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Cullinan Therapeutics (CGEM) CSO exercises options and sells 30,000 shares under 10b5-1 plan

(Neutral)
(Neutral)
Form Type
4

Rhea-AI Filing Summary

Cullinan Therapeutics Chief Scientific Officer Jennifer Michaelson exercised 30,000 stock options for Common Stock at an exercise price of $4.30 per share, then sold 30,000 Common Shares at a weighted average price of $20.26 per share pursuant to a Rule 10b5-1 trading plan adopted on August 7, 2025. The options exercised were from a grant that vested 25% on July 4, 2020, with the remainder vesting in 36 monthly installments, and she continues to hold 82,987 stock options of this series directly, expiring on October 28, 2030.

Positive

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Insider Michaelson Jennifer
Role Chief Scientific Officer
Sold 30,000 shs ($608K)
Approx. gross sale proceeds $608K
Approx. exercise cost $129K
Approx. pre-tax spread $479K
Type Security Shares Price Value
Exercise Stock Option (Right to Buy) F3 30,000 $0.00 $0.00
Exercise Common Stock 30,000 $4.30 $129K
Sale Common Stock F1, F2 30,000 $20.26 $608K
Holdings After Transaction: Stock Option (Right to Buy) — 82,987 shares (Direct); Common Stock — 162,844 shares (Direct)
Footnotes (3)
  1. F1. Transaction effected pursuant to a plan established pursuant to Rule 10b5-1 on August 7, 2025.
  2. F2. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $20.00 to $20.69. The Reporting Person undertakes to provide to the Issuer, any shareholder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.
  3. F3. 25% of the shares vested on July 4, 2020, and the remaining shares vested in 36 equal monthly installments thereafter.
Options exercised 30,000 shares Stock Option (Right to Buy) for Common Stock exercised on August 13, 2026
Exercise price $4.30 per share Conversion or exercise price of stock options exercised for Common Stock
Shares sold 30,000 shares Common Stock sale on August 13, 2026
Weighted average sale price $20.26 per share Weighted average price for 30,000 Common Shares sold, with trades from $20.00 to $20.69
Remaining options 82,987 options Stock Option (Right to Buy) position directly held after the reported exercise
Option expiration date October 28, 2030 Expiration date of the stock options exercised and remaining
10b5-1 plan adoption date August 7, 2025 Date the Rule 10b5-1 trading plan governing the sale was established
Initial vesting date July 4, 2020 25% of the option grant vested on this date; remainder in 36 monthly installments
Rule 10b5-1 regulatory
"Transaction effected pursuant to a plan established pursuant to Rule 10b5-1 on August 7, 2025."
Rule 10b5-1 is a regulation that allows company insiders to buy or sell their shares at predetermined times, even if they have access to non-public information. It acts like setting a schedule in advance for transactions, helping prevent accusations of unfair trading. This rule provides a way for insiders to plan trades transparently, giving investors confidence that these transactions are not based on hidden information.
weighted average price financial
"The price reported in Column 4 is a weighted average price."
Weighted average price is the average price of a security where each trade or component is counted according to its size, so bigger trades pull the average more than smaller ones. Think of it like calculating the average cost of a grocery haul where items you bought more of have greater influence on the final per-item cost. Investors use it to understand the true average price paid or received, judge execution quality, and compare trading performance against market movement.
Stock Option (Right to Buy) financial
"security_title: Stock Option (Right to Buy)"
derivative security financial
"transaction_code_description: Exercise or conversion of derivative security"
A derivative security is a financial contract whose value comes from the price or performance of something else, such as a stock, bond, commodity, or market index. For investors it acts like an insurance policy or a wager: it can be used to protect against losses, lock in prices, or amplify gains and losses, so it can change a portfolio’s risk and potential return without owning the underlying asset directly.
Common Stock financial
"underlying_security_title: Common Stock"
Common stock represents ownership shares in a company, giving investors a stake in its success and a say in important decisions through voting rights. It is the most common type of stock traded on markets and can provide income through dividends, as well as potential for value growth. For investors, holding common stock means sharing in the company’s profits and risks.

FAQ

What did Cullinan Therapeutics (CGEM) Chief Scientific Officer Jennifer Michaelson report in this Form 4?

Jennifer Michaelson reported exercising 30,000 stock options at $4.30 per share and selling 30,000 Common Shares at a weighted average price of $20.26 per share. These transactions occurred on August 13, 2026, and were made under a pre-established Rule 10b5-1 plan.

How many Cullinan Therapeutics (CGEM) shares did Michaelson sell and at what price range?

She sold 30,000 Common Shares at a weighted average price of $20.26 per share. A footnote states the shares were sold in multiple transactions at prices ranging from $20.00 to $20.69, with detailed trade breakdowns available on request.

Were Jennifer Michaelson’s CGEM transactions under a Rule 10b5-1 trading plan?

Yes. A footnote states the sale was effected pursuant to a Rule 10b5-1 plan established on August 7, 2025. The filing’s Rule 10b5-1 checkbox is also marked, indicating the reported transactions were conducted under this pre-arranged trading plan.

What options did Michaelson exercise in Cullinan Therapeutics (CGEM) and how were they vested?

She exercised 30,000 stock options with an exercise price of $4.30 per share, expiring October 28, 2030. A footnote explains 25% vested on July 4, 2020, with the remaining shares vesting in 36 equal monthly installments thereafter.

How many Cullinan Therapeutics (CGEM) stock options does Michaelson still hold after these transactions?

Following the option exercise reported, she directly holds 82,987 stock options of this series. These options relate to Common Stock and carry an expiration date of October 28, 2030, indicating a remaining equity-based incentive position with the company.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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SEC Form 4
FORM 4UNITED 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
Estimated average burden
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).
X
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*
Michaelson Jennifer

(Last)(First)(Middle)
C/O CULLINAN THERAPEUTICS, INC.
ONE MAIN STREET, SUITE 1350

(Street)
CAMBRIDGE MASSACHUSETTS 02142

(City)(State)(Zip)

UNITED STATES

(Country)
2. Issuer Name and Ticker or Trading Symbol
Cullinan Therapeutics, Inc. [ CGEM ]
5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
Director10% Owner
XOfficer (give title below)Other (specify below)
Chief Scientific Officer
2a. Foreign Trading Symbol
3. Date of Earliest Transaction (Month/Day/Year)
08/13/2026
6. Individual or Joint/Group Filing (Check Applicable Line)
XForm filed by One Reporting Person
Form filed by More than One Reporting Person
4. If Amendment, Date of Original Filed (Month/Day/Year)

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)
CodeVAmount(A) or (D)Price
Common Stock08/13/2026M30,000A$4.3192,844D
Common Stock08/13/2026S(1)30,000D$20.26(2)162,844D
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)
CodeV(A)(D)Date ExercisableExpiration DateTitleAmount or Number of Shares
Stock Option (Right to Buy)$4.308/13/2026M30,000 (3)10/28/2030Common Stock30,000$082,987D
Explanation of Responses:
1. Transaction effected pursuant to a plan established pursuant to Rule 10b5-1 on August 7, 2025.
2. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $20.00 to $20.69. The Reporting Person undertakes to provide to the Issuer, any shareholder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.
3. 25% of the shares vested on July 4, 2020, and the remaining shares vested in 36 equal monthly installments thereafter.
/s/ Jacquelyn Sumer, Attorney-in-Fact08/14/2026
** Signature of Reporting PersonDate
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.
* Form 4: SEC 1474 (03-26)