Rhythm Pharmaceuticals, Inc. (RYTM) Institutional Ownership

Ownership Summary

Rhythm Pharmaceuticals, Inc. (NASDAQ:RYTM) showed up in the 13F filings of 271 institutional investors as of December 2025.

• Their combined ownership stood at 108.5% of outstanding shares in December 2025, down from 738.0% in September 2025.
• They decreased total shares held in RYTM by -85.19% quarter over quarter, and investors in Rhythm Pharmaceuticals increased 33.5% from a year ago.
• Of these 271 holders, 155 added to their stakes in Rhythm Pharmaceuticals, 90 trimmed positions, and 26 made no changes.
• Combined, these investors held 71.88Mn shares in RYTM for December 2025, down by 413.61Mn shares quarter on quarter, and up 6.14Mn shares year over year.
• As of December 31, 2025, RA CAPITAL MANAGEMENT, L.P. held the largest stake in Rhythm Pharmaceuticals with 6.67Mn shares, accounting for 10.06% of total shares outstanding.
• Top purchasers of RYTM stock for the quarter ending December 2025 included VANGUARD PORTFOLIO MANAGEMENT LLC (3.04Mn), VANGUARD CAPITAL MANAGEMENT LLC (2.97Mn), PRICE T ROWE ASSOCIATES INC /MD/ (1.65Mn), CITADEL ADVISORS LLC (1.27Mn), Janus Henderson Group Plc (710.18K).
• The largest sellers of Rhythm Pharmaceuticals for the quarter ending December 2025 were Goldman Sachs Group Inc (1.7Mn), DRIEHAUS CAPITAL MANAGEMENT LLC (848.68K), Opaleye Management Inc. (537.0K), Rockefeller Capital Management L.P. (459.82K), Federated Hermes, Inc. (337.54K).
• Rhythm Pharmaceuticals's 10 largest shareholders as of December 2025 include RA CAPITAL MANAGEMENT, L.P. (6.67Mn), BlackRock, Inc. (6.24Mn), BAKER BROS. ADVISORS LP (5.6Mn), PRIMECAP MANAGEMENT CO/CA/ (3.42Mn), VANGUARD PORTFOLIO MANAGEMENT LLC (3.04Mn), VANGUARD CAPITAL MANAGEMENT LLC (2.97Mn), PERCEPTIVE ADVISORS LLC (2.37Mn), State Street Corp (2.27Mn), Goldman Sachs Group Inc (1.97Mn), WESTFIELD CAPITAL MANAGEMENT CO LP (1.93Mn) per Business Quant data.