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  4. [Form 4] Boundless Bio, Inc. Insider Trading Activity

Tang Capital-affiliated funds boost Boundless Bio (BOLD) stake with 286K-share buy

Filing Impact
(Very High)
Filing Sentiment
(Positive)
Form Type
4

Rhea-AI Filing Summary

Boundless Bio, Inc. insider entities affiliated with Tang Capital reported multiple open-market purchases of Common Stock. Across June 25–29, 2026, they bought a net 286,333 shares at weighted-average prices generally between about $2.40 and $2.60 per share.

Individual trades ranged from 134 shares to 145,880 shares per transaction, with reported per-share prices such as $2.48, $2.47, $2.54, $2.55 and $2.56. The positions are held indirectly "By LP" through Tang Capital limited partnership vehicles.

According to the filing, Tang Capital-related entities beneficially own 580,669, 791,839, 580,668 and 580,669 shares in four affiliated vehicles, for an aggregate beneficial holding of 2,533,845 shares after these purchases. Kevin Tang has a pecuniary interest in these indirectly held shares.

Positive

  • None.

Negative

  • None.
Insider TANG KEVIN, TANG CAPITAL MANAGEMENT LLC
Role null | null
Bought 286,333 shs ($715K)
Type Security Shares Price Value
Purchase Common Stock 63,985 $2.47 $158K
Purchase Common Stock 777 $2.48 $2K
Purchase Common Stock 75,047 $2.55 $191K
Purchase Common Stock 134 $2.54 $340.36
Purchase Common Stock 145,880 $2.48 $362K
Purchase Common Stock 510 $2.56 $1K
Holdings After Transaction: Common Stock — 2,533,068 shares (Indirect, By LP)
Footnotes (1)
  1. The prices reported are weighted-average prices. These shares were purchased in multiple transactions at prices ranging from $2.42 to $2.56. The Reporting Persons undertake to provide the Issuer, any security holder of the Issuer or the SEC staff, upon request, all information regarding the number of shares purchased at each price within the ranges set forth in Footnotes 1 and 3 through 7. Tang Capital Partners, LP ("TCP") beneficially owns 580,669 shares, Tang Capital Partners International, LP ("TCPI") beneficially owns 791,839 shares, Tang Capital Partners III, Inc. ("TCP III") beneficially owns 580,668 shares, and Tang Capital Partners IV, Inc. ("TCP IV") beneficially owns 580,669 shares. Kevin Tang is the sole manager of Tang Capital Management, LLC, which is the general partner of TCP and TCPI. Kevin Tang is the sole director and Chief Executive Officer of TCP III and TCP IV, which are indirectly wholly owned by TCP. Mr. Tang has a pecuniary interest in the shares beneficially held by TCP, TCPI, TCP III and TCP IV. These shares were purchased in multiple transactions at prices ranging from $2.53 to $2.60. These shares were purchased in multiple transactions at prices ranging from $2.46 to $2.60. These shares were purchased in multiple transactions at prices ranging from $2.52 to $2.58. These shares were purchased in multiple transactions at prices ranging from $2.40 to $2.59. These shares were purchased in multiple transactions at prices ranging from $2.44 to $2.52.
Net shares purchased 286,333 shares Open-market buys across June 25–29, 2026
Largest single trade 145,880 shares Open-market purchase at $2.48 per share on June 25, 2026
Example trade price $2.47 per share Open-market purchase of 63,985 shares on June 29, 2026
Another trade price $2.55 per share Open-market purchase of 75,047 shares on June 26, 2026
Beneficial ownership TCP 580,669 shares Tang Capital Partners, LP beneficial ownership per footnote
Beneficial ownership TCPI 791,839 shares Tang Capital Partners International, LP beneficial ownership
Aggregate beneficial holdings 2,533,845 shares Total across four Tang Capital-related vehicles after purchases
Number of buy transactions 6 transactions All coded as open-market purchases (P) in Common Stock
open-market purchase financial
"transaction_action: "open-market purchase" for each Common Stock trade"
An open-market purchase is when an investor or a company buys shares on a public stock exchange at the going market price, rather than through a private deal. It matters to investors because these purchases change how many shares are available, can push the stock price up or signal confidence from large buyers, and often affect per-share metrics like earnings—think of it like someone buying lots of apples off a grocery shelf, reducing supply and potentially raising the price.
weighted-average prices financial
"The prices reported are weighted-average prices. These shares were purchased in multiple transactions"
beneficially owns financial
"Tang Capital Partners, LP ("TCP") beneficially owns 580,669 shares"
Beneficially owns means a person or entity enjoys the economic benefits and control of a security even if the legal title or registration is held in another name. Think of it like having the keys and profits from a car that is registered to a friend: you use it, benefit from it, and make decisions about it even though the official paperwork lists someone else. For investors, this matters because it reveals who truly controls shares, affects voting power, potential conflicts of interest, and regulatory disclosure obligations.
pecuniary interest financial
"Mr. Tang has a pecuniary interest in the shares beneficially held by TCP, TCPI, TCP III and TCP IV"
ten percent owner financial
"reportingPersons entry shows is_ten_percent_owner: 1 for both reporting persons"
indirect ownership financial
"direct_or_indirect: "I" and nature_of_ownership: "By LP" for all transactions"
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Form 4 Insider Transactions: What Each Field Means →
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).
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*
TANG KEVIN
(Last)(First)(Middle)
4747 EXECUTIVE DRIVE
SUITE 210
(Street)
SAN DIEGO CALIFORNIA 92121
(City)(State)(Zip)
UNITED STATES
(Country)		2. Issuer Name and Ticker or Trading Symbol
Boundless Bio, Inc. [ BOLD ] 		5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
DirectorX10% Owner
Officer (give title below)Other (specify below)
2a. Foreign Trading Symbol
3. Date of Earliest Transaction (Month/Day/Year)
06/25/2026		6. Individual or Joint/Group Filing (Check Applicable Line)
Form filed by One Reporting Person
XForm 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 Stock06/25/2026P145,880A$2.48(1)2,393,392IBy LP(2)
Common Stock06/25/2026P510A$2.56(3)2,393,902IBy LP(2)
Common Stock06/26/2026P75,047A$2.55(4)2,468,949IBy LP(2)
Common Stock06/26/2026P134A$2.54(5)2,469,083IBy LP(2)
Common Stock06/29/2026P63,985A$2.47(6)2,533,068IBy LP(2)
Common Stock06/29/2026P777A$2.48(7)2,533,845IBy LP(2)
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
1. Name and Address of Reporting Person*
TANG KEVIN
(Last)(First)(Middle)
4747 EXECUTIVE DRIVE
SUITE 210
(Street)
SAN DIEGO CALIFORNIA 92121
(City)(State)(Zip)
UNITED STATES
(Country)
Relationship of Reporting Person(s) to Issuer
DirectorX10% Owner
Officer (give title below)Other (specify below)
1. Name and Address of Reporting Person*
TANG CAPITAL MANAGEMENT LLC
(Last)(First)(Middle)
4747 EXECUTIVE DRIVE
SUITE 210
(Street)
SAN DIEGO CALIFORNIA 92121
(City)(State)(Zip)
UNITED STATES
(Country)
Relationship of Reporting Person(s) to Issuer
DirectorX10% Owner
Officer (give title below)Other (specify below)
Explanation of Responses:
1. The prices reported are weighted-average prices. These shares were purchased in multiple transactions at prices ranging from $2.42 to $2.56. The Reporting Persons undertake to provide the Issuer, any security holder of the Issuer or the SEC staff, upon request, all information regarding the number of shares purchased at each price within the ranges set forth in Footnotes 1 and 3 through 7.
2. Tang Capital Partners, LP ("TCP") beneficially owns 580,669 shares, Tang Capital Partners International, LP ("TCPI") beneficially owns 791,839 shares, Tang Capital Partners III, Inc. ("TCP III") beneficially owns 580,668 shares, and Tang Capital Partners IV, Inc. ("TCP IV") beneficially owns 580,669 shares. Kevin Tang is the sole manager of Tang Capital Management, LLC, which is the general partner of TCP and TCPI. Kevin Tang is the sole director and Chief Executive Officer of TCP III and TCP IV, which are indirectly wholly owned by TCP. Mr. Tang has a pecuniary interest in the shares beneficially held by TCP, TCPI, TCP III and TCP IV.
3. These shares were purchased in multiple transactions at prices ranging from $2.53 to $2.60.
4. These shares were purchased in multiple transactions at prices ranging from $2.46 to $2.60.
5. These shares were purchased in multiple transactions at prices ranging from $2.52 to $2.58.
6. These shares were purchased in multiple transactions at prices ranging from $2.40 to $2.59.
7. These shares were purchased in multiple transactions at prices ranging from $2.44 to $2.52.
Kevin Tang06/29/2026
Kevin Tang, Manager06/29/2026
** 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)

Source: View Original Filing on SEC EDGAR

FAQ

What did Tang Capital-affiliated entities do in the latest Boundless Bio (BOLD) Form 4?

Tang Capital-affiliated entities reported open-market purchases of Boundless Bio Common Stock. They bought 286,333 shares over June 25–29, 2026, at weighted-average prices generally between about $2.40 and $2.60, increasing their indirect ownership through limited partnership vehicles.

How many Boundless Bio (BOLD) shares were purchased in this Form 4 filing?

The filing reports net purchases of 286,333 Boundless Bio Common Stock shares. These came from six separate open-market trades, with individual transaction sizes ranging from 134 shares up to 145,880 shares, all held indirectly through Tang Capital limited partnership entities.

At what prices were the Boundless Bio (BOLD) shares bought by Tang Capital entities?

Reported per-share prices include $2.48, $2.47, $2.54, $2.55 and $2.56. Footnotes state the trades used weighted-average prices, with actual purchase prices falling within ranges such as $2.40–$2.59 and $2.42–$2.56 over multiple small transactions.

Is Kevin Tang personally buying Boundless Bio (BOLD) shares in this Form 4?

The shares are held indirectly through Tang Capital limited partnerships and related entities. Kevin Tang is the sole manager or director of these entities and has a pecuniary interest in their holdings, but the ownership reported is through the funds rather than direct personal accounts.

What does "weighted-average prices" mean in the Boundless Bio (BOLD) Form 4 footnotes?

The filing notes that reported prices are weighted-average prices across multiple trades. Actual purchase prices occurred within stated ranges, like $2.42–$2.56, and the reporting persons offer to provide detailed per-trade pricing information to the issuer, security holders or SEC staff upon request.