SOT106 earned an FDA fast track designation for advanced or recurrent soft tissue sarcoma.
The FDA has granted fast track designation to SOT106, an investigational antibody-drug conjugate (ADC) that targets leucine-rich repeat-containing 15 (LRRC15), for the treatment of patients with soft tissue sarcoma (STS).1
SOT106 has not yet entered clinical testing, but a first-in-human trial is expected to initiate later in 2026. The designation was instead supported by preclinical findings and by the biology of the target.
In preclinical studies, SOT106 produced tumor regression in an LRRC15 low-expressing patient-derived xenograft model of pediatric osteosarcoma in which a first-generation LRRC15-targeting ADC was ineffective, and it generated complete responses across soft tissue sarcoma subtypes, non–small cell lung cancer, and head and neck squamous cell carcinoma.2 LRRC15 is a clinically validated target that is broadly expressed across multiple sarcoma subtypes, which Sotio said positions the agent to potentially address a broad population of patients with limited therapeutic options.1,3
"Receiving fast track designation for SOT106 is an important regulatory milestone that reinforces this program's potential to improve outcomes for patients facing these difficult-to-treat cancers," Vivi Boura, MD, chief medical officer of Sotio, stated in a news release.1
In the release, Boura said that soft tissue sarcomas remain a major unmet medical need, where decades of therapeutic progress have yet to translate into meaningful improvements for patients with advanced or recurrent disease. She added that the company aims to translate the agent's design and LRRC15-targeting strategy into a treatment option for patients across multiple STS subtypes.
SOT106 previously received FDA orphan drug designation for the treatment of osteosarcoma, which Sotio announced in June 2026.4
SOT106 comprises a proprietary antibody directed against LRRC15 conjugated to the microtubule-disrupting agent monomethyl auristatin E (MMAE) through LigaChem Biosciences' ConjuAll platform, which is designed for tumor-specific payload release.2,3 After binding LRRC15 on the cell surface, the ADC is internalized and trafficked to the lysosome, where the payload is released to inhibit microtubule polymerization and drive cell death; as a membrane-permeable agent, MMAE can also diffuse into adjacent cells to produce a bystander effect.
LRRC15 is a cell-surface protein expressed on malignant cells and within the tumor stroma of mesenchymal cancers, including a broad subset of sarcomas, and is largely restricted in normal adult tissues, which supports its use as an ADC target.3 Across preclinical models, the ADC demonstrated a favorable pharmacokinetic and safety profile, good stability in vivo, and a high therapeutic index, according to the company.2 On the basis of these findings, Sotio has characterized SOT106 as a potentially best-in-class LRRC15-directed ADC.
Soft tissue sarcomas comprise a heterogeneous group of mesenchymal malignancies encompassing numerous histologic subtypes, and systemic treatment for advanced or recurrent disease has historically centered on anthracycline-based chemotherapy, with limited long-term benefit.
The broader sarcoma field has seen recent regulatory and clinical activity: In July 2026, the FDA
Sotio expects to advance SOT106 into a first-in-human trial later in 2026; the company said trial information will be posted to ClinicalTrials.gov once available.1,3 No clinical efficacy or safety data for the agent have been reported to date.1
