Avidity Biosciences (RNA) CCO reports merger-related stock disposition

Rhea-AI Filing Summary

Avidity Biosciences Chief Commercial Officer Eric Mosbrooker reported the disposition of stock options and common shares in connection with the company’s merger with Novartis. The filing shows 177,188 and 50,000 stock options and 79,413 shares of common stock were transferred to the issuer.

According to the merger agreement dated October 25, 2025, the common stock, including shares underlying previously reported restricted stock units, was disposed of as part of the transaction. The options were cashed out for a payment equal to the excess of the merger consideration of $72.00 over each option’s exercise price.

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

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X

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^*

Mosbrooker Eric

(Last) (First) (Middle)

C/O AVIDITY BIOSCIENCES, INC.

3020 CALLAN RD.

(Street)

SAN DIEGO CA 92121

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Avidity Biosciences, Inc. [ RNAM ]

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

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chief Commercial Officer

3. Date of Earliest Transaction (Month/Day/Year)
02/27/2026

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
Common Stock	02/27/2026		D		79,413(1)	D	(1)	0	D

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
Stock Option (Right to Buy)	$9.05	02/27/2026		D			177,188	(2)	12/31/2033	Common Stock	177,188	(2)	0	D
Stock Option (Right to Buy)	$31.42	02/27/2026		D			50,000	(2)	01/05/2035	Common Stock	50,000	(2)	0	D

Explanation of Responses:

1. The reported securities represent shares of Common Stock (inclusive of shares of Common Stock issuable upon settlement of previously reported restricted stock units) disposed of pursuant to the terms of the Agreement and Plan of Merger, dated as of October 25, 2025 (the "Merger Agreement"), among Novartis AG ("Novartis"), Ajax Acquisition Sub, Inc., an indirect wholly owned subsidiary of Novartis, and the Issuer.

2. The reported Options were disposed of, pursuant to the Merger Agreement, in exchange for a cash payment equal to the excess of the merger consideration of $72.00 over the exercise price.

	/s/ John B. Moriarty, Jr., J.D., Attorney-in-Fact	02/27/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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FAQ

What did Avidity Biosciences (RNA) officer Eric Mosbrooker report on this Form 4?

Eric Mosbrooker reported disposing of stock options and common shares as part of Avidity Biosciences’ merger with Novartis. The transactions involved 177,188 and 50,000 stock options plus 79,413 common shares transferred back to the issuer under the merger agreement’s terms.

How many Avidity Biosciences (RNA) stock options were disposed of in the Mosbrooker filing?

The filing shows 227,188 Avidity Biosciences stock options disposed of in total, in two blocks of 177,188 and 50,000 options. These options were canceled in exchange for cash based on the merger consideration of $72.00 per share minus each option’s exercise price.

What happened to Eric Mosbrooker’s Avidity Biosciences (RNA) common stock in the merger?

Mosbrooker reported disposing of 79,413 shares of Avidity Biosciences common stock in connection with the Novartis merger. The shares, including those from previously reported restricted stock units, were transferred pursuant to the merger agreement with Novartis and its acquisition subsidiary.

How were Avidity Biosciences (RNA) stock options treated under the Novartis merger for Mosbrooker?

Mosbrooker’s Avidity Biosciences stock options were canceled and converted into cash under the merger terms. Each option received a payment equal to the merger consideration of $72.00 per share minus the option’s exercise price, reflecting only their in-the-money value.

Does the Mosbrooker Form 4 for Avidity Biosciences (RNA) indicate sales on the open market?

The Mosbrooker Form 4 does not show open-market sales. It reports issuer dispositions tied to the Novartis merger, with common shares and options transferred back to the issuer or cashed out according to the merger agreement, rather than traded on public markets.