Emactuzumab[1] (RG-7155) is a humanized monoclonal antibody directed against colony stimulating factor 1 receptor (CSF-1R) expressed on macrophages[2][3] and has demonstrated a profound antitumor effect through interference with the CSF-1/CSF-1R axis, along with a manageable safety profile in patients with diffuse-type tenosynovial giant cell tumors (d-TGCT).

This prevents CSF1R activation and CSF1R-mediated signaling in these cells, which blocks the production of inflammatory mediators by macrophages and reduces inflammation.

TAMs play key roles in immune suppression and promoting inflammation, tumor cell proliferation and survival.

[7] In a Phase Ib clinical study, biopsies were taken from TGCT subjects before and on emactuzumab treatment, and immunohistochemistry was performed with antibodies against CD68/CD163 (biomarkers for TAMs) and CSF-1R.

Altogether, 36 patients (57%) had evaluable paired tumour biopsy samples (taken at baseline and on treatment at four weeks, after two cycles of emactuzumab at doses of 900 – 2000 mg).