Cobimetinib hemifumarate is primarily used in the treatment of certain types of cancer, particularly metastatic melanoma. It is often prescribed in combination with another drug, vemurafenib, to enhance its effectiveness. This combination targets specific genetic mutations in cancer cells, inhibiting their growth and proliferation. The drug works by blocking the activity of the MEK enzyme, which is part of a signaling pathway that promotes cancer cell survival. By disrupting this pathway, cobimetinib hemifumarate helps to slow down or stop the progression of the disease. It is typically administered orally, and its use is closely monitored by healthcare professionals to manage potential side effects and ensure optimal therapeutic outcomes.