Many investors who follow CRISPR Therapeutics (CRSP 2.52%) still treat it as a gene-editing story. That makes sense, as the company's only commercialized drug, Casgevy, is a gene-editing therapy. But this biotech's ambitions are bigger than that modality alone.
In May 2025, it paid $95 million up front to Sirius Therapeutics for CTX611, a clinical-stage long-acting small interfering RNA (siRNA) therapy that's being investigated for the prevention of thrombosis and thromboembolic disorders. That often-overlooked program may turn out to be a major asset for the company; here's why.
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This program is an asymmetrical bet
In a nutshell, CTX611 works by silencing the messenger RNA (mRNA) for the coagulation enzyme Factor XI in the liver. That silencing reduces the production of the coagulation factor, making the patient's blood less likely to form dangerous blood clots.
With CTX611, it may be possible to blunt the production of the coagulation factor without causing detrimental side effects like excessive bleeding, which is a problem with traditional anticoagulant medicines like warfarin. CRISPR Therapeutics' candidate is engineered for twice-yearly subcutaneous dosing, which may also be an advantage compared to alternatives that require daily pills or monthly antibody infusions.
One important thing to note is that CRISPR Therapeutics made a far smaller up-front commitment than its bigger competitors for a shot at the same market. Novartis paid up to $3.1 billion in 2025 to own abelacimab, a monthly antibody targeting the same coagulation factor. Eliquis, the leading anticoagulant (owned by Pfizer and Bristol Myers Squibb), alone generated $14.4 billion in revenue in 2025. While CRISPR Therapeutics owes Sirius additional milestone payments that could bring the deal's total value to over $800 million, and it'll also bear half of all development costs, that's still a fraction of what Novartis committed.
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Key Data Points
There's a catch
Competition in the anticoagulant segment is fierce and growing.
Aside from biologics being tested by players like Novartis, and improved small-molecule drugs (which build on the successes of the prior generation of those medicines) being tested by other big pharma businesses, CTX611 is not the only siRNA therapy targeting Factor XI. Suzhou Ribo Life Science's candidate, vortosiran, reached the clinic first, and is presently in phase 2b trials.
Even if CRISPR Therapeutics manages to get its program approved and out the door first, it'll immediately be competing intensely based on its therapy's cost, convenience, safety, availability, and effectiveness. The takeaway is that CTX611 is most likely to be a follower, rather than a category leader.
Nonetheless, given that the biotech only made $1.4 million in revenue in the first quarter of 2026 (though that figure excludes its 40% share of Casgevy revenue due to the way its collaboration is structured), even getting a foothold in the anticoagulants market with this candidate could be immensely impactful for the stock. The biotech expects to deliver an update on the program's progress through its phase 2 clinical trials in the second half of this year, so stay tuned.
