STORM Therapeutics Closes $56M Series C for Sarcoma

Storm Therapeutics, a Cambridge, UK-based clinical-stage biotechnology company focused on targeting RNA modifications to treat cancer, has closed a USD 56 million Series C financing round. Funding will support development of its lead candidate, STC-15, as it moves into a Phase II monotherapy study in selected sarcoma indications.

The round was funded entirely by existing investors — M Ventures, Pfizer Ventures, Taiho Ventures LLC, IP Group plc, UTokyo Innovation Platform Co., Ltd. (UTokyo IPC), and Fast Track Initiative — with no new investors joining the syndicate. No lead investor was designated in the announcement. The company said proceeds will fund the ongoing Phase II trial, in which the first patient has now been dosed. STORM previously raised a USD 30 million Series B in December 2022, with M Ventures and Pfizer Ventures co-leading that round alongside the same core investor group.

STC-15 is an oral small-molecule inhibitor of METTL3, an RNA-modifying enzyme that regulates mRNA methylation and governs stem cell differentiation. The company's scientific rationale centres on the observation that sarcomas — cancers arising from transformed mesenchymal stem cells — depend on METTL3-driven methylation for growth and survival, in part because they frequently lack the driver mutations or immunogenic features that make them amenable to conventional therapies. Sarcomas account for approximately 1% of adult cancers and 15% of pediatric cancers. In a Phase I monotherapy study, STC-15 produced durable tumour regression across multiple sarcoma subtypes; those results are expected to be presented at a medical conference later in 2026, while Storm previously released data for the molecule in 2024.

The Phase II trial (NCT06975293) is designed to assess anti-tumour activity as monotherapy in select sarcomas and is structured to support a potential accelerated regulatory approval pathway. The company said the study also aims to establish a foundation for broader clinical development across additional oncology indications.

Storm's platform is grounded in epitranscriptomics — the study of chemical modifications made to RNA molecules after transcription. The company targets RNA modifying enzymes (RMEs), specifically the "writers" and "erasers" of these modifications, as a druggable class. METTL3 is the primary catalytic subunit responsible for installing N6-methyladenosine (m6A) marks on mRNA, a modification that influences mRNA stability, translational efficiency, and cell differentiation. By inhibiting METTL3, the company's approach seeks to reprogram malignant progenitor cells rather than kill them directly, pushing them toward cell cycle arrest and apoptosis. The company was founded by University of Cambridge professors Tony Kouzarides and Eric Miska, whose research in RNA biology underpins the platform.

In 2021, Storm entered an exclusive collaboration and licence agreement with Exelixis (Nasdaq: EXEL), under which Exelixis licensed two of Storm's discovery-stage programmes targeting RNA-modifying enzymes, including an ADAR1 programme, for an upfront payment of USD 17 million plus potential milestones and royalties. Exelixis assumed responsibility for subsequent development under that agreement.

Jerry McMahon, Chief Executive Officer, said the Phase II initiation "marks a pivotal breakthrough in tackling cancers characterized by aberrant cell differentiation" and cited the durability of activity seen in Phase I as a basis for the company's continued focus on sarcoma. Jonathan Trent of the University of Miami's Sylvester Comprehensive Cancer Center, commenting on the trial, noted that STC-15's mechanism targets sarcomas "at their vulnerability" by reprogramming malignant cells toward arrest and apoptosis.

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