AMPXAmprius Technologies, Inc. · Insider ownership research

Amprius Technologies, Inc. insiders sold $85.7M in the past 12 months. How much of their stake is that?

Insiders sold $85.7M in the past 12 months.75% was sold under disclosed trading plans, 6% to cover taxes, 19% with no plan disclosed. The largest seller, Kang Sun (Director), sold $57.6M. 83% of these sales were shares from exercising options.Share-of-stake figures for this company are being verified and will be added when that check is finished. Why

Updated Oct 13, 2026 from SEC filings · covers Oct 14, 2025 to Oct 13, 2026

$16.2M

sold with no plan disclosed, past 12 months

75%

of sales were under disclosed trading plans, past 12 months

6 of 10

officers and directors sold shares, past 12 months

Is this normal? More than usual: $85.7M sold, after almost none in the past 3 years. 6 insiders sold; the average is 4 a year. Year by year

Latest filing: Filed Aug 25 for a sale on Aug 21. Kang Sun sold 62K shares ($642K) to cover taxes on vesting stock. Filing

SEC ownership filings: 37 filed in the 12 months to Oct 13, 2026; 152 on record since Mar 1, 2022 · See the evidence

What stands out

Three directors sold $16.0M with no disclosed plan: Wen HSIEH ($7.6M), Steven Chu ($5.9M) and Donald Dixon ($2.5M). The filings don't state a reason.Wen HSIEH: largest such sale, Mar 12, 2026 · Steven Chu: largest such sale, Mar 10, 2026 · Donald Dixon: largest such sale, Jun 15, 2026

A share of stake is shown for 0 of the 6 officers and directors who sold. 10 are left out

i

Left out: Wen HSIEH, Donald Dixon, Thomas Stepien, Kang Sun, Constantin Stefan, Sandra Wallach, Ricardo Rodriguez, Kathleen Bayless, Steven Chu and Livingston Satterthwaite (share of stake is being verified).

Disclosed company stock is not an insider's whole wealth.

Who sold, and how much of their stake

Officers and directors, past 12 months. Their share of stake is being verified and is not shown yet; amounts and trading plans are below.

Kang Sun

Director

Not confirmed

Share of stake not shown: share of stake is being verified. Why

$57.6M95% planned, 5% to cover taxes

Constantin Stefan

Chief Technology Officer

Not confirmed

Share of stake not shown: share of stake is being verified. Why

$10.7M88% planned, 12% to cover taxes

Wen HSIEH

Director

Not confirmed

Share of stake not shown: share of stake is being verified. Why

$7.6MNo plan disclosed

Steven Chu

Director

Not confirmed

Share of stake not shown: share of stake is being verified. Why

$5.9MNo plan disclosed

Donald Dixon

Director

Not confirmed

Share of stake not shown: share of stake is being verified. Why

$2.5MNo plan disclosed

Selling by month

Officers and directors, Oct 2025 to Oct 2026. Each sale is counted once: under a disclosed plan, else to cover taxes, else no plan disclosed.

Disclosed planTo cover taxesNo plan disclosedOne dollar scale for every month; the tallest bar is labeled

Recent activity

Past 30 days, Sep 14, 2026 to Oct 13, 2026

No officer or director trades were reported for the past 30 days. The most recent before that:

Aug 25, 2026Thomas Stepien gave away 15K shares as a gift. 346 shares came in from vesting or option exercises the same day, so the holding fell by 15K net.

Who	Shares	Price	% of total stake	Total stake after	Trade date	Filed
Thomas Stepien Chief Executive Officer, Director	15,346	n/a	n/a	n/a	Aug 25, 2026	Aug 25, 2026

Outside holders, reported separately

Donald Dixon reported no open-market sales in the past 12 months. Large shareholders and the funds or companies that board members represent are not part of management, so they are left out of the figures above.

Common questions

Is the Amprius Technologies, Inc. CEO selling stock?

Yes. Thomas Stepien sold 99K shares ($1.3M) in the past 12 months, none of it under a trading plan disclosed in the filings.

Why are Amprius Technologies, Inc. insiders selling?

Filings rarely give a reason, and we don't guess at one. What they show is how the sales were made: 75% of sales by value ran under 10b5-1 trading plans disclosed in the filings, 6% were to cover taxes and 19% had no disclosed plan. A trading plan schedules sales in advance.

Are any Amprius Technologies, Inc. insiders buying?

No. Officers and directors reported no purchases in the past 12 months.

The evidence

Who sold6 officers and directors: amount, % of holdings, trading plan

Who sold	Amount	% of holdings	Trading plan
Kang Sun Director	$57.6M 4.48M shares	Not confirmed share of stake is being verified. Why	95% under a disclosed plan, 5% to cover taxes
Constantin Stefan Chief Technology Officer	$10.7M 918K shares	Not confirmed share of stake is being verified. Why	88% under a disclosed plan, 12% to cover taxes
Wen HSIEH Director	$7.6M 413K shares	Not confirmed share of stake is being verified. Why	No plan disclosed
Steven Chu Director	$5.9M 322K shares	Not confirmed share of stake is being verified. Why	No plan disclosed
Donald Dixon Director	$2.5M 143K shares	Not confirmed share of stake is being verified. Why	No plan disclosed
Thomas Stepien Chief Executive Officer, Director	$1.3M 99K shares	Not confirmed share of stake is being verified. Why	91% to cover taxes 9% no plan disclosed

Board members representing outside shareholders, reported separately: Donald Dixon. Details

The full ownership picture0 of 10 officers and directors confirmed

Vested shares across all share classes, held directly and through trusts, LLCs and family members, as reported on SEC Forms 3, 4 and 5. Unvested awards and options are never counted as owned shares.

Insider

Held Oct 13, 2025

Sold

Held Oct 13, 2026

Still held

Wen HSIEH

!

Holdings and share of stake are being verified. Share-of-stake figures and holdings for this company are held back while they are verified. Sales and other transactions for Wen HSIEH are complete.

Director

n/a

−413K

n/a

n/a

Vesting, gifts, unvested awards and holding lines for Wen HSIEH

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Wen HSIEH are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Donald Dixon

!

Holdings and share of stake are being verified. Share-of-stake figures and holdings for this company are held back while they are verified. Sales and other transactions for Donald Dixon are complete.

Director

n/a

−143K

n/a

n/a

Vesting, gifts, unvested awards and holding lines for Donald Dixon

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Donald Dixon are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Thomas Stepien

!

Holdings and share of stake are being verified. Share-of-stake figures and holdings for this company are held back while they are verified. See the filing Sales and other transactions for Thomas Stepien are complete.

Chief Executive Officer, Director

n/a

−99K

n/a

n/a

Vesting, gifts, unvested awards and holding lines for Thomas Stepien

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Thomas Stepien are complete; balances and unit counts will be added when the check is finished.

−46Kgifted (net of own trusts)

Kang Sun

!

Holdings and share of stake are being verified. Share-of-stake figures and holdings for this company are held back while they are verified. Sales and other transactions for Kang Sun are complete.

Director

n/a

−4.48M

n/a

n/a

Vesting, gifts, unvested awards and holding lines for Kang Sun

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Kang Sun are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Stock options (not counted as shares):

Options held	Strike price	Expires	Intrinsic value (estimate)
1,171,476	$0.78	Sep 26, 2034	$10.8M
1,787,007	$3.68	Dec 15, 2031	$11.3M

Estimate: options held × ($10.03 − strike price), using the most recent insider trade price on Form 4 (Aug 24, 2026), not a market close.

Constantin Stefan

!

Holdings and share of stake are being verified. Share-of-stake figures and holdings for this company are held back while they are verified. Sales and other transactions for Constantin Stefan are complete.

Chief Technology Officer

n/a

−918K

n/a

n/a

Vesting, gifts, unvested awards and holding lines for Constantin Stefan

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Constantin Stefan are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Stock options (not counted as shares):

Options held	Strike price	Expires	Intrinsic value (estimate)
139,613	$3.68	Dec 15, 2031	$887K

Estimate: options held × ($10.03 − strike price), using the most recent insider trade price on Form 4 (Aug 24, 2026), not a market close.

Sandra Wallach

!

Holdings and share of stake are being verified. Share-of-stake figures and holdings for this company are held back while they are verified. Sales and other transactions for Sandra Wallach are complete.

Chief Financial Officer

n/a

0

n/a

n/a

Vesting, gifts, unvested awards and holding lines for Sandra Wallach

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Sandra Wallach are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Ricardo Rodriguez

!

Holdings and share of stake are being verified. Share-of-stake figures and holdings for this company are held back while they are verified. Sales and other transactions for Ricardo Rodriguez are complete.

Chief Financial Officer

n/a

0

n/a

n/a

Vesting, gifts, unvested awards and holding lines for Ricardo Rodriguez

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Ricardo Rodriguez are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Kathleen Bayless

!

Holdings and share of stake are being verified. Share-of-stake figures and holdings for this company are held back while they are verified. Sales and other transactions for Kathleen Bayless are complete.

Director

n/a

0

n/a

n/a

Vesting, gifts, unvested awards and holding lines for Kathleen Bayless

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Kathleen Bayless are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Steven Chu

!

Holdings and share of stake are being verified. Share-of-stake figures and holdings for this company are held back while they are verified. Sales and other transactions for Steven Chu are complete.

Director

n/a

−322K

n/a

n/a

Vesting, gifts, unvested awards and holding lines for Steven Chu

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Steven Chu are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Stock options (not counted as shares):

Options held	Strike price	Expires	Intrinsic value (estimate)
184,108	$2.61	Apr 13, 2032	$1.4M
173,554	$0.78	Sep 26, 2034	$1.6M

Estimate: options held × ($10.03 − strike price), using the most recent insider trade price on Form 4 (Aug 24, 2026), not a market close.

Livingston Satterthwaite

!

Holdings and share of stake are being verified. Share-of-stake figures and holdings for this company are held back while they are verified. Sales and other transactions for Livingston Satterthwaite are complete.

Director

n/a

0

n/a

n/a

Vesting, gifts, unvested awards and holding lines for Livingston Satterthwaite

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Livingston Satterthwaite are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Holdings and share of stake for Amprius Technologies, Inc. are being verified, so no balances, unit counts or percentages are shown. Sales, proceeds, plan and tax status, titles and dates come straight from individual filings.

What explains the selling$85.7M of sales by plan status, purpose, seller and month

Officer and director open-market sales: $85.7M across 6,372,615 shares. Plan status and stated purpose are separate questions, and a sale can have both.

By plan status

Disclosed plan · $64.0M · 75%

25%

The lighter segment is sales with no plan disclosed in the filing ($21.6M), including tax-related sales outside a plan.

No plan disclosed · $16.2M

Sales with no 10b5-1 plan and no tax reference in the filing. $7.6M of it is Wen HSIEH. No plan disclosed is a statement about the filing, not about why the sale happened. Largest such sale: Wen HSIEH, Mar 12, 2026

Taxes

$5.5M of sales (6.4%) cite tax obligations in their footnotes. Example: Constantin Stefan, Aug 21, 2026

Seller	Shares sold	Proceeds	Under a disclosed plan	Share of total	Sales dates
Kang Sun Director	4.48M	$57.6M	95%	67%	Nov 17, 2025 to Aug 21, 2026
Constantin Stefan Chief Technology Officer	918K	$10.7M	88%	12%	Nov 21, 2025 to Aug 21, 2026
Wen HSIEH Director	413K	$7.6M	0%	9%	Mar 12, 2026 to Mar 12, 2026
Steven Chu Director	322K	$5.9M	0%	7%	Mar 10, 2026 to Mar 12, 2026
Donald Dixon Director	143K	$2.5M	0%	3%	May 26, 2026 to Jun 15, 2026
Thomas Stepien Chief Executive Officer, Director	99K	$1.3M	0%	2%	May 21, 2026 to Aug 24, 2026

Sales by month

Month	Sale proceeds	Disclosed plan	To cover taxes	No plan disclosed
Oct 2025	$0	$0	$0	$0
Nov 2025	$11.5M	$10.6M	$944K	$0
Dec 2025	$2.1M	$2.1M	$0	$0
Jan 2026	$23.4M	$23.4M	$0	$0
Feb 2026	$880K	$0	$880K	$0
Mar 2026	$17.6M	$4.1M	$0	$13.5M
Apr 2026	$23.9M	$23.9M	$0	$0
May 2026	$2.8M	$0	$2.5M	$320K
Jun 2026	$2.3M	$0	$0	$2.3M
Jul 2026	$0	$0	$0	$0
Aug 2026	$1.3M	$0	$1.2M	$80K
Sep 2026	$0	$0	$0	$0
Oct 2026	$0	$0	$0	$0

Board members representing outside shareholders (1)Listed and sourced; not part of the management totals or the answer line

Directors whose reported holdings sit mostly in an investment fund or a corporate shareholder they represent, not in their own name, with beneficial ownership disclaimed except for their own financial interest. Listed and sourced here; not part of the management totals or the answer line. Shares a fund hands to its own investors are distributions, not sales.

Board member	Held Oct 13, 2025	Sold	Held Oct 13, 2026	Still held
Donald Dixon ! Holdings and share of stake are being verified. Share-of-stake figures and holdings for this company are held back while they are verified. Sales and other transactions for Donald Dixon are complete. Director	n/a	0	n/a	n/a
Vesting, gifts, unvested awards and holding lines for Donald Dixon Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Donald Dixon are complete; balances and unit counts will be added when the check is finished. 0gifted (net of own trusts)

Is this normal? Selling year by year3 earlier years to compare with

More than usual: $85.7M sold, after almost none in the past 3 years. 6 insiders sold; the average is 4 a year.

12 months ending	Shares sold	Insiders who sold	Proceeds
Oct 13, 2026 Latest 12 months	6.37M	6	$85.7M
Oct 13, 2025 1 year earlier	532K	4	$1.7M
Oct 13, 2024 2 years earlier	3.19M	5	$7.4M
Oct 14, 2023 3 years earlier	491K	3	$2.6M
Oct 14, 2022 4 years earlier · filings don't cover the whole year	n/a	n/a	n/a
Oct 14, 2021 5 years earlier · filings don't cover the whole year	n/a	n/a	n/a

Open-market sales (Form 4 code S) by people who were officers or directors, in split-adjusted shares. Earlier years include people who have since left. A sale that an outside holder also reports (a family trust, a fund) is counted with outside holders in every year. Shares, not dollars, are compared, so a change in the stock price doesn't look like a change in selling. Years the filings don't fully cover are shown but left out of the average.

Known gaps and uncertainty10 officers and directors not confirmed

Holdings and share of stake are being verified. Balances, unit counts and every share-of-stake figure for Amprius Technologies, Inc. are held back until that check is finished. Sales, proceeds, plan and tax status, titles and dates come straight from individual filings and are complete.

External context: we only cite outside events when a documented connection exists. None is shown for this period.

Sources and methodology152 filings on record, 37 filed in the 12-month period, and how we read them

All 152 Forms 3, 4 and 5 on record for Amprius Technologies, Inc. (SEC CIK 1899287), filed from Mar 1, 2022 to Aug 25, 2026; 37 of them were filed in the 12 months this page covers, retrieved from SEC EDGAR on Oct 13, 2026. Prices are the ones reported in each filing, often weighted averages.

Holdings. Each holding line (a share class plus an owner, such as a trust or LLC) carries its last reported balance forward. Entities first reported during the period start at zero, so transfers between an insider's own trusts don't count as selling. Lines not reported for three years or more are listed separately and left out of totals.

Sales. A sale counts as under a 10b5-1 plan if its footnote cites one or the filing's Rule 10b5-1 box is checked, and as tax-related if its footnote cites tax obligations or sell-to-cover. Shares withheld by the company for taxes are listed separately. Sales with neither attribute are labeled "no plan disclosed".

Full methodology

Former or inactive filers (14)No filing in 18 months; last reported balances, not in any total

Name	Last filed	Last reported balance
Jonathan Bornstein	Mar 12, 2025	1,065,828 shares, last reported balance as of Mar 10, 2025
Amprius, Inc.	Oct 25, 2024	2,500,071 shares, last reported balance as of Oct 23, 2024
Justin Mirro	Sep 5, 2024	4,285,937 shares, last reported balance as of Sep 5, 2024
Mary Gustanski	Jun 7, 2024	31,813 shares, last reported balance as of Jun 7, 2024
Dieter Zetsche		No balance on record
Simon Boag		No balance on record
Nicole Nason		No balance on record
Anders Pettersson		No balance on record
Matthew Simoncini		No balance on record
Robert Remenar		No balance on record
Daniel Huber		No balance on record
Mitchell Quain		No balance on record
Donald Runkle		No balance on record
Thomas LaSorda		No balance on record

Spotted something wrong on this page? Report an error. We check every report against the SEC filing and list what we fix in the corrections log.