Celcuity Inc. (NASDAQ:CELC), a clinical-stage biotechnology company focused on the development of targeted therapies for the treatment of multiple solid tumor indications, today announced detailed efficacy and safety results from the PIK3CA mutant ("MT") cohort of the Phase 3 VIKTORIA-1 clinical trial of gedatolisib, an investigational pan-PI3K/mTORC1/2 inhibitor, in adults with hormone receptor positive ("HR+"), human epidermal growth factor receptor 2 negative ("HER2-"), PIK3CA mutated, locally advanced or metastatic breast cancer ("ABC"), following progression on, or after, treatment with a CDK4/6 inhibitor and an aromatase inhibitor. VIKTORIA-1 is the first Phase 3 clinical trial to compare the efficacy of two PI3K/AKT/mTOR ("PAM") inhibitors in this patient population.

The study results will be presented in a late-breaking abstract ("LBA") oral session at the American Society of Clinical Oncology ("ASCO") Annual Meeting today, Tuesday, June 2, 2026, 12:09 p.m. CDT.

The PAM pathway is a key oncogenic driver of HR+/HER2- breast cancer that requires inhibition of multiple molecular components to comprehensively blockade excessive PAM signaling in tumors with or without a PAM variant. Gedatolisib is the first multitarget PAM inhibitor to demonstrate superior efficacy relative to a single-target inhibitor of this pathway. In the PIK3CA MT cohort of the Phase 3 VIKTORIA-1 trial, the gedatolisib-triplet demonstrated a statistically significant and clinically meaningful improvement in median PFS among patients, increasing the likelihood of survival without disease progression or death by two times compared to alpelisib plus fulvestrant (based on a hazard ratio [HR] of 0.50; 95% CI: 0.37-0.68; p<0.0001). The median PFS, as assessed by blinded independent central review ("BICR"), was nearly two-times longer, 11.1 months versus 5.6 months, compared to alpelisib plus fulvestrant. The ORR of the gedatolisib-triplet was 48.9% compared to 26.0% with alpelisib plus fulvestrant and the median DOR for the gedatolisib triplet was 15.7 months compared to 7.5 months for alpelisib plus fulvestrant.

For the gedatolisib-doublet, the median PFS was more than two-times longer, 11.3 months versus 5.6 months, compared to alpelisib plus fulvestrant (HR=0.51; 95% CI: 0.33-0.79; descriptive p=0.0013). The ORR of the gedatolisib-doublet was 35.7% and the median DOR was 24.2 months.

The topline gedatolisib-triplet efficacy data from the VIKTORIA-1 PIK3CA MT cohort established several new milestones in the history of drug development for HR+/HER2- ABC:

  • First Phase 3 trial to demonstrate superiority of one PAM inhibitor versus another.
  • The median PFS of 11.1 months for the gedatolisib-triplet is the highest reported by any Phase 3 trial for patients with HR+/HER2- ABC receiving a regimen including endocrine therapy as second-line treatment.
  • The objective response rate of 48.9% for the gedatolisib-triplet is the highest reported by any Phase 3 clinical trial for a regimen including endocrine therapy in second-line HR+/HER2- ABC.

     

"Therapies that target only PI3Kα or AKT typically offer modest benefit for patients with PIK3CA mutant HR+/HER2- advanced breast cancer whose disease has progressed while on or after treatment with a CDK4/6 inhibitor," said Sara Hurvitz, MD, Senior Vice President, Clinical Research Division, Fred Hutchinson Cancer Center, Smith Family Endowed Chair in Women's Health and Professor and Head, Division of Hematology and Oncology, University of Washington, Department of Medicine and co-principal investigator for the trial. "By comprehensively blocking the PI3K/AKT/mTOR, or PAM, pathway, gedatolisib combined with fulvestrant, with or without palbociclib, showed it can offer these patients two times the likelihood of survival without disease progression or death relative to a single-target inhibitor of the PAM pathway. With these results, the gedatolisib regimens, if approved, represent a new potential standard of care for patients with HR+, HER2-negative, PIK3CA mutant advanced breast cancer whose disease progressed on or after treatment with a CDK4/6 inhibitor."

The gedatolisib-triplet and -doublet were generally well tolerated in the trial with mostly low-grade treatment-related adverse events ("TRAEs"). The most common Grade 3+ TRAEs for the gedatolisib-triplet, the gedatolisib-doublet, and alpelisib plus fulvestrant groups included neutropenia (58.8%, 0%, and 0.7% of patients, respectively); stomatitis (16.3%, 5.8%, and 5.3% of patients, respectively); rash (6.5%, 5.8%, and 15.1% of patients, respectively); and hyperglycemia (2.6%, 0%, and 14.5% of patients, respectively). TRAEs led to the discontinuation of study treatment in 2.6% of patients in the gedatolisib-triplet group, 3.8% in the gedatolisib-doublet group, and 7.1% in the alpelisib plus fulvestrant group. One Grade 5 TRAE in the gedatolisib-triplet group, which was related to palbociclib, was reported, no Grade 5 TRAEs were reported in the gedatolisib-doublet group, and two Grade 5 TRAEs were reported in the alpelisib plus fulvestrant group.

"Both gedatolisib regimens were well-tolerated with few VIKTORIA-1 patients discontinuing treatment due to an adverse event," said Igor Gorbatchevsky, MD, Chief Medical Officer of Celcuity. "These safety results compare very favorably to those from the patient group treated with alpelisib and fulvestrant, which we believe reflects the benefit of gedatolisib's multi-target mechanism of action, pharmacokinetic profile, and intravenous administration."

Overall survival, a key secondary endpoint in VIKTORIA-1, while immature at the time of the analysis, showed promising trends for both the gedatolisib-triplet and -doublet.

Celcuity intends to submit these data to the U.S. Food and Drug Administration ("FDA") as a supplemental New Drug Application ("sNDA") and to submit VIKTORIA-1 data to other regulatory authorities following the sNDA submission.

"It is rare in oncology for a targeted therapy to offer both improved efficacy and better safety results relative to another drug in its class," said Brian Sullivan, CEO and co-founder of Celcuity. "This second positive Phase 3 data readout further underscores the broad potential of multi-target PAM inhibition and increases our excitement about our two Phase 3 trials in the first-line setting for HR+/HER2- advanced breast cancer. We are on track to launch gedatolisib commercially, in anticipation of its potential FDA approval in the third quarter of 2026, and we look forward to the possibility of bringing this important therapy to physicians treating patients with advanced breast cancer."

The FDA has granted Priority Review of Celcuity's New Drug Application ("NDA") for gedatolisib in patients with HR+/HER2-/PIK3CA wild-type ("WT") ABC and assigned a Prescription Drug User Fee Act ("PDUFA") goal date of July 17, 2026.