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Using capivasertib in the hormone-sensitive setting is preferred because the cancer is more likely dependent on the AKT pathway for growth. In later, castration-resistant stages, additional genetic alterations can emerge, creating redundant growth signals and potentially diminishing the inhibitor's efficacy.
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A patient's time to progression on first-line CDK4/6 inhibitor therapy acts as an informal biomarker. A shorter duration, such as 14 months, is viewed by experts as "not so great" and indicates a degree of underlying endocrine resistance that influences subsequent treatment strategies.
The AKT pathway, activated by PTEN loss, drives cancer growth independently of the androgen receptor, which controls PSA production. This discordance means clinicians cannot rely on PSA alone and must use systematic imaging to detect progression in this specific patient subgroup.
In metastatic breast cancer, approximately one-third of patients are unable to proceed to a second line of therapy due to disease progression or declining performance status. This high attrition rate argues for using the most effective agents, such as ADCs, in the first-line setting.
Despite some positive clinical trial data for AKT inhibitors in prostate cancer, expert opinion suggests this class of drugs is unlikely to see the light of day in routine clinical practice. Skepticism remains about their overall impact, with a feeling that they do not represent a new, meaningful chapter for treatment.
Not all mutations are equal. PIK3CA alterations are often present from the start (truncal mutations), indicating a more aggressive cancer. In contrast, ESR1 mutations are typically acquired later as a direct mechanism of resistance to endocrine therapy, making repeat testing after disease progression crucial.
Despite the presence of PIK3CA mutations in some triple-negative breast cancer (TNBC) tumors, Phase III trials with AKT inhibitors have been negative. Currently, there is insufficient evidence to support using PI3K/AKT pathway inhibitors for TNBC in clinical practice.
The panel suggests AKT inhibitor trials in prostate cancer have been disappointing due to suboptimal biomarker selection (e.g., PTEN IHC). A similar drug in breast cancer showed significant survival benefit when using a more precise NGS-based strategy, indicating a potential path forward if the right patient population is identified genetically.
Exploratory analysis shows that while patients with 100% PTEN loss have a much worse natural history than those with 90% loss, the therapeutic effect of capivasertib is stable across this spectrum. The drug effectively targets the pathway regardless of the magnitude of loss, making it a robust option for this entire subgroup.
Three 2025 trials (AMPLITUDE, PSMA-addition, CAPItello) introduced personalized therapy for metastatic hormone-sensitive prostate cancer. However, significant benefits were confined to narrow subgroups, like BRCA-mutated patients. This suggests future success depends on even more stringent patient selection, not broader application of targeted agents.
Testing for PI3K/AKT alterations at the initial diagnosis of metastatic disease, rather than waiting for progression, provides a crucial window of time. This allows clinicians to implement proactive dietary and medical strategies to mitigate future side effects like hyperglycemia before the targeted therapy is even started.
