Mesirow Institutional Investment Management, Inc. reported AMPHASTAR PHARMACEUTICALS IN (AMPH) in 10 quarterly 13F filings from 2024 Q1 through 2024 Q4. Peak portfolio weight reached 1.53% in 2024 Q3. The latest visible filing shows AMPH at 1.09% of the fund.
This page tracks quarterly shares, estimated market value, portfolio weight, filing dates, and disclosure-aligned stock prices directly from SEC EDGAR 13F filings. Older history is available after unlock; the visible window still shows the most recent pattern.
This page is designed to answer the real investor question behind a 13F filing: how meaningful was Mesirow Institutional Investment Management, Inc.'s position in AMPHASTAR PHARMACEUTICALS IN, and how did that conviction change over time? You can read the holding window, peak weight, latest reported size, disclosure timing, and quarter-by-quarter changes without piecing the story together from raw SEC rows.
AMPH was reported at 1.09% of portfolio in the most recent visible filing.
Peak weight helps separate a token disclosure from a real conviction holding the fund genuinely cared about.
Longer holding windows often tell a very different story from short-lived tactical trades or one-quarter experiments.
Knowing that a fund owned a stock is useful. Knowing whether it was a 0.20% placeholder or a true high-conviction position is where the signal actually starts.
As of 2026 Q2 — sorted by position size
These are the practical questions this page is built to answer before you even open the full history table.
Mesirow Institutional Investment Management, Inc. reported AMPH across 4 quarterly 13F filings, from 2024 Q1 through 2024 Q4.
The largest reported portfolio weight for AMPH was 1.53% in 2024 Q3.
The most recent filing on this page is 2024 Q4, when Mesirow Institutional Investment Management, Inc. reported 380,389 shares, equal to 1.09% of portfolio, with an estimated market value of $14.1M.
The chart compares Mesirow Institutional Investment Management, Inc.'s quarterly AMPH portfolio weight with the stock's indexed share price, so you can see whether the fund was building, trimming, or holding the position as price moved.
Based on 13F filing dates vs. subsequent AMPH price moves, Mesirow Institutional Investment Management, Inc. correctly timed 4 out of 9 reported position changes (44%). The annualised alpha on AMPH relative to SPY over the holding period was -15.1%.