Newly approved capivasertib (Truqap) found to be effective and safe | SABCS 2023

Background

Last month brought the approval of a new kind of drug to treat advanced or metastatic hormone receptor-positive, HER2-negative breast cancer that no longer responds to endocrine therapy. Capivasertib is the first drug to target the AKT pathway, which has been associated with treatment resistance and cancer spread. Yet, early excitement has been offset by concerns about side effects, especially diarrhea.

Results reported in two sessions at the San Antonio Breast Cancer Symposium on December 5, 2023, describe the FDA’s approval process for the drug, the decision to limit its use to people diagnosed with advanced or metastatic breast cancers that have certain genetic mutations, and newly reported quality-of-life data.

Study results lead to FDA approval (initially reported on in December 2022)

The phase III CAPItello-291 trial tested capivasertib plus fulvestrant against capivasertib and placebo in people with advanced or metastatic hormone receptor-positive, HER2-negative breast cancer. Adding capivasertib doubled the time to cancer growth or spread in participants.

Genetic mutations in breast cancer cells are one of many types of biomarkers that can be used as targets for treatment. This study looked at people diagnosed with advanced or metastatic breast cancer (MBC) that had PIK3CA, AKT1, or PTEN genetic mutations, those without these mutations, and overall results. The strongest results were seen in people diagnosed with breast cancers that had the mutations — 7.3 months without cancer progression with the addition of capivasertib versus 3.1 months without.

Initial trial results suggested that the drug might be effective in breast cancer with or without these mutations. Final approval, however, went only to advanced or metastatic breast cancers with these mutations due to limited and weaker results in participants diagnosed with cancers that did not test positive for the relevant mutations. At this meeting, an FDA representative said that concerns about toxicity also influenced this decision. The potential benefit did not outweigh the risk in light of the more severe side effects — particularly diarrhea — experienced by people taking capivasertib. New data presented in a subsequent talk address this concern.

Results of patient-reported outcomes study

New results provide insight into capivasertib tolerability, finding that in general most people tolerated the drug well. Patient-reported outcomes (PROs) measure the experience of the people in the study. In this case, study participants completed three different PRO questionnaires at the beginning of the trial and at follow-up points. Two surveys asked about specific symptoms such as fatigue and diarrhea, as well as quality-of-life issues such as body image, sexual functioning, and emotional health. A third single-question survey asked, “In the last seven days, how bothered were you by the side effects of cancer treatment?”

Results found no significant quality-of-life differences across symptoms between the two study groups except with diarrhea, which people taking capivasertib experienced more. Overall, most people taking the drug reported being not at all or only a little bothered by side effects while on capivasertib.

Capivasertib is taken in pill form twice daily in monthly cycles of four days on/three days off. By the third cycle, participants taking capivasertib had similar quality of life to those not taking the drug.

What does this mean for you?

Capivasertib is a first-of-its-kind drug, offering a new option for many people with advanced or metastatic hormone receptor-positive, HER2-negative breast cancer that has progressed on endocrine therapy. After careful review of data, the FDA approved the drug only for cancers that test positive for altered AKT pathways. Approximately half of people with hormone receptor-positive, HER2-negative advanced or metastatic breast cancer fall into this group. To see if you are eligible for this drug, talk with your doctor about testing the cancer for the PIK3CA, AKT1, or PTEN genetic mutations.

While capivasertib is generally well tolerated, it can cause moderate and severe diarrhea for some. Nearly three-quarters of people taking capivasertib in the trial reported diarrhea. A small number (2%) stopped taking capivasertib due to diarrhea. If you are considering capivasertib, talk with your doctor about potential side effects, including diarrhea, and how to manage them. Most people find that the side effects improve over time.