Rhythm Pharmaceuticals, Inc.
| Security | MX:RYTM / Rhythm Pharmaceuticals, Inc. |
| Institution | Primecap Management Co/ca/ |
| Latest Disclosed Ownership | 3,478,669 shares |
| Ownership | 5.21% |
Primecap Management Co/ca/ ownership in RYTM / Rhythm Pharmaceuticals, Inc.
2026-02-12 - Primecap Management Co/ca/ has filed an SCHEDULE 13G/A form with the Securities and Exchange Commission (SEC) disclosing ownership of 3,478,669 shares of Rhythm Pharmaceuticals, Inc. (MX:RYTM). This represents 5.21 percent ownership of the company. In their previous filing dated 2025-11-14 , Primecap Management Co/ca/ had reported owning 4,262,859 shares, indicating a decrease of -18.40 percent.
Institutional Ownership: 13D/G Filings
This table shows a history of the 13D/G filings made by the investor and/or investor group. Note that the share values in this table are not directly comparable to any numbers shown in the 13F table (if any).
| File Date | Effective Date | Form | Prev Shares |
Latest Shares |
ΔShares (Percent) |
Ownership (Percent) |
ΔOwnership (Percent) |
|---|---|---|---|---|---|---|---|
| 2026-02-12 | 2026-02-12 | 4,262,859 | 3,478,669 | -18.40 | 5.21 | -18.85 | |
| 2025-11-14 | 2025-11-14 | 4,878,037 | 4,262,859 | -12.61 | 6.42 | -16.30 | |
| 2025-08-14 | 2025-08-14 | 5,787,322 | 4,878,037 | -15.71 | 7.67 | -16.17 | |
| 2025-05-13 | 2025-05-13 | 6,571,190 | 5,787,322 | -11.93 | 9.15 | -14.41 | |
| 2025-02-13 | 2025-02-13 | 7,216,911 | 6,571,190 | -8.95 | 10.69 | -9.48 | |
| 2024-11-12 | 2024-11-12 | 8,052,648 | 7,216,911 | -10.38 | 11.81 | -13.35 | |
| 2024-02-12 | 2024-02-12 | 6,911,142 | 8,052,648 | 16.52 | 13.63 | 11.08 | |
| 2023-02-09 | 2023-02-09 | 6,256,991 | 6,911,142 | 10.45 | 12.27 | -1.45 | |
| 2022-02-10 | 2022-02-10 | 5,570,691 | 6,256,991 | 12.32 | 12.45 | 11.76 | |
| 2021-03-08 | 2021-03-08 | 4,342,491 | 5,570,691 | 28.28 | 11.14 | 13.44 | |
| 2021-02-12 | 2021-02-12 | 3,542,591 | 4,342,491 | 22.58 | 9.82 | 22.14 | |
| 2020-04-24 | 2020-04-24 | 3,542,591 | 8.04 |
Important Note: One of the primary uses of the 13D/G filings is to evaluate the ability of a firm to control a company (ie, the "beneficial ownership"). To that end, firms are required to report not just direct holdings in companies, but indirect holdings that they control. For investment firms, these indirect holdings can include shares in funds they manage, advisory accounts, and in the case of activist campaigns, pledged votes. Therefore, share counts listed in 13D/G filings can differ significantly than share counts listed in 13F filings.
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) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2026-05-11 | 2026-03-31 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 3,417,509 | -61,160 | -1.76 | 297,221 | -20.18 | 0.2340 | |||||
| 2026-02-11 | 2025-12-31 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 3,478,669 | -784,190 | -18.40 | 372,357 | -13.51 | 0.2819 | |||||
| 2025-11-12 | 2025-09-30 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 4,262,859 | -615,178 | -12.61 | 430,506 | 39.66 | 0.3297 | |||||
| 2025-08-11 | 2025-06-30 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 4,878,037 | -909,285 | -15.71 | 308,243 | 0.55 | 0.2443 | |||||
| 2025-05-09 | 2025-03-31 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 5,787,322 | -783,868 | -11.93 | 306,554 | -16.66 | 0.2534 | |||||
| 2025-02-10 | 2024-12-31 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 6,571,190 | -645,721 | -8.95 | 367,855 | -2.71 | 0.2849 | |||||
| 2024-11-08 | 2024-09-30 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 7,216,911 | -95,480 | -1.31 | 378,094 | 25.93 | 0.2780 | |||||
| 2024-08-09 | 2024-06-30 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 7,312,391 | -435,200 | -5.62 | 300,247 | -10.56 | 0.2174 | |||||
| 2024-05-14 | 2024-03-31 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 7,747,591 | -305,057 | -3.79 | 335,703 | -9.31 | 0.2504 | |||||
| 2024-02-09 | 2023-12-31 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 8,052,648 | -214,773 | -2.60 | 370,180 | 95.31 | 0.2931 | |||||
| 2023-11-13 | 2023-09-30 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 8,267,421 | -31,896 | -0.38 | 189,531 | 38.49 | 0.1600 | |||||
| 2023-08-11 | 2023-06-30 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 8,299,317 | 692,006 | 9.10 | 136,856 | 0.84 | 0.1144 | |||||
| 2023-05-15 | 2023-03-31 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 7,607,311 | 696,169 | 10.07 | 135,714 | -32.57 | 0.1183 | |||||
| 2023-02-13 | 2022-12-31 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 6,911,142 | -115,750 | -1.65 | 201,252 | 16.90 | 0.1842 | |||||
| 2022-11-14 | 2022-09-30 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 7,026,892 | 662,798 | 10.41 | 172,159 | 551.85 | 0.1666 | |||||
| 2022-08-11 | 2022-06-30 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 6,364,094 | 72,103 | 1.15 | 26,411 | -63.56 | 0.0236 | |||||
| 2022-05-11 | 2022-03-31 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 6,291,991 | 35,000 | 0.56 | 72,484 | 16.08 | 0.0547 | |||||
| 2022-02-11 | 2021-12-31 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 6,256,991 | 75,900 | 1.23 | 62,445 | -22.64 | 0.0432 | |||||
| 2021-11-12 | 2021-09-30 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 6,181,091 | 27,400 | 0.45 | 80,725 | -33.00 | 0.0570 | |||||
| 2021-08-10 | 2021-06-30 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 6,153,691 | 148,098 | 2.47 | 120,489 | -5.68 | 0.0810 | |||||
| 2021-05-14 | 2021-03-31 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 6,005,593 | 1,663,102 | 38.30 | 127,739 | -1.06 | 0.0891 | |||||
| 2021-02-08 | 2020-12-31 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 4,342,491 | 767,800 | 21.48 | 129,102 | 66.66 | 0.0960 | |||||
| 2020-11-13 | 2020-09-30 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 3,574,691 | 29,900 | 0.84 | 77,464 | -2.01 | 0.0639 | |||||
| 2020-08-13 | 2020-06-30 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 3,544,791 | 2,200 | 0.06 | 79,049 | 46.61 | 0.0678 | |||||
| 2020-05-14 | 2020-03-31 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 3,542,591 | 1,448,900 | 69.20 | 53,918 | 12.16 | 0.0529 | |||||
| 2020-02-14 | 2019-12-31 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 2,093,691 | 1,846,714 | 747.73 | 48,071 | 801.56 | 0.0349 | |||||
| 2019-11-13 | 2019-09-30 | 13F | RHYTHM PHARMACEUTICALS | COM | 76243J105 | 246,977 | 246,977 | 5,332 | 0.0043 |
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.
