Inhibrx Biosciences INBX Insider Ownership

NASDAQ INBX

$98.93 +3.63 (+3.80%)

As of: Oct 21, 2026 · 2:32 PM EDT

The most recent Inhibrx Biosciences (INBX) insider transaction: Mark Lappe (Chief Executive Officer) bought 2,470 shares worth about $207.65K on Oct 14, 2026. So far in the quarter ending Dec 31, 2026, insiders were net buyers of 10.04K shares.

Updated Oct 16, 2026 Inhibrx Biosciences (INBX) stock price and overview

Insider Holdings by Owner

3.34Mn Shares

Insider Ownership Statistics

as of 30 Sep, 2026

Insider Ownership

15.27%

▲+0.319% pp QoQ

Shares Held by Insiders

2.39Mn

filed for Sep 2026

▲+2.13% QoQ

Shares Outstanding

15.67Mn

15,669,000 shares

Direct Holdings

20.44K

Indirect: 2.37Mn

Net Shares Traded (QoQ)

+50.00K

net buying in Sep 2026

Insiders Holding Shares

with Form 4 holdings on file

Shares Owned by Insiders

Shares held % of outstanding

Latest —

Average ownership —

Peak ownership —

Shares Purchased/Sold by Insiders

Bought Sold

Latest quarter —

Net over range —

Buying quarters —

Insider Ownership Summary

Updated Oct 16, 2026

Over the trailing 12 months, INBX insiders bought $6.35 million worth of shares (62.54K shares) and sold $279,010 worth (2.5K shares) in open-market trades.

Counted by insider, open-market buying of INBX stock in the past 12 months came from 3 insiders and selling from one insider.
Among Inhibrx Biosciences insiders, Mark Lappe (Chief Executive Officer) led open-market buying over the past 12 months with $4.49 million of purchases (45.04K shares); the latest was on October 14, 2026.
Conversely, Kimberly Manhard (Director) was INBX's largest open-market seller in the past 12 months, with $279,010 of sales (2.5K shares); the latest was on September 15, 2026.
Business Quant data puts insider holdings in INBX at 2.4Mn shares across insiders' latest Form 4 filings, or 15.33% of the 15.67Mn shares outstanding; that total is up 2.56% from 2.34Mn shares at the end of Q2 2026.
Indirect holdings, through trusts, partnerships, family members and other entities, make up 99.15% (2.38Mn shares) of Inhibrx Biosciences' insider total, with the other 0.85% (20.44K shares) held directly.
INBX's insider total is spread across 6 insiders who have filed a Form 4 in the past two years.
INBX's three largest insider shareholders, per their latest Form 4 filings, are Jon Faiz Kayyem (Director, 1.07Mn shares), Mark Lappe (Chief Executive Officer, 970.45K shares) and Douglas Forsyth (Director, 227.06K shares).
Jon Faiz Kayyem holds 44.71% of the combined insider position in Inhibrx Biosciences.
In the last 12 months, 14 Form 4 filings with transactions in INBX stock came from 6 insiders.
Insider figures for INBX include Form 4 filings through October 14, 2026.

Form 4 Holdings

Insiders Holding INBX

Insiders 8

Shares held 3.34Mn

Of outstanding 21.31%

#	Insider	Position	Direct	Indirect	Total	Share of Insiders	Last Filed
1	Inc. Inhibrx,	TenPercentOwner	1,157,926	0	1,157,926	34.7%	31 May, 2024
2	Mark Lappe	Chief Executive Officer	0	915,588	915,588	27.4%	14 Oct, 2026
3	Brendan P. Eckelman	Chief Scientific Officer	0	473,888	473,888	14.2%	30 May, 2024
4	Jon Faiz Kayyem	Director	0	434,360	434,360	13.0%	23 Sep, 2026
5	Douglas Forsyth	Director	0	227,064	227,064	6.8%	08 Sep, 2026
6	Global Investors Lp Viking	TenPercentOwner	0	102,864	102,864	3.1%	09 Oct, 2025
7	Kristiina Md Vuori	Director	20,443	0	20,443	0.6%	07 Oct, 2024
8	Kimberly Manhard	Director	0	7,500	7,500	0.2%	15 Sep, 2026

Each row is that insider’s most recently reported position, from Form 4 filings over the last 60 months — which is why this total does not tie to the quarterly series above, where a quarter counts only the insiders who filed in it. Shares held through a fund or institutional portfolio are counted on the institutional ownership page instead.

Form 4 Filings

94 Insider Transactions

Source SEC Form 4

Latest quarter Sep 2026

Date	Insider	Position	Transaction	Shares	Price	Value	Shares Held After	Ownership
14 Oct, 2026	Mark Lappe	Chief Executive Officer	Acquired P	2,470	$84.07	$207.65K	743,018	Indirect
14 Oct, 2026	Mark Lappe	Chief Executive Officer	Acquired P	2,470	$85.00	$209.95K	745,488	Indirect
14 Oct, 2026	Mark Lappe	Chief Executive Officer	Acquired P	100	$85.76	$8.58K	745,588	Indirect
14 Oct, 2026	Mark Lappe	Chief Executive Officer	Acquired P	2,449	$84.07	$205.89K	167,449	Indirect
14 Oct, 2026	Mark Lappe	Chief Executive Officer	Acquired P	2,451	$85.00	$208.33K	169,900	Indirect
14 Oct, 2026	Mark Lappe	Chief Executive Officer	Acquired P	100	$85.76	$8.58K	170,000	Indirect
25 Sep, 2026	Mark Lappe	Chief Executive Officer	Acquired P	3,324	$98.87	$328.63K	733,872	Indirect
25 Sep, 2026	Mark Lappe	Chief Executive Officer	Acquired P	2,176	$99.60	$216.73K	736,048	Indirect
28 Sep, 2026	Mark Lappe	Chief Executive Officer	Acquired P	1,500	$98.88	$148.32K	737,548	Indirect
28 Sep, 2026	Mark Lappe	Chief Executive Officer	Acquired P	3,000	$101.70	$305.11K	740,548	Indirect
23 Sep, 2026	Jon Faiz Kayyem	Director	Acquired P	5,000	$100.00	$500.00K	434,360	Indirect
16 Sep, 2026	Jon Faiz Kayyem	Director	Acquired P	5,000	$100.00	$500.00K	429,360	Indirect
11 Sep, 2026	Kimberly Manhard	Director	Disposed S	500	$111.78	$55.89K	8,500	Indirect
14 Sep, 2026	Kimberly Manhard	Director	Disposed S	500	$110.26	$55.13K	8,000	Indirect
15 Sep, 2026	Kimberly Manhard	Director	Disposed S	500	$105.05	$52.53K	7,500	Indirect
08 Sep, 2026	Kimberly Manhard	Director	Disposed S	500	$115.14	$57.57K	9,500	Indirect
09 Sep, 2026	Kimberly Manhard	Director	Disposed S	500	$115.80	$57.90K	9,000	Indirect
08 Sep, 2026	Mark Lappe	Chief Executive Officer	Acquired P	5,895	$99.29	$585.34K	711,443	Indirect
08 Sep, 2026	Douglas Forsyth	Director	Acquired P	2,500	$114.65	$286.62K	227,064	Indirect
08 Sep, 2026	Jon Faiz Kayyem	Director	Acquired P	5,000	$113.52	$567.58K	424,360	Indirect

Showing 1 to 20 of 94 transactions