Amphastar Pharmaceuticals, Inc.
US ˙ NasdaqGS ˙ US03209R1032

SecurityAMPH / Amphastar Pharmaceuticals, Inc.
InstitutionD. E. Shaw & Co., Inc.
ManagerDE Shaw
Latest Disclosed Ownership665,542 shares
Latest Disclosed Value $ 13,037,968
D. E. Shaw & Co., Inc. reports 19.47% increase in ownership of AMPH / Amphastar Pharmaceuticals, Inc.

On May 15, 2026 - D. E. Shaw & Co., Inc. filed a 13F-HR form disclosing ownership of 665,542 shares of Amphastar Pharmaceuticals, Inc. (US:AMPH) valued at $13,037,968 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 17, 2026 disclosing 557,066 shares of Amphastar Pharmaceuticals, Inc.. This represents a change in shares of 19.47% during the quarter. The current value of the position is $12,059,621 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)
2026-05-15 2026-03-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 665,542 108,476 19.47 13,038 -12.61 0.0078
2026-02-17 2025-12-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 557,066 39,844 7.70 14,918 8.23 0.0082
2025-11-14 2025-09-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 517,222 223,294 75.97 13,784 104.25 0.0078
2025-08-14 2025-06-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 293,928 264,740 907.02 6,749 697.64 0.0048
2025-05-15 2025-03-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 29,188 -89,663 -75.44 846 -80.83 0.0008
2025-02-14 2024-12-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 118,851 95,192 402.35 4,413 284.32 0.0032
2024-11-14 2024-09-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 23,659 23,659 1,148 0.0010
2024-05-15 2024-03-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 0 -77,080 -100.00 0 -100.00
2024-02-14 2023-12-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 77,080 -23,093 -23.05 4,767 3.50 0.0042
2023-11-14 2023-09-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 100,173 -23,426 -18.95 4,607 -35.15 0.0048
2023-08-14 2023-06-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 123,599 -13,714 -9.99 7,103 37.95 0.0073
2023-05-15 2023-03-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 137,313 79,365 136.96 5,149 217.25 0.0055
2023-02-14 2022-12-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 57,948 69 0.12 1,624 -0.18 0.0018
2022-11-14 2022-09-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 57,879 -3,856 -6.25 1,626 -24.30 0.0019
2022-08-15 2022-06-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 61,735 -3,404 -5.23 2,148 -8.13 0.0025
2022-05-16 2022-03-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 65,139 38,370 143.34 2,338 275.28 0.0022
2022-02-14 2021-12-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 26,769 26,769 623 0.0005
2021-11-15 2021-09-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 0 -35,699 -100.00 0 -100.00
2021-08-16 2021-06-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 35,699 17,921 100.80 720 120.86 0.0006
2021-05-17 2021-03-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 17,778 4,891 37.95 326 25.87 0.0003
2021-02-16 2020-12-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 12,887 12,887 259 0.0002
2016-11-14 2016-09-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 0 -14,208 -100.00 0 -100.00
2016-08-15 2016-06-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 14,208 -8,293 -36.86 229 -15.19 0.0004
2016-05-16 2016-03-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 22,501 -78,974 -77.83 270 -81.30 0.0005
2016-02-16 2015-12-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 101,475 84,153 485.82 1,444 614.85 0.0022
2015-11-16 2015-09-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 17,322 -14,110 -44.89 202 -63.47 0.0003
2015-08-14 2015-06-30 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 31,432 -4,470 -12.45 553 2.98 0.0008
2015-05-15 2015-03-31 13F AMPHASTAR PHARMACEUTICALS IN COM 03209R103 35,902 35,902 537 0.0008
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.