Mark Mossler - 13 Feb 2026 Form 4 Insider Report for C4 Therapeutics, Inc. (CCCC)

Reporting relationship: Chief Accounting Officer
Issuer ticker: CCCC
Reported as of: 13 Feb 2026
Net transaction value: -$6,177
SEC form: 4
Accepted by SEC: 18 Feb 2026, 17:04:38 UTC
Prior SEC filing: 18 Feb 2025
Source filing: View source filing
Reporting owner signature: /s/ Shagha Russell, Attorney-in-Fact

Key filing fact

Mark Mossler filed Form 4 for C4 Therapeutics, Inc. (CCCC) on 18 Feb 2026.

Key facts

This page summarizes Mark Mossler's Form 4 filing for C4 Therapeutics, Inc. (CCCC).
3 reported transactions and 0 derivative rows are listed below.
Accepted by SEC: 18 Feb 2026, 17:04.

Change

Previous filing in this sequence was filed on 18 Feb 2025.
Current net transaction value: -$6,177.

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 0001992219 Primary reporting owner

Mossler Mark

Relationship: Chief Accounting Officer
Address: C/O C4 THERAPEUTICS, INC., 490 ARSENAL WAY #120, WATERTOWN
Signature: /s/ Shagha Russell, Attorney-in-Fact
Signature date: 18 Feb 2026

Reported non-derivative transactions

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

CCCC transaction

Common Stock

Award

Transaction value: $0
Shares: +56,980
Change %: +313%
Price: $0.000000
Shares after: 75,184
Date: 13 Feb 2026
Ownership: Direct
Footnotes: F1

CCCC transaction

Common Stock

Options Exercise

Transaction value: $0
Shares: +9,420
Change %: +14%
Price: $0.000000
Shares after: 75,184
Date: 14 Feb 2026
Ownership: Direct
Footnotes: F2

CCCC transaction

Common Stock

Tax liability

Transaction value: $6,177
Shares: -3,268
Change %: -4.3%
Price: $1.89
Shares after: 71,916
Date: 14 Feb 2026
Ownership: Direct
Footnotes: F3

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

Additional SEC filing notes

Filing notes and footnotes

Explanation of responses 3 footnotes

Footnote F1

Represents restricted stock units ("RSUs"). Each RSU represents the contingent right to receive one share of the Issuer's Common Stock upon vesting and settlement. The RSUs shall vest as follows: (i) 28,490 RSUs shall vest in three equal annual installments following the grant date, with the first installment vesting on February 13, 2027, and (ii) 28,490 RSUs shall vest in full on February 13, 2029, subject to potential acceleration upon achievement of certain performance milestones.

Footnote F2

Reflects the acquisition of shares of Common Stock upon vesting of previously disclosed grants of RSUs. The grants of RSUs were initially reported in Table I of the Forms 4 filed by the Reporting Person on April 10, 2024 and February 18, 2025.

Footnote F3

Represents shares withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting and settlement of RSUs and does not represent a sale by the Reporting Person.