Celcuity’s Phase 3 VIKTORIA-1 Trial Achieves Primary Endpoint With Clinically Meaningful Improvement in Progression-Free Survival in PIK3CA Mutant Cohort (Form 8-K)

Celcuity's Phase 3 VIKTORIA-1 Trial Achieves Primary Endpoint With Clinically Meaningful Improvement in Progression-Free Survival in PIK3CA Mutant Cohort

MINNEAPOLIS, May 1, 2026 - Celcuity Inc. (Nasdaq: CELC), a clinical-stage biotechnology company pursuing development of targeted therapies for oncology, today announced positive topline results from the PIK3CA mutant cohort of the Phase 3 VIKTORIA-1 clinical trial evaluating gedatolisib plus fulvestrant with or without palbociclib in patients with hormone receptor positive ("HR+"), human epidermal growth factor receptor 2 negative ("HER2-"), PIK3CA mutant locally advanced or metastatic breast cancer ("ABC"), following progression on or after treatment with a CDK4/6 inhibitor and an aromatase inhibitor. Detailed results will be presented in a late-breaking abstract ("LBA") oral session at the American Society of Clinical Oncology ("ASCO") Annual Meeting, taking place May 29 - June 2, 2026, in Chicago, Illinois.

The primary efficacy analysis of gedatolisib combined with fulvestrant and palbociclib (the "gedatolisib triplet") demonstrated a statistically significant and clinically meaningful improvement in progression-free survival ("PFS") compared to alpelisib, a PI3Kα inhibitor, and fulvestrant. The secondary endpoint comparing gedatolisib plus fulvestrant (the "gedatolisib doublet") versus alpelisib plus fulvestrant, which was not part of the primary efficacy analysis in the hierarchical order, also demonstrated a statistically significant and clinically meaningful improvement in PFS compared to alpelisib and fulvestrant. Both gedatolisib regimens were generally well tolerated, with manageable safety profiles, and no new safety signals.

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

"Patients with PIK3CA mutant HR+/HER2- advanced breast cancer whose disease has progressed while on or after treatment with a CDK4/6 inhibitor typically derive modest benefit from subsequent therapies that target only PI3Kα or AKT," said Sara Hurvitz, MD, Senior Vice President, Clinical Research Division, Fred Hutch Cancer Center, Smith Family Endowed Chair in Women's Health and Professor and Head, Division of Hematology and Oncology, University of Washington, School of Medicine and co-principal investigator for the trial. "VIKTORIA-1 represents the first Phase 3 study to demonstrate that comprehensively blocking the PI3K/AKT/mTOR, or PAM, pathway can significantly improve outcomes for patients with PIK3CA mutations compared to therapies only targeting a single component of this pathway."

HR+/HER2- breast cancer is the most common subtype of breast cancer, accounting for approximately 70% of all breast cancers.² Among this breast cancer subtype, approximately 40% have PIK3CA mutations.

"These positive topline results demonstrate the potential for gedatolisib to become a transformative new medicine for the treatment of patients with PIK3CA mutant HR+/HER2-advanced breast cancer," said Igor Gorbatchevsky, MD, Chief Medical Officer of Celcuity. "When considered alongside previously presented data from the VIKTORIA-1 PIK3CA wild-type cohort, the gedatolisib regimens have now demonstrated the potential to improve the standard of care in the second-line setting regardless of the PIK3CA status of a patient's tumor."

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.

"We believe the results from the VIKTORIA-1 study validate our pioneering approach to targeting cancers involving the PI3K/AKT/mTOR pathway. Researchers have sought for nearly 20 years to develop a drug that blockades this pathway comprehensively without inducing unacceptable levels of toxicity," commented Brian Sullivan, Chairman, CEO and co-founder of Celcuity.

Mr. Sullivan added, "The implications of these results may extend beyond HR+/HER2- advanced breast cancer patients in the second-line setting, and we are working urgently to explore the development of gedatolisib for additional groups of patients whose cancers involve the PI3K/AKT/mTOR pathway."

Presentation Details

Presenting Author: Sara Hurvitz, MD, Senior Vice President, Clinical Research Division, Fred Hutchinson Cancer Center, Professor and Head, Division of Hematology and Oncology, University of Washington, Department of Medicine

Title: A randomized, open-label, phase 3 study of gedatolisib + fulvestrant ± palbociclib vs standard of care in HR+/HER2−/PIK3CA-mutant advanced breast cancer (VIKTORIA-1 Study 2)

Abstract: LBA1008

Session Type/Title: Oral Abstract Session - Breast Cancer-Metastatic

Date and Time: June 2, 2026, 9:45 AM-12:45 PM CDT

Late-breaking abstracts accepted for an Oral Abstract Session at the ASCO Annual Meeting will be published online via the ASCO website on the day of presentation.

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, 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 Among this breast cancer subtype, approximately 40% have PIK3CA mutations.¹³

Three interconnected signaling pathways, estrogen, cyclin D1-CDK4/6 and PI3K/AKT/mTOR ("PAM"), are primary oncogenic drivers of HR+/HER2- breast cancer.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 clinical trial is fully enrolled. The trial enrolled 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 mutant cohort, 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 pursuing the development of targeted therapies for the treatment of multiple solid tumor indications. The company's lead therapeutic candidate is gedatolisib, a potent, pan-PI3K and mTORC1/2 inhibitor that comprehensively blockades 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. A 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 the PIK3CA WT cohort and topline results for the PIK3CA mutant cohort. A Phase 3 clinical trial, VIKTORIA-2, evaluating gedatolisib plus a CDK4/6 inhibitor and fulvestrant as first-line treatment for patients with endocrine treatment resistant HR+/HER2- ABC, is ongoing. A Phase 1/2 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.