The purpose of this study is to test the safety and tolerability of an experimental anticancer drug currently known as BGB-16673 for men and women who have B-cell malignancies.

Experimental means that it has not yet been approved by the US Food and Drug Administration (FDA).

BGB-16673 is an oral Bruton tyrosine kinase (BTK) targeted protein degrader, which targets and binds to BTK in the body, inhibiting its activity. BTK in the body allows malignant cells to survive and BTK inhibitors interfere with this process.

Participants will join either the dose finding phase of the study or the dose expansion phase of the study. During the dose finding phase, a small group of participants will be given the smallest planned dose of BGB-16673. If this dose is tolerated well by the participants, the next cohort of participants will receive a slightly higher dose of BGB-16673. The study team will let participants know in which phase of the study they are participating and what dose they will receive.
   
Participation in this research will last about 2 years, but may vary based on how participants respond to the study drug.