Blueprint Medicines Corporation, a leader in discovering and developing targeted kinase medicines for patients with genomically defined diseases, has dosed the first patient in a phase 1 clinical trial of BLU-667, an investigational RET inhibitor for patients with non-small cell lung cancer (NSCLC), medullary thyroid cancer (MTC) and other advanced solid tumors that harbor a RET alteration.

"By rapidly initiating a clinical trial for our potent and selective RET inhibitor BLU-667, we have successfully achieved a key 2017 milestone," said Jeff Albers, chief executive officer of Blueprint Medicines. "This continued progress underscores our commitment to build Blueprint Medicines into a sustainable company. BLU-667 has a unique product profile differentiated from our other clinical-stage programs by its potential to address predicted resistance mutations that may arise. With BLU-667 enrollment underway, we are further increasing our diversified pipeline of potent, highly selective investigational medicines that target specific disease drivers in genomically-defined patient populations."

"RET fusions and mutations are recognized as important drivers in multiple cancers, but existing multi-kinase inhibitors with RET activity do not provide sufficient, durable benefit for patients with RET alterations," said Andy Boral, M.D., Ph.D., chief medical officer of Blueprint Medicines. "BLU-667 is being developed to potently inhibit RET, and simultaneously prevent the development of on-target resistance, which we believe will provide more lasting clinical benefit and prevent or delay disease recurrence. We look forward to working with patients and physicians to explore BLU-667's potential."

BLU-667 is an orally available, potent and selective inhibitor designed to target RET mutations, fusions and predicted resistance mutants. RET activating fusions and mutations are a key disease driver in multiple cancers, including NSCLC and MTC, with RET fusions implicated in approximately 1-2% of patients with NSCLC, and RET mutations implicated in approximately 60% of patients with MTC. In addition, genomic analyses published by scientists at Blueprint Medicines have identified RET fusions at low frequencies in colon and breast cancer. Currently, there are no approved therapies that selectively target RET-driven cancers, though there are several approved multi-kinase inhibitors with RET activity being evaluated in clinical trials.  Thus far, clinical activity attributable to RET inhibition has been uncertain for these inhibitors, likely due to insufficient inhibition of RET and off-target toxicities. In preclinical studies using biochemical and cellular assays, and tumor models, BLU-667 was active against RET fusions and mutations, including predicted resistance mutations.