Baker Bros. Advisors RARE Position
Active9-Fund ConvergenceBaker Bros. Advisors held their position in Ultragenyx Pharmaceutical Inc. (RARE) in Q4 2025, holding $63.8M worth of shares across 2,772,692 shares.
The position was first reported in Q1 2023 and has been tracked across 12 quarterly 13F filings.
RARE is a convergence signal: 9 specialist biotech funds hold this stock, suggesting high institutional conviction.
There is an upcoming Phase 3 readout for GTX-102 in 108 days (Jul 31, 2026), making the timing of Baker Bros.'s position particularly relevant.
Short interest stands at 10.6% of float with 4.4 days to cover, indicating significant bearish positioning against Baker Bros.'s long thesis.
About Ultragenyx Pharmaceutical Inc.
Ultragenyx Pharmaceutical Inc., a biopharmaceutical company, focuses on the identification, acquisition, development, and commercialization of novel products for the treatment of rare and ultra-rare genetic diseases in North America, Europe, and internationally. Its biologic products include Crysvita (burosumab), an antibody targeting fibroblast growth factor 23 for the treatment of X-linked hypophosphatemia, as well as tumor-induced osteomalacia; Mepsevii, an enzyme replacement therapy for the treatment of children and adults with Mucopolysaccharidosis VII; Dojolvi for treating long-chain fatty acid oxidation disorders; and Evkeeza (evinacumab) for the treatment of homozygous familial hypercholesterolemia. The company's products candidatures include DTX401, an adeno-associated virus 8 (AAV8) gene therapy clinical candidate for the treatment of patients with glycogen storage disease type Ia; DTX301, an AAV8 gene therapy for the treatment of patients with ornithine transcarbamylase; UX143, a human monoclonal antibody for the treatment of osteogenesis imperfecta; GTX-102, an antisense oligonucleotide for the treatment of Angelman syndrome; UX701, for the treatment of Wilson disease; and UX053 for the treatment of glycogen storage disease type III. Ultragenyx Pharmaceutical Inc. has collaboration and license agreement with Kyowa Kirin Co., Ltd.; Saint Louis University; Baylor Research Institute; REGENXBIO Inc.; Bayer Healthcare LLC; GeneTx; Mereo; University of Pennsylvania; Arcturus Therapeutics Holdings Inc., Solid Biosciences Inc.; and Daiichi Sankyo Co., Ltd. Ultragenyx Pharmaceutical Inc. was incorporated in 2010 and is headquartered in Novato, California.
Full company profile →Short Interest
10.6%
4.4 days to cover
Baker Bros. Advisors RARE Position History
| Quarter | Action | Shares | Change | Value |
|---|---|---|---|---|
| Q4 2025 | Held | 2,772,692 | — | $63.8M |
| Q3 2025 | Held | 2,772,692 | — | $83.4M |
| Q2 2025 | Increased | 2,772,692 | +1,196,578 | $100.8M |
| Q1 2025 | Held | 1,576,114 | — | $57.1M |
| Q4 2024 | Held | 1,576,114 | — | $66.3M |
| Q3 2024 | Increased | 1,576,114 | +109,567 | $87.6M |
| Q2 2024 | Held | 1,466,547 | — | $60.3M |
| Q1 2024 | Held | 1,466,547 | — | $68.5M |
| Q4 2023 | Increased | 1,466,547 | +100,000 | $70.1M |
| Q3 2023 | Increased | 1,366,547 | +583,488 | $48.7M |
| Q2 2023 | Increased | 783,059 | +312,085 | $36.1M |
| Q1 2023 | New | 470,974 | +470,974 | $18.9M |
Frequently Asked Questions
Does Baker Bros. Advisors own RARE?
Yes. As of Q4 2025, Baker Bros. Advisors holds 2,772,692 shares of Ultragenyx Pharmaceutical Inc. (RARE) valued at $63.8M. This data comes from their SEC 13F filing.
How many hedge funds own RARE?
9 specialist biotech hedge funds currently hold RARE, including RTW Investments, Rock Springs Capital, Avoro Capital Advisors and 5 more. When 3 or more specialist funds hold the same stock, BiotechEdge flags it as a convergence signal.
When did Baker Bros. Advisors first buy RARE?
Baker Bros. Advisors's position in RARE was first reported in Q1 2023. 13F filings are reported with a 45-day delay, so the actual purchase may have occurred earlier in the quarter.
Is Baker Bros. Advisors's RARE position increasing or decreasing?
Baker Bros. Advisors held their RARE position unchanged in the most recent quarter.
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