Early Efficacy Analysis of the AE37 Vaccine in Patients with HER2 Low-Expressing and Triple-Negative Breast Cancer.
Elizabeth Ann Mittendorf, Sonia A. Perez, Diane F. Hale, Timothy J. Vreeland, Alan K. Sears, Guy T. Clifton, Alexandros Ardavanis, Nathan M. Shumway, James L. Murray, Sathibalan Ponniah, Michael Papamichail, George Earl Peoples
Background: Peptide vaccines comprised of HLA class II epitopes, which elicit CD4+ T cell responses, play a critical role in potentiating immune responses. We are conducting a randomized phase II trial of AE37, a hybrid peptide created by the addition of the Ii-Key moiety (LRMK) to the HER2 helper epitope, AE36 (HER2 aa776-790). Here, we present efficacy data focusing on outcomes in patients with low HER2 (IHC 1+ or 2+) expression and triple negative breast cancer (TNBC).
Methods: The trial is enrolling node positive or high risk node negative breast cancer patients with any degree of HER2 expression (IHC 1+, 2+ or 3+ or FISH > 1.2) rendered disease-free following standard of care therapy. Patients are randomized to receive either AE37+GM-CSF or GM-CSF alone in 6 monthly intradermal inoculations followed by booster inoculations administered every 6 months.
Results: The trial has enrolled 254 patients; 105 in the vaccine group (VG) and 149 in the control group (CG). After a median follow-up of 22.3 months, the disease-free survival (DFS) rate in the VG is 90.3% vs 81.1% in the CG (p=.46), a 49% risk reduction. Evaluating patients with low HER2 expression (IHC 1+ or 2+), there are 53 VG patients and 77 CG patients. The groups are well-matched with respect to the percentage of patients with high grade tumors, tumors > 2cm, the rate of node positivity and ER/PR status (all p>.5).
The DFS rate in the VG of low HER2 expressers is 89.8% vs 68.2% in the CG (p=.12), a 68% risk reduction.
When limiting analyses to patients with TNBC (ER/PR negative, HER2 1+ or 2+), there are 13 VG patients and 23 CG patients. The groups are again well-matched with the exception of control patients having a larger percentage of tumors > 2 cm (70% vs 31%; p=.02).
The DFS rate in the VG of TNBC patients is 83.3% vs 47.6% in the CG (p=.23), a 68% risk reduction.
Conclusions: Early analyses suggest clinical benefit to vaccination with AE37, particularly in patients with low HER2-expressing tumors. Importantly, the benefit appears to persist in TNBC patients. Patients will continue to be followed per protocol for 5 years; however, these data suggest that a subsequent phase III trial should evaluate the vaccine in patients with low HER2-expressing disease to include TNBC.
Here is a link to the abstract.
Let's get wonky! Generex Pipeline Review's unexpert discussion:
The most differential aspect between the results Dr Mittendorf et all present at this week's ASCO Breast Cancer Symposium vs. the ASCO Annual Meeting from June is the inclusion of disease free survival rates for triple negative cancer subjects. Triple negative patients test negative for estrogen receptors (ER-), progesterone receptors (PR-), and HER2 (HER2-). According to breastcancer.org,
These negative results mean that the growth of the cancer is not supported by the hormones estrogen and progesterone, nor by the presence of too many HER2 receptors. Therefore, triple-negative breast cancer does not respond to hormonal therapy (such as tamoxifen or aromatase inhibitors) or therapies that target HER2 receptors, such as Herceptin (chemical name: trastuzumab). However, other medicines can be used to treat triple-negative breast cancer.
About 10-20% of breast cancers — more than one out of every 10 — are found to be triple-negative. For doctors and researchers, there is intense interest in finding new medications that can treat this kind of breast cancer. Early studies are trying to find out whether certain medications can interfere with the processes that cause triple-negative breast cancer to grow.
In the new AE37 study, a much higher percentage (70%) of triple negative subjects within the control group have a tumor size greater that 2 cm, while 69% of triple negative subjects in the vaccine group have a tumor size less than 2 cm. Share cancersupport.org informs that-
triple negative breast cancer tumors are also classified into four stages on the basis of size and lymph-node involvement. Stage I means that the tumor is less than 2 cm in size and there is no lymph node involvement. Stages II and III indicate larger size and degrees of lymph node involvement. Stage IV means that metastasis has already occurred.
With this in mind, it appears that the majority of triple negative subjects in the control group have Stage II tumors, while the majority of triple negative subjects in the vaccine group have Stage I tumors. The difference is noted by the authors of the abstract as being statistically significant, p=.02. For an optimum comparison, the groupings in a planned Phase III study will need to more evenly matched.
However, all of that aside, the results for triple negative subjects within the AE37 arm of the study are quite promising. These subjects have a disease free survival rate of 83.3% at 23.3 months, and the first 24 months appear to be the most critical.
The Oncologist's 2012 article titled Triple-Negative Breast Cancer: An Unmet Medical Need states that "fundamentally, in the early-stage setting, triple-negative breast cancer is associated with earlier versus later events, as well as a shorter period from the time of recurrence until death." They inform in their conclusion remarks that-
triple-negative breast cancer is clearly a distinct subtype, from the perspective of both ER and HER-2, and there may yet be further distinct subclassifications. This disease presentation clearly represents an important clinical challenge. Triple-negative breast cancer is also a surrogate of basal-like breast cancer. Therefore, trials designed to accrue patients with basal-like breast cancer using ER/PR and HER-2 negativity provide an approximation of the triple-negative population, but, as described in the introduction, there is some discordance, including some HER-2 positives and some ER positives among the basals. At present, there is not a clear, proven effective single agent that targets a driving vulnerability in triple-negative breast cancer. However, there are a number of potential therapies currently under investigation that may eventually improve outcomes in these patients.
WebMD estimates that between 10 - 17% of cancers are triple negative. Previous reports estimated that approximately 80% of breast cancer patients could be treated with AE37 if the vaccine gains approval by the FDA. In this estimate, they appeared to be noting subjects that are low and high expressors of HER2/neu. We now see the researchers adding triple negative subjects to their Phase III plannings, and this certainly is a positive development for Generex and Antigen Express.
Currently, Generex's shareholders are waiting to hear an update on the long planned spin out of Antigen Express. Such an update is long overdue, and until then any plans for a Phase III appear to be in a state of limbo. Hopefully, the continued positive results for AE37 bring Generex much needed momentum in their spinout plans for Antigen Express.
One other quick note- during the ASCO Annual Meeting held in June, the researchers noted that they "have enrolled 201 patients to our phase II trial (Vaccine (VG)=103, Control (CG)=98)." This new abstract notes that they have "enrolled 254 patients; 105 in the vaccine group (VG) and 149 in the control group (CG)." The new abstract shows results at 23.3 months, and the June abstract shows results at 22 months. In this update, only 4 subjects have been added to the AE37 arm, while 51 have been added to the control group. Overall, this is the largest controlled study for a peptide based vaccine to treat breast cancer in the adjuvant setting.
As Generex's stock continues to decline, their AE37 breast cancer vaccine continues to shine. At some point, AE37 should have a long lasting positive effect on shares of GNBT, while the more important goal is to cure early stage breast cancer.