On July 24, 2026, the U.S. Food and Drug Administration (FDA) granted Breakthrough Therapy Designation (BTD) to AMT-253 for injection (a MUC18-directed ADC), a key product of Multitude Therapeutics, Co., Ltd., for the treatment of patients with unresectable locally advanced or metastatic melanoma with progression or recurrence after prior immunotherapy.
AMT-253 is the first and only MUC18-directed ADC to have entered clinical development, and is a potential first ADC therapy for melanoma, with the potential to bring a significant breakthrough in treatment mechanism and paradigm in this indication. AMT-253 is being evaluated in a Phase I study in Australia (NCT05906862) and a Phase I/II study in China (NCT06209580); initial clinical results were presented at the 2025 European Society for Medical Oncology (ESMO) Annual Meeting.
The indication for which AMT-253 received Breakthrough Therapy Designation is “unresectable locally advanced or metastatic melanoma with progression or recurrence after prior immunotherapy.” Treatment options in advanced melanoma are currently limited and consist mainly of targeted therapy, immunotherapy and chemotherapy, with limited overall efficacy, and a considerable unmet clinical need remains.
AMT-253 was previously granted Breakthrough Therapy designation by the Center for Drug Evaluation (CDE) of China’s National Medical Products Administration (NMPA) in December 2025, and Orphan Drug Designation by the FDA in March 2026 for soft tissue sarcoma.
About Breakthrough Therapy Designation
Breakthrough Therapy Designation is a program established by the U.S. FDA to expedite the development and review of drugs for serious or life-threatening conditions, and applies to products for which preliminary clinical evidence indicates the potential for substantial improvement over available therapy. The designation may be granted early in clinical development. Following designation, the sponsor receives more intensive FDA guidance on drug development, and the product may be eligible to submit portions of a marketing application on a rolling basis.
About AMT-253
AMT-253 is a MUC18-directed ADC. It is composed of a proprietary antibody with high binding affinity to MUC18, a protease-cleavable linker, and an exatecan payload (a potent, clinically validated topoisomerase-1 inhibitor). The linker is purpose-designed for conjugation of the exatecan payload, yielding a highly stable and homogeneous ADC. The payload is not a substrate for BCRP/P-gp, drug efflux pumps that contribute to chemotherapy resistance across many therapies. Preclinical data indicate that ADCs based on this linker/payload demonstrate a stronger “bystander effect” than certain competing ADCs.** AMT-253 has a drug-to-antibody ratio of approximately 8. It is currently being evaluated in Phase I/II clinical trials for efficacy in patients with advanced melanoma and other advanced solid tumors. For more information on the Phase I trial in Australia (NCT05906862) and the Phase I/II trial in China (NCT06209580), please visit http://clinicaltrials.gov.
** Weng et al., (2023) Cancer Discovery 13:950–73
About Multitude Therapeutics
Multitude Therapeutics is a clinical-stage company focused on the development of ADC therapeutics. The company employs two technology platforms: MabArray, an antibody platform for the discovery of novel cell-surface oncology targets that enables the pursuit of first-in-class targets; and PAD, a molecular design platform that serves as the backbone of the company’s R&D technology, integrating a clear understanding of tumor biology and existing treatment options with years of experience in ADC design. For identified therapeutic targets in selected indications, this platform supports the rational structural design of ADCs to achieve precise tumor targeting, potent cytotoxicity and minimal off-target effects. The combination of MabArray and PAD generates significant synergy, enabling Multitude Therapeutics to build an ADC “atlas” with the potential to treat malignancies of high unmet medical need and to achieve deeper and more durable responses. Building on these platforms, the company currently has several ADC programs in development, including three programs directed at potential first-in-class targets. Multiple ADC programs, including those against all potential novel targets, have entered clinical development and have demonstrated favorable safety and efficacy, providing initial validation of the company’s platform technologies.