Background: The oral Akt inhibitor IPAT is being evaluated in cancers with a high prevalence of PI3K/Akt pathway activation, including TNBC. Methods: Eligible patients (pts) had measurable inoperable locally advanced/metastatic TNBC previously untreated with systemic therapy. Pts were stratified by prior (neo)adjuvant therapy, chemotherapy-free interval and tumor PTEN status, and randomized 1:1 to P 80 mg/m² (d1, 8 & 15) with either IPAT 400 mg or PBO (d1–21) q28d until progression or unacceptable toxicity. Co-primary endpoints were progression-free survival (PFS) in the ITT population and pts with PTEN-low tumors by IHC. Secondary endpoints included objective response rate (ORR), duration of response (DoR) and overall survival in the ITT and IHC PTEN-low populations, efficacy in pts with PIK3CA/AKT1/PTEN-altered tumors by next-generation sequencing (NGS), and safety. Results: Baseline characteristics were generally balanced between arms. Efficacy is shown below. The most common grade ≥3 AEs (grouped terms) were diarrhea (23% IPAT+P vs 0% PBO+P; no grade 4 or colitis in either arm), neutropenia (18% vs 8%), asthenia (5% vs 6%), peripheral neuropathy (5% vs 5%) and pneumonia (5% vs 0%). More pts receiving IPAT+P than PBO+P had an AE leading to dose reduction of IPAT/PBO (21% vs 6%) or P (38% vs 11%) but median cumulative dose intensity was similar (IPAT/PBO: 99% vs 100%; P: 100% vs 100%). AEs led to IPAT/PBO discontinuation in 13% vs 11% of pts, respectively; 2 pts (3%) discontinued IPAT for grade 3 diarrhea. Conclusions: Adding IPAT to P for TNBC modestly improved PFS in the ITT pts. The effect was more pronounced in the prespecified subgroup with PIK3CA/AKT1/PTEN alterations, warranting further evaluation of IPAT in these pts. AEs were manageable. Clinical trial information: NCT02162719

^aStratified, ^bUnstratified.