Theseus is developing pan-variant tyrosine kinase inhibitors (TKIs) to target all classes of cancer-causing and resistance mutations that lead to clinically relevant variants in a particular protein in a given type of cancer.

The company is developing THE-349, a fourth-generation, selective epidermal growth factor receptor (EGFR) inhibitor for C797X-mediated resistance to first- or later-line osimertinib treatment in patients with non-small cell lung cancer (NSCLC), a pan-variant BCR-ABL inhibitor for the treatment of relapsed/refractory chronic myeloid leukemia (CML) and newly diagnosed Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL), and a next-generation, highly selective, pan-variant KIT inhibitor for the treatment of early-line GIST.