MedPacto's Vactosertib Achieves Complete Remission in Osteosarcoma Phase 2 Trial
Key Insights
MedPacto (search)'s Vactosertib demonstrated a 36.4% objective response rate in Phase 1 osteosarcoma (search) trials, including one complete remission case, representing more than three times the efficacy of existing treatments.
The company has expanded its Phase 2 clinical trial to six major Korean hospitals and received compassionate use requests from prominent US medical institutions including Johns Hopkins and Stanford.
Vactosertib has received orphan drug designation in the US and Europe, along with FDA Fast Track designation, with Breakthrough Therapy designation discussions ongoing.
MedPacto (search) announced breakthrough results from its Phase 1 clinical trial of Vactosertib for osteosarcoma (search) patients, achieving a complete remission in one patient and demonstrating an objective response rate of 36.4% - more than three times higher than existing treatments. The innovative drug development company presented these interim results at the Society for Immunotherapy of Cancer (SITC 2025) annual conference in Maryland from September 7-9.
Clinical Trial Results Show Exceptional Efficacy
In the Phase 1 study involving 11 patients with recurrent or refractory osteosarcoma (search), Vactosertib monotherapy produced one complete remission (CR) and three partial responses (PR), yielding an objective response rate of 36.4%. The treatment demonstrated excellent safety and tolerability profiles, with no dose-limiting toxicity observed.
"It is extremely rare worldwide that complete remission with monotherapy has been observed in osteosarcoma (search) patients who have repeatedly recurred and refused," stated a MedPacto (search) official. The company emphasized that these results clinically prove Vactosertib's anticancer mechanism.
The study results were selected for SITC's prestigious "Late Breaking Abstract (LBA)" track, which is reserved for studies recognized for innovation and scientific completion among the latest clinical data.
Expanded Clinical Program and Growing Medical Interest
MedPacto (search) has significantly expanded its clinical trial infrastructure as it advances into Phase 2. In South Korea, the company has increased its hospital network from three to six institutions, adding Seoul National University Hospital, Asan Medical Center, and Samsung Medical Center to the existing sites at National Cancer Center, Korea Cancer Center Hospital, and Bundang Seoul National University Hospital.
The company reports that a large number of eligible patients are already waiting at the newly added sites, with expectations that the clinical trial will proceed at an accelerated pace.
International interest has grown substantially, with MedPacto (search) receiving compassionate use requests from Johns Hopkins University Hospital (search) and Arkansas Children's Research Institute (ACRI). The company has previously administered Vactosertib to osteosarcoma (search) patients through compassionate use programs at ten overseas medical institutions, including Stanford University Hospital (search), UCLA Medical Center, Oregon Health & Science University Hospital, and Case Western Reserve University Hospital.
Mechanism of Action and Regulatory Recognition
Vactosertib functions by inhibiting the TGF-beta (search) signaling pathway, suppressing the expression of the oncogene C-Myc (search) in the osteosarcoma (search) microenvironment, and improving the immune environment. In ongoing clinical trials for relapsed or refractory patients, the drug has demonstrated a partial response rate of over 35%.
The therapeutic candidate has received significant regulatory recognition, including orphan drug designation in both the United States and Europe, and Fast Track designation from the FDA. MedPacto (search) is currently in discussions with the FDA regarding potential Breakthrough Therapy designation for Vactosertib.
Addressing Critical Unmet Medical Need
Osteosarcoma (search) represents a malignant tumor developing in bone and cartilage, classified as a rare cancer with particularly high incidence in children and adolescents. For the past 50 years, combination chemotherapy has remained the standard treatment approach, but limitations in improving treatment efficacy and survival rates have created high demand for new therapeutic options.
The disease is characterized by low response rates and high recurrence rates with existing treatments, making the development of new therapies a critical medical priority.
A MedPacto (search) representative noted, "As the recent Phase 1 results for Vactosertib in osteosarcoma (search) exceeded expectations, interest from medical professionals at home and abroad is growing. We will accelerate the clinical trial process to obtain early approval and will also actively pursue technology export opportunities."
The company is currently conducting Phase 2 clinical trials for adult osteosarcoma (search) patients while simultaneously running Phase 1 second cohort trials for adolescent patients aged 12 to 17.