STORM Therapeutics Presents STC-15 Preclinical Data Supporting Treatment of Patients with AML at the AACR Acute Myeloid Leukemia and Myelodysplastic Syndrome Conference

• Data demonstrates that STC-15, an oral METTL3 inhibitor, exhibits efficacy as a single agent and in combination with venetoclax using patient-derived tumor models
• STC-15 Phase 1 study in solid tumors aims to identify doses and regimen for potential clinical studies in AML and solid tumors

CAMBRIDGE, England, Jan. 25, 2023 /PRNewswire/ -- STORM Therapeutics Ltd. (STORM), the clinical stage biotechnology company discovering and developing novel small molecule therapies targeting RNA modifying enzymes (RMEs) for oncology and other diseases, presented new data on its lead candidate, the METTL3 inhibitor STC-15. The new data in AML preclinical models was presented at the American Association for Cancer Research (AACR) Special Conference: Acute Myeloid Leukemia and Myelodysplastic Syndrome, hosted in Austin, Texas on the 23-25 January.

The presentation entitled 'STC-15, a novel METTL3 inhibitor, and its combination with venetoclax confer anti-tumour activity in AML models' detailed the study of the pharmacological inhibition of METTL3 as monotherapy or in combination with venetoclax (FDA approved for AML treatment) in models of acute myeloid leukemia (AML) in vitro and in vivo.

Preclinical data demonstrated that:

1. STC-15 inhibited proliferation in some AML cell lines with sub- micromolar IC50 values
2. STC-15 inhibited the growth of 12 patient-derived AML samples in vitro with IC50 values reflecting a mean of approximately 1 micromolar
3. STC-15 reduced BCL2 protein levels in a dose-dependent manner in the majority of AML cell lines tested
4. STC-15 showed synergistic inhibition of tumor cell growth in vitro when combined with venetoclax
5. In an AML patient-derived in vivo model, STC-15 extended survival when compared to a vehicle-treated control group and a venatoclax-treated group of animals
6. In addition, STC-15 showed a decrease in circulating human CD45+ cells and decreased spleen weight when compared to vehicle treated animals

STORMS lead candidate STC-15 is advancing its ongoing Phase 1 study. The details of the study can be found on clinicaltrials.gov under the identifier NCT05584111.

Oliver Rausch, Chief Scientific Officer of STORM Therapeutics, said: "These studies provide evidence for the utility of METTL3 inhibitors as a new therapeutic approach to treat AML. We are delighted with the outcome of the data which further validates our previous publication that treatment with METTL3 inhibitors led to the downregulation of BCL2 protein levels in several AML cell lines and in vivo models and provides the rationale for conducting a clinical trial in AML with STC-15."

Jerry McMahon, Chief Executive Officer & President of STORM Therapeutics, said: "We are excited to present this new data with patient-derived tumor samples supporting the future clinical development of STC-15 in AML. Our ongoing Phase 1 multiple-ascending dose study in solid tumors is focused on establishing a potential dose and regimen of STC-15 to conduct future clinical studies in AML and solid tumors."

Details of the conference and presented poster are as follow:

Poster Presented Title: STC-15, a novel METTL3 inhibitor, and its combination with venetoclax confer anti-tumour activity in AML models

Presenting Authors: Lina Vasiliauskaitė¹, Yaara Ofir-Rosenfeld¹, Mark Albertella¹, Coralie Hoareau-Aveilla², Jerry McMahon¹, Oliver Rausch¹

Date and Time: Tuesday, 24 January, 07.15 – 21.30 ET

¹Storm Therapeutics Ltd., Cambridge, UK

²Evotec SAS, Toulouse, FR

The Poster and Abstract are available on the STORM Therapeutics website: Publications.

STORM has developed potent and selective METTL3 inhibitors which include the first-in-class clinical candidate STC-15, an orally bioavailable, highly selective METTL3 inhibitor which commenced a clinical trial in cancer patients with solid tumors in November 2022.

About STORM Therapeutics

STORM Therapeutics (STORM) is a clinical stage biotechnology company creating novel therapies that inhibit RNA modifying enzymes (RME) for use in oncology and other diseases. There are more than 150 RNA modifications reported and approximately 300 RNA modifying enzymes which represent novel therapeutic targets.

STORM has leveraged its first-mover advantage to establish a novel drug discovery and RNA analytics platform leading to the identification of novel targets and a proprietary pipeline of first-in-class small-molecule drug candidates for potential use in oncology, inflammation, viral infection and CNS diseases.

The pipeline is exemplified by STORM's METTL3 inhibitor, STC-15, which has received IND approval and commenced its Phase 1 clinical study in cancer patients in November 2022. STC-15 represents the first ever RNA modifying enzyme inhibitor to enter clinical evaluation in humans. Additional programs are planned for advancement into IND-track activities in 2023.

Fierce Biotech named STORM as one of its 2022 "Fierce 15", designating it as one of the most innovative, exciting biotechnology companies in the industry, pioneering novel drug targets.

STORM investors include M Ventures, Pfizer Ventures, Taiho Ventures LLC, Cambridge Innovation Capital I Limited, Seroba Life Sciences, IP Group plc, Fast Track Initiative (FTI), and the UTokyo Innovation Platform Co., Ltd. (UTokyo IPC).

For more information, please visit www.stormtherapeutics.com

About STC-15

STORM's lead clinical program STC-15 is a first-in-class inhibitor of RNA modification and is the first ever RNA methyltransferase inhibitor to enter clinical development. STC-15 is an oral small molecule that inhibits METTL3, an RNA methyltransferase implicated in oncology and other diseases. Certain RNA methyltransferases are important regulators of RNA sensing and innate immune activation and represent novel immune-regulatory targets.

STC-15 has also been shown to inhibit tumor growth through mechanisms involving anti-cancer immune responses, such as changes in interferon signaling and synergy with T cell checkpoint blockade. In addition, this compound has demonstrated efficacy in leukemia models via mechanisms such inhibition of leukemia stem cell function.

STORM commenced the dosing of the first patient in a Phase 1 clinical study of STC-15 in patients living with solid tumors in November 2022 and anticipates presenting additional results from its study in 2023. Details of the study can be found on clinicaltrials.gov under the identifier NCT05584111.