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Which funds own AMPH

Amphastar Pharmaceuticals Inc in the Q2 2026 filings. At least 1 of the 91 current managers on file reported a position, worth $37m between them. It is among the largest positions of fewer than a fifth of the current managers on file. Buying and selling roughly cancelled this quarter, which is what a name looks like when the argument is still live.

Managers holding: 1; at least, of 91 current
Combined value: $37m; as reported
Opened: 0; new this quarter
Added to: 1; already held
Trimmed or sold out: 0; 0 sold out entirely

Only each manager’s largest 200 positions are listed here, so a smaller holder may be missing.

Managers reporting a position

Largest first. Weight is the share of that manager’s whole reported book, which is the number worth quoting: $400m is a rounding error in one book and a defining bet in another.

Manager	Value	Weight	Shares	Change on the quarter	Action
Oaktree Capital Management LP Activist · $7.2bn book	$37m	0.5%	40,880,000	+$2.7m+2,844,000	Added

Ownership through time

At least 1 of the 95 managers whose filings are on file listed AMPH in Q1 2026, against 1 in Q4 2015. The same number as in Q4 2025: 1 started a position; 1 no longer listed it among the positions read, which can mean a holding below the listed range, a filing that reported no holdings, or a filing not yet made.

Each manager’s largest 500 positions a quarter are read, so a small holding in a very large book can be missing, and a manager is counted as leaving only where its own filing shows it.

Managers on file listing it

Their combined reported value

Between the quarter ends of Q4 2025 and Q1 2026. Each change in shares is valued at the Q1 2026 price, so the price’s own move is left out; a 13F shows the two quarter ends, not when in between anything was bought or sold.

Started in Q1 2026

PDT Partners LLC$224k

Largest increases, by shares

PDT Partners LLCnew: 11,441 shares+$224k

Largest decreases, by shares

No manager on file sold part of it.

Left it

No manager on file is shown leaving it.

Manager	First listed	Largest	Q1 2026
PDT Partners LLC	Q3 2021	$3.9m	$224k
Neuberger Berman Group LLC	Q2 2023	$105m	last listed Q4 2024
Renaissance Technologies LLC	Q3 2023	$40m	last listed Q4 2023
Marshall Wace LLP	Q3 2019	$33m	last listed Q4 2025
Acadian Asset Management LLC	Q4 2015	$30m	last listed Q2 2022
Voloridge Investment Management LLC	Q2 2023	$17m	last listed Q1 2024
Arrowstreet Capital LP	Q1 2022	$14m	last listed Q2 2022
ExodusPoint Capital Management LP	Q1 2025	$10.0m	last listed Q1 2025
Winton Group Ltd	Q2 2020	$4.5m	last listed Q3 2024
Schonfeld Strategic Advisors LLC	Q4 2016	$1.4m	last listed Q4 2019

What AMPH is worth

Knowing who owns it is half the question. The other half is what it is worth against the companies it trades beside, which is the one an interviewer will follow up with.

Build the comp set around AMPH →

How much of the picture this is

A Form 13F reports US-listed long equity and nothing else: no shorts, no bonds, no cash and no non-US listings. It arrives forty-five days after the quarter ends, so a manager who sold in July still shows the position in a filing published in August. This page reads the managers on file here rather than every filer in the market, and each manager’s largest positions rather than the whole table, so a small position in a very large book may not appear. Say “their last filing showed” rather than “they own”, and the distinction will do you credit.

What to do with a name the funds are buying

Knowing who owns something is the start of a pitch, not the pitch. The next questions are what it is worth and why they were buying.

Comps ExplorerValue it against the peers it trades beside Every managerRead any of these books in full Deal tapeWhat buyers paid for whole companies, not slices Hedge fund interviewsHow the room runs, and the stock pitch it wants

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Illustrative figures. Default values are plausible starting points chosen so a model has somewhere to begin. They are not data, not a view on any company, and not calibrated to anything. Outputs move with whatever you type in.

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The holdings, every quarter, and the week between

One email a week on what moved in the market and what it means for the people interviewing into it, with the 13F changes the quarter they are filed.

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