BOS172738 was already in trials since 2019 but we didn't know much about it. In the phase 1a results recently presented at ASCO 2021 they reported that their drug is highly selective for RET with a response rate of 33% in the 34 patients enrolled with RET driven NSCLC, and 44% in the 21 patients enrolled with RET mutated Medullary Thyroid Cancer. Notably, responses were also seen in patients with parenchymal brain metastases. The median duration of response has not been reached, and the longest responder remains on treatment after 659 days. The side-effect profile also seems overall well tolerated.
Although patients who had been previously treated with the selective RET inhibitors Selpercatinib and Pralsetinib were NOT included within the phase 1a portion of their study, first author and presenter Dr. Patrick Schoffski stated that they are currently enrolling for the phase 1b dose expansion portion of the trial and are looking to enroll a cohort of patients who have already been treated with selective RET inhibitors. With many trial locations outside of the US, BOS172738 may prove to be another viable therapeutic option for people with RET driven malignancies. It is wonderful to have another tool in the arsenal against RET!
BOS172738 is a highly potent and selective RET inhibitor with a differentiated safety profile and clinical activity against RET-altered tumors, including patients with brain metastases. BOS172738 continues to be evaluated in patients with NSCLC, MTC, and in patients previously treated with other selective RET inhibitors. Clinical trial information: NCT03780517