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NCT Number: NCT07624617

Fast-Her: Fasting Effects on Breast Cancer Treatment

We hypothesize that promoting a fasting state will strengthen the anti-cancer effects of PI3K inhibitors in metastatic breast cancer (MBC) treatment. The primary objective of this study is to assess acceptability of prolonged fasting in this population.

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Key information

Conditions

Metastatic Breast Cancer Breast Diseases Breast Neoplasms Neoplasms Neoplasms by Site Skin Diseases Skin and Connective Tissue Diseases

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

University of Minnesota

Minneapolis, Minnesota, 55455, United States

Location status: Recruiting

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Age ≥18 years
  • Histologically confirmed metastatic breast cancer
  • Menopausal or medically ovarian suppressed
  • Currently receiving capivasertib therapy (2 tablets twice daily, 4 days per week)
  • Stable on current capivasertib regimen for at least 2 weeks
  • an ECOG performance status of 0-1
  • BMI ≥25kg/m2
  • Able to provide informed consent
  • Willing to comply with study procedures including CGM wear, food tracking by mCC app and dietary modifications
  • Access to smartphone or tablet for mobile application use

Exclusion criteria

  • Type 1 diabetes mellitus
  • Uncontrolled type 2 diabetes (HbA1c >9.0%)
  • History of severe hypoglycemia
  • Eating disorders or contraindications to fasting
  • Pregnancy or breastfeeding
  • Significant gastrointestinal disorders affecting food absorption
  • Unable to fast for medical reasons
  • Concurrent participation in other dietary intervention studies
  • A history of significantly abnormal lab results within 4 weeks of consent date, such as hematologic (Hgb < 10.0, platelets < 100), hepatic (LFTs > 2X nl), renal (Cr > 1.5)

Treatment and study plan

Normal Eating

Behavioral

During the normal eating intervention period, participants will follow their usual eating pattern. Participants will continue their prescribed PI3K inhibitor dosing, with medications taken at standardized times to ensure consistent pharmacokinetic measurements.

Prolonged fasting

Behavioral

During the prolonged fasting intervention period, participants will eat only once daily (dinner), with water, black coffee, and tea permitted during fasting hours. Participants will continue their prescribed PI3K inhibitor dosing, with medications taken at standardized times to ensure consistent pharmacokinetic measurements.

Primary outcomes

  1. Effect of plasma from fasting in patients on PI3K inhibitors on cell viability

    Time frame: Week 2 of prolonged fasting

    We will culture 2D/3D breast cancer models using plasma from patients in the fed and fasted states. We will assess tumor cell viability by measuring cell proliferation, apoptosis, and cell cycle distribution.

  2. mechanisms by which fasting might enhance PI3K inhibitor efficacy through complementary molecular and cellular studies

    Time frame: Week 7

    We will culture 2D/3D breast cancer models using plasma from patients in the fed and fasted states and perform metabolomic and proteomic analyses to evaluate the effects on insulin and PI3K pathways.

  3. Identify biomarkers/patient characteristics predicting the enhancement of PI3K inhibitor efficacy with fasting.

    Time frame: Week 7

    We will evaluate biomarkers that may predict the influence of fasting on PI3K inhibitor efficacy. Using serial plasma samples, we will analyze PI3K inhibitor pharmacokinetics, metabolic markers (e.g., insulin, glucose), circadian markers (melatonin, cortisol), and tumor-specific markers (circulating tumor DNA).

Interested in participating?

Recruiting

Interested in participating?

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Sponsors and collaborators

Lead sponsor

University of Minnesota

Other

Registry information

Important dates

Study start
2026
Primary completion
2027
Study completion
2027
First posted
Jun 3, 2026
Registry last updated
Jul 13, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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