Subsequent to his coming off-study, NGS of his marrow aspirate, of which 67% were CLL cells (02/15/2024, Table 1), revealed yet another distinctive subclone of CLL cells with a new mutation in BTK c.1283C>A at a VAF of 28%, resulting in BTK p.A428D, but without detectable BTK c1442G>C or BTK c.1421C>T, while maintaining the same mutation in TP53, namely c.730G>A, at a VAF of 62% and same complex karyotype. The gene discussed is BTK; the disease is B-cell chronic lymphocytic leukemia.