Mode
Text Size
Log in / Sign up

Phase Ib trial: Mam-A DNA vaccine plus endocrine therapy induces T cells in ER+ breast cancerCan a breast cancer vaccine help the immune system target tumors?

AI-generated summary of the cited source, checked by automated accuracy review. How we work

Key Takeaway
Note early-phase evidence of Mam-A vaccine-induced T-cell responses in ER+ breast cancer; clinical efficacy is unknown.

This phase Ib clinical trial evaluated a Mammaglobin-A (Mam-A) DNA vaccine added to neoadjuvant endocrine therapy versus endocrine therapy alone in patients with estrogen receptor-positive breast cancer prior to surgery. The final analysis included 21 patients (8 in the control arm, 13 in the vaccination arm). The primary outcome was not reported.

The main immunological findings were descriptive. Mam-A vaccination induced Mam-A-specific T cells in the peripheral blood of 8 out of 13 patients. These induced T cells included both CD4+ and CD8+ polyfunctional subsets. In post-vaccination tumor samples, researchers observed increased CD8+ T-cell prevalence and infiltration of PD-1+CD8+ T cells. Spatial analysis revealed close interactions between cytotoxic CD8+ T cells and both Mam-A+ tumor cells and antigen-experienced CD4+ T cells.

Safety and tolerability data were not reported. Key limitations include the very small sample size, the absence of reported clinical efficacy outcomes (such as pathological complete response or survival), and the descriptive, non-quantified nature of the immunological results. The study's language uses terms like 'induced' and 'was associated with,' which do not establish causation. As a preliminary phase Ib trial, these findings are hypothesis-generating and demonstrate proof-of-concept for immune activation. Their relevance to clinical practice is not established.

When facing breast cancer surgery, the goal is to give the body every possible advantage. A small, early-stage trial explored whether adding an experimental vaccine to standard pre-surgery hormone therapy could help the immune system recognize and attack cancer cells. The vaccine targets a protein called Mammaglobin-A, which is often found on these tumors.

The study involved 21 patients. In the group that received the vaccine plus hormone therapy, the treatment successfully triggered specific tumor-targeting immune cells in the blood of 8 out of 13 patients. Researchers also saw signs that these activated immune cells were traveling to the tumor site and interacting closely with cancer cells.

It's important to understand what this does and doesn't tell us. This was a Phase Ib trial, which is very early research focused primarily on safety and whether a treatment triggers a biological response. The study was small and only looked at immune system markers. We don't know if this immune activity translates to better outcomes, like shrinking tumors or preventing cancer from returning. The results are a promising signal that the vaccine is doing something biologically, but much larger studies are needed to see if it actually helps patients.

What this means for you:
An early breast cancer vaccine study showed it can activate the immune system, but clinical benefits are not yet known.

Study Details

Study typePhase1
Sample sizen = 8
EvidenceLevel 4
PublishedApr 2026
View Original Abstract ↓
Tumor-associated antigen (TAA) vaccines are being explored as a strategy to induce antitumor immune responses. Mammaglobin-A (Mam-A) is a TAA expressed in >50% of patients with breast cancer. Previously, we have shown that Mam-A DNA vaccines induce antitumor immune responses in patients with stable metastatic disease. To further evaluate the potential of the Mam-A vaccine, we initiated a phase Ib clinical trial in patients with estrogen receptor-positive breast cancer prior to surgery. Eight patients were assigned to arm 1 (neoadjuvant endocrine therapy alone) and 17 to arm 2 (neoadjuvant endocrine therapy plus Mam-A vaccination); the final analysis included 8 patients from arm 1 and 13 from arm 2. Ex vivo enzyme-linked immunospot (ELISpot) analysis of peripheral blood mononuclear cells demonstrated that Mam-A vaccination induced Mam-A-specific T cells in 8 of 13 patients. Intracellular cytokine staining and Mam-A-specific tetramer staining revealed that vaccine-induced Mam-A-specific T cells included both CD4+ and CD8+ polyfunctional T cells. Finally, high-throughput imaging mass cytometry identified 24 cellular metaclusters with features of tumor, immune, stromal, and endothelial cells and revealed an increased CD8+ T-cell prevalence in the tumor after Mam-A vaccination. In particular, vaccination was associated with the infiltration of PD-1+CD8+ T cells. In addition, postvaccination tumor samples exhibited close spatial interactions between cytotoxic CD8+ T cells (CTL) and Mam-A+ tumor cells and between CTL and antigen-experienced CD4+ T cells. Together, these results suggest that Mam-A DNA vaccination elicits both systemic and intratumoral antitumor immune responses.
Free Newsletter

Clinical research that matters. Delivered to your inbox.

Join thousands of clinicians and researchers. No spam, unsubscribe anytime.