A Phase II trial evaluating glembatumumab vedotin (GV) in patients with relapsed or refractory osteosarcoma failed to meet its primary endpoint of disease control at 4 months, according to a study published in Clinical Sarcoma Research. The trial, which enrolled patients aged 12 to 50, assessed the efficacy and safety of GV, an antibody-drug conjugate targeting glycoprotein non-metastatic B (gpNMB), a protein highly expressed in osteosarcoma cells. While the drug was generally well-tolerated, the observed anti-tumor activity was insufficient to warrant further investigation in this patient population.
The study enrolled 22 patients with recurrent osteosarcoma, all of whom were evaluable for response. Patients received GV at a dose of 1.9 mg/kg on day 1 of each 21-day cycle. The primary endpoint was disease control at 4 months, assessed by Response Evaluation Criteria in Solid Tumors (RECIST). Secondary endpoints included overall response rate, progression-free survival, and safety.
Results showed that only one patient achieved a partial response, and two patients had stable disease. The remaining patients experienced disease progression. There was no correlation between gpNMB expression levels in tumor samples and response to GV treatment. The most common grade III adverse event was rash. One death occurred during the study due to end-organ failure, potentially related to GV.
"GV was well tolerated in this population. Although there was some antitumour activity, the extent of disease control in stage I did not meet the level required to proceed to stage II," the authors stated.
Background on Osteosarcoma and Glembatumumab Vedotin
Osteosarcoma is a rare primary bone cancer that predominantly affects children and adolescents. Recurrent osteosarcoma carries a poor prognosis, highlighting the need for novel therapeutic strategies. Glembatumumab vedotin is an antibody-drug conjugate consisting of a fully human IgG2 monoclonal antibody (CR011) targeting gpNMB, conjugated to monomethyl auristatin E, a microtubule inhibitor. The rationale behind targeting gpNMB is based on its overexpression in osteosarcoma cells, making it a potential target for antibody-mediated drug delivery.
Implications for Future Research
While this trial did not meet its primary endpoint, the data provide valuable insights into the activity and safety of glembatumumab vedotin in recurrent osteosarcoma. Further research may explore alternative dosing regimens, combination therapies, or patient selection strategies to potentially enhance the efficacy of GV or similar gpNMB-targeted agents in this challenging disease.
