Study of Safety and Efficacy of Dapagliflozin + Metformin XR Versus Metformin XR in Participants With HR+, HER2-, Advanced Breast Cancer While on Treatment With Alpelisib and Fulvestrant

EPIK-B4: A Phase II, Multicenter, Randomized, Open-label, Active-controlled Study to Assess the Safety and Efficacy of Dapagliflozin + Metformin XR Versus Metformin XR During Treatment With Alpelisib (BYL719) in Combination With Fulvestrant in Participants With HR+, HER2-, Advanced Breast Cancer With a PIK3CA Mutation Following Progression on/After Endocrine-based Therapy

This study was designed to assess the safety and efficacy of the combination of dapagliflozin plus metformin extended release (XR) compared with metformin XR during treatment with alpelisib plus fulvestrant in participants with Hormone Receptor (HR)-positive, Human Epidermal growth factor Receptor-2 (HER2)-negative advanced breast cancer with a Phosphoinositide-3-Kinase Catalytic subunit Alpha (PIK3CA) mutation following progression on or after endocrine-based therapy.

This was a multicenter, randomized, open-label, active-controlled trial, stratified by diabetic status at baseline (i.e., normal vs prediabetic/diabetic based on fasting plasma glucose (FPG) and/or Hemoglobin A1c (HbA1c) laboratory values). The study included only participants with at least one baseline risk factor for the development of severe hyperglycemia which were diabetes (FPG ≥ 126 milligram (mg)/deciliter (dL) or ≥ 7.0 millimole (mmol)/liter (L) and/or HbA1c ≥ 6.5%), prediabetes (FPG ≥ 100 mg/dL to < 126 mg/dL or 5.6 to < 7.0 mmol/L and/or HbA1c 5.7 to < 6.5%), obesity (body mass index [BMI] ≥ 30) and age (≥ 75 years).

The planned duration of treatment with alpelisib and fulvestrant was 12 cycles (28 days in each cycle) or until disease progression, unacceptable toxicity, or discontinuation from study treatment for any other reason, whichever came first.

Approximately 66 participants in each treatment arm were planned to be randomized to receive the combination of alpelisib and fulvestrant with either dapagliflozin plus metformin extended release (XR) or metformin XR alone. As a result of the early termination of the study due to emerging data demonstrating the impact of prophylactic metformin and slow recruitment, only 2 participants were enrolled in the study.

Key Inclusion Criteria:

• Participant had a histologically and/or cytologically confirmed diagnosis of estrogen receptor positive (ER+) and/or progesterone receptor positive (PgR+) breast cancer by a local laboratory.

• Participant had a PIK3CA mutation(s) present in the tumor prior to enrollment.

• Participant had prior treatment with an endocrine-based treatment (e.g. letrozole, anastrozole, exemestane, fulvestrant, or oral SERD) and may have fallen into one of the following categories:

  1. Relapsed with documented evidence of progression while on (neo) adjuvant endocrine-based therapy or within 12 months from completion of (neo) adjuvant endocrine-based therapy with no treatment for metastatic disease.
  2. Relapsed with documented evidence of progression more than 12 months from completion of (neo) adjuvant endocrine-based therapy and then subsequently progressed with documented evidence of progression while on or after only one line of endocrine-based therapy for metastatic disease.
  3. Newly diagnosed advanced breast cancer, then relapsed with documented evidence of progression while on or after only one line of endocrine-based therapy.

Note: Participants with newly diagnosed endocrine-based treatment naïve advanced breast cancer were NOT included in the study.

• Participants might or might not have received prior CDK4/6i therapy. If prior CDK4/6i therapy was administered, it may have been in the adjuvant or metastatic setting.
• If female, the participant was postmenopausal.
• Participant had an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.
• Participant had adequate bone marrow and organ function.

Key Exclusion Criteria:

• Participant relapsed with documented evidence of progression more than 12 months from completion of (neo) adjuvant endocrine therapy with no treatment for metastatic disease.
• Participant had more than 1 line of prior treatment in the metastatic setting.
• Participant had received prior treatment with chemotherapy (except for neoadjuvant/adjuvant chemotherapy), any PI3K, Mammalian Target of Rapamycin (mTOR) or Protein Kinase B (Akt) inhibitor.
• Participant had inflammatory breast cancer at screening.
• Participants with an established diagnosis of diabetes mellitus type I or participants with type II diabetes mellitus requiring antihyperglycemic therapy.
• Participant had a history of acute pancreatitis within 1 year of screening or a past medical history of chronic pancreatitis.
• Participant had currently documented pneumonitis/interstitial lung disease.
• Participant had a history of severe cutaneous reaction, such as Steven-Johnson Syndrome (SJS), erythema multiforme (EM), Toxic Epidermal Necrolysis (TEN) or Drug Reaction with Eosinophilia and Systemic Syndrome (DRESS).