Brian Sullivan
Analyst · Needham & Company
Thank you, Robert. Good afternoon, everyone, and thank you for joining us today. As always, we appreciate your continued support of Celcuity. On this call, we'll update you on our second quarter financial results, the status of our gedatolisib program, some recently reported clinical trial results and an update on our CELsignia companion diagnostic programs. Vicky will follow my comments with a discussion of our financial results, and then we'll open up the line for questions.
I'm sure many of you are aware of the transformational step that Celcuity took in April with the in-licensing from Pfizer of gedatolisib, a pan-PI3K/mTOR inhibitor. Gedatolisib is currently in clinical development to treat patients with ER-positive HER2-negative advanced or metastatic breast cancer.
Under the terms of the licensing agreement, Pfizer provided Celcuity with a worldwide license to develop and commercialize gedatolisib. Celcuity paid a license fee of $5 million cash and $5 million of Celcuity's common stock as upfront payments. Pfizer is eligible to receive up to $330 million of back-end loaded development and sales-based milestone payments and tiered royalties on potential sales. We estimate that the potential annual market available for gedatolisib as a treatment for breast cancer is approximately $5 billion. We also believe there are additional opportunities for gedatolisib to treat other tumor types that could further increase its market potential.
Our interest in GEDA was spurred by encouraging data obtained from the expansion portion of an ongoing Phase Ib clinical trial, evaluating GEDA plus the CDK4/6 inhibitor, Ibrance, and an endocrine therapy. As of January 11, 2021, data cutoff, 53 of the 88 evaluable patients or 60% were reported to have had an objective response to the treatment regimen. Gedatolisib was also generally well tolerated, with the majority of treatment-related adverse events, or TRAEs, being Grade 1 or 2. The most common Grade 3 or Grade 4 TRAE related to gedatolisib were stomatitis and rash and are considered to be manageable. A relatively low TRAE drop-out rate of approximately 10% was reported. And we expect to update this data in December, in conjunction with the San Antonio Breast Cancer Symposium.
We continue to plan and prepare for a Type C Meeting with the FDA later this year to get feedback on the design of our Phase III clinical trial for gedatolisib. Subject to FDA feedback, we would expect to initiate a Phase III clinical trial evaluating GEDA in combination with Ibrance and an endocrine therapy in the first half of 2022.
To support our GEDA development program, we closed 2 financings recently. In early April, Celcuity entered into a debt financing agreement that can provide up to $25 million in term loans. The first tranche of $15 million was funded at closing. And in early July, Celcuity closed a follow-on equity offering that raised gross proceeds of approximately $56.3 million. After the follow-on offering, Celcuity had approximately $94.4 million of cash on hand.
As we have previously discussed, our assessment of different PI3K and mTOR inhibitors using our CELsignia platform led us initially to approach Pfizer about our interest in pursuing a collaboration to evaluate gedatolisib. Subsequent to that initial internal study and as part of our due diligence on GEDA's mechanism of action, we conducted additional studies to evaluate GEDA, inavolisib, a PI3K-alpha inhibitor, and navitoclax, a BCL inhibitor, in breast and ovarian patient tumors using our CELsignia platform. We presented the results of these studies at the AACR annual meeting in April. The results showed that GEDA inhibited 9x more signaling test activity in tumors with hyperactive RAS network signaling, on average, than inavolisib, when evaluated at equal concentrations with the CELsignia test. Our CELsignia test also found that GEDA inhibited 5x more signaling activity when evaluated at 1/5 the concentration of inavolisib.
This data supported our hypothesis that hyperactive RAS network signaling involves more than just the PI3K-alpha isoform and that inhibiting all 4 Class I PI3K isoforms as well as mTORC1 and mTORC2 is required to address it. Our study also detected the synergistic cooperation between the PI3K/mTOR and BCL pathways, which suggests the potential patient benefit of combining GEDA with a BCL inhibitor. We plan to conduct similar additional investigations using our CELsignia platform to identify classes of agents that may be appropriate to combine with gedatolisib.
Since we last reported to you, results from a 17-patient Phase I dose-escalation study were published. This study evaluated the safety and preliminary activity of GEDA combined with carboplatin, a platinum-based therapy, and paclitaxel. The intention was to explore the hypothesis that inhibition of the PI3K/mTOR pathway can promote sensitivity to platinum-based therapies. This is relevant because platinum therapies are the backbone of combination therapy for a wide range of tumors, including ovarian, lung, breast and bladder cancers.
Amongst the 17 patients evaluated, 11 or 65% had an objective response. Of these 11 responsive patients, 8 had a partial response and 3 had a complete response. Three additional patients or 17% reported stable disease. 11 of the 17 patients enrolled had advanced ovarian cancer, 10 with clear cell ovarian carcinoma and 1 with low-grade serous ovarian cancer.
Clear cell ovarian cancer is a tumor type with poor prognosis, generally considered to be chemo-resistant. Of the 11 patients with ovarian cancer, 9 or 82% reported an objective response. Among the 9 of 17 patients who had received prior platinum therapy, 4 or 45% had a partial response. These 4 responders included 3 patients with ovarian cancer and 1 patient with non-small cell lung cancer. The drug combination was found to be tolerable with a manageable safety profile.
While the sample size is very small, the data from the ovarian cancer patients is interesting, nonetheless. 9 of the 11 ovarian cancer patients or 82% had an objective response. Of the 7 patients with clear cell ovarian cancer who were platinum-naive, 6 or 86% had an objective response. This compares to objective response rates of 25% to 50% reported in other studies evaluating platinum therapy in platinum-naive clear cell ovarian cancer patients. It's premature for us to assess the priority of pursuing further development of an indication in ovarian cancer. But nonetheless, the study provides additional preliminary evidence of gedatolisib's antitumor activity.
Now I'd like to move on to the diagnostic side of our business. Celcuity -- or CELsignia, Celcuity's third-generation diagnostic platform, identifies the underlying cellular activity, dysregulated pathway signaling, that may be driving a patient's tumor so that a matching targeted therapy can be identified. Since dysregulated signaling is too complex for molecular tests to characterize in most patients, our platform can identify new treatment options for patients who lack actionable molecular biomarkers. Our strategy is to develop companion diagnostics that enable a pharmaceutical company to expand the number of patients eligible to receive their targeted therapy.
To achieve this, we are collaborating with pharmaceutical companies to evaluate the efficacy of their targeted therapies in patient populations selected by a CELsignia Pathway Activity Test. If the clinical trial results are favorable, these collaborations may lead to advancement of a new indication that expands the market for the targeted therapy.
As an example, we believe there is a significant unmet need for new therapeutic options for HER2-negative breast cancer patients. Our research suggests that many of these patients have an undiagnosed and untreated disease mechanism. Our CELsignia test has the potential to identify the disease mechanism for roughly 25% to 35% of these patients and the targeted therapy most likely to benefit them.
Earlier this year, we entered 2 new clinical trial collaborations. In January, as previously announced, we entered a collaboration with the Sarah Cannon Research Institute and Pfizer for a Phase II trial. The trial is evaluating the efficacy and safety of 2 Pfizer-targeted therapies, Vizimpro, a pan-HER inhibitor, and XALKORI, a c-MET inhibitor, in patients with previously treated metastatic HER2-negative breast cancer selected with our CELsignia test. Patient enrollment is expected to begin this quarter, and interim results are expected in the second half of 2022.
In March, we entered into a clinical trial collaboration with MD Anderson, Novartis and Puma Biotechnology to study a new drug regimen. The collaboration will evaluate the efficacy and safety of Novartis' c-MET inhibitor, TABRECTA, and Puma's pan-HER inhibitor, NERLYNX, in patients with metastatic HER2-negative breast cancer selected by the CELsignia platform. And this is the second clinical trial to treat patients diagnosed with hyperactive HER2 and c-MET signaling breast cancers with matching targeted therapies. Patient enrollment is expected to begin in the third quarter of this year. Celcuity now has 5 clinical trial collaborations in place, and we expect to announce additional collaborations by the end of this year.
The ongoing FACT-1 and FACT-2 trials that Celcuity is conducting are evaluating anti-HER2 therapies in early-stage HER2-negative breast cancer patients. The goal of each of these trials is to demonstrate that breast cancer patients identified by our CELsignia HER2 pathway test obtain a higher rate of pathological complete response to neoadjuvant anti-HER2 drug treatment than from current standard-of-care chemotherapies. Patients who receive a pathological complete response to neoadjuvant drug treatment are less likely to have their cancer recur. So we believe our CELsignia test can play a significant role in extending the lives of many breast cancer patients. We continue to expect interim results from our FACT-1 and FACT-2 trials in late 2021 or early 2022.
We are excited about these collaborations and the opportunity to work with some of the world's most prominent cancer research centers. We have additional collaboration discussions in progress, and our goal is to announce new agreements in the coming months.
I'd like to turn the call over now to Vicky Hahne to review our financial results.