CRISPR Therapeutics Expands into siRNA with $95M Sirius Partnership

CRISPR Therapeutics, a leading gene-editing company, has announced a significant expansion of its therapeutic portfolio through a new partnership with Sirius Therapeutics. The collaboration, valued at up to $95 million, focuses on developing siRNA therapeutics for thromboembolic disorders, marking CRISPR's strategic move beyond its core gene-editing technology.

Partnership Details and Financial Terms

The agreement, announced on Monday, involves an upfront payment of $25 million in cash from CRISPR to Sirius, along with a $70 million equity investment. This partnership grants CRISPR the right to co-develop SRSD107, a next-generation, long-acting siRNA therapy targeting Factor XI, a key protein in blood clot formation.

The deal structure reflects a 50-50 split in development costs and profits between the two companies. CRISPR will lead commercialization efforts in the United States, while Sirius will spearhead market initiatives in the Greater China region. Additionally, CRISPR has the option to nominate up to two more siRNA targets, for which it will fund R&D activities and retain opt-in rights for clinical development and commercialization.

SRSD107: A Promising Candidate for Thromboembolic Disorders

SRSD107, the centerpiece of this collaboration, has shown promising results in early-stage clinical trials. Phase I data revealed that the therapy could reduce Factor XI levels by over 93% while more than doubling the activated partial thromboplastin time, a crucial measure of blood clotting speed. These early results also support the safety and tolerability profile of SRSD107.

The partners are now preparing to launch a Phase II trial of SRSD107 in patients undergoing total knee arthroplasty. Beyond this initial indication, CRISPR and Sirius see potential applications for SRSD107 in other patient populations, including those with cancer-associated thrombosis, coronary artery disease, and venous thromboembolism.

Strategic Implications for CRISPR Therapeutics

This partnership represents a significant strategic shift for CRISPR Therapeutics, expanding its modality toolkit beyond gene editing, particularly in the cardiovascular space. Analysts from William Blair view the collaboration positively, noting that it provides additional synergies for CRISPR's cardiovascular pipeline and expands the company's reach beyond "one and done" therapies like its flagship treatment, Casgevy.

The move comes as CRISPR anticipates several key milestones in 2025. In its cardiovascular portfolio, the company awaits data for CTX320, an in vivo therapy for patients with elevated lipoprotein(a) levels, with results expected in the second quarter. Additionally, CRISPR is preparing for a mid-2025 readout of its off-the-shelf CAR T program, CTX112, which is being studied in autoimmune conditions.