The Medicines and Healthcare products Regulatory Agency (MHRA) in the United Kingdom officially approved Nirogacestat hydrobromide, marketed as Ogsiveo, on January 7, 2026, for the treatment of progressing desmoid tumours in adults. This landmark decision provides the first specific systemic treatment option for this rare and often debilitating condition in the UK. Desmoid tumours are non-cancerous growths that develop in the body's connective tissues, typically in the arms, legs, or abdomen. While not malignant, they can be aggressive, causing significant damage to surrounding tissues, leading to chronic pain, restricted movement, and sometimes making surgical removal difficult or impossible. Nirogacestat hydrobromide functions by inhibiting certain proteins crucial for tumour growth. Clinical studies, notably the Phase 3 DeFi trial, demonstrated that patients receiving nirogacestat experienced longer periods without their condition worsening and often avoided the need for surgical intervention. This represents a substantial improvement in managing a disease with limited prior treatment options. Patient safety remains a top priority, and the MHRA has stated it will continue to closely monitor the drug's safety and effectiveness. Common side effects reported include diarrhoea, rash, nausea, fatigue, and headache. A serious potential side effect is premature menopause, which may affect more than one in ten individuals. Furthermore, nirogacestat is contraindicated during pregnancy due to potential harm to an unborn baby, necessitating highly effective contraception. It is important to note that nirogacestat (Ogsiveo) received approval from the U.S. Food and Drug Administration (FDA) on November 27, 2023, marking it as the first-ever approved treatment for desmoid tumours globally. Subsequently, it was also approved in the European Union in 2025. The UK's approval, granted under the International Recognition Procedure, follows these earlier endorsements, bringing this crucial therapy to British patients.