Sickle cell disease (SCD) is a genetic condition causing red blood cells to have an abnormal, sickle shape. This can lead to anemia, which is a condition where you don't have enough healthy red blood cells to carry oxygen, and it can cause serious health problems affecting the lungs, heart, kidneys, and nerves. Traditional treatments for blood clots—common in SCD—can increase bleeding risks. This study aims to test a new drug, fostamatinib, in adults aged 18 to 65 with stable SCD.

The study requires participants to visit the clinic six times over 12 weeks, each lasting 2 to 3 hours. During these visits, participants will undergo physical exams and blood tests. The drug, a tablet, is taken at home twice daily for up to six weeks. If participants tolerate the drug well, the dose may increase after two weeks. A final visit occurs four weeks after stopping the drug to check for side effects.

• The study lasts about 12 weeks with six clinic visits.
• Participants take the drug twice daily for up to six weeks.
• Regular check-ups ensure safety and monitor side effects.