RA Capital boosts Adicet Bio (ACET) stake with open-market share purchases

Rhea-AI Filing Summary

RA Capital–affiliated entities reported open-market purchases of Adicet Bio common stock. RA Capital Healthcare Fund LP, managed by RA Capital Management, L.P., bought 74,577 shares at $7.04 on February 18, 74,268 shares at $7.21 on February 19, and 74,751 shares at $7.27 on February 20. All shares are held directly by the Fund, with RA Capital and individuals Peter Kolchinsky and Rajeev Shah disclaiming beneficial ownership beyond their pecuniary interests. After the latest trade, the indirect holdings reported for the Fund total 1,182,624 shares, and no derivative securities are listed.

Insights

Insider trading analyst

RA Capital’s fund added 223,596 Adicet Bio shares via open-market buys.

The filing shows three consecutive open-market purchases of Adicet Bio common stock by RA Capital Healthcare Fund LP, managed by RA Capital Management, L.P. These total 223,596 shares, bought around the mid-$7 range over three trading days.

The positions are reported as indirect holdings, with the Adviser, its general partner, and individuals Peter Kolchinsky and Rajeev Shah disclaiming beneficial ownership except for their pecuniary interests. No options or other derivatives remain in this filing’s summary.

This pattern reflects incremental accumulation rather than a one-off block trade. The weighted-average price footnotes indicate purchases across intraday price ranges, consistent with typical institutional trading execution rather than a pre-arranged plan specifically mentioned here.

Insider Trade Summary

Net Buyer: 223,596 shares ($1,603,934)

Net Buy 3 txns

Insider RA CAPITAL MANAGEMENT, L.P., RA Capital Healthcare Fund LP, Kolchinsky Peter, Shah Rajeev M.

Role 10% Owner | 10% Owner | 10% Owner | 10% Owner

Bought 223,596 shs ($1.60M)

Type	Security	Shares	Price	Value
Purchase	Common Stock	74,751	$7.27	$543K
Purchase	Common Stock	74,268	$7.21	$535K
Purchase	Common Stock	74,577	$7.04	$525K

Holdings After Transaction: Common Stock — 1,182,624 shares (Indirect, See footnotes)

Footnotes (1)

1. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $6.89 to $7.20 inclusive. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the range set forth in this footnote. RA Capital Management, L.P. (the "Adviser") is the investment manager for RA Capital Healthcare Fund, L.P. (the "Fund"). The general partner of the Adviser is RA Capital Management GP, LLC (the "Adviser GP"), of which Dr. Peter Kolchinsky and Mr. Rajeev Shah are the managing members. Each of the Adviser, the Adviser GP, the Fund, Dr. Kolchinsky and Mr. Shah disclaims beneficial ownership of any of the reported securities, except to the extent of its or his respective pecuniary interest therein. Held directly by the Fund. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $6.89 to $7.48 inclusive. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the range set forth in this footnote. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $7.05 to $7.58 inclusive. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the range set forth in this footnote.

Key Figures

Total shares bought: 223,596 shares February 18 purchase: 74,577 shares at $7.04 February 19 purchase: 74,268 shares at $7.21 +3 more

6 metrics

Total shares bought 223,596 shares Net open-market purchases across three days

February 18 purchase 74,577 shares at $7.04 Common Stock open-market buy

February 19 purchase 74,268 shares at $7.21 Common Stock open-market buy

February 20 purchase 74,751 shares at $7.27 Common Stock open-market buy; latest transaction

Holdings after latest trade 1,182,624 shares Indirect common stock holdings following February 20 transaction

Net buy direction net-buy of 223,596 shares transactionSummary netBuySellShares and direction

Key Terms

weighted average price, beneficial ownership, pecuniary interest, investment manager, +1 more

5 terms

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.

beneficial ownership regulatory

"disclaims beneficial ownership of any of the reported securities"

Beneficial ownership means the person or entity that actually enjoys the benefits of owning shares or other assets — such as receiving dividends, voting rights, or price gains — even if the legal title is held in another name. For investors it matters because knowing who truly controls and profits from a company reveals who can influence decisions, exposes potential conflicts of interest or hidden concentration of power, and affects transparency and risk in the stock.

pecuniary interest financial

"except to the extent of its or his respective pecuniary interest therein"

investment manager financial

"RA Capital Management, L.P. (the "Adviser") is the investment manager"

indirect ownership financial

"ownership_type": "indirect""

Form 4 Insider Transactions: What Each Field Means →

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
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).

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^*

RA CAPITAL MANAGEMENT, L.P.

(Last) (First) (Middle)

C/O RA CAPITAL MANAGEMENT, L.P.

200 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON MASSACHUSETTS 02116

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
Adicet Bio, Inc. [ ACET ]

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

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
02/18/2026

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

	Form filed by One Reporting Person
X	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)
			Code	V	Amount	(A) or (D)	Price
Common Stock	02/18/2026		P		74,577	A	$7.04(1)	1,033,605	I	See footnotes(2)(3)
Common Stock	02/19/2026		P		74,268	A	$7.21(4)	1,107,873	I	See footnotes(2)(3)
Common Stock	02/20/2026		P		74,751	A	$7.27(5)	1,182,624	I	See footnotes(2)(3)

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

1. Name and Address of Reporting Person^*

RA CAPITAL MANAGEMENT, L.P.

(Last) (First) (Middle)

C/O RA CAPITAL MANAGEMENT, L.P.

200 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON MASSACHUSETTS 02116

(City) (State) (Zip)

UNITED STATES

(Country)

Relationship of Reporting Person(s) to Issuer

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

1. Name and Address of Reporting Person^*

RA Capital Healthcare Fund LP

(Last) (First) (Middle)

C/O RA CAPITAL MANAGEMENT, L.P.

200 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON MASSACHUSETTS 02116

(City) (State) (Zip)

UNITED STATES

(Country)

Relationship of Reporting Person(s) to Issuer

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

1. Name and Address of Reporting Person^*

Kolchinsky Peter

(Last) (First) (Middle)

C/O RA CAPITAL MANAGEMENT, L.P.

200 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON MASSACHUSETTS 02116

(City) (State) (Zip)

UNITED STATES

(Country)

Relationship of Reporting Person(s) to Issuer

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

1. Name and Address of Reporting Person^*

Shah Rajeev M.

(Last) (First) (Middle)

C/O RA CAPITAL MANAGEMENT, L.P.

200 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON MASSACHUSETTS 02116

(City) (State) (Zip)

UNITED STATES

(Country)

Relationship of Reporting Person(s) to Issuer

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

Explanation of Responses:

1. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $6.89 to $7.20 inclusive. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the range set forth in this footnote.

2. RA Capital Management, L.P. (the "Adviser") is the investment manager for RA Capital Healthcare Fund, L.P. (the "Fund"). The general partner of the Adviser is RA Capital Management GP, LLC (the "Adviser GP"), of which Dr. Peter Kolchinsky and Mr. Rajeev Shah are the managing members. Each of the Adviser, the Adviser GP, the Fund, Dr. Kolchinsky and Mr. Shah disclaims beneficial ownership of any of the reported securities, except to the extent of its or his respective pecuniary interest therein.

3. Held directly by the Fund.

4. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $6.89 to $7.48 inclusive. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the range set forth in this footnote.

5. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $7.05 to $7.58 inclusive. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the range set forth in this footnote.

	/s/ Peter Kolchinsky, Manager of RA Capital Management, L.P.	04/13/2026
	/s/ Peter Kolchinsky, Manager of RA Capital Healthcare Fund GP, LLC, the General Partner of RA Capital Healthcare Fund, L.P.	04/13/2026
	/s/ Peter Kolchinsky, individually	04/13/2026
	/s/ Rajeev Shah, individually	04/13/2026
	** 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.
* Form 4: SEC 1474 (03-26)

FAQ

What insider activity did RA Capital report for Adicet Bio (ACET)?

RA Capital Healthcare Fund LP reported three open-market purchases of Adicet Bio common stock totaling 223,596 shares. These trades occurred over three consecutive days in February, with prices slightly above $7 per share, and are reported as indirect holdings of the reporting persons.

On what dates did RA Capital’s fund buy Adicet Bio (ACET) shares and at what prices?

The fund bought Adicet Bio common stock on February 18, 19, and 20. It acquired 74,577 shares at $7.04, 74,268 shares at $7.21, and 74,751 shares at $7.27, with each reported price being a weighted average over multiple trades.

How many Adicet Bio (ACET) shares does RA Capital’s fund hold after these transactions?

After the most recent reported purchase, the filing shows 1,182,624 Adicet Bio common shares as indirectly held following the transaction. This total reflects the Fund’s position after the February 20 trade, providing a snapshot of its stake at that time from this single filing.

Who actually holds the Adicet Bio (ACET) shares reported in this Form 4?

The shares are held directly by RA Capital Healthcare Fund LP. RA Capital Management, L.P. acts as investment manager, and related entities plus individuals Peter Kolchinsky and Rajeev Shah disclaim beneficial ownership except for their respective pecuniary interests in the Fund.

What does the weighted average price disclosure mean for the Adicet Bio (ACET) trades?

Each reported transaction price is a weighted average across multiple trades within a specified intraday price range. The reporting persons state they will provide detailed trade-level prices and share amounts upon request to the issuer, any security holder, or SEC staff.

Does this Adicet Bio (ACET) Form 4 include any options or derivative securities?

No derivative securities are listed in the derivativeSummary for this Form 4. All reported activity involves non-derivative common stock purchased in open-market transactions, with no option exercises, warrants, or other derivative conversions disclosed in this filing.