Rhythm Pharmaceuticals, Inc.
US ˙ NasdaqGM ˙ US76243J1051

SecurityRYTM / Rhythm Pharmaceuticals, Inc.
InstitutionCitigroup Inc
Latest Disclosed Ownership12,336 shares
Latest Disclosed Value $ 1,072,862
Citigroup Inc ownership in RYTM / Rhythm Pharmaceuticals, Inc.

On May 11, 2026 - Citigroup Inc filed a 13F-HR form disclosing ownership of 12,336 shares of Rhythm Pharmaceuticals, Inc. (US:RYTM) valued at $1,072,862 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 13, 2026 disclosing 12,720 shares of Rhythm Pharmaceuticals, Inc.. This represents a change in shares of -3.02% during the quarter. The current value of the position is $1,080,757 USD.

Citigroup Inc 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 0 of underlying shares valued at $0 USD and put options representing 0 of underlying shares valued at $0 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.

Upgrade to unlock premium data and export to Excel .

Institutional Put/Call Ratios
(Premium Subscription Required)

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.

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)
2026-05-11 2026-03-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 12,336 -384 -3.02 1,073 -21.23 0.0005
2026-02-13 2025-12-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 12,720 -360 -2.75 1,362 3.11 0.0006
2025-11-10 2025-09-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 13,080 -21,244 -61.89 1,321 -39.11 0.0006
2025-08-11 2025-06-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 34,324 -51,882 -60.18 2,169 -52.52 0.0011
2025-05-12 2025-03-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 86,206 16,429 23.55 4,566 16.90 0.0023
2025-02-12 2024-12-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 69,777 28,580 69.37 3,906 81.00 0.0023
2024-11-12 2024-09-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 41,197 21,205 106.07 2,158 163.17 0.0013
2024-08-12 2024-06-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 19,992 -170,528 -89.51 821 -90.07 0.0005
2024-05-10 2024-03-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 190,520 136,220 250.87 8,255 230.73 0.0054
2024-02-09 2023-12-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 54,300 -14,844 -21.47 2,496 57.48 0.0018
2023-12-06 2023-09-30 13F/A-1 RHYTHM PHARMACEUTICALS COM 76243J105 69,144 -18,921 -21.49 1,585 9.16 0.0012
2023-11-09 2023-09-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 69,144 -18,921 1,585 0.0012
2023-08-10 2023-06-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 88,065 -251,890 -74.10 1,452 -76.06 0.0010
2023-05-11 2023-03-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 339,955 64,394 23.37 6,065 -24.43 0.0043
2023-02-09 2022-12-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 275,561 3,374 1.24 8,024 20.32 0.0064
2022-11-10 2022-09-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 272,187 269,921 11,911.78 6,669 74,000.00 0.0048
2022-08-10 2022-06-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 2,266 -2,266 -50.00 9 -82.69 0.0000
2022-05-12 2022-03-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 4,532 -91,485 -95.28 52 -94.57 0.0000
2022-02-10 2021-12-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 96,017 36,291 60.76 958 22.82 0.0005
2021-11-10 2021-09-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 59,726 -72,173 -54.72 780 -69.80 0.0005
2021-08-10 2021-06-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 131,899 -20,529 -13.47 2,583 -20.33 0.0016
2021-05-13 2021-03-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 152,428 143,603 1,627.23 3,242 1,137.40 0.0021
2021-02-11 2020-12-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 8,825 1,429 19.32 262 63.75 0.0002
2020-11-12 2020-09-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 7,396 -15,938 -68.30 160 -69.23 0.0001
2020-08-12 2020-06-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 23,334 3,299 16.47 520 70.49 0.0004
2020-05-12 2020-03-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 20,035 5,585 38.65 305 -8.13 0.0003
2020-02-12 2019-12-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 14,450 -1,587 -9.90 332 -4.32 0.0002
2019-11-08 2019-09-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 16,037 -8,809 -35.45 347 -36.56 0.0003
2019-08-12 2019-06-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 24,846 21,550 653.82 547 501.10 0.0004
2019-05-13 2019-03-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 3,296 -64,607 -95.15 91 -95.01 0.0001
2019-02-12 2018-12-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 67,903 40,469 147.51 1,825 127.84 0.0018
2018-11-13 2018-09-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 27,434 25,678 1,462.30 801 1,356.36 0.0007
2018-08-10 2018-06-30 13F RHYTHM PHARMACEUTICALS COM 76243J105 1,756 715 68.68 55 161.90 0.0001
2018-05-11 2018-03-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 1,041 113 12.18 21 -22.22 0.0000
2018-02-12 2017-12-31 13F RHYTHM PHARMACEUTICALS COM 76243J105 928 928 27 0.0000
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
(%)
2023-02-09 2022-12-31 13F RHYTHM PHARMACEUTICALS COM Call 0 -100.00 0 -100.00 n/a n/a n/a
2022-11-10 2022-09-30 13F RHYTHM PHARMACEUTICALS COM Call 150,000 3,675 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
(%)
2023-08-10 2023-06-30 13F RHYTHM PHARMACEUTICALS COM Put 0 -100.00 0 -100.00 n/a n/a n/a
2023-05-11 2023-03-31 13F RHYTHM PHARMACEUTICALS COM Put 100,000 11.11 1,784 -31.91 n/a n/a n/a
2023-02-09 2022-12-31 13F RHYTHM PHARMACEUTICALS COM Put 90,000 0.00 2,621 18.82 n/a n/a n/a
2022-11-10 2022-09-30 13F RHYTHM PHARMACEUTICALS COM Put 90,000 2,205 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.