Rhythm Pharmaceuticals, Inc.
US ˙ NasdaqGM ˙ US76243J1051

SecurityRYTM / Rhythm Pharmaceuticals, Inc.
InstitutionMorgan Stanley
Latest Disclosed Ownership703,978 shares
Latest Disclosed Value $ 61,225,064
Morgan Stanley reports 8.07% increase in ownership of RYTM / Rhythm Pharmaceuticals, Inc.

On May 15, 2026 - Morgan Stanley filed a 13F-HR form disclosing ownership of 703,978 shares of Rhythm Pharmaceuticals, Inc. (US:RYTM) valued at $61,224,967 USD as of March 31, 2026. The entity filed a previous 13F-HR/A on May 27, 2026 disclosing 651,402 shares of Rhythm Pharmaceuticals, Inc.. This represents a change in shares of 8.07% during the quarter. The current value of the position is $59,633,976 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 RHYTHM PHARMACEUTICALS COM 76243J105 703,978 52,576 8.07 61,225 -12.19 0.0037
2026-05-27 2025-12-31 13F/A-1 RHYTHM PHARMACEUTICALS COM 76243J105 651,402 186,212 40.03 69,726 48.42 0.0042
2026-02-13 2025-12-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 651,402 186,212 69,726 0.0042
2026-05-27 2025-09-30 13F/A-1 RHYTHM PHARMACEUTICALS COM 76243J105 465,190 -59,290 -11.30 46,980 41.75 0.0028
2025-11-14 2025-09-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 465,190 -59,290 46,980 0.0028
2025-08-15 2025-06-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 524,480 20,431 4.05 33,142 24.13 0.0022
2025-05-15 2025-03-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 504,049 -56,038 -10.01 26,699 -14.84 0.0019
2025-05-15 2024-12-31 13F/A-1 RHYTHM PHARMACEUTICALS COM 76243J105 560,087 95,483 20.55 31,354 28.81 0.0022
2025-02-14 2024-12-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 560,087 95,483 31,354 0.0022
2025-05-14 2024-09-30 13F/A-2 RHYTHM PHARMACEUTICALS COM 76243J105 464,604 -11,047 -2.32 24,341 24.63 0.0018
2025-02-14 2024-09-30 13F/A-1 RHYTHM PHARMACEUTICALS COM 76243J105 464,604 -11,047 24,341 0.0018
2024-11-14 2024-09-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 464,604 -11,047 24,341 0.0002
2025-05-14 2024-06-30 13F/A-2 RHYTHM PHARMACEUTICALS COM 76243J105 475,651 292,781 160.10 19,530 146.50 0.0015
2024-10-17 2024-06-30 13F/A-1 RHYTHM PHARMACEUTICALS COM 76243J105 475,651 292,781 19,530 0.0015
2024-08-14 2024-06-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 475,651 292,781 19,530 0.0015
2024-10-17 2024-03-31 13F/A-2 RHYTHM PHARMACEUTICALS COM 76243J105 182,870 -48,786 -21.06 7,924 -25.60 0.0006
2024-08-16 2024-03-31 13F/A-1 RHYTHM PHARMACEUTICALS COM 76243J105 182,870 -48,786 7,924 0.0006
2024-05-15 2024-03-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 182,870 -48,786 7,924 0.0006
2024-08-16 2023-12-31 13F/A-1 RHYTHM PHARMACEUTICALS COM 76243J105 231,656 -204,752 -46.92 10,649 6.45 0.0009
2024-02-13 2023-12-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 231,656 -204,752 10,649 0.0009
2023-11-15 2023-09-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 436,408 333,227 322.95 10,005 488.12 0.0010
2023-08-14 2023-06-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 103,181 -113,440 -52.37 1,701 -55.98 0.0002
2023-05-15 2023-03-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 216,621 -27,064 -11.11 3,865 -45.55 0.0004
2023-02-14 2022-12-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 243,685 13,488 5.86 7,096 25.84 0.0008
2022-11-14 2022-09-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 230,197 -200,550 -46.56 5,639 215.38 0.0008
2022-10-27 2022-06-30 13F/A-1 RHYTHM PHARMACEUTICALS COM 76243J105 430,747 175,255 68.60 1,788 -39.25 0.0002
2022-08-15 2022-06-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 430,747 175,255 1,788 0.0002
2022-10-27 2022-03-31 13F/A-1 RHYTHM PHARMACEUTICALS COM 76243J105 255,492 -12,871 -4.80 2,943 9.90 0.0004
2022-05-13 2022-03-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 255,492 -12,871 2,943 0.0004
2022-02-14 2021-12-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 268,363 62,897 30.61 2,678 -0.22 0.0003
2021-11-15 2021-09-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 205,466 -241,140 -53.99 2,684 -69.30 0.0004
2021-08-23 2021-06-30 13F/A-1 RHYTHM PHARMACEUTICALS COM 76243J105 446,606 345,757 342.85 8,744 307.65 0.0012
2021-08-16 2021-06-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 446,606 345,757 8,744 0.0002
2021-05-17 2021-03-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 100,849 50,643 100.87 2,145 43.67 0.0003
2021-02-16 2020-12-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 50,206 34,527 220.21 1,493 339.12 0.0002
2020-11-13 2020-09-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 15,679 -8,872 -36.14 340 -37.96 0.0001
2020-08-14 2020-06-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 24,551 13,451 121.18 548 224.26 0.0001
2020-05-26 2020-03-31 13F/A-1 RHYTHM PHARMACEUTICALS COM 76243J105 11,100 -47,774 -81.15 169 -87.50 0.0000
2020-05-15 2020-03-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 11,100 -47,774 169 12.9827
2020-02-14 2019-12-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 58,874 46,135 362.16 1,352 393.43 0.0003
2019-11-14 2019-09-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 12,739 10,888 588.22 274 585.00 0.0001
2019-08-14 2019-06-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 1,851 -2,758 -59.84 40 -68.50 0.0000
2019-05-15 2019-03-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 4,609 -21,005 -82.01 127 -81.57 0.0000
2019-02-14 2018-12-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 25,614 -1,038 -3.89 689 -11.33 0.0002
2019-04-23 2018-09-30 13F/A-2 RHYTHM PHARMACEUTICALS COM 76243J105 26,652 -2,994 -10.10 777 -16.18 0.0002
2018-11-20 2018-09-30 13F/A-1 RHYTHM PHARMACEUTICALS COM 76243J105 26,652 0 777 0.0002
2018-11-14 2018-09-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 26,652 -2,994 777
2019-04-23 2018-06-30 13F/A-1 RHYTHM PHARMACEUTICALS COM 76243J105 29,646 12,866 76.67 927 177.54 0.0003
2018-08-14 2018-06-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 29,646 12,866 927
2019-04-23 2018-03-31 13F/A-1 RHYTHM PHARMACEUTICALS COM 76243J105 16,780 -9,867 -37.03 334 -56.90 0.0001
2018-05-14 2018-03-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 16,780 -9,867 334
2019-04-23 2017-12-31 13F/A-1 RHYTHM PHARMACEUTICALS COM 76243J105 26,647 26,647 775 0.0002
2018-02-14 2017-12-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 26,647 775 0.0002
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.