STRO Insider Trading

Sutro Biopharma, Inc. (STRO) operates in the Healthcare sector, specifically the Biotechnology industry, with a market capitalization near $106.5M, listed on NASDAQ, employing roughly 128 people, carrying a beta of 1.50 to the broader market. Sutro Biopharma, Inc. Led by Jane Chung, public since 2018-09-27.

In the last 12 months, Sutro Biopharma, Inc. insiders made 5 buy transactions and 0 sale transactions.

STRO Insider Activity by Quarter

Reported Form 4 and Form 5 lines under STRO's own SEC company ID, by transaction date, back to Q4 2024. Purchases and sales are code P / S (open market or private) in the company's shares; other lines are purchases and sales of other securities (options, warrants, preferred), awards, exercises, tax withholding, gifts and other acquisitions and dispositions. Later filings and amendments can change the current quarter. Earlier quarters are not shown: the filings read reach back to Nov 22, 2021, and a quarter counts only when every filing for it was read.

STRO Institutional Ownership (13F)

As of Jun 30, 2026 (Q2 2026), 100 institutions reported holding 16,480,214 STRO shares, valued at $545.7M as reported, 136.7% of its market cap (market cap of Jun 26, 2026). That is +22 institutions from the quarter before. Among managers whose reports for both quarters are comparable, 40 opened a position, 17 closed one, 24 added and 18 trimmed.

Top Holders, Q2 2026

By Quarter

From the SEC's Form 13F data sets: investment managers with $100 million or more in Section 13(f) securities report their holdings each quarter, up to 45 days after it ends; a restated filing replaces the original, and values are as the managers reported them (a position whose price runs about 1,000 times below other managers', from a manager whose positions mostly do, is read as reported in thousands of dollars). The same shares can be reported by more than one manager, so totals can count some twice.

ETFs Holding STRO

From each fund's latest holdings file on record that shows STRO's listed security itself. A file counts when its line count is consistent with the fund's reported holdings count (at most twice it plus 10, or at most 1,000 lines for a reported count of exactly 10, which the data source gives many funds as a cap), read with that file or inherited from the fund's last classified file (within 20% of its line count, read within 60 days). Funds whose line for the company could not be confirmed as STRO's listed security, or that hold it through underlying funds (look-through), are not listed. Only long positions count: a fund is left out when any of its lines for STRO reports a negative weight, share count or value, or none of them above zero (a short position, or figures that disagree). Shares, value and weight are as reported in each fund's file, dated by the data source's last update of that file (not the date of the positions); the weight is STRO's share of that fund.

How to Read STRO Insider Activity

Net insider sentiment is bullish over the trailing twelve months: 5 buy transactions versus 0 sales. Cluster buying by officers or directors is one of the cleaner insider signals because purchases require personal capital deployment and carry direct SEC scrutiny for material non-public information violations. The transaction table above includes the filer's reporting name, transaction type, share count, per-share price, and total dollar value where computable. For options traders, insider activity is one input to event-driven sizing alongside earnings calendar, analyst-rating cluster moves, and the implied-vol surface. Form 4 filings (the dominant Section 16 reporting form) must be submitted within two business days of the transaction; clusters of buys across multiple insiders within a short window are the strongest informational pattern. SEC EDGAR carries the underlying source filings for verification and additional historical depth.

Learn how insider trading is reported and how to read the data →

Frequently asked STRO insider trading questions

How active are STRO insiders right now?

Over the trailing twelve months, Sutro Biopharma, Inc. (STRO) insiders made 5 buy transactions and 0 sale transactions. Net insider sentiment over the trailing twelve months tilts to the buy side (5 buys vs 0 sales). The transaction list above shows the most recent filings; each entry includes the insider's name, transaction type, share count, and per-share price.

What counts as an insider transaction?

Section 16 of the Securities Exchange Act requires officers, directors, and 10% beneficial-owner shareholders to disclose changes in their holdings via Form 3 (initial statement), Form 4 (subsequent transactions, filed within two business days), and Form 5 (annual catch-up). Insider transactions cover open-market purchases and sales, exercise of stock options, gifts, and grants. The "transaction type" field on each row distinguishes these subcategories.

Are STRO insider buys a bullish signal?

Insider purchases (Type P, made on the open market or privately; the code covers both) carry more informational weight than insider sales: an insider must commit personal capital, and the SEC scrutinizes purchases under Rule 10b5-1 for material non-public information. Sales, by contrast, are often driven by liquidity, tax planning, or pre-scheduled 10b5-1 trading plans rather than negative information. Cluster buying (multiple insiders buying within a short window) is a stronger signal than isolated buys.

How do STRO insider transactions affect options pricing?

Insider transaction data does not directly drive implied volatility, but Form 4 disclosures can move single-name IV if the size or timing is unusual (e.g. a large CEO buy ahead of an earnings window). Options markets price the marginal informational content; routine transactions under pre-scheduled plans are typically ignored. For event-driven options sizing, pair the insider transaction history with the upcoming earnings calendar.