Mark Jeffrey DeLong - 14 May 2026 Form 4 Insider Report for Apellis Pharmaceuticals, Inc. (APLS)

Reporting relationship: Chief Business & Strat Officer
Issuer ticker: APLS
Reported as of: 14 May 2026
Net transaction value: $0
SEC form: 4
Accepted by SEC: 14 May 2026, 19:23:04 UTC
Prior SEC filing: 13 Feb 2026
Source filing: View source filing
Reporting owner signature: /s/ David Watson, attorney-in-fact for Mark DeLong

Key filing fact

Mark Jeffrey DeLong filed Form 4 for Apellis Pharmaceuticals, Inc. (APLS) on 14 May 2026.

Key facts

This page summarizes Mark Jeffrey DeLong's Form 4 filing for Apellis Pharmaceuticals, Inc. (APLS).
21 reported transactions and 8 derivative rows are listed below.
Accepted by SEC: 14 May 2026, 19:23.

Change

Previous filing in this sequence was filed on 13 Feb 2026.
Current net transaction value: $0.

Research use

This tells you what this filing adds before you inspect full transaction and derivative tables.
You can trace every row back to the original SEC filing document.

Evidence

Filed on Form 4

Ownership activity is grounded in SEC Form 4 disclosures.

View source filing

Reporting Owners (1)

CIK 0001856078 Primary reporting owner

DeLong Mark Jeffrey

Relationship: Chief Business & Strat Officer
Address: C/O APELLIS PHARMACEUTICALS, INC., 100 FIFTH AVENUE, 3RD FLOOR, WALTHAM
Signature: /s/ David Watson, attorney-in-fact for Mark DeLong
Signature date: 14 May 2026

Reported non-derivative transactions

Shares, units, or other non-derivative securities reported in this filing.

APLS transaction

Common Stock

Disposition pursuant to a tender of shares in a change of control transaction

Transaction value
Shares: -114,591
Change %: -100%
Price
Shares after: 0
Date: 14 May 2026
Ownership: Direct
Footnotes: F1, F2, F3

APLS transaction

Common Stock

Award

Transaction value
Shares: +41,250
Change %
Price
Shares after: 41,250
Date: 14 May 2026
Ownership: Direct
Footnotes: F4, F5

APLS transaction

Common Stock

Disposed to Issuer

Transaction value
Shares: -41,250
Change %: -100%
Price
Shares after: 0
Date: 14 May 2026
Ownership: Direct
Footnotes: F4, F5

APLS transaction

Common Stock

Award

Transaction value
Shares: +19,006
Change %
Price
Shares after: 19,006
Date: 14 May 2026
Ownership: Direct
Footnotes: F4, F5

APLS transaction

Common Stock

Disposed to Issuer

Transaction value
Shares: -19,006
Change %: -100%
Price
Shares after: 0
Date: 14 May 2026
Ownership: Direct
Footnotes: F4, F5

APLS transaction

Common Stock

Award

Transaction value
Shares: +36,606
Change %
Price
Shares after: 36,606
Date: 14 May 2026
Ownership: Direct
Footnotes: F6, F7, F8

APLS transaction

Common Stock

Disposed to Issuer

Transaction value
Shares: -36,606
Change %: -100%
Price
Shares after: 0
Date: 14 May 2026
Ownership: Direct
Footnotes: F6, F7, F8

APLS transaction

Common Stock

Award

Transaction value
Shares: +18,303
Change %
Price
Shares after: 18,303
Date: 14 May 2026
Ownership: Direct
Footnotes: F5, F6

APLS transaction

Common Stock

Disposed to Issuer

Transaction value
Shares: -18,303
Change %: -100%
Price
Shares after: 0
Date: 14 May 2026
Ownership: Direct
Footnotes: F5, F6

APLS transaction

Common Stock

Disposed to Issuer

Transaction value
Shares: -36,606
Change %: -100%
Price
Shares after: 0
Date: 14 May 2026
Ownership: Direct
Footnotes: F9, F10

APLS transaction

Common Stock

Disposed to Issuer

Transaction value
Shares: -4,909
Change %: -100%
Price
Shares after: 0
Date: 14 May 2026
Ownership: Direct
Footnotes: F9, F10

APLS transaction

Common Stock

Disposed to Issuer

Transaction value
Shares: -8,482
Change %: -100%
Price
Shares after: 0
Date: 14 May 2026
Ownership: Direct
Footnotes: F9, F10

APLS transaction

Common Stock

Disposed to Issuer

Transaction value
Shares: -21,381
Change %: -100%
Price
Shares after: 0
Date: 14 May 2026
Ownership: Direct
Footnotes: F9, F10

Reported derivative securities

Options, warrants, convertible securities, or similar derivative positions disclosed in the filing.

APLS transaction Derivative

Stock Option (right to buy)

Disposed to Issuer

Transaction value
Shares: -82,500
Change %: -100%
Price
Shares after: 0
Date: 14 May 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 82,500
Exercise price: $19.39
Footnotes: F11

APLS transaction Derivative

Stock Option (right to buy)

Disposed to Issuer

Transaction value
Shares: -14,799
Change %: -100%
Price
Shares after: 0
Date: 14 May 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 14,799
Exercise price: $13.85
Footnotes: F11

APLS transaction Derivative

Stock Option (right to buy)

Disposed to Issuer

Transaction value
Shares: -27,224
Change %: -100%
Price
Shares after: 0
Date: 14 May 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 27,224
Exercise price: $35.46
Footnotes: F11

APLS transaction Derivative

Stock Option (right to buy)

Disposed to Issuer

Transaction value
Shares: -18,750
Change %: -100%
Price
Shares after: 0
Date: 14 May 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 18,750
Exercise price: $44.33
Footnotes: F12

APLS transaction Derivative

Stock Option (right to buy)

Disposed to Issuer

Transaction value
Shares: -30,000
Change %: -100%
Price
Shares after: 0
Date: 14 May 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 30,000
Exercise price: $44.90
Footnotes: F12

APLS transaction Derivative

Stock Option (right to buy)

Disposed to Issuer

Transaction value
Shares: -6,952
Change %: -100%
Price
Shares after: 0
Date: 14 May 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 6,952
Exercise price: $47.12
Footnotes: F13

APLS transaction Derivative

Stock Option (right to buy)

Disposed to Issuer

Transaction value
Shares: -30,845
Change %: -100%
Price
Shares after: 0
Date: 14 May 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 30,845
Exercise price: $52.66
Footnotes: F13

APLS transaction Derivative

Stock Option (right to buy)

Disposed to Issuer

Transaction value
Shares: -24,666
Change %: -100%
Price
Shares after: 0
Date: 14 May 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 24,666
Exercise price: $66.30
Footnotes: F13

^* marks a reported price that did not pass the local price check.

Additional SEC filing notes

Filing notes and footnotes

Section 16 status

Mark Jeffrey DeLong is no longer subject to Section 16 filing requirements. Form 4 or Form 5 obligations may still apply in specific circumstances.

Explanation of responses 13 footnotes

Footnote F1

Pursuant to the terms of that certain Agreement and Plan of Merger (the "Merger Agreement"), by and among Apellis Pharmaceuticals, Inc. (the "Issuer"), Biogen Inc. ("Parent") and Parent's direct wholly-owned subsidiary, Aspen Purchaser Sub, Inc. ("Purchaser"), dated as of March 31, 2026, the shares of common stock, par value $0.0001 per share, of the Issuer (the "Common Stock") that were tendered to Purchaser prior to the expiration time of the tender offer were exchanged 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 "Cash Amount"), plus (ii) one contractual, non-transferable contingent value right per share of Common Stock (each, a "CVR"),

Footnote F2

(continued from footnote 1) which entitles 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 in accordance with the terms and conditions of a contingent value rights agreement (the "CVR Agreement" and the Cash Amount plus one CVR, together, the "Offer Price"). After completion of the tender offer, pursuant to the terms of the Merger Agreement, Purchaser merged with and into the Issuer (the "Merger"), effective as of the filing and acceptance of the certificate of merger relating thereto on May 14, 2026 (the "Effective Time"), with the Issuer continuing as the surviving corporation (the "Surviving Corporation") and a wholly owned subsidiary of Parent. In the Merger, each share of Common Stock issued and outstanding immediately prior to the Effective Time, subject to certain exceptions,

Footnote F3

(continued from footnote 2) was automatically converted into the right to receive the Offer Price from Purchaser, without interest and subject to reduction for any applicable withholding taxes.

Footnote F4

Pursuant to the terms of the Merger Agreement, effective as of immediately prior to the Effective Time, each outstanding RSU that was not a Cash-Out RSU Award (each, a "Converted RSU Award") that was subject to both a time-based and a performance-based vesting schedule (other than RSUs granted in January 2026 and for which performance-based vesting schedule was based on total shareholder return), was automatically cancelled and converted into the contingent right to receive (i) an amount of cash, without interest and less applicable tax withholding, equal to the product of (x) the total number of shares of Common Stock underlying such Converted RSU Award, as determined based on the target level of performance, multiplied by (y) the Cash Amount and (ii) one CVR for each share of Common Stock underlying such Converted RSU Award.

Footnote F5

(continued from footnote 4) Subject to the holder's continued service through the vesting dates applicable to the Converted RSU Award under its terms as in effect immediately prior to the Effective Time, all payments in respect of such Converted RSU Award pursuant to the Merger Agreement will vest and become payable at the same time as the underlying Converted RSU Award would have vested and become settled pursuant to its terms and shall otherwise remain subject to the same terms and conditions (including any "double-trigger" vesting provisions applicable to the Converted RSU Award immediately prior to the Effective Time, as extended as provided by the Merger Agreement) as were applicable to the underlying RSU immediately prior to the Effective Time and the terms of the CVR Agreement, provided that such payments will no longer be subject to performance-based vesting.

Footnote F6

Pursuant to the terms of the Merger Agreement, effective as of immediately prior to the Effective Time, each Converted RSU Award that was granted in January 2026 subject to both a time-based and a performance-based vesting schedule, with the performance-based vesting schedule based on performance with respect to total shareholder return ("TSR") relative to the TSR of the group of companies in the Nasdaq Biotechnology Index ("Relative TSR"), was automatically cancelled and converted into the contingent right to receive (i) an amount of cash, without interest and less applicable tax withholding, equal to the product of (x) the total number of shares of Common Stock underlying such Converted RSU Award, as determined based on the actual performance determined by the compensation committee of the Issuer's board of directors as of May 8, 2026 (which is the latest practicable date prior to the Effective Time),

Footnote F7

(continued from footnote 6) multiplied by (y) the Cash Amount and (ii) one CVR for each share of Common Stock underlying such Converted RSU Award. On May 11, 2026, the compensation committee certified that the Relative TSR as of May 8, 2026 was at the 93.3rd percentile, which resulted in a payout percentage of 200% of target for each such Converted RSU Award, as reported in the table above. Subject to the holder's continued service through the vesting dates applicable to the Converted RSU Award under its terms as in effect immediately prior to the Effective Time, all payments in respect of such Converted RSU Award pursuant to the Merger Agreement will vest and become payable at the same time as the underlying Converted RSU Award would have vested and become settled pursuant to its terms and shall otherwise remain subject to the same terms and conditions (including any "double-trigger" vesting provisions applicable to the Converted RSU Award immediately prior to the Effective Time,

Footnote F8

(continued from footnote 7) as extended as provided by the Merger Agreement) as were applicable to the underlying RSU immediately prior to the Effective Time and the terms of the CVR Agreement, provided that such payments will no longer be subject to performance-based vesting.

Footnote F9

Pursuant to the terms of the Merger Agreement, effective as of immediately prior to the Effective Time, each Converted RSU Award that was subject solely to a time-based vesting schedule (including, for the avoidance of doubt, any Converted RSU Award for which the performance period of any applicable performance metric had already ended) was automatically cancelled and converted into the contingent right to receive (i) an amount of cash, without interest and less applicable tax withholding, equal to the product of (x) the total number of shares of Common Stock underlying such Converted RSU Award multiplied by (y) the Cash Amount and (ii) one CVR for each share of Common Stock underlying such Converted RSU Award.

Footnote F10

(continued from footnote 9) Subject to the holder's continued service through the vesting dates applicable to the Converted RSU Award under its terms as in effect immediately prior to the Effective Time, all payments in respect of such Converted RSU Award pursuant to the Merger Agreement will vest and become payable at the same time as the underlying Converted RSU Award would have vested and become settled pursuant to its terms and shall otherwise remain subject to the same terms and conditions (including any "double-trigger" vesting provisions applicable to the Converted RSU Award immediately prior to the Effective Time, as extended as provided by the Merger Agreement) as were applicable to the underlying RSU immediately prior to the Effective Time and the terms of the CVR Agreement.

Footnote F11

Pursuant to the terms of the Merger Agreement, effective as of immediately prior to the Effective Time, each outstanding and unexercised option to purchase shares of Common Stock that was vested pursuant to its existing terms or that vested as a result of the transactions contemplated by the Merger Agreement (each, a "Cash-Out Option") and had an exercise price per share that was less than $41.00 (the Cash Amount) was automatically cancelled and converted into the right to receive (i) an amount of cash, without interest and less applicable tax withholding, equal to the product of (x) the total number of shares of Common Stock underlying such option, multiplied by (y) the excess of the Cash Amount over the exercise price per share of such option and (ii) one CVR for each share of Common Stock underlying such option.

Footnote F12

Pursuant to the terms of the Merger Agreement, effective as of immediately prior to the Effective Time, each Cash-Out Option that had an exercise price per share that was equal to or greater than the Cash Amount, and less than the sum of (i) $41.00 (the Cash Amount) plus (ii) $4.00 (i.e., the maximum amount payable pursuant to a CVR assuming that the milestones are achieved) (such sum of $45.00, the "Aggregate Amount"), was automatically cancelled and converted into the right to receive one CVR for each share of Common Stock underlying such Cash-Out Option (with any payable milestone payment amounts being reduced by the excess, if any, of the applicable exercise price per share over the Cash Amount).

Footnote F13

Pursuant to the terms of the Merger Agreement, effective as of immediately prior to the Effective Time, each vested or unvested option with an exercise price per share that was equal to or greater than $45.00 (the Aggregate Amount) was cancelled without consideration and will have no further force or effect.