EPIK-B2 is a 2-part Phase 3 study to evaluate ALP plus T+P as 1L maintenance tx in pts with HER2+, PIK3CA-mut ABC....Six of 15 pts (40%; 2 in Cohort A, 4 in Cohort B) had PIK3CA-mut disease. Among these, ORR was 50% (n/N=3/6) and CBR was 100% (n/N=6/6). Tumor response was maintained in 5 of 6 pts with PIK3CA mutations (83%) after ≥21 cycles of tx (range, 21-31)….ALP plus T+P combination is safe; reported AEs align with those in previous ALP studies. Preliminary efficacy data suggest promising clinical benefit with ALP plus T+P for pts with HER2+ PIK3CA-mut disease.