Modified LCH-III Regimen With or Without Luvometinib for Multisystem Pediatric Langerhans Cell Histiocytosis

Lab studies show that when the MAPK pathway is overactive, it makes LCH cells harder to kill (more resistant to dying naturally). Combining an MAPK inhibitor with chemotherapy might make the abnormal cells easier to destroy. Chemotherapy also changes the immune environment in the body, which could help clear out the bad cells more completely.

Several small studies and real-world experiences have already tested this idea in children and adults with hard-to-treat LCH:

One study combined MAPK inhibitors with certain chemotherapy drugs and saw very few relapses, especially when treatment lasted longer.

Another study using a similar approach achieved 100% response in a group of children (including some as first treatment), with most staying in remission afterward, and no extra serious side effects from the combination.

A Chinese study using prednisone, another chemo drug, plus an MAPK inhibitor showed good results with low relapse after stopping.

Early data from our own center found that children who got an MAPK inhibitor together with the standard LCH-III treatment had much lower relapse rates (only 20%) compared to those who got the inhibitor alone (75% relapse).

Based on this growing evidence, this study plans to run a large, carefully designed trial at multiple hospitals. It will randomly assign children with multisystem LCH to receive either the improved (modified) version of the standard LCH-III chemotherapy alone, or the same chemotherapy combined with luvometinib. The goal is to compare how well each approach works and to learn more about whether adding this targeted drug to chemotherapy can improve treatment for children with this disease.

Inclusion criteria

• Children aged 0-18 years, of either sex.
• Pathologically confirmed diagnosis of Langerhans cell histiocytosis (LCH) with positive staining for CD1a and/or CD207 (Langerin), and no prior treatment specifically directed against LCH.
• Multisystem involvement of LCH, as determined by clinical and imaging evaluation.
• Provision of written informed consent (by parent/legal guardian and, where appropriate, assent from the child), with willingness to comply with the study treatment regimen and follow-up assessments.

Exclusion criteria

• Presence of any other significant underlying medical condition, including but not limited to primary immunodeficiency disorders, congestive heart failure, renal insufficiency, chronic viral hepatitis, HIV infection, or status post solid organ transplantation.
• History of a second (secondary) malignancy.
• QTcF interval > 0.47 seconds on electrocardiogram performed prior to enrollment.
• Ophthalmologic screening prior to enrollment revealing retinal vein occlusion, retinal pigment epithelial detachment, or other clinically significant ocular abnormalities that, in the opinion of the investigator, contraindicate participation.
• LCH harboring Class 3 MEK pathway mutations, specifically the following alterations: L98_I103del, L98_K104del, P105_A106del, P105_I107delinsL, L101_I103delinsF, E102_I103delinsF, E102_I103del, E102_I103delinsV, E102_I103delinsVN, E102_K104delinsQ, or I103_A106del.
• Refusal or inability to provide written informed consent (or assent, as applicable).