Amphastar Pharmaceuticals, Inc.
US ˙ NasdaqGS ˙ US03209R1032

SecurityAMPH / Amphastar Pharmaceuticals, Inc.
InstitutionDimensional Fund Advisors Lp
Latest Disclosed Ownership2,027,947 shares
Latest Disclosed Value $ 39,726,234
Dimensional Fund Advisors Lp reports 12.68% increase in ownership of AMPH / Amphastar Pharmaceuticals, Inc.

On May 7, 2026 - Dimensional Fund Advisors Lp filed a 13F-HR form disclosing ownership of 2,027,947 shares of Amphastar Pharmaceuticals, Inc. (US:AMPH) valued at $39,727,482 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 12, 2026 disclosing 1,799,685 shares of Amphastar Pharmaceuticals, Inc.. This represents a change in shares of 12.68% during the quarter. The current value of the position is $36,746,400 USD.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

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Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date		 Effective
Date		Form Security Class ID Avg Price
Paid (Est)		 Reported
Shares		 ΔShares ΔShares
(%)		 Reported
Value
(x1000)		 ΔValue
(%)		 Alloc
(%)		 ΔAlloc ΔAlloc (%) Cost Basis
(x1000)		 Unrealized
Gain/Loss
(x1000)
2026-05-07 2026-03-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 2,027,947 228,262 12.68 39,726 -17.57 0.0018
2026-02-12 2025-12-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,799,685 44,020 2.51 48,196 3.01 0.0101
2025-11-12 2025-09-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,755,665 128,781 7.92 46,789 25.26 0.0100
2025-08-12 2025-06-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,626,884 270,524 19.94 37,354 -5.00 0.0086
2025-05-13 2025-03-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,356,360 157,770 13.16 39,319 -11.65 0.0098
2025-02-13 2024-12-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,198,590 105,288 9.63 44,503 -16.12 0.0107
2024-11-07 2024-09-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,093,302 23,027 2.15 53,057 23.93 0.0129
2024-08-09 2024-06-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,070,275 -113,555 -9.59 42,811 -17.64 0.0112
2024-05-10 2024-03-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,183,830 -155,312 -11.60 51,982 -37.24 0.0141
2024-02-07 2023-12-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,339,142 -548,596 -29.06 82,827 -4.60 0.0242
2023-11-09 2023-09-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,887,738 -42,877 -2.22 86,821 -21.75 0.0285
2023-08-09 2023-06-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,930,615 13,044 0.68 110,948 54.29 0.0354
2023-05-12 2023-03-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,917,571 51,027 2.73 71,909 138,186.54 0.0242
2023-02-09 2022-12-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,866,544 27,410 1.49 52 -99.90 0.0155
2022-11-10 2022-09-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,839,134 13,091 0.72 51,683 -18.64 0.0198
2022-08-12 2022-06-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,826,043 29,774 1.66 63,526 -1.49 0.0228
2022-05-13 2022-03-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,796,269 25,418 1.44 64,488 56.36 0.0199
2022-02-09 2021-12-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,770,851 25,936 1.49 41,243 24.33 0.0125
2021-11-12 2021-09-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,744,915 49,022 2.89 33,171 -2.98 0.0107
2021-08-12 2021-06-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,695,893 6,804 0.40 34,189 10.25 0.0108
2021-05-14 2021-03-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,689,089 -118,296 -6.55 31,011 -14.68 0.0103
2021-03-08 2020-12-31 13F/A-2 AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,807,385 -18,608 -1.02 36,346 6.16 0.0131
2021-02-11 2020-12-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,807,385 -18,608 36,346 13,126.2433
2020-11-12 2020-09-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,825,993 -16,829 -0.91 34,237 -17.28 0.0145
2020-08-13 2020-06-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,842,822 -4,531 -0.25 41,389 50.97 0.0182
2020-05-14 2020-03-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,847,353 38,675 2.14 27,415 -21.42 0.0143
2020-02-14 2019-12-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,808,678 5,645 0.31 34,889 -2.42 0.0127
2019-11-12 2019-09-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,803,033 -14,620 -0.80 35,755 -6.82 0.0139
2019-08-13 2019-06-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,817,653 -106,596 -5.54 38,370 -2.40 0.0149
2019-08-12 2019-03-31 13F/A-2 AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,924,249 23,018 1.21 39,313 3.91 0.0157
2019-05-10 2019-03-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,924,249 23,018 39,313
2019-02-26 2018-12-31 13F/A-1 AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,901,231 -8,652 -0.45 37,835 2.96 0.0171
2019-02-13 2018-12-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,901,231 -8,652 37,835
2018-11-13 2018-09-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,909,883 140,350 7.93 36,746 36.08 0.0140
2018-08-10 2018-06-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,769,533 84,085 4.99 27,004 -14.55 0.0108
2018-05-11 2018-03-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,685,448 53,646 3.29 31,602 0.65 0.0132
2018-02-12 2017-12-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,631,802 73,689 4.73 31,397 12.76 0.0130
2017-11-13 2017-09-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,558,113 226,271 16.99 27,844 17.06 0.0122
2017-08-11 2017-06-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,331,842 270,654 25.50 23,786 54.57 0.0110
2017-05-12 2017-03-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 1,061,188 260,288 32.50 15,388 4.30 0.0074
2017-02-09 2016-12-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 800,900 324,043 67.95 14,753 63.09 0.0074
2016-11-10 2016-09-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 476,857 115,847 32.09 9,046 55.46 0.0049
2016-08-09 2016-06-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 361,010 103,556 40.22 5,819 88.38 0.0033
2016-05-13 2016-03-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 257,454 189,266 277.56 3,089 218.45 0.0018
2016-02-10 2015-12-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 68,188 68,188 970 0.0006
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.