Safety and Efficacy of BMS-986504 in Unresectable Malignant Peripheral Nerve Sheath Tumor

Malignant Peripheral Nerve Sheath Tumors (MPNSTs) are fast-growing, aggressive cancers that develop in soft tissues. They are the main cause of serious illness and death in people with neurofibromatosis type 1 (NF1), a condition that increases the risk of cancer. MPNSTs are rare, affecting about 1 in 100,000 people. In the United States, about 800 to 1,000 new cases are diagnosed each year. The 5-year survival rate is about 50%. However, this drops to about 20% when the cancer has spread or cannot be removed with surgery. Chemotherapy is often less effective, especially when the tumor cannot be removed by surgery, with response rates under 20%. There is a strong need to develop new and more targeted therapies for this type of cancer. When some benign (non-cancerous) nerve tumors, called neurofibromas, turn into MPNST, it is often caused by the loss of a group of genes called CDKN2A on chromosome 9. These genes normally help prevent tumors from forming. When a part of chromosome 9 called 9p21 is deleted, it can also cause the loss of a nearby gene called MTAP. MTAP is missing in about 25-50% of people with MPNST. MTAP plays an important role in the methionine salvage pathway and serves a critical role in methylation reactions. When MTAP is lost, cells have problems with purine metabolism and become more dependent on another pathway, the arginine methylation pathways. This pathway is important for processes like DNA repair and control of the cell cycle. An enzyme called protein arginine methyltransferase 5 (PRMT5) helps carry out arginine methylation by adding small chemical groups (methyl groups) to proteins. When both copies of the MTAP gene are lost (called homozygous deletion), cells rely even more on PRMT5 to survive. At the same time, a substance called methylthioadenosine builds up and partly blocks PRMT5 activity. Because of this, completely blocking PRMT5 can cause MTAP-deficient cancer cells to die, a concept known as "synthetic lethality." For people with MPNST who have homozygous MTAP deletion confirmed by next-generation sequencing (NGS), drugs that block PRMT5 may help shrink tumors. A drug called BMS-986504 is a first-in-class PRMT5 inhibitor designed to specifically target MTAP-deficient tumor cells by binding to the PRMT5-MTA complex. BMS-986504 was recently studied in a Phase 1 trial and showed evidence of anti-tumor activity. People with tumors that could not be removed with surgery with a homozygous MTAP deletion and whose disease had gotten worse since their last treatment were given varying doses of BMS-986504. Three of the 6 people enrolled had disease progression. The remaining 3 participants had partial responses, meaning that there was a \>30% improvement from their baseline per RECIST v1.1 criteria. Each of these 3 participants had different doses of the study drug, which suggests a dose-independent response. Since the current treatments for MPNST that cannot be removed through surgery are poor, it is important to identify new treatment strategies that may improve how long someone lives with this type of cancer and their health outcomes. This study aims to assess the safety and efficacy of BMS-986504 in people with MPNST that cannot be removed with surgery and with homozygous MTAP deletion.