Celcuity’s Gedatolisib Combination Regimens Doubled the Likelihood of Survival without Disease Progression or Death Compared to Alpelisib plus Fulvestrant in the PIK3CA Mutant[...]

Celcuity's Gedatolisib Combination Regimens Doubled the Likelihood of Survival without Disease Progression or Death Compared to Alpelisib plus Fulvestrant in the PIK3CA Mutant Cohort of the Pivotal Phase 3 VIKTORIA-1 Trial

in Patients with HR+/HER2- Advanced Breast Cancer

MINNEAPOLIS, June 2, 2026 - 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:

"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. ¹One Grade 5 TRAE in the gedatolisib-triplet group, which was related to palbociclib, was reported, no Grade 5 TRAE's were reported in the gedatolisib-doublet group, and two Grade 5 TRAE's 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.

About HR+/HER2- Breast Cancer

Breast cancer is the second most common cancer and one of the leading causes of cancer-related deaths worldwide.¹ More than two million breast cancer cases were diagnosed globally in 2022.¹ While survival rates are high for those diagnosed with early breast cancer, only approximately 30% of patients who are diagnosed with or who progress to metastatic disease are expected to live five years after their diagnosis.² HR+/HER2- breast cancer is the most common subtype of breast cancer, accounting for approximately 70% of all breast cancers.²

Three interconnected signaling pathways, estrogen, cyclin D1-CDK4/6, and the PAM pathway , are primary oncogenic drivers of HR+/HER2- ABC.³ Therapies inhibiting these pathways are approved and used in various combinations for ABC. Currently approved inhibitors of the PAM pathway for breast cancer target a single PAM pathway component, such as PI3Kα, AKT, or mTORC1.^4,5,6,7 However, resistance to CDK4/6 inhibitors and current endocrine therapies develops in many patients with advanced disease.⁸ Optimizing the inhibition of the PAM pathway is an active area of focus for breast cancer research.

About the VIKTORIA-1 Phase 3 Trial

VIKTORIA-1 is a Phase 3 open-label, randomized clinical trial to evaluate the efficacy and safety of gedatolisib in combination with fulvestrant, with or without palbociclib, in adults with HR+/HER2- ABC whose disease progressed on or after prior CDK4/6 therapy in combination with an aromatase inhibitor. The trial enrolled 701 subjects regardless of PIK3CA status while enabling separate evaluation of subjects according to their PIK3CA status. Detailed results from the PIK3CA WT cohort of VIKTORIA-1 have been previously reported. For the PIK3CA MT cohort, 350 subjects who met eligibility criteria and had confirmed PIK3CA mutations were randomly assigned (3:3:1) to receive a regimen of either the gedatolisib-triplet, alpelisib and fulvestrant, or the gedatolisib-doublet.

About Gedatolisib

Gedatolisib is an investigational, multi-target PAM inhibitor that potently targets all four class I PI3K isoforms, mTORC1, and mTORC2 to induce comprehensive blockade of the PAM pathway.^9,10,11 As a multi-target PAM inhibitor, gedatolisib's mechanism of action is highly differentiated from currently approved single-target inhibitors of the PAM pathway.¹¹ Inhibition of only a single PAM component gives tumors an escape mechanism through cross-activation of the uninhibited targets. Gedatolisib's comprehensive PAM pathway inhibition ensures full suppression of PAM activity by eliminating adaptive resistance cross-activation that occurs with single-target inhibitors. Unlike single-target inhibitors of the PAM pathway, gedatolisib has demonstrated equal potency and comparable cytotoxicity in PIK3CA-mutant and -wild-type breast tumor cells in nonclinical studies and early clinical data.^11,12

About Celcuity

Celcuity is a clinical-stage biotechnology company focused on the development of targeted therapies for the treatment of multiple solid tumor indications. The company's lead therapeutic candidate is gedatolisib, a kinase inhibitor of the PI3K/AKT/mTOR ("PAM") pathway that binds to all class I PI3K isoforms and the mTOR complexes, mTORC1 and mTORC2. By targeting all class I PI3K isoforms and mTORC1/2, gedatolisib induces comprehensive inhibition of the PAM pathway. Its mechanism of action and pharmacokinetic properties are differentiated from other currently approved and investigational therapies that target PI3Kα, AKT, or mTORC1 alone or together. The company's Phase 3 clinical trial, VIKTORIA-1, evaluating gedatolisib in combination with fulvestrant with or without palbociclib in patients with HR+/HER2- ABC, has reported detailed results for Study 1, which evaluated patients with PIK3CA WT tumors, and for Study 2, which evaluated patients with PIK3CA MT tumors. Our Phase 3 clinical trial, VIKTORIA-2, is ongoing and incorporates two independent studies, Study 1 and Study 2, evaluating two separate cohorts of patients with ABC who are treatment-naive in the advanced setting. Study 1 is evaluating gedatolisib combined with palbociclib and fulvestrant as first-line treatment for patients with endocrine-resistant HR+/HER2- ABC. Study 2 is evaluating gedatolisib combined with palbociclib and letrozole as first-line treatment for patients with endocrine-sensitive HR+/HER2- ABC. A Phase 1b/2 clinical trial, CELC-G-201, evaluating gedatolisib in combination with darolutamide in patients with metastatic castration resistant prostate cancer, is ongoing. More detailed information about Celcuity's active clinical trials can be found at ClinicalTrials.gov. Celcuity is headquartered in Minneapolis. Further information about Celcuity can be found at www.celcuity.com. Follow us on LinkedIn and X.