Celcuity Reports Preliminary Data from Phase 1b Trial of Gedatolisib plus Ibrance and Endocrine Therapy for Patients with ER+/HER2- Metastatic Breast Cancer and Provides Corporate Update

Celcuity Inc. (Nasdaq:CELC), a clinical-stage biotechnology company pursuing an integrated companion diagnostic and therapeutic strategy for treating patients with cancer, today reported preliminary data for the 103 patients enrolled in the expansion portion of an ongoing Phase 1b clinical trial evaluating gedatolisib, a first-in-class PI3K/mTOR inhibitor, plus Ibrance and endocrine therapy, in ER+/HER2- advanced or metastatic breast cancer patients. As of the January 11, 2021 data cut-off date, 53 of the 88 evaluable patients (60%) had an objective response. Gedatolisib was also generally well tolerated, with the majority of treatment-related adverse events (TRAE) being Grade 1 or 2. The most common Grade 3 or 4 TRAEs related to gedatolisib were stomatitis and rash.

“We are very encouraged by this preliminary data for gedatolisib from our ongoing Phase 1b trial in patients with breast cancer,” said Brian Sullivan, CEO and Co-Founder of Celcuity. “The robust response rate and the observed tolerability profile are particularly compelling given the need for a therapeutic regimen that can address endocrine therapy resistance. We look forward to sharing additional data from the study at a future medical conference in 2021. Developing a therapeutic such as gedatolisib allows us to more fully leverage our CELsignia cellular analysis platform.“

Preliminary Phase 1b Data for Gedatolisib:

The preliminary Phase 1b data set for the 103 patients enrolled utilized a January 11, 2021 data cut-off. Patients were enrolled in one of four expansion arms (A, B, C, D), according to their prior treatment history for metastatic breast cancer. All patients received gedatolisib in combination with standard doses of palbociclib and endocrine therapy (either letrozole or fulvestrant). In Arms A, B, and C, patients received an intravenous dose of 180 mg of gedatolisib once weekly. In Arm D, patients received an intravenous dose of 180 mg gedatolisib on a four-week cycle of three weeks-on, one week-off. The primary endpoint was objective response as determined using Response Evaluation Criteria in Solid Tumors v1.0, or RECIST v1.0.

The preliminary efficacy and safety analysis showed:

• 53 of the 88 evaluable patients (60%) had an objective response.
• 66 of the 88 evaluable patients (75%) had a clinical benefit, defined as either a confirmed objective response or stable disease for at least 24 weeks.
• Gedatolisib was also generally well tolerated, with the majority of treatment related adverse events (TRAE) being Grade 1 or 2. The most common Grade 3 or 4 TRAEs associated with gedatolisib were stomatitis and rash. Gedatolisib was discontinued in 10% of patients.
• 22 patients were continuing to receive gedatolisib in combination with the other study drugs, 17 of whom have been on study treatment for more than two years.

In light of these encouraging results, Celcuity is planning to initiate, subject to feedback from the FDA, a Phase 2/3 clinical trial evaluating gedatolisib in combination with palbociclib and an endocrine therapy in patients with ER+/HER2- advanced or metastatic breast cancer in the first half of 2022.