Imatinib (brand name GLEEVEC) is FDA and EMA-approved for the treatment of a form of leukemia in 2003. Imatinib works by targeting a protein in the same family as CSF1. Because the proteins targeted by imatinib are functionally similar to the protein that drives TGCT growth, imatinib works to shrink or stabilize TGCT in a subset of patients.
According to a study that evaluated patients with advanced or recurrent diffuse TGCT, one third of patients treated with daily imatinib for 52 months had significant shrinkage of their TGCT, 27% had partial shrinkage, and 4% of patients had shrinkage so significant that they had unmeasurable disease (1). Sixty-five percent of patients on imatinib had stable disease with no progression at 52 weeks. Symptoms improved in 78% of TGCT patients, even those with stable disease.
Common side effects included:
fatigue (50%)
fluid retention (48%)
nausea (34%)
skin rash/itchy (12%)
Other side effects included abdominal cramps, headache, diarrhea or constipation, weight changes, and appetite changes. Due to side effects, patients electing into surgery, switching to other medical treatments, physicians decision, and other reasons, 66% of patients discontinued imatinib.
References 1. Vespoor F.G.M, Mastboom M.J.L, et al. 2019. Long-term efficacy of imatinib mesylate in patients with advanced Tenosynovial Giant Cell Tumor. Scientific Reports. doi: 10.1038/s41598-019-51211-y
