SCHEDULE: PRIMECAP Maintains Significant Stake in Rhythm Pharma

PRIMECAP Management Co. reports an updated 6.42% beneficial ownership in Rhythm Pharmaceuticals, Inc. as of September 30, 2025.

Summary

• PRIMECAP Management Co./CA/ has filed an Amendment No. 11 to Schedule 13G for Rhythm Pharmaceuticals, Inc.
• The filing reports PRIMECAP's beneficial ownership of 4,262,859 shares of common stock (COM) in Rhythm Pharmaceuticals, Inc.
• This represents 6.42% of the class of securities.
• PRIMECAP Management Co./CA/ holds sole voting power and sole dispositive power over all 4,262,859 shares.
• The securities were acquired and are held in the ordinary course of business, not for the purpose of changing or influencing control of the issuer.

Sentiment

Score: 6

Explanation: The sentiment is neutral to slightly positive, as it indicates a major institutional investor is maintaining a significant stake, suggesting continued confidence without any explicit positive or negative operational news.

Positives

• Continued significant institutional investment by PRIMECAP Management Co. in Rhythm Pharmaceuticals, Inc., indicating ongoing confidence in the company.

Negatives

• NA

Risks

• NA

Future Outlook

NA

Industry Context

This filing reflects a routine disclosure of an institutional investor's stake in a biotechnology company. It does not provide specific insights into broader industry trends but confirms continued institutional interest in the pharmaceutical sector.

Stakeholder Impact

• Shareholders: The continued significant stake by a major institutional investor like PRIMECAP Management Co. may be viewed positively, potentially signaling stability and long-term interest in the company's stock.

Key Dates

Keywords

Rhythm Pharmaceuticals, PRIMECAP Management, Institutional Ownership, Schedule 13G, Beneficial Ownership, Biotechnology, Pharmaceuticals, Investment Adviser