Announcement of Tohoku University’s Press Release on Phase II Clinical Trial Results for Angiosarcoma

Our company, in collaboration with the research group led by Associate Professor Takashi Fujimura of the Department of Dermatology, Graduate School of Medicine, Tohoku University, is working on the development of a novel treatment for the refractory skin tumor, angiosarcoma. From September 2023 to December 2024, a Phase II trial was conducted to examine the safety and efficacy of the combination therapy of paclitaxel²⁾ and the PAI-1 inhibitor RS5614 in 16 patients with cutaneous angiosarcoma¹⁾ who had not responded to paclitaxel. The trial confirmed that paclitaxel safely enhanced the antitumor effect of RS5614 (disclosed on February 10, 2026). We are pleased to announce that Tohoku University has issued a press release regarding these research results.

Angiosarcoma is a highly malignant skin cancer in which vascular endothelial cells³⁾ become cancerous. Its incidence is higher in Japan compared to Western countries and has been increasing in recent years. Paclitaxel is the first-line treatment for angiosarcoma, but overall survival is short at 649 days, making it difficult to achieve long-term remission. After paclitaxel becomes ineffective, there are few effective treatment options, making the creation of new therapies an urgent medical challenge. In this investigator-initiated clinical trial, RS5614 and paclitaxel combination therapy was administered to patients with cutaneous angiosarcoma who had become ineffective with paclitaxel. Analysis showed a median overall survival (OS) ⁴⁾ of 21.1 months, significantly better than the 12.1 months achieved with existing treatments (pazopanib) ⁵⁾. Progression-free survival (PFS) ⁶⁾ also improved to 4.1 months compared to 2.8 months with existing treatments, with disease stabilization confirmed in 86.7% of evaluated patients. Regarding safety, the incidence of serious side effects was lower than with existing treatments, demonstrating good tolerability. A comprehensive report will be compiled and published in a journal.

¹⁾ Angiosarcoma
Angiosarcoma is a type of skin cancer; angiosarcoma of the scalp in particular is rare, occurring in about 2.5 people per 1 million, but it is highly malignant, progresses rapidly, and the 5-year disease-free survival rate has been reported to be 20% or less. There is no established standard treatment.

²⁾ Paclitaxel
A chemotherapy agent (anticancer drug) whose antitumor effect was discovered from the bark of the Pacific yew tree; it is now chemically synthesized. It is thought to bind to microtubules involved in cell division, stopping cancer cells from dividing and causing them to die (cell death).

³⁾ Vascular endothelial cells
Cells that line the inside of blood vessels. In addition to forming part of blood vessels, they serve as a site where blood and tissues exchange substances such as oxygen and nutrients, and they also produce various bioactive substances that help maintain the function of tissues and organs.

⁴⁾ Overall survival (OS)
The period from the start of treatment until the patient’s death; one of the main indicators used to evaluate the effectiveness of cancer treatment.

⁵⁾ Pazopanib: A type of molecular targeted therapy that suppresses blood flow to cancer cells to inhibit their growth. It is mainly used to treat renal cell carcinoma and soft tissue sarcoma. The incidence of adverse events is high at 93.5%, and major side effects include diarrhea, hypertension, fatigue, nausea/vomiting, liver dysfunction, and taste disturbances.

⁶⁾ Progression-free survival (PFS)
One of the indicators used to evaluate cancer treatment efficacy; it refers to the period from the start of treatment until cancer progression or recurrence is confirmed, or until the patient dies. The longer this period is, the more effective the treatment is considered to be.