- Heat-triggered release mechanism unequivocally confirmed
- Favorable safety profile with good tolerability
- Signs of encouraging clinical activity in heavily pre-treated patients including meaningful progression-free survival (PFS)
- One participant with previously unresectable disease in DL2 underwent surgery, indicating no vital tumor cells in the target lesion
Munich, Germany – June 24, 2025 – Thermosome GmbH, a clinical-stage drug development company focused on targeted tumor therapies, today announced new, encouraging data from its ongoing Phase I clinical trial evaluating its lead compound THE001 (DPPG2-TSL-DOX) in combination with regional hyperthermia (RHT) for the treatment of soft tissue sarcomas (STS). The Phase I study is assessing the safety, pharmacokinetics (PK), and preliminary efficacy of THE001 + RHT in participants with locally advanced unresectable or metastatic STS, who have exhausted all prior treatment options, including standard doxorubicin (DOX).
Despite the early stage of development and a small number of participants, signs of meaningful clinical activity have emerged. Among the heavily pre-treated participants – including patients pre-treated with DOX – the median progression-free survival (PFS) following treatment with THE001 + RHT reached 4.5 months across both dose levels (20 and 40 mg/m²). This exceeds the typical median PFS of 2.7 to 3.5 months observed with first-line DOX therapy in treatment-naïve patients at DOX doses of 75 mg/m2, i.e., 2-4x higher than doses of THE001 applied in the Phase I setting.
At dose level 2 (40 mg/m²), the mean PFS reached 7.1 months. Two out of three participants in this dose level achieved a partial response (PR) according to Choi criteria and completed the maximum extended treatment phase of 12 cycles (~8.3 months). Notably, one participant whose tumor was initially considered unresectable, could undergo surgical resection at the end of the extended study treatment. This participant showed a tumor shrinkage of -16% in the sum of target lesions, a partial response according to Choi criteria and no vital tumor cells in the resected target lesion.
Across dose levels 1 and 2, THE001 + RHT demonstrated a favorable safety profile. There were no dose-limiting toxicities or high-grade treatment-related adverse events that led to treatment discontinuation, underscoring the good tolerability of THE001 in combination with RHT.
“These findings not only provide consistent proof of the galenic concept of heat-triggered, largely complete DOX release from THE001, but also demonstrate clinical benefit in a highly challenging patient population,” said Dr. Frank Hermann, Chief Medical Officer of Thermosome. “We are particularly encouraged by the results of one participant who underwent resection after 12 full treatment cycles with THE001 and regional hyperthermia with no vital tumor cells found in the resected target lesion. These results clearly support future exploration in the neoadjuvant setting.”
Alexander Eggermont, Professor of Clinical and Translational Immunotherapy, University Medical Center, Utrecht, and a member of Thermosome´s Clinical Advisory Board, commented: “The Phase I data of THE001, a thermosensitive liposomal DOX, and regional hyperthermia in heavily pre-treated DOX-experienced soft tissue sarcoma patients, particularly from dose level 2, are very encouraging. These results demonstrate the clinical potential of this highly innovative approach and provide the necessary foundation for transitioning into Phase II proof-of-concept development. I am excited to support this important work and look forward to advancing this promising therapy, which has the potential to significantly improve outcomes for patients with soft tissue sarcoma, particularly in the neoadjuvant setting.”
“It is exciting to see the promising results of THE001 combined with regional hyperthermia, demonstrating strong potential to address the high unmet need for better treatments for soft tissue sarcoma,” added Prof. Shreyaskumar Patel, the Robert R. Herring Distinguished Professor of Medicine and Medical Director of the Sarcoma Center at The University of Texas MD Anderson Cancer Center, Houston Texas, and a member of Thermosome’s Clinical Advisory Board. ”Expansion into Phase II, also including the U.S., would offer a much-needed validation of this new therapeutic strategy for patients with STS. I look forward to supporting the advancement of this innovative treatment option to improve outcomes for patients here in the U.S. and globally on the back of the orphan drug designation granted by the FDA.”
Considering supportive feedback from the German Federal Institute for Drugs and Medical Devices (BfArM) on the development of THE001 + RHT in the neoadjuvant setting, the available data from last-line participants are intended to support further development in the neoadjuvant setting.
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About Thermosome
Thermosome is a clinical-stage drug development company focused on targeted tumor therapy combined with immune stimulation for improved cancer therapy. At its core is a novel, proprietary tumor targeting approach that allows for significantly increased local drug concentration and improved tumor penetration to achieve improved clinical treatment efficacy.
The first clinical indication for its lead drug candidate THE001 is soft tissue sarcoma, where the Company aims to improve the current standard of care (free doxorubicin). Thermosome’s approach enables targeted tumor treatment independent of specific molecular targets and covers patient populations across all chemo-sensitive tumor subtypes. More information: www.thermosome.com
About THE001
Thermosome’s clinical-stage lead drug candidate THE001 is a thermosensitive liposomal formulation of the chemotherapeutic drug doxorubicin (DPPG2-TSL-DOX). It has a different mode of action than conventional liposomes. Thermosome’s technology enables intravascular drug release initiated by a mild heat trigger using clinically established hyperthermia devices. This results in up to 15-fold higher local drug concentrations in the tumor and aims to improve clinical treatment efficacy by creating a local boost at the desired site of action. These high local concentrations, which also reach less well perfused areas, are intended to overcome drug resistance. This effect cannot be achieved by administration of conventional doxorubicin due to systemic toxicity. Thermosome intends to further enhance treatment efficacy through an additive immune response induced by regional hyperthermia. THE001 has potential for further development in other anthracycline-sensitive solid tumors, such as breast, bladder, and ovarian cancer. THE001 has been granted Orphan Drug Designation for STS in Europe and the United States.
About the Phase I Study
The Phase I, open-label, interventional dose-escalation trial enrolling patients with (including DOX-) pre-treated locally advanced unresectable or metastatic STS (NCT05858710) is being conducted at two German clinical sites testing THE001 at various different dose levels in initially up to 6 cycles every 3 weeks with option to extend to up to 12 cycles in participants with at least disease control. Both completed dose level (20 mg/m² and 40 mg/m²) were well tolerated and declared safe by the independent data safety monitoring board (DSMB). Primary endpoints of the study are the safety and tolerability of THE001 and the determination of the maximum tolerated dose. A secondary objective is the evaluation of anti-tumor activity. Initial clinical data were presented at the CTOS 2024 Annual Meeting (link).
About Soft Tissue Sarcomas (STS)
STS is an atypical tumor with a patient population that includes many young patients. Locally advanced STS (LA-STS) are large invasive tumors that are difficult or impossible to resect. Neoadjuvant therapy is used to shrink these tumors preoperatively to allow tumor surgery with curative intent. Free doxorubicin in combination with ifosfamide or dacarbazine has been the gold standard for neoadjuvant therapy of all chemo-sensitive LA-STS for several decades. Guidelines also recommend combining DOX-based therapy with regional hyperthermia. However, with response rates of less than 30%, there is a significant unmet need for improved treatment options.
Soft tissue sarcomas occur in more than 50 different subtypes that do not share a common driver mutation, making biologic targeting more difficult than physically controlled targeting with the most active agent.
Company Contact
Thermosome GmbH
Am Klopferspitz 19
82152 Planegg/Martinsried (Germany)
Phone: +49 89 7167760 31
media@thermosome.com
Media Inquiries
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Dr. Ludger Wess / Ines-Regina Buth, Managing Partners
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Phone: +49 40 88 16 59 64 / +49 30 23 63 27 68
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