리듬 파마슈티컬스, Inc.
MX ˙ BMV ˙ US76243J1051
SecurityMX:RYTM / Rhythm Pharmaceuticals, Inc.
InstitutionCitadel Advisors Llc
ManagerKen Griffin
Latest Disclosed Ownership1,418,619 shares
Latest Disclosed Value $ 123,377,295
Citadel Advisors Llc ownership in RYTM / Rhythm Pharmaceuticals, Inc.

On May 15, 2026 - Citadel Advisors Llc filed a 13F-HR form disclosing ownership of 1,418,619 shares of Rhythm Pharmaceuticals, Inc. (MX:RYTM) valued at $123,377,295 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 17, 2026 disclosing 153,322 shares of Rhythm Pharmaceuticals, Inc.. This represents a change in shares of 825.25% during the quarter.

Citadel Advisors Llc has a history of taking positions in derivatives of the underlying security (RYTM) in the form of stock options. The firm currently holds call options representing 30,500 of underlying shares valued at $2,652,585 USD and put options representing 3,900 of underlying shares valued at $339,183 USD .

Note: prior versions of this page mistakenly stated that the share values represented the number of options, not the number of underlying shares. For more information on the data backing these reports, please see the SEC document Frequently Asked Questions About Form 13F.

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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Institutional Put/Call Ratios
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In addition to reporting standard equity and debt issues, institutions with more than 100MM assets under management must also disclose their put and call option holdings. Since put options generally indicate negative sentiment, and call options indicate positive sentiment, we can get a sense of the overall institutional sentiment by plotting the ratio of puts to calls. The chart to the right plots the historical put/call ratio for this instrument.

Using Put/Call Ratio as an indicator of investor sentiment overcomes one of the key deficiencies of using total institutional ownership, which is that a significant amount of assets under management are invested passively to track indices. Passively-managed funds do not typically buy options, so the put/call ratio indicator more closely tracks the sentiment of actively-managed funds.

MX:RYTM / Rhythm Pharmaceuticals, Inc. Historical Put/Call Ratio
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 1,418,619 1,265,297 825.25 123,377 651.79 0.0176
2026-02-17 2025-12-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 153,322 20,696 15.60 16,412 22.53 0.0025
2025-11-14 2025-09-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 132,626 132,626 13,394 0.0020
2025-08-14 2025-06-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 0 -70,068 -100.00 0 -100.00
2025-05-15 2025-03-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 70,068 29,649 73.35 3,712 64.06 0.0007
2025-02-14 2024-12-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 40,419 -62,359 -60.67 2,263 -57.99 0.0004
2024-11-14 2024-09-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 102,778 102,778 5,385 0.0010
2024-08-14 2024-06-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 0 -4,098 -100.00 0 -100.00
2024-05-15 2024-03-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 4,098 -109,817 -96.40 178 -96.62 0.0000
2024-02-14 2023-12-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 113,915 -141,518 -55.40 5,237 -10.57 0.0010
2023-11-14 2023-09-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 255,433 65,901 34.77 5,856 87.36 0.0013
2023-08-14 2023-06-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 189,532 -175,508 -48.08 3,125 -52.01 0.0006
2023-05-15 2023-03-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 365,040 294,342 416.34 6,512 216.42 0.0014
2023-02-14 2022-12-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 70,698 14,863 26.62 2,059 50.44 0.0005
2022-11-14 2022-09-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 55,835 -112,223 -66.78 1,368 95.99 0.0003
2022-08-15 2022-06-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 168,058 -81,866 -32.76 698 -75.76 0.0002
2022-05-16 2022-03-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 249,924 249,924 2,879 0.0006
2022-03-11 2021-09-30 13F/A-1 RHYTHM PHARMACEUTICALS COM 76243J105 0 -32,574 -100.00 0 -100.00
2021-11-15 2021-09-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 0 -32,574 0
2021-08-16 2021-06-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 32,574 -86,134 -72.56 638 -74.73 0.0001
2021-05-21 2021-03-31 13F/A-1 RHYTHM PHARMACEUTICALS COM 76243J105 118,708 40,662 52.10 2,525 8.84 0.0006
2021-05-17 2021-03-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 118,708 40,662 2,525 0.0006
2021-02-16 2020-12-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 78,046 49,648 174.83 2,320 277.24 0.0006
2020-11-16 2020-09-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 28,398 28,398 615 0.0002
2020-08-14 2020-06-30 13F RHYTHM PHARMACEUTICALS Cmn 76243J105 0 -20,758 -100.00 0 -100.00
2020-05-15 2020-03-31 13F RHYTHM PHARMACEUTICALS Cmn 76243J105 20,758 20,758 316 0.0001
2019-05-15 2019-03-31 13F RHYTHM PHARMACEUTICALS Cmn 76243J105 0 -14,521 -100.00 0 -100.00
2019-02-14 2018-12-31 13F RHYTHM PHARMACEUTICALS Cmn 76243J105 14,521 671 4.84 391 -3.22 0.0002
2018-11-13 2018-09-30 13F RHYTHM PHARMACEUTICALS Cmn 76243J105 13,850 -36,365 -72.42 404 -74.27 0.0002
2018-08-14 2018-06-30 13F/A-1 RHYTHM PHARMACEUTICALS Cmn 76243J105 50,215 -4,084 -7.52 1,570 45.24 0.0008
2018-08-10 2018-06-30 13F RHYTHM PHARMACEUTICALS Cmn 76243J105 50,215 -4,084 1,570
2018-05-14 2018-03-31 13F/A-1 RHYTHM PHARMACEUTICALS Cmn 76243J105 54,299 -147,529 -73.10 1,081 -81.57 0.0006
2018-05-11 2018-03-31 13F RHYTHM PHARMACEUTICALS Cmn 76243J105 54,299 -147,529 1,081
2018-02-09 2017-12-31 13F RHYTHM PHARMACEUTICALS Cmn 76243J105 201,828 201,828 5,866 0.0036
Disclosed Call Options
File
Date
Effective
Date
Form Security Class ID Opt Avg Share
Price
Shares ΔShares
(%)
Value
(x1000)
ΔValue
(%)
Prior Allocation
(%)
Allocation
(%)
ΔAllocation
(%)
Cost Basis
(x1000)
Profit
(x1000)
Return
(%)
2026-05-15 2026-03-31 13F RHYTHM PHARMACEUTICALS COM Call 30,500 -19.53 2,653 -34.62 n/a n/a n/a
2026-02-17 2025-12-31 13F RHYTHM PHARMACEUTICALS COM Call 37,900 -25.98 4,057 -21.55 n/a n/a n/a
2025-11-14 2025-09-30 13F RHYTHM PHARMACEUTICALS COM Call 51,200 194.25 5,171 370.43 n/a n/a n/a
2025-08-14 2025-06-30 13F RHYTHM PHARMACEUTICALS COM Call 17,400 -51.40 1,100 -42.04 n/a n/a n/a
2025-05-15 2025-03-31 13F RHYTHM PHARMACEUTICALS COM Call 35,800 -72.52 1,896 -74.01 n/a n/a n/a
2025-02-14 2024-12-31 13F RHYTHM PHARMACEUTICALS COM Call 130,300 177.23 7,294 196.26 n/a n/a n/a
2024-11-14 2024-09-30 13F RHYTHM PHARMACEUTICALS COM Call 47,000 8.05 2,462 37.85 n/a n/a n/a
2024-08-14 2024-06-30 13F RHYTHM PHARMACEUTICALS COM Call 43,500 -34.49 1,786 -37.92 n/a n/a n/a
2024-05-15 2024-03-31 13F RHYTHM PHARMACEUTICALS COM Call 66,400 -10.15 2,877 -15.31 n/a n/a n/a
2024-02-14 2023-12-31 13F RHYTHM PHARMACEUTICALS COM Call 73,900 303.83 3,397 710.74 n/a n/a n/a
2023-11-14 2023-09-30 13F RHYTHM PHARMACEUTICALS COM Call 18,300 16.56 420 62.40 n/a n/a n/a
2023-08-14 2023-06-30 13F RHYTHM PHARMACEUTICALS COM Call 15,700 -51.09 259 -54.90 n/a n/a n/a
2023-05-15 2023-03-31 13F RHYTHM PHARMACEUTICALS COM Call 32,100 -28.98 573 -56.53 n/a n/a n/a
2023-02-14 2022-12-31 13F RHYTHM PHARMACEUTICALS COM Call 45,200 -78.14 1,316 -74.03 n/a n/a n/a
2022-11-14 2022-09-30 13F RHYTHM PHARMACEUTICALS COM Call 206,800 -4.57 5,067 463.63 n/a n/a n/a
2022-08-15 2022-06-30 13F RHYTHM PHARMACEUTICALS COM Call 216,700 10.96 899 -60.04 n/a n/a n/a
2022-05-16 2022-03-31 13F RHYTHM PHARMACEUTICALS COM Call 195,300 1,643.75 2,250 1,908.93 n/a n/a n/a
2022-02-14 2021-12-31 13F RHYTHM PHARMACEUTICALS COM Call 11,200 -11.81 112 -32.53 n/a n/a n/a
2021-11-15 2021-09-30 13F RHYTHM PHARMACEUTICALS Cmn Call 12,700 166 n/a n/a n/a
2021-08-16 2021-06-30 13F RHYTHM PHARMACEUTICALS COM Call 0 -100.00 0 -100.00 n/a n/a n/a
2021-05-21 2021-03-31 13F/A RHYTHM PHARMACEUTICALS COM Call 14,200 -23.66 302 -45.39 n/a n/a n/a
2021-05-17 2021-03-31 13F RHYTHM PHARMACEUTICALS COM Call 14,200 302 n/a n/a n/a
2021-02-16 2020-12-31 13F RHYTHM PHARMACEUTICALS COM Call 18,600 6.29 553 45.91 n/a n/a n/a
2020-11-16 2020-09-30 13F RHYTHM PHARMACEUTICALS COM Call 17,500 379 n/a n/a n/a
Disclosed Put Options
File
Date
Effective
Date
Form Security Class ID Opt Avg Share Price Shares ΔShares
(%)
Value
(x1000)
ΔValue
(%)
Prior Allocation
(%)
Allocation
(%)
ΔAllocation
(%)
Cost Basis
(x1000)
Profit
(x1000)
Return
(%)
2026-05-15 2026-03-31 13F RHYTHM PHARMACEUTICALS COM Put 3,900 339 n/a n/a n/a
2026-02-17 2025-12-31 13F RHYTHM PHARMACEUTICALS COM Put 0 -100.00 0 -100.00 n/a n/a n/a
2025-11-14 2025-09-30 13F RHYTHM PHARMACEUTICALS COM Put 3,000 -89.40 303 -83.11 n/a n/a n/a
2025-08-14 2025-06-30 13F RHYTHM PHARMACEUTICALS COM Put 28,300 1,032.00 1,788 1,254.55 n/a n/a n/a
2025-05-15 2025-03-31 13F RHYTHM PHARMACEUTICALS COM Put 2,500 -76.42 132 -77.74 n/a n/a n/a
2025-02-14 2024-12-31 13F RHYTHM PHARMACEUTICALS COM Put 10,600 -15.20 593 -9.33 n/a n/a n/a
2024-11-14 2024-09-30 13F RHYTHM PHARMACEUTICALS COM Put 12,500 -30.94 655 -11.98 n/a n/a n/a
2024-08-14 2024-06-30 13F RHYTHM PHARMACEUTICALS COM Put 18,100 -16.20 743 -20.53 n/a n/a n/a
2024-05-15 2024-03-31 13F RHYTHM PHARMACEUTICALS COM Put 21,600 61.19 936 52.03 n/a n/a n/a
2024-02-14 2023-12-31 13F RHYTHM PHARMACEUTICALS COM Put 13,400 119.67 616 342.45 n/a n/a n/a
2023-11-14 2023-09-30 13F RHYTHM PHARMACEUTICALS COM Put 6,100 -32.97 140 -7.33 n/a n/a n/a
2023-08-14 2023-06-30 13F RHYTHM PHARMACEUTICALS COM Put 9,100 -56.25 150 -59.57 n/a n/a n/a
2023-05-15 2023-03-31 13F RHYTHM PHARMACEUTICALS COM Put 20,800 433.33 371 228.32 n/a n/a n/a
2023-02-14 2022-12-31 13F RHYTHM PHARMACEUTICALS COM Put 3,900 114 n/a n/a n/a
2022-03-11 2021-09-30 13F/A RHYTHM PHARMACEUTICALS COM Put 0 -100.00 0 -100.00 n/a n/a n/a
2021-11-15 2021-09-30 13F RHYTHM PHARMACEUTICALS COM Put 0 0 n/a n/a n/a
2021-08-16 2021-06-30 13F RHYTHM PHARMACEUTICALS COM Put 12,100 -19.33 237 -25.71 n/a n/a n/a
2021-05-21 2021-03-31 13F/A RHYTHM PHARMACEUTICALS COM Put 15,000 -10.71 319 -36.07 n/a n/a n/a
2021-05-17 2021-03-31 13F RHYTHM PHARMACEUTICALS COM Put 15,000 319 n/a n/a n/a
2021-02-16 2020-12-31 13F RHYTHM PHARMACEUTICALS COM Put 16,800 -33.60 499 -8.94 n/a n/a n/a
2020-11-16 2020-09-30 13F RHYTHM PHARMACEUTICALS COM Put 25,300 548 n/a n/a n/a
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.