Impact of Time of Administration, Fasting, and a Low-Carbohydrate Diet on Alpelisib-Associated Hyperglycemia and Efficacy: A Pilot Randomized Controlled Phase IIb Trial

Background: Alpelisib plus fulvestrant improves outcomes in PIK3CA-mutated, hormone receptor-positive, HER2-negative metastatic breast cancer. However, on-target hyperglycemia often leads to dose modification or discontinuation. We aimed primarily to determine whether evening alpelisib after a ≥5 h fast with low-carbohydrate guidance reduces severe hyperglycemia versus standard morning dosing, and secondarily, to assess time to first grade 3–4 hyperglycemia, efficacy, and quality of life (QoL). Methods: ITACA was an open-label, randomized, phase IIb trial in three Croatian centers. Patients progressing on endocrine therapy were randomized 1:1 to evening alpelisib 300 mg after a ≥5 h fast with low-carbohydrate guidance or standard morning alpelisib, both with fulvestrant. The primary endpoint was the exposure-adjusted incidence rate (EAIR) of first grade 3–4 hyperglycemia within 90 days or 30 days post-discontinuation. Secondary endpoints were time to first grade 3–4 hyperglycemia, efficacy, and QoL. Results: Forty-two patients were randomized (21 per arm). Median age was 60 vs. 63 years in the evening vs. morning arms. In the safety set, EAIR of first grade 3–4 hyperglycemia was 378 vs. 742 per 100 person-years (11/21 vs. 14/20 patients with ≥1 event, unadjusted IRR 0.51, 95% CI 0.23–1.12). Adjusted Poisson models favored evening dosing. Analyses suggested delayed onset (median 73 vs. 9.5 days), with no detriment in efficacy or QoL. Conclusions: Evening alpelisib preceded by fasting and low-carbohydrate guidance may improve metabolic tolerability without compromising efficacy or QoL. These findings support evaluation in a larger trial incorporating prospective metabolic adherence and pharmacokinetic assessments.