Tovorafenib for Progressive, Relapsed, or Refractory Langerhans Cell Histiocytosis

To determine overall response rate for children and young adults with relapsed or refractory BRAFV600E positive (cohort 1) and BRAFV600E negative (cohort 2) Langerhans cell histiocytosis (LCH) treated with tovorafenib (DAY101) after 2 cycles and must be maintained 4 weeks later.

• Children and Adults 180 days - 22 years of age
• Must have progressive, relapsed, or recurrent Langerhans Cell Histiocytosis
• Must have had histologic verification of Langerhans Cell Histiocytosis, measurable disease, documented by radiographic imaging, progressive or refractory disease or experience relapse after at least one previous systemic treatment strategy
• Must have a body surface area of ≥ 0.3 m^2

• Tovorafenib given orally once weekly
• Multigated Acquisition or Echocardiogram scans to assess heart structure and function
• Fluorodeoxyglucose Positron Emission Tomography (FTG-PET) or Computed Tomography (CT) scans
• Blood and urine samples
• Bone marrow biopsy and aspiration and lumbar puncture (Patients with suspicion of bone marrow and/or central nervous system involvement only)