In this study, researchers are seeking to find the highest dose of the investigational drug BGB-16673 that can be given safely in people with lymphoma and other types of B cell cancers that have come back or continued to grow despite prior treatment. BGB-16673 degrades a protein called BTK, which helps B cells live and grow. By degrading BTK, BGB-16673 may stop or slow the growth and activity of B cells, which could lead to improvement in the symptoms associated with B cell cancers. BGB-16673 is taken orally (by mouth).