A Study to Evaluate the Effect of Aficamten in Pediatric Patients With Symptomatic Obstructive Hypertrophic Cardiomyopathy (oHCM).

This study is looking for young people aged between 12 and 17 years old. To join, you must weigh at least 45 kg (about 7 stone). Your doctor will need to confirm you have obstructive hypertrophic cardiomyopathy (oHCM) based on specific measurements of your heart. It's also important that your oHCM is thought to be caused by a genetic issue, and you should be experiencing some symptoms of the condition.

You should have good quality pictures of your heart that can be taken with an echocardiogram, which is a type of ultrasound. If you're already taking certain heart medications like beta-blockers, verapamil, diltiazem, or disopyramide, you need to have been on a steady dose for at least four weeks before starting.

There are also some reasons why you might not be able to join. For example, if you have another significant heart valve problem, you would not be able to take part. The study team will carefully check all these requirements to make sure it's the right study for you.

If you decide to take part, the study will involve different periods. For the first 12 weeks (Period 1), you'll be randomly given either Aficamten or a placebo (a dummy medicine) – you won't know which one you're receiving. During this time, you'll have regular check-ups, probably including heart scans and blood tests, to see how you're responding and to check for any side effects. After these 12 weeks, if you've completed this part and meet certain health checks, you could continue into Period 2, which lasts for 52 weeks. In this period, everyone receives Aficamten, and the study team will keep a close eye on your health. There's also a possibility of continuing into an even longer Period 3, lasting 144 weeks, to monitor long-term effects. The total time you spend in the study depends on which periods you complete, but the initial treatment part is 12 weeks.