Researchers at Shaare Zedek Medical Center observed durable responses with pegylated liposomal doxorubicin plus pembrolizumab in a small group of heavily pretreated patients.
A Phase Ib study led by researchers at Shaare Zedek Medical Center and the Hebrew University Faculty of Medicine has reported encouraging results for a combination of pegylated liposomal doxorubicin and pembrolizumab in estrogen receptor-positive, HER2-negative metastatic breast cancer.
The study was published in July 2026 in Cancer Research Communications.
Immunotherapy has transformed treatment for several cancers, but its role in hormone receptor-positive breast cancer remains less established than in triple-negative disease.
The Israeli team investigated whether pegylated liposomal doxorubicin, a chemotherapy formulation capable of promoting immunogenic cancer-cell death, might improve tumor recognition by the immune system and enhance the activity of pembrolizumab, a PD-1 checkpoint inhibitor.
Results in a heavily pretreated group
Thirty-five patients whose cancer had progressed after hormonal, biological, and cytotoxic therapies received the combination.
Thirty patients completed enough treatment to be evaluated for tumor response. The disease-control rate was 67%: ten patients had an objective response and ten had stable disease.
The median duration of response was 11 months, and the longest response reached 20 months.
The researchers also reported responses in patients with large liver metastases. Median overall survival for the full treated cohort was 25 months.
Among responders, median survival reached 39 months. However, comparisons within a small, non-randomized, early-phase study cannot establish that the combination caused the observed survival difference.
Safety and biological clues
The regimen was generally well tolerated, with no significant neutropenia, no cardiac events, and minimal hair loss reported.
Three patients experienced treatment-related serious adverse events, including severe hepatitis or hemolytic anemia. They discontinued treatment and recovered with appropriate therapy.
Cutaneous toxicity sometimes led to treatment delays in patients receiving more than three cycles.
Tumor gene-expression analysis identified 16 genes that were more active in responders than in nonresponders, including interferon-stimulated genes.
These findings may help future studies explore biomarkers that identify patients more likely to benefit from this combination.
What comes next
The results are promising but preliminary. This was a Phase Ib trial with only 35 treated patients and no randomized control group.
Larger controlled studies are required before the combination can become a standard treatment for estrogen receptor-positive metastatic breast cancer.
Treatment decisions should continue to follow established guidelines and take into account previous therapies, tumor biology, molecular findings, general health, and patient preferences.
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