Galena On Track to Advance NeuVax
By Grant Zeng, CFA
Final Results of NeuVax Phase I/II Trials Presented at the 35th Annual CTRC-AACR San Antonio Breast Cancer Symposium
On December 7, 2012, Galena Biopharma presented data from the completed SN-33 trial and final results from the Phase I/II trials of NeuVax (nelipepimut-S or E75) for breast cancer at the 35th Annual CTRC-AACR San Antonio Breast Cancer Symposium.
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Overview of the Phase I/II Trails
The Phase I/II trials of NeuVax included SN-33 (Node Positive, n=97) and SN-34 (Node Negative, n=90), which evaluated a combined 187 patients with 108 in the vaccine group (VG) and 79 in the unvaccinated control group (CG).
In terms of patient demographics, we think the vaccine and control groups were generally well-matched. Although there were some imbalances between VG and CG, they were not significant. The only statistically significant difference was ER-/PR- status (31.1% in VG vs 17.7% in CG, p=0.04).
The Rational for Booster Inoculation
Patients were initially given a series of up to six inoculations of NeuVax once a month. As the trials progressed, the physicians noticed that E75-specific immunity waned after this initial monthly primary vaccine series (PVS) and translated to late recurrences of cancer in some patients. As a result of this finding, a voluntary booster program was added to the trials to maintain long-term immunity following the initial monthly PVS.
The booster program offered patients an additional inoculation every six months with a maximum of six boosters. Because the booster program was voluntary, not all women chose to receive the full six additional doses.
The Combined SN-33 and SN-34 Results
Trials SN-33 (NP) (n=97) and SN-34 (NN) (n=90) enrolled clinically eligible patients who were rendered disease-free after completion of standard of care multi-modality therapy (n=187). Treatment assignment was then based on HLA type, with HLA-A2/A3 patients vaccinated and HLA-A2/A3 negative patients followed prospectively as controls for recurrence. NeuVax exhibited an excellent safety and tolerability profile, and demonstrated a durable response out to 60 months:
Maximum toxicity for all inoculations produced primarily Grade 1 and some Grade 2 toxicities, with injection site reactions and fatigue most common. No serious adverse events (SAEs) or cardiotoxicity were reported.
At 24-month: 94.3% of NeuVax patients were disease-free versus 86.8% of patients on the control arm (p=0.08).
At 60-month: 89.7% of NeuVax patients remain disease-free versus 80.3% of patients on the control arm (p=0.077)--a recurrence reduction of 47.7% among all patients at any dose. Multiple dose response analyses underscore the efficacy of the vaccine with statistical significance being achieved among the optimally-dosed and boosted patients.
The SN-33 HER2 Negative Booster Results
SN-33 was conducted in node positive patients, and was well balanced between the two arms: Vaccine HLA-A2/A3 positive (n=53) vs Control HLA-A2/A3 negative (n=44). During the conduct of this trial, Herceptin® (trastuzumab; Genentech/Roche) became commercially available for HER2 IHC Positive (3+) patients, and the trial was modified accordingly to allow these patients to receive Herceptin, and exclude this patient group from future enrollment and analysis.
Below are the summary results from the SN-33 trial. SN-33 Intent-to-treat (ITT) population (n=97); NeuVax (n=53) vs. Control (n=44):
At 24-month: 90.6% of NeuVax patients (n=53) were disease-free versus 79.5% of patients on the control arm (n=44) (p=0.1155).
At 60-month: 84.7% of NeuVax patients (n=53) remain disease-free versus 77.1% of patients on the control arm (n=44).
SN-33 HER2 Negative IHC 1+/2+ patients who received boosters (n=45). NeuVax (n=18) vs. Control (n=27).
At 24-month: 0% recurrences for patients treated with NeuVax: statistically significant DFS for NeuVax at 100% vs. 77.8% Control (p=0.0358).
At 36-month: 0% recurrences for patients treated with NeuVax for a statistically significant DFS for NeuVax at 100% vs. 77.8% Control (p=0.035). Of note, no patients receiving booster inoculations had a recurrence through 36 months, which is the Phase III PRESENT study endpoint.
At 60-month: 5.6% recurrence rate with NeuVax versus 25.9% recurrence rate in the control arm. DFS for NeuVax at 94.4% vs. 74.1% Control--a recurrence reduction of 78.4% in the target patient population.
This new, 60-month data analysis shows that breast cancer recurrence is greatly reduced for patients treated with NeuVax and that these results are both clinically relevant and durable over time.
Our assessment of the booster inoculations from the data presented: the booster inoculations are well-tolerated and don’t increase any side effects compared to the primary vaccine series. Further, booster inoculations appear to assist in the maintenance of long-term peptide-specific immunity. In terms of efficacy, boosted patients have better recurrence rates and improved DFS compared to patients who did not receive vaccine. This may be attributed to increased immunity induced by the booster inoculations.
As a result of these findings, booster inoculations have been incorporated into the design of the ongoing Phase III PRESENT study.
The Phase III PRESENT Trial is Underway
Based on the SN-33 booster data, on Jan. 20, 2012, initiated the Phase III PRESENT trial for NeuVax (E75 peptide plus GM-CSF) vaccine in HER2 1+ and 2+ breast cancer patients in the adjuvant setting to prevent recurrence.
The PRESENT (Prevention of Recurrence in Early-Stage, Node-Positive Breast Cancer with Low to Intermediate HER2 Expression with NeuVax Treatment) study is a randomized, multicenter, multinational clinical trial that will enroll approximately 700 breast cancer patients. The trial design has been updated to include current National Comprehensive Cancer Network guidelines and recently received Special Protocol Assessment (SPA) concurrence from the FDA. Based on a successful Phase II trial, which achieved its primary endpoint of disease-free survival (DFS), the FDA has agreed that the design and planned analysis of the Phase III study adequately address the objectives necessary to support an acceptable regulatory submission for marketing approval.
The NeuVax Phase III trial will be conducted in adjuvant breast cancer patients who are node positive, have an HLA status of A2/A3+, and have low or intermediate HER2 expression (IHC 1+, 2+, sometimes referred to as HER2 negative). These patients are not eligible to receive Herceptin (trastuzumab, marketed by Roche-Genentech) therapy that is currently approved only for patients with high HER2, or 3+ expression.
According to the protocol, once qualified patients have achieved a complete response from current standard-of-care treatment (surgery, radiation and/or chemotherapy), they will be randomized and dosed with either NeuVax (E75 + GM-CSF) or control (placebo plus GM-CSF). Patients will receive one intradermal injection every month for six months, followed by a booster inoculation every six months thereafter. The primary endpoint is disease-free survival at three years or 139 events (recurrence of cancer). A data safety monitoring board will conduct an interim analysis for safety and futility after 70 events.
To date, 70 sites are approved globally, with continued expansion to over 100 sites planned.
We think the Phase III trial design is prudent based on the existing data from the Phase I/II trials. This Phase III trial is well designed and better controlled one compared to the Phase I/II trials.
We believe NeuVax has a blockbuster potential if it finally reaches the market.
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