QUANTERIX CORP QTRX

* Summed across managers. Shares that two managers' reports both contain – a subsidiary's holdings that its parent's report includes too, or a sub-adviser's in its client's – are counted once ($2.7k this quarter). Holder counts are more reliable. Shares outstanding: 47.1m as of 2026-04-30, from the company's own SEC filing; the percentage can still exceed 100%: lent-out shares are counted by the lender and the buyer, and some reports overlap without saying so. Implied quarter-end price ≈ $3.52. Options: 3 managers hold calls ($168.3k notional), 2 hold puts ($7.0k).

Trends to Q1 2026

Options at notional value: the value of the shares the contracts control, as filers report them, not what the options cost. Not included in the holders, shares or buying above.

Major shareholders (over 5%)

Anyone who owns more than 5% of a class of the company's shares has to say so: on Schedule 13D if they may try to influence or control the company, on 13G if they're a passive investor, and update it as the stake changes. Each holder's latest filing, from 19 Dec 2024 on; percentages are of the share class, as the holder worked them out.

Fell to 5% or below in the last year: Portolan Capital Management, LLC (4.0%, 2026-08-14), VANGUARD GROUP INC (0.0%, 2026-03-27)

Insider purchases and sales in Q1 2026

Shares bought or sold by the company's own officers, directors and 10% owners, in the open market or privately, as they reported to the SEC on Form 4 (due within two business days of the trade). Grants, option exercises, shares withheld for tax and gifts aren't included.

None reported in Q1 2026.

Holders, Q1 2026