Myeloid Therapeutics Unveils First-in-Human In Vivo mRNA CAR Data, Marking a Breakthrough in RNA-Based Immuno-Oncology at the 2025 ASCO Annual Meeting

– MT-302 and MT-303 embody the first clinical applications of in vivo mRNA CAR therapies administered systemically –

– Initial translational results support proof-of-mechanism with immune reprogramming resulting in tumor penetration and pro-inflammatory alteration in the TME –

CAMBRIDGE, Mass., May 30, 2025 /PRNewswire/ -- Myeloid Therapeutics, Inc. ("Myeloid"), a clinical-stage immunology company advancing RNA therapeutics to conquer cancer, today announced it will present two posters at the 2025 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago taking place from May 30 – June 3, 2025. The presentations will highlight the clinical trial design for MT-303 and preliminary translational findings for MT-302 – the company's lead in vivo mRNA CAR therapies, which together signify a key milestone in the field of RNA-based immuno-oncology.

"Our presentations at ASCO demonstrate the clinical translation of our proprietary mRNA-LNP platform for in vivo immune cell engineering," said Daniel Getts, PhD, CEO and Co-founder of Myeloid Therapeutics. "With MT-302 and MT-303, we are pushing beyond the limits of traditional CAR therapies—removing the need for often complicated ex vivo manipulation while delivering potent, tumor-specific immune activation in patients with advanced solid tumors."

"These data show that we can deliver repeated doses of LNP-mRNA in patients demonstrating that CAR-programmed myeloid cells can penetrate solid tumors and alter the tumor microenvironment (TME), which opens up multiple avenues for potential clinical benefit moving forward," said Matt Maurer, MD, Chief Medical Officer of Myeloid Therapeutics. "The results offer early validation of Myeloid's platform technologies, and could ultimately change how solid tumors are treated, offering patients a more accessible, potentially more tolerable, and highly targeted therapy option in the future without the burdens associated with traditional cell therapies."

MT-302: TROP2-Targeted mRNA CAR Therapy in Advanced Epithelial Tumors

MT-302 is the first intravenously delivered mRNA-based CAR therapy to enter clinical trials. It uses synthetic mRNA encapsulated in lipid nanoparticles (LNPs) to reprogram circulating immune cells in vivo to express a TROP2-targeted CAR.

• Poster Board: 238
• Title: First-in-human mRNA CAR Therapy: Correlative Biomarker analysis from the MT-302 Phase 1 Study Targeting TROP2 in Patients with Advanced Epithelial Tumors
• Lead Author: Dr. Charlotte Lemach, MBBS
• Session Date & Time: June 2, 2025 | 1:30 PM–4:30 PM CDT
• Location: Hall A, McCormick Place, Chicago

Key MT-302 Findings Include:

• Immune Activation: Single-cell RNA sequencing demonstrated selective CAR expression in myeloid cells and increased pro-inflammatory gene signatures across tumor types.
• Target Engagement: Pharmacodynamic markers confirmed successful delivery and CAR expression following systemic administration.
• Continued dose escalation: Dose escalation continues with an optimized liner mRNA based on preclinical demonstration of expression beyond 12 days.

MT-303: GPC3-Targeted mRNA CAR Therapy in Hepatocellular Carcinoma

MT-303 is an innovative in vivo CAR therapy specifically designed to reprogram Fc receptor gamma chain-expressing myeloid cells to recognize and destroy GPC3+ tumor cells following intravenous mRNA-LNP administration.

• Poster Board: 499b
• Title: A First-in-Human Study of MT-303, an Innovative In Vivo mRNA CAR Therapy Targeting GPC3 in Adults with Hepatocellular Carcinoma
• Lead Author: Dr. Timothy Humphries, Linear Clinical Research
• Session Date & Time: May 31, 2025 | 9:00 AM-12:00 PM CDT
• Location: Hall A, McCormick Place, Chicago

MT-303 Clinical Trial Highlights:

• Design: Ongoing multicenter, open-label Phase 1 trial in advanced solid tumors expressing GPC3 (including HCC) employing a Bayesian Optimal Interval (BOIN) dose escalation.
• Mechanism: mRNA encodes a GPC3-targeted CAR construct driven by CD89, restricting expression to myeloid cells.

Myeloid expects to share additional clinical translational data at an upcoming medical meeting upon completion of the Phase 1 studies of MT-302 and MT-303.

About MT-302

MT-302 is a first-in-class, TROP2-FcA-LNP targeting TROP2, which is overexpressed in many epithelial tumors and corresponds with low expression in healthy tissues. MT-302 has demonstrated promising preclinical results to date, including robust expression in myeloid cells and a favorable safety profile in rodents and non-human primates. Unlike other therapies, MT-302 brings the potential advantages of eliciting a full immune response by also presenting tumor neoantigen to stimulate T cells. MT-302 is Myeloid's first in vivo CAR clinical program that further builds on the company's innovative approach to cancer treatment through immune cell programming.

About MT-303

MT-303 is a first-in-class, GPC3-FcA-LNP targeting glypican-3 (GPC3), which is overexpressed in most human hepatocellular carcinomas (HCCs) and exhibits limited expression in healthy tissues. MT-303 has demonstrated promising preclinical results to date, including robust expression in myeloid cells and a favorable safety profile in rodents and non-human primates. Unlike other therapies, MT-303 brings the potential advantages of eliciting a full immune response by also presenting tumor neoantigen to stimulate T cells. MT-303 is Myeloid's second in vivo CAR clinical program that further builds on the company's innovative approach to cancer treatment through immune cell programming.

About Myeloid Therapeutics

Myeloid Therapeutics is a clinical stage immunology company, engineering cutting-edge RNA technology to program immune cells to combat cancer and other deadly diseases. Myeloid is headquartered in Cambridge, MA.

For additional information, please visit, https://www.myeloidtx.com/ and follow us on LinkedIn and X/Twitter. For collaborative interests, write to [email protected].

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SOURCE Myeloid Therapeutics, Inc