RA Capital Management, L.P. disclosed a 23.8% stake in Parabilis Medicines, Inc. common stock. The Schedule 13D was filed on Jun. 18, 2026 following the company’s IPO on June 11. The move includes a board presence through RA Capital partner Dr. Jake Simson and a 180-day IPO lock-up on most pre-IPO shares.

Investor Intent

RA Capital says it holds Parabilis Medicines for investment purposes and “not with an intent, purpose or effect of changing control.” The firm plans to “engage in communications” with shareholders, directors, and management about operations, strategy, governance, capitalization, and possible deals, while Dr. Jake Simson continues to serve on the board.

The funds that bought pre-IPO shares agreed to a 180-day lock-up from June 9, 2026, limiting sales or hedging without underwriter consent. RA Capital may still buy more shares or securities of Parabilis in the future, including certain types of debt tied to potential revenue streams, depending on the company’s progress and market conditions.

Investor's Background

RA Capital Management, L.P. is a Boston-based investment firm focused on healthcare and life sciences across private and public markets. Led by managing partners Peter Kolchinsky and Rajeev Shah, the firm often builds large, research-driven positions and participates in crossover financings and IPOs. RA Capital is known for concentrated bets in biotech companies developing novel therapies.

Original SEC Filing: Parabilis Medicines, Inc. [ PBLS ] - SCHEDULE 13D - Jun. 18, 2026