Question 1

Who are the insiders buying Spero Therapeutics, Inc. stock?

Accepted Answer

InsiderAct tracks all open-market purchases of Spero Therapeutics, Inc. stock by corporate insiders — including officers, directors, and shareholders owning more than 10% — sourced from public SEC Form 4 filings.

Question 2

What does insider buying at a company mean?

Accepted Answer

When a corporate officer, director, or major shareholder purchases their own company's stock on the open market using personal funds, it signals confidence in the company's outlook. This is especially meaningful when multiple insiders buy within the same 7–14 day window (cluster buying) or when the purchase size exceeds $100,000.

Question 3

How do I find cluster buying signals for a company?

Accepted Answer

InsiderAct automatically detects cluster buying — two or more insiders independently purchasing shares within a 14-day window. When a cluster buy signal is active for a company, it appears prominently on the company's InsiderAct page and on the Signals tab.

Question 4

Has Spero Therapeutics, Inc. had any recent large insider purchases?

Accepted Answer

InsiderAct tracks all open-market purchases of $100,000 or more at Spero Therapeutics, Inc.. Large insider purchases are flagged as high-conviction signals because they represent meaningful personal capital commitments by executives or directors who have direct visibility into the company's operations and prospects.

Question 5

Where do the insider transactions on this page come from?

Accepted Answer

All transactions shown on InsiderAct company pages are sourced directly from SEC EDGAR Form 4 filings — the mandatory public disclosures that corporate insiders must submit within 2 business days of any stock transaction. InsiderAct ingests these filings in near real time and filters for open-market purchases and sales.

								1WStock price change 1 week after insider bought. Small number below shows return vs S&P 500.	1MStock price change 1 month after insider bought.
2026-05-07	2026-05-04	Rajavelu Esther	See Remarks	Sale	25,240	$2.51	$63,352	N/A	N/A
2026-02-09	2026-02-06	Rajavelu Esther	See Remarks	Sale	50,816	$2.36	$119,926	N/A	N/A
2026-02-09	2026-02-06	Rajavelu Esther	See Remarks	Sale	37,101	$2.36	$87,558	N/A	N/A
2026-02-09	2026-02-06	Keutzer Timothy	COO	Sale	18,652	$2.36	$44,019	N/A	N/A
2026-02-05	2026-02-02	Keutzer Timothy	COO	Award	137,000	$0.00	$0	N/A	N/A
2026-02-05	2026-02-02	Keutzer Timothy	COO	Award	68,000	$0.00	$0	N/A	N/A
2026-02-05	2026-02-04	Keutzer Timothy	COO	Sale	3,471	$2.24	-$7,775	N/A	N/A
2026-02-05	2026-02-03	Keutzer Timothy	COO	Sale	24,224	$2.14	-$51,839	N/A	N/A
2026-02-05	2026-02-02	Keutzer Timothy	COO	Sale	18,891	$2.20	-$41,560	N/A	N/A
2026-02-04	2026-02-02	Rajavelu Esther	See Remarks	Award	498,000	$0.00	$0	N/A	N/A

SPRO

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