Rock Springs Capital ACLX Position
Active6-Fund ConvergenceRock Springs Capital trimmed their position in Arcellx Inc. (ACLX) in Q4 2025, holding $11.1M worth of shares across 169,859 shares.
The position was first reported in Q2 2025 and has been tracked across 3 quarterly 13F filings.
ACLX is a convergence signal: 6 specialist biotech funds hold this stock, suggesting high institutional conviction.
There is an upcoming Phase 2 readout for anitocabtagene-autoleucel in 259 days (Dec 31, 2026), making the timing of Rock Springs's position particularly relevant.
Short interest stands at 10.9% of float with 1.0 days to cover, indicating significant bearish positioning against Rock Springs's long thesis.
About Arcellx Inc.
Arcellx, Inc., a clinical-stage biotechnology company, engages in the development of various immunotherapies for patients with cancer and other incurable diseases. The company's lead ddCAR product candidate is CART-ddBCMA, which is in phase 1 clinical trial for the treatment of patients with relapsed or refractory (r/r) multiple myeloma (MM). It is also developing ACLX-001, an immunotherapeutic combination composed of ARC-T cells and bi-valent SparX proteins targeting BCMA to treat r/r MM; ACLX-002 and ACLX-003 for treating r/r acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS); and other AML/MDS product candidates, as well as solid tumor programs. The company was formerly known as Encarta Therapeutics, Inc. and changed its name to Arcellx, Inc. in January 2016. Arcellx, Inc. was incorporated in 2014 and is headquartered in Gaithersburg, Maryland.
Full company profile →Short Interest
10.9%
1.0 days to cover
Rock Springs Capital ACLX Position History
Frequently Asked Questions
Does Rock Springs Capital own ACLX?
Yes. As of Q4 2025, Rock Springs Capital holds 169,859 shares of Arcellx Inc. (ACLX) valued at $11.1M. This data comes from their SEC 13F filing.
How many hedge funds own ACLX?
6 specialist biotech hedge funds currently hold ACLX, including Perceptive Advisors, RA Capital Management, Cormorant Asset Management and 2 more. When 3 or more specialist funds hold the same stock, BiotechEdge flags it as a convergence signal.
When did Rock Springs Capital first buy ACLX?
Rock Springs Capital's position in ACLX was first reported in Q2 2025. 13F filings are reported with a 45-day delay, so the actual purchase may have occurred earlier in the quarter.
Is Rock Springs Capital's ACLX position increasing or decreasing?
Rock Springs Capital trimmed their ACLX position in the most recent quarter, reducing by 9,123 shares.
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