Inhibrx Biosciences CEO trusts buy 10,040 shares

Q: What INBX holdings are listed in Mark Lappe’s Roth IRA?

A separate holding entry dated October 14, 2026 lists 54,865 shares of common stock as held indirectly by The Mark Paul Lappe Roth IRA.

The chief executive officer's purchases were reported through two family trusts; a separate Roth IRA holding entry lists 54,865 shares.

Filing Impact

(Very High)

Filing Sentiment

(Positive)How Sentiment works

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Form Type

Rhea-AI Filing Summary

Inhibrx Biosciences, Inc. Chief Executive Officer Mark Lappe reported that the Lappe Family Trust and Lappe Descendants’ Trust purchased 10,040 shares of common stock on October 14, 2026. The Family Trust purchased 2,470 shares at a weighted-average price of $84.0707 and another 2,470 at $84.9992, plus 100 shares at $85.7600. The Descendants’ Trust purchased 2,449 shares at $84.0707, 2,451 at $84.9992, and 100 at $85.7600. Lappe may be deemed to indirectly beneficially own the trust-held shares. No Rule 10b5-1 plan is reported.

Insights

Analyzing...

Insider Trade Summary

Net Buyer: 10,040 shares

Net Buy 7 txns

Insider Lappe Mark

Role Chief Executive Officer

Bought 10,040 shs ($849K)

Type	Security	Shares	Price	Value
Purchase	Common Stock ^{F1, F2}	2,470	$84.0707	$208K
Purchase	Common Stock ^{F3, F2}	2,470	$84.9992	$210K
Purchase	Common Stock ^F2	100	$85.76	$9K
Purchase	Common Stock ^{F1, F4}	2,449	$84.0707	$206K
Purchase	Common Stock ^{F3, F4}	2,451	$84.9992	$208K
Purchase	Common Stock ^F4	100	$85.76	$9K
holding	Common Stock	--	--	--

Holdings After Transaction: Common Stock — 745,588 shares (Indirect, By the Lappe Family Trust); Common Stock — 170,000 shares (Indirect, By Lappe Descendants' Trust); Common Stock — 54,865 shares (Indirect, The Mark Paul Lappe Roth IRA)

Footnotes (4)

F1. The shares were purchased in multiple transactions at prices ranging from $83.61 to $84.59 inclusive. The reported price reflects the weighted-average purchase price. The reporting person hereby undertakes to provide upon request to the Securities and Exchange Commission staff, the Issuer or a security holder of the Issuer full information regarding the number of shares and prices at which the transactions were effected.
F2. These securities are directly owned by the Lappe Family Trust. Mark P. Lappe is a trustee of the Lappe Family Trust and, in such capacity, may be deemed to indirectly beneficially own the securities owned by the Lappe Family Trust.
F3. The shares were purchased in multiple transactions at prices ranging from $84.65 to $85.62 inclusive. The reported price reflects the weighted-average purchase price. The reporting person hereby undertakes to provide upon request to the Securities and Exchange Commission staff, the Issuer or a security holder of the Issuer full information regarding the number of shares and prices at which the transactions were effected.
F4. These securities are directly owned by a trust, for the benefit of the reporting person's immediate family. Mark P. Lappe, as an immediate family member of the beneficiaries of the trust, may be deemed to indirectly beneficially own the securities owned by the trust.

Key Figures

Family Trust purchase: 2,470 shares at $84.0707 per share Family Trust purchase: 2,470 shares at $84.9992 per share Family Trust purchase: 100 shares at $85.7600 per share +4 more

7 metrics

Family Trust purchase 2,470 shares at $84.0707 per share Weighted-average price; October 14, 2026

Family Trust purchase 2,470 shares at $84.9992 per share Weighted-average price; October 14, 2026

Family Trust purchase 100 shares at $85.7600 per share October 14, 2026

Descendants’ Trust purchase 2,449 shares at $84.0707 per share Weighted-average price; October 14, 2026

Descendants’ Trust purchase 2,451 shares at $84.9992 per share Weighted-average price; October 14, 2026

Descendants’ Trust purchase 100 shares at $85.7600 per share October 14, 2026

Shares listed in Roth IRA holding entry 54,865 shares The Mark Paul Lappe Roth IRA; October 14, 2026

Key Terms

weighted-average purchase price, indirectly beneficially own, trustee

3 terms

weighted-average purchase price financial

"The reported price reflects the weighted-average purchase price."

indirectly beneficially own regulatory

"may be deemed to indirectly beneficially own the securities"

trustee technical

"Mark P. Lappe is a trustee of the Lappe Family Trust"

A trustee is a person or institution legally appointed to hold and manage assets or enforce an agreement on behalf of other people (beneficiaries). Think of a trustee as a neutral referee or custodian who must act in the beneficiaries’ best interests, follow the trust or contract rules, and handle distributions, recordkeeping and enforcement. Investors care because a trustworthy trustee protects their rights, ensures promised payments or remedies are delivered, and can influence recoveries if things go wrong.

FAQ

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

What prices did the INBX trusts pay for the October 14 purchases?

For the 2,470-share Family Trust and 2,449-share Descendants’ Trust purchases, the weighted-average price was $84.0707, within a range of $83.61 to $84.59 inclusive. For the 2,470-share Family Trust and 2,451-share Descendants’ Trust purchases, the weighted-average price was $84.9992, within a range of $84.65 to $85.62 inclusive. Each trust also purchased 100 shares at $85.7600.

What INBX holdings are listed in Mark Lappe’s Roth IRA?

A separate holding entry dated October 14, 2026 lists 54,865 shares of common stock as held indirectly by The Mark Paul Lappe Roth IRA.

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

Form 4 Insider Transactions: What Each Field Means →

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Available on EDGAR 10/14/2026 - 06:58 PM EDT Accepted by SEC EDGAR 10/14/2026 - 06:58 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^*

Lappe Mark

(Last)

(First)

(Middle)

C/O INHIBRX BIOSCIENCES, INC.

11025 NORTH TORREY PINES ROAD, SUITE 140

(Street)

LA JOLLA

CALIFORNIA

92037

(City)

(State)

(Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
Inhibrx Biosciences, Inc. [ INBX ]

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

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
10/14/2026

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)
Common Stock	10/14/2026		P		2,470	A	$84.0707⁽¹⁾	743,018	I	By the Lappe Family Trust⁽²⁾
Common Stock	10/14/2026		P		2,470	A	$84.9992⁽³⁾	745,488	I	By the Lappe Family Trust⁽²⁾
Common Stock	10/14/2026		P		100	A	$85.76	745,588	I	By the Lappe Family Trust⁽²⁾
Common Stock	10/14/2026		P		2,449	A	$84.0707⁽¹⁾	167,449	I	By Lappe Descendants' Trust⁽⁴⁾
Common Stock	10/14/2026		P		2,451	A	$84.9992⁽³⁾	169,900	I	By Lappe Descendants' Trust⁽⁴⁾
Common Stock	10/14/2026		P		100	A	$85.76	170,000	I	By Lappe Descendants' Trust⁽⁴⁾
Common Stock								54,865	I	The Mark Paul Lappe Roth IRA

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)

Explanation of Responses:

1. The shares were purchased in multiple transactions at prices ranging from $83.61 to $84.59 inclusive. The reported price reflects the weighted-average purchase price. The reporting person hereby undertakes to provide upon request to the Securities and Exchange Commission staff, the Issuer or a security holder of the Issuer full information regarding the number of shares and prices at which the transactions were effected.

2. These securities are directly owned by the Lappe Family Trust. Mark P. Lappe is a trustee of the Lappe Family Trust and, in such capacity, may be deemed to indirectly beneficially own the securities owned by the Lappe Family Trust.

3. The shares were purchased in multiple transactions at prices ranging from $84.65 to $85.62 inclusive. The reported price reflects the weighted-average purchase price. The reporting person hereby undertakes to provide upon request to the Securities and Exchange Commission staff, the Issuer or a security holder of the Issuer full information regarding the number of shares and prices at which the transactions were effected.

4. These securities are directly owned by a trust, for the benefit of the reporting person's immediate family. Mark P. Lappe, as an immediate family member of the beneficiaries of the trust, may be deemed to indirectly beneficially own the securities owned by the trust.

Remarks:

	/s/ Kelly D. Deck, as attorney-in-fact for Mark P. Lappe	10/14/2026
	** 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