[Form 4] Solid Biosciences Inc. Insider Trading Activity

Rhea-AI Filing Summary

Solid Biosciences (SLDB) reported an equity award to its President and CEO, Alexander Cumbo. On 08/14/2025 Mr. Cumbo was granted an employee stock option to buy 337,500 shares at an exercise price of $6.17 expiring 08/14/2035, and 168,750 restricted stock units (RSUs) each representing one share. Following the grants, he beneficially owns 337,500 option shares and 168,750 RSUs, all held directly. The RSUs and the option were granted the same date and vest over four years: 50% of the original number vests on the second anniversary and 25% of the original number vests on each of the third and fourth anniversaries. The Form 4 was signed on 08/18/2025 by an attorney-in-fact for Mr. Cumbo.

Positive

• Long-term alignment: Grants include options and RSUs with multi-year vesting that align the CEO's financial incentives with long-term shareholder value.
• Retention-focused vesting: 50% vests at the second anniversary, encouraging multi-year continuity in leadership.

Negative

• Potential dilution: The award of 337,500 option shares and 168,750 RSUs could be dilutive depending on total outstanding shares (not disclosed here).
• No performance conditions disclosed: Awards appear time-based only, so pay-for-performance alignment cannot be evaluated from this filing.

Insights

Corporate Governance Expert

TL;DR: Executive equity awards align leadership with shareholders but raise governance questions on vesting timing and disclosure.

The grant to a CEO who is also a director concentrates compensation decisions at the top and is a common tool to align incentives with shareholder value through long-term equity exposure. The multi-year vesting schedule delays realization and encourages retention. From a governance perspective, investors may review the compensation committee's rationale, the award size relative to peers, and whether the award was subject to performance conditions; the filing contains no performance conditions — only time-based vesting — so assessment of pay-for-performance alignment requires additional disclosure not present here.

Compensation Analyst

TL;DR: The package (337,500 options; 168,750 RSUs) is sizable and creates future dilution risk depending on exercise and release.

The option exercisable at $6.17 with a 10-year term and the RSUs represent significant potential issuance. The staggered vesting (50% at year two, then 25% annually) is front-loaded toward retention after two years rather than immediate cliff vesting, which can be typical for CEO hires or renewals. Quantifying dilution impact requires share count data not included in this Form 4; therefore materiality relative to outstanding shares cannot be assessed from this filing alone.

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
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hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Cumbo Alexander

(Last) (First) (Middle)

C/O SOLID BIOSCIENCES INC.

500 RUTHERFORD AVENUE, THIRD FLOOR

(Street)

CHARLESTOWN MA 02129

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Solid Biosciences Inc. [ SLDB ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	President and CEO

3. Date of Earliest Transaction (Month/Day/Year)
08/14/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Employee Stock Option (Right to Buy)	$6.17	08/14/2025		A		337,500		(1)	08/14/2035	Common Stock	337,500	$0.00	337,500	D
Restricted Stock Units	(2)	08/14/2025		A		168,750		(1)	(1)	Common Stock	168,750	$0.00	168,750	D

Explanation of Responses:

1. The RSUs (as defined in footnote 2) together with this option were granted on August 14, 2025 (the "Grant Date") and vest over four years, with 50% of the original number of shares vesting on the second anniversary of the Grant Date and 25% of the original number of shares annually thereafter until the fourth such anniversary.

2. Each restricted stock unit represents a contingent right to receive one share of the issuer's common stock (the "RSUs").

	/s/ Kimberly Cornwell as attorney-in-fact for Alexander Cumbo	08/18/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What did Alexander Cumbo receive according to the SLDB Form 4?

The Form 4 reports an employee stock option for 337,500 shares at an exercise price of $6.17 (expiring 08/14/2035) and 168,750 RSUs, granted 08/14/2025.

When do the RSUs and options vest for SLDB's CEO?

The awards vest over four years: 50% of the original number vests on the second anniversary of 08/14/2025, then 25% of the original number vests on each of the third and fourth anniversaries.

How much does Alexander Cumbo beneficially own after the reported transactions?

Following the reported grants he beneficially owns 337,500 option shares and 168,750 RSUs, all reported as direct ownership.

Does the Form 4 show any performance-based conditions for the awards?

No. The Form 4 discloses only time-based vesting; no performance conditions are stated in the filing.

Who signed the Form 4 and when was it filed?

The Form 4 was signed by Kimberly Cornwell as attorney-in-fact for Alexander Cumbo on 08/18/2025.