Rhythm Pharmaceuticals, Inc.
MX ˙ BMV ˙ US76243J1051
SecurityMX:RYTM / Rhythm Pharmaceuticals, Inc.
InstitutionBnp Paribas Arbitrage, Sa
Latest Disclosed Ownership247,876 shares
Latest Disclosed Value $ 21,557,776
Bnp Paribas Arbitrage, Sa ownership in RYTM / Rhythm Pharmaceuticals, Inc.

On May 12, 2026 - Bnp Paribas Arbitrage, Sa filed a 13F-HR form disclosing ownership of 247,876 shares of Rhythm Pharmaceuticals, Inc. (MX:RYTM) valued at $21,557,776 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 10, 2026 disclosing 164,563 shares of Rhythm Pharmaceuticals, Inc.. This represents a change in shares of 50.63% during the quarter.

Bnp Paribas Arbitrage, Sa 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 .

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)
2026-05-12 2026-03-31 13F Rhythm Pharmaceuticals Equity 76243J105 247,876 83,313 50.63 21,558 22.39 0.0105
2026-02-10 2025-12-31 13F Rhythm Pharmaceuticals Equity 76243J105 164,563 -59,118 -26.43 17,615 -22.02 0.0080
2025-11-13 2025-09-30 13F Rhythm Pharmaceuticals Equity 76243J105 223,681 121,442 118.78 22,590 249.67 0.0121
2025-08-14 2025-06-30 13F Rhythm Pharmaceuticals Equity 76243J105 102,239 16,173 18.79 6,460 41.73 0.0037
2025-05-14 2025-03-31 13F Rhythm Pharmaceuticals Equity 76243J105 86,066 817 0.96 4,559 -4.48 0.0027
2025-02-14 2024-12-31 13F Rhythm Pharmaceuticals Equity 76243J105 85,249 70,824 490.98 4,772 532.05 0.0027
2024-11-13 2024-09-30 13F Rhythm Pharmaceuticals Equity 76243J105 14,425 10,882 307.14 756 420.69 0.0005
2024-08-13 2024-06-30 13F Rhythm Pharmaceuticals Equity 76243J105 3,543 -52,466 -93.67 145 -94.02 0.0001
2024-05-01 2024-03-31 13F Rhythm Pharmaceuticals Equity 76243J105 56,009 -7,076 -11.22 2,427 -16.34 0.0021
2024-02-14 2023-12-31 13F/A-2 Rhythm Pharmaceuticals Equity 76243J105 63,085 7,842 14.20 2,900 129.07 0.0033
2024-02-07 2023-12-31 13F/A-1 Rhythm Pharmaceuticals Equity 76243J105 63,085 7,842 2,900 0.0004
2024-02-07 2023-12-31 13F Rhythm Pharmaceuticals Equity 76243J105 63,085 2,900
2023-11-14 2023-09-30 13F Rhythm Pharmaceuticals Equity 76243J105 55,243 1,888 3.54 1,266 44.03 0.0016
2023-08-09 2023-06-30 13F Rhythm Pharmaceuticals Equity 76243J105 53,355 -33,687 -38.70 880 -43.36 0.0011
2023-05-12 2023-03-31 13F RHYTHM PHARMACEUTICALS EQUITY 76243J105 87,042 34,158 64.59 1,553 0.84 0.0022
2023-02-14 2022-12-31 13F Rhythm Pharmaceuticals Equity 76243J105 52,884 -28,049 -34.66 1,540 -22.35 0.0024
2022-11-16 2022-09-30 13F/A-1 Rhythm Pharmaceuticals Equity 76243J105 80,933 60,347 293.15 1,983 2,231.76 0.0032
2022-11-15 2022-09-30 13F Rhythm Pharmaceuticals Equity 76243J105 80,933 60,347 1,983 0.0005
2022-08-12 2022-06-30 13F Rhythm Pharmaceuticals Equity 76243J105 20,586 8,822 74.99 85 -37.04 0.0001
2022-05-18 2022-03-31 13F/A-1 Rhythm Pharmaceuticals Equity 76243J105 11,764 -25,610 -68.52 136 -63.71 0.0002
2022-02-09 2021-12-31 13F RHYTHM PHARMACEUTICALS EQUITY 76243J105 37,374 26,466 242.63 373 161.97 0.0005
2021-11-16 2021-09-30 13F/A-1 RHYTHM PHARMACEUTICALS EQUITY 76243J105 10,908 5,611 105.93 142 37.86 0.0002
2021-11-12 2021-09-30 13F RHYTHM PHARMACEUTICALS EQUITY 76243J105 7,914 2,617 171 0.0000
2021-08-10 2021-06-30 13F RHYTHM PHARMACEUTICALS EQUITY 76243J105 5,297 -9,437 -64.05 104 -67.09 0.0001
2021-05-07 2021-03-31 13F RHYTHM PHARMACEUTICALS EQUITY 76243J105 14,734 9,920 206.07 313 118.88 0.0005
2021-02-10 2020-12-31 13F RHYTHM PHARMACEUTICALS EQUITY 76243J105 4,814 -3,100 -39.17 143 -16.37 0.0003
2020-10-30 2020-09-30 13F RHYTHM PHARMACEUTICALS EQUITY 76243J105 7,914 5,232 195.08 171 189.83 0.0002
2020-08-06 2020-06-30 13F RHYTHM PHARMACEUTICALS EQUITY 76243J105 2,682 -10,078 -78.98 60 -69.59 0.0001
2020-05-13 2020-03-31 13F RHYTHM PHARMACEUTICALS EQUITY 76243J105 12,760 9,351 274.30 194 148.72 0.0004
2020-02-12 2019-12-31 13F RHYTHM PHARMACEUTICALS EQUITY 76243J105 3,409 -17 -0.50 78 6.85 0.0001
2019-11-07 2019-09-30 13F RHYTHM PHARMACEUTICALS EQUITY 76243J105 3,426 1,739 103.08 74 97.30 0.0001
2019-07-30 2019-06-30 13F RHYTHM PHARMACEUTICALS EQUITY 76243J105 1,687 -1,479 -46.72 37 -56.98 0.0001
2019-04-25 2019-03-31 13F RHYTHM PHARMACEUTICALS EQUITY 76243J105 3,166 3,163 105,433.33 87 107,035.80 0.0002
2019-02-12 2018-12-31 13F RHYTHM PHARMACEUTICALS EQUITY 76243J105 3 -592 -99.50 0 -100.00 0.0000
2018-11-07 2018-09-30 13F RHYTHM PHARMACEUTICALS EQUITY 76243J105 595 137 29.91 17 21.43 0.0000
2018-07-25 2018-06-30 13F RHYTHM PHARMACEUTICALS EQUITY 76243J105 458 -918 -66.72 14 -48.15 0.0000
2018-05-11 2018-03-31 13F RHYTHM PHARMACEUTICALS EQUITY 76243J105 1,376 -264 -16.10 27 -42.55 0.0001
2018-03-05 2017-12-31 13F/A-1 RHYTHM PHARMACEUTICALS EQUITY 76243J105 1,640 1,640 48 0.0001
2018-02-01 2017-12-31 13F RHYTHM PHARMACEUTICALS EQUITY 76243J105 1,640 48 0.0001
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
(%)
2023-08-09 2023-06-30 13F RHYTHM PHARMACEUTICALS OPTION Call 0 -100.00 0 -100.00 n/a n/a n/a
2023-05-12 2023-03-31 13F RHYTHM PHARMACEUTICALS OPTION Call 608 1,085 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.