TLX101 (formerly ACD-101) is a small molecule (4-Iodophenylalanine), radioactively labeled with either 123I for SPECT Imaging, 124I for PET Imaging or 131I for therapy. These molecules target glioma. Orphan drug status for glioma diagnosis was granted to 123I-ACD-101 by EMA in 2006. Orphan drug status for glioma therapy was granted to 131I-ACD-101 in 2006 by the EMA and in 2011 by the FDA.

TLX-101 is a cytostatic molecule with an intrinsic radio-sensitizer effect, increasing the biological effect of external field Radiation (current standard therapy for brain tumors). Intratumoral accumulation of TLX-101 occurs independently from histological tumor type in low- and high-grade gliomas alike (WHO grades II–IV).

123I-TLX-101 and 131I-TLX-101 have entered Phase I clinical trials. 131I-TLX-101 showed a sustained reduction of tumor volume. The patient was still alive 3.5 years after first treatment and no further treatment option. By September 2018, an international multi-center study to evaluate the safety, tolerability, dosing schedule and preliminary efficacy was initiated in patients with recurrent glioblastoma multiforme in conjunction with External radiotherapy (XRT) . Study is expected to be completed by October 2022.

Target/Mechanism: LAT-1

Carrier/Ligand: Phenylalanine

Radiation type: beta electrons (β)