and merger consideration approximately $5.3 billion Cash to be paid for shares, excluding fees and CVRs

Convertible notes outstanding $93,897,000 principal 3.500% Convertible Senior Notes due 2026

Repurchase price on Fundamental Change approximately $1,008.46 per $1,000 Cash plus accrued interest for notes on June 30, 2026

Make-whole conversion value $1,080.77 + 26.3411 CVRs per $1,000 Consideration for notes converted during make‑whole period

Standard conversion reference property $1,039.72 + 25.3405 CVRs per $1,000 Post‑merger reference property for note conversion

Key Terms

contingent value right, Fundamental Change, Make-Whole Fundamental Change, Merger Event, +2 more

6 terms

contingent value right financial

"one contractual, non-transferable contingent value right per Share (each, a “CVR”)"

A contingent value right is a special security that gives its holder the right to receive one or more future payments only if specified events happen, such as a product reaching a sales target or getting regulatory approval. It matters to investors because it offers potential extra payout tied to uncertain outcomes—like a bet that a project will succeed—so it can add upside to a deal while also carrying extra risk and valuation uncertainty.

Fundamental Change financial

"constituted a Merger Event, a Fundamental Change and a Make-Whole Fundamental Change"

A fundamental change is a major shift in how a company or economy operates, like a new technology or a big change in leadership. It matters because such changes can affect the value or stability of investments, making them more or less attractive. Think of it like a major upgrade or shift in the rules of a game that can change the outcome.

Make-Whole Fundamental Change financial

"a Merger Event, a Fundamental Change and a Make-Whole Fundamental Change"

A make-whole fundamental change is a contract clause that requires a company to compensate holders of certain securities (often convertible bonds or preferred shares) if a big event—like a merger, acquisition, or restructuring—removes or reduces the holders’ expected future benefits. Think of it as a shortcut payment that aims to leave investors financially ‘whole’ for lost upside or income, and it matters because it affects how much those investors get paid and how much such an event will cost the company.

Merger Event financial

"constituted a Merger Event, a Fundamental Change and a Make-Whole Fundamental Change"

Contingent Value Rights Agreement financial

"that certain Contingent Value Rights Agreement, dated as of May 14, 2026"

Capped Call Transactions financial

"privately negotiated capped call transactions (the “Capped Call Transactions”) with certain financial institutions"

Capped call transactions are agreements where investors buy options that give them the chance to benefit if a stock's price goes up, but with a limit on how much they can gain. This helps protect them from paying too much if the stock's price rises a lot, similar to having a maximum limit on a reward. They matter because they help investors manage risk while still allowing some upside potential.

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Understanding 8-K Material Events →

false 0001492422 --12-31 0001492422 2026-05-14 2026-05-14

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): May 14, 2026

Apellis Pharmaceuticals, Inc.

(Exact Name of Registrant as Specified in its Charter)

Delaware		001-38276		27-1537290
(State or Other Jurisdiction of Incorporation)		(Commission File Number)		(IRS Employer Identification No.)

100 Fifth Avenue Waltham, MA		02451
(Address of Principal Executive Offices)		(Zip Code)

Registrant’s telephone number, including area code: (617) 977-5700

Not applicable

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class		Trading Symbol(s)		Name of each exchange on which registered
Common Stock, $0.0001 par value per share		APLS		Nasdaq Global Select Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Introductory Note

As previously disclosed, on March 31, 2026, Apellis Pharmaceuticals, Inc., a Delaware corporation (the “Company”), entered into an Agreement and Plan of Merger (the “Merger Agreement”) with Biogen Inc., a Delaware corporation (“Biogen”), and Aspen Purchaser Sub, Inc., a Delaware corporation and a wholly owned subsidiary of Biogen (“Purchaser”).

Pursuant to the Merger Agreement, on April 14, 2026, Purchaser commenced a tender offer (the “Offer”) to acquire any and all of the issued and outstanding shares of common stock, par value $0.0001 per share, of the Company (the “Shares”) in exchange for (i) $41.00 per Share, net to the seller in cash, without interest and subject to reduction for any applicable tax withholding (the “Cash Amount”), plus (ii) one contractual, non-transferable contingent value right per Share (each, a “CVR”), representing the right to receive potential payments of up to an aggregate of $4.00 in cash, without interest and subject to reduction for any applicable tax withholding, upon the achievement of certain specified milestones in accordance with the terms and conditions of that certain Contingent Value Rights Agreement, dated as of May 14, 2026 (the “CVR Agreement”), by and among Biogen, the Company and Equiniti Trust Company LLC (“Equiniti,” and the Cash Amount plus one CVR, collectively, the “Offer Price”).

The Offer and related withdrawal rights expired as scheduled at one minute after 11:59 p.m., Eastern Time, on May 13, 2026 (such date and time, the “Expiration Time”), and was not extended. Equiniti, the depositary for the Offer, advised Purchaser that, immediately prior to the Expiration Time, a total of 105,687,831 Shares were validly tendered (and not validly withdrawn) pursuant to the Offer, representing approximately 82.4% of the Shares outstanding immediately prior to the Expiration Time. The number of Shares validly tendered (and not validly withdrawn) pursuant to the Offer (excluding Shares tendered pursuant to guaranteed delivery procedures that have not yet been “received”, as such term is defined by Section 251(h)(6)(f) of the General Corporation Law of the State of Delaware (the “DGCL”)), together with any Shares beneficially owned by Biogen or any of its subsidiaries, satisfied the Minimum Condition (as defined in the Merger Agreement). All other conditions to the consummation of the Offer having been satisfied or waived, on May 14, 2026, Purchaser irrevocably accepted for payment all Shares that were validly tendered (and not validly withdrawn) pursuant to the Offer, and payment for such Shares will be made promptly in accordance with the terms of the Offer and the Merger Agreement.

Following the completion of the Offer, the remaining conditions to the Merger (as defined below) set forth in the Merger Agreement were satisfied or waived, and on May 14, 2026, pursuant to the terms of the Merger Agreement, Purchaser merged with and into the Company, without a vote of the stockholders of the Company in accordance with Section 251(h) of the DGCL, with the Company continuing as the surviving corporation of the Merger (the “Surviving Corporation”) and as a wholly owned subsidiary of Biogen (the “Merger”, and the date and time at which the Merger became effective, the “Effective Time”). Pursuant to the Merger Agreement, at the Effective Time, each Share (other than Shares that were (i) held in the treasury of the Company, (ii) irrevocably accepted for purchase in the Offer by Purchaser and “received” (as such term is defined by Section 251(h)(6)(f) of the DGCL) by Purchaser, (iii) held by Biogen, Purchaser or any other wholly owned subsidiary of Biogen as of both the commencement of the Offer and immediately prior to the Effective Time and (iv) held by stockholders who were entitled to, and properly demanded, appraisal for such Shares in accordance with Section 262 of the DGCL) was cancelled and converted into the right to receive the Offer Price without interest, subject to reduction for any applicable withholding taxes (the “Merger Consideration”).

Pursuant to the terms of the Merger Agreement, effective as of immediately prior to the Effective Time, any outstanding and unexercised warrant to purchase Shares (each, a “Company Warrant”) was deemed to be exercised in full in a “cashless exercise” pursuant to its terms, and any Shares issued upon such deemed cashless exercise were automatically converted into the right to receive the Merger Consideration, without interest and subject to applicable withholding taxes. As of immediately prior to the Effective Time, no Company Warrants were outstanding.

At the Effective Time, subject to all required withholding taxes and with each CVR payable in accordance with the CVR Agreement, each outstanding equity award of the Company was treated as follows: (i) each option to purchase Shares (each, a “Company Option”) that had vested as of immediately prior to the Expiration Time (including any Company Option that vested as a result of the transactions) with an exercise price less than the Cash Amount was automatically cancelled and converted into the right to receive from the Surviving Corporation a cash payment equal to the product of the total number of Shares underlying such vested Company Option multiplied by the excess of the Cash Amount over the exercise price per Share of such vested

Company Option, plus one CVR per Share underlying such vested Company Option; (ii) each vested Company Option with an exercise price equal to or greater than the Cash Amount but less than the Aggregate Amount (as defined in the Merger Agreement) was cancelled and converted into the right to receive one CVR per Share underlying such vested Company Option (with any Milestone Payment (as defined below) reduced by the excess, if any, of the applicable exercise price per Share over the Cash Amount, as set forth in the CVR Agreement); (iii) each Company Option with an exercise price equal to or greater than the Aggregate Amount was cancelled for no consideration; (iv) each unvested Company Option was cancelled and converted into a contingent right to receive the same consideration as a comparably priced vested Company Option (including the right to receive one CVR per Share underlying such unvested Company Option, subject to the terms of the CVR Agreement), payable in cash subject to the holder’s continued service through the applicable vesting dates and otherwise subject to the same terms and conditions (including any double-trigger vesting provisions, as extended under the terms of the Merger Agreement) as the original award; (v) each award of restricted stock units with respect to Shares (each, a “Company RSU”), including awards subject to both a time-based and performance-based vesting schedule (each, a “Company PSU”), that had vested as of immediately prior to the Expiration Time was automatically cancelled and converted into the right to receive a cash payment equal to the product of the total number of Shares underlying such vested Company RSU or vested Company PSU multiplied by the Cash Amount, plus one CVR per Share underlying such vested Company RSU or vested Company PSU; and (vi) each unvested Company RSU and unvested Company PSU was cancelled and converted into the contingent right to receive the same consideration as a vested award of the same type (including the right to receive one CVR per Share underlying such unvested Company RSU and unvested Company PSU, subject to the terms of the CVR Agreement), subject to the holder’s continued service through the applicable vesting dates (in the case of Company PSUs, through the end of the applicable performance period) and otherwise subject to the same terms and conditions (including any double-trigger vesting provisions, as extended under the terms of the Merger Agreement, but, in the case of Company PSUs, no longer subject to performance-based vesting conditions) as the original award. The number of Shares underlying each Company PSU was determined based on (A) actual performance as determined by the Compensation Committee of the Board of Directors of the Company as of the latest practicable date prior to the Effective Time with respect to total stockholder return-based Company PSUs granted in January 2026 and (B) the target performance levels for all other Company PSUs.

The aggregate amount to be paid by Purchaser in the Offer and the Merger is approximately $5.3 billion, excluding related fees and expenses and, for the avoidance of doubt, any amounts that may become payable pursuant to the CVRs. Biogen and Purchaser will fund the acquisition of the Shares in the Offer and the Merger through a combination of cash and borrowings. Biogen estimates it would need approximately $582 million to pay the maximum aggregate amount that the holders of CVRs (including holders of certain Company Options, Company RSUs, Company PSUs and Company Warrants who received CVRs pursuant to the Merger Agreement) would be entitled to if all of the Milestones are achieved.

The foregoing description of the Merger Agreement and the related transactions does not purport to be complete and is qualified in its entirety by reference to the full text of the Merger Agreement, a copy of which was filed as Exhibit 2.1 to the Current Report on Form 8-K filed by the Company on March 31, 2026 and is incorporated herein by reference.

Item 1.01 Entry into a Material Definitive Agreement.

CVR Agreement

Pursuant to the Merger Agreement and in connection with the irrevocable acceptance for payment by Purchaser of all outstanding Shares validly tendered and not validly withdrawn pursuant to the Offer, on May 14, 2026, Biogen, the Company and Equiniti entered into the CVR Agreement.

Each CVR represents a non-transferable contractual contingent right to receive the following cash payments, without interest and subject to reduction for any applicable tax withholding (the “Milestone Payments”) if the following milestones (each, a “Milestone”) are achieved:

• $2.00 per CVR, upon the achievement of Annual Net Sales (as defined in the CVR Agreement) of at least $1,500,000,000 attributable to SYFOVRE® and related products in the aggregate during the 2027, 2028, 2029 or 2030 calendar years (the “Net Sales Milestone 1”); and

• $2.00 per CVR, upon the achievement of Annual Net Sales (as defined in the CVR Agreement) of at least $2,000,000,000 attributable to SYFOVRE® and related products in the aggregate during the 2027, 2028, 2029, 2030 or 2031 calendar years (the “Net Sales Milestone 2”), provided that if the Net Sales Milestone 1 is not met prior to December 31, 2030 but the Net Sales Milestone 2 is achieved during the 2031 calendar year, then the Net Sales Milestone 2 will be worth $4.00 per CVR.

Each Milestone may only be achieved and paid once; if the Annual Net Sales threshold is met in multiple calendar years, only the first achievement triggers payment.

There can be no assurance that any Milestone will be achieved prior to the expiration or termination of the CVR Agreement, or that payment will be required of Biogen with respect to any Milestone.

The foregoing description of the CVR Agreement does not purport to be complete and is qualified in its entirety by reference to the full text of the CVR Agreement, a copy of which is filed as Exhibit 10.1 hereto and is incorporated herein by reference.

First Supplemental Indenture

The consummation of the Merger constituted a Merger Event, a Fundamental Change and a Make-Whole Fundamental Change, each as defined in the Indenture, dated as of September 16, 2019 (the “Indenture”), between the Company and U.S. Bank Trust Company, National Association, as successor in interest to U.S. Bank National Association, as trustee (the “Trustee”), relating to the Company’s 3.500% Convertible Senior Notes due 2026 (the “Notes”). The effective date of each of the Merger Event, the Fundamental Change and the Make-Whole Fundamental Change was May 14, 2026 (the “Note Effective Date”), the date of the consummation of the Merger.

As a result of the Fundamental Change, each Note holder will have the right to require the Company to repurchase its Notes, pursuant to the terms and procedures set forth in the Indenture, for a cash repurchase price equal to the Fundamental Change Repurchase Price (as defined in the Indenture). In addition, as a result of the Fundamental Change, Make-Whole Fundamental Change and Merger Event, holders of the Notes will have a right to convert their Notes for Reference Property (as defined in the Indenture) commencing on the Note Effective Date, subject to the terms of the Indenture, as supplemented by the First Supplemental Indenture, as described below.

As a result of the Merger Event, pursuant to the Indenture, the Company, Biogen and the Trustee executed the Supplemental Indenture, dated as of May 14, 2026 (the “First Supplemental Indenture”), to, among other things, change each Note holder’s right to convert Notes for Shares on and after the Note Effective Date into a right to convert the Notes for Reference Property (as defined in the Indenture), which consists of $1,039.72 in cash and 25.3405 CVRs per $1,000 principal amount of Notes. After making the necessary conversion rate adjustments for the Make-Whole Fundamental Change, each holder of Notes who elects to convert such Notes during the Make-Whole Fundamental Change Period (as defined in the Indenture) will receive an amount equal to $1,080.77 in cash and 26.3411 CVRs per $1,000 principal amount of Notes.

The foregoing description of the Indenture does not purport to be complete and is qualified in its entirety by reference to the full text of the Indenture, a copy of which was filed as Exhibit 4.1 to the Current Report on Form 8-K filed by the Company on September 16, 2019 and is incorporated herein by reference. The foregoing description of the First Supplemental Indenture is qualified in its entirety by reference to the First Supplemental Indenture, which is filed as Exhibit 4.1 hereto and is incorporated herein by reference.

The information set forth in the Introductory Note of this Current Report on Form 8-K is incorporated herein by reference.

Item 1.02 Termination of a Material Definitive Agreement

In connection with the consummation of the Merger, effective as of immediately prior to the Effective Time, the Company terminated its 2017 Employee Stock Purchase Plan.

In connection with the consummation of the Merger, and concurrently with the Effective Time, the Company terminated all commitments outstanding under, and repaid all outstanding loans and other amounts due under, the Financing Agreement, dated as of June 30, 2025 (and as further amended, restated, amended and restated, supplemented or otherwise modified to date, the “Financing Agreement”), by and among the Company, certain subsidiaries of the Company, as guarantors, the various lenders and other parties from time to time party thereto and Sixth Street Lending Partners, as collateral agent and administrative agent.

The information set forth in the Introductory Note of this Current Report on Form 8-K is incorporated herein by reference.

Item 2.01 Completion of Acquisition or Disposition of Assets.

The information set forth in the Introductory Note and Item 5.01 of this Current Report on Form 8-K is incorporated herein by reference.

Item 3.01 Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing.

On May 13, 2026, the Company (i) notified The Nasdaq Stock Market (“Nasdaq”) of the anticipated consummation of the Merger and (ii) requested that Nasdaq (x) suspend trading of the Shares, effective at 8:00 p.m., Eastern Time, on May 13, 2026, and, following the Effective Time, (y) file with the U.S. Securities and Exchange Commission (the “SEC”) a Form 25, Notification of Removal from Listing and/or Registration, to delist and deregister the Shares under Section 12(b) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). The Company intends to file with the SEC a Certification and Notice of Termination of Registration on Form 15, requesting the termination of registration of the Shares under Section 12(g) of the Exchange Act and the suspension of the Company’s reporting obligations under Sections 13 and 15(d) of the Exchange Act.

The information set forth in the Introductory Note and Item 5.01 of this Current Report on Form 8-K is incorporated herein by reference.

Item 3.03 Material Modification to Rights of Security Holders.

The information set forth in the Introductory Note, Item 3.01, Item 5.01 and Item 5.03 of this Current Report on Form 8-K is incorporated herein by reference.

Item 5.01 Changes in Control of Registrant.

As a result of the consummation of the Offer and the Merger, on May 14, 2026, a change in control of the Company occurred, and the Company is now a wholly owned subsidiary of Biogen.

The information set forth in the Introductory Note, Item 2.01, Item 5.02 and Item 5.03 of this Current Report on Form 8-K is incorporated herein by reference.

Item 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.

Effective as of the Effective Time, Mikael Dolsten, Paul Fonteyne, Stephanie Monaghan O’Brien, A. Sinclair Dunlop, Alec Machiels, Keli Walbert, Gerald Chan, Cedric Francois and Craig Wheeler each resigned from his or her respective position as a member of the Board of Directors of the Company and any committee thereof. These resignations were tendered as a result of the Merger and were not a result of any disagreement between the Company and the directors on any matter relating to the Company’s operations, policies or practices.

In accordance with the terms of the Merger Agreement, effective as of the Effective Time, the director of Purchaser as of immediately prior to the Effective Time, Michael Dambach, became the director of the Company.

Biographical and other information with respect to Michael Dambach is set forth in Schedule I to the Offer to Purchase, a copy of which was filed as Exhibit (a)(1)(A) to the Tender Offer Statement on Schedule TO filed by Biogen on April 14, 2026 and is incorporated herein by reference.

The information set forth in the Introductory Note of this Current Report on Form 8-K is incorporated herein by reference.

Item 5.03 Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year.

Pursuant to the terms of the Merger Agreement, effective as of the Effective Time, the Company’s certificate of incorporation was amended and restated in its entirety. A copy of the Company’s Amended and Restated Certificate of Incorporation is included as Exhibit 3.1 to this Current Report on Form 8-K and is incorporated herein by reference.

Pursuant to the terms of the Merger Agreement, effective as of the Effective Time, the Company’s bylaws were amended and restated in their entirety. A copy of the Company’s Amended and Restated Bylaws is included as Exhibit 3.2 to this Current Report on Form 8-K and is incorporated herein by reference.

Item 7.01 Regulation FD Disclosure.

On the Note Effective Date, the Company issued a notice (the “Notice”) announcing that the consummation of the Merger constituted a Merger Event under the Indenture, and that each of the Merger, the Offer and the delisting of the shares of Shares from Nasdaq constituted a Fundamental Change and Make-Whole Fundamental Change (each as defined in the Indenture). A copy of the Notice is filed as Exhibit 99.1 hereto and is incorporated herein by reference.

The information in this Item 7.01, including Exhibit 99.1, shall not be deemed “filed” for purposes of Section 18 of the Exchange Act, or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such a filing.

Item 8.01 Other Events.

Unwind Agreements

As previously disclosed, in connection with issuing the Notes, the Company entered into privately negotiated capped call transactions (the “Capped Call Transactions”) with certain financial institutions (the “Capped Call Counterparties”). On May 14, 2026, the Company entered into unwind agreements with each Capped Call Counterparty pursuant to which, in the aggregate, all Capped Call Transactions were terminated in exchange for an immaterial payment in favor of the Company.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits.

Exhibit No.		Description
2.1		Agreement and Plan of Merger, dated as of March 31, 2026, by and among Apellis Pharmaceuticals, Inc., Biogen Inc. and Aspen Purchaser Sub, Inc. (incorporated herein by reference to Exhibit 2.1 of the Current Report on Form 8-K filed by Apellis with the SEC on March 31, 2026).†
3.1		Amended and Restated Certificate of Incorporation of Apellis Pharmaceuticals, Inc.
3.2		Amended and Restated Bylaws of Apellis Pharmaceuticals, Inc.
4.1		First Supplemental Indenture, dated as of May 14, 2026, by and among Apellis Pharmaceuticals, Inc., Biogen Inc. and U.S. Bank Trust Company, National Association, as trustee
10.1		Contingent Value Rights Agreement, dated as of May 14, 2026, by and among Biogen Inc., Apellis Pharmaceuticals, Inc. and Equiniti Trust Company, LLC
99.1		Notice of Supplemental Indenture, Fundamental Change and Make-Whole Fundamental Change to Trustee, Paying Agent, Conversion Agent and Holders of the 3.500% Convertible Senior Notes due 2026, dated May 14, 2026
104		Cover Page Interactive Data File (formatted as Inline XBRL).

† Certain exhibits and schedules have been omitted pursuant to Item 601(a)(5) of Regulation S-K. The Company hereby agrees to supplementally furnish to the SEC upon request any omitted schedule, exhibit or similar attachment to Exhibit 2.1.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

				Apellis Pharmaceuticals Inc.
Date: May 14, 2026				By:		/s/ Wendell Taylor
						Name: Wendell Taylor
						Title:  Authorized Signatory

Exhibit 99.1

May 14, 2026

U.S. Bank Trust Company, National Association

Global Corporate Trust

One Federal Street, 10th Floor

Boston, MA 02110

Attention: James Byrnes

The Depository Trust Company

Announcements Department

140 58th Street

Brooklyn, NY 11220

Attention: Announcement Department

Re: Apellis Pharmaceuticals, Inc. – Notice of Supplemental Indenture, Fundamental Change and Make-Whole Fundamental Change to Trustee, Paying Agent, Conversion Agent and Holders of the 3.500% Convertible Senior Notes due 2026 (the “Notes”) (CUSIP: No. 03753U AB2)*

To: Trustee, Paying Agent, Conversion Agent and Holders:

Reference is made to that certain Indenture, dated as of September 16, 2019 (as may be amended or supplemented from time to time, the “Original Indenture”), between Apellis Pharmaceuticals, Inc., a Delaware corporation (the “Company”), and U.S. Bank Trust Company, National Association, as successor in interest to U.S. Bank National Association, as trustee (the “Trustee”) and as the paying agent (the “Paying Agent”) and the conversion agent (the “Conversion Agent”) thereunder, in connection with the Company’s outstanding $93,897,000 aggregate principal amount of its 3.500% Convertible Senior Notes due 2026 (the “Notes”). Capitalized terms used but not otherwise defined herein shall have the meanings given to them in the Original Indenture.

As previously disclosed, on March 31, 2026, the Company entered into that certain Agreement and Plan of Merger, dated as of March 31, 2026 (as it may be amended from time to time, the “Merger Agreement”), by and among Biogen Inc., a Delaware corporation (“Parent”), Aspen Purchaser Sub, Inc., a Delaware corporation and a wholly owned subsidiary of Parent (“Purchaser”), and the Company.

Pursuant to the Merger Agreement, and upon the terms and subject to the conditions therein, Purchaser commenced a tender offer (the “Offer”) to acquire any and all of the issued and outstanding shares of common stock, par value $0.0001 per share, of the Company (the “Common Stock”), in exchange for (i) $41.00 per share of Common Stock, net to the seller in cash, without interest and subject to reduction for any applicable tax withholding (the “Upfront Consideration”), plus (ii) one contractual, non-transferable contingent value right per share of Common Stock (each, a “CVR” and, together with the Upfront Consideration, the “Offer Price”), which entitled the holder to receive potential payments of up to an aggregate of $4.00 in cash, without interest and subject to reduction for any applicable tax withholding, upon the achievement of certain specified milestones. On May 14, 2026 (the “Effective Date”), promptly following the expiration of the Offer (the “Expiration”), in accordance with the General Corporation Law of the State of Delaware (the “DGCL”), Purchaser merged with and into the Company, with the Company continuing as the surviving corporation and a wholly owned subsidiary of Parent (the “Merger”).

At the effective time of the Merger (the “Effective Time”), each share of Common Stock (other than shares of Common Stock (i) held in the treasury of the Company, (ii) irrevocably accepted for purchase in the Offer by Purchaser and “received” (as such term is defined by Section 251(h)(6)(f) of the DGCL) by Purchaser, (iii) held by Parent, Purchaser or any other wholly owned subsidiary of the Parent as of both the commencement of the Offer and immediately prior to the Effective Time and (iv) held by stockholders who were entitled to, and properly demanded, appraisal for such shares of Common Stock in accordance with Section 262 of the DGCL) were cancelled and converted into the right to receive the Offer Price from Purchaser without interest, subject to reduction for any applicable withholding taxes.

On the Effective Date, the Company (i) notified the Nasdaq Stock Market LLC (“Nasdaq”) of the consummation of the Merger and its intent to remove all shares of Common Stock from the Nasdaq Global Select Market (the “Delisting”) and (ii) requested that Nasdaq (A) halt trading of the Common Stock effective before the opening of trading on May 14, 2026, and (B) file with the Securities and Exchange Commission (“SEC”) a Form 25 Notification of Removal from Listing and/or Registration to delist and deregister the Common Stock under Section 12(b) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). Following the effectiveness of such Form 25, the Company intends to file with the SEC a Certification and Notice of Termination of Registration on Form 15 under the Exchange Act, requesting the termination of registration of the Common Stock under Section 12(g) of the Exchange Act and the suspension of the Company’s reporting obligations under Sections 13 and 15(d) of the Exchange Act.

The consummation of the Merger constitutes a “Merger Event” (as defined in Section 14.07(a) of the Original Indenture). In addition, each of the Offer, the Merger and the Delisting constitutes a “Fundamental Change” and a “Make-Whole Fundamental Change” (each as defined in Section 1.01 of the Original Indenture).

Accordingly, this notice (this “Notice”) shall serve as notice (i) under Section 14.10 of the Original Indenture that a Merger Event has occurred, and (ii) under Section 15.02(c) and Section 14.03 of the Original Indenture that a “Fundamental Change” and a “Make-Whole Fundamental Change,” respectively, is deemed to have occurred, in each case, as of the Effective Date.

1. Execution of Supplemental Indenture and Notice of Reference Property

Pursuant to Sections 10.01(g) and 14.07 of the Original Indenture, and as a result of the consummation of the Merger Event on the Effective Date, Parent and the Company and the Trustee executed a first supplemental indenture (the “Supplemental Indenture” and, together with the Original Indenture, the “Indenture”). The Company hereby notifies Holders of the execution of the Supplemental Indenture pursuant to Section 14.07(b) of the Original Indenture.

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The Supplemental Indenture provides:

(i) from and after the Effective Time until the Maturity Date, each $1,000 in principal amount of the Notes is convertible in accordance with the terms of the Indenture into Reference Property, which shall consist of $1,039.72 in cash and 25.3405 CVRs per $1,000 principal amount of Notes so converted; and

(ii) as a result of the Make-Whole Fundamental Change, a Holder who converts its Notes in connection with such Make-Whole Fundamental Change shall be entitled to receive $1,080.77 in cash (reflecting the requisite increase to the Conversion Rate pursuant to Section 14.03 of the Original Indenture) and 26.3411 CVRs per $1,000 principal amount of Notes so converted.

2. Notice of Make-Whole Fundamental Change and Change to Conversion Rate

Pursuant to Section 14.03 of the Original Indenture, the Company hereby notifies the Holders, the Trustee, the Paying Agent and the Conversion Agent that each of the Offer, the Merger and the Delisting constitutes a Make-Whole Fundamental Change as of the Effective Date (the “Merger Make-Whole Fundamental Change”).

Pursuant to Section 14.03 of the Original Indenture, if a Holder elects in connection with the Merger Make-Whole Fundamental Change, and during the applicable Make-Whole Fundamental Change Period, to convert its Notes in the manner prescribed by the Indenture, the Company shall increase the Conversion Rate for the Notes so surrendered by a number of additional shares of Common Stock (the “Additional Shares”).

Pursuant to Section 14.03(e) of the Original Indenture, the Additional Shares in connection with the Merger Make-Whole Fundamental Change equal 1.0006. Based on an Effective Date of May 14, 2026, the Conversion Rate applicable to the Merger Make-Whole Fundamental Change equals 26.3411 shares of Common Stock per $1,000 principal amount of Notes (equal to the sum of the base Conversion Rate of 25.3405 shares and 1.0006 Additional Shares).

Pursuant to Section 2.02 of the Supplemental Indenture and Section 14.03 of the Original Indenture, Holders that elect to properly convert their Notes in connection with the Merger Make-Whole Fundamental Change are entitled to receive cash in an amount equal to $1,080.77 for every $1,000 principal amount of Notes converted. In addition to cash, converting Holders will be entitled to receive 26.3411 CVRs for every $1,000 principal amount of Notes converted.

In order to receive cash of $1,080.77 and 26.3411 CVRs for every $1,000 principal amount of Notes converted, Holders must convert their Notes with a Conversion Date that occurs during the Make-Whole Fundamental Change Period, which commences on the Effective Date and continues until June 29, 2026, the Business Day immediately preceding the Fundamental Change Repurchase Date (as defined below). The Fundamental Change Repurchase Date is June 30, 2026. In order to convert their Notes, Holders must comply with the procedures set forth in Section 14.03 of the Original Indenture.

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Holders whose Notes are held by a broker, dealer, commercial bank, trust company or other nominee must contact such nominee if such Holder desires to exercise its conversion right and instruct such nominee to deliver the appropriate instruction form and the Notes in compliance with the applicable rules and procedures of The Depository Trust Company (“DTC” and, such rules and procedures, the “Applicable Procedures”) prior to the end of the Make-Whole Fundamental Change Period.

Holders may not convert their Notes if they have submitted a Fundamental Change Repurchase Notice, as described below, unless they withdraw such Fundamental Change Repurchase Notice in accordance with Section 15.02 of the Original Indenture, as described below.

3. Notice of Fundamental Change and Fundamental Change Repurchase Date

Pursuant to Section 15.02 of the Original Indenture, as a result of the Fundamental Change, each Holder has the right, subject to and in accordance with Article 15.02 of the Original Indenture, to require the Company to repurchase for cash all of such Holder’s Notes, or any portion thereof that is equal to $1,000 or an integral multiple of $1,000 (the “Fundamental Change Repurchase Right”) on June 30, 2026 (the “Fundamental Change Repurchase Date”). The Company will purchase such Notes at a repurchase price equal to 100% of the principal amount of the Notes to be repurchased, plus accrued and unpaid interest to, but excluding, the Fundamental Change Repurchase Date (the “Fundamental Change Repurchase Price”). The amount payable on the Notes, including accrued and unpaid interest, will be approximately $1,008.46 per $1,000.00 principal amount of Notes validly surrendered for repurchase, and not validly withdrawn.

Pursuant to Section 15.02 of the Original Indenture, Holders may exercise their Fundamental Change Repurchase Right by (i) delivering to the Paying Agent, a duly completed notice (the “Fundamental Change Repurchase Notice”) in compliance with the Applicable Procedures for surrendering interests in Global Notes prior to the close of business on the Business Day immediately preceding the Fundamental Change Repurchase Date (the “Fundamental Change Expiration Date”) and (ii) effecting a book-entry transfer of the Notes in compliance with the Applicable Procedures.

Pursuant to Section 15.02 of the Original Indenture, any Holder may withdraw, in whole or in part, its submission of a Fundamental Change Repurchase Notice by means of a notice of withdrawal that complies with the Applicable Procedures.

As of May 14, 2026, all Notes are held through DTC and there are no certificated Notes in non-global form. Accordingly, all Notes surrendered for repurchase or conversion hereunder must be delivered in compliance with the Applicable Procedures.

The Fundamental Change Repurchase Price for any Notes that are validly surrendered and not validly withdrawn will be paid by the Paying Agent, pursuant to Section 15.04 of the Original Indenture. The Fundamental Change Repurchase Right is subject, in all respects, to the terms and conditions of the Indenture, the Notes and this Notice.

Holders whose Notes are held by a broker, dealer, commercial bank, trust company, or other nominee must contact such nominee if such Holder desires to exercise its Fundamental Change Repurchase Right and instruct such nominee to deliver a Fundamental Change Repurchase Notice and surrender the Notes on such Holder’s behalf in compliance with the Applicable Procedures prior to the close of business on the Fundamental Change Expiration Date.

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Holders who are DTC participants should deliver the Fundamental Change Repurchase Notice and surrender their Notes to the Paying Agent electronically through DTC’s Automated Tender Offer Program (“ATOP”), subject to the terms and procedures of that system prior to the close of business on the Fundamental Change Expiration Date.

You bear the risk of untimely submission of the Fundamental Change Repurchase Notice. You must allow sufficient time for completion of the necessary DTC procedures before the close of business on the Fundamental Change Expiration Date, after which time you will not be able to exercise the Fundamental Change Repurchase Right.

By delivering, or instructing your nominee to deliver, the Fundamental Change Repurchase Notice to the Paying Agent in compliance with the Applicable Procedures, you agree to be bound by the terms of the Fundamental Change Repurchase Right set forth in this Notice.

Alternatively, Holders who wish to convert their Notes in connection with the Merger Make-Whole Fundamental Change as described in Section 2 above cannot do so if they have submitted a Fundamental Change Repurchase Notice with respect to such Notes, unless they withdraw such Fundamental Change Repurchase Notice pursuant to Section 15.03 of the Original Indenture, as described above.

The value that you would currently receive if you validly exercised the Fundamental Change Repurchase Right is substantially less than the value that you would expect to receive if you converted your Notes during the Make-Whole Fundamental Change Period. You should review this Notice carefully and consult with your own financial and tax advisors. You must make your own decision as to whether or not to surrender your Notes for repurchase or to convert your Notes during the Make-Whole Fundamental Change Period and, if you choose to exercise either of these rights, the amount of Notes to surrender or convert. None of the Company or its board of directors, as applicable, or its or their respective employees, advisors, or representatives, Parent or its affiliates, the Trustee, the Paying Agent or Conversion Agent are making any representation or recommendation to any Holder as to whether Holders should elect to require the Company to repurchase their Notes or convert their Notes.

The address of the Trustee, Paying Agent and Conversion Agent:

U.S. Bank Trust Company, National Association

West Side Flats Operations Center

60 Livingston Avenue, Mail Station – EP-MN-WS2N

St. Paul, MN 55107

Attn: Conversion Processing

cts.conversions@usbank.com

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* The CUSIP number listed above is for information purposes only. None of the Company, the Trustee, the Paying Agent or the Conversion Agent shall be responsible for the selection or use of the CUSIP number, nor is any representation made to the correctness or accuracy of the CUSIP number, if any, listed in this or any other notice.

The date of this Notice is May 14, 2026.

Sincerely,

/s/ Timothy Sullivan

Name: Timonthy Sullivan

Title: Chief Financial Officer

Apellis Pharmaceuticals, Inc.

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FAQ

What did Apellis Pharmaceuticals (APLS) shareholders receive in the Biogen acquisition?

Apellis shareholders receive $41.00 in cash per share plus one contingent value right (CVR) per share, which can pay up to an additional $4.00 in cash if specified milestones are achieved, providing fixed cash value with potential milestone-based upside.

How many Apellis (APLS) shares were tendered in Biogen’s offer and what percentage is that?

Immediately before expiration, 105,687,831 Apellis shares were validly tendered and not withdrawn, representing approximately 82.4% of shares outstanding. This level of participation satisfied the minimum condition required to close the tender offer and proceed with the merger.

What happens to Apellis Pharmaceuticals (APLS) common stock after the Biogen merger?

Apellis common stock will be suspended from trading and delisted from Nasdaq. The company plans to file Forms 25 and 15 to deregister the shares and terminate Exchange Act reporting, meaning Apellis will no longer be a publicly traded or reporting company.

How are Apellis 3.500% Convertible Senior Notes due 2026 affected by the merger?

The merger triggers a Merger Event, Fundamental Change and Make-Whole Fundamental Change. Noteholders can require cash repurchase at about $1,008.46 per $1,000 principal or convert during the make‑whole period to receive $1,080.77 in cash plus 26.3411 CVRs per $1,000 principal.

What consideration do Apellis noteholders get if they convert during the Make-Whole Fundamental Change Period?

Noteholders converting during the Make‑Whole Fundamental Change Period receive $1,080.77 in cash plus 26.3411 CVRs for each $1,000 principal of notes. This reflects the adjusted conversion rate after applying the make‑whole increase following the merger and delisting events.

How were Apellis (APLS) stock options and RSUs treated in the Biogen transaction?

Vested options with exercise prices below $41.00 were cashed out for the intrinsic value plus one CVR per underlying share, while vested RSUs and PSUs were paid $41.00 in cash plus one CVR per share. Unvested awards generally converted into contingent cash and CVR rights tied to continued service.

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