Nurix Therapeutics Inc.’s Dec. 12 disclosure that the U.K. Medicines & Healthcare products Regulatory Agency granted to clearance for the company to kick off a phase I study with Bruton tyrosine kinase (BTK) inhibitor NX-5948 pumped more juice into the space, which has been consistently intriguing since the first drug in the class was approved about eight years ago by the FDA. The San Francisco-based firm will start an experiment in patients with relapsed and refractory B-cell malignancies at clinical sites in the U.K., with dosing of the first subject expected in the first half of 2022.