Upstream Bio director granted 17,096 stock options

Upstream Bio, Inc. director Erez Chimovits reported receiving a stock option grant covering 17,096 shares of common stock.

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Form Type

Rhea-AI Filing Summary

Upstream Bio, Inc. director Erez Chimovits reported receiving a stock option grant covering 17,096 shares of common stock. The options have an exercise price of $6.69 per share and expire on June 8, 2036. They vest in full on the earlier of June 9, 2027 or the next Annual Meeting of Stockholders, subject to his continued service. Under an agreement with OrbiMed-affiliated entities, any securities or economic benefits from this award are to be transferred to those OrbiMed funds.

Insider Trade Summary

Grant/Award: 17,096 shares

Grant/Award 1 txn

Insider Chimovits Erez

Role Director

Type	Security	Shares	Price	Value
Grant/Award	Stock Option (Right to Buy)	17,096	$0.00	$0.00

Holdings After Transaction: Stock Option (Right to Buy) — 17,096 contracts (Direct)

Footnotes (2)

F1. The shares underlying this option shall vest in full upon the earlier of (i) June 9, 2027 and (ii) the date of the next Annual Meeting of Stockholders of the Issuer, subject to the Reporting Person's continued service on such vesting date.
F2. Pursuant to an agreement with OrbiMed Advisors LLC, OrbiMed Capital GP VIII LLC, OrbiMed Israel GP II, L.P., and OrbiMed Advisors Israel II Limited, the Reporting Person is obligated to transfer any securities issued under any such stock options or other awards, or the economic benefit thereof, to OrbiMed Advisors LLC, OrbiMed Capital GP VIII LLC, OrbiMed Israel GP II, L.P., and OrbiMed Advisors Israel II Limited, which will in turn ensure that such securities or economic benefits are provided to OrbiMed Private Investments VIII, LP and OrbiMed Israel Partners II, L.P.

Key Figures

Option grant size: 17,096 shares Exercise price: $6.69 per share Expiration date: June 8, 2036 +3 more

6 metrics

Option grant size 17,096 shares Stock Option (Right to Buy) awarded on June 9, 2026

Exercise price $6.69 per share Conversion or exercise price of stock option grant

Expiration date June 8, 2036 Option expiration for the 17,096-share grant

Shares underlying options 17,096 shares Underlying common stock tied to the option grant

Holdings after transaction 17,096 derivative securities Total options held following this reported grant

Vesting date trigger June 9, 2027 or next Annual Meeting Full vesting occurs on earlier of these dates with continued service

Key Terms

Stock Option (Right to Buy), vesting, Annual Meeting of Stockholders, exercise price, +1 more

5 terms

Stock Option (Right to Buy) financial

"security_title: Stock Option (Right to Buy)"

vesting financial

"shares underlying this option shall vest in full upon the earlier of (i) June 9, 2027"

Vesting is the process by which you earn full ownership of something, like company stock or a retirement benefit, over time. It’s like earning the right to keep a gift piece by piece the longer you stay with a company, making sure employees stay committed before they receive all the benefits.

Annual Meeting of Stockholders financial

"earlier of (i) June 9, 2027 and (ii) the date of the next Annual Meeting of Stockholders of the Issuer"

exercise price financial

"conversion_or_exercise_price: 6.6900"

The exercise price is the fixed amount at which you can buy or sell an asset, like a stock, when using an options contract. It matters because it helps determine whether exercising the option will be profitable or not, depending on the current market price. Think of it as the set price you agree on today to buy or sell later.

economic benefit financial

"transfer any securities issued under any such stock options or other awards, or the economic benefit thereof, to OrbiMed"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What insider transaction did Upstream Bio (UPB) report for Erez Chimovits?

Upstream Bio reported a stock option grant to director Erez Chimovits covering 17,096 shares. The options are a compensation-related award, not an open-market purchase, and give him the right to buy common stock at a fixed exercise price.

What are the key terms of Erez Chimovits’ Upstream Bio (UPB) stock options?

The grant covers 17,096 options with an exercise price of $6.69 per share and an expiration date of June 8, 2036. These terms define how long the options last and the price at which shares can be acquired.

When do the new Upstream Bio (UPB) options for Erez Chimovits vest?

The options vest in full on the earlier of June 9, 2027 or the date of Upstream Bio’s next Annual Meeting of Stockholders. Vesting requires Chimovits to continue serving through the applicable vesting date.

How many Upstream Bio (UPB) derivative securities does Erez Chimovits hold after this grant?

After the transaction, the Form 4 shows Chimovits holding 17,096 derivative securities related to this stock option. This figure reflects the total options reported in this filing following the grant.

What is the relationship between Erez Chimovits’ Upstream Bio (UPB) options and OrbiMed entities?

Under an agreement, Chimovits must transfer any securities or economic benefits from these options to specified OrbiMed-affiliated entities. Those entities will ensure the benefits are provided to OrbiMed Private Investments VIII, LP and OrbiMed Israel Partners II, L.P.

Is the Upstream Bio (UPB) Form 4 transaction a market purchase or a grant?

The Form 4 reports a grant or award acquisition of stock options, coded as “A.” This indicates a compensation-related award rather than an open-market purchase or sale of existing Upstream Bio common shares.

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

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Accepted by SEC EDGAR 06/11/2026 - 08:00 PM EDT

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^*

Chimovits Erez

(Last)

(First)

(Middle)

UPSTREAM BIO, INC.

890 WINTER STREET, SUITE 200

(Street)

WALTHAM

MASSACHUSETTS

02451

(City)

(State)

(Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
Upstream Bio, Inc. [ UPB ]

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

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
06/09/2026

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

X	Form 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)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)

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)
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)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
Stock Option (Right to Buy)	$6.69	06/09/2026		A		17,096		⁽¹⁾	06/08/2036	Common Stock	17,096	$0	17,096	D⁽²⁾

Explanation of Responses:

1. The shares underlying this option shall vest in full upon the earlier of (i) June 9, 2027 and (ii) the date of the next Annual Meeting of Stockholders of the Issuer, subject to the Reporting Person's continued service on such vesting date.

2. Pursuant to an agreement with OrbiMed Advisors LLC, OrbiMed Capital GP VIII LLC, OrbiMed Israel GP II, L.P., and OrbiMed Advisors Israel II Limited, the Reporting Person is obligated to transfer any securities issued under any such stock options or other awards, or the economic benefit thereof, to OrbiMed Advisors LLC, OrbiMed Capital GP VIII LLC, OrbiMed Israel GP II, L.P., and OrbiMed Advisors Israel II Limited, which will in turn ensure that such securities or economic benefits are provided to OrbiMed Private Investments VIII, LP and OrbiMed Israel Partners II, L.P.

	/s/ Allison Ambrose, Attorney-in-Fact	06/11/2026
	** 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)

Source: View Original Filing on SEC EDGAR