A phase 3 trial of Celcuity’s breast cancer combination has hit its primary endpoints, blasting past the biotech’s bar for success to tee up a filing for FDA approval in the fourth quarter.
The study tested doublet and triplet combinations of Celcuity’s gedatolisib, a PI3K and mTOR inhibitor, as second-line treatments for PIK3CA wild-type breast cancer. The doublet combined gedatolisib with fulvestrant, the breast cancer drug AstraZeneca sells as Faslodex. The triplet added palbociclib, which Pfizer sells as Ibrance, to the mix. A control arm received fulvestrant as a monotherapy.
Celcuity said the triplet reduced the risk of disease progression or death by 76% compared to fulvestrant alone. The figure for the doublet was 67%. Progression-free survival was 9.3 months on the triplet and 7.4 months on the doublet, compared to two months in the control arm.
The hazard ratios for the triplet and doublet were 0.24 and 0.33, respectively. Talking at a TD Cowen event in May, Celcuity CEO Brian Sullivan said a hazard ratio of 0.5 or below “would be considered very compelling.” Sullivan cited studies of Eli Lilly’s imlunestrant and Menarini’s Orserdu with hazard ratios of 0.55 to 0.62 as references. The CEO pushed back against the idea AstraZeneca’s Serena-6 is a relevant comparison, arguing that the study “is a modified first-line indication” because of its switching design.
After seeing the gedatolisib data, Celcuity hailed the results as new milestones in the treatment of HR-positive, HER2-negative advanced breast cancer. Fred Hutchinson Cancer Center’s Sara Hurvitz, M.D., put the results in context.
“The topline data for both gedatolisib regimens from VIKTORIA-1 are potentially practice-changing,” Hurvitz said in a statement. “To my knowledge, we have not seen phase 3 results in patients with HR-positive, HER2-negative advanced breast cancer before where there was a quadrupling of the likelihood of survival without disease progression relative to the study control.”
Celcuity said the rate of discontinuation because of treatment-related adverse events was lower in the doublet and triplet cohorts than in phase 3 trials of currently approved combinations. The figures were also lower than in a phase 1b cohort that received palbociclib, fulvestrant and gedatolisib.
The biotech plans to share more data at a medical conference this year. Celcuity’s calendar for 2025 also includes the publication of top-line data from a cohort of phase 3 patients with PIK3CA mutations and a filing for FDA approval