Week of May 18, 2026

This week's 13F activity and real-time positioning data reflect a biotech hedge fund landscape characterized by deliberate concentration in high-conviction names, with Baker Bros. Advisors and Avoro Capital Advisors dominating the headline moves. Baker Bros. meaningfully added to three positions during the period, lifting its stake in Insmed (INSM) to approximately $1.2 billion, Celcuity (CELC) to $978.4 million, and Revolution Medicines (RVMD) to $929.3 million. The continued accumulation in INSM suggests sustained confidence in the brensocatib franchise following its commercial launch in bronchiectasis, while the CELC build points to growing conviction around the PI3K alpha inhibitor gedatolisib ahead of pivotal readouts. Baker Bros. also maintained its largest disclosed position in Incyte (INCY) at $2.9 billion, signaling no rotation out of that core holding despite a mixed near-term catalyst calendar for the company.

Avoro Capital Advisors, meanwhile, pursued a more mixed strategy — holding its outsized United Therapeutics (UTHR) position steady at $1.6 billion and Madrigal Pharmaceuticals (MDGL) at $951.8 million, while trimming Ascendis Pharma (ASND) to roughly $1.2 billion. The ASND reduction may reflect profit-taking or risk management ahead of competitive dynamics in the rare endocrine space. More constructively, Avoro added to both argenx (ARGX) at $730.3 million and Arrowhead Pharmaceuticals (ARWR) at $670.9 million, the latter of which continues to attract capital as its RNA interference pipeline matures across cardiometabolic and liver indications. RA Capital Management also stood out this week, increasing its position in Vaxcyte (PCVX) to $666.8 million, a notable accumulation that coincides with heightened attention on next-generation pneumococcal vaccine programs ahead of competitive readouts from Pfizer (PFE) expected May 23rd.

The binary catalyst calendar this week is dense and skews toward large-cap names alongside several emerging-company inflection points. Design Therapeutics (DSGN) faces a Phase 3 readout for its abiraterone program today, May 18th, while Regeneron (REGN) reports Phase 2 data for trevogrumab Part A on the same date — a meaningful test of its muscle and metabolic disease ambitions. Amgen (AMGN) is expected to deliver Phase 3 romipl