Insider transactions

Bruce Booth

CIK 1451612 · last filed 2026-07-02

"Disclosed insider exposure" sums this person's most-recently-reported share counts across each company they're an insider in, multiplied by the current underlying price. It is not net worth — it misses retail holdings, private investments, real estate, index funds, and any company where the person isn't an SEC-reporting insider. For informational purposes only.

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Disclosed Exposure
$59.04M
Companies
8
Total Filings
86
Lifetime Open-Market Net
-$248.00M

Charts

Trading activity, where the exposure sits, and each trade against the stock price.

KYMR price and trades

Daily close with each Form 4 filing on this company marked: green = open-market buy, red = open-market sale, purple = grants, exercises, gifts and other non-market transactions. Marker size scales with the dollar value.

Shares held

Shares owned after each reported transaction on this company (direct holdings as reported).

Open-market buying and selling

by month

Dollar value of open-market purchases (code P, up) and sales (code S, down) across all companies, by filing month. Grants, exercises and gifts are excluded.

Exposure by company

latest
OfficerDirector10% owner* stale (no filing in 3 yrs)

Most recently reported shares × current price. Faded bars (*) have had no filing in 3 years, so the person may no longer hold them. Click a bar to chart that company.

Filer Profile

Reported Address
890 WINTER STREET
SUITE 320
WALTHAM, MA 02451
Profile details as reported on the filer's SEC submissions — for individual insiders the address is often in care of the issuer. Related filers are identified from jointly filed SEC submissions and shared reported addresses. View filings on SEC EDGAR.

Holdings By Company

Latest on-record share count from this person's most recent non-derivative Form 4 transaction in each company. Disclosed exposure = shares × current underlying price.
Symbol Role Shares Price Disclosed Exposure Lifetime OM Net Filings Latest Filed
KYMR Director 475,805 $104.78 $49.85M -$263.36M 27 2026-07-02
SION Director 2,360,156 $3.89 $9.18M -$21.01M 8 2026-06-18
Vigil Neuroscience, Inc. (VIGL) Delisted Director 0 $8.05 $0 $7.49M 11 2025-08-05
Tectonic Therapeutic, Inc. (AVRO) Delisted Director 463,941 $16.80 $7.79M $15.00M 7 2023-06-08
Dianthus Therapeutics, Inc. /DE/ (MGTA) Delisted Director 257,320 $11.19 $2.88M $9.75M 7 2022-06-30
Cogent Biosciences, Inc. (UMRX) Delisted Director 3,184,446 — — $1.13M 12 2020-07-06
Viridian Therapeutics, Inc.\DE (MGEN) Delisted Director 209,505 — — $3.00M 5 2018-06-28
Larimar Therapeutics, Inc. (ZFGN) Delisted Director 386,502 — — $0 7 2018-01-05

Recent Filings · Page 5 of 9

86 filings
Insider activity across all companies, newest first. Form 4 rows are post-trade confirmations (buys, sells, grants, exercises). Notice (144) rows are pre-trade notices of intent to sell restricted or control stock under Rule 144 — they may not all execute. Compare adjacent dates to see which notices became actual sales.
Filed Symbol Action Net Shares Net $ Link
2022-06-30 Dianthus Therapeutics, Inc. /DE/ (MGTA) Delisted Grant (A) — $0 EDGAR
2022-06-16 KYMR Grant (A) — $0 EDGAR
2022-06-13 Vigil Neuroscience, Inc. (VIGL) Delisted Grant (A) — $0 EDGAR
2022-06-10 Tectonic Therapeutic, Inc. (AVRO) Delisted Grant (A) — $0 EDGAR
2022-03-03 Vigil Neuroscience, Inc. (VIGL) Delisted Grant (A) — $0 EDGAR
2022-01-11 Vigil Neuroscience, Inc. (VIGL) Delisted Mixed +4,394,498 $7.49M EDGAR
2021-08-12 KYMR Sell (S) −242,133 -$14.77M EDGAR
2021-06-17 KYMR Grant (A) — $0 EDGAR
2021-06-14 Tectonic Therapeutic, Inc. (AVRO) Delisted Grant (A) — $0 EDGAR
2021-06-03 Dianthus Therapeutics, Inc. /DE/ (MGTA) Delisted Grant (A) — $0 EDGAR
Showing 41–50 of 86
Page 5 of 9
Form 4 codes: P = open-market purchase · S = open-market sale · A = grant/award · M = option exercise · F = tax withholding at vest · G = bona-fide gift · D = disposition to issuer · J = other (see filing footnote). Only P / S codes carry directional signal.
Notice (144 / 144/A): Form 144 is a notice of intent to sell restricted/control stock under Rule 144, filed before the sale; 144/A is an amendment. Many notices are pre-scheduled under Rule 10b5-1 plans. A Form 4 with code S typically follows within a few days when the planned sale executes; missing follow-up Form 4s suggest the notice was cancelled or modified.